SOI Film Bulk Acoustic Resonator With Implanted Lower Electrode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional film bulk acoustic resonators face challenges such as large losses, complex processing, and stress-induced structural reliability issues due to metal electrodes and the need for sacrificial layers, which hinder miniaturization and integration in modern communication devices, especially with the advent of 5G technology.
Innovation Solution
A fabricating method using a silicon-on-insulator (SOI) substrate with a lower electrode formed by ion implantation, eliminating the need for stop and support layers, and growing AlN piezoelectric films with improved crystal quality using vapor phase epitaxy or magnetron sputtering, along with air cavity processing to simplify the structure and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metal electrodes are used in traditional film bulk acoustic resonators, then electrical connection is achieved, but loss increases and structural reliability deteriorates due to stress concentration
Solution Approach 1:
The patent removes the metal lower electrode from the structure, replacing it with a conductive oxide layer formed by ion implantation on the silicon substrate. This extraction of the problematic metal electrode eliminates the source of stress concentration and associated losses while maintaining electrical functionality through the alternative conductive oxide pathway.
Solution Approach 2:
The patent creates a functional copy of the lower electrode using conductive oxide material that replicates the electrical connection function without reproducing the harmful mechanical stress characteristics of metal electrodes. The conductive oxide layer serves as an analogous but superior replacement that achieves the same electrical purpose without the drawbacks.
2Device complexity
If sacrificial layers are used to create air gaps, then air cavity formation is achieved, but process complexity increases due to additional grounding and polishing steps
Solution Approach 1:
The patent eliminates the sacrificial layer approach entirely, extracting this complex intermediate step from the manufacturing process. Instead of depositing sacrificial material, patterning it, filling air gaps, grounding, and polishing, the invention directly forms the air cavity structure through selective removal of silicon, dramatically simplifying the process while achieving the same acoustic wave confinement function.
3Reliability
If AlN piezoelectric films are deposited on patterned electrodes, then electrode connection is achieved, but stress-induced distortion of film thickness occurs, reducing structural reliability
Solution Approach 1:
The patent removes the patterned metal electrode structure that causes stress concentration during deposition. By replacing it with a planar conductive oxide layer on the silicon substrate, the underlying surface remains flat and uniform throughout the deposition process, preventing stress-induced distortion and ensuring consistent film thickness across the entire piezoelectric layer.
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 method results in a film bulk acoustic resonator with low power consumption, high integration density, and improved radiation resistance, meeting the requirements for miniaturization and high performance in future communication devices, including those for 5G technology.
Implementation Method 1
The principle of the film bulk acoustic resonator is to apply an electrical signal between upper and lower electrodes by utilizing the piezoelectric effect of the piezoelectric layer. Because the piezoelectric effect of the piezoelectric layer can generate an acoustic signal, the acoustic signal oscillates between the electrodes.
Implementation Method 2
The lower electrode can be made of a conductive oxide layer formed by ion implantation on the silicon substrate
Implementation Method 3
growing AlN piezoelectric films with improved crystal quality using vapor phase epitaxy or magnetron sputtering
Implementation Method 4
growing AlN piezoelectric films with improved crystal quality using vapor phase epitaxy or magnetron sputtering
Data Source
AI summary
A film bulk acoustic resonator and a fabricating method thereof is provided. The fabricating method includes: fabricating a lower electrode on a first surface of an SOI substrate; forming piezoelectric layers on the first surface of the SOI substrate and the lower electrode; forming top electrodes on the piezoelectric layers; processing an air cavity on a second surface of the SOI substrate, wherein the second surface and the first surface are oppositely arranged. The fabricating method simplifies a preparation process of FBAR, a quality of a AlN film crystal grown though the fabrication method is high, an improvement of a device performance is facilitated, and meanwhile a thickness of a top silicon is controlled through a position of a silicon injected oxygen isolation to regulate a frequency of the film bulk acoustic resonator.