Lateral BJT Asymmetric Interface for Gain and Isolation
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Solution Overview
Problem
Lateral bipolar junction transistors (BJTs) face challenges with low emitter/collector gain and electrical isolation due to their relatively small horizontal interface between the emitter and base, which limits their performance in miniaturized microelectronic devices.
Innovation Solution
A bipolar junction transistor structure is designed with a horizontal interface between the emitter and base being smaller than that between the collector and base, incorporating a gate structure over the base to apply a voltage bias, enhancing current flow and gain by controlling the current modulation through the underlying base.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a lateral BJT structure is used to enable miniaturization and integration, then device size is reduced and integration density increases, but emitter/collector gain and electrical isolation deteriorate
Solution Approach 1:
The patent applies asymmetry by making the collector-base horizontal interface larger than the emitter-base horizontal interface. This asymmetric configuration allows the collector to have better electrical isolation while the emitter maintains effective current injection, thereby improving emitter/collector gain in lateral BJTs without increasing overall device size.
Solution Approach 2:
The patent transitions from vertical stacking to lateral arrangement of emitter, base, and collector regions. By spreading these regions out horizontally rather than stacking them vertically, the design achieves miniaturization while maintaining functional performance through optimized lateral interface areas.
2Area of stationary object
If a lateral BJT structure is used to enable miniaturization, then chip area is reduced, but electrical isolation between emitter and base deteriorates
Solution Approach 1:
The asymmetric design with larger collector-base interface and smaller emitter-base interface optimizes electrical isolation. The larger collector-base interface provides better isolation for the collector region, while the smaller emitter-base interface maintains effective current control, achieving both miniaturization and improved electrical isolation.
Solution Approach 2:
The patent applies local quality by optimizing the horizontal interface area at different locations: the collector-base interface is made larger for better isolation, while the emitter-base interface is kept smaller for effective current control. This localized optimization of interface areas resolves the contradiction between miniaturization and electrical isolation.
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
This configuration improves the electrical isolation and collector/emitter gain of lateral BJTs, enabling stronger current control and performance in miniaturized devices, while being adaptable to various doping profiles and polarities.
Implementation Method 1
a gate structure over the intrinsic base; and a first voltage source coupled to the gate structure, and configured to apply a voltage bias to the intrinsic base
Data Source
AI summary
Embodiments of the disclosure provide a bipolar junction transistor (BJT) structure and related method. A BJT according to the disclosure may include a base over a semiconductor substrate. A collector is over the semiconductor substrate and laterally abuts a first horizontal end of the base. An emitter is over the semiconductor substrate and laterally abuts a second horizontal end of the base opposite the first horizontal end. A horizontal interface between the emitter and the base is smaller than a horizontal interface between the collector and the base.