Patent Publication Number: US-2018041186-A1

Title: Surface acoustic wave elements with protective films

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of co-pending U.S. Provisional Application No. 62/370,851 titled “SURFACE ACOUSTIC WAVE ELEMENTS” and filed on Aug. 4, 2016, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     Conventionally, a surface acoustic wave (SAW) element is protected by a technique for improving resistance against the absorption of moisture into a silicon dioxide (SiO 2 ) film. For example, International Publication No. WO2008/146449(A1) and Japanese Patent Publication No. 2011-254549(A) disclose techniques for forming a silicon oxynitride (SiON) film on a silicon dioxide film as a protection film to improve the moisture resistance capability of the surface acoustic wave element. Japanese Patent Publication No. 2011-061743(A) discloses a technique for forming silicon nitride (SiN) and silicon dioxide films as protection films. 
       FIGS. 1A and 1B  illustrate a conventional surface acoustic wave element provided with a protection film configured as a silicon oxynitride film.  FIG. 1A  is a top view illustrating an electrode arrangement of the surface acoustic wave element, and  FIG. 1B  is a cross sectional view taken along line I-I (which extends in a propagation direction of a surface acoustic wave). A piezoelectric substrate  110  has a surface on which an interdigital transducer (IDT) electrode  111  and reflector electrodes  112 ,  113  are formed (referred to as a top surface  110   a  hereinafter). A silicon dioxide (SiO 2 ) film  121  is formed on the top surface  110   a  and a silicon oxynitride film  122  as a protection film is formed on and in contact with the silicon dioxide film  121 . 
     SUMMARY OF THE INVENTION 
     Aspects and embodiments relate to a surface acoustic wave element using a piezoelectric substrate and filter devices including the surface acoustic wave element. 
     In a conventional surface acoustic wave element such as that shown in  FIGS. 1A and 1B , the silicon oxynitride film has a tendency to be easily oxidized. Accordingly, a part of the silicon oxynitride film may be converted to silicon dioxide such that the frequency characteristics of the surface acoustic wave element may be changed. Further, the silicon nitride can allow an acoustic velocity greater than that of the silicon dioxide and therefore, when a protection film having a certain film thickness is formed on the entire surface of the silicon dioxide film, the propagation characteristics of the surface acoustic wave may be adversely affected. 
     In view of the circumstances described above, aspects and embodiments provide a surface acoustic wave element having a protection film configured to prevent moisture absorption into a silicon dioxide film to improve the moisture resistance capability of the surface acoustic wave element and configured to be unsusceptible to oxidation and stable, such that the propagation characteristics of the surface acoustic wave are not adversely affected. 
     To solve the aforementioned problems, a surface acoustic wave element according to certain embodiments may include a piezoelectric substrate having a top surface, an interdigital transducer (IDT) electrode formed on the top surface of the piezoelectric substrate and including a plurality of electrode fingers configured to excite a surface acoustic wave, a first silicon dioxide film formed to cover the IDT electrode on the top surface of the piezoelectric substrate, a silicon oxynitride film formed in contact with the first silicon dioxide film, and a second silicon dioxide film formed in contact with the silicon oxynitride film. 
     In certain embodiments, the silicon oxynitride film may have a first film thickness and a second film thickness, the second film thickness corresponding to an area for at least one portion of the plurality of electrode fingers, the first film thickness corresponding to a remaining area of the area for the at least one portion, and the second film thickness being greater than the first film thickness. 
     In certain embodiments, the surface acoustic wave element may further include a silicon nitride film formed to be sandwiched between the first silicon dioxide film and the silicon oxynitride film. The silicon nitride film may correspond to an area for at least one portion of the plurality of electrode fingers. 
     Further, another example of a surface acoustic wave element according to certain embodiments may include a piezoelectric substrate having a top surface, an interdigital transducer (IDT) electrode formed on the top surface of the piezoelectric substrate and including a plurality of electrode fingers configured to excite a surface acoustic wave, a first silicon dioxide film formed to cover the IDT electrode on the top surface of the piezoelectric substrate, a silicon nitride film formed in contact with the first silicon dioxide film, a silicon oxynitride film formed in contact with the silicon nitride film, and a second silicon dioxide film formed in contact with the silicon oxynitride film. 
     The silicon nitride film may have a first film thickness and a second film thickness greater than the first film thickness, the second film thickness corresponding to an area for at least one portion of the plurality of electrode fingers and the first film thickness corresponding to a remaining area of the area for the at least one portion. 
     An acoustic velocity of the surface acoustic wave allowed to propagate by the silicon oxynitride film may be adjustable by a composition of nitrogen and oxygen existing in the silicon oxynitride film, and the piezoelectric substrate may be made of lithium niobate or lithium tantalate. 
     Still further, another example of a surface acoustic wave element according to certain embodiments may include a piezoelectric substrate having a top surface, an interdigital transducer (IDT) electrode formed on the top surface of the piezoelectric substrate and including a plurality of electrode fingers configured to excite a surface acoustic wave, a silicon dioxide film formed to cover the IDT electrode on the top surface of the piezoelectric substrate, a moisture absorption prevention film formed to cover the silicon dioxide film, and an oxidation prevention film covering the moisture absorption prevention film. 
     According to certain aspects of the present disclosure, a protection film can be provided to prevent moisture absorption into a silicon dioxide film of a surface acoustic wave element to improve the moisture resistance capability, such that the changes in the frequency characteristics due to the oxidation can be suppressed and the propagation characteristics of the surface acoustic wave are not adversely affected. 
     Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments are discussed in detail below. Embodiments and examples disclosed herein may be combined with other embodiments and examples in any manner consistent with at least one of the principles disclosed herein, and references to “an embodiment,” “some embodiments,” “an alternate embodiment,” “various embodiments,” “one embodiment” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the invention. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures: 
         FIGS. 1A and 1B  show a structure of a conventional surface acoustic wave element; 
         FIGS. 2A and 2B  show cross sectional views of a surface acoustic wave element according to aspects of the present disclosure; 
         FIG. 3  shows a cross sectional view of a first variation of the surface acoustic wave element in accordance with the present disclosure; 
         FIG. 4  shows a cross sectional view of a second variation of surface acoustic wave element in accordance with the present disclosure; 
         FIG. 5  shows a cross sectional view of a third variation of the surface acoustic wave element in accordance with the present disclosure; 
         FIG. 6  shows a cross sectional view of a comparative example of a surface acoustic wave element; 
         FIG. 7  is a block diagram of one example of a filter module that can include one or more surface acoustic wave elements according to aspects of the present disclosure; 
         FIG. 8  is a block diagram of one example of a front-end module that can include one or more filter modules according to aspects of the present disclosure; and 
         FIG. 9  is a block diagram of one example of a wireless device including the front-end module of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Examples of surface acoustic wave (SAW) elements in accordance with aspects of the present disclosure are now described in detail with reference to the accompanying drawings. 
       FIGS. 2A and 2B  are cross sectional views of one example of a surface acoustic wave element according to an aspect of the present disclosure.  FIG. 2A  shows a cross sectional view of the surface acoustic wave element taken along line I-I illustrated in  FIG. 1 , in a propagation direction of the surface acoustic wave.  FIG. 2B  shows a cross sectional view of the surface acoustic wave element taken along line I′-I′ illustrated in  FIG. 1A , in an extending direction of electrode fingers of the IDT electrode. 
     In the surface acoustic wave element, an interdigital transducer (IDT) electrode  211  is formed on a flat top surface  210   a  of a piezoelectric substrate  210  made of lithium niobate (LiNbO 3 ) to excite a surface acoustic wave. The IDT electrode  211  includes a pair of comb-shaped electrodes having electrode fingers that interdigitate with one another. Further, a first reflector electrode  212  and a second reflector electrode  213  are formed on either side of the IDT electrode  211  in a propagation direction of the surface acoustic wave to sandwich the IDT electrode  211  therebetween. 
     The piezoelectric substrate  210  may be made of lithium niobate with a 5° rotated Y-cut and X-propagation. The IDT electrode  211 , the first reflector electrode  212  and the second reflector electrode  213  can be formed to contain aluminum as a main component and each to have a thickness of approximately 150 nanometers (nm). The surface acoustic wave element can be configured as a filter having a center frequency of approximately 2 GHz and may have a wavelength λ of approximately 2 micrometers (μm) for the surface acoustic wave. 
     A first silicon dioxide (SiO 2 ) film  221  having a certain film thickness is formed on the top surface  210   a  of the piezoelectric substrate  210  to cover the IDT electrode  211 , the first reflector electrode  212  and the second reflector electrode  213 . A silicon oxynitride (SiON) film  222  having a certain film thickness is formed in contact with the first silicon dioxide film  221 , and a second silicon dioxide film  223  having a certain film thickness is formed in contact with the silicon oxynitride film  222 . 
     The first silicon dioxide film  221  formed on the top surface  210   a  of the piezoelectric substrate  210  may suppress characteristic changes in the surface acoustic wave element, such as frequency changes of a surface acoustic wave propagating in the device caused by a thermal expansion or contraction due to changes in the ambient temperature of the piezoelectric substrate  210 . 
     The silicon oxynitride film  222  formed in contact with the first silicon dioxide film  221  can block the permeation of moisture such that no moisture can reach the first silicon dioxide film  221  and thus moisture absorption into the first silicon dioxide film  221  can be prevented. The second silicon dioxide film  223  formed in contact with the silicon oxynitride film  222  can block the permeation of oxygen such that it does not reach the silicon oxynitride film  222  and oxidation of the silicon oxynitride film  222  can be prevented. 
     According to an aspect of the present disclosure, the double-layer structure formed by the silicon oxynitride film  222  and the second silicon dioxide film  223  can prevent both the moisture absorption into the first silicon dioxide film  221 , and the oxidation of the silicon oxynitride film  222 . In other words, the silicon oxynitride film  222  and the second silicon dioxide film  223  may function as a moisture absorption prevention film and an oxidation prevention film, respectively. Therefore, a deterioration of the propagation characteristics due to the moisture absorption into the first silicon dioxide film  221  can be prevented and the changes in the frequency characteristics due to the oxidation of the silicon oxynitride film  222  can also be prevented. As a result, it is possible to ensure the stable operation of the surface acoustic wave element and enhance the reliability thereof. 
     According to an aspect of the present disclosure, the composition of the silicon oxynitride constituting the silicon oxynitride film  222  need not be limited to SiON but can include SiO x N 2−x  (0&lt;x&lt;2). In this way, configuring the compositional ratio of nitrogen and oxygen of the silicon oxynitride film  222  can provide adjustability for an acoustic velocity of the silicon oxynitride film  222 . Accordingly, it can be possible to properly control the propagation of the surface acoustic wave to improve the propagation characteristics of the surface acoustic wave element. 
     According to an aspect of the present disclosure, there is no need for a silicon nitride film to be formed with a substantially uniform film thickness on the entire surface of the first silicon dioxide film  221 . Therefore, it can be possible to avoid forming silicon nitride over the entire surface and causing the surface acoustic wave to expand along the entire surface due to the greater acoustic velocity allowed by the silicon nitride, such that an adverse effect of the propagation characteristics can be prevented. 
     It is to be appreciated that, although the piezoelectric substrate  210  of the surface acoustic wave element described above employs lithium niobate, lithium tantalate (LiTaO 3 ) can also be used. Further, regardless of the dimensions for the respective portions as described above, other appropriate dimensions may be chosen. In addition, although only the IDT electrode  211 , the first reflector electrode  212  and the second reflector electrode  213  are illustrated in the surface acoustic wave elements described herein, another IDT electrode, another reflector electrode, other circuitry, and the like can be included. 
       FIG. 3  is a cross sectional view representing a first variation of the surface acoustic wave element according to the present disclosure. Similar to  FIG. 2B ,  FIG. 3  shows a cross sectional view of the surface acoustic wave element taken along line I′-I′ illustrated in  FIG. 1A , in an extending direction of electrode fingers of the IDT electrode  211 . The same applies to  FIGS. 4 to 6  discussed below. 
     The first variation is different from the surface acoustic wave element shown in  FIGS. 2A and 2B  in that a silicon nitride (SiN) film  225  is formed between the first silicon dioxide film  221  and the silicon oxynitride film  222 . Other than the presence of the silicon nitride film  225 , the construction of the surface acoustic wave element illustrated in  FIG. 3  is similar to the surface acoustic wave element described above with respect to  FIGS. 2A and 2B . 
     In particular, according to this first variation, the silicon nitride film  225  is formed in contact with the first silicon dioxide film  221  having a certain film thickness formed to cover the IDT electrode  211  and the like on the top surface  210   a  of the piezoelectric substrate  210 . The silicon nitride film  225  has a first film thickness, but a region  225   a  covering at least one portion of the IDT electrode  211  has a second film thickness greater than the first film thickness. The silicon oxynitride film  222  having a certain film thickness is formed in contact with the silicon nitride film  225 . A second silicon dioxide film  223  is further formed to have a certain film thickness in contact with the silicon oxynitride film  222 . 
     According to this first variation, the double-layer structure formed by the silicon oxynitride film  222  and the second silicon dioxide film  223  can prevent both moisture absorption into the first silicon dioxide film  221  and oxidation of the silicon oxynitride film  222 . Therefore, a deterioration of the propagation characteristics due to the moisture absorption into the first silicon dioxide film  221  can be prevented and the changes in the frequency characteristics due to the oxidation of the silicon oxynitride film  222  can also be prevented. 
     Further, according to this first variation, the silicon nitride film  225  is formed to have a second film thickness greater than the first film thickness in a region  225   a  covering at least one portion of the IDT electrode  211 . Because the silicon nitride has an acoustic velocity greater than that of the silicon dioxide, the surface acoustic wave energy can be intensively distributed around the region  225   a  covering at least one portion of the IDT electrode  211  and accordingly, the propagation characteristics can be improved. In addition, configuring the compositional ratio of nitrogen and oxygen of the silicon oxynitride film  222  can provide adjustability for an acoustic velocity of the silicon oxynitride film  222 . Accordingly, it is possible to properly control the propagation of the surface acoustic wave to improve the propagation characteristics. 
     According to this first variation, disposing the silicon nitride film  225  in addition to the silicon oxynitride film  222  can additionally block the permeation of moisture. Therefore, it is possible to further improve the water resistance capability of the surface acoustic wave element. 
       FIG. 4  is a cross sectional view representing a second variation of the surface acoustic wave element according to the present disclosure. The second variation is structurally different from the surface acoustic wave element shown in  FIGS. 2A and 2B  in that a silicon nitride film  225  is formed to be sandwiched between the first silicon dioxide film  221  and the silicon oxynitride film  222 . Further, the second variation is different from the first variation in that the silicon nitride film  225  covers only a portion of the first silicon dioxide film  221 . However, other than the presence of the silicon nitride film  225  sandwiched between the first silicon dioxide film  221  and the silicon oxynitride film  222 , the construction of the surface acoustic wave element illustrated in  FIG. 4  is similar to the surface acoustic wave element described above with respect to  FIGS. 2A and 2B . 
     In particular, according to this second variation, a silicon nitride film  225  having a certain film thickness is formed in a region  225   a  covering at least one portion of the IDT electrode  211 . The silicon nitride film  225  is in contact with the first silicon dioxide film  221  that has a certain film thickness and is formed to cover the IDT electrode  211  and the like on the top surface  210   a  of the piezoelectric substrate  210 . The silicon oxynitride film  222  having a certain film thickness is formed in contact with the first silicon dioxide film  221  to cover the silicon nitride film  225 . A second silicon dioxide film  223  having a certain film thickness is further formed in contact with the silicon oxynitride film  222 . 
     As with the surface acoustic wave elements described above with respect to  FIGS. 2A and 2B , and  FIG. 3 , the double-layer structure formed by the silicon oxynitride film  222  and the second silicon dioxide film  223  can prevent both the moisture absorption into the first silicon dioxide film  221  and the oxidation of the silicon oxynitride film  222 . Therefore, a deterioration of the propagation characteristics due to the moisture absorption into the first silicon dioxide film  221  can be prevented and the changes in the frequency characteristics due to the oxidation of the silicon oxynitride film  222  can also be prevented. 
     Further, according to this second variation, the silicon nitride film  225  is formed only in the region  225   a  covering at least one portion of the IDT electrode  211 . Because the silicon nitride allows a greater acoustic velocity, the surface acoustic wave energy can be intensively distributed around the region  225   a  covering at least one portion of the IDT electrode  211  and accordingly the propagation characteristics can be improved. In addition, configuring the compositional ratio of nitrogen and oxygen of the silicon oxynitride film  222  can provide adjustability for an acoustic velocity of the silicon oxynitride film  222 . Accordingly, it is possible to properly control the propagation of the surface acoustic wave to improve the propagation characteristics. 
       FIG. 5  is a cross sectional view representing a third variation of the surface acoustic wave element according to the present disclosure. The third variation is structurally different from the surface acoustic wave element shown in  FIGS. 2A and 2B  in that a silicon oxynitride film  222  generally having a first film thickness also has a second film thickness greater than the first film thickness in a region  222   a  covering at least one portion of the IDT electrode  211 . However, other than the variation in the thickness of silicon oxynitride film  222 , the surface acoustic wave element illustrated in  FIG. 5  is similar to the surface acoustic wave element described above with respect to  FIGS. 2A and 2B . 
     In particular, according to the third variation, the silicon oxynitride film  222  is formed in contact with the first silicon dioxide film  221  having a certain film thickness formed to cover the IDT electrode  211  and the like on the top surface  210   a  of the piezoelectric substrate  210 . Although the silicon oxynitride film  222  generally has a first film thickness, the silicon oxynitride film  222  also has a second film thickness greater than the first film thickness in the region  222   a  covering at least one portion of the IDT electrode  211 . A second silicon dioxide film  223  is further formed to have a certain film thickness in contact with the silicon oxynitride film  222 . 
     As with the previously described surface acoustic wave elements, the double-layer structure formed by the silicon oxynitride film  222  and the second silicon dioxide film  223  can prevent both the moisture absorption into the first silicon dioxide film  221  and the oxidation of the silicon oxynitride film  222 . Therefore, a deterioration of the propagation characteristics due to the moisture absorption into the first silicon dioxide film  221  can be prevented and the changes in the frequency characteristics due to the oxidation of the silicon oxynitride film  222  can also be prevented. 
     Further, according to this third variation, the silicon oxynitride film  222  is formed to have a second film thickness greater than the first film thickness in the region  222   a  covering at least one portion of the IDT electrode  211 . Here, the silicon oxynitride film  222  may have the acoustic velocity adjusted to a desired value by configuring the compositional ratio of nitrogen and oxygen contained therein. Therefore, it can be possible to control the energy distribution of the surface acoustic wave, such that the propagation characteristics can be improved. 
       FIG. 6  is a cross sectional view representing an example of a surface acoustic wave element as a comparative example. According to the comparative example, a silicon dioxide film  121  is formed to have a certain film thickness to cover an IDT electrode  111  and the like on the top surface  110   a  of a piezoelectric substrate  110 . The silicon nitride film  125  having a certain film thickness is formed in contact with the silicon dioxide film  121  only in a region  125   a  covering at least one portion of the IDT electrode  111 . A silicon oxynitride film  122  having a certain film thickness is further formed in contact with the silicon dioxide film  121  to cover the silicon nitride film  125 . 
     According to the comparative example, the silicon nitride film  125  is formed only in the region covering at least one portion of the IDT electrode  111  around which the surface acoustic wave energy can be intensively distributed, such that the propagation characteristics can be improved. Further, the silicon oxynitride film  122  can prevent the moisture absorption into the silicon dioxide film  121 . 
     In the surface acoustic wave elements previously described with respect to  FIGS. 2-5 , the second silicon dioxide film  223  is provided as an oxidation prevention film to prevent the oxidation of the silicon oxynitride film  222  corresponding to the silicon oxynitride film  122 , such that changes in the frequency characteristics can be avoided. In contrast, in the comparative example, a surface of the silicon oxynitride film  122  may be oxidized and converted to silicon dioxide, and therefore the frequency characteristics of the surface acoustic wave element may be changed. 
     As discussed above, embodiments of the surface acoustic wave elements can be configured as or used in filters, for example. In turn, a surface acoustic wave (SAW) filter using one or more surface acoustic wave elements may be incorporated into and packaged as a module that may ultimately be used in an electronic device, such as a wireless communications device, for example.  FIG. 7  is a block diagram illustrating one example of a module  300  including a SAW filter  310 . The SAW filter  310  may be implemented on one or more die(s)  320  including one or more connection pads  322 . For example, the SAW filter  310  may include a connection pad  322  that corresponds to an input contact for the SAW filter and another connection pad  322  that corresponds to an output contact for the SAW filter. The packaged module  300  includes a packaging substrate  330  that is configured to receive a plurality of components, including the die  320 . A plurality of connection pads  332  can be disposed on the packaging substrate  330 , and the various connection pads  322  of the SAW filter die  320  can be connected to the connection pads  332  on the packaging substrate  330  via electrical connectors  334 , which can be solder bumps or wirebonds, for example, to allow for passing of various signals to and from the SAW filter  310 . The module  300  may optionally further include other circuitry die  340 , such as, for example one or more additional filter(s), amplifiers, pre-filters, modulators, demodulators, down converters, and the like, as would be known to one of skill in the art of semiconductor fabrication in view of the disclosure herein. In some embodiments, the module  300  can also include one or more packaging structures to, for example, provide protection and facilitate easier handling of the module  300 . Such a packaging structure can include an overmold formed over the packaging substrate  330  and dimensioned to substantially encapsulate the various circuits and components thereon. 
     Various examples and embodiments of the SAW filter  310  can be used in a wide variety of electronic devices. For example, the SAW filter  310  can be used in an antenna duplexer, which itself can be incorporated into a variety of electronic devices, such as RF front-end modules and communication devices. 
     Referring to  FIG. 8 , there is illustrated a block diagram of one example of a front-end module  400 , which may be used in an electronic device such as a wireless communications device (e.g., a mobile phone) for example. The front-end module  400  includes an antenna duplexer  410  having a common node  402 , an input node  404 , and an output node  406 . An antenna  510  is connected to the common node  402 . 
     The antenna duplexer  410  may include one or more transmission filters  412  connected between the input node  404  and the common node  402 , and one or more reception filters  414  connected between the common node  402  and the output node  406 . The passband(s) of the transmission filter(s) are different from the passband(s) of the reception filters. Examples of the SAW filter  310  can be used to form the transmission filter(s)  412  and/or the reception filter(s)  414 . An inductor or other matching component  420  may be connected at the common node  402 . 
     The front-end module  400  further includes a transmitter circuit  432  connected to the input node  404  of the duplexer  410  and a receiver circuit  434  connected to the output node  406  of the duplexer  410 . The transmitter circuit  432  can generate signals for transmission via the antenna  510 , and the receiver circuit  434  can receive and process signals received via the antenna  510 . In some embodiments, the receiver and transmitter circuits are implemented as separate components, as shown in  FIG. 8 , however in other embodiments these components may be integrated into a common transceiver circuit or module. As will be appreciated by those skilled in the art, the front-end module  400  may include other components that are not illustrated in  FIG. 8  including, but not limited to, switches, electromagnetic couplers, amplifiers, processors, and the like. 
       FIG. 9  is a block diagram of one example of a wireless device  500  including the antenna duplexer  410  shown in  FIG. 8 . The wireless device  500  can be a cellular phone, smart phone, tablet, modem, communication network or any other portable or non-portable device configured for voice or data communication. The wireless device  500  can receive and transmit signals from the antenna  510 . The wireless device includes an embodiment of a front-end module  400  similar to that discussed above with reference to  FIG. 8 . The front-end module  400  includes the duplexer  410 , as discussed above. In the example shown in  FIG. 9  the front-end module  400  further includes an antenna switch  440 , which can be configured to switch between different frequency bands or modes, such as transmit and receive modes, for example. In the example illustrated in  FIG. 9 , the antenna switch  440  is positioned between the duplexer  410  and the antenna  510 ; however, in other examples the duplexer  410  can be positioned between the antenna switch  440  and the antenna  510 . In other examples the antenna switch  440  and the duplexer  410  can be integrated into a single component. 
     The front-end module  400  includes a transceiver  430  that is configured to generate signals for transmission or to process received signals. The transceiver  430  can include the transmitter circuit  432 , which can be connected to the input node  404  of the duplexer  410 , and the receiver circuit  434 , which can be connected to the output node  406  of the duplexer  410 , as shown in the example of  FIG. 8 . 
     Signals generated for transmission by the transmitter circuit  432  are received by a power amplifier (PA) module  450 , which amplifies the generated signals from the transceiver  430 . The power amplifier module  450  can include one or more power amplifiers. The power amplifier module  450  can be used to amplify a wide variety of RF or other frequency-band transmission signals. For example, the power amplifier module  450  can receive an enable signal that can be used to pulse the output of the power amplifier to aid in transmitting a wireless local area network (WLAN) signal or any other suitable pulsed signal. The power amplifier module  450  can be configured to amplify any of a variety of types of signal, including, for example, a Global System for Mobile (GSM) signal, a code division multiple access (CDMA) signal, a W-CDMA signal, a Long-Term Evolution (LTE) signal, or an EDGE signal. In certain embodiments, the power amplifier module  450  and associated components including switches and the like can be fabricated on gallium arsenide (GaAs) substrates using, for example, high-electron mobility transistors (pHEMT) or insulated-gate bipolar transistors (BiFET), or on a Silicon substrate using complementary metal-oxide semiconductor (CMOS) field effect transistors. 
     Still referring to  FIG. 9 , the front-end module  400  may further include a low noise amplifier module  460 , which amplifies received signals from the antenna  510  and provides the amplified signals to the receiver circuit  434  of the transceiver  430 . 
     The wireless device  500  of  FIG. 9  further includes a power management sub-system  520  that is connected to the transceiver  430  and manages the power for the operation of the wireless device  500 . The power management system  520  can also control the operation of a baseband sub-system  530  and various other components of the wireless device  500 . The power management system  520  can include, or can be connected to, a battery (not shown) that supplies power for the various components of the wireless device  500 . The power management system  520  can further include one or more processors or controllers that can control the transmission of signals, for example. In one embodiment, the baseband sub-system  530  is connected to a user interface  540  to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system  530  can also be connected to memory  550  that is configured to store data and/or instructions to facilitate the operation of the wireless device, and/or to provide storage of information for the user. 
     Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. It is to be appreciated that embodiments of the methods and apparatuses discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the description or illustrated in the accompanying drawings. The methods and apparatuses are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. Any references to front and back, left and right, top and bottom, upper and lower, and vertical and horizontal are intended for convenience of description, not to limit the present systems and methods or their components to any one positional or spatial orientation Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention should be determined from proper construction of the appended claims, and their equivalents.