阅读说明：本技术 考虑系统耦合特性的光刻机工件台调平调焦方法 (Photoetching machine workpiece table leveling and focusing method considering system coupling characteristics ) 是由 彭超 邹见效 牛凡 谢川 于力 于 2021-07-27 设计创作，主要内容包括：本发明公开了一种考虑系统耦合特性的光刻机工件台调平调焦方法,对光刻机工作台采用基于三点调平法的调平调焦系统,采用位置测量系统测量得到工作台的位置参数,通过预设的控制逻辑转换模型,转换得到三个运动轴的期望高度,计算得到三个运动轴的高度调节量,然后依次进行位置相关解耦和动力学相关解耦,得到解耦后的三个运动轴的高度调节量,输入运动轴控制系统对三个运动轴进行控制。本发明通过降低调平调焦系统各个运动轴之间的耦合,提高调平调焦的准确度。(The invention discloses a leveling and focusing method of a photoetching machine workpiece table considering system coupling characteristics, which comprises the steps of adopting a leveling and focusing system based on a three-point leveling method for a photoetching machine workbench, adopting a position measurement system to measure and obtain position parameters of the workbench, converting to obtain expected heights of three moving shafts through a preset control logic conversion model, calculating to obtain height adjustment quantities of the three moving shafts, then sequentially carrying out position-related decoupling and dynamics-related decoupling to obtain height adjustment quantities of the three decoupled moving shafts, and inputting the height adjustment quantities of the three moving shafts into a moving shaft control system to control the three moving shafts. The invention improves the accuracy of leveling and focusing by reducing the coupling between all the movement axes of the leveling and focusing system.)

1. A photoetching machine workpiece table leveling and focusing method considering system coupling characteristics is characterized by comprising the following steps:

s1: the leveling and focusing system comprises three moving shafts, a moving shaft control system and a position measuring system, wherein the three moving shafts are arranged below the workbench, connecting points of the three moving shafts z1, z2 and z3 and the workbench form an isosceles triangle, connecting points of the moving shafts z2 and z3 and the workbench form the bottom edge of the isosceles triangle, and the three moving shafts are used for jointly adjusting the height and the inclination angle of the workbench under the control of the moving shaft control system; the motion axis control system is used for calculating control parameters of three motion axes according to the position parameters of the workbench measured by the position measuring system; the position measurement system adopts the picture that the workstation was shot to objective, calculates the position parameter who obtains the workstation from the picture according to predetermined space rectangular coordinate system, and space rectangular coordinate system uses the exposure field center of objective among the position measurement system as the initial point, and the vector coincidence of x axle and initial point to isosceles triangle base mid point, and the setting principle of y axle is: the plane formed by the x axis and the y axis is a horizontal plane, and the z axis is made to be upward under the right-hand rule;

s2: the position parameters of the workbench, including defocus z and tilt angle theta of the workbench in the x-axis direction, are obtained by measurement of a position measurement system_xInclination angle theta of the table in the y-axis direction_yObtaining the expected height z of three motion axes through conversion of a preset control logic conversion model_iI is 1,2,3, controlThe expression of the logical transformation model is as follows:

wherein CCM represents a control logic conversion matrix of the leveling and focusing system;

then according to the height of the current motion axisCalculating height adjustment to a motion axis

S3: the following formula is adopted to carry out position correlation decoupling, and the height adjustment z of each motion axis when the mass center of the workbench reaches the desired target is calculated_oi：

Wherein, Δ z_p＝(-0.0027z₁+0.0013z₂+0.0013z₃)x_p+(0.5z₁+0.25z₂+0.25z₃)y_p，(x_p,y_p) The coordinates of the central point of the exposure field under the coordinate system of the center of mass;

s4: performing dynamics correlation decoupling by adopting the following formula, and calculating to obtain the height adjustment z of each motion axis when the mass center of the workbench reaches the desired target_o′_i：

Wherein the content of the first and second substances,representing inverse kinematics decoupling matrices, expressionsThe formula is as follows:

wherein FCM represents a force conversion matrix of the leveling and focusing system;

s5: the height adjustment z of each movement axis obtained in step S4_o′_iAnd inputting a motion axis control system to control the three motion axes.

2. The method for leveling and focusing the workpiece stage of the lithography machine according to claim 1, wherein the expression of the control logic conversion matrix CCM is as follows:

wherein S represents the length of the base of an isosceles triangle formed by the connecting points of the three motion axes and the workbench, and T represents the height of the isosceles triangle.

3. The method of claim 1, wherein the force transformation matrix FCM is expressed as follows:

Technical Field

The invention belongs to the technical field of leveling of a workpiece table of a photoetching machine, and particularly relates to a leveling and focusing method of the workpiece table of the photoetching machine, which considers the coupling characteristic of a system.

Background

The photoetching machine is a device for manufacturing large-scale integrated circuits, the workpiece table is a key component of the photoetching machine, and the workpiece table is used as a key mechanism of a motion control system of the photoetching machine and plays an important role in the silicon wafer alignment, leveling and focusing and exposure photoetching processes of the photoetching machine. At present, the method and the technology for controlling the scanning track tracking of the workpiece stage of the lithography machine have been widely studied, but the research on the leveling and focusing control of the workpiece stage in the motion process is relatively less.

At present, a three-point leveling method is generally adopted by a photoetching machine workpiece table system to level and focus an exposure plane. FIG. 1 is a schematic diagram of the three point square method. As shown in fig. 1, three driving mechanisms, which are respectively called as a z1 axis, a z2 axis and a z3 axis, are arranged at three corner points of a triangle with the width S and the height T of an exposure plane of the worktable, and leveling and focusing of the worktable are realized by sending different control commands to the three motion axes. The three-point leveling method realizes the leveling and focusing movement with three degrees of freedom by using the simplest structure, and effectively avoids the phenomenon of 'virtual legs' in the traditional four-point leveling process. The currently generally adopted leveling and focusing mode is to directly control the rising and falling of three motion axes to directly align the defocusing amount z and the inclination angle theta_x、θ_yThe control method has simple control logic and lower cost. However, in this kind of method, the coupling existing between the three movement axes is not considered in the control process, and an "overshoot" phenomenon easily occurs in the leveling and focusing process, so that the leveling and focusing speed is reduced, the precision is reduced, and the high-performance leveling and focusing of the system cannot be realized.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a leveling and focusing method for a photoetching machine workpiece table, which considers the coupling characteristic of a system, reduces the coupling among all moving shafts of a leveling and focusing system and improves the accuracy of leveling and focusing.

In order to achieve the above object, the method for leveling and focusing a workpiece stage of a lithography machine considering the system coupling characteristic of the present invention comprises the following steps:

s1: the leveling and focusing system comprises three moving shafts, a moving shaft control system and a position measuring system, wherein the three moving shafts are arranged below the workbench, connecting points of the three moving shafts z1, z2 and z3 and the workbench form an isosceles triangle, connecting points of the moving shafts z2 and z3 and the workbench form the bottom edge of the isosceles triangle, and the three moving shafts are used for jointly adjusting the height and the inclination angle of the workbench under the control of the moving shaft control system; the motion axis control system is used for calculating control parameters of three motion axes according to the position parameters of the workbench measured by the position measuring system; the position measurement system adopts an objective lens to shoot a picture of the workbench, and calculates the position parameter of the workbench from the picture according to a preset space rectangular coordinate system; the rectangular coordinate system of space regards exposure field center of objective among the position measurement system as the original point, and the vector coincidence of x axle and original point to isosceles triangle base mid point, the setting principle of y axle is: the plane formed by the x axis and the y axis is a horizontal plane, and the z axis is made to be upward under the right-hand rule;

s2: measuring by using a position measuring system to obtain position parameters of the workbench, including defocus z and inclination angle theta of the workbench in the x-axis direction_xInclination angle theta of the table in the y-axis direction_yObtaining the expected height z of three motion axes through conversion of a preset control logic conversion model_iAnd i is 1,2 and 3, and the expression of the control logic conversion model is as follows:

wherein CCM represents a control logic conversion matrix of the leveling and focusing system;

then according to the height of the current motion axisCalculating height adjustment to a motion axis

S3: the following formula is adopted to carry out position correlation decoupling, and the height adjustment of each motion axis is calculated when the mass center of the workbench reaches a desired targetQuantity z_oi：

Wherein, Δ z_p＝(-0.0027z₁+0.0013z₂+0.0013z₃)x_p+(0.5z₁+0.25z₂+0.25z₃)y_p，(x_p,y_p) The coordinates of the central point of the exposure field under the coordinate system of the center of mass;

s4: performing dynamic correlation decoupling by adopting the following formula, and calculating to obtain the height adjustment z 'of each moving axis when the center of mass of the workbench reaches a desired target'_oi：

Wherein the content of the first and second substances,expressing an inverse dynamics decoupling matrix, the expression is as follows:

wherein FCM represents a force conversion matrix of the leveling and focusing system;

s5: adjusting the height z 'of each of the moving shafts obtained in step S4'_oiAnd inputting a motion axis control system to control the three motion axes.

The invention relates to a leveling and focusing method of a photoetching machine workpiece table considering system coupling characteristics, which comprises the steps of adopting a leveling and focusing system based on a three-point leveling method for a photoetching machine workbench, adopting a position measurement system to measure and obtain position parameters of the workbench, converting through a preset control logic conversion model to obtain expected heights of three movement shafts, calculating to obtain height adjustment quantities of the three movement shafts, then sequentially carrying out position-related decoupling and dynamics-related decoupling to obtain height adjustment quantities of the three movement shafts after decoupling, and inputting the height adjustment quantities into a movement shaft control system to control the three movement shafts.

The invention has the following beneficial effects:

1) according to the invention, before motion control is carried out on three motion axes, position-dependent decoupling and dynamics-dependent decoupling among the three axes are carried out, and motion control is carried out on the three axes after effective decoupling, so that the accuracy of leveling and focusing is improved;

2) the invention considers the coupling between the central point position of the exposure field and the center of mass position of the workbench of the photoetching machine, and can effectively reduce the problem of leveling and focusing precision loss caused by the misalignment of the central point and the center of mass of the exposure field;

3) the invention analyzes the coupling among all the degrees of freedom of the system, so that the coupling among all the degrees of freedom of the workpiece platform of the photoetching machine is reduced, and any one degree of freedom can be conveniently and independently controlled.

4) The decoupling strategy adopted by the invention can convert the control problem in the leveling and focusing process into 3 independently-controlled single-input single-output subsystems, thereby reducing the control difficulty in the leveling and focusing process and heightening the final leveling and focusing precision of the workpiece table.

Drawings

FIG. 1 is a schematic diagram of the three point square method;

FIG. 2 is a flowchart of an embodiment of a method for leveling and focusing a stage of a lithography machine according to the present invention with consideration of system coupling characteristics;

FIG. 3 is a schematic diagram of a rectangular spatial coordinate system according to the present invention;

FIG. 4 is a schematic view of the dynamics of the table in the centroid coordinate system;

FIG. 5 is a graph of excitation response for three axes of motion that are not decoupled;

FIG. 6 is a graph of excitation responses for three axes of motion after decoupling.

Detailed Description

The following description of the embodiments of the present invention is provided in order to better understand the present invention for those skilled in the art with reference to the accompanying drawings. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.

Examples

In order to better implement the technical solution of the present invention, first, the principle on which the present invention is based is briefly described.

For the workbench of the photoetching machine adopting a three-point leveling method, the control system is a 3-input 3-output system, and the input is the defocusing amount z of the workbench and the inclination angle theta of the workbench in the x-axis direction_xInclination angle theta of the table in the y-axis direction_yAnd the output is the control indexes of the three motion axes. Therefore, the control system belongs to a typical MIMO motion system, the invention converts the complex MIMO system into three independent SISO systems by analyzing and modeling an internal coupling mechanism, and then controls each logic axis, so that the control parameter of each motion axis can be independently adjusted.

The coupling of the workbench control system mainly comprises two types: position dependent coupling due to misalignment of the control target point with the actuator position is coupled with force dependent coupling due to the presence of dynamic coupling between the individual motors. During the leveling and focusing movement of the workbench, the control target of the workbench is the center of an exposure field below an objective lens, and control force generated by three actuating motors of the system is logically arranged on a movement axis of the workbench. In addition, because the power input of the motion shaft of the workbench is three Lorentz motors, the relative coordinate with the center of the exposure field is constantly changed, and the position of the coordinate system with the center of mass of the workbench is kept unchanged, corresponding coordinate conversion and control logic conversion are needed before the workbench is controlled. The force dependent coupling is mainly caused by some hard to quantify errors that cause the system to possibly create a situation where the distribution of force is not reasonable. Based on the analysis, the invention takes the center of mass of the workbench as a bridge, converts the control logic of the exposure position into the control logic of the center of mass position according to the geometric relationship, further performs the current distribution of the system, and distributes the control target to each motion axis.

FIG. 2 is a flowchart of an embodiment of a method for leveling and focusing a stage of a lithography machine in consideration of system coupling characteristics. As shown in fig. 2, the method for leveling and focusing a workpiece stage of a lithography machine considering the system coupling characteristic of the present invention specifically comprises the steps of:

s201: setting a leveling and focusing system:

the leveling and focusing system based on a three-point leveling method is adopted for a workbench of a photoetching machine and comprises three moving shafts, a moving shaft control system and a position measuring system, wherein the three moving shafts are arranged below the workbench, and the three moving shafts z1 and z2 form an isosceles triangle with the connecting point of the workbench, wherein the connecting points of the moving shafts z2 and z3 and the workbench form the bottom edge of the isosceles triangle, and the three moving shafts are used for jointly adjusting the height and the inclination angle of the workbench under the control of the moving shaft control system; the motion axis control system is used for calculating control parameters of three motion axes according to the position parameters of the workbench measured by the position measuring system; the position measurement system adopts an objective lens to shoot a picture of the workbench, and the position parameters of the workbench are calculated from the picture according to a preset space rectangular coordinate system. Fig. 3 is a schematic diagram of a rectangular spatial coordinate system according to the present invention. As shown in fig. 3, the spatial rectangular coordinate system in the present invention uses the center of the exposure field of the objective lens in the position measurement system (theoretically coinciding with the center of mass of the isosceles triangle formed by the motion axis and the stage) as the origin, the x-axis coincides with the vector from the origin to the middle point of the bottom side of the isosceles triangle, and the setting principle of the y-axis is as follows: the plane formed by the x-axis and the y-axis is a horizontal plane, and the z-axis is directed upward under the right-hand rule.

S202: preliminarily calculating the height adjustment amount of the motion axis:

measuring by using a position measuring system to obtain position parameters of the workbench, including defocus z and inclination angle theta of the workbench in the x-axis direction_xInclination angle theta of the table in the y-axis direction_yConverting the expected height z of the three motion axes through a preset control logic conversion model_iAnd i is 1,2 and 3, and the expression of the control logic conversion model is as follows:

where CCM denotes a Control-logic Conversion Matrix (Control-logic Conversion Matrix).

Then according to the height of the current motion axisCalculating height adjustment to a motion axisThe height of the current motion axis can be measured by a grating ruler.

In practical application, the control logic conversion model may be selected according to actual needs, and in this embodiment, the control logic conversion model is derived in the following manner: from the geometrical relationship shown in fig. 3, the motion conversion equation between the motion axis and the logic axis of the table can be obtained as follows:

wherein S represents the length of the base of an isosceles triangle formed by the connecting points of the three motion axes and the workbench, and T represents the height of the isosceles triangle.

And because the inclination angles adjusted in the process of leveling and focusing are all adjusted in a small range, under the premise, sin theta can be approximated_x≈θ_x，sin θ_y≈θ_yThen, formula (1) can be rewritten as:

the control logic conversion model can be obtained according to the formula (2):

that is, the expression of the control logic conversion matrix CCM is as follows:

s203: position-dependent decoupling:

according to the previous analysis, in the actual leveling and focusing movement process of the workbench, the control target of the workbench is the center of the exposure field below the objective lens, and is not overlapped with the position of the center of mass of the workbench, so that a position coupling model of the center of the exposure field and the position of the center of mass needs to be established, and the model basically performs position correlation decoupling.

Since the exposure surface passes through z₁、z₂、z₃Three points, z in a rectangular spatial coordinate system₁Point coordinate (-0.5T,0, z)₁)、z₂Point coordinates (0.5T, -0.5S, z)₂)，z₃Point coordinates (0.5T,0.5S, z)₃). The plane equation of the current exposure field can be solved by the three points:

z＝ax+by+c (6)

wherein: a is-0.0027 z₁+0.0013z₂+0.0013z₃，b＝-0.004z₂+0.004z₃，c＝0.5z₁+0.25z₂+0.25z₃. The coordinate of the central point P of the exposure field in the coordinate system of the centroid is assumed to be (x)_p,y_p) Then, the height z of the central point P of the exposure field in the rectangular coordinate system of space can be obtained_pComprises the following steps:

the height difference Deltaz between the center point P and the centroid of the exposure field_pComprises the following steps:

Δz_p＝(-0.0027z₁+0.0013z₂+0.0013z₃)x_p+(0.5z₁+0.25z₂+0.25z₃)y_p (8)

since the height adjustment amount of each motion axis for the exposure field center point P to reach the desired target is calculated in step S202Δ_iThen the height adjustment z of each axis of motion when the center of mass of the table reaches the desired target_oiThe calculation formula of (a) is as follows:

through the formula, the control target of the central point of the exposure field can be converted into the control target of the center of mass, and the decoupling of the system position correlation coupling is completed.

S204: dynamic correlation decoupling:

when the position-dependent decoupling is realized, a dynamic coupling model is required to be modeled so as to realize dynamic decoupling. During the dynamic coupling model building process, the deformation of the worktable generated during the movement process is ignored for the sake of simplicity, that is, the worktable is assumed to be a rigid body, and only pure translational and rotational movement is generated during the movement process of the worktable, which is effective for the movement within a small range. FIG. 4 is a schematic view of the dynamics of the table in the centroid coordinate system. As shown in fig. 4, the force of translation of the table along the z-axis is provided by the thrust generated by the three axes of motion z1, z2, z3, the moment of rotation about the x-axis is provided by the thrust generated by the axes of motion z2, z3, and the moment of rotation about the y-axis is provided by the thrust generated by the axes of motion z1, z2, z 3.

The conversion of the forces and moments of the drive system to produce motion in each degree of freedom to the thrust of each shaft is given by:

wherein, F_zTo produce a force for the system to move in the z-axis degree of freedom, F_ziThrust produced for the axis of motion zi, M_xTo produce theta for the table_xMoment of freedom of movement, M_yTo produce theta for the table_yMoment of freedom motion. From this, the force Conversion matrix fcm (force Conversion matrix) of the leveling focusing system can be obtained as follows:

then for the whole system:

again, based on system dynamics principles, the following equations can be established:

in the above formula, superscript^·Indicating the finding of the first derivative, superscript^··Indicating that the second derivative is taken. M_zDenotes the equivalent mass of the table, J_x、J_yRepresenting the equivalent moments of inertia, C, in the x-and y-axes, respectively_z、C_qx、C_qyRepresenting equivalent damping in the z-, x-and y-axes, respectively, K_z、K_θx、K_θyThe equivalent stiffness coefficients for the z-axis, x-axis and y-axis are shown, respectively.

Transforming the above equation, there are:

wherein, K_fIs a driving force constant, i_z1Coil current of z1 axis, i_z2Coil current of z2 axis, i_z3Coil current for the z3 axis. d_z1Disturbance as sum of z1 axes, d_z2Disturbance as sum of z2 axes, d_z3The sum interference is the z3 axis.

Because for the whole system, there are:

because the system conversion matrix CCM is a constant matrix and each element does not include a variable, the following are provided:

and:

in the formula (14), the formulae (15), (16) and (17) are substituted by:

can be abbreviated as:

where the superscript-1 indicates inversion.

Since the multiplication of the diagonal matrix satisfies the exchange rate, the above formula can be further simplified as follows:

the above equation is a dynamic coupling model of the system, in which: d_z1、d_z2、d_z3The total perturbation for the motion axes z1, z2, z3, respectively, includes the parameter uncertainty and the perturbation due to coupling between the axes.

From equation (20), the matrix CCM^-1The FCM is coupled, and the CCM and the FCM are both reversible, so that an inverse dynamics decoupling matrix can be setCoupled decoupling and inverse dynamic decoupling matrixThe expression of (a) is as follows:

and then calculating to obtain a height adjustment quantity z 'of each moving axis when the center of mass of the workbench reaches the expected target after dynamic decoupling by adopting the following formula'_oi：

S205: controlling a motion axis:

adjusting the height z 'of each of the moving shafts obtained in step S204'_oiAnd inputting a motion axis control system to control the three motion axes.

In order to better illustrate the technical effects of the invention, the invention is experimentally verified by using specific examples. In the experimental verification, the geometric parameters S of the workbench are 251 and T is 372, and the expressions of the control logic conversion matrix are substituted to obtain:

and (3) performing sinusoidal excitation on the three motion axes in sequence, then performing leveling and focusing on the workbench, and drawing excitation response curves of the three motion axes before and after decoupling according to the response of the motion axes. FIG. 5 is a graph of excitation response for three axes of motion that are not decoupled. FIG. 6 is a graph of excitation responses for three axes of motion after decoupling. Comparing fig. 5 and fig. 6, it can be known that, after decoupling control is performed on the height adjustment amount of the moving axis in consideration of the coupling characteristic of the system, a better tracking effect can be obtained on the target moving axis, and on the coupling axis, the coupling displacement of the system is obviously reduced compared with that when a decoupling controller is not used, the maximum coupling amplitude is 0.0085mm, and is reduced by 78.8% compared with that when the decoupling controller is not used, which also proves the effectiveness of the present invention to a certain extent.

Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.