Mask Pattern Correction via Simulation and Rotation
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Solution Overview
Problem
Conventional optical proximity correction methods in photolithography often require repeated adjustments to achieve tolerable critical dimension bias values on both the x and y axes, leading to inefficiencies in the mask pattern correction process, especially as critical dimensions approach the wavelength of light, resulting in prolonged processing times.
Innovation Solution
A mask pattern correction method involving simulation to identify unsaturated patterns, followed by rotation of device patterns using off-axis or quadrupole illumination with a 45-degree rotation angle, ensuring that each pattern edge is illuminated through a single corresponding pupil, thereby simplifying illumination and improving pattern transfer resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical proximity correction is applied to improve critical dimension accuracy, then manufacturing precision is improved, but processing time increases due to repeated adjustments
Solution Approach 1:
The patent applies preliminary action by performing simulation before the actual correction process to identify unsaturated patterns that require rotation. This preliminary identification allows the system to pre-determine which patterns need special handling, avoiding repeated iterative adjustments during the correction process and significantly reducing processing time while maintaining critical dimension accuracy.
Solution Approach 2:
The patent changes the orientation parameter of selected device patterns by rotating them at specific angles (e.g., 45 degrees). This parameter change transforms the illumination geometry for those patterns, ensuring that pattern edges are illuminated through single pupils rather than multiple pupils, thereby improving correction efficiency and reducing the number of iterative adjustments needed.
2Manufacturing precision
If device patterns are rotated to improve illumination uniformity, then manufacturing precision is improved, but device layout complexity increases
Solution Approach 1:
The patent applies local quality by selectively rotating only the unsaturated patterns that require improved illumination, rather than rotating all device patterns uniformly. This localized approach improves illumination uniformity for specific patterns while maintaining the original orientation of other patterns, thereby minimizing the overall increase in layout complexity.
Solution Approach 2:
By performing simulation and analysis before the correction process to identify which patterns need rotation, the system can pre-determine the exact set of patterns that require orientation changes. This preliminary identification minimizes unnecessary rotations and simplifies the final layout while achieving the desired illumination uniformity.
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 enhances the accuracy and reliability of the correction process, reducing the cycle time required for forming mask patterns by ensuring critical dimension errors are within tolerable ranges on both axes, thereby improving the efficiency of the photolithographic process.
Implementation Method 1
The proximity effect refers to the enlargement of a light caused by diffraction when the light passes through a mask to form patterns on a chip
Implementation Method 2
In addition, the light is reflected through a semiconductor substrate and a photoresist layer on the surface of the chip, which results in interference
Implementation Method 3
each pattern edge of each rotated device pattern is illuminated through a corresponding pupil
Data Source
AI summary
A mask pattern correction method is provided. The method comprises the following steps. An original layout, which has a plurality of device patterns, is provided. Then, a simulation process is performed on the device patterns to correspondingly form a plurality of simulated patterns. Thereafter, the simulated patterns are analyzed to select a plurality of unsaturated patterns from the simulated patterns. Finally, the device patterns in the original layout corresponding to the unsaturated patterns respectively are rotated.