Selective and blanket tungsten interconnection and its suitability for 0.2-micron ULSI

Voids and nondeposition were observed in via holes using blanket W and sputter Al because step coverage was significantly affected by the uniformity of the glue layer and by shadowing. In studying integrated multiple metallization (IMM), it was found that selective W adequately fills via holes down to 0.2 μm in diameter and greatly improves step coverage, with optimum coverage even after 40% via-hole filling. Blanket W and Al wiring can thus be used for high-aspect via holes, even if step coverage is poor. The contact resistance of selective W to poly-Si is lower than that of Al/TiN in 0.2-μm contacts. Thus, metallization based on selective W satisfies interconnection requirements in gigabit-scale integration