Wafer Processing Using Polyolefin Sheet Without Adhesive

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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 melting and fixation of adhesive tape layers during the laser-based 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 laser beam application to form shield tunnels and subsequent device chip separation without adhesive layer adherence, using polyethylene, polypropylene, or polystyrene sheets heated within specific temperature ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If adhesive tape is used to hold the wafer during laser processing, then the wafer can be securely positioned 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 tape structure, using only the base layer to hold the wafer. This extraction eliminates the source of the contamination problem while maintaining the holding function through mechanical adhesion of the base layer alone.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs a disposable polyolefin sheet that is discarded after use rather than reused. This single-use approach prevents contamination from recurring and eliminates the need for cleaning or reconditioning adhesive layers, ensuring each processing cycle starts with a clean surface.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Device complexity

If adhesive tape is used to unite wafer and ring frame, then the structure is simplified, but ultraviolet light must be applied to reduce adhesion for chip pickup, adding processing steps

Engineering Contradiction:

Improvestructure complexityVSAvoidprocessing efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent changes the material parameter from adhesive-based tape to polyolefin sheet, which responds differently to thermal and optical processing. This parameter change allows the sheet to be released through heating that reduces its adhesion properties, enabling easy chip pickup without additional ultraviolet lighting infrastructure.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If laser beam is applied to divide the wafer, then precise division lines are formed, but leaked laser light melts the adhesive layer, causing contamination

Engineering Contradiction:

Improvedivision precisionVSAvoidadhesive contamination

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of leaked laser light into a beneficial release mechanism. By using polyolefin material that becomes less adhesive when heated by the laser, the previously harmful thermal energy now serves to facilitate easy chip separation without contamination.

Inventive Principle:

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

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 eliminating the issue of adhesive layer fixation during the chip separation process, enabling efficient and high-quality device chip production.

Implementation Method 1

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

Methodology Applied

Scientific EffectThermocompression bonding:

Implementation Method 2

applying a laser beam to the wafer held on the chuck table in a state in which a focal point of the laser beam is positioned inside the wafer

Methodology Applied

Scientific EffectLaser processing: Laser

Implementation Method 3

When the 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 EffectShield tunnel formation:

Implementation Method 4

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:

Implementation Method 5

heating the polyolefin sheet in each region of the polyolefin sheet corresponding to each device chip, pushing up each device chip through the polyolefin sheet

Methodology Applied

Scientific EffectThermal heating: Heating

Data Source

PatentUS11610815B2Wafer processing method including uniting wafer, ring frame, and polyolefin sheet without using an adhesive layer

Publication Date: 2023.03.21 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 heating the polyolefin sheet, pushing up each device chip through the polyolefin sheet, and picking up each device chip from the polyolefin sheet.