Semiconductor Wafer Laser Cleaving via Boundary Crack Propagation

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Solution Overview

Problem

Current laser processing methods for semiconductor wafers are inefficient in terms of processing time and result in uneven cut surfaces, with significant laser irradiation effects on the workpiece.

Innovation Solution

A laser processing method that forms modified spot rows in a second region of the workpiece, intersecting the boundary with a first region, to create cracks extending from the second region to the first region, thereby reducing processing time and improving surface flatness while minimizing laser irradiation impact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If modified spots are formed in the first region to create cracks, then the crack formation is direct, but the processing time is extended and the cut surface flatness deteriorates

Engineering Contradiction:

Improveprocessing timeVSAvoidcut surface flatness

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

Instead of forming modified spots directly in the first region to create cracks, the patent inverts the approach by forming modified spots in the second region. This indirect method allows cracks to propagate from the second region into the first region, achieving both shorter processing time and better cut surface flatness by avoiding direct laser irradiation in the critical first region.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The second region acts as an intermediary zone that facilitates crack formation without directly impacting the first region. By forming modified spots in this intermediate area, the patent enables crack propagation into the first region while maintaining the integrity and flatness of the cut surface in the device-containing area.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If laser light is irradiated extensively to ensure complete crack formation, then crack coverage is improved, but the influence of laser irradiation on the work piece increases

Engineering Contradiction:

Improvecrack formation completenessVSAvoidlaser irradiation influence

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by differentiating the treatment of different regions. The second region receives laser irradiation to form modified spots and initiate cracks, while the first region containing devices is spared from direct irradiation. This localized approach ensures complete crack formation where needed while minimizing harmful laser effects on sensitive components.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If modified spot rows are arranged parallel to the boundary, then the arrangement is simple, but the crack extension from second region to first region is less effective

Engineering Contradiction:

Improvemodified spot row arrangementVSAvoidcrack extension efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent employs asymmetric arrangement of modified spot rows relative to the boundary between first and second regions. By positioning and orienting the modified spot rows at specific angles or positions within the second region rather than symmetrically parallel to the boundary, the crack propagation is directed more effectively into the first region, improving crack extension efficiency while maintaining manufacturing simplicity.

Inventive Principle:

Principle #4Asymmetry

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 significantly shortens processing time, enhances the flatness of the cut surface, and reduces the influence of laser irradiation on the workpiece, particularly on device portions.

Implementation Method 1

a plurality of modified spots along the imaginary plane inside the work piece are formed by irradiating an inside of the work piece with laser light from the surface

Methodology Applied

Scientific EffectLaser irradiation: Laser

Implementation Method 2

irradiating an inside of the work piece with laser light from the surface

Methodology Applied

Scientific EffectOptical energy absorption: Absorption (EM radiation)

Implementation Method 3

a plurality of modified spot rows formed of the plurality of modified spots arranged along a boundary between the first region and the second region are formed in the second region

Methodology Applied

Scientific EffectStress concentration:

Implementation Method 4

a crack extending from the second region to the first region is formed by forming the plurality of modified spot rows

Methodology Applied

Scientific EffectCrack propagation: Fracture Mechanics

Data Source

PatentUS20230405725A1Laser processing method, semiconductor device manufacturing method, and laser processing device

Publication Date: 2023.12.21 HAMAMATSU PHOTONICS KK

AI summary

A laser processing method includes: a forming step of forming a plurality of modified spots along an imaginary plane inside a work piece by irradiating an inside of the work piece with laser light from a surface. The work piece includes a first region and second region when viewed in a direction perpendicular to the surface. In the forming step, a plurality of modified spot rows formed of the plurality of modified spots arranged along a boundary between the first region and the second region are formed in the second region, the plurality of modified spot rows being arranged along a direction intersecting an arrangement direction of the plurality of modified spots, and a crack extending from the second region to the first region is formed by forming the plurality of modified spot rows.