Patent Grant
11901873
A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by anyone of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever.
This disclosure relates to radio frequency filters using acoustic wave resonators, and specifically to filters for use in communications equipment.
A radio frequency (RF) filter is a two-port device configured to pass some frequencies and to stop other frequencies, where “pass” means transmit with relatively low signal loss and “stop” means block or substantially attenuate. The range of frequencies passed by a filter is referred to as the “pass-band” of the filter. The range of frequencies stopped by such a filter is referred to as the “stop-band” of the filter. A typical RF filter has at least one pass-band and at least one stop-band. Specific requirements on a pass-band or stop-band depend on the specific application. For example, a “pass-band” may be defined as a frequency range where the insertion loss of a filter is better than a defined value such as 1 dB, 2 dB, or 3 dB. A “stop-band” may be defined as a frequency range where the rejection of a filter is greater than a defined value such as 20 dB, 30 dB, 40 dB, or greater depending on application.
RF filters are used in communications systems where information is transmitted over wireless links. For example, RF filters may be found in the RF front-ends of cellular base stations, mobile telephone and computing devices, satellite transceivers and ground stations, IoT (Internet of Things) devices, laptop computers and tablets, fixed point radio links, and other communications systems. RF filters are also used in radar and electronic and information warfare systems.
RF filters typically require many design trade-offs to achieve, for each specific application, the best compromise between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size and cost. Specific design and manufacturing methods and enhancements can benefit simultaneously one or several of these requirements.
Performance enhancements to the RF filters in a wireless system can have broad impact to system performance. Improvements in RF filters can be leveraged to provide system performance improvements such as larger cell size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, higher reliability, etc. These improvements can be realized at many levels of the wireless system both separately and in combination, for example at the RF module, RF transceiver, mobile or fixed sub-system, or network levels.
The desire for wider communication channel bandwidths will inevitably lead to the use of higher frequency communications bands. The current LTE′ (Long Term Evolution) specification defines frequency bands from 3.3 GHz to 5.9 GHz. Some of these bands are not presently used. Future proposals for wireless communications include millimeter wave communication bands with frequencies up to 28 GHz.
High performance RF filters for present communication systems commonly incorporate acoustic wave resonators including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic wave resonators (FBAR), and other types of acoustic resonators. However, these existing technologies are not well-suited for use at the higher frequencies proposed for future communications networks.
Throughout this description, elements appearing in figures are assigned three-digit or four-digit reference designators, where the two least significant digits are specific to the element and the one or two most significant digit is the figure number where the element is first introduced. An element that is not described in conjunction with a figure may be presumed to have the same characteristics and function as a previously-described element having the same reference designator.
Description of Apparatus
The XBAR 100 is made up of a thin film conductor pattern formed on a surface of a piezoelectric plate 110 having parallel front and back surfaces 112, 114, respectively. The piezoelectric plate is a thin single-crystal layer of a piezoelectric material such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride. The piezoelectric plate is cut such that the orientation of the X, Y, and Z crystalline axes with respect to the front and back surfaces is known and consistent. In the examples presented in this patent, the piezoelectric plates are Z-cut, which is to say the Z axis is normal to the front and back surfaces 112, 114. However, XBARs may be fabricated on piezoelectric plates with other crystallographic orientations.
The back surface 114 of the piezoelectric plate 110 is attached to a surface of the substrate 120 except for a portion of the piezoelectric plate 110 that forms a diaphragm 115 spanning a cavity 140 formed in the substrate. The portion of the piezoelectric plate that spans the cavity is referred to herein as the “diaphragm” 115 due to its physical resemblance to the diaphragm of a microphone. As shown in
The substrate 120 provides mechanical support to the piezoelectric plate 110. The substrate 120 may be, for example, silicon, sapphire, quartz, or some other material or combination of materials. The back surface 114 of the piezoelectric plate 110 may be bonded to the substrate 120 using a wafer bonding process. Alternatively, the piezoelectric plate 110 may be grown on the substrate 120 or attached to the substrate in some other manner. The piezoelectric plate 110 may be attached directly to the substrate or may be attached to the substrate 120 via one or more intermediate material layers.
“Cavity” has its conventional meaning of “an empty space within a solid body.” The cavity 140 may be a hole completely through the substrate 120 (as shown in Section A-A and Section B-B) or a recess in the substrate 120 (as shown subsequently in
The conductor pattern of the XBAR 100 includes an interdigital transducer (IDT) 130. The IDT 130 includes a first plurality of parallel fingers, such as finger 136, extending from a first busbar 132 and a second plurality of fingers extending from a second busbar 134. The first and second pluralities of parallel fingers are interleaved. The interleaved fingers overlap for a distance AP, commonly referred to as the “aperture” of the IDT. The center-to-center distance L between the outermost fingers of the IDT 130 is the “length” of the IDT.
The first and second busbars 132, 134 serve as the terminals of the XBAR 100. A radio frequency or microwave signal applied between the two busbars 132, 134 of the IDT 130 excites a primary acoustic mode within the piezoelectric plate 110. As will be discussed in further detail, the primary acoustic mode is a bulk shear mode where acoustic energy propagates along a direction substantially orthogonal to the surface of the piezoelectric plate 110, which is also normal, or transverse, to the direction of the electric field created by the IDT fingers. Thus, the XBAR is considered a transversely-excited film bulk wave resonator.
The IDT 130 is positioned on the piezoelectric plate 110 such that at least the fingers of the IDT 130 are disposed on the portion 115 of the piezoelectric plate that spans, or is suspended over, the cavity 140. As shown in
For ease of presentation in
A front-side dielectric layer 214 may optionally be formed on the front side of the piezoelectric plate 110. The “front side” of the XBAR is, by definition, the surface facing away from the substrate. The front-side dielectric layer 214 has a thickness tfd. The front-side dielectric layer 214 is formed between the IDT fingers 238. Although not shown in
The IDT fingers 238 may be aluminum, a substantially aluminum alloy, copper, a substantially copper alloy, tungsten, molybdenum, beryllium, gold, or some other conductive material. Thin (relative to the total thickness of the conductors) layers of other metals, such as chromium or titanium, may be formed under and/or over the fingers to improve adhesion between the fingers and the piezoelectric plate 110 and/or to passivate or encapsulate the fingers. The busbars (132, 134 in
Dimension p is the center-to-center spacing or “pitch” of the IDT fingers, which may be referred to as the pitch of the IDT and/or the pitch of the XBAR. Dimension w is the width or “mark” of the IDT fingers. The IDT of an XBAR differs substantially from the IDTs used in surface acoustic wave (SAW) resonators. In a SAW resonator, the pitch of the IDT is one-half of the acoustic wavelength at the resonance frequency. Additionally, the mark-to-pitch ratio of a SAW resonator IDT is typically close to 0.5 (i.e. the mark or finger width is about one-fourth of the acoustic wavelength at resonance). In an XBAR, the pitch p of the IDT is typically 2 to 20 times the width w of the fingers. In addition, the pitch p of the IDT is typically 2 to 20 times the thickness is of the piezoelectric slab 212. The width of the IDT fingers in an XBAR is not constrained to one-fourth of the acoustic wavelength at resonance. For example, the width of XBAR IDT fingers may be 500 nm or greater, such that the IDT can be fabricated using optical lithography. The thickness tm of the IDT fingers may be from 100 nm to about equal to the width w. The thickness of the busbars (132, 134 in
An acoustic Bragg reflector is a stack of multiple layers that alternate between materials having high acoustic impedance and materials have low acoustic impedance. “High” and “low” are relative terms. For each layer, the standard for comparison is the adjacent layers. Each “high” acoustic impedance layer has an acoustic impedance higher than that of the adjacent low acoustic impedance layer or layers. Each “low” acoustic impedance layer has an acoustic impedance lower than that of the adjacent high acoustic impedance layer or layers. Each of the layers has a thickness equal to, or about, one-fourth of the acoustic wavelength in the respective material at predetermined frequency such that reflections from the interfaces between adjacent layers add in-phase. The predetermined frequency may be, for example, the resonance frequency or anti-resonance frequency of an acoustic resonator, or a frequency within a passband of a filter incorporating the acoustic resonator. Materials having comparatively low acoustic impedance include silicon dioxide, silicon oxycarbide, aluminum, and certain plastics such as cross-linked polyphenylene polymers. Materials having comparatively high acoustic impedance include silicon nitride, aluminum nitride, silicon carbide, and metals such as molybdenum, tungsten, gold, and platinum. Note that metal layers cannot be used in a Bragg reflector for an XBAR device. The presence of a metal layer distorts the electric field generated by the IDT and greatly reduces electromechanical coupling. All of the high acoustic impedance layers of an acoustic Bragg reflector are not necessarily the same material, and all of the low acoustic impedance layers are not necessarily the same material. Depending on the materials used, an acoustic Bragg reflector may have a few as five layers or as many as twenty layers.
The IDT fingers 338 may be aluminum, a substantially aluminum alloy, copper, a substantially copper alloy, tungsten, molybdenum, beryllium, gold, or some other conductive material. Thin (relative to the total thickness of the conductors) layers of other metals, such as chromium or titanium, may be formed under and/or over the fingers to improve adhesion between the fingers 338 and the piezoelectric plate 310 and/or to passivate or encapsulate the fingers. The busbars (e.g. 132, 134 in
Dimension p is the center-to-center spacing or “pitch” of the IDT fingers, which may be referred to as the pitch of the IDT and/or the pitch of the XBAR. Dimension w is the width or “mark” of the IDT fingers.
A front-side partial Bragg reflector 350 is formed on the front side (i.e. the upper side as shown in
A back-side partial Bragg reflector 360 is formed on the back side (i.e. the lower side as shown in
A primary benefit of incorporating the partial Bragg reflectors 350, 360 into the XBAR 300 is the increased thickness of the diaphragm. Depending on the materials used in the partial Bragg reflectors 350, 360, the thickness of the diaphragm of the XBAR 300 will be three to five times the thickness of the diaphragm 115 of the XBAR 100 of
The thicker diaphragm of the XBAR 300 will also have higher thermal conductivity, particularly if one or more layers in the partial Bragg reflectors is a high thermal conductivity dielectric material such as aluminum nitride. Higher thermal conductivity results in more efficient removal of heat from the diaphragm, which may allow the use of a smaller resonator area for a given heat load or power dissipation.
The XBAR 300 will also have higher capacitance per unit as compared with the XBAR 100 of
The dashed line 520 is a plot of the magnitude of admittance as a function of frequency for a conventional XBAR (i.e. an XBAR without partial Bragg reflectors). The piezoelectric plate is lithium niobate 400 nm thick. The IDT is aluminum 100 nm thick. The pitch and mark of the IDT fingers are 3.7 μm and 0.47 μm, respectively. The resonance frequency is 4.71 GHz and the anti-resonance frequency is 5.32 GHz. The different between the anti-resonance and resonance frequencies is 610 MHz, or about 12.2% of the average of the resonance and anti-resonance frequencies.
The incorporation of partial Bragg reflectors in the XBAR devices 300, 400 results in a stiffer diaphragm with substantially higher thermal conductivity and potentially lower excitation of spurious modes compared to a conventional XBAR device. These benefits come at the cost of reducing electromechanical coupling and a correspondingly lower difference between the resonance and anti-resonance frequencies.
The dashed line 620 is a plot of the magnitude of admittance as a function of frequency for a similar XBAR with the same construction except the pitch and mark of the IDT fingers are 3.75 μm and 1.12 μm, respectively. The resonance frequency is 4.67 GHz and the anti-resonance frequency is 5.01 GHz. Changing the IDT pitch from 4.25 μm to 3.75 μm increases the resonance and anti-resonance frequencies by about 50 MHz. Varying the pitch over a range from 3 μm to 5 μm will provide a tuning range of about 200 MHz.
Description of Methods
The flow chart of
Thin plates of single-crystal piezoelectric materials bonded to a non-piezoelectric substrate are commercially available. At the time of this application, both lithium niobate and lithium tantalate plates are available bonded to various substrates including silicon, quartz, and fused silica. Thin plates of other piezoelectric materials may be available now or in the future. The thickness of the piezoelectric plate may be between 300 nm and 1000 nm. The piezoelectric plate may be, for example, Z-cut, rotated Z-cut, or rotated Y-cut lithium niobate or lithium tantalate. The piezoelectric plate may be some other material and/or some other cut. The substrate may be silicon. When the substrate is silicon, a layer of SiO2 may be disposed between the piezoelectric plate and the substrate. The substrate may be some other material that allows formation of deep cavities by etching or other processing.
In one variation of the method 700, one or more cavities are formed in the substrate at 710A, before the piezoelectric plate is bonded to the substrate at 730. A separate cavity may be formed for each resonator in a filter device. The one or more cavities may be formed using conventional photolithographic and etching techniques. For example, the cavities may be formed using deep reactive ion etching (DRIE). Typically, the cavities formed at 710A will not penetrate through the substrate.
At 720 a lower partial acoustic Bragg reflector is formed by depositing layers of high acoustic impedance and low acoustic impedance dielectric materials onto the surface of the piezoelectric plate. Each layer has a thickness equal to or about one-fourth of the acoustic wavelength in the respective material at a predetermined frequency. The predetermined frequency may be, for example, the resonance frequency of the XBAR device, the antiresonance frequency of the XBAR device, or a frequency with the passband of a filter incorporating the XBAR device.
Materials having comparatively low acoustic impedance include silicon dioxide, silicon oxycarbide, and certain plastics such as cross-linked polyphenylene polymers. Materials having comparatively high acoustic impedance include silicon nitride and aluminum nitride. Both layers of the lower partial acoustic Bragg reflector may be deposited on either the surface of the piezoelectric plate on the sacrificial substrate 702 or a surface of the device substrate 704. Alternatively, the low acoustic impedance layer of the acoustic Bragg reflector may be deposited on the surface of the piezoelectric plate on the sacrificial substrate 702 and the high acoustic impedance layer of the acoustic Bragg reflector may be deposited on a surface of the device substrate 704.
At 730, the piezoelectric plate on the sacrificial substrate 702 and the device substrate 704 may be bonded such that the layers of the lower partial acoustic Bragg reflector are sandwiched between the piezoelectric plate and the device substrate. The piezoelectric plate on the sacrificial substrate 702 and the device substrate 704 may be bonded using a wafer bonding process such as direct bonding, surface-activated or plasma-activated bonding, electrostatic bonding, or some other bonding technique. Note that, when layers of the partial acoustic Bragg reflector are deposited on both the piezoelectric plate and the device substrate, the bonding will occur between the layers of the partial acoustic Bragg reflector. It is not necessary, although possible, to pattern the layers of the lower partial acoustic Bragg reflector. The layers of the lower partial acoustic Bragg reflector may extend between the piezoelectric plate and the substrate over all, or substantially all, of the area of the device.
After the piezoelectric plate on the sacrificial substrate 702 and the device substrate 704 are bonded, the sacrificial substrate, and any intervening layers, are removed at 740 to expose the surface of the piezoelectric plate (the surface that previously faced the sacrificial substrate). The sacrificial substrate may be removed, for example, by material-dependent wet or dry etching or some other process.
Conductor patterns and dielectric layers defining one or of XBAR devices are formed at 750. Typically, a filter device will have two or more conductor layers that are sequentially deposited and patterned. The conductor layers may include bonding pads, gold or solder bumps, or other means for making connection between the device and external circuitry. The conductor layers may be, for example, aluminum, an aluminum alloy, copper, a copper alloy, molybdenum, tungsten, beryllium, gold, or some other conductive metal. Optionally, one or more layers of other materials may be disposed below (i.e. between the conductor layer and the piezoelectric plate) and/or on top of the conductor layer. For example, a thin film of titanium, chrome, or other metal may be used to improve the adhesion between the conductor layers and the piezoelectric plate. The conductor layers may include bonding pads, gold or solder bumps, or other means for making connection between the device and external circuitry.
Conductor patterns may be formed at 750 by depositing the conductor layers over the surface of the piezoelectric plate and removing excess metal by etching through patterned photoresist. Alternatively, the conductor patterns may be formed at 750 using a lift-off process. Photoresist may be deposited over the piezoelectric plate and patterned to define the conductor pattern. The conductor layer may be deposited in sequence over the surface of the piezoelectric plate. The photoresist may then be removed, which removes the excess material, leaving the conductor pattern.
At 760, both layers of the upper partial acoustic Bragg reflector may be deposited on the surface of the piezoelectric plate between and, optionally, over the conductors of the conductor pattern formed at 750.
In a second variation of the process 700, one or more cavities are formed in the back side of the substrate at 710B after all of the conductor patterns and dielectric layers are formed at 750 and 760. A separate cavity may be formed for each resonator in a filter device. The one or more cavities may be formed using an anisotropic or orientation-dependent dry or wet etch to open holes through the back-side of the substrate to the piezoelectric plate.
In a third variation of the process 700, one or more cavities in the form of recesses in the substrate may be formed at 710C by etching the substrate using an etchant introduced through openings in the piezoelectric plate and partial Bragg reflectors. A separate cavity may be formed for each resonator in a filter device. The one or more cavities formed at 710C will not penetrate through the substrate.
When the one or more cavities are formed by etching the substrate at either 710B or 710C, it is preferable that the lower partial acoustic Bragg reflector act as an etch-stop to limit the extent of the etching process. To this end, the layer of the lower partial acoustic Bragg reflector adjacent to the substrate be resistant or impervious to the etchant used to form the cavities.
In all variations of the process 700, the filter device is completed at 770. Actions that may occur at 770 include depositing an encapsulation/passivation layer such as SiO2 or Si3O4 over all or a portion of the device and/or forming bonding pads or solder bumps or other means for making connection between the device and external circuitry if these steps were not performed at 730. Other actions at 770 may include excising individual devices from a wafer containing multiple devices; other packaging steps; and testing. Another action that may occur at 770 is to tune the resonant frequencies of the resonators within the device by adding or removing metal or dielectric material from the front side of the device. After the filter device is completed, the process ends at 795.
A variation of the process 700 starts with a single-crystal piezoelectric wafer at 702 instead of a thin piezoelectric plate on a sacrificial substrate of a different material. Ions are implanted to a controlled depth beneath a surface of the piezoelectric wafer (not shown in
Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and procedures disclosed or claimed. Although many of the examples presented herein involve specific combinations of method acts or system elements, it should be understood that those acts and those elements may be combined in other ways to accomplish the same objectives. With regard to flowcharts, additional and fewer steps may be taken, and the steps as shown may be combined or further refined to achieve the methods described herein. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments.
As used herein, “plurality” means two or more. As used herein, a “set” of items may include one or more of such items. As used herein, whether in the written description or the claims, the terms “comprising”, “including”, “carrying”, “having”, “containing”, “involving”, and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of”, respectively, are closed or semi-closed transitional phrases with respect to claims. Use of ordinal terms such as “first”, “second”, “third”, etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. As used herein, “and/or” means that the listed items are alternatives, but the alternatives also include any combination of the listed items.
This patent claims priority from provisional patent application 62/818,568, filed Mar. 14, 2019, entitled XBAR WITH PARTIAL BRAGG REFLECTOR. This patent is related to application Ser. No. 16/230,443, filed Dec. 21, 2018, entitled TRANSVERSELY-EXCITED FILM BULK ACOUSTIC RESONATOR, now U.S. Pat. No. 10,491,192.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5446330 | Eda et al. | Aug 1995 | A |
| 5552655 | Stokes et al. | Sep 1996 | A |
| 5726610 | Allen et al. | Mar 1998 | A |
| 5853601 | Krishaswamy | Dec 1998 | A |
| 6377140 | Ehara et al. | Apr 2002 | B1 |
| 6516503 | Ikada et al. | Feb 2003 | B1 |
| 6540827 | Levy et al. | Apr 2003 | B1 |
| 6707229 | Martin | Mar 2004 | B1 |
| 6710514 | Ikada et al. | Mar 2004 | B2 |
| 7345400 | Nakao et al. | Mar 2008 | B2 |
| 7463118 | Jacobsen | Dec 2008 | B2 |
| 7535152 | Ogami et al. | May 2009 | B2 |
| 7684109 | Godshalk et al. | Mar 2010 | B2 |
| 7728483 | Tanaka | Jun 2010 | B2 |
| 7868519 | Umeda | Jan 2011 | B2 |
| 7941103 | Iwamoto et al. | May 2011 | B2 |
| 7965015 | Tai | Jun 2011 | B2 |
| 8278802 | Lee et al. | Oct 2012 | B1 |
| 8294330 | Abbott et al. | Oct 2012 | B1 |
| 8344815 | Yamanaka | Jan 2013 | B2 |
| 8816567 | Zuo et al. | Aug 2014 | B2 |
| 8829766 | Milyutin et al. | Sep 2014 | B2 |
| 8932686 | Hayakawa et al. | Jan 2015 | B2 |
| 9093979 | Wang | Jul 2015 | B2 |
| 9130145 | Martin et al. | Sep 2015 | B2 |
| 9219466 | Meltaus | Dec 2015 | B2 |
| 9276557 | Nordquist et al. | Mar 2016 | B1 |
| 9369105 | Li | Jun 2016 | B1 |
| 9425765 | Rinaldi | Aug 2016 | B2 |
| 9525398 | Olsson | Dec 2016 | B1 |
| 9640750 | Nakanishi et al. | May 2017 | B2 |
| 9748923 | Kando et al. | Aug 2017 | B2 |
| 9762202 | Thalmayr et al. | Sep 2017 | B2 |
| 9780759 | Kimura et al. | Oct 2017 | B2 |
| 9837984 | Khlat et al. | Dec 2017 | B2 |
| 10079414 | Guyette et al. | Sep 2018 | B2 |
| 10187039 | Komatsu et al. | Jan 2019 | B2 |
| 10200013 | Bower et al. | Feb 2019 | B2 |
| 10211806 | Bhattacharjee | Feb 2019 | B2 |
| 10284176 | Solal | May 2019 | B1 |
| 10389332 | Bhattacharjee | Aug 2019 | B2 |
| 10491192 | Plesski et al. | Nov 2019 | B1 |
| 10601392 | Plesski et al. | Mar 2020 | B2 |
| 10637438 | Garcia et al. | Apr 2020 | B2 |
| 10644674 | Takamine | May 2020 | B2 |
| 10756697 | Plesski et al. | Aug 2020 | B2 |
| 10790802 | Yantchev et al. | Sep 2020 | B2 |
| 10797675 | Plesski | Oct 2020 | B2 |
| 10797680 | Mimura | Oct 2020 | B2 |
| 10826462 | Plesski et al. | Nov 2020 | B2 |
| 10868512 | Garcia et al. | Dec 2020 | B2 |
| 10917070 | Plesski et al. | Feb 2021 | B2 |
| 20020079986 | Ruby et al. | Jun 2002 | A1 |
| 20020158714 | Kaitila et al. | Oct 2002 | A1 |
| 20020189062 | Lin et al. | Dec 2002 | A1 |
| 20030080831 | Naumenko et al. | May 2003 | A1 |
| 20030199105 | Kub et al. | Oct 2003 | A1 |
| 20040100164 | Murata | May 2004 | A1 |
| 20040261250 | Kadota et al. | Dec 2004 | A1 |
| 20050185026 | Noguchi et al. | Aug 2005 | A1 |
| 20050218488 | Matsuo | Oct 2005 | A1 |
| 20050264136 | Tsutsumi et al. | Dec 2005 | A1 |
| 20060179642 | Kawamura | Aug 2006 | A1 |
| 20070182510 | Park | Aug 2007 | A1 |
| 20070188047 | Tanaka | Aug 2007 | A1 |
| 20070194863 | Shibata et al. | Aug 2007 | A1 |
| 20070267942 | Matsumoto et al. | Nov 2007 | A1 |
| 20080246559 | Ayazi | Oct 2008 | A1 |
| 20100064492 | Tanaka | Mar 2010 | A1 |
| 20100123367 | Tai et al. | May 2010 | A1 |
| 20110018389 | Fukano et al. | Jan 2011 | A1 |
| 20110018654 | Bradley et al. | Jan 2011 | A1 |
| 20110109196 | Goto | May 2011 | A1 |
| 20110278993 | Iwamoto | Nov 2011 | A1 |
| 20120286900 | Kadota et al. | Nov 2012 | A1 |
| 20130234805 | Takahashi | Sep 2013 | A1 |
| 20130271238 | Onda | Oct 2013 | A1 |
| 20130278609 | Stephanou et al. | Oct 2013 | A1 |
| 20130321100 | Wang | Dec 2013 | A1 |
| 20140130319 | Iwamoto | May 2014 | A1 |
| 20140145556 | Kadota | May 2014 | A1 |
| 20140151151 | Reinhardt | Jun 2014 | A1 |
| 20140152145 | Kando et al. | Jun 2014 | A1 |
| 20140173862 | Kando et al. | Jun 2014 | A1 |
| 20140225684 | Kando et al. | Aug 2014 | A1 |
| 20150042417 | Onodera et al. | Feb 2015 | A1 |
| 20150319537 | Perois et al. | Nov 2015 | A1 |
| 20150333730 | Meltaus | Nov 2015 | A1 |
| 20160028367 | Shealy | Jan 2016 | A1 |
| 20170063332 | Gilbert et al. | Mar 2017 | A1 |
| 20170179928 | Raihn et al. | Jun 2017 | A1 |
| 20170214381 | Bhattacharjee | Jul 2017 | A1 |
| 20170214387 | Burak et al. | Jul 2017 | A1 |
| 20170222617 | Mizoguchi | Aug 2017 | A1 |
| 20170222622 | Solal et al. | Aug 2017 | A1 |
| 20170370791 | Nakamura et al. | Dec 2017 | A1 |
| 20180005950 | Watanabe | Jan 2018 | A1 |
| 20180026603 | Iwamoto | Jan 2018 | A1 |
| 20180033952 | Yamamoto | Feb 2018 | A1 |
| 20180062615 | Kato et al. | Mar 2018 | A1 |
| 20180062617 | Yun et al. | Mar 2018 | A1 |
| 20180123016 | Gong | May 2018 | A1 |
| 20180191322 | Chang et al. | Jul 2018 | A1 |
| 20190068164 | Houlden et al. | Feb 2019 | A1 |
| 20190123721 | Takamine | Apr 2019 | A1 |
| 20190131953 | Gong | May 2019 | A1 |
| 20190273480 | Lin | Sep 2019 | A1 |
| 20190348966 | Campanella-Pineda | Nov 2019 | A1 |
| 20200036357 | Mimura | Jan 2020 | A1 |
| 20200235719 | Yantchev et al. | Jul 2020 | A1 |
| Number | Date | Country |
|---|---|---|
| 2016017104 | Feb 2016 | WO |
| 2018003273 | Jan 2018 | WO |
| Entry |
|---|
| T. Takai, H. Iwamoto, et al., “I.H.P.Saw Technology and its Application to Microacoustic Components (Invited). ” 2017 IEEE International Ultrasonics Symposium, Sep. 6-9, 2017. pp. 1-8. |
| R. Olsson III, K. Hattar et al. “A high electromechanical coupling coefficient SHO Lamb wave lithiumniobate micromechanical resonator and a method for fabrication” Sensors and Actuators A: Physical, vol. 209, Mar. 1, 2014, pp. 183-190. |
| M. Kadota, S. Tanaka, “Wideband acoustic wave resonators composed of hetero acoustic layer structure,” Japanese Journal of Applied Physics, vol. 57, No. 7S1. Published Jun. 5, 2018. 5 pages. |
| Y. Yang, R. Lu et al. “Towards Ka Band Acoustics: Lithium Niobat Asymmetrical Mode Piezoelectric MEMS Resonators”, Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign, May 2018. pp. 1-2. |
| Y. Yang, A. Gao et al. “5 Ghz Lithium Niobate Mems Resonators With High Fom of 153”, 2017 IEEE 30th International Conference in Micro Electro Mechanical Systems (MEMS). Jan. 22-26, 2017. pp. 942-945. |
| USPTO/ISA, International Search Report and Written Opinion for PCT Application No. PCT/US2019/036433 dated Aug. 29, 2019. |
| USPTO/ISA, International Search Report and Written Opinion for PCT Application No. PCT/US2019/058632 dated Jan. 17, 2020. |
| G. Manohar, “Investigation of Various Surface Acoustic Wave Design Configurations for Improved Sensitivity.” Doctoral dissertation, University of South Florida, USA, Jan. 2012, 7 pages. |
| Ekeom, D. & Dubus, Bertrand & Volatier, A.. (2006). Solidly mounted resonator (SMR) FEM-BEM simulation. 1474-1477. 10.1109/ULTSYM.2006.371. |
| Mizutaui, K. and Toda, K., “Analysis of lamb wave propagation characteristics in rotated Ycut Xpropagation LiNbO3 plates.” Electron. Comm. Jpn. Pt. 1, 69, No. 4 (1986):47-55. doi:10.1002/ecja.4410690406. |
| Naumenko et al., “Optimal orientations of Lithium Niobate for resonator SAW filters”, 2003 IEEE Ultrasonics Symposium—pp. 2110-2113. (Year: 2003). |
| Buchanan “Ceramit Materials for Electronics” 3rd Edition, first published in 2004 by Marcel Dekker, Inc. pp. 496 (Year 2004). Jan. 2004. |
| Sorokin et al. Study of Microwave Acoustic Attenuation in a Multi-frequency Bulk Acoustic Resonator Based on a Synthetic Diamond Single Crystal Published in Acoustical Physics, vol. 61, No. 6, 2015 pp. 675 (Year 2015) Jan. 2015. |
| Material Properties of Tibtech Innovations, © 2018 TIBTECH Innovations (Year 2018) Jan. 2018. |
| Zou, Jie “High-Performance Aluminum Nitride Lamb Wave Resonators for RF Front-End Technology” University of California, Berkeley, Summer 2015, pp. 63 (Year 2015) Jan. 2015. |
| Santosh, G. , Surface acoustic wave devices on silicon using patterned and thin film ZnO, Ph.D. thesis, Feb. 2016, Indian Institute of technology Guwahati, Assam, India Feb. 2016. |
| Merriam Webster, dictionary meaning of the word “diaphragm”, since 1828, Merriam Webster (Year: 1828) 1828. |
| Kadota et al. “5.4 Ghz Lamb Wave Resonator on LiNbO3 Thin Crystal Plate and Its Application,” published in Japanese Journal of Applied Physics 50 (2011) 07HD11. (Year: 2011) 2011. |
| USPTO/ISA, International Search Report and Written Opinion for PCT Application No. PCT/US2020/45654 dated Oct. 29, 2020. 2020. |
| Safari et al. “Piezoelectric for Transducer Applications” published by Elsevier Science Ltd., pp. 4 (Year: 2000). 2020. |
| Moussa et al. Review on Triggered Liposomal Drug Delivery with a Focus on Ultrasound 2015, Bentham Science Publishers, pp. 16 (Year 2005) 2005. |
| Acoustic Properties of Solids ONDA Corporation 592 Weddell Drive, Sunnyvale, CA 94089, Apr. 11, 2003, pp. 5 (Year 2003). 2003. |
| Bahreynl, B. Fabrication and Design of Resonant Microdevices Andrew William, Inc. 2018, NY (Year 2008). 2008. |
| Namdeo et al. “Simulation on Effects of Electrical Loading due to Interdigital Transducers in Surface Acoustic Wave Resonator”, published in Procedia Engineering 64 ( 2013) of Science Direct pp. 322-330 (Year: 2013) 2013. |
| Rodriguez-Madrid et al., “Super-High-Frequency SAW Resonators on AIN/Diamond”, IEEE Electron Device Letters, vol. 33, No. 4, Apr. 2012, pp. 495-497. Year: 2012) 2012. |
| A. C. Guyette, “Theory and Design of Intrinsically Switched Multiplexers With Optimum Phase Linearity,” in IEEE Transactions on Microwave Theory and Techniques, vol. 61, No. 9, pp. 3254-3264, Sep. 2013, doi: 10.1109/TMTT.2013.2274963. Sep. 2013. |
| Yanson Yang, Ruochen Lu, Songbin Gong, High Q Antisymmetric Mode Lithium Niobate MEMS Resonators With Spurious Mitigation, Journal of Microelectromechanical Systems, vol. 29, No. 2, Apr. 2020. Apr. 2, 2020. |
| Yu-Po Wong, Luyan Qiu, Naoto Matsuoka, Ken-ya Hashimoto, Broadband Piston Mode Operation for First-order Antisymmetric Mode Resonators, 2020 IEEE International Ultrasonics Symposium, Sep. 2020. Sep. 2020. |
| Number | Date | Country | |
|---|---|---|---|
| 20200295729 A1 | Sep 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62818568 | Mar 2019 | US |
