Stabilization of mesoporous silica films using multiple organosilanes

Abstract

Mesoporous silica (MPS) thin films are attractive for electrically isolating Cu wiring in nanodevices. While porosity is conducive for realizing low-dielectric permittivity k necessary for low signal propagation delays, it renders the MPS susceptible to moisture uptake and metal diffusion. Here, we show that passivating MPS with more than one organosilane with different molecular termini provides several fold greater protection against such instabilities than improvements observed by functionalizing MPS with either type of organosilane individually. MPS films functionalized with bis[3-(triethoxysilyl)propyl] tetrasulfide (BTPTS) and trimethylchlorosilane (TMCS) exhibit at least three orders of magnitude greater time to dielectric breakdown. Bias thermal annealing and infrared spectroscopy measurements indicate that the increased stability is due to Cu blocking by the tetrasulfide groups in BTPTS and decreased moisture uptake is caused by hydrophobic passivation with TMCS. These findings are germane for realizing high-stability low k dielectrics for nanodevice architectures.