MECHANICAL EFFECTS OF HAFNIUM AND BORON ADDITION TO ALUMINUM-ALLOY FILMS FOR SUBMICROMETER LSI INTERCONNECTS

This is the first report on the mechanical properties of hafnium- and boron-added Al-Si-Cu alloy film for LSI interconnects. Two to three hu ndred ppm of hafnium and boron addition into Al-Si-Cu alloy film does not influence the Al alloy properties for metal lines as LSI interconn ects, such as its low resistivity, low ohmic contact resistance with S i, and fine-line patterning feasibility. The mechanical properties of the Al alloy film, however, change greatly. Vertical hillock and later al hillock formation is considerably suppressed during heat treatments used in LSI fabrication processes. Stress-induced void formation is a lso reduced during aging test at 125-degrees-C. These effects due to h afnium and boron addition are considered to be an impurity precipitati on effect ihat was confirmed by X-ray diffraction analysis and electro n probe microanalysis.