Piezoelectric Layer Transfer with Room-Temperature Adhesive Bonding
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Solution Overview
Problem
The existing methods for manufacturing donor substrates for piezoelectric layer transfer in RF devices face issues such as substrate curvature, high production costs, and insufficient mechanical strength due to thermal expansion coefficient differences, which limit the effectiveness of consolidation annealing and lead to bonding interface breakage during thinning.
Innovation Solution
A method involving a photo-polymerizable adhesive layer is used to assemble a heterostructure with a handling substrate, allowing for bonding at room temperature and polymerization without high-temperature processes, thereby enhancing mechanical strength and reducing curvature, while using substrates with similar thermal expansion coefficients to minimize deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If consolidation annealing is performed to strengthen oxide-oxide bonding, then bonding strength is improved, but substrate deformation increases due to thermal expansion coefficient differences
Solution Approach 1:
The patent changes the bonding mechanism from thermal oxide-oxide bonding to room-temperature photopolymerizable adhesive bonding. This parameter change in bonding temperature and method allows achieving strong bonding without subjecting the piezoelectric substrate to high temperatures that cause deformation due to thermal expansion coefficient differences between materials
Solution Approach 2:
The patent replaces the thermal field (consolidation annealing) with a photopolymerization field. Instead of using heat to strengthen bonds, a photopolymerizable adhesive layer is cured through photopolymerization at room temperature, substituting the thermal bonding mechanism with a chemical bonding mechanism that avoids thermal deformation
2Strength
If oxide layers are deposited on substrates for bonding, then adhesion is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent extracts the oxide layer deposition step from the bonding process. Instead of requiring oxide layer deposition and subsequent thermal consolidation, the invention uses a photopolymerizable adhesive layer that can be applied and cured more quickly, eliminating the time-consuming oxide deposition and high-temperature annealing steps
Solution Approach 2:
The patent changes the bonding process parameters from requiring high-temperature consolidation annealing of oxide layers to room-temperature photopolymerization of adhesive. This parameter change significantly reduces manufacturing time while maintaining or improving bonding strength
3Ease of manufacture
If photopolymerizable adhesive layer is used for bonding, then manufacturing cost is reduced and curvature is minimized, but bonding strength must be sufficient without consolidation annealing
Solution Approach 1:
The patent replaces the thermal consolidation annealing mechanism with photopolymerization chemistry. The photopolymerizable adhesive layer forms strong bonds through photopolymerization at room temperature, providing sufficient bonding strength without requiring high-temperature consolidation annealing, thereby reducing manufacturing complexity and cost
Solution Approach 2:
The photopolymerizable adhesive layer acts as an intermediary bonding agent between the piezoelectric substrate and the support substrate. This adhesive mediator provides strong adhesion through photopolymerization while being compatible with room-temperature processing, eliminating the need for high-temperature consolidation and reducing overall manufacturing cost
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 approach results in a more cost-effective, mechanically robust donor substrate with reduced curvature, enabling successful transfer of a thin piezoelectric layer without deformation, and allows for subsequent thermal annealing without degrading the bonding interface.
Implementation Method 1
a photopolymerizable adhesive layer is used to assemble a heterostructure with a handling substrate, allowing for bonding at room temperature and polymerization without high-temperature processes
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
The invention relates to a method for transferring a piezoelectric layer (3) onto a support substrate (6), comprising: - providing a donor substrate (40) consisting of a heterostructure (4) comprising a piezoelectric substrate (3) bonded to a handling substrate (2), and a polymerized adhesive layer (10) at the interface between the piezoelectric substrate (3) and the handling substrate (2), - forming a weakened zone (7) in the piezoelectric substrate (3), so as to delimit the piezoelectric layer to be transferred (31), - providing the support substrate (6), - forming a dielectric layer (8) on a main face of the support substrate (6) and/or of the piezoelectric substrate (3), - bonding the donor substrate (40) to the support substrate (6), said dielectric layer (8) being at the bonding interface, - fracturing and separating the donor substrate (40) along the weakened zone (7), at a temperature below or equal to 300°C.