Optical Metrology Parameter Constraint for Small Measurement Box
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Solution Overview
Problem
Achieving a small measurement box size in optical metrology systems is challenging, especially at large oblique angles of incidence and longer wavelengths, due to diffraction and geometric scaling effects, which limits the resolution and yield in semiconductor manufacturing.
Innovation Solution
Selectively constraining subsets of measurement system parameters such as illumination wavelength, polarization state, polar angle of incidence, and azimuth angle of incidence to control the measurement box size, allowing for a smaller measurement box than would be achievable with the full range of parameters, and using a multi-dimensional space of available metrology parameters to achieve this constraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the full range of measurement system parameters (multiple angles of incidence, several wavelength bands) is used, then measurement resolution and data completeness are improved, but measurement box size enlarges due to diffraction and geometric scaling effects
Solution Approach 1:
The patent applies parameter changes by selectively constraining subsets of measurement system parameters (illumination wavelength, polarization state, polar angle of incidence, azimuth angle of incidence) rather than using the full range. This selective parameter constraint resolves the contradiction by maintaining sufficient measurement precision while reducing the measurement box size caused by diffraction and geometric scaling effects at extreme parameter values
Solution Approach 2:
The patent implements local quality by applying different parameter constraints to different measurement conditions. Instead of uniformly using all parameters or none, the system selectively applies constraints based on the specific measurement requirements, allowing optimal measurement precision in critical areas while minimizing measurement box size where possible
2Area of stationary object
If a small measurement box size is achieved by constraining measurement parameters, then wafer area is preserved and device yield is maintained, but the range of available measurement data is reduced
Solution Approach 1:
The patent resolves this contradiction by making selective parameter changes - constraining only those parameters that cause measurement box enlargement (such as extreme angles of incidence and certain wavelength bands) while maintaining other parameters that provide measurement information. This approach preserves wafer area while minimizing information loss by retaining useful measurement data within the constrained parameter space
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the achievement of a measurement box size of less than 30 μm or 10 μm in any direction, preserving valuable wafer area and maintaining device yield by controlling diffraction, aberration, and geometric effects, thus overcoming limitations in existing metrology systems.
Implementation Method 1
diffraction, aberration, and other limiting effects must be controlled
Data Source
AI summary
Methods and systems for achieving a small measurement box size specification across a set of metrology system parameters are presented. The small measurement box size specification is achieved by selectively constraining one or more of the sets of system parameters during measurement. A subset of measurement system parameters such as illumination wavelength, polarization state, polar angle of incidence, and azimuth angle of incidence is selected for measurement to maintain a smaller measurement box size than would otherwise be achievable if the full, available range of measurement system parameters were utilized in the measurement. In this manner, control of one or more factors that affect measurement box size is realized by constraining the measurement system parameter space. In addition, a subset of measurement signals may be selected to maintain a smaller measurement box size than would otherwise be achievable if all available measurement signals were utilized in the measurement.