Photolithography Mask Analysis Using 3D Multicontour Profiles
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Solution Overview
Problem
Current methods for analyzing photolithography masks are complex and time-consuming, particularly when evaluating different focus stacks and energy doses, making it difficult to simplify and accelerate the analysis process.
Innovation Solution
A method that generates an aerial image of the mask for a first focus setting, simulates the photolithographic wafer exposure, and determines contours at specific energy doses, storing these as two-dimensional contour data records, which can be combined to form a three-dimensional multicontour data record, allowing for the evaluation of the photoresist layer's profile and behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional simulation methods simulate the whole process taking account of exposure and development of the three-dimensional photoresist layer, then measurement precision is improved, but device complexity and calculation time increase significantly
Solution Approach 1:
The patent extracts and separates the essential factors from the complete three-dimensional photoresist simulation process. It isolates the aerial image intensity distribution and applies a simplified two-dimensional model that focuses only on the critical exposure and development parameters, excluding less significant three-dimensional effects. This extraction maintains sufficient measurement precision while dramatically reducing computational complexity.
Solution Approach 2:
The patent changes the parameter dimensionality from three-dimensional to two-dimensional by approximating the photoresist layer as a plane. This parameter change simplifies the mathematical model from a complex 3D partial differential equation system to a more manageable 2D model, reducing calculation time and device complexity while preserving the essential physics of photoresist behavior during exposure and development.
2Reliability
If multiple aerial images at different focus settings are recorded and simulated, then reliability of mask analysis is improved, but loss of time and computational resources increase
Solution Approach 1:
The patent performs preliminary actions by generating contour data records at predetermined heights from the aerial image intensity distribution before conducting full simulations. This preliminary contour extraction provides a simplified representation that can be processed more efficiently, reducing the time required for subsequent analysis while maintaining the reliability needed for accurate mask defect detection across different focus settings.
Data Source
AI summary
The invention relates to a method for analyzing masks for photolithography. In this method, an aerial image of the mask for a first focus setting is generated and stored in an aerial image data record. The aerial image data record is transferred to an algorithm that simulates a photolithographic wafer exposure on the basis of this data record. In this case, the simulation is carried out for a plurality of mutually different energy doses. Then, at a predetermined height from the wafer surface, contours which separate regions with photoresist from those regions without photoresist are in each case determined. The result, that is to say the contours, are stored for each of the energy doses in each case in a contour data record with the energy dose as a parameter. Finally, the contour data records are combined to form a three-dimensional multicontour data record with the reciprocal of the energy dose as a third dimension, and, on the basis of the transitions from zero to values different than zero in the contours, a three-dimensional profile of the reciprocal of the energy dose depending on the position on the mask is generated. This profile, the so-called effective aerial image, is output or stored or automatically evaluated. The same can also occur with sections through said profile.