Micro-nano device multilayer overlay alignment method

Abstract

This invention relates to the field of micro / nano manufacturing technology, specifically disclosing a multi-layer overlay alignment method for micro / nano devices. The method includes the following steps: substrate pre-alignment, calibration of the unit length of the microscopic imaging system coordinate system and selection of the main observation area, calculation of the deflection angle between coordinate systems and the axis deflection angle of the stage coordinate system, phase and attitude adjustment of the substrate and mask, relative position adjustment of the substrate and mask, and relative position and attitude alignment judgment. The method integrates error correction and compensation functions, reducing the impact of machining errors, assembly errors, and mechanism repeatability errors in precision stages, microscopic imaging systems, etc., on the alignment process, thereby improving alignment accuracy and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano manufacturing technology, and specifically relates to a multi-layer overlay alignment method for micro-nano devices. Background Technology

[0002] Micro- and nano-devices refer to devices with functional structures whose minimum feature size is at the micrometer or nanometer scale, including semiconductor chips, microsensors / actuators, and micro- and nano-electromechanical integrated systems. Photolithography is a key process step in the fabrication of micro- and nano-devices. It involves using short-wavelength energy-carrying waves such as ultraviolet light, lasers, ion beams, and electron beams to solidify photoresist in specific areas, thereby transferring the structural pattern from a photomask to substrates such as silicon, quartz, metal, and polymers. With the continuous development of micro- and nano-devices, their functional integration is constantly increasing. The functional units on the substrate are not only becoming smaller and denser, but also developing towards multi-layer stacking, which requires multiple photolithography steps. Pre-photolithography alignment is a crucial step in the fabrication of multi-layer stacked devices, ensuring accurate spatial positioning between different structural pattern layers.

[0003] To achieve proper alignment during fabrication, photomasks typically contain at least two alignment regions, each marked with alignment marks. The positional difference between these alignment marks on the photomask and the fabricated structural pattern on the substrate is observed using a microscope imaging system. A three-dimensional precision stage is then used to adjust the relative positions of the photomask and the substrate, ensuring that the corresponding alignment marks on the photomask and substrate coincide. This results in a precise spatial alignment between the multilayer structural patterns fabricated on the substrate. The development of alignment technology has gone through several stages. Early methods relied primarily on manual observation and adjustment. However, this approach suffers from drawbacks such as significant human error, low alignment efficiency, and large batch-to-batch variations, making it unsuitable for large-scale mass production of micro and nano-devices.

[0004] With the development of machine vision technology and automatic control technology, lithography machines with fully automatic alignment functions have emerged. They use a microscope imaging system to replace the human eye in observing the alignment area, use image recognition technology to analyze and measure position differences, and use servo motors and other actuators to drive a precision worktable to achieve relative position and attitude adjustment, thus realizing fully automatic alignment between the mask and the substrate. Typically, during automatic alignment, the substrate is pre-aligned and leveled to ensure that the alignment area appears in the field of view of the microscope imaging system. Image recognition software identifies the alignment marks on the mask and substrate within the alignment area, characterizing the position of the alignment marks with their feature points (structural center points or specific vertices, etc.), and reads the absolute position coordinates of the feature points in the field of view coordinate system of the microscope imaging system, or the relative position coordinates between the two feature points. The automatic controller calculates the displacement or rotation of the precision stage in different adjustment directions based on the read relative position difference, and drives the precision stage actuator to achieve relative position and attitude adjustment. The relative position difference between the alignment marks in each alignment area on the mask and substrate is read again. If it is greater than the set threshold, the above alignment steps are repeated until the relative position difference between the alignment marks in each alignment area is less than the set threshold. Due to machining errors, assembly errors, and repeated positioning errors in components such as precision stages and microscope imaging systems, it is impossible to achieve complete alignment between the observation coordinate system of the microscope imaging system and the motion coordinate system of the precision stage. It is also impossible to guarantee that the motion directions of each adjustment axis of the precision stage are completely orthogonal. However, most existing automatic alignment methods do not consider these errors. The alignment motion direction of the precision stage is inconsistent with the observation coordinate direction of the microscope imaging system, resulting in a large error between the relative position and orientation of the substrate and the mask after alignment and adjustment and the ideal solution. This requires repeated alignment and may even lead to a dead loop. Therefore, there is an urgent need for an efficient and accurate alignment method that integrates error correction and compensation functions. Summary of the Invention

[0005] The purpose of this invention is to provide a multilayer overlay alignment method for micro / nano devices to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for multilayer overlay alignment of micro / nano devices includes the following steps:

[0008] Step 1: Roughly align the substrate and the mask so that the alignment marks in the corresponding alignment areas on the substrate and the mask can appear in the field of view at the same time.

[0009] Step 2: Using the actual size and pixel size of the feature lines in the field of view of the microscope camera, calibrate the unit length of the coordinate system of the microscope camera system, convert the relative position information such as the observed pixel coordinates and calculated distances into information with units, and select the alignment area with a large relative distance between the alignment marks on the substrate and the mask as the main observation area.

[0010] Step 3: Move the precision stage horizontally along the X-axis and Y-axis by known displacements a and b respectively. Sample the data through the microscopic imaging system and compare the relative position changes of the alignment marks on the substrate and the alignment marks on the mask before and after the movement. Calculate the deflection angle α of the precision stage Y-axis from the ideal orthogonal direction of the X-axis, and the deflection angle θ between the X-axis of the microscopic imaging system's field of view coordinate system and the X-axis of the precision stage.

[0011] Step 4: Select a known distance L on the substrate. b Points e and f are considered. Point e is located on the positive side of the X-axis or Y-axis of the precision worktable. A virtual line connecting the two points serves as the attitude characterization baseline. The difference between the relative coordinates of the two points in the microscope's field of view and the corresponding points on the substrate is calculated to determine the attitude of the substrate relative to the mask and adjust the rotation angle. If |x de -x df |and|y de -y df If the value of | is 0 or its absolute value is less than a specific threshold, then there is no need to adjust the horizontal rotation axis τ of the precision worktable; if |x de -x df |>|y de -y df If |>0 or the threshold, then the horizontal rotation axis τ needs to be rotated by an angle of arccos[(x de -x df ) / L b ], and if y de -y df If the value is greater than 0, the rotation direction is positive; if the value is 0 or the threshold is less than |x de -x df |<|y de -y df | Then the horizontal rotation axis τ needs to be rotated by an angle of arcsin[(y de -y df ) / L b (Clockwise is positive);

[0012] Step 5: Collect the relative position difference (x) of the alignment marks on the substrate and mask in the main observation area. dm ,y dm The adjustment motion vector for integrated error correction compensation is calculated as (X). m ,Y m )={-x dm (cosθ-sinθ·tanα)-ydm (sinθ+cosθ·tanα)],-[x dm (sinθ / cosα)+y dm (cosθ / cosα)]};

[0013] Step 6: Determine the relative positional deviation of each alignment area after adjustment. If D i 、|x de -x df |and| yde -y df If all values ​​are less than the set threshold, alignment is achieved; otherwise, D is reselected. m The largest alignment area is the main observation area; readjust the alignment again.

[0014] Preferred, the method for achieving rough alignment between the substrate and the photomask includes, but is not limited to, manual, machine vision, and mechanical positioning methods, and the alignment area set on the substrate or photomask is no less than two.

[0015] Preferred, the alignment mark pattern set on the substrate or mask includes, but is not limited to, cross, quadrilateral, triangle, array of spaced line segments, sector or arc.

[0016] Preferred, the position of the alignment mark is characterized by feature points of the graphic, which are identified by image recognition or manually marked. Feature points include, but are not limited to, the structural center point of the alignment mark, line intersections, and graphic vertices.

[0017] Preferred, the points used to determine the attitude characterization baseline include, but are not limited to, the structural center point of the alignment mark, line intersections, graphic vertices, or other points with known spacing.

[0018] Preferably, the step of calibrating the coordinate system per unit length of the microscopic imaging system includes: identifying feature lines on the mask and reading the pixel coordinates of their endpoints (i... g1 ,j g1 ) and (i g2 ,j g2 The pixel length coefficient is calculated by dividing the actual length of the feature line design by its pixel length. Calculate the arithmetic mean of the pixel length coefficients of multiple feature lines, and use it as the unit length calibration coefficient of the microscope imaging system coordinate system. Pixel coordinates via Convert to coordinates with length units.

[0019] Preferably, the form of the feature lines used for calibration includes, but is not limited to, feature lines with the side length of the graphic outline within the alignment area, line width or spacing, arc radius, and known actual length. The number of feature lines used for unit length calibration of the coordinate system within the same alignment area is at least one, and the number of feature lines n used in the calibration process is not less than two.

[0020] Preferably, the display sampling ratio is the same along different axes of the microscopic imaging coordinate system. For coordinate systems with different display sampling ratios, the pixel length coefficient S for different coordinate axes is solved separately. xg =L xg / |i g1 -i g2 |with S yg =L yg / |j g1 -j g2 | and Pixel coordinates via Convert to coordinates with length units.

[0021] Preferred, the error correction and compensation calculation method includes: selecting the X-axis adjustment direction in the horizontal plane of the precision worktable as the reference direction; adjusting the precision worktable to move sequentially along its horizontal X and Y drive axes, with motion vectors of (a,0) and (0,b) respectively, and recording the relative position coordinates (Δx1,Δy1) and (Δx2,Δy2) of the alignment mark relative to the initial position after movement in the field of view coordinate system of the microscope imaging system; calculating the deflection angle θ = arctan(Δy1 / Δx1) between the X-axis adjustment axis of the precision worktable and the x-axis of the field of view coordinate system of the microscope imaging system; and calculating the deflection angle α = arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ between the Y-axis of the precision worktable and the ideal orthogonal direction of the X-axis.

[0022] Preferably, the X and Y adjustment axes in the horizontal plane of the precision worktable are used as reference directions, and the a and b in the motion vector are set to non-zero lengths.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The method for adjusting the relative position and attitude of the substrate and the mask provided by this invention filters the position information of different alignment areas and selects the alignment area with the largest distance between the alignment marks on the substrate and the mask as the main observation area. Based on the position information of the alignment marks on the substrate in the main observation area, compared with the existing method that uses the center position information of the line connecting two alignment marks on the substrate as the calculation basis, the method reduces the impact of the measurement error of the microscope imaging system on the calculation results of each step. It integrates an error correction and compensation solution step, which uses the change of alignment mark position data during the alignment process to calculate the manufacturing error and assembly error of the precision stage and the microscope imaging system. Furthermore, it proposes a correction and compensation algorithm for the alignment adjustment of each axis of the precision stage, thereby improving the alignment accuracy and efficiency. Attached Figure Description

[0025] Figure 1 This diagram illustrates the steps of the multilayer overlay alignment method for micro / nano devices according to an embodiment of the present invention.

[0026] Figure 2 A schematic diagram of the alignment mechanism according to an embodiment of the present invention is shown;

[0027] Figure 3 This illustrates the alignment marks in the field of view of the microscope imaging system described in an embodiment of the present invention;

[0028] Figure 4 This diagram illustrates the coordinate system and adjustment motion in the error correction and compensation steps described in this embodiment of the invention.

[0029] In the diagram: 201-Microscopic imaging system, 202-Mask holder, 203-Controller, 204-Mask, 205-Substrate, 206-Slab stage, 207-Precision stage Y-axis adjustment, 208-Precision stage X-axis adjustment, 209-Precision stage Z-axis adjustment, 210-Precision stage τ-rotation adjustment, 301-Alignment mark on substrate, 302-Feature point of alignment mark on substrate, 303-Alignment mark on mask, 304-Feature point of alignment mark on mask, 305-Endpoint of identified calibration feature line, 401-Precision stage coordinate system, 402-Deflection angle between actual Y-axis and ideal Y'-axis of precision stage, 403-Microscopic imaging field of view coordinate system, 404-Deflection angle θ between microscopic field of view coordinate system and precision stage coordinate system. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] This invention comprises three aspects: a method for relative pose adjustment and alignment of the substrate and the mask, a method for unit length calibration of the coordinate system of a microscopic imaging system, and a method for calculating error correction compensation. The specific technical solutions are as follows:

[0032] In a first aspect, the present invention provides a relative pose adjustment alignment method, the method comprising:

[0033] Step S1: Substrate pre-alignment: The substrate and the mask are roughly aligned using a manual or automatic pre-alignment device. After the substrate is placed on the stage of the precision worktable, the microscopic imaging system observes the specific alignment area and observes the corresponding alignment marks on the substrate and the mask. The alignment marks or manual marks on the substrate within the alignment area are identified by image recognition software, and the position of the alignment marks is characterized by feature points (structural center points or specific vertices).

[0034] Step S2: Calibration of the unit length of the microscope camera system coordinate system and selection of the main observation area: Optionally, the calibration method of the unit length of the microscope camera system coordinate system described in this invention is used to solve for the calibration coefficient of the unit length of the microscope camera system coordinate system. Or directly call the solution obtained during the previous alignment process. Convert pixel coordinates to coordinates with length units. The microscopic imaging system samples n alignment regions (n ​​not less than 2) on the substrate and mask, recording the position information of alignment marks on the substrate in each alignment region (in the microscopic imaging system's field-of-view coordinate system). The position information of the i-th alignment mark includes: absolute position coordinates (x...). si ,y si ), relative position coordinates (x, y) of the alignment marks on the mask di ,y di Calculate the distance between the alignment marks on the substrate and the alignment marks on the mask in each alignment region. Select D i The largest alignment area, m, is the main observation area.

[0035] Step S3: Calculation of the deflection angle between coordinate systems and the axis deflection angle of the stage coordinate system: Relative position adjustment is performed, and the error correction and compensation calculation method described in this invention is used to calculate the deflection angle α of the precision stage's Y-axis deviating from the ideal orthogonal direction of the X-axis, and the deflection angle θ between the x-axis of the microscope imaging system's field of view coordinate system and the X-axis of the precision stage. Optionally, the displacements a and b of the sequential movement of the precision stage's X and Y axes can be set as x, y, and y respectively, based on the relative position coordinates of the main observation area. dm and y dm Or set to a specific known value.

[0036] Step S4: Relative orientation adjustment of the substrate and the mask: Optionally, select two relatively far alignment regions (referred to as regions e and f, respectively, with region e located on one side of region f along the positive direction of the X-axis or Y-axis of the precision stage). Use the virtual line connecting the alignment marker feature points in the two regions as the orientation characterization baseline, with a length of L. b This helps determine the orientation of the substrate relative to the mask. If |x de -x df |and|y de -y df If the value of | is 0 or its absolute value is less than a specific threshold, then there is no need to adjust the horizontal rotation axis τ of the precision worktable; if |x de -x df |>|y de -y df If |>0 or the threshold, then the horizontal rotation axis τ needs to be rotated by an angle of arccos[(x de -x df ) / L b ], and determine y de -y df >0 indicates positive rotation direction; if 0 or threshold <|x de -x df |<|y de -y df | Then the horizontal rotation axis τ needs to be rotated by an angle of arcsin[(y de -y df ) / L b (Clockwise is positive).

[0037] Step S5: Adjust the relative position of the substrate and the mask: Based on the sampling of the main observation area by the microscope imaging system, read the relative position difference (x) of the alignment marks on the substrate and the mask. dm ,y dm The automatic controller calculates the adjustment motion of each axis of the precision worktable and outputs the adjustment motion vector with integrated error correction compensation as (X). m ,Y m )={-[x dm (cosθ-sinθ·tanα)-y dm (sinθ+cosθ·tanα)],-[x dm (sinθ / cosα)+y dm (cosθ / cosα)]}.

[0038] Step S6: Determine the relative position and orientation of the substrate and photomask: Determine the relative positional deviation of each alignment area after adjustment. If D i 、|x de -x df |and|y de -y dfIf all values ​​are less than the set threshold, alignment is achieved; otherwise, D is reselected. m The largest alignment area is the main observation area, and alignment is adjusted again.

[0039] Optionally, the order of steps S2, S3, and S4 in the relative pose adjustment alignment method of the present invention can be adjusted according to the actual situation. If a microscopic imaging system with low latency real-time sampling and a high computing power controller is selected, steps S2, S3, and S4 in the alignment process can be calculated independently in real time and run in parallel with other steps to achieve real-time calibration of measurement results, real-time screening of the main observation area, and real-time correction and compensation of errors, thereby further improving alignment accuracy and efficiency.

[0040] Secondly, step S2 in the relative pose adjustment alignment method of the present invention relates to a method for calibrating the unit length of the coordinate system of a microscope imaging system, which specifically includes:

[0041] Step S21: Sample different alignment areas using a microscopic imaging system, observe feature lines of known actual length such as the side length of the graphic outline, line width or spacing, and arc radius within the alignment area on the mask, and mark the endpoints of the feature lines by manual marking or image recognition software. There should be no less than 2 alignment areas sampled on the same mask, and the number of observed feature lines n should be no less than 2.

[0042] Step S22: Read the endpoint pixel coordinates of each feature line, where the pixel coordinates of the two endpoints of the g-th feature line are (i... g1 ,j g1 ) and (i g2 ,j g2 ), calculate its pixel length and divide it by its known design length L g The pixel length coefficient of the g-th feature line is obtained.

[0043] Step S23: Calculate the arithmetic mean of the pixel length coefficients of the n feature lines, and use it as the unit length calibration coefficient of the microscope imaging system coordinate system.

[0044] In step S24, during the subsequent alignment step, the pixel coordinates of the points in the microscope imaging system coordinate system can be converted into coordinates with length units.

[0045] Optionally, if the pixel length coefficients of the x and y coordinate axes within the field of view of the microscope imaging system are different, S should be solved separately in step S22. xg =L xg / |i g1 -i g2 |with S yg =L yg / |j g1 -j g2 | Calculate the unit length calibration coefficient of the coordinate system and Coordinate transformation in step S24

[0046] Thirdly, in step S3 of the relative pose adjustment alignment method described in this invention, this invention provides an error correction and compensation calculation method, which specifically includes:

[0047] Step S31, optionally, set the X-axis or Y-axis within the horizontal plane of the precision worktable as the reference coordinate axis of the precision worktable.

[0048] Step S32: Adjust the precision stage to move sequentially along the X and Y drive axes in its horizontal plane, with motion vectors of (a,0) and (0,b) respectively, and record the relative coordinates (Δx1,Δy1) and (Δx2,Δy2) of the alignment mark relative to the initial position after each movement in the field of view coordinate system of the microscope imaging system.

[0049] Step S33: If the X-axis adjustment direction is selected as the reference coordinate axis, calculate the deflection angle θ = arctan(Δy1 / Δx1) between the X-axis of the precision worktable and the x-axis of the field of view coordinate system of the microscope imaging system.

[0050] Step S34: Calculate the deflection angle α of the Y-axis of the precision worktable from the ideal orthogonal direction of the X-axis, which is α = arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ.

[0051] Implementation list:

[0052] Please see Figures 1 to 4 As shown,

[0053] This allows for the alignment of the relative positions and orientations of the substrate and the photomask, and the process is as follows: Figure 1 As shown. A schematic diagram of the alignment mechanism described in this application embodiment is shown below. Figure 2 As shown, during the alignment process, the alignment marks on the mask 204 and the substrate 205 are observed by the binocular microscope imaging system 201, and the image sampling data is identified and analyzed by the controller 203. The mask 204 is fixed to the lower surface of the mask holder 202 by vacuum adsorption, and the substrate 205 is attached to the upper surface of the stage 206 by vacuum adsorption. The Y-axis 207, X-axis 208, Z-axis 209 and τ-axis 210 of the precision stage move under the control of the controller 203, and drive the stage 206 at the top of the stage to move, adjusting the relative position and orientation between the substrate 205 and the mask 204 to achieve overlay alignment.

[0054] A method for multilayer overlay alignment of micro / nano devices includes the following steps:

[0055] Step S101: Substrate pre-alignment: Before being placed into the alignment mechanism, the substrate 205 is roughly adjusted in orientation by the pre-alignment mechanism. It is manually confirmed that the alignment marks on the mask 204 and the substrate 205 can be observed simultaneously in both fields of view of the microscope imaging system 201. The controller 203 acquires and analyzes the images observed in both fields of view. The acquired alignment area image is shown below. Figure 3 As shown, the geometric symmetry center points of the identified pattern are feature point 302 of the alignment mark on the substrate and feature point 304 of the alignment mark on the mask, which characterize the positions of alignment mark 301 on the substrate and alignment mark 303 on the mask.

[0056] Step S102: Microscopic imaging system coordinate system unit length calibration and main observation area selection: Controller 203 acquires images from both fields of view, identifies the lower edge of the alignment mark box on the mask as the calibration feature line, and reads the pixel coordinates (i) of the endpoint 305 of the feature line in the right field of view image. 11 ,j 11 ) and (i 12 ,j 12 Given that the length of the feature line is 1500 μm, calculate... Similarly, calculate S2 in the left visual field; calculate In the subsequent alignment step, the controller 203 will acquire the pixel coordinates in the image and, through the formula... Convert to coordinates in micrometers; compare the relative position coordinates (x, y) between alignment mark feature point 302 and alignment mark feature point 304 on the substrate in the two field-of-view images. di ,y di And calculate the relative distance. Since D1 > D2, the right-side field of view, which is relatively larger, is selected as the main observation area.

[0057] Step S103: Calculation of the deflection angle between coordinate systems and the axis of deflection of the stage coordinate system: The adjustment trajectory of the alignment mark feature point 302 on the substrate observed in the field of view of the microscope imaging system 201 is as follows: Figure 4 As shown; the X-axis of the precision stage coordinate system 401 is selected as the reference coordinate axis. The Y-axis is not actually completely orthogonal to the X-axis, and the deflection angle 402 from the ideal Y' is represented as α; the deflection angle 404 between the microscope imaging field of view coordinate system 403 and the precision stage coordinate system 401 is represented as θ; the relative position coordinates (x, y) between the two alignment marks in the main observation area are used as the reference coordinates. d1 ,y d1 Based on this, the controller 203 controls the precision worktable to move the X-axis 208 and Y-axis 207 sequentially. d1 and y d1The controller 203 samples and calculates the relative position coordinates (Δx1, Δy1) and (Δx2, Δy2) of the alignment mark feature point 302 on the substrate after two adjustments relative to its initial position; according to... Figure 4 Given the triangular relationship, the deflection angle between the microscopic field of view coordinate system and the precision stage coordinate system is calculated as 404θ=arctan(Δy1 / Δx1)=1.17°, and the deflection angle of the precision stage Y-axis from the ideal orthogonal direction Y' is calculated as 402α=arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ=0.14°.

[0058] Step S104: Relative attitude adjustment between the substrate and the mask: The virtual connection between the alignment mark feature points 302 on the substrate in the two fields of view is used as the attitude representation baseline of the substrate, and the virtual connection between the alignment mark feature points 304 on the mask is used as the attitude representation baseline of the mask. The attitude representation baseline length is known to be 80mm. The controller 203 calculates the threshold (0.2μm) < |x using the relative position between the alignment marks. d1 -x d2 |=481.7μm<|y d1 -y d2 |=1658.6μm, indicating that the attitude characterization baselines of the substrate and the mask are not parallel; the rotation angle of the horizontal rotation axis τ of the stage is calculated as arcsin[(y d1 -y d2

[80000] = 1.1875° (clockwise is positive).

[0059] Step S105: Adjusting the relative position of the substrate and the mask: The controller 203, through the microscope imaging system 201, acquires the relative position difference (x) between the alignment marks on the substrate and the mask in the main observation area. d1 ,y d1 (572.5μm, -396.8μm), controller 203 calculates the adjustment amount of the precision worktable X adjustment axis 208 as X. m = -[572.5(cosθ-sinθ·tanα)+396.8(sinθ+cosθ·tanα)]μm=-581.9μm, the adjustment amount of the Y adjustment axis 208 is Y m =-[572.5(sinθ / cosα)-396.8(cosθ / cosα)]μm=384.7μm.

[0060] Step S106: Determine the relative position and orientation of the substrate and the mask: The controller 203 acquires images from two fields of view of the microscope imaging system 201, D1, D2, |x d1 -x d2 |、|y d1 -y d2If all values ​​are less than the set threshold (0.2μm), it indicates that alignment has been achieved.

[0061] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for multi-layer overlay alignment of micro / nano devices, characterized in that, Includes the following steps: Step 1: Roughly align the substrate and the mask so that the alignment marks in the corresponding alignment areas on the substrate and the mask can appear in the field of view at the same time. Step 2: Using the actual size and pixel size of the feature lines in the field of view of the microscope camera, calibrate the unit length of the coordinate system of the microscope camera system, convert the relative position information such as the observed pixel coordinates and calculated distances into information with units, and select the alignment area with a large relative distance between the alignment marks on the substrate and the mask as the main observation area. Step 3: Move the precision stage along the horizontal X-axis and Y-axis by known displacements a and b respectively. Sample the data using a microscope imaging system and compare the relative position changes of the alignment marks on the substrate and the alignment marks on the mask before and after the movement. Calculate the deflection angle of the precision stage's Y-axis from the ideal orthogonal direction of the X-axis. The deflection angle between the x-axis of the field of view coordinate system of the microscope imaging system and the x-axis of the precision stage. ; Step 4: Select a known distance on the substrate. Points e and f are given. Point e is located on the positive side of the X-axis or Y-axis of the precision worktable. A virtual line connecting the two points serves as the attitude characterization baseline. The difference between the relative coordinates of the two points in the microscopic imaging field of view and the corresponding points on the substrate is calculated to determine the attitude of the substrate relative to the mask and adjust the rotation angle. If and If the value is 0 or the absolute value is less than a certain threshold, then there is no need to adjust the horizontal rotation axis of the precision worktable. ;like > If the value is greater than 0 or the threshold, then the horizontal rotation axis... The required rotation angle is , and if If the value is greater than 0, the rotation direction is positive; if it is 0 or the threshold, the rotation direction is positive. < Then the horizontal rotation axis The required rotation angle is ; wherein, is the coordinate value of the baseline end point e in the X-axis direction of the field of view coordinate system of the microphotography system. The coordinates of the endpoint f of the attitude characterization baseline on the substrate in the X-axis direction of the field-of-view coordinate system of the microscope imaging system; The coordinates of the endpoint e of the attitude characterization baseline on the substrate in the Y-axis direction of the field-of-view coordinate system of the microscope imaging system; is the coordinate value of the baseline end point f in the Y-axis direction of the field of view coordinate system of the microphotography system for the pose representation on the substrate; Step 5, collecting the relative position difference of the alignment marks on the substrate and the mask in the subjective observation area , and calculating the adjustment motion vector of the integrated error correction compensation as ​ Step 6: Determine the relative positional deviation of each alignment area after adjustment. If... , and If all values ​​are less than the set threshold, alignment is achieved; otherwise, reselect. The largest alignment area is the main observation area; readjust the alignment again. in, This represents the relative positional deviation between the alignment marks on the substrate and the photomask in the i-th alignment region; This represents the deviation value corresponding to the maximum relative positional deviation between the substrate and the alignment marks on the mask in each alignment region.

2. The method of claim 1, wherein: Methods for achieving rough alignment between the substrate and the photomask include manual alignment, machine vision alignment, and mechanical positioning alignment. There should be no fewer than two alignment areas on the substrate or photomask.

3. The method of claim 1, wherein: Alignment marking patterns set on a substrate or mask, including cross, quad, triangle, array of spaced line segments, sector, or arc.

4. The method of claim 1, wherein: The position of the alignment mark is characterized by the feature points of the graphic. The feature points are marked by image recognition or manual marking. The feature points include the structural center point of the alignment mark, the line intersection point, and the graphic vertex.

5. The method of claim 1, wherein: Points used to determine the baseline for attitude representation include the structural center point of alignment marks, line intersections, graphic vertices, or other points with known spacing.

6. The method of claim 1, wherein: The steps for calibrating the coordinate system per unit length of the microscopic imaging system include: identifying feature lines on the mask and reading the pixel coordinates of their endpoints. and The pixel length coefficient is calculated by dividing the actual length of the feature line design by its pixel length. Calculate the arithmetic mean of the pixel length coefficients of multiple feature lines, and use it as the unit length calibration coefficient of the microscope imaging system coordinate system. Pixel coordinates are obtained through Convert to coordinates with length units.

7. The method of claim 6, wherein: The forms of feature lines used for calibration include feature lines with the side length of the graphic outline within the alignment area, line width or spacing, arc radius, and known actual length. The number of feature lines used for unit length calibration of the coordinate system within the same alignment area is at least one, and the number of feature lines n used in the calibration process is no less than two.

8. The method of claim 7, wherein: The display sampling ratio is the same along different axes of the microscopic imaging coordinate system. For coordinate systems with different display sampling ratios, the pixel length coefficients for different coordinate axes are solved separately. and ,as well as , Pixel coordinates are obtained through Convert to coordinates with length units; in, The length of a feature line per unit length in the X-axis direction of the coordinate system of a microscope camera system is given in the actual scene. The length of the characteristic line in the actual scene is used to calibrate the unit length of the Y-axis direction of the microscopic camera system coordinate system. Lg is the pixel length coefficient corresponding to the gth characteristic line pair for calibrating the unit length of the X-axis direction; Yg is the pixel length coefficient corresponding to the gth characteristic line pair for calibrating the unit length of Y-axis direction; It is the arithmetic mean of the pixel length coefficients of multiple feature lines in the X-axis direction; is the arithmetic average of the pixel length coefficients of the characteristic lines in the Y-axis direction.

9. The method of claim 7, wherein: The error correction and compensation calculation method includes: selecting the X-axis adjustment direction within the horizontal plane of the precision worktable as the reference direction; adjusting the precision worktable to move sequentially along its horizontal plane X and Y drive axes, with the motion vectors being respectively... and It also records the relative position coordinates of the alignment mark relative to the initial position after movement in the field-of-view coordinate system of the microscope imaging system. and ; Calculate the deflection angle between the X-axis of the precision stage and the x-axis of the microscope imaging system's field of view coordinate system. ; Calculate the deflection angle of the precision worktable's Y-axis from the ideal orthogonal direction of the X-axis. .

10. The method for multilayer overlay alignment of micro / nano devices according to claim 9, characterized in that: In the horizontal plane of the precision worktable, the X or Y adjustment axis is the direction, and the a and b in the motion vector are set to non-zero lengths.

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