Piezoelectric Composite Substrate with Li Diffusion Recovery
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Solution Overview
Problem
The manufacturing of composite substrates with piezoelectric layers using ion implantation methods results in variations in lithium (Li) amounts, leading to characteristic variations in surface acoustic wave devices, particularly affecting the performance of LiTaO3 layers, which is challenging to resolve with conventional polishing and grinding methods.
Innovation Solution
A method involving ion implantation into a piezoelectric substrate, followed by bonding with a support substrate, separating the piezoelectric layer, and diffusing lithium into the layer while applying a temperature and electric field treatment to maintain or restore the piezoelectric properties, ensuring a quasi-stoichiometric composition and reduced Li amount variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to manufacture composite substrates, then thin film thickness and film thickness uniformity are improved, but Li amount variation occurs leading to characteristic variation
Solution Approach 1:
The patent applies Li diffusion treatment to change the concentration parameter of Li in the piezoelectric layer, transforming the composition from non-stoichiometric to quasi-stoichiometric. This resolves the Li amount variation caused by ion implantation while maintaining the thin film thickness and uniformity advantages.
Solution Approach 2:
The patent converts the harmful effect of Li amount variation and composition deviation into a benefit by applying Li diffusion treatment. The diffusion process utilizes the concentration gradient created by ion implantation to redistribute Li atoms, transforming the composition defect into a controlled quasi-stoichiometric state that improves device characteristics.
2Stability of the object's composition
If conventional polishing and grinding methods are used, then Li amount variation can be reduced, but film thickness uniformity and manufacturing precision deteriorate
Solution Approach 1:
The patent replaces the mechanical polishing and grinding methods with a chemical/physical Li diffusion treatment. Instead of mechanically removing material to reduce Li variation, the invention uses thermal diffusion to redistribute Li atoms in situ, preserving the thin film thickness and uniformity while achieving composition stability.
Solution Approach 2:
The patent changes the physical state and distribution parameter of Li through diffusion treatment, transforming the composition uniformity without affecting the geometric uniformity of the thin film. This allows simultaneous achievement of both composition stability and manufacturing precision.
3Reliability
If Li diffusion is applied to restore piezoelectric properties, then temperature characteristics improve, but processing complexity increases
Solution Approach 1:
The patent merges the Li diffusion treatment with the existing ion implantation process and subsequent heat treatment steps. The Li diffusion is performed during the same thermal processing sequence used for other purposes, combining multiple functions into a single integrated process step rather than adding a separate independent operation.
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 enables the stable manufacturing of composite substrates with reduced Li amount variation, resulting in improved characteristics such as enhanced electromechanical coupling coefficients and temperature stability for surface acoustic wave devices.
Implementation Method 1
a step of performing ion implantation into a piezoelectric substrate
Implementation Method 2
a step of diffusing Li into the piezoelectric layer after the separating step
Implementation Method 3
a step of increasing the temperature of the piezoelectric substrate to recover a piezoelectric property
Data Source
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AI summary
An object of the present invention is to provide a method of manufacturing a composite substrate including a piezoelectric layer with less Li amount variation and a support substrate. A method of manufacturing a composite substrate of the present invention includes a step of performing ion implantation into a piezoelectric substrate, a step of bonding the piezoelectric substrate and the support substrate, a step of separating the bonded substrate, at an ion-implanted portion of the piezoelectric substrate, into the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate after the step of bonding the piezoelectric substrate and the support substrate, and a step of diffusing Li into the piezoelectric layer after the separating step.