Ultrasonic characterization of electrochemically etched porous silicon
Résumé
This paper presents a non-destructive characterization of porous silicon wafer using ultrasound based on the strong relationship between porosity and acoustical parameters. Transmission coefficients are measured using broadband water immersion method and compared to theoretical ones using a genetic algorithm optimization. Retrieved parameters are thickness and acoustic impedance. Porosity is deduced from acoustic impedance. Two set of porous silicon wafers, with different porosities and thicknesses, have been etched using hydrofluoric acid based solution and galvanostatic etching method. Their thicknesses and porosities are measured using destructive methods after ultrasonic measurements. A good agreement is observed. Hypothesis to explain discrepancies are proposed.