CN106814557B

CN106814557B - Alignment system and alignment method

Info

Publication number: CN106814557B
Application number: CN201510859907.8A
Authority: CN
Inventors: 于大维; 杜荣
Original assignee: Shanghai Micro Electronics Equipment Co Ltd; Shanghai Micro and High Precision Mechine Engineering Co Ltd
Current assignee: Shanghai Xinshang Microelectronics Technology Co ltd; Shanghai Micro Electronics Equipment Co Ltd
Priority date: 2015-11-30
Filing date: 2015-11-30
Publication date: 2019-04-30
Anticipated expiration: 2035-11-30
Also published as: CN106814557A

Abstract

The present invention proposes a kind of pair of Barebone and alignment methods, this includes: mask to Barebone, provides projection exposure pattern and alignment mark；Projection objective focal plane measurement markers are set on the mask；Projection objective is imaged onto silicon wafer side's image space focal plane to exposing patterns, the label on mask；Work stage, same lens shaft, datum plate and silicon wafer are carried, wherein alignment mark, projection objective focal plane measurement markers and focusing label are imaged with lens shaft, datum plate carries focusing label and reference marker, and horizontal direction and vertical measuring basis are provided, silicon wafer carries silicon wafer alignment mark；Focusing and leveling system levels silicon chip surface, and control silicon wafer upper surface is overlapped with silicon wafer focal plane；Off-axis alignment system is directed at silicon wafer pattern.The present invention is directed to establish unified measuring basis for focusing and leveling, alignment, focal plane detection, the adaptability for situations such as vertical, horizontal direction measurement subsystem is to temperature change is improved.

Description

A kind of pair of Barebone and alignment methods

Technical field

Semiconductor integrated circuit manufacturing field of the present invention, and in particular to a kind of pair of Barebone and alignment methods.

Background technique

In semiconducter IC ic manufacturing process, a complete chip is usually required by multiple photolithographic exposure It can complete.Each time exposure before be required to carry out silicon wafer face leveled, and between projection exposure camera lens focal plane into Row focusing, other than first time photoetching, the photoetching of remaining level before exposure will expose the figure of the level and former level The figure that light leaves is accurately positioned, and just can guarantee has correct relative position and exposure effect in this way between each layer pattern Fruit.

Under normal conditions, alignment precision is the 1/3~1/5 of litho machine resolution ratio index, for 100 nanometers of litho machines Speech, alignment precision index request are less than 35nm.Alignment precision is one of the key technical indexes of projection mask aligner, and mask and silicon Alignment precision between piece is the key factor for influencing alignment precision.When characteristic size CD requires smaller, to alignment precision It is required that and the requirement of resulting alignment precision become more stringent, as the CD size of 90nm requires 10nm or smaller right Quasi- precision.Meanwhile silicon wafer upper surface also can be higher to the leveling and focusing requirement of projection objective focal plane.Therefore, each survey is being improved It is unified and establish stable vertical measuring basis and be also very important outside the precision for measuring module.

Patent CN102455247 proposes a kind of device and method of optimal focal plane of projection objective detection, utilizes work stage On Electro-Optical Sensor Set on mask grating marker be imaged, determine lens by judging the readability of grating marker The optimal focal plane position of object lens.The vertical measuring basis of the method is still the test surface of photoelectric sensor, and photoelectric sensor is visited Survey face still will receive the influences such as temperature, vibration and generate vertical offset, to reduce the accuracy of projection objective focal plane detection.

Summary of the invention

The present invention proposes a kind of pair of Barebone and alignment methods, it is intended to establish for focusing and leveling, alignment, focal plane detection unified Measuring basis, improve the adaptability for situations such as vertical, horizontal direction measurement subsystem is to temperature change.

In order to achieve the above object, the present invention proposes a kind of pair of Barebone, comprising:

Mask provides projection exposure pattern and alignment mark；

Projection objective focal plane measurement markers are set on the mask；

Projection objective is imaged onto silicon wafer side's image space focal plane to exposing patterns, the label on mask；

Work stage carries same lens shaft, datum plate and silicon wafer, and provides horizontal direction and vertical movement, wherein described The alignment mark, projection objective focal plane measurement markers and focusing label are imaged with lens shaft, the datum plate carrying There are focusing label and reference marker, provides horizontal direction and vertical measuring basis, the silicon wafer carries silicon wafer alignment mark；

Focusing and leveling system levels silicon chip surface, and control silicon wafer upper surface is overlapped with silicon wafer focal plane；

Off-axis alignment system is directed at silicon wafer pattern.

Further, the projection objective focal plane measurement markers are that one-dimensional or two-dimensional grating marks, and characteristic size meets Following relationship:

The λ of p≤1.22 M/NA, λ are the dominant wavelength of coaxial imaging system, and M is the enlargement ratio of projection objective, and NA is same The numerical aperture of imaging shaft system.

Further, the focusing is marked labeled as phase shift, and the structure of the phase shift label is the glass in the datum plate One layer of lighttight label is set in glass substrate and with a thickness of a, the phase shift layer that refractive index is n, defines other transmissions of substrate of glass Partial phase is zero, and the phase difference of the phase shift layer and substrate of glass is pi/2, it is known that, the thickness of phase difference and phase shift layer Relationship are as follows:

Pi/2=2 π a (n-1)/λ.

Further, the focusing is labeled as confocal label, and the confocal label is or two-dimensional grating marks, special Sign size should meet following relationship:

P2≤1.22 λ/NA+ Δ x, λ is the dominant wavelength of coaxial imaging system, and NA is the numerical aperture of coaxial imaging system Diameter, Δ x are additional minor shifts amount.

In order to achieve the above object, the present invention also proposes a kind of alignment methods, characterized in that it comprises the following steps:

Step 1, work stage drive within the scope of the imaging viewing field with lens shaft to projection objective, pass through coaxial shot detection Projection objective focal plane measurement markers and focusing label, catenary motion work stage search for optimal imaging focal plane, and record work stage and hang down To position；

Step 2, work stage drive in datum plate to focusing and leveling systematic survey field range, and focusing and leveling system is to base Quasi- plate surface measures, detection focusing label, and corrects focusing and leveling internal system error as benchmark；

Step 3, focusing and leveling system measure to silicon wafer upper surface, level and make silicon wafer upper surface and above-mentioned best Imaging focal plane is overlapped；

The reference marker on datum plate is imaged in step 4, off-axis alignment system, establishes horizontal direction measuring basis, and to silicon The imaging of piece alignment mark, establishes the positional relationship between silicon wafer and datum plate；

Datum plate reference marker and mask alignment mark is imaged in step 5, coaxial alignment system, establishes mask and base Positional relationship between quasi- plate, so far establishes the positional relationship of mask pattern Yu silicon wafer pattern, and alignment is completed.

Further, the focusing is marked labeled as phase shift, further includes machine constant recording step before step 1, i.e., With lens shaft on datum plate phase shift label and reference marker be imaged, two position of the label under same axis coordinate system of record and work For machine constant.

Further, in the step 1, coaxial shot detection projection objective focal plane measurement markers and phase shift label, and it is right Projection objective focal plane measurement markers and phase shift label imaging.

Further, further include step 6, after one surveys the school period, with lens shaft to phase shift label and reference marker at Picture analyzes the horizontal direction offset of reference marker and repays horizontal direction drift according to this value complement, analyzes phase shift mark level to offset Amount, removes the part of coaxial alignment system level offset, and remaining phase shift mark level is to offset and coaxial alignment system phase It is related for the vertical drift of datum plate, by vertical offset distance and directional compensation to vertical control machine constant.

Further, the focusing is labeled as confocal label, in the step 1, by projection objective focal plane measurement markers and Confocal label exactitude position, coaxial shot detection penetrate the energy value of confocal label.

It is proposed by the present invention to Barebone and alignment methods, use the phase shift with certain phase difference to mark the side to be imaged The defocus of formula detection coaxial alignment sensor or the focal plane that projection objective is measured using the mode of confocal energy detection, and built with this Unified vertical measuring basis is found, measurement result is not acted upon by temperature changes；Using the alignment reference marker on datum plate, build Vertical alignment horizontal direction measuring basis, improves the measurement stability to Barebone.

Detailed description of the invention

Fig. 1 show the alignment system structure diagram of present pre-ferred embodiments.

Fig. 2 a- Fig. 2 c show the projection objective focal plane measurement mask mark structure schematic diagram of present pre-ferred embodiments.

Fig. 3 a and Fig. 3 b show the phase shift mark structure schematic diagram of present pre-ferred embodiments.

Fig. 4 show the phase shift label measurement defocus principle index path of present pre-ferred embodiments

Fig. 5 a and Fig. 5 b show datum plate phase shift label, the reference marker schematic layout pattern of present pre-ferred embodiments.

The phase shift that Fig. 6 show present pre-ferred embodiments marks vertical measurement and horizontal displacement relation schematic diagram.

Fig. 7 show the alignment methods flow chart of present pre-ferred embodiments.

Fig. 8 show the alignment system structure diagram of another embodiment of the present invention.

Fig. 9 a- Fig. 9 c show the projection objective focal plane measurement markers structural schematic diagram of another embodiment of the present invention.

Figure 10 a- Figure 10 e show the datum plate focal plane measurement markers structural schematic diagram of present pre-ferred embodiments.

Figure 11 show the confocal energy method measurement defocus principle index path of present pre-ferred embodiments.

Figure 12 show the vertical defocus of focal plane and detection energy relationship schematic diagram of present pre-ferred embodiments.

It is quasi- that Figure 13 show the mask of present pre-ferred embodiments, benchmark focal plane measurement dislocation grating energy extreme value place It closes.

Figure 14 a and Figure 14 b show the datum plate focal plane measurement markers of present pre-ferred embodiments, reference marker layout is shown It is intended to.

Figure 15 show the alignment methods flow chart of another embodiment of the present invention.

Specific embodiment

A specific embodiment of the invention is provided below in conjunction with attached drawing, but the present invention is not limited to the following embodiments and the accompanying drawings.Root According to following explanation and claims, advantages and features of the invention will be become apparent from.It should be noted that attached drawing be all made of it is very simple The form of change and use non-accurate ratio, be only used for conveniently, lucidly aid in illustrating the embodiment of the present invention purpose.

Referring to FIG. 1, the present invention proposes a kind of pair of Barebone, comprising:

Mask 001 provides projection exposure pattern, alignment mark and is provided with projection objective focal plane measurement markers 002；

Projection objective focal plane measurement markers 002 provide sensibility preferable marking style for projection objective focal plane measurement；

Projection objective 003 is imaged onto silicon wafer side's image space focal plane to exposing patterns, alignment mark on mask；

Work stage 005, for same lens shaft 006, datum plate 007, the carrying of silicon wafer 008 and horizontal direction, catenary motion；

With lens shaft 006, to alignment mark, projection objective focal plane measurement markers 002, phase shift label 007a, b carry out at Picture has the function of mask registration and measurement optimal focal plane of projection objective；

Datum plate 007, carrying phase shift label 007a, b and reference marker 007c, and vertical, horizontal direction measuring basis is provided；

Phase shift marks 007a, b, and coaxially it is imaged, and imaging position offset is related to vertical defocusing amount, as shown in Figure 6；

Reference marker 007c, it is off-axis, it is imaged with lens shaft can establish horizontal direction measuring basis, inhibit temperature drift；

Silicon wafer 008, carrying silicon wafer alignment mark, the silicon wafer 008 provide the duplication of projection exposure pattern；

Focusing and leveling system 009 levels silicon chip surface, and control silicon wafer upper surface is overlapped with silicon wafer focal plane；

Off-axis alignment system 010 is directed at silicon wafer pattern.

Preferred embodiment according to the present invention, the projection objective focal plane measurement markers 002 are that one-dimensional or two-dimensional grating marks, As shown in Fig. 2 a- Fig. 2 c, characteristic size should meet following relationship:

The principle of the defocus of measurement alignment sensor is marked using phase shift:

The structure of phase shift label is as shown in Figure 3a and Figure 3b shows, and one layer of lighttight mark is done in 007 substrate of glass of datum plate Remember 007a and with a thickness of a, the phase shift layer 007b that refractive index is n, the phase for defining other permeation parts of substrate of glass is zero, phase shift Layer 007b and the phase difference of substrate of glass are pi/2, it is known that, the relationship of the thickness of phase difference and phase shift layer 007b are as follows:

Pi/2=2 π a (n-1)/λ.

As shown in Fig. 4 phase shift label defocus principle index path, focal length is respectively f₁、f₂Lens composition imaging system, should The point spread function of imaging system is h (x', f₂·x/f₁), the difference x that phase shift marks₁、x₂By the system in image planes Coherent superposition, the light distribution on imaging surface are as follows:

Wherein Δ z is the defocusing amount of optical system.

Similar system defocusing amount and phase shift label imaging position variation such as Fig. 6 focusing pip displacement and defocus schematic diagram institute Show.

Phase shift label and reference marker are laid out as shown in figure 5 a and 5b, and wherein the marking layout of Fig. 5 b can measure more simultaneously The arrangement form of the defocus location information of a point, phase shift label is not limited thereto two kinds, phase shift label and reference marker 007C Relative position on datum plate 007 is with no restrictions；

Referring to FIG. 7, Fig. 7 show the alignment methods flow chart of present pre-ferred embodiments.The present invention proposes a kind of right Quasi- method, including the following steps:

Step S110: phase shift label 007a, b and reference marker 007c on datum plate is imaged with lens shaft 006, record Two positions of the label under same axis coordinate system and as machine constant, work stage 005, which drives, arrives projection objective with lens shaft 006 Within the scope of 003 imaging viewing field, 007a, b are marked to projection objective focal plane measurement markers 002 and phase shift by same lens shaft 006 Imaging, catenary motion work stage 005 searches for optimal imaging focal plane, and records Workpiece stage vertical position；

Step S120: work stage 005 drives datum plate 007 to measure in field range to focusing and leveling system 009, and focusing is adjusted Flat system 009 measures 007 surface of datum plate, and detection phase shift marks 007a, b, corrects focusing and leveling system as benchmark It unites 009 internal error；

Step S130: focusing and leveling system 009 to 008 upper surface of silicon wafer measure, level and make silicon wafer upper surface with Optimal focal plane of projection objective 004 is overlapped；

Step S140: the reference marker 007c on datum plate 007 is imaged in off-axis alignment system 010, establishes horizontal direction survey Benchmark is measured, and silicon wafer alignment mark is imaged, establishes the positional relationship between silicon wafer 008 and datum plate 007；

Step S150: coaxial alignment system (i.e. with lens shaft 006) is to datum plate reference marker and mask alignment mark Imaging, establishes the positional relationship between mask and datum plate, so far establishes the positional relationship of mask pattern Yu silicon wafer pattern, is aligned It completes.

Preferred embodiment according to the present invention, after one surveys the school period, with lens shaft 006 to the phase shift mark on datum plate 007 Remember 007a, b and reference marker 007c imaging, analyze the horizontal direction offset of reference marker 007c and horizontal direction is repaid according to this value complement Drift, analysis phase shift mark 007a, b horizontal direction offset, and the part for removing 006 horizontal-shift of coaxial alignment system is (coaxial right Barebone horizontal direction is obtained with temperature, the offset of vibration by measuring), remaining phase shift label 007a, b horizontal direction offset with Coaxial alignment system 006 is related relative to the vertical drift of datum plate 007, by vertical offset distance and the vertical control of directional compensation Machine constant.Because coaxial alignment system horizontal direction and it is vertical can survey and can compensate for temperature, the offset of vibration, it is vertical, horizontal It is unified to measuring basis, it can solve since environment unstability bring is vertical, horizontal direction measurement error.

Referring to FIG. 8, Fig. 8 show the alignment system structure diagram of another embodiment of the present invention.The present invention is also It is proposed a kind of pair of Barebone, comprising:

Mask 101 provides projection exposure pattern, alignment mark, projection objective focal plane measurement markers 102；

Projection objective focal plane measurement markers 102 provide sensibility preferable marking style for projection objective focal plane measurement；

Projection objective 103 is imaged onto silicon wafer side's image space focal plane to figure, label on mask；

Work stage 105, for same lens shaft 106, datum plate 107, the carrying of silicon wafer 108 and horizontal direction, catenary motion；

With lens shaft 106, to alignment mark, projection objective focal plane measurement markers 102, confocal label 107a1,107a2, 107b1,107b2,107c and reference marker 107d are imaged, the function with mask registration and measurement optimal focal plane of projection objective Energy；

Datum plate 107 carries confocal label 107a1,107a2,107b1,107b2,107c and reference marker 107d, provides Vertical, horizontal direction measuring basis；

Confocal label 107a1,107a2,107b1,107b2,107c, confocal energy detection method benchmark diaphragm, size shadow The sensitivity of vertical detection is rung, the relative energy detected by it is related to defocusing amount, as shown in figure 12；

Reference marker 107d, it is off-axis, it is imaged with lens shaft can establish horizontal direction measuring basis, inhibit temperature drift；

Silicon wafer 108 carries silicon wafer alignment mark and provides the duplication of projection exposure pattern

Focusing and leveling system 109 levels silicon chip surface, and control silicon wafer upper surface is overlapped with silicon wafer focal plane；

Off-axis alignment system 110 is directed at silicon wafer pattern.

Preferred embodiment according to the present invention, the projection objective focal plane measurement markers 102 are that one-dimensional or two-dimensional grating marks, As shown in Fig. 9 a- Fig. 9 c, characteristic size should meet following relationship:

The λ of p1≤1.22 M/NA, λ are the dominant wavelength of coaxial imaging system, and M is the enlargement ratio of projection objective, and NA is The numerical aperture of coaxial imaging system；

Described confocal label 107a1,107a2,107b1,107b2,107c are that one-dimensional or two-dimensional grating marks, as Figure 10 a, 107a1,107b1,107c structure are marked shown in Figure 10 c and Figure 10 e, characteristic size should meet following relationship:

P2≤1.22 λ/NA+ Δ x, λ is the dominant wavelength of coaxial imaging system, and NA is the numerical aperture of coaxial imaging system Diameter, Δ x are additional minor shifts amount.One grating marker can be divided into four parts of dislocation p3, as shown in Figure 10 b and Figure 10 d Label 107a2,107b2 structure.

For confocal label with reference marker layout as shown in Figure 14 a and Figure 14 b, the arrangement form of label is not limited thereto two Kind, confocal label and relative position of the reference marker 107d on datum plate 107 are with no restrictions.

Figure 15 is please referred to, Figure 15 show the alignment methods flow chart of another embodiment of the present invention.The present invention also mentions A kind of alignment methods out, including the following steps:

Step S210: work stage 105 drives within the scope of the imaging viewing field with lens shaft 106 to projection objective 103, will project Object lens focal plane measurement markers 102a, 102b, 102c and confocal label 107a1,107a2,107b1,107b2,107c exactitude position (projection objective focal plane measurement markers 102a is corresponding with confocal label 107a1,107a2 to be used, projection objective focal plane measurement markers 102b is corresponding with confocal label 107a2 to be used, and projection objective focal plane measurement markers 102c is corresponding with confocal label 107c to be used), With the detection of lens shaft 106 through the energy value of confocal label 107a1,107a2,107b1,107b2,107c, catenary motion workpiece It is optimal imaging focal plane that platform 105, which searches for the maximum position of energy, and records Workpiece stage vertical position；

Step S220: work stage 105 drives datum plate 107 to measure in field range to focusing and leveling system 109, and focusing is adjusted Flat system 109 measures 107 surface of datum plate, and 109 internal error of focusing and leveling system is corrected on the basis of this surface；

Step S230: focusing and leveling system 109 to 108 upper surface of silicon wafer measure, level and make silicon wafer upper surface with Projection objective focal plane 104 is overlapped；

Step S240: the reference marker 107d on datum plate 107 is imaged in off-axis alignment system 110, establishes horizontal direction survey Benchmark is measured, and silicon wafer alignment mark is imaged, establishes the positional relationship between silicon wafer and datum plate；

Step S250: datum plate reference marker 107d and mask alignment mark is imaged in coaxial alignment system 106, establishes Positional relationship between mask and datum plate, so far establishes the positional relationship of mask pattern Yu silicon wafer pattern, and alignment is completed.

Preferred embodiment according to the present invention, when detecting optimal focal plane of projection objective using same lens shaft 106, same to lens shaft 106 are only used as an energy-probe, and vertical measuring basis is the focal plane measurement markers 107a/b/c on benchmark plate 107, because This will not influence vertical measurement result with the long term drift of lens shaft 106 itself；The similarly reference marker on displacement datum plate 107 107d is horizontal direction measuring basis, and vertical, horizontal direction measuring basis unification can solve to hang down due to environment unstability bring To, horizontal direction measurement error.

Utilize the principle of the defocus of confocal energy detection method measurement alignment sensor:

As shown in figure 11, the projection objective focal plane measurement grating marker 102 on mask has the transmission region of P1/2, thoroughly Light is penetrated grating marker 102 is imaged near 107 upper surface of datum plate by projection objective 103, confocal label 107a1, 107a2,107b1,107b2,107c and 102 exactitude position of grating marker, since P2 is different from the size of P1, the two has small Difference Δ x can find the point and energy maximum point of a horizontal aligument, as shown in figure 13 in a series of gratings in this way；Together Reason, a grating is divided into four parts of dislocation, as marked shown in 107a2,107b2, also for average level to bit errors Or influence of the mismachining tolerance of label to measurement result.

The energy after datum plate projection objective focal plane measurement markers is penetrated as energy-probe detection with lens shaft 106, Defocusing amount Δ z is inversely proportional with the energy size detected, as shown in figure 12.

Catenary motion work stage 105 obtains the corresponding energy value in different vertical positions, ceiling capacity with same lens shaft 106 Corresponding vertical position is the optimal focal plane position of projection objective.

Although the present invention has been disclosed as a preferred embodiment, however, it is not to limit the invention.Skill belonging to the present invention Has usually intellectual in art field, without departing from the spirit and scope of the present invention, when can be used for a variety of modifications and variations.Cause This, the scope of protection of the present invention is defined by those of the claims.

Claims

1. an alignment system, is characterized in that, comprises:

Reticles, providing projected exposure patterns and alignment marks;

a projection objective lens focal plane measurement mark, arranged on the reticle;

The projection objective lens is used to image the exposure pattern and mark on the reticle to the focal plane of the silicon wafer square image;

The workpiece stage carries a coaxial lens, a reference plate and a silicon wafer, and provides horizontal and vertical movement, wherein the coaxial lens images the alignment marks, the focal plane measurement marks of the projection objective and the focusing marks , constitutes a coaxial imaging system, the reference plate carries focusing marks and reference marks to provide horizontal and vertical measurement benchmarks, and the silicon wafer carries silicon wafer alignment marks;

Focusing and leveling system, leveling the surface of the silicon wafer and controlling the upper surface of the silicon wafer to coincide with the focal plane of the silicon wafer;

Off-axis alignment system for pattern alignment on silicon wafers,

Wherein, the focusing mark is a phase shift mark, and the structure of the phase shift mark is to set a layer of opaque marks and a phase shift layer with a thickness of a and a refractive index of n on the glass substrate of the reference plate , it is defined that the phase of the other transparent parts of the glass substrate is zero, and the phase difference between the phase shift layer and the glass substrate is π2. It can be seen that the relationship between the phase difference and the thickness of the phase shift layer is: π2=2·π·a·[ n-1]λ, λ is the dominant wavelength of the coaxial imaging system.

2. The alignment system according to claim 1, wherein the measurement mark of the focal plane of the projection objective lens is a one-dimensional or two-dimensional grating mark, and its characteristic size satisfies the following relationship:

p≤1.22·λ·M/NA, λ is the dominant wavelength of the coaxial imaging system, M is the magnification of the projection objective lens, and NA is the numerical aperture of the coaxial imaging system.

3. An alignment method, using the alignment system according to any one of claims 1-2, characterized in that, comprising the following steps:

Step 1: The workpiece table drives the coaxial lens to the imaging field of view of the projection objective lens, detects the focal plane measurement mark and focus adjustment mark of the projection objective lens through the coaxial lens, moves the workpiece table vertically to search for the best imaging focal plane, and records the workpiece vertical position of the table;

Step 2: The workpiece table drives the reference plate to the measurement field of view of the focusing and leveling system. The focusing and leveling system measures the surface of the reference plate, detects the focusing marks, and uses this as a reference to correct the internal errors of the focusing and leveling system. ;

Step 3, the focusing and leveling system measures and levels the upper surface of the silicon wafer, and makes the upper surface of the silicon wafer coincide with the above-mentioned optimal imaging focal plane;

Step 4, the off-axis alignment system images the reference marks on the reference plate, establishes a horizontal measurement benchmark, and images the silicon wafer alignment marks to establish the positional relationship between the silicon wafer and the reference plate;

In step 5, the coaxial lens images the reference mark of the reference plate and the alignment mark of the reticle, establishes the positional relationship between the mask and the reference plate, and thus establishes the positional relationship between the mask pattern and the silicon wafer pattern, and the alignment is completed.

4. The alignment method according to claim 3, characterized in that, before step 1, it also includes a machine constant recording step, that is, the coaxial lens images the phase shift mark and the reference mark on the reference plate, and records the two marks at the same time. The position in the axis coordinate system and as a machine constant.

5 . The alignment method according to claim 4 , wherein in the step 1, the coaxial lens detects the focal plane measurement mark and the phase shift mark of the projection objective lens, and measures the mark and the phase shift mark on the focal plane of the projection objective lens. 6 . imaging.

6. The alignment method according to claim 5, further comprising step 6: after a calibration period, the coaxial lens images the phase shift mark and the reference mark, and analyzes the horizontal offset of the reference mark And compensate the horizontal drift according to this value, analyze the horizontal offset of the phase shift marker, remove the part of the horizontal offset of the coaxial lens, and the remaining horizontal offset of the phase shift marker is the same as that of the coaxial lens relative to the reference board. Vertical drift correlation, compensating vertical offset distance and direction to vertical control machine constants.