Crystalline characteristics of annealed AlN films by pulsed laser treatment for solidly mounted resonator applications

Abstract

AlN films were deposited on Si substrates using a reactive RF magnetron sputtering process and then the films were annealed by using different laser powers and wavelengths (355 nm, 532 nm and 1064 nm). For all three laser systems, the (002) peak intensity was obviously improved following laser irradiation. The improvement in the crystalline property was particularly obtained in the AlN film processed at 355 nm. In particular, given the use of the optimal laser power (0.025 W), the (002) peak intensity was 58.7% higher than that of the as-deposited film. The resonant frequency and 3 dB bandwidth of a SMR filter with an unprocessed AlN film were found to be 2850 MHz and 227.81 MHz, respectively. Following laser treatment with a wavelength of 1064 nm and a power of 0.25 W, the resonant frequency changed from 2850 to 2858 MHz. Moreover, 3 dB bandwidth changed from 227.81 to 202.49 MHz and the return loss of the filter reduced from 17.28 to 16.48 dB. Overall, the results thus show that the frequency response of the SMR filter can be adjusted and the return loss reduced by means of laser treatment with an appropriate wavelength.

Materials, Design, and Characteristics of Bulk Acoustic Wave Resonator: A Review

“…When AlN film was treated with a laser with a wavelength of 355 nm and a power of 0.025 W, the crystallinity of the film was significantly improved. The peak intensity of (002) was 58.7% higher than the untreated peak intensity [ 33 ]. However, high temperature and long treatment may have a negative impact [ 34 ], and the enhanced crystal quality of the films due to RTA hardly contributes to a significant improvement in k t 2 .…”

Refining silicon nitride waveguide quality through femtosecond laser annealing

“…To date, pulsed laser annealing is the next promising candidate to further relieve the thermal budget of the laser annealing process, especially for the process at the back-end-of-line (BEOL) 2 , 6 . Previous studies showed the possibility of improving crystalline structures of aluminum nitride (AlN) 7 , 8 or zinc oxide (ZnO) nanofilms 9 when the structural voids can be minimized with better surface morphology 10 . Meanwhile, the laser annealing technique has also been applied to dopant activation of Be-implanted gallium nitride (GaN) 11 or silicon/germanium 12 .…”