Inverse Lithography Source Pattern Optimization
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Solution Overview
Problem
The increasing complexity of determining write patterns and mask patterns in photolithography due to decreasing minimum dimensions on integrated-circuit dies and semiconductor wafers leads to computational challenges and distortions, making it difficult to design and manufacture photo-masks effectively.
Innovation Solution
A method using a computer system to determine a source pattern by generating functions based on level-set functions and cost gradients, which correspond to source patterns that improve the photolithographic process by enhancing resolution, accuracy, and process control, allowing for additional design degrees of freedom and improved manufacturability of photo-masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Optical Proximity Correction or resolution enhancement techniques are used to improve wafer pattern accuracy, then manufacturing precision is improved, but computational complexity increases significantly
Solution Approach 1:
The patent inverts the conventional approach by determining the source pattern from the desired wafer pattern rather than calculating the mask pattern from the source pattern. This inverse approach simplifies the computational problem by working backward from the known target pattern, avoiding the complex forward propagation calculations required by traditional OPC methods.
Solution Approach 2:
The patent changes the representation of the source pattern from a binary mask format to a continuous function space representation using level-set functions. This parameter transformation allows for more efficient computation by enabling gradient-based optimization methods to directly adjust the source pattern parameters to achieve the desired wafer pattern.
2Ease of manufacture
If additional design degrees of freedom are added to reduce computational complexity, then ease of manufacture is improved, but device complexity increases
Solution Approach 1:
The patent introduces a new dimension to the design space by using level-set functions with multiple parameters (amplitude, phase, frequency) to represent the source pattern. This dimensional expansion provides additional design degrees of freedom that simplify the optimization problem while the resulting source patterns remain manufacturable using conventional photolithography equipment.
Data Source
AI summary
Embodiments of a computer system, a process, a computer-program product (i.e., software), and a data structure or a file for use with the computer system are described. These embodiments may be used to determine or generate source patterns that define illumination patterns on photo-masks during a photolithographic process. Moreover, a given source pattern may be determined concurrently with an associated mask pattern (to which a given photo-mask corresponds) or sequentially (i.e., either the given source pattern may be determined before the associated mask pattern or vice versa.). During the determining, the given source pattern may be represented using one or more level-set functions. Additionally, the source pattern may be determined using an Inverse Lithography (ILT) calculation.