Bipolar Transistor Base Horizontal Displacement

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Solution Overview

Problem

Conventional bipolar transistors have higher base-to-collector capacitance due to vertical overlap between the base and collector, which is undesirable in certain technical applications and limits the miniaturization of structural features and microelectronic devices.

Innovation Solution

A bipolar transistor structure is designed with a base that is horizontally displaced from the collector, utilizing trench isolation to separate the base and collector, thereby reducing capacitance and allowing for a more compact design without sacrificing functionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional approaches form an extrinsic base linked to an intrinsic base via conventional epitaxy, then the bipolar transistor can be formed with standard fabrication processes, but portions of the collector and extrinsic base vertically overlap causing higher base-to-collector capacitance

Engineering Contradiction:

Improvefabrication process standardizationVSAvoidbase-to-collector capacitance

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent applies dimensionality change by transitioning from vertical stacking to horizontal displacement. The extrinsic base is positioned horizontally adjacent to the collector rather than vertically overlapping it, eliminating the capacitance issue while maintaining electrical connectivity through the semiconductor substrate.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent introduces an intermediary structure (the semiconductor substrate acting as a common base region) that electrically connects the extrinsic base and collector without requiring direct vertical contact. This intermediary approach allows electrical functionality while preventing capacitive coupling.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the base and collector are vertically overlapped to simplify structure, then fabrication is easier, but the capacitance increases which is undesirable in certain technical applications

Engineering Contradiction:

Improvestructural simplicityVSAvoidbase-to-collector capacitance

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent resolves the contradiction by changing the spatial arrangement from vertical (one dimension) to horizontal (another dimension). The extrinsic base extends horizontally from the intrinsic base region, placing it adjacent to rather than overlapping the collector, thus reducing capacitance while maintaining structural simplicity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Volume of moving object

If device size is reduced to increase device density, then chip size decreases, but base-to-collector capacitance increases due to closer proximity

Engineering Contradiction:

Improvedevice footprintVSAvoidbase-to-collector capacitance

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent enables miniaturization by utilizing horizontal space instead of vertical overlap. The extrinsic base is displaced horizontally, allowing the device footprint to be reduced in the vertical dimension while maintaining adequate separation from the collector to minimize capacitance.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 horizontal displacement of the base from the collector reduces base-to-collector capacitance and allows for a smaller footprint, enhancing operational reliability and enabling higher device densities and smaller chip sizes while maintaining performance.

Implementation Method 1

the TI is vertically between the sub-collector and the second portion of the base to define a capacitive coupling between the sub-collector and the second portion of the base

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS11728380B2Bipolar transistor with base horizontally displaced from collector

Publication Date: 2023.08.15 GLOBALFOUNDRIES US INC

AI summary

Aspects of the disclosure provide a bipolar transistor structure with a sub-collector on a substrate, a first collector region on a first portion of the sub-collector, a trench isolation (TI) on a second portion of the sub-collector and adjacent the first collector region, and a second collector region on a third portion of the sub-collector and adjacent the TI. A base on first collector region and a portion of the TI. An emitter is on a first portion of the base above the first collector region. The base includes a second portion horizontally displaced from the emitter in a first horizontal direction, and horizontally displaced from the second collector region in a second horizontal direction orthogonal to the first horizontal direction.