POI Substrate Acoustic Impedance Matching With Graded SiOxNy Layer
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Solution Overview
Problem
The existing piezoelectric-on-insulator (POI) substrates suffer from performance losses due to significant differences in acoustic impedance between the silicon-based support substrate and the dielectric layer of silicon oxide, leading to parasitic modes in acoustic wave devices.
Innovation Solution
A POI substrate is designed with an intermediate layer of variable composition, specifically silicon oxynitride (SiOxNy), that gradually adjusts its acoustic impedance between the values of the support substrate and the dielectric layer, reducing the impedance mismatch and associated performance losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silicon-based support substrate is used with a silicon oxide dielectric layer, then good adhesion is achieved, but significant acoustic impedance difference creates parasitic modes and performance loss
Solution Approach 1:
An intermediate layer of silicon oxynitride (SiOxNy) with variable composition is introduced between the silicon-based support substrate and the silicon oxide dielectric layer. This intermediate layer acts as an acoustic impedance matcher, with its composition gradually varying from silicon-rich at the support substrate interface to oxygen-rich at the dielectric layer interface, thereby reducing acoustic impedance mismatch and eliminating parasitic modes while maintaining structural adhesion.
2Object-affected harmful factors
If an intermediate layer with variable composition is introduced, then acoustic impedance matching is improved, but device complexity increases
Solution Approach 1:
The composition of the silicon oxynitride intermediate layer is varied continuously or in steps, changing the ratio of oxygen to nitrogen atoms throughout the layer thickness. This parameter change allows the acoustic impedance to be tuned gradually from the high impedance of silicon at the support interface to the lower impedance of silicon oxide at the dielectric interface, achieving impedance matching without requiring multiple discrete layers.
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 introduction of the variable composition intermediate layer effectively reduces the difference in acoustic impedance, thereby minimizing parasitic effects and enhancing the performance of acoustic wave devices by improving the matching of acoustic impedances.
Implementation Method 1
the intermediate layer is a layer having a variable composition, more particularly along its thickness, such that the acoustic impedance of the intermediate layer varies, especially in a gradual manner, between the values of the first and the second acoustic impedance
Implementation Method 2
A piezoelectric-on-insulator (POI) substrate comprises a thin layer of piezoelectric material on a support substrate
Data Source
AI summary
A piezoelectric-on-insulator substrate comprises a support substrate having a first acoustic impedance, a piezoelectric layer, especially a layer of lithium tantalate, lithium niobate, aluminum nitride, lead zirconate titanate, langasite or langatate, a dielectric layer having a second acoustic impedance and sandwiched between the piezoelectric layer and the support substrate, an intermediate layer positioned between the support substrate and the dielectric layer. The intermediate layer is a layer having a variable composition, in particular along its thickness, such that the acoustic impedance of the intermediate layer varies, in particular gradually, between the values of the first and the second acoustic impedances. The present disclosure also relates to a method for producing such a piezoelectric-on-insulator substrate and also to a surface acoustic wave device comprising such a piezoelectric-on-insulator substrate.