Amorphous Silicon Laser Separation for SiC Substrate Handling

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Solution Overview

Problem

Existing methods for manufacturing semiconductor substrates face challenges such as substrate warping, cracking, and contamination due to the use of adhesives with low heat resistance, especially when handling SiC substrates, which require high-temperature treatments and are prone to defects from exposure to acids, alkalis, or plasmas during processing.

Innovation Solution

A method involving bonding a supporting plate to a semiconductor substrate using an amorphous silicon intermediate layer, which absorbs laser energy to fracture and separate from the substrate, allowing for high-temperature processing and preventing substrate cracking, while using a vacuum environment to prevent surface oxidation and using ion or atomic beams to clean and activate bonding surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thin semiconductor substrate is used to reduce drift layer thickness and achieve high breakdown voltage, then the on-voltage and forward voltage drop are reduced, but the substrate becomes more prone to warping, cracking, and chipping due to low mechanical strength

Engineering Contradiction:

Improvebreakdown voltageVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

A supporting plate is bonded to the semiconductor substrate to serve as an intermediary that provides mechanical strength and prevents warping, cracking, and chipping during handling and processing, while allowing the substrate to maintain its thin profile for electrical performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The substrate handling process is segmented into stages: bonding to supporting plate for mechanical support during processing, then separation after device fabrication to achieve the final thin substrate structure

Inventive Principle:

Principle #1Segmentation

2Strength

If adhesive materials are used to bond the supporting plate to the semiconductor substrate, then the substrate mechanical strength is improved, but the adhesive may melt, contaminate surrounding areas, or cause chemical changes that prevent separation when exposed to high temperatures

Engineering Contradiction:

Improvemechanical strengthVSAvoidcontamination and separation failure

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The bonding method uses a sacrificial bonding approach where the bond between supporting plate and substrate is intentionally designed to be breakable through laser irradiation, allowing clean separation after the supporting plate has served its protective function

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The bonding and separation process replaces traditional mechanical or chemical adhesive systems with a laser-based separation mechanism, where laser irradiation at specific wavelengths breaks the bond between supporting plate and substrate without affecting the substrate or device

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If conventional bonding methods are used with adhesives, then the substrate can be reinforced, but the adhesive layer may form voids, melt, or undergo chemical changes during high-temperature heat treatment

Engineering Contradiction:

Improvemechanical strengthVSAvoidbonding integrity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 method enhances the mechanical strength of semiconductor substrates, prevents cracking, and allows for high-temperature processing without substrate contamination, improving manufacturing efficiency and yield by using a vacuum and laser separation technique with a suitable wavelength for the substrate materials.

Implementation Method 1

after the laser light is radiated from a side of the supporting plate and the intermediate layer absorbs laser energy

Methodology Applied

Scientific EffectLaser absorption: Absorption (EM radiation)

Data Source

PatentUS9779968B2Method for processing semiconductor substrate and method for manufacturing semiconductor device in which said processing method is used

Publication Date: 2017.10.03 FUJI ELECTRIC CO LTD

AI summary

Provided are a method of processing a semiconductor substrate and a method of manufacturing a semiconductor device that uses this method of processing. The method of processing the semiconductor substrate includes: a bonding step in which a supporting plate, which is composed primarily of a material that substantially transmits laser light of prescribed wavelength, and a principal surface of a semiconductor substrate, which is composed primarily of a material that substantially transmits the laser light of the prescribed wavelength, are arranged to face each other in a vacuum and then pressed together in the vacuum with an intermediate layer that includes an amorphous silicon layer interposed therebetween; and a separating step in which, after the laser light is radiated from a side of the supporting plate and the intermediate layer absorbs laser energy, the semiconductor substrate and the supporting plate are separated from each other.