Wafer Division Laser Strategy to Prevent Triangular Chip Scratches

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Solution Overview

Problem

During the process of dividing a wafer into individual device chips by forming modified layers along division lines and grinding the back side, triangular chips from the peripheral region adhere to the wafer and are dragged by grinding stones, causing scratches and damage to the device chips.

Innovation Solution

A wafer processing method that includes forming modified layers using a laser beam with a focusing point inside the wafer at division lines, attaching a protective member to the wafer, and grinding the back side to prevent the formation of triangular chips by stopping the laser application in regions where these chips would form, thus preventing them from adhering and causing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the laser beam is applied to the entire division lines extending to the peripheral marginal region to form modified layers, then the wafer can be completely divided into individual device chips, but triangular chips are formed in the peripheral region which scatter and adhere to the back side during grinding, causing scratches and damages

Engineering Contradiction:

Improvewafer division completenessVSAvoidchip scattering and adhesion causing scratches

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different laser processing strategies to different regions of the wafer. In the device region, modified layers are formed along the entire division lines to enable complete chip separation. In the peripheral marginal region, the laser beam application is stopped before reaching the edge to prevent formation of triangular chips that would scatter during grinding. This local differentiation of processing quality resolves the contradiction between complete division and prevention of chip scattering.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The wafer processing is segmented into two distinct regions: the device region where complete laser-induced modified layers are formed for full division, and the peripheral marginal region where laser application is truncated to prevent harmful triangular chip formation. This segmentation allows the system to achieve both complete division in the functional area and avoidance of scattering in the peripheral area.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the back side of the wafer is ground to thin the wafer and divide it into individual device chips, then the wafer division is completed, but the grinding stones drag the adhered triangular chips causing scratches on the back side and damages to the device chips

Engineering Contradiction:

Improvewafer thinning and divisionVSAvoidchip integrity and surface quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent performs preliminary action by controlling the laser beam application to stop before forming modified layers in the peripheral marginal region where triangular chips would form. This preventive measure is taken before the grinding step, ensuring that no triangular chips are present to scatter and adhere during the subsequent back side grinding process, thereby protecting chip integrity and surface quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by intentionally preventing the formation of triangular chips in the peripheral region through controlled laser beam termination. This counteracts the potential harmful effect of chip scattering and adhesion that would occur during grinding, maintaining both manufacturing precision and reliability.

Inventive Principle:

Principle #9Preliminary anti-action

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 the formation of triangular chips that could adhere and be dragged by grinding stones, thereby minimizing scratches and damage to the device chips during the wafer division process.

Implementation Method 1

applying a laser beam of a wavelength having transmitting property to the wafer with a focusing point of the laser beam positioned inside the wafer at positions corresponding to the division lines, thereby to form modified layers

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

the region is not held by an adhesive force of the protective tape

Methodology Applied

Scientific EffectAdhesive force: Adhesive

Data Source

PatentUS11328956B2Wafer processing method

Publication Date: 2022.05.10 DISCO CORP

AI summary

A wafer processing method includes a modified layer forming step of applying a laser beam of a wavelength having transmitting property to a wafer with a focusing point of the laser beam positioned inside the wafer at positions corresponding to division lines, thereby to form modified layers, and a back side grinding step of holding the wafer on a chuck table of a grinding apparatus, grinding a back side of the wafer to thin the wafer, and dividing the wafer into individual device chips from cracks that are generated from the modified layers formed inside the wafer along the division lines to the division lines formed on a front side of the wafer. In the modified layer forming step, in a case where triangular chips each having a surface area smaller than the device chips are to be formed, the application of the laser beam is stopped in a region where the triangular chips are to be formed.