Area selective grafting of siloxane molecules on low-k dielectric with respect to copper surface

Abstract

The selective pore sealing of porous organosilica glass (OSG k = 2.4) dielectrics by self-assembled monolayers (SAM) is studied, using three precursors: (3-trimethoxysilylpropyl) diethylenetriamine (DETA), 3-aminopropyltrimethoxysilane (APTMS) and trimethylmethoxysilane (TMMS), combined with a citric-acid based metal surface cleaning. The sealing effectiveness of the SAM films derived from amino-containing precursors is demonstrated. The selectivity of the SAM grafting to the dielectric surface with respect to the copper surface is investigated. Post-SAM deposition cleaning in citric acid-based solution leads to desorption of the amino-containing precursors from the copper surface while the low-k surface remains partially covered and sealed. On copper, the SAM cleaning process occurs through interface copper oxide removal, by means of a lift-off mechanisms.