CMUT Transducer with Dielectric Stop Structure
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Solution Overview
Problem
Conventional CMUT transducers face issues such as dielectric breakdown due to high electric fields and parasitic capacitive coupling, which affect the accuracy and reliability of ultrasound measurements.
Innovation Solution
The CMUT transducer design incorporates a conductive or semiconductor substrate with a stack of dielectric layers, a cavity, and a conductive membrane, featuring a stop structure made of dielectric material to prevent membrane collapse and reduce electric field strength, along with a method of manufacturing that includes forming dielectric and conductive regions to minimize parasitic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the membrane is allowed to collapse fully towards the substrate, then the electric field strength is increased to improve transducer sensitivity, but dielectric breakdown occurs reducing reliability
Solution Approach 1:
The stop structure is preliminarily positioned in the cavity to prevent the membrane from collapsing onto the substrate. This preliminary protective action limits the maximum displacement of the membrane, thereby preventing dielectric breakdown while maintaining sufficient electric field strength for sensitive measurements.
Solution Approach 2:
The stop structure acts as an intermediary element between the membrane and the substrate. It provides a controlled stopping point that mediates the interaction between the collapsing membrane and the substrate, preventing direct contact that would cause dielectric breakdown while still allowing sufficient membrane displacement for high sensitivity.
2Power
If the conductive region is made continuous across the substrate, then the lower electrode efficiency is improved, but parasitic capacitive coupling increases reducing measurement accuracy
Solution Approach 1:
The conductive region is segmented by introducing interruptions or discontinuities in its continuous path across the substrate. This segmentation reduces the parasitic capacitive coupling area while maintaining sufficient conductive coverage for effective lower electrode operation, thereby improving measurement accuracy without sacrificing electrode efficiency.
Solution Approach 2:
The conductive region is designed with varying local properties - continuous in areas where electrical connection is needed and interrupted in areas where parasitic coupling should be minimized. This local differentiation allows the structure to optimize both lower electrode efficiency and measurement accuracy by placing conductive material only where functionally necessary.
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 significantly reduces charge injection phenomena and parasitic capacitive coupling, enhancing the reliability and accuracy of ultrasound measurements by controlling membrane displacement and electric field distribution.
Implementation Method 1
dielectric breakdown due to high electric fields
Implementation Method 2
stack of one or a plurality of dielectric layers
Implementation Method 3
parasitic capacitive coupling
Implementation Method 4
the flexible membrane starts vibrating under the effect of the electrostatic force applied between the lower and upper electrodes
Implementation Method 5
the appearing of an alternative voltage between the lower and upper electrodes of the transducer under the effect of the capacitance variation between the electrodes
Data Source
AI summary
The present disclosure relates to a CMUT transducer (200) comprising: —a conductive or semiconductor substrate (201) coated with a stack of one or a plurality of dielectric layers (203, 213); —a cavity (205, 215) formed in said stack; —a conductive or semiconductor membrane (221) suspended above the cavity; —at the bottom of the cavity, a conductive region (209) in contact with the upper surface of the substrate, said conductive region being interrupted on a portion of the upper surface of the substrate; and—in the cavity, a stop structure (207) made of a dielectric material localized on or above the area of interruption of the conductive region (209).