Laser Wafer Slicing Hexagonal Ingot Separation

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Solution Overview

Problem

The existing methods for slicing hexagonal single crystal ingots, such as those made of SiC or GaN, are inefficient, leading to high material wastage and reduced productivity due to the difficulty in cutting these hard materials with wire saws, and previous laser-based techniques do not adequately improve productivity despite using small laser beam pitches.

Innovation Solution

A wafer producing method that involves setting the focal point of a laser beam at a predetermined depth within the ingot, forming a modified layer parallel to the surface and cracks along the c-plane, and using an alternating scanning pattern to create a separation start point, allowing for efficient separation of wafers with reduced material loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If wire saw is used to slice hexagonal single crystal ingot, then wafer can be produced, but 70 to 80% of the ingot is discarded causing poor economy and low productivity

Engineering Contradiction:

Improveingot wastageVSAvoidwafer production efficiency

Core Design Contradiction:

Loss of substanceVSProductivity

Solution Approach 1:

The patent replaces the mechanical wire saw cutting system with a laser-based processing system. The laser beam forms a modified layer and induces cracks along the c-plane within the ingot, enabling separation without mechanical contact. This substitution eliminates the need for extensive material removal and allows precise cutting along crystallographic planes, dramatically reducing ingot wastage from 70-80% to approximately 30% while improving productivity through faster processing.

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 irradiation. By controlling laser parameters (power, scanning speed, focal depth), a modified layer is formed at a predetermined depth, and subsequent thermal stress induces cracks along the c-plane. This parameter-controlled transformation enables precise separation with minimal material loss and reduced processing time compared to mechanical cutting.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If wire saw is used to cut hexagonal single crystal ingot, then wafer can be sliced, but considerable time is required due to high Mohs hardness causing reduced productivity

Engineering Contradiction:

Improvewafer production efficiencyVSAvoidcutting time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs periodic laser scanning to form the modified layer and induce cracks. The laser beam scans along a predetermined path, creating periodic modifications that coalesce to form continuous separation planes. This periodic action allows efficient processing of the entire ingot surface while maintaining precise control over the separation geometry, reducing overall processing time.

Inventive Principle:

Principle #19Periodic action

3Manufacturing precision

If laser beam is scanned with small pitch (1 to 10 μm) to form modified layer and cracks, then separation can be achieved, but productivity improvement is insufficient due to extensive scanning required

Engineering Contradiction:

Improveseparation precisionVSAvoidwafer production efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies laser irradiation with specific local quality control, focusing the beam at a predetermined depth to create a modified layer only where needed. The scanning pitch and pattern are optimized to create cracks along the c-plane with sufficient precision for separation, without requiring excessive overlap. This localized processing approach achieves the necessary manufacturing precision while minimizing the total scanning time and improving productivity.

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 method significantly improves productivity by properly forming modified layers and cracks, reducing ingot wastage to about 30% and enhancing the efficiency of wafer production from hexagonal single crystal ingots.

Implementation Method 1

applying the laser beam to the first surface as relatively moving the focal point and the ingot to thereby form a modified layer parallel to the first surface

Methodology Applied

Scientific EffectLaser melting and resolidification: Melting

Implementation Method 2

form a modified layer parallel to the first surface and cracks extending from the modified layer along the c-plane

Methodology Applied

Scientific EffectThermal stress cracking: Thermal Shock

Data Source

PatentUS10076804B2Wafer producing method

Publication Date: 2018.09.18 DISCO CORP

AI summary

A crystal wafer is produced from a hexagonal crystal ingot. A separation start point is formed by setting the focal point of a laser beam inside the ingot at a predetermined depth, which depth corresponds to the thickness of the wafer to be produced. The laser beam is applied to the upper surface of the ingot while relatively moving the focal point and the ingot to form a modified layer parallel to the upper surface of the ingot and cracks extending from the modified layer along a c-plane in the ingot, thus forming the separation start point. First the laser beam is scanned from a scanning start point to a scanning end point on the ingot. Then the laser beam is scanned from the scanning end point to the scanning start point. The first and second steps are alternately repeated to separate the cracks from the modified layer.