QUENCHING OF ELECTRON-TEMPERATURE AND ELECTRON-DENSITY IN IONIZED PHYSICAL VAPOR-DEPOSITION

The addition of sputtered metal atoms to a high density plasma results in the ionization of the metal species. The ionized physical vapor de position technique allows the deposition of metal films from ionic spe cies and is a potential method for the fabrication of integrated circu its with high aspect ratio interconnect features. Maximizing the tempe rature and density of the plasma electrons is important to optimizing the ionization of metal. The present work reports that the electron te mperature and electron density of the plasma decrease with increasing metal density. Direct measurement of electron temperature quenching us ing a rf compensated Langmuir probe demonstrates a similar to 20% decr ease in electron temperature due to metal additions of similar to 10(1 2) atoms/cm(3). The electron density is determined using microwave int erferometry and decreases by similar to 15% as metal atoms are added t o the discharge. A fixed temperature global model, however, indicates that thermalized metal atoms should increase the electron density. Gas heating due to energetic sputtered neutrals is shown to be responsibl e for the observed decrease in electron density. (C) 1997 American Vac uum Society.