Lateral Bipolar Transistor Collector Biasing for Speed-Voltage Tradeoff
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Solution Overview
Problem
Existing lateral bipolar transistors face challenges in achieving a balance between increasing switching speed and breakdown voltage, with existing designs often compromising on one aspect at the expense of the other.
Innovation Solution
A lateral bipolar transistor design featuring a heavily doped emitter region, a lightly doped collector region with a doping asymmetry, and a substrate bias circuit to modulate electrostatic doping, along with a silicon-germanium alloy base region, is implemented. This design includes extrinsic and intrinsic base regions, insulating trenches, and a substrate region devoid of the silicon layer, allowing for adjustable bias voltages to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the collector region is heavily doped to increase switching speed, then switching speed is improved, but breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating different doping concentrations in different regions of the collector. The collector is divided into a first sub-region with light doping (for high breakdown voltage) and a second sub-region with heavy doping (for high switching speed). This spatial variation in doping quality allows simultaneous optimization of both speed and voltage characteristics.
Solution Approach 2:
The patent employs asymmetry by designing the collector region with unequal doping distribution - the first sub-region has significantly lower doping concentration than the second sub-region. This asymmetric doping profile enables the collector to exhibit both high-voltage withstand capability (from the lightly doped region) and fast switching performance (from the heavily doped region).
2Strength
If the collector region width is increased to improve breakdown voltage, then breakdown voltage is improved, but device area increases
Solution Approach 1:
The patent uses local quality by concentrating the voltage-blocking function in the first sub-region of the collector with light doping and extended width, while the second sub-region with heavy doping provides compact high-speed switching. This spatial differentiation allows the wide first sub-region to handle voltage stress without requiring the entire device to be large.
Solution Approach 2:
The patent segments the collector region into two functional sub-regions: the first sub-region optimized for voltage blocking (light doping, wider dimension) and the second sub-region optimized for charge injection (heavy doping, smaller dimension). This segmentation allows independent optimization of voltage and area parameters in different parts of the collector.
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 design enhances switching speed and breakdown voltage characteristics, enabling a flexible compromise between these parameters through substrate biasing, thereby improving the transistor's operational efficiency.
Implementation Method 1
a bias circuit connected to said substrate region and adapted to provide said substrate region with a bias voltage so as to modulate the electrostatic doping of the collector region
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
The present description relates to a lateral bipolar transistor (100) comprising: - an emitter region (112) doped with a first type of conductivity and having a first width (L12); - a collector region (116) doped with the first type of conductivity, having a second width (L16) greater than the first width and an average doping concentration lower than the average doping concentration of the emitter region; - a base region (114) between the emitter and collector regions doped with the second type of conductivity; said regions being arranged in a silicon layer (110) on an insulator layer (104) on a substrate (102); - a substrate region (106) devoid of the silicon and insulator layers, and positioned on the side of the collector region (116);and - a biasing circuit (150) connected, and adapted to provide, to the substrate region a biasing voltage so as to modulate the electrostatic doping of the collector region.;