ABSTRACT
Interface induced diffusion had been identified in a thin film system damaged by electron bombardment. This new phenomenon was observed in Al2O3 (some nm thick)/Si substrate system, which was subjected to low energy (5 keV) electron bombardment producing defects in the Al2O3 layer. The defects produced partially relaxed. The rate of relaxation is, however, was different in the vicinity of the interface and in the "bulk" parts of the Al2O3 layer. This difference creates an oxygen concentration gradient and consequently oxygen diffusion, resulting in an altered layer which grows from the Al2O3/Si substrate interface. The relative rate of the diffusion and relaxation is strongly temperature dependent, resulting in various altered layer compositions, SiO2 (at room temperature), Al2O3 + AlOx + Si (at 500 °C), Al2O3 + Si (at 700 °C), as the temperature during irradiation varies. Utilizing this finding it is possible to produce area selective interface patterning.
ABSTRACT
Al2O3 (5 nm)/Si (bulk) sample was subjected to irradiation of 5 keV electrons at room temperature, in a vacuum chamber (pressure 1 × 10-9 mbar) and formation of amorphous SiO2 around the interface was observed. The oxygen for the silicon dioxide growth was provided by the electron bombardment induced bond breaking in Al2O3 and the subsequent production of neutral and/or charged oxygen. The amorphous SiO2 rich layer has grown into the Al2O3 layer showing that oxygen as well as silicon transport occurred during irradiation at room temperature. We propose that both transports are mediated by local electric field and charged and/or uncharged defects created by the electron irradiation. The direct modification of metal oxide/silicon interface by electron-beam irradiation is a promising method of accomplishing direct write electron-beam lithography at buried interfaces.
ABSTRACT
Medium-energy (some tens of keV) ion irradiation is frequently used in various technologies. It is well known that during this irradiation serious alterations are introduced to the material, changing its structure, composition, etc. While there are studies on the amorphization, no results have been reported on the medium-energy ion beam-induced mixing, however. In this work, we present Auger electron spectroscopy (AES) depth profiling measurements of Si/Cr multilayer samples, which were irradiated by various ions (Ga+, Ar+, CF4+) of 20 keV applying angles of incidence of 5 degrees (Ga+), 65 degrees (Ga+) and 75 degrees (Ar+, CF4+). The ion beam-induced mixing at the Si/Cr interface (the broadening of the interface) was measured as a function of the removed layer thickness. The weakest and strongest ion mixing (for a given removed layer thickness) were found for CF4+ and Ga+ 5 degrees irradiations, respectively. In the case of Ga+ irradiation, the larger the angle of incidence the weaker the ion mixing. The extent of mixing does not correlate with the corresponding projected range. Comparison of the experimentally measured ion mixed profiles with those given by dynamic TRIM simulations gave poor agreement for Ar+ and fails for Ga+ irradiations, respectively.
