We introduce defects into (1120) oriented highly N-doped 4H-SiC by surface scratching, bending and annealing in the brittle regime. Emerging defects at the sample surface are revealed by chemical etching of the deformed samples. The etch patterns are constituted of straight bulges and grooves exhibiting various topographical features. These etch figures correspond to the emergence of double stacking faults dragged by a pair of partial dislocations. In this paper, we discuss the links between the etch figure characteristics and the defect nature. Results obtained by optical and atomic force microscopy are completed by structural analysis of defects performed by transmission electron microscopy. Mobility of partial dislocations in 4H-SiC is discussed and correlated to their core composition and to the effect of the applied mechanical stress.

High resolution transmission electron microscopy observations show for the first time the presence of two orientations of pure silver precipitates in nanocavities induced in bulk silicon by implantation at 1.6 MeV with a dose of 5×1016 He+ cm−2 and a two hour annealing at 1050°C. These precipitates were called A and B to refer to the two well-known nickel silicide (NiSi2) precipitates or Ag films on a {111} silicon surface. Thus, the A precipitate corresponds to a growth of silver nanocrystal on {111} cavity walls in epitaxy with the Si matrix with an orientation relationship Ag(-111)[211]||Si(-111)[211]. The B precipitate develops on a {111} plane parallel to a {111} cavity wall as well, but in a twin orientation with respect to the Si matrix defined by Ag(-111)[211]||Si(-111)[-2-1-1]. The Ag nanocrystals have a size ranging from a few nm to 50 nm. Most of them have the faceted-shape characteristic of “clean” cavities. They are either A precipitates or they contain alternatively A and B bands in good agreement with both the low stacking fault energy of silver and the two types of nanocrystal orientations obtained by Ag deposition on (111) Si substrate at room temperature. Some Ag precipitates were also found at dislocations located at the He+ projection range, but these trapping sites were found thermally unstable as compared to the cavity ones. Indeed, during a second identical annealing, the precipitates grow in cavities whereas they fade at dislocations.

When platinum is diffused at temperatures higher than 900°C in Cz or FZ low doped n-type silicon samples, which are then cooled slowly in the range [1-10]°C/min, a p-type doping leading to the formation of a pn junction can be observed by spreading resistance measurement. The lower the cooling rate, the deeper the junction is. This junction disappears after a second thermal treatment finishing with a quenching step. A platinum related complex formation is considered to explain this reversible doping behaviour. Different possible interactions between platinum and other impurities such as dopant atoms, intrinsic point defects, and common residual impurities (C, Oi, transition metallic atoms) are studied here. Experimental results from Pt diffusion processes in different qualities of silicon wafers, and simulation results, lead to the conclusion that the platinum related p-type doping effect is due to the formation of a Pts-Oi complex.

Silicon samples were implanted with He+ ions at energies varying from 10keV to 1.55MeV using doses ranging from 1.45×1016 cm-2 to 5×1016cm-2 to obtain similar He concentration at each projection range (Rp). In few samples, gold, platinum, nickel or silver was introduced prior to He+ implantation by diffusion at temperatures ranging from 870°C to 1050°C. All samples were annealed in the 400°C–1050°C temperature range to determine the equilibrium stage of the growth of the cavity. The cavity characteristics (distribution, shape and size) were studied by cross section transmission electron microscopy (XTEM). Their morphology demonstrates the validity of the chemisorption hypothesis when they grow in silicon intentionally contaminated by metal. A consequence of the surface proximity on the cavity characteristics was verified and allows stepping forward two regimes of cavity growth: one, very fast, taking place in a He-free environment and another one, slower, occurring in a He-rich atmosphere.

4H-SiC samples are bent in compression mode at 550°C and 620°C. The introduced-defects are identified by Weak Beam and HRTEM techniques. They consist of double stacking faults bounded by 30° Si(g) partial dislocations whose glide locally transforms the material in its cubic phase. The velocity of partial dislocations is measured after chemical etching of the sample surface. The formation and the expansion of the double stacking faults are discussed.

Silicon samples were implanted with He ions at 1.6 MeV using doses ranging from 1×1016 cm-2 to 1×1017cm-2 with different fluxes (0.4νA/cm2 - 2.0νA/cm2) and annealed at high (1000°C) and low temperatures (800°C). The implantation induced-defect structure and their distribution in the depth of the sample were studied by cross section electron microscopy (XTEM). An unexpected consequence of the flux on the defect population and density was found solely for 2×1016 cm-2, which is the upper threshold to get nano-bubbles at such large implantation depth. Nuclear Reaction Analysis (NRA) were performed to measure the ratio of He remaining in the bubbles as a function of time and temperature anneal. Some samples were gold or nickel diffused at temperatures ranging from 870°C to 1050°C prior to He implantation. The gettering efficiency of the implantation-induced defects was measured by secondary ion mass spectroscopy (SIMS), after a high temperature getter annealing. SIMS profiles exhibit a shape and a width closely related to the presence of the defects (observed by XTEM) which are very efficient sinks for all kinds of metal impurities. The bubbles were found to be more efficient traps than the dislocation loops.