Assist Feature Placement for Mask Pattern Optimization
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Solution Overview
Problem
Current methods for arranging assist features on masks in semiconductor fabrication are time-consuming and inefficient, particularly when dealing with complex patterns, as they rely on manual trial and error and do not effectively optimize exposure and depth of focus across the entire mask area.
Innovation Solution
A method that determines the optimal position of assist features by discretizing neighboring regions into finite areas, using representative values to calculate the contribution of assist features to image intensity, and applying optical proximity correction and mask rule checks to improve mask performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual trial and error method is used to arrange assist features, then the engineer can arrange assist features on the mask, but the process requires a large amount of time and the assist features may not be arranged on a broad area of the mask
Solution Approach 1:
The patent replaces the manual mechanical process of arranging assist features with an automated computer-based system that uses optical simulation and calculation algorithms. The system automatically determines optimal assist feature positions by simulating light interaction with mask patterns, eliminating the need for manual trial and error while significantly reducing the time required for assist feature arrangement.
Solution Approach 2:
The system enables self-service by allowing the mask pattern design to automatically generate and position assist features without human intervention. The computer-based system performs self-optimization by calculating the most effective assist feature placements based on the main pattern geometry and optical properties, making the process autonomous and efficient.
2Ease of manufacture
If manual trial and error method is used to arrange assist features, then the engineer can arrange assist features on the mask, but the assist features may not be arranged on a broad area of the mask relative to the overall pattern
Solution Approach 1:
The patent implements a universal computer-based system that can handle various mask patterns and automatically determine assist feature positions across the entire mask area. The system is designed to process different pattern types and geometries, ensuring that assist features are appropriately arranged across the full extent of the mask rather than being limited to specific regions.
Solution Approach 2:
By replacing manual arrangement with automated optical simulation, the system can evaluate and optimize assist feature placement across the entire mask area, including regions that would be difficult or time-consuming to address manually. This enables comprehensive coverage of the mask surface with optimally positioned assist features.
3Adaptability or versatility
If various different patterns are present on the mask, then the mask can accommodate complex circuit designs, but it becomes very difficult to generate the assist features in a stable manner
Solution Approach 1:
The patent employs parameter-based optimization where the computer system adjusts various parameters (such as assist feature size, spacing, and position) based on the specific pattern geometry and optical conditions. By systematically varying these parameters through simulation and calculation, the system achieves stable and consistent assist feature generation across different pattern types, eliminating the instability associated with manual methods.
Solution Approach 2:
The automated computer-based system provides stability by using consistent algorithms and optical simulation models to determine assist feature positions, regardless of pattern complexity. This replaces the variable and unstable manual trial-and-error process with a deterministic computational approach that yields reproducible results across diverse pattern configurations.
4Length of moving object
If the microscopic size of mask features is reduced, then the circuit density is increased, but it becomes difficult for light to pass through holes or lines in the mask
Solution Approach 1:
The patent introduces assist features as intermediary elements that mediate between the main pattern features and the light transmission. These assist features, positioned strategically around the microscopic features, act as optical intermediaries that enhance light interaction and improve image intensity on the wafer, compensating for the reduced light transmission caused by smaller feature sizes.
Solution Approach 2:
The system optimizes the parameters of assist features (such as their size, shape, and position) to compensate for the reduced light transmission through microscopic features. By adjusting these parameters through computational optimization, the system maintains adequate image intensity on the wafer even when the main features are reduced to microscopic dimensions.
Data Source
AI summary
Methods and apparatus are disclosed that arrange mask patterns in response to the contribution of an assist feature to image intensity. In some methods of arranging mask patterns, a distribution of functions h(ξ−x) is obtained which represents the contribution of an assist feature to image intensity on a main feature. Neighboring regions of the main feature are discretized into finite regions, and the distribution of the functions h(ξ−x) is replaced with representative values h(x,ξ) of the discretized regions. A position of the assist feature is determined using polygonal regions having the same h(x,ξ). As described, the term x is the position of the main feature and the term ξ is the position of the assist.