SiC Buffer Region Doping Profile for Stacking Fault Suppression
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices experience increased on-voltage and reduced reliability due to lattice defects and impurity concentration variations in the buffer regions, leading to poor controllability of epitaxial growth and increased stress in the semiconductor substrate.
Innovation Solution
A silicon carbide semiconductor device with a specific impurity concentration gradient in the second buffer region, where the impurity concentration continuously increases and then decreases, reducing the stress and occurrence of lattice defects by forming a mountain-like shape in the depth direction, thereby suppressing the growth of stacking faults and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-layer buffer region structure with different impurity concentrations is provided, then stacking fault growth is suppressed, but device complexity increases
Solution Approach 1:
The buffer region is divided into two distinct layers: a first buffer region with lower impurity concentration near the starting substrate, and a second buffer region with higher impurity concentration near the drift region. This segmentation allows each layer to perform its specific function - the first layer transforms basal plane dislocations into threading edge dislocations, while the second layer suppresses stacking fault growth through hole recombination, thereby resolving the contradiction between reliability improvement and structural complexity.
Solution Approach 2:
Different impurity concentrations are assigned to different spatial locations within the buffer region. The first buffer region has lower impurity concentration to maximize dislocation transformation, while the second buffer region has higher impurity concentration to maximize hole recombination and stacking fault suppression. This local differentiation of material properties enables simultaneous achievement of multiple reliability goals without requiring a completely complex structure.
2Reliability
If the impurity concentration of the second buffer region is increased to suppress stacking faults, then reliability improves, but measurement precision of buffer region thickness becomes difficult
Solution Approach 1:
The first buffer region with lower impurity concentration acts as an intermediary layer between the starting substrate and the second buffer region. This intermediary structure provides a measurable interface that enables infrared reflection measurement of the second buffer region's thickness. The lower impurity concentration in the first region creates a distinct optical interface that serves as a reference point for measurement, thereby resolving the contradiction between high impurity concentration needs for reliability and measurement precision requirements.
3Manufacturing precision
If a three-region structure with continuous impurity concentration variation is provided, then manufacturing precision of impurity distribution improves, but device complexity increases
Solution Approach 1:
The impurity concentration is varied continuously across three regions: the first buffer region has lower concentration, the second buffer region has higher concentration, and the drift region has intermediate concentration. This parameter change strategy enables precise control over dislocation transformation and stacking fault suppression while maintaining a relatively simple three-region overall structure. The continuous variation in impurity concentration allows optimization of each region's function without requiring complex multi-layer or heterostructure designs.
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 impurity concentration gradient in the second buffer region effectively reduces stress and lattice defects, improving the controllability of epitaxial growth and maintaining low on-voltage fluctuations, thus enhancing the reliability of the silicon carbide semiconductor device.
Implementation Method 1
the impurity concentration continuously increases by a first impurity concentration gradient from a first depth position that is relatively close to a first interface between the third semiconductor region and the first semiconductor region to a second depth position that is relatively close to a second interface between the second semiconductor region and the third semiconductor region
Implementation Method 2
an epitaxial layer is epitaxially grown on a starting substrate containing silicon carbide
Data Source
AI summary
First and second buffer regions and an n−-type drift region are sequentially formed by epitaxial growth on an n+-type starting substrate. An impurity concentration of the first buffer region is higher than that of the n−-type drift region and lower than that of the n+-type starting substrate. An impurity concentration of the second buffer region is higher than that of the first buffer region and continuously increases by a first impurity concentration gradient from a first gradient changing point toward the n−-type drift region to a second gradient changing point toward the first buffer region; continuously decreases by a second impurity concentration gradient from the first gradient changing point to a first interface; and continuously decreases by a third impurity concentration gradient from the second gradient changing point to a second interface. The second impurity concentration gradient is lower than the third impurity concentration gradient.