| AVS 55th International Symposium & Exhibition | |
| Applied Surface Science | Wednesday Sessions |
| Session AS-WeA |
| Session: | Frontiers of Analysis and Combined Materials |
| Presenter: | G. Gillen, National Institute of Standards and Technology |
| Authors: | G. Gillen, National Institute of Standards and Technology C. Szakal, National Institute of Standards and Technology A. Herzing, National Institute of Standards and Technology I. Anderson, National Institute of Standards and Technology S. Hues, Micron Technology J. Bennett, Process Characterization Laboratories, ATDF |
| Correspondent: | Click to Email |
There is continued interest in the development of novel cluster primary ion beams for applications in Secondary Ion Mass Spectrometry (SIMS). A C60 primary ion incident on a silicon substrate with an impact energy of 3000 eV would dissociate into 60 carbon atoms, each with an impact energy of only 50 eV. Since the depth resolution of a SIMS depth profile is directly related to the primary projectile energy, the use of such a cluster ion provides a possible method for obtaining ultra-high resolution SIMS depth profiles. Based on our previous experience with depth profiling of semiconductor materials using smaller cluster beams, it was hoped that C60 cluster SIMS would provide large improvements in depth resolution over conventional SIMS. Unexpectedly, initial evaluation of C60 SIMS depth profiling using delta-doped test samples demonstrated that deposition of an amorphous carbon layer on the silicon substrate was common, limiting the utility of C60 for depth profiling at impact energies below ~12 keV. Higher bombardment energies can minimize deposition but substantial degradation in depth resolution is observed compared to conventional SIMS depth profiling. This degradation was initially thought to result only from the formation of surface topography. In this work we have investigated the nature of the altered layer produced by C60 bombardment of silicon using SIMS and cross sectional transmission electron microscopy (TEM). Surprisingly, TEM imaging suggests the depth of penetration of carbon into the silicon substrate is substantially greater than would be predicted by simple ion implantation models. Furthermore, the buried interface between crystalline silicon and the carbon-rich altered layer exhibits nm scale roughness. These observations may help to explain the degradation in depth resolution commonly observed in C60 depth profiling of silicon materials. The enhanced diffusion of carbon beyond the penetration depth of the C60 may by explained by the enhanced diffusion of carbon in silicon resulting from strain produced in the silicon by high dose carbon implantation.