Trench MOSFET Source Contact Structure for Lower Cell Pitch
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Solution Overview
Problem
Conventional trench gate MOSFETs fail to meet the requirements of on-state resistance (Ron), breakdown voltage, and miniaturization in power electronic applications, and require complex photolithography and self-aligned contact processes.
Innovation Solution
A semiconductor device with a source contact structure formed in a trench, reducing cell pitch and specific on-resistance (Rsp) without enhancing photolithography accuracy or using complex self-aligned contact processes, by electrically connecting to source regions on both sides of the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional trench gate MOSFET structures are used, then the device can achieve basic power switching functionality, but the cell pitch is large and specific on-resistance is high
Solution Approach 1:
The source contact structure is formed within the trench structure itself, utilizing the vertical dimension of the trench to accommodate the source contact. This allows the source contact to be positioned inside the trench rather than requiring additional lateral space, thereby reducing cell pitch while maintaining proper electrical connection to source regions on both sides of the trench.
Solution Approach 2:
The source contact structure is nested within the trench structure, with the source contact occupying the trench space. This nesting approach allows the source contact to be integrated into the existing trench geometry without requiring additional lateral space, effectively reducing the cell pitch while maintaining all necessary electrical connections.
2Manufacturing precision
If photolithography accuracy is enhanced to improve contact alignment, then contact alignment precision improves, but manufacturing cost and process complexity increase
Solution Approach 1:
The source contact structure is designed to be self-aligned within the trench, utilizing the trench walls and existing structures to automatically position the source contact correctly. This self-alignment mechanism eliminates the need for high-precision photolithography alignment, as the source contact naturally positions itself relative to the source regions through the trench geometry and material deposition processes.
3Manufacturing precision
If self-aligned contact processes are used to improve alignment accuracy, then contact alignment improves, but device structure and fabrication process become more complex
Solution Approach 1:
The source contact structure leverages the trench geometry and material deposition sequences to achieve self-alignment with the source regions. The trench walls and layer deposition processes automatically guide the source contact to the correct position, eliminating the need for complex self-aligned contact fabrication processes while maintaining high alignment precision.
Data Source
AI summary
A semiconductor device includes a substrate having a first conductivity type and an epitaxial layer disposed on the substrate. A first trench and a second trench are disposed in the epitaxial layer. A first body region and a second body region both having a second conductivity type are disposed in the epitaxial layer, and located on two sides of the first trench, respectively. A first source region and a second source region both having the first conductivity type are disposed on the first body region and the second body region, respectively. A first electrode is disposed in the first trench. A source contact structure includes a first portion disposed in the first trench and is electrically connected to the first source region and the second source region. A first gate is disposed in the second trench.