F. A. Stevie

Enhanced tail diffusion of ion implanted boron in silicon

The enhanced diffusion tail of implanted boron in Si was studied using conventional furnace annealing. Surface layer stripping was applied to remove part of the sample before annealing in order to distinguish the effect of the defect‐rich surface region from the tail region on the enhanced diffusion of boron. The boron concentration profiles were obtained with secondary ion mass spectrometry (SIMS). Spreading resistance profiles were also measured to compare with the SIMS profiles. The results show that implantation‐induced damage in the surface region is responsible for the enhanced boron diffusion. Channeled boron in the tail of the implantation profile becomes activated during annealing and has little effect on the tail redistribution during annealing.

Interface State Density Reduction and Effect of Oxidation Temperature on Fluorine Incorporation and Profiling for Fluorinated Metal Oxide Semiconductor Capacitors

The effect of fluorine incorporation on the as‐grown interface state density of the system was investigated using MOS capacitors with fluorinated oxide dielectrics grown by oxidation as test structures. A clear reduction of the interface trap density, attributed to fluorine‐induced passivation of interfacial dangling bonds, weak bonds, and weak interactions, was shown for additions in the parts‐per‐million range as compared to dry oxides. Fluorine incorporation in the oxide was investigated with SIMS profiling. The application of a pulsed oxidation process in which the fluorine source is added to the oxidant in intervals within the total oxidation time demonstrated that the variation of oxidation processing parameters strongly influences the resulting fluorine profile. A two‐peak pattern of the fluorine profile, with one peak in the interfacial area and the other corresponding to the oxide area grown during the step, was observed. This pattern was strongly dependent on the oxidation temperature, with the interfacial fluorine accumulation more pronounced with increasing temperature. The pronounced influence of the oxidation temperature on the fluorine profile resulting from oxidation was ascribed to a thermally activated replacement reaction of bonded fluorine by oxygen.

Microscopic studies of semiconductor lasers utilizing a combination of transmission electron microscopy, electroluminescence imaging, and focused ion beam sputtering

The microstructure of semiconductor laser diodes is studied using a combination of focused ion beam sputtering, electroluminescence imaging, and cross‐sectional transmission electron microscopy. Careful control of focused ion beam sputtering allows fabrication of high quality thin membranes for transmission electron microscope imaging, which can be located to submicron accuracy at a given position on the laser active stripe. By correlation with electroluminescence imaging, the membrane may then be positioned at an optically degraded region of the active stripe. In addition, imaging of the complete cross‐sectional laser structure, from substrate to surface contact layers is possible. The applications of these techniques to studies of laser degradation mechanisms are demonstrated and discussed.

Observation of strong contrast from doping variations in transmission electron microscopy of InP‐based semiconductor laser diodes

We report strong transmission electron microscope (TEM) contrast between p‐, i‐, and n‐doped InP layers in semiconductor laser diodes. For doping concentrations ∼1018 cm−3, contrast levels on the order 30% are observed between p‐ and n‐type layers. A critical feature of these experiments is that the samples imaged in the TEM are relatively perfect, plane‐parallel sided membranes fabricated with a focused ion beam. This technique offers the ability to detect and map doping variations with nm‐scale resolution, simultaneously with the other compositional and defect information inherent to TEM.We report strong transmission electron microscope (TEM) contrast between p‐, i‐, and n‐doped InP layers in semiconductor laser diodes. For doping concentrations ∼1018 cm−3, contrast levels on the order 30% are observed between p‐ and n‐type layers. A critical feature of these experiments is that the samples imaged in the TEM are relatively perfect, plane‐parallel sided membranes fabricated with a focused ion beam. This technique offers the ability to detect and map doping variations with nm‐scale resolution, simultaneously with the other compositional and defect information inherent to TEM.

Silicon‐fluorine bonding and fluorine profiling in SiO2 films grown by NF3‐enhanced oxidation

The incorporation and chemical bonding of fluorine introduced in SiO2 thin films by NF3‐enhanced oxidation of silicon has been studied by means of x‐ray photoelectron spectroscopy and secondary ion mass spectrometry depth profiling. Fluorine bonding in the oxide network is observed, indicated to occur in the area of the oxidizing interface and resulting in depth profiles which reflect the manner of the exposure of the growing oxide to the NF3 fluorine source during oxidation.

The Effect of Fluorine Additions to the Oxidation of Silicon

Experiments were carried out to study the effects of fluorine additions to a dry oxidation ambient. Two distinct classes of fluorine sources, liquid dichlorofluoroethane (C 2 H 3 Cl 2 F), and gaseous nitrogen trifluoride (NF 3 ), were investigated. We experimentally found that small fluorine additions caused large enhancements in oxidation kinetics. The oxidation kinetics data were analyzed by both the power of time and linear-parabolic models as a function of fluorine addition, temperature, and the type of fluorine additive

Rapid thermal processing to improve the epitaxy of (100) silicon on (11̄02) sapphire

The heteroepitaxial quality of (100) Si films on (1102) sapphire substrates (SOS) as measured by Rutherford backscattering (RBS) and x‐ray pole figure analysis is improved by a rapid thermal anneal (RTA) after deposition which brings the Si temperature above 1350 °C for at least several seconds. For a 6000‐A (100) SOS film the (100) aligned to random RBS yield improves from 10% and 54% at the front and back interfaces, to as low as 3.2% and 13% after the RTA. The microtwin volume shows a corresponding decrease to under 1% from the as‐grown value of 2.7%. A model based on isothermal solid phase epitaxial regrowth from the untwinned material near the front surface is proposed to account for these results.

SiO2 Film Stress—Thickness Dependence, Non‐Planar Oxidation, and Fluorine‐Related Effects

The thickness dependence of oxide stress for dry and fluorinated oxide films grown by NF 3 enhanced thermal oxidation was investigated. A small variation of stress with thickness was observed, Non-planar structures were oxidized and rounder corner structures were found to result in the case of fluorinated oxidation. Furthermore, pronounced oxide stress differences were observed for samples grown using two distinct fluorinated oxidation procedures and were ascribed to different fluorine profiles in the oxides

Tailoring of electron and hole energies in strained GaAsP/AlGaAs quantum wells using fluorine‐impurity‐induced layer disordering

Restoration or removal of the light‐ and heavy‐hole degeneracy of the exciton transitions for light polarized parallel to the layers in strained GaAs0.91P0.09/Al0.3Ga0.7As single quantum wells has been demonstrated by fluorine‐impurity‐induced layer disordering. Disordering due to As and P interdiffusion has also been observed at the quantum‐well interfaces. For only a 15‐min anneal at 750 °C, accumulation of P and a depletion of As at a distance of 0.05–0.1 μm beneath the surface is found to be closely associated with the redistribution of the implanted F in this region.

Hydrogen passivation of Si δ-doped GaAs grown by molecular beam epitaxy

Hydrogen passivation of Si δ‐doped GaAs grown by molecular beam epitaxy is studied. Just as in uniformily Si‐doped GaAs, exposure of the δ‐doped material to a low frequency (30 kHz) hydrogen plasma at 250 °C for 30 min deactivates the Si donors in the δ spikes. For samples with Si doping of (1–6)×1018 cm−3, carrier concentration in the spikes decreased by nearly three orders of magnitude following hydrogenation. Secondary‐ion mass spectrometric analysis of deuterated samples confirmed trapping of deuterium in the Si‐doped spikes. Consistent with the deactivation of Si donors following hydrogenation, changes were observed in the near‐band edge luminescence spectrum at 4.2 K, which showed in the hydrogenated sample the absence of Burstein–Moss shift that was observed in the as‐grown sample. This hydrogen‐induced passivation of Si donors in the δ spikes can be of benefit in selectively deactivating donor atoms in device applications, and also provide a method for tailoring the hydrogen distribution in an epi...