Application of Surface Reformed Thick Spin‐on‐Glass to MOS Device Planarization

Abstract

A simple planarization technology is proposed, using an organosiloxane which gives a thicker film than conventional spin‐on‐glass (SOG) film. The new SOG material, HSG2200 (Hitachi Chemical Company, HSG), exhibits far better planarizing capability than the conventional one. A drawback to this film has been crack generation when it is exposed to an oxygen plasma in a resist ashing reactor. A new pretreatment, which we have named reactive glass stabilization (RGS), has been developed. RGS is the exposure of the film to an energetic plasma at low temperature using a parallel electrode sputtering reactor. The surface layer of the film is converted to an condensed state which prevents the oxygen plasma from reaching the inner unconverted layer and delays further reaction between the plasma and the organosiloxane film. Three‐layered interlevel dielectric using the RGS‐treated HSG film as a middle layer was used to planarize a two‐metal level interconnection that had superior characteristics compared to those of conventional SOGs. The resistance increase of Al‐2 lines on the HSG sandwich structure was merely 4% over 0.7 μm line and space, which is far less than that of 76% on the conventional SOG sandwich structure. MOS devices with a two‐metal level interconnection exhibited good electric characteristics and no hot carrier degradation.