Bipolar Junction Transistor Layout with Segmented Base

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional BJT devices have poor performance due to high emitter series resistance and low current conduction capability, primarily because the emitter is smaller than the base, leading to increased base leakage current and limited current gain β, which cannot be improved without violating design rules.

Innovation Solution

The BJT layout structure features a collector-base arrangement at two adjacent sides of the emitter, with the base area reduced and the emitter positioned between collectors, utilizing fin structures and epitaxial layers to enhance current conduction and lower contact resistance, thereby increasing current gain β without violating design rules.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the base area is reduced to increase current gain β, then the current gain β increases, but the base area becomes too small which may violate design rules and limit further improvement

Engineering Contradiction:

Improvecurrent gain βVSAvoidbase area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The base is segmented into multiple regions (first base region, second base region, third base region) with different doping concentrations and geometries. This segmentation allows different parts of the base to serve different functions: the first base region provides low resistance contact, the second base region enables efficient carrier injection, and the third base region maintains proper spacing. This resolves the contradiction by allowing the base area to be sufficiently large to satisfy design rules while still achieving high current gain through optimized regional structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the base are assigned different local qualities through varying doping concentrations and geometries. The first base region has higher doping concentration for low resistance, while the second base region has optimized doping for carrier injection efficiency. This local quality differentiation allows the base to simultaneously satisfy design rule requirements for minimum area while achieving high current gain through optimized local structures.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the emitter is made smaller than the base to follow conventional design, then the layout is simple, but the emitter series resistance increases and current conduction capability decreases

Engineering Contradiction:

Improvelayout simplicityVSAvoidemitter series resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The conventional design rule that emitter area should be smaller than base area is inverted. In this invention, the emitter area is designed to be larger than the base area, which fundamentally changes the current conduction path. This inversion allows the emitter to provide sufficient current conduction capability and low series resistance while the base remains optimized for carrier injection, thereby improving reliability without complicating the layout.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If the collector area is increased to improve current gain β, then the current gain β increases, but the device area increases which may violate design rules

Engineering Contradiction:

Improvecurrent gain βVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The collector structure transitions from a planar two-dimensional layout to a three-dimensional vertical structure with multiple tiers. The first collector tier is positioned adjacent to the emitter in the planar direction, while the second collector tier extends in the vertical direction above the first tier. This dimensional change allows the collector area to be effectively increased for higher current gain without proportionally increasing the planar device footprint, thus satisfying design rules.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Reliability

If the base width is reduced to increase current gain β, then the current gain β increases, but the base becomes too thin which may cause manufacturing difficulties

Engineering Contradiction:

Improvecurrent gain βVSAvoidbase width control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The base is segmented into multiple regions with different effective widths and doping concentrations. The first base region provides a wider effective area for low resistance contact, while the second base region has optimized width for carrier injection. This segmentation allows the base to have sufficient width in critical regions for manufacturability while maintaining narrow dimensions in injection regions for high current gain, thereby resolving the contradiction between reliability and manufacturing precision.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9899502B2Bipolar junction transistor layout structure

Publication Date: 2018.02.20 UNITED MICROELECTRONICS CORP

AI summary

A bipolar junction transistor layout structure includes a first emitter including a pair of first sides and a pair of second sides, a pair of collectors disposed at the first sides of the first emitter, and a pair of bases disposed at the second sides of the first emitter. The first sides are perpendicular to the second sides. The first emitter is disposed in between the pair of collectors and in between the pair of bases.