화학공학소재연구정보센터
Solid-State Electronics, Vol.150, 28-34, 2018
Design, fabrication and characterization of SAW devices on LiNbO3 bulk and ZnO thin film substrates
In this paper, surface acoustic wave (SAW) devices with various designs were fabricated on two types of piezoelectric substrates of LiNbO3 bulk material and thin piezoelectric ZnO film on silicon. Different sizes, orientation and types of SAW devices were laid out on the same mask to compare their RF performance with a same fabrication. Devices were fabricated using lift-off technology with a double photoresist technique to achieve a steeper and narrower SAW pattern with a depth-to-width ratio of 1.27 and a steep resist angle of 85 degrees. The devices were then characterized using RF probe station together with vector network analyzer. RF performance was also verified by 2D computer simulation implementing both electrical and piezoelectric physics models using the same device dimensions in the mask layout. RF response of 128 degrees Y LiNbO3 from experiments agrees with simulation fairly well while the devices on ZnO/Si have larger frequency distribution due to process variation of the ZnO thin film on silicon wafer. Quality factor of 34,000 was obtained from the SAW device fabricated in LiNO3 substrate and this Q value has a strong dependency on the numbers electrodes of IDT fingers and reflectors. Temperature dependency was also measured for future wireless sensor application. The temperature coefficient of frequency of 16 mu m wavelength devices of LiNbO3 substrate was -87.5 ppm/degrees C and was -72.41 ppm/degrees C for 12 mu m wavelength devices.