电容式微机械超声传感器的工艺综述

Overview of manufacturing technologies of capacitive micromachined ultrasonic transducer

电容式微机械超声传感器（CMUT）自出现以来,因其频谱宽、分辨率高、声阻抗匹配好等优势,在超声成像领域大有取代传统压电式传感器的趋势。围绕CMUT最主要的两种制造工艺方法,重点简述了表面微加工技术和晶圆键合技术的基本方法、工艺材料、薄膜形成等相关概念,并介绍了基于这两种方法加工制造CMUT的基本流程。从表面微加工方法中薄膜的沉积材料和结构以及晶圆键合方法中键合方式和键合温度等方面进行论述,总结介绍了CMUT加工工艺的研究现状。在此基础上对CMUT加工工艺的未来进行展望,提出应从工艺温度、薄膜材料、晶圆粗糙度和粘滞现象等4个主要方面进行重点研究,从而使CMUT早日实现推广应用。

The capacitive micromachined ultrasonic transducer（ CMUT） has thetendency to replace the piezoelectric based ultrasonic transducers for imaging due to itslargebandwidth,high resolution and better acoustic impedance matching. In this study,the main manufacturing technologies of CMUT are reviewed,including the surface micromachining and the wafer bonding. The principle of fabrication method（ i. e., the main processing materials, the film formation process and other related aspects of the surface micromachining） and the wafer bonding technologyareintroduced. Then,the basic fabrication procedures ofthese two methods are described. The research and development status of the CMUT processing technologiesare summarized in terms of the depositional materials and structures of the membranes in the surface micromachining technology,as well as the bonding mode and the bonding temperature in the wafer bondingtechnology. The trend of CMUTtechnologies is also forecasted. It indicates that major progress on CMUT technologies will rely on the membrane materials,the process temperature,as well as thecontrol on wafer roughness and the viscous phenomena.