PNNL

Abstract

In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO2) films grown by atomic layer deposition using TEMA-Hf/H2O at 250 ^{0}C substrate temperature. HfO2 is currently being studied as a possible replacement for Silicon Oxide (SiO2) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K Xray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2 kV Ar+ ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar+ sputtering there was still only trace amounts of carbon at ~1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar+ used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO2 film.