Hydrogen in buried SiO2 layers

Mobile protons are generated at the buried-oxide (BOX)/top-Si interface in Si/SiO2/Si structures by H atoms which permeate the top Si layer during heat treatment in H-2. About 1/1000 of the arriving protons form hydroxonium-like configurations with the O atoms associated with "strained" Si-O bonds (those with bridging bond angles between 110 degrees and 120 degrees) and by transferring an electron from the H atom to the silicon. The strained bonds are generated thermally during the high temperature processing and the related compressive mechanical stress caused by the confined nature of the BOX, as well as by edge effects. The interaction between protons and Si/SiO2 interfaces is limited or even nil from the standpoint of generating interface states. The probable reason is that the Si/SiO2 interfaces of structures with a confined oxide layer (BOX) are different from those of conventional structures with un-confined oxide.