IMF2017

Surface acoustic wave devices have widespread applications in various fields including in communication and wireless sensing devices. However there are some shortcomings like lower sensitivity and the corrosion of IDT’s limit their application as sensing devices. Lamb wave SAW devices have proved to be promising for sensing applications. Rayleigh wave SAW devices fabricated over a membrane with the thickness of membrane smaller than the acoustic wavelength leads to the generation of the lamb waves. The Rayleigh waves travel on both sides of the membrane causing the formation of the antisymmetric and symmetric modes of lamb waves. This design gives the feasibility of integrating the liquid media as required for biosensors from the back side protecting the IDTs. Moreover lamb wave SAW devices are fabricated on silicon membrane making them IC compatible. In the present work lamb wave SAW devices have been fabricated with four different acoustic wavelengths (20 μm, 40 μm, 60 μm and 80 μm). The devices have been fabricated using conventional photolithography technique on Silicon substrate. Piezoelectric ZnO thin film deposited using rf sputtering technique has been integrated with the Si substrate. The bulk etching of Silicon has been carried out from back side of each device using wet etching. The devices are packaged and frequency response is studied using a network analyzer. The antisymmetric and symmetric modes in these devices have been identified and variation of acoustic velocity for both the mode is plotted as a function of the normalized thickness of the plate.