Trench Gate Electrode Structure for Low Resistance and Vth Control
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Solution Overview
Problem
Current semiconductor devices with trench gate structures face challenges in optimizing gate resistance and threshold voltage while maintaining breakdown voltage and switching speed, particularly with increasing epitaxial layer impurity concentrations.
Innovation Solution
The semiconductor device incorporates a gate electrode with a polysilicon first conductive portion and a metal second conductive portion, where the polysilicon portion contacts the gate insulation layer, and the metal portion is embedded in a recess, allowing for reduced gate resistance while limiting changes in threshold voltage, and includes a field plate electrode to maintain breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate electrode is made entirely of polysilicon, then the threshold voltage can be controlled, but the gate resistance becomes too high
Solution Approach 1:
The gate electrode is constructed as a composite structure with a polysilicon layer (first conductive portion) providing threshold voltage control and a metal layer (second conductive portion) providing low resistance. This composite configuration allows simultaneous achievement of both threshold voltage control and low gate resistance, resolving the technical contradiction between these two requirements.
2Object-affected harmful factors
If the gate electrode is made entirely of metal, then the gate resistance is reduced, but the threshold voltage control becomes difficult
Solution Approach 1:
The gate electrode combines metal (second conductive portion) for low resistance with polysilicon (first conductive portion) for threshold voltage control. The metal portion reduces gate resistance while the polysilicon portion maintains threshold voltage control capability, resolving the contradiction between low resistance and controllable threshold voltage.
3Productivity
If the epitaxial layer impurity concentration is increased, then the breakdown voltage decreases, but the switching speed increases
Solution Approach 1:
The patent optimizes the thickness parameters of the insulation layer and conductive portions, and controls the impurity concentration distribution in the epitaxial layer to achieve a balance between breakdown voltage and switching speed. By carefully adjusting these parameters, both performance metrics can be optimized simultaneously.
Data Source
AI summary
A semiconductor device includes a semiconductor layer; a trench formed in the semiconductor layer and including a side wall, an insulation layer formed on the semiconductor layer; and a gate electrode arranged in the trench. The insulation layer includes a gate insulation portion located between the semiconductor layer and the gate electrode, and covering the side wall of the trench. The gate electrode includes a first conductive portion contacting the gate insulation portion, and a second conductive portion including a side surface contacting the first conductive portion. The first conductive portion is formed from polysilicon, and the second conductive portion is formed from metal.