Fabrication of high frequency SAW devices with buffer layer Al2O3 thin film applied with AlN thin film by RF magnetron sputteing

• Main Authors: Jia-Ling Wu, 吳佳玲
• Other Authors: Wen-Ching Shih
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/11772960269367729202

碩士 === 大同大學 === 光電工程研究所 === 96 === Now communication elements are developing towards high frequency. SAW devices must have high velocity, high electromechanical coupling coefficient, low insertion loss. SAW devices composed of the piezoelectric thin film and different substrate materials or buffer layers can improve the operating frequency of SAW devices and the electromechanical coupling coefficient. Consequently, SAW devices have been widely applied in mobile communication due to their small size and light weight. This study employs Al2O3 as the experimental buffer layer and AlN as the piezoelectric material to contrast the frequency responses of SAW devices. We use Al2O3 buffer layers with different thicknesses and compare with the SiO2/Si and sapphire substrates. We hope the electron beam evaporation to develop buffer layers with high velocity of wave has been proved to lower the cost and shorten the time of production. The method is sure of producing high frequency SAW devices. We find the fabrication of AlN (002) C-axis parameters of the total pressure was kept at 7 mtorr. The nitrogen percentage in the gas mixture was 30 %. The RF power delivered by the RF generator was 178 W. The deposition time was fixed at 2 hr The substrate was kept at temperatures on 400 °C. The AlN thin film devices were fabricated on Al2O3(0.2 μm)/SiO2/Si、Sapphire and SiO2/Si substrates. The frequency response for the SAW filter were measured on these three structures using a network analyzer. The center frequency of the SAW devices were 315.8 MHz、350.2 MHz and 318.8 MHz, respectively. We prove that AlN thin film has great piezoelectric property.