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Nanoporous Structure in Low-Dielectric Films with Positronium Annihilation Lifetime Spectroscopy |
| HU Yi-Fan1;SUN Jia-Ning2;D. W. Gidley2 |
| 1Department of Physics, Huazhong University of Science and Technology, Wuhan 430074
2Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA |
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| Cite this article: |
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HU Yi-Fan, SUN Jia-Ning, D. W. Gidley 2005 Chin. Phys. Lett. 22 1488-1491 |
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Abstract We investigate nano-porous structures in thin low-dielectric films, i.e. the pore sizes, distributions, and interconnectivity, by using depth profiled positronium annihilation lifetime spectroscopy (PALS). It is found that PALS has good sensitivity to probe both interconnected and closed pores in the range from 0.3nm to 30nm, even in the film buried beneath a diffusion barrier. A series of low dielectric constant films of organosilicon-silsequioxane with different weight percentages of porogen have been comparatively investigated. The PALS technique can be used to distinguish the open porosity from the closed one, to determine the pore size, and to detect the percolation threshold with the increasing porosity that represents the transition from closed pores to interconnected pores. Furthermore, the pore percolation length can be derived.
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68.55.Jk
78.70.Bj
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Published: 01 June 2005
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