AVS 58th Annual International Symposium and Exhibition
    Surface Science Division Thursday Sessions
       Session SS-ThA

Invited Paper SS-ThA6
An Atomic View of ALD of Dielectrics on Semiconductors Using STM

Thursday, November 3, 2011, 3:40 pm, Room 107

Session: Semiconducting & Ferroelectric Surface
Presenter: Andrew Kummel, University of California, San Diego
Authors: A.C. Kummel, University of California, San Diego
W. Melitz, University of California, San Diego
J.B. Clemens, University of California, San Diego
J.S. Lee, University of California, San Diego
T. Kaufman-Osborn, University of California, San Diego
T. Kent, University of California, San Diego
E.A. Chagarov, University of California, San Diego
J. Shen, University of California, San Diego
R. Droopad, Texas State University-San Marcos
Correspondent: Click to Email
Scaling of gate oxides on MOSFETs requires nucleating oxide ALD in every unit cell of the semiconductor channel surface without disrupting the semiconductor surface (high mobility) while eliminating dangle bond states (low Dit). The reaction of TMA on the group III rich (4 × 2) reconstructions of the InAs(0 0 1) and InGaAs(0 0 1) surfaces were been studied using in-situ STM, scanning tunneling spectroscopy (STS), in-situ XPS, and density functional theory (DFT). When an As2 capped III-V sample is decapped in UHV and the substrate is dosed to with TMA at 300K at annealed at 200C, the TMA reaction products (dimethyl aluminum, DMA) spontaneously forms monolayer islands insuring ALD nucleation in each unit cell. For integration of III-V MOSFETs on 300 mm silicon wafers, it is possible that a gate last process may be required for which As-decapping is not suitable. A combination of atomic hydrogen dosing, annealing, and TMA dosing is observed to produce an ordered unpinned passivation layer on air exposed InGaAs(001)-(4×2) surface with only monatomic steps. This TMA passivation layer on H cleaned air exposured III-V has the same horizontal rows of dimethyl aluminum (STM) and the same unpinned interface (STS) observed with the TMA/decapped InGaAs(100). While TMA directly reacts to create a high density of sites to nucleate gate oxide ALD on III-V surface, for Ge(100) surface functionalization is required. The direct reaction of TMA on a Ge(100) surface and the effect of monolayer H2O pre-dosing were investigated. At 300K, a saturation TMA dose produced 0.8 monolayer (ML) of semi-ordered species on a Ge(100) surface due to the dissociative chemisorption of TMA. XPS analysis of the 200oC annealed TMA/Ge(100) surface showed that only carbon content was reduced during annealing, while the Al coverage was maintained at 0.15 ML, consistent with the alow density of nucleation sites due to site blocks by reaction products. Conversely, saturation TMA dosing at RT on the monolayer H2O pre-dosed Ge(100) surface followed by annealing at 200oC formed a saturation layer of Al-O bonds with an Al coverage a factor of two greater than the TMA only dosed Ge(100). The Ge-OH sites catalyze the dissociative chemisorption of TMA even at 300K to create a a semiordered surface of Ge-O-Al bonds with an Al coverage double the coverage from a TMA surface without the H2O predose.