SiC MOSFET Gate Electrode Segmentation for Resistance Control
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Solution Overview
Problem
Silicon carbide semiconductor devices face challenges in achieving fast switching properties and reducing electrical resistance while maintaining threshold voltage suppression, particularly when using high-resistance materials like p-type polysilicon for gate electrodes, which can lead to increased resistance and short circuits.
Innovation Solution
The silicon carbide semiconductor device incorporates a connection electrode with a narrower width than the gate electrode, made of low-resistance materials such as aluminum alloys, and includes a barrier layer to prevent reaction with the interlayer insulating film, ensuring reliable formation and reducing leak current, while using p-type polysilicon for the gate electrode to suppress threshold voltage reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-type polysilicon is used for the gate electrode to suppress threshold voltage reduction, then threshold voltage control is improved, but electrical resistance increases
Solution Approach 1:
The gate electrode is segmented into two distinct parts: the gate electrode made of p-type polysilicon for threshold voltage control, and the connection electrode made of low-resistance material for current conduction. This segmentation allows each part to optimize its function independently, resolving the contradiction between threshold voltage control and electrical resistance.
Solution Approach 2:
Different regions of the gate structure are assigned different material properties: the gate electrode region uses p-type polysilicon with appropriate resistance characteristics for threshold control, while the connection electrode region uses low-resistance materials (aluminum alloy, titanium nitride, or tungsten) to minimize energy loss. This local quality differentiation resolves the contradiction by optimizing each region for its specific function.
2Loss of energy
If connection electrode is added to reduce resistance, then electrical resistance is reduced, but device complexity increases
Solution Approach 1:
The connection electrode is merged with the gate electrode to form an integrated gate structure. The connection electrode is formed in continuity with the gate electrode, eliminating the need for separate connection structures and reducing overall device complexity while still providing the low-resistance pathway needed to reduce energy loss.
Solution Approach 2:
The connection electrode serves multiple functions: it provides a low-resistance electrical pathway to reduce energy loss, maintains electrical continuity with the gate electrode, and can be formed using the same deposition process as the gate electrode. This multi-functionality reduces the need for additional components and simplifies the overall device structure.
3Reliability
If barrier layer is added to prevent reaction with interlayer insulating film, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
A barrier layer is introduced as an intermediary between the connection electrode and the interlayer insulating film. This barrier layer prevents direct contact and potential harmful reactions between the two materials, thereby improving reliability. The barrier layer can be formed as a thin interface layer during the deposition process, minimizing the impact on manufacturing complexity.
Data Source
AI summary
A MOSFET includes an SiC layer including main surfaces. The SiC layer includes an n type drift region, a p type body region, and an n type source region. The MOSFET further includes a gate insulating film formed to be located on a channel region, a gate electrode formed to be located above the channel region, the gate insulating film being sandwiched between said gate electrode and said channel region, and a connection electrode which includes a contact portion having a width smaller than a width of the gate electrode, has electric resistance lower than electric resistance of the gate electrode, and is formed on the gate electrode.