BJT Layout to Raise BVceo by Removing STI Between Emitters
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Solution Overview
Problem
The breakdown voltage of bipolar junction transistors (BJTs) is limited by the accumulation of phosphorus at the sidewalls of shallow trench isolation (STI) in the collector region, leading to a decrease in breakdown voltage BVceo, making it difficult to increase this voltage without reaching the minimum dose limitation of the ionized metal plasma (IMP) process.
Innovation Solution
Increasing the oxide diffusion (OD) area surrounding the emitter regions to create a larger distance between the emitter and STI regions, eliminating the STI cumulated phosphorus effect, and eliminating STI regions between emitter regions to enhance the breakdown voltage BVceo.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ionized metal plasma (IMP) process is used to increase breakdown voltage, then breakdown voltage can be improved, but the dose limitation prevents further voltage increase
Solution Approach 1:
The patent extracts and removes the STI regions from between the emitter regions, eliminating the source of phosphorus accumulation that limits breakdown voltage improvement through conventional IMP dosing
Solution Approach 2:
The patent increases the oxide diffusion area in the horizontal plane surrounding each emitter region, creating additional separation distance between emitters and STI regions to reduce phosphorus accumulation effects
2Device complexity
If STI regions are present between emitter regions, then device structure is simplified, but phosphorus accumulates at STI sidewalls reducing breakdown voltage
Solution Approach 1:
The patent removes STI regions from between emitter regions, eliminating the harmful phosphorus accumulation sites at STI sidewalls while maintaining overall device structure
Solution Approach 2:
The patent converts the harmful phosphorus accumulation effect into a benefit by increasing the oxide diffusion area, which creates a larger distance that prevents phosphorus accumulation and enhances breakdown voltage
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 approach increases the breakdown voltage BVceo of BJTs, preventing permanent damage from high voltage and rapidly increasing current, and allowing for higher voltage applications without the limitations of traditional IMP doses.
Implementation Method 1
Increasing the oxide diffusion (OD) area surrounding the emitter regions to create a larger distance between the emitter and STI regions, eliminating the STI cumulated phosphorus effect
Data Source
AI summary
Methods for fabricating a bipolar junction transistor (BJT) are provided. A method includes forming a collector region, forming base regions over the collector region, and forming emitter regions over the base regions. The method further includes forming base dielectric layers over the collector region and on opposite sides of the base regions, forming base conductive layers over the base dielectric layers and on the opposite sides of the base regions, and forming base contacts over the base conductive layers. The top surface of the collector region is coplanar with bottom surfaces of the base regions and bottom surfaces of the base dielectric layers. The base contacts are divided into a first group of base contacts disposed between the base regions and a second group of base contacts disposed between the base regions and the STI region.