We propose a new method for high-k film growth and demonstrate its usefulness in terms of improvements of electrical characteristics of MOSCAPs and nMOSFETs. mer-by-mer 12eposition & &tealing (LL-D&A) is a key concept to reduce impurities incorporated in the film through decomposition of precursors. For HfA& (Hf75at.%), it is shown that there are big differences in physical and electrical properties between LL-D&A and conventional ALD+PDA. The maximum film thickness for annealing to effectively remove impurities and presumably to cure imperfections should be less than 1.8nm. The excellent properties for such as a very small flatband voltage shift (SVPB) less than 0.06V for MOSCAP, a well controlled subthreshold swing of 77mV/dec, a peak mobility of 210cm2Ns and 10-year lifetime at V =-I 9V for poly-Si gate nMOSFET, manifest the superiority 08 LLLD&A to the conventional ALWPDA.

We propose a new extraction method for mobility limited by high-k dielectrics, and discuss the scattering mechanism for halfnium aluminate (HfAlO x ) in the strong inversion region. In our method, mobility degradation properties are evaluated as a function of interfacial SiO2 thickness. The temperature dependence of the mobility in the strong inversion region is analyzed with the expression 1/µ=1/µRexp (-2k F T int)+1/µSiO2/Si, where µ is the measured mobility, µR is the prefactor mobility limited by a high-k dielectric, k F is the Fermi wavenumber of the channel carriers, T int is the thickness of the interfacial SiO2 layer, and µSiO2/Si is the mobility for n+poly-Si/SiO2 n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs). This analysis method is applied to n+poly-Si/HfAlO x [Hf/(Hf+Al)=60 at. %]/SiO2/p-Si n-channel MOSFETs. It is found that the mobility limited by the HfAlO x film, µR, decreases with a temperature increase in the range of 77–297 K. This temperature dependence indicates the predominance of non-Coulomb scattering for the mobility limited by HfAlO x in the strong inversion region. The mobility due to the non-Coulomb scattering shows a weak temperature dependence that is explainable by surface optical phonons (i.e., those appearing at the Si-surface channel region due to the longitudinal-optical (LO) modes of HfAlO x ) with the corresponding transverse-optical (TO) phonon energy in the range of 10–20 meV.

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Electrical characteristics and suppressed boron penetration behavior of thermally stable HfTaO gate dielectrics with polycrystalline-silicon gateWe have investigated impacts of nitrogen incorporation into HfAlO x films on the gate leakage currents and the flat band voltage V FB shifts. Also, a role of O-Hf-N bonding states in HfAlO x (N) in suppression of boron penetration is discussed. The nitrogen concentration C N in HfAlO x (N) was controlled by changing the NH 3 annealing temperature at the step of the layer-by-layer deposition and annealing process as well as the O 2 annealing temperature of post-deposition annealing. The C N over 10 at. % in HfAlO x (N) films effectively suppressed boron penetration as revealed by very slow diffusion in Hf 3 N 4 films and the formation of boron-nitrogen remote complex in HfO x (N), preserved the amorphous structure and reduced the V FB shift compared to the case of HfAlO x without nitrogen incorporation, while C N exceeding 13 at. % led to a significant increase of the gate leakage current. This suggests the excess O-Hf-N bond formation enhanced the leakage current.

The carrier conduction mechanism of leakage current in n+-gate p-channel metal-insulator-semiconductor field-effect-transistors with HfAlOx (Hf:60at%,Al:40at%)∕SiO2 dielectric layers has been investigated using the carrier separation method. Since the gate current depends on the substrate voltage and both electron and hole currents are independent of temperature in the range of 25–150°C, the conduction mechanism for both currents is a tunneling process. It is shown that the dominant carrier in the leakage current depends on the structure of the high-k stack. When the interfacial SiO2 layer (IL) thickness increases at a fixed high-k thickness (Thigh-k), the dominant carrier in the leakage current changes from hole to electron at ∼2.0–2.3-nm-thick IL, because of asymmetric barrier height for electron and hole in the SiO2∕Si system. In contrast, for the case of a fixed IL thickness of 1.3nm, the hole current dominates in the leakage current, regardless of Thigh-k, due to symmetric barrier height of the conduction and valence bands in the HfAlOx∕Si system.