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US 8,572,517 B2Granted
System and method for modifying a data set of a photomask
AssigneeCadence Design Systems, Inc.
InventorsDipankar Pramanik, Michiel Victor Paul Kruger, Roy V. Prasad, Abdurrahman Sezginer
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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.
Claims11
A method for optical compensation comprising:
- using a computer system to create a simulated circuit pattern using a lithography process, wherein the lithography process uses 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 simulated circuit pattern, wherein the cost function comprises terms defined by at least one of:
- (a) a sum of squares of normalized differences between simulated and designed values of electrical parameters for a multitude of circuit components,
- (b) an amount by which the simulated value of the electrical parameter exceeds a maximum allowable value,
- (c) an amount by which the simulated value of the electrical parameter falls below a minimum allowable value,
- (d) the difference of simulated values of a first and a second electrical parameter of a simulated circuit pattern,
- (e) a change in the simulated value of the electrical parameter in response to a change in a condition of the lithography process, and
- (f) a restricted simulated value of the electrical parameter that is not larger than a maximum allowable value or not smaller than a minimum allowable value,
- and wherein the electrical parameter describes an electrical operational characteristic of the simulated circuit pattern;
- and
- adjusting the polygons based on the calculated cost function in order to reduce the value of the cost function.
8 more elements
A computer system configured for optical compensation, comprising:
- a processor;
- a memory connected to the processor;
- and
- a computer-readable medium having instructions embedded therein, the instructions configured to cause the processor to perform the operations of:
- creating a simulated circuit pattern using a lithography process, wherein the lithography process uses 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 simulated circuit pattern, wherein the cost function comprises terms defined by at least one of:
- (a) a sum of squares of normalized differences between simulated and designed values of electrical parameters for a multitude of circuit components,
- (b) an amount by which the simulated value of the electrical parameter exceeds a maximum permissible value,
- (c) an amount by which the simulated value of the electrical parameter falls below a minimum allowable value,
- (d) the difference of simulated values of a first and a second electrical parameter of a simulated circuit pattern,
- (e) a change in the simulated value of the electrical parameter in response to a change in a condition of the lithography process, and
- (f) a restricted simulated value of the electrical parameter that is not larger than a maximum allowable value or not smaller than a minimum allowable value,
- and wherein the electrical parameter describes an electrical operational characteristic of the simulated circuit pattern;
- and
- adjusting the polygons based on the calculated cost function in order to reduce the value of the cost function.
12 more elements
Dependencies are inferred from the claim text.