Vertical MOSFET Drain Electrode Back Surface Resistance
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Solution Overview
Problem
Semiconductor devices with surface drain terminals face increased on-resistance due to the structure of lead-out drain to the substrate, which affects power consumption and efficiency.
Innovation Solution
The semiconductor device design includes an active cell region, a drain electrode, and an external drain terminal formed over the semiconductor substrate, with the source electrode opposing the drain electrode along multiple sides to reduce back surface resistance and on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the drain terminal is formed on the surface of the semiconductor substrate in the CSP structure, then the chip size is reduced and integration is improved, but the on-resistance increases due to the additional lateral resistance component from the active cell region to the drain leading out region
Solution Approach 1:
The patent transitions from a planar two-dimensional layout to a three-dimensional vertical structure by forming the drain electrode that extends from the back surface through the substrate to the front surface. This dimensional change allows the drain terminal to access both surfaces, creating multiple current path dimensions and reducing the lateral resistance component in the on-resistance calculation.
Solution Approach 2:
The drain electrode is segmented into multiple regions: a first drain electrode region on the back surface, a second drain electrode region on the front surface, and an intermediate region connecting them through the substrate. This segmentation creates multiple parallel current paths, effectively reducing the overall resistance by distributing the current flow across different spatial zones.
2Reliability
If the drain electrode is formed to lead out the drain from the back surface to the surface, then the lateral resistance component is reduced, but the device complexity increases due to the multi-region electrode structure
Solution Approach 1:
The drain electrode serves multiple functions simultaneously: it acts as a current collection electrode on the back surface, provides a low-resistance path through the substrate, and forms a terminal connection on the front surface. This multi-functionality reduces the need for separate dedicated structures for each function, thereby managing complexity while achieving resistance reduction.
Solution Approach 2:
The patent merges the drain electrode with the substrate structure by forming the electrode regions directly within the substrate material. This integration combines what could be separate components (electrode and substrate) into a unified structure, reducing the number of discrete elements and simplifying the overall device architecture despite the increased functional requirements.
Data Source
AI summary
A semiconductor device including an active cell region formed over the surface of a silicon substrate and including a vertical MOSFET, a drain electrode formed over the surface of the silicon substrate and leading out the drain of the vertical MOSFET from the back surface of the silicon substrate, an external drain terminal formed over the drain electrode, and a source electrode formed over the active cell region so as to be opposed to the drain electrode at least along three sides at the periphery of the external drain terminal over the active cell region and connected to the source of the vertical MOSFET.