Research On The Fabrication Of C-axis Oriented AlN Thin Film On TC4

Surface acoustic wave(SAW) devices are widely applied to aerospace, commercial production, bio-medicine and wireless communication for the high accuracy and sensitivity, excellent anti-electromagnetic interference ability, ultra stability and easy industrialization. Especially in structural health monitoring, the manufacture of metal structure-integrated thin film SAW devices is in great demand to precisely grasp information of metal structures under test, like temperature, strain, etc. So the research of technological parameters of highly c-axis oriented AlN thin film on the TC4 Titanium alloy has important significance on development of the TC4-integrated SAW sensor.Firstly, using Mid-Frequency Magnetron sputtering, this paper systematically studied the influence on c-axis oriented AlN thin film deposited on the TC4 Titanium alloy of the factors, like sputtering power, pressure, substrate-target distance and substrate temperature. Conclusions are drawn out that sputtering power, sputtering pressure and substrate-target distance have little impact on the manufacture of AlN thin film on the TC4 substrate while the temperature of substrate affects the c-axis oriented of AlN thin film a lot. And AlN(002) crystal surface FWHM=8.2 ° has been fabricated under the circumstances that temperature is 400 ℃, with substrate-target distance 8 cm,sputtering pressure 0.94 Pa, sputtering power 2000 W, sputtering time 2 hours.Secondly, this paper proposes a two-step technique that the growth of thin film is processed on substrate under 400 ℃ followed by a process of naturally cooling down and the influence on film of the two steps is studied, which turns out to be that FWHM,the size of crystalline grain and RMS of AlN(002) crystal surface firstly decrease to a minimum after 30 min under constant temperature and then increase and that these factors decrease when cooling down themselves, reaching a stable state after 4.5 hour.Finally, with 0.5 hour and 5.5 hours for the two steps mentioned above, highly c-axis oriented AlN thin film is fabricated on the TC4 Titanium alloy. Analysis of XRD,AFM and SEM shows that the film is threadiness on the TC4 Titanium alloy with FWHM of 4.1 ° and RMS of 4.3 nm, which is good enough to manufacture film SAW sensors directly on the TC4 Titanium alloy.