A chemical-mechanical polishing process for forming a metallic interconnect includes
the steps of providing a semiconductor substrate having a first metallic line thereon,
and then forming a dielectric layer over the substrate and the first metallic line.
Next, a chemical-mechanical polishing method is used to polish the surface of the
dielectric layer. Thereafter, a thin cap layer is formed over the polished dielectric
layer. The thin cap layer having a thickness of between 1000-3000 can
be, for example, a silicon dioxide layer, a phosphosilicate glass layer or a silicon-rich
oxide layer. The method of forming the cap layer includes depositing silicon oxide
using a chemical vapor deposition method with silicane (SiH4) or tetra-ethyl-ortho-silicate
(TEOS) as the main reactive agent. Alternatively, the cap layer can be formed by
depositing silicon nitride using a chemical vapor deposition method with silicane
or silicon dichlorohydride (SiH2Cl2) as the main reactive
agent. Finally, a via opening is formed through the dielectric layer and the cap
layer, and a second metallic line that couples electrically with the first metallic
line through the via opening is formed.
