Tuning of NiSi∕Si Schottky barrier heights by sulfur segregation during Ni silicidation

Abstract

The Schottky barrier height ͑SBH͒ of NiSi on Si͑100͒ was tuned in a controlled manner by the segregation of sulfur ͑S͒ to the silicide/silicon interface. S was implanted into silicon prior to silicidation. During subsequent Ni silicidation, the segregation of S at the NiSi/ Si interface leads to the change of the SBH. The SBH of NiSi decreased gradually on n-Si͑100͒ from 0.65 eV to 0.07 eV and increased correspondingly on p-Si͑100͒. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1863442͔ Self-aligned silicidation is one of the key technologies in the state-of-art complementary metal-oxide-semiconductor ͑CMOS͒ process to make Ohmic or Schottky contacts at source/drain and gate. Amongst of them, NiSi silicide has emerged as a leading choice in Si nanometer electronics due to its low resistivity and high scalability. Recently, Schottky barrier source/drain metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒ have been receiving a lot of attention because of the lower parasitic series resistance at source/ drain, possible zero junction depth and simpler fabrication process.1-4 However, for a typical Schottky barrier ͑SB͒ MOSFET, the on-current is limited by the tunneling through the Schottky barrier at the source. If a very low or a negative SBH could be realized, the on-current of SB-MOSFET could be increased substantially. 4 NiSi has an experimental SBH of 0.65 eV on n-Si͑100͒. This high SBH value hinders the application of NiSi in SB-MOSFETs. If we can lower the SBH of silicides to very low value, the device exhibits the same intrinsic performance as conventional MOSFET but also benefits from the advantages of SB-MOSFETs mentioned above.In an ideal metal-semiconductor system the SchottkyMott theory suggests that the SBH ͑⌽ B ͒ is simply determined by the difference between the work function of the metal ͑ M ͒ and the electron affinity of the semiconductor5 In practice, however, the presence of interface states leads to the SBH being less dependent on the metal work function. Dangling bonds at the semiconductor surface can be eliminated by valence-mending adsorbates. 6 S and Se are two possible valence-mending candidates for the Si͑100͒ surface.6 Lacharme et al. 7 reported that surface states on Si can be removed by S exposure at room temperature. Tao et al. [8][9][10] have used a monolayer of Se to eliminate the surface states on the Si͑001͒ surface by terminating dangling bond and relaxing strained bonds. Pure metals, like Mg, Al, Cr, and Ti, on Se-passivated n-Si͑001͒ showed very low and even negative SBH values which can be predicted by the Schottky-Mott theory.8-10 However, deposition of these elements seems inappropriate for silicide contacts on Si due to the suppression of silicide formation. 10 In order to benefit from advantages of silicides in state-of-art MOSFET technology, methods to tune the SBH of silicides on Si are required. In this paper we show an effective method to tune the SBH value of NiSi on both n-and p-type Si͑100͒. A small dose of S ions was implanted into Si before Ni de...

Experimental and simulation study of the Schottky barrier lowering by substrate doping variation for PtSi Source/Drain SBFETs

“…by inserting a thin insulator layer [3] or by creating a highly doped region located at the silicide/Si interface with a dopant segregation technique [5]- [6]. To our knowledge, no such reports were available for hole SBH modulation.…”

In situ study of the growth properties of Ni-rare earth silicides for interlayer and alloy systems on Si(100)

“…More specifically, a NiSi contact to n-type Si(100) still suffers from a reasonably high Schottky barrier (∼ 0.65 eV) deteriorating the contact resistance [2]. The midrange band gap of NiSi in fully silicided (FUSI) gates on the other hand requires a modulation of the work function [3].…”

Schottky-Barrier Height Lowering by an Increase of the Substrate Doping in PtSi Schottky Barrier Source/Drain FETs

“…To make the SBFETs comparable to state-of-the-art short-channel MOSFETs in terms of drivability, the intrinsic SBH should be lowered to ∼100 meV [3]. Recently, it has been shown that the effective electron SBH could be lowered by inserting a thin insulator [3] or a highly doped layer (defined with a dopant segregation technique [5], [6]) at the silicide/Si junction. To our knowledge, no such method has already been reported for hole SBH.…”