Interaction between Co and SiO2 during ion-beam mixing and rapid thermal annealing

For the application in self-aligned processes, it was supposed that CoSi2 could be superior to TiSi2, since, unlike Ti, a reaction between Co and SiO2 was not observed up to now. We studied the reaction of Co and SiO2 during ion-beam mixing and rapid thermal annealing (RTA). The influences of As and Ge implantation energy and dose were investigated in the range of 50 to 200 keV and 1x10high14 to 5x10high15 cmhighminus2. The annealing temperature was varied between 700 degree C and 1100 degree C. It could be demonstrated that the Co concentration in SiO2 rises with increasing Ge and As energy and dose up to values of 5x10high15 cmhighminus2 compared to 2x10high12 cmhighminus2 in unimplanted, annealed samples. The Co profiles in SiO2 were also studied by secondary ion mass spectroscopy (SIMS) and compared with Monte-Carlo simulations indicating pure ballistic mixing. Planview and cross-section transmission electron microscopy (TEM) were used to examine the SiO2 surface as well as the Co- SiO2 interface. These investigations revealed that ion- beam mixing with doses at or above 5x10high14 cmhighminus2 and subsequent annealing does not damage the SiO2 unlike to unimplanted, annealed samples which show a rather severe structural change of the SiO2 surface increasing with rising annealing temperatures