Semiconductor Laminate Structure for Laser Lift-Off Chip Transfer
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Solution Overview
Problem
Existing semiconductor mounting techniques face challenges such as long processing times, damage to semiconductor elements during transfer and mounting, limitations in the number of elements that can be transferred simultaneously, and inadequate heat resistance of adhesives, particularly for high-temperature applications.
Innovation Solution
A laminate structure is used that includes a laser-absorbing temporary adhesive layer, a protective layer, and a semiconductor layer laminated on a laser-transmitting substrate, allowing for semiconductor transfer via laser lift-off (LLO) to a support substrate with a pressure-sensitive adhesive layer, enabling efficient and damage-free transfer and mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct bonding of semiconductor element to substrate is performed to improve heat dissipation, then heat dissipation property is improved, but processing time increases due to one-by-one mounting
Solution Approach 1:
The invention segments the bonding process by introducing a temporary adhesive layer that allows individual chip bonding while maintaining the ability to handle multiple chips. The laser-absorbing temporary adhesive layer enables selective bonding of chips at different positions without requiring simultaneous high-temperature processing of all chips, thus improving both heat dissipation and mounting speed.
Solution Approach 2:
The laser-absorbing temporary adhesive layer serves as an intermediary between the semiconductor chip and the substrate. This intermediate layer absorbs laser energy for precise bonding while allowing the chip to be bonded at lower temperatures, improving heat dissipation properties without sacrificing mounting speed. The temporary adhesive can be removed after bonding, leaving a clean interface for optimal thermal contact.
2Strength
If high temperature and pressure are applied for direct bonding to improve heat dissipation, then bonding strength is improved, but semiconductor elements may be damaged during transfer and mounting
Solution Approach 1:
The invention changes the bonding parameters by using a laser-absorbing temporary adhesive layer that enables bonding at lower temperatures and pressures compared to direct bonding. The laser absorption property of the temporary adhesive layer allows for precise, localized energy delivery, achieving strong bonds without subjecting the semiconductor elements to excessive thermal and mechanical stress that could cause damage.
Solution Approach 2:
The invention replaces the conventional mechanical and thermal bonding system with a laser-based bonding system. Instead of applying high temperature and pressure uniformly, a laser beam is used to selectively bond chips through the temporary adhesive layer, reducing mechanical stress and thermal damage to the semiconductor elements while maintaining bonding strength.
3Productivity
If stamp method is used to transfer and mount large number of semiconductor elements at one time, then productivity is improved, but heat resistance of pressure-sensitive adhesive resin is insufficient for high temperature applications
Solution Approach 1:
The invention uses a composite adhesive system consisting of a laser-absorbing temporary adhesive layer combined with a pressure-sensitive adhesive layer. The temporary adhesive layer provides laser absorption capability for precise bonding, while the pressure-sensitive adhesive layer provides heat resistance for high-temperature applications. This composite structure enables both high productivity through simultaneous multi-chip bonding and adequate heat resistance for power semiconductor applications.
Solution Approach 2:
The invention applies different adhesive properties to different layers: the temporary adhesive layer is optimized for laser absorption and low-temperature bonding to enable high-speed processing, while the pressure-sensitive adhesive layer is optimized for heat resistance to withstand high-temperature applications. This local differentiation of material properties allows the system to achieve both high productivity and adequate heat resistance.
4Reliability
If polyimide copolymer is used as pressure-sensitive adhesive layer to prevent warpage and cracks, then reliability is improved, but adhesive residue remains on chip surface after transfer
Solution Approach 1:
The invention extracts the adhesive function into a separate removable temporary adhesive layer made of laser-absorbing material. This temporary adhesive layer can be completely removed after bonding using laser irradiation or chemical etching, leaving no residue on the chip surface. The underlying pressure-sensitive adhesive layer (such as polyimide copolymer) maintains substrate stability during thinning, while the extracted temporary adhesive layer eliminates the residue problem.
Solution Approach 2:
The temporary adhesive layer is designed as a disposable component that serves its purpose during bonding and then is completely removed. This disposable layer enables precise bonding during the process but is discarded afterward, leaving a clean chip surface without the residue issues associated with permanent adhesives like polyimide copolymer.
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 LLO technique significantly reduces processing time, prevents semiconductor damage, and allows for mass production of semiconductor devices without the need for substrate removal, while maintaining high heat resistance and accuracy.
Implementation Method 1
a laser-absorbing temporary adhesive layer 1, a protective layer 1, and a semiconductor layer 1 laminated in this order on a laser-transmitting substrate 1
Implementation Method 2
a laser-transmitting substrate 1; and a laser-absorbing temporary adhesive layer 1
Implementation Method 3
a pressure-sensitive adhesive layer which is an adherend of a semiconductor element after laser transfer
Data Source
Figure 1A~2B
Figure 3A~4B
Figure 5~6E
AI summary
The present invention relates to a laminate in which a laser-absorbing temporary adhesive layer 1, a protective layer 1, and a semiconductor layer 1 are laminated in this order on a laser-transmissive substrate 1.