Bulk Acoustic Wave Resonator Cavity Formation in LiNbO3/LiTaO3
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Solution Overview
Problem
Conventional deposition methods cannot be used to form a piezoelectric layer constituted by lithium niobate crystal or lithium tantalate crystal for bulk acoustic wave resonators, as these crystals cannot be deposited using physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes.
Innovation Solution
A method involving ion implantation to define a cleavage plane in a piezoelectric substrate, followed by annealing to split the substrate and expose the piezoelectric layer, allowing for the formation of a resonant cavity with electrode structures and dielectric layers, enabling the use of lithium niobate or lithium tantalate crystals for improved bulk acoustic wave resonator manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional deposition methods (PVD or CVD) are used to form a piezoelectric layer, then the manufacturing process is simple and controllable, but lithium niobate crystal or lithium tantalate crystal cannot be deposited
Solution Approach 1:
The patent changes the fundamental parameter of piezoelectric layer formation from vapor deposition to mechanical thinning. By using ion implantation to create a cleavage plane and subsequent mechanical thinning processes, the method enables the use of lithium niobate and lithium tantalate crystals that cannot be deposited by conventional PVD or CVD methods
Solution Approach 2:
The patent replaces the chemical/vapor deposition system with a mechanical thinning system. Instead of depositing piezoelectric material through vapor phases, the invention uses mechanical processes (ion implantation, cleavage, thinning) to prepare the piezoelectric layer from bulk crystal substrates
2Adaptability or versatility
If ion implantation and annealing processes are used to split the piezoelectric substrate, then lithium niobate or lithium tantalate crystals can be utilized, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by performing ion implantation to pre-create a cleavage plane within the piezoelectric substrate before thinning. This preliminary structuring enables subsequent easy separation and thinning to achieve the desired piezoelectric layer thickness
Solution Approach 2:
The patent segments the piezoelectric substrate into distinct portions through the cleavage plane created by ion implantation. The substrate is divided into a first portion (retained for the piezoelectric layer) and a second portion (removed), allowing precise thickness control
3Reliability
If the piezoelectric substrate is thinned to form a piezoelectric layer, then the resonator performance is improved, but the substrate must be split and portions removed
Solution Approach 1:
The patent applies local quality by creating a specific cleavage plane at a predetermined depth within the piezoelectric substrate. This localized modification enables precise thickness control of the piezoelectric layer while minimizing unnecessary material removal compared to bulk thinning methods
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 allows for the effective formation of bulk acoustic wave resonators with enhanced performance by utilizing lithium niobate or lithium tantalate crystals, improving the resonator's bandwidth and avoiding the limitations of traditional deposition methods.
Implementation Method 1
performing an ion implantation process on the piezoelectric substrate to define a cleavage plane in the piezoelectric substrate
Implementation Method 2
performing an annealing process on the piezoelectric substrate to split the piezoelectric substrate along the cleavage plane
Implementation Method 3
performing an annealing process on the piezoelectric substrate to split the piezoelectric substrate along the cleavage plane
Data Source
AI summary
Provided is a method of manufacturing a bulk acoustic wave resonator, which includes: providing a piezoelectric substrate for forming a piezoelectric layer; forming a first electrode structure on the portion of the piezoelectric substrate for forming the piezoelectric layer; forming a dielectric layer on the first electrode structure, and performing a patterning process on the dielectric layer to form a patterned dielectric layer comprising a sacrificial dielectric part and a periphery dielectric part; forming a boundary layer on the patterned dielectric layer, the boundary layer covering a surface of the patterned dielectric layer and surrounding the sacrificial dielectric part; thinning the piezoelectric substrate to form the piezoelectric layer, the first electrode structure being located at a first side of the piezoelectric layer; forming a second electrode structure on a second side of the piezoelectric layer; and removing the sacrificial dielectric part to form a resonant cavity.