Lithographic Image Log Slope Optimization
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Solution Overview
Problem
Current lithographic processes face challenges in accurately reproducing patterns with features smaller than the classical resolution limit, leading to issues such as line edge roughness and critical dimension uniformity, which affect the production of integrated circuits and other devices.
Innovation Solution
A computer-implemented method is introduced to improve the lithographic process by computing a multi-variable cost function that accounts for stochastic variations like line edge roughness and blurred image log slope, allowing for the adjustment of design variables such as dose and illumination settings to optimize the imaging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional lithographic processes are used to pattern features smaller than the classical resolution limit, then the manufacturing of advanced integrated circuits is enabled, but line edge roughness and critical dimension uniformity deteriorate
Solution Approach 1:
The patent changes the physical parameters of the illumination system by introducing a condenser lens between the light source and patterning device to create a focused illumination beam. This parameter change in the illumination geometry enables better control of the imaging process for sub-resolution features, improving line edge roughness and critical dimension uniformity while maintaining advanced feature size patterning capability
Solution Approach 2:
The patent introduces a condenser lens as an intermediary optical element between the light source and the patterning device. This intermediary component focuses and conditions the illumination beam, mediating the interaction between light and the patterning device to achieve improved imaging precision for sub-resolution features without compromising the ability to manufacture advanced integrated circuits
2Measurement precision
If illumination settings are optimized for resolution, then pattern accuracy improves, but stochastic variations such as line edge roughness increase
Solution Approach 1:
The patent implements a feedback mechanism where the condenser lens dynamically adjusts illumination parameters based on detected imaging conditions. By monitoring the imaging process and adjusting illumination in response, the system maintains high pattern accuracy while reducing stochastic variations and line edge roughness that would otherwise increase with resolution-optimized illumination
3Manufacturing precision
If process parameters are tightly controlled to reduce defects, then manufacturing precision improves, but process window and throughput decrease
Solution Approach 1:
The patent introduces dynamic control of illumination parameters through the condenser lens, allowing the system to adapt illumination conditions in real-time based on process requirements. This dynamic approach enables tight defect control when needed while maintaining a larger effective process window and higher throughput by avoiding overly restrictive static parameter control
Data Source
AI summary
A method to improve a lithographic process of imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method including: computing a multi-variable cost function, the multi-variable cost function being a function of a stochastic variation of a characteristic of an aerial image or a resist image, or a function of a variable that is a function of the stochastic variation or that affects the stochastic variation, the stochastic variation being a function of a plurality of design variables that represent characteristics of the lithographic process; and reconfiguring one or more of the characteristics of the lithographic process by adjusting one or more of the design variables until a certain termination condition is satisfied.