Photomask Defect Inspection Using Virtual Simulation Models
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Solution Overview
Problem
Current photomask inspection methods are time-consuming and non-economical, requiring an actual exposure-and-development process on a wafer to detect defects, which is inefficient and costly.
Innovation Solution
A method that uses virtual simulation models calibrated with real silicon data to generate a simulation contour of the photomask defect image, allowing for rapid inspection without the need for an actual exposure-and-development process, incorporating optical proximity effect correction and lithography rule checks to determine acceptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an actual exposure-and-development process is performed on a wafer to inspect photomask defects, then defect detection accuracy is improved, but inspection time and cost increase significantly
Solution Approach 1:
The patent uses virtual simulation models to create a digital copy of the exposure-and-development process, eliminating the need for actual physical processing. The virtual models replicate the optical and chemical effects to predict defect impacts, providing accurate inspection results without consuming real wafers or photoresist materials.
Solution Approach 2:
The patent replaces the physical mechanical-chemical process (exposure and development on actual wafers) with a computational simulation system. Virtual simulation models perform the inspection function that previously required physical processing, substituting mechanical/chemical operations with algorithmic calculations.
2Measurement precision
If an actual exposure-and-development process is performed on a wafer to inspect photomask defects, then defect detection accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent creates virtual copies of the fabrication process through simulation models, eliminating the need for expensive physical materials including wafers, photoresist, and processing chemicals. The virtual inspection provides the same defect detection capability without material consumption costs.
Solution Approach 2:
The patent replaces expensive physical resources (wafers, photoresist layers, processing chemicals) with inexpensive computational resources. The virtual simulation consumes minimal energy compared to the material and equipment costs of actual exposure and development processes.
3Productivity
If virtual simulation models are used for photomask inspection, then inspection speed is improved, but model accuracy may be compromised
Solution Approach 1:
The patent performs preliminary calibration of virtual simulation models using real fabrication data before actual inspection. The models are trained and validated in advance against known defect cases, ensuring they accurately predict defect impacts. This preliminary preparation enables both high speed and high accuracy during production inspection.
Solution Approach 2:
The patent incorporates feedback mechanisms where simulation results are continuously refined based on comparison with actual fabrication outcomes. The virtual models learn from real data and improve their accuracy over time, maintaining precision while preserving the speed advantage of simulation-based inspection.
Data Source
AI summary
A method of inspecting defect of a mask is provided. In this method, a database for storing a plurality of virtual simulation models is created. The virtual simulation models are determined by a plurality of factors including an optical effect and a chemical effect during the transferring the pattern of a mask to the photoresist layer on a wafer. A mask defect image is acquired. A simulation contour of the mask defect image is generated from at least one virtual simulation model in the database. Next, the acceptability of the mask is determined.