SiC Epitaxial Wafer Defect Mitigation via Two-Step Growth
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Solution Overview
Problem
Silicon carbide epitaxial wafers often suffer from carrot and triangular defects due to lack of crystallographic uniformity, leading to high voltage leakage and reduced non-defective product rates in semiconductor devices, primarily caused by threading screw dislocations and changes in the C/Si ratio during epitaxial growth.
Innovation Solution
The method involves forming a silicon carbide epitaxial wafer with a substrate having an off-angle orientation and using a two-step epitaxial growth process with etching in between to maintain a consistent C/Si ratio, reducing distortion and defects by forming steps within the epitaxial layer, thereby alleviating carrot and triangular defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a silicon carbide epitaxial layer is grown continuously without interruption, then productivity is improved, but carrot and triangular defects increase due to distortion accumulation
Solution Approach 1:
The continuous epitaxial growth process is divided into multiple stages: a first growth stage forming an initial layer, followed by an etching stage that removes part of this layer, and then a second growth stage. This segmentation allows distortion to be reset during etching while maintaining overall productivity through continuous processing.
Solution Approach 2:
The patent implements periodic etching during the epitaxial growth process, where growth is interrupted at regular intervals to perform selective etching of distorted regions. This periodic action prevents defect accumulation while maintaining high overall growth efficiency through automated cycle management.
2Ease of manufacture
If threading screw dislocations are present in the substrate, then ease of manufacture is improved, but carrot and triangular defects are generated during epitaxial growth
Solution Approach 1:
The patent converts the harmful effect of threading screw dislocations into a beneficial process feature. By performing selective etching at specific growth stages, the dislocation sites that would normally generate defects are instead used as markers for targeted distortion removal, transforming the manufacturing challenge into a controlled defect mitigation strategy.
Solution Approach 2:
The etching process acts as an intermediary mechanism between the substrate with dislocations and the final defect-free epitaxial layer. The selective etching removes distorted regions while preserving the underlying dislocation structure, allowing the dislocations to remain in the substrate without propagating defects into the device region.
3Manufacturing precision
If the C/Si ratio is changed during epitaxial growth to reduce defects, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the C/Si ratio during different growth stages to control defect formation. By adjusting the carbon-to-silicon ratio specifically during the etching and regrowth phases, the process targets distortion removal while maintaining overall process manageability through defined parameter ranges.
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 significantly reduces the occurrence of carrot and triangular defects without altering the C/Si ratio, enhancing the uniformity and quality of the epitaxial layer, leading to improved electrical characteristics and increased yield in silicon carbide semiconductor devices.
Implementation Method 1
a film whose impurity concentration is controlled with high accuracy is epitaxially grown on a silicon carbide substrate by a chemical vapor deposition method (CVD method)
Implementation Method 2
epitaxially grown on a silicon carbide substrate by a chemical vapor deposition method (CVD method)
Data Source
AI summary
A silicon carbide epitaxial wafer includes a silicon carbide substrate and silicon carbide epitaxial layers formed on the silicon carbide substrate. Each of the silicon carbide epitaxial layers has a triangular defect. The silicon carbide epitaxial layer each have a step inside the triangular defect in the surface morphology of the triangular defect.