The formation of thick buried oxide layers using ion implantation from water plasma

An implanter without an ion mass analyzer has been used to successfully fabricate silicon-on-insulator (SOI) materials by H2O+, HO+, and O+ ion implantation using water plasma. Based on the consideration that the masses of those three ions are very close, this fabrication makes it possible to form a single buried oxide (BOX) layer by choosing the appropriate implantation energy and dose. Cross-sectional transmission electron microscopy (XTEM) results indicated that the BOX thickness of the SOI materials fabricated using a water plasma approach is increased more than 50% over that of the conventional separation by implantation of oxygen (SIMOX) process. Secondary ion mass spectroscopy (SIMS) depth profile analysis on the as-implanted wafers showed that there are two hydrogen enrichment peaks around both sides of the projected range Rp of oxygen, which correspond to the two interfaces of the BOX layer of the annealed samples. Additional designed experiments revealed that the heavily damaged region with hydrogen-induced defects appears to be the adsorption center for the outside oxygen to diffuse into the silicon during the high-temperature annealing process, and consequently, thicken the BOX layer of the SOI structure. The findings in the present work may provide a possible solution to reduce the cost of the conventional SIMOX-SOI wafers while maintaining a desirable BOX thickness.