[19p-P6-1~17] 6.4 Thin films and New materials

▲ [19p-P6-12] The influence of Si doping on inversing the polarity of aluminum nitride thin films

〇Sri Ayu Anggraini¹, Masato Uehara¹, Hiroshi Yamada¹, Morito Akiyama¹ (1.AIST)

Keywords:piezoelectric, nitride, polarity

Aluminun nitride (AlN) in thin film form has been a widely-used material for bulk acoustic wave (BAW) resonator, owing to its stability at high temperature, decent piezoelectric response (d₃₃) and high acoustic velocity. The performance of AlN relies heavily on structure of the thin film, particularly whether it grown properly in c-axis orientation on the substrate. In general, a c-axis oriented wurzite structure AlN is either Al-polar-type or N-polar-type [1]. It has been reported that stacking the Al-polar-type thin film with the N-polar-type-thin film could promote higher frequency BAW resonator [2]. Since demand for high performance BAW resonator and filter raise with the ever-growing market of wireless telecommunication devices, controlling the polarity of AlN thin film become one of the important routes in improving the performance of a device. In this study, we introduce the use of silicone (Si) as a dopant that could promote the inversion of AlN polarity without degrading the piezoelectric response (d₃₃). Addition of 1 at.% of Si is sufficient to inverse the polarity from positive to negative without massively reducing the magnitude of the piezoelectric response. The piezoelectric response of AlN thin film is 6.9 pC/N, while that of Si_0.03Al_0.97N was found to be -6.2 pC/N.
REFERENCES
[1] M. Suzuki, T. Yanigatani, H. Odagawa, Appl. Phys. Lett., 104 (2013) 172905.
[2] T. Mizuno, K. Mizuno, Y. Aida, A. Honda, M. Akiyama, T. Nagase, M. Kobayashi, Transducer 2017, DOI: 10.1109/TRANSDUCERS.2017.7994440