SiC Wafer Peel-Off Detection via Laser and Ultrasonic Separation

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Solution Overview

Problem

The existing methods for producing wafers from hexagonal single-crystal ingots are inefficient due to difficulties in peeling and determining the completion of peeling, leading to high waste and low productivity, especially with hexagonal single-crystal SiC ingots which are hard and expensive to work with.

Innovation Solution

A method involving a laser beam to form a peel-off layer within the ingot, combined with ultrasonic waves to break the layer and an image capturing unit to detect the peeling process, allowing for easy wafer separation and confirmation of completion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a laser beam is used to form a peel-off layer in hexagonal single-crystal SiC ingot, then wafer separation becomes easier, but it becomes difficult to determine when peeling is completed

Engineering Contradiction:

Improvewafer separationVSAvoidpeeling completion detection

Core Design Contradiction:

Ease of manufactureVSDifficulty of detecting and measuring

Solution Approach 1:

The patent utilizes optical reflection characteristics to detect peeling completion. The image capturing unit detects changes in reflected light from the ingot surface, which change as the wafer is peeled away. This allows automatic detection of peeling completion without direct visual observation of the peeling front.

Inventive Principle:

Principle #32Color changes

Solution Approach 2:

The patent introduces an image capturing unit and control system as intermediaries to detect peeling completion. Instead of directly observing the peeling process, the system uses optical fields and electronic signal processing to indirectly detect when peeling is complete, solving the detection difficulty.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If traditional wire saw cutting is used on hexagonal single-crystal SiC ingot, then wafer production is possible, but productivity is low and material waste is high (70-80% waste)

Engineering Contradiction:

Improvewafer production efficiencyVSAvoidingot material waste

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The patent replaces the mechanical wire saw cutting system with a laser-based peel-off system. The laser forms a peel-off layer through thermal processing, and ultrasonic waves separate the wafer, eliminating the need for mechanical cutting and dramatically reducing material waste while improving productivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and properties of the ingot material through laser heating. By controlling temperature parameters and creating phase changes in the material structure, the system enables easy wafer separation without mechanical force, solving both productivity and waste issues.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If hexagonal single-crystal SiC ingot is used for wafer production, then high-quality wafers for power devices and LEDs can be produced, but the ingot is hard to work with and expensive

Engineering Contradiction:

Improvewafer qualityVSAvoidprocessing difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces difficult mechanical processing of hard SiC material with laser-based thermal processing and ultrasonic separation. This substitution maintains wafer quality while dramatically easing the manufacturing process by avoiding mechanical cutting of the hard crystal structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables efficient peeling of wafers from hexagonal single-crystal ingots with improved productivity by forming a modified region with isotropic cracks and using ultrasonic waves to break the peel-off layer, while image detection ensures completion, thus reducing waste and increasing efficiency.

Implementation Method 1

forming a peel-off layer in the hexagonal single-crystal ingot by applying a laser beam having a wavelength transmittable through the hexagonal single-crystal ingot while positioning a focal point of the laser beam in the hexagonal single-crystal ingot

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

generating ultrasonic waves from an ultrasonic wave generating unit positioned in facing relation to the wafer to be produced across a water layer interposed therebetween, thereby to break the peel-off layer

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Data Source

PatentUS11114307B2Method of producing a wafer from an ingot including a peel-off detecting step

Publication Date: 2021.09.07 DISCO CORP

AI summary

A method of producing a wafer includes a peel-off layer forming step to form a peel-off layer in a hexagonal single-crystal ingot by applying a laser beam having a wavelength transmittable through the hexagonal single-crystal ingot while positioning a focal point of the laser beam in the hexagonal single-crystal ingot at a depth corresponding to the thickness of a wafer to be produced from an end face of the hexagonal single-crystal ingot, an ultrasonic wave generating step to generate ultrasonic waves from an ultrasonic wave generating unit positioned in facing relation to the wafer to be produced across a water layer interposed therebetween, thereby to break the peel-off layer, and a peel-off detecting step to detect when the wafer to be produced is peeled off the hexagonal single-crystal ingot by positioning an image capturing unit sideways of the wafer to be produced.