Gap-filling capability and adhesion strength of the electroless-plated copper for submicron interconnect metallization

Abstract

The major goal of this study is to combine the plasma immersion ion implantation (PIII) to implant Pd catalyst onto a TaN diffusion barrier layer and the electroless plated Cu to accomplish the ultralarge scale integrated interconnection metallization. Both patterned and nonpatterned wafers were employed using Pd as a catalyst by PIII after which copper was electroless plated onto a TaN/FSG/Si multilayer structure. The Pd atoms were sputtered from a negatively biased target and ionized in an argon inductively coupled plasma. The Pd ions were adequately implanted into the substrate with a highly pulsed negative bias (∼4000 V). Characterized by field enhanced scanning electron microscopic (FESEM) cross-section images of FESEM, and under the circumstances of higher substrate bias voltage and plasma ionization, the electroless copper grows upward from the bottom of the vias (width: 0.25 μm, aspect ratio: 7), with an excellent gap filling ability. The result of this process, by employing the mechanical pull-up tests, showed that higher substrate bias and higher plasma ionization can effectively enhance the adhesion strength between the copper film and the TaN layer.