METHODS AND DEVICES FOR DETECTING AND MEASURING ENVIRONMENTAL CONDITIONS IN HIGH PERFORMANCE DEVICE PACKAGES
An environmental condition sensing device includes an interferometric modulator with optical properties, which change in response to being exposed to a predetermined environmental threshold or condition. The device includes an environmental reactive layer, which alters composition, in an optically-detectable manner, in response to being exposed to a predetermined environmental threshold or condition.
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This application is a continuation of U.S. patent application Ser. No. 12/613,396, filed Nov. 5, 2009, and entitled “METHODS AND DEVICES FOR DETECTING AND MEASURING ENVIRONMENTAL CONDITIONS IN HIGH PERFORMANCE DEVICE PACKAGES,” and assigned to the assignee of the present application. The disclosure of this prior application is incorporated herein by reference in its entirety.
BACKGROUND1. Field of the Invention
The present invention relates to devices sensitive to environmental exposure including organic light emitting diode devices (OLED) and microelectromechanical systems (MEMS).
2. Description of Related Technology
Microelectromechanical systems (MEMS) include micro mechanical elements, actuators, and electronics. Micromechanical elements may be created using deposition, etching, 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 MEMS device is called an interferometric modulator. 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 certain embodiments, an interferometric modulator may comprise a pair of conductive plates, one or both of which may be transparent and/or reflective in whole or part and capable of relative motion upon application of an appropriate electrical signal. In a particular embodiment, one plate may comprise a stationary layer deposited on a substrate and the other plate may comprise a metallic membrane separated from the stationary layer by an air gap. As described herein in more detail, the position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Such devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of these types of devices so that their features can be exploited in improving existing products and creating new products that have not yet been developed.
The following detailed description is directed to certain specific embodiments. However, the teachings herein can be applied in a multitude of different ways. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. The embodiments may be implemented in any device that is configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual or pictorial. More particularly, it is contemplated that the embodiments may be implemented in or associated with a variety of electronic devices such as, but not limited to, mobile telephones, wireless devices, personal data assistants (PDAs), hand-held or portable computers, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, computer monitors, auto displays (e.g., odometer display, etc.), cockpit controls and/or displays, display of camera views (e.g., display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., display of images on a piece of jewelry). MEMS devices of similar structure to those described herein can also be used in non-display applications such as in electronic switching devices.
Many devices, including MEMS devices, are extremely sensitive to environmental conditions and require special packaging (encapsulation) that is extremely impermeable. Even small changes in environmental conditions, such as the presence of a small amount of a gas species, can adversely affect the functionality of such a device. Certain materials readily react in the presence of specific gas species (e.g. water, oxygen, etc.). The reaction may then cause certain optical properties of the material to change. Depending on the materials used and the detection method, it can be inferred what amount of gas the material has been exposed to, which under specific conditions can be used to advantage. Methods and devices are described herein which are configured to alter in response to exposure to a pre-determined environmental condition or set of conditions. These devices may comprise interferometric modulators which, given their enhanced optical properties, are capable of detecting such alterations. These devices can be used in various applications, such as consumer-level packaging where conditions during shipping and/or storage must be monitored to ensure quality. These devices can also be used to monitor environmental conditions in the packaging of MEMS devices.
One interferometric modulator display embodiment comprising an interferometric MEMS display element is illustrated in
The depicted portion of the pixel array in
The optical stacks 16a and 16b (collectively referred to as optical stack 16), as referenced herein, typically comprise several fused layers, which can include an electrode layer, such as indium tin oxide (ITO), a partially reflective layer, such as chromium, and a transparent dielectric. The optical stack 16 is thus 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 partially reflective layer can be formed from a variety of materials that are partially reflective such as various metals, 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 embodiments, the layers of the optical stack 16 are patterned into parallel strips, and may form row electrodes in a display device as described further below. The movable reflective layers 14a, 14b may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of 16a, 16b) 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, the movable reflective layers 14a, 14b are separated from the optical stacks 16a, 16b by a defined gap 19. A highly conductive and reflective material such as aluminum may be used for the reflective layers 14, and these strips may form column electrodes in a display device. Note that
With no applied voltage, the gap 19 remains between the movable reflective layer 14a and optical stack 16a, with the movable reflective layer 14a in a mechanically relaxed state, as illustrated by the pixel 12a in
In one embodiment, the processor 21 is also configured to communicate with an array driver 22. In one embodiment, the array driver 22 includes a row driver circuit 24 and a column driver circuit 26 that provide signals to a display array or panel 30. The cross section of the array illustrated in
As described further below, in typical applications, a frame of an image may be created by sending a set of data signals (each having a certain voltage level) across the set of column electrodes in accordance with the desired set of actuated pixels in the first row. A row pulse is then applied to a first row electrode, actuating the pixels corresponding to the set of data signals. The set of data signals is then changed to correspond to the desired set of actuated pixels in a second row. A pulse is then applied to the second row electrode, actuating the appropriate pixels in the second row in accordance with the data signals. The first row of pixels are unaffected by the second row pulse, and remain in the state they were set to during the first row pulse. This may be repeated for the entire series of rows in a sequential fashion to produce the frame. Generally, the frames are refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second. A wide variety of protocols for driving row and column electrodes of pixel arrays to produce image frames may be used.
In the
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 is generally 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. In one embodiment the housing 41 includes 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 of exemplary display device 40 may be any of a variety of displays, including a bi-stable display, as described herein. In other embodiments, the display 30 includes a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD as described above, or a non-flat-panel display, such as a CRT or other tube device. However, for purposes of describing the present embodiment, the display 30 includes an interferometric modulator display, as described herein.
The components of one embodiment of exemplary display device 40 are schematically illustrated in
The network interface 27 includes the antenna 43 and the transceiver 47 so that the exemplary display device 40 can communicate with one ore more devices over a network. In one embodiment the network interface 27 may also have some processing capabilities to relieve requirements of the processor 21. The antenna 43 is any antenna for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.11 standard, including IEEE 802.11(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS, W-CDMA, or other known signals that are used to communicate within a wireless cell phone network. The transceiver 47 pre-processes 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 processes signals received from the processor 21 so that they may be transmitted from the exemplary display device 40 via the antenna 43.
In an alternative embodiment, the transceiver 47 can be replaced by a receiver. In yet another alternative embodiment, network interface 27 can be replaced by an image source, which can store or generate image data to be sent to the processor 21. For example, the image source can be a digital video disc (DVD) or a hard-disc drive that contains image data, or a software module that generates image data.
Processor 21 generally controls the overall operation of the exemplary 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 then sends the processed data to the driver controller 29 or to 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.
In one embodiment, the processor 21 includes a microcontroller, CPU, or logic unit to control operation of the exemplary display device 40. Conditioning hardware 52 generally includes amplifiers and filters for transmitting signals to the speaker 45, and for receiving signals from the microphone 46. Conditioning hardware 52 may be discrete components within the exemplary display device 40, or may be incorporated within the processor 21 or other components.
The driver controller 29 takes the raw image data generated by the processor 21 either directly from the processor 21 or from the frame buffer 28 and reformats the raw image data appropriately for high speed transmission to the array driver 22. Specifically, the driver controller 29 reformats 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 a 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. They 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.
Typically, the array driver 22 receives the formatted information from the driver controller 29 and reformats the video data into a parallel set of waveforms that are applied many times per second to the hundreds and sometimes thousands of leads coming from the display's x-y matrix of pixels.
In one embodiment, the driver controller 29, array driver 22, and display array 30 are appropriate for any of the types of displays described herein. For example, in one embodiment, driver controller 29 is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, array driver 22 is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, a driver controller 29 is integrated with the array driver 22. Such an embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment, display array 30 is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).
The input device 48 allows a user to control the operation of the exemplary display device 40. In one embodiment, input device 48 includes a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a touch-sensitive screen, a pressure- or heat-sensitive membrane. In one embodiment, the microphone 46 is an input device for the exemplary display device 40. When the microphone 46 is used to input data to the device, voice commands may be provided by a user for controlling operations of the exemplary display device 40.
Power supply 50 can include a variety of energy storage devices as are well known in the art. For example, in one embodiment, power supply 50 is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment, power supply 50 is a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell, and solar-cell paint. In another embodiment, power supply 50 is configured to receive power from a wall outlet.
In some implementations control programmability resides, as described above, in a driver controller which can be located in several places in the electronic display system. In some cases 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 details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,
In embodiments such as those shown in
The selective absorption and reflection of light by an interferometric modulator can be used in connection with methods of detecting small chemical changes in a variety of materials. In this way, the interferometric modulator may be configured in to act as an environmental condition monitoring device. Depending on the particular configuration of the device and depending on the environmental conditions to which the device is exposed, the optical properties of the device change significantly.
In embodiments such as those shown in
In one embodiment, the high sensitivity of the device 800 allows for unaccelerated detection of extremely low permeation of gas into a package even when a small total area for the environmental reactive layer 804 is chosen. Further, the high sensitivity allows for detection of sub-nm changes in composition and/or thickness of the environmental reactive layer 804.
In one embodiment, the optical enhancement layer 808 comprises materials chosen to create an optical resonance in the environmental reactive layer 804. The environmental reactive layer 804 acts as an optical absorber layer in this embodiment. The environmental reactive layer 804 may be a metal (e.g., Al, Ca, Ni). The thickness of the environmental reactive layer 804 may be chosen to be less than a skin depth of the metal chosen. The skin depth of the metal is the depth to which electromagnetic radiation (e.g., light) can penetrate the surface of the metal. Further, the thickness of the environmental reactive layer 804 may be chosen to act as an absorber in conjunction with the optical enhancement layer 808.
In an embodiment, the optical enhancement layer 808 comprises a dielectric layer 806 and a reflector layer 807. The reflector layer 807 may comprise a metal (e.g., Al). The thickness of the reflector layer 807 may be greater than a skin depth of the metal chosen. Accordingly, the reflector layer 807 reflects light efficiently. Further, the thickness of the dielectric layer may be chosen such that the device 800 exhibits certain optical properties. For example, the thickness chosen for the dielectric layer 806 may shift the reflectivity spectrum of the device 800 with respect to wavelength as discussed below with respect to
As discussed above, in one embodiment of
In other exemplary embodiments, a semiconductor such as silicon may be chosen for the environmental reactive layer 804. Other exemplary materials include silica, aluminum, nickel, etc.
In the embodiment of
One of ordinary skill in the art will recognize that changing the initial thickness and/or material of the dielectric layer 806, the reflector layer 807, and/or the environmental reactive layer 804, and/or changing the exposure to an environmental condition changes the reflectivity response of the device 800. For example, changing the thickness of the dielectric layer 806 may shift the lines 1004-1044 along the x-axis (wavelength). Therefore, the wavelength of light having a high delta value for varying thicknesses of the environmental reactive layer 804 may be shifted. Accordingly, the thickness of the dielectric layer 806 may be selected to choose a particular wavelength of light for analysis. In one embodiment, the wavelength of light chosen for analysis is based on the optimal wavelength for detection by monitoring equipment used to detect the change in reflectivity.
In another embodiment, the chromaticity of the device 800 may change as the level of chemical modification of the environmental reactive layer 804 changes.
In one embodiment, the device 800 is manufactured according to the process 1400 of
A particular thickness for the environmental reactive layer 804 may be chosen by the manufacturer in the first step 1404 to enhance the optical response to changes in the environmental layer 804. In one embodiment, the initial thickness of the environmental reactive layer 804 may be chosen to be less than a skin depth of the metal chosen as described above with respect to
The surface area of the environmental reactive layer 804 may be also chosen by the manufacturer in first step 1404 according to desired sensitivity of the device 800 and overall size of the device 800. In an exemplary embodiment, the overall size of the device 800 is limited by the size of the package 1300 in which the device 800 is to be used as seen in
Next, at step 1408, in process 1400 of manufacturing the device according to the embodiment of
Further, in step 1408, the thickness of the optical enhancement layer 808 may be chosen by the manufacturer such that the device 800 has a desired optical response. In an embodiment, the thickness is chosen such that a desired wavelength of light is substantially absorbed in the environmental reactive layer 804. This is due to the concentration of the electric field of the desired wavelength in the environmental reactive layer 804 as light is incident. In this embodiment, the appearance of the device 800 changes as the thickness and/or composition of the environmental reactive layer 804 changes. The optical enhancement layer 808 is configured to enhance the optical properties of the environmental reactive layer 804. In one embodiment the optical enhancement layer 808 includes about 133 nm of SiO2 on top of about 100 nm of Al. Other materials and thicknesses known to persons of ordinary skill in the art to selectively reflect and absorb light may also be used.
Continuing to step 1416 of the manufacturing process of
At step 1504, in process 1500, the device 800 is exposed to an environmental condition. As described with respect to
Optical response properties of the device 800 and/or environmental reactive layer 804 may already be known and such data may not need to be gathered by the process of
In one embodiment of step 1608, the spatial map of the device 800 at a given moment can be compared to pre-collected data for the same configuration of device 800. In other exemplary embodiments of step 1608, the comparison may occur via a chart, or a data table, or other known means of relational graphing. The comparison can be done by hand or implemented by means of a computer or other data processing device. In exemplary embodiments, the processing device may be built into the same housing as the measuring equipment or may be separate.
In one embodiment, the device 800 is configured to change color at a specific amount of exposure to an environmental condition, where the change in color is detectable without measuring equipment (e.g., detectable with the naked eye). In this embodiment, step 1612 does not require a specific calculation, but rather the amount of exposure to an environmental condition is the amount at which the device 800 is configured to change color.
While the above processes 1400, 1500, and 1600 are described in the detailed description as including certain steps and are described in a particular order, it should be recognized that these processes may include additional steps or may omit some of the steps described. Further, each of the steps of the processes does not necessarily need to be performed in the order it is described. For example, step 1416 of process 1400 may be omitted, or step 1408 may be performed before step 1404.
In other exemplary embodiments, sensitivity of the device 800 to an environmental condition further depends on the rate at which the environmental reactive layer 804 reacts to the presence of an environmental condition. In such embodiments, the faster the rate of reaction, the sooner optical properties of device 800 change in response to exposure to an environmental condition.
The rate at which the composition of the environmental reactive layer 804 changes may depend on its exposure to certain conditions. For instance, in the embodiment where a metal is chosen for the environmental reactive layer 804, the pressure and/or temperature to which the environmental reactive layer 804 is exposed may change the rate at which it reacts with environmental conditions. Raising the temperature may increase the speed at which the layer 804 chemically modifies. In one embodiment, the device 800 is exposed to a particular temperature and/or pressure to adjust the rate at which the environmental reactive layer 804 reacts to the pre-determined environmental condition.
In the embodiment where a semi-conductor is chosen for the environmental reactive layer 804, the dose of light to which the environmental reactive layer 804 is exposed changes the rate at which it chemically modifies in the presence of a pre-determined environmental condition. For example, electron hole generation caused by absorption of light in a semiconductor can greatly accelerate chemical changes of the semiconductor material. In one embodiment, where silicon is used for the environmental reactive layer 804, this acceleration is based on electrochemical effects, such as the reactivity of silicon to oxidizing agents when light with energy larger than the electronic bandgap is incident on environmental reactive layer 804. In an exemplary embodiment, the environmental reactive layer 804 changes from an electrically conductive composition (optical absorbing) to chemically modified layer 812, an insulator composition (less optical absorbing) at a faster rate when exposed to a higher does of light.
In one embodiment where a semi-conductor is chosen for the environmental reactive layer 804, the device 800 acts as a light-enhanced chemical detection device, or monitor (e.g. dose-meter) for radiation. In this embodiment, the intensity of UV radiation incident on the device 800 can be correlated to the chemical change of the environmental reactive layer 804 (e.g. oxidation of silicon in presence of oxygen and water, common atmospheric conditions, under the influence of UV). This correlation is achieved by monitoring, as in step 1508 of
While the above detailed description has shown, described and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the spirit of the invention. As will be recognized, the present invention may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others.
Claims
1. An environmental condition monitoring device, comprising:
- an interferometric modulator (IMOD) comprising: a substrate; an optical enhancement layer disposed on the substrate, the optical enhancement layer comprising a reflector layer; and an environmental reactive layer disposed on the optical enhancement layer, the environmental reactive layer having a composition capable of being altered in response to exposure to an environmental condition.
2. The environmental condition monitoring device of claim 1, wherein the environmental reactive layer and reflector layer define boundaries for an interferometric cavity of the IMOD.
3. The environmental condition monitoring device of claim 1, wherein the environmental reactive layer is capable of acting as an absorber layer.
4. The environmental condition monitoring device of claim 1, wherein a thickness of the environmental reactive layer is less than a thickness of the reflector layer.
5. The environmental condition monitoring device of claim 1, wherein a thickness of the environmental reactive layer is less than 10 nm.
6. The environmental condition monitoring device of claim 1, wherein the environmental condition is at least one of exposure to a gas species or water.
7. The environmental condition monitoring device of claim 1, wherein a rate at which the composition of the environmental reactive layer alters in response to exposure to an environmental condition is altered by at least one of an amount of light or a temperature to which the environmental reactive layer is exposed.
8. The environmental condition monitoring device of claim 1, further comprising a dielectric layer.
9. The environmental condition monitoring device of claim 1, wherein the environmental reactive layer is at least one of a semi-conductor or a metal.
10. The environmental condition monitoring device of claim 1, wherein the reflectivity of the IMOD at a selected wavelength is a function of the composition of the environmental reactive layer.
11. The environmental condition monitoring device of claim 1, wherein a chromaticity of the IMOD is a function of the composition of the environmental reactive layer.
12. The environmental condition monitoring device of claim 1, wherein the substrate is glass.
13. An environmental condition monitoring device, comprising:
- means for modulating light, comprising: a substrate; an optical enhancement means disposed on the substrate, the optical enhancement means comprising a light reflecting means; and an absorbing means for altering the reflectivity spectrum of the light reflecting means in response to exposure to an environmental condition, wherein the absorbing means is disposed on the optical enhancement means.
14. The environmental condition monitoring device of claim 13, further comprising an interferometric modulator (IMOD).
15. The environmental condition monitoring device of claim 13, wherein the absorbing means comprises an environmental reactive layer having a composition, the composition capable of altering in response to exposure to an environmental condition.
16. The environmental condition monitoring device of claim 15, wherein a thickness of the environmental reactive layer is less than a thickness of the reflector layer.
17. The environmental condition monitoring device of claim 15, wherein a thickness of the environmental reactive layer is less than 10 nm.
18. A method of manufacturing an environmental condition monitoring device, comprising:
- providing a substrate;
- forming an optical enhancement layer on the substrate, the optical enhancement layer including a reflector layer; and
- forming an environmental reactive layer on the optical enhancement layer; the environmental reactive layer and reflector layer defining boundaries for an interferometric cavity of an interferometric modulator (IMOD).
19. The method of claim 18, further comprising configuring the IMOD or the environmental reactive layer, so the reflectivity of the IMOD at a selected wavelength is a function of the composition of the environmental reactive layer.
20. The method of claim 18, further comprising configuring the IMOD to track changes in chromaticity of the IMOD and the appearance of pinholes in the environmental reactive layer in response to exposure to the environmental condition.
Type: Application
Filed: Apr 25, 2014
Publication Date: Aug 21, 2014
Applicant: Qualcomm Incorporated (San Diego, CA)
Inventor: Ion Bita (San Jose, CA)
Application Number: 14/262,545
International Classification: G01N 33/18 (20060101);