Effects of the Underlayer Surface State on the Interconnecting Aluminum Film Properties

Abstract

A gradual change in thermal oxide surface state from hydrophilic to hydrophobic was observed with time -delay in a clean room environment. Surface quality and reflectivity for the Al/Ti metal layers showed a strong dependency on the oxide surface state. From the hydrophilic oxide substrate, a lower (002) Ti preferred orientation was obtained than from hydrophobic ones. This resulted in a degraded (111) Al preferred orientation and rough metal surface. The RF-etch process increased the smoothness and hydrophobic surface property for the inter -metal dielectric (IMD) oxides, and therefore greatly improved Al/Ti surface quality. When conventional CMOS double layer metal interconnection process is performed, metal inter-line bridge yield was strongly affected by the surface state of substrate oxides.