WO1992008144A1 - Alignment of wafer test probes - Google Patents

Alignment of wafer test probes Download PDF

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Publication number
WO1992008144A1
WO1992008144A1 PCT/US1991/001366 US9101366W WO9208144A1 WO 1992008144 A1 WO1992008144 A1 WO 1992008144A1 US 9101366 W US9101366 W US 9101366W WO 9208144 A1 WO9208144 A1 WO 9208144A1
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WO
WIPO (PCT)
Prior art keywords
reference pattern
transport device
probes
test
stepping
Prior art date
Application number
PCT/US1991/001366
Other languages
French (fr)
Inventor
Stuart Howard Bullard
Paul Matthew Gaschke
Dean Frederick Herring
Andrew Alfred Herz
Mark Raymond Laforce
Jay Jeffrey Mendelson
Mark Karl Stephenson
Original Assignee
International Business Machines Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Business Machines Corporation filed Critical International Business Machines Corporation
Publication of WO1992008144A1 publication Critical patent/WO1992008144A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/02—General constructional details
    • G01R1/06—Measuring leads; Measuring probes
    • G01R1/067—Measuring probes
    • G01R1/073—Multiple probes
    • G01R1/07307—Multiple probes with individual probe elements, e.g. needles, cantilever beams or bump contacts, fixed in relation to each other, e.g. bed of nails fixture or probe card
    • G01R1/07314—Multiple probes with individual probe elements, e.g. needles, cantilever beams or bump contacts, fixed in relation to each other, e.g. bed of nails fixture or probe card the body of the probe being perpendicular to test object, e.g. bed of nails or probe with bump contacts on a rigid support
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/28—Testing of electronic circuits, e.g. by signal tracer
    • G01R31/282—Testing of electronic circuits specially adapted for particular applications not provided for elsewhere
    • G01R31/2831—Testing of materials or semi-finished products, e.g. semiconductor wafers or substrates

Definitions

  • This invention relates to VLSI circuit testers and particularly to the wafer prober portions thereof. More particularly, in a preferred embodiment, this invention relates to methods and apparatus for aligning high density wafer test probes with the chip contacts on the wafers or single chips under test when the contacts cannot be observed from above the test probes because of the density of the test probes.
  • Exposure devices used for the manufacture of the semiconductor wafers typically utilize through the lens ali ⁇ n ent svstems. Such svstems are disclosed in Nishi, U.S. Patent 4,897,553; Ina, U.S. Patent
  • Hassing IBM Technical Disclosure Bulletin, Vol. 22, No. 3, August 1979, pp. 1143-1144.
  • a scrap wafer is mounted on the wafer chuck in the test wafer mounting position and is moved under the probes. The probes are then pressed into the scrap wafer, causing indentations. These indentations can then be detected by a means of a microscope or other suitable optical means and the positional relationship between the probe array and a reference position determined.
  • a probing apparatus similar to that disclosed in Hassing is disclosed in Yamatsu, U.S. Patent 4,786,867.
  • Yamatsu forms the indentations in a non-chip region of the wafer, rather than in a scrap wafer.
  • the wafer probers in Hassing and Yamatsu may potentially cause damage to the probes when these indentations are made. Additionally, Hassing and Yamatsu do not provide a direct means of measuring the position of the probe needles.
  • the probe needle contacts a needle sensing plate, the position of which is detected by a laser beam and suitable arrangement of lenses and detectors.
  • the invention of Sato detects the probe tip by direct physical contact with a needle sensing unit which contains the needle sensing plate, the laser, the lenses and the detectors.
  • Another method of aligning dense probe arrays with wafer contacts utilizes a rotable mirror inserted between the probes and the wafer with the z stage and platen of the wafer handling system retracted.
  • the mirror is rotated to a first position so that a camera and attached microscope can observe the probes.
  • the mirror is then rotated 90 degrees so that the camera and attached microscope can view the wafer.
  • the mirror is then shuttled away so that the z stage and platen can be raised to allow the probes to contact the wafer.
  • This method has several potential errors.
  • the rotation of the mirror must be exactly 90 degrees, and the travel of the platen and the z stage must be exactly orthogonal to the line of observation between the camera and microscope and the rotary mirror.
  • an object of the present invention to provide methods and apparatus for determining the position of a dense probe array using simple electrical measurements .
  • a method for aligning an array cf test probes with positions on a test substrate is provided.
  • the test substrate is mounted on a transport device and the test probes have an operational side for contacting the substrate.
  • the methods first includes calibrating reference axes of the transport device with reference axes of the substrate under fixed optics, where the fixed optics have a reference position.
  • the method next includes aligning this reference position of the fixed optics with a reference pattern on a positioning device which is attached to the transport device and thereby determining a first location of the positioning device.
  • the reference pattern has a fixed spatial relationship with the transport device, as does the test substrate.
  • the test substrate in turn has a position which corresponds to the desired point of contact with a predetermined test probe.
  • the method then includes translating the transport device to a position opposite the test probes and aligning the reference pattern of the positioning device with the predetermined test probe to determine a second position of the positioning device.
  • the necessary transport device translation for testing the substrate can then be calculated using the coordinates of the first location under the fixed optics and the second location under the test probes.
  • the invention also provides a test apparatus which includes a transport device for mounting a test substrate and fixed optics for calibrating reference axes of the transport device with references axes of the test substrate, the fixed optics having a reference position.
  • the test apparatus also includes a plurality of test probes for testing the test substrate, the test probes having an operational side wherein they contact the test substrate.
  • the apparatus then includes a positioning device which is attached to the transport device.
  • the positioning device has a reference pattern which has a predetermined spatial relationship with the transport device, as does the test substrate.
  • the test substrate in turn has a position which corresponds to the desired point of contact of the test substrate with a predetermined test probe.
  • the positioning device is alignable with the reference position of the fixed optics and is alignable with the predetermined test probe from the operational side of the test probes.
  • FIG. 1 is a perspective schematic view of one embodiment of the present invention.
  • FIG. 2 is a perspective schematic view of an alternative embodiment of the present invention.
  • FIGS. 3A - 3C are detailed views of a predetermined set of test probes superimposed over a reference pattern on a selectively conductive substrate of the present invention.
  • FIGS. 4A-4C are cross-sectional views showing the alignment of a test probe in a reference pattern of a selectively conductive substrate.
  • FIG. 5 is a side view showing an optics assembly mounted on the chuck in one embodiment of the present invention. Detailed Description of the Invention
  • a transport device of a wafer handling system for mounting a test substrate includes chuck 20 mounted to z stage 19, which in turn is mounted on platen 18.
  • the test substrate (not shown) is a semiconductor wafer comprising a plurality of identical chips.
  • Other examples of possible test substrates include single chips and semiconductor chip packaging substrates.
  • Fixed optics 15 comprises a camera and is connected to monitor 17 by line 16. Reticle 42 of camera 15 is the reference position of the fixed optics. Fixed optics 15 is used to calibrate the reference axes x , y of the platen 18
  • Test apparatus 10 also comprises a plurality of test probes 14 for testing the substrate, the test probes having an operational side wherein they contact the test substrate.
  • the probes 14, in a preferred embodiment, are so-called “cobra” probes, such as those disclosed in Lorber, et al., IBM
  • Test probes 14 are connected through space transformer 13, which fans out the connections from the dense array of probes, to test electronics 11 by line 12.
  • Test electronics 11 control application of test signals to the semiconductor wafer under test.
  • An important aspect of the present invention is positioning device 21 attached to chuck 20 of the transport device.
  • the positioning device is alignment substrate 21, which has at least one reference pattern having a predetermined spatial relationship with the transport device. Alignment substrate 21 is attached to chuck 20 of the transport device in the test substrate mounting position.
  • the desired point of contact of the test substrate with a predetermined probe also has a predetermined spatial relationship with the transport device.
  • These predetermined spatial relationships are established by having precisely controlled distances between the mounting position of the test substrate and the electrical contact and between the mounting position of the alignment substrate and the reference pattern.
  • the alignment substrate 21 has two reference patterns 40, 41.
  • the reference patterns have a first conductivity and are located on the surface of alignment substrate 21, which has a second electrical conductivity.
  • Alignment substrate 21 is alignable with reticle 42 of fixed optics 15 and is alignable with a predetermined test probe from the operational side of test probes 14 in a manner which will be hereinafter described.
  • reference patterns 40, 41 on alignment substrate 21 are possible. Configurations having 1, 2, and 4 reference patterns have been tested, but the invention is by no means limited to these numbers of reference patterns.
  • the test patterns are cross-shaped substantially electrically non-conductive structures of predetermined dimensions on alignment substrate 21, the surface of which is substantially electrically conductive.
  • the operation of this embodiment in the invention depends upon the difference in electrical conductivity between alignment substrate 21 surface and reference patterns 40, 41. It should therefore be obvious to those skilled in the art that the invention is equally operative in the case where the surface of alignment substrate 21 is substantially electrically non-conductive and the reference patterns are electrically conductive or in the case where the patterns and the substrate surface are both conductive, but have different conductivities. The operation of this embodiment of the invention will now be described with reference to
  • Operation of the test apparatus of the present invention provides a method for aligning an array of test probes with positions on a test substrate, in a preferred embodiment the positions being contacts on a semiconductor wafer under test.
  • the substrate to be tested is mounted on chuck 20 of the transport device and test probes 14 have an operational side wherein they contact the test substrate. Alignment substrate
  • the alignment substrate is a separate part containing the reference patterns, this example is only for purposes of illustration.
  • the test substrate can also contain the reference patterns, in which case the test substrate and alignment substrate are the same part. Since the described alignment is only performed periodically, however, it will usually be most economical that the alignment substrate be a separate part.
  • the surface of alignment substrate 21 is electrically conductive, being coated with a gold plating.
  • the substrate itself is composed of a substantially nonconductive material.
  • Reference patterns 40, 41 are substantially non-conductive cross-shaped structures, which have been masked during the plating process so that there is no gold plating on these structures.
  • these cross-shaped structures are 0.01 in. wide and are used for aligning 0.004 in. diameter cobra test probes.
  • a slightly depopulated 29 x 29 array of these probes is provided on 0.008 in. centers with approximately 800 probes for testing a semiconductor chip located on the wafer.
  • the chip is approximately 6.5mm square.
  • platen 18 After removal of the theta error, platen 18 then translates alignment substrate 21 such that reticle 42 of fixed optics 15 is aligned with at least one of the reference patterns on alignment substrate 21.
  • reticle 42 is aligned with reference pattern 40 on alignment substrate 21. This determines a first location of alignment substrate 21 which becomes a reference position for the transport device. As has been previously described, this reference pattern 40 has a predetermined spatial relationship with the transport device. This position is then set as a first location of the alignment substrate in absolute position of 0.0001 inches, or 0.1 mil, resolution.
  • Platen 18 then translates chuck 20 to a position opposite test probes 14.
  • the positio -to which chuck 20 is translated is determined by a calibration which is performed prior to delivery of the tester system.
  • This calibration establishes a circle of radius R within which a predetermined test probe with which the reference pattern will be aligned is located. Although not necessary for operation of the present invention, this step greatly simplifies the alignment procedure.
  • the probes in the pairs are shorted together in test electronics 11 to allow current to flow between the probes when a voltage is applied across the probes. Current will flow when both of the the probes in a pair contact a conductive surface and current will not flow when one probe conducts a conductive service and another probe does not, or when neither probe in a pair contacts a conductive surface. It should be obvious to those skilled in the art that this description is for purposes of illustrating the preferred embodiment and that other methods to electrically sense the probes may be used.
  • At least one reference pattern of alignment substrate 21 is aligned through probe searching with at least a predetermined test probe to determine a second location of alignment substrate 21. This entire process is performed from the operational side of test probes 14. Platen 18 and Z stage 19 are first translated in the Z direction so that alignment substrate 21 is brought into contact with probes 14. The probes have spring characteristics and are not damaged or permanently deformed by this contact. In a preferred embodiment, probe deflection from this contact is approximately 0.005 in.
  • Chuck 20 is then stepped in two axes to roughly position the alignment substrate such that a predetermined set of the probes is in contact with reference pattern 40. Specifically, the chuck is stepped in the X direction in one mil (0.001 in.) increments until no current flows in probe pairs 25 and 26, as shown in Fig. 3A, thus locating a side 46 of reference pattern 40. The continuity of the probes is sensed at each step in test electronics 11 bv means which are well known to those skilled in the art. Chuck 20 then translates in the Y direction in one mil increments until no current flows in probe pairs 43, 44, as shown in Fig. 3B, thus locating side
  • FIG. 4A a case is shown where a probe from pair 26 overhangs reference pattern 40 but still has a
  • the center of reference pattern 40 may be precisely located by finely positioning alignment substrate 21.
  • the first step in this fine positioning is to switch the resolution of the stepper platen 18 from 1 mil to 0.1 mil (0.0001 in.) .
  • the maximum number of steps to locate a side of the reference pattern assuming that the probe is displaced by 0.0009 inches frors the actual center, will be half the width of the 10 mil reference pattern plus 0.0009 inches, namely 0.0059 inches, or fifty-nine 0.1 mil increments.
  • chuck 20 is first stepped in the X direction to detect side 46 of a first portion of the reference pattern, the first portion being that portion aligned with the Y direction. As with the rough positioning, the continuity of the pairs of probes is sensed at each step. Once the location of side 46 has been determined, the position of the center line of that first portion can easily be calculated, since the exact width is predetermined. The chuck 20 can then translate to center the probe pairs 25, 26 in this portion of the reference pattern, as shown in FIG. 4C. In like manner, chuck 20 car. then be stepped in the Y direction to detect side 47 of a second portion of *the reference pattern which is orthogonal to the first portion, namely that portion aligned in the X direction.
  • center probe 45 which corresponds to the desired point of contact on the test wafer, to be aligned with center 49 of reference pattern 40 to within 0.1 mil in both the X and ⁇ directions. This procedure determines the second location of the alignment substrate.
  • the necessary transport device translation for testing a test substrate can easily be calculated using the coordinates of the first and second locations and testing can be performed.
  • the alignment substrate is first replaced v/ith a test substrate.
  • the desired point of contact of the test substrate with the predetermined probe is aligned with reticle 42 of fixed optics 15, which corresponds with the first location of the alignment substrate.
  • the test substrate can then translate to the position corresponding to the second position of the alignment substrate and testing can commence. It is not necessary that the same reference pattern be used for both the rough and fine positioning. For instance, first reference pattern
  • reference pattern 40 can be used for the rough positioning and second reference pattern 41 can be used for the fine positioning. This may be desired if the rough positioning results in galling the sides of reference pattern 40. There is a predetermined precise spatial relationship between reference patterns 40 and 41.
  • the chuck can translate the alignment substrate 21 to that rough position on reference pattern 41 before finely positioning the alignment substrate.
  • the center of reference pattern 40 is thus located by performing the fine positioning using reference pattern 41. All other steps of the process are identical to those previously described.
  • the invention is equally operable with the reference patterns being conductive and the remainder of the surface of the substrate being nonconductive.
  • the continuity of the probes is still sensed at each step during the rough and fine positioning, but the reference patterns locations are determined when current flows in the pairs of probes, not when current ceases to flow.
  • the invention is otherwise the same as previously described.
  • the method of the invention can also be used to detect angular misalignment between the alignment substrate and the probe array.
  • the probe array may be stepped in the X direction.
  • angular misalignment alpha probe pair 26 will lose continuity prior to probe pair 25 losing continuity.
  • the X-axis positions when these probe pairs lose continuity can be recorded.
  • the actual distance between probe pairs 25 and 26 is, of course, a predetermined value. Using this predetermined value and difference between the X positions at which the probe pairs lose continuity, the angle alpha can easily be calculated.
  • FIG. 2 an alternative embodiment 50 of the present invention is shown.
  • Many of the components shown in the embodiment in Fig. 2 are the same as those shown in Fig. 1 and these identical components are identified by the same reference numbers in Fig. 2 as in Fig. 1.
  • the positioning device cf the embodiment shown in Fig. 2 is optics assembly 23 -which i ⁇ opposed to fixed optics 15 and probes 14 such -chat the fixed optics and probes are directly observable by optics assembly 23.
  • the test substrate 22 may be mounted directly on chuck 20 as opposed to the previously described embodiment, where a separate alignment substrate is used if the reference patterns are not incorporatsd into the test substrate. Referring to Fig.
  • the light is transmitted to a ring light 32 for illuminating the reticle 31.
  • Spacer 33 separates ring light 32 and objective lens 34.
  • Spacer 36 separates objective lens 34 and CCD camera
  • Test apparatus 50 also includes video device monitor 17 connected to optics assembly 23 by line
  • Video device 17 also has a reticle which corresponds to the optics assembly reticle 31.
  • the tester is operative to allow manual operator alignment of the video device reticle and thus mechanical reticle 31 with the predetermined test probe and with the fixed optics reticle 42.
  • test substrate 22 may be directly mounted to chuck 20.
  • the reference axes of platen 18 of the transport device are calibrated with the reference axes of test substrate 22 and therefore with the corresponding reference axes of chuck 20 under fixed optics 15.
  • Reticle 42 of camera 15 is the reference position of fixed optics 15.
  • Reticle 31 of optics assembly 23 is then aligned with reticle 42 of fixed optics 15 to determine a first location of reticle 31.
  • Reticle 31 and test substrate 22 have predetermined spatial relationships with the transport device by virtue of the fixed mounting positions of the optics assembly and the test substrate.
  • a position on the test substrate corresponds to a desired point of contact with a predetermined test probe, in a preferred embodiment an electrical connection on a semiconductor v/afer chip.
  • Chuck 20 is then translated to a position opposite the test probes and mechanical reticle 31 is aligned with the predetermined test probe by direct observation of the predetermined test probe by the optics assembly to determine a second location of mechanical reticle 31.
  • This alignment of mechanical reticle 31 with the predetermined test probe includes a rough positioning and a fine positioning step.
  • the rough positioning step consists of first scanning the optics assembly 23, by translating chuck 20, in one axis across the probe array to determine the position of two opposing peripheral edges. This determination is made by aligning mechanical reticle 31 on video monitor 17 with these opposing edges. The optics assembly is then scanned in like manner in an orthogonal direction to the first axis to determine the position of the other two opposing edges of the probe array.
  • the position of any predetermined test probe can be calculated and the chuck 20 translated so that the reticle 21 is roughly aligned with that predetermined test probe.
  • the chuck 20 then is finely translated to align the optics device reticle 31 with the predetermined test probe
  • Both the fine and coarse alignment steps are accomplished by observing the test probes on video device 17 connected to optics assembly 23 by line 24.
  • Chuck 20 is translated by operator interaction until the predetermined test probe and the video device reticle, which corresponds to rhe optics assembly reticle 31, are aligned on the video device 17.
  • the fine positioning step determines a second location of the reticle, namely that location which corresponds to the predetermined test probe. Once the coordinates of the second location and the first location of the reticle have been determined, the necessary chuck 20 translation for wafer testing is easily determined by subtracting the X and Y coordinates of the first location from the X and Y coordinates of the second location.

Abstract

A method and apparatus for aligning an array of test probes with positions on a semiconductor wafer uses a positioning device having a reference pattern. The positionning device is attached to a substrate transport device. A first location of the positioning device is located under fixed optics. A second location of the positioning device is located under the probe array which corresponds to a predetermined test probe. Both of these steps are accomplished from the operational side of the test probes. The reference pattern of the positioning device and the semiconductor wafer have predetermined spatial relationships with the transport device. Necessary transport device translation for testing can then be calculated using the first and second locations of the reference pattern of the positioning device. In one embodiment the positioning device is an alignment substrate mounted in the test substrate position. Selectively conductive patterns on the alignment substrate can be used to determine the position of the predetermined test probe by measuring the continuity of shorted probe pairs as the alignment substrate is translated. In another embodiment of the invention an optics assembly mounted to the wafer chuck directly observes the fixed optics reticle and the predetermined test probe.

Description

ALIGNMENT OF WAFER TEST PROBES
Technical Field
This invention relates to VLSI circuit testers and particularly to the wafer prober portions thereof. More particularly, in a preferred embodiment, this invention relates to methods and apparatus for aligning high density wafer test probes with the chip contacts on the wafers or single chips under test when the contacts cannot be observed from above the test probes because of the density of the test probes.
Background of the Invention
Current integrated circuit manufacturing techniques incorporate a plurality of identical chips on a large silicon wafer. These chips are tested at the wafer or individual chip level to determine which ones may be utilized in subsequent manufacturing steps. The apparatus for performing these tests genericall consists of two sections: circuitry for applying the necessary electronic test signals to the chips and a wafer prober for making contact with the connections on the individual semiconductor chips. Because of the small size of the chips, the number of contacts on an individual chip, and the small size of these contacts, it is necessary to precisely align the test probes with the connections on the chip.
Exposure devices used for the manufacture of the semiconductor wafers typically utilize through the lens aliσn ent svstems. Such svstems are disclosed in Nishi, U.S. Patent 4,897,553; Ina, U.S. Patent
4,861,162; Nishi, U.S. Patent 4,856,905; Totsuka, et al., U.S. Patent 4,834,540; Umatate, U.S. Patent 4,833,621; Kuroki, et al., U.S. Patent 4,830,500. An analogous alignment system has been used in wafer probers where the probe density is not high and the probes contact the edges of the chip. In Sato, et al., U.S. Patent 4,677,474 a TV camera positioned above the probes views the wafer contacts through an opening in the probes to achieve the necessary alignment.
As integrated circuit densities increase and connection counts grow greater, the technique disclosed in Sato becomes less feasible. This is particularly true when the chip connections are not along the edges of the chip but are dispersed across the entire surface of the chip. Some high density integrated circuits currently require testers with hundreds of test probes to contact a chip several millimeters square.
One method for probing high density chips is disclosed in Hassing, IBM Technical Disclosure Bulletin, Vol. 22, No. 3, August 1979, pp. 1143-1144. A scrap wafer is mounted on the wafer chuck in the test wafer mounting position and is moved under the probes. The probes are then pressed into the scrap wafer, causing indentations. These indentations can then be detected by a means of a microscope or other suitable optical means and the positional relationship between the probe array and a reference position determined. A probing apparatus similar to that disclosed in Hassing is disclosed in Yamatsu, U.S. Patent 4,786,867. The invention of Yamatsu forms the indentations in a non-chip region of the wafer, rather than in a scrap wafer. The wafer probers in Hassing and Yamatsu may potentially cause damage to the probes when these indentations are made. Additionally, Hassing and Yamatsu do not provide a direct means of measuring the position of the probe needles.
Another wafer prober for determining probe tip location for dense probe arrays from the wafer side of the probe is disclosed in Sato, U.S. Patent
4,864,227. In Sato the probe needle contacts a needle sensing plate, the position of which is detected by a laser beam and suitable arrangement of lenses and detectors. The invention of Sato detects the probe tip by direct physical contact with a needle sensing unit which contains the needle sensing plate, the laser, the lenses and the detectors.
Another method of aligning dense probe arrays with wafer contacts utilizes a rotable mirror inserted between the probes and the wafer with the z stage and platen of the wafer handling system retracted. The mirror is rotated to a first position so that a camera and attached microscope can observe the probes. The mirror is then rotated 90 degrees so that the camera and attached microscope can view the wafer. The mirror is then shuttled away so that the z stage and platen can be raised to allow the probes to contact the wafer. This method has several potential errors. The rotation of the mirror must be exactly 90 degrees, and the travel of the platen and the z stage must be exactly orthogonal to the line of observation between the camera and microscope and the rotary mirror.
Other means for aligning semiconductor wafers either for wafer probing or for wafer exposure, none of which provide the capability of aligning dense probe arrays from the wafer side, include Stoehr, U.S. Patent 4,908,571; Nakata, et al, U.S. Patent
4,906,852; Mehnert, et al. , U.S. Patent 4,854,709;
Waldo, et al. , U.S. Patent 4,768,883; Perloff, et al., U.S. Patent 4,703,252; and Iwai, U.S. Patent
4,418,467.
SUMMARY OF THE INVENTION
Current wafer prober configurations show that a need exists for methods and apparatus for aligning very dense probe arrays. Existing approaches to this problem either have the potential for damaging the probes and do not provide direct measurement of probe position, or contain sophisticated lasers and complicated optics. A need exists for determining the position of dense probe arrays from the wafer side of the probes either by direct observation or by structures incorporating simple electrical measurements.
It is, therefore, an object of the present invention to provide methods and apparatus for determining the position of a dense probe array using simple electrical measurements .
It is a further object of the invention to provide method and apparatus for detecting probe array position by direct optical observation. It is yet a further object of the present invention to use the same apparatus as used for the probe alignment to align the test substrate with fixed optics.
In accordance with these and other objects of the present invention, a method for aligning an array cf test probes with positions on a test substrate is provided. The test substrate is mounted on a transport device and the test probes have an operational side for contacting the substrate. The methods first includes calibrating reference axes of the transport device with reference axes of the substrate under fixed optics, where the fixed optics have a reference position. The method next includes aligning this reference position of the fixed optics with a reference pattern on a positioning device which is attached to the transport device and thereby determining a first location of the positioning device. The reference pattern has a fixed spatial relationship with the transport device, as does the test substrate. The test substrate in turn has a position which corresponds to the desired point of contact with a predetermined test probe. The method then includes translating the transport device to a position opposite the test probes and aligning the reference pattern of the positioning device with the predetermined test probe to determine a second position of the positioning device. The necessary transport device translation for testing the substrate can then be calculated using the coordinates of the first location under the fixed optics and the second location under the test probes. The invention also provides a test apparatus which includes a transport device for mounting a test substrate and fixed optics for calibrating reference axes of the transport device with references axes of the test substrate, the fixed optics having a reference position. The test apparatus also includes a plurality of test probes for testing the test substrate, the test probes having an operational side wherein they contact the test substrate. The apparatus then includes a positioning device which is attached to the transport device. The positioning device has a reference pattern which has a predetermined spatial relationship with the transport device, as does the test substrate. The test substrate in turn has a position which corresponds to the desired point of contact of the test substrate with a predetermined test probe. The positioning device is alignable with the reference position of the fixed optics and is alignable with the predetermined test probe from the operational side of the test probes.
The foregoing and other objects, features, and advantages of the present invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings.
Brief Description of the Drawings
In the accompanying drawings forming a material part of this disclosure:
FIG. 1 is a perspective schematic view of one embodiment of the present invention.
FIG. 2 is a perspective schematic view of an alternative embodiment of the present invention.
FIGS. 3A - 3C are detailed views of a predetermined set of test probes superimposed over a reference pattern on a selectively conductive substrate of the present invention.
FIGS. 4A-4C are cross-sectional views showing the alignment of a test probe in a reference pattern of a selectively conductive substrate. FIG. 5 is a side view showing an optics assembly mounted on the chuck in one embodiment of the present invention. Detailed Description of the Invention
Referring to the drawings in more detail and particularly referring to FIG. 1 of the invention, there is shown one embodiment of the test apparatus 10 according to the present invention. A transport device of a wafer handling system for mounting a test substrate includes chuck 20 mounted to z stage 19, which in turn is mounted on platen 18. In one embodiment the test substrate (not shown) is a semiconductor wafer comprising a plurality of identical chips. Other examples of possible test substrates include single chips and semiconductor chip packaging substrates. Fixed optics 15 comprises a camera and is connected to monitor 17 by line 16. Reticle 42 of camera 15 is the reference position of the fixed optics. Fixed optics 15 is used to calibrate the reference axes x , y of the platen 18
P P of the transport device with reference axes x , y of the test substrate, which in turn correspond to reference axes of chuck 20. The manner in which this calibration is performed will be further described hereinafter.
Test apparatus 10 also comprises a plurality of test probes 14 for testing the substrate, the test probes having an operational side wherein they contact the test substrate. The probes 14, in a preferred embodiment, are so-called "cobra" probes, such as those disclosed in Lorber, et al., IBM
Technical Disclosure Bulletin, Vol. 26, No. 1, June 1983, p. 251, the disclosure of which is incorporated by reference herein. Test probes 14 are connected through space transformer 13, which fans out the connections from the dense array of probes, to test electronics 11 by line 12. Test electronics 11 control application of test signals to the semiconductor wafer under test. An important aspect of the present invention is positioning device 21 attached to chuck 20 of the transport device. In one embodiment of the invention as shown in FIG. 1, the positioning device is alignment substrate 21, which has at least one reference pattern having a predetermined spatial relationship with the transport device. Alignment substrate 21 is attached to chuck 20 of the transport device in the test substrate mounting position. The desired point of contact of the test substrate with a predetermined probe , typically an electrical contact of one of the chips of a semiconductor wafer, also has a predetermined spatial relationship with the transport device. These predetermined spatial relationships are established by having precisely controlled distances between the mounting position of the test substrate and the electrical contact and between the mounting position of the alignment substrate and the reference pattern.
In the illustrated embodiment, the alignment substrate 21 has two reference patterns 40, 41. The reference patterns have a first conductivity and are located on the surface of alignment substrate 21, which has a second electrical conductivity. Alignment substrate 21 is alignable with reticle 42 of fixed optics 15 and is alignable with a predetermined test probe from the operational side of test probes 14 in a manner which will be hereinafter described.
Many different configurations of reference patterns 40, 41 on alignment substrate 21 are possible. Configurations having 1, 2, and 4 reference patterns have been tested, but the invention is by no means limited to these numbers of reference patterns. In the illustrated embodiment, the test patterns are cross-shaped substantially electrically non-conductive structures of predetermined dimensions on alignment substrate 21, the surface of which is substantially electrically conductive. The operation of this embodiment in the invention depends upon the difference in electrical conductivity between alignment substrate 21 surface and reference patterns 40, 41. It should therefore be obvious to those skilled in the art that the invention is equally operative in the case where the surface of alignment substrate 21 is substantially electrically non-conductive and the reference patterns are electrically conductive or in the case where the patterns and the substrate surface are both conductive, but have different conductivities. The operation of this embodiment of the invention will now be described with reference to
Figures 1, 3, and 4. Operation of the test apparatus of the present invention provides a method for aligning an array of test probes with positions on a test substrate, in a preferred embodiment the positions being contacts on a semiconductor wafer under test. During testing the substrate to be tested is mounted on chuck 20 of the transport device and test probes 14 have an operational side wherein they contact the test substrate. Alignment substrate
21 is mounted on chuck 20 of the transport device in the test substrate mounting position. It should be emphasized that although in the illustrated embodiment the alignment substrate is a separate part containing the reference patterns, this example is only for purposes of illustration. The test substrate can also contain the reference patterns, in which case the test substrate and alignment substrate are the same part. Since the described alignment is only performed periodically, however, it will usually be most economical that the alignment substrate be a separate part.
In a preferred embodiment, the surface of alignment substrate 21 is electrically conductive, being coated with a gold plating. The substrate itself is composed of a substantially nonconductive material. Reference patterns 40, 41 are substantially non-conductive cross-shaped structures, which have been masked during the plating process so that there is no gold plating on these structures. In the illustrated embodiment, these cross-shaped structures are 0.01 in. wide and are used for aligning 0.004 in. diameter cobra test probes. In a tested embodiment of the present invention, a slightly depopulated 29 x 29 array of these probes is provided on 0.008 in. centers with approximately 800 probes for testing a semiconductor chip located on the wafer. The chip is approximately 6.5mm square.
After placing alignment substrate 21 on chuck 20, platen 18 translates z stage 19 and chuck 20 so that alignment substrate 21 is beneath fixed optics 15. Fixed optics 15 is then used to remove the angular misalignment (theta error) between alignment substrate 21 and platen 18, thereby calibrating the reference axes X , Y of platen 18 of the transport device with reference axes X , Y of the alignment substrate and therefore with the corresponding reference axes of chuck 20. This step also calibrates the transport device reference axes with the test substrate reference axes in the illustrated embodiment where the alignment substrate and test substrate are separate parts, because the reference axes of the test substrate also corresponds with the aligned reference axes of the chuck. Reticle 42 of fixed optics 15 is used to perform this calibration.
This entire operation may be viewed on monitor 17, connected to fixed optics 15 by line 16.
After removal of the theta error, platen 18 then translates alignment substrate 21 such that reticle 42 of fixed optics 15 is aligned with at least one of the reference patterns on alignment substrate 21.
This operation may also be viewed on monitor 17. In a preferred embodiment, reticle 42 is aligned with reference pattern 40 on alignment substrate 21. This determines a first location of alignment substrate 21 which becomes a reference position for the transport device. As has been previously described, this reference pattern 40 has a predetermined spatial relationship with the transport device. This position is then set as a first location of the alignment substrate in absolute position of 0.0001 inches, or 0.1 mil, resolution.
Platen 18 then translates chuck 20 to a position opposite test probes 14. The positio -to which chuck 20 is translated is determined by a calibration which is performed prior to delivery of the tester system.
This calibration establishes a circle of radius R within which a predetermined test probe with which the reference pattern will be aligned is located. Although not necessary for operation of the present invention, this step greatly simplifies the alignment procedure.
Referring now to Figs. 3A-3C, probe pairs 25,
26, 43, 44 are shown from the array of test probes. For purposes of clarity, the majority of the other probes in the array are not shown. In the preferred embodiment, the probes in the pairs are shorted together in test electronics 11 to allow current to flow between the probes when a voltage is applied across the probes. Current will flow when both of the the probes in a pair contact a conductive surface and current will not flow when one probe conducts a conductive service and another probe does not, or when neither probe in a pair contacts a conductive surface. It should be obvious to those skilled in the art that this description is for purposes of illustrating the preferred embodiment and that other methods to electrically sense the probes may be used.
At least one reference pattern of alignment substrate 21 is aligned through probe searching with at least a predetermined test probe to determine a second location of alignment substrate 21. This entire process is performed from the operational side of test probes 14. Platen 18 and Z stage 19 are first translated in the Z direction so that alignment substrate 21 is brought into contact with probes 14. The probes have spring characteristics and are not damaged or permanently deformed by this contact. In a preferred embodiment, probe deflection from this contact is approximately 0.005 in.
Chuck 20 is then stepped in two axes to roughly position the alignment substrate such that a predetermined set of the probes is in contact with reference pattern 40. Specifically, the chuck is stepped in the X direction in one mil (0.001 in.) increments until no current flows in probe pairs 25 and 26, as shown in Fig. 3A, thus locating a side 46 of reference pattern 40. The continuity of the probes is sensed at each step in test electronics 11 bv means which are well known to those skilled in the art. Chuck 20 then translates in the Y direction in one mil increments until no current flows in probe pairs 43, 44, as shown in Fig. 3B, thus locating side
47 and corner 48 of reference pattern 40. This completes the rough positioning of the alignment substrate.
This rough positioning may not precisely locate sides 46 and 47 of reference pattern 40. Referring to Fig. 4A, a case is shown where a probe from pair 26 overhangs reference pattern 40 but still has a
0.0001 inches of contact with the gold plated surface of alignment substrate 21, allowing current to flow in the probe pair. After the next 1 mil step, shown in Fig. 4B, there will no longer be continuity between the probes of pair 26, but there will be a
0.0009 inch gap between the probes of probe pair 26 and side 46 of reference pattern 40. The chuck could then translate the probes half the distance of the predetermined width of reference pattern 40 to locate a theoretical center line 51, but the probe would be misplaced from the actual center of reference pattern
40 by 0.0009 inches.
The center of reference pattern 40 may be precisely located by finely positioning alignment substrate 21. The first step in this fine positioning is to switch the resolution of the stepper platen 18 from 1 mil to 0.1 mil (0.0001 in.) .
This resolution is not practical for the rough positioning step of the method of the present invention, because it would require far too many steps to cover the previously described circle of radius R. In the fine positioning, the maximum number of steps to locate a side of the reference pattern, assuming that the probe is displaced by 0.0009 inches frors the actual center, will be half the width of the 10 mil reference pattern plus 0.0009 inches, namely 0.0059 inches, or fifty-nine 0.1 mil increments.
From the position shown in FIG. 3B, chuck 20 is first stepped in the X direction to detect side 46 of a first portion of the reference pattern, the first portion being that portion aligned with the Y direction. As with the rough positioning, the continuity of the pairs of probes is sensed at each step. Once the location of side 46 has been determined, the position of the center line of that first portion can easily be calculated, since the exact width is predetermined. The chuck 20 can then translate to center the probe pairs 25, 26 in this portion of the reference pattern, as shown in FIG. 4C. In like manner, chuck 20 car. then be stepped in the Y direction to detect side 47 of a second portion of *the reference pattern which is orthogonal to the first portion, namely that portion aligned in the X direction. The position of the center line of this portion is then calculated ar.ά the probes are centered in this second portion. The above operations cause center probe 45, which corresponds to the desired point of contact on the test wafer, to be aligned with center 49 of reference pattern 40 to within 0.1 mil in both the X and Ϋ directions. This procedure determines the second location of the alignment substrate.
Once these first and second locations of the alignment substrate have been determined, the necessary transport device translation for testing a test substrate can easily be calculated using the coordinates of the first and second locations and testing can be performed. Ir. the illustrated embodiment in which the test substrate and alirnmer.t substrate are separate parts, the alignment substrate is first replaced v/ith a test substrate. The desired point of contact of the test substrate with the predetermined probe is aligned with reticle 42 of fixed optics 15, which corresponds with the first location of the alignment substrate. The test substrate can then translate to the position corresponding to the second position of the alignment substrate and testing can commence. It is not necessary that the same reference pattern be used for both the rough and fine positioning. For instance, first reference pattern
40 can be used for the rough positioning and second reference pattern 41 can be used for the fine positioning. This may be desired if the rough positioning results in galling the sides of reference pattern 40. There is a predetermined precise spatial relationship between reference patterns 40 and 41.
After the center lines of reference pattern 40 have been located by the rough positioning step, the chuck can translate the alignment substrate 21 to that rough position on reference pattern 41 before finely positioning the alignment substrate. The center of reference pattern 40 is thus located by performing the fine positioning using reference pattern 41. All other steps of the process are identical to those previously described.
The invention is equally operable with the reference patterns being conductive and the remainder of the surface of the substrate being nonconductive.
In this case, the continuity of the probes is still sensed at each step during the rough and fine positioning, but the reference patterns locations are determined when current flows in the pairs of probes, not when current ceases to flow. The invention is otherwise the same as previously described.
The method of the invention can also be used to detect angular misalignment between the alignment substrate and the probe array. Referring to Fig. 3C the probe array may be stepped in the X direction. With angular misalignment alpha, probe pair 26 will lose continuity prior to probe pair 25 losing continuity. The X-axis positions when these probe pairs lose continuity can be recorded. The actual distance between probe pairs 25 and 26 is, of course, a predetermined value. Using this predetermined value and difference between the X positions at which the probe pairs lose continuity, the angle alpha can easily be calculated.
Referring now to Figs. 2 and 5, an alternative embodiment 50 of the present invention is shown. Many of the components shown in the embodiment in Fig. 2 are the same as those shown in Fig. 1 and these identical components are identified by the same reference numbers in Fig. 2 as in Fig. 1. The positioning device cf the embodiment shown in Fig. 2 is optics assembly 23 -which i≤ opposed to fixed optics 15 and probes 14 such -chat the fixed optics and probes are directly observable by optics assembly 23. In this embociment the test substrate 22 may be mounted directly on chuck 20 as opposed to the previously described embodiment, where a separate alignment substrate is used if the reference patterns are not incorporatsd into the test substrate. Referring to Fig. 5;- the optics assembly 23 comprises charge coupled deτic=. .'CC ; camera 37, objective lens 34, mechanical reticle 31, and fiber optics light source 52. The light is transmitted to a ring light 32 for illuminating the reticle 31. Spacer 33 separates ring light 32 and objective lens 34.
Spacer 36 separates objective lens 34 and CCD camera
37. The mechanical reticle 31 is the reference pattern of the optics assembly 23 positioning device. Test apparatus 50 also includes video device monitor 17 connected to optics assembly 23 by line
24. Video device 17 also has a reticle which corresponds to the optics assembly reticle 31. The tester is operative to allow manual operator alignment of the video device reticle and thus mechanical reticle 31 with the predetermined test probe and with the fixed optics reticle 42.
The operation of this embodiment of the invention will now be described. As previously stated, test substrate 22 may be directly mounted to chuck 20. In the same manner as described with respect to the first embodiment of the present invention, the reference axes of platen 18 of the transport device are calibrated with the reference axes of test substrate 22 and therefore with the corresponding reference axes of chuck 20 under fixed optics 15. Reticle 42 of camera 15 is the reference position of fixed optics 15. Reticle 31 of optics assembly 23 is then aligned with reticle 42 of fixed optics 15 to determine a first location of reticle 31. Reticle 31 and test substrate 22 have predetermined spatial relationships with the transport device by virtue of the fixed mounting positions of the optics assembly and the test substrate. A position on the test substrate corresponds to a desired point of contact with a predetermined test probe, in a preferred embodiment an electrical connection on a semiconductor v/afer chip. Chuck 20 is then translated to a position opposite the test probes and mechanical reticle 31 is aligned with the predetermined test probe by direct observation of the predetermined test probe by the optics assembly to determine a second location of mechanical reticle 31. This alignment of mechanical reticle 31 with the predetermined test probe includes a rough positioning and a fine positioning step.
The rough positioning step consists of first scanning the optics assembly 23, by translating chuck 20, in one axis across the probe array to determine the position of two opposing peripheral edges. This determination is made by aligning mechanical reticle 31 on video monitor 17 with these opposing edges. The optics assembly is then scanned in like manner in an orthogonal direction to the first axis to determine the position of the other two opposing edges of the probe array.
Once the positions of the edges of the probe array are known, the position of any predetermined test probe can be calculated and the chuck 20 translated so that the reticle 21 is roughly aligned with that predetermined test probe. The chuck 20 then is finely translated to align the optics device reticle 31 with the predetermined test probe
Both the fine and coarse alignment steps are accomplished by observing the test probes on video device 17 connected to optics assembly 23 by line 24. Chuck 20 is translated by operator interaction until the predetermined test probe and the video device reticle, which corresponds to rhe optics assembly reticle 31, are aligned on the video device 17. The fine positioning step determines a second location of the reticle, namely that location which corresponds to the predetermined test probe. Once the coordinates of the second location and the first location of the reticle have been determined, the necessary chuck 20 translation for wafer testing is easily determined by subtracting the X and Y coordinates of the first location from the X and Y coordinates of the second location.
While the invention has been illustrated and described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the precise construction herein disclosed and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:
A method for aligning an array of test probes with positions on a test substrate, wherein the test substrate is mounted on a transport device and the test probes have an operational side wherein they contact the test substrate, comprising the steps of:
calibrating reference axes of the transport device with reference axes of the test substrate under fixed optics, the fixed optics having a reference position;
aligning the reference position of the fixed optics with at least one reference pattern on a positioning device attached to the transport device to determine a first location cf the positioning device, wherein the at least one reference pattern and the test substrate have predetermined spatial relationships with the transport device;
translating the transport device to a position opposite the pest probes and aligning at least one reference pattern of the positioning device with at least the predetermined test probe to determine a second location of the positioning device; and
calculating the necessary transport device translation for positioning the predetermined test probe with respect to a desired point of contact on the test substrate, using the coordinates of the first location and the coordinates of the second location.
2. The method of claim 1 further comprising the step of mounting the test substrate on the transport device and positioning the predetermined test probe with respect to the desired point of contact on the test substrate.
3. The method of claim 1 wherein the reference pattern is a predetermined reference pattern.
4. The method of claim 3 wherein the aligning the reference pattern with the test probe is performed from the operational side of the test probes.
5. The method of claim 4 wherein the positioning device is an alignment substrate having at least one reference pattern of a first electrical conductivity on a surface of a second electrical conductivity and aligning the reference pattern with the test probe comprises:
translating the transport device to bring the alignment substrate into contact with the probes;
stepping the transport device in two axes to roughly position the alignment substrate such that a predetermined set of the probes is in contact with at least one reference pattern; and
stepping the transport device in the two axes to finely position the alignment substrate such that the predetermined probes are centered on respective portions of at least one reference pattern.
6. The method of claim 5 wherein the alignment substrate and the test substrate are the same substrate.
7. The method of claim 5 wherein the surface of the alignment substrate is electrically conductive and at least one reference pattern is substantially nonconductive and wherein stepping the transport device to roughly position the alignment substrate comprises stepping in x and y directions until at least one pair of probes for each of the respective directions is positioned in at least one reference pattern wherein the reference pattern is a first reference pattern, wherein the probes in each of the pairs are shorted together and the stepping includes sensing the electrical continuity of the pairs of probes at each step.
8. The method of claim 7 wherein the reference patterns comprise cross-shaped substantially nonconductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises
. stepping the transport device in the x direction to detect a side of a first portion of the first reference pattern; calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the first reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
The method of claim 7 wherein the at least one reference pattern comprises the first reference pattern and a second reference pattern, wherein the reference patterns comprise cross-shaped substantially nonconductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the second reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the second reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
10. The method of claim 9 wherein the second reference pattern has a predetermined spatial relationship with respect to the first reference pattern.
11. The method of claim 5 wherein the surface of the alignment is substantially electrically nonconductive and at least one reference pattern is electrically conductive and wherein stepping the transport device to roughly position the alignment substrate comprises stepping in x and y directions until at least one pair of probes for each of the respective directions is positioned in at least one reference pattern wherein the reference pattern is a first reference pattern, wherein the probes in each of the pairs are shorted together and the stepping includes sensing the electrical continuity of the pairs of probes at each step.
12. The method of claim 11 wherein the reference patterns comprise cross-shaped electrically conductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises: stepping the transport device in the x direction to detect a side of a first portion of the first reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the first reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
13. The method of claim 11 wherein the at least one reference pattern comprises the first reference pattern and a second reference pattern, wherein the reference patterns comprise cross-shaped electrically conductive structures of predetermined dimensions and - wherein the stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the second reference pattern;
calculating the position of a center line of the first portion; and centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the second reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
14. The method of claim 13 wherein the second reference pattern has a predetermined spatial relationship with respect to the first reference pattern.
15. The method of claim 1 wherein the positioning device is an optics assembly, the at least one reference pattern is a reticle, and the aligning the reference pattern of the positioning device with the test probe comprises directly observing at least the predetermined test probe with the optics assembly.
16. The method of claim 15 wherein the optics assembly has a single reticle and wherein the aligning the reference pattern with the test probe comprises:
determining the position of peripheral edges of the probe array by aligning the reticle with each of the edges; calculating the position of the predetermined test probe and translating the transport device such that the reticle is roughly aligned with the predetermined test probe; and
translating the transport device to finely align the optics assembly reticle with the predetermined test probe.
17. .The method of claim 16 wherein the aligning the reference pattern with the test probe further comprises:
observing the test probes on a video device connected to the optics assembly, the video device having a reticle corresponding to the optics assembly reticle; and
translating the transport device until the predetermined test probe and the video device reticle are aligned on the video device.
18. A method for aligning an array of test probes with positions on a test substrate comprising the steps of:
positioning an alignment substrate at a predetermined location on a transport device, the alignment substrate having at least one reference pattern of a first electrical conductivity on a surface of a second electrical conductivity, wherein the at least one reference pattern and the test substrate have predetermined spatial relationships with the transport device; translating the transport device to bring the alignment substrate into contact with the probes;
stepping the transport device in two axes to roughly position the alignment substrate such that a predetermined set of the probes is in contact with at least one reference pattern; and
stepping the transport device in the two axes to finely position the alignment substrate such that the predetermined probes are centered on respective portions of at least one reference pattern.
19. The method of claim 18 further comprising the step of mounting the test substrate on the transport device and positioning the predetermined test probe with respect to the desired point of contact on the test substrate.
20. The method of claim 18 wherein the alignment substrate and the test substrate are the same substrate.
21. The method of claim 18 wherein the surface of the alignment substrate is electrically conductive and at least one reference pattern is substantially nonconductive and wherein stepping the transport device to roughly position the alignment substrate comprises stepping in x and y directions until at least one pair of probes for each of the respective directions is positioned in at least one reference pattern wherein the reference pattern is a first reference pattern, wherein the probes in each of the pairs are shorted together and the stepping including sensing the electrical contact of the pairs of probes at each step.
22. The method of claim 21 wherein the reference pattern comprises cross-shaped substantially nonconductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the first reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the first reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion;
23. The method of claim 22 wherein the at least one reference pattern comprises the first reference pattern and a second reference pattern, wherein the reference patterns comprise cross-shaped substantially nonconductive structures of predetermined dimensions and wherein the stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the second reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the second reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
24. The method of claim 23 wherein the second reference pattern has a predetermined spatial relationship with the first reference pattern.
25. The method of claim 18 wherein the surface of the alignment substrate is substantially electrically nonconductive and at least one reference pattern is electrically conductive and wherein stepping the transport device to roughly position the alignment substrate comprises stepping in x and y directions until at least one pair of probes for each of the respective directions is positioned in at least one reference pattern wherein the reference pattern is a first reference pattern, wherein the probes in each of the pairs are shorted together and the stepping including sensing the electrical contact of the pair of probes at each step.
26. The method of claim 25 wherein the reference patterns comprise cross-shaped electrically conductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the first reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the first reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
27. The method of claim 25 wherein the at least one reference pattern comprises the first reference pattern and a second reference pattern, wherein the reference patterns comprise cross-shaped electrically conductive structures of predetermined dimensions and wherein stepping the transport device to finely position the alignment substrate comprises:
stepping the transport device in the x direction to detect a side of a first portion of the second reference pattern;
calculating the position of a center line of the first portion;
centering the probes in the first portion;
stepping the transport device in the y direction to detect a side of a second portion of the second reference pattern, the second portion being orthogonal to the first portion;
calculating the position of a center line of the second portion; and
centering the probes in the second portion.
28. The method of claim 26 wherein the second reference pattern has a predetermined spatial relationship with the first reference pattern.
29. A method for aligning an array of test probes with positions on a test substrate comprising the steps of: aligning reference axes of a transport device upon which the test substrate is mounted with reference axes of the test substrate under fixed optics, the fixed optics having a reference position;
aligning the reference position of the fixed optics with a reticle of an optics assembly to determine a first location of the reticle wherein the optics assembly is attached to the chuck and opposed to the fixed optics and wherein the reticle and the test substrate have predetermined spatial relationships with the transport device;
translating the transport device to a position opposite the test probes and aligning the reticle with the predetermined test probe by direct observation of the predetermined test probe by the optics assembly to determine a second location of the reticle; and
calculating the necessary transport device translation for positioning the predetermined test probes with respect to a desired point of contact on the test substrate by subtracting the coordinates of the first location from the coordinates of the second location.
30. The method of claim 29 wherein the optics device has a single reticle and wherein the aligning the reference pattern with the test probe comprises: determining the position of peripheral edges of the probe array by aligning the reticle with each of the edges;
calculating the position of the predetermined test probe and translating the transport device such that the reticle is roughly aligned with the predetermined test probe; and
translating the transport device to finely align the optics device reticle with the predetermined test probe.
31. The method of claim 30 wherein optics assembly includes a CCD camera and wherein aligning the reticle of the optics assembly with the predetermined test probe further comprises:
observing the test probes on a video device connected to the optics assembly, the video device having a reticle corresponding to the optics device reticle; and
translating the transport device until the predetermined test probe and the video device reticle are aligned on the video device.
32. A test apparatus comprising:
a transport device for mounting a test substrate;
fixed optics including means for calibrating reference axes of the transport device with reference axes of the test substrate, the fixed optics having a reference position;
a plurality of test probes for testing the test substrate, the test probes having an operational side wherein they contact the test substrate; and
a positioning device attached to the transport device, the positioning device having at least one reference pattern, the reference pattern and the test substrate having predetermined spatial relationships with the transport device, wherein the positioning device is alignable with the reference position of the fixed optics and is alignable with at least the predetermined test probe from the operational side of the test probes.
33. The test apparatus of claim 32 wherein the positioning device is an alignment substrate having at least one reference pattern of a first electrical conductivity on a surface of a second electrical conductivity and the alignment substrate is attached to the transport device in the test substrate mounting position.
34. The method of claim 33 wherein the alignment substrate and the test substrate are the same substrate.
35. The test apparatus of claim 33 wherein the alignment substrate surface is electrically conductive and at least one reference pattern is substantially electrically nonconductive.
36. The test apparatus of claim 35 wherein at least one reference pattern comprises cross-shaped substantially electrically nonconductive structures of predetermined dimensions.
37. The test apparatus of claim 33 wherein the alignment substrate surface is substantially electrically nonconductive and at least one reference pattern is electrically conductive.
38. The test apparatus of claim 37 wherein at least one reference pattern comprises cross-shaped electrically conductive structures of predetermined dimensions.
39. The test apparatus of claim 32 wherein the positioning device is an optics assembly opposed to the fixed optics and the probes such that the fixed optics and probes are directly observable by the optics assembly.
40. The test apparatus of claim 39 wherein the optics assembly comprises:
a CCD camera;
an objective lens;
a mechanical reticle; and
a fiber optics light source.
41. The test apparatus of claim 39 further comprising a video device connected to the optics assembly, the optics assembly having a single reticle and the video device having a, reticle corresponding to the single reticle, wherein the tester is operative to allow manual operator alignment of the video device reticle and the predetermined test probe.
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EP0675366A2 (en) * 1994-03-31 1995-10-04 Tokyo Electron Limited Probe system and probe method
EP0675366A3 (en) * 1994-03-31 1996-07-24 Tokyo Electron Ltd Probe system and probe method.
US5585738A (en) * 1994-03-31 1996-12-17 Tokyo Electron Limited Probe system having vertical height detection and double focal image pickup coinciding with probe contact in height adjustment
US5640101A (en) * 1994-03-31 1997-06-17 Tokyo Electron Limited Probe system and probe method
WO1995032432A1 (en) * 1994-05-20 1995-11-30 Luther & Maelzer Gmbh Process and system for testing the correct position of printed circuit boards having contact islands and conductor paths in a testing device
EP0744626A1 (en) * 1995-05-23 1996-11-27 DASSAULT SERCEL Navigation-Positionnement Method and device for accurate fixing of points on the surface of the earth by means of satellite-radiolocation
FR2734643A1 (en) * 1995-05-23 1996-11-29 Soc Et Rech Et Const Electroni METHOD AND DEVICE FOR THE ACCURATE IMPLANTING OF EARTH SURFACE POINTS BY RADIO SATELLITE LOCATION
US5745074A (en) * 1995-05-23 1998-04-28 Dassault Sercel Navigation-Positionnement Staking out method and device using a satellite positioning system
DE10137669A1 (en) * 2001-08-01 2002-10-02 Infineon Technologies Ag Method of aligning contact support onto countercontact support for chip test head
US7759955B2 (en) 2007-12-21 2010-07-20 Infineon Technologies Ag Method and device for position detection using connection pads
CN102222632A (en) * 2011-07-07 2011-10-19 北京思比科微电子技术股份有限公司 Wafer testing method and device
CN102222632B (en) * 2011-07-07 2013-04-24 北京思比科微电子技术股份有限公司 Wafer testing method and device

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