SiC Graded Channel Structure for Threshold Stability and Punch-Through
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Solution Overview
Problem
As SiC power devices scale down, issues such as threshold voltage instability and punch-through effects arise due to geometrical profiles and high interface state density, affecting channel mobility and on-resistance.
Innovation Solution
A graded channel with a lightly doped region and a heavily doped pocket is implemented in a SiC power semiconductor device, utilizing a self-aligned implantation method without a tilt angle to form the pocket, which improves threshold voltage control and prevents punch-through effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device size is scaled down, then power device performance is improved, but threshold voltage instability and punch-through effects occur
Solution Approach 1:
The patent implements a graded channel doping profile where the dopant concentration varies spatially along the channel depth. Specifically, a lightly doped first region is positioned near the surface while a heavily doped second region is positioned deeper in the channel. This local variation in doping concentration allows different regions to serve different functions: the lightly doped region maintains high carrier mobility and low on-resistance, while the heavily doped region prevents punch-through effects and stabilizes threshold voltage, thus resolving the contradiction between device scaling and reliability.
2Length of moving object
If channel length is reduced, then device size is reduced, but short channel effects become significant
Solution Approach 1:
The patent changes the doping concentration parameter along the channel depth to create a graded channel structure. By transitioning from a uniform doping profile to a graded profile with increasing dopant concentration from the surface toward the bulk, the patent能够有效 control carrier distribution and electric field characteristics. This parameter change allows the channel to maintain proper electrostatic control and prevent short channel effects even when the channel length is reduced for device scaling.
3Ease of manufacture
If uniform doping is used, then manufacturing is simplified, but carrier mobility and on-resistance are degraded
Solution Approach 1:
The patent applies local quality by implementing a graded channel doping profile where dopant concentration varies spatially rather than being uniform. The lightly doped first region near the surface optimizes carrier mobility and reduces on-resistance by minimizing scattering effects, while the heavily doped second region deeper in the channel provides necessary electrostatic control. This localized differentiation in doping concentration resolves the contradiction between manufacturing simplicity and device performance.
Data Source
AI summary
A power device includes a silicon carbide substrate. A gate is provided on a first side of the silicon carbide substrate. A graded channel includes a first region having a first dopant concentration and a second region having a second dopant concentration, the second dopant concentration being greater than the first dopant concentration.