The Direct Patterning of Porous Low-k Films by Nanoimprint Lithography



There is an interest in directly patterning multi-tier dielectric structures for semiconductor applications by nanoimprint lithography (NIL). To the best of our knowledge, these initial studies have only focused on imprinting non-porous low dielectric (low-k) resins. However, next generation devices require ultralow-k dielectric materials with nanoscopic pores. The integration of these ultralow-k materials, however, is a challenge because the fabrication of the multilevel interconnect structures of ultralow-k dielectric material brings numerous technical obstacles and reliability concerns. Here we demonstrate the direct patterning of a porous ultralow-k material by NIL. 100 nm line and space patterns with a pattern height of 170 nm are transferred into a poly(methylsilsesquioxane) type organosilicate glass (OSG) film, that when cured, has a very high modulus (10.5 GPa) and low dielectric constant (k=2.84). A porous version of this material is prepared by adding 20 % by volume of a poly(ethyleneoxide) (PEO) and poly(propylene) (PPO) block copolymer porogen. Imprints are made into the spin cast films under vacuum for 3 min at 200 C with 3.44 MPa. After imprinting the samples are heated to 450 C in a N2 environment to fully convert the OSG and burn out the porogen in the case of the porous material. Specular X-ray reflectivity (SXR) is used to quantify the residual layer thickness and the height of the imprinted patterns, with sub-nm precision. X-ray porosimetry (XRP) is used to quantify the porosity levels as a function of pattern height.












Hyun Wook Ro

Guest Researcher
National Institute of Standards and Technology
100 Bureau Drive
Gaithersburg, MD 20899-8541, USA
Building 224, Room A321
Tel: (301) 975-4736

Fax: (301) 975-4977



Mentor: Christopher L. Soles