SiC Buffer Layer BPD Detection Using UV Photoluminescence Imaging
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Solution Overview
Problem
Existing inspecting methods struggle to detect basal plane dislocations (BPD) in the buffer layer of silicon carbide substrates without causing adverse effects, which are a major cause of forward current degradation in power devices, affecting long-term reliability.
Innovation Solution
An inspecting method using a combination of reflected light and photoluminescence images with specific wavelength and irradiance conditions, along with a tailored light receiving filter, to detect BPD in the buffer layer, employing a confocal or differential interference optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If existing inspecting methods are used to detect BPD in the buffer layer, then detection capability is improved, but forward current degradation and reduced long-term reliability occur due to adverse effects on the buffer layer
Solution Approach 1:
The patent applies parameter changes by precisely controlling the wavelength (≤386 nm) and cumulative irradiance (≥1.6 W·cm−2·sec) of the excitation light, and by using a light receiving filter with specific wavelength range (≥excitation wavelength and ≤399 nm). These parameter optimizations enable effective BPD detection while preventing adverse effects on the buffer layer, thus resolving the contradiction between detection capability and device reliability
Solution Approach 2:
The patent replaces conventional detection methods with a specialized optical inspection system that uses photoluminescence imaging. This substitution enables non-contact, non-invasive detection of BPD in the buffer layer without causing mechanical or thermal damage, thereby maintaining long-term reliability while improving detection capability
2Measurement precision
If high-irradiance ultraviolet ray is used to extend SSF to BPD for detection, then detection sensitivity is improved, but the buffer layer suffers damage causing forward current degradation
Solution Approach 1:
The patent optimizes the irradiance parameter to be ≥1.6 W·cm−2·sec (avoiding excessive irradiance that causes damage) and sets the wavelength ≤386 nm. This precise parameter control enables sufficient detection sensitivity while preventing buffer layer damage and forward current degradation
Solution Approach 2:
The patent uses a light receiving filter as an intermediary component with specific wavelength transmission characteristics (≥excitation wavelength and ≤399 nm). This filter mediates between the excitation light source and the detector, enabling sensitive BPD detection while blocking harmful wavelengths that could damage the buffer layer
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
Effectively detects BPD in the buffer layer, reducing its density and thereby improving the long-term reliability of silicon carbide-based power devices by minimizing forward current degradation.
Implementation Method 1
a second image based on a photoluminescence light caused by irradiation with an excitation light on the buffer layer
Implementation Method 2
The photoluminescence light is received through a light receiving filter. A wavelength of the received light is equal to or more than the wavelength of the excitation light and equal to or less than 399 nm
Data Source
AI summary
An inspection method of detecting “BPD” in a buffer layer is established. An inspecting method is an inspecting method of detecting a crystal defect in a buffer layer by using a first image based on a reflected light caused by irradiation with a light on the buffer layer and a second image based on a photoluminescence light caused by irradiation with an excitation light on the buffer layer. The buffer layer is made of silicon carbide into which a conductive impurity is introduced. A wavelength of the excitation light is equal to or less than 386 nm. A cumulative irradiance of the excitation light is equal to or more than 1.6 W·cm−2·sec. The photoluminescence light is received through a light receiving filter. The light receiving filter is a filter transmitting light having a wavelength being equal to or more than the wavelength of the excitation light and equal to or less than 399 nm.