Porosity evaluation of PoSi wafer using a nondestructive ultrasonic technic

Julien Bustillo , Jérôme Fortineau (1) , Marie Capelle , François Vander Meulen (1) , Lionel Haumesser (1) , Gael Gautier , Marc Lethiecq

1 iBraiN - Imaging, Brain & Neuropsychiatry

The manufacturing processes of porous silicon (PoSi) by electrochemical etching now allow samples with variable depths and variable degrees of porosity to be obtained. However, thickness and porosity measurement methods of PoSi are generally destructive. Therefore in this study a nondestructive ultrasonic method is investigated. For this, an immersion insertion-substitution technique has been used. Samples with different porosities and depths are studied. The thickness of the wafer (550 microns) and high sound speed in pure silicon (8450 m.s-1) require transducers with high central frequencies (from 15 to 50MHz). The acoustic parameters of the wafer, such as velocity and attenuation are measured. These measurements are compared with those obtained through a one-dimensional multilayer model of the wafer, using a homogenisation approach for the porous layer. An inverse method is used to find the PoSi parameters, such as the thickness of the layers or the porosity.

Mots clés: Porous silicon; nondestructive testing; ultrasound

Domaines: Acoustique [physics.class-ph]

Julien Bustillo, Jérôme Fortineau, Marie Capelle, François Vander Meulen, Lionel Haumesser, et al.. Porosity evaluation of PoSi wafer using a nondestructive ultrasonic technic. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810963⟩