CN117666366A - Wafer workpiece table height self-adaptive control method and control system - Google Patents
Wafer workpiece table height self-adaptive control method and control system Download PDFInfo
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Abstract
The invention relates to the technical field of height control of a wafer workpiece table, in particular to a wafer workpiece table height self-adaptive control method and a wafer workpiece table height self-adaptive control system, which comprise the following steps: recording a grating image of the workpiece table at a reference height as a reference image, wherein the surface height of the wafer is the reference height; adjusting the height of a workpiece table, and collecting grating images in real time; performing image processing on the grating image and the reference image acquired in real time, and outputting a height difference value between the real-time height of the surface of the wafer and the reference height; taking the height difference value as a control target value of a PID control algorithm, smoothing the control target value, and then driving the inching mechanism to adjust the height of the workbench; and (3) circulating the steps until the height difference between the real-time height of the surface of the wafer and the reference height is smaller than a preset value, stopping the circulating control step, and maintaining the current control output.
Description
Technical Field
The invention relates to the technical field of height control of wafer workpiece tables, in particular to a wafer workpiece table height self-adaptive control method and a wafer workpiece table height self-adaptive control system.
Background
In order to output a stable scanned image of an electron beam, the electron beam wafer measurement device is required to keep the height of the wafer surface stable during the process of scanning the electron beam, but in the whole working process, the height of the wafer surface of the wafer area receiving the scanning of the electron beam changes to a certain extent due to the influence of factors such as a mechanical structure, the stability of a driving part, the flatness of the wafer and the like along with the position movement of a workpiece table carrying the wafer, and the height change needs to be eliminated as much as possible at the moment so as to ensure the stability of scanning and imaging of the electron beam.
Currently, an electron beam wafer measurement device commonly uses a triangulation method to directly measure or estimate the height, and then controls a micro-motion mechanism to compensate the height deviation according to the obtained height deviation data; the triangulation method generally uses single-point measurement, grating image projection measurement and the like, and the micro-motion structure generally uses control modes such as a self-closing loop controller, table lookup, interpolation approximation and the like.
However, in the actual working process of the device, due to the changes of the conditions such as the material of the wafer, the design of the circuit pattern, the process node and the like, it is difficult to ensure the consistency and the imaging quality of the optical signal or the optical image reflected by the wafer, which leads to the increase or even the failure of the deviation of the height measurement or estimation, and the control quantity is generally directly output to the driving unit, which often causes the problems of large amplitude oscillation of the workpiece table, long convergence time and low control efficiency.
Therefore, how to provide a control method and system for measuring the height of the workpiece table with high accuracy and improving the height control efficiency is one of the technical problems to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a wafer workpiece table height self-adaptive control method and a control system, which are characterized in that through grating matching light path design, a characteristic matching algorithm is utilized to carry out matching operation on grating image characteristics of positions before and after the workpiece table height changes to obtain a correlation value, and then a more accurate position deviation estimated value is obtained; and after the height difference data of the workpiece table are obtained, iteration is carried out for a plurality of times through a PID algorithm, the PID control quantity is smoothly output, the impact and vibration of the system are effectively reduced, and the control efficiency is further improved.
In order to achieve the above purpose, the present invention provides the following technical solutions:
in a first aspect, the present invention provides a method for adaptively controlling the height of a wafer stage, including the following steps:
s1, setting a grating on a light source path of an emission light path, setting a workpiece table to a reference height, and recording a grating image reflected by the surface of a wafer at the moment as a reference image, wherein the surface height of the wafer at the moment is the reference height;
s2, based on the step S1, enabling a control system of the wafer measurement equipment to enter a closed-loop control state, adjusting the height of a workpiece table, and collecting grating images in real time;
s3, performing image processing on the grating image and the reference image acquired in real time based on the step S2, extracting image characteristics, and outputting a height difference value between the real-time height of the surface of the wafer and the reference height through image matching;
s4, based on the step S3, taking the height difference value as a control target value of a PID control algorithm, and driving the inching mechanism to adjust the height of the workbench after smoothing the control target value, namely adjusting the height of the wafer;
s5, circulating the steps S2-S4 until the difference value between the real-time height of the surface of the wafer and the reference height is smaller than a preset value, stopping circulating the control step, and keeping the current control output.
Preferably, the grating is composed of at least two groups of periodic gratings, and the period of each group of periodic gratings has a certain difference, so that the grating image has uniqueness in the whole range of the height variation of the wafer surface.
Further, the specific method in step S3 is as follows:
s31, carrying out partial feature interception on the reference image to obtain a first feature image, recording the position P0 of the first feature image on the reference image, and summing or calculating an average value of gray values of the first feature image according to columns to obtain a reference feature image;
s32, based on the step S31, carrying out feature interception on the grating image acquired in real time on all heights to obtain a second feature image, wherein the width of the second feature image is equal to that of the first feature image, and carrying out column summation or calculation on the gray value of the second feature image to obtain a target feature image;
s33, based on the step S32, intercepting parts with the same length as the reference feature map from the target feature map one by one, performing feature matching on the two groups of features through a feature matching algorithm, searching an optimal matching position, and recording the position of the reference feature map in the target feature map as P1;
s34. based on step S33, the difference between the position P1 and the position P0 is the height difference P, i.e. the height difference p=p1-p0.
Preferably, the method for calculating the position P1 in step S33 may further be: and intercepting parts with the same length as the reference feature map from the target feature map one by one, calculating the correlation of the two groups of features to obtain a correlation curve, calculating a step of a correlation value in the correlation curve, and performing mathematical model fitting to obtain a fitting curve, wherein the zero crossing point of the fitting curve is the position P1.
Further, in step S4, the specific method for driving the micro-motion mechanism to adjust the height of the workbench after smoothing the control target value is as follows: and establishing a seven-segment S-curve acceleration and deceleration algorithm model, obtaining a smooth displacement curve through the seven-segment S-curve acceleration and deceleration algorithm model, and outputting a control target value to a micro-motion mechanism driver according to the smooth displacement curve.
Further, the smooth displacement curve comprises seven sections of S curves, wherein the seven sections of S curves are an acceleration section, a uniform acceleration section, a deceleration section, a uniform speed section, an acceleration and deceleration section, a uniform deceleration section and a deceleration and deceleration section in sequence, and the duration time of the seven sections is T1-T7 respectively, wherein:
T1=T3=T5=T7=
and t4=0 when the displacement is too small to reach the maximum speed, t2=t6=0 when the maximum acceleration cannot be reached; where Amax is the maximum acceleration and Jmax is the maximum jerk.
Further, the step of outputting the control target value to the inching mechanism driver according to the smooth displacement curve is as follows:
s41, calculating a target speed Vtar, an acceleration Atar and a jerk Jtar according to a control target value Star obtained by a PID control algorithm;
s42, calculating the minimum displacement amount Lmin according to the target speed Vtar, the acceleration Atar and the jerk Jtar;
wherein,is the minimum displacement, +.>For the initial speed +.>For ending speed +.>For the target speed +.>For acceleration period time, +.>For accelerating period of time +.>To reduce the acceleration period time, +.>For a constant speed period>For the time of the acceleration/deceleration period,for uniform deceleration period>For reducing the period of time;
s43, judging the relation between the minimum displacement Lmin and a control target value Star; when LminAnd when Star, executing steps S44-S45, and when Lmin>During Star, executing steps S46-S48;
s44, calculating acceleration and deceleration process time T1-T7 according to the seven-segment S curve acceleration and deceleration algorithm model;
s45, interpolating and calculating a smooth displacement quantity Si according to the seven-segment S curve acceleration and deceleration algorithm model and outputting the smooth displacement quantity Si to a micro-motion mechanism driver;
s46, searching the maximum speed Vmax which can be achieved under the control target value Star according to a dichotomy, repeating the step S42, and calculating a new minimum displacement distance Lnew according to the latest maximum speed Vmax;
s47, judging whether the minimum displacement distance Lnew is close to a control target value Star, if so, returning to the steps S44-S45, otherwise, executing the step S48;
s48, circulating the steps S46-S47.
In a second aspect, the present invention provides a control system for implementing the wafer stage height adaptive control method according to any one of the first aspects, comprising:
the workpiece table is used for bearing the wafer;
the optical grating is used for forming a grating image on the surface of the wafer of the workpiece table under the condition of being irradiated by the light source and reflecting the grating image to the receiving optical path;
a receiving optical path including an optical imaging device for receiving a grating image;
a computer including an image processing unit for performing image processing on the grating image and the reference image and outputting a height difference value; the device also comprises a smooth displacement unit, a micro-motion mechanism driver and a control target value processing unit, wherein the smooth displacement unit is used for performing curve smoothing on the control target value and outputting the control target value to the micro-motion mechanism driver;
the micro-motion mechanism is arranged below the workpiece table and used for adjusting the height of the workpiece table, and the micro-motion mechanism is electrically connected with the micro-motion mechanism controller.
The beneficial effects of the invention are as follows:
1) The grating image features at the positions before and after the height change of the workpiece table are matched by utilizing a feature matching algorithm through the grating matching light path design to obtain a correlation value, so that a more accurate position deviation estimated value is obtained; and because the signal characteristics of the grating image are directly used in the method, the risk of failure caused by distortion of reflection measurement points or reflection images due to the change of conditions such as materials of wafers, design of circuit patterns, process nodes and the like when single-point measurement or single-characteristic measurement is relied on is greatly reduced.
2) According to the method, an output quantity smoothing mechanism is added on the basis of PID control, a seven-segment S-curve acceleration and deceleration algorithm model is established to obtain acceleration and deceleration process time and a smooth displacement quantity Si and output the acceleration and deceleration process time and the smooth displacement quantity Si to a micro-mechanism driver, so that impact and vibration of a system can be effectively reduced, and further control efficiency is improved.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 is a schematic view of a structural framework of the present invention;
FIG. 2 is a schematic diagram of an embodiment of a grating according to the present invention;
FIG. 3 is a grating image obtained by the grating of FIG. 2 on an optical imaging device;
FIG. 4 is a schematic diagram of the process of the present invention for obtaining height differences;
FIG. 5 is a schematic diagram of raster image displacement;
FIG. 6 is a schematic diagram of the results of algorithm execution of a seven-segment S-curve acceleration and deceleration algorithm model;
FIG. 7 is a flow chart of the control target value output in a smooth displacement curve;
FIG. 8 is a graph of the step response of an algorithm of the seven segment S-curve acceleration and deceleration algorithm model with a step of 1;
FIG. 9 is a graph of the step response of an algorithm of the seven segment S-curve acceleration and deceleration algorithm model with a step of 3;
FIG. 10 is a graph of the step response of an algorithm of the seven segment S-curve acceleration and deceleration algorithm model with a step of 5;
FIG. 11 is a graph of the step response of an algorithm of the seven segment S-curve acceleration and deceleration algorithm model with a step of 10;
FIG. 12 is a schematic diagram of a control system of the present invention;
the labels in the figure: 1 is a transmitting light path, 11 is a light source, 12 is a grating, 2 is a receiving light path, 21 is an optical imaging device, 3 is a computer, 4 is a micro-mechanism driver, 5 is a micro-mechanism, and 6 is a workbench.
Detailed Description
Example 1
As shown in fig. 1-7, the present invention provides a wafer stage height adaptive control method, in this embodiment 1, as shown in fig. 1, comprising the following steps:
s1, setting a grating on a light source path of an emission light path, setting a workpiece table to a reference height, and recording a grating image reflected by the surface of a wafer at the moment as a reference image, wherein the surface height of the wafer at the moment is the reference height;
the grating is composed of at least two groups of periodic grids, and the period of each group of periodic grids has a certain difference, so that the grating image has uniqueness in the full range of the height change of the wafer surface; in a specific embodiment of the grating, as shown in fig. 2, narrow grating strips with equal width are taken as a basic grating image, three wide strips with equal width are generated through the fusion of the strips in three areas, the light transmittance of the three wide strips is different, black in a grating design graph is a light-transmitting part, and white is a light-impermeable part; the final raster image shown in fig. 3 is obtained on the optical imaging device.
S2, based on the step S1, enabling a control system of the wafer measuring equipment to enter a closed-loop control state, adjusting the height of a workpiece table, and collecting grating images in real time.
S3, performing image processing on the grating image and the reference image acquired in real time based on the step S2, extracting image characteristics, and outputting a height difference value between the real-time height of the surface of the wafer and the reference height through image matching;
as shown in fig. 4, the specific method in step S3 is as follows:
s31, carrying out partial feature interception on the reference image to obtain a first feature image, recording the position P0 of the first feature image on the reference image, and summing or calculating an average value of gray values of the first feature image according to columns to obtain a reference feature image;
s32, based on the step S31, carrying out feature interception on the grating image acquired in real time on all heights to obtain a second feature image, wherein the width of the second feature image is equal to that of the first feature image, and carrying out column summation or calculation on the gray value of the second feature image to obtain a target feature image;
s33, based on the step S32, intercepting parts with the same length as the reference feature map from the target feature map one by one, performing feature matching on the two groups of features through a feature matching algorithm, searching an optimal matching position, and recording the position of the reference feature map in the target feature map as P1, wherein the feature matching algorithm is the prior art and is not repeated herein;
s34. based on step S33, the difference between the position P1 and the position P0 is the height difference P, i.e. the height difference p=p1-p0.
Because the grating image has uniqueness, when the image matching is carried out, a unique maximum/minimum value can be obtained at the optimal matching position, and the image matching correlation value monotonically decreases/increases along with the distance from the optimal matching position; under this condition, the correlation value of the image matching can be considered as a continuously-derivable function, and the derivative at its maximum point is zero.
Therefore, in one specific embodiment, the method of calculating the position P1 in step S33 may further be: and intercepting parts with the same length as the reference feature map from the target feature map one by one, calculating the correlation of the two groups of features to obtain a correlation curve, calculating a step of a correlation value in the correlation curve, and performing mathematical model fitting, wherein the mathematical model for fitting is a Sigmod curve to obtain a fitting curve, the zero crossing point of the fitting curve is a position P1, and the pattern matching precision of sub-pixel precision can be obtained.
S4, based on the step S3, taking the height difference value as a control target value of a PID control algorithm, and driving the inching mechanism to adjust the height of the workbench after smoothing the control target value, namely adjusting the height of the wafer;
the specific method for driving the micro-motion mechanism to adjust the height of the workbench after smoothing the control target value in the step S4 is as follows: and establishing a seven-segment S-curve acceleration and deceleration algorithm model, obtaining a smooth displacement curve through the seven-segment S-curve acceleration and deceleration algorithm model, and outputting a control target value to a micro-motion mechanism driver according to the smooth displacement curve.
The smooth displacement curve includes seven sections of S curves, as shown in FIG. 6, the seven sections of S curves are an acceleration section AB, a uniform acceleration section BC, a deceleration section CD, a uniform velocity section DE, an acceleration and deceleration section EF, a uniform deceleration section FG and a deceleration and deceleration section GH in sequence, and the duration time of the seven stages is T1-T7 respectively, wherein:
T1=T3=T5=T7=
and t4=0 when the displacement is too small to reach the maximum speed, t2=t6=0 when the maximum acceleration cannot be reached; where Amax is the maximum acceleration and Jmax is the maximum jerk.
As shown in fig. 6, the X-axis is the time axis, the Y-axis is the displacement s, the velocity v, the acceleration a, and the jerk j, T1-T7 are the duration of each phase, T0-T7 are the time points of each phase, for example, time point T0 to time point T1 are phase T1, and time point T6 to time point T7 are phase T7; vmax, amax, jmax are algorithm maximum speed, acceleration, jerk, respectively.
The seven-segment S-curve acceleration and deceleration algorithm model is established by adopting an integration method, and firstly, the jerk function j (t) is as follows:
J(t)=
integrating the jerk function to obtain an acceleration function a (t):
a(t)==/>
integrating the acceleration function to obtain a velocity function v (t):
v(t)==/>
further integrating the velocity function to obtain a displacement function curve s (t):
s(t)==
the complete seven-segment S-curve acceleration and deceleration algorithm model is obtained through multiple integration.
As shown in fig. 7, the steps of outputting the control target value to the inching mechanism driver in the smooth displacement curve are as follows:
s41, calculating a target speed Vtar, an acceleration Atar and a jerk Jtar according to a control target value Star obtained by a PID control algorithm;
s42, calculating the minimum displacement amount Lmin according to the target speed Vtar, the acceleration Atar and the jerk Jtar;
wherein,is the minimum displacement, +.>For the initial speed +.>For ending speed +.>For the target speed +.>For acceleration period time, +.>For accelerating period of time +.>To reduce the acceleration period time, +.>For a constant speed period>For the time of the acceleration/deceleration period,for uniform deceleration period>For reducing the period of time;
s43, judging the relation between the minimum displacement Lmin and a control target value Star; when LminAnd when Star, executing steps S44-S45, and when Lmin>During Star, executing steps S46-S48;
s44, calculating acceleration and deceleration process time T1-T7 according to the seven-segment S curve acceleration and deceleration algorithm model;
s45, interpolating and calculating a smooth displacement quantity Si according to the seven-segment S curve acceleration and deceleration algorithm model and outputting the smooth displacement quantity Si to a micro-motion mechanism driver;
s46, searching the maximum speed Vmax which can be achieved under the control target value Star according to a dichotomy, repeating the step S42, and calculating a new minimum displacement distance Lnew according to the latest maximum speed Vmax;
s47, judging whether the minimum displacement distance Lnew is close to a control target value Star, if so, returning to the steps S44-S45, otherwise, executing the step S48; in one embodiment, the displacement refers to the amount of change in mv, and when the minimum displacement distance Lnew is within ±1 of the control target value Star, it is determined that both are close;
s48, circulating the steps S46-S47.
S5, circulating the steps S2-S4 until the difference value between the real-time height of the surface of the wafer and the reference height is smaller than a preset value, stopping circulating the control step, and keeping the current control output, wherein in a specific embodiment, the preset value is plus or minus 200 nanometers.
According to the steps, step inputs of 1, 3, 5 and 10 units are respectively set, and control tests are carried out on the algorithm of the seven-section S-curve acceleration and deceleration algorithm model to obtain a step response curve as shown in fig. 8-11, wherein a solid line is a traditional uniform output control feedback curve, a dotted line is a 7-section S-curve smooth output control feedback curve, tss is an S-curve smooth control steady-state time, and tsc is a uniform control steady-state time.
As can be seen from the step response curves of fig. 8 to 11, the method disclosed in the present application effectively reduces the generation of vibration of the workbench, and the amplitude is about one third of the constant speed control; as shown in fig. 8, when the step is 1, the steady state time is: tss 1/tsc1=0.167; as shown in fig. 9, when the step is 3, the steady state time is: tss 3/tsc3=0.284; as shown in fig. 10, when the step is 5, the steady state time is: tss 5/tsc5=0.268; as shown in fig. 11, when the step is 10, the steady state time is: tss10/tsc10=0.387; the steady state time is shorter and the response speed is faster than the constant speed output.
In a specific embodiment, a large amount of data transmission and operation are needed in the links of image feature matching calculation and model fitting parameter adjustment, so that a platform with higher calculation power and supporting multi-thread synchronous calculation can be selected, and meanwhile, code optimization is performed to improve the logic efficiency of calculation.
Example 2
As shown in fig. 12, the present invention provides a control system for implementing the wafer stage height adaptive control method according to any one of embodiment 1, comprising:
a workpiece stage 6 for carrying a wafer;
a light emitting path 1, wherein a grating 12 is arranged on a light source 11 path of the light emitting path 1, and the grating 12 is used for forming a grating image on the surface of a wafer of the workpiece 6 table and reflecting the grating image to a receiving light path 2 under the condition of being irradiated by the light source 11;
a receiving optical path 2, the receiving optical path 2 including an optical imaging device 21, the optical imaging device 21 being configured to receive a grating image;
a computer 3 including an image processing unit for performing image processing on the grating image and the reference image and outputting a height difference value; the device also comprises a smooth displacement unit, a micro-motion mechanism driver 4 and a control target value control unit, wherein the smooth displacement unit is used for performing curve smoothing on the control target value and outputting the control target value to the micro-motion mechanism driver 4;
and the micro-motion mechanism 5 is arranged below the workpiece table 6 and used for adjusting the height of the workpiece table 6, and the micro-motion mechanism 5 is electrically connected with the micro-motion mechanism controller 4.
The foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The wafer workpiece stage height self-adaptive control method is characterized by comprising the following steps of:
s1, setting a grating on a light source path of an emission light path, setting a workpiece table to a reference height, and recording a grating image reflected by the surface of a wafer at the moment as a reference image, wherein the surface height of the wafer at the moment is the reference height;
s2, based on the step S1, enabling a control system of the wafer measurement equipment to enter a closed-loop control state, adjusting the height of a workpiece table, and collecting grating images in real time;
s3, performing image processing on the grating image and the reference image acquired in real time based on the step S2, extracting image characteristics, and outputting a height difference value between the real-time height of the surface of the wafer and the reference height through image matching;
s4, based on the step S3, taking the height difference value as a control target value of a PID control algorithm, and driving the inching mechanism to adjust the height of the workbench after smoothing the control target value, namely adjusting the height of the wafer;
s5, circulating the steps S2-S4 until the difference value between the real-time height of the surface of the wafer and the reference height is smaller than a preset value, stopping circulating the control step, and keeping the current control output.
2. The wafer stage height adaptive control method according to claim 1, wherein: the grating is composed of at least two groups of periodic grids, and the period of each group of periodic grids has a certain difference, so that the grating image has uniqueness in the whole range of the height change of the wafer surface.
3. The method for adaptively controlling the height of a wafer stage according to claim 1, wherein the specific method in step S3 is as follows:
s31, carrying out partial feature interception on the reference image to obtain a first feature image, recording the position P0 of the first feature image on the reference image, and summing or calculating an average value of gray values of the first feature image according to columns to obtain a reference feature image;
s32, based on the step S31, carrying out feature interception on the grating image acquired in real time on all heights to obtain a second feature image, wherein the width of the second feature image is equal to that of the first feature image, and carrying out column summation or calculation on the gray value of the second feature image to obtain a target feature image;
s33, based on the step S32, intercepting parts with the same length as the reference feature map from the target feature map one by one, performing feature matching on the two groups of features through a feature matching algorithm, searching an optimal matching position, and recording the position of the reference feature map in the target feature map as P1;
s34. based on step S33, the difference between the position P1 and the position P0 is the height difference P, i.e. the height difference p=p1-p0.
4. The method for adaptively controlling the height of a wafer stage according to claim 3, wherein the method for calculating the position P1 in step S33 further comprises: and intercepting parts with the same length as the reference feature map from the target feature map one by one, calculating the correlation of the two groups of features to obtain a correlation curve, calculating a step of a correlation value in the correlation curve, and performing mathematical model fitting to obtain a fitting curve, wherein the zero crossing point of the fitting curve is the position P1.
5. The method for adaptively controlling the height of a wafer stage according to claim 1, wherein the specific method for performing the stage height adjustment by driving the jog mechanism after smoothing the control target value in step S4 comprises the steps of: and establishing a seven-segment S-curve acceleration and deceleration algorithm model, obtaining a smooth displacement curve through the seven-segment S-curve acceleration and deceleration algorithm model, and outputting a control target value to a micro-motion mechanism driver according to the smooth displacement curve.
6. The method for adaptively controlling the height of a wafer stage according to claim 5, wherein: the smooth displacement curve comprises seven sections of S curves, the seven sections of S curves are an acceleration section, a uniform acceleration section, a deceleration section, a uniform speed section, an acceleration and deceleration section, a uniform deceleration section and a deceleration and deceleration section in sequence, and the duration time of the seven stages is T1-T7 respectively, wherein:
T1=T3=T5=T7=
and t4=0 when the displacement is too small to reach the maximum speed, t2=t6=0 when the maximum acceleration cannot be reached; where Amax is the maximum acceleration and Jmax is the maximum jerk.
7. The method of claim 5, wherein the step of outputting the control target value to the micro-motion mechanism driver according to the smooth displacement curve is as follows:
s41, calculating a target speed Vtar, an acceleration Atar and a jerk Jtar according to a control target value Star obtained by a PID control algorithm;
s42, calculating the minimum displacement amount Lmin according to the target speed Vtar, the acceleration Atar and the jerk Jtar;
wherein,is the minimum displacement, +.>For the initial speed +.>For ending speed +.>For the target speed +.>For acceleration period time, +.>For accelerating period of time +.>To reduce the acceleration period time, +.>For a constant speed period>For acceleration and deceleration period time->To even outTime of fast period->For reducing the period of time;
s43, judging the relation between the minimum displacement Lmin and a control target value Star; when LminAnd when Star, executing steps S44-S45, and when Lmin>During Star, executing steps S46-S48;
s44, calculating acceleration and deceleration process time T1-T7 according to the seven-segment S curve acceleration and deceleration algorithm model;
s45, interpolating and calculating a smooth displacement quantity Si according to the seven-segment S curve acceleration and deceleration algorithm model and outputting the smooth displacement quantity Si to a micro-motion mechanism driver;
s46, searching the maximum speed Vmax which can be achieved under the control target value Star according to a dichotomy, repeating the step S42, and calculating a new minimum displacement distance Lnew according to the latest maximum speed Vmax;
s47, judging whether the minimum displacement distance Lnew is close to a control target value Star, if so, returning to the steps S44-S45, otherwise, executing the step S48;
s48, circulating the steps S46-S47.
8. A control system for implementing the wafer stage height adaptive control method of any one of claims 1-7, comprising:
the workpiece table is used for bearing the wafer;
the optical grating is used for forming a grating image on the surface of the wafer of the workpiece table under the condition of being irradiated by the light source and reflecting the grating image to the receiving optical path;
a receiving optical path including an optical imaging device for receiving a grating image;
a computer including an image processing unit for performing image processing on the grating image and the reference image and outputting a height difference value; the device also comprises a smooth displacement unit, a micro-motion mechanism driver and a control target value processing unit, wherein the smooth displacement unit is used for performing curve smoothing on the control target value and outputting the control target value to the micro-motion mechanism driver;
the micro-motion mechanism is arranged below the workpiece table and used for adjusting the height of the workpiece table, and the micro-motion mechanism is electrically connected with the micro-motion mechanism controller.
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