Interface Studies of III-V Semiconductors and Oxides with an I n-Situ Spectroscopic Ultra-High Vacuum (UHV) System Capable of Atomic Layer Deposition (ALD) and Atomic Layer Etch (ALEt)

Abstract

Preparation of gate dielectrics and high-quality interfaces by atomic layer deposition onto III-V and other sensitive substrates, which typically have multicomponent native oxides after air exposure, is a challenging problem that cannot be completely understood by ex-situ surface analysis techniques. Surface oxides can be detrimental or, in specific cases, even beneficial to device performance depending on how the interface affects the Fermi-level of the semiconductor.1,2 One such system is GaSb, which is a case study here for a high mobility p-type material. In this work, surfaces of GaSb <001> have been examined, with methods of oxide removal including H-atoms, Ar+ ions, and both, simultaneously tested as a function of temperature for determining the threshold of surface damage. The re-oxidation of the interface is examined after oxygen and water exposure, and after oxide films growth. Description of the unique system designed and built at NRL for these type of studies will be presented.3 It combines a surface science UHV chamber; with X-ray photoelectron and Auger electron spectroscopies (XPS & AES), transmission or reflection-absorption thin-film FTIR spectroscopy, low-energy electron diffraction (LEED), reflection electron energy loss spectroscopy (REELS), and surface preparation, with a chamber-within-a-chamber design for performing ALD and ALEt at pressures from mTorr to Torr. Without exposure to ambient, the ALD system is pumped out and opened to the UHV environment for spectroscopy. A quantified, micro-dosing gas reagent delivery system is also implemented, so quantitative ALD reactant exposure may be correlated with actual surface reactions.4 Spectroscopic results and surface reconstruction patterns for GaSb interfaces acquired in above system will be presented. 1L.B. Ruppalt et al., Appl. Phys. Lett. 101, 231601 (2012). 2V.M. Bermudez, J. Appl. Phys. 114, 024903 (2013). 3V.M. Bermudez, Rev. Sci. Instrum. 85, 114101 (2014). 4T.J. Larrabee, T.E. Mallouk, D.L. Allara, Rev. Sci. Instrum. 84, 014102 (2013).