Lateral Bipolar Transistor Layout With Low Base Resistance
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Solution Overview
Problem
Vertical bipolar transistors face increased collector resistance and higher fabrication costs due to complex structures and numerous process steps, while lateral bipolar transistors are simpler but require optimization for improved performance.
Innovation Solution
The design incorporates a shallow trench isolation structure overlapping the base contact region, reducing base resistance and simplifying the fabrication process by integrating a base contact region adjacent to the emitter and collector, with a gate structure between them, and using a deep N-well for isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical bipolar transistor structure is used, then the transistor can be formed with standard vertical fabrication processes, but the collector resistance increases and transistor performance is limited for high-speed operation
Solution Approach 1:
The patent transitions from a vertical bipolar transistor configuration to a lateral configuration, changing the current flow direction from vertical to lateral. This dimensional change allows the collector to be formed closer to the surface, reducing collector resistance and improving high-speed performance while maintaining compatibility with standard fabrication processes
2Manufacturing precision
If a vertical bipolar transistor with deep collector region is used, then the transistor structure is well-defined, but the number of process steps increases and manufacturing costs increase
Solution Approach 1:
By switching to a lateral bipolar transistor configuration, the patent reduces the number of required process steps. The lateral structure allows for simpler formation of the collector region without requiring deep trench isolation and high-concentration buried layers, thereby reducing manufacturing complexity and costs while maintaining precise region definition
3Ease of manufacture
If a lateral bipolar transistor with simple structure is used, then the fabrication process is simplified, but the base resistance may increase and performance optimization is required
Solution Approach 1:
The patent applies local quality by forming a lightly-doped base region with specific doping characteristics in the lateral structure. This localized doping optimization reduces base resistance in the critical current flow path while maintaining the overall simplicity of the lateral transistor structure and fabrication process
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to bipolar transistors and methods of manufacture. The structure includes: an emitter in a semiconductor substrate; a collector in the semiconductor substrate; a base contact region in the semiconductor substrate and adjacent to the collector and the emitter; and a shallow trench isolation structure overlapping the base contact region and separating the base contact region from the emitter and the collector.