SiC Trench-Gate MOSFET Sidewall Compensation
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Solution Overview
Problem
Trench-gate SiC-MOSFETs formed on off-angle substrates exhibit variations in drain current and threshold voltage due to differences in sidewall crystal surfaces, leading to unstable dynamic characteristics and current concentration issues.
Innovation Solution
A silicon carbide semiconductor device with a drift region, well region, source region, trench, gate electrode, source electrode, drain electrode, and a high-concentration well region is designed, where the distance from the sidewall surface to the high-concentration well region is adjusted to minimize variations, ensuring consistent ON states across sidewall surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a trench-gate SiC-MOSFET is formed on a substrate having an off-angle, then the device can be manufactured with standard processes, but variations in drain current and threshold voltage occur due to different crystal surfaces of sidewall surfaces
Solution Approach 1:
The patent applies local quality by forming a high-concentration well region at specific positions adjacent to selected sidewall surfaces of the trench. This creates non-uniform impurity distribution that compensates for the inherent non-uniformity of different crystal surfaces, with each sidewall surface receiving appropriate local compensation to achieve uniform overall characteristics
Solution Approach 2:
The patent changes the impurity concentration parameter by introducing a high-concentration well region with impurity concentration higher than the surrounding well region. This parameter change compensates for the variations caused by different off-angle crystal surfaces, allowing uniform electrical characteristics across all sidewall surfaces
2Device complexity
If the trench is formed with standard geometry, then the manufacturing process is simple, but current concentration occurs in particular sidewall surfaces leading to unstable characteristics
Solution Approach 1:
The patent introduces local quality variations by forming high-concentration well regions at specific positions adjacent to selected sidewall surfaces. This local modification compensates for the non-uniform electrical characteristics caused by different crystal orientations, achieving uniform ON states across all sidewall surfaces without changing the overall trench geometry
Solution Approach 2:
The patent uses a mask pattern that defines multiple high-concentration well regions corresponding to different sidewall surfaces. By copying the compensation structure to each relevant sidewall position, uniform characteristics are achieved across all surfaces while maintaining manufacturing simplicity
Data Source
AI summary
A silicon carbide semiconductor device that reduces an influence of an off-angle of a silicon carbide substrate on characteristics of the semiconductor device and achieves improved operational stability and reduced resistance. In a trench-gate silicon carbide MOSFET semiconductor device, a high-concentration well region is formed in a well region, and a distance from a first sidewall surface of a trench of the silicon carbide semiconductor to the high-concentration well region is smaller than a distance from a second sidewall surface of the trench to the high-concentration well region, the second sidewall surface facing the first sidewall surface of the trench through the gate electrode.