Surface characterization of a low dielectric constant polymer-SiLK* polymer, and investigation of its interface with Cu

The integration of copper and new low dielectric constant materials is a fu ndamental challenge to be met for further miniaturization of high speed int egrated circuits. In this preliminary work, core level x-ray photoelectron spectroscopy (XPS) has been used for the first characterization of the surf ace composition of Dow Chemical's SiLK* semiconductor dielectric (*trademar k of the Dow Chemical Company), its behavior during annealing in vacuo, and its interface formation with thermally evaporated copper in situ. The full y conjugated SiLK* resin shows a C is spectrum with intense shake-up struct ures, quite similar to those of polystyrene; a small amount of oxygen is de tected. Upon annealing in ultrahigh vacuum (7.10(-9) Pa) no significant out gassing is observed; no noticeable change in intensity, width, position of the C 1 s and O 1 s core level peaks or satellite structures is measured. A fter annealing, the interface formation between SiLK* dielectric and copper has been characterized as a function of incremental coverages from 0.5 to 10 Angstrom of Cu. While the XPS C is spectrum shows only a normal intensit y decrease, the Cu 2p(3/2) levels shift from a high binding energy to a pur ely metallic value: this is interpreted as the formation of small Cu cluste rs, evolving to a more continuous layer for higher Cu coverage. Annealing i n vacuo of the as-prepared Cu(10 Angstrom)-SiLK* interface at 400 degrees C for 1 h does induce an increase of the carbon signal, attributed to furthe r coalescence of copper in metallic clusters. (C) 1999 American Vacuum Soci ety. [S0734-211X(99)05205-1].