SiC Semiconductor Device Side Wall Passivation

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Solution Overview

Problem

Electric discharges occur during the evaluation of electrical properties in silicon carbide semiconductor devices due to electric field concentration and exposure of side surfaces after segmentation into chips, as the conventional passivation film does not cover the side walls, leading to increased risk of discharge during chip testing.

Innovation Solution

A method involving the formation of a groove on the silicon carbide semiconductor substrate to a depth that covers the epitaxial layer, followed by the application of a polyimide insulating film to cover the electrode ends and side surfaces, preventing exposure and thus suppressing electric discharges during chip testing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the polyimide passivation film is formed only on the surface without covering side walls, then the manufacturing process is simple, but electric discharges occur during chip testing due to exposed side surfaces

Engineering Contradiction:

Improveelectric discharge preventionVSAvoidpassivation film structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The passivation film is extended from the traditional two-dimensional surface coverage to three-dimensional coverage including side walls. The groove structure allows the polyimide film to wrap around and cover the side surfaces of the semiconductor substrate, transitioning from planar to volumetric protection against electric discharge.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The groove is formed on the substrate surface before applying the polyimide passivation film. This preliminary structural preparation ensures that when the film is deposited, it automatically conforms to and covers the side walls within the groove, preventing electric discharge at critical locations before testing occurs.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the polyimide film is applied to cover side surfaces within grooves, then electric discharge is suppressed, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvechip testing reliabilityVSAvoidpassivation film formation

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The substrate surface is segmented by forming grooves that create distinct regions. The polyimide film is then applied to specifically cover the side walls within these segmented groove regions, allowing selective passivation where needed while maintaining manufacturing efficiency through standardized groove patterns.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The groove depth and width parameters are optimized to ensure the polyimide film can effectively cover the side walls. By controlling the geometric parameters of the groove structure, the process balances between achieving sufficient side wall coverage for discharge prevention and maintaining ease of manufacture through achievable dimensional specifications.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If the polyimide film coverage is extended to side surfaces, then moisture absorption is reduced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvemoisture absorptionVSAvoidgroove depth and film coverage

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The groove structure acts as an intermediary form that guides the polyimide film deposition. Rather than requiring direct precise control of film thickness on vertical side walls, the groove geometry serves as a template that naturally channels the film material to cover the side surfaces, reducing the precision demands on the deposition process itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The groove structure is formed beforehand to provide a protective cushioning geometry. This pre-formed structure ensures that even with variations in polyimide film deposition, the side walls within the groove remain covered, providing a margin of error that cushions against manufacturing precision variations and ensures consistent moisture protection.

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 solution effectively prevents electric discharges by covering the side surfaces with the polyimide film, enhancing the reliability of silicon carbide semiconductor devices and improving mass productivity by ensuring the polyimide film can be formed efficiently within the groove, reducing the risk of moisture absorption and maintaining breakdown voltage properties.

Implementation Method 1

an insulating film formed by covering at least an end of the electrode and an end and a side surface of the epitaxial layer

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS9263525B2Silicon carbide semiconductor device and manufacturing method thereof

Publication Date: 2016.02.16 MITSUBISHI ELECTRIC CORP

AI summary

The present invention includes an n+ type substrate, a drift epitaxial layer formed on the n+ type substrate and having a lower concentration of impurity than the n+ type substrate, a Schottky electrode formed on the drift epitaxial layer, and a PI formed as an insulating film by covering at least an end of the Schottky electrode and an end and a side surface of the drift epitaxial layer.