Multi-layer overlay alignment method for micro-nano device

Abstract

The invention relates to the technical field of micro-nano manufacturing, and particularly discloses a multi-layer overlay alignment method for a micro-nano device. Comprising the following steps: pre-aligning a substrate, calibrating unit length of a coordinate system of a microscopic camera system, selecting a main observation area, resolving a deflection angle between the coordinate systems and an axis deflection angle of a coordinate system of a workbench, adjusting a phase attitude of the substrate and a mask plate, adjusting a relative position of the substrate and the mask plate, performing alignment judgment on the relative position attitude, and the like. According to the method, the error correction and compensation function is integrated, the influence of machining errors, assembly errors, mechanism repeated positioning errors and the like of parts such as a precision workbench and a microscopic camera system on the alignment adjustment process is weakened, and the alignment precision and efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano manufacturing technology, and in particular relates to a multi-layer overlay alignment method for a micro-nano device. Background Art

[0002] Micro-nano devices refer to devices whose minimum feature size of functional structures is in the micrometer or nanometer scale, including semiconductor chips, microsensors / actuators, micro-nano electromechanical integrated systems, etc. Photolithography is a key process step in the manufacture of micro-nano devices. It refers to the technology of using shorter wavelength energy-carrying waves such as ultraviolet rays, lasers, ion beams, and electron beams to solidify the photoresist in a specific area, thereby realizing the transfer of the structural pattern on the mask to substrates such as silicon, quartz, metal, and polymers. With the continuous development of micro-nano devices, their functional integration continues to improve. The functional units on the substrate are not only smaller in size and higher in density, but also develop in the direction of multi-layer stacking, which requires multiple photolithography. Overlay alignment before photolithography is a key link in the manufacture of multi-layer stacked devices. It is the basis for ensuring that different structural pattern layers have accurate spatial position matching relationships.

[0003] In order to achieve overlay alignment, there are generally no less than two alignment areas in the mask, and alignment marks are drawn in each area. The position difference between the alignment marks in the mask and the manufactured structure graphics on the substrate is observed by a microscopic camera system, and the relative position of the mask and the substrate is adjusted using a three-dimensional precision workbench so that the alignment marks at the corresponding positions on the mask and the substrate coincide, so that the multi-layer structure graphics manufactured on the substrate have an accurate spatial position matching relationship. The development of overlay alignment technology has gone through several stages. In the early days, overlay alignment was mainly achieved by manual observation and manual adjustment. This method has the disadvantages of large human errors, low alignment efficiency, and large batch differences, and cannot adapt to the large-scale batch production of micro-nano devices.

[0004] With the development of machine vision technology and automatic control technology, lithography machines with fully automatic alignment functions have emerged. A microscope camera system is used to replace the human eye to observe the alignment area, image recognition technology is used to analyze and measure position differences, and servo motors and other actuators are used to drive the precision workbench to achieve relative position and posture adjustment, thereby achieving fully automatic alignment of the mask and substrate. Typically, during the automatic alignment process, the substrate is pre-aligned and leveled so that the alignment area of ​​the substrate appears in the field of view of the microscope camera system; the image recognition software identifies the alignment marks on the mask and the substrate in the alignment area, characterizes the position of the alignment marks with their feature points (structural center points or specific vertices, etc.), and reads out the absolute position coordinates of the feature points in the coordinate system of the microscope camera system field of view, or the relative position coordinates between the two feature points; the automatic controller calculates the displacement or rotation amount in different adjustment directions of the precision worktable based on the read relative position difference, and drives the precision worktable actuator to achieve relative position and posture adjustment; the relative position difference between the alignment marks in each alignment area on the mask and the substrate is read again, and if it is greater than the set threshold, the above alignment steps are repeated again until the relative position difference between the alignment marks in each alignment area is less than the set threshold. Due to processing errors, assembly errors, and repeated positioning errors of the parts of the precision workbench, microscope camera system, etc., it is impossible to achieve complete overlap between the observation coordinate system of the microscope camera system and the motion coordinate system of the precision workbench, and it is impossible to ensure that the motion directions of the adjustment axes of the precision workbench are completely orthogonal. However, most of the existing automatic alignment methods do not take these errors into consideration. The alignment motion direction of the precision workbench is inconsistent with the observation coordinate direction of the microscope camera system, resulting in a large error between the relative position and posture of the substrate and the mask after alignment and adjustment and the ideal solution result. Repeated alignment is required, and even an infinite loop may occur. Therefore, an efficient and precise alignment method with integrated error correction and compensation functions is urgently needed. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-layer overlay alignment method for micro-nano devices to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A multi-layer overlay alignment method for a micro-nano device comprises 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 appear in the observation field at the same time;

[0009] Step 2: Using the actual size and pixel size of the characteristic lines in the microscopic imaging field of view, the unit length of the coordinate system of the microscopic imaging system is calibrated, and the relative position information such as the observed pixel coordinates and the calculated distance is converted into information with units, and the alignment area with a larger relative distance between the substrate and the alignment mark on the mask is selected as the main observation area;

[0010] Step 3, the X-axis and Y-axis of the horizontal plane of the precision worktable move respectively by known displacements a and b, and sample through the micro-camera system, compare the relative position changes of the alignment marks on the substrate and the alignment marks on the mask before and after the movement, and solve the deflection angle α of the Y-axis of the precision worktable from the ideal orthogonal direction of the X-axis, and the deflection angle θ of the x-axis of the field of view coordinate system of the micro-camera system and the x-axis of the precision worktable;

[0011] Step 4: Select a known distance L on the substrate b The two points e and f are located on the positive side of the X-axis or Y-axis of the precision workbench as e. The virtual line between the two points is used as the baseline for posture characterization. The difference between the relative coordinates of the two points in the microscope field of view and the corresponding points on the substrate is calculated to determine the posture of the substrate relative to the mask and adjust the rotation angle. de -x df |with|y de -y df | is 0 or its absolute value is less than a certain threshold, there is no need to adjust the horizontal rotation axis τ of the precision worktable; if |x de -x df |>|y de -y df |>0 or threshold, the horizontal rotation axis τ needs to rotate by an angle of arccos[(x de -x df ) / L b ], and if y de -y df >0, the rotation direction is positive; if 0 or threshold <|x de -x df |<|y de -y df |, then the horizontal rotation axis τ needs to rotate by an angle of arcsin[(y de -y df ) / L b ](clockwise is positive);

[0012] Step 5: Collect the relative position difference (x dm ,y dm ), calculate the adjustment motion vector of the integrated error correction compensation 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 position deviation of each alignment area after adjustment. If D i 、|x de -x df |with| yde -y df | are both less than the set threshold, then alignment is achieved, otherwise D is reselected m The largest alignment area is the main observation area, and the alignment is adjusted again.

[0014] Preferably, the method of achieving rough alignment between the substrate and the mask includes but is not limited to manual, machine vision, and mechanical limiting methods, and the number of alignment areas set on the substrate or the mask is no less than 2.

[0015] Preferably, the alignment mark pattern provided on the substrate or mask includes but is not limited to a cross, a quadrilateral, a triangle, an array of spaced line segments, a fan or an arc.

[0016] Preferably, the position of the alignment mark is characterized by feature points of the graphic, through image recognition or manual marking of feature points, and the feature points include but are not limited to the structural center point of the alignment mark, the intersection point of lines, and the vertex of the graphic.

[0017] Preferably, the points used to determine the baseline of the posture representation include, but are not limited to, structural center points of alignment marks, intersection points of lines, vertices of figures, or other points with known spacing.

[0018] Preferably, the step of calibrating the unit length of the coordinate system of the microscope camera system includes: identifying the characteristic lines on the mask, reading the pixel coordinates of their endpoints (i g1 ,j g1 ) and (i g2 ,j g2 ) ; Calculate the pixel length coefficient 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 as the unit length calibration coefficient of the microscope camera system coordinate system Pixel coordinates are obtained by Convert to coordinates with length units.

[0019] Preferably, the form of the characteristic lines used for calibration includes but is not limited to the characteristic lines of the contour length of the figure in the alignment area, the line width or spacing, the arc radius and the known actual length. The number of characteristic lines used for unit length calibration of the coordinate system in the same alignment area is at least 1, and the number of characteristic lines n used in the calibration process is not less than 2.

[0020] Preferably, the display sampling ratios of different axes of the microscopic imaging coordinate system are the same. For coordinate systems with different display sampling ratios, the pixel length coefficients S of different coordinate axes are solved separately. xg =L xg / |i g1 -i g2 |With S yg =L yg / |j g1 -j g2 |, and Pixel coordinates are obtained by Convert to coordinates with length units.

[0021] Preferably, the error correction and compensation solution method includes: selecting the X adjustment axis direction in the horizontal plane of the precision worktable as the reference direction; adjusting the precision worktable to move along the X and Y drive axes in its horizontal plane in turn, with the motion vectors being (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 camera system; solving the deflection angle θ=arctan(Δy1 / Δx1) between the X adjustment axis of the precision worktable and the x axis of the field of view coordinate system of the microscope camera system; solving the deflection angle α=arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ of the Y axis of the precision worktable from the ideal orthogonal direction of the X axis.

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The method for adjusting the relative position and posture of a substrate and a mask provided by the present invention screens the collected position information of different alignment areas, selects the alignment area with the largest distance between the alignment marks on the substrate and the mask as the main observation area, and takes the position information of the alignment marks on the substrate in the main observation area as the basis. Compared with the existing method which often uses the central position information of the connecting line of two alignment marks on the substrate as the basis for calculation, the influence of the measurement error of the microscope camera system on the calculation results of each step is reduced; an error correction and compensation solution step is integrated, and the change of the alignment mark position data during the alignment process is used to realize the solution of the manufacturing error and the assembly error of the precision workbench and the microscope camera system, and a correction and compensation algorithm for the alignment adjustment amount of each axis of the precision workbench is proposed, thereby improving the alignment accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram showing the steps of the multi-layer 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 The alignment mark in the field of view of the microscopic imaging system according to the embodiment of the present invention is shown;

[0028] Figure 4 A schematic diagram showing a coordinate system and adjustment motion in the error correction and compensation step according to an embodiment of the present invention;

[0029] In the figure: 201-microscope system, 202-mask holder, 203-controller, 204-mask, 205-substrate, 206-film stage, 207-precision worktable Y adjustment axis, 208-precision worktable X adjustment axis, 209-precision worktable Z adjustment axis, 210-precision worktable τ rotation adjustment axis, 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-identified endpoint of calibration feature line, 401-precision worktable coordinate system, 402-deflection angle between actual Y axis and ideal Y' axis of precision worktable, 403-microscope field of view coordinate system, 404-deflection angle θ between microscopic field of view coordinate system and precision worktable coordinate system. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present invention includes three aspects: a relative posture adjustment and alignment method between a substrate and a mask, a unit length calibration method of a microscopic camera system coordinate system, and a method for calculating an error correction compensation amount. The specific technical scheme is as follows:

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

[0033] Step S1: Pre-alignment of substrate: The substrate and the mask are roughly aligned by manual or automatic pre-alignment device. After the substrate is placed on the wafer stage on the precision workbench, the microscope camera system field of view of the specific alignment area is observed, and the corresponding alignment marks on the substrate and the mask are observed at the same time. The alignment marks or manual marks on the substrate in the alignment area are identified by image recognition software, and the positions of the alignment marks are characterized by feature points (structural center points or specific vertices).

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

[0035] Step S3: Calculate the deflection angle between the coordinate systems and the axis deflection angle of the workbench coordinate system: perform relative position adjustment, and use the error correction and compensation calculation method described in the present invention to calculate the deflection angle α of the Y axis of the precision workbench from the ideal orthogonal direction of the X axis, and the deflection angle θ of the x axis of the microscopic camera system field of view coordinate system and the X axis of the precision workbench. Optionally, the displacements a and b of the X and Y axes of the precision workbench can be set as x and y, respectively, according to the relative position coordinates of the main observation area. dm and dm , or set to a specific known value.

[0036] Step S4: Relative posture adjustment between substrate and mask: Optionally, two alignment areas with a relatively large distance are selected (represented as areas e and f, respectively, and area e is located on the positive side of area f along the X-axis or Y-axis of the precision workbench), and the virtual line connecting the alignment mark feature points in the two areas is used as the posture characterization baseline, and its length is L b , to assist in determining the posture of the substrate relative to the mask. de -x df |with|y de -y df | is 0 or its absolute value is less than a certain threshold, there is no need to adjust the horizontal rotation axis τ of the precision worktable; if |x de -x df |>|y de -y df |>0 or threshold, the horizontal rotation axis τ needs to rotate by an angle of arccos[(x de -x df ) / L b ], and judge y de -y df >0 rotation direction is positive; if 0 or threshold <|x de -x df |<|y de -y df |, then the horizontal rotation axis τ needs to rotate 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: Sample the main observation area according to the microscope camera system, read the relative position difference (x) of the alignment marks on the substrate and the mask. dm ,y dm ), the adjustment motion of each axis of the precision worktable is solved by the automatic controller, and the adjustment motion vector of the integrated error correction compensation is output 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 posture of the substrate and the mask: Determine the relative position deviation of each alignment area after adjustment. If D i 、|x de -x df |with|y de -y df| are both less than the set threshold, then alignment is achieved, otherwise D is reselected m The largest alignment area is the main observation area, and adjustment and alignment are performed again.

[0039] Optionally, the steps described in the relative posture adjustment alignment method of the present invention can adjust the order of S2, S3 and S4 according to actual conditions; if a low-latency real-time sampling micro-camera system and a high-computing power controller are selected, the steps S2, S3 and S4 in the above alignment process can be independently calculated in real time and run in parallel with other steps, so as to realize 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 the alignment accuracy and efficiency.

[0040] In a second aspect, step S2 in the relative posture adjustment and alignment method of the present invention relates to a method for calibrating the unit length of a coordinate system of a microscope camera system, and the method specifically comprises:

[0041] Step S21, sampling different alignment areas through a microscope camera system, observing characteristic lines of known actual lengths such as the length of the contour of the graphic, the line width or spacing, the arc radius, etc. in the alignment area on the mask, marking the endpoints of the characteristic lines by manual marking or image recognition software, the number of sampled alignment areas on the same mask is not less than 2, and the number n of observed characteristic lines is not less than 2.

[0042] Step S22, reading the pixel coordinates of the endpoints of each feature line, wherein 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 , get the pixel length coefficient of the g-th feature line

[0043] Step S23, calculating the arithmetic mean of the pixel length coefficients of the n characteristic lines as the unit length calibration coefficient of the microscope camera system coordinate system

[0044] Step S24: In the subsequent alignment step, the pixel coordinates of the point in the microscope camera 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 in the field of view of the microscope camera 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 |, respectively calculate the coordinate system unit length calibration coefficient and In step S24, coordinate transformation

[0046] In a third aspect, in step S3 of the relative posture adjustment alignment method described in the present invention, the present invention provides a method for error correction and compensation solution, which specifically includes:

[0047] Step S31, optionally, setting the X adjustment axis direction or the Y adjustment axis in the horizontal plane of the precision workbench as the reference coordinate axis of the precision workbench.

[0048] Step S32, adjust the precision workbench to move along the X and Y drive axes in its horizontal plane in sequence, with the motion vectors being (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 camera system.

[0049] Step S33, if the X adjustment axis direction is selected as the reference coordinate axis, the deflection angle θ=arctan(Δy1 / Δx1) between the X axis direction of the precision workbench and the x axis of the field of view coordinate system of the microscope camera system is calculated.

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

[0051] Implementation column:

[0052] See also Figures 1 to 4 As shown,

[0053] Among them, the relative position and posture alignment between the substrate and the mask can be achieved, and the process is as follows: Figure 1 The schematic diagram of the alignment mechanism described in the embodiment of the present application is shown in 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 camera 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 wafer stage 206 by vacuum adsorption. The Y adjustment axis 207, X adjustment axis 208, Z adjustment axis 209 and τ rotation adjustment axis 210 of the precision workbench move under the control of the controller 203, and drive the wafer stage 206 at the top of the workbench to move, so as to adjust the relative position and posture between the substrate 205 and the mask 204 and realize the overlay alignment.

[0054] A multi-layer overlay alignment method for a micro-nano device comprises the following steps:

[0055] Step S101: Pre-alignment of substrate: Before being placed in the alignment mechanism, the substrate 205 is roughly adjusted in posture by the pre-alignment mechanism, and the microscopic camera system 201 manually confirms that the alignment marks on the mask 204 and the substrate 205 can be observed simultaneously in both fields of view; the controller 203 collects images observed in the two fields of view and performs recognition analysis. The collected alignment area images are as follows: Figure 3 As shown, the geometric symmetry center point of the identification pattern is the characteristic point 302 of the alignment mark on the substrate and the characteristic point 304 of the alignment mark on the mask, which represents the position of the alignment mark 301 on the substrate and the alignment mark 303 on the mask.

[0056] Step S102: Calibration of unit length of the microscope camera system coordinate system and selection of the main observation area: The controller 203 collects images observed in both fields of view, identifies the lower side of the alignment mark box on the mask as the calibration feature line, and reads the pixel coordinates (i 204) 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 characteristic line length is 1500 μm, calculate Similarly, calculate S2 in the left field of view; calculate In the subsequent alignment step, the controller 203 collects the pixel coordinates in the image through the formula Converted into coordinates with length in micrometers; comparing the relative position coordinates (x di ,y di ) and calculate the relative distance Since D1>D2, the right field of view with a relatively larger distance is selected as the main observation area.

[0057] Step S103: Calculation of the deflection angle between coordinate systems and the axis deflection angle of the workbench coordinate system: The adjustment motion trajectory of the alignment mark feature point 302 on the substrate observed in the field of view of the microscopic camera system 201 is as follows: Figure 4 As shown; the X-axis of the precision workbench 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 with the ideal Y' is represented as α; the deflection angle 404 between the microscopic imaging field coordinate system 403 and the precision workbench coordinate system 401 is represented as θ; the relative position coordinates (x d1 ,y d1 ) is used as the basis, and the controller 203 controls the precision workbench X adjustment axis 208 and Y adjustment axis 207 to move x in sequence. d1 and d1; The 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 the initial position; according to Figure 4 The trigonometric relationship shown in FIG. 4 is used to solve the deflection angle 404θ=arctan(Δy1 / Δx1)=1.17° between the microscope field coordinate system and the precision workbench coordinate system, and the deflection angle 402α=arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ=0.14° of the Y-axis of the precision workbench from the ideal orthogonal direction Y'.

[0058] Step S104: Adjust the relative posture of the substrate and the mask: The virtual line of the alignment mark feature points 302 on the substrate in the two fields of view is used as the baseline for the posture characterization of the substrate, and the virtual line of the alignment mark feature points 304 on the mask is used as the baseline for the posture characterization of the mask. The length of the baseline for the posture characterization is known to be 80 mm. The controller 203 uses the relative position calculation between the alignment marks, and the threshold value (0.2 μm) <|x 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 worktable is calculated as arcsin[(y d1 -y d2 ) / 80000]=1.1875°(clockwise is positive).

[0059] Step S105: Adjustment of relative position between substrate and mask: The controller 203 collects the relative position difference (x) of the alignment marks on the substrate and mask in the main observation area through the microscopic camera system 201. d1 ,y d1 )=(572.5μm,-396.8μm), the controller 203 calculates the adjustment amount of the precision table 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 posture of the substrate and the mask: The controller 203 collects images of the two fields of view of the micro-camera system 201, D1, D2, |x d1 -x d2 |、|y d1 -y d2| are all smaller than the set threshold (0.2μm), indicating that alignment is achieved.

[0061] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-layer overlay alignment method for micro-nano devices, characterized in that: The following steps are involved: 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 appear in the observation field at the same time; Step 2: Using the actual size and pixel size of the characteristic lines in the microscopic imaging field of view, the unit length of the coordinate system of the microscopic imaging system is calibrated, and the relative position information such as the observed pixel coordinates and the calculated distance is converted into information with units, and the alignment area with a larger relative distance between the substrate and the alignment mark on the mask is selected as the main observation area; Step 3, the X-axis and Y-axis of the horizontal plane of the precision worktable move respectively by known displacements a and b, and sample through the micro-camera system, compare the relative position changes of the alignment marks on the substrate and the alignment marks on the mask before and after the movement, and solve the deflection angle α of the Y-axis of the precision worktable from the ideal orthogonal direction of the X-axis, and the deflection angle θ of the x-axis of the field of view coordinate system of the micro-camera system and the x-axis of the precision worktable; Step 4: Select a known distance L on the substrate b The two points e and f are located on the positive side of the X-axis or Y-axis of the precision workbench as e. The virtual line between the two points is used as the baseline for posture characterization. The difference between the relative coordinates of the two points in the microscope field of view and the corresponding points on the substrate is calculated to determine the posture of the substrate relative to the mask and adjust the rotation angle. de -x df |with|y de -y df | is 0 or its absolute value is less than a certain threshold, there is no need to adjust the horizontal rotation axis τ of the precision worktable; if |x de -x df |>|y de -y df |>0 or threshold, the horizontal rotation axis τ needs to rotate by an angle of arccos[(x de -x df ) / L b ], and if y de -y df >0, the rotation direction is positive; if 0 or threshold <|x de -x df |<|y de -y df |, then the horizontal rotation axis τ needs to rotate by an angle of arcsin[(y de -y df ) / L b ](clockwise is positive); Step 5: Collect the relative position difference (x dm ,y dm ), calculate the adjustment motion vector of the 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)]}; Step 6: Determine the relative position deviation of each alignment area after adjustment. If D i 、|x de -x df |with|y de -y df | are both less than the set threshold, then alignment is achieved, otherwise D is reselected m The largest alignment area is the main observation area, and adjustment and alignment are performed again.

2. A micro-nano device multi-layer overlay alignment method according to claim 1, characterized in that: The method of achieving rough alignment between the substrate and the mask includes but is not limited to manual, machine vision, and mechanical limiting methods, and the number of alignment areas set on the substrate or the mask is no less than 2.

3. A multi-layer overlay alignment method for micro-nano devices according to claim 1, characterized in that: The alignment mark pattern provided on the substrate or mask includes but is not limited to a cross, a quadrilateral, a triangle, an array of spaced line segments, a fan or an arc.

4. A micro-nano device multi-layer overlay alignment method according to claim 1, characterized in that: The position of the alignment mark is characterized by the feature points of the graphic, which are identified by image recognition or manually marked. The feature points include but are not limited to the structural center point of the alignment mark, the intersection point of the lines, and the vertex of the graphic.

5. The method for multi-layer overlay alignment of a micro-nano device according to claim 1, characterized in that: The points used to determine the baseline of the posture representation include, but are not limited to, the structural center point of the alignment mark, the intersection point of the lines, the vertex of the figure, or other points with known spacing.

6. A micro-nano device multi-layer overlay alignment method according to claim 1, characterized in that: The step of calibrating the unit length of the coordinate system of the microscope camera system includes: identifying the characteristic lines on the mask, reading the pixel coordinates of their endpoints (i g1 ,j g1 ) and (i g2 ,j g2 ) ; Calculate the pixel length coefficient 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 as the unit length calibration coefficient of the microscope camera system coordinate system Pixel coordinates are obtained by Convert to coordinates with length units.

7. A micro-nano device multi-layer overlay alignment method according to claim 6, characterized in that: The forms of the characteristic lines used for calibration include but are not limited to the length of the contour of the figure in the alignment area, the line width or spacing, the arc radius and the characteristic lines of known actual length. The number of characteristic lines used for unit length calibration of the coordinate system in the same alignment area is at least 1, and the number of characteristic lines n used in the calibration process is not less than 2.

8. A micro-nano device multi-layer overlay alignment method according to claim 7, characterized in that: The display sampling ratios of different axes of the microscopic imaging coordinate system are the same. For coordinate systems with different display sampling ratios, the pixel length coefficients S of different coordinate axes are solved respectively. xg =L xg / |i g1 -i g2 |With S yg =L yg / |j g1 -j g2 |, and Pixel coordinates are obtained by Convert to coordinates with length units.

9. A micro-nano device multi-layer overlay alignment method according to claim 7, characterized in that: The error correction and compensation solution method comprises: selecting the X adjustment axis direction in the horizontal plane of the precision workbench as the reference direction; adjusting the precision workbench to move along the X and Y driving axes in the horizontal plane in turn, with the motion vectors being (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 the movement in the field of view coordinate system of the microscope camera system; solving the deflection angle θ=arctan(Δy1 / Δx1) between the X adjustment axis of the precision workbench and the x axis of the field of view coordinate system of the microscope camera system; solving the deflection angle α=arctan[(Δx2-Δx1) / (Δy2-Δy1)]-θ of the Y axis of the precision workbench from the ideal orthogonal direction of the X axis.

10. A micro-nano device multi-layer overlay alignment method according to claim 9, characterized in that: The X or Y adjustment axis in the reference direction in the horizontal plane of the precision workbench is the direction, and a and b in the motion vector are set to non-zero lengths.

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