Cost Function Based OPC and SBAR Optimization
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Solution Overview
Problem
In optical lithography, achieving precise pattern transfer with small feature sizes becomes challenging due to non-linear processes and optical proximity effects, where features on the mask undergo unintended distortions affecting the final pattern on the wafer, especially as dimensions approach the wavelength of light used, leading to complex interactions and reduced process windows.
Innovation Solution
A method involving model-based optical proximity correction (OPC) that evaluates and adjusts edge segments of features using control points to minimize edge placement errors and critical dimension variations across various process conditions, employing a cost function to optimize feature layouts and assist features to counteract distortions, ensuring accurate pattern transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical lithography is used to pattern small features, then the manufacturing process becomes simpler and faster, but the pattern transfer precision deteriorates due to optical proximity effects and non-linear processes
Solution Approach 1:
The patent applies preliminary action by performing optical proximity correction (OPC) during the mask design phase before lithography. The system pre-calculates and applies corrections to the mask pattern to compensate for expected optical distortions and non-linear effects during exposure, ensuring accurate pattern transfer without requiring complex real-time adjustments during the lithography process itself.
Solution Approach 2:
The patent implements feedback through an iterative optimization process that uses measured or simulated lithographic outcomes to refine the mask pattern. The system evaluates the actual pattern transfer results and adjusts the mask design accordingly, creating a closed-loop system that continuously improves pattern accuracy despite optical limitations.
2Productivity
If feature dimensions are reduced to sub-wavelength scales, then the device density and integration are improved, but the pattern transfer fidelity deteriorates due to increased optical proximity effects
Solution Approach 1:
The patent applies local quality by implementing spatially varying corrections in the mask pattern. Different regions of the mask receive different OPC treatments based on their specific optical environment and proximity to other features. The system adjusts the correction magnitude and type locally for each feature or feature group, allowing sub-wavelength patterning while maintaining fidelity through customized local compensation.
Solution Approach 2:
The patent utilizes parameter changes by modifying various mask design parameters such as feature dimensions, spacing, and shape to compensate for optical effects. The system changes these geometric parameters in the mask pattern to counteract the non-linear optical response, enabling accurate sub-wavelength feature formation despite the reduced dimensions.
3Manufacturing precision
If optical proximity correction is applied to compensate for distortions, then the pattern transfer precision is improved, but the mask design and process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the mask pattern into discrete correctable elements or regions. The OPC process segments the complex distortion compensation into manageable corrections applied to individual features or feature groups. This segmentation allows the system to handle the complexity of sub-wavelength patterning by processing corrections locally rather than attempting a monolithic solution.
Solution Approach 2:
The patent uses copying by creating a corrected version of the mask pattern through computational modeling. The system generates an optimized mask design that incorporates pre-calculated OPC corrections, effectively copying and modifying the original pattern to account for optical effects. This approach separates the correction calculation from the physical mask fabrication, managing complexity through digital design.
4Manufacturing precision
If the process window is narrowed to achieve higher precision, then the manufacturing precision is improved, but the productivity and yield deteriorate
Solution Approach 1:
The patent implements beforehand cushioning by incorporating robust OPC corrections that account for process variations and uncertainties. The mask design includes built-in compensation for potential deviations in exposure conditions, focus, and dose, creating a cushioning effect that maintains accuracy across a broader process window. This prevents the process window from being unnecessarily narrowed while maintaining high precision.
Data Source
AI summary
Described herein is a method for obtaining a preferred layout for a lithographic process, the method comprising: identifying an initial layout including a plurality of features; and reconfiguring the features until a termination condition is satisfied, thereby obtaining the preferred layout; wherein the reconfiguring comprises evaluating a cost function that measures how a lithographic metric is affected by a set of changes to the features for a plurality of lithographic process conditions, and expanding the cost function into a series of terms at least some of which are functions of characteristics of the features.