Photolithography Simulation Stability Range Determination
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Solution Overview
Problem
Current methods for determining the wafer structure from an aerial image of a mask lack a systematic approach to account for fluctuations in exposure parameters such as defocusing and illumination intensity, making it difficult to establish a process window for reliable wafer structure generation.
Innovation Solution
A method that simulates the photolithographic process by providing an aerial image of a mask, determining auxiliary wafer structures for varying threshold values, and identifying a stability range where the number of structure elements remains constant, allowing for the determination of a wafer structure without prespecifying a threshold value, thereby establishing a process window for dose and focus variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an arbitrary threshold value is chosen to determine wafer structure from aerial image, then the determination process is simple, but the reliability of the wafer structure is low due to sensitivity to parameter fluctuations
Solution Approach 1:
The patent performs preliminary simulation of aerial images at multiple focus positions and illumination intensities before determining the final wafer structure. By pre-calculating aerial images across a range of exposure parameters and identifying a stability range where structure elements remain constant, the method establishes a reliable threshold selection basis in advance, rather than arbitrarily choosing a threshold value.
Solution Approach 2:
The patent systematically varies exposure parameters (focus position and illumination intensity) to simulate different aerial images, then identifies a stability range where the number of structure elements remains constant despite parameter changes. This approach transforms the arbitrary threshold selection into a parameter-driven process that accounts for exposure fluctuations.
2Reliability
If the process window is determined by extensive simulations covering all parameter variations, then the reliability increases, but the determination time becomes excessively long
Solution Approach 1:
The patent segments the parameter space by evaluating aerial images at discrete focus positions and illumination intensities, then identifies a stability range where structure elements remain constant. This segmented approach allows systematic coverage of parameter variations without requiring exhaustive simulation of every possible combination, reducing determination time while maintaining reliability.
Solution Approach 2:
The patent replaces extensive physical experimentation and exhaustive simulations with a computational stability range determination method. By using image processing techniques to automatically identify regions where structure element counts remain constant across parameter variations, the method achieves rapid and reliable process window determination.
3Productivity
If a fixed threshold value is used to convert aerial image to wafer structure, then the process is quick and easy, but the structure is highly sensitive to defocusing and illumination intensity fluctuations
Solution Approach 1:
The patent performs preliminary evaluation of aerial images at multiple focus positions and illumination intensities to identify a stability range before finalizing the wafer structure determination. This pre-analysis ensures that the selected threshold value produces stable structure elements even when exposure parameters fluctuate, without significantly increasing the overall determination time.
Solution Approach 2:
The patent uses feedback from simulated aerial images at varying parameters to adjust and validate the threshold value selection. By checking whether structure element counts remain constant across different focus and intensity conditions, the method provides feedback that confirms the robustness of the chosen threshold, ensuring stable wafer structure determination.
Data Source
AI summary
A method for the simulation of a photolithographic process for generating a wafer structure includes providing an aerial image of a region of a mask that includes the mask structure, prescribing a range of intensities, determining auxiliary or potential wafer structures for different threshold values within the range of intensities, determining the number of structure elements for each of the auxiliary or potential wafer structures, determining a stability range consisting of successive threshold values from the threshold values that were used for the determination of auxiliary or potential wafer structures, within the stability range the number of structure elements of the auxiliary or potential wafer structures remaining constant or lying within a prescribed range, and determining the wafer structure on the basis of the aerial image and a threshold value within the stability range. A microscope for carrying out the method is also provided.