AVS 47th International Symposium
    Dielectrics Wednesday Sessions
       Session DI+EL+MS-WeM

Invited Paper DI+EL+MS-WeM1
Ultra Low k Mesoporous Silica Dielectrics for Semiconductor Interconnects

Wednesday, October 4, 2000, 8:20 am, Room 312

Session: Low K Dielectrics
Presenter: S. Baskaran, Pacific Northwest National Laboratory
Authors: S. Baskaran, Pacific Northwest National Laboratory
J. Liu, Pacific Northwest National Laboratory
X. Li, Pacific Northwest National Laboratory
C. Coyle, Pacific Northwest National Laboratory
J. Birnbaum, Pacific Northwest National Laboratory
G.C. Dunham, Pacific Northwest National Laboratory
G.E. Fryxell, Pacific Northwest National Laboratory
C. Jin, International SEMATECH
Correspondent: Click to Email
The semiconductor industry is currently targeting new intermetal dielectric (IMD) films with dielectric constants (k) less than 2.5 for interconnect applications in the 100 nm technology node, and films with k less than 2.0 for the 70 nm technology node. To meet extreme low k needs for advanced on-chip interconnects, films with incorporated porosity will most certainly be required. Porous dielectric films with k values less than 2.2 ("ultra low k") are not easily synthesized using conventional vacuum based technology such as chemical vapor deposition. A simple approach to nanoporous dielectric films involves spin-on deposition of formulations consisting of silicate, polymeric, or hybrid organosilicate precursors with thermally degradable pore-formers. Ultra low k mesoporous silica films have been synthesized with molecularly templated porosity using this approach. Molecularly organized nanostructured aggregates between 2 and 10 nm in size can function as templates for pore formation in spin coated sol-gel silicate films. The use of a structurally organized template during synthesis results in a uni-modal pore size distribution in the final film. In this paper, we present information on precursor chemistry for designing mesoscale porosity, pore architecture and surface chemistry, and the critical dielectric and mechanical properties for mesoporous silica films. Using formulations developed at PNNL, mesoporous films have also been prepared at SEMATECH on production-size wafers, and evaluated. Copper single-damascene one-level test structures were built using mesoporous silica as the intermetal dielectric. No major structural failures were observed after chemical mechanical planarization on both blanket films and patterned wafers, indicating relatively good mechanical integrity for a highly porous structure. With controlled film synthesis and dehydroxylation conditions, mesoporous silica films with k@super 2@ 2.0 and elastic modulus of 4.0 GPa have been synthesized at PNNL. The results of the one-level metal screening tests at SEMATECH combined with properties obtained at PNNL indicate that mesoporous molecularly-templated silicate films hold promise as ultra low k intermetal dielectrics.