Wafer Laser Grooving and Plasma Strain Layer Formation

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Solution Overview

Problem

The generation of electric discharge during plasma processing of wafers can lead to breakage of devices due to the presence of metal burs formed when cutting dummy patterns with a cutting blade, which compromises the gettering effect and die strength of the wafer.

Innovation Solution

A method involving laser processing to remove patterns with a metal layer on the wafer, followed by forming cut grooves with a thinner cutting blade, applying a protective member, grinding the back surface, removing the crushed layer, and forming a strain layer using plasma processing with an inert gas to prevent electric discharge and enhance die strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a cutting blade is used to cut dummy patterns including metal layer on streets, then the wafer can be divided into device chips, but metal burs are generated on the wafer surface

Engineering Contradiction:

Improvewafer division efficiencyVSAvoidmetal bur generation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies laser processing before cutting to remove metal layers and patterns from street regions. This preliminary action eliminates metal burs that would otherwise be generated during subsequent cutting operations, preventing harmful factors before they occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and removes metal layers and dummy patterns from street regions using laser processing before the cutting step. This extraction eliminates the source of metal bur generation, allowing clean cutting without bur formation.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If plasma processing is applied to wafer with metal burs, then strain layer can be formed for gettering effect, but electric discharge occurs causing device breakage

Engineering Contradiction:

Improvegettering effectVSAvoidelectric discharge

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes metal layers and patterns before plasma processing through laser ablation and cutting. This preliminary removal eliminates metal burs that would cause electric discharge during plasma processing, ensuring safe formation of strain layer for gettering effect.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful metal layers into removable debris through laser processing, transforming a harmful factor (metal burs causing electric discharge) into a controllable removal process that enables safe plasma processing and strain layer formation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Strength

If crushed layer is removed by polishing to enhance die strength, then die strength increases, but gettering effect is lost

Engineering Contradiction:

Improvedie strengthVSAvoidgettering effect

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent replaces mechanical polishing with laser processing for removing metal layers. This substitution allows selective removal of metal without creating a crushed layer, enabling subsequent formation of a thin strain layer that provides both die strength enhancement and gettering effect simultaneously.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from removing the crushed layer entirely to forming a controlled thin strain layer with specific parameters (thickness, density). This parameter control allows the strain layer to provide gettering effect while maintaining sufficient die strength, avoiding the trade-off between the two properties.

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

This method effectively prevents electric discharge and breakage of devices by removing metal burs and maintaining the gettering effect without significantly lowering the die strength of the wafer, ensuring reliable wafer processing.

Implementation Method 1

a laser processing step of applying a laser beam of such a wavelength as to be absorbed in the wafer along the streets formed with the patterns, to form laser processed grooves while removing the patterns

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

a strain layer forming step of forming a strain layer on the back surface side of the wafer deprived of the crushed layer, by plasma processing using an inert gas

Methodology Applied

Scientific EffectPlasma processing: Plasma

Data Source

PatentUS10790192B2Wafer processing method

Publication Date: 2020.09.29 DISCO CORP

AI summary

A method for processing a wafer in which patterns including a metal layer are formed on streets. The method includes: a step of applying a laser beam along the streets formed with the patterns to form laser processed grooves while removing the patterns; a step of forming cut grooves having a depth in excess of a finished thickness of the wafer, inside the laser processed grooves; a step of grinding the back surface side of the wafer to thin the wafer to the finished thickness and to expose the cut grooves to the back surface of the wafer, thereby dividing the wafer into a plurality of device chips; a step of removing a crushed layer formed on the back surface side of the wafer; and a step of forming a strain layer on the back surface side of the wafer by plasma processing using an inert gas.