CN100527000C - Aligning mark and aligning system - Google Patents
Aligning mark and aligning system Download PDFInfo
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- CN100527000C CN100527000C CNB2007100454964A CN200710045496A CN100527000C CN 100527000 C CN100527000 C CN 100527000C CN B2007100454964 A CNB2007100454964 A CN B2007100454964A CN 200710045496 A CN200710045496 A CN 200710045496A CN 100527000 C CN100527000 C CN 100527000C
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Abstract
The present invention provides an alignment system, alignment method and alignment mark. The alignment mark comprises a long cycle fiber grating branch and a short cycle fiber grating branch. The present invention adopts an optical-path-splitting detection system, simultaneously has signal acquisition, treatment and fitting for plus or minus 1 grade diffraction light coherent imaging of the long cycle fiber grating branch and the plus or minus 1 grade diffraction light coherent imaging of the short cycle fiber grating branch which constitute a fiber grating mark, and further combines phase information of two combinations of the signals to determine the accurate alignment position. Due to only adopting the plus or minus 1 grade diffraction light coherent imaging, the present invention avoids the adoption of a space separation device with a wedge plate regulating device required by high-grade diffraction light. By adopting the short cycle fiber grating branch, the obtainment of the higher alignment accuracy can be guaranteed. The present invention avoids crosstalk phenomenon between coarse alignment signals and fine alignment signals by adopting the optical-path-splitting detection system.
Description
Technical field
The present invention relates to a kind of alignment system and alignment mark, relate in particular to a kind of and integrated circuit or other microdevice and make relevant alignment system and the alignment mark of lithographic equipment in the field.
Background technology
Lithographic equipment of the prior art is mainly used in the manufacturing of integrated circuit (IC) or other microdevice.By lithographic equipment, the multilayer mask with different mask patterns is imaged on the wafer that is coated with photoresist under accurately aiming at successively, for example semiconductor crystal wafer or LCD plate.Lithographic equipment is divided into two classes substantially, one class is the stepping lithographic equipment, the mask pattern single exposure is imaged on an exposure area of wafer, wafer moves with respect to mask subsequently, next exposure area is moved to mask pattern and projection objective below, again mask pattern is exposed in another exposure area of wafer, repeat the picture that this process all exposure areas on wafer all have mask pattern.Another kind of is the step-scan lithographic equipment, and in said process, mask pattern is not the single exposure imaging, but the scanning mobile imaging by the projection light field.In the mask pattern imaging process, mask and wafer move with respect to optical projection system and projected light beam simultaneously.
Critical step is with mask and wafer alignment in the lithographic equipment.After exposing on wafer, the ground floor mask pattern from device, removes, after the PROCESS FOR TREATMENT that wafer is correlated with, carry out the exposure of second layer mask pattern, but for guarantee second layer mask pattern and subsequently the picture of mask pattern mask and wafer accurately need be aimed at respect to the accurate location of exposed mask pattern image on the wafer.IC device by the photoetching technique manufacturing needs multiexposure, multiple exposure to form multilayer circuit in wafer, for this reason, requires the configuration alignment system in the lithographic equipment, realizes the accurate aligning of mask and wafer.When characteristic dimension requires more hour, the requirement of alignment precision and consequent requirement to alignment precision are become strict more.
The alignment system of lithographic equipment, its major function are to realize mask-wafer alignment before the alignment exposure, promptly measure the coordinate (X of wafer in coordinate system of machine
W, Y
W, Φ
WZ), and the coordinate (X of mask in coordinate system of machine
R, Y
R, Φ
RZ), and calculate the position of mask with respect to wafer, to satisfy the water of wanting of alignment precision.Prior art has two kinds of alignment scheme.A kind of is the TTL technique of alignment that sees through camera lens, the alignment mark of the periodic phase optical grating construction that laser lighting is provided with on wafer, diffraction light or scattered light by the collected wafer alignment mark of the projection objective of lithographic equipment shine on mask alignment mark, and this alignment mark can be amplitude or phase grating.Behind the mask mark detector is set, when scanning wafer under projection objective, surveys the light intensity that sees through the mask mark, the maximal value of detector output is represented correct alignment position.This aligned position provides zero reference for the position measurement that is used to monitor the laser interferometer that moves wafer platform position.Another kind is an OA off-axis alignment technology, is positioned at the reference mark of datum plate on a plurality of alignment marks on the wafer and the wafer platform by the off-axis alignment systematic survey, realizes that wafer alignment and wafer platform aim at; The reference mark of datum plate is aimed at mask alignment mark on the wafer platform, realizes mask registration; The position relation of mask and wafer be can obtain thus, mask and wafer alignment realized.
At present, the most alignment so that adopts of lithographic equipment is a grating alignment.Grating alignment is meant that even illumination beam on the grating alignment mark diffraction takes place, and the emergent light behind the diffraction carries the full detail about alignment mark structure.Senior diffraction light scatters from the phase alignment grating with wide-angle, after filtering zero order light by spatial filter, gather diffraction light ± 1 order diffraction light, the perhaps raising that requires along with CD, gather multi-level diffraction light (comprising senior) simultaneously in picture plane interference imaging, through photodetector and signal Processing, determine the centering adjustment position.
Chinese patent CN03164859.2 discloses a kind of off-axis alignment system of 4f system architecture, and this alignment system adopts voussoir array or wedge group to realize the overlapping and relevant of multi-level diffraction light; By surveying the alignment mark picture, obtain the registration signal of sinusoidal output through transmitted light intensity with reference to grating; The grating branch that comprises two different cycles that is labeled as owing to this alignment system employing, have small periodic inequality between the cycle of each grating branch, based on vernier caliper principle, the signal of collection is at some weeks after date, to there be a peak value alignment point, thereby determine accurate aligned position.Adopt voussoir array or wedge to make up and realize the overlapping, relevant of multi-level diffraction light.The face type and the angle of wedge coherence request of two voussoirs that the positive and negative same stages of birefringence is inferior are very high; And the requirement of the processing and manufacturing of wedge group, assembling and adjustment is also very high, and the specific implementation engineering difficulty of getting up is bigger, costs dearly.
U.S. Pat .6,297,876B1 has introduced a kind of off-axis alignment method, also is the aligning of realizing mask mark and wafer mark 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 carries out match 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, in the reality along with mark (particularly silicon chip mark) reflected signal (particularly high order signal) power is low excessively, the highest alignment precision then may cause to utilize in the reality high order signal, so can not be provided reliably.
Summary of the invention
The object of the present invention is to provide a kind of improved alignment system and alignment mark that is used for lithographic equipment, to realize bigger capture range and higher alignment precision.
To achieve the above object, the invention provides a kind of alignment system that is used for lithographic equipment, this alignment system comprises:
Light source module is used to provide the alignment system illuminating bundle; Lighting module is used for described aligning illuminating bundle is transferred to alignment mark; Mark module is used to make the coarse alignment signal to be imaged on first with reference to grating, and the fine alignment signal is imaged on second with reference on the grating; Image-forming module; Be used for collecting the diffraction light or the reflected light of alignment mark, and utilize first imaging optical path to the coarse alignment grating branch coherent imaging of forming alignment mark and utilize second imaging optical path forming the fine alignment grating branch coherent imaging of alignment mark by object lens; Input and processing module are used to handle first light signal and second light signal, and determine the positional information of alignment mark in conjunction with the phase information of the phase information of first light signal and second light signal; Described image-forming module comprises object lens, beam splitter and imaging optical system at least, and the diffraction light of alignment mark after entering imaging optical system behind the beam-splitting surface of beam splitter, is imaged on reference on the grating after collimated; Described beam splitter comprises reflector space and regional transmission, and reflector space is positioned at the outer ring position of beam-splitting surface, and regional transmission is positioned at the endocyclic position of beam-splitting surface; Described first light signal derive from alignment mark coarse grating branch ± 1 order diffraction light coherent imaging scanned first is with reference to grating; Described second light signal derive from alignment mark fine grating branch ± 1 order diffraction light coherent imaging scanned second is with reference to grating.
Wherein light source module provides the illuminating bundle that comprises a plurality of discrete wavelength, comprises the illuminating bundle of two discrete wavelength at least.
Wherein lighting module comprises Transmission Fibers and lamp optical system, and lamp optical system comprises the polarizer, lens, illuminating aperture diaphragm, polarization beam apparatus and polarization beam splitting face,
Wherein mark module comprises alignment mark and with reference to grating, be used for the emergent light behind the illuminating bundle diffraction is carried full detail about alignment mark structure, and will through intensity modulation sinusoidal signal with constant cycle with reference to grating.Wherein the alignment mark system can be one or more two-way grating marker, one or more unidirectional grating marker; With reference to grating, also can be for one or more two-way grating marker with reference to grating, also can be for one or more unidirectional grating marker with reference to grating.With reference to grating comprise first with reference to grating and second with reference to grating, first is used for the detection of coarse alignment signal with reference to grating, second is used for the detection of fine alignment signal with reference to grating.
Wherein reflector space can be realized whole reflections of diffraction light by the plating reflectance coating, regional transmission can be realized whole transmissions of diffraction light by the plating anti-reflection film, regional transmission also can be dug through the form in hole by the appropriate location, realize whole transmissions of diffraction light, regional transmission also can be realized whole transmissions of diffraction light by all hollowing out.
Input and processing module comprise photodetector, photosignal conversion and amplifier, analog to digital converter, match signal processor, position data processor, position data conversion and sampling thief, base station motion controller, work schedule controller.
Wherein first light signal is the fixed cycle signal of two groups of sinusoidal forms, and there is a small periodic inequality in the cycle of two groups of signals, second light signal can be the fixed cycle signal of two groups of sinusoidal forms, and can there be a small periodic inequality in the cycle of two groups of signals, and second light signal also can be the fixed cycle signal of one group of sinusoidal form.
The present invention also provides a kind of alignment mark system that is used for lithographic equipment, this system comprises, two-way grating marker, be used for supporting to X to Y to scan mode, also can support the diagonal line scan mode, obtain simultaneously X to Y to aligned position, improve to aim at efficient or unidirectional grating marker, be used for the detection of single direction; With reference to grating, be used for the detection of light intensity signal; Described unidirectional grating marker is combined by following several modes:
(1), two than the less periodic optical grating of large period grating branch and two branch;
(2) only there are two than the large period grating branch;
(3) two less periodic optical grating branches are only arranged;
(4) two than the less periodic optical grating of large period grating branch and branch;
(5) two less periodic optical grating branches and one are than the large period grating branch.
Be used to produce the coarse alignment signal than the large period grating branch in the described alignment mark, less periodic optical grating branch is used to produce the fine alignment signal; The sinusoidal form signal that described coarse alignment signal is the constant cycle; The sinusoidal form signal that described fine alignment signal is the constant cycle.
Wherein two-way grating marker by x to forming to marker combination with y, the mark of each direction comprises one group of large period grating branch and one group of minor cycle grating branch, can be used for simultaneously x to y to detection, fine grating branch and the cross arrangement of coarse grating branch, whole mark is formed quadrilateral structure, but the center etching has crosshair, is used for manual the aligning and Video Detection.
Wherein unidirectional grating marker can be made up of one group of unidirectional big grating cycle and one group of unidirectional little grating cycle, also can only be made up of one group of unidirectional large period grating or one group of unidirectional minor cycle grating.
Wherein the large period grating branch is used to produce the coarse alignment signal in the alignment mark, and the minor cycle grating branch is used to produce the fine alignment signal.
Wherein with reference to grating comprise first with reference to grating and second with reference to grating, be respectively applied for the detection of large period grating branch and minor cycle grating branch light intensity signal, first with reference to grating on the locus distributes, coarse grating branch in the corresponding two-way mark of difference, and on the cycle size, be respectively 1/2 of coarse grating branch cycle in the corresponding two-way mark.Second with reference to grating on the locus distributes, fine grating branch in the corresponding two-way mark respectively, and on the cycle size is respectively 1/2 of fine grating branch cycle in the corresponding two-way mark.
Basic alignment principles of the present invention is:
After alignment scanning finishes, at first utilize first to survey first light signal (coarse alignment signal) that light path obtains, the peak value coincide point of coarse alignment signal is determined in the match of the signal that passes through, the position of this point is the coarse alignment position; Be benchmark with the coarse alignment position then, the peak value coincide point on second light signal (fine alignment signal) that the searching second detection light path obtains is aligned position.
When if second light signal only comprises the signal of a sinusoidal form, aim at strategy and be this moment: with the coarse alignment position is benchmark, seeks immediate wave crest point on this second light signal, and this wave crest point is aligned position.
The invention provides a kind of alignment system, alignment methods and alignment mark, this alignment mark comprises large period grating branch and minor cycle grating branch, adopt and divide the light path detection system, simultaneously large period grating branch ± 1 order diffraction light coherent imaging and the minor cycle grating branch ± 1 order diffraction light coherent imaging of forming grating marker carried out signals collecting, processing and match respectively, and, determine accurate aligned position in conjunction with the phase information of two groups of signals.Owing to only adopt ± 1 diffraction light coherent imaging, the apart device of having avoided senior diffraction light need adopt to have the wedge regulating device; Adopt the minor cycle grating branch, can guarantee to obtain high alignment precision; Adopt and divide the light path detection system, avoided crosstalk phenomenon between coarse alignment signal and the fine alignment signal.
Description of drawings
Fig. 1 is for using litho machine alignment system synoptic diagram of the present invention;
Fig. 2 is a wafer alignment system architecture synoptic diagram of the present invention;
Fig. 3 for be used for simultaneously x to y to the two-way mark structural representation of aiming at;
Fig. 4 is the two-way mark structural representation that has crosshair;
Fig. 5 is the diagonal line scan mode synoptic diagram of two-way mark;
Fig. 6 is the structural representation of a kind of x to the marking groove mark;
Fig. 7 is the structural representation of a kind of x to the marking groove mark;
Fig. 8 is the structural representation of a kind of x to the marking groove mark;
Fig. 9 is the structural representation of a kind of x to the marking groove mark;
Figure 10 is a kind of distribution form synoptic diagram on wafer of marking groove mark;
Figure 11 is a kind of distribution form synoptic diagram on wafer of marking groove mark;
Figure 12 is the structural representation of beam-splitting surface;
Figure 13 is first with reference to the grating structural representation;
Figure 14 is second with reference to the grating structural representation;
Figure 15 is the citation form of first light signal (coarse alignment signal);
Figure 16 is the citation form of second light signal (fine alignment signal).
Embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present invention is further described.
Accompanying drawing 1 shows a kind of prior art alignment system synoptic diagram that litho machine uses.The formation of lithographic equipment comprises: the illuminator 8 that is used to provide exposing light beam; Be used to support the mask platform 6 of mask 4, the alignment mark 2 that mask pattern is arranged on the mask 4 and have periodic structure; Be used for the mask pattern on the mask 4 is projected to projection optical system PL on the wafer 7; Be used for the base station 9 of supporting wafer 7, be carved with alignment mark 3 on the base station 9; What be used for base station and wafer alignment aims at the aligning radiation source 300 that throws light on from shaft alignement optical system 500 with providing; The signal processing unit 200 that is used for registration signal collection, processing and match; The drive system 10 and measuring system IFx and the IFy that are used for the base station servo motion.
Wherein, illuminator 8 comprises that a light source, one make the lens combination of illumination homogenising, catoptron, a condenser (all not shown among the figure).As a light source cell, adopt KrF excimer laser (wavelength 248nm), ArF excimer laser (wavelength 193nm), F
2Laser instrument (wavelength 157nm), Kr
2Laser instrument (wavelength 146nm), Ar
2Laser instrument (wavelength 126nm) or use ultrahigh pressure mercury lamp (g-line, i-line) etc.The exposing light beam IL of illuminator 8 uniform irradiations is radiated at the alignment mark 2 on the mask 4, 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, carry out process of fitting treatment 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, promptly mask and base station aims at.
Fig. 2 is the wafer alignment system architecture synoptic diagram in the embodiment of the invention, and this alignment system mainly is made up of light source module, lighting module, mark module, image-forming module, input and processing module etc.The principal character of this alignment system is, based on the alignment mark imaging that comprises a plurality of periodic optical grating branch, adopt the method for coarse alignment and fine alignment separate detection, the different cycles grating branch of separate detection alignment mark, when improving alignment precision, avoided crosstalking mutually between coarse alignment and the fine alignment signal.After coarse alignment was only surveyed large period grating branch ± 1 order diffraction light coherent imaging, the light intensity of transmission after coarse alignment is with reference to grating was determined bigger capture range and coarse alignment location by the phase information of transmitted light intensity; After fine alignment was surveyed minor cycle grating branch ± 1 order diffraction light coherent imaging, the light intensity of transmission after fine alignment is with reference to grating was determined the fine alignment position by the phase information of transmitted light intensity.Because fine alignment mark live width is less, improved alignment precision on the one hand, have stronger Technological adaptability on the other hand, can reduce of the influence of alignment mark asymmetrical deformation to alignment precision.Fine alignment and coarse alignment signal are through single pass, and synchronized sampling obtains; Being separated into of fine alignment and coarse alignment looks like and detection on the hardware, and group lens and input and processing module are shared before lighting module, the image-forming module.
The alignment system light source module provides the illuminating bundle that comprises a plurality of discrete wavelength, comprises the illuminating bundle of two discrete wavelength at least, for example, and 633nm and 785nm; Four discrete wavelength of preferential employing, and wherein have two wavelength at least near infrared or infrared band, for example, 532nm, 633nm, 785nm and 850nm.Multi-wavelength (λ
1, λ
2, λ
3And λ
4) illuminating bundle is through single-mode polarization maintaining fiber 301 transmission, is coupled into bundling device 303 through fiber coupler 302 then, outputs to the lighting module of alignment system again by single-mode polarization maintaining fiber 304.
Lighting module comprises Transmission Fibers and lamp optical system, and the multi-wavelength illuminating bundle passes through the polarizer 505, lens 506, illuminating aperture diaphragm 507 and lens 508 successively, and the polarization beam splitting face 509a through polarization beam apparatus 509 impinges perpendicularly on image-forming module then.511 form the Kohler illumination system from aperture diaphragm 507 to object lens.
Mark module comprises alignment mark and with reference to grating two parts.Wherein alignment mark is amplitude type or phase grating, is positioned on wafer 7 or the base station 9.Diffraction takes place in illumination beam to alignment mark, the emergent light behind the diffraction carries the full detail about alignment mark structure, forms light and dark periodicity hot spot striped behind image-forming module.Alignment mark is divided into unidirectional mark and two-way mark, unidirectional mark support x to or y to scan mode, two-way mark can support x to, y to the diagonal line scan mode.Be positioned at reference to grating on the picture plane of image-forming module, make for there is the optical material in striated chromium plating district on the surface, its fringe period size is equal with corresponding hot spot fringe period, and the chromium plating district is used for absorbing and the flare striped, non-chromium plating removes to be used for transmission hot spot striped, to realize the modulation light intensity signal.When light and dark hot spot strip-scanning is crossed with reference to grating, see through and to be modulated to sinusoid signal with constant cycle with reference to the light intensity behind the grating.Whole mark system can by first with reference to grating (seeing Figure 13) and second with reference to grating (seeing Figure 14), single or several two-way marks (seeing Fig. 3, Fig. 4), single or several x to (seeing Fig. 6～Fig. 9) constitute to mark with y, also can constitute with reference to grating, single or several two-way marks with reference to grating and second by first, perhaps by first with reference to grating and second with reference to grating, single or several x to constituting to mark with y.
Image-forming module comprises first imaging optical path (being the coarse alignment imaging optical path), second imaging optical path (being the fine alignment imaging optical path).Illuminating bundle impinges perpendicularly on base station alignment mark 1 that is positioned at base station 9 or the wafer alignment mark 5 that is positioned at wafer 7 through object lens 511, as Fig. 3～shown in Figure 9, through behind λ/4 wave plates 510, the hot spot that incides on the mark is a circularly polarized light, reflection and diffraction take place, on the frequency plane of object lens 511, produce a series of diffraction patterns, respectively the grating part of alignment mark different cycles.The diffraction light of alignment mark is behind lens 511 collimation, and the multi-wavelength diffraction light is at first through a spatial filter 512, and zero order light and senior diffraction light of the whole grating branch of mark filtered, and only keeps ± 1 order diffraction light and passes through.Be divided into two-way (Figure 12 is met personally in beam splitting) through the beam-splitting surface 513a of beam splitter 513 then, the one tunnel enters first imaging optical path, and another road enters second imaging optical path.First imaging optical path is the coarse alignment light path, the corresponding large period grating image of forming alignment mark; Second imaging optical path is the fine alignment light path, the corresponding minor cycle grating image of forming alignment mark.
When the illuminating bundle that adopts a plurality of discrete wavelength (for example: 532nm, 633nm, 785nm, when 850nm) throwing light on alignment mark simultaneously, the diffraction light of different wave length is overlapped, therefore, the signal of different wave length must separate detection.In first imaging optical path (coarse alignment light path), the first polychromatic light piece-rate system 514 is set, make the diffraction light of different wave length separate; Only provided wherein a kind of wavelength X among Fig. 2
1Light path, wavelength is λ
1Coarse grating branch ± 1 order diffraction light is through lens 515 coherent imagings, is imaged on first with reference to (first see Figure 13 with reference to grating) on the grating 516.
Another part multi-wavelength diffraction light through the beam-splitting surface 513a of beam splitter 513 beam splitting enters second imaging optical path (being the fine alignment light path), fine grating branch ± 1 order diffraction light of forming mark makes the diffraction light of different wave length separate through the second polychromatic light piece-rate system 517; Only provided wherein a kind of wavelength X among Fig. 2
1Light path, wavelength is λ
1± 1 order diffraction light is through lens 518 coherent imagings, is imaged on second with reference to (second see Figure 14 with reference to grating) on the grating 519.
Input and processing module mainly comprise photodetector, photosignal conversion and amplifier, analog to digital converter, match signal processor, position data processor, position data conversion and sampling thief, base station motion controller, work schedule controller etc.
In the alignment scanning process, the picture of forming the coarse grating branch of mark in first imaging optical path scans first with reference to grating 516, by being placed on optical fiber 102 with reference to the grating back, collect and pass through with reference to the light intensity signal behind the grating, and corresponding light intensity signal guided to photodetector 201a, light intensity signal is carried out the conversion of electric signal.Because the image of wafer mark is the continuous hot spot striped consistent with the optical grating construction form, when mark is at the uniform velocity mobile with respect to alignment optical system, these stripeds are also at the uniform velocity mobile 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, according to Fourier optics, can obtain the sinusoidal form signal of constant cycle, i.e. first light signal (coarse alignment signal), as shown in figure 15.The picture of forming the fine grating branch of mark in second imaging optical path scans second with reference to grating 519, by being placed on optical fiber 102 with reference to the grating back, collect and pass through with reference to the light intensity signal behind the grating, and corresponding light intensity signal guided to photodetector 201a, light intensity signal is carried out the conversion of electric signal, obtain the sinusoidal form signal of constant cycle, i.e. second light signal (fine alignment signal), as shown in figure 16.
Electric signal after photodetector changes is triggered by the unified of work schedule controller 207, and the collection that can guarantee to aim at electric signal is with synchronous through the displacement numerical value that position data is changed and sampling thief 205 is gathered, and the collection of coarse alignment signal and fine alignment signal is synchronous.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 match 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 match signal processor 203 through process of fitting treatment.
Accompanying drawing 3 show be used for simultaneously x to y to the two-way mark structural representation of aiming at.Wherein x is to comprising P1_x, P2_x, P3_x and four grating branch of P4_x, and its cycle is respectively P1, P2, P3 and P4; Y is to comprising P1_y, P2_y, P3_y and four grating branch of P4_y, and its cycle is respectively p1, p2, p3 and p4; X to mark and y to the center that is marked as be symmetrically distributed.Each grating branch cycle magnitude relationship of mark is:
P1〉p2〉p3〉p4 (formula 1)
P1 and P2 grating branch are the large period grating branch, are used for coarse alignment, exist fixing small periodic inequality, i.e. p1=p2+ Δ p between P1 and the P2 grating branch
1(formula 2); P3 and P4 grating branch are the minor cycle grating branch, are used for fine alignment, exist fixing small periodic inequality, i.e. p3=p4+ Δ p between P3 and the P4 grating branch
2(formula 3).This two-way alignment mark give the grating branch layout for the minor cycle grating branch is arranged between the large period grating branch, also can be the large period grating branch and be arranged between the minor cycle grating branch.
Accompanying drawing 4 shows the two-way mark structural representation that has crosshair R.Crosshair is positioned at the center of two-way mark, can image on the CCD camera photosurface, is used for the monitoring of manual alignment and video.
Accompanying drawing 5 shows the diagonal line scan mode synoptic diagram of two-way mark.Two-way mark not only support x to y to scan mode, also can support the diagonal line scan mode, obtain simultaneously x to y to aligned position, improve to aim at efficient.
Accompanying drawing 6 shows the structural representation of a kind of x to the marking groove mark.This mark is used for x to be aimed to scanning, comprises two fine alignment grating branch P3_x and P4_x.Here only provided the marking groove alignment mark of the type x direction, the alignment mark of y direction similarly.
Accompanying drawing 7 shows the structural representation of a kind of x to the marking groove mark.This mark is used for x to be aimed to scanning, comprises two coarse alignment grating branch P1_x and P2_x.Here only provided the marking groove alignment mark of the type x direction, the alignment mark of y direction similarly.
Accompanying drawing 8 shows the structural representation of a kind of x to the marking groove mark.This mark is used for x to be aimed to scanning, comprises three grating branch, and the center of mark is fine alignment grating branch P3_x or P4_x, and the place, two ends is respectively coarse alignment grating branch P1_x and P2_x.Here only provided the marking groove alignment mark of the type x direction, the alignment mark of y direction similarly.
Accompanying drawing 9 shows the structural representation of a kind of x to the marking groove mark.This mark is used for x to be aimed to scanning, comprises four grating branch, is distributed as fine alignment grating branch P3_x and P4_x about the center of mark, and the place, two ends is respectively coarse alignment grating branch P1_x and P2_x.Here only provided the marking groove alignment mark of the type x direction, the alignment mark of y direction similarly.
In the marking groove alignment mark shown in accompanying drawing 7, accompanying drawing 8 and the accompanying drawing 9, but also crosshair in the etching of the blank space of mark center image on the CCD face camera photosurface, be used for manual aim at and video is monitored.
Accompanying drawing 10 and accompanying drawing 11 have provided two kinds of distribution forms on wafer of marking groove mark respectively.For Fig. 3 and two-way mark shown in Figure 4, need on wafer, to mark certain zone separately, be used for the cloth tagging, can be arranged in the imperfect die of crystal round fringes.
Accompanying drawing 12 shows beam-splitting surface 513a projection structural representation on surface level.Beam-splitting surface comprises two regional A and B, and regional A is positioned at the outer ring position of beam-splitting surface, is coated with reflectance coating, is reflector space, make to constitute alignment mark fine grating ± 1 order diffraction light reflects fully; Area B is positioned at the endocyclic position of beam-splitting surface, is coated with anti-reflection film, is regional transmission, make to constitute alignment mark coarse grating ± 1 order diffraction light directly sees through.Another form of beam-splitting surface can be that the diffraction light position of regional transmission correspondence forms through hole, allows diffracted beam directly therefrom pass, and as shown in Figure 12, need not to plate anti-reflection film this moment.Beam-splitting surface another more simple form be that directly regional transmission B to be dug be a through hole, the diffracted beam that allows expectation see through all therefrom passes through.Adopt so beam splitter of design, can make the coarse grating branch that forms alignment mark ± 1 order diffraction light enters first fully and surveys light path, and fine grating branch ± 1 order diffraction light enters second fully and surveys light path, improved the utilization factor of luminous energy.
Accompanying drawing 13 shows first with reference to the grating structural representation.First comprises four with reference to grating branch with reference to grating, be respectively x to reference grating branch RG1_x and RG2_x, y on the locus distributes, distinguishes the P1_x of coarse grating branch, P2_x, P1_y and P2_y in the alignment mark corresponding shown in Figure 2 to reference grating branch RG1_y and RG2_y.Owing to only adopt ± 1 grade of optical diffraction imaging, thus first the cycle with reference to grating branch be correspondence the alignment mark grating branch cycle 1/2.
Accompanying drawing 14 shows second with reference to the grating structural representation.Second comprises four with reference to grating branch with reference to grating, be respectively x to reference grating branch RG3_x and RG4_x, y on the locus distributes, distinguishes the P3_x of fine grating branch, P4_x, P3_y and P4_y in the alignment mark corresponding shown in Figure 2 to reference grating branch RG3_y and RG4_y.Owing to only adopt ± 1 grade of optical diffraction imaging, thus second the cycle with reference to each branch of grating be correspondence the alignment mark grating branch cycle 1/2.
Accompanying drawing 15 shows the citation form of first light signal (coarse alignment signal).The coarse alignment signal comprises the fixed cycle signal SP1 and the SP2 of two groups of sinusoidal forms and since only adopt to form the P1 of coarse grating branch of alignment mark and P2 ± 1 grade of optical diffraction imaging, so its signal period is 1/2 of P1 and the P2 grating branch cycle.Because have small periodic inequality between P1 of coarse grating branch and the P2, based on vernier caliper principle, in certain number of cycles, the two will have the coincide point x of a peak value
01
Accompanying drawing 16 shows the citation form of second light signal (fine alignment signal).The fine alignment signal can comprise the fixed cycle signal SP3 and the SP4 of two groups of sinusoidal forms and since only adopt to form the P3 of fine grating branch of alignment mark and P4 ± 1 grade of optical diffraction imaging, so its signal period is 1/2 of thick P3 and the P4 grating branch cycle.Because have small periodic inequality between P3 of fine grating branch and the P3, by vernier caliper principle, in certain number of cycles, the two will have the coincide point x of a peak value
02For marking groove mark shown in Figure 8, the fine alignment signal also can be the signal SP3 or the SP4 of a sinusoidal form.
In theory, by rational design, can guarantee coarse alignment signal peak coincide point x
01With fine alignment signal peak coincide point x
02Overlap fully, but because deformed mark, stochastic error in the actual production, and the influence of the factors such as systematic error that cause of coarse alignment and fine alignment separate detection, x
01And x
02Between have small site error.
The present invention is used for the alignment methods of lithographic equipment, comprising:
The ultimate principle of aiming at is: after alignment scanning finishes, at first utilize first to survey first light signal (coarse alignment signal) that light path obtains, the peak value coincide point x of coarse alignment signal is determined in the match of the signal that passes through
01, the position of this point is the coarse alignment position; Then with coarse alignment position x
01Be benchmark, the peak value coincide point x on second light signal (fine alignment signal) that the searching second detection light path obtains
02, be aligned position.When if second light signal only comprises the signal of a sinusoidal form, the aligning strategy of this moment is: with coarse alignment position x
01Be benchmark, seek on this second light signal near x
01Wave crest point, this wave crest point is aligned position.
Claims (24)
1, a kind of alignment system that is used for lithographic equipment comprises:
Light source module is used to provide the alignment system illuminating bundle;
Lighting module is used for described aligning illuminating bundle is transferred to alignment mark;
Mark module is used to make emergent light behind the illuminating bundle diffraction to carry full detail about alignment mark structure, will be the sinusoidal signal with constant cycle through the intensity modulation with reference to grating;
Image-forming module, be used for collecting the diffraction light or the reflected light of alignment mark, and utilize first imaging optical path to the coarse alignment grating branch coherent imaging of forming alignment mark and utilize second imaging optical path forming the fine alignment grating branch coherent imaging of alignment mark by object lens;
Input and processing module are used to handle first light signal and second light signal, and determine the positional information of alignment mark in conjunction with the phase information of the phase information of first light signal and second light signal;
It is characterized in that: described image-forming module comprises object lens, beam splitter and imaging optical system at least, and the diffraction light of alignment mark after entering imaging optical system behind the beam-splitting surface of beam splitter, is imaged on reference on the grating after collimated; Described beam splitter comprises reflector space and regional transmission, and reflector space is positioned at the outer ring position of beam-splitting surface, and regional transmission is positioned at the endocyclic position of beam-splitting surface;
Described first light signal derive from alignment mark coarse grating branch ± 1 order diffraction light coherent imaging scanned first is with reference to grating; Described second light signal derive from alignment mark fine grating branch ± 1 order diffraction light coherent imaging scanned second is with reference to grating.
2, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described light source module comprises the illuminating bundle of two or more discrete wavelength.
3, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described lighting module comprises Transmission Fibers and lamp optical system, wherein illuminating bundle enters illuminator through Transmission Fibers.
4, according to the described alignment system that is used for lithographic equipment of claim 3, it is characterized in that: described lamp optical system is the Kohler illumination system.
5, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described mark module comprises alignment mark and with reference to grating, illumination beam is behind alignment mark, form light and dark periodicity hot spot striped, through with reference to behind the grating, be modulated into sinusoidal signal.
6, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described reflector space is coated with reflectance coating.
7, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described regional transmission is coated with anti-reflection film.
8, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described regional transmission has dug through hole.
9, the alignment system that is used for lithographic equipment according to claim 1, it is characterized in that: described regional transmission all hollows out.
10, the alignment system that is used for lithographic equipment according to claim 1 is characterized in that: described first light signal is the fixed cycle signal that has two groups of sinusoidal forms of one-period difference.
11, the alignment system that is used for lithographic equipment according to claim 1 is characterized in that: described second light signal is the fixed cycle signal that has two groups of sinusoidal forms of one-period difference.
12, the alignment system that is used for lithographic equipment according to claim 1 is characterized in that: the fixed cycle signal that described second light signal is one group of sinusoidal form.
13, a kind of alignment mark system of the employing of alignment system according to claim 1, described alignment mark system comprises:
Two-way grating marker, be used for supporting to X to Y to scan mode, also can support the diagonal line scan mode, obtain simultaneously X to Y to aligned position;
Unidirectional grating marker is used for the detection of single direction;
With reference to grating, be used for the detection of light intensity signal;
Described unidirectional grating marker is combined by following several modes:
(1), two than the less periodic optical grating of large period grating branch and two branch;
(2) only there are two than the large period grating branch;
(3) two less periodic optical grating branches are only arranged;
(4) two than the less periodic optical grating of large period grating branch and branch;
(5) two less periodic optical grating branches and one are than the large period grating branch.
Be used to produce the coarse alignment signal than the large period grating branch in the described alignment mark, less periodic optical grating branch is used to produce the fine alignment signal; The sinusoidal form signal that described coarse alignment signal is the constant cycle; The sinusoidal form signal that described fine alignment signal is the constant cycle.
14, the alignment mark system that adopts according to the described alignment system of claim 13, it is characterized in that: described alignment mark system comprises: with reference to grating, single or a plurality of two-way mark, single or a plurality of unidirectional mark.
15, the alignment mark system that adopts according to the described alignment system of claim 13, it is characterized in that: described alignment mark system comprises with reference to grating, single or a plurality of two-way grating marker.
16, the alignment mark system that adopts according to the described alignment system of claim 13, it is characterized in that: described alignment mark system comprises: with reference to grating, single or a plurality of unidirectional grating marker.
17, the alignment mark system that adopts according to the described alignment system of claim 13, it is characterized in that: described two-way grating marker by x to forming to marker combination with y, the mark of each direction comprises one group of large period grating branch and one group of minor cycle grating branch, be used for simultaneously x to y to detection.
18, the alignment mark system that adopts according to the described alignment system of claim 13 is characterized in that: in the described two-way grating marker, and fine grating branch and the cross arrangement of coarse grating branch, whole mark is formed quadrilateral structure.
19, the alignment mark system that adopts according to the described alignment system of claim 13, it is characterized in that: the etching of described two-way grating mark center has crosshair.
20, the alignment mark system that adopts according to the described alignment system of claim 13 is characterized in that: on the described picture plane that is positioned at image-forming module with reference to grating, its surface is for there to be the optical material in striated chromium plating district to make.
21, the alignment mark system that adopts according to the described alignment system of claim 13 is characterized in that: the cycle size of the striped in the chromium plating district on the described picture plane equates with corresponding hot spot fringe period.
22, the alignment mark system that adopts according to the described alignment system of claim 13 is characterized in that: described first with reference to grating on the cycle size, be respectively 1/2 of coarse grating branch cycle in the corresponding two-way mark.
23, the alignment mark system that adopts according to the described alignment system of claim 13 is characterized in that: described second with reference to grating on the cycle size, be respectively 1/2 of fine grating branch cycle in the corresponding two-way mark.
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| CNB2007100454964A CN100527000C (en) | 2007-08-31 | 2007-08-31 | Aligning mark and aligning system |
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| CN101299132B (en) * | 2008-05-27 | 2010-06-02 | 上海微电子装备有限公司 | Aligning mark used for photolithography equipment aligning system and its use method |
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| CN105108330A (en) * | 2015-08-20 | 2015-12-02 | 京东方科技集团股份有限公司 | Beam splitter, laser generator and excimer laser annealing device |
| JP6969361B2 (en) * | 2017-12-21 | 2021-11-24 | 日本電信電話株式会社 | Optical element |
| JP2019196511A (en) * | 2018-05-08 | 2019-11-14 | 住友重機械工業株式会社 | Plate processor and plate processing method |
| CN108735645A (en) * | 2018-05-24 | 2018-11-02 | 德淮半导体有限公司 | Wafer alignment method and wafer alignment device |
| CN113655695B (en) * | 2021-09-02 | 2023-11-07 | 西华大学 | Composite photoetching alignment system and method based on medium microsphere super-resolution imaging |
| CN115031626B (en) * | 2022-05-05 | 2023-08-18 | 智慧星空(上海)工程技术有限公司 | Substrate coordinate measuring method |
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