Mask Pattern Optimization Reducing Drawing Shots
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Solution Overview
Problem
The semiconductor industry faces challenges in mask manufacturing due to complex patterns requiring numerous drawing shots, leading to increased operation time, cost, and yield rate issues, as existing techniques fail to optimize mask patterns considering both cost and image performance effectively.
Innovation Solution
A method involving a computer-based pattern determining system that calculates evaluation functions for cost and image quality, iteratively adjusting mask patterns, illumination conditions, and drawing conditions until optimal parameters are met, reducing the number of drawing shots and maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If OPC or ILT is used to determine mask patterns for finer devices, then image quality is improved, but pattern complexity increases leading to more drawing shots and higher mask cost
Solution Approach 1:
The patent changes the parameter representation from complex curved shapes to simple rectangular shapes defined by coordinate parameters. The mask pattern is represented using only rectangular drawing shots with parameters (x1, y1, x2, y2, dose), transforming a complex pattern description into a simplified parametric form that reduces drawing shot count while maintaining image quality through optimization.
2Ease of manufacture
If fracturing is performed for complex patterns, then pattern drawing capability is improved, but the number of drawing shots increases explosively leading to longer operation time and higher mask cost
Solution Approach 1:
The patent performs preliminary optimization of the mask pattern before fracturing. By optimizing the pattern parameters (coordinates and doses of rectangular shots) in advance using computational methods, the system determines the minimum set of drawing shots needed, preventing explosive increase in shot count during subsequent fracturing operations.
3Manufacturing precision
If drawing shot size is reduced to improve accuracy, then manufacturing precision is improved, but the number of drawing shots increases and mask cost increases
Solution Approach 1:
The patent uses rectangular drawing shots that can be larger than traditionally used, covering more area per shot. By optimizing the position, size, and dose of each rectangular shot, the system achieves required manufacturing precision with fewer, larger shots rather than many small shots, reducing the total drawing shot count while maintaining accuracy.
4Manufacturing precision
If mask pattern complexity increases, then image quality for finer devices is improved, but mask manufacturing cost increases
Solution Approach 1:
The patent extracts the essential pattern information into a simplified parametric representation using rectangular shots with coordinate parameters. By separating the pattern definition into simple geometric primitives (rectangles) with adjustable parameters (position, size, dose), the system maintains image quality while dramatically reducing pattern complexity and associated manufacturing costs.
Data Source
AI summary
A method of determining a pattern of a mask to be used in an exposure apparatus. The mask is arranged on an object plane of a projection optical system. The method includes calculating a value of a first evaluation function used to evaluate a cost of drawing a provisional pattern on a mask blank to manufacture the mask, calculating a value of a second evaluation function used to evaluate an image of the provisional pattern, which is formed on an image plane of the projection optical system when a mask having the provisional pattern is arranged on the object plane, and changing the provisional pattern. The calculations are repeated, and the provisional pattern is determined as the pattern of the mask, when the value of the first evaluation function meets a first predetermined standard and the value of the second evaluation function meets a second predetermined standard.