CMUT Electrode Protection via Filled Hole Insulator
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Solution Overview
Problem
Conventional capacitive micromachined ultrasonic transducers (CMUTs) face challenges in reducing the distance between electrodes without risking etchant exposure, which can dissolve the electrodes during manufacturing, leading to reduced sensitivity and yield.
Innovation Solution
The ultrasonic transducer design includes a cavity layer with a pair of electrodes and insulating layers, featuring a filled hole that penetrates through the insulating layer, with non-electrode regions on the electrodes to prevent etchant exposure, allowing for reduced electrode distance without electrode dissolution, thereby increasing sensitivity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between upper and lower electrodes is reduced to increase sensitivity, then the sensitivity of the ultrasonic transducer is improved, but the through-hole may reach the electrodes during manufacturing, causing etchant to dissolve the electrodes and reducing yield
Solution Approach 1:
An insulating layer is introduced as an intermediary substance between the through-hole and the electrodes. This insulating layer fills the through-hole and prevents direct contact between the etchant and the electrodes, thereby protecting the electrodes from dissolution while allowing the through-hole to extend closer to the electrodes for improved sensitivity
Solution Approach 2:
The insulating layer is deposited in advance before the etching process, creating a protective barrier that prevents the harmful action of etchant on the electrodes. This preliminary protective measure allows the through-hole to be formed deeper without risking electrode damage
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 reduces parasitic capacitance, enhances sensitivity, and ensures a high-yield manufacturing process by preventing etchant contact with the electrodes, resulting in a highly sensitive and reliable ultrasonic transducer.
Implementation Method 1
CMUTs utilize the phenomenon whereby electrostatic force is generated in a membrane on top of the cavity as a result of voltage being applied between the upper electrode and the lower electrode
Implementation Method 2
a through-hole that penetrates the insulating layer is formed and an etchant is introduced via the through-hole. As a result, the sacrifice layer is etched and removed
Data Source
AI summary
A highly-sensitive ultrasonic transducer with good yield is provided. The ultrasonic transducer includes a cavity layer, a pair of electrodes positioned above and below the cavity layer, insulating layers disposed above and below each of the pair of electrodes, and a filled hole that penetrates, in a vertical direction, at least a portion of the insulating layers positioned above the cavity layer. When the ultrasonic transducer is viewed from above, each electrode of the pair of electrodes includes, at a position that overlaps the embedded hole, a non-electrode region where the electrodes are not formed.