RESURF Oxide Semiconductor Structure for Low Rdson Breakdown Control
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Solution Overview
Problem
Existing semiconductor devices face challenges in managing the drain side substrate spreading resistance, which is fixed for any voltage class, leading to increased total drain-source on resistance (Rdson) particularly for low breakdown voltage classes.
Innovation Solution
The semiconductor device incorporates a substrate, a channel, a drift, a first poly positioned within the channel and drift, and a second poly isolated by a gate oxide and a RESURF oxide, respectively, to achieve improved breakdown voltage and reduced Rdson.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional semiconductor device structure is used with fixed substrate spreading resistance, then the device structure is simple, but the total drain-source on resistance (Rdson) increases particularly for low breakdown voltage classes
Solution Approach 1:
The device is segmented into multiple functional regions including a first semiconductor region with first conductivity type, a second semiconductor region with second conductivity type, and a third semiconductor region with first conductivity type. This segmentation allows independent optimization of each region's properties to reduce overall Rdson while managing substrate spreading resistance through the specific configuration of doped regions and drift areas.
Solution Approach 2:
Different regions of the semiconductor device are assigned different local properties: the first semiconductor region has high doping concentration for low resistance contact, the second region forms a drift area with optimized doping for breakdown voltage control, and the third region provides substrate isolation. This local quality differentiation enables simultaneous optimization of conductivity and breakdown characteristics.
2Reliability
If the substrate spreading resistance is increased to reduce total Rdson, then the total Rdson decreases, but the breakdown voltage capability is compromised
Solution Approach 1:
The invention transitions from a single-layer planar structure to a multi-layer vertical structure with alternating n-type and p-type regions. This dimensional complexity allows the device to achieve low Rdson through horizontal conductivity paths while maintaining high breakdown voltage through vertical field distribution across multiple drift regions, effectively decoupling these two parameters.
Solution Approach 2:
The semiconductor device employs a composite structure with alternating regions of first conductivity type and second conductivity type, creating a multi-material system where each layer contributes specific properties. The n-type drift regions provide high breakdown voltage capability while the p-type regions and highly doped contact regions provide low resistance paths, achieving optimal balance between Rdson and breakdown voltage.
Data Source
AI summary
A semiconductor device is provided that includes a substrate, a channel with the channel positioned on the top of the substrate, and a drift with the drift positioned on the top of the channel. The semiconductor device further includes a first poly positioned in the channel and the drift, and a second poly positioned on the top of the first poly and positioned in the drift. The first poly and the second poly are isolated by a gate oxide and a RESURF oxide, respectively, from the channel and from the drift.