Single-Crystal Piezoelectric Thin Films With Stress-Neutral Templates
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Solution Overview
Problem
Conventional bulk acoustic wave resonators using polycrystalline piezoelectric AlN thin films face degradation in quality at thicknesses below 0.5 um, limiting their performance for high-frequency applications, and the growth of single crystalline piezoelectric films on patterned electrodes complicates crystalline orientation and quality control.
Innovation Solution
The use of single crystalline or epitaxial piezoelectric thin films, formed using stress-neutral template layers and deposited via methods like MOCVD or MBE, allows for high-quality piezoelectric films with low stress, enabling reliable and high-performance bulk acoustic wave resonators for high-frequency applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric AlN thin films are used in conventional bulk acoustic wave resonators, then manufacturing is simpler and cost is lower, but quality factor degrades at thicknesses below 0.5 um limiting high-frequency performance
Solution Approach 1:
The patent changes the crystalline structure parameter from polycrystalline to single crystal, and controls film thickness parameter to be greater than 0.5 um, thereby achieving high quality factor while maintaining manufacturability through established single crystal growth techniques
Solution Approach 2:
The patent uses a composite structure combining single crystal piezoelectric material with carefully engineered thickness to achieve both high quality factor and manufacturability, leveraging the superior properties of single crystal while controlling dimensions to avoid degradation
2Manufacturing precision
If single crystalline piezoelectric films are grown on patterned electrodes, then crystalline quality can be improved, but the process complexity increases due to orientation control difficulties
Solution Approach 1:
The patent performs preliminary preparation of the substrate surface and electrode pattern before single crystal growth, ensuring proper orientation and quality conditions are established in advance, thereby simplifying the subsequent growth process and reducing overall complexity
Solution Approach 2:
The patent introduces a buffer layer or template structure as an intermediary between the patterned electrode and the single crystal piezoelectric film, facilitating crystalline growth with correct orientation while decoupling the complexity of pattern alignment from the crystal growth 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 approach results in enhanced quality factor and electro-mechanical coupling for RF filters, overcoming limitations of polycrystalline films and enabling effective high-frequency performance with improved cost-efficiency.
Implementation Method 1
depositing a material on a first surface of a Si substrate to provide a stress neutral template layer
Implementation Method 2
A piezoelectric thin film including a Group III element and nitrogen can be sputtered onto the stress neutral template layer
Implementation Method 3
A piezoelectric resonator can be formed on the remaining portion of the piezoelectric thin film
Data Source
AI summary
A method of forming a piezoelectric thin film can include depositing a material on a first surface of a Si substrate to provide a stress neutral template layer. A piezoelectric thin film including a Group III element and nitrogen can be sputtered onto the stress neutral template layer and a second surface of the Si substrate that is opposite the first surface can be processed to remove that Si substrate and the stress neutral template layer to provide a remaining portion of the piezoelectric thin film. A piezoelectric resonator can be formed on the remaining portion of the piezoelectric thin film.