Zero Temperature Coefficient Surface-Acoustic-Wave Devices Using Epitaxial AlN Films

Tsubouchi, Kazuo; Sugai, K.; Mikoshiba, Nobuo

doi:10.1109/ultsym.1982.197842

Cited by 39 publications

(20 citation statements)

References 19 publications

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“…Figure 3 shows the linear dependence of the displacement of the sample surface on the applied voltage measured at a sputtered aluminium nitride film. The piezoelectric constant d 33 was calculated to 5.4 ± 0.2 pm/V which is in good agreement with values reported elsewhere [8,10,11]. Additional measurements using a homodyne Michelson interferometer set-up supported the above obtained results.…”

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confidence: 91%

Piezoelectric properties of thin AlN layers for MEMS application determined by piezoresponse force microscopy

Tonisch

Cimalla

Foerster

et al. 2006

Phys. Status Solidi (c)

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Piezoelectric properties of aluminium nitride thin films were measured using both, the piezoresponse force microscopy and an interferometric technique. Wurtzite AlN thin films were prepared on Si (111) substrates by reactive DC-sputtering and by metalorganic chemical vapor deposition. Direct measurements of the inverse piezoelectric effect in the picometer range showed that the acceptable tolerance in the crystal orientation is much larger for MEMS applications than expected previously. The value of the piezoelectric coefficient d 33 for the prepared AlN thin films was determined to be 5.36 ± 0.25 pm/V for highly textured as well as for polycrystalline thin films with a (002) preferential orientation. 1 Introduction Micromechanical resonators show significant promise for many sensor applications such as chemical and biological sensing, electrometry and scanning probe techniques. In these applications, a change in mass, temperature, charge, or any other applied force induces a small shift in the resonance frequency of the oscillator [1]. Typically, resonators require both an actuation and a detection of the resonance frequency. The main advantage of using the (inverse) piezoelectric effect is the possibility to use it in both ways, the inverse effect as actuation and the direct one as detection.The exceptional properties of wide-bandgap III-V nitride semiconductors are promising for such applications. Among the nitrides AlN has the largest piezoelectric coefficients and good mechanical strength [2], which makes AlN a favourite material for electromechanical devices in micro-and nanometer scale. Unfortunately, epitaxial growth of AlN only occurs at high temperatures which makes the epitaxial deposition incompatible for the integration in CMOS or other technologies sensitive to heat. Therefore much effort has been made to grow highly textured polycrystalline films with low temperature processes like reactive sputtering.The piezoelectricity of wurtzite AlN is characterized by three independent piezoelectric coefficients d 33 , d 31 (= d 32 ) and d 15 (= d 24 ) [3]. While measuring the piezoelectric effects of thin films, it is important to bear in mind that the macroscopic piezoelectric response is the result of the contributions of all the dipoles (grains) of the film. The highest values are reached when all the dipoles are aligned along the same direction and have the same polarity, thus contributing with the same sign to the net piezoelectric response [4]. Therefore a c-axis preferential orientation is crucial for a high piezoelectric response of thin films. However, as we will show by direct measurements in the picometer range, the inverse piezolelectric effect is much less effected by the crystal quality than the coupling factor k 2 , which is usually measured for SAW applications [5]. In fact, the acceptable tolerance in the crystal orientation for actuator and resonator applications is much larger than expected, because the inverse piezoelectric effect is mainly

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supporting

confidence: 91%

Piezoelectric properties of thin AlN layers for MEMS application determined by piezoresponse force microscopy

Tonisch

Cimalla

Foerster

et al. 2006

Phys. Status Solidi (c)

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“…In addition, the impact of viscous damping, which is a critical factor for stable operation of many types of transducers and actuators, was thoroughly analyzed, in order to obtain the analytical expression for the dependence of vibration amplitude on the operational pressure of viscous gas. [13,14] 4.50-5.53 [4,7,9] 2 Experimental conditions AlN films were deposited in a Leybold Z550 RF magnetron system directly on 4" (001) Si substrates (5-20 mΩ·cm) films using an Ar/N 2 mixture, nominally at room temperature. The AlN thickness distribution over the substrate has been characterized by means of spectral ellipsometry revealing a deviation of ~2.5%.…”

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Evaluation of AlN material properties through vibration analysis of thin membranes

Lebedev

Knöbber

Heidrich

et al. 2011

Phys. Status Solidi C

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In this work, the mechanical properties of thin piezoelectric AlN films along with the methods and instruments to obtain this information with sufficient accuracy via dynamic (vibration) and static analyses of thin membranes are reported. In addition, the impact of different damping mechanisms on the amplitude of forced oscillations have been considered in order to obtain the analytical expression relating the resonant amplitude of membrane to the ambient gas pressure

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“…[5] and [6], see also below). On the other hand, experiments [7][8][9][10][11][12] directly access the d ij measuring the strain ǫ i caused by an applied field E via the converse piezoelectric effect…”

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confidence: 99%

“…In Table I we report all the d ij 's calculated within GGA and LDA (the latter are given in square brackets), compared with indirect predictions obtained via Eq.3 using elastic and e-piezoconstants calculated separately [5], and with the available experimental data [7][8][9][10][11][12]. The calculated results depend considerably on the choice of the exchange-correlation functional, the LDA values being always larger than those of GGA.…”

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First-principles calculation of the piezoelectric tensor d⇊ of III–V nitrides

Bernardini¹,

Fiorentini²

2002

Applied Physics Letters

136

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We report direct first-principles density-functional calculations of the piezoelectric tensor d The piezoelectric tensor d ↔ of a polar material relates to linear order the induced polarization P to the applied stress viaIt is an especially relevant quantity in the field of III-V nitride compounds, whose piezoelectric and polarization properties are prominent [1] and unusual [2]. As implied by its definition, d↔ is relevant to electroacustic applications [3], and to the determination of polarization and electrostatic fields induced by applied stress or strain in devices or epitaxial nanostructures [4].The piezoelectric tensor e ↔ [1,5] connecting polarization and strain ǫ i viais related to the d ↔ tensor of interest here bywhere the C ij are the elastic stiffness constants at constant electric field. It is thus possible to compute d ↔ from the knowledge of elastic constants and e-piezoconstants (using e.g. the theoretical estimates of Refs.[5] and [6], see also below). On the other hand, experiments [7][8][9][10][11][12] directly access the d ij measuring the strain ǫ i caused by an applied field E via the converse piezoelectric effectThe d ij 's in Eqs. 1 and 4 are by definition identical [13], so that a direct comparison is possible, and especially interesting and useful. Here we compute directly the d ij constants in the III-V binary nitrides as derivatives of the polarization with respect to stress, calculating the Berryphase polarization of a primitive cell explicitly subject to a given external stress. This approach enables us to directly compare the calculated values with experiment, and with indirect theoretical predictions using Eq. 3, and separately calculated C ↔ and e ↔ tensors. The binary III-V nitrides AlN, GaN, and InN crystallize in the wurtzite structure, and they possess three independent components of the piezoelectric tensor, namely d 33 , d 31 (=d 32 ), and d 15 (=d 24 ). To compute these constants we run a damped Parrinello-Rahman-like dynamics [14,15] for each of the compounds considered, with the constraint that the system be subject to a given non-zero stress. The external stress is applied to the zero-stress equilibrium structure, which is identical to that reported in Ref. [5]. As a compromise between the contrasting needs for sufficiently large stresses to obtain polarizations outside the numerical noise, and for sufficiently small stresses to avoid large deformations and non-linearity, we separately apply stress components σ 1 = σ 2 = ±50 Kbar in the basal plane, and σ 3 = ±50 Kbar along the singular axis, to determine d 31 and d 33 ; for d 15 we apply a shear stress σ 5 = ±50 kBar. In the case of InN, these stresses and the ensuing deformations may lead to metallization because of the very small calculated DFT band gap. This must be avoided because macroscopic polarization cannot be defined or computed in metallic systems. We found that the maximum applied stress had to be reduced to 5 Kbar for InN (incidentally, this does not causes numerical noise problems in the polarization cal...

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Zero Temperature Coefficient Surface-Acoustic-Wave Devices Using Epitaxial AlN Films

Cited by 39 publications

References 19 publications

Piezoelectric properties of thin AlN layers for MEMS application determined by piezoresponse force microscopy

Piezoelectric properties of thin AlN layers for MEMS application determined by piezoresponse force microscopy

Evaluation of AlN material properties through vibration analysis of thin membranes

First-principles calculation of the piezoelectric tensor d⇊ of III–V nitrides

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