SiC Trench Gate Electrode Structure for Lower On-State Resistance
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Solution Overview
Problem
There is a need to further improve the on-state resistance of silicon carbide semiconductor devices while maintaining their high voltage blocking capability, as existing devices face limitations in reducing on-state resistance without compromising their size or performance.
Innovation Solution
The implementation of a semiconductor device with a gate electrode that extends into a silicon carbide body, featuring a metal structure and a semiconductor layer between the metal structure and the gate dielectric, which reduces line resistance and distributes on-state current uniformly, thereby improving switching behavior and maintaining low channel resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the device size is reduced to improve integration, then the on-state resistance increases
Solution Approach 1:
The gate electrode uses a composite structure combining metal (tungsten or molybdenum) and polysilicon layers. The metal provides low resistance while the polysilicon ensures good adhesion to the gate dielectric, enabling reduced device size without compromising on-state resistance performance
Solution Approach 2:
The gate electrode structure is optimized locally at the gate region with specific metal and polysilicon layer thicknesses tailored to provide both low resistance and good adhesion in the critical gate area, allowing compact device design while maintaining electrical performance
2Reliability
If a metal gate electrode is used directly on the gate dielectric, then the adhesion is insufficient
Solution Approach 1:
A polysilicon layer is introduced as an intermediary between the metal gate electrode and the gate dielectric. This intermediate layer provides excellent adhesion to the gate dielectric while allowing the metal layer to provide low resistance, solving the adhesion problem without requiring complex multi-layer metal structures
Solution Approach 2:
The gate electrode combines metal and polysilicon in a composite structure where each material performs its optimal function: polysilicon for adhesion and metal for low resistance, achieving reliable electrical connection without excessive structural complexity
3Device complexity
If the gate electrode structure is simplified, then the line resistance increases
Solution Approach 1:
The metal-polysilicon composite gate electrode structure achieves low line resistance through the metal component while keeping the overall structure relatively simple with just two main layers, avoiding the need for complex multi-layer metal interconnects
Data Source
AI summary
A method includes providing a silicon carbide substrate, wherein a gate trench extends from a main surface of the silicon carbide substrate into the silicon carbide substrate and wherein a gate dielectric is formed on at least one sidewall of the gate trench, and forming a gate electrode in the gate trench, the gate electrode including a metal structure and a semiconductor layer between the metal structure and the gate dielectric.