Heterojunction Bipolar Transistor Base Contact Structure
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Solution Overview
Problem
Heterojunction bipolar transistors (HBTs) face limitations in operating frequency due to high contact resistance between the base and contact layers, which affects their performance in high-frequency applications.
Innovation Solution
The semiconductor device design includes a first epitaxial layer with a conductive type, a second epitaxial layer of complementary type, and a semiconductor layer structure where the emitter extends vertically with a body portion and an extending portion, with the base contact layer laterally surrounding the emitter, increasing the contact area and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional HBT structure with simple base contact is used, then the device structure is simple, but the contact resistance between base and contact layers is high
Solution Approach 1:
The base contact layer is extended from a simple planar contact into a three-dimensional structure that laterally surrounds the emitter. This dimensional extension increases the contact area with the base without increasing the vertical footprint, thereby reducing contact resistance while maintaining a compact device layout.
Solution Approach 2:
The base contact layer is divided into multiple segments that wrap around different portions of the emitter. This segmentation allows the contact to access the base from multiple locations, increasing the total contact area and reducing resistance through distributed contact paths.
2Reliability
If the contact area between base and contact layers is increased, then the contact resistance is reduced, but the device area increases
Solution Approach 1:
The contact structure utilizes the lateral dimension to increase contact area without proportionally increasing the device footprint. By wrapping the base contact layer around the emitter in a lateral direction, the contact area is multiplied while maintaining a compact overall device area.
Data Source
AI summary
A semiconductor device and a manufacturing method thereof are provided. The semiconductor device includes first and second epitaxial layers, and first and second semiconductor layers. The second epitaxial layer is disposed on the first epitaxial layer. The first semiconductor layer extends from above the second epitaxial layer to a top surface of the second epitaxial layer. A vertically extending region of the first semiconductor layer has a body portion and an extending portion extending from a bottom end of the body portion to the second epitaxial layer. A width of the body portion is greater than a width of the extending portion. The second semiconductor layer is disposed on the second epitaxial layer, and laterally surrounds the vertically extending region of the first semiconductor layer. A portion of the second semiconductor layer extends between and overlaps with the body portion of the first semiconductor layer and the second epitaxial layer.