Wafer Division via Shield Tunnels in Single-Crystal Silicon

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Solution Overview

Problem

Single-crystal silicon wafers cannot be properly divided into individual device chips using existing laser processing methods that form shield tunnels or modified layers, as these methods are ineffective for silicon substrates, limiting the ability to create individual device chips with high flexural strength.

Innovation Solution

A laser processing method involving a protective member, pulsed laser beam with a wavelength of 1950 nm or higher, and a condensing lens with a numerical aperture range of 0.05 to 0.2 is used to form shield tunnels in single-crystal silicon wafers, allowing for successful division into device chips through plasma etching, even with metal or low-k films deposited on the surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a laser beam with wavelength transmittable through single-crystal silicon is applied to form shield tunnels, then device chips can be divided with high flexural strength, but existing laser processing methods are ineffective for silicon substrates

Engineering Contradiction:

Improveflexural strength of device chipsVSAvoideffectiveness of laser processing method

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies a laser beam with a specific wavelength range (1950 nm or higher, preferably 2100 nm) that is transmittable through single-crystal silicon, changing the optical parameter to enable shield tunnel formation in silicon substrates where conventional methods failed. This parameter change allows the laser energy to pass through the silicon and create the necessary structural modifications for effective dicing.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If shield tunnels are formed in sapphire, silicon carbide, or gallium arsenide wafers, then proper division is achieved, but shield tunnels cannot be formed in single-crystal silicon wafers

Engineering Contradiction:

Improveability to form shield tunnelsVSAvoidapplicability to different wafer materials

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent extends the shield tunnel formation capability to single-crystal silicon wafers, making the laser processing method universally applicable to multiple wafer materials including silicon, sapphire, silicon carbide, and gallium arsenide. By using a wavelength transmittable through silicon (1950 nm or higher), the method achieves multi-material versatility while maintaining the effectiveness of shield tunnel formation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If modified layers are formed in single-crystal silicon wafer, then division is possible, but metal film or low-k film deposited on projected dicing lines prevents successful division

Engineering Contradiction:

Improveability to divide waferVSAvoidinterference from metal or low-k film

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent performs shield tunnel formation before the plasma etching step, creating fine pores and amorphous regions that penetrate through the entire wafer thickness. This preliminary action ensures that even when metal films or low-k films are present on the surface, the laser-created pathways enable subsequent effective division by plasma etching, as the shield tunnels provide pre-formed channels through the deposited layers.

Inventive Principle:

Principle #10Preliminary 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

The method effectively forms shield tunnels in single-crystal silicon wafers, enabling the division of device chips with high flexural strength, and allows for the separation of metal or low-k films along fine pores, ensuring successful chip separation.

Implementation Method 1

applying a laser beam, which has a wavelength that is transmittable through single-crystal silicon, to areas of the wafer that correspond to the projected dicing lines from a reverse side of the wafer, thereby successively forming a plurality of shield tunnels in the wafer, each including a fine pore extending from the reverse side to the face side of the wafer and an amorphous region surrounding the fine pore

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

forming grooves serving as division initiating points in the workpiece according to an ablation process

Methodology Applied

Scientific EffectAblation: Ablation

Implementation Method 3

dividing the wafer into individual device chips by etching the shield tunnels according to plasma etching

Methodology Applied

Scientific EffectPlasma etching: Plasma

Data Source

PatentUS10483149B2Wafer processing method for dividing a wafer, including a shield tunnel forming step

Publication Date: 2019.11.19 DISCO CORP

AI summary

A wafer processing method includes: a protective member placing step of placing a protective member on the face side of a wafer; a shield tunnel forming step of applying a laser beam, which has a wavelength that is transmittable through single-crystal silicon, to areas of the wafer that correspond to projected dicing lines from a reverse side of the wafer, thereby successively forming a plurality of shield tunnels in the wafer, each including a fine pore extending from the reverse side to the face side of the wafer and an amorphous region surrounding the fine pore; and a dividing step of dividing the wafer into individual device chips by etching the shield tunnels according to plasma etching. The pulsed laser beam used in the shield tunnel forming step has a wavelength of 1950 nm or higher.