WO2007131194A2

WO2007131194A2 - Apparatus and methods for processing, testing, and packaging of semiconductor ics and image sensors

Info

Publication number: WO2007131194A2
Application number: PCT/US2007/068285
Authority: WO
Inventors: W.R. Bottoms; Fu Chiung Chong; Roman Milter; Thomas Edward Dinan; Erh-Kong Chieh; David Thanh Doan; Pierre H. Giauque; Douglas N. Modlin
Original assignee: Nanonexus, Inc.
Priority date: 2006-05-05
Filing date: 2007-05-04
Publication date: 2007-11-15
Also published as: WO2007131194A4; TW200804829A; WO2007131194A3

Abstract

Enhanced optical probe structures and associated methods comprise improvements to spring structures, wherein optical signals can be transmitted through the resultant substrate by fabricating openings of sufficient size through the substrate through which the optical signals can be transmitted. The holes may be unfilled or filled with optically conducting materials including but not limited to polymers, glasses, air, vacuum, etc. Lenses, diffraction gratings and other optical elements, e.g. refractive or diffractive, can be integrated to improve the coupling efficiency or provide frequency discrimination as desired. Enhanced spring structures and associated methods are also used in conjunction with the enhanced optical probe architectures, such as for processing, testing, and/or packaging of semiconductor ICs and image sensors.

Description

APPARATUS AND METHODS FOR

PROCESSING, TESTING, AND PACKAGING OF

SEMICONDUCTOR ICs and IMAGE SENSORS

FIELD OF THE INVENTION

The present invention relates generally to the field of miniaturized spring contacts and spring probes for high-density optical and electrical interconnection systems. More particularly, the present invention relates to optical structures and systems having microfabricated spring contacts and associated structures, and improvements thereto, for making electrical and optical connections, such as for processing, testing, and/or packaging of semiconductor ICs and/or image sensors.

BACKGROUND OF THE INVENTION

There are several problems associated with conventional semiconductor image sensor testing and laser processing, such as for memory repair or laser trimming processes. Systems required for such testing and processing require a large number of high density electrical connections, while simultaneously requiring optical access to the workpiece, e.g. device, to be tested and/or repaired. The devices and associated testing and processing systems are typically sensitive to debris, such as generated by the process structure probes, which is often left on the device or sensor array. As well, the mechanical process structure itself can interfere with optical procedures, which may result in light scattering and/or masking, such as from the probe pins and/or other components of probe card and illumination system.

Obtaining uniform illumination for multi-site testing and processing using prior art processing systems has become increasingly problematic, due to the need to meet the requirements of newer generations of IC devices and image sensors, such as to meet illumination wavelength, intensity, angle, and other geometric requirements. Furthermore, device performance is often required to be characterized over a wide temperature range, and this has been problematic using prior art processing systems, particularly those having cantilever probes.

Advances in semiconductor integrated circuit design, processing, and packaging technologies have resulted in increases in the number and density of input/output (I/O) connections on each die and as well as in an increase in the diameter of the silicon wafers used in device fabrication.

With each new generation of IC technology, the I/O pitch tends to decrease and the I/O density tends to increase. These trends place increasingly stringent requirements on the probe tips. Fine pitch probe tips are required to be smaller in width and length while continuing to generate the force required to achieve and maintain good electrical connections with the device under test. The force required to achieve a good electrical connection is a function of the processing history of the IC contact pad, such as but not limited to the manner of deposition, the temperature exposure profile, the metal composition, shape, surface topology, and the finish of the spring probe tip. The required force is also typically a function of the manner in which the probe tip "scrubs" the surface of the contact pad.

As the probe pitch decreases, the linear dimensions of the IC connection terminal contact areas also decreases leaving less room available for the probe tips to scrub. Additionally, the probes must be constructed so as to not damage the passivation layer that is sometimes added to protect the underlying IC devices (typically 5-10 mm in thickness). Additionally, as the spring probe density increases, the width and length of the probes tends to decrease and the stress within the probe tends to increase, to generate the force required to make good electrical contact to the IC connection terminal contact areas.

There is a need for probe cards for fine pitch probing comprised of an array of spring probe contacts capable of making simultaneous good electrical connections to multiple devices on a semiconductor wafer under test in commercially available wafer probers using specified overdrive conditions over large areas of a semiconductor wafer and or over an entire wafer. To accomplish this, the array of spring probe contacts on the probe card should be co-planar and parallel to the surface of the semiconductor wafer to within specified tolerances such that using specified overdrive conditions, the first and last probes to touch the wafer will all be in good electrical contact with the IC device yet not be subject to over stressed conditions which could lead to premature failure. Additionally, any changes in the Z position, e.g. due to set or plastic deformation, or condition of the probe tips, e.g. diameter, surface roughness, etc., over the spring probe cycle life should remain within specified acceptable limits when operated within specified conditions of use, such as but not limited to overdrive, temperature range, and/or cleaning procedures.

Micro-fabricated spring contacts are potentially capable of overcoming many of the limitations associated with conventionally fabricated spring contacts, e.g. tungsten needle probes, particularly in fine pitch probing applications over large substrate areas. Micro-fabricated spring contacts can be fabricated using a variety of photolithography based techniques known to those skilled in the art, e.g. Micro-Electro-Mechanical Systems (MEMS) fabrication processes and hybrid processes such as using wire bonds to create spring contact skeletons and MEMs or electroplating processes to form the complete spring contact structure. Arrays of spring contacts can be either be mounted on a contactor substrate by pre-fabricating and transferring them (either sequentially or in mass parallel) to the contactor substrate or by assembling each element of the spring contact array directly on the contactor substrate using a wire bonder along with subsequent batch mode processes, e.g. electroplating, as disclosed in U.S. Patent No. 6,920,689 (Khandros et al.), U.S. Patent No. 6,827,584 (Mathieu et al.), U.S. Patent No. 6,624,648 (Eldridge et al.); U.S. Patent No. 6,336,269 (Eldridge et al.), U.S. Patent No. 6,150,186 (Chen et al.), U.S. Patent No. 5,974,662 (Eldridge et al.),U.S. Patent No. 5,917,707 (Khandros et al.), U.S. Patent No. 5,772,452 (Dozier et al.), and U.S. Patent No. 5,476,211 (Khandros et al.). Micro-fabricated spring contacts may be fabricated with variety of processes known to those skilled in the art. Exemplary monolithic micro-fabricated spring contacts may comprise stress metal springs having one or more layers of built-in or initial stress that are photolithographically patterned and fabricated on a substrate using batch mode semiconductor manufacturing processes. As a result, the spring contacts are fabricated en masse, and can be fabricated with spacings equal to or less than that of fine pitch semiconductor device electrical connection terminals or with spacings equal to or greater than those of printed circuit boards, i.e. functioning as an electrical signal space transformer.

Photolithographically patterned spring structures are particularly useful in electrical contactor applications where it is desired to provide high density electrical contacts which may extend over relatively large contact areas and which also may exhibit relatively high mechanical compliance in the normal direction relative to the contact area. Such electrical contactors are useful for applications including integrated circuit device testing (both in wafer and packaged formats), integrated circuit packaging (including singulated device packages, wafer scale packaging, and multiple chip packages) and electrical connectors (including board level, module level, and device level, e.g. sockets.

In addition to providing compliance in the direction normal to the contact plane, photolithographically patterned spring contacts also compensate for thermal and mechanical variations and other environmental factors. An internal stress gradient within the spring contact causes a free portion of the spring to bend up and away from the substrate to a lift height which is determined by the magnitude of the stress gradient. The stress gradient can be any of a gradient within the free portion and between the free portion and the substrate. An anchor portion remains fixed to the substrate and is electrically connected to a first contact pad on the substrate. The spring contact is made of an elastic material and the free portion compliantly contacts a second contact pad, thereby contacting the two contact pads. Variations in the internal stress gradient across the substrate surface can cause variations in spring contact lift height. The ability to produce uniform stress gradients over large substrate areas depends on being able to controllably create a sequence of one or more thin layers of deposited metal, each having controlled levels of mechanical stress. Deposited films having internal stress gradients are characterized by a first layer having a first stress level, a series of intermediate layers having varying stress levels, and a last layer having a last stress. The magnitude of the internal stress gradient is determined by the difference in stress levels between each layer in the film. The curvature of a lifted spring is a function of the magnitude of the internal stress and/or stress gradient, geometrical factors, e.g. thickness, shape, and material properties, e.g. Young's modulus. After release from the substrate, the free portion of the spring deflects upward until the stored energy is minimized.

For a given curvature, thicker springs require a greater stress or range of stresses than do thinner springs. Thicker springs are preferred when higher forces at a given deflection are required. For example, in certain electrical contactor applications, it is desirable to fabricate spring contacts having a relatively high contact force and a high lift height to provide low electrical resistance and a high mechanical compliance range. The combination of relatively high force and relatively high lift height requires both a relatively high stress gradient and a relatively large range of stress within the deposited film. In other words, springs having relatively large forces and high lift heights typically are relatively thick and have relatively high magnitude internal stress gradients extending over a larger range of stresses.

The stress range is increased when the spring comprises at least one layer of high compressive stress and at least one layer of high tensile stress. There is an upper limit to the compressive and tensile stresses that a thin film can sustain without loosing mechanical integrity.

It would be advantageous to provide a method and structure to create improved optical probe assemblies capable of providing simultaneous electrical connection and delivery of optical radiation to one or more high pin count, fine pitch, or high performance IC devices on a semiconductor wafer. Such a development would provide a significant technical advance.

As well, it would also be desirable to provide improved methods and structures for processing, testing, and/or packaging of semiconductor ICs and image sensors. Such improved structures and methods would constitute a further significant technical advance.

SUMMARY OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a probe side perspective view of a portion an exemplary optical probe assembly having optical access to the active area of a device under test (DUT);

Figure 2 is a detailed partial probe side perspective view of a portion an exemplary optical probe assembly having optical access to the active area of a device under test (DUT); Figure 3 is a detailed partial cutaway view of an exemplary probe chip assembly having optical access, wherein a portion of light is transmitted through an optical channel region, and blocked in a surrounding substrate region;

Figure 4 is a back side perspective view of a portion an exemplary optical probe assembly having optical access to the active area of a device under test (DUT), wherein the optical region further comprises an optical element, and wherein the assembly includes separable connectors of the back surface of the probe chip mounting substrate;

Figure 5 is a detailed perspective view of a camera lens optical element mounted in an optical region defined through a probe chip mounting substrate;

Figure 6 is a detailed perspective view of a pinhole optical element mounted in an optical region defined through a probe chip mounting substrate;

Figure 7 is an expanded assembly view of a portion of an exemplary optical probe chip assembly configured for optical access to the active area of a device;

Figure 8 is a cross sectional view through a portion of an exemplary optical probe assembly having optical access to the active area of a device, wherein a camera lens optical element mounted in a optical region defined through a probe chip mounting substrate and a probe chip;

Figure 9 is a detailed partial cross sectional view through a portion of an exemplary optical probe assembly having optical access to the active area of a device, wherein a camera lens optical element mounted in a optical region defined through a probe chip mounting substrate and a probe chip;

Figure 10 is a cross sectional view through a portion of an exemplary optical probe assembly having optical access to the active area of a device, wherein a pin hole optical element mounted in a optical region defined through a probe chip mounting substrate and a probe chip;

Figure 11 is a detailed partial cross sectional view through a portion of an exemplary optical probe assembly having optical access to the active area of a device, wherein a pin hole optical element mounted in a optical region defined through a probe chip mounting substrate and a probe chip;

Figure 12 is a detailed partial perspective view of an optically configured probe contactor assembly having multiple optically configured probe chips mounted to an optically configured probe support substrate;

Figure 13 is a rear perspective view of a portion of an exemplary optical probe assembly having multiple optical access regions to the active area of a device, wherein multiple lens elements are mounted in respective optical regions defined through a probe chip mounting substrate;

Figure 14 is a rear perspective view of a portion of an exemplary optical probe assembly having multiple optical access regions to the active area of a device, wherein multiple pin hole optical elements are mounted in respective optical regions defined through a probe chip mounting substrate;

Figure 15 is an expanded assembly view of a portion of an exemplary optical probe assembly configured for optical access to the active area of one or more devices, wherein the assembly comprises multiple optical access regions and multiple optical elements;

Figure 16 is a front perspective view of an exemplary image sensor test architecture for a quad site image sensor probe chip;

Figure 17 is a front perspective view of exemplary image sensor test architecture for an image sensor probe chip, having a controllable multi-wavelength light source;

Figure 18 is a partial cutaway view of exemplary image sensor test architecture for an image sensor probe chip, having a light source;

Figure 19 is a partial cutaway view of an exemplary image sensor test architecture for an image sensor probe chip and adaptable to a variety of light sources;

Figure 20 is a partial cross section of an exemplary nanospring contactor;

Figure 21 is a partial cross sectional view of a spring extending from a substrate having a decoupling surface structure, wherein the spring has an etched-back contact structure;

Figure 22 is a partial cross sectional view of a spring extending from a substrate having a decoupling surface structure, wherein the spring has a multiple plated layer contact structure;

Figure 23 is a partial cutaway view of a NanoContactor Image Sensor package/socket with solder option;

Figure 24 is a plan view of multiple NanoContactor connections to image sensor contacts;

Figure 25 is a partial cutaway view of a NanoContactor image sensor package/socket assembly having a back side thinned sensor;

Figure 26 is an expanded assembly view of a NanoContactor solderless image sensor package, wherein the printed circuit board and the optical window are separably connectable; Figure 27 is an assembled view of a NanoContactor solderless image sensor package having a separable connection between the printed circuit board and the optical window;

Figure 28 is a detailed view of a NanoContactor solderless image sensor package, having travel stops located between the image sensor assembly and the printed circuit board;

Figure 29 is a detailed view of a NanoContactor image sensor package, having solder bonds between nanocontactors and contact pads or bumps;

Figure 30 is a schematic view of a solderless image sensor package assembly having nanocontactor connections between an image sensor and a printed circuit board, and connection terminals between the image sensor and an optical window;

Figure 31 is a solderless image sensor package assembly having nanocontactor connections between a backside thinned image sensor and a printed circuit board, and lamination adhesive between the image sensor and an optical window;

Figure 32 is a schematic view of a solderless image sensor module assembly having a wire-bonded image sensor and passive components; and

Figure 33 is a schematic view of a solderless image sensor module assembly having a flip sensor bonded image sensor and passive components.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 is a probe side perspective view of a portion an exemplary optical probe assembly 10 having optical access therethrough, such as to the active area of a device 44, e.g. a device under test (DUT) (FIG. 11 ). Figure 2 is a detailed partial probe side perspective view of a portion an exemplary probe chip assembly 12 mounted to a support substrate 20. The probe chip assembly 12 seen in Figure 1 and Figure 2 has at least one hollow region, i.e. channel 14 extending between a front surface 33a and a rear surface 33b of the probe chip substrate 32.

The hollow opening region 14 defined between a front surface 33a and a rear surface 33b of the probe chip substrate 32 preferably provides an optical channel for a wide variety of applications, such as for processing, packaging, and/or packaging of semiconductor ICs and/or image sensors.

A plurality of elastic core members 18, e.g. spring contacts 18, are located on the front surface 33a of the probe substrate 32. The exemplary elastic members 18 seen in Figure 1 and Figure 2 are typically arranged in one or more probe arrays 16, such as surrounding the hollow region 14, wherein the probe chip 12 is connectable to one or more external structures, such as to one or more devices 44 on a wafer, e.g. a device under test (DUT).

As seen in Figure 1 and Figure 2, a support substrate 20 is fixedly attachable to the probe chip 12, such as through solder bonds and/or through other means for attachment. The support substrate 20 has a front surface 23a and an opposing back surface 23b, and also typically has one or more similar hollow regions 34 defined therethrough, between the surfaces 23a, 23b, such as substantially aligned to the neighboring hollow region 14 in the probe substrate 32, to define an optical channel through both substrates 20,32.

While the hollow region 34 in the support substrate 20 may be unfilled, the hollow region 34 may alternately be filled with optically conducting materials including but not limited to polymers, glasses, air, and/or a vacuum. Lenses, diffraction gratings and other optical elements may preferably be integrated in the optical region 34, such as to improve the coupling efficiency or provide frequency discrimination when desired.

While one or more hollow regions 34 may typically be established in the probe substrate 32 before the establishment of the spring contacts 18, alternate embodiments of the optic probe chip 12 may comprise one or more hollow regions 34 that are fabricated, etched or otherwise fabricated after the establishment of the spring contacts 18.

The support substrate 20 also typically comprises means 22, e.g. mounting holes 22, for mechanically affixing, i.e. mounting, the support substrate 20 to an external assembly, and means 24, e.g. one or more separable connectors 24, for making electrical connections between the support substrate 20 and an external assembly.

Optical probe assemblies 10 provide masking for low profile optical access, such as to a portion of the active region of a device 44. Some embodiments of optical probe chips 12 provide accurate masking for low profile optical access for the entire active region of a device 44, such as within a proximity of 200 microns. Optical probe chips 12 can be configured for a wide variety of applications, such as but not limited to image sensor chips, laser repair, or laser trimming.

The integration of an enhanced probe card architecture 12 within semiconductor image sensor and laser processing probe structures addresses several problems associated with prior architectures.

For example, the integration of stress metal springs 18 provides independent control over any of probe attack angle, probe force, tip diameter, and/or probe metallurgy. As well, the use of enhanced stress metal spring contacts 18 provides superior planarity to allow reliable contact with minimum overdrive, with largely maintenance free operation. Furthermore, the integration of stress metal springs 18 allows highly controlled spring contact tip geometry and metallurgy, such as to minimize potential redistribution of debris. Debris removal is also possible through the use of non-abrasive materials such as silicone based films, such as Probe Polish^®, available through International Test Solutions, of Reno, NV. The optical probe assembly 10 also minimizes or eliminates light scattering, such as seen in prior art probe pins and other probe card components.

Figure 3 is a detailed partial cutaway view 40 of an exemplary probe chip assembly 12 having optical access 14, wherein a portion 28 of incident light 42 is transmitted through an optical channel region 14, and blocked 43 in a surrounding substrate region 32. As also seen in Figure 3, electrical paths 48, e.g. vias 48, typically extend through the probe substrate 32 from the elastic spring contact members 18, e.g. stress metal NanoContactors 18, on the front surface 33a to electrical contacts 50 on the back surface 33b. In some embodiments of the probe chips 12, the spacing between elastic members 18 substantially matches the spacing of the contact pads of the device 44, such as but not limited to a spacing of approximately 10 to 100 microns. As well, the spacing between electrical contacts 50 on the back surface 33b may preferably match the spacing requirements of connected components or support substrates 20, such as having an exemplary spacing of approximately 1 to 100 mils.

Figure 4 is a back side perspective view 60 of a portion an exemplary probe chip assembly having optical access to the active area of a device under test (DUT) 44, wherein the optical region further comprises an optical assembly 62 may preferably be located proximate to the substrate optical channel 34, and wherein the assembly includes separable connectors 24 of the back surface 23b of the probe chip mounting substrate 20. The optical assembly 62 is typically mechanically affixed to the support substrate, and may preferably be substantially aligned, i.e. centered upon, the substrate optical channel 34. In some embodiments, the optical assembly 62 may include any of a lens, a pinhole lens, a diffraction grating, and any other optical element 86.

As seen in Figure 4, the separable connectors 24 typically comprise electrical connections 64, e.g. such as comprising an array of contacts, pads, pins or sockets. Each of the connectors 24 is typically separably connectable to a mating connector 72, e.g. forming mating connector assemblies 72. The support substrate 20 seen in Figure 4 is therefore typically removably attachable to an external assembly, such as for ease of assembly, replacement and/or service.

The optical assembly 62 typically comprises a frame structure 82, having a hollow element mounting region 84, and an optical element 86 mounted within the hollow region 84. For example, Figure 5 is a detailed perspective view 80 of an optical assembly 62a comprising a camera lens optical element 86a mounted in an optical region 84 in a frame structure 82. Figure 6 is a detailed perspective view 90 of an alternate optical assembly 62b comprising a pin-hole lens optical element 86b mounted in an optical region 84 in a frame structure 82.

Figure 7 is an expanded assembly view 100 of a portion an exemplary optical probe assembly 10 configured for optical access to the active area of a device 44. Figure 8 is a cross sectional view 110 through a portion an exemplary optical probe assembly 10a having optical access to the active area of a device 10, wherein a camera lens optical element 86a is mounted in a optical region 34 defined through a probe chip mounting substrate 20 and a probe chip 12. Figure 9 is a detailed partial cross sectional view 130 through a portion an exemplary optical probe assembly 10a having optical access to the active area of a device 10.

As seen in Figure 8 and Figure 9, incoming light 42, such as emitted from an attached light source 334 (FIG. 18), is typically transmitted through the optical element 86, e.g. 86a, and passes through subsequent optical window regions 34 and 14 before reaching the device 44.

As also seen in Figure 8 and Figure 9, an optical probe assembly 10, e.g. 10a, typically provides electrical paths 111 through the assembly 10, such as comprising electrical connections 112 between the probe chip 12 and the support substrate 20, electrical conduits114, e.g. vias 114 extending between the front surface 23a and the back surface 23b of the support substrate 20, electrical connections 112 between the support substrate 20 and the separable connectors 24, and connector paths 118 within the connectors 24, which terminate at the connector arrays 64 (FIG. 4).

Figure 10 is a cross sectional view 140 through a portion an exemplary optical probe assembly 10b having optical access to the active area of a device 44, wherein a pin hole optical element 86b is mounted in a optical region 34 defined through a probe chip mounting substrate 20 and a probe chip 28. Figure 11 is a detailed partial cross sectional view 160 through a portion an exemplary optical probe assembly 10b having optical access to the active area of a device 10.

As seen in Figure 11 , incoming light 42, such as emitted from an attached light source 334 (FIG. 18), is typically transmitted through a pin hole 92 defined through an optical element 86a. The light 42 then passes through subsequent optical window regions 34 and 14 before reaching the device 44.

Exemplary Multi-Site Probe Card Optical System Configuration Options. Figure 12 is a detailed partial perspective view 180 of an optically configured probe contactor assembly 10d having multiple optically configured probe chips 12 mounted to an optically configured probe support substrate 20. The optical probe chips 12 may either be separated from each other, e.g. such as comprising discrete substrates 32, or may be integrated with a single substrate 32, such as seen in Figure 12.

The optical probe chip 12 seen in Figure 12 includes a plurality of optical channels 14, e.g. 14a-14n, and a corresponding plurality of arrays 16, e.g. 16a-16n, of elastic electrically conductive members, e.g. nanocontactors 18. As seen in Figure 12, the probe substrate optical channels 14a-14n are substantially aligned with corresponding optical channels 34 in the support substrate 20

Figure 13 is a rear perspective view 200 of a portion an exemplary optical probe assembly 10d having multiple optical access regions 34,14 to the active area of one or more devices 44, wherein multiple lens elements 62a are mounted in respective optical regions 34 defined through a probe chip mounting substrate 20. Figure 14 is a rear perspective view 220 of a portion an exemplary optical probe assembly 10e having multiple optical access regions 34,14 to the active area of one or more devices, wherein multiple pin hole optical elements 62b are mounted in respective optical regions 34 defined through a probe chip mounting substrate 20. Figure 15 is an expanded assembly view 240 of a portion an exemplary optical probe assembly 10 configured for optical access to the active area of a one or more devices 44, wherein the assembly 10 comprises multiple optical access regions 34 and multiple optical elements 86.

Image Sensor Test Architectures. Figure 16 is a front perspective view of an exemplary image sensor test system 300 having a quad site image sensor probe assembly 12. Figure 17 is a front perspective view 320 of an exemplary image sensor test system 300, having for an image sensor probe assembly 12, and having a controllable multi-wavelength light source 322. Figure 18 is a partial cutaway view 330 of an exemplary image sensor test system 300 for an image sensor probe assembly 10, having a light source 322. Figure 19 is a partial cutaway view 350 of an exemplary image sensor test architecture for an image sensor probe chip 12 and adaptable to a variety of light sources 322.

The exemplary image sensor test system 300 seen in Figure 16, Figure 17, Figure 18 and Figure 19 typically comprises an optic module 306 that is coupled to an image sensor probe assembly 12 (FIG. 18), such as through an interface structure 304 and a mounting plate 302. The interface structure 304 may comprise a test head, such as having test head electronics 344 that are connectable 335 through the mounting plate interface 302 to the optic probe assembly 10, and may include or be connectable 337 to external test electronics 346.

The interface structure 304 typically includes a central follow region 340 defined axially therethrough, which allows the passage of light 42 toward the mounting plate 302.

Similarly, the mounting plate 302 typically includes at least one central hollow region

339 (FIG. 18) defined axially therethrough, which allows the passage of light 42 toward the optic probe assembly 10. As well, the mounting plate 302 also typically includes electrical pathways therethrough, such as to and/or from the probe assembly 11 , which may preferably be mated to the probe assembly 12 by separable connector halves 72

(FIG. 4). The exemplary image sensor test system 300 seen in Figure 16, Figure 17, Figure 18 and Figure 19 also comprises means. 310 for removably affixing the mounting plate 302 to the interface structure 304.

The exemplary optic module 306 seen in Figure 18 comprises a light source 322 having output light 332, and may further comprise conventional and/or diffractive optics 336, through which light 332 output from a light source 322 is processed to provide process light output 42, such as to provide uniform illumination 342 in the plane of the optic image sensor assembly 10.

Figure 19 is a partial cutaway view 350 of an exemplary image sensor test architecture for an image sensor probe chip assembly 10 that is adaptable to a variety of light sources 322, e.g. 322a, 322b, 322c, such as but not limited to incandescent and solid state sources. Lights sources 322 may preferably comprise any of a wide variety of bandwidths, such as broad or narrowband light, such as provided by any of incandescent, electroluminescent, florescent, laser, and LED sources 322.

The image sensor test system 300 provides uniform illumination on the plane of an image sensor device 44, and may preferably comprise a multisite probe card 12 with integrated illumination masking. As well, some embodiments of the image sensor test system 300 can vary any of wavelength, density, and applied light, such as with controlled pulse bandwidth and/or frequency, including high frequency.

In contrast to prior art structures, the image sensor test system 300 provides significant advantages over prior art structures. For example, the image sensor test system 300 may preferably include advanced spring probe contacts 18, such as to reduce any of pad damage, debris pickup, and/or maintenance requirements. The image sensor test system 300 inherently provides integrated masking (FIG. 2), such as to reduce test artifacts due to scattered illumination. The image sensor test system 300 also allows the integration of one or more optical elements, such as to support testing of sensitivity to illumination angle, and can readily provide multisite capability, such as to match the channel capacity of the tester. Improved Image Sensor Sockets and Packages. Elastic members 18, such as micro- fabricated spring contacts 18, may be fabricated with a variety of processes known to those skilled in the art. Exemplary monolithic micro-fabricated spring contacts 18 may comprise stress metal springs that are photolithographically patterned and fabricated on a substrate using batch mode semiconductor manufacturing processes. As a result, the spring contacts are fabricated en masse, and can be fabricated with spacings equal to or less than that of semiconductor bonding pads or with spacings equal to or greater than those of printed circuit boards, i.e. functioning as an electrical signal space transformer.

Fabrication of high density arrays 16 (FIG. 1 ) of spring contacts 18 are also possible using monolithic micro-fabrication processes wherein arrays of elastic, i.e. resilient, core members, i.e. spring contact skeleton structures, are fabricated directly on a contactor substrate, e.g. 32 (FIG. 2), utilizing thick or thin film photolithographic batch mode processing techniques such as those commonly used to fabricate semiconductor integrated circuits.

The spring constant of the spring is a function of the Young's modulus of the material used to fabricate the spring and the length, width, and thickness of the spring. The spring constant of the spring can be increased by enveloping the springs 18 with a coating 430,432 of a metal including but not limited to electroplated, or sputtered, or CVD deposited nickel or a nickel alloy, gold, or a palladium alloy such as palladium cobalt (see FIG. 22).

The spring constant can be varied over many orders of magnitude by controlling the thickness of the deposited coating layer, the geometrical characteristics of the spring, and the choice of metal and the thickness and number of coatings. Making the springs thicker both increases the contact force and the robustness of the physical and electrical contact between the spring and its contact pad. Figure 20 is a partial cross section 400 of an exemplary nanospring contactor 18 which may preferably be used in various embodiments of optical probes 10, test structures 300, and/or image sensor package assemblies 500. Figure 21 is a partial cross sectional view 440 of a spring 18 extending from a substrate 32 having a decoupling surface structure 448, wherein the spring 18 has an etched-back contact structure 442. Figure 22 is a partial cross sectional view 470 of a spring 18 extending from a substrate 32 having a decoupling surface structure 448, wherein the spring 18 has a multiple plated contact tip structure 429.

Monolithic micro-fabricated spring contacts 18, such as seen in Figure 20, Figure 21 and Figure 22, may preferably comprise a unitary, i.e. integral construction or initially fabricated using planar semiconductor processing methods, whereas non-monolithic spring contacts are typically assembled from separate pieces, elements, or components. Non-monolithic or monolithic micro-fabricated spring contacts can be fabricated on one or both sides of rigid or flexible contactor substrates, e.g. probe substrate 32, having electrically conductive through-vias and multiple electrical signal routing layers on each side of the substrate to provide electrically conductive paths for electrical signals running from spring contacts on one side of the substrate to spring contacts or other forms of electrical connection points on the opposite side of the substrate through signal routing layers on each side of the substrate and one or more electrically conductive vias fabricated through the substrate.

An exemplary monolithic micro-fabricated spring contact 18 comprising a stress metal spring i.e. an elastic core member, is fabricated by sputter depositing a titanium adhesion/release layer having a thickness of 1 ,000 to 5,000 angstrom on a ceramic or silicon substrate (approximately 10-40 mils thick) having 1-10 mil diameter electrically conductive vias pre-fabricated in the substrate. Electrically conductive traces fabricated with conventional photolithographic processes connect the spring contacts to the conductive vias and to the circuits to which they ultimately connect. A common material used to fabricate stress metal springs is MoCr, however other metals with similar characteristics, e.g. elements or alloys, may be used. An exemplary stress metal spring contact is formed by depositing a MoCr film in the range of 1-5 mm thick with a built-in internal stress gradient of about 1-5 GPa/mm. An exemplary MoCr film is fabricated by depositing 2-10 layers of MoCr, each layer about 0.2-1.0 mm thick. Each layer is deposited with varying levels of internal stress ranging from up to 1.5 GPa compressive to up to 2 GPa tensile.

Individual micro-fabricated stress metal spring contact "fingers" are photolithographically patterned and released from the substrate, using an etchant to dissolve the release layer. The sheet resistance of the finger and its associated trace can be reduced by electroplating with a conductive metal layer (such as copper, nickel, or gold). The force generated by the spring contact can be increased by electrodepositing a layer of a material, such as nickel, on the finger to increase the spring constant of the finger. In interposer applications (see FIG. 3), the quality of the electrical contact can be improved by electrodepositing depositing a material, such as Rhodium 104, onto the tip 86 through a photomask, prior to releasing the finger from the substrate.

The lift height of the spring contacts 18 is a function of the thickness and length of the spring and the magnitude of the stress gradient within the spring. The lift height is secondarily a function of the stress anisotropy and the width of the spring and the crystal structure and stress in the underlying stress metal film release layer. The spring constant of the spring is a function of the Young's modulus of the material used to fabricate the spring and the length, width, and thickness of the spring. The spring constant of the spring can be increased to the degree desired by enveloping the springs 40 with one or more electrodeposited, sputtered, or CVD metal coatings, e.g. 430,432, such as seen in Figures 20-22. Coatings can be applied with thicknesses of between 1 micron and 100 microns using metals including nickel, gold, palladium, platinum, rhodium, tungsten, cobalt, iron, copper, and combinations thereof. The spring constant can be varied by controlling the thickness of the deposited coating layers, the geometrical characteristics of the spring, the choice of metal, and the number of coatings. The microstructure and hence mechanical properties of the resulting spring contacts are a function of the metals deposited as well as the deposition and subsequent processing conditions. The process conditions for fabricating spring contacts according to the present invention comprise, electrodeposition current densities in the range of about 0.3 to about 30 Amperes/ square decimeter (typically 3 Amperes per square decimeter) and saccharine added at a concentration of greater than about 1 gram/liter or preferably greater than 4.5 grams per liter. One or more heat treatment processes are preferably included, such as to provide any of probe tip planarization relative to the support substrate and/or annealment to provide increased resistance to set and cracking through repeated cycles of deflection over the life of the spring contact.

Grain sizes for spring coating or plating layers, e.g. 430,432 (FIG. 20,FIG. 21 ,FIG. 22), such as comprising nickel coatings 430,432 fabricated using the above conditions, may typically range from about 200 nm to about 400 nm, e.g. as measured by SEM cross sections, but may range from as low as about 100 nm to about 500 nm before the anneal processing step. After the annealing processing step, the grain sizes typically grow to larger than about 400 nm, and may even exceed about 1000 nm.

It should be noted that methods for depositing coatings of both insulating and conductive materials are discussed in Yin et al., Scripta mater: 44(2001 ) 569-574; Feenstra, et al, Materials Science and Engineering: A, Volume 237, Number 2, September 1997, pp. 150-158(9); Kumar et al., Acta Materialia 51 (2003) 387^105), and patent applications, such as U.S. Patent No. 6,150,186. Electrodeposited layers of metals such as nickel and nickel alloys such as nickel cobalt are characterized as having "nanocrystalline" microstructures when the grain sizes range from less than a few tens of nanometers to an extreme upper limit of 100 nm. From this description, the materials fabricated as described above would not be characterized as having nanocrystalline microstructures.

Setting, i.e. plastic deformation, of the probes during the useful life of the product can be minimized by carrying out an annealing process at an optimal time and temperature. For example, using a 250 C anneal temperature, it was observed that a minimum set occurred for a 3 hour anneal (5 microns) whereas for 1 hour and 12 hours annealing times, set was observed to be 28 microns and 12 microns respectively. Additionally, accelerated aging studies, i.e. repeated, cycling of the spring probes on a probe card using a wafer prober have shown that the spring contacts are resistant to cracking when fabricated with an anneal time selected to reduce set such as for the annealing process described above. However, it has also been observed that resistance to cracking decreases with anneal times in excess of that required to minimize set.

The above teachings describe the manufacture of an exemplary monolithic micro- fabricated stress metal spring, however, those skilled in the art will understand that spring contacts having the characteristics required to practice the present invention can provide many possible variations in design and/or fabrication processes. Such variations may include but are not limited to, for example, choice of processes, process chemicals, process step sequence, base spring metal, release layer metal, coating metals, spring geometry, etc. The structures and processes disclosed herein may preferably be applied to a wide variety of non-monolithic spring contacts and monolithic micro-fabricated spring contacts, such as but not limited to spring structures disclosed in D. Smith and A. Alimonda, Photolithographically Patterned Spring Contact, U.S. Patent Nos. 5,613,861 , 6,184,699, and 6,264,477; M. Little, J. Grinberg and H. Garvin, 3-D Integrated Circuit Assembly Employing Discrete Chips, U.S. Patent No. 5,032,896; M. Little, Integrated Circuit Spring Contacts, U.S. Patent No. 5,663,596; M. Little, Integrated Circuit Spring Contact Fabrication Methods, U.S. Patent No. 5,665,648; and/or C. Tsou, S. L. Huang, H. C. Li and T. H. Lai, Design and Fabrication of Electroplating Nickel Micromachined Probe with Out-of-Plane Deformation, Journal of Physics: Conference Series 34 (2006) 95-100, International MEMS Conference 2006.

As seen in Figure 20, an elastic spring member 18 typically comprises a stress metal core 422, which provides the initial shape of the elastic spring member 18. A stress metal core 422 typically comprises one or more layers 424, e.g. 424a-424n, having different initial levels of stress, such as defined between the elastic member 422 and the release layer 410, or between at least two of layers 424 of the spring member 422. The elastic member 18 comprises a fixed portion 426 that extends to a face, i.e. non-planar portion 428, toward a tip region 429. The spring member 18 generally defines a lift height 425 from the surface of the substrate, e.g. substrate 32, from which it extends. The elastic spring member 18 typically comprises one or more layers 424a-424n of metal, e.g. molybdenum chromium (MoCr), i.e. molychrome, having different initial layers of stress before release from the substrate they are formed upon, such as directly or indirectly upon a substrate 32, e.g. comprising ceramic.

Subsequent plating layers are also typically formed on the one or more elastic spring members 18, such as comprising a first structural layer 430, e.g. nickel (Ni) or nickel cobalt (NiCo) and a second structural layer 432, e.g. nickel (Ni) or nickel cobalt (NiCo).

An adhesion layer 472 (FIG. 22), e.g. such as comprising gold, may be located between the structural layers, such as between the first structural layer 430 and the second structural layer 432. As well, an outer layer 434, e.g. such as nickel cobalt (NiCo), may preferably be formed on the second structural layer 432. In some embodiments, the optional outer layer 434 is provided to prevent solder wetting, and may comprise polyimide. An additional layer 436 may also be applied on the tip 429, such as to provide a solder wetable surface for solder bonding to an adjacent metal structure.

Micro-fabricated contactors, such as comprising the structures 18 seen in Figure 20, Figure 21 and Figure 22, may comprise a plurality of spring layers 424, wherein each spring contact 18 typically has an anchor portion 426 attached to a substrate, e.g. 32 or a decoupling layer 450 (FIG. 21 , FIG. 22), and a free portion 428, initially attached to the substrate 32, which upon release, extends to a tip lift height 425 away from the substrate 32, due to an inherent stress gradient in the respective layers 424.

Such core members 18 typically have their exposed surfaces enveloped with at least one electrodeposited metal coating layer, such as 430, 432, 434, 436 and/or 472, such as without a mask on the elastic core member(s) 18, and typically using a backside contact as an electrode connected to an electric potential source, which is also typically connected, to an electrodeposition source, e.g. a plating bath. The electrodeposited layers are preferably deposited under specified conditions, to controllably achieve one or more of desired characteristics.

For example, one or more of the coating or plating layers may preferably be deposited to minimize variations in tip lift heights 425 of each member 18 of a plurality of core members 18, such as relative to either the front or the back surface of the substrate 32, subsequent to a planarization process.

During a planarization process, the tips 429 of the plurality of core members 18 are constrained by a mechanical fixture at a fixed distance from either the front or the back surface of the substrate 32, and are then subjected to a controlled temperature cycle. The planarization process accelerates plastic deformation of each member 18 of the plurality of spring contacts 18, preferably without causing delamination of any member 18 from the substrate 32, such as due to stresses generated by thermal shock or thermal coefficient of expansion mismatch between the substrate 32 and the anchor region 426 of the spring contacts.

In some embodiments of the enhanced spring contacts 18, one or more of the coating or plating layers provide sufficient force, such as at a specified wafer prober overdrive, to insure good electrical contact to the electrical connection terminals of the device 44 over the useful life of the spring contacts 18.

In some embodiments of the optical probe assemblies 10, probe chips 12, optical probe systems 300, or image sensor packages 500, one or more of the coating or plating layers are designed to minimize changes in the tip lift height due to set while resisting cracking of any of the members of the plurality of core members 18 over the operating temperature range and useful life of the spring contacts 18, such as subsequent to an annealing process at a specified time and temperature designed to promote grain growth and at least partial internal stress relief without causing delamination of any member of the plurality of elastic spring contacts 18 from the substrate 32, due to stresses generated by thermal shock or thermal coefficient of expansion mismatch between the substrate 32 and the anchor region 426 of the spring contacts 18.

In some embodiments of the optical probe assemblies 10, probe chips 12, optical probe systems 300, or image sensor packages 500, one or more of the coating or plating layers are designed to lower the electrical resistance through each member of the plurality of spring contacts 18, and/or to provide a low contact resistance to the electrical connection points of a device under test 44 at a specified overdrive during operation.

In some embodiments of the spring contacts 18, one or more of the coating or plating layers, e.g. 430, 432, 434, 436 and/or 472, comprise electrodeposited metal coatings that are fabricated to a thickness of between 1 micron and 100 microns, such as using metals selected from the group comprising any of nickel, gold, palladium, platinum, rhodium, tungsten, cobalt, iron, copper, and combinations thereof.

In some embodiments of the elastic members 18, one or more of the coating or plating layers, e.g. 430, 432, 436 and/or 472, comprise electrodeposited metal coatings that are fabricated under specified electrodeposition conditions to cause diffusion limited transport of the depositing species and, optionally, by the addition of additives such as saccharine at a concentration of greater than about 1 gram/liter or preferably greater than 4.5 grams per liter, produce a plated metal layer, optionally, with an inherent compressive stress.

For example, a typical electrodeposition current density for some layers, such as but not limited to Ni and NiCo, is about 3 amperes per square decimeter, but may range from about 0.3 to about 30 amperes per square decimeter. In some embodiments, the typical electrodeposition conditions for PdCo range from about 0.3 to about 0.5 amperes per square decimeter. In some embodiments, the typical deposition conditions for rhodium are about 1 ampere per square decimeter. In some embodiments of the spring contacts 18, the temperature cycle of the planarization process comprises:

• a ramp up time ranging from about 15 minutes to about 2 hours;

• a dwell time of about 10 minutes to about 2 hours, depending on the planarization temperature which ranges from about 180C to about 300 C or preferably from about 185 C to about 275 C; and

• a ramp down time of about 15 minutes to about 6 hours.

In some embodiments of the spring contacts 18, at least one of the coating or plating layers, e.g. 430, 432, 434 and/or 436, generates a force ranging from about 0.5 gram to about 15 grams at wafer prober overdrives ranging from about 15 microns to about 100 microns.

Some embodiments of the spring contacts 18 may also preferably be annealed, wherein the annealing process conditions comprise:

• a ramp up time ranging from about 15 minutes to about 2 hours;

• a dwell time ranging from about 10 minutes to about 60 hours depending on the annealing temperature which ranges from about 180C to about 300 C or preferably from about 185 C to about 275 C; and • a ramp down time of about 15 minutes to 6 hours, to cause grain growth from about 0.05 - 0.3 mm to about 0.5 -1.2 mm.

In some embodiments of the spring contacts 18, at least one of the coating or plating layers, e.g. 430, 432, 434 and/or 436, provides an electrical resistance through each member of the plurality of core members of less than about 2 ohms.

In some embodiments of the spring contacts 18, one or more of the coating or plating layers, e.g. 430, 432, 434 and/or 436, preferably provide any of a contact resistance to the electrical connection points or terminals of a connected device 44 at less than about 2 ohms; and/or a robust low resistance electrical connection to the device connection terminals. In some embodiments of the spring contacts 18, one or more of the coating or plating layers, e.g. 430, 432, 434 and/or 436, are deposited without a mask, by supplying plating current from the back of the substrate 32 through a via contact 48 through the substrate 32, and enveloping all exposed surfaces of the underlying spring contacts 18, and optionally, without any discontinuities.

In some embodiments of the spring contacts 18, one or more of the coating or plating layers, e.g. 430, 432, 434 and/or 436, are electrodeposited through a mask, such as a mask that covers at least a portion of the spring contact tip extending from the tip 429 toward the anchor portion 426, the mask formed from any of spray coated photo resist, spin coated photo resist, and electrodeposited photo resist.

While exemplary elastic spring members 18, such as seen in Figure 22, may comprise self-assembling self assembling stress metal spring contacts, e.g. NanoContacts 18, those skilled in the art will recognize that some or all of the optical structures disclosed herein, e.g. 10, 12, 300, 500 can alternately be practiced using spring contacts 18 which are equivalent to stress metal spring contacts 18.

While the exemplary substrate structure 32 seen in Figure 20 may comprise a substrate 32, e.g. such as ceramic or silicon, the substrate structure 32 may alternately comprise a wide variety of structures, such as including a stress decoupling structure 448 (FIG. 21 , FIG. 22), e.g. having a stress decoupling layer 450. As noted above, the elastic spring member 18 may typically comprise one or more layers 424, e.g. 424a-424n having different inherent levels of stress before release from the substrate structure 32.

Figure 21 is a partial cross sectional view 440 of a spring extending from a substrate 32 preferably including a decoupling surface structure 448, wherein the spring 18 has an etched-back contact structure 442. The enhanced spring embodiment seen in Figure 21 can be fabricated using either negative or positive photo resist processes. In some embodiments, the photoresist used for probe spring fabrication is electrodeposited photoresist (EDPR), which inherently forms a relatively uniform, defect free conformal coating with constant thickness enveloping the surface of a 3-D spring contact structure. EDPR can be photolithographically patterned to allow etching or plating in areas defined by a mask.

EDPR can interact chemically with certain process chemicals, causing artifacts such as electroplating through the layer of EDPR. These chemical interactions can be minimized, such as by modifying the process, i.e. adjusting plating or etching solution pH, temperature, electrolyte concentrations, additive concentrations, etc.

In some embodiments of decoupled spring contacts 18, the photoresist comprises conventional photoresist (CPR), which is applied by spray or spin processes. CPR processes are preferably modified to achieve uniform and defect free coatings in the region of the spring contact tips, i.e. by process modifications to remove bubbles from uncoated areas of the spring contacts and by reducing optical reflections, i.e. by adding an absorbing dye to the CPR. In some embodiments, the photoresist is deposited from the vapor phase, to achieve a uniform and defect free coating in the region of the spring contact tips 429.

Figure 22 is a partial cross sectional view 470 of a spring 18 extending from a substrate 32 having a decoupling surface structure 448, wherein the spring 18 has a multiple layers continuously plated on the stress metal spring core 422 and extending toward the contact tip structure 429.

For example, the stress metal spring contact core member 422 typically comprises one or more layers 424a-424n of metal, e.g. molybdenum chromium (MoCr), i.e. molychrome, having different initial layers of stress before release from the substrate they are formed upon, such as directly or indirectly upon a composite substrate 32. The exemplary composite substrate seen in Figure 22 comprises a base substrate 446 e.g. ceramic, as well as a decoupling structure 448. The exemplary decoupling structure 448 shown in Figure 22 comprises a decoupling layer 450, e.g. such as comprising polyimide, and may preferably comprise a interface layer 474, such as comprising a base metal layer 474, between the decoupling layer 450 and the base substrate 446.

Subsequent plating layers are also typically formed on the one or more elastic spring members 18, such as comprising a first structural layer 430, e.g. nickel (Ni) or nickel cobalt (NiCo) and a second structural layer 432, e.g. 0.1 to 2 um rhodium (Rh), hard gold (Au), or nickel cobalt (NiCo).

An adhesion layer 472, such as comprising gold, e.g. having a 0.1 to 1 um thickness, may be located between the structural layers, such as between the first structural layer 430 and the second probe layer 432.

Decoupled Spring Contactors. Microfabricated spring contacts formed directly on support substrates 32, or having a single adhesion/release layer 410 (FIG. 20) between the elastic spring members 18 and a support substrate 32, are relatively simple to form and process, and have been demonstrated over time.

However, for some contactor embodiments, such microfabricated spring contacts have demonstrated disadvantages for some applications. For example, springs formed directly on some support substrates 32, or having a single adhesion/release layer 410 between the elastic spring members 18 and a support substrate 32, may have a limited adhesion margin, and may be weakened by process temperatures. As well, as key process parameters are coupled, the effective fulcrum point 454 (FIG. 21 , 22) for such microfabricated springs may change with process variations. In addition, these types of behaviors for such springs may be hard to model.

Some factors which may limit the use of microfabricated spring contacts formed directly on support substrates 32, or having a single adhesion/release layer 410 between the elastic spring members 18 and a support substrate, may include any of: • Adhesion margin limitations; • Ceramic-metal thermal coefficient of expansion (TCE) mismatch;

• Interface stress from structural sources;

• Process variation in fulcrum locations; and/or

• Contact requirements for contact pads having passivation layers, e.g. about 3 to about 10 micron thick passivation layers.

Factors which may limit adhesion margin for microfabricated spring contacts formed directly on support substrates 32, or having a single adhesion/release layer 410 between the elastic spring members 18 and a support substrate 32, may comprise any of:

• Bond strength between support substrates and adhesion release layers, e.g. Ti-ceramic bonds;

• Anchor characteristics; and/or

• Elevated temperature process steps (temperatures and times).

As well, a TCE mismatch between typical support substrates, e.g. comprising ceramic, to neighboring metal layers, e.g. an adhesion layer, can be significant, such as for temperatures associated with any of planarization, annealing, testing, and/or operation. Such a TCE mismatch can create interface stresses, which may lead to delamination, such as during thermal process steps, e.g. heat treatment and anneal.

Furthermore, the use of some metals for springs, such as NiCo, NiW, NiFe, can produce springs capable of higher force then nickel for the same cross sectional area due to higher Young's Modulus, ultimate tensile strength, and fracture toughness. Springs having finer pitch can be fabricated using these materials and for the same probing force, the interfacial stresses tend to increase.

However, the use of such metals for microfabricated spring contacts formed directly on support substrates 32, or having a single adhesion/release layer 90 between the elastic spring members 18 and a support substrate 32, can be problematic, since the higher temperatures and/or longer times are often required for elevated temperature processing steps of such metals, e.g. such as for heat treatment and/or annealing processes can lead to delamination.

Structural sources of interface stress in prior microfabricated spring contacts formed directly on support substrates 30 may comprise any of finger plating overhang on edges (a vertical components of stress), finger plating width (a horizontal component of stress), and/or finger plating length (a horizontal component of stress).

Improved Image Sensor Packages. Figure 23 is a partial cutaway view of a NanoContactor image sensor package/socket assembly 500a, which may preferably include a solder option. A support substrate 502, such as comprising silicon or ceramic, is mechanically and electrically mounted to a board substrate, e.g. printed circuit board,

504. For example, as seen in Figure 23, the support substrate 502 is confined by a frame structure 530, and electrical connections 518 are established between the support substrate 502 and pads 512 on a printed circuit board 504. One or more optional spacers 528 may also be located between the support substrate 502 and a printed circuit board 504.

Electrically conductive vias 516 extend through the support substrate 502, and provide electrical conduits between the electrical connection 518 and one or more electrically conductive elastic spring members 18. As well, one or more electrically conductive elastic spring members 18 provide electrical connections to electrically conductive pads 512, e.g. such as comprising gold or aluminum, on an image sensor 506.

The image sensor 506 seen in Figure 23 is also fixedly retained by the frame structure 530, which is attached to the board substrate 504. The exemplary image sensor 506 seen in Figure 23 comprises electrically conductive vias 510 that extend through the sensor substrate. The vias 510 may preferably comprise double-sided deep vias 510, such as to resist via fall-out. The vias 510 seen in Figure 23 extend to image sensor connection terminals 508. As seen in Figure 23, the electrical connections between the elastic members 18 and the sensor pads 512 may preferably include a solder bump or coating 514. As well, the interface between the image sensor 506 and the support substrate 502 may include any of a lamination adhesive 526 and/or one or more spacers 524.

Figure 24 is a plan view 534 of multiple NanoContactor connections to image sensor contacts 512. For example, the support substrate 502 seen in Figure 23 may preferably comprise multi-contact stress metal springs 18, with one or more contacts 18 per pad 512. In some embodiments, such pairs of contacts 18 apply balanced forces, and avoid the central region of a bump/pad 512.

Figure 25 is a partial cutaway view 550 of a NanoContactor image sensor package assembly for a back-side thinned sensor 506, having construction similar to the image sensor package assembly 500a seen in Figure 23.

The image sensor package assemblies 500 inherently provide several advantages over prior art image sensor packages. For example, the level of compliance inherently provided through the elastic members 18, e.g. stress metal spring NanoContactors 18, decouples inherent stresses due to temperature differentials and/or TCE mismatches between the image sensor substrate 506 and the electrical interconnect support substrate 502. As well, many embodiments of the image sensor package assemblies 500 are demountable, thereby eliminating a need for soldering between an image sensor and the associated substrate 502, wherein sockets can be used for testing, and wherein field replacement and/or upgrading is possible.

Furthermore, while some embodiments of the image sensor package assemblies 500 are initially demountable, the assemblies can selectably provide permanent connections. For example, in some embodiments 500, devices 44 can be mounted and demounted, and subsequently soldered in place. Similarly, systems 500 can be tested with IC devices 44 in place, and repairs or changes can be made prior to reflow and subsequent conversion to permanent mounting. As well, spring contact tip 429 can optionally be designed to wet solder, whereas the support structure or base of spring member "fingers" 18 can optionally be designed to be non-wetting to solder.

While the image sensor package assemblies 500a, 500b seen in Figure 23, Figure 34, and Figure 25 include elastic spring members 18 on a support substrate 502 that provide electrical connections to an image sensor 506, the elastic spring members 18 can alternately be located on the image sensor 506 itself.

Figure 26 is an expanded assembly view 580 of a NanoContactor solderless image sensor package 500c, wherein the printed circuit board and the optical window are separably connectable 584. Figure 27 is an assembled view 590 of a NanoContactor solderless image sensor package 500c having a separable connection 584, such as comprising mating connectors 586a, 586b, between the printed circuit board 504 and the optical window 585. The sensor package 500c may preferably include electrical pathways, e.g. vias 510 and contacts between the spring contacts 18 and the optical window 585. As seen in Figure 26 and 27, the connection means 584 may preferably comprise a combined guide, travel stop and latch 584 between the optical window 585 and the printed circuit board 504.

Figure 28 is a detailed view 600 of a NanoContactor solderless image sensor package 50Od, having travel stops 602 located between the image sensor assembly 506 and the printed circuit board 504. A separable latch 584, such as a combined guide, travel stop and latch 584, may preferably be used between the optical window 585 and the printed circuit board 504.

Figure 29 is a detailed view 620 of a NanoContactor image sensor package 50Oe, having travel stops 602 located between the image sensor assembly 506 and the printed circuit board 504, and solder bonds between nanocontactors 18 and contact pads or bumps 582. An X-Y alignment guide 584 may preferably be used between the optical window 585 and the printed circuit board 504. The exemplary image sensors 506 seen in Figure 28 and Figure 29 include electrically conductive vias 510 that extend through the sensor substrate. The vias 510 may preferably comprise double-sided deep vias 510, such as to resist via fall-out. The vias 510 seen in Figure 23 extend to image sensor connection terminals 588.

Figure 30 is a schematic view 640 of a solderless image sensor package assembly 50Of having nanocontactor connections 18 between an image sensor 506 and a printed circuit board 504, and connection terminals 588 between the image sensor 506 and an optical window 585. The image sensor 506 may include vias 510 extending through the substrate 506, between the front probe spring surface and the rear surface. The vias 510 may preferably comprise double sided deep vias 510, such as to resist via fall out. The assembly 50Of may also preferably comprise a heat pipe 650 extending from the outer surface of the printed circuit board 504, toward a cooler or heater as desired. A lamination adhesive 606 may also preferably be located between the image sensor 506 and the optical window 585, such as to provide any of a mechanical bond and a reflection free optical transition, e.g. such as an optically transparent mechanical bond, having an optical index selected to minimize reflection of light, e.g. 42, coming into the image sensor 506, and/or a hermetic seal to keep water out of the assembly.

Figure 31 is a partial cutaway view 660 of a solderless image sensor package assembly 50Og having nanocontactor connections 18 between an image sensor 506 and a support substrate 504, such as a printed circuit board 504. Lamination adhesive 606 may preferably be used between the image sensor 506 and support substrate 504. The assembly 50Og may also preferably comprise a heat pipe 650 extending from the outer surface of the support substrate 504, such as for cooling or heating as desired. Lamination adhesive 606 may also preferably be located between the image sensor 506 and an optional optical window 585. In some embodiments, the image sensor 506 comprises a backside thinned image sensor 506.

Figure 32 is a schematic view of a solderless image sensor module assembly 50Oh having a wire-bonded image sensor 506 and passive components 694. Figure 33 is a schematic view of a solderless image sensor module assembly 50Oi having a flip sensor bonded image sensor 506 and passive components 694.

In the image sensor module assemblies 50Oh and 50Oi seen in Figure 32 and Figure 33 respectively, a support substrate 502, such as comprising silicon or ceramic, is mechanically and electrically mounted to a board substrate, e.g. printed circuit board,

504. For example, as seen in Figure 32 and Figure 33, the support substrate 502 is confined by a mechanism 692 comprising both mounting clips as wells as one or travel stops. Electrical connections 518 are established between Nanocontactors 18 that are located on and compliantly extend from the support substrate 502, and pads 582 on the printed circuit board substrate 504.

While some embodiments of the microfabricated optic probe structures and image sensor package structures and methods are implemented with photolithographically patterned springs, the structures and methods may alternately be used for with wide variety of compliant spring structures, such as to provide mechanical compliance and/or electrical connections between any of contacts, connectors, and/or devices or assemblies, over a wide variety of processing and operating conditions.

Accordingly, although the invention has been described in detail with reference to a particular preferred embodiment, persons possessing ordinary skill in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the claims that follow.

Claims

1. An apparatus, comprising: a probe substrate having a front surface and a back surface, and at least one hollow region defined through the substrate extending between the front surface and the back surface; and one or more microfabricated spring contacts, each spring contact having an anchor portion attached to the front surface of the probe substrate and a free portion extending toward the hollow region and away from the front surface of the probe substrate.

2. The apparatus of Claim 1 , wherein the microfabricated spring contacts comprise stress metal springs.

3. The apparatus of Claim 1 , wherein the substrate comprises any of silicon and ceramic.

4. The apparatus of Claim 1 , further comprising: means for providing electrical connections between the back surface of the probe substrate and a front surface of a support substrate.

5. The apparatus of Claim 4, wherein the support substrate comprises at least one hollow window region extending therethrough and corresponding to at least one of the hollow regions in the probe substrate.

6. The apparatus of Claim 4, further comprising: means for attaching an optical element to the support substrate.

7. The apparatus of Claim 6, wherein the optical element is associated with one or more of the hollow window regions extending through the support substrate.

8. The apparatus of Claim 7, wherein the optical element comprises any of a light source, an optical lens, a pin hole lenses, and a diffraction grating.

9. The apparatus of Claim 1 , further comprising: at least one separable connector fixedly attached proximate to the rear surface of the probe substrate.

10. The apparatus of Claim 1 , further comprising: a first electrodeposited metal layer enveloping each member of the plurality of microfabricated spring contacts for imparting a first set of predetermined performance characteristics to each member of the plurality of microfabricated spring contacts.

11. The apparatus of Claim 10, further comprising: at least a second electrodeposited metal layer enveloping the first metal layer for imparting a second set of predetermined performance characteristics to each member of the plurality of microfabricated spring contacts.

12. A structure, comprising: an image sensor comprising a sensor substrate having a first side and a second side, and a plurality of electrical contacts located on the first side; a secondary substrate comprising any of a support substrate and a circuit board substrate; and one or more stress metal spring contacts extending between the first side of the image sensor and the secondary substrate, each spring contact having an anchor portion attached to the front surface of a base substrate comprising any of the sensor substrate and the secondary substrate, and a free portion away from the front surface of the base substrate to establish and electrical connection between the image sensor and the secondary substrate.

13. The structure of Claim 12, wherein the secondary substrate comprises any of silicon and ceramic.

14. The structure of Claim 12, wherein the image sensor further comprises electrically conductive vias extending between the first side and the second side.

15. The structure of Claim 14, wherein the electrically conductive vias comprise double sided deep vias.

16. The structure of Claim 14, further comprising electrically conductive connection terminals on the second side of the image sensor.

17. The structure of Claim 16, further comprising: an optical window mechanism electrically connected to the image sensor through the electrically conductive connection terminals on the second side of the image sensor.

18. The structure of Claim 17, further comprising: means for attaching the secondary substrate to the optical window.

19. The structure of Claim 12, wherein the electrical connections between the image sensor and the secondary substrate further comprise solder connections between the spring contacts and electrical contacts on the secondary substrate.

20. The structure of Claim 12, further comprising: a first electrodeposited metal layer enveloping each member of the plurality of spring contacts for imparting a first set of predetermined performance characteristics to each member of the plurality of stress metal spring contacts.

21. The structure of Claim 20, further comprising: at least a second electrodeposited metal layer enveloping the first metal layer for imparting a second set of predetermined performance characteristics to each member of the plurality of stress metal spring contacts.