Wafer Processing Without Adhesive Layer

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Solution Overview

Problem

The existing wafer processing methods result in adhesive layer adherence to device chips, degrading their quality due to the use of adhesive tapes with adhesive layers during the division process.

Innovation Solution

A wafer processing method utilizing a polyolefin sheet without an adhesive layer for thermocompression bonding with the wafer and ring frame, allowing for the formation of shield tunnels and easy device chip separation without adhesive layer adherence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If an adhesive tape with adhesive layer is used to hold the wafer during laser processing, then the wafer can be securely held and processed, but the adhesive layer melts and adheres to the device chips, degrading their quality

Engineering Contradiction:

Improveholding strengthVSAvoidchip quality

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent removes the adhesive layer from the holding structure. Instead of using adhesive tape, the invention uses a porous plate with suction holes that physically holds the wafer through vacuum suction, completely eliminating the adhesive layer that causes contamination of device chips during laser processing

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a porous plate as an intermediary holding structure between the chuck table and the wafer. This porous plate with suction holes provides a non-contact, contamination-free holding method that secures the wafer during laser processing without risking chip quality

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If ultraviolet light is applied to reduce adhesive tape adhesion for chip pickup, then chips can be easily separated, but the melted adhesive layer already fixed to chips cannot be removed

Engineering Contradiction:

Improvechip pickup easeVSAvoidchip quality

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent eliminates the adhesive layer entirely by using a porous plate with suction holes for holding and chip pickup. Without an adhesive layer, there is no melted adhesive to contaminate the chips, and chip pickup is achieved by releasing the vacuum suction rather than applying ultraviolet light

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If the laser beam is applied inside the wafer to form shield tunnels, then precise division is achieved, but leaked laser light reaches and melts the adhesive layer

Engineering Contradiction:

Improvedivision precisionVSAvoidadhesive layer melting

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent removes the adhesive layer that absorbs leaked laser light by using a porous plate structure. This eliminates the harmful effect of adhesive layer melting while maintaining the precise laser division process that forms shield tunnels inside the wafer

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The porous plate is a disposable holding structure that can be easily replaced. It serves its purpose of holding the wafer during laser processing and then is discarded, avoiding the need to clean or reuse it, which prevents any potential contamination from repeated use

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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

Prevents adhesive layer adherence to device chips, maintaining their quality by using a polyolefin sheet for thermocompression bonding and subsequent laser processing, facilitating efficient chip separation and mounting.

Implementation Method 1

a laser beam is applied to the wafer, a filament-like region called a shield tunnel is sequentially formed along each division line

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

heating the polyolefin sheet as applying a pressure to the polyolefin sheet, thereby uniting the wafer and the ring frame through the polyolefin sheet by thermocompression bonding

Methodology Applied

Scientific EffectThermocompression bonding:

Implementation Method 3

ultraviolet light is applied to the adhesive tape in advance, for example, to thereby reduce the adhesion of the adhesive tape

Methodology Applied

Scientific EffectUltraviolet light treatment:

Data Source

PatentUS11587832B2Wafer processing method including uniting wafer, ring frame and polyolefin sheet without using an adhesive layer

Publication Date: 2023.02.21 DISCO CORP

AI summary

A wafer processing method includes a polyolefin sheet providing step of positioning a wafer in an inside opening of a ring frame and providing a polyolefin sheet on a back side or a front side of the wafer and on a back side of the ring frame, a uniting step of heating the polyolefin sheet as applying a pressure to the polyolefin sheet to thereby unite the wafer and the ring frame through the polyolefin sheet by thermocompression bonding, a dividing step of applying a laser beam to the wafer to form shield tunnels in the wafer, thereby dividing the wafer into individual device chips, and a pickup step of cooling the polyolefin sheet, pushing up each device chip through the polyolefin sheet, and picking up each device chip from the polyolefin sheet.