Daniel Alvarez

Low temperature thermal ALD of a SiNx interfacial diffusion barrier and interface passivation layer on SixGe1− x(001) and SixGe1− x(110)

Atomic layer deposition of a silicon rich SiNx layer on Si0.7Ge0.3(001), Si0.5Ge0.5(001), and Si0.5Ge0.5(110) surfaces has been achieved by sequential pulsing of Si2Cl6 and N2H4 precursors at a substrate temperature of 285 °C. XPS spectra show a higher binding energy shoulder peak on Si 2p indicative of SiOxNyClz bonding while Ge 2p and Ge 3d peaks show only a small amount of higher binding energy components consistent with only interfacial bonds, indicating the growth of SiOxNy on the SiGe surface with negligible subsurface reactions. Scanning tunneling spectroscopy measurements confirm that the SiNx interfacial layer forms an electrically passive surface on p-type Si0.70Ge0.30(001), Si0.50Ge0.50(110), and Si0.50Ge0.50(001) substrates as the surface Fermi level is unpinned and the electronic structure is free of states in the band gap. DFT calculations show that a Si rich a-SiO0.4N0,4 interlayer can produce lower interfacial defect density than stoichiometric a-SiO0.8N0.8, substoichiometric a-Si3N2, or stoichiometric a-Si3N4 interlayers by minimizing strain and bond breaking in the SiGe by the interlayer. Metal-oxide-semiconductor capacitors devices were fabricated on p-type Si0.7Ge0.3(001) and Si0.5Ge0.5(001) substrates with and without the insertion of an ALD SiOxNy interfacial layer, and the SiOxNy layer resulted in a decrease in interface state density near midgap with a comparable Cmax value.

Measurement and Control of Airborne Molecular Contamination during Wafer Storage and Transport

A method was developed to measure total hydrocarbons (THCs) to 1 part-per-trillion (ppt) concentration levels using gas chromatography. This method was applied to measuring THCs in a front opening universal pod (FOUP) under static and purge conditions. XCDA® purge gas was used for this experiment. XCDA gas is clean dry air (CDA) purified with Aeronex® purification technology to remove moisture to less than 1 part-per-billion (ppb) and hydrocarbons, sulfur, and siloxane contaminants to less than 1ppt. The experiment reveals that a FOUPs environment contains ppb levels of THCs under static conditions and ppt concentration levels of THCs under purge conditions. This test demonstrates that ppt purity gas can be delivered to and maintained in a FOUP. Finally, a silicon wafer is exposed to a FOUP environment under static and purge conditions. Desorption studies show that hydrocarbon contamination on the wafer is reduced under purge conditions.