Evolution of the microstructure during annealing of porous silicon multilayers

We investigate the structural changes in porous silicon multilayers during annealing. Porous silicon multilayers play an important role in layer transfer technologies, where a thin crystalline silicon layer is separated from a wafer and transferred to a foreign substrate. High processing temperatures during epitaxial growth on top of the porous silicon layer lead to a restructuring of the porous layer. With transmission electron microscopy, we evaluate porous silicon monolayers and double-layers. The pore shape changes from open channel-like pores to closed facetted pores during anneal. In double-layers we observe a strong interaction between the two layers leading to an enhanced porosity in the high porosity layer. The observed microstructural evolution is discussed by means of the classical theory of sintering.