Substrate Heating Temperature Research Articles

Epitaxial growth of Co-Cr films and their characterization

In recent years, much attention has been devoted to the study of Co-Cr thin films. There are mainly two different models of magnetization mechanisms which have been proposed in the literature, typified by the work of Iwasaki et al. and that of Wielinga et al. To further clarify this matter, epitaxial Co-Cr films have been grown by rf sputtering onto (001) MgO single-crystal substrates. The cleanliness of the substrate and target were found to be the most critical parameters. The substrate bias and too high a substrate heating temperature were also found to be unfavorable for epitaxial growth of Co-Cr films. These epitaxial films were characterized by x-ray diffraction, electron diffraction, Auger spectroscopy, VSM, and torque magnetometer. It is found that low argon pressure ranging from 1 to 2 mTorr favors the epitaxial growth of Co-Cr films. The values of Ku, K1 and Hk of the epitaxial films are higher than those of the polycrystal Co-Cr films.

Effect of Annealing on the Structure of Buried SiO2 Layers Formed By Elevated Temperature High Dose Oxygen Implantation

ABSTRACTOxygen has been implanted into Si wafers at high doses and elevated temperatures to form a buried SiO2 layer for use in silicon-on-insulator (SOI) structures. Substrate heater temperatures have been varied (300, 400, 450 and 500°C) to determine the effect on the structure of the superficial Si layer through a processing cycle of implantation, annealing, and epitaxial growth. Transmission electron microscopy was used to characterize the structure of the superficial layer. The structure of the samples was examined after implantation, after annealing at 1150°C for 3 hours, and after growth of the epitaxial Si layer. There was a marked effect on the structure of the superficial Si layer due to varying substrate heater temperature during implantation. The single crystal structure of the superficial Si layer was preserved at all implantation temperatures from 300 to 500°C. At the highest heater temperature the superficial Si layer contained larger precipitates and fewer defects than did wafers implanted at lower temperatures. Annealing of the as-implanted wafers significantly reduced structural differences. All wafers had a region of large, amorphous 10 to 50 nm precipitates in the lower two-thirds of the superficial Si layer while in the upper third of the layer there were a few threading dislocations. In wafers implanted at lower temperatures the buried oxide grew at the top surface only. During epitaxial Si growth the buried oxide layer thinned and the precipitate region above and below the oxide layer thickened for all wafers. There were no significant structural differences of the epitaxial Si layer for wafers with different implantation temperatures. The epitaxial layer was high quality single crystal Si and contained a few threading dislocations. Overall, structural differences in the epitaxial Si layer due to differences in implantation temperature were minimal.