Copper metallization with an electron cyclotron resonance

Abstract

An "electron cyclotron resonance" plasma source, used for physical vapor deposition of copper into sub-micron features, was studied to determine whether parameters, such as gas atom density, electron density and temperature, surface bias, and copper ionization fraction at the deposition surface, influenced fill quality of the features. The results indicated that the fill quality was insensitive to all parameters except for the surface biasing conditions; however, with the use of an argon plasma, the bias was limited to less than ~- 40V due to the sputtering of the dielectric features by the argon ions (a phenomenon know as faceting). Switching to a copper evaporative system allowed for a pure copper plasma, enabling the use of greater (in magnitude) surface bias, ; I- 200V , before faceting by copper ions was observed. The fill quality of the features degraded with moderate bias (</= - 100V) but improved with bias > 150V . These results suggest that one formula for successful metallization is the use of an etch-resistant dielectric material in conjunction with large negative surface bias.