Si Nitrogen Research Articles

Heavy atomic-layer doping of nitrogen in Si 1 − xGe x film epitaxially grown on Si(100) by ultraclean low-pressure CVD

N atomic-layer doping in a nanometer-order Si/Si 1 − x Ge x /Si(100) heterostructure using ultraclean low-pressure chemical vapor deposition and its thermal stability at 650 °C were investigated. In the Si 0.5Ge 0.5 epitaxial layer, it is found that a N doping dose of 6 × 10 14 cm − 2 can be confined within an about 1.5 nm-thick region even after 650 °C heat treatment in contrast to the result for Si cap layer growth on the thermally nitrided Si(100) with a N doping dose of 6 × 10 14 cm − 2 which was found to be amorphous. Moreover, it is suggested that the confined N atoms in Si 1 − x Ge x preferentially form Si–N bonds and that formation of Si 3N 4 is enhanced by the heat treatment at 650 °C.

Estimation of nitrogen ion energy calculated using distribution for nitrogen in Si implanted by PBII

Plasma-based ion implantation (PBII) using N2 gas is examined as a sterilization technique for three-dimensional targets. The application of a pulsed negative voltage (5μs pulse width, 300 pulses/s, −800V to −13kV) at an N2 gas pressure of 2.4Pa is shown to reduce the number of Bacillus pumilus survivors by up to 105 times after just 5min of exposure. The energy of nitrogen ions is calculated based on the depth profile of nitrogen concentration in Si implanted by PBII, and it is revealed that the actual nitrogen ion energy is much lower than that calculated based on the voltage applied during processing.

Atomic Structure and Diffusion in Amorphous Si-B-C-N by Molecular Dynamics Simulation

We carried out molecular dynamics simulation of amorphous silicon nitride containing boron and carbon, in order to investigate the short-range atomic arrangement and diffusion behavior. In amorphous Si–B–N, boron atoms are in a nearly threefold coordinated state with nitrogen atoms, while boron atoms in amorphous Si–B–C–N have bonding with both carbon and nitrogen atoms. Carbon atoms in Si–B–C–N are also bonded to silicon atoms. The self-diffusion constant of nitrogen in Si–B–N becomes much smaller than that in amorphous Si3N4. Also, amorphous Si–B–C–N exhibits smaller self-diffusion constants of constituent atoms, even compared to Si–B–N. Addition of boron and carbon is important in decreasing atomic mobility in amorphous Si–B–C–N. This may explain the increased thermal stability of the amorphous state observed experimentally.

Plasma immersion ion implantation of nitrogen in Si: formation of SiO 2, Si 3N 4 and stressed layers under thermal and sputtering effects

Plasma immersion ion implantation (PIII) of nitrogen in silicon (Si) wafers was carried out using a dc glow discharge plasma source and a hard tube pulser. Ion irradiation times ranging from 3 to 60 min were used to accumulate different doses. Surface analysis of these samples was carried out by Auger electron spectroscopy (AES), revealing a high atomic concentration of nitrogen (up to 60%) in the as-implanted Si wafer, besides the presence of different impurities as oxygen and carbon in significant quantities. Depth profiles of these elements were obtained as well as of compound species as SiO 2 and Si 3N 4, using this high-energy resolution AES. Comparing the concentration profiles of implanted nitrogen in Si and the corresponding retained doses in these samples, it was possible to understand the thermal and sputtering effects in our present PIII experiment. High-resolution XRD results corroborate the formation of highly stressed layers in the as-implanted substrates. These experimental results are compared to simulations obtained by TRIDYN code.

On nitrogen sorption during high energy milling of silicon powders in ammonia and nitrogen

A systematic study on nitrogen sorption during high energy milling of Si powder in NH3 and N2 has been conducted. X-ray diffraction (XRD), transmission electron microscopy (TEM), and nuclear magnetic resonance (NMR) have been used to analyze the milled powder and correlate the enhanced nitrogen sorption to the structural change of Si powder during milling. It is found that the amount of the sorbed nitrogen in Si is substantially higher than that predicted by the equilibrium phase diagram. Further, the sorbed nitrogen is primarily present in the amorphous phase. NH3 is found to be much more effective than N2 in enhancing the sorption of nitrogen. Mechanisms responsible for these phenomena are discussed based on the structural change of Si powder and mechanical activation induced by high energy milling.

Annealing behavior of N–O complexes in Si grown under nitrogen atmosphere

The temperature-dependent annealing behavior of N–O complexes [D(N, O)] in Cz–Si grown under a reduced pressure of light pure nitrogen atmosphere has been studied by using infrared absorption spectra. The experimental results show that the D(N, O) have different thermal stability. The most efficient production of the D(N, O) occurs when the second annealing temperature is 650°C. Furthermore, the presence of nitrogen in Si probably suppresses the formation of thermal donors related to oxygen.

Behavior of Implanted Nitrogen in Si with the Buried Layer of SiO2 Precipitates

Behavior of Implanted Nitrogen in Si with the Buried Layer of SiO₂ Precipitates

(Invited) Recent Advances in Photoluminescence Analysis of Si: Application to an Epitaxial Layer and Nitrogen in Si

The photoluminescence (PL) technique has been applied for the first time to the characterization of shallow impurities in Si epitaxial crystals and of nitrogen in bulk Si crystals. The species of impurities incorporated intentionally or unintentionally in an epitaxial layer can be definitely determined by the PL analysis. The new PL line at 1.1223±0.0001 eV observed in N-doped crystals is identified to be due to nitrogen. Epitaxial samples show a quantitative relationship between the intensity ratio of the PL line from an epitaxial layer to that from its substrate and the impurity concentration in the epitaxial layer. In N-doped crystals, the PL intensity ratio between the intrinsic and the 1.1223 eV lines increases linearly with the N concentration. It is demonstrated that these PL intensity ratios can be used as measures of the respective impurity concentrations.

The concentration profiles of projectiles and recoiled nitrogen in Si after ion implantation through Si3N4 films

The concentration profiles of ion-implanted boron, phosphorus, and arsenic, and recoil-implanted nitrogen atoms after ion implantation through Si3N4 films on Si have been measured using secondary ion mass spectrometry. The concentration profiles of the implanted ions in Si after ion implantation through Si3N4 films were found to agree with those implanted into bare Si within experimental errors, with the exception of a shifting of the concentration peak position. The concentration profiles of recoil-implanted nitrogen in Si are generally composed of high-concentration regions with steeply decaying distributions near the silicon surface and the exponential tails whose slopes are independent of ion mass, energy, dose, and film thickness. The concentration level of recoil-implanted nitrogen and maximum penetration range relative to the implanted ion range depend strongly on ion mass, film thickness, and ion energy. It was demonstrated that the concentration profiles for recoiled nitrogen in Si calculated using the Thomas-Fermi interaction potential agree better with the measured profiles than those calculated using 1/r2 potential, such as presented in the theory by Moline et al.

Depth distribution of knock-on nitrogen in Si by phosphorus implantation through Si3N4 films

The concentration profiles of phosphorus and knock-on nitrogen in silicon after phosphorous implantations into Si3N4-Si systems have been investigated by using secondary ion mass spectrometry (SIMS). The tails were found on the phosphorus distribution in silicon after the implantation through Si3N4 films. The concentration profiles of knock-on nitrogen in silicon have been determined by measuring both the in-depth profiles of knock-on nitrogen and those of nitrogen after additional nitrogen implantation into a bare silicon embedded with knock-on nitrogen. The concentration profiles of knock-on nitrogen show a very high concentration near the surface and extending tails. It was found that the tails were observed at the deeper portion in silicon as energy increased, for a given Si3N4 layer.