Showing papers by "Thao N. Nguyen published in 1987"

Nonequilibrium boron doping effects in low‐temperature epitaxial silicon films

Abstract: We report the first preparation of in situ boron‐doped epilayers by a low‐temperature chemical vapor deposition process (T=550 °C). Boron incorporation is approximately linear in source gas concentration, and active levels of boron incorporation exceeding 1×1020 B/cm3 have been achieved in as‐deposited 550 °C epilayers. This value exceeds solid solubility limits for boron in silicon at these temperatures by two orders of magnitude, and highlights the nonequilibrium nature of this process. High resolution transmission electron microscopy lattice imaging of this material shows it to be free of boron precipitates, while both plane view transmission electron microscopy and x‐ray topography fail to reveal extended defects. Utilizing low‐temperature processing throughout, p/n junctions have been fabricated in several of the in situ doped layers, with essentially ideal junction quality factors (n=1.0 –1.05) found for junctions of 1×106 μm2.

Evidence of the role of defects near the injecting interface in determining SiO2 breakdown

Abstract: Experimental results on oxide breakdown in thin insulator metal‐oxide‐semiconductor structures are presented to show that at a microscopic level breakdown is related to defects located near the injecting interface. In addition, breakdown is found to be almost independent of electron fluence.

A New Failure Mode of Very Thin (<50Å) Thermal SiO2 Films

Abstract: Very thin (< 50 A) thermal oxides are shown to exhibit a new failure mode which is undetected by conventional tests and can lead to erroneous time-zero and time-dependent breakdown data. Breakdown in these films proceeds gradually from an increased low-field leakage current induced by electrical stress to catastrophic failure. The low-field leakage is not caused by positive charge generation and accumulation but is likely due to localized defect-related weak spots in the oxide. The leakage conduction mechanism appears to be thermally-assisted tunneling through locally-reduced injection barriers of about 0.9 eV and the model seems to be fully consistent with I-V measurements at temperatures from 77 to 523 K and theoretical calculations of the temperature dependence. Thin oxide breakdown is found to evolve by enlarging the area of the weak spots rather than propagating from one interface to the other.

Electron avalanche injection on 10-nm dielectric films

Abstract: Uniform electron avalanche injection has been successfully performed on 10‐nm SiO2 and on composite 8‐nm SiO2+4‐nm Si3N4 gate dielectrics. The films were grown on boron‐implanted substrates to obtain the optimum surface impurity concentration for uniform injection. The electrical properties indicated high‐quality and low‐defect density dielectrics with no deleterious effects introduced by the ion implantation. A voltage flat‐band Vfb shift and trap analysis were performed on both structures with and without post oxidation anneal, using metal or n‐polysilicon gate. The results obtained have confirmed the trends found in thicker oxides and pointed out the presence of deep water‐related centers. The composite structure, SiO2+Si3N4, showed high electron trapping due to two Coulombic centers normally invoked for Poole–Frenkel conduction in Si3N4. These centers are usually undetected by high‐field injection experiments.