Binarization method and freeform mask optimization flow

Patent metadata

Field	Value
Publication number	US-10990003-B2
Application number	US-201916967789-A
Country	US
Kind code	B2
Filing date	Feb 15, 2019
Priority date	Feb 18, 2018
Publication date	Apr 27, 2021
Grant date	Apr 27, 2021

Abstract

A method to determine a mask pattern for a patterning device. The method includes obtaining a target pattern to be printed on a substrate, an initial continuous tone image corresponding to the target pattern, a binarization function (e.g., a sigmoid, an arctan, a step function, etc.) configured to transform the initial continuous tone image, and a process model configured to predict a pattern on the substrate from an output of the binarization function; and generating a binarized image having a mask pattern corresponding to the initial continuous tone image by iteratively updating the initial continuous tone image based on a cost function such that the cost function is reduced. The cost function (e.g., EPE) determines a difference between a predicted pattern determined by the process model and the target pattern.

First claim

What is claimed is:

1. A method comprising:
obtaining (i) a target pattern to be printed on a substrate subjected to a patterning process, (ii) an initial continuous tone image corresponding to the target pattern, (iii) a binarization function configured to transform the initial continuous tone image, and (iv) a process model configured to predict a pattern on the substrate from an output of the binarization function; and
generating, by a hardware computer system, a binarized image having a mask pattern for a patterning device and corresponding to the initial continuous tone image by iteratively updating the initial continuous tone image based on a cost function such that the cost function is reduced,
wherein the cost function determines a difference between a predicted pattern determined by the process model and the target pattern.

2. The method of claim 1 , wherein the binarization function is a sigmoid function, an arctan function, and/or a step function.

3. The method of claim 1 , wherein the mask pattern is a curvilinear pattern and/or a Manhattan pattern.

4. The method of claim 1 , wherein an iteration of determining the curvilinear pattern comprises:
generating a transformed image by applying a binarization function to the initial continuous tone image;
predicting, via simulation of the process model, a pattern from the transformed image;
determining a gradient of the cost function; and
modifying a value of one or more mask variables corresponding to the initial continuous tone image and/or one or more parameters of the binarization function based on the gradient of the cost function such that the cost function is reduced.

5. The method of claim 4 , wherein the determining the gradient of the cost function involves computing a complete gradient over mask variables for the binarization function.

6. The method of claim 4 , wherein modifying a value of one or more mask variables and/or the one or more parameters of the binarization function comprises:
applying an optimization process to the gradient of the cost function; and
identifying a value of one or more the mask variables and/or one or more parameters of the binarization function that result in a minimum gradient value.

7. The method of claim 6 , comprising modifying a value of one or more mask variables and wherein the one or more mask variables are intensity values of pixels within the initial continuous tone image.

8. The method of claim 6 , comprising modifying one or more parameters of the binarization function and wherein the one or more parameters of the binarization function comprise a steepness and threshold.

9. The method of claim 1 , wherein the cost function is minimized.

10. The method of claim 1 , wherein the cost function is an edge placement error and/or a mask rule check violation probability.

11. The method of claim 1 , wherein the initial continuous tone image is a continuous transmission mask image comprising features corresponding to the target pattern and sub-resolution assist features.

12. The method of claim 1 , further comprising manufacturing a patterning device including structural features corresponding to the binarized image.

13. The method of claim 1 , further comprising performing, by a lithographic apparatus, a patterning step using a patterning device having structural features corresponding to the binarized image to print a corresponding pattern on the substrate.

14. The method of claim 12 , wherein the structural features correspond to optical proximity corrections including assist features and/or contour modification.

15. A computer program product comprising a non-transitory computer readable medium having instructions therein, the instructions, when executed by a computer, configured to cause the computer to at least:
obtain (i) a target pattern to be printed on a substrate subjected to a patterning process, (ii) an initial continuous tone image corresponding to the target pattern, (iii) a binarization function configured to transform the initial continuous tone image, and (iv) a process model configured to predict a pattern on the substrate from an output of the binarization function; and
generate a binarized image having a mask pattern for a patterning device and corresponding to the initial continuous tone image by iterative updating of the initial continuous tone image based on a cost function such that the cost function is reduced,
wherein the cost function determines a difference between a predicted pattern determined by the process model and the target pattern.

16. The computer program product of claim 15 , wherein the binarization function is a sigmoid function, an arctan function, and/or a step function.

17. The computer program product of claim 15 , wherein an iteration of determination of the curvilinear pattern comprises:
generation of a transformed image by applying a binarization function to the initial continuous tone image;
prediction, via simulation of the process model, of a pattern from the transformed image;
determination of a gradient of the cost function; and
modification of a value of one or more mask variables corresponding to the initial continuous tone image and/or one or more parameters of the binarization function based on the gradient of the cost function such that the cost function is reduced.

18. The computer program product of claim 15 , wherein the cost function is an edge placement error and/or a mask rule check violation probability.

19. The computer program product of claim 15 , wherein the initial continuous tone image is a continuous transmission mask image comprising features corresponding to the target pattern and sub-resolution assist features.

20. The computer program product of claim 15 , wherein the instructions are further configured to cause the computer to output information for manufacturing a patterning device including structural features corresponding to the binarized image.

Assignees

• Asml Netherlands Bv

Inventors

• Hsu Duan-Fu Stephen
• Liu Jingjing
• Howell Rafael C
• Peng Xingyue

Classifications

• G03F1/70 Primary

  Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging · CPC title

• Y02P90/02

  Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS] · CPC title

• G06F30/398

  Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] (optical proximity correction [OPC] design processes G03F1/36) · CPC title

• G03F1/36 Primary

  Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes · CPC title

• G06F2119/18

  Manufacturability analysis or optimisation for manufacturability · CPC title