Semiconductor Device Two-Part Dummy Active Trench Gate Structure
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Solution Overview
Problem
The existing semiconductor devices face increased turn-on loss due to current-dependent recovery dV/dt of freewheeling diodes, which is exacerbated by a two-part gate structure with a polysilicon configuration that reduces the Cgc/Cge ratio, leading to longer switching times and higher turn-on losses.
Innovation Solution
A semiconductor device with a two-part dummy active trench structure, where the upper dummy part is not connected with the gate electrode and the lower active part is connected with the gate electrode, covered by an insulating film, is implemented to increase the Cgc/Cge ratio, thereby reducing the dependency of recovery dV/dt on collector current and minimizing turn-on loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate resistance is determined so that the recovery dV/dt on the low-current side is 20 kV/μs, then the recovery dV/dt of the diode is controlled, but the dV/dt on the rated-current side becomes 10 kV/μs resulting in long switching time and increased turn-on loss
Solution Approach 1:
The patent changes the capacitance parameters of the semiconductor device by adjusting the gate structure. Specifically, it modifies the ratio of gate-collector capacitance (Cgc) to gate-emitter capacitance (Cge) by changing the physical configuration of the gate electrode and insulating film, which alters the electrical characteristics to achieve better dV/dt control across different current conditions
2Ease of manufacture
If a two-part gate structure with polysilicon is used, then the gate structure is formed, but the Cgc/Cge ratio decreases leading to longer switching times and higher turn-on losses
Solution Approach 1:
The patent applies local quality by creating different regions within the gate structure with different properties. The gate electrode is configured to have different capacitance characteristics in different areas, specifically enhancing the gate-collector capacitance region while controlling the gate-emitter capacitance region, thereby optimizing the Cgc/Cge ratio locally to improve switching performance
3Device complexity
If the upper dummy part is connected with the gate electrode, then the gate structure is complete, but the Cgc/Cge ratio is reduced and turn-on loss increases
Solution Approach 1:
The patent segments the gate structure into functionally distinct parts: an upper dummy part and a lower active part. The upper dummy part is intentionally left unconnected to the gate electrode to serve as a capacitance-enhancing element without active switching function, while the lower active part remains connected for actual switching operation. This segmentation allows independent optimization of each part's function
Data Source
AI summary
A semiconductor device includes; a semiconductor substrate; an emitter electrode provided on the semiconductor substrate; a gate electrode provided on the semiconductor substrate; a drift layer of a first conduction type provided in the semiconductor substrate; a source layer of the first conduction type provided on an upper surface side of the semiconductor substrate; a base layer of a second conduction type provided on the upper surface side of the semiconductor substrate; a collector electrode provided below the semiconductor substrate; and a two-part dummy active trench including, at an upper part, an upper dummy part not connected with the gate electrode and including, at a lower part, a lower active part connected with the gate electrode and covered by an insulating film, in a trench of the semiconductor substrate, wherein a longitudinal length of the lower active part is larger than a width of the lower active part.