Lateral Bipolar Transistor With Wraparound Base Contact
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Solution Overview
Problem
Vertical bipolar transistors face limitations in high-speed operation due to increased collector resistance and complex manufacturing processes, while lateral bipolar transistors are simpler but require efficient contact structures to minimize base resistance and address current crowding and self-heating.
Innovation Solution
A lateral bipolar transistor with a wraparound contact and shallow trench isolation structures, featuring a narrow base width and epitaxial semiconductor regions, is fabricated using integrated circuit technology, including photolithographic processes and rapid thermal anneal, to reduce base resistance and enhance heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical bipolar transistor structure is used, then the transistor can be manufactured with standard processes, but the collector resistance increases due to the deep collector region formation, limiting high-speed operation
Solution Approach 1:
The patent inverts the conventional vertical transistor architecture to a lateral configuration where the current flow direction is changed from vertical to lateral. This inversion allows the collector to be positioned at the surface level rather than deep in the substrate, enabling direct surface contact and eliminating the deep trench requirements, thus achieving low base resistance and high-speed operation while maintaining manufacturing feasibility
2Reliability
If a vertical bipolar transistor structure is used, then the transistor can provide adequate current flow, but the manufacturing process complexity increases due to requirements for high-concentration buried layer, collector epitaxial layer, and deep trench isolation
Solution Approach 1:
The patent extracts and eliminates the complex deep trench isolation structure and high-concentration buried layer requirements by transitioning to a lateral configuration. The lateral structure allows the collector to access the base region directly at the surface, removing the need for deep substrate modifications and simplifying the manufacturing process while maintaining adequate current flow capability
Solution Approach 2:
By inverting from vertical to lateral architecture, the patent fundamentally changes the structural requirements, eliminating the need for complex epitaxial layers and deep trench isolation that are mandatory in vertical structures, thus reducing manufacturing complexity
3Ease of manufacture
If a lateral bipolar transistor structure is used, then the manufacturing process is simplified and collector electrode can be directly contacted with collector region, but base resistance must be minimized through special contact structures to address current crowding and self-heating
Solution Approach 1:
The patent extends the base contact from a conventional planar surface contact to a three-dimensional wraparound configuration that contacts the base region on multiple sides. This dimensional extension increases the effective contact area and provides multiple current paths, thereby reducing base resistance and mitigating current crowding effects while maintaining the manufacturing simplicity of the lateral structure
Solution Approach 2:
The wraparound contact structure is formed by nesting the contact material around the base region, creating a multi-layered configuration where the contact envelops the base from multiple directions. This nested arrangement maximizes the contact interface area with minimal additional process complexity, effectively reducing base resistance
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a lateral bipolar transistor and methods of manufacture. The structure includes: an extrinsic base region composed of semiconductor material; an emitter region on a first side of the extrinsic base region; a collector region on a second side of the extrinsic base region; and an extrinsic base contact wrapping around the semiconductor material of the extrinsic base region.