TAILIEUCHUNG - Capacitive Micromachined Ultrasonic Transducers: Fabrication Technology

Although assembling of a number of device parts is not really a problem in the macroscaleworld, it needs to be delicately handled in themicroscaleworld. Themain point is the adjustment and alignment accuracy of the parts. Moreover, problems of sealing, fixation and bonding technology may also occur depending on the material and the parameters of the designated process of the on the surface quality and the bonding technology applied, aligning errors may reach similar dimensions compared to themicrostructure itself. An example of the same is shown in Figure . Here, a number of wet chemically etched microstructure foils have been aligned in a poor way to form elliptically. | 2242 IEEE TRANSACTIONS on ULTRASONICS FERROELECTRICS AND FREQUENCy CONTROL VOL. 52 no. 12 DECEMBER 2005 Capacitive Micromachined Ultrasonic Transducers Fabrication Technology Arif Sanli Ergun Member IEEE Yongli Huang Student Member IEEE Xuefeng Zhuang Student Member IEEE Omer Oralkan Member IEEE Goksen G. Yaralioglu Member IEEE and Butrus T. Khuri-Yakub Fellow IEEE Abstract Capacitive micromachined ultrasonic transducer cMUT technology is a prime candidate for next generation imaging systems. Medical and underwater imaging and the nondestructive evaluation NDE societies have expressed growing interest in cMUTs over the years. Capacitive micromachined ultrasonic transducer technology is expected to make a strong impact on imaging technologies especially volumetric imaging and to appear in commercial products in the near future. This paper focuses on fabrication technologies for cMUTs and reviews and compares variations in the production pro cesses. We have developed two main approaches to the fabrication of cMUTs the sacrificial release process and the recently introduced wafer-bonding method. This paper gives a thorough review of the sacrificial release processes and it describes the new wafer-bonding method in detail. Process variations are compared qualitatively and quantitatively whenever possible. Through these comparisons it was concluded that wafer-bonded cMUT technology was superior in terms of process control yield and uniformity. Because the number of steps and consequent process time were reduced from six-mask process to four-mask process turn-around time was improved significantly. I. INTRODUCTION CAPACITIVE micromachined ultrasonic transducers cMUTs were introduced to the ultrasound community about a decade ago. Initially the interest in cMUTs was for airborne applications such as nondestructive evaluation NDE mainly because at the time the cavity could not be sealed. Once techniques were developed to seal their cavity cMUTs began to appear in immersion

• Cơ khí - Chế tạo máy
• Adaptive Composite Materials
• Bionics Principles
• Abnormal Elasticity
• Moving Interfaces
• Mechanics
• Composite Beams