FORMATION OF COPPER SILICIDES FROM CU(100)/SI(100) AND CU(111)/SI(111) STRUCTURES

The reaction between copper and silicon is studied using differently oriented Si and Cu. Copper films, deposited by electron-beam evaporation at room temperature without intentional heating of the substrates, show an epitaxial relation with the Si substrates, resulting in (100)- and (111)-oriented Cu films on the (100) and (111) Si, respectively. An orientation dependence is observed for the Cu-Si reaction, with different phases of the silicides formed. At 200 °C, for example, the silicide formation rate is about five times faster for the (100)-oriented structures than for the (111) ones. An interface bonding model is used to relate to the orientation dependence observed, and is compared with previous work on the Au-Si and Au-Cu systems. The diamond structure of Si favors the (100) surface for reaction, as is observed for the Au-Si reaction. The face-centered-cubic structure of Cu, however, favors the (111) orientation for reaction. The latter is observed for the Au-Cu reaction using epitaxial Cu films on Si. Combined bonding consideration for both Cu and Si indicates a dominant role of Si release at these temperatures.