Bernhard F. Cordts

Formation of Si islands in the buried oxide layers of ultra-thin SIMOX structures implanted at 65 keV

Abstract The microstructures of separation by implanted oxygen (SIMOX) wafers, implanted at 65 keV with doses of 1.5–7.0×10 17 O + /cm 2 at 500°C followed by a high temperature (1350°C) annealing with and without a protective cap, were studied using transmission electron microscopy to investigate the relationship between the formation of ultra-thin SIMOX structures and a variety of different preparation parameters. The study found that there is an optimum dose range corresponding to the implantation energy used. The samples synthesized at an oxygen dose of 2×10 17 O + /cm 2 (annealed without a cap) or 2.5×10 17 O + /cm 2 (annealed with a cap) consist of a thin silicon top layer with a low threading dislocation density, and a thin continuous buried oxide (BOX) layer free of Si islands. For samples implanted below the optimum dose, the BOX layer is discontinuous. Capping or non-capping the sample surface during annealing affects the formation of the BOX layer. For samples without a cap, internal thermal oxidation happens even in an ambient of low concentration of oxygen and makes the BOX layer grow continuously and free of Si islands.

Formation of multiply faulted defects in oxygen implanted silicon-on-insulator material

A multiply faulted defect (MFD), has been observed at a density of 108 cm−2 in oxygen implanted silicon‐on‐insulator material at implantation temperatures of ≥600 °C over a dose range from 0.3 to 1.8×1018 cm−2. The MFDs are 40–140 nm long and are created at the upper edge of the high‐dose implantation region. They consist of combinations of several discontinuous stacking faults within 2–8 atomic layers which generate an irregularity along the defect. The atomic arrangement of the MFDs indicates that they form by shearing of the lattice due to the volume change associated with oxide precipitation. The defects have a randomly faulted arrangement from cross slip and from the presence of several inhomogeneous nucleation sites along the edge of the same defect.

Effect of annealing ambient on the removal of oxide precipitates in high-dose oxygen implanted silicon

The effect of annealing ambient on the precipitate removal processes in high‐dose oxygen implanted silicon [separation by implantation of oxygen (SIMOX)] has been studied with transmission electron microscopy, electron energy‐loss spectroscopy, and secondary ion mass spectroscopy. The rate of removal of oxide precipitates from the top silicon layer in SIMOX is higher during annealing in argon than in nitrogen. The removal is reduced in nitrogen due to the formation of an oxynitride complex at the precipitate surfaces which inhibits oxygen diffusion across the interfaces. Similar effects have been observed for oxide precipitation during nitrogen ambient annealing in bulk silicon.

TEM analysis of SIMOX produced by multiple implantation and annealing

The authors present a TEM (transmission electron microscopy) analysis of the structural evolution of SIMOX (separation by implanted oxygen) through three subsequent implantation/anneal cycles. Optimizing the process parameters on the basis of the TEM analysis resulted in a better understanding of the mechanisms of defect formation, and the reduction of defect density. The structural evolution of defects through the processing steps is described. A set of silicon

Effects of cleaning techniques on residual contamination in SIMOX

Since SIMOX (separation by implanted oxygen) material is formed by a high-fluence process and subsequent high-temperature anneal, any contamination in the starting material and any residual contamination from the implant process may be critical for the further device performance and yield. The residual contamination level in SIMOX substrates was evaluated with respect to a variety of wet and dry cleaning techniques. The authors used total X-ray fluorescence analysis (TXRF) and SIMS (secondary ion mass spectrometry) analysis to determine the residual contamination from transition metals and aluminum, respectively Utilizing the TXRF sensitivity, incoming bulk wafers were examined for heavy metal contamination. Unacceptable residual levels of zinc ( approximately 4*10/sup 12/ cm/sup -2/) were found on the wafers. Wafers were also examined by TXRF and SIMS after the ion implantation process. An aluminum peak areal density on the order of 1*10/sup 12/ to 1*10/sup 13/ atoms/cm/sup 2/ was identified by SIMS analysis on the ion implanted wafers. Effective reduction in aluminum contamination after traditional wet cleans for the as-implanted wafers is shown.<<ETX>>