Stress Release Metal Electrodes for Semiconductor Devices

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Solution Overview

Problem

The large difference in thermal expansion coefficients between metal electrodes and semiconductor materials in transistors leads to significant strain and stresses during fabrication and operation, causing microscopic defects and performance degradation in devices.

Innovation Solution

Incorporating stress release sections in metal electrodes with cavities to distribute and absorb induced stresses, reducing the unwanted strain on semiconductor layers through slight deformation of these sections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metal electrodes with standard continuous structure are used, then good electrical conductivity and adhesion are achieved, but significant thermal expansion stresses are induced in semiconductor layers during fabrication and operation

Engineering Contradiction:

Improvedevice reliabilityVSAvoidthermal expansion stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The metal electrode is divided into multiple discrete sections separated by gaps, allowing each section to expand and contract independently during thermal cycles, thereby reducing cumulative stress on the semiconductor layers while maintaining electrical connectivity through the segmented structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure transitions from uniform continuous design to non-uniform segmented design, where specific regions (gap locations) are modified to have different mechanical properties, enabling stress concentration in benign areas while protecting critical semiconductor interfaces

Inventive Principle:

Principle #3Local quality

2Reliability

If metal electrodes are deposited to ensure low resistance and good adhesion, then electrical performance is improved, but the large thermal expansion coefficient difference causes severe stress during temperature changes

Engineering Contradiction:

Improveelectrical performanceVSAvoidthermal stress

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The continuous metal electrode is segmented into discrete sections with gaps between them, allowing independent thermal expansion of each segment while maintaining overall electrical conductivity, thus reducing stress on semiconductor layers during temperature variations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure parameters are modified by introducing gaps that change the thermal expansion behavior from collective to individual segment expansion, reducing the overall stress impact on underlying semiconductor layers while preserving low resistance characteristics

Inventive Principle:

Principle #35Parameter changes

3Power

If high power density is used in power devices, then power handling capability is improved, but elevated temperatures cause more severe stress and defect formation in semiconductor channels

Engineering Contradiction:

Improvepower handling capabilityVSAvoidchannel temperature

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The metal electrode is segmented into multiple sections separated by gaps, allowing each section to independently accommodate thermal expansion at elevated temperatures, thereby reducing stress concentration in semiconductor channels during high power operation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The segmented electrode structure pre-accommodates thermal expansion stresses through the gap spaces before they can transfer to the semiconductor layers, providing stress cushioning that protects against defect formation during high temperature operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 introduction of stress release sections effectively reduces the induction of stresses in semiconductor layers, minimizing defects and improving the reliability and longevity of transistors.

Implementation Method 1

a portion of the stresses to be induced in the semiconductor layers will be distributed to the stress release sections and absorbed by them through slight deformation of the stress release sections

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

Due to the large difference in the thermal expansion coefficients between epitaxial materials and metal electrodes, significant strain and stresses can be induced in the devices during the fabrication and operation

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9276131B2Stress release structures for metal electrodes of semiconductor devices

Publication Date: 2016.03.01 SHIH ISHIANG

AI summary

This invention teaches stress release metal electrodes for gate, drain and source in a field effect transistor and stress release metal electrodes for emitter, base and collector in a bipolar transistor. Due to the large difference in the thermal expansion coefficients between semiconductor materials and metal electrodes, significant strain and stresses can be induced in the devices during the fabrication and operation. The present invention provides metal electrode with stress release structures to reduce the strain and stresses in these devices.