MOSFET Drain Captive Air Gap Structure for Low RON and High Breakdown
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Solution Overview
Problem
MOSFET devices face a trade-off between high breakdown voltage and low on-state resistance, as techniques to increase breakdown voltage typically increase on-state resistance, and vice versa, making it challenging to achieve both high switching speed and low on-state resistance simultaneously.
Innovation Solution
A semiconductor device design featuring a substrate with a source and drain region, a gate between them, a conductive field plate, and a drain captive structure with an air gap trench in the interlevel dielectric layer, which is laterally spaced from the gate sidewalls, to enhance breakdown voltage without increasing on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping levels in the drift well are reduced to increase breakdown voltage, then breakdown voltage is improved, but on-state resistance increases
Solution Approach 1:
The drift well region is segmented into multiple zones with different doping levels. The drift well includes a first drift well portion with a first doping level and a second drift well portion with a second doping level, creating a graded doping profile that resolves the contradiction between breakdown voltage and on-state resistance
Solution Approach 2:
Different regions of the drift well are assigned different doping characteristics. The first drift well portion has higher doping to reduce on-state resistance, while the second drift well portion has lower doping to increase breakdown voltage, allowing each region to optimize for its specific function
Data Source
AI summary
A semiconductor device may include a substrate having a source region and a drain region, and a gate arranged over the substrate and between the source region and the drain region. A first interlevel dielectric (ILD) layer may be at least partially arranged over the substrate and the gate. A conductive field plate may be arranged over the first ILD layer. At least one drain contact may extend through the first ILD layer over the drain region and may be coupled to the conductive field plate. A drain captive structure may be disposed in the first ILD layer and adjacent to the drain region, the drain captive structure having a trench comprising an air gap, wherein the drain captive structure is laterally spaced apart from sidewalls of the gate.