A Selective Etching Solution for Use with Patterned Self-Assembled Monolayers of Alkanethiolates on Gold

Chemistry of Materials

Volumn 7, Issue 12, 1995, Pages 2332-2337

  Xia, Younan ^a   Zhao, Xiao Mei ^a   Kim, Enoch ^a   Whitesides, George M ^a  

^a HARVARD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33751154943     PISSN: 08974756     EISSN: 15205002     Source Type: Journal    
DOI: 10.1021/cm00060a023     Document Type: Article

References (36)

1. See, for example: Wilbur, J. L.; Kumar, A.; Kim, E.; Whitesides, G. M. Adv. Mater. 1994, 6, 600.
2. Review of SAMs: Whitesides, G. M.; Laibinis, P. E. Langmuir 1990, 6, 87.
3. Dubois, L. H.; Nuzzo, R. G.Annu. Rev. Phys. Chem. 1992, 43, 437.
4. Xia, Y.; Kim, E.; Whitesides, G. M. J. Electrochem. Soc., in press.
5. Xia, Y.; Kim, E.; Mrksich, M.; Whitesides, G. M. Chem. Mater., Submitted.
6. Xia, Y.; Mrksich, M.; Kim, E.; Whitesides, G. M. J. Am. Chem. Soc. 1995, 117, 9576.
7. Kumar, A.; Biebuyck, H.; Abbott, N. L.; Whitesides, G. M. J. Am. Chem. Soc. 1992, 114, 9188.
8. Kendall, D. L. Annu. Rev. Mater. Sci. 1979, 9, 373.
9. Peterson, K. E. Proc. IEEE 1982, 70, 420.
10. Kim, E.; Kumar, A.; Whitesides, G. M. J. Electrochem. Soc. 1995, 142, 628.
11. Abbott, N. L.; Rolison, D. R.; Whitesides, G. M. Langmuir 1994, 8, 2672.
12. Kumar, A.; Biebuyck, H.; Whitesides, G. M. Langmuir 1994, 10, 1498.
13. Xia, Y.; Whitesides, G. M. J. Am. Chem. Soc. 1995,117, 3274.
14. Xia, Y.; Whitesides, G. M. Adv. Mater. 1995, 7, 471.
15. Wilbur, J. L.; Kim, E.; Xia, Y.; Whitesides, G. M. Adv. Mater. 1995, 7, 649.
16. Material Safety Data Sheets (CD-ROM), Sigma-Aldrich-Fluka: Milwaukee, WI, 1994.
17. Material Safety Data Sheets (CD-ROM), MDL Information Systems, Inc.: Washington DC, 1994.
18. Zhao, X.-M.; Wilbur, J. L.; Whitesides, G. M., unpublished results.
19. Goldstein. J. I.; Newbury, D. E.; Schlin, P.; Joy, D. C.; Roming, A. D. Jr.; Lyman, C. E.; Fiori, C.; Lifshin, E. Scanning Electron Microscopy and X-ray Microanalysis, 2nd ed.; Plenum Press: New York, 1994; pp 69-90.
20. The times (ti-tf) for complete etching of 1000 and 1200 A thick gold films are 29-32 and 39-42 min, respectively.
21. Randle, T. H. J. Chem. Educ. 1994, 71, 261.
22. Mattsson, E. CHEMTECH 1985, April, 234.
23. We assume that the gold ions produced in the etching process are Au(I), since the redox potential of ferricyanide is not high enough to oxidize Au(0) to Au(III). We also assume that the coordination number for Au(I) is two, the most common coordination state for complexes of Au(I).22 The exact value of this number does not affect the discussion made in the text.
24. Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th ed.; John Wiley & Sons, Inc.: New York, 1988, p 940.
25. Au+ + e = Au CE° = 1.69 eV); Au(OH)2“ + e = Au + 20H“ (E° = O.40 eV).
26. Antelman, M. S. The Encyclopedia of Chemical Electrode Potentials, Plenum Press: New York, 1982, p 93.
27. Hillis, M. R. Trans. Inst. Met. Finish. 1979, 57(2), 73.
28. Beyer, S. J.; Lukes, R. M. US 71-142065 710510.
29. Palanisamy, R.; Sozhan, G.; Narasimham, K. C. Indian J. Technol. 1993, 31(8), 597.
30. The concentration of each ligand was O.1 M.; the concentrations of other components were the same as those in the standard etching solution of ferri/ferrocyanide
31. The aqueous solution of Kl/I2 has been used to selectively etch gold with thin films of photoresists as the masks.29 This etchant, however, had no selectivity when patterned SAMs of alkanethiolates were used as the masks.
32. Eidelloth, W.; Sandstrom, R. L. Appl. Phvs. Lett. 1991,59,1632
33. The concentration of each oxidant was O.01 M.; the concentrations of other components were the same as those in the standard etching solution containing thiosulfate.
34. The composition of this etchant was 1 mL of HC1 (6 N), 1 mL of H202 (15%, w/w), and 20 mL of thiourea (5%, w/v), with water as the solvent.-
35. Ferri-and ferrocyanides have very high association constants (K = 1037, 1044, respectively);34 the concentration of free CN-(formed from the dissociation of ferri/ferrocyanide) in the ferri/ferrocyanide etching solution is very low, and we believe its contribution to the etching of gold can be neglected.
36. Douglas, B.; McDaniel D. H.; Alexander, J. J. Concepts and Models of Inorganic Chemistry, 2nd ed.; John Wiley & Sons, Inc.: New York, 1983, p 333.