Method for time-evolving rectilinear contours representing photo masks
First Claim
1. A computer-implemented method for determining a mask pattern to be used on a photo-mask in a photolithographic process, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, comprising:
- providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask;
using a processor to calculate a gradient of a function, wherein the function depends on the first mask pattern and an estimate of a wafer pattern that results from the photolithographic process utilizing at least a portion of the first mask pattern, and wherein the gradient is a closed-form expression; and
generating a second mask pattern based, at least in part, on the gradient of the function.
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Abstract
Photomask patterns are represented using contours defined by level-set functions. Given target pattern, contours are optimized such that defined photomask, when used in photolithographic process, prints wafer pattern faithful to target pattern. Optimization utilizes “merit function” for encoding aspects of photolithographic process, preferences relating to resulting pattern (e.g. restriction to rectilinear patterns), robustness against process variations, as well as restrictions imposed relating to practical and economic manufacturability of photomasks.
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Citations
20 Claims
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1. A computer-implemented method for determining a mask pattern to be used on a photo-mask in a photolithographic process, wherein the photo-mask has a plurality of distinct types of regions having distinct optical properties, comprising:
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providing a first mask pattern that includes a plurality of distinct types of regions corresponding to the distinct types of regions of the photo-mask; using a processor to calculate a gradient of a function, wherein the function depends on the first mask pattern and an estimate of a wafer pattern that results from the photolithographic process utilizing at least a portion of the first mask pattern, and wherein the gradient is a closed-form expression; and generating a second mask pattern based, at least in part, on the gradient of the function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification