Laser Processing Silicon Substrates with Dual-Depth Modified Regions

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Solution Overview

Problem

The existing laser processing methods for silicon substrates often result in damage to the surface and deterioration of functional elements due to the convergence of high-transmittance laser light, leading to inefficient processing and crack formation.

Innovation Solution

A laser processing method that forms a first modified region along a cutting line by converging laser light on a silicon substrate with a back surface incident, and then forms a second modified region with a converging point offset towards the effective region, minimizing damage to the surface and controlling crack extension in the thickness direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If laser light with high transmittance is converged on the silicon substrate to form a modified region along the cutting line, then processing efficiency is improved by reducing the number of scanning rows, but cracks greatly extend from the modified region in the thickness direction causing damage to the opposite surface and deterioration of functional element characteristics

Engineering Contradiction:

Improveprocessing efficiencyVSAvoidsurface damage and functional element deterioration

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The laser processing is divided into multiple scanning rows with different converging point positions. The first scanning row forms a modified region at a first distance from the surface, and the second scanning row forms another modified region at a second distance from the surface. This segmentation allows control over crack extension while maintaining processing efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution introduces a new dimensional parameter - the distance of the converging point from the surface (depth positioning). By controlling the converging point position in the thickness direction rather than only moving along the cutting line, the patent achieves precise control over where the modified region forms and where cracks extend, thereby protecting the functional element surface.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If the number of scanning rows is reduced to improve processing efficiency, then productivity increases, but crack extension in the thickness direction causes damage to reach the opposite surface

Engineering Contradiction:

Improvenumber of scanning rowsVSAvoiddamage control on opposite surface

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the parameter of converging point position (distance from surface) to control the depth at which the modified region forms. By adjusting this parameter, the crack extension is controlled to stop before reaching the opposite surface, even when using fewer scanning rows, thus maintaining both productivity and manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If laser light is converged to form modified regions along the cutting line, then cutting efficiency is improved, but damage occurs to the surface on the side opposite to the laser incident surface

Engineering Contradiction:

Improvecutting efficiencyVSAvoiddamage to opposite surface

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The first scanning row performs a preliminary action by forming a modified region that serves as a barrier to crack extension. This preliminary modified region prevents cracks from the second scanning row from reaching the opposite surface, thereby protecting the functional element surface while maintaining cutting efficiency.

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

This method effectively reduces surface damage and minimizes the deterioration of functional elements by shifting damage to the ineffective region, thereby improving processing efficiency and maintaining the integrity of the functional elements.

Implementation Method 1

a laser light source L1 that emits laser light L

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 2

by converging laser light on an object to be processed including a semiconductor substrate

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 3

a converging optical system configured to converge the laser light emitted from the laser light source on the object to be processed

Methodology Applied

Scientific EffectFocusing: Focusing

Data Source

PatentUS11103959B2Laser processing method, and laser processing device

Publication Date: 2021.08.31 HAMAMATSU PHOTONICS KK

AI summary

Provided is a laser processing method including a first step of forming a first modified region along a cutting line by converging laser light on an object having a surface and a back surface with the back surface as an incident surface and moving a first converging point along the cutting line set to pass between an effective region and an ineffective region adjacent to each other while maintaining a distance between a surface and the first converging point at a first distance, and a second step of forming a second modified region along the cutting line by converging the laser light on the object with the back surface as the incident surface and moving a second converging point along the cutting line while maintaining a distance between the surface and the second converging point at a second distance larger than the first distance.