Surface Shape Measuring Apparatus Spatial Frequency Analysis
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Solution Overview
Problem
Existing surface shape measuring apparatuses face challenges in accurately measuring micro roughness across the entire wafer surface due to limitations in spatial frequency resolution and consideration of scattered light distribution, particularly for structures like step-terrace structures on epitaxial growth wafers, where peak intensities are buried in spatial frequency components.
Innovation Solution
A surface shape measuring apparatus that uses multiple detection optical systems with differently oriented optical axes to continuously obtain spatial frequency spectra, scanning the wafer surface with a spot beam through rotation and linear movements, and calculating feature quantities by comparing detection signals to a library, enabling detailed spatial frequency analysis and 3D shape measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple detection optical systems are used to measure spatial frequency regions, then measurement coverage is improved, but spatial frequency resolution deteriorates due to rough step size
Solution Approach 1:
The detection space is divided into multiple discrete detection optical systems, each responsible for a specific spatial frequency region. This segmentation allows comprehensive coverage of different spatial frequency ranges while maintaining specialized detection capabilities for each region.
Solution Approach 2:
The patent transitions from discrete multi-directional detection to continuous spatial frequency spectrum analysis. By calculating the spatial frequency spectrum continuously from detection signals, the system achieves high resolution in the spatial frequency domain, effectively adding a dimensional transformation that resolves the resolution limitation.
2Device complexity
If scattered light detection is limited to specific directions, then detection system complexity is reduced, but information loss occurs from scattered light not entering detection space
Solution Approach 1:
The detection optical systems are configured to detect scattered light from multiple directions (front, back, sides), making the detection system universal in capturing various scattering patterns. This multi-directional capability ensures comprehensive information collection without excessive complexity.
Solution Approach 2:
The system uses the detection signals from multiple directions to calculate the spatial frequency spectrum, creating a feedback mechanism that reconstructs complete surface shape information. The calculation process integrates information from all detection directions, compensating for any individual direction's limitations and preventing information loss.
3Device complexity
If detection optical systems use fixed optical axes, then device complexity is reduced, but measurement accuracy deteriorates for step-terrace structures with sharp peaks
Solution Approach 1:
The detection optical systems are pre-configured with specific optical axis orientations that correspond to expected scattering directions of step-terrace structures. This preliminary arrangement ensures that when such structures are detected, their characteristic sharp peaks in specific directions can be captured effectively without requiring real-time adjustment.
Solution Approach 2:
The patent transforms the detection approach from fixed directional measurement to continuous spatial frequency spectrum calculation. By processing detection signals through spatial frequency analysis, the system can resolve sharp peaks and fine structures that would be missed by fixed optical axes, achieving high measurement precision through dimensional transformation in the frequency domain.
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 allows for a more accurate and detailed measurement of micro roughness across the entire wafer surface, improving measurement accuracy and resolving issues related to spatial frequency resolution and scattered light distribution, enabling precise control of semiconductor manufacturing processes.
Implementation Method 1
a surface shape measuring apparatus using light scattering
Data Source
AI summary
In related art, consideration is not given to that a spatial distribution of scattered light changes in various direction such as forward/backward/sideways according to a difference in micro roughness. Particularly, although a step-terrace structure appearing on an epitaxial growth wafer produces anisotropy in the scattered light distribution, consideration is not given to this point in the related art. The invention includes a process in which light is illuminated to a sample surface, plural detection optical systems mutually different in directions of optical axes detect a spatial distribution of scattered light, and a spatial frequency spectrum of the sample surface is calculated.