SiC Substrate Defect Mapping via High-Power Photoluminescence
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Solution Overview
Problem
Existing methods, such as photoluminescence, are inadequate for identifying defects in SiC substrates before epitaxial film formation, as they cannot detect defects at deep positions beneath the surface, leading to unidentified causative defects in SiC devices.
Innovation Solution
A non-destructive SiC substrate evaluation method using photoluminescence to irradiate and measure the first surface of an SiC substrate before epitaxial film lamination, allowing for defect identification through increased excitation power density and spot irradiation, which helps in pinpointing defect locations on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photoluminescence measurement is performed on SiC substrate before epitaxial film formation, then defect locations can be identified, but excitation light cannot reach deep positions from the surface
Solution Approach 1:
The patent changes the parameter of excitation light power density from conventional levels to high power density (10^3 to 10^5 W/cm²). This parameter change enables the excitation light to penetrate deeper into the SiC substrate while maintaining sufficient signal intensity for photoluminescence detection, thereby resolving the contradiction between measurement precision and measurement depth.
2Measurement precision
If SIMS is used to measure impurity concentration in SiC substrate, then impurity aggregation can be identified, but the measurement is destructive and specific destroyed portions are measured
Solution Approach 1:
The patent replaces the destructive mechanical sputtering process of SIMS with non-destructive optical photoluminescence measurement. By using high power density excitation light, the method achieves impurity detection through optical means without physical destruction of the sample, thus substituting a mechanical destruction-based system with an optical non-destructive system.
Solution Approach 2:
The photoluminescence measurement method serves multiple functions: it identifies defect locations, detects impurity aggregation, and evaluates overall substrate quality, all in a single non-destructive measurement process. This multi-functionality replaces the need for separate SIMS measurements on destroyed sample portions.
3Measurement precision
If conventional photoluminescence method is used on SiC epitaxial wafer, then surface defects can be detected, but causative defects in the substrate cannot be confirmed
Solution Approach 1:
The patent performs photoluminescence measurement on the SiC substrate before epitaxial film formation (preliminary action). This timing allows direct detection of substrate defects and impurity aggregation locations without the obscuring effect of the epitaxial film, preserving complete substrate defect information that can later be correlated with device performance.
Solution Approach 2:
By changing the excitation light power density to high levels, the measurement can penetrate through the substrate and detect defects at greater depths, providing comprehensive substrate defect information that conventional surface-level photoluminescence measurements cannot obtain.
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 method enables the identification of defect-causing impurities and regions on the SiC substrate, reducing the likelihood of defects in the subsequent SiC epitaxial wafer and improving device reliability by mapping defect locations on the substrate.
Implementation Method 1
A photoluminescence method is a method of irradiating a material with excitation light and measuring light which is emitted when excited electrons return to a ground state.
Data Source
AI summary
Provided is an SiC substrate evaluation that includes irradiating a first surface of an SiC substrate which is cut out from an SiC ingot with excitation light before an epitaxial film is laminated on the first surface to perform photoluminescence measurement.