Wafer Processing Method for Removing Heat-Affected Layers

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Solution Overview

Problem

The existing methods for wafer processing, such as dicing before grinding, can lead to defects like chipping and reduced flexural strength in device chips due to the formation of heat-affected layers and processing distortions during laser processing, which lower the quality of the device chips.

Innovation Solution

A processing method that involves forming laser processed grooves to remove the functional layer, followed by cut groove formation with a cutting blade, and then using a protective component and plasma treatment to remove processing distortions and heat-affected layers, thereby preventing these defects and maintaining the flexural strength of the device chips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If laser beam irradiation is used to remove the functional layer along the streets, then the functional layer is effectively removed and device breakage is prevented, but heat-affected layers and processing distortions are formed that reduce flexural strength

Engineering Contradiction:

Improvedevice breakage preventionVSAvoidflexural strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies preliminary action by forming laser processed grooves to remove the functional layer before the cutting blade divides the wafer. This prevents the functional layer from being caught and separated during cutting, avoiding device breakage. The laser processing is performed in advance to create clean grooves that guide subsequent mechanical cutting.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful heat-affected layer and processing distortions created by laser irradiation into a beneficial process by introducing plasma treatment. The plasma processing step specifically targets and removes the heat-affected layer and distortions from the back surface of the wafer, transforming the previously harmful thermal effects into a controlled removal process that restores material quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Manufacturing precision

If a cutting blade is used to divide the wafer after laser processing, then precise division is achieved, but the heat-affected layer remains in the device chips reducing quality

Engineering Contradiction:

Improvewafer division accuracyVSAvoidheat-affected layer presence

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies the extraction principle by introducing a plasma treatment step that specifically removes the heat-affected layer and processing distortions from the back surface of the wafer after laser processing and cutting. This extraction process separates the harmful thermal effects from the beneficial structural divisions, eliminating the heat-affected layer while preserving the precise wafer division achieved by the cutting blade.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the functional layer is removed by laser before cutting, then contact between cutting blade and functional layer is avoided, but laser processed grooves create distortion that weakens the device chips

Engineering Contradiction:

Improvefunctional layer integrityVSAvoiddevice chip strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces plasma processing as an intermediary step between laser processing and the final product. This intermediary process acts as a mediator that removes the harmful heat-affected layer and processing distortions created by the laser, while preserving the beneficial functional layer removal and groove formation. The plasma treatment mediates between the laser's structural modifications and the final device chip quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively prevents the heat-affected layers from remaining in the device chips, thereby maintaining their flexural strength and improving their quality by removing distortions and ensuring accurate division of the wafer into device chips.

Implementation Method 1

a laser processing step of forming laser processed grooves along the streets while removing the functional layer along the streets by irradiating the front surface side of the wafer with a laser beam

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

a processing distortion removal step of supplying a gas in a plasma state to the back surface side of the wafer and removing processing distortion formed in the back surface side and side parts of the plurality of device chips

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS11456213B2Processing method of wafer

Publication Date: 2022.09.27 DISCO CORP

AI summary

There is provided a processing method of a wafer having a functional layer on a front surface side. The processing method includes a laser processing step of forming laser processed grooves along streets while removing the functional layer along the streets by executing irradiation with a laser beam and a cut groove forming step of forming cut grooves inside the laser processed grooves along the streets by cutting the wafer by a cutting blade. The processing method also includes a grinding step of causing the cut grooves to be exposed on a back surface side of the wafer and dividing the wafer into plural device chips by grinding the back surface side of the wafer and thinning the wafer and a processing distortion removal step of supplying a gas in a plasma state to the back surface side of the wafer and removing processing distortion.