MULTILAYER FORMATION DURING ANNEALING OF THIN TB LAYERS ON SIO2 SUBSTRATES

A 2000 Angstrom layer of Tb followed by a 200 Angstrom layer of Si was deposited onto an SiO2 substrate. The samples were annealed from 480 degrees C for 4 min to 800 degrees C for 120 min in a high vacuum (p l ess than or equal to 2 x 10(-7) Torr). It was inferred from Auger dept h profiles and peak shapes that the reaction between Tb and SiO2 start s by the dissociation of SiO2 at the Tb/SiO2 interface. The released o xygen diffuses into the deposited Tb, forming a Tb-O solid solution. T erbium silicide initially forms at the Tb/SiO2 interface. After anneal ing for 25 min at 480 degrees C, terbium oxide started to grow next to the SiO2 substrate. After annealing for 80 min at 480 degrees C, the oxide/silicide (with oxygen)/oxide layers were well separated on the S iO2 substrate. Annealing at 600 degrees C for 16 min and at 800 degree s C for 120 min resulted in an additional layer that formed next to th e SiO2, which consists of Tb, Si and oxygen. We assume that this layer is the beginning of the formation of another silicide layer with embe dded oxygen in the layer. The sample eventually consists of SiO2(subst rate)/silicide (with oxygen)/metal oxide/silicide (with oxygen)/metal oxide. The metal oxides contain an Si concentration of <4 at.%. The de pth profile of the sample annealed at 800 degrees C for 120 min does n ot differ significantly from the depth profile of the sample annealed at 600 degrees C for 16 min, except that the profiles show that the si licide layer of the 800 degrees C annealed sample is more oxidized. (C ) 1998 John Wiley & Sons, Ltd.