Material Characterization of Metal Germanide Gate Electrodes Formed by Fully Germanided Gate Process

Abstract

The work functions and thermal stability of metal (Pt, Ni, Ta, and Er) germanide gate electrodes formed by the fully germanided (FUGE) gate process were investigated. Germanides have approximately 0.3 eV higher effective work function ( Φeff) values than silicides. The Φeff values corresponding to Si conduction and valence band edges (Ec and Ev, respectively) were realized with these germanides as well as the Si midgap (Pt3Ge2: 5.19 eV, NiGe: 5.01 eV, TaGe2: 4.70 eV, Er2Ge3: 4.05 eV). The Φeff values of germanide and silicide change linearly with the geometric mean of the electronegativities of the constituent metal and Ge(Si), which is the same as that in the case of pure metals. Low-level gate leakage current and stable Φeff values are maintained up to 400 °C for Ni germanide and up to 600 °C for Pt germanide, respectively. A W cap layer effectively improves the gate leakage current degradation, and makes Ni germanide gate electrodes sufficiently stable up to 600 °C. Fermi level pinning occurs at the germanide/HfSiON interface as in the case of the silicide/HfSiON interface. However, the Φeff values corresponding to almost Ev (>4.9 eV) were maintained with Ni and Pt germanides. In addition, a good thermal stability is maintained even on HfSiON.

Composition Dependence of Work Function in Metal (Ni,Pt)–Germanide Gate Electrodes

“…The reported values of other gate materials are also plotted for comparison. 2,4,13,22,23) Except for Ni and Er, these values were measured from the C-V characteristics of MOS capacitors with SiO 2 or SiON dielectric films. The values for both Ni and Er are obtained by the photoelectric effect.…”

Transmission electron microscopy study of the platinum germanide formation process in the Ge/Pt/Ge/SiO2/Si structure

“…Metal-germanides can be formed * Corresponding author. very easily by the solid-state reaction at the metal/Ge interface in a similar mechanism of the formation as metal-silicides [3][4][5].…”

Effectiveness of Aluminum Incorporation in Nickel Silicide and Nickel Germanide Metal Gates for Work Function Reduction

“…Ni fully-germanided (Ni-FUGE) metal gate has also attracted interest due to its p-type È m corresponding to Si valence-band edge, and can be easily formed though solidphase reaction with an annealing condition similar to that of Ni-FUSI gate. 11,12) In addition, thermal stability of NiGe gate was reported for back-end processing temperatures up to 600 C. 12) Therefore, NiGe gate is also a viable candidate for future metal-gate technology. In view of this, a suitable NMOS solution would realize dual gate integration employing either Ni-FUSI or Ni-FUGE gates.…”