Ultrasonic Oscillator Structure for Higher CMUT Capacitance
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Solution Overview
Problem
Current capacitive micromachined ultrasonic transducers face challenges in increasing capacitance value to enhance sensitivity, which is essential for improving the efficiency of miniaturized ultrasonic systems used in nondestructive testing, medical imaging, ultrasonic microscopy, fingerprint recognition, and Internet of Things applications.
Innovation Solution
The ultrasonic oscillator element design significantly reduces electrode separation distance by configuring a first cavity between the first and second lower electrodes, allowing for increased capacitance and improved working efficiency through the application of DC and AC signals to different electrode portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrode separation distance is reduced to increase capacitance, then the sensitivity and working efficiency of the transducer is improved, but the device structure becomes more complex
Solution Approach 1:
The patent divides the electrode structure into multiple segments: first and second lower electrodes, first and second upper electrodes, with insulating layers separating them. This segmentation allows the creation of multiple cavities (first cavity and second cavity) that collectively reduce the effective electrode separation distance while maintaining a manageable structural organization through modular design
Solution Approach 2:
The patent implements a nested structure where the first cavity is formed between the first insulating layer and second insulating layer, and the second cavity is formed between the third insulating layer and fourth insulating layer. These cavities are positioned to overlap in the stacking direction, creating a nested arrangement that maximizes capacitance within a compact vertical footprint
2Reliability
If multiple insulating layers and electrodes are added to reduce electrode separation distance, then capacitance increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies different properties to different regions: the first and second insulating layers have different dielectric constants, and the first and second upper electrodes have different areas. This local differentiation allows optimization of capacitance in specific regions while maintaining overall structural feasibility and reducing the need for ultra-precise uniform alignment throughout the entire device
3Reliability
If the electrode separation distance is reduced significantly, then the capacitance value increases to enhance sensitivity, but the difficulty of detecting and measuring oscillation increases
Solution Approach 1:
The patent makes the insulating layers dynamic by allowing them to be deformed during operation. The first insulating layer can be deformed by applying a first voltage, and the second insulating layer can be deformed by applying a second voltage. This dynamic capability allows the effective electrode separation distance to be modulated, enabling oscillation detection while maintaining high capacitance
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 design enhances capacitance, thereby significantly improving the working efficiency of capacitive micromachined ultrasonic transducers, particularly in reducing electrode separation distance and increasing signal quality.
Implementation Method 1
the first upper electrode is driven by a DC signal to cause the second insulating layer to be concave toward the first cavity
Implementation Method 2
the second lower electrode overlaps at least part of the first lower electrode in a stacking direction... the second portion of the first upper electrode is driven by an AC signal to oscillate relative to the second lower electrode
Data Source
AI summary
An ultrasonic oscillator element, including a substrate, a first lower electrode, a first insulating layer, a second insulating layer, a second lower electrode, a first upper electrode, and a third insulating layer. The first lower electrode is disposed on the substrate. The first insulating layer is disposed so that the first lower electrode is located between the first insulating layer and the substrate. The second insulating layer and the first insulating layer form a first cavity. The second lower electrode is disposed adjacent to the first side of the second insulating layer and located in the outer region of the first cavity. The first upper electrode is disposed on the second side of the second insulating layer. The third insulating layer is disposed so that the second lower electrode is located between the third insulating layer and the first insulating layer.