AVS 58th Annual International Symposium and Exhibition
    Electronic Materials and Processing Division Monday Sessions
       Session EM-MoM

Invited Paper EM-MoM5
Novel Organosilicate Polymers for Ultralow-Dielectric Films with High Modulus, Low CTE, and Closed-Pore Morphology

Monday, October 31, 2011, 9:40 am, Room 210

Session: Dielectrics for Novel Devices and Process Integration
Presenter: DoYeung Yoon, Seoul National University, Korea
Authors: D.Y. Yoon, Seoul National University, Korea
J.H. Sim, Seoul National University, Korea
M. Liu, University of Michigan
H.W. Ro, National Institute of Standards and Technology
C.L. Soles, National Institute of Standards and Technology
D.W. Gidley, University of Michigan
Correspondent: Click to Email
Novel organosilicate polymers are prepared using porogen bridged comonomers for ultralow-dielectric constant insulator applications. We synthesize silsesquioxane based terpolymers with methyltrimethoxysilane, ethylene bridged silane (1,2-bis(triethoxysilyl)ethane) and a porogen bridged silane comonomer via sol-gel reaction. The conventional route to generate nanoporous organosilicate films is to blend in a low molecular mass porogen that phase separates from the organosilicate network into isolated nanoscale domains that template the pores. However, using this approach it is difficult to achieve isolated nanopores with diameters below 2 nm when the total porosity becomes greater than 20 % by volume, which is essential for obtaining ultralow-k ( k<2.2 ) films. Our novel approach here is to covalently tether the both terminal ends of linear organic porogen to the trialkoxysilane monomers. This helps minimize the phase separation of the porogen during the thermal curing process of organosilicate polymers and keeps the resultant pores both smaller and less interconnected. For comparison we also prepare an analogous grafted version of this terpolymer series where only one end of the linear porogen is tethered to a trialkoxysilane monomer. The pore structures and porosities of this series of bridged and grafted porogen films are fully characterized with positron annihilation lifetime spectroscopy (PALS) and X-ray porosimetry (XRP). The resulting nanoporous films from the porogen bridged organosilicate polymers show much smaller pore sizes (1 nm to 2 nm), reduced interconnectivity of the pore structure, and superior mechanical properties in comparison with their analogs using the porogen grafting approach, especially at the high porosities (ca. 30 %) that are relevant for ultralow-k (2.0 to 2.2) insulators for advanced microprocessor applications.