Lateral Bipolar Transistor With Graded SiGe Base for High-Speed RF

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 additional layers for high-speed performance.

Innovation Solution

A lateral bipolar transistor structure with a SiGe base having a gradient concentration of Ge is developed, utilizing fully depleted semiconductor on insulator (SOI) technology, featuring an ultra-narrow base and raised emitter and collector regions, fabricated using integrated circuit technologies like photolithographic processes and epitaxial growth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If vertical bipolar transistor structure is used, then transistor performance for high-speed operation is limited due to increased collector resistance, but the structure provides deep collector region formation capability

Engineering Contradiction:

Improvehigh-speed operationVSAvoidcollector resistance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent inverts the conventional vertical bipolar transistor architecture by adopting a lateral configuration where the collector electrode is positioned at the surface level rather than deep in the wafer. This inversion allows the collector to be directly brought into contact with the collector region, eliminating the need for deep trench isolation and reducing collector resistance, thereby enabling high-speed operation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from a vertical current flow configuration to a lateral current flow configuration. By changing the dimension of carrier flow from vertical to lateral, the collector electrode can be directly contacted with the collector region at the surface level, reducing the number of process steps and improving high-speed performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If vertical bipolar transistor structure is used, then transistor performance is improved through deep collector region formation, but the number of process steps and manufacturing costs increase

Engineering Contradiction:

Improvetransistor performanceVSAvoidnumber of process steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional vertical bipolar transistor architecture by adopting a lateral configuration where the collector electrode is positioned at the surface level rather than deep in the wafer. This inversion allows the collector to be directly brought into contact with the collector region, eliminating the need for deep trench isolation and reducing collector resistance, thereby enabling high-speed operation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent transitions from a vertical current flow configuration to a lateral current flow configuration. By changing the dimension of carrier flow from vertical to lateral, the collector electrode can be directly contacted with the collector region at the surface level, reducing the number of process steps and improving high-speed performance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Device complexity

If lateral bipolar transistor structure is used, then manufacturing complexity and costs are reduced, but performance for high-voltage RF device applications is insufficient

Engineering Contradiction:

Improvemanufacturing complexityVSAvoidhigh-voltage RF device applications

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by implementing a graded Ge concentration profile specifically in the sidewalls of the extrinsic base region. The Ge concentration varies from 0% at the emitter side to 50% at the collector side, creating localized material properties that optimize carrier transport and enable high-voltage RF device applications while maintaining the simpler lateral structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite semiconductor materials with a core of first semiconductor material (e.g., Si) and sidewalls of second semiconductor material (e.g., SiGe) with graded concentration. This composite structure combines the advantages of different materials to achieve both manufacturing simplicity and high-voltage RF performance.

Inventive Principle:

Principle #40Composite materials

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 enables high-voltage RF device applications with reduced capacitance and noise isolation, improving transistor performance for high-speed operations while simplifying the manufacturing process and reducing costs.

Implementation Method 1

an extrinsic base comprising at least one sidewall with a gradient concentration of semiconductor material

Methodology Applied

Scientific EffectGraded concentration semiconductor material: Diffusion

Data Source

PatentUS20240297242A1Lateral bipolar transistors

Publication Date: 2024.09.05 GLOBALFOUNDRIES US INC

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 having at least one sidewall with a gradient concentration of semiconductor material; an emitter on a first side of the extrinsic base; and a collector on a second side of the extrinsic base.