LDMOS Drift Region Segmentation for On-Resistance and Breakdown Voltage
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Solution Overview
Problem
Conventional LDMOS devices achieve high off-state breakdown voltage but fail to provide low on-resistance, as increasing dopant concentration in the drift region reduces breakdown voltage while attempting to decrease on-resistance.
Innovation Solution
The semiconductor device incorporates an epitaxial layer with a first conductivity type, a drift region of the same conductivity type, and a plurality of doped region pairs with opposite and same conductivity type doped regions, arranged from the drain to the source, to maintain breakdown voltage while reducing on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dopant concentration of the drift region is increased to reduce on-resistance, then the on-resistance decreases, but the off-state breakdown voltage decreases
Solution Approach 1:
The drift region is segmented into multiple alternating doped regions (first conductivity type) and undoped regions (second conductivity type), creating a series of depletion regions that collectively provide high breakdown voltage while the doped regions maintain low on-resistance through reduced carrier path length
Solution Approach 2:
Different regions within the drift region are assigned different doping characteristics: doped regions provide low resistance paths for current flow, while undoped regions provide high breakdown voltage through extended depletion regions, allowing each local area to optimize for its specific function
Data Source
AI summary
A semiconductor device includes an epitaxial layer disposed over a semiconductor substrate, a drift region disposed in the epitaxial layer and adjacent to an upper surface of the epitaxial layer, a gate structure disposed over the epitaxial layer, a source region disposed in the epitaxial layer outside the drift region, and a drain region disposed in the drift region. The epitaxial layer and the drift region have a first conductivity type. The semiconductor device also includes a plurality of doped region pairs disposed in the drift region and arranged in a direction from the drain region toward the source region. Each of the plurality of doped region pairs includes a first doped region having a second conductivity type opposite to the first conductivity type, and a second doped region disposed over the first doped region. The second doped region has the first conductivity type.