Calibration method for combination non-consistency error of grating reading head

Abstract

The invention provides a method for grating reading head combination non-consistency error calibration, and the method comprises the steps: respectively and independently planning the moving path of a workbench, taking a reading head 123 combination as a reference, and respectively calculating the six degrees of freedom of the measurement models of other reading head combinations; obtaining a deviation value between the reading head combinations; performing data fitting on the six-degree-of-freedom variable influencing the deviation value and the deviation value between the reading head combinations to obtain an updated non-consistency error coefficient between the reading head combinations; and recalculating the position of the workbench by using the compensated coefficient to complete the calibration of the non-consistency error between the grating reading head combinations. The method can be used for theoretical analysis of non-consistency errors between grating reading head combinations and algorithm optimization of a nanoscale grating ruler displacement measurement system.

Description

(I) Technical field

[0001] The present invention relates to a method for calibrating the inconsistency error of a grating reading head combination, which can be used in the fields of optimization and calibration of a nanometer-level grating ruler displacement measurement system, and belongs to a precision measurement technology. (II) Background technology

[0002] As the minimum critical size of a single transistor decreases, the laser interferometer measurement system used in semiconductor lithography can no longer meet the positioning requirements of the lithography machine workpiece stage due to the influence of environmental sensitivity. The grating interferometer has better environmental stability than the laser interferometer due to its shorter air path, and has become the mainstream choice of displacement measurement sensors for immersion lithography scanning systems.

[0003] Based on the principle of secondary diffraction of grating and geometric optical path, the analytical relationship between the actual displacement of the workpiece stage, the installation error of the grating reader, the grating installation error and the ideal displacement was derived, and a measurement model of geometric error and angle with six degrees of freedom of grating interferometer was established.

[0004] According to the moving measurement trajectory of the workbench, when solving the six-degree-of-freedom position measured by the grating reading head, the installation error and the coupling error of the mutual influence between the degrees of freedom are not considered. It is assumed that the system is in an ideal condition, with the reading head 123 combination as a reference, and the positions measured by other different reading head combinations are consistent with the reference position; in order to more accurately obtain the inconsistency error between each combination, the installation error and coupling influence should be considered.

[0005] The measurement model of the reading head combination contains multiple coefficients. An update iteration method is adopted to calculate each updated coefficient value separately and then substitute it into the measurement model to gradually reduce the inconsistency error value between each reading head combination. (III) Summary of the invention

[0006] The present invention provides a method for calibrating the inconsistency error of a grating reading head combination, which is used to calibrate the inconsistency of each reading head combination caused by a grating installation error, a reading head installation error, etc. in a grating interferometer displacement measurement system, thereby improving the measurement accuracy of the grating displacement measurement system.

[0007] The present invention discloses a method for calibrating the inconsistency error of a grating reading head combination, which specifically includes the following contents:

[0008] In the method: P1 plans the measurement paths of the workpiece stage in X, Y, Z, Rx, Ry, Rz, RxRy, etc. respectively according to the influence of the variable coefficients in the grating six-degree-of-freedom measurement model, and the remaining degrees of freedom are set at zero position and remain unchanged.

[0009] In the method: P2 uses the six-degree-of-freedom position of the reading head 123 combination as a reference value, calculates the six-degree-of-freedom positions of the remaining degree-of-freedom combinations under different measurement paths, and subtracts the two to obtain the inconsistency deviation value of the reading head combination. Diff_X1234_123=X1234-X123 Diff_Y1234_123=Y1234-Y123 Diff_Z1234_123=Z1234-Z123 Diff_Rx1234_123=Rx1234-Rx123 Diff_Ry1234_123=Ry1234-Ry123 Diff_Rz1234_123=Rz1234-Rz123 Diff_X124_123=X124-X123 Diff_Y124_123=Y124-Y123Diff_Z124_123=Z124-Ry123 Diff_Rx124_123=Rx124-Rx123 Diff_Ry124_123=Ry124-Ry123 Diff_Rz124_123=Rz124-Rz123 Diff_X134_123=X134-X123 Diff_Y134_123=Y134-Y123 Diff_Z134_123=Z134-Ry123 Diff_Rx134_123=Rx134-Rx123 Diff_Ry134_123=Ry134-Ry123 Diff_Rz134_123=Rz134-Rz123Diff_X234_123=X234-X123 Diff_Y234_123=Y234-Y123 Diff_Z234_123=Z234-Ry123 Diff_Rx234_123=Rx234-Rx123 Diff_Ry234_123=Ry234-Ry123 Diff_Rz234_123=Rz234-Rz123

[0010] In the method: P3 fits the six-degree-of-freedom variables that affect the inconsistency error under different path planning with the inconsistency deviation value to obtain updated and compensated coefficients.

[0011] In the method: P4 replaces the updated compensated error coefficients into the measurement model of the reading head combination one by one through an updating iteration, recalculates the updated six-degree-of-freedom position, compares the compensated six-degree-of-freedom position with the data before compensation, and completes the calibration of the inconsistency error of the grating interferometer reading head combination. (IV) Description of the drawings

[0012] Figure 1The present invention is a flow chart of a calibration method for grating readhead combination non-uniformity error. (V) Specific implementation methods

[0013] The present invention is further described below with reference to specific examples.

[0014] See also Figure 1 The present invention discloses a calibration method for grating reading head combination non-consistency error, which can be specifically divided into the following four steps.

[0015] Step P1: Based on the measurement model of the grating interferometer readhead combination, analyze the size of the degree of freedom variables that affect the non-consistency error of the grating readhead combination, and plan the movement path of the workpiece stage separately according to the size of the influence. Set the moving positions of X and Y from 0 to 0.168mm, the moving ranges of Z, Rx, and Ry from 0 to 0.001mm, and the moving path of Rz from 0 to 0.0005mm. When setting separate movements, the movement of the workpiece stage in other degrees of freedom directions should be zero.

[0016] Step P2: According to the path planned in step 1, obtain the measurement results of the reading head, substitute them into the measurement model of each reading head combination to calculate the six-degree-of-freedom position. Due to the difference in the reading head installation error and the grating installation error, the six-degree-of-freedom positions calculated by the five reading head combinations are different. Taking the reading head 123 combination as a reference, the six-degree-of-freedom positions calculated by other reading head combinations are subtracted from it to obtain the six-degree-of-freedom deviation values ​​under different reading head combinations, that is, the inconsistency error of the reading head combination.

[0017] Step P3: According to different path planning, under the current path, it is preferred to fit the six-degree-of-freedom variables with large influence with the six-degree-of-freedom error values ​​under different combinations to obtain the compensation coefficient with large influence, substitute it into the measurement model, calculate the compensated inconsistency residual, and then fit the six-degree-of-freedom variables with small influence with the inconsistency residual, substitute the fitting result into the model, further update the coefficients in the measurement model, and repeat the above method until all coefficients in the measurement model are compensated.

[0018] Step P4: After completing the error coefficient compensation of step P3, the obtained coefficients are substituted into the measurement model one by one, and the six-degree-of-freedom position of the workpiece table under each reading head combination is recalculated. Then, with the reading head 123 combination as a reference, the six-degree-of-freedom deviation value under each reading head combination is calculated, and the changes in the inconsistency error before and after are compared.

Claims

1. A method for calibrating the inconsistency error of a grating reading head combination. The method comprises: According to the influence coefficient of the combined measurement model of the reading heads, the moving path of the workbench is planned separately, and the six-degree-of-freedom position is obtained by substituting the combined measurement model of each reading head into it; Taking the calculation results of the reading head combination 123 as a reference, the deviation values ​​of the other different reading head combinations are obtained respectively, and the inconsistency error value is obtained; the six-degree-of-freedom variables that affect the deviation value are fitted with the error value respectively to obtain the updated error coefficient; the updated compensated error coefficient is re-substituted into the measurement model of each reading head combination, and the six-degree-of-freedom position is recalculated to complete the compensation of the inconsistency error of the reading head combination.

2. A method for calibrating the inconsistency error of a grating reading head combination according to claim 1, characterized in that: In the six-degree-of-freedom expression of each reading head combination, the moving paths of the workbench in the directions of X, Y, Z, Rx, Ry, Rz, RxRy, etc. are planned separately according to the six-degree-of-freedom variables that affect the non-consistency error of the reading head combination. The non-consistency error coefficient of the grating reading head combination is composed of the influence coefficients of each degree of freedom variable. Therefore, the measurement paths for separate movement in each degree of freedom should be planned separately, and the influence coefficients under different paths should be calculated.

3. A method for calibrating the inconsistency error of a grating reading head combination according to claim 1, characterized in that: Taking the calculation result of the reading head combination 123 as a reference, the remaining different reading head combinations are subtracted from it to obtain the inconsistency error of the grating reading head combination.

4. A method for calibrating the inconsistency error of a grating reading head combination according to claim 1, characterized in that: According to different planned paths, the six-degree-of-freedom variables are fitted with the error values ​​to obtain the updated coefficients affecting the inconsistency error. Through the update iteration method, the error coefficients after each compensation are substituted one by one in the combined measurement model of the reading head to calculate the six-degree-of-freedom position.

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