Silicon Elastic Wave Structure for Suppressing Higher-Order Modes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Elastic wave devices with silicon substrates face significant higher-order mode responses due to varying crystal orientations, which affect acoustic velocities and impede efficient operation.
Innovation Solution
The elastic wave device incorporates a silicon support substrate with a piezoelectric LiTaO3 film and a dielectric SiO2 film, where the higher-order mode acoustic velocity is matched or exceeded by adjusting the crystal orientation and film thicknesses to prevent higher-order mode responses, and includes a high acoustic velocity film and a low acoustic velocity film to control wave propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon substrate is used as support substrate, then the device can be manufactured with standard semiconductor processes, but higher-order mode responses become significant depending on crystal orientation
Solution Approach 1:
The patent changes the physical parameter of acoustic velocity by selecting specific crystal orientations of the silicon substrate. By controlling the crystal orientation parameters (such as <100>, <110>, or <111> orientations), the acoustic velocity is adjusted so that higher-order mode acoustic velocity becomes equal to or higher than the acoustic velocity Vsi defined by formula (1), thereby suppressing higher-order mode responses while maintaining standard semiconductor manufacturing processes
Solution Approach 2:
The patent creates a composite structure by stacking multiple layers including the silicon substrate, piezoelectric film, and interdigital transducer electrode. This composite configuration allows the system to leverage the advantageous properties of each material: the silicon substrate provides manufacturability and controlled acoustic velocity, while the piezoelectric film provides the necessary piezoelectric effect for transducer operation
2Power
If the film thickness of the piezoelectric film is increased to about 1λ, then the transducer efficiency is improved, but higher-order mode responses become more significant
Solution Approach 1:
The patent changes the parameter of acoustic velocity through crystal orientation selection, which fundamentally alters the relationship between the piezoelectric film and the silicon substrate. This parameter change allows the system to maintain thicker piezoelectric films (about 1λ) for improved transducer efficiency while simultaneously suppressing higher-order mode responses that would normally occur with increased film thickness
3Speed
If the acoustic velocity through the silicon substrate is increased, then the device operates at higher frequencies, but higher-order mode responses increase
Solution Approach 1:
The patent utilizes crystal orientation to precisely control the acoustic velocity parameter. By selecting specific crystal orientations, the acoustic velocity is optimized to achieve the desired operating frequency while maintaining the condition that higher-order mode acoustic velocity equals or exceeds the fundamental mode acoustic velocity Vsi, thereby preventing higher-order mode responses even at higher operating frequencies
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 configuration effectively reduces higher-order mode responses, improves the Q factor of the main mode, and minimizes temperature coefficient of resonant frequency, enhancing the performance of high-frequency front-end circuits and communication devices.
Implementation Method 1
a piezoelectric film disposed directly or indirectly on the support substrate
Implementation Method 2
an interdigital transducer electrode disposed on one surface of the piezoelectric film
Data Source
AI summary
An elastic wave device includes a support substrate made of silicon, a piezoelectric film disposed directly or indirectly on the support substrate, and an interdigital transducer electrode disposed on one surface of the piezoelectric film. A higher-order mode acoustic velocity of propagation through the piezoelectric film is equal or substantially equal to an acoustic velocity Vsi=(V1)1/2 of propagation through silicon or higher than the acoustic velocity Vsi, where Vsi is specified by V1 among solutions V1, V2, and V3 with respect to x derived from Ax3+Bx2+Cx+D=0.