Property characterization of AlN thin films in composite resonator structure

Abstract

AlN thin films with c-axis orientation have been investigated for fabricating thin film bulk acoustic wave resonators in the past few years. Characterization of thin film material properties including density, elastic modulus, and piezoelectric coefficient is essential in processing study and for predicting the performance of the acoustic devices. In this paper, we present our results on the fabrication of highly c-axis oriented AlN thin films on Pt∕Ti∕Si (100) substrates by dc reactive magnetron sputtering method. The crystalline structure and the surface morphology of AlN films are characterized by x-ray diffraction and scanning electron microscopy. The effective piezoelectric coefficient d33eff of the AlN films was measured by a laser interferometer method and the piezoelectric coefficient d33 was estimated. A recently developed resonance spectrum method is applied to characterize the electromechanical properties of AlN thin films based on the input electrical impedance equation derived by one-dimensional transmission line theory for composite resonators. Using the experimental impedance spectrum data, the density and elastic constant of the piezoelectric AlN thin film in the four-layer composite resonator structure are evaluated. The calculated results reveal that the piezoelectric coefficient d33, density, and velocity of the c-axis oriented AlN thin film are 4.19pm∕V, 3187.3kg∕m3, and 10631m∕s, respectively.

Impedance response of lead zirconate titanate thick film structures on silicon substrates for a high frequency ultrasonic transducer

“…Because the PZT film is clamped with the substrate, behavior of these series resonant peaks is caused by an oscillation of the PZT film structure including the film and the substrate like a composite resonator. 22), 23) The multiple resonances of the composite resonator are determined mainly by the acoustic properties of the materials and the thickness. The PZT film thickness corresponds to half-wavelength of the fundamental resonance, and the substrate thickness roughly corresponds to half-wavelength of the interval frequency.…”

Rectifying the output of vibrational piezoelectric energy harvester using quantum dots

“…The length L , width w , and thickness g of the piezoelectric layer are designated as 5  mm , 0.5  mm , and 50  μm for the later numerical demonstration. AlN is chosen as the piezoelectric material with density ρ of 3300  kg/m 3  25, Poisson’s ratio ν and Young’s modulus Y of 350  GPa 26. The quantum dots layer is so thin (normally <1  μm ), and it can also be neglected in the mechanical analysis.…”

Characterization of Structure, Morphology, Optical and Electrical Properties of AlN–Al–V Multilayer Thin Films Fabricated by Reactive DC Magnetron Sputtering

“…The literature contains a significant amount of information about the formation of various multilayer thin films, where one of the layers is AlN [24][25][26][27][28][29][30]. The lower layer, which acts as a substrate that increases adhesion, and sometimes as an electrode, can be pure metal, such as Pt, Ni, Mo, or Al [24][25][26], or material of another type, e.g., III-V compounds like TiN [26] or non-metal oxides like SiO 2 [27].…”