Germanium interactions with Si-etched silicon dioxide

The structure and activity of defects resulting from the etching reaction between Si adatoms and SiO2 was probed by desorption of GeHx (x = 1, 2, 3) dosed by hot-wire chemical vapor deposition. GeHx has been shown, in previous studies, to be inert to the SiO2 surface and only accumulates through the formation of Ge clusters formed by reactions between adsorbed GeHx species. Temperature programmed desorption (TPD) of GeHx off SiO2 surfaces subjected to varying degrees of etching reveals that the surface is activated toward GeHx resulting in the deposition of Ge. Examination of the H2 signal during GeHx TPD, reveals two distinct peaks, one from 475 K to 675 K and another from 750 K to 900 K. The first H2 peak is associated with the reaction of GeHx species with the hydrated form of the defect created by the Si etching reaction, while the second H2 peak results from the reaction of GeHx species with Ge captured in the earlier reaction. Annealing a Si-etched SiO2 surface under a diborane atmosphere deactivates the defect toward GeHx, while also deactivating intrinsic hydroxyl groups towards the adsorption of GeHx. A defect structure is proposed composed of vicinal and geminal hydroxyl groups flanking a Si vacancy.