Vertical control method of lithography equipment and lithography equipment

Abstract

The present invention provides a vertical control method for lithography equipment and the lithography equipment. The vertical control method for lithography equipment comprises: during a scanning exposure process, using a substrate focusing and leveling system to measure the position of a substrate surface shape in real time, and extrapolating the substrate surface shape to below an objective lens by calculating an extrapolation point position, thereby obtaining a substrate surface shape measurement value below the field of view of the objective lens at the current moment, wherein the substrate surface shape measurement value includes an instantaneous vertical position change of a workpiece stage; simultaneously, using a mask stage vertical sensor to obtain a position change of the mask stage in real time, wherein the mask stage position change causes a focal plane change, and the mask stage position is updated to the exposure focal plane, thereby obtaining the exposure focal plane at the current moment; and then controlling the workpiece stage and an upper movable lens of the objective lens and a lower movable lens of the objective lens so that the substrate surface shape and the exposure focal plane coincide with each other, thereby solving the problem of the influence of the vertical position change of the movable stage at the moment of surface shape measurement and the moment of exposure on the surface shape and the focal plane.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit equipment manufacturing, and in particular to a vertical control method of a lithography device and the lithography device. Background Art

[0002] Material fluctuations include the surface shape of the lithography mask caused by gravity deformation and the surface shape caused by the unevenness of the substrate surface. The substrate surface shape can be divided into global and local surface shapes. Global surface shape describes the overall variation trend of the substrate's top surface and corresponds to low-order quantities in the substrate surface shape. Local surface shape describes the irregular ups and downs of the substrate's top surface within a local area of ​​the exposure field of view and corresponds to high-order quantities in the substrate surface shape. Gravitational deformation of the reticle causes image curvature, causing the image plane to deviate from its nominal position. The substrate surface shape can cause the top surface of the exposure field to not coincide with the exposure focal plane, resulting in defocus. Both surface shapes adversely affect the actual exposure effect.

[0003] Existing technology uses a combined adjustment method for the workpiece stage and the movable lens of the objective lens to compensate for mask gravity deformation and substrate surface shape separately. During scanning exposure, real-time adjustment of the upper movable mechanism of the lens compensates for higher-order aspects of the mask surface shape; real-time adjustment of the lower movable mechanism of the lens compensates for higher-order aspects of the substrate surface shape. However, this solution uses a feedforward adjustment method for real-time lens adjustment during scanning exposure, failing to consider the impact of changes in the vertical position of the movable stage between the time of surface measurement and exposure on the surface shape and focal plane. Summary of the Invention

[0004] The object of the present invention is to provide a vertical control method for a lithographic device to solve the problem of the influence of the vertical position change of a moving stage on the surface shape and focal plane at the time of surface shape measurement and exposure.

[0005] To solve the above technical problems, the present invention provides a vertical control method for a lithographic apparatus, comprising:

[0006] Before scanning exposure, the substrate surface shape is measured by the substrate focusing and leveling system, and the mask surface shape is measured by the mask focusing and leveling system;

[0007] During the scanning exposure process, the closed-loop processing unit of the focusing and leveling system receives the measurement value of the upper surface shape of the substrate obtained by the substrate focusing and leveling system in real time, and extrapolates the substrate to the bottom of the objective lens array to obtain the measurement value of the substrate surface shape under the field of view of the objective lens array at the current moment. The closed-loop processing unit of the focusing and leveling system receives the position change information of the mask stage obtained by the vertical sensor of the mask stage, and updates the mask stage to the focal plane position to obtain the exposure focal plane at the current moment; and the closed-loop processing unit of the focusing and leveling system receives the position information of the workpiece stage obtained by the vertical sensor of the workpiece stage in real time, and calculates the workpiece stage adjustment amount according to the substrate surface shape, the mask surface shape and the workpiece stage position information to control the movement of the workpiece stage in real time in a closed loop; the closed-loop processing unit of the focusing and leveling system calculates the image plane adjustment amount of the movable lens under the objective lens of the objective lens array according to the substrate surface shape to control the movement of the movable lens under the objective lens of the objective lens array in a closed loop in real time, so that the substrate surface shape and the exposure focal plane coincide with each other.

[0008] Optionally, the substrate is measured by the substrate focusing and leveling system to obtain substrate surface shape measurement data of the substrate, and the substrate surface shape measurement data of the substrate is processed to obtain the substrate surface shape.

[0009] Optionally, a method for processing the substrate surface shape measurement data of the substrate to obtain the substrate surface shape includes optical axis rotation processing, filtering processing and extrapolation processing.

[0010] Optionally, the extrapolation processing of the substrate surface shape is plane extrapolation processing.

[0011] Optionally, the mask is measured by the mask focusing and leveling system to obtain mask surface shape measurement data of the mask, and the mask surface shape measurement data of the mask is processed to obtain the mask surface shape.

[0012] Optionally, a method for processing the mask surface shape measurement data of the mask to obtain the mask surface shape includes deviation calculation processing, filtering processing, extrapolation processing, sliding average processing and polynomial fitting processing.

[0013] Optionally, the deviation calculation processing method includes calculating the surface difference between the mask surface and the relative reference object surface.

[0014] Optionally, the polynomial coefficients calculated by the polynomial fitting process are sent to the closed-loop processing unit of the focusing and leveling system using feedforward closed-loop control. During the scanning exposure process, the closed-loop processing unit of the focusing and leveling system controls the adjustment of the movable lens on the objective lens of the objective lens array.

[0015] Optionally, the adjustment amount of the workpiece stage during the scanning exposure process is calculated in real time based on the overall height and overall tilt of the mask surface obtained by extrapolation processing based on the mask surface processing unit, the focal plane height change and tilt change caused by the change in the position of the mask stage tested by the vertical sensor of the mask stage during the scanning exposure process, the height value and tilt value of the substrate surface fitting under the field of view of the objective lens array during the scanning exposure process, and the height value and tilt value of the reference exposure focal plane. The workpiece stage adjustment amount calculation formula is:

[0016]

[0017] Where: dz_s is the height adjustment of the workpiece stage; dRx_s is the tilt adjustment of the workpiece stage in the x direction; dRy_s is the tilt adjustment of the workpiece stage in the y direction; z_BF, is the reference exposure focal plane height value; Rx_BF is the reference exposure focal plane tilt value in the x direction; Ry_BF is the reference exposure focal plane tilt value in the y direction; dz reticle is the overall height of the mask surface; dRx reticle The mask surface is tilted in the x direction; dRy reticle The mask surface is tilted in the y direction; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS Ry is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage; RS is the change in the focal plane tilt in the y direction caused by the change in the position of the mask stage; PO Rx is the height value of the substrate surface height point fitting under the six objective lens fields of view; PO is the x-direction tilt value and Ry of the height point fitting of the substrate surface under the six objective lens fields of view. PO is the y-direction tilt value of the substrate surface height point fitting under the six objective lens fields of view.

[0018] Optionally, during the scanning exposure process, the image plane adjustment amount of the movable lens at the current moment is calculated based on the height of the substrate surface under the objective lens field of view and the height values ​​and tilt values ​​of the substrate surface height fitting at six objective lens field of view points. The calculation formula for the image plane adjustment amount of the movable lens at the current moment is:

[0019] dz down_i =z PO_i -(Z PO +Rx PO ·y POi -Ry PO ·x POi )

[0020] Among them: dz down_i is the image plane adjustment amount corresponding to objective lens No. i; z PO_i is the extrapolated height of the substrate point under the center of the i-th objective lens; z PORx is the height value of the extrapolated height points under the six objective lenses; PO Ry is the x-direction tilt value of the extrapolated height points fitted under the six objective lenses; PO is the y-direction tilt value of the extrapolated height points fitted under the six objective lenses; POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction.

[0021] Optionally, the focus change caused by the change in the position of the mask stage is compensated according to the current position of the mask stage during scanning exposure. The compensation formula for the change in the position of the mask stage is:

[0022]

[0023] Where: z ENC Rx is the height change of the mask stage at the exposure time. ENC Ry is the x-direction tilt variation of the mask stage position at the exposure time. ENC is the y-direction tilt variation of the mask stage position at the exposure moment; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage, Ry RS is the change in focal plane tilt in the y direction caused by the change in mask stage position; M is the objective lens magnification.

[0024] Optionally, the current position of the mask stage is a real-time test of a vertical sensor of the mask stage during the scanning exposure process.

[0025] Based on the same inventive concept, the present invention also provides a lithography device, which adopts the vertical control method of the above-mentioned lithography device.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] In the vertical control method of the lithography equipment provided by the present invention, first, before the scanning exposure process, the substrate surface shape is measured and processed using the substrate focusing and leveling system, and the mask surface shape is measured and processed using the mask focusing and leveling system, wherein the mask surface shape eliminates the influence of the position change of the mask stage; then, at the time of the scanning exposure process, the substrate surface shape position is measured in real time using the substrate focusing and leveling system, and the substrate surface shape is extrapolated to the bottom of the objective lens by calculating the position of the extrapolation point, thereby obtaining the substrate surface shape measurement value below the field of view of the objective lens at the current moment, wherein the substrate surface shape measurement value includes the instantaneous vertical position change of the workpiece stage; at the same time, the position change of the mask stage is obtained in real time using the mask stage vertical sensor, and the position change of the mask stage will cause the focal plane to change, and the mask stage position is updated to the exposure focal plane to obtain the exposure focal plane at the current moment; then, the workpiece stage and the upper movable lens of the objective lens and the lower movable lens of the objective lens are controlled to make the substrate surface shape and the exposure focal plane coincide, thereby solving the problem of the influence of the vertical position change of the movable stage at the time of surface shape measurement and exposure on the surface shape and focal plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a schematic structural diagram of a lithography apparatus according to an embodiment of the present invention;

[0029] Figure 2 is a vertical control data flow chart of an embodiment of the present invention;

[0030] Figure 3 This is a flow chart of substrate surface processing according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of the movement of the workpiece stage according to an embodiment of the present invention;

[0032] Figure 5 is a flowchart of mask surface processing according to an embodiment of the present invention;

[0033] Figure 6 is a flowchart of mask surface processing according to an embodiment of the present invention;

[0034] Figure 7 Schematic diagram of the positional relationship between the substrate focusing and leveling system and the objective lens according to an embodiment of the present invention;

[0035] In the figure,

[0036] 1-Illumination system; 2-Mask; 3-Mask stage; 4-Mask stage vertical sensor; 5-Mask focusing and leveling system; 6-Substrate focusing and leveling system; 7-Objective lens array; 8-Substrate; 9-Workpiece stage; 10-Workpiece stage vertical sensor; A-Workpiece stage moving surface; B-Light spot of substrate focusing and leveling system; C-Light spot under the field of view of a single objective lens. DETAILED DESCRIPTION

[0037] The vertical control method for a lithographic apparatus according to the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clarify the purpose of illustrating the embodiments of the present invention.

[0038] The inventors discovered that in a photolithography device, due to the influence of gravity and frame deformation, the vertical positions of the workpiece stage and the mask stage are not fixed at different times at the same position. When the material measurement point is far away from the control point, the surface shape of the control point cannot be compensated, resulting in low vertical control accuracy.

[0039] Based on this, in an embodiment of the present invention, before exposure, the substrate surface shape is measured and processed using a substrate focusing and leveling system, and the mask surface shape is measured and processed using a mask focusing and leveling system, wherein the mask surface shape eliminates the influence of the position change of the mask stage; then at the moment of exposure, the substrate surface shape position is measured in real time using the substrate focusing and leveling system, and the substrate surface shape is extrapolated to the bottom of the objective lens by calculating the position of the extrapolation point, thereby obtaining the substrate surface shape value below the field of view of the objective lens at the current moment, wherein the substrate surface shape value includes the instantaneous vertical position change of the workpiece stage; at the same time, the position change of the mask stage is obtained in real time using a mask stage vertical sensor, and the position change of the mask stage will cause the focal plane to change. The position of the mask stage is updated to the exposure focal plane, and the exposure focal plane at the current moment is obtained; finally, the workpiece stage and the movable lens on the objective lens and the movable lens under the objective lens are controlled to make the substrate surface shape coincide with the exposure focal plane.

[0040] For details, please refer to Figure 1, which is a schematic structural diagram of a lithography apparatus according to an embodiment of the present invention. This embodiment provides a lithography apparatus, comprising: an illumination system 1, a mask 2, a mask stage 3, a mask stage vertical sensor 4, a mask focusing and leveling system (FLS-R) 5, a substrate focusing and leveling system (FLS-P) 6, an objective lens array 7, a substrate 8, a workpiece stage 9, and a workpiece stage vertical sensor 10. The illumination system 1 is used to provide a lithography beam. The mask 2 is located on the mask stage 3, and the mask stage 3 is used to support the mask 2. The mask stage vertical sensors 4 are located on opposite sides of the mask stage 3, and are used to detect and control the vertical position of the mask stage 3. In this embodiment, the mask stage vertical sensor 4 is, for example, a laser triangle ruler. The objective lens array 7 is composed of two columns of objective lenses composed of multiple single objective lenses. In this embodiment, the objective lens array 7 includes six single objective lenses, each of which includes a movable lens above the objective lens and a movable lens below the objective lens. The movable lens above the objective lens can adjust the object plane, and the movable lens below the objective lens can adjust the image plane. The mask focusing and leveling system 5 and the substrate focusing and leveling system 6 are located between the two columns of objective lenses, and the mask focusing and leveling system 5 is located directly above the substrate focusing and leveling system 6. In this embodiment, the mask focusing and leveling system 5 and the substrate focusing and leveling system 6 are respectively configured in six numbers. The mask focusing and leveling system 5 is used to measure the surface shape of the mask 2, and the substrate focusing and leveling system 6 is used to measure the surface shape of the substrate 8. The workpiece stage 9 is used to carry the movement of the substrate 8; the workpiece stage vertical sensor 10 is located on opposite sides of the workpiece stage 9, and the workpiece stage vertical sensor 10 is used to detect and control the vertical position of the workpiece stage 9. In this embodiment, the workpiece stage vertical sensor 10 is, for example, a grating ruler.

[0041] Figure 2 This is a vertical control data flow chart of an embodiment of the present invention. Figure 2 As shown, based on the same inventive concept, this embodiment further provides a vertical control method for a lithographic apparatus, comprising:

[0042] Before scanning exposure, the substrate surface shape is measured by the substrate focusing and leveling system, and the mask surface shape is measured by the mask focusing and leveling system;

[0043] During the scanning exposure process, the closed-loop processing unit of the focusing and leveling system receives the measurement value of the upper surface shape of the substrate obtained by the substrate focusing and leveling system in real time, and extrapolates the substrate to the bottom of the objective lens array to obtain the measurement value of the substrate surface shape under the field of view of the objective lens array at the current moment. The closed-loop processing unit of the focusing and leveling system receives the position change information of the mask stage obtained by the vertical sensor of the mask stage, and updates the mask stage to the focal plane position to obtain the exposure focal plane at the current moment; and the closed-loop processing unit of the focusing and leveling system receives the position information of the workpiece stage obtained by the vertical sensor of the workpiece stage in real time, and calculates the workpiece stage adjustment amount according to the substrate surface shape, the mask surface shape and the workpiece stage position information to control the movement of the workpiece stage in real time in a closed loop; the closed-loop processing unit of the focusing and leveling system calculates the image plane adjustment amount of the movable lens under the objective lens of the objective lens array according to the substrate surface shape to control the movement of the movable lens under the objective lens of the objective lens array in a closed loop in real time, so that the substrate surface shape and the exposure focal plane coincide with each other.

[0044] Figure 3 This is a flow chart of substrate surface processing according to an embodiment of the present invention. Figure 2 and Figure 3 , the specific steps of substrate surface processing are as follows:

[0045] In step S11, the workpiece stage vertical sensor 10 controls the height and tilt of the workpiece stage 9 to remain unchanged during the movement, and uses the substrate focusing and leveling system 6 to measure the substrate surface shape, and records the measurement value of each light spot of the substrate focusing and leveling system 6 at the sampling point to obtain the substrate surface shape measurement data (Mapping), and at the same time records the measurement value of the workpiece stage vertical sensor 10.

[0046] Prior to step S11, global leveling is performed. There are generally two types of global leveling: overall global leveling and field-by-field global leveling. Before scanning exposure, either only overall global leveling, only field-by-field global leveling, or both can be performed. The goal of global leveling is to ensure that the entire upper surface of the substrate is substantially aligned with the global leveling target surface. In other words, the workpiece stage vertical sensor 10 in step S10 controls the workpiece stage height and tilt to be equal to the height and tilt after global leveling.

[0047] Step S12: Based on the substrate surface shape processing unit, the substrate surface shape measurement data is subjected to optical axis rotation processing to obtain the original substrate surface shape.

[0048] like Figure 3 and Figure 4As shown, the worktable 8 is located on a marble platform. PO is the optical axis of the objective lens, spot is the light spot of the substrate focusing and leveling system, BF is the reference exposure focal plane, and A is the worktable moving surface. The substrate surface measurement data is processed by optical axis rotation. Specifically, the difference between the substrate surface measurement data measured by the substrate focusing and leveling system 6 and the worktable measurement value measured by the worktable vertical sensor 10 is calculated. Since the lower surface of the substrate 8 always moves along a fixed surface when measuring the substrate surface shape, there is a height and tilt difference between the zero plane FLS-P-0 of the substrate focusing and leveling system 6 and the workpiece stage moving surface A. The tilt between the zero plane FLS-P-0 of the substrate focusing and leveling system 6 and the workpiece stage moving surface A is equal to the sum of the workpiece stage tilt and the focal plane BF tilt. That is, the tilt between the zero plane FLS-P-0 of the substrate focusing and leveling system 6 and the workpiece stage moving surface A is equal to the tilt from the workpiece stage moving surface A to the focal plane BF plus the tilt from the zero plane FLS-P-0 of the substrate focusing and leveling system 6 to the focal plane BF. The measurement values ​​of each light spot of the substrate focusing and leveling system 6 must first be converted to the optical axis to obtain the original substrate surface shape.

[0049] The formula for converting the original measurement value of each spot of the substrate focusing and leveling system 6 into the height under the optical axis is:

[0050] z spot_FLS (x,y)=z spot_raw +Ry*x spot -Rx*y spot (1)

[0051] Among them, x spot The x-axis horizontal position of the light spot in the substrate focusing and leveling system; y spot The y-axis horizontal position of the light spot in the substrate focusing and leveling system; z spot_raw is the original measured height value of each spot in the substrate focusing and leveling system; spot_FLS (x, y) represents the height of each spot after conversion in the substrate focusing and leveling system. Rx represents the x-axis tilt between the zero plane of the substrate focusing and leveling system and the workpiece stage's moving surface, and Ry represents the y-axis tilt between the zero plane of the substrate focusing and leveling system and the workpiece stage's moving surface. x represents the x-axis horizontal position of the measurement point, and y represents the y-axis horizontal position of the measurement point.

[0052] x and y are the horizontal positions of the measurement points, and the formula is as follows:

[0053]

[0054] where x s The x-direction position and y-direction position of the workpiece stage during measurement s is the y-direction position of the workpiece stage during measurement;

[0055] The measurement values ​​of the workpiece table vertical sensor 10 (grating ruler, ENC) corresponding to each spot measurement point are:

[0056] z_s spot_ENC (x,y)=z_s (3)

[0057] Among them, z_s is the current height value of the workpiece table 9, which is equal to the measurement value of the workpiece table vertical sensor 10; z_s spot_ENC It is the measurement value of the vertical sensor of the workpiece stage corresponding to the measurement position of each light spot under the optical axis.

[0058] The difference between the height of the workpiece stage 9 plus the height of the exposure focal plane and the height of each spot originally measured by the substrate focusing and leveling system 6 converted to the height under the optical axis is the original substrate surface shape. The original substrate surface shape is expressed as:

[0059] z plate_map (x,y)=z_s spot_ENC (x,y)+Z_BF-z spot_FLS (x,y) (4)

[0060] Among them, z spot_FLS (x, y) is the height value of each spot after conversion; z_s spot_ENC (x, y) is the ENC height measurement value corresponding to each spot measurement position under the optical axis; Z_BF is the height value of the exposure focal plane; z plate_map (x,y) is the original substrate surface shape.

[0061] Step S13: filtering the original substrate surface.

[0062] Since the substrate surface measurement data (mapping) contains many abnormal points and invalid points, which will affect the vertical control effect, it is necessary to filter the substrate surface measurement data. This method uses a polynomial cyclic progressive filtering method. The main steps are as follows:

[0063] 1) Remove invalid points, i.e. points equal to 0 or infinity in the substrate surface measurement data;

[0064] 2) Remove measurement points with duplicate locations;

[0065] 3) Fit all measurement points into an nth-order standard polynomial, calculate the residual and 3sigma value, and remove the measurement points with residuals greater than 3sigma;

[0066] 4) Repeat step 3) for the remaining points until the residuals of all points are less than 3sigma value, and set the maximum number of cycles to terminate the decision;

[0067] 5) The first fitting is of order 1, the second fitting is of order 1+m polynomial, and so on.

[0068] In step S14, the original substrate surface shape is extrapolated to obtain the overall height, overall tilt and surface shape of the substrate. The overall height and overall tilt of the substrate are used to set the vertical position of the workpiece stage before scanning exposure to avoid excessive difference in the vertical position of the workpiece stage before and after exposure.

[0069] During the scanning exposure process, when entering or exiting the scanning field of view, the measurement system's light spot may have already left the substrate, making it impossible to obtain the current measurement value. In this case, the substrate surface shape needs to be extrapolated. This embodiment uses a plane extrapolation method. The specific method is as follows: first, a plane is fitted based on the existing substrate surface shape data, then the position of the extrapolated point is calculated, and finally, the extrapolated point is substituted into the plane equation to obtain the extrapolated substrate surface shape.

[0070] Figure 5 This is a flowchart of mask surface processing according to an embodiment of the present invention. Figure 5 , the specific steps of mask surface processing are as follows:

[0071] Step S21: The mask stage 3 is kept vertically unchanged and scanned along the Y direction. The mask surface shape is measured using the mask focusing and leveling system 5. The height measurement values ​​and tilt measurement values ​​of each spot of the mask focusing and leveling system 5 at the sampling point are recorded to obtain the mask surface shape measurement data (Mapping). At the same time, the height measurement value z of the mask stage 3 measured by the mask stage vertical sensor 4 is recorded. ENC and tilt measurement value Rx ENC 、Ry ENC .

[0072] Step S22: performing deviation calculation processing on the mask surface shape measurement data based on the mask surface shape processing unit.

[0073] like Figure 5 As shown, the original mask surface shape is first calculated. The original mask surface shape is the surface shape difference between the mask surface shape measurement data (mapping) and the reference object plane. The original mask surface shape is also the difference between the measurement values ​​of each light spot of the mask focusing and leveling system 5 and the measurement value of the mask stage 3 measured by the mask stage vertical sensor 4. The reference object plane is a virtual plane, that is, the deviation calculation processing is performed on the mask surface shape measurement data. The formula is as follows:

[0074] Δz reticle (x i ,y i )=z FLS_spot -(z ENC +Rx ENC *yspot-Ry ENC *xspot)-z reticle (5)

[0075] Among them, zENC is the mask stage height measurement value, Rx ENC is the x-direction tilt measurement value of the mask stage, Ry ENC is the y-direction tilt measurement value of the mask stage; Z FLS_spot Δz is the measured height value of each spot in the mask focusing and leveling system; reticle (x i ,y i ) is the original mask shape; z reticle is the reference plane; x i The horizontal position of each measurement point on the mask in the x direction; i The horizontal position of each measurement point on the mask in the y direction; spot is the horizontal position of the light spot in the x direction; y spot is the horizontal position of the light spot in the y direction.

[0076] x i ,y i For the horizontal position of each measurement point on the mask,

[0077]

[0078] Among them, x rs is the x-direction position of the mask stage during measurement; y rs is the y-direction position of the mask stage during measurement; x spot is the horizontal position of the light spot in the x direction, y spot is the horizontal position of the light spot in the y direction.

[0079] Step S23: performing filtering processing on the mask surface measurement data based on the mask surface processing unit.

[0080] Since the mask surface measurement data (mapping) contains many abnormal points and invalid points, which will affect the vertical control effect, the mask surface measurement data needs to be filtered. This method uses a polynomial cyclic progressive filtering method. The main steps are as follows:

[0081] 1) Remove invalid points, i.e. points in the mask surface measurement data that are equal to 0 or infinity.

[0082] 2) Remove measurement points with duplicate locations.

[0083] 3) Fit all measurement points into an nth-order standard polynomial, calculate the residual and 3sigma value, and remove the measurement points with residuals greater than 3sigma.

[0084] 4) Repeat step 3) for the remaining points until the residuals of all points are less than the 3sigma value, and set the maximum number of cycles to terminate the decision.

[0085] 5) The first fitting is of order 1, the second fitting is of order 1+m polynomial, and so on.

[0086] In step S24 , the mask surface shape processing unit performs extrapolation processing on the mask surface shape measurement data to obtain the overall mask height and the overall mask tilt.

[0087] During the scanning exposure process, when entering or exiting the scanning field of view, the measurement system's spot may have already left the mask, making it impossible to obtain the current measurement value. In this case, the surface shape needs to be extrapolated. This method uses plane extrapolation. Specifically, a plane is first fitted based on the existing mask surface shape measurement data, the positions of the extrapolated points are then calculated, and finally the extrapolated points are substituted into the plane equation to obtain the extrapolated mask surface shape.

[0088] Between step S24 and step S25, the mask surface shape processing unit further performs least squares fitting processing on the mask surface shape measurement data.

[0089] The overall height dz of the mask is obtained by fitting the plane using the least squares method using all the mask surface points after extrapolation. reticle and the overall tilt of the mask dRx reticle 、dRy reticle , used to compensate for changes in the reference focal plane during the scanning exposure process.

[0090] Step S25 : performing sliding average processing on the mask surface shape measurement data based on the mask surface shape processing unit.

[0091] Use the static field of view (Slit) sliding average to calculate the object plane adjustment at a series of y positions along the scanning exposure direction.

[0092] like Figure 6 As shown, during the sliding process of the static field of view, the plane is fitted using the measurement points in the static field of view:

[0093] z i =ax i +by i +c (7)

[0094] Among them, x i ,y i ,z i Represents all the measurement points in the static field of view sliding at each y position; a, b, c are the plane coefficients of the six-spot measurement values ​​of the mask focusing and leveling system fitted at different y positions.

[0095] Calculate the average value of all measurement points under a single objective lens at each y position:

[0096]

[0097] Among them, zij is the surface measurement data of all masks under the i-th lens; is the average value of z of j points under the i-th lens.

[0098] Step S26 , based on the mask surface processing unit, performing object plane adjustment on the mask surface, and using the movable lens on the objective lens to adjust the object plane so that the object plane and the mask plane coincide with each other.

[0099] The object plane adjustment of the single lens is calculated by the fitting plane in formula (7) and the average value of all measurement points under the single objective lens at each y position in formula (8), so as to adjust the object plane by using the movable lens on the objective lens so that the object plane and the mask plane coincide with each other; the object plane adjustment amount of the single lens is:

[0100]

[0101] Among them, dz i (y) is the adjustment amount of a single lens; a, b, c are the plane coefficients of the six-spot measurement values ​​of the mask focusing and leveling system fitted at different y positions; x i The x-direction position of each lens center, y i The y-direction position of the center of each lens.

[0102] Step S27, based on the mask surface shape processing unit, the single-lens object plane adjustment amount of the mask surface shape is subjected to polynomial fitting processing to obtain the object plane adjustment amount polynomial coefficients and the mask surface shape. The object plane adjustment amount polynomial coefficients are used for feedforward control during the scanning exposure process. During the scanning exposure process, the movable lens under the objective lens is subjected to real-time closed-loop control according to the calculated image plane adjustment amount.

[0103] The object plane adjustment amount of a single lens is fitted with Legendre or other orthogonal polynomials to obtain the polynomial coefficients C0i, C1i, C2i,…, Cni, where n is the polynomial fitting order and i is the single objective lens.

[0104] Step S31: During the scanning exposure process, based on the closed-loop processing unit of the focusing and leveling system, the adjustment amount of the workpiece stage and the image plane adjustment amount of the movable lens under the objective lens are obtained at the current moment according to the current measurement value of the focusing and leveling system, the position of the mask stage, the substrate surface shape, the overall height tilt of the mask, the exposure focal plane and the static deformation compensation table.

[0105] like Figure 2As shown, the closed-loop processing unit of the focusing and leveling system is used to receive the real-time measurement values ​​of the basic focusing and leveling system 6, the mask focusing and leveling system 5, the mask stage vertical sensor 4 and the workpiece stage vertical sensor 10, as well as the data substrate overall height, substrate overall tilt and first substrate surface shape obtained by the substrate processing unit; the mask overall height, mask overall tilt and object plane adjustment amount polynomial coefficients obtained by the mask surface shape processing unit; the closed-loop processing unit of the focusing and leveling system can also obtain the reference exposure focal plane and energy deformation compensation table. At the same time, the closed-loop processing unit of the focusing and leveling system can calculate according to the above real-time measurement values ​​to obtain the workpiece stage adjustment amount and the image plane adjustment amount of the movable lens under the objective lens at the current moment. The closed-loop processing unit of the focusing and leveling system controls the worktable to compensate for the mask surface shape and substrate surface shape in real-time closed-loop and controls the movable lens under the objective lens to adjust the image plane in real-time closed-loop. The closed-loop processing unit of the focusing and leveling system adjusts the object plane according to the feedforward closed-loop control of the movable lens on the objective lens to make the basic surface shape coincide with the exposure focal plane.

[0106] Specifically, by combining the processed substrate surface shape and mask surface shape, as well as the measurement values ​​of the substrate focusing and leveling system and the mask stage position at the exposure time, the workpiece stage adjustment amount and the objective lens movable lens adjustment amount can be calculated in real time.

[0107] like Figure 7 As shown, it is a schematic diagram of the relationship between the substrate focusing and leveling system and the objective lens position. Figure 7 It includes 6 objective lens fields of view, as well as the light spot B of the substrate focusing and leveling system and the light spot C under the single objective lens field of view. The light spot B of the substrate focusing and leveling system is fitted into the substrate surface fitting plane. The substrate surface shape difference is calculated based on the substrate surface fitting plane and the light spot deviation under the single objective lens field of view. The substrate surface height under the objective lens viewing range is calculated based on the substrate surface shape measurement value of the current substrate focusing and leveling system and the substrate surface shape difference between the substrate surface fitting plane and the light spot under the single objective lens field of view.

[0108] Interpolation is performed according to the substrate surface shape table, and the substrate surface shape under the light spot in the objective lens and substrate focusing and leveling system can be obtained by linear interpolation of the substrate surface shape.

[0109] The substrate surface shape under each spot in the substrate focusing and leveling system is obtained by interpolating the substrate surface shape:

[0110] z spoti (x,y)=dz(x+x spoti ,y+y spoti ) (10)

[0111] Among them, z spoti (x, y) is the substrate surface shape under the No. i spot in the substrate focusing and leveling system; dz(x+x spoti ,y+y spoti) is the processed substrate surface data; x is the current workpiece stage x-direction position; y is the current workpiece stage y-direction position; x spoti is the horizontal position of the light spot No. i in the substrate focusing and leveling system in the x direction; y spoti is the horizontal position of the i-th light spot in the substrate focusing and leveling system in the y direction.

[0112] Perform linear interpolation calculation on the substrate surface to obtain the substrate surface shape under the field of view of a single objective lens:

[0113]

[0114] Where: z POi (x, y) is the surface shape of the substrate under the objective lens No. i; n is the number of interpolation points under the field of view of a single objective lens; j is the jth interpolation point under the field of view of a single objective lens, is the substrate surface shape after interpolation processing; x is the current x-direction position of the workpiece stage, y is the current y-direction position of the workpiece stage; x POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction; L PO is the length of the field of view in the y direction of the single objective lens.

[0115] The substrate surface shape fitting plane under the light spot in the substrate focusing and leveling system in formula (10) is the upper surface of the substrate surface shape, which is the high-order surface shape of the substrate, and can also be the residual of the substrate surface shape. The substrate surface shape fitting plane formula is:

[0116]

[0117] Among them, z spoti is the high-order surface shape of the substrate under the spot No. i of the substrate focusing and leveling system; x spoti is the horizontal position of the light spot No. i in the substrate focusing and leveling system in the x direction; y spoti is the horizontal position of the i-th light spot in the substrate focusing and leveling system in the y direction; a, b, and c are the high-order surface fitting plane coefficients of the substrate under the six light spots of the substrate focusing and leveling system.

[0118] The surface shape difference between the light spot in the field of view of the objective lens and the substrate measurement point under the light spot in the focusing and leveling system is calculated by the deviation of the substrate surface shape in the field of view of the single objective lens (formula (11)) and the substrate surface shape fitting plane (formula (12)). The surface shape difference formula between the light spot in the field of view of the objective lens and the substrate measurement point under the light spot in the focusing and leveling system is:

[0119] dz POi =z POi -(a+b·x POi +c·y POi ) (13)

[0120] Among them, dz POi is the high-order surface difference between the objective lens No. i and the substrate under the corresponding light spot; z POi is the high-order surface shape of the substrate under objective lens No. i; a, b, c are the fitting plane coefficients of the high-order surface shape of the substrate under the six light spots of the substrate focusing and leveling system; x POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction.

[0121] The height of the substrate under the objective lens field of view is calculated by the total height measurement value and tilt measurement value of the current substrate focusing and leveling system, the spot under the objective lens field of view in formula (13), and the surface difference of the substrate measurement point under the spot in the focusing and leveling system. The offline calibration value of the workbench is also considered in the calculation process. The offline calibration value of the workbench is the offline calibration of the position change of the objective lens No. i and the workpiece stage at the corresponding spot position before scanning exposure. The calculation formula of the substrate surface height under the objective lens field of view is:

[0122] z PO_i =(z FLS +Rx FLS ·y POi -Ry FLS ·x POi )+dz POi -dz FCTi (x,y) (14)

[0123] Where: z PO_i is the height of the substrate point under the center of objective lens No. i; z FLS Rx is the total height measurement value of the substrate surface of the current substrate focusing and leveling system; FLS The measured value of the substrate surface tilt in the x direction of the current substrate focusing and leveling system; Ry FLS The measured value of the substrate surface tilt in the y direction of the current substrate focusing and leveling system; x POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction; dz POi Rz is the high-order surface difference between objective lens No. i and the substrate under the corresponding light spot; FCTi (x, t) is the position change of the workpiece stage at the objective lens No. i and the corresponding spot position; x is the current x-direction position of the workpiece stage; y is the current y-direction position of the workpiece stage.

[0124] The plane fitting formula of the height points of the substrate surface under the six objective lens fields of view of the objective lens array 7 is:

[0125]

[0126] Thus we get:

[0127]

[0128] Where: x POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of the objective lens No. i in the y direction; a0, b0, c0 are the plane fitting coefficients of the height points of the substrate surface under the six objective lens fields of view; z PO_i is the height of the substrate point under the center of objective lens No. i; z PO Rx is the height of the fitting plane at the six height points of the substrate surface under the field of view of the objective lens; PO Ry is the x-direction tilt value of the fitting plane of the substrate surface height point under the six objective lens fields of view; PO is the y-direction tilt value of the fitting plane of the substrate surface height points under the six objective lens fields of view.

[0129] The workpiece stage adjustment amount at the current moment is calculated based on the height values ​​and tilt values ​​of the substrate surface height points fitted under the six objective lens fields of view in formula (16-17), as well as the overall height and overall tilt of the mask surface obtained by extrapolation based on the reference exposure focal plane and the mask surface processing unit. The workpiece stage adjustment amount at the current moment is:

[0130]

[0131] Where: dz_s is the height adjustment of the workpiece stage; dRx_s is the tilt adjustment of the workpiece stage in the x direction; dRy_s is the tilt adjustment of the workpiece stage in the y direction; z_BF, is the reference exposure focal plane height value; Rx_BF is the reference exposure focal plane tilt value in the x direction; Ry_BF is the reference exposure focal plane tilt value in the y direction; dz reticle is the overall height of the mask surface; dRx reticle The mask surface is tilted in the x direction; dRy reticle The mask surface is tilted in the y direction; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS Ry is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage; RS is the change in the focal plane tilt in the y direction caused by the change in the position of the mask stage; PO Rx is the height value of the substrate surface height point fitting under the six objective lens fields of view; PO is the x-direction tilt value and Ry of the height point fitting of the substrate surface under the six objective lens fields of view. PO is the y-direction tilt value of the substrate surface height point fitting under the six objective lens fields of view.

[0132] The image adjustment amount of the movable lens at the current moment is calculated by the height of the substrate surface under the objective lens field of view in formula (15) and the height value and tilt value of the substrate surface height fitting at the six objective lens field of view points. The calculation formula of the image adjustment amount of the movable lens at the current moment is:

[0133] dz down_i =Z PO_i -(z PO +Rx PO ·y POi -Ry PO ·x POi ) (18)

[0134] Among them: dz down_i is the image plane adjustment amount corresponding to objective lens No. i; z PO_i is the height of the substrate point under the center of objective lens No. i; z PO Rx is the height value of the substrate surface height point fitting under the six objective lens fields of view; PO Ry is the x-direction tilt value of the extrapolated height points fitted under the six objective lenses; PO is the y-direction tilt value of the extrapolated height points fitted under the six objective lenses; POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction.

[0135] During the actual exposure process, in addition to compensating for the mask and substrate surface shapes, the workpiece stage also needs to compensate for focal plane changes caused by changes in the mask stage position based on the current position of the mask stage during exposure. The mask vertical sensor measures the height change and tilt change of the mask stage position at the moment of exposure in real time, and calculates the compensation formula for the mask stage position change during exposure using the objective lens magnification:

[0136]

[0137] Where: z ENC Rx is the height change of the mask stage at the exposure time; ENC Ry is the x-direction tilt variation of the mask stage position at the exposure moment; ENC is the y-direction tilt variation of the mask stage position at the exposure moment; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage, Ry RS is the change in focal plane tilt in the y direction caused by the change in mask stage position; M is the objective lens magnification.

[0138] In step S32, the workpiece stage is subjected to real-time closed-loop control according to the calculated workpiece stage adjustment amount, and the movable lens on the objective lens is subjected to feed-forward control according to the polynomial coefficient of the object plane adjustment amount.

[0139] The polynomial coefficients of the mask surface shape calculation are directly sent to the objective lens, and the movable lens on the objective lens performs feedforward closed-loop control during exposure. The formula for the object plane adjustment of the movable lens on the objective lens is as follows:

[0140]

[0141] Among them: dz up_i is the object plane adjustment amount corresponding to objective lens No. i; f i (y) is Legendre or other orthogonal polynomial basis function; c j_i are the coefficients of the Legendre polynomial calculated above.

[0142] In summary, the vertical control method of the lithography equipment provided in the embodiment of the present invention first uses the substrate focusing and leveling system to measure and process the substrate surface shape and the overall height and tilt of the substrate before exposure, and uses the mask focusing and leveling system to measure and process the mask surface shape, the overall height of the mask, the overall tilt of the mask and the polynomial coefficients of the object plane adjustment amount, and the mask surface shape eliminates the influence of the position change of the mask stage; then, at the exposure time, the substrate focusing and leveling system is used to measure the position of the substrate surface shape in real time, and the substrate surface shape is extrapolated to the bottom of the objective lens by calculating the position of the extrapolation point, thereby obtaining The surface shape measurement value of the substrate below the field of view of the objective lens at the current moment is obtained, and the substrate surface shape measurement value includes the instantaneous vertical position change of the workpiece stage; at the same time, the position change of the mask stage is obtained in real time using the vertical sensor of the mask stage. The position change of the mask stage will cause the focal plane to change. The position of the mask stage is updated to the exposure focal plane to obtain the exposure focal plane at the current moment; finally, the workpiece stage and the upper movable lens of the objective lens and the lower movable lens of the objective lens are controlled to make the substrate surface shape and the exposure focal plane coincide with each other, thereby solving the problem of the influence of the vertical position change of the movable stage at the time of surface shape measurement and exposure on the surface shape and focal plane.

[0143] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A vertical control method for a lithographic apparatus, characterized in that: include: Before scanning exposure, the substrate surface shape is measured by the substrate focusing and leveling system, and the mask surface shape is measured by the mask focusing and leveling system; During the scanning exposure process, the closed-loop processing unit of the focusing and leveling system receives the measurement value of the upper surface shape of the substrate obtained by the substrate focusing and leveling system in real time, and extrapolates the substrate to the bottom of the objective lens array to obtain the measurement value of the substrate surface shape under the field of view of the objective lens array at the current moment. The closed-loop processing unit of the focusing and leveling system receives the position change information of the mask stage obtained by the vertical sensor of the mask stage, and updates the mask stage to the focal plane position to obtain the exposure focal plane at the current moment. In addition, the closed-loop processing unit of the focusing and leveling system receives the position information of the workpiece stage obtained by the vertical sensor of the workpiece stage in real time, and calculates the workpiece stage adjustment amount according to the substrate surface shape, mask surface shape and workpiece stage position information to control the movement of the workpiece stage in real time in a closed loop. The closed-loop processing unit of the focusing and leveling system calculates the image plane adjustment amount of the movable lens under the objective lens of the objective lens array according to the substrate surface shape to control the movement of the movable lens under the objective lens of the objective lens array in real time in a closed-loop manner so that the substrate surface shape and the exposure focal plane coincide with each other.

2. The vertical control method of the lithographic equipment according to claim 1, characterized in that: The substrate focusing and leveling system is used to measure the substrate to obtain substrate surface shape measurement data of the substrate, and the substrate surface shape measurement data of the substrate is processed to obtain the substrate surface shape.

3. The vertical control method of the lithographic equipment according to claim 2, wherein: The processing method for processing the substrate surface shape measurement data of the substrate to obtain the substrate surface shape includes optical axis rotation processing, filtering processing and extrapolation processing.

4. The vertical control method of the lithographic equipment according to claim 3, wherein: The extrapolation process of the substrate surface shape is a plane extrapolation process.

5. The vertical control method of the lithographic equipment according to claim 1, wherein: The mask focusing and leveling system is used to measure the mask to obtain mask surface shape measurement data of the mask, and the mask surface shape measurement data of the mask is processed to obtain the mask surface shape.

6. The vertical control method of the lithographic equipment according to claim 5, characterized in that: The method for processing the mask surface shape measurement data of the mask to obtain the mask surface shape includes deviation calculation processing, filtering processing, extrapolation processing, sliding average processing and polynomial fitting processing.

7. The vertical control method of the lithographic equipment according to claim 6, wherein: The deviation calculation processing method includes calculating the surface difference between the mask surface and the relative reference object surface.

8. The vertical control method of the lithographic equipment according to claim 6, wherein: The polynomial coefficients calculated by the polynomial fitting process are sent to the focusing and leveling system closed-loop processing unit using feedforward closed-loop control. During the scanning exposure process, the focusing and leveling system closed-loop processing unit controls the adjustment of the movable lens on the objective lens of the objective lens array.

9. The vertical control method of the lithographic equipment according to claim 6, wherein: The adjustment amount of the workpiece stage during the scanning exposure process is calculated in real time based on the overall height and overall tilt of the mask surface obtained by extrapolation processing based on the mask surface processing unit, the focal plane height change and tilt change caused by the change in the position of the mask stage tested by the vertical sensor of the mask stage during the scanning exposure process, the height value and tilt value of the substrate surface fitting under the field of view of the objective lens array during the scanning exposure process, and the height value and tilt value of the reference exposure focal plane. The workpiece stage adjustment amount calculation formula is: Where: dz_s is the height adjustment of the workpiece stage; dRx_s is the tilt adjustment of the workpiece stage in the x direction; dRy_s is the tilt adjustment of the workpiece stage in the y direction; z_BF, is the reference exposure focal plane height value; Rx_BF is the reference exposure focal plane tilt value in the x direction; Ry_BF is the reference exposure focal plane tilt value in the y direction; dz reticle is the overall height of the mask surface; dRx reticle The mask surface is tilted in the x direction; dRy reticle The mask surface is tilted in the y direction; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS Ry is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage; RS is the change in the focal plane tilt in the y direction caused by the change in the position of the mask stage; PO Rx is the height value of the substrate surface height point fitting under the six objective lens fields of view; PO is the x-direction tilt value and Ry of the height point fitting of the substrate surface under the six objective lens fields of view. PO is the y-direction tilt value of the substrate surface height point fitting under the six objective lens fields of view.

10. The vertical control method of the lithographic equipment according to claim 1, wherein: During the scanning exposure process, the image adjustment amount of the movable lens at the current moment is calculated based on the height of the substrate surface under the objective lens field of view and the height value and tilt value of the substrate surface height fitting at the six objective lens field of view points. The calculation formula for the image adjustment amount of the movable lens at the current moment is: dz down_i =z PO_i -(z PO +Rx PO ·y POi -Ry PO ·x POi ) Among them: dz down_i is the image plane adjustment amount corresponding to objective lens No. i; z PO_i is the extrapolated height of the substrate point under the center of the i-th objective lens; z PO Rx is the height value of the extrapolated height points under the six objective lenses; PO Ry is the x-direction tilt value of the extrapolated height points fitted under the six objective lenses; PO is the y-direction tilt value of the extrapolated height points fitted under the six objective lenses; POi is the horizontal position of the center of objective lens No. i in the x direction; y POi is the horizontal position of the center of objective lens No. i in the y direction.

11. The vertical control method of the lithographic equipment according to claim 1, wherein: The focus change caused by the change of the mask stage position is compensated according to the current position of the mask stage during scanning exposure. The compensation formula for the mask stage position change is: Where: z ENC Rx is the height change of the mask stage at the exposure time; ENC Ry is the x-direction tilt variation of the mask stage position at the exposure moment; ENC is the y-direction tilt variation of the mask stage position at the exposure moment; z RS Rx is the focal plane height change caused by the change in the mask stage position; RS is the change in the focal plane tilt in the x direction caused by the change in the position of the mask stage, Ry RS is the change in focal plane tilt in the y direction caused by the change in mask stage position; M is the objective lens magnification.

12. The vertical control method of the lithographic equipment according to claim 11, wherein: The current position of the mask stage is a real-time test of the mask stage vertical sensor during the scanning exposure process.

13. A photolithography apparatus, characterized in that: A vertical control method for a lithographic apparatus according to any one of claims 1 to 12 is adopted.

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