Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly

2009   Vol. 10   No. 3   p. 464~470

Preparation of AlN thin films for film bulk acoustic resonator application by radio frequency sputtering

Kan LI, Hao JIN^†‡, De-miao WANG, Yi-fei TANG

(Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China)
^‡ Corresponding Author
^†E-mail: hjin@zju.edu.cn
Received July 29, 2008; revision accepted Oct. 18, 2008

Abstract: Aluminum nitride (AlN) thin films with high c-axis orientation have been prepared on a glass substrate with an Al bottom electrode by radio frequency (RF) reactive magnetron sputtering. Based on the analysis of Berg’s hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AlN thin films is proposed. The N₂ concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 °C, a target-substrate distance of 60 mm and a N₂ concentration of 25%, AlN thin film with preferential (002) orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction (XRD) analysis, the full width at half maximum (FWHM) of AlN (002) was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AlN thin film. With other parameters held constant, any increase or decrease in N₂ concentration results in an increase in the FWHM of AlN.

Key words: Aluminum nitride (AlN), Piezoelectric thin film, Radio frequency (RF) reactive sputtering, Preferred orientation, Film bulk acoustic resonator (FBAR)
doi:10.1631/jzus.A0820572             CLC number: O484

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