Surface Acoustic Wave (Saw) Delay Lines & Rfid on Silicon/ Aluminium Nitride

Surface Acoustic Wave (SAW) devices exploit the principle of transducing radio frequency waves into mechanical sound waves propagating across surface of piezoelectric material. These mechanical waves are generated, detected, or reflected by set of metal electrodes. Physical phenomena or unique identification code information can be extracted from the measured /reflected waves based on its different properties such as time delay, phase change or frequency change. Radio identification code implementation methods as well as simulation of SAW device are reviewed in this report. Time pulse position coding is chosen because it provides less sensitivity to variations in temperature and SAW wave velocity. In addition, it is straightforward to implement and simplifies the reader design. To successfully implement the device, proper modeling and simulation is carried out to extract device physical and response parameters such as centre frequency, finger pairs’ number, spacing, scattering parameters and frequency response of the system. The equivalent circuit model is used in this study due to faster simulation speed and efficiency. Aluminum nitride (AlN) is chosen as piezoelectric material due to its high SAW velocity speed, higher coupling factor, cheaper fabrication cost and its chemical characteristics close to that of Silicon Non-reactive with normal semiconductor process chemicals and gases. Data processing and analysis is performed on SAW delay lines implemented on Aluminum nitride to extract device characteristics such as surface acoustic wave velocity, coupling coefficient and center resonance frequency.