Abstract
Phase formation and transition between Pd 2 Si and PdSi in Pd thin films on (111)Si has been investigated by X-ray diffraction and transmission electron microscopy. In as-deposited and 200 °C/1 h annealed Pd(30nm)/(lll)Si samples, epitaxial Pd 2 Si was found to coexist with the unreacted Pd layer. In samples annealed at 250-800 °C, epitaxial Pd 2 Si is the only suicide phase present. PdSi was found to form along with Pd 2 Si in samples annealed at 850 °C. Pd 2 Si was found to be the predominant phase along with PdSi in samples annealed at 900-1000 °C. Pd 2 Si and PdSi were found to be the stable phases at 300-800 and 850-875 °C, respectively. The phase transition between Pd 2 Si and PdSi is reversible. In samples annealed at 900 °C, epitaxial Pd 2 Si is initially the only suicide phase present; then polycrystalline PdSi becomes the dominant phase. After annealing for more than 240 s, polycrystalline Pd 2 Si predominates over PdSi. The peculiar Pd 2 Si to PdSi, then back to Pd 2 Si phase transition behavior is correlated with the formation of PdSi islands, which is thought to alter the order of the total energy of the system. © 1995.