Mechanistic aspects of anisotropic dissolution of materials Etching of single-crystal silicon in alkaline solutions

Abstract

The origin of chemical anisotropy in the dissolution of single-crystal silicon in alkaline solutions is discussed in terms of the atomic configuration of silicon in the pentacoordinated transition state for (100) and (111) surfaces. It is proposed that tetravalent silicon, which is bonded in a tetrahedral geometry, is attacked in the etch process by the hydroxide ion, forming a pentacoordinated transition state. Owing to the number of bond angles that are fixed by the atomic arrangement at the surface, the energetically favoured trigonal bipyramidal geometry for a pentacoordinated complex is only slightly distorted for the former plane but significantly distorted for the latter, resulting in a higher activation energy for the dissolution of (111) surfaces. The difference in the activation energies for the dissolution of Si(100) and (111) surfaces, arising from steric hindrance in the transition state, can be estimated from the activation energy for a pseudo-rotation of a similar system.

References

1. C. Burrer, J. Esteve and E. Lora-Tamayo, J. Microelectromech. Syst., 1996, 5, 122.
2. T. A. Kwa, P. J. French, R. F. Wolffenbuttel, P. M. Sarro, L. Hellemans and J. J. Snauwaert, J. Electrochem. Soc., 1995, 142, 1226.
3. S. S. Lee, P. P. Ried and R. M. White, J. Microelectromech. Syst., 1996, 5, 239.
4. S. A. Campbell, D. J. Schiffrin and D. J. Tufton, J. Electroanal. Chem., 1993, 344, 211.
5. J. Rappich, H. J. Lewerenz and H. Gerischer, J. Electrochem. Soc., 1993, 140, L187.
6. P. Allongue, V. Costa-Kieling and H. Gerischer, J. Electrochem. Soc., 1993, 140, 1009.
7. P. M. M. C. Bressers, S. A. S. P. Pagano and J. J. Kelly, J. Electrochem. Soc., 1995, 391, 159.
8. E. D. Palik, V. M. Bermdez and O. J. Glembocki, J. Electrochem. Soc., 1985, 132, 871.
9. H. Seidel, L. Csepregi, A. Heuberger and H. Baumgärtel, J. Electrochem. Soc., 1990, 137, 3612.
10. P. Jacob, Y. J. Chabal, K. Raghavachari, R. S. Becker and A. J. Becker, Surf. Sci., 1992, 274, 407.
11. G. S. Higashi, Y. J. Chabal, G. W. Trucks and K. Raghavachari, Appl. Phys. Lett., 1990, 56, 656.
12. P. Jacob and Y. J. Chabal, J. Chem. Phys., 1991, 95, 2897.
13. P. Allongue, V. Costa-Kieling and H. Gerischer, J. Electrochem. Soc., 1993, 140, 1018.
14. E. Saker and A. Yelon, Phys. Rev. Lett., 1991, 66, 1647.
15. J. S. Blackmore, Solid State Physics, Cambridge University Press, Cambridge, 2nd edn., 1993, p. 24.
16. T. Taketsugu and M. S. Gordon, J. Phys. Chem., 1995, 99, 14597.
17. F. A. Carey and J. Sundberg, Advanced Organic Chemistry, Plenum Press, New York, 3rd edn., 1990.
18. K. P. C. Vollhardt, Organic Chemistry, Freeman, New York, 1st edn., 1987, p. 196.
19. L. S. Bartell and K. W. Hansen, Inorg. Chem., 1995, 4, 1777.
20. R. S. Berry, J. Chem. Phys., 1960, 32, 933.
21. F. Carré, R. J. P. Corriu, A. Kpoton, M. Poirier, G. Royo and J. C. Young, J. Organomet. Chem., 1994, 470, 43.
22. M. S. Gordon, T. L. Windus, L. W. Burggraf and L. P. Davis, J. Am. Chem. Soc., 1994, 112, 7167.
23. T. L. Windus, M. S. Gordon, L. P. Davis and L. W. Burggraf, J. Am. Chem. Soc., 1994, 116, 3568.
24. G. W. Trucks, K. Raghavachari, G. S. Higashi and Y. J. Chabal, Phys. Rev. Lett., 1990, 65, 504.
25. K. D. Dobbs and D. J. Doren, J. Am. Chem. Soc., 1993, 115, 3731.
26. A. L. Allred, J. Inorg. Nucl. Chem., 1961, 17, 215.