M. Voelskow

DENSITY AND STRUCTURAL CHANGES IN SIC AFTER AMORPHIZATION AND ANNEALING

The density of amorphous SiC layers formed by 2 MeV Si+ implantation into single-crystalline 6H–SiC was measured by x-ray reflectometry and compared with the results of step height measurements. Reactive ion etching was used to investigate the density as a function of depth. The density of the as-amorphized SiC is about 12% less than that of the crystalline material. Within experimental accuracy, the density reduction is homogeneous across the whole layer thickness. Low-temperature annealing leads to the formation of relaxed amorphous SiC with a density about 7% below the crystalline one. These large density changes are in contrast to results in amorphous Si. They can be explained by the high atomic density of SiC and the chemical disorder in the amorphous state of SiC.

Heavily Ga-doped germanium layers produced by ion implantation and flash lamp annealing: Structure and electrical activation

Heavily p-type doped Ge layers were fabricated by 100 keV Ga implantation and subsequent flash lamp annealing for 3 ms in the temperature range between 700 and 900 °C. For comparison, some samples were annealed in a rapid thermal processor for 60 s. Ga fluences of 2×1015, 6×1015, and 2×1016 cm−2 were chosen in order to achieve Ga peak concentrations ranging from values slightly below the equilibrium solid solubility limit of 4.9×1020 cm−3 up to 3.5×1021 cm−3 which corresponds to a maximum Ga content of about 8 at. %. The structure of the doped layer and the Ga distribution were investigated by Rutherford backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy, and secondary ion mass spectrometry. Temperature dependent Hall effect measurements were carried out in order to determine the electrical properties of the Ga-doped Ge layers. It is shown that by flash lamp annealing Ga diffusion into the bulk can be completely avoided and the Ga loss by outdiffusion from ...

Modeling and regrowth mechanisms of flash lamp processing of SiC-on-silicon heterostructures

This paper describes the development of a thermal model for flash lamp processing of 3C-SiC on silicon substrates in the millisecond regime, the FLASiC process. The model is a numerical solution of the enthalpy equation, using a modified implicit Crank-Nicholson scheme to combine accurate prediction of melt depths with reasonable computation times. The model has been calibrated against experiments and then used to compute the temperature distribution in the wafer during annealing. The results show the time and extent of melting as a function of layer thickness, wafer preheat temperature, and pulse intensity and duration. The kinetics of melting and regrowth have also been considered.

CRYSTALLIZATION AND SURFACE EROSION OF SIC BY ION IRRADIATION AT ELEVATED TEMPERATURES

The effects of high dose ion irradiation through amorphous surface layers on single crystalline 6H–SiC at elevated temperatures are studied in detail. Material swelling, subsequent densification, and surface erosion are quantified for irradiation at 500 °C. Ion beam induced recrystallization is investigated in the temperature range between 300 and 1300 °C. The results demonstrate that undisturbed epitaxial regrowth of an amorphous surface layer in (0001)-oriented 6H–SiC cannot be achieved by ion irradiation. The shift of the amorphous/crystalline interface observed by Rutherford backscattering spectrometry/channeling analysis is a consequence of columnar growth and surface erosion. The columnar growth starts inside the heavily damaged transition region between the amorphous surface layer and the single crystalline bulk material. It is stopped by random nucleation which is strongly enhanced by ion irradiation in the temperature range between 300 and 1000 °C. Neither the interface roughness nor the kind of ...

Radiation damage and annealing behaviour of Ge+-implanted SiC

Abstract In recent years, single-crystal SiC has become an important electronic material due to its excellent physical and chemical properties. The present paper reports a study of the defect reduction and recrysallisation during annealing of Ge+-implanted 6H-SiC. Implants have been performed at 200 keV with doses of 1 × 1014 and 1 × 1015 cm−2. Furnace annealing has been carried out at temperatures of 500, 950 and 1500°C. Three analytical techniques including Rutherford backscattering spectrometry in conjunction with channelling (RBS/C), positron annihilation spectroscopy (PAS) and cross-sectional transmission electron microscopy (XTEM) have been employed for sample characterisation. It has been shown that damage removal is more complicated than in ion-implanted Si. The recrystallisation of amorphised SiC layers has been found to be unsatisfactory for temperatures up to 1500°C. The use of ion-beam-induced epitaxial crystallisation (IBIEC) has been more successful as lattice regrowth, although still imperfect, has been observed to occur at a temperature as low as 500°C.

The effect of rare-earth clustering on charge trapping and electroluminescence in rare-earth implanted metal-oxide-semiconductor light-emitting devices

The effect of rare-earth clustering in dielectric media on the electroluminescence (EL) intensity, the charge trapping and the EL quenching was investigated using the example of Tb and Eu-implanted SiO2 layers. It was shown that the increase in the REOX cluster size induced by an increase in the furnace annealing temperature resulted in an increase in the concentration of electron traps with capture cross sections from 2×10−15 to 2×10−18 cm2. This is probably associated with an increase in the concentration of oxygen deficiency centers as well as with strained and dangling bonds in the SiO2 matrix which leads to an enhanced scattering of hot electrons and a decrease in the excitation cross section of the main EL lines of RE3+ ions. For the main EL lines of Tb3+ and Eu3+ ions the relation of the EL quenching to negative and positive charge generation in the SiO2 was considered. It was demonstrated that in case of REOX nanoclusters with small sizes (up to 5 nm) the EL quenching process can mainly be explain...

Influence of annealing on the Er luminescence in Si-rich SiO2 layers coimplanted with Er ions

The impact of rapid thermal annealing (RTA) in producing samples by sequential implantation of Si and Er ions into a 200 nm SiO2 layer combined with different annealing cycles as well as the corresponding room-temperature visible and infrared photoluminescence (PL) have been studied. The Er-related PL intensity at 1533 nm for the samples prepared by implanting Si with subsequent annealing, followed by Er implantation, and final annealing (type I) was found to be stronger than the one produced similarly but without the first annealing step (type II). In fact, the 1533 nm peak intensity in the optimized RTA processed sample is comparable to the PL yield of the furnace-annealed sample. Moreover, the excitation wavelength (405 nm) was found to be suitable for exciting the Si=O related point defects in the SiO2 layer and can provide a PL band with a maximum at ∼580 nm. While this band was further intensified in the presence of Si nanocrystals (Si NCs), it became weaker by introducing additional Er3+ ions with ...

Dose rate effects in focused ion beam synthesis of cobalt disilicide

The influence of the dwell-time in focused ion beam synthesis has been investigated. Cobalt disilicide layers have been produced by 70 keV Co2+ implantation into silicon and have been investigated by Rutherford backscattering spectroscopy and scanning electron microscopy. At an implantation temperature of about 400 °C it is only possible to form continuous CoSi2 layers using sufficiently short pixel dwell-times. This result is explained by an enhanced damage accumulation for longer dwell-times.

Ultra-doped n-type germanium thin films for sensing in the mid-infrared

A key milestone for the next generation of high-performance multifunctional microelectronic devices is the monolithic integration of high-mobility materials with Si technology. The use of Ge instead of Si as a basic material in nanoelectronics would need homogeneous p- and n-type doping with high carrier densities. Here we use ion implantation followed by rear side flash-lamp annealing (r-FLA) for the fabrication of heavily doped n-type Ge with high mobility. This approach, in contrast to conventional annealing procedures, leads to the full recrystallization of Ge films and high P activation. In this way single crystalline Ge thin films free of defects with maximum attained carrier concentrations of 2.20 ± 0.11 × 1020 cm−3 and carrier mobilities above 260 cm2/(V·s) were obtained. The obtained ultra-doped Ge films display a room-temperature plasma frequency above 1,850 cm−1, which enables to exploit the plasmonic properties of Ge for sensing in the mid-infrared spectral range.

Dwell-time related effects in focused ion beam synthesis of cobalt disilicide

The influence of the high current density of a focused ion beam on the ion beam synthesis of CoSi2 layers has been investigated. After 35 keV Co+ or 70 keV Co2+ implantation into a heated Si(111) substrate and subsequent annealing, the layers have been investigated by scanning electron microscopy and Rutherford backscattering spectroscopy (RBS). It is shown that the mode of beam scanning influences the CoSi2 layer formation significantly. At a given substrate temperature, a sufficient low dwell time is required to obtain a continuous layer rather than a laterally disrupted structure. With increasing target temperature, the dwell-time window becomes less restricted. The results are discussed in terms of damaging and dynamic annealing of the silicon crystal. RBS channeling investigations demonstrate that continuous or disrupted CoSi2 layers are formed when the substrate remains crystalline or becomes amorphous, respectively.