The impact of thermal post deposition annealing in oxygen at different temperatures on the Ge/Y2O3 interface is investigated using metal oxide semiconductor capacitors, where the yttrium oxide was grown by atomic layer deposition from tris(methylcyclopentadienyl)yttrium and H2O precursors on n-type (100)-Ge substrates. By performing in-situ X-ray photoelectron spectroscopy, the growth of GeO during the first cycles of ALD was proven and interface trap densities just below 1 × 1011 eV−1 cm−2 were achieved by oxygen annealing at high temperatures (550 °C–600 °C). The good interface quality is most likely driven by the growth of interfacial GeO2 and thermally stabilizing yttrium germanate.
Y2O3 and L2O3/ZrO2 stacks have been examined in terms of their electrical properties in Ge capacitors. It is discussed that scaling of L2O3/ZrO2 stacks into the sub 1 nm EOT regime can be achieved either by using thin amorphous La2O3 capped by a thin ZrO2 layer or by stabilizing the tetragonal or cubic very high-k phase of ZrO2 induced by diffused La and Ge atoms during a PDA step. Y2O3 shows very good interfacial qualities in terms of a low interface trap density and hysteresis when an annealing in O2 atmosphere is applied. Fowler-Nordheim tunneling is identified as the primary leakage current mechanism at high gate bias whereas for the low bias regime leakage current is primary conducted by direct tunneling through the Y2O3 layer.
In order to improve the electrical behaviour of metal-insulator-metal capacitors with ZrO2 insulator grown by Atomic Layer Deposition, the influence of the insertion of interfacial Cr layers between Pt electrodes and the zirconia is investigated. An improvement of the α-voltage coefficient of capacitance as low as 567 ppm/V2 is achieved for a single layer of Cr while maintaining a high capacitance density of 10.7 fF/μm2 and a leakage current of less than 1.2 × 10−8 A/cm2 at +1 V. The role of the interface is discussed by means of X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy showing the formation of Zr stabilized chromia oxide phase with a dielectric constant of 16.
Rhodium Schottky barrier contacts on germanium substrates are investigated in terms of electrical, physical, and chemical properties. The Rh, deposited by electron beam evaporation on a n-type (100)-Ge substrate, has been annealed in N2H2 at different temperatures ranging from 450°C up to 800°C. Rh/Ge Schottky diodes were fabricated to extract the Schottky barrier height, the ideality factor as well as the forward to backward current ratio. By using various analyzing techniques such as Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), and High-resolution Transmission Electron Microscopy (HR-TEM), the formation of polycrystalline Rh-germanide RhxGey phases has been proven. At 500°C germanidation temperature an effective SBH of 0.59 eV is extracted showing a high current ratio of 5 × 103 and a remarkable low ideality factor of 1.07.
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