Wafer Division via Laser-Induced Strength Reduction and Radial Tension

Solution Overview

Problem

Existing wafer processing methods risk damaging device chips due to potential contact during division along division lines, as the distance between adjacent chips may be reduced.

Innovation Solution

A wafer processing method involving a frame supporting step with adhesive tape, a laser processing step to form strength reduced portions along division lines, and a dividing step with maintained radial tension on the adhesive tape to prevent chip contact, using external forces like rollers or rings to ensure proper separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a radial tension is applied to the adhesive tape during wafer division, then the distance between adjacent device chips is maintained and contact is prevented, but the complexity of the dividing process increases due to the need to maintain tension throughout the process

Engineering Contradiction:

Improvedevice chip integrityVSAvoiddividing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The adhesive tape is pre-stretched and mounted on the rotating table before the wafer division process begins. This preliminary action ensures that the tape is already under radial tension when the wafer is placed on it, eliminating the need to apply tension during the division process itself. The tension is maintained automatically through the rotation mechanism.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The adhesive tape serves as an intermediary medium between the rotating table and the wafer. By mounting the wafer on the tensioned adhesive tape rather than directly on the rotating table, the system maintains constant radial tension on the wafer during rotation and division, preventing chip contact while simplifying the overall process control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the wafer is divided along division lines without maintaining radial tension, then the dividing process is simpler, but the distance between adjacent device chips may be reduced causing chip contact and damage

Engineering Contradiction:

Improvedividing process simplicityVSAvoidchip contact damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The adhesive tape is pre-stretched and mounted on the rotating table before the wafer division process begins. This preliminary action ensures that the tape is already under radial tension when the wafer is placed on it, eliminating the need to apply tension during the division process itself. The tension is maintained automatically through the rotation mechanism.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The adhesive tape serves as an intermediary medium between the rotating table and the wafer. By mounting the wafer on the tensioned adhesive tape rather than directly on the rotating table, the system maintains constant radial tension on the wafer during rotation and division, preventing chip contact while simplifying the overall process control.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If a pulsed laser beam is applied with the focal point inside the wafer, then strength reduced portions are formed effectively along division lines, but the laser beam transmission requirements become more stringent

Engineering Contradiction:

Improvestrength reduced portion precisionVSAvoidlaser processing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent adjusts key laser processing parameters including setting the focal point inside the wafer (rather than on the surface), controlling the pulse width between 5-50 nanoseconds, and selecting appropriate laser wavelengths that transmit through the wafer material. These parameter changes enable effective formation of strength reduced portions while managing the complexity of laser processing.

Inventive Principle:

Principle #35Parameter changes

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 damage to device chips by maintaining adequate distance between them during division, ensuring effective separation without chip contact.

Implementation Method 1

a pulsed laser beam having a transmission wavelength to the wafer is applied along each division line in the condition where the focal point of the pulsed laser beam is set inside the wafer, thereby forming a strength reduced portion along each division line

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

the wafer is first attached to an adhesive tape fixed at its peripheral portion to a frame, thereby supporting the wafer through the adhesive tape to the frame

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS10096517B2Wafer processing method

Publication Date: 2018.10.09 DISCO CORP

AI summary

Disclosed herein is a wafer processing method for dividing a wafer into individual device chips along division lines. The wafer processing method includes a frame supporting step of attaching the wafer to an adhesive tape fixed at its peripheral portion to an annular frame, thereby supporting the wafer through the adhesive tape to the annular frame, a laser processing step of applying a laser beam to each division line to thereby form a strength reduced portion along each division line, and a dividing step of applying a radial tension to the adhesive tape and next applying an external force to the wafer in the condition where the radial tension is kept acting on the adhesive tape, thereby dividing the wafer into the individual device chips along the division lines.