CMUT Cavity Bonding Structure for Low-Frequency Diaphragm Stability
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Solution Overview
Problem
Existing fabrication methods for capacitive micromachined ultrasonic transducers (CMUTs) are complex, time-consuming, and prone to incomplete etching and residue formation, especially when applied to low-frequency ultrasound and large-size array elements, which can lead to diaphragm collapse.
Innovation Solution
A method involving separate fabrication of array and opposite substrates, followed by alignment and attachment, allowing for adjustable thickness and radius of the vibrating diaphragm layer, and using glass-based materials with low-temperature bonding to form an airtight cavity, simplifying the process and reducing etching time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing fabrication methods are used for CMUTs, then the transducer can be manufactured, but the fabrication process is complex and time-consuming with incomplete etching and residue formation
Solution Approach 1:
The patent divides the CMUT fabrication into two independent substrates (array substrate and opposite substrate) that are fabricated separately and then bonded together. This segmentation allows each substrate to be optimized independently, eliminating the complex multi-step etching process required in conventional single-substrate methods and preventing residue formation from incomplete etching.
Solution Approach 2:
The cavity structure is pre-formed on the array substrate before bonding with the opposite substrate. This preliminary action eliminates the need for complex post-bonding etching processes, ensuring complete cavity formation without residue while simplifying the overall fabrication workflow.
2Reliability
If existing fabrication methods are used for low-frequency ultrasound and large-size array elements, then the transducer can be manufactured, but diaphragm collapse occurs due to incomplete etching and residue formation
Solution Approach 1:
By segmenting the device into two separately fabricated substrates that are subsequently bonded, the method eliminates the problematic etching process entirely. This prevents residue formation that would compromise diaphragm integrity, especially critical for large-size array elements and low-frequency applications where structural perfection is paramount.
Solution Approach 2:
The patent introduces a bonding interface as an intermediary between the array substrate and opposite substrate. This bonding approach allows the cavity to be formed without aggressive etching that could compromise diaphragm integrity, ensuring structural reliability for sensitive low-frequency and large-element applications.
3Productivity
If the array substrate and opposite substrate are fabricated separately and then attached, then productivity is enhanced and cavity formation time is shortened, but additional alignment and bonding steps are required
Solution Approach 1:
The patent segments the fabrication into parallel processes for array substrate and opposite substrate, which can be manufactured simultaneously in different locations or by different teams. This segmentation dramatically improves productivity by eliminating sequential dependencies, and the alignment/bonding steps are simplified by using pre-formed cavity structures that require minimal precision.
Solution Approach 2:
The cavity is preliminarily formed on the array substrate before bonding, which simplifies the final assembly process. This preliminary action eliminates the need for complex real-time alignment during bonding, as the pre-formed cavity provides natural registration features, thereby improving productivity without significantly increasing assembly complexity.
4Adaptability or versatility
If adjustable thickness and radius of the vibrating diaphragm layer are implemented, then design flexibility for different frequency bands is improved, but additional fabrication control steps are required
Solution Approach 1:
The segmentation into two independent substrates allows the vibrating diaphragm layer thickness and cavity radius to be independently controlled during the fabrication of each substrate. This independence enables easy adjustment for different frequency bands without requiring complex coordinated control of multiple process parameters, as each substrate can be optimized separately for the desired performance characteristics.
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 enhances productivity and performance of CMUTs by shortening cavity formation time, facilitating adjustable design for different frequency bands, and improving structural integrity.
Implementation Method 1
the opposite substrate and the array substrate are attached to each other, the opposite substrate and the array substrate form a cavity in the groove
Implementation Method 2
in an emitting stage, the transducer converts input electric energy into mechanical energy under an action of an excitation signal to transmit it out so as to implement emission of ultrasonic waves
Implementation Method 3
in a receiving stage, the transducer converts a sound wave into an electrical signal so as to implement receiving of the ultrasonic waves
Data Source
AI summary
Provides are an ultrasonic transducer, a fabrication method thereof and an electronic device. The ultrasonic transducer includes: an array substrate having a groove, a bottom electrode and an insulation layer, wherein an orthographic projection of the groove on the array substrate is within an orthographic projection of the bottom electrode on the array substrate, and the insulation layer covers the bottom electrode; and an opposite substrate, the opposite substrate and the array substrate are oppositely arranged and are attached to each other, the opposite substrate and the array substrate form a cavity in the groove, the opposite substrate has a top electrode and a vibrating diaphragm layer which are arranged in stack, and an orthographic projection of the top electrode on the array substrate is within the orthographic projection of the bottom electrode on the array substrate.