Stress in oxidized porous silicon layers

Stress was determined in oxidized porous silicon layers using x‐ray diffraction to measure the substrate curvature. Stress is always compressive and its magnitude depends on oxide quality. The maximum value is reached when the oxide obtained from porous silicon is densified by a high‐temperature process and is equivalent to standard thermal silicon dioxide. The stress magnitude decreases when oxide porosity increases. An increase in layer thickness is always observed when oxidation conditions lead to a porous oxide or when the initial porosity of the layer is lower than 56%, due to volumic expansion of silica relative to silicon, otherwise the thickness decreases.