Transport and exchange of hydrogen isotopes in silicon-device-related stacks

Abstract

Thermally driven transport and exchange of hydrogen and deuterium in silicon-based metal-oxide-semiconductor (MOS) device-related structures were experimentally investigated using elastic recoil detection analysis. The samples were planar stacks of different materials on crystalline silicon. The materials studied included silicon oxide prepared by thermal growth, polycrystalline silicon silicon nitride, silicon oxynitride, and borophosphosilicate glass (BPSG) prepared by chemical vapor deposition (CVD). CVD was performed using either standard (hydrogen-containing) or deuterated precursors. Thermal annealing was carried out at 350–800 °C for 10–300 min in argon or in forming gas, either standard (90 vol. % N2,10 vol. % H2) or deuterated. All materials except silicon nitride were permeable to hydrogen and deuterium in the temperature range studied. Isotope exchange in the polycrystalline Si/SiO2 structure was observed above 450 °C. BPSG showed very little relative isotope exchange. Implications to MOS device processing are discussed.