Optical Production Simulation With Path-Dependent Illumination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for simulating illumination and imaging properties of optical production systems are inadequate in accurately accounting for object displacement path-dependent aberrations and field height dependencies, leading to inaccuracies in the simulation of optical production systems, particularly in EUV lithography.
Innovation Solution
A simulation method that adapts to actual production conditions by varying the illumination setting with respect to object displacement, utilizing multiple pupil stops and measurement illumination settings with increased pupil filling degrees, and incorporating corrections for optical system influences to improve accuracy and reduce artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the simulation uses a fixed illumination setting, then the measurement process is simple and fast, but the simulation accuracy deteriorates due to ignoring object displacement path-dependent aberrations and field height dependencies
Solution Approach 1:
The illumination setting is made dynamic by adapting it to the actual object displacement path and field height variations during measurement. The system determines the object displacement path, identifies field heights where illumination settings vary, and adjusts the illumination setting accordingly for each field height region, rather than using a fixed illumination setting throughout the measurement process.
Solution Approach 2:
The illumination setting parameters are changed based on the measured object displacement path and field height. The system varies illumination parameters such as numerical aperture and illumination angle according to the specific field height and displacement position, allowing the simulation to accurately reflect the actual optical conditions at different measurement locations.
2Use of energy by moving object
If multiple measurement illumination settings with increased pupil filling degrees are used, then measurement light throughput is improved, but the complexity of the measurement process increases
Solution Approach 1:
The system uses measurement illumination settings with increased pupil filling degrees (excessive illumination) to maximize light throughput during the measurement phase. After measurement, the actual production illumination settings (more accurate but lower throughput) are used for simulation. This allows the system to benefit from both high light throughput during measurement and accurate production conditions during simulation.
Solution Approach 2:
The measurement process is segmented into multiple measurement locations along the object displacement path, with each location using appropriately optimized illumination settings. This allows the system to collect sufficient light at each specific measurement point while maintaining overall measurement efficiency through the segmented approach.
3Measurement precision
If the simulation accounts for variations in illumination setting with object displacement, then simulation accuracy is improved, but the measurement and processing time increases
Solution Approach 1:
The system performs preliminary determination of the object displacement path and identifies in advance which field heights have varying illumination settings. This preliminary analysis allows the system to pre-plan the measurement approach, reducing the time required during actual measurement and processing by avoiding unnecessary measurements at locations where illumination settings do not vary.
Solution Approach 2:
The system applies varying illumination settings only at specific field heights and displacement positions where actual variations occur, rather than uniformly across the entire measurement field. This localized approach maintains high simulation accuracy where needed while minimizing the overall measurement and processing time by using standard settings in regions where variations are negligible.
Data Source
AI summary
To simulate illumination and imaging properties of an optical production system when illuminating and imaging an object by use of an optical measurement system of a metrology system, a pupil stop of the optical measurement system is initially provided for the purpose of specifying at least one measurement illumination setting created by use of the pupil stop. Measurement aerial images Imeas are recorded in an image plane of an imaging optics unit of the optical measurement system for different displacement positions of the object perpendicular to an object plane (xy) for the at least one measurement illumination setting. A complex mask transfer function M is reconstructed from the recorded measurement aerial images Imeas. A 3-D aerial image Isim of the optical production system is determined from the reconstructed mask transfer function M and a specified illumination setting σtarget of the optical production system as the result of the simulation method. The reconstruction includes the fact that the optical production system to be simulated comprises a production illumination setting BPy1, BPy2) to be simulated, with the latter varying in the object displacement direction (y). This yields an improved simulation method.