Molecular Caulk: A Pore Sealing Technology for Ultra-low k Dielectrics Jay J. Senkevich 1 , Christopher Jezewski 1,2 , Deli Lu 1 , William A Lanford 2 , Gwo-Ching Wang 1 and Toh-Ming Lu 1 1 Rensselaer Polytechnic Institute, Dept. of Physics, Troy, NY 12180 2 University at Albany, Dept. of Physics, 1400 Washington Ave., Albany, NY 12222 Abstract Much effort has been undertaken to develop high performance ultra-low k (≤ 2.2) (ULK) dielectrics to improve the interconnect speed of ultra-large scale integrated devices. Metallization issues and their poor mechanical properties have plagued the successful integration of these porous ULK dielectrics. Both of these issues are exasperated by their open pore structure. We have developed a pore sealing technology, which may allow the successful integration of these materials. We have coined the term Molecular Caulking to describe the materials that use the parylene platform for the chemical vapor deposition of these polymers. They are very unique since they can be conformally coated on demanding geometries pin-hole free at a thickness of ~10 Å. We have shown that the 1 st generation material, poly(p-xylylene), is selective with respect to copper and can completely seal porous-MSQ (methyl silsesquioxane) after 30 Å of deposition. This is roughly the pore diameter of this porous ULK dielectric. These materials exhibit very fast lateral growth rates and the penetration of the sealant into the ULK dielectric can be controlled. An overview will be give with respect to the Molecular Caulking technology. Introduction In future gigascale integrated circuits resistive-capacitive (RC) delay is an increasingly important issue [1]. Dense hybrid chemical vapor deposited dielectrics with a siloxane backbone are the current materials of choice [2]. These materials can be made nanoporous to reduce their dielectric constant further; however, the introduction of porosity results in a number of undesirable properties such as a reduction in mechanical strength and susceptibility to penetration of chemicals. Most important, during chemical vapor (CVD) or atomic layer (ALD) deposition of the barrier layer, the gas-phase precursors have a tendency to infiltrate the porous dielectric. Significant penetration of these metallic species will significantly damage the electrical properties of the ULK dielectric [3-6]. A recent review addresses some of the currently proposed strategies to seal porous dielectrics [7]. One method is to conformally deposit a dielectric layer to seal the porous dielectric. However, the primary drawback of this method is the lack of selectivity to the copper via. The dielectric material presented here, Molecular Caulk, retains selectivity over Cu and its penetration into the porous dielectric can be controlled to address fracture mechanics issues of the barrier layer/dielectric interface. Molecular Caulk is deposited via chemical vapor deposition at room temperature utilizing a free-radical polymerization mechanism. The approach taken was to measure the new sealant’s ability to prevent penetration of metal precursors (copper, cobalt) during CVD. The depth distribution of deposited metals was measured by Rutherford backscattering spectrometry (RBS). In addition, changes in dielectric constant as a result of Molecular Caulk deposition were determined by metal insulator semiconductor (MIS) capacitance measurements. Deposited film thickness was determined by both ellipsometry and ion beam backscattering using the 4.28 MeV 4 He elastic nuclear resonance of 12 C. Finally, the Mat. Res. Soc. Symp. Proc. Vol. 812 © 2004 Materials Research Society F1.2.1