Thickness dependence of Young's modulus and residual stress of sputtered aluminum nitride thin films

Abstract

Aluminum nitride thin films are commonly used as active layer in micro-/nanomachined devices due to their piezoelectric properties. In order to predict the performance of advanced device architectures, careful modelling and simulation using techniques such as finite element analysis are of the utmost importance. An accurate knowledge of the corresponding thin film material properties is therefore required. This work focuses on the mechanical properties residual stress and Young's modulus over a wide thickness range from 100 to 1200 nm. The load-deflection technique is used to measure the bending curve of a circumferentially clamped, circular aluminum nitride diaphragm under a uniformly distributed pressure load. The bending curves are analyzed using an advanced analytical approach rather than commonly used models for load-deflection methods, thus resulting in a higher accuracy. It is found that the Young's modulus is nearly independent of film thickness, whereas the tensile residual stress exhibits a maximum at a thickness of about 600 nm. A thorough discussion of possible error sources is presented and approaches to minimize their impact are discussed.

A semi-analytical modeling approach for laterally-vibrating thin-film piezoelectric-on-silicon micromechanical resonators

“…The stiffness constants provided in [19] are close to those measured by Brillouin light scattering for sputtered AlN films from an target [20]. This value of Young's modulus (283 GPa) is about 10% higher than other literature sources reporting on the elastic properties of sputter deposited AlN films [21]. For a given Q and mode shape, the model proposed in section 2 can be used to predict the key lumped parameters as shown in table 2.…”

Intrinsic Mechanical Properties of Free-Standing SiNx Thin Films Depending on PECVD Conditions for Controlling Residual Stress

“…A PECVD system (LG display) was used to fabricate SiN x thin films with controlled residual tensile (T), neutral (N), and compressive (C) stresses using three representative deposition conditions; the prepared SiN x thin films are denoted as T-SiN x , N-SiN x , and C-SiN x , respectively. The thicknesses of the SiN x thin films were specified within the range of 130–150 nm to exclude the thickness dependency of the mechanical properties . As summarized in Table , silane (SiH 4 ), ammonia (NH 3 ), and nitrogen (N 2 ) were used as the feed gas species.…”

“…The thicknesses of the SiN x thin films were specified within the range of 130−150 nm to exclude the thickness dependency of the mechanical properties. 24 As summarized in Table 1, silane (SiH 4 ), ammonia (NH 3 ), and nitrogen (N 2 ) were used as the feed gas species. For conditions T, N, and C, the RF power was increased from 450 to 700 W, while the chamber pressure was decreased from 1250 to 750 mTorr.…”

Switching performance of bistable membranes activated with integrated piezoelectric thin film transducers

“…Here, C xy represents the entries in the elasticity tensor C in different crystallographic directions, d 31 the piezoelectric coefficient in lateral direction, E 3 the electrical field strength between the bottom and top electrode and Δσ AlN the stress change caused by the electrical field between the electrodes. The AlN layer features an intrinsic stress caused by the deposition process which depends on different parameters of the sputter deposition process [22]. Consequently, the effective stress in the AlN layer can be calculated from the intrinsic stress in the AlN layer after sputter deposition with σ 0_AlN and Δσ AlN with the applied electrical field E. In this work the coefficients given in table 2 were used.…”