Bipolar Transistor Isolation Oxide for Stable Current Gain
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Solution Overview
Problem
Existing semiconductor devices with bipolar transistors face challenges in achieving high current amplification factors due to collector currents being trapped by crystal defects at the junction interface between the base and emitter regions.
Innovation Solution
Incorporating an element isolation insulating film with a thermal oxide film that contacts the junction interface between the base and emitter regions, and using a common photomask to implant impurity ions for forming the base and emitter regions, thereby stabilizing the junction interface and reducing crystal defect trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common photomask is used to implant impurity ions for forming base and emitter regions, then manufacturing cost is reduced and productivity is improved, but manufacturing precision may be compromised due to alignment challenges
Solution Approach 1:
The patent combines the formation of base and emitter regions into a single ion implantation step using a common photomask. The photomask is designed with patterns that simultaneously define both the base region (through boron implantation) and the emitter region (through phosphorus implantation), eliminating the need for separate masking steps and reducing overall manufacturing complexity
Solution Approach 2:
The patent applies different impurity types and concentrations to different regions through the same photomask. The base region receives boron implantation with specific concentration and depth, while the emitter region receives phosphorus implantation with different parameters. This local differentiation of material properties is achieved within a unified manufacturing step
2Device complexity
If the junction interface between base and emitter regions is left exposed, then manufacturing simplicity is maintained, but current amplification factor is reduced due to collector currents being trapped by crystal defects
Solution Approach 1:
The patent introduces an element isolation insulating film as an intermediary structure that contacts the junction interface between the base and emitter regions. This insulating film acts as a mediator that prevents harmful interactions at the junction interface while maintaining the overall simplicity of the device structure. The film reduces crystal defects and prevents collector current trapping, thereby improving current amplification factor without adding complex processing steps
Solution Approach 2:
The patent converts the potentially harmful effect of the junction interface (which can generate crystal defects that trap collector currents) into a beneficial configuration. By having the element isolation insulating film contact the junction interface, the interface becomes a controlled feature rather than a defect source. The insulating film passivates the interface, transforming it from a harmful element into a protective feature that enhances device 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
This configuration enhances the current amplification factor and stabilizes the current conversion rate, allowing for the production of semiconductor devices with improved performance at a lower cost.
Implementation Method 1
an element isolation insulating film having a thermal oxide film
Implementation Method 2
using a common photomask to implant impurity ions for forming the base and emitter regions
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a base region, an emitter region, a collector region, and an element isolation insulating film. The semiconductor substrate has a main surface. The base region has a first conductivity type and is disposed in a surface layer of the semiconductor substrate that is close to the main surface. The emitter region has a second conductivity type and is disposed in a surface layer of the base region. The collector region has the second conductivity type and is disposed at a portion in the surface layer of the semiconductor substrate apart from the emitter region. The element isolation insulating film is disposed on the main surface, and has a thermal oxide film being in contact with a junction interface between the base region and the emitter region.