Μελέτη διεπιφανειών μετάλλου / ανθρακοπυριτίου με επιφανειακά ευαίσθητες τεχνικές

Abstract

Silicon carbide (SiC) single crystals are very important for numerous high temperature microelectronic devices. Industrial production of such devices takes advantage of the superior properties that metal/SiC contacts can achieve, like the electrical behavior (Schottky barrier) and their thermal stability. In the present work, we studied the early stages of metal/SiC interface formation in UHV conditions and at room temperature. Additionally, we studied the stability of the contacts at high temperature conditions. For this purpose, we developed ultrathin metallic films of Re, Er and Cu on both polar surfaces (Si-face or (0001) and C-face or (000-1)) of n-type hexagonal single crystal 6H-SiC. The resulting contacts were heated afterwards up to 1000K. Surface sensitive techniques were used for data collection, such as X-ray Photoelectron and Auger Electron Spectroscopy (XPS/XAES), Ultraviolet Photoelectron Spectroscopy (UPS), Low Energy Electron Diffraction (LEED) and Work Function (WF) measurements (Kelvin Probe technique). Furthermore, the height of the interfacial Schottky barrier and its behavior upon annealing were obtained from the XPS data. Based upon our experimental data, we reached the following conclusions: The Re/6H-SiC{0001} contact was found to be appropriate for use in microelectronic devices that require ohmic contacts consisting of materials with an absolute stability of structural and electronic properties at high temperature conditions, given that the Re/SiC Schottky barrier height is small and Re metallic films are particularly stable at high temperatures. ix The extended silicide phase and the existence of low Schottky barrier height known from Er/Si contacts was not observed in the Er/6H-SiC{0001} contact, which was found to have a good and stable rectifying behavior. The Er film demonstrated structural stability at high temperatures. Possible use of the Er/SiC contact for microelectronic devices, that require Schottky barrier thermal stability along with the existence of only traces of some silicide interaction at the interface, is considered promising. It was also found that oxygen might play an important role in the Er/SiC interfacial behavior. Finally, for Cu/6H-SiC{0001} the conclusions were correspondingly positive: the electrical behavior of the Cu/SiC contact was found to be rectifying and relatively stable at high temperatures. Considering that SiC is well known as a very good thermal conductor (just like copper), the Cu/SiC contact could meet the standards in a lot of applications in power microelectronic devices.