On pyramidal protrusions in anisotropic etching of <100 > silicon

Abstract

Abstract In the anisotropic etching of phosphorus-doped n-type bulk crystalline silicon of 1–2 Ω cm resistivity, using an ethylenediamine pyrocatechol solution, the presence of pyramidal protrusions on the etched surface is observed. These tiny pyramids, with their square bases on the etched plane, are bound by the etch-resistant planes. As the etching proceeds, these pyramids appear and then disappear on the etch plane. Experimental evidence shows that these pyramids are not caused by particulates in the etching solution. The occurrence, location and areal number densities of these pyramids are observed to be affected by the thermal history of the samples, and hence by the residual stresses in the overlying thin films. It is suggested that the pyramids originate from structural defects in the bulk crystalline silicon, as well as from an incomplete dissolution of the hydrated oxide.