Semiconductor Insulating Film Roughness for Thermal Stress Reliability

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Solution Overview

Problem

The increase in current density of semiconductor devices leads to higher operating temperatures, causing thermal stress that can result in detachment or cracking of the protection insulating film due to differences in linear expansion coefficients, compromising insulation properties and reliability.

Innovation Solution

The semiconductor device is configured with an insulating film having a smaller arithmetic average roughness on its upper surface compared to the interface with the electrode layer, featuring corners and a concave edge design to enhance connection stability under thermal stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the current density of the semiconductor device is increased to downsize the device and reduce manufacturing cost, then the device size and cost are improved, but the temperature difference between operation and non-operation states increases causing thermal stress that leads to detachment or cracking of the protection insulating film

Engineering Contradiction:

Improvedevice sizeVSAvoidinsulating film integrity

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent applies local quality by creating different roughness characteristics at different locations of the insulating film. The lower surface (interface with electrode layer) has higher roughness to enhance mechanical interlocking and connection rigidity, while the upper surface has lower roughness to maintain smooth insulation. This localized differentiation of surface properties allows the insulating film to simultaneously achieve strong attachment at the interface and reliable insulation at the upper surface, preventing detachment and cracking under thermal stress while maintaining the downsized device structure.

Inventive Principle:

Principle #3Local quality

2Productivity

If the current density is increased to reduce device size, then productivity and cost are improved, but thermal expansion stress causes detachment of the protection insulating film compromising reliability

Engineering Contradiction:

Improvemanufacturing cost efficiencyVSAvoidconnection stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies parameter changes by modifying the surface roughness parameter of the insulating film at different locations. By controlling the arithmetic average roughness (Ra) values - setting the lower surface Ra to be higher than the upper surface Ra - the patent changes the physical parameters of the insulating film to achieve both reliable connection and insulation. This parameter optimization allows the device to maintain high current density operation with improved connection stability, preventing thermal stress-induced detachment while preserving the cost-effective downsized design.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the protection insulating film is used to ensure insulation properties, then electrical insulation is improved, but thermal stress from temperature differences causes cracking and detachment reducing reliability

Engineering Contradiction:

Improveinsulation propertiesVSAvoidresistance to thermal stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by differentiating the surface roughness of the insulating film between its upper and lower surfaces. The lower surface (interface with electrode layer) has higher roughness to provide strong mechanical interlocking and resistance to thermal stress-induced detachment, while the upper surface has lower roughness to maintain smooth electrical insulation properties. This localized differentiation allows the insulating film to simultaneously achieve both functions - strong thermal stress resistance at the interface and effective electrical insulation at the upper surface - preventing cracking and maintaining reliability under operational thermal cycling.

Inventive Principle:

Principle #3Local quality

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

This configuration enhances the rigidity of the connection between the insulating film and the electrode, reducing detachment and cracking, thereby improving the reliability of the semiconductor device.

Implementation Method 1

stress due to thermal expansion and thermal shrinkage caused by a difference of a linear expansion coefficient of each constituent element from an electrode layer or a mold resin surrounding the protection insulating film

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

Methodology Applied

Scientific EffectThermal shrinkage: Thermal Contraction

Data Source

PatentUS20250273527A1Semiconductor device, power conversion apparatus, and method of manufacturing semiconductor device

Publication Date: 2025.08.28 MITSUBISHI ELECTRIC CORP

AI summary

A technique disclosed in the specification of the present application is a technique for increasing reliability of a semiconductor device. A semiconductor device relating to a technique disclosed in the specification of the present application includes: a semiconductor layer; a first electrode layer covering a part of an upper surface of the semiconductor layer; and an insulating film covering another part of the upper surface of the semiconductor layer and a part of an upper surface of the first electrode layer. An arithmetic average roughness of an upper surface of the insulating film is smaller than an 10 arithmetic average roughness of an interface between the insulating film and the first electrode layer.