Patent Application
20170170805
The demand for small, high performance wireless communication devices has pushed research interests towards the design and development of low power, small footprint, and single-chip Complementary Metal-Oxide Semiconductor (CMOS) integrated wireless-transceivers. The potential of Micro Electro Mechanical Systems (MEMS) technology to meet some of these requirements has led to the recent development and adoption of miniaturized, silicon micro-machined mechanical resonators for operation as timing references. These silicon MEMS resonators provide high mechanical quality factors (Q), low static power dissipation, and CMOS manufacturing compatibility, making them attractive alternatives to quartz based timing references.
To be used as a low-power, frequency stable electronic clock, a MEMS resonator should exhibit reduced motional resistance (Rx) and increased Q. The motional resistance Rxof a MEMS resonator can be defined as the series resistance in the Butterworth-Van Dyke (BVD) model, where Rx is equal to the driving voltage divided by the sensing current at resonance frequency. The quality factor Q of a MEMS resonator can be defined as 2π times the stored energy divided by the energy dissipated per cycle; equivalently, Q can also be defined as the angular frequency (ω) times the stored energy divided by power loss, or as the resonance peak frequency divided by half power bandwidth (ω/Δω).
Wireless communication devices also rely on high performance bandpass transmission filters, which are used to reject any unwanted incoming RF signals. In some wireless communication applications (e.g., GSM telephony, 3G, LTE, WiFi, etc.), bandpass transmission filters let through only a very narrow portion of the incoming frequency spectrum. To achieve this frequency selectivity, electronics manufacturers, phone manufacturers, and wireless communication developers use Thin-Film Bulk Acoustic Wave Resonators (FBARs) and/or Surface Acoustic Wave (SAW) resonators. Such FBAR/SAW devices are micro-electro-mechanical (MEM) acoustic cavities that can achieve large Q and very low Rx values. Neither FBAR nor SAW resonators, however, can be monolithically integrated with other CMOS devices. Instead, they are surface-mounted to the printed-circuit-boards (PCBs) of the wireless communication devices and are manufactured separately from the integrated circuits. This separate manufacturing increases the cost, time, and complexity of fabrication.
Deep trench (DT) MEMS resonators are high aspect-ratio resonators that address many of the problems associated with FBARs and SAW resonators. A DT MEMS resonator generally includes a periodic array of unit cells, each of which includes a single DT formed in a semiconductor substrate (e.g., silicon). Each DT is filled with a material (e.g., poly-silicon) whose acoustic impedance is different than that of the substrate. The filled DT is used as both an electrical capacitor and a mechanical structure at the same time, making it an elegant design that reduces footprint and fabrication complexity.
The periodic array of unit cells in a DT MEMS resonator forms an acoustic Bragg reflector (ABR) structure whose reflection band is determined by the unit cell width, the trench width, and the acoustic impedance mismatch between the substrate and the trench filling. PolySi-filled trenches in a Si substrate can form a “weak reflector” that traps the standing wave inside the ABR layer instead of scattering the standing wave off into the substrate. By trapping the standing wave, the weak reflector enhances the DT MEMS resonator's quality factor, Q.
DT MEMS resonators offer many advantages over QBARs and SAW resonators. For example, DT MEMS resonators may be solidly embedded and do not require a release step or extensive packaging. The frequency of a DT MEMS resonator can be defined lithographically, with the cavity and reflectors fabricated in the same mask and self-aligned. And a DT MEMS device can function as a mechanical reflector and/or an electrical capacitor. For more information on DT MEMS devices, see, e.g., U.S. Pat. No. 9,041,492 and International Application No. PCT/US2015/035116, which are incorporated herein by reference in their entireties.
Nevertheless, the inventors have recently recognized several potential areas for improving the weak reflector system formed by Si-polySi in a more conventional DT MEMS resonator. First, using a single DT per unit cell limits the range of mechanical bandgap sizes due to the small acoustic impedance mismatch between Si and polySi. Limits on the range of mechanical bandgap sizes limit the range of frequencies over which the DT MEMS resonator transmits and/or reflects acoustic waves. Filling the DTs with another conductive material, such as metal, increases attenuation and reduces the Q of the mechanical mode. But, depositing metal uniformly on the trench sidewalls and filling the trenches can be a challenge in terms of fabrication. Non-uniform deposition and filling may make the mechanical bandgap more difficult to control, which in turn could reduce the production yield of a device with metal-filled trenches. Second, a weak reflector system may need more layers (and hence a larger footprint) than a strong reflector system to generate a high Q. Third, the size of the resonant cavity can be difficult to determine during layout design, which can lead to low fabrication yield. Fourth, fabrication defects, such as voids and surface dents, can affect the weak mechanical bandgap from Si-poly Si, which can also lead to low fabrication yield.
Embodiments of the dual-trench deep-trench (DTDT) MEMS resonators disclosed herein address the issues of fabrication yield and sensitivity to fabrication non-idealities associated with single-trench DT MEMS resonators. A DTDT MEMS resonator takes advantage of a weak mechanical bandgap structure, yet has a mechanical bandgap size controllable through fabrication to reduce susceptibility to manufacturing defects, etc.
An example DTDT MEMS resonator may include a substrate that defines a plurality of unit cells arranged in a first direction. Each unit cell in the plurality of unit cells comprises at least one first material disposed in a first trench defined in the substrate and at least one second material disposed in a second trench defined in the substrate. The first and second materials each have an acoustic impedance that is different than the acoustic impedance of the substrate. In operation, the first material senses, conducts, and/or generates an acoustic wave. In some cases, the length of at least one unit cell in the plurality of unit cells is selected based on a desired frequency of the acoustic wave. The spacing between a center of the first trench and a center of the second trench in a first unit cell in the plurality of unit cells may be about half of a length of the first unit cell.
The first material in a first unit cell in the plurality of unit cells can be electrically connected to a source of an electrical signal. In this, the second material in the first unit cell is electrically isolated from the source of the electrical signal.
The first material may comprise a conductive material and a dielectric layer disposed to form a capacitor. The first material may also comprise a piezoelectric material.
The second material may be selected based on a desired frequency of the acoustic wave. The acoustic impedance of the second material may be lower than the acoustic impedance of the substrate. In some cases, the second material comprises at least two materials selected to define a resonance frequency of at least a portion of the plurality of unit cells. In these cases, one of these two materials comprises an oxide of silicon whose thickness is selected to define the mechanical bandgap.
In operation, an electrical signal may be applied to the first material of the example DTDT MEMS resonator so as to generate an acoustic wave. At least a portion of the acoustic wave is coupled to a second unit cell in the plurality of unit cells via the second material disposed in the second trench of the first unit cell. The electrical signal may be applied to at least a subset of the plurality of unit cells. At least a portion of the acoustic wave may be sensed via the second material in the second trench of a second unit cell in the plurality of unit cells. For instance, some or all of the acoustic wave may be sensed via the second materials in the second trenches in each of a subset of the plurality of unit cells. The acoustic wave may also be at least partially reflected towards the first unit cell, e.g., by a reflector formed by other unit cells.
Embodiments of the present technology also include methods of making DTDT MEMS resonators. An example method includes forming a plurality of unit cells in or on a substrate, with each unit cell in the plurality of unit cells comprising a first material disposed within a first trench and a second material disposed in a second trench. Forming the unit cells may be accomplished by: forming a plurality of trenches in the substrate; depositing the first material within the plurality of trenches; removing the first material from every other trench in the plurality of trenches; and depositing the second material in the every other trench in the plurality of trenches. In some cases, all or substantially all of the first material is removed from every other trench before the second material is deposited; in other cases, only a portion of the first material is removed from every other trench before the second material is deposited.
It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.
The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).
A dual-trench deep-trench (DTDT) resonator has a unit cell that includes two deep trenches (DTs): a first DT for electrical transduction and a second DT that modulates the mechanical bandgap size, which in turn determines the DTDT resonator's resonance frequency and the band over which the DTDT resonator transmits and/or reflects acoustic waves. The second DT may have a size and filling selected to define a mechanical bandgap that is small enough to provide low reflectivity and trap acoustic waves, yet large enough not to be affected by process variations or to cause cavity matching problems. For example, by partially filling the second DT of a DT unit cell with oxide, the mechanical bandgap can be tuned to just the right size to support a high Q mode, and at the same time be large enough not to be eliminated due to process variations. The use of two DTs per unit cell enables a greater range of mechanical bandgap sizes without breaking the translational symmetry that leads to high quality factors.
An array-based DTDT solid-state resonator design is also relatively robust against unexpected process variations. Periodic defects, such as voids inside either DT or surface scattering voids generated from material deposition, are well-handled by a DTDT solid-state resonator. The reason is that because such defects shift the waveguide modes in both the transducer region and the reflector region together, preserving the resonance mode. The resonance frequency may still be shifted after the introduction of periodic defects, but no over-design is necessary during the layout design stage to protect against such variations. This saves layout space and increases the fabrication yield.
Unit Cells for DTDT MEMS Resonators
In operation, the first material 112 in the first DT 110 functions as an electrical capacitor or a piezoelectric transducer, depending on the composition of the first material 112. If functioning as an electrical capacitor, the first material 112 may include a conductive material deposited within a thin layer of insulating material. If functioning as a piezoelectric transducer, the first material 112 may include a piezoelectric or piezoresistive material deposited within a thin layer of insulating material. For more information, see International Application No. PCT/US2015/035116, which is incorporated herein by reference in its entirety.
The insulating material 122 in the second DT 120, which is electrically isolated from the first DT 110 by the substrate 102 and the insulating layer 104, functions as an acoustic reflector. In other words, the second DT 120 and the insulating material 122 in the second DT help to determine the frequency and width of the resonance of the unit cell 100. Depending on the unit cell's function, the frequency and width of the unit cell's resonance may be selected to transmit or reflect radiation at one or more acoustic wavelengths.
The resonance frequency of the unit cell 100 depends on the pitch L of the unit cell 100, the width wDT of the second DT 120, and, in the unit cell 101 shown in
The pitch L of the unit cell 100 can be expressed in terms of the acoustic wavelength λ within the unit cell 100. Depending on the unit cell's function, the pitch may be one-quarter (λ/4) to one-half (λ/2) of the acoustic wavelength λ, depending on the unit cell's function (e.g., transduction or sensing). In physical dimensions, the acoustic path length of the unit cell 100 can range from about 100 nm to about 100 μm (e.g., 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1μm, 5μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm). Depending on the unit cell's desired acoustic and mechanical properties, the thickness of each DT 110, 120 may range from about 1 nm to about 100 μm (e.g., 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1μm, 5μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm).
Example DTDT MEMS Resonators
The first DT 110 and second DT 120 are formed in a substrate 102 (e.g., silicon) whose acoustic impedance is different (e.g., higher) than that of the first material 112 and the second material 122. These acoustic impedance differences, together with the dimensions of the unit cells 100, determine the acoustic properties of the DTDT MEMS resonator 100. In this case, the transducer array 210 includes unit cells 100a whose dimensions—including pitch L, trench widths, and trench locations—are selected to resonate at one or more acoustic frequencies. The reflector arrays 220, also called acoustic Bragg reflectors (ABRs), include unit cells 100b whose dimensions are selected to provide an acoustic path length of about λ/4, where λ is the wavelength of the acoustic wave(s).
In operation, the reflector arrays 220 confine the resonant acoustic wave(s) to a cavity defined by the transducer array 210. In some cases, the transducer array 210 may generate the acoustic wave(s), e.g., via piezoelectric or electrostatic transduction in response to an electrical signal from a signal source in electrical communication with the transducer array 210 via the exposed first material 112. In other cases, the transducer array 210 may sense the acoustic wave(s), e.g., via piezoelectric or electrostatic transduction.
The DTDT MEMS resonator 250 also includes electrodes, shown in
In addition, the DTDT MEMS resonator 250 has an insulating layer 104 that covers the exposed portion of the substrate, the second DTs 120, and the second material 122. Depending on the electrode configuration, the insulating layer 104 may also cover some or all of the first DTs 110 and first material 112 in the reflector arrays 220. The first material 112 in the transducer array 210 pokes through the insulating layer 104 to form electrical connections with a signal source and/or a signal detector, depending on whether the transducer array 210 generates or detects acoustic waves propagating within the DTDT MEMS resonator 200.
A DTDT MEMS resonator can include other layers or regions. For instance, it may include several resonant cavities, one or more of which act as sensors and one or more of which act as signal generators. These resonant cavities can be coupled together by acoustic Bragg grating couplers (ABGCs), which are arrays of unit cells dimensioned to transmit acoustic waves at selected frequencies. Typically, the acoustic path length of an ABGC unit cell is about equal to the acoustic wavelength, λ. Likewise, the number of unit cells in each region in a DTDT MEMS resonator (transducer array/resonant cavity, GRIN, ABR, or ABGC) may be selected based on the desired performance characteristics of the DTDT MEMS resonator. For example, ABGCs and ABRs with more layers tend to have higher finesses. And a DTDT MEMS resonator may include additional surface layers, including a protective coating, an acoustic reflector, and/or additional electromechanical interfaces for signal transduction and/or sensing with one or more external sources.
Fabrication of DTDT MEMS Resonators
A DTDT MEMS resonator can be fabricated according to the processes described below and shown in
Generally, a process for fabricating a DTDT MEMS resonator starts with deposition of 1 μm plasma-enhanced chemical vapor deposition (PECVD) SiO2 onto a fresh low resistivity bulk n type Si wafer. Afterwards, the PECVD oxide is patterned using a hard mask to form 0.8 μm wide deep-trench (DT) arrays using stepper photo-lithography. The hard oxide mask is re-patterned into field oxide layer I (FOX I) to reduce capacitance from the subsequent electrical paths. It is patterned through a photoresist mask and wet 7:1 buffered HF (BHF) etch. This mask is also used as the ion implantation mask afterwards. The Si wafer is ion implanted with phosphorous twice, each time at tilt angle of 8°. The tilt reduces or avoids the channeling effect, and achieves implantation on the trench sidewall as well. CVD oxide is grown, then pattered into an alternating geometry through photo-lithography and wet etch in BHF. The oxide deposition can either fully fill the trench or just partially fill the trenches as desired. Whether the oxide filled trenches are fully filled or partially filled does not necessarily affect the process flow significantly.
After RCA clean, the trenches are lined with 10 nm SiO2 and filled with n type doped polySi. The polySi grows uniformly on top surfaces and sidewalls, filling all the trenches, including the ones that are partially filled with SiO2 if the oxide DTs are indeed partially filled. The polySi is lined with a thin layer of Al to reduce RC delay, and these layers are subsequently patterned into electrical paths for the top electrode of the DT capacitor. This step also opens the contact area for substrate grounding. The solid state structure is capped with a 500 nm field oxide II (FOX II) to reduce scattering of elastic wave from the top free surface and to isolate the electrical signal between metal layers. The FOX II is patterned for metal contacts to the transducer DTs and substrate. Finally, a Ti—Al metal layer is sputtered, patterned by Cl2/BCl3 RIE, and sintered at 450° C. in H2/N2 gases.
TABLE 2 (below) provides a detailed description of a process for fabricating a DT MEMS resonator, including process parameters and tools. It also includes the additional steps used to fabricate a DTDT MEMS resonator.
Simulated Performance of DTDT MEMS Resonators
Reflectivity of DTDT Acoustic Bragg Reflectors (ABRs)
Generally, the high reflectivity band shifts in frequency as the number of cells increases. Such peak reflectivity and center frequencies can be extracted as well, plotted in
Dispersion Relations for DTDT Unit Cells
In each dispersion analysis the DTDT pitch size is the only study variable, while all the other parameters including trench width, depth, thickness of each materials, etc., are kept constant. In
Overlaying the dispersion curves for the different DTDT pitch sizes shows how the modes shift after perturbing the pitch size. If, for example, the pitch size of the transducer DTs is 3.4 μm, and the pitch size of the reflector DTs is 3.5 μm, the wave can propagate when operating on the lighter curves, but this same mode becomes evanescent after reaching the reflector since it is not on the darker curves. Even when using array transduction to operate at k/ko=1, k spans a certain width around the targeted value because the array size is not infinite. Therefore, to construct high Q resonators, such modes should be as far away from the sound cone as possible, and the two modes should be separated as far as possible at both the targeted k value and its vicinity. For example, mode (4) of both pitch sizes is well separated over the entire plotted range of k, and the mode is almost pure longitudinal, which couples to the driving forces. It may operate closer to the sound cone than the other modes, but this sound cone coupling effect can be reduced by using larger transduction arrays (which leads to purer k value).
Resonator Eigenmodes and Q Enhancement Approaches
Resonator Eigenmodes
The full frequency response of the entire structure and many resonator properties, including Q, can be extracted from a finite element analysis model of the DTDT MEMS resonator. For example, a MATLAB optimizer can be used to control a COMSOL finite element solver at each iteration of a finite element analysis to find a solution that generates a desired Q. The optimizing program can search the transducer array pitch size (Ltrans) and the reflector array pitch size (Lref), while the other parameters are kept constant. This numerical simulation procedure can be applied on DTDT resonator structures with fully filled or partially filled mechanical bandgap tuning trenches.
The simulations illustrated in
Further Q Enhancement Approaches
The quality factor Q of a solid state DTDT resonator can be enhanced by using a GRIN structure, longer transduction arrays, or both. The effect of the GRIN structure is to gradually transit the pitch size from the transducer pitch size to the reflector pitch size. This gradual transition reduces waves scattering at each reflection, and therefore improves Q.
Effects of Process Variations on DTDT Resonators
As discussed at above, solid state resonators based on weak mechanical bandgap structures are susceptible to fabrication variations. One example of an imperfect surface structure is the existence of non-periodic surface defects, which can cause scattering and distort the modeshape. For designs based on matching the cavity size to the reflector mechanical bandgap, such fabrication variations may shift the mechanical bandgap and cause the design match to fail. One common solution is to include a lot of over-designs in the layout, in order to hit a match even after the mechanical bandgap shifts. But this method wastes layout area and could still fail when unforeseen defects happen.
On the other hand, the array transduction design methodology disclosed herein is more robust to process variations. Assuming the process condition is uniform across the DTs in one device, the defects may depend largely, if not entirely, on the designed geometry. Since the designed geometry preserves translational symmetry as much as possible, including the details on the surface layers, any defects, if they exist at all, should have the same type of translational symmetry as well. One benefit of such periodic defects is that they should cause the transducer waveguide mode and the reflector waveguide mode to shift together, leaving the gap between these two modes almost unperturbed.
In comparison with
For a design based on two waveguides that are of slightly different pitch sizes, the goal of the mode design is usually to have a tiny offset between the two mode branches. As seen from
For such auto-adjustment to happen, the mode should still exist out of the sound cone. For example, in
Without being bound to any particular theory, the energy heat plot of mode (4) in
Conclusion
While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
The above-described embodiments can be implemented in any of numerous ways. For example, embodiments of designing and making the technology disclosed herein may be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers.
Further, it should be appreciated that a computer may be embodied in any of a number of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, a computer may be embedded in a device not generally regarded as a computer but with suitable processing capabilities, including a Personal Digital Assistant (PDA), a smart phone or any other suitable portable or fixed electronic device.
Also, a computer may have one or more input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include printers or display screens for visual presentation of output and speakers or other sound generating devices for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or in other audible format.
Such computers may be interconnected by one or more networks in any suitable form, including a local area network or a wide area network, such as an enterprise network, and intelligent network (IN) or the Internet. Such networks may be based on any suitable technology and may operate according to any suitable protocol and may include wireless networks, wired networks or fiber optic networks.
The various methods or processes (e.g., of designing and making the technology disclosed above) outlined herein may be coded as software that is executable on one or more processors that employ any one of a variety of operating systems or platforms. Additionally, such software may be written using any of a number of suitable programming languages and/or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine.
In this respect, various inventive concepts may be embodied as a computer readable storage medium (or multiple computer readable storage media) (e.g., a computer memory, one or more floppy discs, compact discs, optical discs, magnetic tapes, flash memories, circuit configurations in Field Programmable Gate Arrays or other semiconductor devices, or other non-transitory medium or tangible computer storage medium) encoded with one or more programs that, when executed on one or more computers or other processors, perform methods that implement the various embodiments of the invention discussed above. The computer readable medium or media can be transportable, such that the program or programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the present invention as discussed above.
The terms “program” or “software” are used herein in a generic sense to refer to any type of computer code or set of computer-executable instructions that can be employed to program a computer or other processor to implement various aspects of embodiments as discussed above. Additionally, it should be appreciated that according to one aspect, one or more computer programs that when executed perform methods of the present invention need not reside on a single computer or processor, but may be distributed in a modular fashion amongst a number of different computers or processors to implement various aspects of the present invention.
Computer-executable instructions may be in many forms, such as program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically the functionality of the program modules may be combined or distributed as desired in various embodiments.
Also, data structures may be stored in computer-readable media in any suitable form. For simplicity of illustration, data structures may be shown to have fields that are related through location in the data structure. Such relationships may likewise be achieved by assigning storage for the fields with locations in a computer-readable medium that convey relationship between the fields. However, any suitable mechanism may be used to establish a relationship between information in fields of a data structure, including through the use of pointers, tags or other mechanisms that establish relationship between data elements.
Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of” “only one of” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” 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” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.
This application is a bypass continuation of International Application No. PCT/US2016/012794, filed on Jan. 11, 2016, and entitled “Dual Trench Deep Trench-Based Unreleased MEMS Resonators,” which in turn claims priority, under 35 U.S.C. §119(e), from U.S. Application No. 62/150,399, filed Apr. 21, 2015, and entitled “Dual Trench Deep Trench based Unreleased Coupled MEMS Resonators.” Each of these applications is hereby incorporated herein by reference in its entirety.
This invention was made with Government support under Grant No. N66001-13-1-4022 awarded by the Space and Naval Warfare Systems Center and under Grant No. ECCS-1150493 awarded by the National Science Foundation. The Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62150399 | Apr 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2016/012794 | Jan 2016 | US |
| Child | 15285223 | US |
