SYSTEM AND METHOD FOR MODIFYING A DATA SET OF A PHOTOMASK

• US 20090307649A1
• Filed: 06/10/2008
• Published: 12/10/2009
• Est. Priority Date: 06/10/2008
• Status: Active Grant

• Current Assignee: Cadence Design Systems Incorporated (Cadence Group)
• Original Assignee: Cadence Design Systems Incorporated (Cadence Group)
• Inventors: Prasad, Roy V., Pramanik, Dipankar, Kruger, Michiel Victor Paul, Sezginer, Abdurrahman
• Granted Patent: US 8,572,517 B2
• Time in Patent Office: Days
• US Class Current: 716/50
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

The present invention provides a method for compensating, infidelities of a process that transfers a pattern to a layer of an integrated circuit, by minimizing, with respect to a photomask pattern, a cost function that quantifies the deviation between designed and simulated values of circuit parameters of the pattern formed on a semiconductor wafer.

Claims

1. A method for modifying a data set used to produce a photomask comprising:

calculating a demerit function using an electrical parameter of a circuit pattern created with the photomask; and

modifying the data set based on the calculated demerit function in order to reduce the value of the demerit function.

2. The method of claim 1, wherein the data set comprises a polygon and modifying the data set further comprises:

dividing an edge of the polygon into a plurality of segments;

moving one of the plurality of segments based on the calculated demerit function.

3. The method of claim 1, wherein the electrical parameter comprises one or more parameters from the group consisting of saturation current, leakage current, threshold voltage, gain, resistance, capacitance, and inductance.

4. The method of claim 1, wherein calculating the demerit function further comprises calculating a measure of geometric difference between the created circuit pattern and a target circuit pattern.

5. The method of claim 1, wherein the method further comprises modifying at least one of distribution and polarization variables of the illumination in a pupil of an optical projector

6. The method of claim 1, wherein calculating the demerit function further comprises calculating an electrical parameter of a circuit pattern created using the photomask and a lithography process, for a multitude of conditions of the lithography process.

7. The method of claim 1, wherein the demerit function comprises a plurality of demerit functions, including a first demerit function based on a differential of a first simulated electrical parameter of a device of the circuit pattern and a desired electrical parameter of the device.

8. The method of claim 7, wherein the demerit function further comprises a second demerit function, the second demerit function is based on a differential of the first simulated electrical parameter and a maximum allowable electrical parameter of the device.

9. The method of claim 7, wherein the demerit function further comprises a second demerit function, the second demerit function is based on a differential of a minimum allowable electrical parameter of the device and the first simulated electrical parameter.

10. The method of claim 7, wherein the demerit function further comprises a second demerit function, the second demerit function based on a differential of the first simulated electrical parameter and a second simulated electrical parameter of a second device in the circuit pattern.

11. The method of claim 6, wherein the demerit function comprises a plurality of demerit functions, including a first demerit function based on a differential of a first simulated process condition and a second simulated process condition,.

12. The method of claim 1, wherein modifying the data set comprises minimizing the value of the demerit function.

13. A method for optical compensation comprising:

creating a circuit pattern using a lithography process with a photomask defined by a data set having a plurality of polygons that define patterns on the photomask;

calculating a cost function based on an electrical parameter of the created circuit pattern for one or more process conditions; and

adjusting the polygons based on the calculated cost function in order to reduce the value of the cost function.

14. The method of claim 13, wherein adjusting the polygons comprises any combination of:

segmenting an edge of a polygon, altering a polygon by moving a segment of its edge, moving a polygon, adding a polygon to the data set, removing a polygon from the data set.

15. The method of claim 14, wherein the cost function comprises a first term defined by a sum of squares of normalized differences between simulated and designed values of electrical parameters for a multitude of circuit components.

16. The method of claim 15, wherein the cost function further comprises a second term defined by an amount by which the simulated value of an electrical parameter exceeds a maximum permissible value for the electrical parameter.

17. The method of claim 16, wherein the cost function further comprises a third term defined by an amount by which the simulated value of an electrical parameter falls below a minimum allowable value for the electrical parameter.

18. The method of claim 17, wherein the cost function further comprises a fourth term defined by the difference of values of a first and a second electrical parameter of a simulated wafer pattern.

19. The method of claim 17, wherein the cost function further comprises a fourth term defined by a change in the value of a circuit parameter in response to a change in the condition of a patterning process.

20. The method of claim 15, wherein the cost function further comprises at least one term that restricts the simulated value of an electrical parameter as being not larger than a maximum allowable value or not smaller than a minimum allowable value.

21. The method of claim 13, wherein the electrical parameter comprises one or more parameters from the group consisting of saturation current, leakage current, threshold voltage, gain, resistance, capacitance, and inductance.

22. The method of claim 13, wherein calculating the demerit function further comprises using geometric variables derived from comparing the created circuit pattern with a target circuit pattern.

23. The method of claim 13, further comprising adjusting distribution or polarization variables of the illumination in a pupil of an optical projector in a way to reduce the value of the cost function.

24. The method of claim 13, wherein the method is performed using a computer program product having computer readable program code functions embedded in a computer useable medium.