Lateral Bipolar Transistor Layout for Low Parasitic Capacitance
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Solution Overview
Problem
Lateral bipolar transistors face challenges with high parasitic capacitance and resistance, limiting device scaling and high-speed operation due to their current integration schemes, which are not effectively addressed by existing technologies.
Innovation Solution
A lateral heterojunction bipolar transistor structure is developed with an intrinsic base, an extrinsic base vertically above it, a raised collector region, and a raised emitter region, all formed using epitaxial semiconductor material, along with a gate structure and isolation regions to minimize parasitic capacitance and provide tunability in base width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current integration schemes are used in lateral bipolar transistors, then device scaling is enabled, but parasitic capacitance (Ccb) and base resistance (Rb) increase, limiting high-speed operation
Solution Approach 1:
The base region is divided into two distinct parts: an intrinsic base region and an extrinsic base region. The intrinsic base region has minimal doping to reduce parasitic capacitance, while the extrinsic base region provides low-resistance contact. This segmentation allows the transistor to achieve both low Ccb and low Rb, resolving the contradiction between device scaling and high-speed operation performance.
Solution Approach 2:
Different regions of the base are assigned different doping qualities: the intrinsic base region maintains very low doping concentration (1E16 to 1E18 atoms/cm³) to minimize capacitance, while the extrinsic base region has higher doping (1E18 to 1E20 atoms/cm³) to reduce resistance. This local quality differentiation enables simultaneous optimization of both parasitic capacitance and base resistance for improved high-speed performance.
2Reliability
If vertical bipolar transistor structure is used, then carrier flow is controlled, but collector region depth increases emitter-collector resistance, disadvantaging high-speed operation
Solution Approach 1:
Instead of the conventional vertical structure where the collector is deep and the emitter is at the surface, this invention inverts the approach by using a lateral structure where both emitter and collector are at the surface level, connected through a shallow intrinsic base region. This inversion eliminates the deep collector issue, reducing emitter-collector resistance while maintaining carrier flow control through the base width modulation.
Solution Approach 2:
The invention transitions from a vertical three-dimensional structure to a lateral planar structure. By moving the carrier flow path to the lateral dimension rather than vertical depth, the collector region can be formed shallowly at the surface, dramatically reducing the resistance path while still achieving effective carrier control through the intrinsic base region width.
3Device complexity
If lateral bipolar transistor structure is used, then structure simplicity and direct collector contact are achieved, but current integration schemes result in high parasitic capacitance and base resistance
Solution Approach 1:
The base is segmented into intrinsic and extrinsic regions, allowing the simple lateral structure to be enhanced with functional differentiation. The intrinsic region maintains structural simplicity while the extrinsic region compensates for parasitic effects, achieving low Ccb and low Rb without significantly increasing overall device complexity.
Solution Approach 2:
The base region uses a composite doping structure combining lightly-doped intrinsic semiconductor material with more heavily-doped extrinsic semiconductor material. This composite approach within the base region enables the simple lateral transistor structure to achieve superior electrical characteristics by combining the benefits of low capacitance and low resistance regions.
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
The solution minimizes parasitic capacitance and enhances high-speed operation by allowing precise tuning of the base width, improving Ft/Fmax performance and reducing base resistance, thereby enabling better device scaling and performance.
Implementation Method 1
a lateral heterojunction bipolar transistor on a substrate material, the lateral heterojunction bipolar transistor comprising: an intrinsic base region in a channel region of the substrate material; an extrinsic base region over the intrinsic base region; a raised collector region comprising epitaxial semiconductor material adjacent to the extrinsic base; and a raised emitter region comprising the epitaxial semiconductor material adjacent to the extrinsic base
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.