D. M. Jamba

Mg and Be Ion Implanted GaAs

p‐type layers have been produced in GaAs by implantation of either Mg or Be ions, with the substrate at room temperature, followed by annealing at higher temperatures. The ion source in both cases was a hot‐cathode electron‐bombardment type. The Mg ions were generated by placing metallic Mg in an axial probe inserted into the source, while the Be ions were produced by placing BeCl2 in the probe. n‐type 〈111〉 substrates were implanted with 45‐keV Mg or 40‐keV Be ions, and were subsequently annealed for 15 min at temperatures up to 900°C. The dependence of surface carrier concentration and mobility on ion dose and on postimplantation anneal temperatures was determined using the van der Pauw‐Hall technique.

Chromium concentrations, depth distributions, and diffusion coefficient in bulk and epitaxial GaAs and in Si

Implantation of 200‐keV chromium fluences from 4.5×1012 to 1.0×1015 cm−2 and SIMS profiling were used to measure the atom densities and depth distribution of Cr in bulk GaAs (Cr), in undoped liquid‐phase epitaxial GaAs grown on a GaAs(Cr) substrate, and in Si. The Cr atom density in both GaAs(Cr) substrates was ∼1.6×1017 cm−3. The background‐limited detection sensitivity of SIMS for Cr in GaAs was ⩽3×1015 cm−3. Chromium outdiffused into the epitaxial layer during growth at 800 °C. The diffusion coefficient for CR at 800 °C in GaAs was determined to be 6.7×10−12 cm2/sec. Channeling tails were observed for the Cr implanted in Si and in the undoped epitaxial GaAs, but not in the bulk GaAs(Cr). Ranges, range straggles, and other Pearson IV moments for the implanted Cr distributions are given.

Dependence of implanted Se and S profiles on GaAs implantation temperature and crystallinity

Atom depth distributions of Se implanted into GaAs show that the deep sides of the depth distributions are the result of interstitial diffusion of Se during implantation of crystalline GaAs. The effect saturates at an ion fluence of ∼1014 cm−2 for 25 °C implants and continues uninhibited up to the 1016 cm−2 fluence for 250 °C implantation temperature, implying that the GaAs implantation damage is annealed during implantation at 250 °C. Annealed Se profiles are unchanged for all fluences for both 25 and 250 °C implantation temperatures. Se implants into a self‐amorphized GaAs surface yield more abrupt profiles than corresponding ones into crystalline GaAs, further indicating that when crystal channels are absent, implant tails are absent. Sulfur implants into crystalline and amorphized GaAs held at −130, 25, and 250 °C show that S behaves like Se for the unannealed case; the profiles for implants into crystalline GaAs are deeper the higher the substrate temperature during implantation, implying that diffus...

Dosimetry measurement in ion implanters

Abstract Measurement of ion beams by electronic techniques is analyzed in detail, looking at such problems as collector designs, suppression of secondaries, monitoring of beam uniformity, purity of the ion beam, integrator accuracy and other sources of errors.

Secondary particle collection in ion implantation dose measurement

The measurement of ion implantation doses in the presence of secondary ions and electrons emitted from the target is discussed. A circuit and electrode geometry for obtaining accurate ion beam current measurements in the presence of both positive and negative secondary particles is presented.

Comparison of sources of boron, phosphorus, and arsenic ions

A number of boron, phosphorus, and arsenic compounds, viz., B2H6, B10H14, B3N3H6, B2S3, BF3, BCl3, BBr3, BI3, HBO2, P, PH3, PF3, PF5, PCl3, POCl3, P2O5, As, AsH3, AsF3, AsCl3, and As2O5, are compared as sources of boron, phosphorus, and arsenic ion beams in a hot‐filament electron‐impact or oscillating‐electron‐discharge (OED) ion source. Performance comparison data, including the percentage of B+, P+, P2+, P+2, As+, As2+ and As+2 in the total beam and the maximum ion currents observed at the target of a 150‐kV ion implantation system, are given for a common set of source and system conditions. BF3 and BCl3 are evaluated as the first and second best materials for B+, with any other compound providing only a poor third choice. The pure elements P and As provide large currents of both monatomic and diatomic ions and have no other interfering ion components. PH3 is a good source of P+ but has strong nearby hydride ions. The fluorides of P and As provide good currents of monatomic ions and have proved conveni...

SOLUBILITY EFFECTS OF IMPLANTED IONS IN SEMICONDUCTORS

Hall effect and sheet resistivity measurements combined with layer removal techniques indicated carrier concentrations for 20‐kV antimonyimplants into silicon that exceed the thermal equilibrium solubility.Annealing caused the carrier concentration to decrease toward solubility values. Supersaturation effects were not observed for gallium implants. For samples annealed at 800 to 900°C, the concentration of carriers increased linearly with implanted dose and leveled off at a value close to the thermal equilibrium solubility.

Surface Ionization Source for Ion Implantation

A surface ionization source was designed and developed to produce useful ion beams of elements with ionization potentials up to about 6 eV by using iridium (work function 5.27 eV) as the ionizing surface. Sources were operated successfully producing stable ion beams of aluminum, gallium, indium, and thallium with current densities up to 10 μA/cm2. Neutral atoms are shielded from the beam as it leaves the source by a special design geometry. The construction, developmental details, and operating parameters of the source are described.

Depth distributions of sulfur implanted into GaAs as a function of ion energy, ion fluence, and annealing temperature and encapsulation

Depth distributions are shown for sulfur implants into GaAs at energies from 40 to 600 keV and implant fluences from 4×1012 to 4×1016 cm−2. The four Pearson IV moments, including range and range straggle, are tabulated and plotted versus ion energy for these profiles. Redistributed sulfur profiles are shown for these same implants following annealing under three conditions. Annealed profiles are compared with electrical profiles from other work. Fractions of sulfur atoms in various locations are described. Annealed sulfur profiles are shown as a function of temperature for SiO2 and Si3N4 caps.

Range and shape factors, damage, regrowth, and redistribution for Ag implants in (100) and (111) Si

The nature of regrowth of implantation‐damaged (100) and (111) Si was investigated by measuring the depth distribution of implanted Ag atoms following annealing at 550 °C for fluences of 1×1012 to 1×1015 cm−2. Cross‐section transmission electron microscope measurements were made for a few conditions to compare damage depth distributions. Other factors studied were anneal time, Si growth technique, Ag atom densities, and the transition region between amorphous and crystalline Si. Ranges and profile shape factors are reported for 150, 300, 450, and 600 keV Ag implants into Si.