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.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
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
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
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
Callister W (2001) Fundamentals of materials science and engineering. Wiley, New York. ISBN 0-471-39551-x
Cheng H, Lin T, Chen W (2003) Preparation of  oriented AlN thin films by mid frequency reactive sputtering technique. Thin Solid Films 425:85
Dubois M (2003) Thin film bulk acoustic wave resonators: a technology overview. In: Proceedings of the 4th MEMSWAVE Workshop, Toulouse, 2–4 July (2003)
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
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
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
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
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
Liufu D, Kao KC (1998) Piezoelectric, dielectric, and interfacial properties of aluminium nitride films. J Vac Sci Technol A 16:2360
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
Mileham JR, Pearton SJ, Abernathy CR, MacKenzie JD, Shul RJ, Kilcoyne SP (1995) Wet chemical etching of AlN. Appl Phys Lett 67:1119
Ng H, Weimann N, Chowdhury A (2003) GaN nanotip pyramids formed by anistropic etching. J Appl Phys 94:650
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
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
About this article
Cite this article
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
- Aluminium nitride
- Thin film
- Sputter deposition
- Wet etching behaviour
- Activation energy
- Etch rate