Elastic surface wave device with reduced size

Abstract

In some embodiments, an elastic surface wave device may include a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the elastic surface wave device supports an elastic surface wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0. In some embodiments, the phase velocity is less than 2,000 m / s, and the elastic surface wave may include a lowest asymmetric (A0) mode. In some embodiments, such an elastic surface wave device may be implemented in products such as radio frequency filters, radio frequency modules, and radio devices.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 346,959, entitled "Reduced - Size Surface Acoustic Wave Devices," filed on May 30, 2022, the disclosure of which is hereby expressly incorporated by reference in its entirety.

[0002] This disclosure relates to surface acoustic wave devices and related methods.

Background Art

[0003] Surface acoustic wave (SAW) resonators typically include interdigital transducer (IDT) electrodes mounted on one surface of a piezoelectric layer. Such electrodes include two sets of comb - shaped fingers, and in such a configuration, the distance between two adjacent fingers of the same set is approximately the same as the wavelength λ of the surface acoustic wave supported by the IDT electrodes.

[0004] In many applications, the SAW resonator can be utilized as a radio frequency (RF) filter based on the wavelength λ. Such a filter can provide a certain number of desired characteristics.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0006] According to a number of implementation examples, the present disclosure relates to an elastic surface wave device including a piezoelectric substrate and interdigital transducer electrodes mounted on one surface of the piezoelectric substrate. The elastic surface wave device supports an elastic surface wave having a wavelength λ and a phase velocity of less than 3,000 m / s, and an electromechanical coupling coefficient of at least 9.0.

[0007] In some embodiments, the phase velocity can be less than 2,000 m / s.

[0008] In some embodiments, the elastic surface wave can include a lowest asymmetric (A0) mode.

[0009] In some embodiments, the piezoelectric substrate can include a LiNbO crystal having Euler angles (φ, θ, ψ). 3 In some embodiments, the angle θ can be in the range of 30 degrees < θ < 50 degrees. In some embodiments, the angle θ can be in the range of 35 degrees < θ < 45 degrees. In some embodiments, the LiNbO piezoelectric substrate can have a thickness in the range of 0.15λ to 0.40λ, 0.16λ to 0.35λ, 0.17λ to 0.30λ, or 0.18λ to 0.25λ. 3 In some embodiments, the interdigital transducer electrodes can be formed from aluminum, molybdenum, copper, tungsten, or platinum. The interdigital transducer electrodes can have a thickness in the range of 0.02λ to 0.10λ.

[0010] In some embodiments, the elastic surface wave device can further include a layer mounted on or under the piezoelectric substrate. This layer can be configured to improve the frequency temperature coefficient (TCF) characteristics of the SAW device. In some embodiments, the layer can be formed from silicon dioxide (SiO₂). In some embodiments, the SiO₂ layer can be mounted under the piezoelectric substrate. In some embodiments, the SiO₂ layer can have a thickness in the range of 0.01λ to 0.05λ.

[0011] In some embodiments, the elastic surface wave device can further include a layer mounted on or under the piezoelectric substrate. This layer can be configured to improve the frequency temperature coefficient (TCF) characteristics of the SAW device. In some embodiments, the layer can be formed from silicon dioxide (SiO₂). In some embodiments, the SiO₂ layer can be mounted under the piezoelectric substrate. In some embodiments, the SiO₂ layer can have a thickness in the range of 0.01λ to 0.05λ. 2 In some embodiments, the SiO₂ layer can be formed from silicon dioxide (SiO₂). In some embodiments, the SiO₂ layer can be mounted under the piezoelectric substrate. In some embodiments, the SiO₂ layer can have a thickness in the range of 0.01λ to 0.05λ. 2 In some embodiments, the SiO₂ layer can be mounted under the piezoelectric substrate. In some embodiments, the SiO₂ layer can have a thickness in the range of 0.01λ to 0.05λ.2 The layer may have a thickness in the range from 0.03λ to 0.1λ.

[0012] In some embodiments, the surface acoustic wave device may further include a support substrate mounted under the piezoelectric substrate. In some embodiments, the support substrate may be formed of silicon, quartz, sapphire, glass, silica, germanium, or alumina. In some embodiments, the support substrate may be present directly under the piezoelectric substrate.

[0013] In some embodiments, the layer providing improved TCF characteristics may be present between the support substrate and the piezoelectric substrate. In some embodiments, the support substrate may define a cavity that exposes a portion of the layer.

[0014] In some implementations, the present disclosure relates to a radio frequency filter including an input node that receives a signal and an output node that provides a filtered signal. The radio frequency filter further includes a surface acoustic wave device mounted to be electrically present between the input node and the output node. The surface acoustic wave device includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports a surface acoustic wave having a phase velocity of less than 3,000 m / s and a wavelength λ with an electromechanical coupling coefficient of at least 9.0.

[0015] In some embodiments, the phase velocity may be less than 2,000 m / s. In some embodiments, the surface acoustic wave may include a lowest asymmetric (A0) mode. In some embodiments, the piezoelectric substrate may include a LiNbO 3 crystal. In some embodiments, the interdigital transducer electrodes may be formed of aluminum, molybdenum, copper, tungsten, or platinum.

[0016] In some embodiments, the radio frequency filter further includes a layer mounted above or below the piezoelectric substrate, and the layer is configured to improve the frequency temperature coefficient (TCF) characteristic of the SAW device. In some embodiments, the layer may be formed from silicon dioxide (SiO 2 ). In some embodiments, the SiO 2 layer may be mounted below the piezoelectric substrate.

[0017] In some embodiments, the radio frequency filter may further include a support substrate mounted below the piezoelectric substrate. In some embodiments, the support substrate may be formed from silicon, quartz, sapphire, glass, silica, germanium, or alumina. In some embodiments, the support substrate may be present directly below the piezoelectric substrate.

[0018] In some embodiments, the layer providing the improved TCF characteristic may be present between the support substrate and the piezoelectric substrate. In some embodiments, the support substrate may define a cavity that exposes a portion of the layer.

[0019] In some teachings, the present disclosure relates to a radio frequency module including a packaging substrate configured to receive a plurality of components and a radio frequency circuit mounted on the packaging substrate and configured to support one or both of signal transmission and reception. The radio frequency module further includes a radio frequency filter configured to filter at least some of the signals. The radio frequency filter includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports a surface acoustic wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0.

[0020] According to some implementation examples, the present disclosure relates to a wireless device including a transceiver, an antenna, and a wireless system electrically implemented between the transceiver and the antenna. The wireless system includes a filter configured to provide a filtering function for the wireless system. The filter includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports surface acoustic waves having a phase velocity of less than 3,000 m / s and a wavelength λ with an electromechanical coupling coefficient of at least 9.0.

[0021] In some teachings, the present disclosure relates to a method of fabricating a surface acoustic wave device. The method includes forming or providing a piezoelectric substrate and mounting interdigital transducer electrodes on the surface of the piezoelectric substrate, and the surface acoustic wave device supports surface acoustic waves having a phase velocity of less than 3,000 m / s and a wavelength λ with an electromechanical coupling coefficient of at least 9.0.

[0022] In some embodiments, the phase velocity can be less than 2,000 m / s. In some embodiments, the surface acoustic wave can include a lowest asymmetric (A0) mode.

[0023] In some embodiments, the piezoelectric substrate can include a LiNbO crystal having Euler angles (φ, θ, ψ). 3 In some embodiments, the angle θ can range from 30 degrees < θ < 50 degrees. In some embodiments, the angle θ can range from 35 degrees < θ < 45 degrees. In some embodiments, the LiNbO piezoelectric substrate can have a thickness in the range of 0.15λ to 0.40λ, 0.16λ to 0.35λ, 0.17λ to 0.30λ, or 0.18λ to 0.25λ. 3 The piezoelectric substrate can have a thickness in the range of 0.15λ to 0.40λ, 0.16λ to 0.35λ, 0.17λ to 0.30λ, or 0.18λ to 0.25λ.

[0024] In some embodiments, the interdigital transducer electrodes can be formed from aluminum, molybdenum, copper, tungsten, or platinum. In some embodiments, the interdigital transducer electrodes can have a thickness in the range from 0.02λ to 0.10λ.

[0025] In some embodiments, the method can further include implementing a layer on or under the piezoelectric substrate to improve the frequency temperature coefficient (TCF) characteristics of the SAW device. In some embodiments, the layer can be formed from silicon dioxide (SiO 2 ). In some embodiments, the SiO 2 layer can be implemented under the piezoelectric substrate. In some embodiments, the SiO 2 layer can have a thickness in the range from 0.03λ to 0.1λ.

[0026] In some embodiments, the method can further include implementing a support substrate under the piezoelectric substrate. In some embodiments, the support substrate can be formed from silicon, quartz, sapphire, glass, silica, germanium, or alumina. In some embodiments, the support substrate can be present directly under the piezoelectric substrate.

[0027] In some embodiments, the layer providing the improved TCF characteristics can be present between the support substrate and the piezoelectric substrate. In some embodiments, the support substrate can define a cavity that exposes a portion of the layer.

[0028] In some embodiments, the surface acoustic wave device can be part of a radio frequency filter.

[0029] For the purpose of summarizing the present disclosure, certain aspects, advantages, and novel features of the present invention have been described herein. It should be understood that not all of these advantages necessarily are achieved in accordance with any particular embodiment of the present invention. That is, the present invention may be embodied or implemented in a manner that achieves or optimizes one advantage or a group of advantages taught herein without necessarily achieving other advantages that may be taught or suggested herein.

Brief Description of the Drawings

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DETAILED DESCRIPTION

[0031] The headings given here are for convenience only, if any, and do not necessarily affect the scope or meaning of the claimed invention.

[0032] In many radio frequency (RF) applications, the die size of the filter significantly contributes to the size of the corresponding RF module. One size reduction technique involves using a low velocity propagation mode to reduce the size of surface acoustic wave (SAW) resonators.

[0033] Disclosed herein are examples related to SAW resonators having low velocity characteristics. In some embodiments, the low velocity includes the phase velocity of the propagation mode, and the phase velocity is less than 3,000 m / s, less than 2,500 m / s, or less than 2,100 m / s. In some embodiments, the SAW resonators described herein can be configured to support the A0 (lowest asymmetric) mode by a thin lithium niobate 3 (LN) layer and generate a very low velocity propagation mode. For example, a phase velocity of about 2,000 m / s can be achieved, which is significantly slower than conventional solutions.

[0034] FIG. 1A is a plan view of a surface acoustic wave (SAW) device 100 having a piezoelectric substrate 101 and interdigital transducer (IDT) electrodes 102 mounted thereon. FIG. 1B shows a side cross-sectional view of the SAW device 100 of FIG. 1A. In some embodiments, as shown in FIG. 1B, the IDT electrodes 102 may be formed on the piezoelectric substrate 101.

[0035] Referring to FIGS. 1A and 1B, the distance between two adjacent fingers of the IDT electrodes 102 is approximately the same as the wavelength λ of the surface acoustic wave associated with the IDT electrodes 102. Further, each finger of the IDT electrodes 102 is shown to have a lateral width F, and a gap distance G is shown to be provided between two adjacent fingers formed in a comb shape.

[0036] Referring to FIG. 1B, the piezoelectric substrate 101 has a thickness of h piezo and the IDT electrodes 102 are shown to have a thickness of h IDT .

[0037] FIG. 2 shows an example of a SAW device 100 configured to operate in the lowest asymmetric mode (A0 mode) of a wave with a wavelength λ = 4 μm, which is a piezoelectric substrate (Piezo) 101 formed from LiNbO piezo (LN) having an Euler angle (0, 40, 0) and a thickness h 3 = 0.2λ, and IDT electrodes 102 formed from aluminum (Al) having a thickness h IDT = 0.08λ. The representative finger count NIDT of the IDT electrodes in FIG. 2 is 75λ, and the finger width is 80 μm.

[0038] In the configuration of the foregoing method, by simulation including an example of an admittance coefficient plot, FIG. 2 further shows the admittance response 120 of the SAW device 100 including the A0 mode in region 123 and the A1 (first-order asymmetric) mode in region 124.

[0039] As an example of size comparison, the exemplary admittance plot of FIG. 2 further shows LN having an Euler angle (0, 38, 0) and SiO with a thickness of 0.3λ 2The admittance response 121 for a temperature-compensated (TC) SAW device having [parameters not specified], and the admittance response 122 of a non-TC SAW device having an LN with Euler angles (0, 132, 0) and an aluminum (Al) IDT electrode with a thickness of 0.08λ are shown. Each of the admittance responses 121, 122 is shown to have an A1 mode in a region generally denoted as 124.

[0040] In the exemplary simulation of FIG. 2, it can be seen that the A1 mode of the TCSAW device (having response 121) gives a phase velocity V of 3,588 m / s and an IDT electrode capacitance C of 2.81 pF, thereby obtaining a ratio V / C that serves as a size metric. When compared with the V / C ratio of the aforementioned TCSAW device, the non-TCSAW device (response 122) gives a phase velocity V of 4,108 m / s and an IDT electrode capacitance C of 2.48 pF, thereby obtaining a ratio V / C that is 1.3 times the V / C ratio of the TCSAW device. For the SAW device 100 (having response 120), the A0 mode gives a phase velocity V of 1,896 m / s and an IDT electrode capacitance C of 2.80 pF, thereby obtaining a ratio V / C that is 0.53 times the V / C ratio of the TCSAW device. That is, it can be seen that an exemplary size reduction of 53% (compared to the TCSAW device) is significant.

[0041] Figure 3 shows the phase velocity curves of various modes as a function of the thickness of an LN piezoelectric substrate having Euler angles (0, 0, 0). Specifically, simulation plots of the A1 (first-order asymmetric) mode, S0 (lowest symmetric) mode, SH0 (lowest shear horizontal) mode, and A0 (lowest asymmetric) mode are shown. When the LN piezoelectric substrate is less than 0.7λ or less than 0.6λ, it can be seen that the A0 mode generally gives a lower phase velocity than the other modes (SH0, S0, A1). It has been shown that within such a range of the thickness of the LN piezoelectric substrate, the phase velocity of the A0 mode increases monotonically with the thickness of the LN. That is, by making the LN piezoelectric substrate thinner, for example, to a thickness of 0.2λ indicated as 125, a desirable low phase velocity value can be obtained. Thus, in some embodiments, a SAW device having one or more of the features described herein may have a thin piezoelectric substrate such as a thin LN piezoelectric substrate having a thickness of less than 0.4λ, less than 0.35λ, less than 0.3λ, or less than 0.25λ.

[0042] Figure 4 shows that in some embodiments, a SAW device configured to support the A0 mode described herein may include a preferred range of the piezoelectric substrate cut angle θ of the Euler angles (φ, θ, ψ). Specifically, Figure 4 shows the electromechanical coupling coefficient k for a SAW device 100 that is otherwise the same as the example of Figure 2 except that the cut angle θ varies as the cut angle θ is swept in the range from 0 degrees to 180 degrees. 2 of the plot.

[0043] k 2shows good values when the cut angle θ has a value in the range of 20 degrees < θ < 70 degrees, and shows an approximate peak value of 10% when the cut angle θ has a value of approximately 40 degrees. That is, in some embodiments, a SAW device having one or more of the features described herein may have a piezoelectric substrate, such as an LN piezoelectric substrate, having a cut angle θ within the range of 20 degrees < θ < 70 degrees, within the range of 20 degrees < θ < 60 degrees, within the range of 25 degrees < θ < 55 degrees, within the range of 30 degrees < θ < 50 degrees, or within the range of 35 degrees < θ < 45 degrees. In FIG. 4, a preferred range of such a cut angle θ is generally shown as 126.

[0044] In the example of FIG. 4, it can be seen in the lower panel that the phase velocity remains less than 2,000 m / s or close to 2,000 m / s throughout the range of cut angle θ from 0 degrees to 180 degrees, including the preferred range of cut angle θ indicated as 127.

[0045] FIG. 5 shows that, in some embodiments, a SAW device configured to support the A0 mode described herein may include a preferred range of the thickness of the piezoelectric substrate. Specifically, FIG. 5 shows the electromechanical coupling coefficient k for a SAW device 100 that is the same as the example of FIG. 2 except that the LN thickness changes as the thickness of the LN piezoelectric substrate is swept through the range from 0.1λ to 0.45λ. 2 plots are shown.

[0046] It can be seen that k 2 has good values when the LN thickness has a value within the range of 0.15λ to 0.45λ. However, as shown in the lower panel of FIG. 5, if a phase velocity of less than 3,000 m / s (when the LN thickness is about 0.45λ) is desired, the LN thickness range from 0.15λ to 0.40λ provides a low phase velocity and a high k 2It is preferable when a higher value is desired. That is, in some embodiments, a SAW device having one or more features described herein may have a piezoelectric substrate such as an LN piezoelectric substrate having a thickness in the range from 0.15λ to 0.40λ, in the range from 0.16λ to 0.35λ, in the range from 0.17λ to 0.30λ, or in the range from 0.18λ to 0.25λ.

[0047] Referring to FIG. 5, it can be seen that the selected LN thickness of 0.2λ (displayed as 128 in the upper panel) does not give the maximum value of k. 2 However, such a selected LN thickness of 0.2λ (displayed as 129 in the lower panel) gives a phase velocity of less than 2,000 m / s and a TCF (temperature coefficient of frequency) of -55 / -66 ppm / deg. Thus, a LN thickness of 0.2λ can be an example of a desired parameter set having a value of k 2 of 10 or more and a phase velocity of 2,000 m / s or less.

[0048] FIG. 6 shows that in some embodiments, the SAW device 100 may include an undercoat layer 104 provided under the piezoelectric substrate 101 to improve the temperature coefficient of frequency (TCF) characteristics of the SAW device. In the example of FIG. 6, the IDT electrode 102 is shown to be formed on the piezoelectric substrate 101 similar to the SAW device 100 of FIG. 1B. In some embodiments, the undercoat layer 104 may be formed of a material such as silicon dioxide (SiO SiO2 ) having a thickness h 2 .

[0049] FIG. 7 shows that in some embodiments, a SAW device may include an overcoat layer 104 provided on an IDT electrode 102 and a piezoelectric substrate 101 to improve the frequency temperature coefficient (TCF) characteristics of the SAW device. In the example of FIG. 7, the IDT electrode 102 is shown to be formed on the piezoelectric substrate 101 in the same manner as the SAW device 100 of FIG. 1B. In some embodiments, the overcoat layer 104 may completely cover the IDT electrode 102. In some embodiments, the overcoat layer 104 has a constant thickness h SiO2 and may be formed of a material such as silicon dioxide (SiO 2 ).

[0050] FIG. 8 shows plots of k 2 , phase velocity, and TCF by simulation of the SAW device 100 of FIG. 6 when the thickness h SiO2 of the silicon dioxide (SiO 2 ) layer (104) is swept from 0 to 0.2λ. In the example of FIG. 8, the LN piezoelectric substrate 101 and the IDT electrode 102 are configured in the same manner as the SAW device 100 of FIG. 2, with an LN Euler angle (0, 40, 0), an LN thickness h piezo = 0.2λ, and an IDT electrode thickness h IDT = 0.08λ made of Al.

[0051] Referring to the k 2 plot of FIG. 8, when compared with the approximate k 2 value of about 10 for the h piezo = 0.2λ configuration of FIG. 5 without the SiO SiO2 layer (the configuration of FIG. 8 with h 2 = 0 is the same), it can be seen that in the range of SiO 2 thickness h SiO2 (e.g., from about 0.03λ to 0.1λ, generally denoted as 130), the k 2 performance is improved (e.g., k 2 ≥ 10.4).

[0052] Referring to the phase velocity plot of FIG. 8, for the thickness h 2 of SiO SiO2As it increases, it can be seen that the phase velocity increases monotonically. h piezo = 0.2λ in the example of FIG. 5 (without SiO 2 layer), similar to that, the phase velocity in FIG. 8 is less than 2,000 m / s when h SiO2 = 0. The phase velocity then increases to about 2,500 m / s when h SiO2 = 0.2λ.

[0053] Referring to the bottom panel of FIG. 8, the two curves displayed as 132 and 131 correspond to the TCF of the resonance frequency and the TCF of the anti-resonance frequency, respectively, when the thickness of the SiO 2 layer is swept from 0 to 0.2λ. It can be seen that the presence of the SiO 2 layer 104 generally improves the TCF performance.

[0054] FIG. 9 shows plots of k 2 , phase velocity, and TCF by simulation of the SAW device 100 of FIG. 7 when the thickness h SiO2 of the silicon dioxide (SiO 2 ) layer (104) is swept from 0.1λ to 0.2λ. In the example of FIG. 9, the LN piezoelectric substrate 101 and the IDT electrode 102 are configured in the same manner as the SAW device 100 of FIG. 2, with an LN Euler angle (0, 40, 0), an LN thickness h piezo = 0.2λ, and an IDT electrode thickness h IDT = 0.08λ made of Al.

[0055] Referring to the k 2 plot in FIG. 9, for the entire range of the thickness h 2 of SiO SiO2 (from 0.1λ to 0.2λ), compared with the approximate k 2 value of the h piezo = 0.2λ configuration in FIG. 5 without the SiO 2 layer, it can be seen that the k 2 performance deteriorates (for example, k 2 ≤ 9).

[0056] Referring to the phase velocity plot in FIG. 9, for the thickness h 2 of SiO SiO2As it increases, it can be seen that the phase velocity increases monotonically. For example, the phase velocity is approximately 2,500 m / s when h SiO2 = 0.1λ, and is approximately 2,500 m / s when h SiO2 = 0.2λ.

[0057] Referring to the bottom panel of FIG. 9, two curves labeled 134 and 133 correspond to the TCF of the resonance frequency and the TCF of the anti-resonance frequency, respectively, when the thickness of the SiO 2 layer is swept from 0.1λ to 0.2λ. It can be seen that the presence of the SiO 2 layer 104 generally improves the TCF performance.

[0058] Referring to the examples of FIGS. 8 and 9, in some embodiments, when an improvement in k 2 performance is desired, the configuration of FIG. 8 (with the SiO 2 undercoat layer 104) is found to be more preferable than the configuration of FIG. 9 (with the SiO 2 overcoat layer 104).

[0059] FIG. 10 shows plots of the phase velocity and k 2 as a function of the thickness of the IDT electrode, obtained from simulations of SAW devices having different IDT electrode materials. In the example of FIG. 10, the SAW device 100 has an LN piezoelectric substrate 101 similar to the SAW device 100 of FIG. 2, and the LN Euler angles (0, 40, 0) and the LN thickness h piezo = 0.2λ are shown. Such a SAW device includes an IDT electrode 102 formed of aluminum (Al) having a density of 2.70 g / cm 3 , copper (Cu) having a density of 8.96 g / cm 3 , molybdenum (Mo) having a density of 10.28 g / cm 3 , tungsten (W) having a density of 19.25 g / cm 3 , or platinum (Pt) having a density of 21.45 g / cm 3 .

[0060] As shown in the phase velocity plot of FIG. 10, the thickness h of the IDT electrode IDT As it increases from 0.02λ to 0.10λ, it can be seen that the phase velocity generally decreases (in the case of Cu, Mo, W, Pt), or generally remains about the same (in the case of Al). For all exemplary material and thickness values, the phase velocity value is less than 2,000 m / s.

[0061] k in FIG. 10 2 As shown in the plot, as the thickness h of the IDT electrode IDT increases from 0.02λ to 0.10λ, it can be seen that k 2 generally increases. For all exemplary material and thickness values, the phase velocity value is less than 2,000 m / s.

[0062] Referring to the k 2 and phase velocity plots of FIG. 10, generally, the higher the density of the IDT electrode, the lower the phase velocity value and the higher the value of k 2 become. For example, high-density IDT electrodes such as W electrodes and Pt electrodes give lower phase velocity values than low-density IDT electrodes such as Al electrodes and Mo electrodes. Furthermore, high-density IDT electrodes such as W electrodes and Pt electrodes give lower phase velocity values than low-density IDT electrodes such as Al electrodes. Combining these, in some embodiments, it can be seen that high-density IDT electrodes may be desirable to give the SAW device low phase velocity characteristics and high k 2 characteristics.

[0063] FIGS. 11 to 14 show that in some embodiments, a SAW device having one or more of the features described herein may include a support substrate. For example, FIG. 11 shows a SAW device 100 including a piezoelectric substrate 101 and an IDT electrode 102 mounted thereon to provide one or more of the characteristics described herein, such as one or more of the characteristics related to the SAW device 100 of FIG. 2. In FIG. 11, the SAW device 100 is further shown to include a support substrate 105 provided in contact with the surface of the piezoelectric substrate 101 opposite to the surface on which the IDT electrode 102 is provided.

[0064] In another example, FIG. 12 shows a SAW device 100 including a piezoelectric substrate 101, an IDT electrode 102 mounted thereon, and an overcoat layer 104 covering the IDT electrode 102 to provide one or more of the characteristics described herein, such as one or more characteristics related to the SAW device 100 of FIG. 7. In FIG. 12, the SAW device 100 is further shown to include a support substrate 105 provided in contact with the surface of the piezoelectric substrate 101 opposite to the surface on which the IDT electrode 102 is provided.

[0065] In yet another example, FIG. 13 shows a SAW device 100 including a piezoelectric substrate 101, an IDT electrode 102 mounted thereon, and an undercoat layer 104 provided to contact the surface of the piezoelectric substrate 101 opposite to the surface on which the IDT electrode 102 is mounted, to provide one or more of the characteristics described herein, such as one or more characteristics related to the SAW device 100 of FIG. 5. In FIG. 13, the SAW device 100 further includes a support substrate 105 provided in contact with the surface of the undercoat layer 104, and the undercoat layer 104 is shown to be present between the piezoelectric substrate 101 and the support substrate 105.

[0066] In yet another example, FIG. 14 shows a SAW device 100 similar to the SAW device 100 of FIG. 13. In the example of FIG. 14, the support substrate 105 is shown to define a cavity 106 that exposes respective portions below the undercoat layer 104. In some embodiments, such a cavity may be dimensioned and arranged to generally be below the IDT electrode 102.

[0067] In some embodiments, the support substrate 105 in the examples of FIGS. 11 to 14 may be formed of a semiconductor or insulator such as silicon, quartz, sapphire, glass, silica, germanium, or alumina. In some embodiments, such a support substrate may be configured to support respective piezoelectric substrates, particularly when the piezoelectric substrates are relatively thin.

[0068] In some embodiments, a SAW resonator having one or more of the features described herein can be implemented as a product, and such a product can be included in other products. Examples of such different products are described with reference to FIGS. 8 through 12.

[0069] FIG. 15 shows that in some embodiments, multiple units of SAW resonators can be fabricated while in an array configuration. For example, wafer 200 includes an array of units 100', and such units are processed together through a number of process steps while remaining coupled.

[0070] Upon completion of the process steps in the wafer form described above, the units 100' of the array can be singulated to provide a number of SAW resonators 100. FIG. 15 depicts one such SAW resonator 100, and such SAW resonator can include one or more of the features described herein.

[0071] FIG. 16 shows that in some embodiments, a SAW resonator 100 having one or more of the features described herein can be implemented as part of a packaged device 300. Such a packaged device can include a packaging substrate 302 configured to receive and support one or more components including the SAW resonator 100.

[0072] FIG. 17 shows that in some embodiments, the SAW resonator-based packaged device 300 of FIG. 16 can become a packaged filter device 300. Such a filter device can include a packaging substrate 302 suitable for receiving and supporting a SAW resonator 100 configured to provide a filtering function such as an RF filtering function.

[0073] FIG. 18 shows that in some embodiments, the radio frequency (RF) module 400 may include an assembly 406 of one or more RF filters. Such filters may be SAW resonator-based filters 100, package filters 300, or some combination thereof. In some embodiments, the RF module 400 of FIG. 18 may also include, for example, an RF integrated circuit (RFIC) 404 and an antenna switch module (ASM) 408. Such a module may be, for example, a front-end module configured to support wireless operations. In some embodiments, some or all of the components described above may be attached and supported by a packaging substrate 402.

[0074] In some implementations, a device and / or circuit having one or more of the features described herein may be included in an RF device such as a wireless device. Such a device and / or circuit may be implemented directly in a wireless device, in the modular form described herein, or in some combination thereof. In some embodiments, such wireless devices may include, for example, cellular phones, smartphones, handheld wireless devices with or without telephone functionality, wireless tablets, and the like.

[0075] FIG. 19 depicts an example of a wireless device 500 having one or more of the advantageous features described herein. In the context of a module having one or more of the features described herein, such a module is generally depicted by a dashed square 400 and can be implemented, for example, as a front-end module (FEM). In such an example, one or more of the SAW filters described herein may be included in a filter assembly such as a duplexer 526.

[0076] Referring to FIG. 19, a plurality of power amplifiers (PAs) 520 can receive corresponding RF signals from transceiver 510. Transceiver 510 can be configured and operate in well-known manners to generate RF signals to be amplified and transmitted and to process received signals. Transceiver 510 is shown to interact with baseband subsystem 408. Baseband subsystem 408 is configured to provide conversion between appropriate data and / or voice signals for the user and appropriate RF signals for transceiver 510. Transceiver 510 can also communicate with a power management component 506 configured to manage power for the operation of wireless device 500. Such power management can also control the operation of baseband subsystem 508 and module 400.

[0077] Baseband subsystem 508 is shown to be connected to user interface 502 to facilitate various inputs and outputs of voice and / or data provided to and received from the user. Baseband subsystem 508 is also connected to a memory 504 configured to store data and / or instructions to facilitate the operation of the wireless device and / or to store information for the user.

[0078] In an example of wireless device 500, the outputs of the plurality of PAs 520 are shown to be routed to corresponding duplexers 526. Such amplified and filtered signals are routed to antenna 516 via antenna switch 514 for the purpose of transmission. In some embodiments, duplexer 526 enables simultaneous transmission and reception operations using a common antenna (e.g., 516). In FIG. 19, received signals are shown to be routed to an "Rx" path (not shown) that can include, for example, a low noise amplifier (LNA).

[0079] Here, although various examples are described in the context of a piezoelectric substrate including LiNbO 3 (LN), one or more features of the present disclosure are applicable to LiTaO 3It is understood that the implementation can also be carried out using other piezoelectric substrates such as (LT).

[0080] Unless the context clearly requires otherwise, throughout the specification and claims, terms such as "including", "comprising", etc. shall be construed in an inclusive sense, opposite to an exclusive or exhaustive sense, that is, in the sense of "including but not limited to". The term "coupled" as generally used herein refers to the possibility that two or more elements can be either directly connected or connected via one or more intermediate elements. In addition, when used in this application, the terms "herein", "above", "below", and terms of similar meaning refer to the entire application and not to any particular part of the application. Where context permits, the terms in the above descriptions using singular or plural numbers may also include plural or singular numbers respectively. The terms "or" and "or" referring to a list of two or more items cover all of the following interpretations of the term, that is, any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0081] The above description of the embodiments of the present invention is not intended to be exhaustive or to limit the present invention to the exact form of the above disclosure. Specific embodiments and examples of the present invention have been described above for illustrative purposes, but as will be recognized by those skilled in the art, various equivalent modifications are possible within the scope of the present invention. For example, while a process or block is presented in a given order, alternative embodiments can execute a routine having steps in a different order or use a system having blocks, and some processes or blocks can be deleted, moved, added, subdivided, combined, and / or modified. These processes or blocks may each be implemented in various different manners. Also, while a process or block may be shown to be executed serially, these processes or blocks may instead be executed in parallel or at different times.

[0082] The teachings of the present invention provided herein can be applied to other systems that are not necessarily the systems described above. The elements and operations of the various embodiments described above may be combined to provide further embodiments.

[0083] Certain embodiments of the invention have been described, but these embodiments are presented by way of example only and are not intended to limit the scope of the disclosure. In fact, the novel methods and systems described herein may be embodied in various other forms, and furthermore, various omissions, substitutions, and changes in the forms of the methods and systems described herein may be made without departing from the spirit of the disclosure. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the disclosure.

Claims

1. A surface acoustic wave device, comprising a piezoelectric substrate, and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, wherein the surface acoustic wave device supports a surface acoustic wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.

0.

2. The surface acoustic wave device according to claim 1, wherein the phase velocity is less than 2,000 m / s.

3. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave includes a lowest asymmetric (A0) mode.

4. The piezoelectric substrate includes a LiNbO crystal having Euler angles (φ, θ, ψ). ３ The surface acoustic wave device according to claim 1, including the crystal.

5. The surface acoustic wave device according to claim 4, wherein the angle θ is in the range of 30° < θ < 50°.

6. The surface acoustic wave device according to claim 5, wherein the angle θ is in the range of 35° < θ < 45°.

7. The LiNbO ３ The piezoelectric substrate has a thickness in the range from 0.15λ to 0.40λ, in the range from 0.16λ to 0.35λ, in the range from 0.17λ to 0.30λ, or in the range from 0.18λ to 0.25λ, of the surface acoustic wave device according to claim 4.

8. The surface acoustic wave device according to claim 1, wherein the interdigital transducer electrodes are formed of aluminum, molybdenum, copper, tungsten, or platinum.

9. The surface acoustic wave device according to claim 8, wherein the interdigital transducer electrodes have a thickness in the range of 0.02λ to 0.10λ.

10. further comprising a layer mounted above or below the piezoelectric substrate, wherein the layer is configured to improve the frequency temperature coefficient (TCF) characteristics of the SAW device.

11. The one layer is formed of silicon dioxide (SiO ２ ), the surface acoustic wave device according to claim 10.

12. The SiO ２ layer is mounted under the piezoelectric substrate, the surface acoustic wave device according to claim 11.

13. The SiO ２ layer has a thickness in the range from 0.03λ to 0.1λ, the surface acoustic wave device according to claim 11.

14. The surface acoustic wave device according to claim 1, further comprising a support substrate mounted below the piezoelectric substrate.

15. The surface acoustic wave device according to claim 14, wherein the support substrate is formed of silicon, quartz, sapphire, glass, silica, germanium, or alumina.

16. The surface acoustic wave device according to claim 14, wherein the support substrate is present directly below the piezoelectric substrate.

17. The surface acoustic wave device according to claim 14, wherein the layer for improving the TCF characteristics is present between the support substrate and the piezoelectric substrate.

18. The surface acoustic wave device according to claim 17, wherein the support substrate defines a cavity that exposes a portion of the layer.

19. A radio frequency filter, comprising an input node for receiving a signal, an output node for providing a filtered signal, and a surface acoustic wave device mounted electrically between the input node and the output node. wherein The surface acoustic wave device includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports an elastic surface wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0, a radio frequency filter.

20. The radio frequency filter according to claim 19, wherein the phase velocity is less than 2,000 m / s.

21. The radio frequency filter according to claim 19, wherein the elastic surface wave includes a lowest asymmetric (A0) mode.

22. The piezoelectric substrate includes LiNbO ３ crystal, and the radio frequency filter according to claim 19.

23. The radio frequency filter according to claim 19, wherein the interdigital transducer electrodes are formed of aluminum, molybdenum, copper, tungsten, or platinum.

24. Further including a layer mounted on or under the piezoelectric substrate, The radio frequency filter according to claim 19, wherein the layer is configured to improve the frequency temperature coefficient (TCF) characteristics of the SAW device.

25. The radio frequency filter according to claim 24, wherein the layer is formed of silicon dioxide (SiO2).

26. The SiO ２ layer is mounted under the piezoelectric substrate, the radio frequency filter of claim 25.

27. The radio frequency filter according to claim 19, further including a support substrate mounted under the piezoelectric substrate.

28. The radio frequency filter according to claim 27, wherein the support substrate is formed of silicon, quartz, sapphire, glass, silica, germanium, or alumina.

29. The radio frequency filter according to claim 27, wherein the support substrate is present directly under the piezoelectric substrate.

30. The radio frequency filter according to claim 27, wherein the layer for improving the TCF characteristics is present between the support substrate and the piezoelectric substrate.

31. The radio frequency filter according to claim 30, wherein the support substrate defines a cavity that exposes a part of the layer.

32. A radio frequency module, A package substrate configured to receive a plurality of components, A radio frequency circuit mounted on the package substrate and configured to support one or both of transmission and reception of a plurality of signals, A radio frequency filter configured to provide filtering for at least a part of the signals And including The radio frequency filter includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports a surface acoustic wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0, a radio frequency module.

33. A wireless device, comprising: a transceiver; an antenna; and a wireless system mounted so as to be electrically present between the transceiver and the antenna, wherein the wireless system includes a filter configured to provide a filtering function to the wireless system, the filter includes a piezoelectric substrate and interdigital transducer electrodes mounted on the surface of the piezoelectric substrate, and the surface acoustic wave device supports a surface acoustic wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0, a wireless device.

34. A method of manufacturing a surface acoustic wave device, comprising: forming or providing a piezoelectric substrate; and mounting interdigital transducer electrodes on the surface of the piezoelectric substrate, wherein the surface acoustic wave device supports a surface acoustic wave having a wavelength λ and a phase velocity of less than 3,000 m / s with an electromechanical coupling coefficient of at least 9.0, a method.

35. The method according to claim 34, wherein the phase velocity is less than 2,000 m / s.

36. The method according to claim 34, wherein the surface acoustic wave includes a lowest asymmetric (A0) mode.

37.

38. The method according to claim 37, wherein the angle θ is in the range of 30 degrees < θ < 50 degrees. The piezoelectric substrate includes a LiNbO crystal having Euler angles (φ, θ, ψ). ３ The method of claim 34, comprising a crystal.

39. The method according to claim 38, wherein the angle θ is in the range of 35 degrees < θ < 45 degrees.

40.

41. The method according to claim 34, wherein the interdigital transducer electrodes are formed of aluminum, molybdenum, copper, tungsten, or platinum. The LiNbO ３ The piezoelectric substrate has a thickness in the range from 0.15λ to 0.40λ, from 0.16λ to 0.35λ, from 0.17λ to 0.30λ, or from 0.18λ to 0.25λ, the method of claim 37.

42. The method according to claim 41, wherein the interdigital transducer electrodes have a thickness in the range of 0.02λ to 0.10λ.

43. The method according to claim 34, further comprising mounting a layer on or under the piezoelectric substrate to improve the frequency temperature coefficient (TCF) characteristics of the SAW device.

44.

45.

46. The one layer is formed from silicon dioxide (SiO ２ ), the method of claim 43.

47. The SiO ２ layer is mounted under the piezoelectric substrate, the method of claim 44. ​ The SiO ２ layer has a thickness in the range from 0.03λ to 0.1λ, the method of claim 44. ​ The method of claim 34, further comprising mounting a support substrate under the piezoelectric substrate. **Claim 48** The method of claim 47, wherein the support substrate is formed from silicon, quartz, sapphire, glass, silica, germanium, or alumina. **Claim 49** The method of claim 47, wherein the support substrate is present directly under the piezoelectric substrate. **Claim 50** The method of claim 47, wherein the layer for improving TCF characteristics is present between the support substrate and the piezoelectric substrate. **Claim 51** The method of claim 50, wherein the support substrate defines a cavity that exposes a portion of the layer. **Claim 52** The method of claim 34, wherein the elastic surface device is part of a radio frequency filter.

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