CN100526995C - Marker for photo-etching machine aligning and aligning using the same - Google Patents

Abstract

The present invention discloses an alignment mark and an alignment signal treatment method used for projection scanning lithography machine based on four-cycle phase grating. The method makes use of a marked coarse grating branch signal for the determination of capture range and position of the coarse alignment, and makes use a marked fine grating branch signal for the determination of the fine alignment position, thereby ensuring the obtainment of high-precision alignment position by only adopting diffraction optical signal of plus or minus 1 grade, improving the alignment efficiency and simplifying the alignment optical system.

Description

A kind of mark of litho machine aligning and alignment methods of using this mark of being used for

Technical field

The present invention relates to photoetching machine technique, particularly the technique of alignment of scanning projection litho machine.

Background technology

Use advanced scanning projecting photoetching machine and finish the figure transfer task of microfabrication, basically can relate to workpiece loads, workpiece zone to be processed is aimed at mask, basic steps such as workpiece exposure and workpiece unloading, wherein referring more particularly to workpiece need carry out under the situation of multilayer processing technology, workpiece zone to be processed is to guarantee constantly to dwindle the prerequisite that workpiece is correctly processed under the situation in live width with accurate aligning of mask, when figure is projected to a workpiece zone to be processed or a new layer pattern accurately alignment is projected on the workpiece zone to be processed that has before formed figure accurately, to when the suitable exposure of anterior layer, can realize figure accurate transfer or requirement of interlayer alignment of (being workpiece to be processed) from the mask to the substrate.

Early stage lithographic projection apparatus adopts the coaxial alignment method more, patent US.4,251,160 have introduced a kind of coaxial alignment device, realize aiming at of mask sheet mark and substrate marker, its implementation structure comprises to be aimed at light source, mask sheet and mask mark, optical system for alignment (by means of the projection objective light path) and substrate and substrate marker.Yet, along with the processing minimum feature is constantly dwindled, be forced to adopt shorter exposure wavelength, because object lens must be not that alignment wavelengths is optimized design according to exposure wavelength, the intensity of registration signal certainly will be affected.And because introducing CMP technology makes substrate marker asymmetric, thereby make the coaxial alignment method no longer reliable.In addition, various processing steps change alignment mark, comprise the variation of the groove significant depth of introducing asymmetry and substrate grating marker.Other job operation or step are often introduced dissimilar errors.For example, copper-mosaic process can be introduced alignment error in the stochastic distribution of integrated circuit surface.Along with the size of the structure of photoetching technique structure reduces and complicacy improves, constantly require to improve alignment precision.Do not improve alignment precision, just can not realize the raising of resolution.In addition, the raising of micro element complicacy more need technology control and with in the manufacture process because alignment error and the substrate quantity that must abandon is reduced to minimum.

In addition, how to realize that bigger capture range guarantees that comprising centering adjustment also is the problem that pay close attention to, because the restriction of technical conditions and job order, the prealignment precision of substrate last slice also is not easy the degree that reaches very high, so to finishing the precondition that substrate that prealignment is placed on base station later on aims at is the zone that alignment device can guarantee to find place, alignment mark center, and obtain the signal that comprises central area information, finally obtain the centering adjustment position by processing, this just so-called capture range problem to this type signal.Document 1 (A new interferometric alignment technique, D.C.Flanders and HenryI.Smith, Appl.Phys.Lett., vol.31, no.7, p.426,1977) introduced a kind of be used for X ray projection mask aligner utilize had the substrate marker of period p with the mask mark with period p+Δ p between the positive level time light group that obtains of spatial modulation interfere between the phase signal of the phase signal that forms and time light group interference formation of negative level the phase zero intersection location as the position of fine alignment, simultaneously, can obtain P=[p (p+ Δ p) like this]/Δ p ≈ p ²The capture range of the mark center position of/Δ p, promptly can guarantee has an alignment point in the P scope.

Further, document 2 (Automatic Alignment System for Optical ProjectionPrinting, Gijs Bouwhuis and Stefan Wittekoek, IEEE Transactions on ElectronDevices, VOL.ED-26, NO.4, April 1979) proposed a kind of be used for stepping projection mask aligner a kind of utilize the cycle for the substrate phase grating of p and cycle carry out for the mask phase grating of p '=R * p/2 (wherein R is the optics multiplying power) is relative scanning motion obtain one with the corresponding to quadratic form phase signal of substrate location, can utilize the largest light intensity value to determine aligned position, prerequisite is that the prealignment precision reaches p/4, signal peak in prealignment precision allowed band is exactly the aligned position of being asked, can realize such prealignment precision with the method that increases observation optical path though mention in the literary composition, but better method be add the another one cycle be p+ Δ p (Δ p＜＜p) grating, guarantee that by design there is zero intersection location in the grating in these two cycles, the zero intersection location of the signal that forms of these two gratings will be with P=[p (p+ Δ p) like this]/Δ p ≈ p ²/ Δ p repeats in the cycle, so if can guarantee to have only a unique zero intersection location in less than the scope of P, this position just can be used as accurate aligned position.(Critical Dimension, CD) reducing of size is to the also feasible requirement that can't satisfy higher alignment precision merely in this way of the requirement of alignment precision raising but along with characteristic line breadth.Because if reduce p, then P also will reduce, to corresponding must the raising that require of prealignment; And if increase p, though then P can increase, if only utilize one-level light can't better realize more high-precision aligning.

The introducing of off-axis alignment system for some time.Such as, patent US.4,937,618 have introduced a kind of off-axis alignment technology, wherein used two-way off-axis alignment unit, finish the aligning of mask mark and substrate marker in conjunction with one road coaxial alignment unit, in two-way off-axis alignment unit, it is high that each road can provide, detection mode at the bottom of low two kinds of enlargement factors, be respectively applied for fine alignment and coarse alignment, its detectable signal is relatively introduced CCD (charge coupled device) and testing circuit and display in the back through a reference marker, by testing circuit picture signal is carried out integration line by line, compares by threshold level value V1 and a low level value V2 with the representative mark center of presetting after the entire image of acquisition plurality of continuous hardwood, can find value above V2, the image that serves as a mark, and the value that the surpasses V1 center that serves as a mark, x to y to surveying simultaneously.Obviously, detect centering adjustment by the predetermined threshold value level value, its precision is except being subjected to CCD pixel size and system's enlargement ratio (the excessive image quality that then be difficult for to guarantee of enlargement ratio) influence easily, also is subjected to the influence of the average noise that superposes on the signal, so actual alignment precision and repeatability are relatively poor.

Patent US.5,243,195 have introduced a kind of off-axis alignment technology, also are the alignings of realizing mask mark and substrate marker in conjunction with the coaxial alignment device.By with a differentiation plate with mark x to being imaged on respectively on separately the ccd sensor to part with y, obtain aligned position in conjunction with analysis then to picture signal, yet, the variation of deformed mark and different coverings material reflectance makes picture contrast and Strength Changes very big, thereby influence obtains result preferably.

Patent US.6,297,876B1 has introduced a kind of off-axis alignment method, also is the aligning of realizing mask mark and substrate marker in conjunction with the coaxial alignment device.The diffraction light of 7 orders by gathering a mark, make the positive and negative component of these 7 orders in the image planes coherence stack through apart device with wedge regulating device, light signal to these 7 orders fits then, find 7 orders all maximum a bit, the center that serves as a mark.The advantage of this scheme is can realize catching automatically and higher alignment precision, but shortcoming is to need special wedge regulating device and complicated debuging, in addition, high order signal in the diffraction light a little less than, and but this method realizes higher alignment precision by high order signal, the highest alignment precision along with mark (particularly silicon chip mark) reflected signal (particularly high order signal) power is low excessively, then actually can't utilize high order signal in the reality, so can not be provided reliably.

Summary of the invention

The object of the present invention is to provide a kind of mark of litho machine aligning and alignment methods of using this mark of being used for, catch with fine alignment with the coarse alignment of realizing litho machine and locate.

To achieve the above object, the invention provides a kind of mark that the projection scanning litho machine is aimed at that is used for, the grating that contains 4 different cycles in one direction, comprising two large period grating branch and two minor cycle grating branch, utilize two large period grating branch to obtain big capture range and coarse alignment position, utilize two minor cycle grating branch to obtain the fine alignment position.The cycle of described two large period grating branch at 10um between the 20um, the cycle of two minor cycle grating branch at 1um between the 5um.The cycle of this large period grating branch should be 3 to 9 times of cycle of this minor cycle grating branch.There is periodic inequality between two large period grating branch less than 2um.There is periodic inequality between two minor cycle grating branch less than 1um.This alignment mark can be positioned on the base station, also can be positioned in the substrate.

This alignment mark can comprise two groups of gratings that are distributed on the orthogonal directions, and every group of grating all contains 4 different cycles.These two groups of gratings can spaced apart, can cross arrangements, can also in surface level, become other assembled arrangement modes.

The grating of spaced apart, arrangement separately can be in line.Distribution arrangement can be parallel with the direction of grating fringe, becomes block form phase mark structure all around, also can be vertical with the direction of grating fringe, become tandem phase structure all around.

This alignment mark can become isometric lines to arrange along the gap, graduation border for the treatment of alignment area.

The present invention also provides a kind of alignment methods of using this alignment mark, may further comprise the steps:

(1) gathers each grating branch ± 1 grade light intensity signal and relative position signals in the scanning process in real time;

(2) the coarse alignment signal of in the future arrogant periodic optical grating branch and the fine alignment signal of described minor cycle grating branch carry out match;

(3) determine the coarse alignment position by this coarse alignment signal;

(4) on this fine alignment signal, seek the peak point nearest apart from the coarse alignment position;

(5) comprehensive utilization is determined the fine alignment position from the peak point on the fine alignment signal of different fine grating branch.

Determine that by the coarse alignment signal method of coarse alignment position can be by the addition with the alignment mark signal of two large period grating branch, in moving, obtain the position of the alignment mark signal sum maximum of two large period grating branch, promptly the alignment mark signal of two large period grating branch all is in the position of peak state, with the position of the alignment mark signal sum maximum of two large period grating branch as the coarse alignment position.

The method of determining the fine alignment position can be near this coarse alignment position, the alignment mark signal that obtains two nearest minor cycle grating branch from the coarse alignment position in moving is in the position of peak state respectively, and the flat accurate value of position that is in peak state with the alignment mark signal of two minor cycle grating branch respectively is as accurate aligned position.

Alignment mark provided by the present invention and to use the alignment methods of this mark be to utilize to determine capture range and coarse alignment position than the coarse alignment grating branch signal of large period utilizes less fine alignment grating branch signal of cycle to determine high-precision aligned position.Two coarse alignment signals adopt the specific mathematical model to carry out the real-time sampling match, and according to the model after the match, determine that peak value overlaps or the closest approach, is the coarse alignment position; Adopt the specific mathematical model that the fine alignment signal is carried out the real-time sampling match, and be benchmark with the coarse alignment position, seek each fine alignment signal upward peak point nearest respectively apart from this benchmark, fully utilize a plurality of fine alignment signals, determine final fine alignment position, reach the purpose of accurate aligning.

Description of drawings

Fig. 1 is a litho machine alignment system synoptic diagram;

Fig. 2 is one dimension x of the present invention phase mark synoptic diagram around tandem;

Fig. 3 is one dimension x of the present invention phase mark synoptic diagram around block form;

Fig. 4 is one dimension y of the present invention phase mark synoptic diagram around tandem;

Fig. 5 is one dimension y of the present invention phase mark synoptic diagram around block form;

Fig. 6 is two groups of grating marker synoptic diagram that are orthogonal and arrange of the present invention;

Fig. 7 is two groups of grating marker synoptic diagram of a kind of modified that are orthogonal and arrange of the present invention;

Fig. 8 is two groups of grating marker synoptic diagram of a kind of modified that are orthogonal and arrange of the present invention;

Fig. 9 is marked at suprabasil distribution schematic diagram for the phase around the one dimension of the present invention;

Figure 10 is marked at suprabasil distribution schematic diagram for the phase around the two dimension of the present invention;

Figure 11 be around phase grating space diffraction synoptic diagram;

Figure 12 is a 4f system architecture synoptic diagram;

Figure 13 is a spatial filter principle of work synoptic diagram;

Figure 14 is the spatial filter structural representation;

Figure 15 be around phase alignment work principle and light channel structure synoptic diagram;

Figure 16 is with reference to the grating structural representation;

Figure 17 arranges the cross section structure synoptic diagram for detection optical fiber;

Figure 18 is for using a kind of implementation synoptic diagram of phase alignment system all around of the present invention;

Figure 19 is desirable phase registration signal all around;

Figure 20 is actual phase registration signal all around;

Figure 21 is the alignment procedures synoptic diagram.

In the accompanying drawing: 1, base station mark; 2, mask mark; 3, base station mark; 4, mask; 5, substrate marker; 6, mask stage; 7, substrate; 9, base station; 100, alignment device; 101, alignment mark signal; 102, Transmission Fibers; 103, Transmission Fibers; 104, total reflection prism; 105, spatial filter; 106, with reference to grating; 107, detection optical fiber; 110, beam splitter; 200, signal processor; 201, opto-electronic conversion and amplifier; 201a, electrooptical device; 202, analog to digital converter; 203, fit signal processor; 204, position data processor; 205, position data conversion and sampling thief; 206, base station motion controller; 207, work schedule controller; 300, aim at radiation source; 303, lens; 302, aperture diaphragm; 301, lens; Basad displacement measuring device laser interferometer of IFx, x; Basad displacement measuring device laser interferometer of IFy, y; PL, projection objective; L1, preceding group of lens; L2, back group lens; IB, calibration beam; P1, tag plane; P2, imaging plane; RG, with reference to grating; FB, detection optical fiber.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is further described.

Fig. 1 shows a kind of embodiment of the alignment methods of phase alignment mark around alignment system that prior art uses and the use of the present invention, and the primary structure of litho machine comprises: mask stage 6, mask 4, projection objective PL, base station 9.

In the system that prior art is used, utilize the mask mark 2 on the mask 4 of non-exposure wavelength radiation source irradiates mask stage 6 carryings of more low-energy exposure source or other, by projection objective PL the reduced image of mask mark 2 is projected on the base station mark 3 as the reference mark set on the base station 9, the sensor that utilizes base station mark 3 to be transmitted under it carries out the photosignal conversion, by a series of scanning collection signal, fit processing in conjunction with the locus signal that records by x basad displacement measuring device laser interferometer IFx and basad displacement measuring device laser interferometer of y IFy, set up the coordinate transformation relation of mask and base station.

The alignment system that the present invention uses provides one or more lighting source with suitable wavelength by Transmission Fibers 103 irradiation base station marks 1 by aiming at radiation source 300, collects the alignment mark signal 101 that reflects on the mark by alignment device 100.Adopt the form of Fig. 6 when the arrangement of base station mark 1, carry out x to measure have 4 cycle x to the first-order diffraction light signal have 4 the tunnel, carry out y to measure have y to the first-order diffraction light signal have 4 the tunnel, 8 road signals are collected through alignment device 100 altogether, guide to than finishing in the registration signal processing unit 200 at a distance by Transmission Fibers 102 and leave in the storage address of appointment after opto-electronic conversion and signal amplify conditioning and analog to digital conversion.Simultaneously, can obtain the movement position information of answering simultaneously by x basad displacement measuring device laser interferometer IFx and basad displacement measuring device laser interferometer of y IFy.To record numerical value and fit processing, can find base station mark 1 corresponding alignment point coordinate figure (x under the base station coordinate system ₁, y ₁).

In like manner, alignment device 100 can be measured substrate marker 5, obtains substrate marker 5 corresponding coordinate figure (x under the base station coordinate system ₅, y ₅).

By (x ₁, y ₁) and (x ₅, y ₅) can set up the transformational relation between base station coordinate origin and the substrate coordinate origin, and then set up the transformational relation between two coordinate systems.

Fig. 2 shows a kind of x of being used for of the present invention phase mark structure around aiming at.Fig. 2 comprises the grating branch of four of p0_ax, p0_bx, p1x, p2x, and its cycle is respectively p0_a, p0_b, p1, p2, and four grating distribution arrangements are vertical with the direction of grating fringe, is phase mark structure around the tandem.

Fig. 3 shows another kind of the present invention and is used for x phase mark structure around aiming at.Fig. 3 comprises the grating branch of four of p0_ax, p0_bx, p1x, p2x, and its cycle is respectively p0_a, p0_b, p1, p2, and four grating distribution arrangements are parallel with the direction of grating fringe, is phase mark structure around the block form.

Fig. 4 shows a kind of y of being used for of the present invention phase mark structure around aiming at.Fig. 4 comprises the grating branch of four of p0_ay, p0_by, p1y, p2y, and its cycle is respectively p0_a, p0_b, p1, p2, and four grating distribution arrangements are vertical with the direction of grating fringe, is phase mark structure around the tandem.

Fig. 5 shows another kind of the present invention and is used for y phase mark structure around aiming at.Fig. 3 comprises the grating branch of four of p0_ay, p0_by, p1y, p2y, and its cycle is respectively p0_a, p0_b, p1, p2, and four grating distribution arrangements are parallel with the direction of grating fringe, is phase mark structure around the block form.

Fig. 6, Fig. 7, Fig. 8 show of the present invention be used for simultaneously x to y phase mark structure around aiming at.X comprises the grating branch of four of p1x, p2x, p0_ax, p0_bx to mark, and its cycle is respectively p1, p2, p0_a, p0_b.Y comprises the grating branch of four of p1y, p2y, p0_ay, p0_by to mark, and its cycle is respectively p1, p2, p0_a, p0_b.The effect of this mark can be supported diagonal line scanning, promptly along with x to or y become the directions of 45 degree to scan to coordinate axis, then can obtain simultaneously x to y to the mark center position.

The distribution of substrate marker 5 in substrate 7 can be adopted the form of Fig. 9 or Figure 10.

The grating of 4 different cycles, wherein the cycle of two large period grating branch can be 10um, 11um, 15um, 16um, 19um and 20um, the cycle of two minor cycle grating branch can be 1um, 1.5um, 2.5um, 4.5um and 5um.The cycle of large period grating branch should be 3 to 9 times of cycle of this minor cycle grating branch.There is periodic inequality between two large period grating branch less than 2um.There is periodic inequality between two minor cycle grating branch less than 1um.Adopt p1=14um, p2=15.4um, p0_a=2.2um, p0_b=2um in the present embodiment.

Situation when Figure 11 shows phase mark around of the present invention carried out one-dimensional scanning.When vertical or near normal projects phase mark around the one dimension surperficial as calibration beam IB, at four different cycles grating places of mark diffraction take place, according to the angle of diffraction formula:

$\sin \mathrm{\α}=n\frac{\mathrm{\λ}}{p}$ (formula 1)

(wherein, p represents the pitch of grating, α represents the angle of diffraction beamlet and grating normal, λ represents lambda1-wavelength, n represents the order of diffraction time) incident beam takes place behind the diffraction becomes positive and negative level a plurality of beamlets that time are symmetrically distributed at each grating place, in free space, will propagate along corrugated separately.The present invention only needs to utilize the first-order diffraction light of each grating to aim at.In fact, when diffraction takes place, also can produce senior diffraction light except that first-order diffraction light, not need these diffraction components here, but in design, avoid of the interference of senior diffraction light of certain branch as far as possible other branch's first-order diffraction light at every place.On the other hand, the zero-order sub-beam of diffracted beam also is unwanted diffraction components, avoid it that four branch's first-order diffraction light are impacted in design.

Figure 12 is the structural representation of 4f system.Mark on tag plane P1 be positioned at the 4f system preceding group of lens L1 front focal plane and be positioned at the paraxial region of optical axis, the positive and negative two-beam of certain grade of arbitrary branch diffraction time becomes the two-way collimated light beam through behind preceding group of lens L1 from the mark; After back group of lens L2 of process 4f system converges, this two-way collimated light beam is focused on the back focal plane of back group lens L2, owing to have stable phase differential between positive and negative level is inferior, frequency identical and on reference grating face projection components be parallel to each other, satisfy coherent condition, the two-way beamlet is coherent imaging herein.

In fact, have the entrance pupil that the inferior beamlet of a plurality of levels can enter this 4f system in the diffraction components on mark in each branch, the present invention only uses first-order diffraction light beam wherein, so at the back focal plane place of preceding group of lens L1 an aperture diaphragm device is set, makes that can optionally see through us needs the inferior beamlet of level.

Figure 13 is the fundamental diagram as the aperture diaphragm device of spatial filter.Spatial filter 105 is positioned at the back focal plane of L1, the printing opacity place of aperture diaphragm, and the first-order diffraction light light path of corresponding four grating branch of difference, and between the senior diffraction light of the first-order diffraction light of minimum period grating and other periodic optical gratings enough offsets are arranged.

Figure 14 is a kind of structural representation of spatial filter.Corresponding to phase mark around the two groups of gratings arranging of being orthogonal shown in Figure 6, it comprise x to the spatial filter structure and y to the spatial filter structure.Only can by x to around phase mark and y to around the first-order diffraction light of phase mark.

For vivider explanation principle of work, Figure 15 has adopted the mode of exaggeration to draw four cycles and has gone up diffraction and imaging process.In fact, incident laser is a branch of light, and its color is a monochromatic light.Because f1 is much larger than label size, can think that primary optical axis that each cycle of mark all is positioned at optics 4f system goes forward to organize the front focus place of lens L1, so behind preceding group of lens L1, the first-order diffraction light in four cycles all is the approximate light that is parallel to primary optical axis, reason in order to distinguish among Figure 15, the deliberately slightly deflection of drawing.As shown in Figure 15, incident beam IB is vertically projected on the mark of substrate surface after by total reflection prism 104 deflections, and this incoming laser beam enough covers four cycles of mark, so when mark generation diffraction, branch can produce diffraction lights at different levels.Because period p 0_b＜p0_a＜p1＜p2, in time diffracted ray at the same level, secondly branch's p0_bx virgin beam diffraction angle maximum is the p0_ax virgin of branch light beam, is p1x virgin light beam once more, and branch's p2x virgin beam diffraction angle minimum.When we during only to the first-order diffraction light sensation interest in four cycles, can the schematic ray tracing of each first-order diffraction beamlet only shown in Figure 11.Because the effect of blocking of total reflection prism 104 and aperture diaphragm 105 is arranged, and the Zero-order diffractive component can not cause interference to each first-order diffraction beamlet.The one-level light b0_a+1 of branch's p0_ax grating place diffraction and b0_a-1 become collimated light beam b0_a+1 ', the b0_a-1 ' of pair of parallel and primary optical axis behind preceding group of lens L1, and the light hole by diaphragm 105 forms the picture p0_ax ' of p0_ax after 2 the beamlet b0_a+1 ＂ of back focal plane place and the b0_a-1 ＂ that converging in back group lens L2 of back group lens L2 interfere near the primary optical axis place at image planes P2.In like manner, p0_bx place diffraction beamlet can be imaged on p0_bx ' through this 4f system and locate, and p1x place diffraction beamlet can be imaged on p1x ' through this 4f system and locate, and p2x place diffraction beamlet can be imaged on p2x ' through this 4f system and locate.Simultaneously, on image planes P2, placing one with reference to grating, comprising the RG0_ax corresponding with the p0_ax cycle with primary optical axis is centrosymmetric, the RG0_bx corresponding with the p0_bx cycle, the RG1x corresponding with the p1x cycle, each sections such as RG2x corresponding with the p2x cycle, its concrete structure pattern can be referring to Figure 16; All placing corresponding detection optical fiber at each with reference to each section back of grating, can collect by with reference to the light intensity signal behind the grating, its arrangement can be referring to Figure 17.And these detection optical fibers guide to electrooptical device with corresponding light intensity signal, and light intensity signal is changed and handled.Because the image of substrate marker is the continuous hot spot striped consistent with the optical grating construction form, when mark moves with respect to alignment optical system, these stripeds also can move with respect to the reference grating, being the imaging striped with the degree that overlaps with reference to grating continuous variation takes place, the result is that signal light intensity on photodetector is also along with this mobile generation changes continuously, because fringe spacing is cyclical variation, the variation of this light intensity signal also is periodic.According to Fourier optics, what form on detector is a kind of signal of sinusoidal form, if keep the mutually accurate uniform motion of mark and alignment system, then can obtain the sinusoidal signal of a constant cycle.Corresponding to each section (marker image-with reference to grating), the sinusoidal signal of a constant cycle that is directly proportional with the grating cycle can be arranged all.

Figure 18 be around a kind of synoptic diagram of implementation of phase alignment system, its objective is explain better one's duty=utilization, and not should be understood to limitation of the present invention.Aim at radiation source that radiation source 300 sends through lens 303, aperture diaphragm 302 and lens 301 and Transmission Fibers 103 (passing the light polarization maintaining optical fibre) through total reflection prism 104 deflections, through preceding group of lens L1 vertical irradiation to the base station mark 1 that is positioned at base station 9 or be positioned on the substrate marker 5 of substrate 7, this moment mark with around the phase alignment mark be example, be deflected and the approximately parallel collimated light beam of optical axis behind the group lens L1 before the 1 order diffraction beamlet in each cycle of generation diffraction is transmitted into, 0 order diffraction light of each periodic optical grating returns former incident light direction in addition.Comprising some in each collimated light beam in fact is regarded as disturbing with reference to the order of diffraction of grating surface imaging time and parasitic light component, so be provided with a spatial filter 105 that only can optionally see through the 1 order diffraction light component in four cycles at the back focal plane (also being simultaneously the front focal plane of back group lens L2) of preceding group of lens L1.These light beams are focused on the reference grating 106 that is placed on back group lens L2 back focal plane by back group lens L2 and form interference image, when carrying out the alignment scanning of base station mark 1 or substrate marker 5, imaging is at the uniform velocity mobile with respect to reference grating 106, and then on placing, form the sinusoidal light intensity signal of continually varying with reference to 107 receiving planes of the detection optical fiber behind the grating, become electric signal be sent to the electrooptical device 201a of the opto-electronic conversion of signal processing unit 200 and amplifier 201 by Transmission Fibers 102 after.Trigger via the unified of work schedule controller 207, can guarantee that collection to this alignings electric signal is with synchronous through the displacement numerical value that position data is changed and sampling thief 205 is gathered.Simultaneously, the signal after opto-electronic conversion and amplifier 201 are handled also will convert digital signal to through analog to digital converter 202, delivers to and fits signal processor 203; And 203 receive the position data from position data processor 204 simultaneously, it comes from position data conversion and sampling thief 205, these data offer base station motion controller 206 simultaneously, carry out mark scannng by base station motion controller 206 control base station according to desired speed and direction.In conjunction with the synchronously sampled data that comes from analog to digital converter 202 and position data processor 204, can determine the aligned position of this scanning by fitting signal processor 203 through fitting processing.

When the single direction of mark was four grating branch, its cycle fundamental relation was: p2〉p1〉p0_a〉p0_b.P1 and p2 are the large period grating branch, and exist fixing small periodic inequality between the two cycle; P0a and p0b are the minor cycle grating branch, and exist fixing small periodic inequality between the two cycle.Accompanying drawing 16 shows when scanning perpendicular to grating orientation, the signal S of four different cycles of acquisition _{P0_a}, S _{P0_b}, S _P1, S _P2, p2〉and p1〉p0_a〉p0_b, p0_b, p0_a, p1, p2 are respectively S _{P0_b}, S _{P0_a}, S _P1, S _P2Cycle.Utilize the signal of these four different cycles, can obtain very high alignment precision when realizing big capture range, the ultimate principle of a kind of method that the present invention uses is as follows:

1) utilizes two than large period p1 and the big capture range of p2 acquisition.

Two of alignment mark are expressed as than the small periodic inequality that exists between the large period:

Δ p=p2-p1 (formula 2)

The maximum capture range that can be provided by the independent p1 of branch is

Or be expressed as This is because the cycle is cycle of the interference fringe of positive and negative one-level light after relevant on the image planes of the branch of p1 to be

And capture range allow promptly that the desired locations error drops on signal certain determine in the cycle; And the corresponding cycle for the maximum capture range that the branch of p2 can provide is The maximum capture range that two independent branches can provide is

Its capture range is not very big, the prealignment deviation greater than

Situation under can't determine the mark center position definite be positioned at which signal period.And if we use the grating in two cycles simultaneously, then can expand capture range to P ', wherein:

$P\&prime;=\frac{\frac{1}{2}\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="C200710045495E00212.png,C200710045495E00231.png"\; state="\{\{state\}\}">p</figure-callout>}1\&times;\frac{1}{2}\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="C200710045495E00161.png"\; state="\{\{state\}\}">p</figure-callout>}2}{\frac{1}{2}\mathrm{\&Delta;p}}=\frac{1}{2}\frac{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="C200710045495E00212.png,C200710045495E00231.png"\; state="\{\{state\}\}">p</figure-callout>}1\&times;p2}{(p2-p1)}$ (formula 3)

If promptly the error of mark center and desired locations less than P ' or

In, be center when scanning then according to the desired locations of appointment, can obtain the coarse alignment position of mark center.

2) utilize specific mathematical model, sampled signal is carried out match, obtain model parameter and peak.

Adopt following mathematical model, carry out match for the signal model of different cycles grating branch.

(formula 4)

(formula 5)

(formula 6)

Wherein, I (x) represents light intensity signal amplitude, P _iBe the cycle of each grating branch, a _iBe the linear fit parameter,

It is the initial phase fitting parameter.By the match of signal, thus the peak point of definite signal.

3) obtain the fine alignment position in conjunction with two coarse alignment position and two less period p 0_a, p0_b cycles than large period p1 and p2 acquisition.

Ideally, the coarse alignment position is S _P1And S _P2Phase coincidence point C _P1And C _P2(two signal phases are identical herein) in addition, by the appropriate design layout to four branches of mark, can guarantee fine alignment signal S _{P0_a}, S _{P0_b}Also at C _{P0_a}, C _{P0_b}A phase coincidence point appears in the place, and four phase coincidence point can be thought alignment point ideally, as shown in Figure 19; Under the actual conditions, because in the device manufacturing processes, mark and all can not accomplish accurate symmetry with reference to grating, and substrate marker is in technological process, various distortion situations can appear, so, in fact there is not the absolute accurate phase coincidence point of four periodic signals.And for four different cycles, technology causes that the situation of distortion is also different, under present technological conditions, be subject to the influence that technology causes distortion than large period, and processes is to also less than the minor cycle influence.Truth is four signal S _{P0_b}S _{P0_a}, S _P1, S _P2Whenever all can there be some deviations each other, as shown in Figure 20.In the case, four signal coincide point C of comprehensive utilization _{P0_a}, C _{P0_b}, C _P1And C _P2Information is determined the fine alignment position.The method of a kind of definite accurate aligned position of the present invention is:

At first in capture range, with S _P1, S _P2One of them signal is that benchmark finds both phase deviation smallest point C _P1And C _P2, these 2 are the coarse alignment position range, optional C _P1And C _P2Perhaps C is put as coarse alignment in the centre position between these 2 _CorSecondly with C _Cor, be reference point, seek S _{P0_a}Distance C on the signal _CorThe phase deviation smallest point C that point is nearest _{P0_a}And S _{P0_b}Distance C on the signal _CorThe phase deviation smallest point C that point is nearest _{P0_b}, be aligned position point C with the two centre position _Fin, that is:

C _Fin=0.5 (C _{P0_a}+ C _{P0_b}) (formula 8)

Accompanying drawing 21 shows litho machine scanning on time, determines the basic step of aligned position:

(a) gather each grating branch ± 1 grade light intensity signal and relative position signals in the alignment scanning process in real time;

(b) by model of fit (formula 4～6), finish match from the fine alignment signal of large period grating branch coarse alignment signal and minor cycle grating branch;

(c) determine the coarse alignment position by the coarse alignment signal;

(d) on the fine alignment signal, seek the peak point nearest apart from the coarse alignment position;

(e) comprehensive utilization is determined the fine alignment position from the peak point on the fine alignment signal of different fine grating branch.

Claims (15)

1, a kind of mark that is used for the litho machine aligning, described mark contains the grating of 4 different cycles in one direction, comprising two large period grating branch and two minor cycle grating branch, it is characterized in that: utilize two large period grating branch to obtain big capture range and coarse alignment position, utilize two minor cycle grating branch to obtain the fine alignment position.

2, according to claim 1ly be used for the mark that litho machine is aimed at, it is characterized in that: the cycle of described two large period grating branch at 10um between the 20um, the cycle of two minor cycle grating branch at 1um between the 5um.

3, according to claim 2ly be used for the mark that litho machine is aimed at, it is characterized in that: the cycle of described large period grating branch should be 3 to 9 times of cycle of described minor cycle grating branch.

4, the mark that is used for the litho machine aligning according to claim 3 is characterized in that: have the periodic inequality less than 2um between described two large period grating branch.

5, the mark that is used for the litho machine aligning according to claim 3 is characterized in that: have the periodic inequality less than 1um between described two minor cycle grating branch.

6, the mark that is used for the litho machine aligning according to claim 1, it is characterized in that: described alignment mark is positioned on the base station, or is positioned in the substrate.

7, the mark that is used for the litho machine aligning according to claim 1, it is characterized in that: described alignment mark comprises two groups of described gratings that are distributed on the orthogonal directions, and every group of described grating all contains 4 different cycles.

8, the mark that is used for the litho machine aligning according to claim 7, it is characterized in that: the arrangement mode of described two groups of gratings comprises spaced apart, cross arrangement, or in surface level, become other array modes to arrange.

9, the mark that is used for the litho machine aligning according to claim 8, it is characterized in that: the grating of described spaced apart, arrangement separately is in line.

10, the mark that is used for the litho machine aligning according to claim 9 is characterized in that: the described grating that is in line and arranges, distribution arrangement is parallel with the direction of grating fringe, becomes block form phase mark structure all around.

11, the mark that is used for the litho machine aligning according to claim 9 is characterized in that: the described grating that is in line and arranges, distribution arrangement is vertical with the direction of grating fringe, becomes tandem phase structure all around.

12, the mark that is used for the litho machine aligning according to claim 1 is characterized in that: described alignment mark becomes isometric lines to arrange along the gap, graduation border for the treatment of alignment area.

13, a kind of alignment methods of using the described mark of claim 1 is characterized in that, may further comprise the steps:

(1) gathers each grating branch ± 1 grade light intensity signal and relative position signals in the scanning process in real time;

(2) will carry out match from the coarse alignment signal of described large period grating branch and the fine alignment signal of described minor cycle grating branch;

(3) determine the coarse alignment position by described coarse alignment signal;

(4) on described fine alignment signal, seek the peak point nearest apart from the coarse alignment position;

(5) comprehensive utilization is determined the fine alignment position from the peak point on the described fine alignment signal of different fine grating branch.

14, alignment methods according to claim 13, it is characterized in that: describedly determine that by the coarse alignment signal method of coarse alignment position is by the addition with the alignment mark signal of described two large period grating branch, in moving, obtain the position of the alignment mark signal sum maximum of described two large period grating branch, be the position that the alignment mark signal of described two large period grating branch all is in peak state, with the position of the alignment mark signal sum maximum of described two large period grating branch as the coarse alignment position.

15, alignment methods according to claim 13, it is characterized in that: the method for described definite fine alignment position is near described coarse alignment position, obtain to be in respectively from the alignment mark signal of nearest described two the minor cycle grating branch in described coarse alignment position the position of peak state in moving, the flat accurate value of position that is in peak state with the alignment mark signal of described two minor cycle grating branch respectively is as accurate aligned position.

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