Semiconductor Base Region Segmentation for High Breakdown Voltage
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Solution Overview
Problem
Conventional bipolar transistors face challenges in achieving high off-breakdown voltage exceeding 100 V due to increased base region density, which reduces avalanche voltage, and experience characteristic changes over time due to surface breakdown.
Innovation Solution
A semiconductor device with a two-layer base structure, where a high impurity density first base region is surrounded by a low impurity density second base region, allowing selective depletion and increased avalanche breakdown voltage, preventing punch-through and maintaining high base region density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer base structure is used, then the manufacturing process is simple, but the breakdown voltage cannot exceed 100 V and characteristics change over time
Solution Approach 1:
The base region is segmented into two layers with different impurity densities, enabling the structure to achieve breakdown voltages exceeding 100 V while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
Solution Approach 2:
The two-layer base structure is designed in advance to prevent future degradation. The specific impurity density configuration is predetermined to ensure stable breakdown voltage characteristics over time, preventing the characteristic changes that occur in conventional single-layer structures.
2Reliability
If the base region density is increased to raise off-breakdown voltage, then punch-through is prevented, but surface breakdown occurs and characteristics change over time
Solution Approach 1:
By segmenting the base region into two layers, the high impurity density is confined to the first base region near the emitter-collector interface, preventing punch-through. The second base region extends deeper with low density, positioning the avalanche breakdown away from the surface and preventing surface breakdown and its associated characteristic degradation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively raises the breakdown voltage beyond 100 V, maintains transistor characteristics over time, and allows for adjustable avalanche breakdown voltage through layout adjustments, preventing surface breakdown and ensuring reliable operation.
Implementation Method 1
a breakdown is caused and a current flows into the base extraction region from the collector extraction region through the deep well on the surfaces of the semiconductor layer and the base region, when a voltage is applied to the collector and the collector voltage reaches a avalanche breakdown voltage between the collector and the bases in the bipolar transistor
Data Source
AI summary
In a semiconductor device including a bipolar transistor, a base region has a two layer structure including a first base region, and a second base region which is provided around the first base region and has a lower impurity density than that of the first base region and has a shallower depth than that of the first base region.