Compact Modeling for Negative Tone Development Processes
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Solution Overview
Problem
Compact modeling for negative tone development processes in photolithography struggles to achieve accurate simulation due to computational expense and limited output data, particularly in incorporating mechanical effects like volume change during post-exposure resist processing, which degrades runtime performance.
Innovation Solution
A computer-implemented method for modeling photolithography in optical proximity correction using a sampling pattern that includes nodes and antinodes, scaled by coefficients obtained through regression analysis, to modify image output intensity and account for mechanical effects in optical phenomena, thereby enhancing simulation accuracy without increasing runtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If first principle simulations are used to achieve accurate modeling of negative tone development processes, then simulation accuracy is improved, but computational expense increases significantly
Solution Approach 1:
The patent extracts and models only the essential physical-chemical mechanisms of the negative tone development process (acid diffusion, deprotection reactions, volume change) rather than simulating all electromagnetic field interactions. This selective extraction of key mechanisms enables accurate prediction of pattern formation while significantly reducing computational requirements compared to full first-principle electromagnetic simulations.
Solution Approach 2:
The patent transforms the complex first-principle simulation parameters into simplified effective parameters that capture the essential behavior of the resist system. By changing from detailed electromagnetic field parameters to effective diffusion coefficients, reaction rates, and volume change parameters, the model achieves comparable accuracy with much lower computational cost.
2Measurement precision
If mechanical effects like volume change are incorporated into compact models to accurately represent negative tone development, then modeling accuracy is improved, but runtime performance degrades
Solution Approach 1:
The patent replaces complex mechanical volume change calculations with an optimized computational approach that uses pre-calculated volume change factors based on local pattern density. Instead of performing full mechanical stress-strain simulations, the model uses analytical expressions that capture the essential volume expansion effects during development, maintaining accuracy while achieving runtime performance suitable for full-chip OPC.
3Productivity
If compact models are optimized to work with optical effects, then computational efficiency is improved, but ability to model mechanical effects deteriorates
Solution Approach 1:
The patent merges optical proximity correction modeling with negative tone development modeling into a unified framework. The model combines optical intensity calculations with physical-chemical resist behavior (acid diffusion, deprotection, volume change) in a single integrated simulation that maintains computational efficiency while accurately representing both optical and mechanical effects specific to NTD processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides accurate simulation of negative tone development processes with minimal impact on computation time, enabling more precise modeling of optical and mechanical effects, thus improving the accuracy of photolithography in integrated circuit manufacturing.
Implementation Method 1
compact models are optimized to work with optical effects such as diffraction
Implementation Method 2
The volume change that modifies the critical dimensions (CD) during post exposure resist processing is mechanical in nature
Data Source
AI summary
A photolithography model used in an optical proximity correction process modifies an image output intensity of a point disposed along a two dimensional plane and having coordinates (x,y) in accordance with a gradient of a convolution of a mask value at the point and a sampling pattern function selected at the point. The sampling pattern function includes, in part, a first subset of sampling patterns and a second subset of sampling patterns. The first subset of sampling patterns includes first and second nodes. The second subset of sampling patterns include first and second antinodes. The gradient of the convolution of the mask value and the first and second nodes of the first subset are scaled by a first coefficient. The gradient of the convolution of the mask value and the first and second antinodes of the second subset are scaled by a second coefficient.