Contact reaction between Si and Pd-W alloy films

Contact reactions in the temperature range 250-650 °C between (100) Si and Pd-W binary alloy films of composition Pd₈₀W₂₀ and Pd₃₀W₇₀ have been studied by a combination of ion backscattering, x-ray diffraction, and current-voltage measurement of Schottky barrier height. For the Pd-rich alloy, the reaction around 400 °C produced the silicide Pd₂Si by depleting Pd from the alloy and resulted in the formation of a two-layer structure, W/Pd₂Si/Si. We have found that the W layer has served effectively as a diffusion barrier for the subsequently deposited Al, indicating that a rectifying contact and its diffusion barrier can be fabricated simultaneously. At higher reaction temperatures, the W layer transforms to WSi₂ with some mixture of Pd₂Si. The alloying of Pd with W has been found to increase the formation temperature of Pd₂Si but decrease that of WSi₂. In the Pd ₈₀W₂₀ reaction, Pd₂Si forms around 400 °C and WSi₂ around 500 °C. In the Pd₃₀W₇₀ reaction, Pd₂Si forms around 500 °C and WSi₂ around 650 °C.