SiC Wafer Production via Laser-Detected Feed Direction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing methods for producing wafers from single-crystal SiC ingots are inefficient due to high material wastage and difficulty in slicing, leading to poor productivity and high costs.

Innovation Solution

A method involving a processing feed direction detecting step to determine the optimal direction for laser beam irradiation, forming reduced strength areas, and peeling planes to efficiently produce wafers with minimal material loss, using a laser processing apparatus to create modified layers and cracks that allow for precise wafer peeling from the SiC ingot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a wire saw is used to slice an SiC ingot into wafers, then wafers can be produced, but productivity is poor and costs are high due to the difficulty of slicing hard material

Engineering Contradiction:

Improvewafer production productivityVSAvoidease of slicing SiC ingot

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical wire saw slicing system with a laser-based system. A laser beam is used to irradiate the SiC ingot, forming modified layers and reduced strength areas without mechanical contact. This substitution eliminates the difficulty of mechanically slicing hard SiC material while maintaining wafer production capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and properties of the SiC ingot through laser irradiation. By controlling laser parameters (wavelength, power, scanning speed, focal depth), the ingot material undergoes transformation to form modified layers with reduced strength, enabling easy peeling into wafers without mechanical force.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If a wire saw slicing method is used, then wafers can be produced, but 70%-80% of the ingot must be thrown away leading to high material wastage

Engineering Contradiction:

Improvematerial utilization efficiencyVSAvoidingot material wastage

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The laser irradiation is applied locally and selectively to specific regions of the SiC ingot where wafers need to be produced. The modified layers and reduced strength areas are formed only in the necessary locations, preserving the rest of the ingot material for subsequent wafer production, thereby minimizing waste.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The laser preprocessing steps (forming modified layers and reduced strength areas) are performed in advance before wafer separation. This preliminary action prepares the material structure to enable easy peeling and maximizes the usable portion of the ingot, reducing the need to discard material.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If multiple adjacent modified layers are formed in the SiC ingot, then wafers can be produced, but productivity remains poor due to the time-consuming process

Engineering Contradiction:

Improvewafer production speedVSAvoidtime for forming multiple modified layers

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The laser beam continuously irradiates the SiC ingot while scanning through it, forming multiple modified layers and reduced strength areas in a single continuous operation. This eliminates the need for repeated positioning and processing steps, significantly reducing the time required to produce multiple wafers.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The laser processing is performed periodically at predetermined intervals to form multiple peeling planes at different depths. By optimizing the interval and depth spacing, multiple wafers can be prepared in sequence without stopping the laser, improving overall production efficiency.

Inventive Principle:

Principle #19Periodic action

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 wafer production productivity by reducing material wastage and enabling efficient peeling of wafers with desired thickness, enhancing the overall efficiency of the wafer production process from single-crystal SiC ingots.

Implementation Method 1

irradiating the cylindrical single-crystal SiC ingot with a laser beam having a wavelength that transmits SiC, thereby forming a straight reduced strength area made up of a modified layer parallel to the circular upper surface and cracks extending from the modified layer along the c-plane

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS10406635B2Wafer producing method and processing feed direction detecting method

Publication Date: 2019.09.10 DISCO CORP

AI summary

A wafer is produced from an ingot by confirming whether or not an inclined c-axis of the ingot and a second orientation flat of the ingot are perpendicular to each other, and detecting a processing feed direction perpendicular to the direction in which the c-axis is inclined. The method includes performing sampling irradiation of the ingot with a laser beam, along a direction parallel to the second orientation flat and a plurality of directions inclined clockwise and counterclockwise by respective predetermined angles from the second orientation flat, thereby forming a plurality of sampled reduced strength areas in the ingot; measuring the number of nodes which exist per unit length on each of the sampled reduced strength areas, and determining a direction in which the sampled reduced strength area where the measured number of nodes is zero extends as a processing feed direction.