The anisotropic silicon (Si) etching characteristics of Si (100) in 25 wt.% tetramethyl ammonium hydroxide (TMAH) solutions containing Triton X-100 and isopropyl alcohol (IPA) were studied. The etch rate, convex corners and roughness of the etched surface were investigated. In this reported work two central goals, a mirror-like surface finish and a high reduction of undercutting, have been achieved. The best etched result was obtained in 25 wt.% TMAH + 0.25%v/v Triton + 16%v/v IPA, which has minimum convex corner undercutting and a smooth etched surface (R_a = 1 nm). This study is useful for engineering applications where the fabrication of microstructures for high-quality devices should simultaneously contain smooth surfaces on a large area and less convex corner undercutting.

References

1. 1)
  - 4. Merlos, A., Acero, M., Bao, M.H., et al: ‘TMAH/IPA anisotropic etching characteristics’, Sens. Actuators A, 1993, 37–38, pp. 737–743 (doi: 10.1016/0924-4247(93)80125-Z).
2. 2)
  - 5. Pal, P., Sato, K.: ‘Various shapes of silicon freestanding microﬂuidic channels and microstructures in one step lithography’, J. Micromech. Microeng., 2009, 19, pp. 55003 (doi: 10.1088/0960-1317/19/5/055003).
3. 3)
  - 9. Zubel, I., Kramkowaka, M.: ‘The effect of isopropyl alcohol on etching rate and roughness of (100) Si surface etched in KOH and TMAH solutions’, Sens. Actuators A, 2001, 93, pp. 138–147 (doi: 10.1016/S0924-4247(01)00648-3).
4. 4)
  - 1. Yang, M.Z., Dai, C.L., Hong, J.Y.: ‘Manufacture and characterization of high Q-factor inductors based on CMOS-MEMS techniques’, Sensors, 2011, 11, pp. 9798–9806 (doi: 10.3390/s111009798).
5. 5)
  - 3. Sundaram, K.B., Vijayakumar, A., Subramanian, G.: ‘Smooth etching of silicon using TMAH and isopropyl alcohol for MEMS applications’, Microelectron. Eng., 2005, 77, pp. 230–241 (doi: 10.1016/j.mee.2004.11.004).
6. 6)
  - 6. Tang, B., Sato, K., Xi, S.W., et al: ‘Process development of an all-silicon capacitive accelerometer with a highly symmetrical spring-mass structure etched in TMAH + Triton-X-100’, Sens. Actuator A, 2014, 217, pp. 105–110 (doi: 10.1016/j.sna.2014.05.011).
7. 7)
  - 8. Zubel, I., Kramkowaka, M., Rola, K.: ‘Silicon anisotropic etching in TMAH solutions containing alcohol and surfactant additives’, Sens. Actuators A, 2012, 178, pp. 126–135 (doi: 10.1016/j.sna.2012.02.018).
8. 8)
  - 12. Zana, R.: ‘Aqueous surfactant-alcohol systems: a review’, Adv. Colloid Interface Sci., 1995, 57, pp. 1–64 (doi: 10.1016/0001-8686(95)00235-I).
9. 9)
  - 7. Tang, B., Sato, K., Zhang, D., et al: ‘Fast Si (100) etching with a smooth surface near the boiling temperature in surfactant-modified tetramethylammonium hydroxide solutions’, Micro Nano Lett., 2014, 9, pp. 582–584 (doi: 10.1049/mnl.2014.0214).
10. 10)
  - 10. Tang, B., Pal, P., Gosalvez, M.A., et al: ‘Elipsometry study of the adsorbed surfactant thickness on Si{110} and Si{100} and the effect of pre-adsorbed surfactant layer on etching characteristics in TMAH’, Sens. Actuators A, 2009, 156, pp. 334–341 (doi: 10.1016/j.sna.2009.10.017).
11. 11)
  - 11. Gosálvez, M.A., Tang, B., Pal, P., et al: ‘Orientation- and concentration-dependent surfactant adsorption on silicon in aqueous alkaline solutions: explaining the changes in the etch rate, roughness and undercutting for MEMS applications’, J. Micromech. Microeng., 2009, 19, p. 125011 (doi: 10.1088/0960-1317/19/12/125011).
12. 12)
  - 2. Pal, P., Gosálvez, M.A., Sato, K.: ‘Etched profile control in anisotropic etching of silicon by TMAH + Triton’, J. Micromech. Microeng., 2012, 22, p. 65013 (doi: 10.1088/0960-1317/22/6/065013).

Silicon anisotropic etching in Triton-mixed and isopropyl alcohol-mixed tetramethyl ammonium hydroxide solution

References

Related content