Laser Detachment Region Control for Kerf-Free Wafer Separation

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Solution Overview

Problem

Conventional methods for producing wafers result in significant material loss (kerf loss) and produce wafers with high thickness variations, making them unsuitable for many applications due to crack formation issues, especially at the edges where LASER beam damage is inefficient.

Innovation Solution

A method involving LASER beam modifications to create a detachment region on a donor substrate, followed by material removal to produce an indentation and stress-inducing layer, which induces mechanical stresses to propagate a crack along the modifications, allowing for kerf-free wafering with reduced thickness variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If LASER beams are used to produce modifications within the donor substrate, then the detachment region can be precisely defined and crack formation is controlled, but edge effects cause damage beyond the intended damage layer and reduce coupling efficiency

Engineering Contradiction:

Improvedetachment region precisionVSAvoidedge damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by making the LASER beam focus adaptive to the local geometry. At the edge of the donor substrate, the focus is shifted away from the edge to compensate for the missing material on one side, ensuring that the damage layer is created at the correct depth without extending beyond the intended detachment region. This local adjustment of focus position resolves the edge effect problem while maintaining precise detachment region definition.

Inventive Principle:

Principle #3Local quality

2Productivity

If conventional sawing methods are used to produce wafers, then material can be separated, but significant material loss occurs as kerf loss

Engineering Contradiction:

Improvewafer production efficiencyVSAvoidkerf loss

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The patent replaces the mechanical sawing system with a LASER-based modification system. Instead of using a physical saw blade that removes material as kerf, the invention uses LASER beams to create controlled modifications within the donor substrate that define a detachment region. This allows wafers to be separated without the material loss associated with conventional mechanical cutting, significantly reducing kerf loss while maintaining production efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If LASER beams are focused directly at the edge of the material, then the detachment region can be created at the edge, but only half or a fraction of the LASER radiation is coupled into the material

Engineering Contradiction:

Improveedge detachment precisionVSAvoidLASER radiation coupling efficiency

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by shifting the LASER focus position before the beam reaches the edge of the donor substrate. The focus is positioned at a distance from the edge that accounts for the edge effect, allowing the full LASER radiation to be coupled into the material while still achieving the desired detachment region at the edge. This pre-positioning of the focus ensures both efficient energy coupling and precise edge detachment.

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 enables the production of wafers with low total thickness variation, reducing material waste and improving the suitability of wafers for various applications by minimizing crack formation and edge damage.

Implementation Method 1

producing modifications within the donor substrate by means of LASER beams, wherein a detachment region is predefined by the modifications

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

removing material from the donor substrate, starting from a surface extending in the peripheral direction

Methodology Applied

Scientific EffectAblation: Ablation

Implementation Method 3

mechanical stresses are produced in the donor substrate by a thermal treatment of the stress-inducing layer

Methodology Applied

Scientific EffectThermal treatment: Heat Treatment

Implementation Method 4

mechanical stresses are produced in the donor substrate by a thermal treatment of the stress-inducing layer, wherein the mechanical stresses produce a crack

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 5

On account of the difference in refractive index, this causes damage at the side of the solid body, way beyond the actually intended damage layer after refractive index correction

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10676386B2Method for guiding a crack in the peripheral region of a donor substrate

Publication Date: 2020.06.09 SILTECTRA GMBH

AI summary

The present invention relates to a method for separating solid-body slices (1) from a donor substrate (2). The method comprises the steps of: producing modifications (10) within the donor substrate (2) by means of laser beams (12), wherein a detachment region is predefined by the modifications (10), along which detachment region the solid-body layer (1) is separated from the donor substrate (2), and removing material from the donor substrate (2), starting from a surface (4) extending in the peripheral direction of the donor substrate (2), in the direction of the centre (Z) of the donor substrate (2), in particular in order to produce a peripheral indentation (6).