GaAs HBT Conductive Layer for Moisture Resistance

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Solution Overview

Problem

Semiconductor devices using compound semiconductors, such as gallium arsenide, face moisture resistance issues due to the degradation of the isolation region in the outer peripheral region when operated, leading to impurity ingress and faulty operation.

Innovation Solution

A semiconductor device with a conductive layer formed in the outer peripheral portion of the chip, set to a reference potential (GND), which prevents the degeneration of the semiconductor layer and subsequent impurity ingress by ensuring adhesion between the conductive layer and protective films.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the isolation region is formed in the outer peripheral region of the semiconductor chip, then the transistors are isolated from each other, but the isolation region degrades when operated, leading to impurity ingress and faulty operation

Engineering Contradiction:

Improvemoisture resistanceVSAvoidintegrity of isolation region

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The outer peripheral region is segmented into two functional zones: an inner region with the isolation region for transistor isolation, and an outer region with the conductive layer for moisture protection. This segmentation allows each zone to perform its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The conductive layer acts as an intermediary protective barrier between the external environment (moisture, impurities) and the semiconductor chip structures. It mediates the protection function by maintaining adhesion with protective films and preventing impurity ingress to the isolation region.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If voltage is applied during operation, then the semiconductor device functions, but the isolation region degrades faster, causing impurity entry

Engineering Contradiction:

Improveoperational functionalityVSAvoidresistance to impurity ingress

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The conductive layer is formed in advance during manufacturing, before the device operates. It is preliminarily positioned to cover the outer peripheral region and establish adhesion with protective films, creating a pre-established defense mechanism against impurity ingress during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The conductive layer provides beforehand cushioning protection by being positioned in the outer peripheral region to absorb or block the harmful effects of moisture and impurities before they can reach and degrade the isolation region during voltage application.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the conductive layer is formed in the outer peripheral portion and set to reference potential, then moisture resistance is enhanced, but the device complexity increases

Engineering Contradiction:

Improvemoisture resistanceVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive layer performs multiple functions simultaneously: it serves as an electrode connected to reference potential, acts as a protective barrier against moisture and impurities, and maintains adhesion with protective films. This multi-functionality reduces the need for separate protective structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The conductive layer is formed with uniform material properties and continuous coverage in the outer peripheral region, creating a homogeneous protective structure that simplifies manufacturing and ensures consistent protection without requiring complex heterogeneous structures.

Inventive Principle:

Principle #33Homogeneity

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 effectively enhances moisture resistance by maintaining the integrity of the semiconductor chip and preventing impurity entry, even under specified temperature and humidity conditions with applied voltage.

Implementation Method 1

ensuring adhesion between the conductive layer and protective films

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

preventing impurity entry

Methodology Applied

Scientific EffectPhysical barrier: Physical Containment

Data Source

PatentUS7723753B2Semiconductor device and manufacturing method of the same

Publication Date: 2010.05.25 MURATA MFG CO LTD

AI summary

In a GaAs substrate as a semi-insulating substrate, a heterojunction bipolar transistor (HBT) is formed in an element formation region, while an isolation region is formed in an insulating region. The isolation region formed in the insulating region is formed by introducing helium into the same semiconductor layers as the sub-collector semiconductor layer and collector semiconductor layer of the HBT. In an outer peripheral region, a conductive layer is formed to be exposed from protective films and coupled to a back surface electrode. Because a GND potential is supplied to the back surface electrode, the conductive layer is fixed to the GND potential. The conductive layer is formed of the same semiconductor layers as the sub-collector semiconductor layer and collector semiconductor layer of the HBT.