Lateral Bipolar Transistor with Under-Base Thermal Conduction
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Solution Overview
Problem
Bipolar transistors face challenges in thermal dissipation and stress management, which affect their performance and electron mobility, particularly in high-performance applications.
Innovation Solution
Incorporating a thermal conductive material, such as SiC, underneath the base region of a lateral SiGe heterojunction bipolar transistor to enhance thermal dissipation and connect thermally with the semiconductor substrate, while maintaining electrical isolation through a buried insulator layer and shallow trench isolation structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional bipolar transistor structure is used, then the device is simple to manufacture, but thermal dissipation is poor affecting performance
Solution Approach 1:
A thermal conductor layer is introduced as an intermediary component between the base and the substrate. This thermal conductor acts as a mediator that facilitates heat transfer from the base to the substrate, resolving the thermal dissipation issue without requiring fundamental changes to the transistor structure. The thermal conductor layer with higher thermal conductivity than the substrate provides a dedicated thermal pathway while maintaining the overall device architecture.
Solution Approach 2:
The thermal management solution is implemented by adding a vertical dimension to the heat dissipation pathway. Instead of relying solely on lateral heat spreading in the substrate, the invention creates a vertical thermal conduction path through the thermal conductor layer underneath the base, enabling heat to be conducted downward to the substrate more efficiently.
2Speed
If thermal dissipation is improved by adding thermal conductor, then electron mobility increases, but device complexity increases
Solution Approach 1:
The thermal conductor layer serves as an intermediary that indirectly benefits electron mobility by managing thermal conditions. Rather than directly affecting charge carrier transport, the thermal conductor improves electron mobility by maintaining lower operating temperatures through enhanced heat dissipation, thereby reducing thermal scattering of carriers.
3Temperature
If thermal conductor material is placed under the base, then thermal dissipation improves, but manufacturing complexity increases
Solution Approach 1:
The thermal conductor layer is integrated into the substrate preparation stage before transistor fabrication begins. By pre-forming the thermal conductor layer and establishing its thermal pathways ahead of time, the subsequent transistor manufacturing steps can proceed without additional complexity. This preliminary integration of the thermal management function into the substrate structure allows standard fabrication processes to be used.
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
Improves thermal dissipation and electron mobility, leading to enhanced performance metrics like Ft/Fmax, making the bipolar transistor suitable for high-performance applications.
Implementation Method 1
a thermal conductive material under the base and extending to an underlying semiconductor material
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A lateral bipolar transistor (10) on an SOI substrate (12a, 12b, 12c) comprising: a base (16) formed within the semiconductor substrate (12c); a thermal conductive material (12d') under the base and extending to an underlying semiconductor material (15); an emitter (22) on a first side of the base (16); and a collector (24) on a second side of the base (16).