G. Weyer

The nature of electrically inactive antimony in silicon

Supersaturated solutions of substitutional, electrically active Sb in 〈100〉 silicon single crystals have been obtained by ion implantation, followed by short‐duration incoherent‐light annealing. Substitutional and nonsubstitutional fractions have been studied as functions of implanted dose and anneal temperature by Rutherford backscattering and channeling techniques, transmission‐electron microscopy, Hall‐effect and resistivity measurements (combined with layer removal), and Mossbauer spectroscopy. The maximum electrically active concentration, which can be incorporated on undisturbed substitutional sites, is found to be 4.5×1020 Sb/cm3 for 700 °C annealing. Upon further annealing, the supersaturated solution is reduced and approaches the Trumbore solubility value at temperatures of about 1100 °C. The Sb going out of solution is shown for the first time to be created in two different surroundings: Sb is predominantly found in Sb‐vacancy complexes for low doses and low annealing temperatures and in Sb prec...

Covalency effects on implanted119Sn in group IV semiconductors studied by Mössbauer and channeling experiments

Radioactive119mSn has been implanted with an isotope separator in single crystals of germanium, silicon, and diamond. Implantations of low doses (∼1013 atoms/cm2) at room temperature were performed as well as of higher doses at temperatures of about 400°C. The Mössbauer spectra of these sources show mainly one line. This line originates from119mSn on substitutional lattice sites as determined from channeling experiments with 2 MeV He+ ions on the same samples. The observed systematics of the isomer shifts for119Sn is explained on the basis of the average electronic configuration nsZsnpZp characterizing chemical bonding in the host crystals. The Debye-Waller factors measured at room temperature are compared to values calculated in a high temperature approximation which accounts for impurity-host mass difference.

Oxidation and reduction kinetics of eutectic SnPb, InSn and AuSn: a knowledge base for fluxless solder bonding applications

For microelectronics and especially for upcoming new packaging technologies in micromechanics and photonics fluxless, reliable and economic soldering technologies are needed. In this article, we consequently focus on the oxidation and reduction kinetics of three commonly used eutectic solder alloys: (1) SnPb; (2) InSn; (3) AuSn. The studies of the oxidation kinetics show that the growth of the native oxide, which covers the solder surfaces from the start of all soldering operations is self-limiting. The rate of oxidation on the molten, metallic solder surfaces is significantly reduced with decreasing O/sub 2/ partial-pressure. Using in situ Auger electron spectroscopy (AES) it could be shown for the first time, that H/sub 2/ can reduce Sn-oxide as well as In-oxide at moderate heating duration and temperatures. In the second part of this study, the results, obtained by the investigation of oxidation and reduction kinetics, are applied to flip-chip (FC) bonding experiments in vacuum with and without the injection of H/sub 2/. Wetting in vacuum is excellent but the self-alignment during flip-chip soldering is restricted. The desired, perfectly self-aligned FC-bonds have been only achieved, using evaporated and reflowed AuSn(80/20) and SnPb(60/40) after the introduction of H/sub 2/.

Charge state dependence of the diffusivity of interstitial Fe in silicon detected by Mössbauer spectroscopy

Interstitial 57mFe atoms excited in the 14.4 keV Mossbauer state have been created in silicon at 400–800 K as a result of the recoil imparted on these daughter atoms in the β− decay of ion-implanted, substitutional 57Mn. Diffusional jumps of the interstitial 57mFe cause a line broadening in their Mossbauer spectra, which is directly proportional to their diffusivity. Thus, the charge-state-dependent diffusivity has been determined in differently doped material.

Conversion electron Mössbauer spectroscopy study of iron disilicide films grown by MBE

Abstract Bulk stable (α-FeSi 2 ,β-FeSi 2 ) and epitaxially stabilized ( γ - FeSi 2 , Fe 0.5 Si which has the CsCl structure and 50% Fe vacancies) phases with the stoichiometry Fe : Si = 1:2 grown on Si(111) by molecular beam epitaxy have been studied by 57 Fe conversion electron Mossbauer spectroscopy. The Mossbauer parameters are discussed with respect to the local surrounding of the Fe atoms. From the angular dependence of the line intensities in the case of β-FeSi 2 the hitherto accepted interpretation of the spectra in terms of quadrupole coupling of the lines is discarded. Information about the defect (Fe vacancies) distributions in Fe 0.5 Si and α-FeSi 2 obtained from the population fractions of the different sites are reported. The possible nature of the observed spectrum for the γ - FeSi 2 phase is also discussed.

EFG sign for Sn in Zn, Cd, and Sb

Mössbauer spectroscopy on ion-implanted sources of119Cd in single-crystals was applied to study the electric field gradients (EFG) at119Sn in three non-cubic metals. The signs and magnitudes determined are in agreement with presently known systematics. The measured isomer shifts and the recoilless fractions are discussed.

Conversion electron Mössbauer spectroscopy study of iron silicide films grown by MBE

Conversion Electron Mossbauer Spectroscopy has been applied to the study of different novel expitaxially stabilized phases of the Fe-Si system and also of Fe3Si films. The silicides have been grown by Molecular Beam Epitaxy on Si(111). The 57Fe Mossbauer parameters (isomer shift δ, linewidth Γ, quadrupole splitting Δ and magnetic field H at the nucleus) are reported and discussed in terms of the local surrounding of the Fe nucleus.

Interstitial Implantation of Iron into Aluminium

Direct implantation into interstitial sites has been found for Fe in Al at temperatures below 200 K. This result was obtained from an in-beam Mossbauer experiment, which assures that each Fe atom comes to rest in its own isolated defect cascade.

The electronic configuration of Fe in

The experimental results obtained by conversion electron Mossbauer spectroscopy on the electronic configuration of Fe in are discussed in the light of ab initio full-potential linear muffin-tin orbital calculations of the isomer shift , quadrupole splitting and asymmetry parameter for the two Fe sites.

Direct comparison of Mössbauer and channeling studies of implanted 119sn in silicon single crystals

Abstract Mossbauer parameters, measured with a resonance counter, have been compared with channeling results on the same samples, for ′119mSn implanted into silicon single crystals. The implantation dose was varied between ∼1014 and ∼1017 atoms/cm2, for target temperatures of 2O°C and 400°C. The channeling results in hot implants show that Sn is embedded substitutionally, and the Mossbauer parameters are nearly dose independent in the range indicated above. Except for a very low-dose implant (∼1013 atoms/cm2) the room-temperature implants lead to complete damage (no channeling dip) and significantly different Mossbauer parameters. Subsequent annealing at 700°C, however, leads to values close to those characteristic of hot implants. The small dose dependence for hot implants, even for doses leading to ∼80% damage, as measured by channeling, indicates that the microscopic ordering is preserved.