Piezoelectric Composite Substrate Bonding at Low Heat Treatment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing piezoelectric composite substrates face issues with film-thickness uniformity, temperature stability, and high manufacturing costs due to thermal expansion differences between substrates, leading to incomplete transfer of piezoelectric thin films and limited bonding strength at low heat treatment temperatures.
Innovation Solution
A piezoelectric composite substrate is created by successively stacking an insulating substrate with a Si-containing amorphous interlayer and a piezoelectric layer, where the insulating substrate has a lower linear expansion coefficient than the piezoelectric layer, allowing for sufficient bonding strength through ion implantation at temperatures of 100°C or less, using materials like quartz and Si-containing amorphous materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a piezoelectric substrate is thinned by grinding to improve temperature properties, then temperature stability is improved, but film-thickness uniformity deteriorates
Solution Approach 1:
An ion-implanted layer is introduced as an intermediary between the piezoelectric substrate and the insulating substrate. This layer serves as a release interface that enables controlled separation, allowing the piezoelectric substrate to be thinned while maintaining thickness uniformity through the mediator's structured interface
Solution Approach 2:
The physical and chemical parameters of the piezoelectric substrate are changed through ion implantation, creating a modified layer with different properties. This parameter change enables the substrate to be separated at a specific depth while maintaining the integrity and uniformity of the remaining thin film
2Stability of the object's composition
If thermal expansion coefficients of substrates are made different to improve temperature properties, then temperature stability is improved, but bonding strength deteriorates due to warping and cracking
Solution Approach 1:
The bonding structure is segmented into three distinct layers: the piezoelectric substrate, the ion-implanted intermediate layer, and the insulating substrate. This segmentation allows each layer to accommodate thermal expansion differences independently, preventing warping and cracking while maintaining overall bonding strength
Solution Approach 2:
The ion-implanted layer acts as a mediator between substrates with different thermal expansion coefficients. This intermediate layer absorbs and distributes the thermal stress generated by coefficient differences, preventing direct stress transmission that would cause bonding failure
3Stability of the object's composition
If heat treatment temperature is reduced to prevent substrate warping, then warping is suppressed, but bonding strength becomes insufficient
Solution Approach 1:
The ion-implanted layer serves as a mediator that enables effective bonding at lower temperatures. This intermediate layer provides a controlled interface that facilitates bond formation without requiring high thermal energy, thus preventing substrate warping while achieving sufficient bonding strength
4Strength
If ion implantation is used to enable low-temperature bonding, then bonding strength is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process utilizes parameter changes through ion implantation to achieve a specific depth profile in the intermediate layer. This controlled parameter change enables low-temperature bonding while maintaining a systematic and controllable manufacturing process
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 achieves stable bonding and improved temperature properties for piezoelectric layers like lithium tantalate or lithium niobate on insulating substrates, preventing warping and cracking, and enabling efficient transfer of thin films across the entire substrate surface.
Implementation Method 1
sufficient bonding strength through ion implantation at temperatures of 100°C or less
Implementation Method 2
heat treating the bonded body to thermally release the ion implantation layer
Implementation Method 3
the insulating substrate has a linear expansion coefficient smaller than that of the piezoelectric layer, allowing for sufficient bonding strength through ion implantation at temperatures of 100°C or less
Data Source
AI summary
Provided are a piezoelectric substrate and a manufacturing method thereof, by which bonding strength enough for forming a piezoelectric layer on an insulating substrate having a significantly small linear expansion coefficient can be obtained through ion implantation even by heat treatment at 100° C. or less. A piezoelectric composite substrate 10 having successively stacked insulating substrate 2, interlayer 3, and piezoelectric layer 1a is manufactured by laminating a piezoelectric single-crystal substrate surface having an ion implantation layer 1a thereon and an insulating substrate 2 having a linear expansion coefficient less than that of the piezoelectric single-crystal substrate 1 with a difference in a range of 14×10−6/K to 16×10−6/K via the interlayer 3 to obtain a bonded body 4, and after heat treatment, leaving the ion implantation layer 1a as a piezoelectric layer and releasing the remaining portion 1b of the piezoelectric single-crystal substrate from the bonded body 4. The insulating substrate 2 and the interlayer 3 are each made of a Si-containing amorphous material.