Bonded Substrate Separation Using Laser-Induced Interface Stress
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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
Engineering Contradiction Analysis
1Manufacturing precision
If laser beam is radiated to separate substrates, then separation is achieved, but regions with insufficient laser radiation cause improper separation and potential device layer damage
Solution Approach 1:
A separation facilitating layer is formed on the substrate surface before the separation process. This layer is specifically designed to have high laser absorption capability, so that when laser beam is radiated, the separation facilitating layer absorbs the laser energy first and generates stress to initiate separation, ensuring that even regions with lower laser radiation intensity can achieve proper separation without damaging the device layer.
Solution Approach 2:
The separation facilitating layer acts as an intermediary between the laser beam and the substrate. It mediates the laser energy absorption and stress generation process, converting laser radiation into controlled stress at the separation interface. This intermediary layer protects the device layer from direct laser exposure while ensuring effective separation initiation.
2Productivity
If laser beam intensity is increased to ensure separation in all regions, then separation completeness is improved, but device layer damage risk increases
Solution Approach 1:
The separation facilitating layer is distributed locally across the substrate surface where separation is needed. This layer has localized laser absorption properties, concentrating the laser energy absorption function at specific locations (the separation interface) rather than requiring high-intensity laser radiation across the entire substrate. This enables complete separation while protecting the device layer from excessive laser exposure.
Solution Approach 2:
The optical parameters of the separation facilitating layer are specifically designed to have high laser absorption coefficient. By changing the material parameters of this layer, it can efficiently absorb laser energy at lower intensities, initiating separation without requiring high laser power that would damage the device layer.
3Device complexity
If traditional laser lift-off method is used, then separation process is simple, but bonding strength is not sufficiently reduced in all regions leading to improper separation
Solution Approach 1:
The separation facilitating layer is formed in advance on the substrate surface before the laser separation process. This preliminary preparation ensures that when laser beam is radiated, the separation facilitating layer is already in position to absorb laser energy and generate stress uniformly across all regions, achieving consistent separation without requiring complex laser scanning patterns or high-intensity radiation.
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 layer, reducing the risk of wafer peeling and improving transcription efficiency.
Implementation Method 1
a laser absorption layer P is formed on a second wafer W2... radiating laser beam to the laser absorption layer... generating a stress in the laser absorption layer
Implementation Method 2
radiating laser beam to the laser absorption layer while generating a stress in the laser absorption layer
Data Source
AI summary
A 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.