Semiconductor Structure with Field Plate for BJT Breakdown Voltage
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Solution Overview
Problem
The breakdown voltage between the emitter and base in bipolar junction transistors (BJTs) is compromised when increasing dopant concentration in the emitter to enhance injection efficiency, leading to decreased performance.
Innovation Solution
A semiconductor structure with a field plate made of poly silicon is introduced between doped regions to enhance breakdown voltage and prevent punch-through effects, while increasing the dopant concentration of the emitter doped region to improve injection efficiency and current gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dopant concentration of the emitter is increased to enhance injection efficiency, then the current gain is improved, but the breakdown voltage between emitter and base is decreased
Solution Approach 1:
A third doped region with opposite polarity is introduced between the first doped region (emitter) and second doped region (base), serving as an intermediary that modifies the electric field distribution. This intermediary region prevents direct interaction between the high-dopant emitter and base, allowing the emitter to maintain high dopant concentration for improved injection efficiency while the intermediate region protects the breakdown voltage by creating a more gradual potential gradient.
Solution Approach 2:
The invention changes the doping parameters by introducing a third doped region with opposite polarity between the emitter and base regions. This parameter change in the doping profile creates a compensated region that modifies the electric field characteristics, enabling the system to simultaneously achieve high injection efficiency (through high emitter dopant concentration) and high breakdown voltage (through the field-modulating intermediate region).
Data Source
AI summary
A semiconductor structure includes a substrate, a first well having a first conductive type, a second well having a second conductive type, a body region, a first doped region, a second doped region, a third doped region and a field plate. The first and second wells are formed in the substrate. The body region is formed in the second well. The first and second doped regions are formed in the first well and the body region, respectively. The second and first doped regions have the same polarities, and the dopant concentration of the second doped region is higher than that of the first doped region. The third doped region is formed in the second well and located between the first and second doped regions. The third and first doped regions have reverse polarities. The field plate is formed on the surface region between the first and second doped regions.