High pressure CVD tungsten-stud formation using RIE cluster processes

Abstract

The use of CVD tungsten for filling of contacts and vias has been reported in many multilevel interconnection technology applications. W-stud formation is done by blanket tungsten deposition and subsequent either etchback or Chemical-Mechanical polishing(CMP).1 This paper presents the integration of both tungsten deposition and etchback processes in a commercial cluster tool, as compared to W-stud formation by CMP. Tungsten films were deposited at a high pressure of 70 Torr to fill high aspect ratio(3.5) contact holes without voids. Tensile stress of 10E9 dynes/cm2 measured for these films was higher by almost a factor of 2 than the low pressure tungsten films deposited at 0.85 Torr. A composite W film, deposited by both high and low pressure regime, has been utilized to have both advantages of via-filled characteristic and low film stress. A multistep RIE process had been used with the majority of W removed using a SF6/C12 plasma and the remaining W was then removed with Cl2/O2 to minimize the microloading phenomenon.2 3 The maximum W-plug recess, observed at the edge of the wafers, is only 0.1μm. Electrical test results of W contact studs formed by clustered processes is compared to W-stud formation by CMP.