Fabrication of Ta2O5∕GeNx gate insulator stack for Ge metal-insulator-semiconductor structures by electron-cyclotron-resonance plasma nitridation and sputtering deposition techniques

Abstract

The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)∕2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011cm−2eV−1 at the midgap.

Ge incorporated epitaxy of (110) rutile TiO2 on (100) Ge single crystal at low temperature by pulsed laser deposition

“…These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage (C-V) characteristic [8,9]. To overcome these problems, some groups have demonstrated the formation of stable GeO 2 [10,11] and the surface passivation of Ge such as GeN (GeON) passivation [12,13], Si passivation [14], and F passivation [15]. These approaches achieved the improvements of electrical properties such as reduced C-V characteristic hysteresis and reduced leakage current.…”

Excellent surface passivation of germanium by a-Si:H/Al2O3 stacks

“…Several approaches have been investigated to reduce the D it including the use of an ultrathin epitaxial silicon interlayer, [33][34][35] a germanium oxide (GeO x ) interlayer, [36][37][38][39][40][41] surface sulfurization, [42][43][44][45] and nitride-based interlayers. [46][47][48][49] Of these approaches, the GeO x interlayer approach, in particular, has been investigated extensively in the last two decades yielding promising D it values for GeO x interlayers grown by plasma oxidation (D it ≈ 4.5 × 10 10 -1 × 10 11 eV −1 cm −2 ) [34][35][36] and thermal oxidation in O 2 or O 3 (D it ≈ 7.5 × 10 10 -3 × 10 11 eV −1 cm −2 ). 36,37,41 For optoelectronic devices, passivation entails a reduction in the surface recombination rate of electrons and holes, which depends not only on D it , but also on the capture cross sections of these states and the fixed charge concentration Q f .…”

Chemical Bonding, Interfaces, and Defects in Hafnium Oxide∕Germanium Oxynitride Gate Stacks on Ge(100)

“…Engineering a stable interface layer between the high-k film and Ge is vital to achieving dimensionally-scaled, high speed, field effect transistors. Previous studies on high-k/Ge gate stacks with interfacial layers such as germanium nitride and oxynitride have been reported 2,3,4,5 and high-k film should be substantially thinner than 2 nm in order to allow scaling of the gate capacitance density. Moreover, interface layers must exhibit resistance to oxidation during postdeposition thermal processes.…”