CMUT Dielectric Layer Structure for Collapsed-Mode Output and Life

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Solution Overview

Problem

Micromachined ultrasonic transducers (MUTs), particularly capacitive MUTs (CMUTs), face challenges in achieving high sound pressure output and extended operational life due to dielectric coating wear and breakdown voltage degradation when operating in collapsed mode.

Innovation Solution

The CMUT design includes an actuation membrane and a sensing dielectric layer spaced apart by a cavity, with the sensing dielectric layer's thickness extended to accommodate high Vdc-bias for collapsed mode operation, thereby enhancing sound pressure output and frequency response adjustability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the CMUT operates in collapsed mode with high Vdc-bias to achieve greater sound pressure output, then the sound pressure output is improved, but the dielectric coating experiences wear and breakdown voltage degradation

Engineering Contradiction:

Improvesound pressure outputVSAvoidbreakdown voltage

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent divides the dielectric structure into two separate layers: a first dielectric layer and a second dielectric layer. This segmentation allows each layer to serve specific functions - the first layer provides mechanical support and stress management, while the second layer handles the electrical breakdown voltage requirements, thereby resolving the contradiction between high power output and reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the electrical parameters by distributing the voltage stress across two dielectric layers with different thicknesses and material properties. The second dielectric layer is specifically designed with sufficient thickness to withstand the high breakdown voltage requirements, enabling the CMUT to operate in collapsed mode without dielectric failure

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the dielectric layer thickness is increased to accommodate high Vdc-bias for collapsed mode operation, then the breakdown voltage is improved, but the device complexity increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoiddielectric layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The first dielectric layer serves multiple functions: it provides mechanical support to the actuation membrane, manages stress in the structure, and contributes to the overall electrical insulation. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity while still achieving high breakdown voltage

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If the CMUT operates in collapsed mode to achieve greater sound pressure output, then the sound pressure is improved, but the operational life is reduced due to premature wear

Engineering Contradiction:

Improvesound pressure outputVSAvoidoperational life

Core Design Contradiction:

PowerVSDuration of action of moving object

Solution Approach 1:

The patent implements prior cushioning by designing the first dielectric layer to absorb mechanical stress and protect the dielectric coating from wear before damage can occur. This preventive structure allows the CMUT to operate in collapsed mode for extended periods without premature failure, thereby extending operational life while maintaining high sound pressure output

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 allows the CMUT to operate at a sustained high breakdown voltage, reducing the likelihood of premature wear and extending the operational life, while achieving greater sound pressure output and adjustable frequency response.

Implementation Method 1

capacitive MUTs (CMUTs)

Methodology Applied

Scientific EffectCapacitive effect: Capacitance

Implementation Method 2

sensing dielectric layer's thickness extended to accommodate high Vdc-bias for collapsed mode operation

Methodology Applied

Scientific EffectDielectric breakdown: Dielectric

Data Source

PatentUS20250058353A1Semiconductor ultrasonic transducer device and methods of formation

Publication Date: 2025.02.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A micro-electromechanical-system (MEMS) device may include a capacitive micromachined ultrasonic transducer (CMUT) that includes an actuation membrane and a sensing dielectric layer that are spaced apart by a cavity. The sensing dielectric layer may be formed such that the thickness of the sensing dielectric layer may extend the operational of the CMUT while enabling the CMUT to accommodate a sufficiently high direct current voltage bias for collapsed mode operation. In this way, the thickness of the sensing dielectric layer enables the CMUT to operate in the collapsed mode, which enables the CMUT to achieve greater sound pressure output relative to other operational modes and enables the frequency response of the CMUT to be adjustable, thereby enabling the frequency response to be optimized for specific use cases and applications.