Wafer Edge Laser Trimming for Thin-Wafer Chipping Control

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Solution Overview

Problem

Existing wafer processing methods face challenges in forming an annular modified layer and cracks along the outer peripheral edge of wafers without causing damage to devices, due to variations in plane orientations, thickness, and laser beam reflectance.

Innovation Solution

A wafer processing method that involves forming an annular modified layer and cracks by irradiating the wafer with a laser beam of appropriate wavelength in an annular pattern, while storing anticipated regions with different irradiation conditions to prevent crack propagation to devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a wafer is ground extremely thin to enable low-profile and high-integration device chips, then the wafer thickness is reduced to achieve miniaturization, but the outer peripheral edge forms a knife edge that is prone to edge chipping during grinding

Engineering Contradiction:

Improvewafer thicknessVSAvoidedge strength

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent applies preliminary action by forming an annular modified layer and cracks at the outer peripheral edge of the wafer before the thinning grinding process. This pre-treatment creates a stress relief structure that prevents edge chipping during subsequent grinding operations, allowing the wafer to be thinned to extreme thicknesses without compromising edge integrity.

Inventive Principle:

Principle #10Preliminary action

2Strength

If laser beam irradiation is applied uniformly along the outer peripheral edge to form an annular modified layer, then edge chipping is suppressed, but differences in plane orientations, thickness variations, and reflectance cause inconsistent crack formation and potential device damage

Engineering Contradiction:

Improveedge strengthVSAvoidcrack formation consistency

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent implements local quality by dividing the annular irradiation region into multiple segments with different laser irradiation conditions. Each segment is irradiated with customized parameters (power, speed, pulse width) tailored to local characteristics such as plane orientation and thickness variation. This ensures consistent crack formation across the entire periphery while preventing device damage through localized parameter optimization.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies dynamics by making the laser irradiation conditions variable rather than static. The laser parameters (output power, irradiation speed, pulse width) are dynamically adjusted based on real-time feedback about wafer characteristics at different angular positions. This dynamic adaptation allows the system to compensate for thickness variations and orientation differences, achieving uniform crack formation throughout the annular region.

Inventive Principle:

Principle #15Dynamics

3Strength

If the annular modified layer is formed closer to the outer peripheral edge to better prevent chipping, then edge protection is improved, but the risk of crack propagation to devices increases

Engineering Contradiction:

Improveedge protectionVSAvoiddevice damage risk

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies segmentation by dividing the annular irradiation region into multiple concentric zones or angular segments, each with different laser parameters. By controlling the depth, density, and distribution of the modified layer in different segments, the system optimizes the balance between edge protection and device safety. The modified layer is formulated to stop crack propagation at the edge while preventing excessive stress concentration that could propagate to devices.

Inventive Principle:

Principle #1Segmentation

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

The method effectively forms annular modified layers and cracks along the wafer's outer peripheral edge, thereby suppressing edge chipping and device damage during grinding, while ensuring precise control over the trimming process.

Implementation Method 1

a wafer having a device region with devices formed therein, which will hereinafter be referred to as a 'device wafer,' is bonded to a support wafer, and the device wafer is then irradiated with a laser beam along an outer peripheral edge of the device region to form an annular modified layer inside the device wafer

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS20250073821A1Processing method of wafer

Publication Date: 2025.03.06 DISCO CORP

AI summary

A processing method of a wafer includes irradiating the wafer with a laser beam in an annular pattern a predetermined distance from an outer peripheral edge of the wafer, thereby forming an annular modified layer and cracks spreading from the modified layer, before forming the modified layer, storing anticipated regions indicating regions which are part of an annular region that extends along the outer peripheral edge and is to be irradiated with the laser beam and in each of which a failure of formation of the cracks spreading from the modified layer is anticipated, and after the modified layer is formed, grinding the wafer on a side of a back surface thereof to thin the wafer to a finish thickness. In forming the modified layer, the anticipated regions are irradiated with the laser beam under irradiation conditions different from those for the annular region excluding the anticipated regions.