SiC Semiconductor Device Resin Detachment Prevention

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Solution Overview

Problem

Silicon carbide semiconductor devices face challenges with resin detachment due to thermal expansion mismatch between the silicon carbide substrate and the resin, leading to stress and cracking, especially under temperature cycling, which is exacerbated by the difficulty in extending a stress buffer layer like polyimide to the outer peripheral end portions during wafer dicing.

Innovation Solution

A silicon carbide semiconductor device configuration that includes a silicon carbide substrate with a first and second insulating film, where the second insulating film has a lower Young's modulus than the resin and a higher thermal expansion coefficient than both the silicon carbide substrate and resin, with specific end portions and angular shoulders to distribute stress and prevent resin detachment, and the use of laser cutting to form the stress buffer layer without clogging diamond blades.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a resin is used to cover the silicon carbide semiconductor chip, then the chip is protected and packaged, but thermal expansion mismatch causes stress and resin detachment

Engineering Contradiction:

Improvechip protection and packagingVSAvoidthermal expansion mismatch stress

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A stress buffer layer (second insulating film) is introduced as an intermediary between the silicon carbide substrate and the resin. This intermediate layer has a thermal expansion coefficient higher than that of the silicon carbide substrate and higher than that of the resin, serving as a thermal expansion buffer that absorbs stress during temperature cycling, thereby preventing resin detachment while maintaining protective packaging functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a stress buffer layer like polyimide is extended to the outer peripheral end portions, then stress distribution is improved, but diamond blade clogging occurs during wafer dicing

Engineering Contradiction:

Improvestress distributionVSAvoidwafer dicing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Laser cutting is used to replace the mechanical diamond blade dicing process. This substitution eliminates the clogging problem that occurs when diamond blades cut through soft polyimide material at the outer peripheral end portions, while still achieving clean separation of wafers and maintaining the stress buffer layer's stress distribution functionality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If the second insulating film has a lower Young's modulus than the resin, then stress on the resin is reduced, but the film becomes more compliant and harder to control

Engineering Contradiction:

Improvestress on resinVSAvoidfilm compliance control

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The Young's modulus of the second insulating film is specifically controlled to be lower than that of the resin, creating a compliant stress buffer layer that effectively reduces stress on the resin during thermal cycling. This parameter optimization ensures the film is soft enough to absorb thermal expansion stress while maintaining sufficient structural integrity for manufacturing and assembly processes

Inventive Principle:

Principle #35Parameter changes

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 configuration effectively reduces stress on the resin and suppresses detachment, maintaining chip integrity under temperature cycling and high-humidity conditions, and allows for the use of polyimide as a stress buffer layer extending to the outer peripheral surface, enhancing reliability and operational stability.

Implementation Method 1

The second insulating film has a thermal expansion coefficient higher than that of the silicon carbide substrate and higher than that of the resin

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the use of laser cutting to form the stress buffer layer without clogging diamond blades

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS11387156B2Silicon carbide semiconductor device including a resin covering a silicon carbide semiconductor chip

Publication Date: 2022.07.12 MITSUMI ELECTRIC CO LTD

AI summary

The silicon carbide semiconductor chip includes a silicon carbide substrate, a first insulating film on the silicon carbide substrate, and a second insulating film on the first insulating film. The silicon carbide substrate has a first main surface in contact with the first insulating film, a second main surface, and an outer peripheral surface. The resin covers both of the outer peripheral surface and the second insulating film. The second insulating film has a Young's modulus lower than that of the resin. The second insulating film has a thermal expansion coefficient higher than that of the silicon carbide substrate and higher than that of the resin. The second insulating film includes a first outer peripheral end portion. In a cross section perpendicular to the first main surface, the first outer peripheral end portion is provided along the outer peripheral surface.