Silicon Substrate Screening by Infrared Depolarization for Epitaxy
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Solution Overview
Problem
Conventional methods for determining slip resistance of silicon substrates during epitaxy and post-epitaxy thermal treatments are destructive and unable to evaluate different substrates under various epitaxial and thermal processes effectively.
Innovation Solution
A non-destructive method using infrared depolarization to image epitaxial wafers and determine infrared depolarization parameters, allowing for the quantitative evaluation and comparison of substrate suitability for epitaxy, including imaging the entire wafer or specifically the annular edge region to assess slip resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional destructive testing methods are used to determine slip resistance, then measurement capability is achieved, but the wafer is destroyed and cannot be used further
Solution Approach 1:
The patent replaces mechanical destructive testing with optical measurement using infrared depolarization imaging. The infrared imaging system detects stress-induced birefringence in the wafer without physical contact or damage, allowing slip resistance evaluation while preserving the wafer for further processing.
Solution Approach 2:
The patent introduces infrared light as an intermediary to indirectly measure slip resistance. Instead of applying mechanical stress that destroys the wafer, the method uses infrared depolarization to detect internal stress states, providing measurement information without direct mechanical intervention that would compromise wafer integrity.
2Measurement precision
If conventional methods are used to evaluate substrates, then some measurement is obtained, but different substrates under different epitaxial and thermal treatments cannot be compared
Solution Approach 1:
The patent creates a universal evaluation platform that can assess different substrate compositions and process conditions using the same infrared depolarization methodology. The system handles various epitaxial treatments and thermal processes through a single consistent measurement approach, enabling cross-comparison of substrate performance across diverse manufacturing conditions.
Solution Approach 2:
The patent leverages the ability to vary and control multiple parameters including substrate composition, epitaxial growth conditions, and thermal treatment parameters while maintaining consistent infrared measurement methodology. This allows systematic evaluation of how different parameters affect slip resistance and enables comparison across diverse processing scenarios.
3Measurement precision
If full wafer imaging is performed by infrared depolarization, then complete slip resistance data is obtained, but processing time increases
Solution Approach 1:
The patent segments the wafer imaging process into distinct regions of interest, particularly focusing on the annular edge region where slip defects are most likely to occur. This selective imaging approach captures the critical information needed for slip resistance evaluation while reducing the total imaging area and processing time compared to full-wafer scanning.
Solution Approach 2:
The patent applies partial imaging by concentrating measurement efforts on the annular edge region rather than the entire wafer surface. This partial action provides sufficient data for slip resistance determination since edge regions are most susceptible to slip defects, achieving adequate measurement precision with reduced time investment.
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
Enables the quantitative characterization and comparison of slip resistance across different substrates and thermal treatments, preserving wafers for further use and providing higher sensitivity than conventional methods, with the ability to differentiate substrate suitability based on composition and thermal performance.
Implementation Method 1
The silicon-containing gas decomposes to form an epitaxial silicon layer on the silicon substrate
Implementation Method 2
The epitaxial wafer is imaged by infrared depolarization to determine an infrared depolarization parameter
Data Source
AI summary
Methods for determining suitability of a silicon substrate for epitaxy and/or for determining slip resistance during epitaxy and post-epitaxy thermal treatment are disclosed. The methods involve evaluating different substrates of the epitaxial wafers by imaging the wafer by infrared depolarization. An infrared depolarization parameter is generated for each epitaxial wafer. The parameters may be compared to determine which substrates are well-suited for epitaxial and/or post-epi heat treatments.