X-ray photoemission and X-ray absorption studies of Hf-silicate dielectric layers

• Published in: Applied surface science 2006-12, Vol.253 (5), p.2770-2775
• Main Authors: O’Connor, R., Hughes, G., Glans, P.-A., Learmonth, T., Smith, K.E.
• Format: Article
• Language: English
• Subjects: ABSORPTION; ABSORPTION SPECTROSCOPY; ANNEALING; Band offsets; CHEMICAL SHIFT; DIELECTRIC MATERIALS; Hafnium silicate; HAFNIUM SILICATES; INCLUSIONS; LAYERS; MATERIALS SCIENCE; national synchrotron light source; NITROGEN; PARTICLE ACCELERATORS; PHOTOELECTRON SPECTROSCOPY; PHOTOEMISSION; SILICATES; SILICON; Soft X-ray photoemission; SUBSTRATES; SYNCHROTRON RADIATION; TRANSISTORS; VALENCE; X-ray absorption
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2006.05.053

Photoelectron spectroscopy and X-ray absorption spectroscopy (XAS) measurements have been performed on HfSi x O y and HfSi x O y N z dielectric layers, which are potential candidates as high- k transistor gate dielectrics. The hafnium silicate layers, 3–4 nm thick, were formed by codepositing HfO 2 and SiO 2 (50%:50%) by MOCVD at 485 °C on a silicon substrate following an IMEC clean. Annealing the HfSi x O y layer in a nitrogen atmosphere at 1000 °C resulted in an increase in the Si 4+ chemical shift from 3.5 to 3.9 eV with respect to the Si 0 peak. Annealing the hafnium silicate layer in a NH 3 atmosphere at 800 °C resulted in the incorporation of 10% nitrogen and the decrease in the chemical shift between the Si 4+ and the Si 0 to 3.3 eV. The results suggest that the inclusion of nitrogen in the silicate layer restricts the tendency of the HfO 2 and the SiO 2 to segregate into separate phases during the annealing step. Synchrotron radiation valence band photoemission studies determined that the valence band offsets were of the order of 3 eV. X-ray absorption measurements show that the band gap of these layers is 4.6 eV and that the magnitude of the conduction band offset is as little as 0.5 eV.