Wafer Division via Back-Surface Laser Grooving

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Solution Overview

Problem

The presence of test metal patterns on semiconductor wafers interferes with laser beam processing, leading to non-uniform groove or deteriorated layer formation and potential device contamination during wafer division, as well as the risk of company secrets being leaked due to detectable test metal patterns on individual chips.

Innovation Solution

A method involving laser beam application from the back surface of the wafer to form deteriorated layers or grooves on both sides of the test metal patterns, followed by external force application to divide the wafer, ensuring the test metal patterns remain on the streets and are non-functional on the divided chips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a laser beam is applied along streets on the front surface of the wafer to form grooves or deteriorated layers, then the wafer can be divided along the streets, but the test metal patterns on the streets interfere with the laser beam, making it impossible to form grooves or deteriorated layers uniformly

Engineering Contradiction:

Improveuniformity of groove or deteriorated layer formationVSAvoidinterference from test metal patterns

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies the laser beam from the back surface of the wafer instead of the front surface. This inversion of the processing direction allows the laser to form grooves or deteriorated layers uniformly along the streets without being blocked or interfered with by the test metal patterns that are located on the front surface streets.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the processing dimension by switching from front-surface processing to back-surface processing. By approaching the streets from the opposite dimension (back surface instead of front surface), the laser beam can effectively process the wafer without encountering the test metal patterns that obstruct front-surface processing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If the wafer is divided by exerting external force after forming grooves or deteriorated layers from the back surface, then uniform dividing start points can be formed, but the test metal patterns are broken into sawtooth shapes generating dust that causes contamination

Engineering Contradiction:

Improveuniformity of dividing start pointsVSAvoiddust generation from broken test metal patterns

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent extracts or removes the test metal patterns from the streets before dividing the wafer. By selectively eliminating the test metal patterns through laser processing, the subsequent mechanical division no longer encounters these patterns, thereby preventing the generation of sawtooth-shaped fragments and dust that would cause contamination.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary laser processing to remove or modify the test metal patterns before the mechanical division step. This preliminary action eliminates the source of dust generation (the test metal patterns) before they can be broken into harmful fragments during the division process.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If test metal patterns remain on the divided chips, then the function of each device can be tested, but the constitution of each device can be detected, leading to leakage of company secrets

Engineering Contradiction:

Improvedevice function testing capabilityVSAvoidleakage of device constitution

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent converts the potentially harmful presence of test metal patterns (which could reveal device secrets) into a beneficial outcome by using the laser beam to selectively remove or modify these patterns. The same test metal patterns that could leak information are transformed into a means of protecting secrecy, while still allowing functional testing to be performed on the divided chips.

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

Enables uniform formation of dividing start points without interference from test metal patterns, preventing device constitution detection and maintaining company secrecy by ensuring test metal patterns are non-functional on the divided chips.

Implementation Method 1

applying a pulse laser beam capable of passing through the wafer from the back surface of the wafer with its focal point set to the inside of the wafer

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

with its focal point set to the inside of the wafer

Methodology Applied

Scientific EffectFocal point concentration: Focusing

Implementation Method 3

destroying the test metal patterns by applying a laser beam to the test metal patterns

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS7618878B2Wafer dividing method

Publication Date: 2009.11.17 DISCO CORP

AI summary

A method of dividing a wafer having a plurality of devices, which are formed in a plurality of areas sectioned by streets formed in a lattice pattern on the front surface, and having test metal patterns which are formed on the streets, comprising the steps of: a laser beam application step for carrying out laser processing to form a dividing start point along a street on both sides of the test metal patterns by applying a laser beam along the street on both sides of the test metal patterns in the street formed on the wafer; and a dividing step for dividing the wafer which has been laser processed to form dividing start points along the dividing start points by exerting external force to the wafer, resulting in leaving the streets having the test metal patterns formed thereon behind.