Jos G.E. Klappe

Rapid thermal oxidation for passivation of porous silicon

Chemical and mechanical stability of porous silicon layers (PSL) is the prerequisite of any active (luminescent) or passive (e.g. porous substrate) integrated applications. In this work X-ray diffraction (XRD) was used to analyze quantitatively the strain distribution obtained in different morphology PSL that were prepared on (100) p and p + Si substrates. Tetragonal lattice constant distortion can be as high as 1.4% in highly porous “as-prepared” samples. Incoherent optical heating RTO is governed by the absorption in the oxidized specimen. PSL show vertical inhomogeneity according to interpretation of spectroscopic ellipsometry (SE) data. Oxygen incorporation during RTO is controlled by specific surface (in p + proportional, in p inversely proportional with porosity), while the developing compressive stress depends on pore size, and decreases with porosity in both morphologies.

Optimization of ion implantation damage annealing by means of high-resolution X-ray diffraction

High-resolution X-ray diffraction (HR-XRD) was investigated as a possible technique for the qualitative analysis of damage annealing of low-dose, high-energy implanted (001) silicon, implanted with dopants smaller than the host atom. The choice of proper Bragg reflection for the rocking-curve measurements is shown to be of crucial importance. The graphic construction of the Ewald sphere is a useful aid for this purpose. As the in-plane lattice constant is confined by the underlying substrate, a change occurs in the perpendicular direction only. Therefore the (026)1 reflection appears to be the most suitable for the detection of changes in lattice constant caused by implantation damage. Qualitative analysis of rocking curves of P- and B-implanted Si samples was compared with electrical measurements and cross-section transmission electron micrographs. It could be established that the minimum implantation doses of P and B at energies ranging from 0.5 to 1.5 MeV, for which HR-XRD is sensitive enough, are about 1.5 × 1014 cm?2 and 5 × 1013 cm?2respectively. The minimum peak temperature needed for complete damage anneal by transient-rapid thermal annealing was about 1400 K for all doses considered.

Rapid Thermal Annealing of Low-Energy P and B Implants in Silicon, Optimized by High Resolution X-Ray Diffraction

In this paper, low-energy (45 keV) implantations of phosphorous and boron into silicon were studied. A comparison of doping profiles, secondary defect formation, electrical activation and diode leakage was made between Rapid Thermal Annealing (RTA) and conventional furnace annealing. The samples were analysed by High-Resolution X-Ray Diffraction (HR-XRD), X-TEM, SIMS, spreading resistance (SRP) and sheet resistance measurements. The non-destructive HR-XRD technique combined with the novel simulation software was a very useful tool for the defect characterisation and for the choice of the optimum annealing temperature. Furthermore estimations of electrically active dopant atoms were made with HR-XRD by measurement of the strain. With RTA a substitutional dopant concentration of a factor 2 to 4 higher than with furnace annealing can be obtained, for P and B respectively. Electrical measurements show that not all of the substitutional dopants are electrically active, however. Thus estimates of the electrically active dopant atoms with HR-XRD require further study. Furthermore it appeared that RTA was superior to furnace anneal for lowering sheet resistances, defect removal and dopant profile broadening. However, furnace anneal gave the best results for diode leakage currents. This indicates that RTA processing needs to be further refined or that combined RTA/furnace processes need to be developed.

Ion implantation defect characterization by high-resolution X-ray diffraction

High-energy ion-implantation is one of the roost critical processing steps regarding the formation of defects in mono-crystalline silicon. High- as well as low-doses implanted at various energies can result in relatively high residual defect concentrations after post-implantation annealing. Before annealing, the crystal lattice strain is mainly caused by the point defects. After annealing, the accommodation of substitutional impurities is the main origin of the residual lattice strain. High-Resolution X-ray Diffraction (HRXD) has been frequently used for the characterization of these structures. Dislocation loops formed during the high temperature step, however, cause enhanced diffuse X-ray scattering, which can dominate the measured X-ray intensity in conventional HRXD. Triple axis diffractometry is used in this study to analyze the size, type and location of defects in a boron implanted and rapid thermally annealed silicon sample.

Characterization of stress and texture in RTCVD poly-Si layers by X-ray diffraction

The properties of polycrystalline silicon layers deposited by RTCVD have been studied by texture, stress and electrical analyse. The intrinsic layers intended for applications in integrated IC processing are very much textured with the preferred orientation depending on deposition temperature and atmosphere. Very low residual film stress in the order of 10 dyn/cm 2 was detected, and a transition from compressive to tensile stress with increasing deposition temperature around 800°C was observed. This was associated with the development of the columnar structure by the (110) orientation becoming dominant at the expense of the (100) texture. Also the effect of post-deposition anneal ambience on the grain structure has been studied. Grain size and grain-boundary trapping in after doped layers have been evaluated in P-implanted RTA activated layers.