Compensation of oxygen defects in La-silicate gate dielectrics for improving effective mobility in high-k/metal gate MOSFET using oxygen annealing process

• Published in: Solid-state electronics Vol. 68; pp. 68 - 72
• Main Authors: Kawanago, T., Suzuki, T., Lee, Y., Kakushima, K., Ahmet, P., Tsutsui, K., Nishiyama, A., Sugii, N., Natori, K., Hattori, T., Iwai, H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-02-2012; Elsevier
• Subjects: Annealing; Applied sciences; Compensation; Defects; Dielectrics; Effective mobility; Electronics; Exact sciences and technology; Fermi surfaces; Gates; High-k gate dielectrics; Interfacial properties; Oxygen vacancy; Rare earth oxides; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicate; Silicon substrates; Transistors; Silicate; High-k gate dielectrics; Rare earth oxides; Oxygen vacancy; Effective mobility; MOSFET; Lanthanide; Oxygen; Annealing; Oxide layer; Vacancy; Hole mobility; Transistor gate; Valence band; Controlled atmosphere; Thickness; Interface properties; Flat band voltage; Fermi level; Chemical reaction; High k dielectric; X-ray photoelectron spectra
• ISSN: 0038-1101; 1879-2405
• DOI: 10.1016/j.sse.2011.10.006

► Compensation of oxygen defects in La-silicate dielectrics without EOT increase by oxygen annealing. ► Although the interfacial property is degraded by oxygen annealing, subsequent FGA can recover the interfacial property. ► The additional oxygen in La-silicate is maintained even after annealing in reducing ambient. ► Movement of Fermi level toward the Si valence band edge caused by oxygen incorporation is successfully observed by XPS. ► Effective mobility in MOSFET with La-silicate dielectrics can be improved by oxygen annealing in conjunction with FGA.
Oxygen incorporation for compensation of oxygen defects is investigated with La-silicate dielectrics in directly contacted with the Si substrate. The amount of oxygen is controlled by the temperature of annealing in oxygen atmosphere (oxygen annealing) and the thickness of the gate electrode. The positive shift in flatband voltage (
V
FB) by oxygen incorporation is an experimental evidence for defects compensation in La-silicate dielectrics. Optimum oxygen annealing provides the
V
FB shift toward positive direction without increasing equivalent oxide thickness (EOT). Although the oxygen annealing degrades the interfacial property at La-silicate/Si interface, subsequent forming gas annealing (FGA) can recover the interfacial property. It is experimentally revealed that the positive
V
FB shift of La-silicate dielectrics is stable even after subsequent FGA. The supplied oxygen in La-silicate is expected to maintain even after reducing process. Movement of Fermi level toward the Si valence band edge caused by oxygen incorporation is successfully observed by XPS. Moreover, no chemical reaction between La-silicate and Si substrate by oxygen annealing are confirmed from TEM observation and analyses of X-ray photoelectron spectra. It is experimentally demonstrated that effective hole mobility can be improved without increase in EOT by combination of oxygen annealing and FGA.