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HIGH TEMPERATURE CAPACITIVE MICROMACHINED ULTRASOUND TRANSDUCERS

IP.com Disclosure Number: IPCOM000199106D
Publication Date: 2010-Aug-26

Publishing Venue

The IP.com Prior Art Database

Abstract

A high temperature capacitive micromachined ultrasound transducer (cMUT) for non-destructive evaluation applications is disclosed. High temperature cMUT can be permanently installed as a thickness gauge sensor for thickness testing of process piping and tanks in oil and gas refineries. The present invention provides a low cost sensor which operates at high temperature (500°C) and provides intrinsic safety and reduces the cost of access to the thickness measurement locations (TMLs).

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RP13474

HIGH TEMPERATURE CAPACITIVE MICROMACHINED ULTRASOUND TRANSDUCERS

BRIEF ABSTRACT

    A high temperature capacitive micromachined ultrasound transducer (cMUT) for non-destructive evaluation applications is disclosed. High temperature cMUT can be permanently installed as a thickness gauge sensor for thickness testing of process piping and tanks in oil and gas refineries. The present invention provides a low cost sensor which operates at high temperature (500°C) and provides intrinsic safety and reduces the cost of access to the thickness measurement locations (TMLs).

KEYWORDS

    High temperature ultrasonic transducers, capacitive transducers, thin films, surface technology, Micromachined ultrasonic transducers and acoustic imaging.

DETAILED DESCRIPTION

    Conventional techniques used for inspection of oil and gas refineries include periodic inspection of the thickness measurement locations (TMLs) using hand held ultrasonic thickness gauges. These ultrasonic thickness gauges utilize piezo-electric transducers to generate and receive the ultrasonic pulses. However, piezo-electric transducers do not function properly at high temperatures. Furthermore, piezo-electric solutions suffer from inherently high manufacturing costs.

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RP13474

    Therefore there is a need in the art for efficient ultrasonic transducers that can be used at high temperatures in non-destructive evaluation applications.

    The present invention provides a a high temperature (500°C) Capacitive Micromachined Ultrasonic Transducer (cMUTs) for non-destructive evaluation (NDE) applications. The high temperature cMUT provide stable operation and sensitivity. Further, mass produced cMUT sensors allow low costs.

    In order to develop high temperature cMUTs, different materials and technologies are used. Figure 1 illustrates the most challenging areas for high temperature cMUT development: conductor technology, membrane material, insulation material technologies, and bonding technologies.

    High temperature metal combinations, such as Ni/Au, W/Au, are used for HT cMUT operation at high temperature. A wide bandgap (WBG) material, such as SiC or GaN, are used as membrane material. The WBG material provides stable electrical and mechanical properties at elevated temperature compared to cMUTs with Si membrane.

    SiC does not bond easily to a substrate, thus an intermediate layer is required to ensure a good bonding. A variety of intermediate materials, such as Low pressure chemical vapor deposition (LPCVD) Poly-Si, LPCVD oxide, HTO, LTO, Plasma enhanced chemical vapor deposition (PECVD) Oxide, PECVD nitride, PSG are used for HT cMUTs. A high temperature insulation, such as ALD Al2O3, LPCVD undoped SiC or poly-Si etc are used to provide good electrical isolation at 500°C. In order to perform a good intermediate layer bonding, Chemical Mechanical Polishing (CMP) is performed on either SiC or intermediate film to ensure their smooth surfaces for bonding with high strength and yie...