J.F. Barbot

Helium desorption from cavities induced by high energy 3He and 4He implantation in silicon

A detailed study has been made of helium release from silicon wafers implanted with MeV helium ions at fluences of 5 × 10 16 cm -2 and 10 17 cm -2 . Thermal desorption spectrometry (TDS), neutron depth profiling (NDP), non-Rutherford elastic backscattering (NREBS) and nuclear reaction analysis (NRA) have been employed to measure the helium content and release rate during isothermal annealing at annealing temperatures of 800 and 1000°C. TDS has also been used for isochronal annealing. Transmission electron microscopy (TEM) is used to monitor changes in morphology in the formed bubble layer. The helium release results can be modeled rather well when it is assumed that the helium initially is present in overpressurized bubbles. The present study reveals a single activation energy for helium release of 1.83 (0.05) eV.

Evolution of shallow donors with proton fluence in n‐type silicon

Bipolar components that consist of p+n junctions have been irradiated by MeV protons at fluences ranging from 1011 to 1013 particlesu2009cm−2. Capacitance‐voltage measurements have been used to investigate changes in the carrier concentration profiles. Shallow donors that can induce harmful effects in electronic devices have been studied as a function of fluence, flux, and annealing parameters.

Low temperature proximity gettering of platinum in proton irradiated silicon via interstitial cluster dissociation

Abstract Epitaxial silicon samples of n-type have been implanted with 850 keV protons at a dose of 5xa0×xa01013H+ cm−2. Subsequent in-diffusion of platinum at 700°C for 30 min resulted in the presence of a single deep level, which is attributed to the platinum acceptor level, at 0.23 eV below the conduction band edge. Depth profiling of this level shows that the substitutional platinum is following the vacancy profile in the peak region around the projected range for the protons. In addition, at more shallow depths, a strong increase of the platinum concentration is also observed. Without ion-implantation, no deep levels are detected after in-diffusion at 700°C, while at 800°C, the Pt deep level concentration is inferior to the one reached after pre-implantation with the above dose. After in-diffusion at 600°C into the implanted sample, many defects are observed. One of these is the substitutional platinum, while the others are considered to be of interstitial nature, due to the fact that their maximum concentration is found to be deeper than the projected range of the irradiation. The role of these latter defects in the process of platinum proximity gettering is discussed.

Study of Al ion implantation in Hg0.3Cd0.7Te

Abstract We have implanted Hg 0.3 Cd 0.7 Te compounds with various ions (aluminium, xenon and krypton) at different substrate temperatures (300 and 15 K). Implantations were performed with impinging ions having a kinetic energy in the range 60–320 keV, their fluence varying between 5 × 10 11 and 5 × 10 14 ionscm −2 . Samples have been characterized before and after annealing (300° C, 2 h) by SIMS, EBIC, TEM, RBS and differential Hall effect. The overall result is that the p/n transformation is linked to defects induced during implantation. The saturation in the sheet carrier concentration n s for φ > 5 × 10 13 Alcm −2 could be caused by fact that the recombination volume has then been reached.

Defect levels of proton-irradiated silicon with a dose of 3.6 × 1013cm−2

Abstract Deep levels created in n-epitaxial silicon by 1.85 MeV proton implantation at a dose of 3.6 × 10 13 H + cm −2 have been investigated by Deep Level Transient Spectroscopy (DLTS). Following irradiation, three hole traps and seven electron traps, two of these for the first time, are observed. They are considered to be (multi-) vacancy- and/or impurity-related defects. After subsequent annealing at 400°C for 5 min, only five electron traps and four hole traps are found. Capture cross-sections for all levels have been determined and their respective identities have been discussed. The evolution of the spectra due to the annealing and profiles of the levels have been studied. It is suggested, that the level E C − 0.30 eV is vacancy related.

Residual defects in Cz-silicon after low dose self-implantation and annealing from 400°C to 800°C

Abstract Si(1xa00xa00) samples of n-type have been implanted with 5.6 MeV 28Si3+ at room temperature using a dose of 1xa0×xa0108 cm−2. Thereafter the samples were annealed in nitrogen ambient for 30 min at temperatures from 400°C to 800°C using steps of 50°C. Deep level transient spectroscopy (DLTS) was used for sample analysis. Deep levels, not previously reported in the literature, are observed to arise, evolve, and to vanish again in the described temperature interval, while above 650°C only two defects levels remain. Depth profiles of these levels show, that the maximum concentrations of the defects are located deeper than the projected range, as is characteristic for secondary implantation defects. Their possible identities are discussed.

Effect of shallow donors induced by hydrogen on P+N junctions

Abstract We have evaluated the effect of shallow donors induced by proton irradiation on P + N junctions. We have combined the capacitance–voltage (C–V) technique, which provides the shallow donor profile, and a numerical simulation, based on the solution of Poisson’s equation, to determine the electric field as a function of depth in the N region. This procedure can be applied to study the breakdown voltage of P + N junctions as a function of proton irradiation, i.e. its energy and dose.

THE EFFECT OF PARTICLE FLUENCE AND FLUX IN ALPHA-IRRADIATED SILICON

Abstract We have irradiated N-type silicon with MeV alpha particles at fluences ranging from 10 10 to 5 × 10 12 particles/cm 2 and at various fluxes. The as-irradiated and post-annealed samples were analyzed by Cue5f8V measurements carried out as a function of the sample temperature. It clearly appears that as the fluence increases from lower value to higher values, a large change occurs in the nature of the defects created by the irradiation. In particular, two deep donors appear when higher fluences are used whereas only deep acceptors appear at low fluences.

Comparison of N- and P-type silicon irradiated by MeV protons and post-annealed at different temperatures

Abstract We irradiated N- and P-type silicon with 1.5 MeV protons at fluences of 10 12 , 10 13 and 10 14 cm −2 . After irradiation, the irradiated samples were studied by the spreading resistance method in order to determine the profiles of the defects before and after different thermal annealings. The measurements were performed as a function of annealing temperature and time. While P- and N-type silicon present the same behaviour after irradiation, many differences arise after annealing. In particular, the N-type samples show a conductivity layer at the end of the proton range (Rp) unlike the P-type samples.

TYPE CONVERSION BY HIGH-ENERGY PARTICLES IN HG1-XCDXTE COMPOUNDS

p‐type crystals of the ternary compounds Hg1−xCdxTe have been irradiated with high‐energy ions and electrons. Electron‐beam‐induced current signals on xenon‐ and krypton‐irradiated Hg1−xCdxTe show that n‐type conversion, occurring all along the ion path, is related to the presence of mercury atoms. Resistivity and Hall measurements on carbon‐, oxygen‐, xenon‐ and electron‐irradiated Hg0.8Cd0.2Te crystals allow us to determine the effective cross section for atomic displacement. We observe, for electron‐irradiated samples, a saturation in carrier concentration interpreted as the pinning of the Fermi level at a resonant donor state 370 meV above the bottom of the conduction band. Comparison between ion and electron irradiations shows that electrically active produced defects are mainly due to atomic collisions. Additional reduction of defect production efficiency for xenon ions may be the onset of some energy transfer from electronic loss to target atoms.