E. te Kaat

Range and range straggling of oxygen implanted into silicon at energies between 2 and 20 MeV

Oxygen profiles in silicon implanted with energies between 2 and 20 MeV by means of a Tandem accelerator have been investigated with a microprobe after bevelling the sample surface. It is shown that the measured profiles correspond to the implantation profiles when the microprobe is operated with a well focussed 2 keV electron beam. The projected ion ranges and the profiles thus obtained are compared with theoretical profiles which have been calculated by a Monte Carlo simulation of the stopping procedure. Takingk=1.30kLSS for the electronic stopping coefficient in the LSS region up to 2.55 MeV and a constant value of 162 eV/Å for the electronic stopping at higher energies the calculation yields satisfactory range estimates, whereas the range straggling is systematically too small up to 13% in comparison with the experimental results.

Ion track doping

Abstract Longitudinal dopant distribution along ion tracks in soft (polymers [1–5]) and hard (diamond [6,7]) condensed carbonaceous matter have been studied by neutron depth profiling and cathodoluminesence. Both in-diffusion from the aqueous phase and energetic ion implantation were used in primary track doping. In-situ self-decoration of tracks and post-implantation with a secondary ion species were used in the specific case of ion implantation. Radial dopant distributions were also studied by means of a modified tomographic procedure. Decorative doping of ion bombarded solids is useful in probing track structure, and especially in pointing the way to potential development of nanometric-sized electronic devices.

Optical characterization of damage and concentration profiles in H ion implanted amorphous silicon

Abstract 190 keV H ions are implanted with doses ranging from 1 × 1015 to 1.4 × 1018 cm−2 into pure amorphous silicon layers prepared by 2 MeV Silicon irradiation of crystalline silicon. Depth profiles of the changed complex refractive index (n + ik) are determined from high-resolution reflection and transmission measurements across bevelled surfaces. The increase of the reflectivity of annealed amorphous silicon (a-Si) resulting from collision induced Si bonding defects is used to determine the nuclear stopping power depth profile. A nuclear energy density of 3.1 eV per Si atom has to be deposited by the H projectiles in order to transform the relaxed structure of a-Si into the state of saturated disorder which is characteristic for irradiation amorphized silicon (ia-Si). On account of the saturated damage in pre-amorphized ia-Si targets the observed reduction of n and k is associated with the implanted H concentration c H. Projected range, range straggling, and skewness are evaluated from the optically ...

Spatial correlation between primary and secondary defect profiles after high dose self-irradiation of Si crystals

Abstract Primary and secondary defect profiles in silicon crystals have been investigated after 2 MeV and 80 keV Si+ irradiation by electronmicroscopy and optical reflectivity measurements. The primary irradiation damage leads to a more or less amorphous layer in the sample depending on target temperature and dose. The distance from the surface and the thickness of the amorphous layer determine the residual damage structure after annealing. In general two defect layers exist: one consisting of interstitial loops and misfit dislocations is formed approximately in the center of the region which was amorphous and where the two recrystallization fronts meet each other during annealing in the temperature range from 450 to 600°C. The other layer consisting of extrinsic stacking faults due to precipitation of implanted excess interstitials develops below the amorphous region. The appearance of this general defect profile after different implantation and annealing treatments is discussed.

Vergrabene Nitrid-Schichten in Silicium für Kalibrierproben zur quantitativen Auger-Elektronenspektrometrie (AES)

SummaryBuried layers of silicon nitride in silicon are produced by high-dose ion implantation and are checked for their suitability as calibration samples for quantitative thin film analysis. For this purpose, N+ ions (150 and 300 keV; 0.35 to 1×1018 N+ cm−2) are implanted into silicon single crystals and the samples annealed at 1,200°C for up to 15 h. The signal intensities and the sputter time obtained by AES/ sputtering can be converted into nitrogen content and sample depth by means of independent calibration measurements. The absolute depth scale is obtained by AES microanalysis at angle lapped surfaces (angle <1°) and by comparison with Monte Carlo simulation. The accuracy obtained is about 30 nm at a profile depth of 0.3 μm. The nitrogen content is determined quantitatively by means of the measured implantation dose.Additional methods of calibration are discussed. It is shown that the samples used are suitable as calibration samples for the silicon/nitrogen system.ZusammenfassungVergrabene Nitridschichten in Silicium werden durch Hochdosis-Ionenimplantation hergestellt und auf ihre Eignung als Kalibriermaterial für die quantitative Dünnschichtanalyse geprüft. Dafür werden N+-Ionen (150 und 300 keV; 0,35–1·1018 N+ cm−2) in Si-Einkristallen implantiert und durch Temperung (1200°C, bis 15 h) formiert. Die mit AES/Sputtering erhaltenen Signalintensitäten als Funktion der Sputterzeit können mit Hilfe unabhängiger Kalibriermessungen in die Stickstoffgehalte als Funktion der Probentiefe transformiert werden. Die Tiefenzuordnung wird durch AES-Mikroanalyse an Schrägschliffen (<1°) und durch Vergleich mit Monte-Carlo-Simulation mit einer Genauigkeit von ca. 30 nm bei 0,3 μm Profiltiefe erhalten. Der Stickstoffgehalt wird mittels der gemessenen Implantationsdosis bestimmt. Weitere zusätzliche Bestimmungsmethoden werden diskutiert.Es zeigt sich, daß die beschriebenen Proben als Kalibriermaterial für das Stoffsystem Silicium/Stickstoff geeignet sind.

Approaches for quantitative Auger electron spectroscopy of silicon after high dose nickel implantation

SummarySilicon samples of well-known nickel content have been produced by ion implantation in the dose range from 1017 to 1018 Ni/cm2. Such implants are used for the comparison of different approaches for quantitative Auger electron analysis. Considerable differences are found between results obtained from peak-to-peak heights in the differentiated energy spectrum, neglecting composition-dependent changes of the line widths, and those results calculated with consideration of variations of the line widths. Matrix effects are taken into account by the inclusion of backscattering factors and escape depths. The results show that the elemental composition for the Ni/Si system cannot be accurately determined over the whole dose range. The discrepancies are attributed to sputter-induced composition changes or incorrect theoretical matrix factors.