Rare-Earth SiC Composite Substrate for Dislocation and Warpage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
SiC single crystals used in semiconductor devices suffer from high dislocation densities, leading to warping and reduced device reliability, with existing methods focusing on reducing threading screw dislocations while neglecting basal plane dislocations, which affects device performance and longevity.
Innovation Solution
A biaxially oriented SiC composite substrate is developed, featuring a first SiC layer with threading screw and basal plane dislocations, and a second SiC layer with a rare earth element concentration of 1×10^16 to 1×10^19 atoms/cm^3, which reduces surface defect density and warpage by suppressing defect propagation and alleviating lattice mismatch and thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SiC single crystal substrate is used, then the device can be manufactured with wide bandgap material properties, but the high dislocation density (10³ to 10⁴ cm⁻²) degrades device reliability and performance
Solution Approach 1:
The substrate is divided into two distinct layers: a first biaxially oriented SiC layer that serves as a buffer containing the dislocations, and a second biaxially oriented SiC layer that provides the high-quality surface for device fabrication. This segmentation isolates defects in the first layer while maintaining a low-defect second layer for device manufacturing.
Solution Approach 2:
Different regions of the composite substrate have different quality characteristics. The first layer is designed to tolerate high dislocation density and contains mechanisms to suppress defect propagation, while the second layer is engineered to have low surface defect density (≤10² cm⁻²) suitable for high-performance devices. Each layer serves its specific function with appropriate quality standards.
2Manufacturing precision
If threading screw dislocations are reduced by converting them into stacking faults via macro-steps, then threading screw dislocation density decreases, but extensive warping occurs and basal plane dislocations are not addressed
Solution Approach 1:
The invention extracts and isolates the defect-containing first SiC layer from the high-quality second SiC layer. By separating the functions of defect tolerance (first layer) and defect sensitivity (second layer), the harmful warping effects are confined to the first layer while the second layer maintains planarity suitable for device fabrication.
Solution Approach 2:
The composite substrate combines two biaxially oriented SiC layers with different defect characteristics. The first layer uses rare earth elements to suppress defect propagation, while the second layer provides a low-defect surface. This composite structure achieves both warping suppression and low surface defect density without requiring extreme measures in either layer.
3Reliability
If rare earth elements are added to SiC single crystals to suppress dislocation emergence, then thermal stress dislocations are inhibited, but the element concentration must be precisely controlled to avoid adverse effects on semiconductor properties
Solution Approach 1:
The invention optimizes the rare earth element concentration parameter within a specific range (1×10¹⁶ to 1×10¹⁹ atoms/cm³) in the second biaxially oriented SiC layer. This parameter control achieves effective dislocation suppression while maintaining compatibility with semiconductor device requirements. The concentration is high enough to suppress defect propagation but low enough to avoid adverse effects on semiconductor properties.
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
The biaxially oriented SiC composite substrate achieves a low surface defect density, reducing warpage and enhancing semiconductor device performance by minimizing threading screw and basal plane dislocations, thus improving long-term reliability and energy efficiency.
Implementation Method 1
a second biaxially oriented SiC layer that is formed continuously from one surface of the first biaxially oriented SIC layer and that contains 1×10^16 atoms/cm^3 or more and 1×10^19 atoms/cm^3 or less of a rare earth element, wherein: a defect density of a surface of the second biaxially oriented SiC layer is smaller than a defect density of the first biaxially oriented SiC layer
Implementation Method 2
which reduces surface defect density and warpage by suppressing defect propagation and alleviating lattice mismatch and thermal stress
Implementation Method 3
which reduces surface defect density and warpage by suppressing defect propagation and alleviating lattice mismatch and thermal stress
Data Source
AI summary
A biaxially oriented SiC composite substrate includes a first biaxially oriented SiC layer that contains a threading screw dislocation and a basal plane dislocation, and a second biaxially oriented SiC layer that is formed continuously from the first biaxially oriented SiC layer and that contains 1×1016 atoms/cm3 or more and 1×1019 atoms/cm3 or less of a rare earth element. The defect density of a surface of the second biaxially oriented SiC layer is smaller than the defect density of the first biaxially oriented SiC layer.