STABILITY OF A NEW POLYIMIDE SILOXANE FILM AS INTERLAYER DIELECTRICS OF ULSI MULTILEVEL INTERCONNECTIONS

Stability of a new polyimide siloxane (PSI) film as interlayer dielect rics of ULSI multilevel interconnections is studied. The PSI films, in volving Si-phenyl bonds, are designed to have a three-dimensional poly mer structure by crosslinking through Si-O bonds. It has been revealed that the PSI films are more stable than conventional polyimide films in terms of thermal and electrical properties at high temperatures. Th e PSI film's decomposition temperature is as high as 500-degrees-C. Th e coefficient of thermal expansion is 4 x 10(-5) K-1 in the temperatur es of 25-450-degrees-C. The abrupt thermal expansion that usually occu rs at around 270-degrees-C for conventional polyimide films is elimina ted. The residual stress for the PSI films is less than 20 MPa, and is lower than for conventional polyimide films. Leakage currents through the PSI films at temperatures above 100-degrees-C are over one order of magnitude lower than those through conventional polyimide films. Go od surface planarization characteristics are obtained for the PSI film s by decreasing the molecular weight and viscosity of the polyamic aci d solutions. No void is observed in the films formed on 2.4 mum thick silicon dioxide lines with 1.1 mum width and 1.5 mum spacing, using po lyamic acid solutions with precursor molecular weights ranging from 29 00 to 9600.