In this study, a novel approach was proposed to improve the characterization of HfO 2 . Fluorine was incorporated by CF 4 plasma to improve the HfO 2 gate dielectric properties including leakage current, breakdown voltage and hysteresis. The hysteresis of capacitance-voltage characteristics can be reduced to approximately 10% hysteresis voltage for the samples with CF 4 plasma treatment. An inner-interface trapping model is presented to explain the hysteresis. The secondary-ion mass spectroscopy (SIMS) results show that there is a significant incorporation of fluorine (F) at the interface between the HfO 2 thin film and silicon substrate. The incorporation of F effectively suppressed leakage current and improved carrier trapping without an increase in interfacial layer thickness.
Fluorine-terminated chemical bonds and dipole structures within an Al2O3 layer were investigated in this study. Spectroscopic ellipsometry (SE) was employed to estimate the characteristics of fluorinated Al2O3. The parameters S0 and λ0 extracted from SE were analyzed to detect the influence of F-terminated bonding. Al–O bonds were replaced by the Al–F bonds after fluorine was implanted on the silicon substrate. A physical model of dipole structures was proposed explaining the F incorporation phenomenon.
The characteristics of atomic layer deposited ͑ALD͒-Al 2 O 3 gate dielectrics with CF 4 plasma surface treatment have been studied in this paper. Fluorine atoms were observed to be incorporated at bulk Al 2 O 3 and pile-up at both Al/Al 2 O 3 and Al 2 O 3 /Si interfaces. X-ray photoelectron spectroscopy analysis demonstrated that Al-O bonds were replaced by Al-F and F-Al-O bonds as samples were treated in CF 4 plasma. A physical model was proposed to explain the capacitance-equivalent-thickness ͑CET͒ degradation and capacitance-frequency-dispersion phenomenon. The CF 4 plasma-treatment approach can immunize capacitance dispersion due to its excellent capability of interface trap passivation by fluorine atoms in Al 2 O 3 dielectrics. Fluorine incorporation was proven to improve the Al 2 O 3 dielectric characteristics of hysteresis, oxide reliability, and capacitance dispersion.
In this article, the work functions (È m ) of hafnium-molybdenum (Hf x Mo y ) alloys were modified using nitrogen in dc reactive cosputtering for the first time. The Hf x Mo y N z alloys show low resistivity and excellent thermal stability up to 900 C. In addition, the work functions (È m ) of the Hf x Mo y N z alloys were tuned from the conduction band (4.17 eV) to the valence band (5.16 eV) by increasing the nitrogen flow ratio. From the X-ray diffraction (XRD) data, the MoN(200) peak can be observed for samples with a nitrogen ratio higher than 6%, which was responsible for the work function (È m ) increase in the Hf x Mo y N z alloys.
A novel manufacturable multiple gate oxynitride thickness technology is proposed in this work. An ultrathin dielectric film (E
OT=2.5 nm) of lower oxidation growth rate than conventional films was fabricated by NH3 plasma nitridation. Oxide thickness was reduced by about 80% for samples treated by NH3 plasma nitridation. However, the thickness limitation is 1.3 nm for NH3 plasma nitridation. This is believed to be due to nitrogen incorporated in the silicon surface to form a nitridelike thin film, which retarded oxide growth. The effects of NH3 plasma nitridation were systematically studied, and the rapid thermal N2O reoxidation of an NH3 plasma sample was also demonstrated in this work. This novel process improves the gate oxide reliability, decreases bulk trap densities, provides better SILC immunity, and produces less charge trapping and a higher Q
bd.
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