Photomask Corner Curvature for More Accurate Pattern Transfer
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Solution Overview
Problem
The photolithography process in semiconductor manufacturing often results in discrepancies between the designed circuit pattern on a mask and the transferred pattern on a wafer due to optical proximity and loading effects, which current process proximity correction techniques struggle to fully address.
Innovation Solution
A method is introduced that generates a second target pattern from a first target pattern by changing corner portions into curved edges, followed by optical proximity correction to create a mask pattern, which includes varying densities of mask control points on straight and curved edges, thereby improving the accuracy of the mask fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical proximity correction is performed on a target pattern with straight edges to correct pattern transfer discrepancies, then the accuracy of pattern transfer is improved, but the complexity of the mask fabrication process increases
Solution Approach 1:
The patent applies curvature to corner portions of the target pattern by replacing sharp corners with curved edges. This modification to the target pattern geometry simplifies the optical proximity correction process while maintaining or improving pattern transfer accuracy, as curved edges naturally reduce the severity of optical diffraction effects at corners.
2Manufacturing precision
If conventional optical proximity correction is applied to correct layout deformation, then the transferred circuit pattern accuracy is improved, but the manufacturing time and process complexity increase
Solution Approach 1:
The patent performs preliminary modification of the target pattern by changing corner portions to curved edges before the optical proximity correction step. This preliminary action pre-compensates for expected pattern transfer discrepancies, reducing the amount of correction needed in subsequent steps and thereby decreasing overall mask fabrication time while maintaining pattern accuracy.
3Measurement precision
If the number of mask control points is increased to improve correction precision, then the optical proximity correction accuracy is improved, but the computational complexity and processing time increase
Solution Approach 1:
The patent applies different densities of mask control points to different regions of the target pattern. Specifically, corner portions with curved edges are assigned a different (typically lower) density of control points compared to straight edge regions. This local differentiation maintains correction accuracy where needed while reducing computational complexity in regions where fewer control points are sufficient.
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
This approach reduces the time and complexity of mask fabrication, enhances the accuracy of pattern transfer, and minimizes the number of mask control points, leading to a more efficient and precise semiconductor device manufacturing process.
Implementation Method 1
This difference is due to an optical proximity effect in the photolithography process or a loading effect in the etch process. A scheme for accurately transferring the circuit pattern on the mask onto the wafer employs a process proximity correction (PPC) technique to correct the circuit pattern in consideration of deformation of the transferred circuit pattern on the wafer.
Data Source
AI summary
A method for fabricating mask is provided. The method includes generating a second target pattern from a first target pattern, where the first target pattern includes first straight edges, and the second target pattern includes second straight edges and curved edges. Optical proximity correction is performed on the second target pattern to generating a mask pattern. The mask is fabricated using the mask pattern. Generating the second target pattern includes changing corner portions of the first target pattern into a curve to generate the curved edges.