Laser Processing Inspection Using Light Transmission Imaging

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Solution Overview

Problem

The result of laser processing on semiconductor wafers is difficult to determine objectively due to variability in laser beam spot diameter and optical element alignment, relying heavily on operator experience and skill for evaluation.

Innovation Solution

A method using a chuck table with light-emitting bodies and an image capturing unit to apply a laser beam to the workpiece, capture images, detect unprocessed regions, and determine if the processing is acceptable based on the ratio of unprocessed areas to the total length, allowing for quantitative assessment and adjustment of the laser processing apparatus.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If visual inspection by operator is used to determine processing quality, then the evaluation can be performed without additional equipment, but the evaluation criteria become indefinite and dependent on operator experience and skill

Engineering Contradiction:

Improveinspection equipmentVSAvoidprocessing quality evaluation

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical/visual inspection system with an optical detection system. Light-emitting bodies illuminate the workpiece, and an image capturing unit detects light transmission through processed regions. This substitution transforms subjective visual evaluation into objective optical measurement, resolving the contradiction between simple equipment and precise measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces light as an intermediary to evaluate processing quality. Light-emitting bodies emit light that passes through the workpiece, and the image capturing unit detects light transmission characteristics. This intermediary enables objective measurement of processing results without direct operator contact or subjective visual judgment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If quantitative evaluation method with light-emitting bodies and image capturing unit is implemented, then measurement precision and objectivity are improved, but device complexity increases

Engineering Contradiction:

Improveprocessing quality evaluationVSAvoidinspection system

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The chuck table is designed with multi-functionality, serving both as a workpiece holding device and as a platform for light emission and image capture. The light-emitting bodies are integrated into the chuck table structure, allowing the same device to perform both clamping and illumination functions, thereby reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the illumination system and image capture system into a unified inspection apparatus. The light-emitting bodies and image capturing unit are integrated to form a compact inspection system that can be implemented within existing laser processing equipment, reducing the need for separate standalone devices.

Inventive Principle:

Principle #5Merging (Combining)

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 provides a quantitative evaluation of the processing result, reducing operator dependency and measurement errors, ensuring consistent processing outcomes and minimizing the need for manual visual inspection.

Implementation Method 1

light-emitting bodies disposed sideways of a surface of the holding member remote from the holding surface

Methodology Applied

Scientific EffectLight emission: Light Emitting Diode

Implementation Method 2

a laser beam applying unit for applying a laser beam having a wavelength that is absorbable to the workpiece to the workpiece held on the chuck table

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 3

a laser beam having a wavelength that is absorbable to the workpiece

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS11623300B2Method of determining whether or not result of processing process of laser processing apparatus is acceptable

Publication Date: 2023.04.11 DISCO CORP

AI summary

There is provided a method of determining whether or not a result of a processing process of a laser processing apparatus is acceptable including a laser processing step of applying a laser beam to predetermined processing regions of a workpiece held on a chuck table, thereby performing a piercing process on the workpiece, an image capturing step of capturing images of all the processing regions while moving the image capturing unit and the workpiece relatively to each other, a detecting step of detecting regions where light is not transmitted through the workpiece among the processing regions in the image captured in the image capturing step, and a determining step of determining that the laser processing apparatus needs to be readjusted if the regions where light is not transmitted through the workpiece is equal to or more than the predetermined quantity.