Laser Lift-Off Separation Layer for Controlled Substrate Release

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Solution Overview

Problem

Existing laser lift-off methods for semiconductor devices face issues with improper separation of substrates due to regions where bonding strength is not reduced by laser radiation, leading to potential damage and improper transcription of device layers.

Innovation Solution

A substrate processing method involving the formation of a separation facilitating layer and a laser absorption layer, where a laser beam is used to generate stress in the laser absorption layer, facilitating separation along the boundary between the layers, with stress accumulation at the interface to reduce bonding strength and enable controlled separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If laser beam is radiated to the laser absorption layer, then stress is generated to reduce bonding strength, but regions with insufficient stress accumulation result in improper separation and potential damage to device layers

Engineering Contradiction:

Improveseparation controlVSAvoidimproper separation damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A separation facilitating layer is formed on the second substrate before laser processing. This layer is specifically designed to accumulate stress generated by laser radiation, ensuring that sufficient stress is concentrated at the separation interface even in regions where laser beam coverage might be insufficient. The preliminary formation of this layer prevents improper separation and device layer damage by ensuring reliable stress accumulation throughout the entire separation area.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If laser beam radiation is used to separate substrates, then separation speed is improved, but incomplete stress generation leads to regions where bonding strength is not reduced

Engineering Contradiction:

Improveseparation speedVSAvoidseparation completeness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The separation facilitating layer acts as an intermediary between the laser absorption layer and the separation interface. It receives and accumulates stress energy from the laser radiation and mediates its transfer to the bonding interface. This intermediary layer ensures that stress is effectively distributed and accumulated throughout the separation region, enabling complete separation without requiring excessive laser power or prolonged exposure time, thus maintaining both high productivity and manufacturing precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If stress is generated in the laser absorption layer, then bonding strength is reduced for separation, but without proper stress accumulation the separation boundary is not properly formed

Engineering Contradiction:

Improvebonding strength reductionVSAvoidseparation boundary definition

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The separation facilitating layer is designed with specific local properties that enable selective stress accumulation at the separation interface. The layer has controlled thickness and material characteristics that favor stress concentration at the boundary between the first and second substrates. This local quality ensures that stress is preferentially accumulated where needed (at the separation boundary) rather than being distributed uniformly, resulting in well-defined separation boundaries with high manufacturing precision.

Inventive Principle:

Principle #3Local quality

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 allows for precise and controlled separation of substrates without damaging the device layers, reducing the risk of wafer peeling and improving transcription efficiency.

Implementation Method 1

A separation facilitating layer and a laser absorption layer are formed on a second substrate in this order. A separation modification layer is formed by radiating laser beam to the laser absorption layer while generating a stress in the laser absorption layer

Methodology Applied

Scientific EffectLaser absorption: Absorption (EM radiation)

Implementation Method 2

radiating laser beam to the laser absorption layer while generating a stress in the laser absorption layer

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12512336B2Substrate processing method and substrate processing apparatus

Publication Date: 2025.12.30 TOKYO ELECTRON LTD

AI summary

A substrate processing method of a combined substrate in which a first substrate and a second substrate are bonded to each other is provided. A separation facilitating layer and a laser absorption layer are formed on the second substrate in this order. The substrate processing method includes forming a separation modification layer by radiating laser beam to the laser absorption layer while generating a stress in the laser absorption layer; and separating the second substrate from the first substrate along a boundary between the second substrate and the separation facilitating layer.