Laser Substrate Division Preventing Die Shift

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Solution Overview

Problem

Existing methods for dividing optical device wafers along division lines often result in die shift and incomplete separation, leading to complications in processing and potential damage during the separation process, especially with transparent crystal materials.

Innovation Solution

A method involving the application of a pulsed laser beam from the side of the substrate to form modified regions that extend through the substrate, reducing its strength and allowing for precise removal of material along the division lines without the need for external forces, thereby ensuring accurate and reliable separation of individual chips or dies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If external force is applied to the wafer using a breaking tool to divide the wafer along division lines, then the wafer can be separated into individual optical devices, but die shift occurs and chips or dies may be damaged

Engineering Contradiction:

Improvewafer separation efficiencyVSAvoidchip alignment accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies segmentation by creating multiple modified regions along the division lines through laser processing. These modified regions are formed by melting and resolidifying the substrate material, creating a weakened path that allows clean separation without mechanical force. The division is achieved by segmenting the substrate along predetermined lines rather than applying external force to the entire wafer at once.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the mechanical breaking tool system with a laser-based thermal processing system. Instead of using mechanical force to separate the wafer, the invention uses laser beams to create modified regions that facilitate separation. This substitution eliminates the die shift problem inherent in mechanical breaking methods while maintaining effective wafer division.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If external force is applied using a breaking tool to separate chips or dies, then wafer division is achieved, but complete separation is not ensured and inspection is still required

Engineering Contradiction:

Improvewafer division speedVSAvoidseparation completeness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by creating modified regions along the division lines before performing the actual separation. The laser processing pre-weakens the substrate material by melting and resolidifying it along the division paths, ensuring that subsequent separation will be complete and clean. This preliminary modification guarantees thorough division without requiring post-processing inspection.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the focal point of the pulsed laser beam is located inside the wafer to form a modified layer, then the wafer can be divided along division lines, but die shift and potential damage occur during separation

Engineering Contradiction:

Improvewafer division feasibilityVSAvoidchip integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies dimensionality change by forming modified regions that extend from the front surface toward the back surface of the wafer, creating a three-dimensional modified structure. This volumetric modification approach, rather than creating a simple surface layer, ensures that the weakened path extends through the entire thickness of the substrate, enabling clean separation without die shift or damage to the chips.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 approach prevents die shift and ensures complete separation with high accuracy and efficiency, reducing the risk of damage and the need for subsequent inspection, while maintaining sufficient substrate strength for further handling.

Implementation Method 1

Each modified region is formed by melting substrate material by means of the pulsed laser beam and allowing the molten substrate material to resolidify

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

applying a pulsed laser beam to the substrate from the side of the first surface, at least in a plurality of positions along the at least one division line, so as to form a plurality of modified regions in the substrate

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS10727127B2Method of processing a substrate

Publication Date: 2020.07.28 DISCO CORP

AI summary

A method of processing a substrate, having a first surface with at least one division line formed thereon and a second surface opposite the first surface, includes applying a pulsed laser beam to the substrate from the side of the first surface, at least in a plurality of positions along the at least one division line, so as to form a plurality of modified regions in the substrate, each modified region extending at least from the first surface towards the second surface. Each modified region is formed by melting substrate material by means of the pulsed laser beam and allowing the molten substrate material to resolidify. The method further comprises removing substrate material along the at least one division line where the plurality of modified regions has been formed.