Pore sealing of k 2.0 dielectrics assisted by self-assembled monolayers deposited from vapor phase

Abstract

Self-assembled monolayers (SAMs) derived from 11-cyanoundecyltrichlorosilane precursor are deposited in vapor phase and characterized on ultra-low-k Chemical Vapor Deposition (CVD) dielectric films (k=2.0) with open porosity up to 50% and pore diameter as large as 3.5nm. Two surface preparation methods, such as Ar/H2 and Ar/N2 plasma pretreatments, are investigated and the pore sealing efficiency after SAM deposition is quantified from the experimental determination of open porosity and pore size measurements derived from toluene adsorption isotherms. In parallel, low-k damage is evaluated after surface preparation and SAM deposition by XPS depth profiling and by monitoring the change in refractive index, thickness and k value together with the –CH3 and –CH2 normalized FTIR peak areas vs. the pristine dielectric. Subsequently, a 10nm HfO2 thin film was deposited by Atomic Layer Deposition (ALD) in order to assess the pore-sealing capability of the proposed approach. When combining surface activation, SAM deposition and ALD, it was possible to accomplish a wide range of pore sealing. By adequate optimization, it was possible to obtain complete pore sealing after ALD, without precursor penetration into the porous low-k film, but at the expense of a 37% k increase for a 90nm dielectric thickness.