Angled Grating Resist Modeling via Segmented Verification
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Solution Overview
Problem
Conventional lithography techniques struggle to form accurate resist models for optical devices with angled gratings, as lines with different angles result in varying resist metrology critical dimensions, making it difficult to achieve consistent patterning.
Innovation Solution
A method involving the design of a model area and verification area on an optical device substrate with initial mask patterns, fabrication of test masks, patterning, measurement, and verification to determine if the verification angles and critical dimensions meet desired thresholds, allowing for the creation of new device masks that implement optical proximity correction for angled gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography techniques use vertical or horizontal lines to build a resist model, then the model can be formed with simple geometry, but the model cannot accurately represent angled gratings with different critical dimensions
Solution Approach 1:
The substrate is divided into distinct model area and verification area, each with specific grating patterns at different orientations. This segmentation allows independent optimization and measurement of different angular configurations, enabling accurate resist modeling for angled gratings while maintaining manageable process complexity
Solution Approach 2:
Different regions of the substrate are assigned different grating angles and critical dimensions tailored to specific measurement needs. The model area contains gratings at various angles to capture angle-dependent resist behavior, while the verification area contains target patterns for validating the model's predictive accuracy for angled structures
2Measurement precision
If test masks are fabricated with model area and verification area to measure angled gratings, then accurate metrology can be achieved, but additional fabrication and measurement steps increase process time
Solution Approach 1:
The resist model is constructed in advance using measured data from the model area before final device fabrication. This preliminary modeling and verification process allows the development of accurate angle-dependent resist parameters that can then be applied to optimize device mask design, reducing the need for iterative trial-and-error fabrication cycles
Solution Approach 2:
The model area and verification area are combined into a single test mask structure that can be fabricated and measured together. This integration allows simultaneous acquisition of both model-building data and model-validation data in one process cycle, improving measurement efficiency while maintaining precision
Data Source
AI summary
Methods of forming a resist model for angled gratings on optical devices. In one example, a method includes designing a model with a model area and a verification area with initial mask patterns having a first grating pattern with a first angle and a first critical dimension and fabricating test masks with the model area having a first model angle and a first model critical dimension and the verification area having a first verification angle and a first verification critical dimension. The method also includes patterning a substrate with the test masks, measuring the first model angle, the first model critical dimension, the first verification angle and the first verification critical dimension, and fabricating a new device mask if the first verification angle is within the threshold range of the first desired angle and the first verification critical dimension is within the threshold range of the first desired critical dimension.