Thickness dependence of the properties of highlyc-axis textured AlN thin films

Abstract

The influence of film thickness on the material properties of aluminum nitride (AlN) thin films deposited on Pt(111) electrodes has been investigated experimentally by means of x-ray diffraction, dielectric response, atomic force microscopy, interferometry measurement of effective d33, and residual stress measurement. The thickness was varied between 35 nm and 2 μm. Full width at mid-height of the rocking curve decreased from 2.60 to 1.14°, rms roughness increased from 3.8 to 18.6 Å, the effective d33, namely d33,f, from 2.75 to 5.15 pm/V. The permittivity εAlN was stable at 10.2, whereas the dielectric losses decreased from 1% to 0.1%. The breakdown electric field under dc voltages varied between 4.0 and 5.5 MV/cm.

Piezoelectric nanoelectromechanical resonators based on aluminum nitride thin films

“…These values ͑ϳ2.5 pm/ V͒ are only slightly lower than those reported for single crystals. 17 This demonstrates the high performance that can be attained with 100 nm polycrystalline AlN films. We further demonstrate operation of tunable, doubly clamped beam AlN resonators.…”

“…Thin film tests indicate that piezoelectric coefficients close to those of bulk AlN can be preserved down to ϳ250-500 nm films. 17 Figure 1 displays a four-mask surface nanomachining process we have developed to fabricate suspended cantilevers and beams using the Mo/AlN/Mo/seed-AlN ͑100 nm/ 100 nm/100 nm/20 nm͒ stack. A key requirement for piezoelectric actuation is to make electrical contacts to both top and bottom Mo electrodes, as illustrated in Fig.…”

Low temperature aluminum nitride thin films for sensory applications

“…4,8,11,17,27 Furthermore, AlN films deposited on (111)-Pt covered substrates exhibit the highest piezoelectric coefficients compared to films grown on other materials. 7 Conventionally, Pt is sputter deposited at approximately 300 • C with subsequent annealing completed at 550 • C in order to ensure a high (111) texture quality. 2,4,9 Since such process conditions are well above the temperature limits of this investigation, no heat treatment was applied to Pt during or after deposition.…”

“…7,[19][20][21] In particular, reasonably high piezoelectric coefficients for films deposited at 200 • C and on nominally unheated substrates were recently presented. 8,22 Other than the individual properties, only a few reports emphasize on all the piezoelectric, dielectric and sensory coefficients of AlN films deposited on nominally unheated substrates.…”

“…1,2 Despite having lower piezoelectric coefficients compared to popular piezoelectric materials, such as ferroelectric lead-zirconate-titanate (PZT) or ZnO, AlN is preferred in many MEMS applications due to its lower dielectric loss tangent and higher signal-to-noise ratio (SNR). [2][3][4][5][6][7][8][9] Most common applications include bulk resonators, ultrasonic transducers, sensors, actuators, bandpass filters and energy harvesters. 10 Non-epitaxial AlN films are usually prepared by means of chemical and/or physical vapor deposition (CVD and PVD) techniques.…”