讲座名称: ScAlN: A New Piezoelectric Thin Film for SAW Sensor and Filter Applications

时间:2013年3月18日(星期一) 上午10:00-11:30

地点:电信群楼2号楼314仪器科学与工程系会议室

主讲人: Prof. Ken-ya Hashimoto

       Graduate School of Engineering, Chiba University, Chiba, Japan

内容简介：

Wireless and batteryless sensors based on surface acoustic wave (SAW) technology have been paid much attention for the use in harsh environment. As the piezoelectric substrate, LiNbO₃ and LiTaO₃ have been used because of their high electromechanical coupling factor K² determining achievable device insertion loss and passband width. Since the SAW velocity V on these substrates is relatively low (<4,000 m/s), piezoelectric materials with large V and K² are strongly demanded for the operation in multi GHz range. Although AlN may seem feasible for the purpose, achievable K² is limited.

This talk is aimed at discussing applicability of Sc_rAl_1-rN for the SAW sensor and filter applications.

Piezoelectric Sc_rAl_1-rN films can be deposited by the dual radio frequency magnetron reactive co-sputtering using metal Sc and Al targets. Deposited films are chemically inert, and thermally quite stable. It is interesting that they are paraelectric, but the piezoelectricity is enhanced surprisingly with an increase in the Sc content r. Although bulk wave velocities decrease with r, they are still relatively large. These features seem very attractive for the use of wireless and batteryless SAW sensors as well as RF SAW filters operating in the 1-3 GHz range.

It is shown theoretically that large V and lage K² are simultaneously achievable when the ScAlN film is combined with a base substrate with extremely high acoustic wave velocities such as diamond and SiC. For example. the second (Sezawa) mode on the ScAlN/6H-SiC structure exhibits relatively large K² of 5.26% when the ScAlN thickness is 0.58 wavelengths, where V is also large (6,310 m/s).

SAW delay lines are fabricated on the ScAlN/6H-SiC and ScAlN/single-crystal diamond (SCD) structures. Measured SAW properties are simulated well theoretically, and it is also found that the SAW propagation loss is very small. This may be owed to the very high SAW velocity.

Finally, one-port SAW resonators are fabricated on the structure, and it is shown how high performances are achievable in 1-3 GHz range by use of the structure. For example, the resonance quality factor of 520 is obtained at 3.63 GHz by a SAW resonator on the ScAlN/SCD structure.

主讲人简介：

Ken-ya Hashimoto was born in Fukushima, Japan, on March 2, 1956. He received his B.S. and M.S. degrees in electrical engineering in 1978 and 1980, respectively, from Chiba University, Japan, and his Dr. Eng. degree from Tokyo Institute of Technology, Japan, in 1989.

In 1980, he joined Chiba University as a Research Associate, and is now a Professor of the University. In 1998, he was a Visiting Professor of Helsinki University of Technology, Finland. In the winter of 1998/1999, he was a Visiting Scientist of the Laboratoire de Physique et Metrologie des Oscillateurs, CNRS, France. In 1999 and 2001, he was a Visiting Professor of the Johannes Kepler University of Linz, Austria. He was a Visiting Scientist of the Institute of Acoustics, Chinese Academy of Science, Beijing, China in 2005/2006. For 2009-2012, he was a Visiting Professor of the University of Electronic Science and Technology of China, Chengdu, China.

In 2001, he served as a guest co-editor of the IEEE (Institute of Electrical and Electronics Engineers) Transactions on Microwave Theory and Techniques (MTT) Special Issue on Microwave Acoustic Wave Devices for Wireless Communications, and a publicity co-chair of the 2002 IEEE International Ultrasonics Symposium. He was appointed to a member of the speaker’s bureau of the IEEE MTT Society. He also served as an International Distinguished Lecturer of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) Society from 2005 to 2006, an Administrative Committee (ADCOM) Member of the IEEE UFFC Society from 2007 to 2009, a Distinguished Lecturer of IEEE Electron Device Society from 2007 to 2009, and a general co-chair of the 2011 IEEE International Ultrasonics Symposium.

His current research interests include simulation and design of various high-performance surface and bulk acoustic wave devices, acoustic wave sensors and actuators, piezoelectric materials and RF circuit design.

Dr. Hashimoto is a Fellow of IEEE, and a Member of the Institute of Electronics, Information and Communication Engineers of Japan, the Institute of Electrical Engineers of Japan, and the Acoustical Society of Japan.