Mask Position Determination via Iterative Aerial Image Simulation
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Solution Overview
Problem
Current methods for position determination in microlithography fail to achieve accurate results due to unconsidered mask and optical parameters, leading to inaccuracies in structure positioning and line width measurement.
Innovation Solution
A method involving multiple simulations with varying input parameters to approximate actual conditions, allowing for the simultaneous determination of mask and optical parameters, using rigorous electromagnetic simulations and iterative comparisons to optimize image correspondence between measured and simulated aerial images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single fixed simulation result is used for comparison with measured aerial image, then the measurement process is simple and fast, but the position determination accuracy is insufficient due to unconsidered mask and optical parameters
Solution Approach 1:
The patent applies dynamics by transforming the static simulation approach into a dynamic iterative process. Instead of using a single fixed simulation result, the system performs multiple simulations with varying input parameters (mask parameters, optical parameters, positioning error) and iteratively adapts these parameters to match the measured aerial image, thereby achieving higher accuracy while managing complexity through systematic iteration
Solution Approach 2:
The patent implements parameter changes by systematically varying multiple input parameters including mask parameters (three-dimensional extent, layer thicknesses, etching angles, sidewall angles, undercuts, material refractive indexes), optical parameters (illumination settings, numerical aperture, imaging scale, wavelength, partial coherence, aberrations, pupil apodization, field uniformity), and positioning error to optimize the simulation results and achieve accurate position determination
2Measurement precision
If multiple simulations with varying parameters are performed to approximate actual conditions, then the position determination accuracy is improved, but the measurement time and computational effort increase
Solution Approach 1:
The patent applies feedback by using the measured aerial image as a reference to evaluate and adjust the simulation parameters iteratively. The system compares simulated aerial images with the measured one, determines deviations, and uses this feedback to adapt the input parameters (mask parameters, optical parameters, positioning error) in subsequent simulations, converging toward accurate results while managing computational time through targeted iterations
Data Source
AI summary
A method and an apparatus for determining the position of a structure on a mask for microlithography, in which the position is determined by comparing an aerial image, measured by a recording device, of a portion of the mask with an aerial image determined by simulation. The position determination includes carrying out a plurality of such comparisons which differ from one another with regard to the input parameters of the simulation.