Effects of a Ta interlayer on the phase transition of TiSi2 on Si(111)

This study examines the effects of a thin Ta interlayer on the formation of TiSi2 on Si(111) substrate. The Ta interlayer was introduced by depositing Ta and Ti films sequentially on an atomically clean Si(111) substrate in a n ultrahigh vacuum (UHV) system. Samples of 100 A Ti with 5 and 10 A Ta int erlayers were compared to similar structures without an interlayer. After d eposition, the substrates were annealed for 10 min, in situ, at temperature s between 500 and 750 degrees C in 50 degrees C increments. The TiSi2 forma tion with and without the Ta interlayer was analyzed with an X-ray diffract ometer, Auger electron spectroscopy (AES), Scanning electron microscopy (SE M), transmission electron microscopy (TEM), and a four-point probe. The AES analysis data showed a 1:2 ratio of Ti:Si in the Ti-silicide layer and ind icated that the Ta layer remained at the interface between TiSi2 and the Si (111) substrate. The C 49-C 54 TiSi2 phase transition temperature was lower ed by similar to 200 degrees C. The C 49-C 54 TiSi2 phase transition temper ature was 550 degrees C for the samples with a Ta interlayer and was 750 de grees C for the samples with no Ta interlayer. The sheet resistance of the Ta interlayered Ti silicide showed lower values of resistivity at low tempe ratures which indicated the change in phase transition temperature. The C 5 4 TiSi2 displayed different crystal orientation when the Ta interlayer was employed. The SEM and TEM micrographs showed that the TiSi2 with a Ta inter layer significantly suppressed the tendency to islanding and surface agglom eration. (C) 2000 American Institute of Physics. [S0021-8979(00)02216-7].