Lateral BJT ESD Protection via Collector Doping
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Solution Overview
Problem
Lateral bipolar junction transistors (BJTs) are not as effective as vertical BJTs in electrostatic discharge protection performance and increasing their size to improve this performance results in increased volume, making them unsuitable for compact applications.
Innovation Solution
The structure of a lateral BJT is modified by forming a high concentration doping area in the collector region and adding a second base area, which allows for improved electrostatic discharge protection without increasing the size by enhancing triggering voltage, sustain voltage, and maximum electrostatic discharge current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the size of a lateral BJT is increased to improve electrostatic discharge protection performance, then the electrostatic discharge protection performance is improved, but the volume of the transistor increases
Solution Approach 1:
The patent applies local quality by creating a high concentration doping area specifically in the collector region rather than uniformly increasing the entire transistor size. This localized modification of doping concentration in a specific region enhances the electrostatic discharge protection performance while maintaining a compact overall transistor structure, thus resolving the contradiction between improved reliability and reduced volume.
2Speed
If the positions of emitter and base are switched to advance the triggering point, then the tunneling effect occurs faster, but satisfactory electrostatic discharge protection performance cannot be achieved alone
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration parameter in the collector region through high concentration doping. This parameter modification enhances both the triggering speed and the electrostatic discharge protection performance simultaneously, resolving the contradiction where simply switching emitter and base positions could advance triggering but insufficiently improve overall protection performance.
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 modified BJT structure effectively improves electrostatic discharge protection performance by adjusting triggering voltage, increasing sustain voltage, and enhancing maximum electrostatic discharge current, thereby protecting semiconductor devices without increasing the transistor's size.
Implementation Method 1
when the positions of the emitter 17 and the base 19 are switched, the tunneling effect of a BJT occurs faster, so that this may advance the triggering point
Implementation Method 2
A first well 12 is formed by implanting a p-type impurity into the semiconductor substrate 11 at the lower side of the first device isolation layer 14, and a second well 13 is formed by implanting an n-type impurity into the semiconductor substrate 11 at the lower side of the third device isolation layer 16
Data Source
AI summary
A bipolar junction transistor (BJT) is provided. The BJT can include a semiconductor substrate, a first well disposed in the substrate and implanted with a first impurity, a second well disposed at one side of the first well and implanted with a second impurity, a first device isolation layer disposed in the first well and defining an emitter area, and a second device isolation layer disposed in the second well and defining a collector area, The BJT can also include an emitter having a second impurity, a base having a first impurity, a collector having a second impurity, and a high concentration doping area having a second impurity at high concentration. The high concentration doping area can be provided at one side of the collector in the second well.