Design of silicon membranes for ultrasonic transducers and its fabrication by anisotropic wet etching

Abstract

The aim of this work is to calculation and fabrication silicon membranes for acoustic sensors with operating ranges of resonant frequencies from 10 kHz to 100 MHz and pressures from 0.1 to 103 kPa. In this paper, analytical dependences of pressure and resonance frequency on geometrical parameters of membranes are presented. The ranges of the thickness (30-50 μm) and the length of the edge membranes (0.2-1.0 mm) were defined. Experimental studies of the etching of the silicon wafer with a solution of 30% KOH were carried out and the etching rate was found to be 1.2-1.8 μm/min. Anisotropic wet etching was used to form square-shaped silicon membranes with a thickness of 30-50 μm and an edge length of 0.2 to 1.0 mm with resonant frequencies in the range of 0.7 to 30 MHz. The obtained results can be used in the development of acoustic sensors based on of monocrystalline silicon.