Composite Piezoelectric Substrate Bonding for Temperature Stability
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Solution Overview
Problem
Elastic wave filters made from lithium tantalate (LiTaO3) and lithium niobate (LiNbOx) suffer from poor temperature stability, leading to variations in passband with temperature changes.
Innovation Solution
A support layer substrate with a main support surface achieving a target roughness is used, where each sampling area has a length and width of up to 400 microns, and the roughness is filtered to have a maximum peak height of less than 20 nanometers and an arithmetic mean height of less than 0.7 nanometers. This substrate is bonded with a piezoelectric layer using a direct pressing method, enhancing bonding area and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lithium tantalate or lithium niobate piezoelectric materials are used to achieve wide-band filtering characteristics, then the electromechanical coupling coefficient is improved, but temperature stability deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a piezoelectric layer (lithium tantalate or lithium niobate) bonded to a support layer substrate. This composite structure allows the piezoelectric material to provide high electromechanical coupling coefficient while the support substrate provides temperature stability, resolving the contradiction between these two properties.
2Stability of the object's composition
If the piezoelectric layer is bonded to the support layer substrate, then temperature stability is improved, but bonding quality becomes critical and difficult to control
Solution Approach 1:
The patent specifies precise surface roughness parameters for the support layer substrate (Sa≤0.7nm, Sp≤20nm) to optimize bonding quality. By controlling these surface parameters within specific ranges, the bonding process becomes more predictable and controllable, reducing variability in bonding quality.
Solution Approach 2:
The patent performs preliminary surface treatment and roughness control on the support layer substrate before bonding. By pre-establishing the optimal surface conditions (specific roughness parameters), the subsequent bonding process achieves consistent high-quality results without requiring complex real-time adjustments.
3Strength
If the surface roughness is reduced to improve bonding quality, then bonding strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent defines specific surface roughness parameters (Sa≤0.7nm, Sp≤20nm) that balance bonding performance with manufacturing feasibility. These quantified parameters provide clear manufacturing targets that can be achieved through standard polishing processes, avoiding excessive complexity while ensuring adequate bonding strength.
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
The approach improves bonding efficiency and strength between the support layer substrate and the piezoelectric layer, resulting in enhanced temperature stability and reduced production costs for elastic wave devices.
Implementation Method 1
a support layer material is polished to obtain a polished support layer material
Implementation Method 2
a piezoelectric layer is bonded to the main support surface of the support layer substrate by a direct pressing method
Data Source
AI summary
A support layer substrate, a composite substrate and an electronic device are provided. The support layer substrate has a main support surface, each sampling area on the main support surface achieves a target roughness, and each sampling area is defined as an area with a length and a width each smaller than or equal to 400 μm. The target roughness is represented by a maximum peak height after Gaussian filtering of smaller than 20 nm, and the target roughness is represented by an arithmetic mean height after Gaussian filtering of smaller than 0.7 nm. The support layer substrate can achieve better bonding results and improve a bonding efficiency. The obtained composite substrate has higher bonding strength and a high production yield, thereby ensuring quality of the electronic device and reducing production costs.