Wafer Thinning With Laser Edge Separation to Prevent Chipping

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Solution Overview

Problem

Existing wafer processing methods face challenges in removing peripheral surplus regions during grinding, which can lead to device damage and contamination due to chipping and unremoved edge parts.

Innovation Solution

A method involving bonding wafers, forming an annular modified layer using a laser beam, and applying external forces, such as ultrasonic waves or fluid jets, to facilitate the separation of peripheral surplus regions without damaging the devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the wafer is ground to be extremely thin, then the wafer thickness is reduced, but the peripheral edge becomes a knife edge and chipping of the edge is liable to occur during grinding

Engineering Contradiction:

Improvewafer thicknessVSAvoidedge chipping resistance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

An annular modified layer is formed along the peripheral edge of the wafer before the grinding process. This modified layer, created by laser irradiation, strengthens the peripheral edge region and prevents chipping from occurring during subsequent thinning operations, allowing the wafer to be ground to extremely thin dimensions without compromising edge integrity

Inventive Principle:

Principle #10Preliminary action

2Reliability

If edge trimming is performed by cutting the peripheral edge, then the knife edge problem is addressed, but a large amount of sawdust is generated and devices are liable to be contaminated

Engineering Contradiction:

Improveedge integrityVSAvoiddevice contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The mechanical cutting process is replaced with laser irradiation to form the modified layer. This non-contact method eliminates the generation of sawdust and mechanical debris that would otherwise contaminate the devices during edge trimming operations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The physical state of the peripheral edge is changed through laser-induced modification rather than mechanical removal. The laser irradiation creates a modified layer with altered material properties that prevents chipping without requiring material removal, thus avoiding contamination

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a modified layer is formed in the wafer in an inner region than an adhesion region, then device protection is improved, but an end part of peripheral surplus region may not be peeled off and remain unremoved upon grinding

Engineering Contradiction:

Improvedevice protectionVSAvoidperipheral surplus region removal completeness

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The modified layer is positioned at the peripheral edge in the radial dimension, creating a gradient structure that extends from the adhesion region toward the outer edge. This dimensional arrangement allows the modified layer to provide protective function while still enabling complete removal of the peripheral surplus region through controlled chipping at the outermost edge

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Effectively removes peripheral surplus regions during grinding while minimizing damage to devices and preventing contamination, ensuring precise thinning of wafers.

Implementation Method 1

forming an annular modified layer along a boundary of the device region and the peripheral surplus region of the first wafer by applying a laser beam having such a wavelength as to be transmitted through the first wafer to the first wafer from another surface of the first wafer that is opposite to the one surface thereof, with a focal point of the laser beam placed at the boundary

Methodology Applied

Scientific EffectLaser beam transmission and focusing: Laser

Implementation Method 2

applying a laser beam having such a wavelength as to be transmitted through the first wafer to the first wafer from another surface of the first wafer

Methodology Applied

Scientific EffectLaser heating: Heating

Implementation Method 3

an ultrasonic wave applying step of, during or after the grinding step, applying an ultrasonic wave to the peripheral surplus region that is close to the peripheral edge with respect to a region in which the modified layer is formed in the modified layer forming step, to thereby facilitate separation of the peripheral surplus region

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Data Source

PatentUS20240128087A1Wafer processing method

Publication Date: 2024.04.18 DISCO CORP

AI summary

A wafer processing method includes bonding one surface of a first wafer to a second wafer, the first wafer having a device region on the one surface, a peripheral surplus region, and a chamfered peripheral edge; forming an annular modified layer along a boundary of the device region and the peripheral surplus region by applying a laser beam to the first wafer from the other surface of the first wafer with a focal point of the laser beam placed at the boundary; after forming the modified layer, grinding the first wafer from the other surface to thin the first wafer to a finished thickness; and exerting an external force on the peripheral surplus region that is close to the peripheral edge with respect to a region in which the modified layer is formed, to thereby facilitate the separation of the peripheral surplus region.