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Etching behaviour of sputter-deposited aluminium nitride thin films in H3PO4 and KOH solutions

Abstract

Aluminium nitride (AlN) reactively sputter deposited from an aluminium target is an interesting compound material due to its CMOS compatible fabrication process and its piezoelectric properties. For the implementation in micromachined sensors and actuators an appropriate patterning technique is needed to form elements made of AlN. Therefore, the influence of different sputtering conditions on the vertical etch rate of AlN thin films with a typical thickness of 600 nm is investigated in an etch mixture based on phosphoric acid. Under comparable conditions, such as temperature and concentration of the etchant, thin films with a high c-axis orientation are etched substantially slower compared to films with a low degree of (002) orientation. When a high c-axis orientation is present detailed analyses of the etched topographies reveal surface characteristics with a low porosity and hence, low roughness values. From temperature dependant etching experiments an activation energy of 800(± 30) meV is determined showing a reaction-controlled etching regime independent of sputter deposition conditions. For comparison, AlN films synthesized under the same conditions were etched in potassium hydroxide (KOH) at room temperature revealing comparable etching characteristics as a function of deposition parameters. Depending on the degree of (002) orientation the topography of the etched samples show a strong increase in surface roughness with time due to a selective etching behaviour between (002) and residual crystallographic planes.

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References

  1. Ababneh A, Kreher H, Seidel H, Schmid U (2007) The influence of varying sputter deposition conditions on the wet chemical etch rate of AlN thin films.In: SPIE-Conference on “Microtechnologies for the New Millenium”, Gran Canaria, vol. 6589, pp 65890U, 2.5.–4.5

  2. Adam T, Kolodzey J, Swann CP, Tsao MW, Rabolt JF (2000) The electrical properties of MIS capacitors with AlN gate dielectrics. Appl Surf Sci 175:428

    Article  Google Scholar 

  3. Assouar MB, Elmazria O, Elhakiki M, Alnot P (2004) Study of structural and microstructural properties of AlN films deposited on silicon and quartz substrates for surface acoustic wave devices. J Vac Sci Technol B 22:1717

    Article  Google Scholar 

  4. Callister W (2001) Fundamentals of materials science and engineering. Wiley, New York. ISBN 0-471-39551-x

    Google Scholar 

  5. Cheng H, Lin T, Chen W (2003) Preparation of [002] oriented AlN thin films by mid frequency reactive sputtering technique. Thin Solid Films 425:85

    Article  Google Scholar 

  6. Dubois M (2003) Thin film bulk acoustic wave resonators: a technology overview. In: Proceedings of the 4th MEMSWAVE Workshop, Toulouse, 2–4 July (2003)

  7. Engelmark F, Iriarte GF, Katardjiev IV, Ottosson M, Muralt P, Berg S (2001) Structural and electroacoustic studies of AlN thin films during low temperature radio frequency sputter deposition. J Vac Sci Technol A 19:2664

    Article  Google Scholar 

  8. Günthner S, Egretzberger M, Kugi A, Kasper K, Hartmann B, Schmid U, Seidel H (2006) Compensation of parasitic effects for a silicon tuning fork gyroscope. IEEE Sensors Jl 6:596

    Article  Google Scholar 

  9. Gudovskikh AS, Alvarez J, Kleider JP, Afanasjev VP, Luchinin VV, Sazanov AP, Terukov EI (2004) Polycrystalline AlN films deposited at low temperature for selective UV detectors. Sens Actuat A 113:355

    Article  Google Scholar 

  10. Kao K, Chung C, Chung Y, Shing T (2004) The influence of varied sputtering condition on piezoelectric coefficients of AlN thin films. In: Proceedings of the IEEE international ultrasonics, ferroelectrics, and frequency joint 50th anniversary conference, p 181

  11. Lee Jung W, Cuomo Jerome J (2004) Plasma characteristics in pulsed direct reactive magnetron sputtering of aluminium nitride thin films. J Vac Sci Technol A 22:260

    Article  Google Scholar 

  12. Liufu D, Kao KC (1998) Piezoelectric, dielectric, and interfacial properties of aluminium nitride films. J Vac Sci Technol A 16:2360

    Article  Google Scholar 

  13. Mackenzie JD, Abernathy CR, Peatron SJ, Krishnamoorthy V, Bharatan S, Jones KS (1995) Growth of AlN by metal organic molecular beam epitaxy. Appl Phys Lett 67:253

    Article  Google Scholar 

  14. Mileham JR, Pearton SJ, Abernathy CR, MacKenzie JD, Shul RJ, Kilcoyne SP (1995) Wet chemical etching of AlN. Appl Phys Lett 67:1119

    Article  Google Scholar 

  15. Ng H, Weimann N, Chowdhury A (2003) GaN nanotip pyramids formed by anistropic etching. J Appl Phys 94:650

    Article  Google Scholar 

  16. Rodriguez-Clements R, Aspar B, Azema N, Armas B, Combescure C, Durand J, Figueras A (1993) Morphological properties of chemical vapour deposited AlN films. J Crystal Growth 133:59

    Article  Google Scholar 

  17. Xu X, Wu H, Zhang C, Jin Z (2000) Morphological properties of AlN piezoelectric thin films deposited by DC reactive magnetron sputtering. Thin Solid Films 388:62

    Article  Google Scholar 

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Correspondence to A. Ababneh.

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Ababneh, A., Kreher, H. & Schmid, U. Etching behaviour of sputter-deposited aluminium nitride thin films in H3PO4 and KOH solutions. Microsyst Technol 14, 567–573 (2008). https://doi.org/10.1007/s00542-007-0450-x

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Keywords

  • Aluminium nitride
  • Thin film
  • Sputter deposition
  • Wet etching behaviour
  • Activation energy
  • Etch rate