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Aluminum nitride (AlN) thin films have aroused the interest of researchers due to their unique physicochemical properties. However, further studies on these semiconductor materials are still necessary to establish the manufacturing of high-performance devices for applications in various areas, such as telecommunications, microelectronics, and biomedicine. This chapter introduces AlN thin film technology that has made a wide range of applications possible. First, the main physicochemical properties of AlN, its wurtzite crystalline structure, and the incorporation of oxygen during the thin film deposition process are presented. Furthermore, the growth of AlN films by different techniques and their applications as a buffer layer and sensing layer are summarized. Special attention was given to the sputtering deposition process and the use of sputtered AlN films in SAW sensors.
*Address all correspondence to: cicerocunha@unifei.edu.br
1. Introduction
Aluminum nitride (AlN) thin films have attracted much attention due to their excellent properties suitable for the manufacture of devices, which meet various applications [1, 2, 3, 4, 5, 6, 7]. In addition to their properties highlighted in Figure 1, these materials have been much investigated due to their high piezoelectricity and high surface acoustic velocity (v⊥ = 5600 m/s and v∥ = 11,000 m/s) [2, 3], suitable electromechanical coupling, chemical stability [3, 8, 9, 10, 11, 12, 13] and good transparency in the region of the visible, infrared and ultraviolet [10, 13].
Figure 1.
Some properties of AlN.
In recent years, AlN has been shown as an outstanding candidate for the development of micro-electro-mechanical systems (MEMS), particularly surface acoustic wave (SAW) devices operating in high frequency and in thermally and chemically harsh environments [3].
It has been observed that the thin film deposition technique influences the preferred orientation of the AlN film. Different techniques, such as chemical vapor deposition (CVD), molecular beam epitaxy (MBE), and reactive sputtering (RF or DC, with or without magnetron), have been used for the growth of AlN films [3, 12]. The advantages of RF magnetron sputtering technique are that besides the deposition parameters can be easily controlled, it uses low temperature (<400°C) and has compatibility with CMOS technology [3, 9]. Generally, the deposition vacuum systems used in industries have limitations due to the use of large vacuum chambers and of the laborious tasks of environment cleaning processes (chamber, substrates, and everything other system parts). In deposition systems used in microelectronics applications, there is also the possibility of incorporation of oxygen in the films due to the native oxygen on the silicon wafers and the residual relative to the background pressure 1.33 × 10−4 Pa (≈10−6 Torr). Thus, in these conditions, it is difficult to deposit crystalline and highly oriented textural AlN (100) films with low oxygen concentration in their structure, good stoichiometry Al/N (≈1∶1), and thickness close to 500 nm [14, 15].
In this chapter, an overview of the AlN thin film technology is presented. First, the structure and orientation of AlN material are described. Next, the incorporation of oxygen in this material is discussed. The largest section of the chapter is devoted to the growth of AlN films and their use as a buffer layer and sensing layer. Finally, some examples of SAW sensors based on AlN films are presented.
2. Structure and crystal orientation of the AlN material
In the non-excited state, the aluminum has three electrons in its valence layer, distributed as 3s23p1, so it presents a sublevel s complete with two electrons and one p sublevel semi-complete with an electron and two p sublevels empty, as shown in Figure 2a. On the other hand, the nitrogen has five electrons in the valence layer distributed as 2s22p3, where the s sublevel is filled with two electrons and the three sublevels px, py, and pz are semi-complete with one electron each, as shown in Figure 1b. Now, in the excited state, the aluminum sublevels 3s23p1 rise to four hybrids 3sp3 sublevels, in which three sublevels are semi-complete with one electron each, and the remaining sublevel 3sp3 is empty, as indicated in Figure 2a.
Figure 2.
Hybridization of aluminum and nitrogen. (a) Valence layer in the non-excited state and hybrid sublevels of aluminum, 3sp3, in the excited state. (b) Valence layer in the non-excited state and hybrid sublevels of nitrogen, 2sp3, in the excited state.
Also, the nitrogen hybridization rises sublevels 2s22p3, which yields four hybrids 2sp3 sublevels; one is a 2sp3 sublevel full of two electrons, and three sublevels 2sp3 are semi-complete with one electron each. Therefore, in the bonds between the atoms of aluminum and nitrogen, as shown in Figure 2b, there are three covalent bonds between three semi-complete sublevels hybrids of one aluminum atom (atom 4) with three atoms of nitrogen (atoms 1, 2, and 3), forming a tetrahedron of a length l1 = 0.1885 nm and 110.5° angle. There is also one covalent bond between the empty hybrid sublevel of aluminum (atom 4) and the complete hybrid sublevel of nitrogen (atom 5), of ionic character, of length l2 = 0.1917 nm, and angle of 107.7° between l1 and l2. The nitrogen atom (atom 5) joins with three additional aluminum atoms (atoms 6, 7, and 8) through covalent bonds between semi-complete hybrid sublevels, forming another tetrahedron of length l1 and angle of 110.5°. The three aluminum atoms (atoms 6, 7, and 8) also bind to other three nitrogen atoms (atoms 9, 10, and 11) through covalent bonds between the aluminum empty hybrid sublevel and the nitrogen complete hybrid sublevel, of ionic character, having a length of l2 and 107.7° angle between l1 and l2. Those 11 atoms of aluminum and nitrogen (atoms 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11) have the form of a prism of triangular base. This prismatic structure originates the wurtzite hexagonal AlN unit cell, as shown in Figure 3a, that presents the following lattice parameters a = b≅0.3100 nm and c = 0.4980 nm. The orientation of the crystal axes and of the planes for the hexagonal unit shown in Figure 4a are (100, 001), respectively.
Figure 3.
(a) Bonds between aluminum and nitrogen atoms forming a hexagonal wurtzite AlN unit cell with the following lattice parameters a = b≅0.3100 nm and c = 0.4980 nm. (b) Bonds between atoms of aluminum and nitrogen form a prism of triangular base.
Figure 4.
(a) Hexagonal unit cell of the AlN (a = b≠c, α = β = 90°, and γ = 120°) with your crystal axis a1, a2, and a3 plus the identification of the planes (100) and (001). (b) Vibrational phonon modes of the thin film AlN, actives in the IR, E1(TO), and A1(TO).
The vibrational phonon modes of the AlN film, E1(TO), and A1(TO) active in the IR are associated with the respective covalent bonds l1 and l2 as indicated in Figure 2b. In addition, they absorb energy according to the crystal orientation of the AlN film and polarization of the electric field of the IR beam, so this feature can be used to identify the preferred orientation of the film. In the IR analysis, the electric field of the beam is polarized in parallel to surface of the thin film, that is, the incident electric field is perpendicular to the c axis. The ratio between the energy absorbed by the phonon modes E1(TO) and A1(TO) is defined by Eq. (1).
If the ratio Af is much smaller than one, it indicates a high degree of AlN (001) crystalline orientation. On the other hand, Af greater than one indicates a degree of AlN (100) crystal orientation. Thus, it can be concluded that when the phonon mode E1(TO) absorbs more energy than mode A1(TO), the crystalline orientation degree tends to AlN (001), whereas if phonon mode A1(TO) absorbs very more energy that mode E1(TO) the preferred orientation tends strongly to AlN (100).
Figure 5 shows, highlighted in red, the thin film growth units AlN (100) and AlN (001). The atoms and/or clusters of atoms, that reach the surface of the substrate and are adsorbed, move along the surface, colliding and combining, giving rise to nucleation, which grows with the arrival of more species (atoms and/or clusters) forming larger nuclei (islands), that by coalescence end up forming a larger whole, until a continuous layer emerges, and this whole process repeats itself until a thin film is produced. A better explanation for the formation process of AlN (100)/Si (100) thin films, in which the c-axis is parallel to the substrate surface is: when the mean free path is much smaller than the target substrate distance, the collisions between Al and N species occur more often in the space between the target and the substrate, thus forming dimers many Al-N, which are deposited on the substrate and the AlN (100) preferential orientation is achieved [16]. When the species involved in the growth are atoms and ions, then during the growth of AlN (100), Figure 4a, there are four difficult depositions (atoms 5, 6, 7, and 8) and, in the case of AlN (001), Figure 4b, there are two difficult depositions (atoms 4 and 5); Consequently, this favors the growth of the AlN with the c-axis perpendicular to the surface of the substrate. If the species involved in the growth are dimers, Al-N, then in the formation of AlN (100), Figure 4a, we have two difficult depositions (dimers 5-7 and 8-6) and in the formation of AlN (001), Figure 4b, two difficult depositions (dimers 4-3 and 6-5) and also, since all bonds of the AlN (100) growth unit are difficult to break and in the growth AlN (001) unit only one ionic bond easy to break, the AlN film has a good chance of growing with the c-axis parallel to the surface of the substrate.
Figure 5.
Aluminum Nitride hexagonal unit cell growth units highlighted in red: (a) AlN (100) and (b) AlN (001).
During the deposition of AlN films (reactive magnetron sputtering and RF source) the degree of crystal orientation of the AlN films, (100) and (001), is strongly influenced by the energy of the species involved in the process. The energy of species that reach the substrate can be controlled by adjusting some parameters during deposition (i.e., mean free path, temperature, pressure, target-substrate distance). In this scenario, the mean free path (L) and the collision probability (Q) of the species are given by [17]:
L=κBT2(4πrMean2)PE2
and
Q=1−exp(−DTS/L)E3
Where T is the absolute temperature, P is the plasma pressure, DTS is the target-substrate distance, and rMean is the mean radius of the constituent species of the plasma, and κB = 1.38 × 10−23 J/K is the Boltzmann constant. Figure 6 shows the estimation of the three deposition parameters: temperature, working pressure, and mean free path. For these deposition parameters, Figure 7 shows the high probability of obtaining crystalline and highly oriented AlN (100) thin films.
Figure 6.
Deposition parameters: L versus P. The curves were implemented for and typical plasma temperature values, and rMean = 150 nm. Reproduced from [17] with permission.
Figure 7.
Probability of obtaining crystalline and highly oriented AlN (100) thin films. Curves implemented for glow discharge, different values of DTS, and rMean = 150 nm. Reproduced from [17] with permission.
The species energy can be increased by increasing the RF power or the substrate temperature, or decreasing the working pressure, or the distance between the target and the substrate. The Al and N species arrive with too much energy on the substrate surface, favoring the degree of crystal orientation AlN (001), where the (001) plane is parallel to the substrate surface. Now, the orientation degree of AlN (100) with (100) plane parallel to the substrate surface is strongly favored when the energy of Al-N species (dimer) is smaller, in which case many collisions occur prior to deposition.
3. Incorporation of oxygen into AlN crystal lattice
Generally, thin films are found to be defective due to the presence of impurities. A common defect in AlN thin films is the presence of a substitutional defect - N3− ions of the AlN crystal lattice are replaced by O2− ions - according to Figure 8.
Figure 8.
The substitutional defect: layers of atoms in the formation of the wurtzite lattice of the AlN with the incorporation of some oxygen atoms in place of some nitrogen atoms.
This occurs because the characteristics (ionic radius and electronegativity) of oxygen and nitrogen are quite similar. The ionic radius of the oxygen is rO = 0.140 nm and of the nitrogen rN = 0.146 nm gives a difference of ionic radii Δr = 4.11%. The electronegativity of oxygen is ξO = 3.5, of aluminum ξAl = 1.6, of nitrogen ξN = 3.0, and therefore the differences in electronegativity with respect to Al are ΔξO-Al = 1.9 (ionic covalent bonds) and ΔξN-Al = 1.4 (polar covalent bonds). The impurity atoms give rise to stress in the AlN (100) crystalline lattice since the ionic radius difference between N and O is very small (Δr<15%) [18]. Otherwise, the impurity atoms will create substantial distortions in the crystalline lattice and may form a new phase. Also, during the process of thin film growth, there is a strong competition between oxygen and nitrogen because the high electropositivity of aluminum and high electronegativity of the oxygen favors the formation of an intermediate compound (Al2O3), instead of material with substitutional defect.
Aluminum nitride (AlN) films can be deposited on various substrate types via physical and chemical deposition methods as shown in Figure 9. Typical deposition methods include sputtering processes, metalorganic chemical vapor deposition (MOCVD), Molecular-beam epitaxy (MBE), and pulsed laser deposition (PLD).
Figure 9.
Overview of the main methods for deposition of AlN films.
Sputtering methods are the most used to grow AlN films due to their advantages such as low temperature, low cost, and flexibility. The sputtering deposition allows the development of devices and sensors on different types of substrates including polymeric substrates. Recently, Cunha et al. reported growth of highly (100)-oriented aluminum nitride (AlN) thin films on (100) Si substrate, in poor vacuum systems, by radio frequency magnetron sputtering (Figure 10a). High-quality films with good stoichiometry Al/N (≈1:1) and low oxygen concentration (<10%) were produced by varying the target-substrate distance and the deposition time, whereas the temperature, the nitrogen flow, RF power, and sputtering pressure were fixed [17].
Figure 10.
Examples of systems used to grow AlN films: (a) sputtering [17], (b) MBE [19], (c) MOCVD [20] and (d) PLD [21].
Ghosh et al. discussed the growth of both the undoped and doped AlN films on GaN/Sapphire templates in an MBE chamber (Figure 10b) using a plasma-assisted process called PAMBE (plasma-assisted molecular beam epitaxy). The authors concluded that employing an excimer laser annealing with optimized power and frequency rather than the conventional thermal annealing can be a potential alternative route toward improving the structural and electrical properties of AlN layers [19].
An AlN interfacial passivation layer prepared in an MOCVD system (Figure 10c) was reported by Aoki et al. The proposed of this study was to present a route for the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS) structures comprising an Al2O3 gate oxide, deposited via atomic layer deposition (ALD) and using an AlN interfacial passivation layer [20].
Pulsed-laser-deposited AlN films were produced by Vispute et al. using the system shown in Figure 10d at substrate temperatures ranging from 25°C (room temperature) to 1000°C. The AlN films were employed in the fabrication of device-quality AlN heterostructures grown on SiC for high-temperature electronic devices [21].
In relation to emerging advanced AlN deposition methods, atomic layer deposition (ALD) can be highlighted. Amorphous AlN films obtained by ALD were investigated by Parkhomenko et al. using trimethylaluminum and monomethylhydrazine as the precursors at a deposition temperature of 375–475°C. The ALD AlN films exhibited an oxygen content of as low as 4%. In addition, they were compact, continuous and with mechanical properties comparable to those of AlN films produced by other techniques [22]. ALD of AlN on different SiC surfaces with different crystallographic orientation was also investigated recently [23]. For all layers, the surface morphology and the chemical composition results showed that the ALD AlN films exhibit good characteristics films for surface acoustic wave (SAW) devices. The same authors also reported the morphological evolution of ALD AlN films on 4H-SiC substrates [24].
The growth of AlN films has been exploited on different substrates to form both a buffer layer and a sensing layer (Figure 11). The AlN buffer layer is used to improve the growth and properties of other thin films, such as GaN, SiC, ZnO, and diamond among others, for several applications, whereas AlN sensing layers are used mainly in piezoelectric devices, for example SAW (surface acoustic wave) sensors.
Figure 11.
Illustration of AlN structure, thin film deposition and thin film application as sensing layer and buffer layer.
4.2 Growth of AlN buffer layer
Several studies have been devoted to the growth of AlN buffer layers to be used in different applications as those illustrated in Figure 12.
Figure 12.
Examples of applications of AlN buffer layers.
Zhang et al. discussed the growth of sputtered highly oriented AlN films on Si (100) and Si (111) substrates to use them as a proper buffer layer for epitaxial growth of gallium nitride (GaN) films. It was observed that the AlN (0001) films grown on Si (100) exhibit large strain due to the large lattice mismatch between these materials, whereas the AlN films grown on Si (111) have strain dependent on the discharge power in sputtering. Therefore, they concluded that the orientation of the Si substrates and the discharge power impact greatly the strain of sputtered AlN films [25].
The growth of sputtered AlN buffer layer on Si (111) was also reported by Núñez-Cascajero et al. In their paper, they addressed the use of AlN as a buffer layer for the development of AlInN/p-Si heterojunction solar cells. For this, it was investigated the influence of power applied to the Al target on the properties of AlN on Si (111). They found that the presence of the AlN buffer layer leads to an improvement of the structural quality of the Al0.37In0.63N and that the solar cells based on this material show good rectifying behavior in the dark [26].
The growth of amorphous SiC thin films on AlN buffer layers deposited on glass and Si substrates was reported by Wang et al. It evaluated the effect of AlN buffer layer thickness on the morphological and mechanical properties of the SiC. Overall, their results indicated that the AlN buffer layer can effectively improve the adhesion strength of SiC thin films [27]. In another study focused on a comparison among substrates for the development of SiC thin film piezoresistive sensors, Fraga et al. evaluated the piezoresistive properties of SiC films grown on AlN/Si [28]. It evidenced the importance of growing SiC film on AlN in order to develop piezoresistive sensors for high-temperature applications.
In addition to silicon, other substrates are being used in the deposition of AlN buffer layer by sputtering. In a recent paper published in the Journal Materials Science in Semiconductor Processing, the effects of the use of sputtered AlN buffer layer on the carrier transport properties of p-NiO/n-InN heterojunction diode were investigated. In this study, AlN films were grown Al2O3 substrates with varying N2 flow rates in the sputtering process. In order to analyze the reasons for the deterioration of the device characteristics, the influence of AlN buffer layer on I–V characteristics of the heterojunction diode was studied in the temperature range of 30–110°C. A good performance was observed for the heterojunction diode fabricated [29]. Chen et al. also investigated sputtered AlN films on sapphire substrates. However, their focus was to release the film stress using a post-deposition rapid thermal annealing (RTA) at 700–900°C for 5 min. The Raman spectra showed that the in-plane tensile stress of deposited AlN films is released by the RTA [30].
Regarding the use of AlN films as a buffer layer for diamond growth, Mandal et al. carried out the growth of thick (>100 μm) CVD diamond layers on AlN with low thermal boundary resistance between diamond and AlN. In their study, they used a metalorganic chemical vapor deposition (MOCVD) system to grow a 250-nm-thick AlN layer on 150 mm Si substrates. It was highlighted that diamond/AlN could be used for thermal management of GaN high-power devices [31]. Most recently, Forsberg et al., a high sensitivity infrared spectroscopy with a diamond waveguide on aluminum nitride [32].
Zinc oxide (ZnO) films have been also grown on AlN buffer layer for electronic device applications. A recent paper evaluated the temperature-dependent electrical transport properties of n-ZnO/AlN/p-Si heterojunction diodes [33]. Both AlN and ZnO films were deposited by RF magnetron sputtering. Results showed that the use of AlN buffer layer improved electrical and structural characteristics because the AlN between ZnO and Si lowers the mismatch in thermal expansion coefficient/lattice. In a previous study, Xiong et al. exploited the growth of ZnO films on a 150 nm AlN buffer layer on -sapphire substrates. It was noted that c-plane ZnO growth on c-plane sapphire by PLD at slight rough surface morphology of AlN buffer layer can result in a significant variation of ZnO crystallinity [34].
4.3 Growth of AlN active sensing layer
The excellent piezoelectric properties of AlN films have motivated studies on the development of sensors based on these materials. Tonisch et al. reported the piezoelectric properties of polycrystalline AlN thin films on Si (111) substrates for MEMS applications [35]. Reactive dc-sputtering and metalorganic chemical vapor deposition (MOCVD) were used to deposit the AlN films. The piezoelectric coefficient d33eff of AlN thin films was measured using two techniques: piezoresponse force microscopy and an interferometric technique. The value of the effective piezoelectric coefficient d33 for the prepared AlN thin films remained as high as 5.1 pm/V even for lower degrees of texture.
In the same year, the temperature dependence of the piezoelectric coefficient d33 of sputtered AlN film on a polycrystalline silicon/silicon dioxide/silicon wafer measured at temperatures up to 300°C was reported by Kano et al. It was observed that the piezoelectric coefficient d33 has a constant value at temperatures ranging between 20°C and 300°C [36].
A more recent paper shows that the high (002) orientation AlN films have uniform piezoelectric performance [37]. In this study, AlN thin films were grown on Pt/Ti/SiO2/Si (100) substrates by an optimized magnetron sputtering process. A high-frequency SAW device (fo = 4.47 GHz) was constructed based on optimal AlN films. In another study on optimization of AlN growth, Cao et al. optimized DC magnetron sputtering, the process by controlling the distance target-substrate in the deposition of AlN thin films deposited on Si and Pt substrates [38]. A (002) AlN preferred orientation was obtained with DTS = 4 cm. They concluded that under optimum conditions, the as-deposited AlN films show uniform piezoelectric properties and favorable read and write performance [38].
The piezoelectric properties of sputtered Sc-doped AIN polycrystalline films on 200 mm Si wafers were also evaluated in order to use them as active layers for high frequency (GHz range) acoustic resonators [39]. The piezoelectric activity of the as-deposited AlScN films were improved after a 15 min post-deposition annealing at 600°C, leading to a 20% increase in the electromechanical coupling factor [39].
The influence of He implantation on piezoelectric properties of epitaxial AlN thin films were discussed recently [40]. It was noted that while He implantation induces uniaxial strain, it decreases d33 due to implantation-induced N site disorder [40].
Pressure gradient sputtering (PGS) has also been used to grow AlN films. The piezoelectric constant (d33) of the AlN grown by the PGS method was higher than that of the conventional method indicating which the PGS technique has an advantage in the growth of AlN films with highly c-axis oriented and a single dielectric domain [41].
In September 2021, an open research knowledge graph (ORKG) comparison devoted to aluminum nitride films and their applications in piezoelectric devices was published [42]. Table 1 summarizes the characteristics of some piezoelectric devices based on AlN films.
Device type
AlN film deposition method
Substrate
AlN film orientation
AlN film thickness (nm)
Piezoelectric coeficient (pm/V)
Implantable biomedical MENS devices
Sputtering
Pt/Ti/UNCD
(002)
200
5.3
Flexible SAW sensors
Middle-frequency magnetron sputtering
Y2O3/Hastelloy
(002)
3000
5.02
Sensory devices
Magnetron sputtering
(100) Silicon
(002)
2000
5.57
SMA ME sensor
DC reactive sputtering
TiNiCu shape memory alloys
(002)
2000
6.3
Piezoelectric accelerometers
DC sputtering
Pt/Ti/SiO2/Si
(002)
1000
5.92
High-frequency flexible SAW sensors
DC reactive magnetron sputtering
Mo/Polymide
(002)
800
8.01
Biocompatible piezo-optrodes devices
DC sputtering
Mo/Optical fiber
(002)
1000
5.4
Table 1.
Piezoelectric device types based on sputtered AlN films. Adapted from [42].
In recent years, much progress has been carried out on surface acoustic wave (SAW) sensors and applications have been reported in the fields of microfluidics, chemical, biomedical, and mechanical as illustrated in Figure 13.
Figure 13.
Some relevant applications of SAW sensors.
In the literature, various AlN-based sensors are reported. In 1991, Odintzov MA et al. evaluated sputtered AlN films for SAW sensors. AlN films were grown on glass substrates by reactive RF magnetron sputtering and their piezoelectric properties were analyzed. The obtained film was used to implement a SAW temperature sensor. Moreover, it discussed the importance of obtaining polycrystalline AlN-oriented films with perfect crystallization [43].
A SAW-based sensor pressure with a sensibility of 0.33 MHz/bar based on AlN deposited on free-standing diamond substrates was developed by Rodríguez-Madrid. The influence of the piezoelectric film thickness on the SAW response was evaluated. Optimized AlN thin films of 300 nm were used to fabricate one-port SAW resonators operating in the 10–14 GHz frequency range, which were used as SAW pressure sensors [44].
A 3 μm-thick AlN/Sapphire-based SAW resonators with high-quality factors for high-temperature applications (up to 600°C) were fabricated by Streque et al. The quasi-synchronous resonators proposed remained well-tuned for temperatures up to 400°C, and show high-quality factors, as high as 3400 at 400°C [45].
A new two-step growth process integrating metalorganic chemical vapor deposition (MOCVD) and physical vapor deposition (PVD) technologies were proposed to grow AlN films on Si substrates by Xinyan et al. [46]. High-quality AlN-based FBARs wafers were obtained, showing that the Q-factor of FBARs with two-step grown AlN precedes FBARs with one-step grown PVD AlN by 57.6% [46].
As shown in this book chapter, the excellent physical, chemical, dielectric, thermal and mechanical properties of aluminum nitride (AlN) thin films have stimulated great interest in these materials and their wide applications. Until today, sputtering processes are the most used to grow AlN films. In recent years, the ALD technique, an outstanding process in nanotechnology, has been explored to grow AlN films. This book chapter also presented various applications for AlN films as a buffer layer and as a sensing layer. Among the applications, the use of AlN sensing layers is the most discussed in the literature due to their excellent piezoelectric properties and the good performance of SAW sensors based on these materials. In summary, this book chapter presents the key aspects of aluminum nitride thin film technology and its applications in electronic devices and sensors.
This work was supported by the Federal University of Itajubá (UNIFEI), Coordination for the Improvement of Higher Education Personnel (CAPES), National Council of Technological and Development (CNPq), and Minas Gerais State Research Support Foundation (FAPEMIG).
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Written By
Cícero L.A. Cunha, Tales C. Pimenta and Mariana Amorim Fraga
Submitted: 02 June 2022Reviewed: 05 July 2022Published: 01 August 2022
Open access peer-reviewed chapter
