SiC Semiconductor Device Defect Blocking Epitaxial Layers
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Solution Overview
Problem
The existing semiconductor devices formed in silicon carbide substrates suffer from defect transfer from the buried layer to the base layer during epitaxial growth, leading to leak current generation when voltage is applied between the drain and source.
Innovation Solution
Incorporating a first epitaxial layer with a higher impurity concentration between the buried layer and the base layer to block defect propagation, and a second epitaxial layer with a lower impurity concentration between the first epitaxial layer and the base layer to relax electric field strength, thereby preventing leak current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a buried layer is formed by ion-implantation and a base layer is formed by epitaxial growth on the buried layer, then the manufacturing process is simplified, but defects in the buried layer are transferred to the base layer causing leak current
Solution Approach 1:
An intermediate layer is introduced between the buried layer and the base layer. This intermediate layer acts as a buffer that prevents defect transfer from the buried layer to the base layer, while still allowing the epitaxial growth process to proceed. The intermediate layer absorbs or blocks the defects (such as threading dislocations) generated during ion-implantation of the buried layer, thereby protecting the base layer from defect contamination and preventing leak current.
2Reliability
If a trench is formed to reduce electric field strength at the trench end, then voltage resistance is improved, but the device structure becomes more complex
Solution Approach 1:
The solution extends the buried layer in the depth dimension beyond the trench depth. By making the buried layer deeper than the trench, the electric field lines are redistributed in the vertical dimension, allowing the electric field strength at the trench end to be reduced without requiring additional lateral structures. This dimensional extension achieves voltage resistance improvement while maintaining relatively simple planar device geometry.
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 solution effectively reduces defect transfer and improves voltage resistance by preventing leak current and enhancing the semiconductor device's performance.
Implementation Method 1
When epitaxial growth is used to form a base layer on the front surface of the buried layer as described above, the defects of the buried layer may be transferred to the base layer
Implementation Method 2
a first epitaxial layer with a higher impurity concentration between the buried layer and the base layer to block defect propagation
Implementation Method 3
a second epitaxial layer with a lower impurity concentration between the first epitaxial layer and the base layer to relax electric field strength
Data Source
AI summary
A semiconductor device formed on a silicon carbide substrate that has a front surface on which an electrode is provided and a back surface on which an electrode is provided includes a drain layer, a drift layer, a base layer, a gate electrode that is located in a trench that extends from the front surface into the drift layer and is insulated by an insulating film, a source layer, a buried layer that is provided between the drift layer and the base layer and is formed such that the depth from the front surface to an end thereof on the side of the drift layer is greater than the depth from the front surface to a distal end of the trench, and a first epitaxial layer that is provided between the buried layer and the base layer and has a higher impurity concentration than the buried layer.