Chemical Bonding , Interfaces and Defects in Hafnium Oxide /

Correlations among interface properties and chemical bonding characteristics in HfO 2 /GeO x N y /Ge MIS stacks were investigated using in-situ remote nitridation of the Ge (100) surface prior to HfO 2 atomic layer deposition (ALD). Ultra thin (~1.1 nm), thermally stable and aqueous etch-resistant GeO x N y interfaces layers that exhibited Ge core level photoelectron spectra (PES) similar to stoichiometric Ge 3 N 4 were synthesized. To evaluate GeO x N y /Ge interface defects, the density of interface states (D it) was extracted by the conductance method across the band gap. Forming gas annealed (FGA) samples exhibited substantially lower D it (~1x10 12 cm-2 eV-1) than did high vacuum annealed (HVA) and inert gas anneal (IGA) samples (~1x10 13 cm-2 eV-1). Germanium core level photoelectron spectra from similar FGA-treated samples detected out-diffusion of germanium oxide to the HfO 2 film surface and apparent modification of chemical bonding at the GeO x N y /Ge interface, which is related to the reduced D it. 3 Germanium is an attractive material for high performance metal oxide semiconductor field effect transistor (MOSFET) channels because of its high hole and electron mobilities 1. However, compared to the SiO 2 /Si system, Ge oxides grown on Ge semiconductor have undesirable physical and electrical properties for field effect devices. Their poor thermal stability, solubility in water and tendency for nonstoichiometry make it difficult to utilize germanium oxides as an interface layer interposed between high-k dielectrics and the Ge substrate surface in a practical MOSFET fabrication process. 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. However, the relationships among electrical properties, and the binding states of Ge in the interface and thermal stability of the gate stacks are not yet well understood. Maeda et al 3. and Otani et al 4. obtained low D it (1.8 x 10 11 , 4 x 10 11 cm-2 eV-1) with HfO 2 and Ta 2 O 5 on the top of relatively thick Ge 3 N 4 layers (~2 nm), respectively. They reported that Ge 3 N 4 layers were not oxidized during high-k metal oxide deposition, and that an interface between Ge 3 N 4 and Ge with reasonably low …