Activation energy for fluorine transport in amorphous silicon

The transport of ion implanted F in amorphous Si is studied using secondary ion mass spectroscopy and transmission electron microscopy. Significant redistribution of F is observed at temperatures in the range 600°C to 700°C. The measured F depth-profiles are modelled using a simple Gaussian solution to the diffusion equation, and the diffusion coefficient is deduced at each temperature. An activation energy of 2.2eV±0.4eV for F transport is extracted from an Arrhenius plot of the diffusion coefficients. It is shown that the F transport is influenced by implantation induced defects

Non-Linear Pomeron Trajectory in Diffractive Deep Inelastic Scattering

Recent experimental data on diffractive deep inelastic scattering collected by the H1 and ZEUS Collaborations at HERA are analysed in a model with a non-linear trajectory in the pomeron flux. The $t$ dependence of the diffractive structure function $F_2^{D(4)}$ is predicted. The normalization of the pomeron flux and the (weak) $Q^2$ dependence of the pomeron structure function are revised as well.Comment: 16 pages, Latex + 3 figures, postscrip

Improved base current ideality in polysilicon emitter bipolar transistors due to fast fluorine diffusion through oxide

The fast diffusion of fluorine in polysilicon and silicon dioxide is shown to improve the base current ideality of polysilicon emitter bipolar transistors. This behaviour is explained by the passivation of interface states at the oxide/silicon interface around the perimeter of the emitter

The influence of BF2 and F implants on the 1/f noise in SiGe HBTs with a self-aligned link base

A study is made of 1/f noise in SiGe HBTs fabricated using selective growth of the Si collector and non-selective growth of the SiGe base and Si emitter cap. The transistors incorporate a self-aligned link base formed by BF2 implantation into the field oxide below the p+ polysilicon extrinsic base. The influence of this BF2 implant on the 1/f noise is compared with that of a F implant into the polysilicon emitter. Increased base current noise SIB and base current are seen in transistors annealed at 975?C, compared with transistors annealed at 950 or 900?C. At a constant collector current, both the BF2 and F implants reduce SIB, whereas at a constant base current, only the BF2 implant reduces SIB. This result indicates that the BF2 implant decreases the intensity of the base current noise source whereas the F implant decreases the base current. The proposed explanation for the increased 1/f noise is degradation of the surface oxide by viscous flow at 975?C under the influence of stress introduced during selective Si epitaxy. The influence of the BF2 implant on the noise is explained by the relief of the stress and hence the prevention of viscous oxide flow

TEM and SIMS study of the behaviour of fluorine in as-deposited amorphous and polysilicon annealed at 600 to 950C

The behaviour of fluorine in as-deposited polysilicon (p-Si) and as-deposited amorphous Si (a-Si) layers after annealing in the range 600-950C us investigated. The p-Si and a-Si were deposited by LPCVD at 610 and 560C, respectively, implanted with F (5E15cm-2, 30keV) and annealed. The microstructure and fluorine distributions were investigated by TEM and SIMS. The results show that at >=650C F segregates to form inclusions of similar size and shape in both as-deposited a-Si and p-Si, the amount of F in the layer decreases and at the interface increases with increasing temperature. For the same anneal, more F reaches the interface in p-Si than in a-Si. Mechanisms explaining the microstructure and F distributions are discussed

Leakage current mechanisms in SiGe HBTs fabricated using selective and nonselective epitaxy

SiGe heterojunction bipolar transistors (HBTs) have been fabricated using selective epitaxy for the Si collector, followed in the same growth step by nonselective epitaxy for the p+ SiGe base and n-Si emitter cap. DC electrical characteristics are compared with cross-section TEM images to identify the mechanisms and origins of leakage currents associated with the epitaxy in two different types of transistor. In the first type, the polysilicon emitter is smaller than the collector active area, so that the extrinsic base implant penetrates into the single-crystal Si and SiGe around the perimeter of the emitter and the polycrystalline Si and SiGe extrinsic base. In these transistors, the Gummel plots are near-ideal and there is no evidence of emitter/collector leakage. In the second type, the collector active area is smaller than the polysilicon emitter, so the extrinsic base implant only penetrates into the polysilicon extrinsic base. In these transistors, the leakage currents observed depend on the base doping level. In transistors with a low doped base, emitter/collector and emitter/base leakage is observed, whereas in transistors with a high doped base only emitter/base leakage is observed. The emitter/collector leakage is explained by punch through of the base caused by thinning of the SiGe base at the emitter perimeter. The emitter/base leakage is shown to be due to a Poole-Frenkel mechanism and is explained by penetration of the emitter/base depletion region into the p+ polysilicon extrinsic base at the emitter periphery. Variable collector/base reverse leakage currents are observed and a variety of mechanisms are observed, including Shockley-Read-Hall recombination, trap assisted tunneling, Poole-Frenkel and band to band tunneling. These results are explained by the presence of polysilicon grains on the sidewalls of the field oxide at the collector perimeter</p