Masked Laser Wafer Processing for Uniform GaN Modified Layers

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Solution Overview

Problem

Laser processing methods for GaN wafers face challenges due to varying laser beam intensities entering the workpiece through different surfaces, leading to irregular modified layer formation and unexpected crack directions in the outer peripheral area, which affects the quality of the GaN wafers.

Innovation Solution

A laser processing method that adjusts the intensity of the pulsed laser beam using a masking unit, such as a spatial light phase modulator or metal mask, to ensure the beam intensity entering the workpiece via the outer peripheral surface is below the processing threshold, while branching the beam into multiple focused spots for uniform processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a pulsed laser beam is applied to the outer peripheral area of a workpiece, then modified layers can be formed for wafer separation, but the laser beam intensity varies due to different entry paths (face side vs. outer peripheral side surface), causing irregular modified layer formation and unexpected crack directions

Engineering Contradiction:

Improvemodified layer formation uniformityVSAvoidadverse effects from laser beam entering via outer peripheral side surface

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and eliminates the harmful component of the laser beam by using a masking unit to block the portion of the laser beam that enters through the outer peripheral side surface. This selective extraction of the harmful beam path prevents irregular modified layer formation and unexpected cracking while preserving the beneficial modification from face-side entry

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The masking unit serves as an intermediary element positioned between the laser beam source and the workpiece. It selectively blocks the harmful beam path through the outer peripheral side surface while allowing the beneficial beam path through the face side to pass through, thereby mediating the interaction between laser and workpiece to achieve uniform modified layer formation

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the laser beam is applied to form modified layers in the outer peripheral area, then wafer separation can be achieved, but cracks may extend in unexpected directions affecting wafer quality

Engineering Contradiction:

Improvewafer separation reliabilityVSAvoidunexpected crack extension

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by using the masking unit to pre-block the harmful laser beam path before it can cause irregular modified layer formation and unexpected crack extension. This preventive measure ensures that only controlled laser modification occurs through the face side entry, maintaining crack propagation in expected directions and preserving wafer quality

Inventive Principle:

Principle #9Preliminary anti-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 approach reduces adverse effects on the workpiece by maintaining consistent modified layer formation and preventing unexpected cracks, resulting in higher quality GaN wafers with improved mechanical strength and uniformity.

Implementation Method 1

a pulsed laser beam having a wavelength transmittable through a column-shaped or plate-shaped workpiece

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

having adjusted a height of a focused spot of a pulsed laser beam so as to position the focused spot within the workpiece

Methodology Applied

Scientific EffectFocused spot formation: Focusing

Implementation Method 3

masking part of a pulsed laser beam... such that part of the laser beam that enters the workpiece via the outer peripheral side surface has an intensity smaller than a processing threshold value

Methodology Applied

Scientific EffectLight absorption and blocking: Absorption (EM radiation)

Implementation Method 4

the masking unit has a spatial light phase modulator for at least partly modulating the laser beam

Methodology Applied

Scientific EffectPhase modulation: Phase Modulation

Data Source

PatentUS20250001520A1Laser processing method

Publication Date: 2025.01.02 DISCO CORP

AI summary

A laser processing method includes a laser beam applying step of applying, while masking, with a masking unit, part of a pulsed laser beam having a wavelength transmittable through a workpiece such that the part of the laser beam that enters the workpiece via an outer peripheral side surface thereof has an intensity smaller than a processing threshold value of the workpiece, adjusting the height of a focused spot of the laser beam to position the focused spot within the workpiece, and moving the focused spot and the workpiece relatively to each other so as to move the focused spot along an outer peripheral area of the workpiece, thereby forming a modified layer in the workpiece.