ABOUT THE ORIGIN AND THE MECHANISMS INVOLVED IN THE CRACKING OF HIGHLY POROUS SILICON LAYERS UNDER CAPILLARY STRESSES

The effects of the capillary stresses during the drying of p + -type p orous silicon (PS) layers are reported. The cracking of the PS layers occurs for samples thicker than a critical thickness value h(c). Takin g into account the elastic properties ofp + -type PS material, a simpl e model shows that h(c) varies as (1 - p)(3) and 1/gamma(LV)(2), where p is the porosity and gamma(LV) is the surface tension of the drying liquid. A good agreement with experimental results is observed. This s tudy leads also to a very easy and simple method which increases the h (c) value by a factor of about 25 when using pentane as the drying liq uid (instead of water).