Lateral Bipolar Transistor Structure for Lower Parasitic Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lateral bipolar transistors face challenges with high parasitic capacitance and resistance, limiting device scaling and high-speed operation due to complex integration schemes and structural limitations of vertical bipolar transistors.
Innovation Solution
A lateral heterojunction bipolar transistor structure is developed with a self-aligned trench on a fully depleted semiconductor on insulator (FDSOI) substrate, featuring a SiGe intrinsic base, an extrinsic base with spacers for isolation, and raised epitaxial collector and emitter regions, along with a silicide for improved base contact, allowing for tunability and reduced parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a vertical bipolar transistor structure is used, then the transistor can be manufactured with conventional processes, but the emitter-collector resistance increases and the number of process steps increases
Solution Approach 1:
The patent transitions from a vertical bipolar transistor structure to a lateral bipolar transistor structure, changing the current flow direction from vertical to lateral. This dimensional change allows the collector electrode to be directly contacted with the collector region, reducing emitter-collector resistance while maintaining manufacturability through adapted fabrication processes.
Solution Approach 2:
The patent inverts the conventional vertical structure by implementing a lateral configuration where the collector and emitter are positioned on the same surface level rather than at different depths. This inversion enables direct contact between the collector electrode and collector region, eliminating the need for deep trenches and complex buried layers.
2Productivity
If current integration schemes are used in lateral bipolar transistors, then device integration is achieved, but parasitic capacitance and base resistance increase
Solution Approach 1:
The patent segments the base region into distinct components: an intrinsic base in the channel region and an extrinsic base vertically above it. This segmentation allows independent optimization of each region, enabling precise control of base width to minimize parasitic capacitance while maintaining integration benefits.
Solution Approach 2:
The patent applies different doping characteristics to different parts of the base structure. The intrinsic base in the channel region has specific doping properties, while the extrinsic base above it has different doping characteristics. This local quality differentiation enables optimization of electrical properties in each region to reduce overall parasitic effects.
3Reliability
If the base width is reduced to improve high-frequency performance, then Ft/Fmax figures improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a self-aligned fabrication process where the intrinsic base and extrinsic base are automatically positioned relative to each other through the channel region structure. This self-alignment mechanism eliminates the need for complex alignment steps, enabling precise base width control without increasing manufacturing complexity.
Solution Approach 2:
The patent pre-defines the base width through the channel region dimensions before forming the extrinsic base. By establishing the intrinsic base boundaries first and using them as reference for subsequent steps, the design enables precise base width control while simplifying the fabrication process sequence.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a lateral bipolar transistor and methods of manufacture. A structure includes: an intrinsic base comprising semiconductor material in a channel region of a semiconductor substrate; an extrinsic base vertically above the intrinsic base; a raised collector region on the semiconductor substrate and laterally connected to the intrinsic base; and a raised emitter region on the semiconductor substate and laterally connected to the intrinsic base.