Effect of contact metals on the piezoelectric properties of aluminum nitride thin films

Harman, John; Kabulski, A.; Pagán, V. R.; Famouri, Parviz; Kasarla, K. R.; Rodak, L. E.; Hensel, J. Peter; Korakakis, D.

doi:10.1116/1.2958253

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…Sputtered AlN mesa structures have been fabricated using a bottom-up and topdown approach with different metals used for top and bottom contacts. The Pt/Pt contact combination exhibits the highest measured piezoelectric response in mesa structures fabricated using both techniques which is consistent with literature [16]. The residual stress in the metallic thin films was not directly measured in this study; however there is reportedly no correlation between the stress caused by the AlN/electrode mismatch (10.9% for Pt) and the measured d33 value.…”

Section: 6) Discussionsupporting

confidence: 89%

“…Substrate material has also been reported to increase the piezoelectric response in AlN films due to different nucleation surfaces created by the different materials [15]. Studies have shown that the difference in the piezoelectric effect is closely related to the work function of the substrate and contact metal [16].…”

Section: 3) Introduction To Aluminum Nitridementioning

confidence: 99%

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High temperature studies of thin film Aluminum Nitride and piezoelectric characterization of mesa structures

Farrell¹

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Aluminum Nitride (AlN) is a group III-V compound that grows in a hexagonal wurtzite crystal structure and is a popular material for microelectromechanical systems (MEMS) due in part to its piezoelectricity, inertness and tolerance to high temperatures. High temperature stability is an essential characteristic for numerous MEMS applications, so one of the goals of this work is to determine how the material properties of AlN are affected by exposure to high temperatures and harsh environments. 3D AlN devices are also investigated to determine the effect of electric field isolation on the piezoelectric response of AlN. A Rapid Thermal Annealing (RTA) system was used to anneal the AlN films at temperatures up to 1000°C in ambient and controlled environments. The oxygen content of films annealed in an ambient environment was measured along with the piezoelectric coefficient (d 33) to determine the effect of oxygen incorporation on the piezoelectric response of the films. A high temperature test chamber was designed and built for in-situ high temperature piezoelectric measurements of AlN. The results of the ex-situ and in-situ high temperature experiments, the effects of oxidation on the piezoelectric response of AlN, and methods used to protect the films from oxidation are discussed. Typically, a metal layer covering the entire AlN film is used as a top electrode in d 33 measurements. In this work, circular AlN mesa structures, consisting of an AlN layer, with thicknesses between 200-1000nm, between two ~200nm metal layers, have been created. By decreasing the contact size and limiting the surface area of the AlN film, clamping effects are reduced. This configuration also minimizes non-normal electric field lines between the top and bottom contacts and further isolates the d 33 piezoelectric coefficient. The devices are constructed using two different fabrication methods and the piezoelectric and electrical properties have been studied. iii ACKNOWLEDGMENTS I would like to express my deepest gratitude to everyone who made this work possible. First I would like to thank my family, who has provided me with love and support throughout this process. Without them, none of this would be possible. I would like to thank my research advisor, Dr. Korakakis, for his guidance, support, and patience throughout my undergraduate and graduate career. I would also like to thank the other members of my committee, Dr. Famouri and Dr. Cao, who have provided valuable technical guidance. I could not have completed this work without helpful discussions and

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Section: 6) Discussionsupporting

confidence: 89%

Section: 3) Introduction To Aluminum Nitridementioning

confidence: 99%

High temperature studies of thin film Aluminum Nitride and piezoelectric characterization of mesa structures

Farrell¹

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“…40 However, these results are dependent on a complex interplay of deposition parameters, substrate, and seed layers to reduce residual stress. In addition to built-in stress issues, which bias cantilever bending radii, work function effects of contact metal layers 41 were found to alter the piezoelectric response. Also, dielectric losses were found to increase at small AlN thickness 38 which greatly affects the noise behavior in sensors.…”

Section: Theorymentioning

confidence: 99%

Static magnetoelectric and magnetoelastic response of composite cantilevers: Theory of short vs. open circuit operation and layer sequence effects

2015

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The static bending-mode transverse magnetoelectric effect and the magnetic field-induced bending response of composite cantilevers with thin magnetostrictive (MS), piezoelectric (PE), and substrate (Sub) layers is investigated for the PE layer subjected to open and short circuit conditions. Analytic theories are presented for strain-coupled three layer composites of PE, MS, and Sub layers in all layer sequences. We use constitutive equations with linear coupling of stress, strain, H, E, and D fields and present results for the open and short circuit magnetoelectric and bending responses for arbitrary layer thickness ratios for the FeCoBSi-AlN-Si materials system. Besides a rich sequence dependent behavior the theory predicts great and systematic differences between the open and short circuit magnetoelectric response yielding maxima at similar MS and PE layer thicknesses in the open circuit and near vanishing PE layer thicknesses in the short circuit cases. In contrast, the open vs. short circuit bending response differences are pronounced but much smaller. Layer sequence systematics and implications for static H-field sensors will be discussed.

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“…using Laser Doppler Vibrometer, platinum contacts were deposited using image reversal photolithography. The choice of platinum as top and bottom (p and n) contacts is based on the results reported by Harman et al [35], where it is reported that piezoelectric coefficient d33 is not only function of the crystalline quality of the thin films, but also depends on the work function of the contact metals. have an even, about 1.4 µm thick layer of photoresist.…”

Section: Measurementsmentioning

confidence: 99%

Deep Features based Hierarchical Classification Scheme for Face Recognition in Heterogeneous Environments

Narang¹

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Erbium alloyed AlN thin films: Structural, piezoelectric and magnetic properties Vishal Narang This research was undertaken to determine the effect of Erbium in Erbium-alloyed AlN thin films on their structural, piezoelectric and magnetic properties. For this purpose, Erbium-alloyed AlN thin films with Er concentration of 0, 1, 3 and 4 atomic percent were deposited on (001) p-type Si substrates by reactive magnetron sputtering. The samples were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Variable Angle Spectroscopic Ellipsometry (VASE). XRD measurements showed that Er alloying leads to preferential c-axis film deposition with a decrease in grain size and an increase in the lattice constant. XPS analysis was used to determine the Er concentration and its possible chemical state. VASE measurements were used to determine the thickness and refractive indices of the thin films. Refractive indices were used as metric to determine the structural order of polycrystalline thin films. Piezoelectric measurements showed that Er alloying results in the higher magnitude of the piezoelectric coefficient d 33. Values of as high as 15.0 pm/V is measured for AlN:Er whereas the maximum value obtained for pure AlN thin films is 6.9 pm/V. iii ACKNOWLEDGEMENTS I would like to use this opportunity to thank people who helped me in completing the research presented in this dissertation. First and foremost of all, I would like to express my deep heartfelt thanks to my advisor and committee chair Dr. Mohindar S. Seehra, for his invaluable guidance, patience and encouragement. His hard working nature is always a source of inspiration for me. His ideas guided me in formulating and completing this research. I owe my deepest gratitude to my advisor and committee co-chair, Dr. Dimitris Korakakis, for his support, guidance and technical inputs during my research. Working with Dr. Korakakis enabled me develop a wide range of engineering skills for which I am very thankful to him.

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Effect of contact metals on the piezoelectric properties of aluminum nitride thin films

Cited by 6 publications

References 7 publications

High temperature studies of thin film Aluminum Nitride and piezoelectric characterization of mesa structures

High temperature studies of thin film Aluminum Nitride and piezoelectric characterization of mesa structures

Static magnetoelectric and magnetoelastic response of composite cantilevers: Theory of short vs. open circuit operation and layer sequence effects

Deep Features based Hierarchical Classification Scheme for Face Recognition in Heterogeneous Environments

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