Facile chemical rearrangement for photopatterning of POSS derivatives

We report a useful acid-catalyzed crosslinking reaction which enables the direct photopatterning of POSS derivatives to form robust nanoporous matrices. Octakis(dimethylacetoxyethyl siloxy) POSS and octakis(dimethylacetoxypropyl siloxy) POSS were synthesized from commercially available octahydrido-POSS. Both the acetoxyethyl-and acetoxypropyl functionalities were observed to undergo thermal rearrangement at temperatures above 300 degrees C to form Si-O-Si bonds, thus forming a crosslinked POSS network. Interestingly, the same functionalities were also acid sensitive, and the chemical rearrangement occurred at much lower temperatures. Thus, patterned nanoporous features were lithographically generated when a photoacid generator (PAG) was used as a photosensitive agent to initiate the crosslinking of the POSS derivatives. The dielectric properties were evaluated for the crosslinked POSS films, which had a dielectric constant similar to 2.3 and an elastic modulus of similar to 2.0 GPa. These materials hold great promise for developing a photopatternable low-k material which eliminates the need for sacrificial layers when patterning low-k dielectric films.