INTERFACE REACTION OF AL W AND CHEMICAL-PROPERTIES OF AL-W BIMETALLICBONDING/

Suppression mechanism by a thin interface W oxide layer is investigate d for intermetallic reaction at Al/W interfaces. The interface reactio n scheme of Al/W was analyzed by in situ x-ray photoemission spectrosc opy for the interface formation and subsequent annealing in ultrahigh vacuum. Without the W oxide layer at the interface, annealing at tempe ratures higher than 450 degrees C leads to an intermetallic reaction f orming the bimetallic compound WAl12 through the entire metal layer, w hile no reaction between Al and W occurs at room temperature. The inte rmetallic reaction causes the lowering of W 4f core level by 0.7 eV. T his is explained by the donation of a lone electron pair from an Al 3s orbital to a vacant W 6s orbital in bimetallic bonding. The interface thin W oxide layer, composed of WO3, is consumed in the oxidation-red uction reaction with metallic Al. The reaction product Al2O3 inhibits the intermetallic reaction. This results in an increase in annealing t emperatures to as high as 600 degrees C and longer annealing time to f orm WAl12. (C) 1995 American Vacuum Society.