Donor behavior in indium-alloyed silicon

The anomalous doping behavior of Si regrown from In solution was studied by (1) Schottky barrier evaluation of conductivity type, (2) electron microprobe analysis for phosphorus, and (3) channeling effect measurements for interstitial In. The latter showed In present at ~ 10^19 cm^–3, but not occupying a regular substitutional or interstitial position. A correlation was found in the first two measurements between phosphorus contamination and n-type conductivity. When the In was contacted only by quartz freshly etched in HF, the n-type behavior and phosphorus contamination disappeared. The anomalous doping behavior is most likely due to phosphorus inpurity picked up by the In

Analysis of thin-film structures with nuclear backscattering and x-ray diffraction

Backscattering of MeV ^(4)He ions and Seemann-Bohlin x-ray diffraction techniques have been used to study silicide formation on Si and SiO_2 covered with evaporated metal films. Backscattering techniques provide information on the composition of thin-film structures as a function of depth. The glancing-angle x-ray technique provides identification of phases and structural information. Examples are given of V on Si and on SiO_2 to illustrate the major features of these analysis techniques. We also give a general review of recent studies of silicide formation

XPS study of the chemical structure of the nickel/silicon interface

The chemical nature of the Ni/Si, Ni/Ni_(2)Si and Si/Ni_(2)Si interfaces have been investigated using x‐ray photoelectron spectroscopy. Peak position, line shapes, and envelope intensities are used to probe the compositional structure of these systems. Two approaches have been employed: one approach examines the advancing planar silicide front by dynamically monitoring the in situ formation of Ni_(2)Si. This has the advantage of allowing examination of a realistic interface which is bounded on either side by an extended solid. The second approach follows the development of the Si/Ni interface using UHV depositions of thin layers of Ni on Si . ^(4)He^+ backscattering is used to follow the progression of the thin film reaction and to provide quantitative information on atomic composition. These experiments demonstrate that the Ni/Ni_(2)Si interface consists of a Ni‐rich silicide transitional phase while the Si/Ni_(2)Si interface shows a transitional structure which is correspondingly Si‐rich. Intensity analysis indicates that these interfacial regions are at least 22 Å wide for α‐Si substrates and 9–14 Å wide for crystalline Si. The as‐deposited Ni/Si interface cannot be described as a unique single‐phase, but rather as a chemically graded transitional region showing a composition which varies from Si‐rich to Ni‐rich silicides

Exploratory study on microanalysis of thin films by backscattering techniques

Solid phase epitaxial growth of Si layers was studied by backscattering spectrometry for controllable electrical characteristics. Samples were fabricated by vacuum deposition on a thin layer of Sb before deposition of the amorphous Si layer. Analysis of the resulting SPEG layer showed that Sb was present in the SPEG layer of Si. The characteristic of the SPEG layer against the Si substrate was rectifying. A scanning microprobe picture of a cleaved sample established the presence of a depletion region more than 1 micron below the surface. Hall effect data indicated that the SPEG layer was n-type, with average free carrier concentration of about 10 to the 19th power cm/3 and average electron mobility of about 40 sq cm/Vs. SPEG with Pd silicide or Ni silicide transport layers showed fast initial transient growth regimes with slower growth in the steady state regimes

Space charge effects in current transport Quarterly status report

Space charge limitations of currents for use in dosimeter

Kinetics of silicide formation by thin films of V on Si and SiO_2 substrates

The reaction rate of vacuum‐evaporated films of V of the order of 1000 Å thick is investigated by MeV He backscattering spectrometry. On substrates of single‐crystal Si and for anneal times up to several hours in the temperature range 570–650°C, VSi_2 is formed at a linear rate in time. The activation energy of the process is 1.7±0.2 eV. The presence of oxygen in amounts of 10% can significantly decelerate the reaction. On substrates of SiO_2 in the temperature range 730–820°C and anneal times of several hours or less, V_3Si is formed at a square‐root rate in time. The activation energy of this process is 2.0±0.2 eV

Influence of atomic mixing and preferential sputtering on depth profiles and interfaces

Atomic mixing and preferential sputtering impose a depth resolution limit on the use of sputter sectioning to measure the composition of metal–semiconductor interfaces. Experimental evidence obtained with the Pt–Si system is used to demonstrate ion‐induced atomic mixing and then its effect on sputter etching and depth profiling. Starting with discrete layer structures, a relatively low ion dose (≳3×10^(15) cm^(−2)) first produced a mixed surface layer with thickness comparable to the ion range. Higher ion doses then result in successive sputter etching and continual atomic mixing over a constant surface layer thickness. A model is developed that is based on a sputter removal (including preferential sputtering) of atoms at the surface and a uniform mixing of atoms over a constant thickness. The model predicts the influences of atomic mixing and preferential sputtering on the depth profiling of thin‐film structures and interfaces

Ion implantation in semiconductors

Ion implantation is being applied extensively to silicon device technology. Two principle features are utilized- 1) charge control in MOS structures for threshold shift, autoregistration, and complementary wells and 2) distribution control in microwave and bipolar structures. Another feature that has not been extensively exploited is to combine the advantages of the high resolution capabilities of electric beam pattern delineation with the low lateral spread inherent in the implantation process. This talk reviews some of the general features of the characteristics of implanted layers in terms of depth distribution, radiation damage and electron activity. Implantation processes in silicon are reasonably well understood. There remain areas which require further clarification. For compound semiconductors, particularly GaAs, implantation techniques offer attractive possibilities for the fabrication of high frequency devices. In these materials, the substrate temperature during implantation and the dielectric coating required to prevent dissociation during thermal anneal play major roles

Relevance of cosmic gamma rays to the mass of gas in the galaxy

The bulk of the diffuse gamma-ray flux comes from cosmic ray interactions in the interstellar medium. A knowledge of the large scale spatial distribution of the Galactic gamma-rays and the cosmic rays enables the distribution of the target gas to be examined. An approach of this type is used here to estimate the total mass of the molecular gas in the galaxy. It is shown to be much less than that previously derived, viz., approximately 6 x 10 to the 8th power solar masses within the solar radius as against approximately 3 x 10 to the 9th power based on 2.6 mm CO measurements

Ti and V layers retard interaction between Al films and polycrystalline Si

Fine-grained polycrystalline Si (poly Si) in contact with Al films recrystallizes at temperatures well below the Si-Al eutectic (577 °C). We show that this interaction can be deferred or suppressed by placing a buffer layer of Ti or V between the Al film and the poly Si. During annealing, Ti or V form TiAl3 or Val3 at the buffer-layer–Al-film interface, but do not react with the poly Si so that the integrity of the poly Si is preserved as long as some unreacted Ti or V remains. The reaction between the Ti or V layer and the Al film is transport limited ([proportional]t^1/2) and characterized by the diffusion constants 1.5×10^15 exp(–1.8eV/kT) Å^2/sec or 8.4×10^12 exp(–1.7eV/kT) Å^2/sec, respectively