Simultaneous Optical Proximity Correction and Decomposition for Double Exposure Lithography

• US 20120040280A1
• Filed: 08/13/2010
• Published: 02/16/2012
• Est. Priority Date: 08/13/2010
• Status: Active Grant

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Agarwal, Kanak B., Banerjee, Shayak
• Granted Patent: US 8,415,077 B2
• Time in Patent Office: Days
• US Class Current: 430/30
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 7/70433 Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors
• CPC Class Codes: G03F 7/70441 Optical proximity correction [OPC]
• CPC Class Codes: G03F 7/70466 Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature stitching G03F7/70475

Abstract

A mechanism is provided for simultaneous optical proximity correction (OPC) and decomposition for double exposure lithography. The mechanism begins with two masks that are equal to each other and to the target. The mechanism simultaneously optimizes both masks to obtain a wafer image that both matches the target and is robust to process variations. The mechanism develops a lithographic cost function that optimizes for contour fidelity as well as robustness to variation. The mechanism minimizes the cost function using gradient descent. The gradient descent works on analytically evaluating the derivative of the cost function with respect to mask movement for both masks. It then moves the masks by a fraction of the derivative.

Claims

1. A method, in a data processing system, for simultaneous optical proximity correction and decomposition, the method comprising:

setting a first lithographic mask and a second lithographic mask equal to a target;

performing simultaneous optical proximity correction and decomposition using the first lithographic mask and the second lithographic mask; and

performing a first lithographic exposure with the first lithographic mask and performing a second lithographic exposure with the second lithographic mask to produce a final layout target closely resembling the original.

2. The method of claim 1, wherein performing simultaneous optical proximity correction and decomposition comprises:

performing image simulation based on the first lithographic mask and the second lithographic mask;

developing a lithographic cost function that determines contour fidelity as well as robustness of the image to process variations; and

moving the first lithographic mask and the second lithographic mask based on the lithographic cost function.

3. The method of claim 2, wherein performing simultaneous optical proximity correction and decomposition further comprises:

repeating performing image simulation, developing a lithographic cost function, and moving the first lithographic mask and the second lithographic mask a predetermined number of times.

4. The method of claim 2, wherein the cost function is determined according to the following equation:

C_OPC/Decomp=w(Δ

I)²+(1−

w)exp(−

|∂

I/∂

x|)

where I is the light intensity at a particular site, Δ

I is the intensity error and x is distance, and w is a weight that can be dynamically tuned at each iteration in order to prioritize slope optimization over fidelity and vice versa.

5. The method of claim 4, wherein moving the first lithographic mask and the second lithographic mask based on the lithographic cost function comprises:

minimizing the cost function using gradient descent;

finding analytically a derivative of the cost function with respect to mask movement for the first lithographic mask and the second lithographic mask;

utilizing the kernels representing the two exposures to analytically obtain the derivative of the image intensity and slope while determining the derivative of the cost function; and

moving the first lithographic mask, m₁, and the second lithographic mask, m₂, by a pre-specified fraction of the derivative.

6. The method of claim 5, further comprising:

determining first lithographic mask movement, Δ

m₁, and determining second lithographic mask movement, Δ

m₂, according to the following equations;

7. The method of claim 6, wherein finding analytically a derivative of the cost function with respect to mask movement for the first lithographic mask and the second lithographic mask comprises determining the derivative of the cost function with respect to mask movement according to the following equation:

8. A computer program product comprising a computer readable storage medium having a computer readable program stored therein, wherein the computer readable program, when executed on a computing device, causes the computing device to:

set a first lithographic mask and a second lithographic mask equal to a target;

perform simultaneous optical proximity correction and decomposition on the first lithographic mask and the second lithographic mask; and

perform a first lithographic exposure with the first lithographic mask and performing a second lithographic exposure with the second lithographic mask.

9. The computer program product of claim 8, wherein performing simultaneous optical proximity correction and decomposition comprises:

performing image simulation based on the first lithographic mask and the second lithographic mask;

developing a lithographic cost function that determines contour fidelity as well as robustness of the image to process variations; and

moving the first lithographic mask and the second lithographic mask based on the lithographic cost function.

10. The computer program product of claim 9, wherein performing simultaneous optical proximity correction and decomposition further comprises:

repeating performing image simulation, developing a lithographic cost function, and moving the first lithographic mask and the second lithographic mask a predetermined number of times.

11. The computer program product of claim 9, wherein the cost function at a site is determined according to the following equation:

C_OPC/Decomp=w(Δ

I)²+(1−

w)exp(−

|∂

I/∂

x|)

where I is the light intensity at a particular site, Δ

I is the intensity error and x is distance, and w is a weight that can be dynamically tuned at each iteration in order to prioritize slope optimization over fidelity and vice versa.

12. The computer program product of claim 11, wherein moving the first lithographic mask and the second lithographic mask based on the lithographic cost function comprises:

minimizing the cost function using gradient descent;

finding analytically a derivative of the cost function with respect to mask movement for the first lithographic mask and the second lithographic mask;

utilizing the kernels representing the two exposures to analytically obtain the derivative of the image intensity and slope white determining the derivative of the cost function; and

moving the first lithographic mask, m₁, and the second lithographic mask, m₂, by a pre-specified fraction of the derivative.

13. The computer program product of claim 12, further comprising:

determining first lithographic mask movement, Δ

m1, and determining second lithographic mask movement, Δ

m2, according to the following equations;

14. The computer program product of claim 13, wherein finding analytically a derivative of the cost function with respect to mask movement for the first lithographic mask and the second lithographic mask comprises determining the derivative of the cost function with respect to mask movement according to the following equation:

15. The computer program product of claim 8, wherein the computer readable program is stored in a computer readable storage medium in a data processing system and wherein the computer readable program was downloaded over a network from a remote data processing system.

16. The computer program product of claim 8, wherein the computer readable program is stored in a computer readable storage medium in a server data processing system and wherein the computer readable program is downloaded over a network to a remote data processing system for use in a computer readable storage medium with the remote system.

17. An apparatus, comprising:

a processor; and

a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to;

set a first lithographic mask and a second lithographic mask equal to a target;

perform simultaneous optical proximity correction and decomposition on the first lithographic mask and the second lithographic mask; and

perform a first lithographic exposure with the first lithographic mask and performing a second lithographic exposure with the second lithographic mask.

18. The apparatus of claim 17, wherein performing simultaneous optical proximity correction and decomposition comprises:

performing image simulation based on the first lithographic mask and the second lithographic mask;

developing a lithographic cost function that determines contour fidelity as well as robustness of the image to process variations; and

moving the first lithographic mask and the second lithographic mask based on the lithographic cost function.

19. The apparatus of claim 18, wherein performing simultaneous optical proximity correction and decomposition further comprises:

repeating performing image simulation, developing a lithographic cost function, and moving the first lithographic mask and the second lithographic mask a predetermined number of times.

20. The apparatus of claim 18, wherein moving the first lithographic mask and the second lithographic mask based on the lithographic cost function comprises:

minimizing the cost function using gradient descent;

finding analytically a derivative of the cost function with respect to mask movement for the first lithographic mask and the second lithographic mask;

utilizing the kernels representing the two exposures to analytically obtain the derivative of the image intensity and slope while determining the derivative of the cost function; and

moving the first lithographic mask and the second lithographic mask by a pre-specified fraction of the derivative.