Vertical control method for use in lithography machine

Patent metadata

Field	Value
Publication number	US-11042101-B2
Application number	US-201816494097-A
Country	US
Kind code	B2
Filing date	Mar 14, 2018
Priority date	Mar 15, 2017
Publication date	Jun 22, 2021
Grant date	Jun 22, 2021

Abstract

A method for vertical control of a lithography machine includes step 1, prior to a scanning exposure, controlling vertical measurement sensors to measure workpiece to obtain overall surface profile data of the workpiece; step 2, performing a global leveling based on the overall surface profile data of the workpiece; and step 3, during the scanning exposure of each exposure field, measuring a local surface profile of the workpiece in real time by the vertical measurement sensors and controlling at least one of a mask stage, a workpiece stage and a projection objective to move vertically according to a Z-directional height value, an Rx-directional tilt value and an Ry-directional tilt value corresponding to the local surface profile of the workpiece, to compensate for the local surface profile of the workpiece in real time, so that an upper surface of each exposure field coincides with a reference focal plane for the exposure field. This method enables flexible vertical control with high accuracy by providing multiple control options.

First claim

What is claimed is:

1. A method for vertical control of a lithography machine, wherein the lithography machine comprises, from top to bottom, illumination systems, mask stages, projection objectives and a workpiece stage, each mask stage corresponding to one of the projection objectives, the method comprising the steps of:
step 1, prior to a scanning exposure, controlling vertical measurement sensors to measure a workpiece to obtain overall surface profile data of the workpiece;
step 2, performing a global leveling based on the overall surface profile data of the workpiece; and
step 3, during the scanning exposure of each exposure field, measuring a local surface profile of the workpiece in real time by the vertical measurement sensors and controlling at least one of the mask stages, the workpiece stage and the projection objectives conduct a vertical movement according to a Z-directional height value, an Rx-directional tilt value and an Ry-directional tilt value corresponding to the local surface profile of the workpiece, to compensate for the local surface profile of the workpiece in real time, so that an upper surface of each exposure field coincides with a reference focal plane for the exposure field,
wherein the vertical movement is performed by:
configuring the workpiece stage to perform an overall global leveling, configuring the mask stages to perform a field-by-field global leveling, and controlling the mask stages to conduct the vertical movement to compensate for the local surface profile of the workpiece in real time; or
configuring the workpiece stage to perform a field-by-field global leveling and controlling the mask stages to conduct the vertical movement to compensate for the local surface profile of the workpiece in real time.

2. The method for vertical control of a lithography machine according to claim 1 , wherein step 2 comprises: fitting the surface profile data of the workpiece to obtain a global plane surface profile; and deriving vertical movement control parameters for the global leveling based on differences between the global plane surface profile and a target plane for the global leveling, and controlling, prior to the exposure, vertical movements of the workpiece stage to perform an overall global leveling according to the vertical movement control parameters for the global leveling, and wherein the target plane for the global leveling is an optimum focal plane for the projection objective.

3. The method for vertical control of a lithography machine according to claim 2 , wherein the lithography machine comprises a plurality of projection objectives, and the target plane for the global leveling is an average of optimum focal planes for the plurality of projection objectives.

4. The method for vertical control of a lithography machine according to claim 1 , wherein step 2 comprises: prior to the scanning exposure of each exposure field, performing fitting based on the surface profile data to obtain a local wedge for each exposure field; and controlling the workpiece supported by the workpiece stage to conduct a field-by-field global leveling based on the local wedge for each exposure field.

5. The method for vertical control of a lithography machine according to claim 4 , wherein performing fitting based on the overall surface profile data to obtain a local wedge for each exposure field comprises:
performing a curved surface fitting to the overall surface profile data to obtain a curved surface profile of the workpiece, based on which, the local wedge for each exposure field is obtained from a first-order Taylor expansion performed at a center of each exposure field.

6. The method for vertical control of a lithography machine according to claim 4 , wherein, prior to scanning exposure each exposure field, performing fitting based on the overall surface profile data to obtain a local wedge for each exposure field and controlling the workpiece supported by the workpiece stage to conduct a field-by-field global leveling based on the local wedge for each exposure field comprises:
performing a curved surface fitting to the overall surface profile data to obtain a curved surface profile of the workpiece, based on which, a linear interpolation is performed to obtain interpolated points distributed throughout an upper surface of the workpiece; mapping corresponding ones of the interpolated points to each exposure field; in each exposure field, performing plane fitting to the mapped interpolated points within a static angular field moving from a start point to a finish point of the exposure field to obtain vertical movement fitted values of the exposure field during movement of the static angular field; performing orthogonal polynomials fitting based on the vertical movement fitted values to obtain an orthogonal polynomial path of the workpiece stage in Z direction, Rx direction, and Ry direction; and controlling the workpiece stage to move according to the orthogonal polynomial path to perform the field-by-field global leveling.

7. The method for vertical control of a lithography machine according to claim 6 , wherein the orthogonal polynomial comprises a basis function derived from Legendre polynomials, Chebyshev polynomials or Gram-Schmidt orthogonalization.

8. The method for vertical control of a lithography machine according to claim 1 , wherein step 2 comprises: prior to scanning exposure of each exposure field, performing fitting based on the overall surface profile data to obtain a local wedge for each exposure field; dividing a Z-directional height value corresponding to the local wedge by square of a magnification of the projection objective, dividing an Rx-directional tilt value corresponding to the local wedge by the magnification of the projection objective, and dividing an Ry-directional tilt value corresponding to the local wedge by the magnification of the projection objective, so that an image-to-object conversion of the local wedge is accomplished; controlling the mask stage to conduct a field-by-field global leveling based on the local wedge after image-to-object conversion.

9. The method for vertical control of a lithography machine according to claim 8 , wherein step 2 further comprises: during scanning exposure of each exposure field, controlling the projection objective to move along an orthogonal polynomial path to compensate for the local surface profile of the workpiece.

10. The method for vertical control of a lithography machine according to claim 9 , wherein performing fitting based on the overall surface profile data to obtain a local wedge for each exposure field comprises:
performing a plane fitting to the overall surface profile data to obtain a global plane surface profile of the workpiece; calculating differences between the global plane surface profile and a target plane for the global leveling; subtracting the differences from the overall surface profile data of the workpiece to obtain a set ϕ′ of points; mapping corresponding ones of the points in the set ϕ′ to each exposure field; and performing plane fitting to data of the exposure field to obtain the local wedge for the exposure field, wherein the target plane for the global leveling is an optimum focal plane for the projection objective.

11. The method for vertical control of a lithography machine according to claim 10 , wherein controlling the projection objective to move along an orthogonal polynomial path to compensate for the local surface profile of the workpiece comprises:
removing the local wedge for the exposure field from the set ϕ′; performing plane fitting to the data in the static angular field moving from a start point to a finish point of the exposure field, to obtain vertical move

Assignees

• Shanghai Micro Electronics Equipment Group Co Ltd

Inventors

• Chen Dan
• Wang Xianying
• Yang Zhiyong

Classifications

• G03F7/70725 Primary

  control · CPC title

• G03F7/70641 Primary

  Focus · CPC title

• G03F7/70775

  Position control, e.g. interferometers or encoders for determining the stage position · CPC title

• G03F7/70483

  Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring · CPC title

• G03F7/70275

  Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems · CPC title