Bonded Wafer Separation by Laser Ablation of Curable Bonding Layer
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Solution Overview
Problem
Existing methods for separating bonded wafers with epitaxial functional layers face challenges in maintaining a high survival rate of device structures due to thermal constraints and permanent bonding issues when using organic materials, limiting the flexibility in device design and manufacturing processes.
Innovation Solution
A method involving the use of a curable bonding material, where the bonded wafer is irradiated with a laser beam to decompose the bonding material and separate the support from the device structure portion, reducing mechanical stress and improving the survival rate of the device structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermocompression bonding is used to bond the epitaxial substrate and temporary support substrate, then the bonding strength is improved, but the thermal conditions are restricted to below a certain level which limits device manufacturing flexibility
Solution Approach 1:
A curable bonding material is introduced as an intermediary layer between the epitaxial substrate and the support substrate. This bonding material can be cured at lower temperatures compared to direct thermocompression bonding, thereby achieving sufficient bonding strength while avoiding the need for high thermal conditions that would restrict device manufacturing flexibility.
Solution Approach 2:
The bonding process transitions from relying solely on thermal parameters (thermocompression) to incorporating chemical curing parameters. The curable bonding material allows bonding to be achieved through chemical reactions at lower temperatures, changing the bonding mechanism from purely thermal to chemically-assisted, thus resolving the contradiction between bonding strength and thermal condition restrictions.
2Reliability
If thermal process is applied to create ohmic contact after removing the starting substrate, then the electrical contact is improved, but the temporary support becomes permanent bonding making separation difficult
Solution Approach 1:
The support substrate is removed by laser beam irradiation before the thermal process for creating ohmic contact. This preliminary removal action eliminates the permanent bonding issue that would occur if thermal processing were applied after substrate removal, as the curable bonding material has already been decomposed and the support is already separated.
Solution Approach 2:
The mechanical/thermal separation process is replaced with laser beam irradiation to remove the support substrate. This substitution allows the support to be removed without applying thermal conditions that would cause permanent bonding, thereby maintaining ease of manufacture while achieving reliable electrical contact through subsequent thermal processing.
3Ease of manufacture
If machining or etching is used to remove the support, then the separation is achieved, but the survival rate of the device structure portion is reduced
Solution Approach 1:
Mechanical machining and chemical etching processes are replaced with laser beam irradiation to remove the support substrate. The laser beam selectively decomposes the curable bonding material and removes the support without applying mechanical stress or harsh chemicals to the device structure portion, thereby achieving separation while maintaining a high survival rate of the device structures.
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 increases the survival rate of the device structure portion by minimizing mechanical stress during separation, compared to traditional machining or etching methods, while allowing for more flexible device design and manufacturing processes.
Implementation Method 1
by irradiating the bonded wafer with a laser beam, the curable bonding material and/or at least a portion of the surface of the device structure portion that comes into contact with the curable bonding material absorb(s) the laser beam to decompose the curable bonding material and/or the surface of the device structure portion
Data Source
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Figure 6~9
AI summary
The present invention is a method for separating a bonded wafer, the method comprises separating a support from a bonded wafer which comprises a device structure portion having two or more electrodes with different polarities on one side of an epitaxial functional layer, and the device structure portion being bonded to a support made of a foreign substrate using a curable bonding material, wherein, by irradiating the bonded wafer with a laser beam, the curable bonding material and/or at least a portion of the surface of the device structure portion that comes into contact with the curable bonding material absorb(s) the laser beam to decompose the curable bonding material and/or the surface of the device structure portion, and thus the device structure portion and the support are separated. As a result, it is provided a method for separating a bonded wafer with a high survival rate of device structure portion in the separation of a bonded wafer that is firmly bonded with a curable bonding material, as a bonded wafer, which has the device structure portion having two or more electrodes with different polarities on one surface of an epitaxial functional layer and the device structure portion is bonded to a support made of a foreign substrate with the curable bonding material.