Patent Application
20130135264
This disclosure relates generally to electromechanical systems resonators, and more specifically to multilayer piezoelectric thin film contour mode resonator (CMR) structures.
Electromechanical systems (EMS) include devices having electrical and mechanical elements, transducers such as actuators and sensors, optical components (including mirrors), and electronics. Electromechanical systems can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about one micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than one micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical, mechanical, and electromechanical devices.
One type of EMS device is called an interferometric modulator (IMOD). As used herein, the term IMOD or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an IMOD may include a pair of conductive plates, one or both of which may be transparent and/or reflective, wholly or in part, and capable of relative motion upon application of an appropriate electrical signal. In an implementation, one plate may include a stationary layer deposited on a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the IMOD. IMOD devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with display capabilities.
Various electronic circuit components can be implemented at the EMS level, including resonators. Some conventional resonator structures provide less than desirable electrical and mechanical energy conversion. In some resonator designs, the efficiency of this electromechanical coupling is based on the effectiveness of translation of electrical energy, from an input electrical signal delivered to an input terminal, to mechanical motion of a piezoelectric material that is translated back to electrical energy at the input terminal or an output terminal. Conventional resonator devices having poor electromechanical coupling can have sub-optimal operational efficiency and signal throughput.
Some conventional resonator devices produce and sense electric fields across the thickness of the piezoelectric layer. These configurations do not couple well to two-dimensional Lamb wave strain fields at high (e.g., GHz) frequencies and exhibit relatively small electromechanical coupling coefficient (kt2) values that limit filter fractional bandwidth and insertion loss.
The structures, devices, apparatus, systems, and processes of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.
Disclosed are example implementations of electromechanical systems resonator structures, such as contour mode resonators (CMR), devices, apparatus, systems, and related fabrication processes.
According to one innovative aspect of the subject matter described in this disclosure, a resonator structure includes a lower conductive layer of electrodes; a lower piezoelectric layer disposed on the lower conductive layer; a middle conductive layer of electrodes disposed on the lower piezoelectric layer opposite the lower conductive layer; an upper piezoelectric layer disposed on the middle conductive layer opposite the lower piezoelectric layer; and an upper conductive layer of electrodes disposed on the upper piezoelectric layer opposite the middle conductive layer. In some implementations, a first arrangement of the electrodes is located at a first position along a width of the structure and generally aligned along a thickness of the structure, the first arrangement including a first-type drive electrode in the lower conductive layer, a second-type drive electrode in the middle conductive layer, and a first-type drive electrode in the upper conductive layer. In some implementations, a second arrangement of the electrodes is located at a second position along the width and generally aligned along the thickness, the second arrangement including a second-type drive electrode in the lower conductive layer, a first-type drive electrode in the middle conductive layer, and a second-type drive electrode in the upper conductive layer. In some implementations, the first-type drive electrodes are coupled to receive a first input signal and the second-type drive electrodes are coupled to receive a second input signal.
In some implementations, the first arrangement and the second arrangement are periodically repeated at least once along the width such that there are at least two instances of the first arrangement and at least two instances of the second arrangement and such that each instance of the first arrangement is separated by an adjacent instance of the first arrangement by an instance of the second arrangement, and vice versa. In some such implementations, a center-to-center distance from each electrode to its closest neighbor electrode along the same conductive layer is substantially equal to half of the acoustic wavelength, λ, of the structure, and a center-to-center distance from each electrode to the next electrode of the same type along the same conductive layer is substantially equal to λ.
In some implementations, the resonator structure further includes a third arrangement of the electrodes located at a third position along the width and generally aligned along the thickness, the third arrangement including a first-type signal electrode in the lower conductive layer, a second-type signal electrode in the middle conductive layer, and a first-type signal electrode in the upper conductive layer. In some such implementations, the first-type signal electrodes are coupled to output an output signal.
In some implementations, the electrodes in the middle conductive layer in the first and second arrangements each have a width that is substantially greater than that of each of the respective overlying or underlying electrodes of the upper and lower conductive layers.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a process for forming a resonator structure. In some implementations, the process includes: forming a lower conductive layer of electrodes; forming a lower piezoelectric layer over the lower electrode layer; forming a middle conductive layer of electrodes over the lower piezoelectric layer; forming an upper piezoelectric layer over the middle conductive layer; and forming an upper conductive layer of electrodes over the upper piezoelectric layer. In some implementations, the described layers are arranged such that a first arrangement of the electrodes is located at a first position along a width of the structure and generally aligned along a thickness of the structure, the first arrangement including a first-type drive electrode in the lower conductive layer, a second-type drive electrode in the middle conductive layer, and a first-type drive electrode in the upper conductive layer. In some implementations, the described layers are arranged such that a second arrangement of the electrodes is located at a second position along the width and generally aligned along the thickness, the second arrangement including a second-type drive electrode in the lower conductive layer, a first-type drive electrode in the middle conductive layer, and a second-type drive electrode in the upper conductive layer. In some implementations, the first-type drive electrodes are coupled to receive a first input signal and the second-type drive electrodes are coupled to receive a second input signal.
In some implementations, forming the lower conductive layer of electrodes includes forming the lower conductive layer of electrodes over a sacrificial layer. In some such implementations, the process can further include forming the sacrificial layer on a substrate prior to forming the lower conductive layer of electrodes over the sacrificial layer; and removing at least a portion of the sacrificial layer to define a cavity such that at least a substantial portion of the lower electrode layer is spaced apart from the substrate.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for using a resonator structure. The method can include: providing a piezoelectric resonator structure; applying a first input signal to the first-type drive electrodes; and applying a second input signal to the second-type drive electrodes. In some implementations, applying the first and second input signals causes one or more modes of vibration in the piezoelectric resonator structure.
In some implementations, the piezoelectric resonator structure further includes a third arrangement of the electrodes located at a third position along the width and generally aligned along the thickness, the third arrangement including a first-type signal electrode in the lower conductive layer, a second-type signal electrode in the middle conductive layer, and a first-type signal electrode in the upper conductive layer. In some such implementations, the method can further include: sensing, using the third arrangement of electrodes, displacements associated with the d33 piezoelectric field component resulting from vibrations caused by vertical and lateral electric field components resulting from the applied first and second input signals; and outputting an output signal based on the sensing.
Another innovative aspect of the subject matter described in this disclosure can be implemented in apparatus including first conductive means of electrodes; first piezoelectric means including a first piezoelectric material disposed over the first conductive means of electrodes; second conductive means of electrodes disposed over the first piezoelectric means opposite the first conductive means of electrodes; second piezoelectric means including a second piezoelectric material disposed over the second conductive means of electrodes opposite the first piezoelectric means; and third conductive means of electrodes disposed over the second piezoelectric means opposite the second conductive means of electrodes; first coupling means; and second coupling means. In some implementations, a first arrangement of the electrodes is located at a first position along a width of the structure and generally aligned along a thickness of the structure, the first arrangement including a first-type drive electrode in the first conductive means, a second-type drive electrode in the second conductive means, and a first-type drive electrode in the third conductive means. In some implementations, a second arrangement of the electrodes is located at a second position along the width and generally aligned along the thickness, the second arrangement including a second-type drive electrode in the first conductive means, a first-type drive electrode in the second conductive means, and a second-type drive electrode in the third conductive means. In some such implementations, the first-type drive electrodes are coupled to receive a first input signal via the first coupling means and the second-type drive electrodes are coupled to receive a second input signal via the second coupling means.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Although the examples provided in this disclosure are primarily described in terms of electromechanical systems (EMS) and microelectromechanical systems (MEMS)-based displays, the concepts provided herein may apply to other types of displays, such as liquid crystal displays, organic light-emitting diode (“OLED”) displays and field emission displays. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
Like reference numbers and designations in the various drawings indicate like elements.
The following detailed description is directed to certain implementations for the purposes of describing the innovative aspects. However, the teachings herein can be applied and implemented in a multitude of different ways.
The disclosed implementations include examples of structures and configurations of electromechanical systems resonator devices, including contour mode resonators (CMR). Related apparatus, systems, and fabrication processes and techniques are also disclosed. CMRs are referred to as “contour mode” because of their substantially lateral in-plane modes of vibration, as described in greater detail below. In the case of piezoelectric resonators, electrodes are generally disposed in contact with or in proximity to a piezoelectric material. For instance, the electrodes can be located on the same surface or on opposite surfaces of a layer of the piezoelectric material.
An electric field applied between first and second electrodes in
The electromechanical coupling coefficient, kt2, is a property of a resonator that determines the bandwidth and insertion loss of, for example, a filter incorporating the resonator. The kt2 value of some CMRs is limited by the d31 piezoelectric coefficient, which is typically about a factor of 3 smaller than the d33 coefficient associated with film bulk acoustic resonators (FBAR) and bulk acoustic wave (BAW) resonators. For reference,
Many higher frequency CMRs employ Lamb wave modes of vibration. A Lamb wave consists of a superposition of transverse (out-of-plane) and longitudinal (in-plane) components, where the relative amplitude of each component varies as a function of the ratio of the piezoelectric layer thickness, d, to acoustic wavelength, λ. For the first order symmetric mode, S0, at frequencies of a few hundred MHz or less, where the ratio of d/λ is small (such as around 0.01), the amplitude of the longitudinal component is much greater than the transverse component, and piezoelectric layer motion is thus predominantly in the plane of the substrate.
Some CMR electrode topologies generate vertical electric fields across the thickness of the piezoelectric layer and excite lateral deformation through the d31 piezoelectric coefficient.
In the configurations shown in
While there may be regions of lateral motion at odd quarter-wavelength intervals in the examples above, there also may be alternating regions of predominantly vertical displacement. Furthermore, both transverse and longitudinal components may be symmetric about the thickness of the piezoelectric layer. CGE and DGE topologies can be less efficient at exciting the high frequency S0 mode since the electric field emanating from the electrodes is generally misaligned to the strain and polarization fields, and at some positions, is completely 180 degrees out of phase. The afore-described single- and two-piezoelectric layer CGE and DGE topologies fail to account both for symmetry in the strain across the thickness of the piezoelectric layer and for the transverse displacement. This may explain the decrease in kt2 that has been observed with some conventional CMR structures at higher frequencies.
Particular implementations of the subject matter described in this disclosure include two piezoelectric layers and patterned lower, middle, and upper electrode layers configured to utilize the symmetry and transverse displacement inherent at high (e.g., GHz) frequencies. Some example implementations include a CMR that efficiently couples to GHz S0 Lamb waves. In such implementations, the resonator transduces vibration through displacement associated with both the d31 and the d33 piezoelectric coefficients, resulting in a higher kt2 than can be achieved in traditional topologies that only drive and sense vibration through displacement associated with the d31 coefficient. In particular implementations, an example CMR device includes an upper conductive layer of first electrodes and second electrodes. The first electrodes are coupled to a first port and the second electrodes are coupled to a second port. A middle conductive layer of electrodes is situated underneath the upper conductive layer of electrodes on the opposite side of an upper piezoelectric layer. A lower piezoelectric layer is situated below the middle conductive layer. A lower conductive layer of electrodes is situated underneath the middle conductive layer of electrodes on the opposite side of the lower piezoelectric layer. In some implementations, the middle conductive layer includes a similar arrangement of first electrodes underlying the first electrodes of the upper conductive layer and coupled to the second port. In such an implementation, the middle conductive layer also includes a similar arrangement of second electrodes underlying the second electrodes of the upper conductive layer and coupled to the first port. In some implementations, the lower conductive layer includes a similar arrangement of first electrodes underlying the first electrodes of the upper conductive layer and coupled to the first port and a similar arrangement of second electrodes underlying the second electrodes of the upper conductive layer and coupled to the second port.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. By taking advantage of the strain/displacement associated with the d33 piezoelectric coefficient, the Q and kt2 of the desired modes can be enhanced. The proposed solutions can produce CMRs with larger kt2 values since the transduction schemes utilize the strains associated with both the d31 and d33 piezoelectric coefficients. A larger kt2 value results in, for example, filters with lower insertion loss and wider bandwidth.
Some implementations described herein are based on a contour mode resonator configuration. In such implementations, the resonant frequency of a CMR can be substantially controlled by engineering the lateral (e.g., length and width) dimensions of the piezoelectric material layers and the electrode layers as well as engineering the periodicity of the electrodes and the thickness of the piezoelectric layer. One benefit of such a construction is that multi-frequency RF filters, clock oscillators, transducers or other devices, each including one or more CMRs depending on the desired implementation, can be fabricated on the same substrate. For example, this may be advantageous in terms of cost and size by enabling compact, multi-band filter solutions for RF front-end applications on a single chip. In some examples, by co-fabricating multiple CMRs with different finger widths, as described in greater detail below, multiple frequencies can be addressed on the same die. In some examples, arrays of CMRs with different frequencies spanning a range from MHz to GHz can be fabricated on the same substrate.
Furthermore, with the disclosed CMRs, direct frequency synthesis for spread spectrum communication systems can be enabled by multi-frequency narrowband filter banks including high quality factor (Q) resonators, without the need for phase-locked loops (PLLs). The disclosed CMR implementations can provide for piezoelectric transduction with low motional resistance while maintaining high Q values and appropriate reactance values that facilitate their interface with contemporary circuitry. Some examples of the disclosed laterally vibrating resonator structures provide the advantages of compact size, e.g., on the order of 100 um (micrometers) in length and/or width, low power consumption, and compatibility with high-yield mass-producible components.
In one or more implementations of the disclosed CMRs, the resonator structure is suspended in a cavity of a supporting structure. The resonator structure can be suspended in the cavity by specially designed tethers coupling the resonator structure to the supporting structure, as further explained below. These tethers are often fabricated in the layer stack of the resonator structure itself. The resonator structure can be acoustically isolated from the surrounding structural support and other apparatus by virtue of the cavity.
The disclosed resonator structures can be fabricated on a low-cost, high-performance, large-area insulating substrate, which, in some implementations, forms at least a portion of the supporting structure described herein. In some implementations, the insulating substrate on which the disclosed resonator structures are formed can be made of display-grade glass (alkaline earth boro-aluminosilicate) or soda lime glass. Other suitable insulating materials of which the insulating substrate can be made include silicate glasses, such as alkaline earth aluminosilicate, borosilicate, modified borosilicate, and others. Also, ceramic materials such as aluminum oxide (AlOx), yttrium oxide (Y2O3), boron nitride (BN), silicon carbide (SiC), aluminum nitride (AlNx), and gallium nitride (GaNx) can be used as the insulating substrate material. In some other implementations, the insulating substrate is formed of high-resistivity silicon. In some implementations, silicon-on-insulator (SOI) substrates, gallium arsenide (GaAs) substrates, indium phosphide (InP) substrates, and plastic (polyethylene naphthalate or polyethylene terephthalate) substrates, e.g., associated with flexible electronics, also can be used. The substrate can be in conventional Integrated Circuit (IC) wafer form, e.g., 4-inch, 6-inch, 8-inch, 12-inch, or in large-area panel form. For example, flat panel display substrates with dimensions such as 370 mm×470 mm, 920 mm×730 mm, and 2850 mm×3050 mm, can be used.
In some implementations, the disclosed resonator structures are fabricated by depositing a sacrificial (SAC) layer on the substrate; forming one or more lower (first) electrode layers on the SAC layer; depositing a lower (first) piezoelectric layer on the lower electrode layer; forming one or more middle (second) electrode layers on the lower piezoelectric layer; forming an upper (second) piezoelectric layer on the middle electrode layer; forming one or more upper (third) electrode layers on the upper piezoelectric layer; and removing at least part of the SAC layer to define a cavity. The resulting resonator cavity separates at least a portion of the lower electrode layer from the substrate and provides openings along the sides of the resonator structure, as illustrated in the accompanying figures, to allow the resonator to vibrate and move in one or more directions with substantial elastic isolation from the remaining substrate. In some other implementations, a portion of the substrate itself serves as a SAC material. In these implementations, designated regions of the insulating substrate below the resonator structure can be removed, for example, by etching to define the cavity.
In the example of
In
Features of the proposed solutions include patterning all three electrode layers to efficiently drive the natural mode of vibration of the piezoelectric resonator structure at GHz frequencies. Another feature is the use of single-ended (signal, ground, and floating) or differential (+signal, −signal, ground, floating) electrical routing across all layers of the multilayer piezoelectric resonator. Furthermore, the two-port implementations can reduce feed-through capacitance and improve rejection.
More detailed descriptions of example implementations of the proposed solutions and processes for the fabrication of such will now be described.
In the examples of
In the examples shown in
The resonator structures of
In
The CMR structure can be driven into resonance by applying a harmonic electric potential, for example, to Ports 1B, 2B and 3A (or alternatively to Ports 1A, 2A and 3B when Ports 1B, 2B and 3A are grounded) that varies in time across the patterned conductive layers. The layout and interconnectivity of the periodic electrodes transduce the desired mode of vibration while suppressing the response of undesired spurious modes of vibration of the structure. For example, a specific higher order vibrational mode can be transduced without substantially transducing other modes. Compared to its response to a constant DC electric potential, the amplitude of the mechanical response of the resonator is multiplied by the Q factor (the typical Q factor is on the order of 500 to 5000). Engineering the total width of the resonator structure, the number of electrode periods, and or the thickness of the piezoelectric layers provides control over the impedance of the resonator structure by scaling the amount of charge generated by the motion of the piezoelectric material.
In
DrivePort(+) can be coupled to receive the input electrical signal from various components, such as an amplifier or an antenna. In the illustrated implementation, an alternating current (AC) voltage source 1504 simulates the electrical signal delivered by such a component. The AC voltage source 1504 has a first terminal 1506a coupled to DrivePort(+) and a second terminal 1506b coupled to DrivePort(−), which is coupled to ground in this example. In this way, an input AC signal can be provided from voltage source 1504 to DrivePort(+) and, hence, to second electrodes 602b, second electrodes 604b, and first electrodes 606a, of the upper, lower, and middle layers of the resonator, respectively. An electric field caused by the alternating voltage of the AC signal is applied in the piezoelectric layers 608 and 610, as well as across the width of the piezoelectric layers 608 and 610, as described above with reference to
As referenced above, the thickness of the structure 600 is generally measured along the Z axis, and the length is measured along the Y axis, in the example of
As described above,
In
In
In some implementations, there are two resonant modes of the structure 600, that is, in the form of the two resonant frequencies. This is due to the incorporation of the two sub-resonators in regions 1560 and 1564, respectively, of the single structure 600. At resonance, an AC input signal delivered to Port 1B and having a frequency coinciding with the natural resonant frequency of the structure 600 causes the structure 600 to vibrate. In one example of this second order system, in a first mode, the sub-resonators vibrate in phase with one another, essentially moving in the manner of a single resonator. In a second mode, the two sub-resonators vibrate out of phase with one another.
A filter bandwidth of the structure 600 can be defined by the difference between the higher resonant frequency and the lower resonant frequency of the structure 600. The finger width, Wfin, in the structure 600 can be engineered to control, set, and adjust the resonant frequencies, and thus set the filter bandwidth. In some examples, Wfin directly determines the lower resonant frequency. In some examples, the higher resonant frequency is indirectly determined by Wfin and also affected by the manner in which an acoustic wave travels in structure 600 back and forth along the X axis. A center frequency between the higher and lower resonant frequencies also can be determined by Wfin. The total width, Wt, of the structure also can be engineered to control, set, and adjust the filter bandwidth defined by the difference between the higher and lower resonant frequencies. The finger width, Wfin, can be defined by layout and photolithography in fabrication of the structure. In some applications, the resonant frequencies can provide multiple frequency operation, e.g., from 10 MHz up to microwave frequencies on a single chip.
The piezoelectric layers 608 and 610 of the disclosed resonators can vibrate and move in all directions at resonant frequencies, for instance, in planes oriented along the X and Y axes, X and Z axes, and Y and Z axes. In one example of a CMR, electrical fields with varying horizontal and vertical components are induced in piezoelectric layers 608 and 610 along the X and Z axes, causing, through the d31 and d33 piezoelectric coefficients, mechanical stress and resulting strain in the piezoelectric layer with components along the width and thickness of the structure. This mechanical energy causes an electric potential to be generated across third electrodes 602c and 606c and an electric potential to be generated across third electrodes 606c and 604c. This transduced potential is sensed as an output electrical signal at SensePort(+) and can be measured by one or more sensors 1520 coupled between SensePort(+) and SensePort(−).
The fundamental frequency for the displacement of the piezoelectric layer can be set in part lithographically by the planar dimensions of the upper electrodes, the middle electrodes, the lower electrodes, and/or the piezoelectric layers. At the device resonant frequency, the electrical signal across the device is reinforced and the device behaves as an electronic resonant circuit. For instance, the resonator structures described above can be implemented by patterning the input electrodes and output electrodes of a respective conductive layer symmetrically.
In some implementations, the resonant frequency of a CMR can be directly controlled by setting the finger widths. One benefit of such a control parameter is that multi-frequency filters can be fabricated on the same chip. The CMR 600 has a resonant frequency associated with the finger width, which is based on the spacing in combination with the electrode width of electrodes 602a and 602b, that is, along the X axis. The finger width in a conductive layer of the CMR structure can be altered to adjust the resonant frequency. For instance, in some implementations, the resonant frequency is lowered as the finger width increases, and vice versa.
The total width, length, and thickness of the resonator structure are parameters that also can be designated to optimize performance. In some CMR implementations, the finger width of the resonator is the main parameter that is controlled to adjust the resonant frequency of the structure, while the total width multiplied by the total length of the resonator (total area) can be set to control the impedance of the resonator structure. In one example, the lateral dimensions, i.e., the width and length of resonator structure 600 can be on the order of several 100 μm by several 100 μm for a device designed to operate around 1 GHz. In another example, the lateral dimensions are several 1000 μm by several 1000 μm for a device designed to operate at around 10 MHz. A suitable thickness of each of the piezoelectric layers 608 and 610 can be about 0.01 to 10 μm thick.
The pass band frequency can be determined by the layout of the resonator structure, as can the terminal impedance. For instance, by changing the shape, size and number of electrodes, the terminal impedance can be adjusted. In some examples, longer fingers yield smaller impedance. This, in turn, is inversely proportional to the capacitance of the CMR. The resonant frequencies of the CMR structures described herein are generally insensitive to the fabrication process, to the extent that the piezoelectric thickness and thicknesses of the conductive layers do not significantly impact the frequency. The impedance and the frequency can be controlled independently, since the length and the width/spacing of electrodes are in perpendicular directions.
In
In block 1712, a post oxide layer 1812 is deposited over SAC layer 1808 and exposed surface portions 1810 of glass substrate 1804. In block 1716, to form the staggered structure of
In block 1720, a first metal layer 1816 is deposited such that it overlays the post oxide anchors 1812a and 1812b as well as the exposed region of SAC layer 1808. Metal layer 1816 can be formed of aluminum (Al), Al/titanium nitride (TiN)/Al, aluminum copper (AlCu), Mo, or other appropriate materials, and have a thickness of 750 to 3000 Angstroms depending on the desired implementation. In some cases, the metal layer 1816 is deposited as a bi-layer with a metal such as Mo deposited on top of a seed layer such as AlN. An appropriate thickness for the seed layer can be, for example, 100 to 1000 Angstroms. When Mo is used, the total thickness of the metal layer 1816 can be about 3000 Angstroms. In some implementations or applications, suitable thicknesses range from about 0.1 μm to 0.3 μm. In yet other implementations or applications, suitable thicknesses may range from about 0.01 μm to 10 μm. Other suitable materials for metal layer 1816 include aluminum silicon (AlSi), AlCu, Ti, TiN, Al, platinum (Pt), nickel (Ni), tungsten (W), ruthenium (Ru), and combinations thereof. Thicknesses can range from about 0.1 μm to about 0.3 μm, depending on the desired implementation. As shown in
In block 1728, a first lower piezoelectric layer, such as film 1820, is deposited on the structure. In block 1732, the lower piezoelectric film 1820 is patterned using an appropriate mask such that strip 1822 of the piezoelectric film 1820 directly overlays the lower electrode portion 1818, shown in
In
In block 1744, a second upper piezoelectric layer, such as film 1821, is deposited on the structure. In block 1748, the upper piezoelectric film 1821 is patterned using an appropriate mask such that strip 1823 of the piezoelectric film 1821 directly overlays the lower electrode portion 1818, the lower strip 1822 of the piezoelectric film 1820, and the middle electrodes 1826, shown in
In
In some implementations, following the formation of the third metal layer 1825, a release protection layer 1828 such as AlOx can be deposited using atomic layer deposition (ALD), physical vapor deposition (PVD), or other appropriate techniques and patterned to protect sidewalls of the electrodes in the first, second, and third metal layers 1816, 1824, and 1825 and the sandwiched piezoelectric layers 1820 and 1821, as shown in
In block 1760, the SAC layer 1808 is then removed to define an air cavity 1832, as shown in
In some implementations, prior to the release operation of block 1760, a metal interconnect layer can be deposited and patterned outside of the resonator structure to define transmission lines to the first, second, and third metal layers 1816, 1824, and 1825, respectively. AlSi, AlCu, plated Cu, or other appropriate material can be used to form the metal interconnect layer.
The piezoelectric materials that can be used in fabrication of the piezoelectric layers of electromechanical systems resonators and dielectric layers of passive components disclosed herein include, for example, aluminum nitride (AlN), zinc oxide (ZnO), gallium arsenide (GaAs), aluminum gallium arsenide (AlGaAs), gallium nitride (GaN), quartz and other piezoelectric materials such as zinc-sulfide (ZnS), cadmium-sulfide (CdS), lithium tantalite (LiTaO3), lithium niobate (LiNbO3), lead zirconate titanate (PZT), members of the lead lanthanum zirconate titanate (PLZT) family, doped aluminum nitride (AlN:Sc), and combinations thereof. The conductive layers described above may be made of various conductive materials including platinum (Pt), aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), niobium (Nb), ruthenium (Ru), chromium (Cr), doped polycrystalline silicon, doped aluminum gallium arsenide (AlGaAs) compounds, gold (Au), copper (Cu), silver (Ag), tantalum (Ta), cobalt (Co), nickel (Ni), palladium (Pd), silicon germanium (SiGe), doped conductive zinc oxide (ZnO), and combinations thereof. In various implementations, the upper metal electrodes and/or the lower metal electrodes can include the same conductive material(s) or different conductive materials.
The description herein is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device or system that can be configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual, graphical or pictorial. More particularly, it is contemplated that the described implementations may be included in or associated with a variety of electronic devices such as, but not limited to: mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, Bluetooth® devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, tablets, printers, copiers, scanners, facsimile devices, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (i.e., e-readers), computer monitors, auto displays (including odometer and speedometer displays, etc.), cockpit controls and/or displays, camera view displays (such as the display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (such as in electromechanical systems (EMS), microelectromechanical systems (MEMS) and non-MEMS applications), aesthetic structures (e.g., display of images on a piece of jewelry) and a variety of EMS devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes and electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art.
An example of a suitable electromechanical systems (EMS) or MEMS device, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulators (IMODs) to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMODs can include an absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. The reflector can be moved to two or more different positions, which can change the size of the optical resonant cavity and thereby affect the reflectance of the IMOD. The reflectance spectrums of IMODs can create fairly broad spectral bands which can be shifted across the visible wavelengths to generate different colors. The position of the spectral band can be adjusted by changing the thickness of the optical resonant cavity, i.e., by changing the position of the reflector.
The IMOD display device can include a row/column array of IMODs. Each IMOD can include a pair of reflective layers, i.e., a movable reflective layer and a fixed partially reflective layer, positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap or cavity). The movable reflective layer may be moved between at least two positions. In a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a relatively large distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel. In some implementations, the IMOD may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when unactuated, reflecting light outside of the visible range (e.g., infrared light). In some other implementations, however, an IMOD may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the pixels to change states. In some other implementations, an applied charge can drive the pixels to change states.
The depicted portion of the pixel array in
In
The optical stack 16 can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer and a transparent dielectric layer. In some implementations, the optical stack 16 is electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate 20. The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals, including chromium (Cr), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, the optical stack 16 can include a single semi-transparent thickness of metal or semiconductor which serves as both an optical absorber and conductor, while different, more conductive layers or portions (such as the optical stack 16 or of other structures of the IMOD) can serve to bus signals between IMOD pixels. The optical stack 16 also can include one or more insulating or dielectric layers covering one or more conductive layers or a conductive/absorptive layer.
In some implementations, the layer(s) of the optical stack 16 can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer 14, and these strips may form column electrodes in a display device. The movable reflective layer 14 may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack 16) to form columns deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. When the sacrificial material is etched away, a defined gap 19, or optical cavity, can be formed between the movable reflective layer 14 and the optical stack 16. In some implementations, the separation between posts 18 may be approximately 1-1000 um, while the gap 19 may be less than 10,000 Angstroms (Å).
In some implementations, each pixel of the IMOD, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer 14 remains in a mechanically relaxed state, as illustrated by the IMOD 12 on the left in
Here, the electronic device includes a controller 21, which may include one or more general purpose single- or multi-chip microprocessors such as an ARM®, Pentium®, 8051, MIPS®, Power PC®, or ALPHA®, or special purpose microprocessors such as a digital signal processor, microcontroller, or a programmable gate array. Controller 21 may be configured to execute one or more software modules. In addition to executing an operating system, the controller 21 may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application.
The controller 21 is configured to communicate with device 11. The controller 21 also can be configured to communicate with an array driver 22. The array driver 22 can include a row driver circuit 24 and a column driver circuit 26 that provide signals to, e.g., a display array or panel 30. Although
The display device 40 includes a housing 41, a display 30, an antenna 43, a speaker 45, an input device 48 and a microphone 46. The housing 41 can be formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing 41 may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber and ceramic, or a combination thereof. The housing 41 can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.
The display 30 may be any of a variety of displays, including a bi-stable or analog display, as described herein. The display 30 also can be configured to include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display 30 can include an IMOD display, as described herein.
The components of the display device 40 are schematically illustrated in
The network interface 27 includes the antenna 43 and the transceiver 47 so that the display device 40 can communicate with one or more devices over a network. The network interface 27 also may have some processing capabilities to relieve, for example, data processing requirements of the processor 21. The antenna 43 can transmit and receive signals. In some implementations, the antenna 43 transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, and further implementations thereof. In some other implementations, the antenna 43 transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna 43 is designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G or 4G technology. The transceiver 47 can pre-process the signals received from the antenna 43 so that they may be received by and further manipulated by the processor 21. The transceiver 47 also can process signals received from the processor 21 so that they may be transmitted from the display device 40 via the antenna 43.
In some implementations, the transceiver 47 can be replaced by a receiver. In addition, in some implementations, the network interface 27 can be replaced by an image source, which can store or generate image data to be sent to the processor 21. The processor 21 can control the overall operation of the display device 40. The processor 21 receives data, such as compressed image data from the network interface 27 or an image source, and processes the data into raw image data or into a format that is readily processed into raw image data. The processor 21 can send the processed data to the driver controller 29 or to the frame buffer 28 for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation and gray-scale level.
The processor 21 can include a microcontroller, CPU, or logic unit to control operation of the display device 40. The conditioning hardware 52 may include amplifiers and filters for transmitting signals to the speaker 45, and for receiving signals from the microphone 46. The conditioning hardware 52 may be discrete components within the display device 40, or may be incorporated within the processor 21 or other components.
The driver controller 29 can take the raw image data generated by the processor 21 either directly from the processor 21 or from the frame buffer 28 and can re-format the raw image data appropriately for high speed transmission to the array driver 22. In some implementations, the driver controller 29 can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array 30. Then the driver controller 29 sends the formatted information to the array driver 22. Although a driver controller 29, such as an LCD controller, is often associated with the system processor 21 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor 21 as hardware, embedded in the processor 21 as software, or fully integrated in hardware with the array driver 22.
The array driver 22 can receive the formatted information from the driver controller 29 and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display's x-y matrix of pixels.
In some implementations, the driver controller 29, the array driver 22, and the display array 30 are appropriate for any of the types of displays described herein. For example, the driver controller 29 can be a conventional display controller or a bi-stable display controller (such as an IMOD controller). Additionally, the array driver 22 can be a conventional driver or a bi-stable display driver (such as an IMOD display driver). Moreover, the display array 30 can be a conventional display array or a bi-stable display array (such as a display including an array of IMODs). In some implementations, the driver controller 29 can be integrated with the array driver 22. Such an implementation can be useful in highly integrated systems, for example, mobile phones, portable-electronic devices, watches or small-area displays.
In some implementations, the input device 48 can be configured to allow, for example, a user to control the operation of the display device 40. The input device 48 can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, a touch-sensitive screen integrated with the display array 30, or a pressure- or heat-sensitive membrane. The microphone 46 can be configured as an input device for the display device 40. In some implementations, voice commands through the microphone 46 can be used for controlling operations of the display device 40.
The power supply 50 can include a variety of energy storage devices. For example, the power supply 50 can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. In implementations using a rechargeable battery, the rechargeable battery may be chargeable using power coming from, for example, a wall socket or a photovoltaic device or array. Alternatively, the rechargeable battery can be wirelessly chargeable. The power supply 50 also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply 50 also can be configured to receive power from a wall outlet.
In some implementations, control programmability resides in the driver controller 29 which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver 22. The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.
The various illustrative logics, logical blocks, modules, circuits and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and steps described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system.
The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular steps and methods may be performed by circuitry that is specific to a given function.
In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus.
Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the IMOD as implemented.
Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.
