Patent Application
20130106875
This disclosure relates generally to electromechanical systems devices and more particularly to fabrication methods for electromechanical systems devices.
Electromechanical systems (EMS) include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components (such as mirrors and optical film layers) 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 a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a 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 and electromechanical devices.
One type of electromechanical systems device is called an interferometric modulator (IMOD). As used herein, the term interferometric modulator 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 interferometric modulator 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 interferometric modulator. Interferometric modulator 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.
An EMS device may be packaged to protect it from the environment and from operational hazards, such as mechanical shock. One way of packaging an EMS device to protect it from the environment can include various encapsulation techniques, including macro-encapsulation and thin-film encapsulation. A thin-film encapsulation process can involve depositing one or more thin film layers over the EMS device.
The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.
One innovative aspect of the subject matter described in this disclosure can be implemented in a method of sealing an electromechanical systems device. The method can include etching a sacrificial layer that is between a surface of a substrate and a shell layer formed over the electromechanical systems device. The sacrificial layer can be etched through etch holes in the shell layer. In some implementations, the etch holes can have a diameter greater than about 1 micron. After etching the sacrificial layer, the shell layer can be treated, with a seal layer then deposited on the treated shell layer. The seal layer can hermetically seal the electromechanical systems device.
In some implementations, etching the sacrificial layer can form a release passage connected to an etch hole. Depositing the seal layer may block the release passage. In some implementations, depositing the seal layer may include depositing a layer of aluminum oxide and depositing a layer of silicon oxynitride.
One innovative aspect of the subject matter described in this disclosure can be implemented in a method of sealing an electromechanical systems device. The method can include providing a substrate having an electromechanical systems device on a surface of the substrate. The substrate can also include a shell layer at least partially enclosing the electromechanical systems device. In some implementations, the shell layer can be substantially nonporous and include an etch hole. A sacrificial layer can then be etched from the substrate though the etch hole. Etching the sacrificial layer can form a release passage connected to the etch hole. In some implementation, a release passage can have a height of less than about 1 micron and a width of greater than about 1 micron. After etching the sacrificial layer, an adhesion improvement layer can be deposited on the shell layer. A seal layer can then be deposited on the shell layer. The seal layer can block a release passage and hermetically seal the electromechanical systems device.
In some implementations, the adhesion improvement layer may include at least a monolayer of aluminum oxide.
One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus including an electromechanical systems device formed on a substrate. The apparatus may further include a supporting means including a sealed etch hole and a sealing means for hermetically sealing the electromechanical systems device. The sealing means may be over the supporting means. The sealing means also may seal the etch hole with a portion of the sealing means blocking an opening of a release passage connected to the etch hole. In some implementations, the supporting means may be a shell layer and the sealing means may be a seal layer.
One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus including an electromechanical systems device formed on a substrate. A shell layer can at least partially enclose the electromechanical systems device between the shell layer and the substrate. The shell layer can include a sealed etch hole. In some implementations, a seal layer over the shell layer can hermetically seal the etch hole in the shell layer. A portion of the seal layer can block an opening of a release passage connected to the etch hole. In some implementations, the seal layer may include a layer of silicon oxynitride and a layer of aluminum oxide overlying the layer of silicon oxynitride.
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. 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 description 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.
Some implementations described herein relate to EMS devices and methods of their fabrication. In some implementations, an EMS device may be packaged with a thin-film encapsulation process. The thin film encapsulation process may involve treatments and/or processes that aid in making the thin-film encapsulation materials hermetic.
For example, in some implementations described herein to fabricate an EMS device, a substrate with an EMS device on the surface of the substrate is provided. A shell layer may be formed over the electromechanical systems device and on a sacrificial layer. The sacrificial layer may be etched through etch holes in the shell layer. The shell may be treated. A seal layer may be deposited on the treated shell layer, with the seal layer hermetically sealing the electromechanical systems device.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Implementations of the methods may be used in a thin-film encapsulation process to provide a hermetic seal or to improve a non-hermetic seal. A hermetic seal may improve the performance of an EMS device by protecting it from components in the atmosphere, including water vapor, which may cause stiction. Stiction (i.e., static friction) may cause surfaces in the EMS device to adhere to one another and may result in failure of the EMS device.
An example of a suitable 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 interferometric modulator. 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. One way of changing the optical resonant cavity is 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, absorbing and/or destructively interfering light within the visible range. 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, such as 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 electrical conductor, while different, electrically more conductive layers or portions (e.g., of 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 an electrically conductive/optically 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 ordinary 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 spacing 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 pixel 12 on the left in
The processor 21 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, for example, a display array or panel 30. The cross section of the IMOD display device illustrated in
In some implementations, a frame of an image may be created by applying data signals in the form of “segment” voltages along the set of column electrodes, in accordance with the desired change (if any) to the state of the pixels in a given row. Each row of the array can be addressed in turn, such that the frame is written one row at a time. To write the desired data to the pixels in a first row, segment voltages corresponding to the desired state of the pixels in the first row can be applied on the column electrodes, and a first row pulse in the form of a specific “common” voltage or signal can be applied to the first row electrode. The set of segment voltages can then be changed to correspond to the desired change (if any) to the state of the pixels in the second row, and a second common voltage can be applied to the second row electrode. In some implementations, the pixels in the first row are unaffected by the change in the segment voltages applied along the column electrodes, and remain in the state they were set to during the first common voltage row pulse. This process may be repeated for the entire series of rows, or alternatively, columns, in a sequential fashion to produce the image frame. The frames can be refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second.
The combination of segment and common signals applied across each pixel (that is, the potential difference across each pixel) determines the resulting state of each pixel.
As illustrated in
When a hold voltage is applied on a common line, such as a high hold voltage VCHOLD
When an addressing, or actuation, voltage is applied on a common line, such as a high addressing voltage VCADD
In some implementations, hold voltages, address voltages, and segment voltages may be used which produce the same polarity potential difference across the modulators. In some other implementations, signals can be used which alternate the polarity of the potential difference of the modulators from time to time. Alternation of the polarity across the modulators (that is, alternation of the polarity of write procedures) may reduce or inhibit charge accumulation which could occur after repeated write operations of a single polarity.
During the first line time 60a: a release voltage 70 is applied on common line 1; the voltage applied on common line 2 begins at a high hold voltage 72 and moves to a release voltage 70; and a low hold voltage 76 is applied along common line 3. Thus, the modulators (common 1, segment 1), (1,2) and (1,3) along common line 1 remain in a relaxed, or unactuated, state for the duration of the first line time 60a, the modulators (2,1), (2,2) and (2,3) along common line 2 will move to a relaxed state, and the modulators (3,1), (3,2) and (3,3) along common line 3 will remain in their previous state. With reference to
During the second line time 60b, the voltage on common line 1 moves to a high hold voltage 72, and all modulators along common line 1 remain in a relaxed state regardless of the segment voltage applied because no addressing, or actuation, voltage was applied on the common line 1. The modulators along common line 2 remain in a relaxed state due to the application of the release voltage 70, and the modulators (3,1), (3,2) and (3,3) along common line 3 will relax when the voltage along common line 3 moves to a release voltage 70.
During the third line time 60c, common line 1 is addressed by applying a high address voltage 74 on common line 1. Because a low segment voltage 64 is applied along segment lines 1 and 2 during the application of this address voltage, the pixel voltage across modulators (1,1) and (1,2) is greater than the high end of the positive stability window (i.e., the voltage differential exceeded a predefined threshold) of the modulators, and the modulators (1,1) and (1,2) are actuated. Conversely, because a high segment voltage 62 is applied along segment line 3, the pixel voltage across modulator (1,3) is less than that of modulators (1,1) and (1,2), and remains within the positive stability window of the modulator; modulator (1,3) thus remains relaxed. Also during line time 60c, the voltage along common line 2 decreases to a low hold voltage 76, and the voltage along common line 3 remains at a release voltage 70, leaving the modulators along common lines 2 and 3 in a relaxed position.
During the fourth line time 60d, the voltage on common line 1 returns to a high hold voltage 72, leaving the modulators along common line 1 in their respective addressed states. The voltage on common line 2 is decreased to a low address voltage 78. Because a high segment voltage 62 is applied along segment line 2, the pixel voltage across modulator (2,2) is below the lower end of the negative stability window of the modulator, causing the modulator (2,2) to actuate. Conversely, because a low segment voltage 64 is applied along segment lines 1 and 3, the modulators (2,1) and (2,3) remain in a relaxed position. The voltage on common line 3 increases to a high hold voltage 72, leaving the modulators along common line 3 in a relaxed state.
Finally, during the fifth line time 60e, the voltage on common line 1 remains at high hold voltage 72, and the voltage on common line 2 remains at a low hold voltage 76, leaving the modulators along common lines 1 and 2 in their respective addressed states. The voltage on common line 3 increases to a high address voltage 74 to address the modulators along common line 3. As a low segment voltage 64 is applied on segment lines 2 and 3, the modulators (3,2) and (3,3) actuate, while the high segment voltage 62 applied along segment line 1 causes modulator (3,1) to remain in a relaxed position. Thus, at the end of the fifth line time 60e, the 3×3 pixel array is in the state shown in
In the timing diagram of
The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,
As illustrated in
In implementations such as those shown in
The process 80 continues at block 84 with the formation of a sacrificial layer 25 over the optical stack 16. The sacrificial layer 25 is later removed (see block 90) to form the cavity 19 and thus the sacrificial layer 25 is not shown in the resulting interferometric modulators 12 illustrated in
The process 80 continues at block 86 with the formation of a support structure such as post 18, illustrated in
The process 80 continues at block 88 with the formation of a movable reflective layer or membrane such as the movable reflective layer 14 illustrated in
The process 80 continues at block 90 with the formation of a cavity, such as cavity 19 illustrated in
As noted above, an EMS device, including an IMOD, may be packaged to protect the EMS device from the environment and from operational hazards, such as mechanical shock. One packaging technique is a thin-film encapsulation process. To protect an EMS device from the environment, the thin-film encapsulation process may hermetically seal the EMS device. For example, the EMS device may be hermetically sealed between the substrate (and any associated layers) and a hermetic seal layer (and any associated layers).
A hermetic seal has the quality of being substantially airtight; i.e., a hermetic seal is substantially impervious to air, including water vapor and other gases in the air. Hermetic seals may serve to improve the performance of some EMS devices. For example, some EMS devices, including IMODs, include surfaces and/or parts that may come in and out of contact with one another. Adhesion of two separated layers of material to one another when the two layers come into contact with one another is an issue in some EMS devices. The phenomenon of two such layers adhering to one another in this manner is called stiction (i.e., static friction). Stiction in EMS devices may be exacerbated by water vapor in the air. Thus, hermetic seals that serve to protect an EMS device from water vapor may prolong the operational life of the EMS device.
For example, in the IMOD 12 shown in
Various implementations described herein involve processes of forming thin-film encapsulation layers. For example, in some implementations, a shell layer and a seal layer may be included in the thin-film encapsulation layers. The surface of the shell layer may be treated before forming a seal layer on the shell layer. The treatment may be performed, for example, after etching a sacrificial layer in the EMS device, after etching away sacrificial layers under the shell layer, or after patterning structural materials. After the treatment, the seal layer is formed on the shell layer. Implementations of the methods disclosed herein may result in a thin-film encapsulated EMS device in which the thin-film encapsulation hermetically seals the EMS device.
The process 900 in
The different components in the EMS assemblies 1000 and 1050 and their methods of fabrication are described further below. Additional details related to the components and their methods of fabrication are described in U.S. patent application Ser. No. 12/976,647, titled “METHOD OF FABRICATION AND RESULTANT ENCAPSULTED ELECTROMECHANICAL DEVICE.”
The substrate 1002 may be any number of different substrate materials, including transparent materials and non-transparent materials. In some implementations, the substrate is silicon, silicon-on-insulator (SOI), a glass (such as a display glass or a borosilicate glass), a flexible plastic, or a metal foil. In some implementations, the substrate on which an EMS device is fabricated has dimensions of a few microns to hundreds of microns. The stationary electrode 1004 may include an optical stack over the substrate 1002 and while it is illustrated as including two layers in
The first sacrificial layer 1010 may provide a support for the movable electrode 1012 during fabrication of the movable electrode 1012. In some implementations, the first sacrificial layer may be a polymer or a photoresist. In some other implementations, the first sacrificial layer may be a fluorine-etchable material, such as Mo, tungsten (W), or amorphous silicon (a-Si). The second sacrificial layer 1014 is on the movable electrode 1012, a portion of the post layer 1006, and a portion of the first sacrificial layer 1010. In some implementations, the second sacrificial layer 1014 provides a support for the shell layer 1008 during fabrication of the shell layer. The second sacrificial layer 1014 may be the same material as the first sacrificial layer 1010 or a different material from the first sacrificial layer 1010. In some implementations, the second sacrificial layer may be a polymer or a photoresist. In some other implementations, the second sacrificial layer may be a fluorine-etchable material, such as Mo, W, or a-Si.
The shell layer 1008 may be any number of different materials, including Al, aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (SiN), SiO2, SiON, polysilicon (poly-Si), silicon (Si), benzocyclobutene (BCB), acrylic, polyimide, other similar materials, and combinations thereof. In some implementations, the shell layer may at least partially enclose the EMS device. In some other implementations, the shell layer may be formed over the EMS device. In some implementations, the thickness of the shell layer may be sufficient to mechanically isolate the EMS device. In some implementations, the thickness of the shell layer may be about 100 nanometers to 20 microns, or about 1 micron to 3 microns.
In some implementations, the shell layer may be substantially nonporous. When the shell layer is substantially nonporous, liquids and/or gases generally cannot pass through the shell layer. For example, when the shell layer is substantially nonporous, the sacrificial layer may not be removed by the diffusion of etchants or other chemicals through the shell layer.
In some implementations, the shell layer includes an etch hole 1022. The etch hole 1022 may expose the first sacrificial layer 1010 without directly exposing the second sacrificial layer 1014. The etch hole allows for the removal of the first sacrificial layer and the second sacrificial layer, in some implementations. In some implementations, the etch hole may have a circular, annular, or other geometry. In some implementations, the etch hole may have a diameter greater than about 1 micron. In some implementations, the etch hole may have diameter of about 2 microns to 10 microns.
The process 900 in
In some implementations, etching a sacrificial layer forms a release passage connected to the etch hole (such as release passage 1034 in
At block 904 of the process 900, the shell layer is treated. The shell layer may be treated by many different techniques. In some implementations, the treatment includes depositing an adhesion improvement layer on the shell layer, for example at least a monolayer of material. In some implementations, the treatment includes thermally treating the shell layer at an elevated temperature, exposing the shell layer to ultraviolet light, exposing the shell layer to a chemical reactant, or forming a self-assembled monolayer (SAM) on the shell layer. In some implementations, the treatment includes treating an area of the shell layer adjacent to the etch hole and a portion of the sidewall of the etch hole.
In some implementations, a monolayer of material or a layer of material may be deposited by an atomic layer deposition (ALD) process. In some implementations, such a layer can serve as a treatment for a shell layer that improves the adhesion of subsequently deposited layers. ALD is a thin-film deposition technique performed with one or more chemical reactants, also referred to as precursors. ALD processes can be based on sequential, self-limiting surface reactions. The precursors can be sequentially admitted to a reaction chamber in a gaseous state where they contact a surface, such as a shell layer surface, that is being coated with a material. For example, a first precursor may be adsorbed onto the surface when it is admitted to a reaction chamber. Then, the first precursor reacts with a second precursor at the surface when the second precursor is admitted to the reaction chamber. By repeatedly exposing a surface to alternating sequential pulses of the precursors, a thin film of material is deposited. ALD processes also include processes in which a surface is exposed to sequential pulses of a single precursor, which deposits a thin film of material on the surface. ALD processes generally form a conformal layer, i.e., a layer that follows the contours of the underlying surface. In some implementations, one ALD process cycle or multiple ALD process cycles are performed to treat the shell layer. For example, in some implementations, about 40 ALD process cycles may be performed.
In some implementations, the material deposited by an ALD process is Al2O3 also referred to as alumina. In some implementations, operations for depositing Al2O3 by an ALD process include contacting a surface with a pulse of an aluminum precursor gas followed by a pulse of an oxygen precursor gas. For example, in some implementations, Al2O3 is deposited by an ALD process using trimethyl aluminum (TMA) as an aluminum precursor gas and at least one of water (H2O) or ozone (O3) as an oxygen precursor gas. Other suitable aluminum precursor gases include tri-isobutyl aluminum (TIBAL), tri-ethyl aluminum (TEA), tri-ethyl/methyl aluminum (TEA/TMA), dimethylaluminum hydride (DMAH), and the like.
In some implementations, a treatment of the shell layer may cover residues on the shell layer. For example, when a sacrificial layer is removed using an etchant, such as XeF2, residues from the etchant or from the chemical reaction between the sacrificial layer and the etchant may remain on the shell layer. Depositing at least a monolayer of material or a layer of material on the shell layer may cover such residues and improve the bond between the shell layer and the seal layer. Covering the residues also may result in a seal layer that is not contaminated or otherwise affected by any existing residues on the shell layer, which may improve the performance of the seal layer.
In some other implementations, treating the shell layer may chemically alter and/or remove any residues on the shell layer. For example, exposing the shell layer to a chemical reactant or to the precursors used in an ALD process may alter the composition of any residues on the shell layer or remove any residues on the shell layer. As another example, treating the shell layer at an elevated temperature or exposing the shell layer to ultraviolet (UV) light may oxidize or otherwise chemically alter any residues on the shell layer. Wavelengths of ultraviolet light may range from about 10 to 400 nanometers, for example.
Returning to
The seal layer may include any number of different materials, including a metal, or SiON, SiO2, Al2O3, and other dielectric materials. The seal layer also may be a multilayered material. In some implementations, the seal layer is a multilayered material including a layer of Al2O3 on a layer of SiON. For example, a layer of SiON may be deposited on the shell layer, and a layer of Al2O3 may be deposited on the SiON layer, forming a SiON/Al2O3 seal layer. In some implementations, a SiON/Al2O3 seal layer includes a SiON layer having a thickness between about 0.5 microns to 2.5 microns and an Al2O3 layer having a thickness of about 30 nanometers to 90 nanometers. In some implementations, a SiON/Al2O3 seal layer includes a SiON layer having a thickness of about 1.5 microns and an Al2O3 layer having a thickness of about 60 nanometers. In some implementations, a SiON layer may be formed with a PECVD process. In some implementations, an Al2O3 layer may be formed with about 200 to 600 ALD process cycles, or about 400 ALD process cycles. In some other implementations, the seal layer is a multilayered material including a layer of Al2O3 between two layers of SiON, forming a SiON/Al2O3/SiON seal layer. In some implementations, the SiON layers of a SiON/Al2O3/SiON seal layer may each be about 0.5 microns to 2.5 microns thick and the Al2O3 layer may be about 30 nanometers to 90 nanometers thick. In some implementations, the SiON layers may each be about 1.5 microns thick and the Al2O3 layer may be about 60 nanometers thick.
The EMS assembly 1100 shown in
The shell layer 1008 at least partially encloses the EMS device 1102 between the shell layer 1008 and the substrate 1002. The shell layer 1008 also includes an etch hole 1022. The seal layer 1042 hermetically seals the etch hole 1022 in the shell layer 1008 by blocking an opening of a release passage 1034 connected to the etch hole. In some implementations, the shell layer 1008 is treated according to a method disclosed herein before formation of the seal layer 1042 to improve the hermetic properties of the seal layer.
The top-down view of the EMS assembly 1100 shown in
At block 1202 of the process 1200, a substrate having an EMS device on the surface of the substrate is provided. A shell layer at least partially encloses the EMS device. The shell layer also is substantially nonporous, and includes an etch hole. Various substrates, EMS devices, and shell layers are described above.
At block 902, a sacrificial layer is etched. The sacrificial layer is etched from the substrate through the etch hole. Etching the sacrificial layer can form a release passage. In some implementations, the release passage has a height of less than about 1 micron and a width of greater than about 1 micron. Block 902 is described further, above.
At block 1204, after etching the sacrificial layer, an adhesion improvement layer is deposited on the shell layer. The adhesion improvement layer can improve the adhesion of the subsequently deposited seal layer onto the shell layer after the sacrificial material is etched from beneath the shell layer. In some implementations, the adhesion improvement layer includes at least a monolayer of aluminum oxide that is deposited on the shell layer with an ALD process. The process operation at block 1204 is a treatment of the shell layer; i.e., the process operation at block 1204 is a specific implementation of the process operation at block 904 of the manufacturing process 900, described above. Process operations in an ALD process are also described above.
At block 906, a seal layer is deposited on the shell layer. The seal layer blocks the release passage and hermetically seals the electromechanical systems device. Block 906 is described further, above.
An experiment was performed on the thin-film encapsulation materials produced using the processes disclosed here. In “process 1”, a seal layer was deposited on a shell layer of an EMS assembly. The seal layer included an about 1.5 micron layer of SiON, an about 60 nanometer layer of Al2O3 on the SiON layer, and an about 1.5 micron layer of SiON on the Al2O3 layer. The Al2O3 layer was deposited by an ALD process. In “process 2”, the shell layer was treated by exposing the shell layer to 35 ALD process cycles for depositing Al2O3. The 35 ALD process cycles deposited an about 4 nanometer thick layer of Al2O3. Then, a seal layer similar to the seal layer of “process 1” was deposited onto the treated shell layer. Both the “process 1” and the “process 2” EMS assemblies were then exposed to an environment of about 85° C. and about 85% relative humidity.
The hermetic properties of the seal layer of the “process 1” EMS assembly failed in the environment of about 85° C. and about 85% relative humidity before 50 hours of exposure had elapsed. In contrast, the seal layer of the “process 2” EMS assembly maintained its hermetic properties for 300 hours in the environment of about 85° C. and about 85% relative humidity, but failed before 500 hours of exposure had elapsed. Some seal layers formed with treatment processes similar to the “process 2” treatment process, however, have maintained their hermetic properties for over 2,500 hours in an environment of about 85° C. and about 85% relative humidity.
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 interferometric modulator 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 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, such as 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. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The steps of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and blue-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above also may be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine readable medium and computer-readable medium, which may be incorporated into a computer program product.
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 possibilities or 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 an 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, a person having ordinary skill in the art will readily recognize that such operations need not 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.
This application is related to U.S. patent application Ser. No. 12/976,647, titled “METHOD OF FABRICATION AND RESULTANT ENCAPSULTED ELECTROMECHANICAL DEVICE,” filed Dec. 22, 2010, which is herein incorporated by reference.
