Bipolar Transistor Nested Well Structure for Beta BVCEO Tradeoff
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Solution Overview
Problem
High-voltage NPN bipolar junction transistors face a tradeoff between beta (collector current/base current) and BVCEO (breakdown voltage between collector and emitter with base open), limiting their performance in applications such as audio amplifiers and electrostatic discharge devices.
Innovation Solution
The design incorporates a deep n-well and n-well region structure in a p-well substrate with shallow trench isolation, allowing for higher beta and BVCEO values without additional processing steps, utilizing existing IC technology and materials like Si and SiGe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional NPN BJT structure is used, then manufacturing simplicity is maintained, but beta and BVCEO product is limited to constant value
Solution Approach 1:
The patent implements a nested well structure where a deep n-well region is formed within an n-well region, which itself is formed in a p-well substrate. This nested configuration (deep n-well inside n-well inside p-well) enables simultaneous achievement of high beta and high BVCEO by creating multiple junctions that independently control different performance parameters, breaking the conventional constant product limitation.
2Reliability
If deep n-well and n-well regions are added, then beta and BVCEO values increase, but manufacturing complexity increases
Solution Approach 1:
The deep n-well and n-well regions serve multiple functions simultaneously: the deep n-well provides high-voltage breakdown characteristics (BVCEO) while the n-well region contributes to current gain (beta). This multi-functionality allows a single nested structure to address multiple performance requirements without requiring separate processing sequences for each function, thereby limiting the increase in manufacturing complexity.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to high-voltage, analog bipolar devices and methods of manufacture. The structure includes: a base region formed in a substrate; a collector region formed in the substrate and comprising a deep n-well region and an n-well region; and an emitter region formed in the substrate and comprising a deep n-well region and an n-well region.