Photolithography Mask Repair Verification via Aerial Image Simulation
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Solution Overview
Problem
The verification of repairs on photolithography masks is time-consuming and imprecise, especially for masks with complex structures like those used in logic circuits, due to the need for manual comparison with identical, unrepaired structures, which is not always feasible.
Innovation Solution
A method that involves simulating an aerial image of the desired structure based on the mask layout, comparing it with the captured aerial image, and using threshold values to analyze deviations, allowing for automated verification of repair success and iterative correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual comparison with identical, unrepaired structures is used for verification, then verification accuracy is improved, but verification time and complexity increase significantly
Solution Approach 1:
The patent creates a virtual copy of the desired structure through simulation. A simulation model is generated from the mask layout data, and a simulated aerial image is produced. This virtual copy serves as the reference for comparison with the actual captured aerial image of the repaired structure, eliminating the need to find and manually compare with physical identical structures on the mask.
Solution Approach 2:
The patent replaces the manual mechanical comparison process with automated computational simulation and image analysis. Instead of manually locating and comparing physical structures, the system uses computer-based simulation to generate reference images and automated algorithms to compare them with captured images, significantly reducing verification time and human effort.
2Measurement precision
If manual verification methods are used, then detailed analysis is possible, but the process becomes too time-consuming for complex mask structures
Solution Approach 1:
The verification system performs self-service by automatically generating simulation models from mask layout data, producing simulated aerial images, capturing actual aerial images of repaired structures, and comparing them using automated evaluation algorithms. The system evaluates whether target parameters meet tolerance criteria without requiring manual intervention, enabling high-volume verification of complex mask structures efficiently.
3Reliability
If identical, unrepaired structures are required for comparison, then verification reliability is improved, but feasibility decreases when such structures are not available on the mask
Solution Approach 1:
Instead of requiring physical copies of identical structures to exist on the mask, the patent creates virtual copies through simulation. The simulation model is derived from the mask layout data, which describes the desired structure. This virtual copy serves as the reference standard for verification, making the process feasible even when no identical unrepaired structures exist on the physical mask.
4Productivity
If simulation and automated comparison methods are used, then verification speed is improved, but complexity of the verification system increases
Solution Approach 1:
The patent introduces a simulation model as an intermediary between the mask layout data and the verification process. The simulation model acts as a mediator that translates layout data into a simulated aerial image, which then serves as the reference for comparison with captured images. This intermediary approach automates the verification process while managing system complexity through modular simulation and evaluation components.
Data Source
AI summary
A method for verifying repairs on masks for photolithography is provided. A mask fabricated based on a mask layout is inspected for defects, and the positions at which defects are found on the mask are stored in a position file. In a repair step, the defects are repaired and, for each repaired position, in a verification step, an aerial image of the mask is taken at that position and the aerial image is analyzed to determine whether at that position the mask meets tolerance criteria established for one or more selected target parameters, and if the tolerance criteria have been met, the repair is verified. The verification can include a) based on the position file, a desired structure is defined in the mask layout at the repaired position, b) an aerial image is simulated for the desired structure, c) the captured aerial image is compared with the simulated one, and d) based on the comparison, a decision is made as to whether the repair at that position is verified.