AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuP

Paper EM-TuP17
Investigation of Oxide/InAs Interface via STM, STS, and KPFM

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Electronic Materials and Processing Poster Session
Presenter: J. Shen, University of California, San Diego
Authors: W. Melitz, University of California, San Diego
J. Shen, University of California, San Diego
A.C. Kummel, University of California, San Diego
Correspondent: Click to Email
III-V MOSFETs have the potential to produce superior devices but formation of low defect density oxide-semiconductor interfaces is critical. While silicon surfaces are highly reactive due to their partially filled dangling bonds, some III-V surfaces have very low reactivity due to absence of partially filled dangling bonds and therefore might be able to form superior interface to high-k dielectrics if processes induce defect formation is avoided. Atomically resolved scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) were employed to determine the atomic and electronic structure of clean InAs surface and oxide/InAs semiconductor interfaces. Kelvin probe force microscopy (KPFM) can be utilized to support the STS and to provide further information on the surface or interface electronic properties. The InAs samples are first annealed at low temperatures to remove a protective arsenic cap, and heated to high temperature to prepare clean InAs(001)-(4×2) surfaces; the (4×2) surface is indium rich and therefore oxidation resistant which is favorable for oxide deposition. An oxide is deposited with a high temperature effusion cell and STS/KPFM measurements are performed to probe the surface Fermi level. SiO has the potential to form an excellent interface to ALD deposited HfO2 since the Si/SiO2/HfO2 gate stack is known to have excellent electronic properties. STM images reveal that SiO forms cluster structures on the InAs(001)-(4×2) after annealing and does not desorb from the surface nor diffuse into the substrate after 800 K annealing. STS spectra for submonolayer SiO coverages deposited at 300 K on InAs(001)-(4×2) have shown the Fermi level is close to the conduction band for both n-type and p-type samples consistent with KPFM studies. For submonolayer SiO coverages deposited at 700 K on p-type InAs(001)-(4×2), STS shows the Fermi level near midgap consistent with partial unpinning; better electronic structure is expected for higher coverages of SiO. In2O could act as a protection layer during high-k ALD and can be removed after ALD by high temperature annealing. STM images of In2O deposited InAs(001)-(4×2) and annealed at 650 K show that In2O forms has highly ordered structures. After annealing above 700 K, the In2O desorbs from the surface and the pristine original clean InAs(001)-(4×2) is observed with no additional defects. Oxides are known to diffuse through HfO2 and ZrO2 so ALD deposition on In2O could be followed by an annealing step which removes the In2O to form a high-k/InAs without any ALD induced defects. STS and KPFM experiments on In2O are ongoing.