SiC MOSFET Multi-Depth Source Contacts for Lower On-Resistance
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Solution Overview
Problem
Silicon carbide MOSFETs face challenges in reducing on-resistance due to high parasitic resistance, particularly in the source region and contact resistance between the source electrode and source region, which hinders performance improvement.
Innovation Solution
The semiconductor device incorporates a silicon carbide layer with specific conductivity type regions and gate electrodes, featuring multiple contact faces and regions with varying impurity concentrations, and a source electrode with multiple contact portions to increase contact area and reduce effective electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact area between source electrode and source region is increased, then parasitic resistance is reduced, but device complexity increases
Solution Approach 1:
The source electrode is divided into multiple segments (first source electrode segment, second source electrode segment, third source electrode segment) that contact different regions (first contact region, second contact region, third contact region) of the source region. This segmentation increases the total contact area and reduces parasitic resistance while maintaining manageable device complexity through modular structure.
Solution Approach 2:
The patent introduces a third dimension by forming source region regions at different depth levels (first contact region at shallowest level, second contact region at intermediate level, third contact region at deepest level). This vertical stacking in the third dimension increases contact area without expanding the planar footprint, effectively reducing parasitic resistance without proportionally increasing device complexity.
2Reliability
If the distance between source electrode and source region is reduced, then on-resistance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The source region regions (first contact region, second contact region, third contact region) are pre-formed at different depth levels within the drift region before the source electrode is deposited. This preliminary formation of contact regions at optimized positions allows the source electrode to make immediate contact at multiple depths, reducing the effective distance and on-resistance without requiring post-formation precision adjustments.
Solution Approach 2:
Different regions of the source electrode are designed with different contact characteristics: the first source electrode segment contacts the first contact region with specific impurity concentration, the second segment contacts the second contact region with different impurity concentration, and the third segment contacts the third contact region. This local differentiation optimizes contact resistance at each interface while managing overall manufacturing precision requirements.
Data Source
AI summary
A semiconductor device according to an embodiment includes: a silicon carbide layer having a first face and a second face; first and second gate electrodes; a first silicon carbide region; a second silicon carbide region between the first silicon carbide region and the first face; a third silicon carbide region between the second silicon carbide region and the first face; a fourth silicon carbide region between the third silicon carbide region and the first face; a first electrode; and a second electrode. The first electrode includes a first portion, and the first portion includes a first contact face in contact with the fourth silicon carbide region, a second contact face in contact with the fourth silicon carbide region, a third contact face in contact with the fourth silicon carbide region and the third silicon carbide region, and a fourth contact face in contact with the third silicon carbide region.