AVS 52nd International Symposium
    Electronic Materials and Processing Wednesday Sessions
       Session EM-WeA

Paper EM-WeA9
Metal Germanide Schottky Contacts to Relaxed and Strained Germanium

Wednesday, November 2, 2005, 4:40 pm, Room 309

Session: Contacts to Semiconductors
Presenter: A. Khakifirooz, Massachusetts Institute of Technology
Authors: A. Khakifirooz, Massachusetts Institute of Technology
O.M. Nayfeh, Massachusetts Institute of Technology
M.L. Lee, Massachusetts Institute of Technology
E. Fitzgerald, Massachusetts Institute of Technology
D.A. Antoniadis, Massachusetts Institute of Technology
Correspondent: Click to Email
Significant mobility enhancement offered by germanium channel MOSFETs and especially strained-Ge devices makes them very attractive for the deca-nanometer transistor scaling. A low resistivity contact to the S/D junctions is, however, the key to successful integration of such devices. Since high doping levels are difficult to achieve in Ge, Schottky S/D MOSFET is considered as an interesting option that also relaxes the constraints on the S/D junction abruptness. A systematic study of the formation of different metal germanide phases has been recently performed and they were characterized in terms of their electrical resistivity.@footnote 1@ In this work we study the Schottky barrier formed between germanium and Ni, Pd, and Pt germanides that were previously identified as the low-resistivity phases and offer a relatively wide processing window. Metal germanide is formed by annealing a very thin layer of metal (~15 nm) deposited onto HF-last Ge samples and patterned by lift-off. Samples are annealed in a furnace for 15 min. or in an RTA chamber for 1 min at different temperatures in the range of 350-500°C. Some diodes are also fabricated on strained Ge epitaxially grown on relaxed Si@sub 0.4@Ge@sub 0.6@ buffer with an ultrathin silicon cap. In this case, the metal thickness is selected in a way to consume the Si cap and almost the entire strained-Ge layer without touching the SiGe buffer layer to avoid excessive leakage. XRD and XTEM analysis are performed to study the crystallinity and morphology of the germanide layers, whereas I-V and C-V measurements are used to characterize the Schottky barrier. While nearly ideal barriers (ideality factor as good as 1.01), with a barrier height of 0.55-0.57 eV are obtained on bulk germanium, diodes fabricated on strained-Ge samples show excessive leakage current and high ideality factor (~1.8). Possible mechanisms responsible for this non-ideality are discussed. @FootnoteText@ @footnote 1@S. Gaudet et al., AVS 51st Int. Symp., 2004.