Patent Publication Number: US-11031432-B2

Title: Vertical microbolometer contact systems and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 15/396,100 filed Dec. 30, 2016 and entitled “VERTICAL MICROBOLOMETER CONTACT SYSTEMS AND METHODS,” which is a continuation of International Patent Application No. PCT/US2015/039138 filed Jul. 2, 2015 and entitled “VERTICAL MICROBOLOMETER CONTACT SYSTEMS AND METHODS,” which in turn claims priority to and the benefit of U.S. Provisional Patent Application No. 62/020,747 filed on Jul. 3, 2014 and entitled “VERTICAL MICROBOLOMETER CONTACT SYSTEMS AND METHODS,” the contents all of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     One or more embodiments of the invention relate generally to infrared cameras and, more particularly, to microbolometer contact systems and methods, such as vertical leg contacts for microbolometer focal plane arrays. 
     BACKGROUND 
     A microbolometer is an example of a type of infrared detector that may be used within an infrared imaging device (e.g., an infrared camera). For example, the microbolometer is typically fabricated on a monolithic silicon substrate to form an infrared (image) detector array, with each microbolometer of the infrared detector array functioning as a pixel to produce a two-dimensional image. The change in resistance of each microbolometer is translated into a time-multiplexed electrical signal by circuitry known as the read out integrated circuit (ROIC). The combination of the ROIC and the infrared detector array (e.g., microbolometer array) is commonly known as a focal plane array (FPA) or infrared FPA (IRFPA). Additional details regarding FPAs and microbolometers may be found, for example, in U.S. Pat. Nos. 5,756,999, 6,028,309, 6,812,465, and 7,034,301, which are herein incorporated by reference in their entirety. 
     Each microbolometer in the array is generally coupled to one or more contacts that extend vertically from the array down to the ROIC. The contacts can be used for providing a reference voltage for the microbolometer and/or a signal path from the microbolometer to the ROIC. Microbolometers often include a light-sensitive portion formed from resistive material suspended on a bridge, with the resistive material coupled to its contacts via legs that run from the bridge to the contacts. The legs attach to resistive material through a resistive material contact. 
     One of the challenges in designing efficient microbolometers is increasing the ratio of the light-sensitive area or the active pixel area to the total area of the array, sometimes referred to as the fill factor of the array. Leg supports for each microbolometer can occupy a significant portion of the array area and can therefore limit the fill factor of the array. It would therefore be desirable to reduce the amount of area occupied by the legs. However, in order to maintain device performance, the width and length of each leg support should scale with the area of each pixel. It can therefore be difficult to reduce the leg area and increase the fill factor. As a result, there is a need for improved techniques for implementing leg supports, such as for microbolometer-based focal plane arrays. 
     SUMMARY 
     Systems and methods are disclosed, in accordance with one or more embodiments, which are directed to microbolometer legs for an infrared detector. For example, in accordance with an embodiment of the invention, vertical legs are disclosed, such as for infrared detectors within a focal plane array, that may be more area efficient as compared to conventional legs that extend horizontally substantially in plane with the infrared detector. For one or more embodiments, the leg systems and methods disclosed herein may provide certain advantages over conventional leg approaches, especially as semiconductor processing technologies transition to smaller dimensions. 
     In accordance with one embodiment, an infrared imaging device includes an array of microbolometers each having a bridge that is coupled to a contact by at least one vertical bolometer leg. The legs and bridges of the microbolometer array may be suspended above a readout integrated circuit for the microbolometer array. The vertical bolometer legs may be formed using spacer deposition and etch processing operations that form at least portions of the vertical bolometer legs on the sidewalls of an opening in a sacrificial layer that is then removed to release the bolometer legs. 
     According to various embodiments, a vertical bolometer leg may run along a path that is disposed in a plane that is parallel to a plane defined by the bridge of the microbolometer and/or a plane that is defined by a surface of a substrate of the device such as a readout integrated circuit substrate and may have an extended dimension that extends in a direction that is perpendicular to the plane of the path, the substrate surface, and/or the plane of the bridge. In this way, the area of the bolometer leg that would otherwise occupy a relatively larger fraction of the surface area of the microbolometer array can be reduced without reducing the area of the bolometer leg. 
     According to various embodiments, the leg structure may or may not be encapsulated in an insulating layer such as a silicon dioxide or a silicon nitride. The leg structure may be formed from multiple layers of insulating material to optimize performance. A leg conductive layer may be fully or partially encapsulated with an insulation layer, or may be free of any insulation layer. The leg conductive layer may be a homogeneous film of a single material type or a multilayer conductive layer formed from, for example, several depositions. 
     The scope of the invention is defined by the claims, which are incorporated into this Summary by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a block diagram illustrating an infrared camera in accordance with one or more embodiments. 
         FIG. 2  shows a block diagram illustrating an implementation example for an infrared camera in accordance with one or more embodiments. 
         FIG. 3  shows a physical layout diagram of a microbolometer of a microbolometer array having vertical legs in accordance with an embodiment. 
         FIGS. 4A and 4B  show a top view and a cross-sectional side view respectively of a conventional horizontal leg for a microbolometer. 
         FIGS. 5A and 5B  show a top view and a cross-sectional side view respectively of a vertical leg such as for a leg for coupling an infrared detector element to a contact, in accordance with an embodiment. 
         FIGS. 6A through 6F  illustrate a processing overview for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIGS. 7A through 7F  illustrate another processing overview for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIGS. 8A through 8C  illustrate a yet another processing overview for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIG. 9  shows a cross-sectional side view, in the vicinity of a vertical contact between an infrared detector array and a readout integrated circuit, of a portion of a focal plane array having vertical legs that are formed below a surface of the array, in accordance with an embodiment. 
         FIG. 10  shows a cross-sectional side view, in the vicinity of a sensor of the array, of a portion of a focal plane array having vertical legs that are formed below a surface of the array, in accordance with an embodiment. 
         FIG. 11  shows a cross-sectional side view, in the vicinity of a vertical contact between an infrared detector array and a readout integrated circuit, of a portion of a focal plane array having vertical legs that are formed below a surface of the array, in accordance with an embodiment. 
         FIG. 12  shows a cross-sectional side view, in the vicinity of a sensor of the array, of a portion of a focal plane array having vertical legs that are formed below a surface of the array, in accordance with an embodiment. 
         FIGS. 13A through 13Q  show various arrangements of a vertical leg, such as for the vertical legs of  FIGS. 5A and 5B , in accordance with various embodiments. 
         FIG. 14  shows a cross-sectional side view, in the vicinity of a vertical contact between an infrared detector array and a readout integrated circuit, of a portion of a focal plane array having vertical legs formed at or above a surface of the array, in accordance with an embodiment. 
         FIG. 15  shows a cross-sectional side view, in the vicinity of a sensor of the array, of a portion of a focal plane array having vertical legs formed above a surface of the array, in accordance with an embodiment. 
         FIG. 16  shows a top view of a bend portion of a vertical leg, such as for the vertical legs of  FIG. 3  in the vicinity of a bend in the vertical leg, in accordance with an embodiment. 
         FIG. 17  shows a cross-sectional view of an example arrangement of the vertical leg of  FIG. 16 , in accordance with an embodiment. 
         FIG. 18  shows a cross-sectional view of another example arrangement of the vertical leg of  FIG. 16 , in accordance with an embodiment. 
         FIG. 19  shows a cross-sectional view of a portion of a focal plane array having legs, such as legs for an infrared detector, that are formed at least partially beneath a bridge portion of the infrared detector, in accordance with an embodiment. 
         FIG. 20  illustrates a flow diagram for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIG. 21  illustrates another flow diagram for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIG. 22  illustrates yet another flow diagram for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3 , in accordance with an embodiment. 
         FIGS. 23A through 23F  illustrate a processing overview for manufacturing a vertical leg, such as for the vertical legs of  FIG. 3  using an etch stop layer, in accordance with an embodiment. 
         FIG. 24  shows a cross-sectional view of a portion of a focal plane array having legs, such as legs for an infrared detector, that are formed at least partially beneath a bridge portion of the infrared detector, in accordance with an embodiment. 
         FIG. 25  illustrates a flow diagram for manufacturing a focal plane array having legs, such as legs for an infrared detector, that are formed at least partially beneath a bridge portion of the infrared detector, in accordance with an embodiment. 
     
    
    
     Embodiments of the invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. 
     DETAILED DESCRIPTION 
     Systems and methods are disclosed herein to provide vertically oriented legs for an infrared detector, in accordance with one or more embodiments. For example, in accordance with an embodiment, vertical bolometer legs are disclosed, such as for microbolometers within a focal plane array. As an implementation example,  FIG. 1  shows a block diagram illustrating a system  100  (e.g., an infrared camera, including any type of infrared imaging system) for capturing images and processing in accordance with one or more embodiments. System  100  comprises, in one implementation, an image capture component  102 , a processing component  104 , a control component  106 , a memory component  108 , and a display component  110 . Optionally, system  100  may include a sensing component  112 . 
     System  100  may represent, for example, an infrared imaging device, such as an infrared camera, to capture and process images, such as video images of a scene  101 . The system  100  may represent any type of infrared camera that employs infrared detectors having contacts, which may be implemented as disclosed herein. System  100  may comprise a portable device and may be incorporated, e.g., into a vehicle (e.g., an automobile or other type of land-based vehicle, an aircraft, or a spacecraft) or a non-mobile installation requiring infrared images to be stored and/or displayed or may comprise a distributed networked system (e.g., processing component  104  distant from and controlling image capture component  102  via the network). 
     In various embodiments, processing component  104  may comprise any type of a processor or a logic device (e.g., a programmable logic device (PLD) configured to perform processing functions). Processing component  104  may be adapted to interface and communicate with components  102 ,  106 ,  108 , and  110  to perform method and processing steps and/or operations, such as for example, controlling biasing and other functions (e.g., values for elements such as variable resistors and current sources, switch settings for biasing and timing, and other parameters) along with other conventional system processing functions as would be understood by one skilled in the art. 
     Memory component  108  comprises, in one embodiment, one or more memory devices adapted to store data and information, including for example infrared data and information. Memory device  108  may comprise one or more various types of memory devices including volatile and non-volatile memory devices, including computer-readable medium (portable or fixed). Processing component  104  may be adapted to execute software stored in memory component  108  so as to perform method and process steps and/or operations described herein. 
     Image capture component  102  comprises, in one embodiment, one or more infrared sensors (e.g., any type of multi-pixel infrared detector, such as a focal plane array having one or more vertical legs as disclosed herein) for capturing infrared image data (e.g., still image data and/or video data) representative of an image, such as scene  101 . In one implementation, the infrared sensors of image capture component  102  provide for representing (e.g., converting) the captured image data as digital data (e.g., via an analog-to-digital converter included as part of the infrared sensor or separate from the infrared sensor as part of system  100 ). In one or more embodiments, image capture component  102  may further represent or include a lens, a shutter, and/or other associated components along with the vacuum package assembly for capturing infrared image data. Image capture component  102  may further include temperature sensors (or temperature sensors may be distributed within system  100 ) to provide temperature information to processing component  104  as to operating temperature of image capture component  102 . 
     In one aspect, the infrared image data (e.g., infrared video data) may comprise non-uniform data (e.g., real image data) of an image, such as scene  101 . Processing component  104  may be adapted to process the infrared image data (e.g., to provide processed image data), store the infrared image data in memory component  108 , and/or retrieve stored infrared image data from memory component  108 . For example, processing component  104  may be adapted to process infrared image data stored in memory component  108  to provide processed image data and information (e.g., captured and/or processed infrared image data). 
     Control component  106  comprises, in one embodiment, a user input and/or interface device, such as a rotatable knob (e.g., potentiometer), push buttons, slide bar, keyboard, etc., that is adapted to generate a user input control signal. Processing component  104  may be adapted to sense control input signals from a user via control component  106  and respond to any sensed control input signals received therefrom. Processing component  104  may be adapted to interpret such a control input signal as a parameter value, as generally understood by one skilled in the art. In one embodiment, control component  106  may comprise a control unit (e.g., a wired or wireless handheld control unit) having push buttons adapted to interface with a user and receive user input control values. In one implementation, the push buttons of the control unit may be used to control various functions of the system  100 , such as autofocus, menu enable and selection, field of view, brightness, contrast, noise filtering, high pass filtering, low pass filtering, and/or various other features as understood by one skilled in the art. 
     Display component  110  comprises, in one embodiment, an image display device (e.g., a liquid crystal display (LCD) or various other types of generally known video displays or monitors). Processing component  104  may be adapted to display image data and information on the display component  110 . Processing component  104  may be adapted to retrieve image data and information from memory component  108  and display any retrieved image data and information on display component  110 . Display component  110  may comprise display electronics, which may be utilized by processing component  104  to display image data and information (e.g., infrared images). Display component  110  may be adapted to receive image data and information directly from image capture component  102  via the processing component  104 , or the image data and information may be transferred from memory component  108  via processing component  104 . 
     Optional sensing component  112  comprises, in one embodiment, one or more sensors of various types, depending on the application or implementation requirements, as would be understood by one skilled in the art. The sensors of optional sensing component  112  provide data and/or information to at least processing component  104 . In one aspect, processing component  104  may be adapted to communicate with sensing component  112  (e.g., by receiving sensor information from sensing component  112 ) and with image capture component  102  (e.g., by receiving data and information from image capture component  102  and providing and/or receiving command, control, and/or other information to and/or from one or more other components of system  100 ). 
     In various implementations, sensing component  112  may provide information regarding environmental conditions, such as outside temperature, lighting conditions (e.g., day, night, dusk, and/or dawn), humidity level, specific weather conditions (e.g., sun, rain, and/or snow), distance (e.g., laser rangefinder), and/or whether a tunnel or other type of enclosure has been entered or exited. Sensing component  112  may represent conventional sensors as generally known by one skilled in the art for monitoring various conditions (e.g., environmental conditions) that may have an effect (e.g., on the image appearance) on the data provided by image capture component  102 . 
     In some implementations, optional sensing component  112  (e.g., one or more of sensors) may comprise devices that relay information to processing component  104  via wired and/or wireless communication. For example, optional sensing component  112  may be adapted to receive information from a satellite, through a local broadcast (e.g., radio frequency (RF)) transmission, through a mobile or cellular network and/or through information beacons in an infrastructure (e.g., a transportation or highway information beacon infrastructure), or various other wired and/or wireless techniques. 
     In various embodiments, components of system  100  may be combined and/or implemented or not, as desired or depending on the application or requirements, with system  100  representing various functional blocks of a related system. In one example, processing component  104  may be combined with memory component  108 , image capture component  102 , display component  110 , and/or optional sensing component  112 . In another example, processing component  104  may be combined with image capture component  102  with only certain functions of processing component  104  performed by circuitry (e.g., a processor, a microprocessor, a logic device, a microcontroller, etc.) within image capture component  102 . Furthermore, various components of system  100  may be remote from each other (e.g., image capture component  102  may comprise a remote sensor with processing component  104 , etc. representing a computer that may or may not be in communication with image capture component  102 ). 
       FIG. 2  shows a block diagram illustrating a specific implementation example for an infrared camera  200  in accordance with one or more embodiments. Infrared camera  200  may represent a specific implementation of system  100  ( FIG. 1 ), as would be understood by one skilled in the art. 
     Infrared camera  200  (e.g., a microbolometer readout integrated circuit with bias-correction circuitry and interface system electronics) includes a readout integrated circuit (ROIC)  202 , which may include the microbolometer unit cell array having one or more contacts coupled to microbolometer bridges via vertical legs as disclosed herein, control circuitry, timing circuitry, bias circuitry, row and column addressing circuitry, column amplifiers, and associated electronics to provide output signals that are digitized by an analog-to-digital (A/D) converter  204 . The A/D converter  204  may be located as part of or separate from ROIC  202 . 
     The output signals from A/D converter  204  are adjusted by a non-uniformity correction circuit (NUC)  206 , which applies temperature dependent compensation as would be understood by one skilled in the art. After processing by NUC  206 , the output signals are stored in a frame memory  208 . The data in frame memory  208  is then available to image display electronics  210  and a data processor  214 , which may also have a data processor memory  212 . A timing generator  216  provides system timing. 
     Data processor  214  generates bias-correction data words, which are loaded into a correction coefficient memory  218 . A data register load circuit  220  provides the interface to load the correction data into ROIC  202 . In this fashion, variable circuitry such as variable resistors, digital-to-analog converters, biasing circuitry, which control voltage levels, biasing, frame timing, circuit element values, etc., are controlled by data processor  214  so that the output signals from ROIC  202  are uniform over a wide temperature range. 
     It should be understood that various functional blocks of infrared camera  200  may be combined and various functional blocks may also not be necessary, depending upon a specific application and specific requirements. For example, data processor  214  may perform various functions of NUC  206 , while various memory blocks, such as correction coefficient memory  218  and frame memory  208 , may be combined as desired. 
       FIG. 3  shows a physical layout diagram of a microbolometer  300  in accordance with an embodiment of the invention. Microbolometer  300  includes a bridge portion  302  having a light sensor  304  and bridge contacts  306  that couple sensor  304  to a first end of legs  308 . Legs  308  each couple sensor  304  to one of contacts  310 . 
     Each contact  310  may couple one or more associated microbolometers  300  to associated readout circuitry of a readout integrated circuit (ROIC, not shown). For example, a first contact  310  may be used to provide a reference or bias voltage to the microbolometer and a second contact  310  may be used to a signal path from the microbolometer to the ROIC by which signals corresponding to infrared light absorbed by the microbolometer can be readout. Further descriptions of ROIC and microbolometer circuits may be found in U.S. Pat. No. 6,028,309, which is incorporated by reference in its entirety herein for all purposes. 
     Sensor  304  may be arranged to convert incident light such as infrared light into detectable electrical signals based on changes in electrical properties of the sensor (e.g., changes in resistivity) due to changes in temperature of the sensor when the light is incident. According to an embodiment, sensor  304  may include a resistive material, which may be formed of a high temperature coefficient of resistivity (TCR) material (e.g., vanadium oxide (VOx) or amorphous silicon). The resistive material may be suspended above the ROIC on bridge  302  and coupled to its contacts  310  via legs  308 . 
     According to various embodiments, each contact  310  may be attached to a portion of a leg  308  that bends downward toward the ROIC (e.g., contact  310  may be formed on a substrate such as the ROIC and leg  308  may include a portion that runs at a non-perpendicular angle to the substrate from a first height above the substrate such as the height of the bridge downward to the substrate contact) and/or each contact  310  may include a portion that extends downward (e.g., in the negative z-direction of  FIG. 3 ) from leg  308  to the surface of the ROIC. Legs  308  may be formed from one or more layers of conductive material such as, for example, titanium, nickel chromium, and/or other suitable conductive materials. 
     In order to provide legs  308  having a width and a length that is sufficient to provide suitable performance for microbolometer  300  without reducing the fill-factor of an array of microbolometers in which microbolometer  300  is included, legs  308  may be vertically oriented legs that run along paths in and/or parallel to the x-y plane of  FIG. 3  as shown and have an extended dimension that extends in a direction parallel to the z-direction of  FIG. 3 . Legs  308  may include bend portions  312 . Bend portions  312  may have additional electrical coupling and/or support structures as described in further detail hereinafter. 
     A plane such as the x-y plane of  FIG. 3  may be defined by the bridge of the microbolometer (e.g., the bridge may include a planar sensor layer such as a resistive layer that defines a plane or a plane may be defined that passes through multiple bridges in a microbolometer array) or by the surface of a substrate (e.g., an ROIC substrate) to which the microbolometer array is coupled and disposed above. 
       FIGS. 4A and 4B  respectively show top and cross-sectional views of a conventional microbolometer  400  having horizontally oriented legs  406 . As shown in the top view of  FIG. 4A , a bridge  402  of microbolometer  400  is connected by a bridge contact  404  to horizontally oriented leg  406  having an extended dimension of width WP that extends in the x-y plane of  FIG. 4A . In the cross sectional view of  FIG. 4B , taken along line A-A of  FIG. 4A , it can more easily be seen that contact  404 , leg  406 , and resistive material  403  of microbolometer  400  all extend along the same plane or parallel planes that are parallel to the x-y plane of  FIG. 4B . 
     In contrast,  FIGS. 5A and 5B  respectively show top and cross-sectional views of a microbolometer  500  according to an embodiment of the present disclosure that includes a vertically oriented leg  308 . As shown, vertically oriented leg  308  may have a width W in the x-y plane of  FIGS. 5A and 5B . Width W may be comparatively smaller than the width WP of a conventional microbolometer leg without sacrificing the overall volume of the leg by allowing the leg  308  to extend in the vertical direction (e.g., in a direction parallel to the z-direction of  FIGS. 5A and 5B ) so that vertical leg  308  is perpendicular to a plane defined by bridge  302  (e.g., by resistive material  501  of bridge  302 , by bridge contact  306 , and or by an array of bolometer bridges formed at a common height above an ROIC) and/or a plane defined by a surface of the substrate over which the bridge is formed. 
     As shown, according to an embodiment, a vertical leg  308  may include a conductive (e.g., metal) portion  506  and, if desired, insulating material  508  on one or more sides of the conductive portion. However, this is merely illustrative. According to various embodiments, conductive portion  506  may be partially or completely surrounded by dielectric material or may be free of dielectric material. Various examples of implementations of vertical legs  308  are described hereinafter in connection with  FIGS. 13A-13Q . However, first, processes that may be used to form vertical bolometer legs such as vertical legs  308  of  FIGS. 3, 5A, and 5B  will be discussed according to various embodiments. 
       FIGS. 6A-6F  show cross sectional side views of a portion of a microbolometer array at various stages during production of microbolometer legs for the microbolometer array. 
     Turning now to  FIG. 6A , a portion  601  of a microbolometer array is shown having a contact  310  and a bridge  302 . As shown, bridge  302  includes a sensor layer (e.g., a layer of temperature sensitive resistive material such as VOx)  606  and one or more additional layers  604  such as absorber layers. As shown, contact  310  may be formed from a vertical conductive portion such as metal stud  608  and one or more layers such as a metal contact layer  614  in contact with metal stud  608 . Contact  310  may include additional layers such as a dielectric layer  616  disposed over the metal layer  614  and an additional layer  612  such as a passivation layer disposed under portions of metal layer  614 . As shown, layer  612  may be formed on a portion of a top surface  603  of a sacrificial layer  600 . 
     Sacrificial layer  600  may be formed from, for example, polyimide. Layers  612  and  616  may be formed from, as examples, silicon dioxide or silicon nitride. Metal layer  614  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     Metal stud  608  may be conductively coupled to a conductive contact such as contact  610  of a substrate such as a readout integrated circuit (ROIC) substrate such as a complementary metal-oxide-semiconductor (CMOS) ROIC. In the example of  FIG. 6A , contact  610  is disposed in an overglass layer  602  (e.g., a CMOS overglass layer) of the ROIC. Prior to forming vertical legs between the bridge  302  and the contact  310 , bridge  302  may be disposed on a sacrificial layer  600  that supports bridge  302  and fills a gap between bridges of the microbolometer array and the ROIC and runs continuously between the bridges and contacts of the microbolometer array. 
     According to one embodiment, a process for forming vertical legs between bridge  302  and contact  310  may include depositing and patterning an additional sacrificial layer  620  on sacrificial layer  600  as shown in  FIG. 6B . Patterning the additional sacrificial layer  620  may include forming openings  622  in the additional sacrificial layer (e.g., at least partially between the bridge  302  and the contact  310 ) so that remaining portions of additional sacrificial layer  620  have vertical sidewalls  625 . Openings  622  may extend into sacrificial layer  600  or may extend only to the top surface  603  of sacrificial layer  600  (as examples). 
     Following the deposition and patterning of additional sacrificial layer  620 , a dielectric layer  624  may be deposited and patterned so that portions of the dielectric layer  624  remain on sidewalls  625  of additional sacrificial layer  620  in openings  622  as shown in  FIG. 6C . A metal layer such as a leg metal layer  626  may then be deposited over contact  310 , portions of sacrificial layer  600 , dielectric layer  624  on sidewalls  625 , portions of additional sacrificial layer  620 , and bridge  302  as shown in  FIG. 6D . If desired, openings may be formed in a dielectric layer of contact  310  and bridge  302  to expose portions of metal layer  614  and sensor layer  606  so that metal layer  626  can be deposited in contact with metal layer  614  and sensor layer  606 . Metal layer  626  may be deposited in a blanket deposition process. 
     As shown in  FIG. 6E , an additional dielectric layer  628  may be deposited over metal layer  626  and then metal layer  626  and additional dielectric layer  628  may be etched (e.g., in a masked spacer etch process) to remove portions of metal layer  626  and additional dielectric layer  628  from sacrificial layer  600  and additional sacrificial layer  620 . In this way, a dielectric-metal-dielectric stack may be formed vertically on sidewalls  625  of openings  622 . Portions of the dielectric-metal-dielectric stack that are continuously coupled with the portions on sidewalls  625  may also remain on contact  310  and bridge  302 , thereby forming bridge contact  306  and a leg metal contact with metal layer  614  of contact  310 . 
     Dielectric layers  624  and  628  may be formed from, as examples, silicon dioxide or a silicon nitride. Metal layer  626  may be a single metal layer formed form a homogeneous film of a single material or may include multiple materials (e.g., multiple layers of the same or different materials formed in multiple deposition operations). For example, metal layer  626  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     As shown in  FIG. 6F , sacrificial layers  600  and  620  may then be removed to release bridge  302  and vertical legs  308  which remain suspended above the ROIC with a space  650  interposed between the vertical legs and the ROIC. Although the vertical legs  308  of  FIG. 6F  appear to be floating, this is merely because of the particular cross section through the device that is shown. It will be understood by one skilled in the art that vertical legs  308  of  FIG. 6F  run along the x-y plane of  FIG. 6F  as, for example, illustrated in  FIG. 3  so that metal layer  626  forms a continuous conductive path between bridge contact  306  and contact  310 . Vertical legs  308  of  FIG. 6F  may include at least a portion that runs non-perpendicularly to a plane defined by the surface  699  of substrate  602 . For example, vertical legs  308  may run along a path that is parallel to the surface  699 . In another example, vertical legs  308  may run along a path that includes a portion that is parallel to surface  699  and an additional portion that bends downward toward surface  699  at a non-perpendicular angle. 
     The process illustrated by  FIGS. 6A-6F  is merely illustrative. According to various embodiments, vertical legs for a microbolometer array may be formed using other processes. For example, in one embodiment, a process such as the process shown in  FIGS. 7A-7F  may be performed to form vertical legs that are disposed below the plane at which bridge  302  is formed (e.g., in contrast with the vertical legs of  FIG. 6F  that are disposed substantially in a common plane with bridge  302 ). 
     Turning now to  FIG. 7A , a portion  701  of a microbolometer array is shown having a contact  310  and a bridge  302 . As shown, bridge  302  includes a sensor layer (e.g., a layer of temperature sensitive resistive material such as VOx)  709  and one or more additional layers  707  such as absorber layers. As shown, contact  310  may be formed from a vertical conductive portion such as metal stud  708  and one or more layers such as a metal contact layer  714  in contact with metal stud  708 . Contact  310  may include additional layers such as a dielectric layer  716  disposed over the metal layer  714  and an additional layer  712  such as a passivation layer disposed under portions of metal layer  714 . As shown, passivation layer  712  may be formed on a portion of a top surface  703  of a sacrificial layer  700 . 
     Sacrificial layer  700  may be formed from, for example, polyimide. Layers  712  and  716  may be formed from, as examples, silicon dioxide or silicon nitride. Metal layer  714  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     Metal stud  708  may be conductively coupled to a conductive contact such as contact  750  of a readout integrated circuit (ROIC) such as a complementary metal-oxide-semiconductor (CMOS) ROIC. In the example of  FIG. 7A , contact  750  is disposed in an overglass layer  702  (e.g., a CMOS overglass layer) of the ROIC. Prior to forming vertical legs between the bridge  302  and the contact  310 , bridge  302  may be disposed on a sacrificial layer  700  that supports bridge  302  and fills a gap between bridges of the microbolometer array and the ROIC and runs continuously between the bridges and contacts of the microbolometer array. 
     According to one embodiment, a process for forming vertical legs between bridge  302  and contact  310  may include forming openings  704  in the sacrificial layer  700  that supports bridge  302  (e.g., by etching through surface  703 ) as shown in  FIG. 7B . Openings  704  may be formed in a portion of sacrificial layer  700  that is disposed at least partially between the bridge  302  and the contact  310  so that openings  704  have vertical sidewalls  705  at various locations between bridge  302  and contact  310 . As shown, sidewalls  705  may be located substantially below a plane defined by bridge  302  (e.g., the x-y plane of  FIG. 7B ). 
     As shown in  FIG. 7C , a dielectric layer  706  may be deposited and patterned so that portions of the dielectric layer  706  remain on sidewalls  705  of sacrificial layer  700  in openings  704 . Openings such as openings  713  in layers  707  of bridge  302  and dielectric layer  716  may also be formed to expose portions of sensor layer  709  and metal layer  714  respectively as shown in  FIG. 7D . 
     A metal layer such as a leg metal layer  710  may then be deposited over contact  310 , portions of sacrificial layer  700 , dielectric layer  706  on sidewalls  705 , and bridge  302  as shown in  FIG. 7E . Metal layer  710  may be deposited in a blanket deposition process. As shown, portions of metal layer  710  may be formed within openings  713  (see  FIG. 7D ) and in contact with sensor layer  709  and metal layer  714 . 
     An additional dielectric layer  711  ( FIG. 7F ) may be deposited over metal layer  710  and metal layer  710  and additional dielectric layer  711  may be etched (e.g., in a masked spacer etch process) to remove portions of metal layer  710  and additional dielectric layer  711  from sacrificial layer  700 . In this way, a dielectric-metal-dielectric stack may be formed vertically on sidewalls  705  of openings  704  and portions of the dielectric-metal-dielectric stack that are continuously coupled with the portions on sidewalls  705  may also remain on contact  310  and bridge  302 , thereby forming bridge contact  306  and a leg metal contact with metal layer  714  of contact  310 . 
     Dielectric layers  706  and  711  may be formed from, as examples, silicon dioxide or a silicon nitride. Metal layer  710  may be a single metal layer formed form a homogeneous film of a single material or may include multiple materials (e.g., multiple layers of the same or different materials formed in multiple deposition operations). For example, metal layer  710  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     As shown in  FIG. 7F , sacrificial layer  700  may then be removed to release bridge  302  and vertical legs  308  formed from metal layer  710  and dielectric layers  706  and  711  that partially surround metal layer  710 . As shown, vertical legs  308  remain suspended above the ROIC with a space  720  interposed between the vertical legs and the ROIC. In this way, vertical legs  308  may be formed perpendicular to the x-y plane of  FIG. 7F  and run along a path (e.g., as illustrated in  FIG. 3 ) that is disposed below the x-y plane of  FIG. 7F  between bridge  302  and contact  310  so that metal layer  710  forms a continuous conductive path between bridge contact  306  and contact  310  via legs  308 . 
     Vertical legs  308  of  FIG. 7F  may include at least a portion that runs non-perpendicularly to a plane defined by the surface  799  of substrate  702 . For example, vertical legs  308  may run along a path that is parallel to the surface  799 . In another example, vertical legs  308  may run along a path that includes a portion that is parallel to surface  799  and an additional portion that bends downward toward surface  799  at a non-perpendicular angle. 
     In the example of  FIG. 7F , the legs that couple bridge  302  to contact  310  may include vertical portions  308  and horizontal portions  718  that extend between bridge  302  and a first end of vertical leg  308  and between a second opposing end of vertical leg  308  and contact  310 . In various embodiments, legs  308  may include any suitable combination of vertical and horizontal portions for providing sufficient performance for the microbolometer while avoiding reduction of the fill factor of the microbolometer array due to the area occupied by the legs. 
       FIGS. 8A-8C  are cross sectional side views of a portion of a microbolometer array at various stages during formation of vertical legs that illustrate yet another alternative process of vertical leg formation. 
     Turning now to  FIG. 8A , a portion  801  of a microbolometer array is shown having a contact  310  and a bridge  302 . As shown, bridge  302  includes a sensor layer (e.g., a layer of temperature sensitive resistive material such as VOx)  806  and one or more additional layers  807  such as absorber layers. As shown, contact  310  may be formed from a vertical conductive portion such as metal stud  803  and one or more layers such as a metal contact layer  814  in contact with metal stud  803 . Contact  310  may include additional layers such as a dielectric layer  816  disposed over the metal layer  814  and an additional layer  812  such as a passivation layer disposed under portions of metal layer  814  and covering a top surface of a sacrificial layer  800 . Passivation layer  812  may extend between bridge  302  and contact  310  on the top surface sacrificial layer  800 . 
     Sacrificial layer  800  may be formed from, for example, polyimide. Layers  812  and  816  may be formed from, as examples, silicon dioxide or silicon nitride. Metal layer  814  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     Metal stud  803  may be conductively coupled to a conductive contact such as contact  809  of a readout integrated circuit (ROIC) such as a complementary metal-oxide-semiconductor (CMOS) ROIC. In the example of  FIG. 8A , contact  809  is disposed in an overglass layer  802  (e.g., a CMOS overglass layer) of the ROIC. Prior to forming vertical legs between the bridge  302  and the contact  310 , bridge  302  may be disposed on a sacrificial layer  800  that supports bridge  302  and fills a gap between bridges of the microbolometer array and the ROIC and runs continuously between the bridges and contacts of the microbolometer array. 
     According to one embodiment, a process for forming vertical legs between bridge  302  and contact  310  may include forming openings  804  in the sacrificial layer  800  that supports bridge  302  and in the passivation layer  812  that is disposed on the sacrificial layer as shown in  FIG. 8A . Openings  804  may be formed in a portion of sacrificial layer  800  and passivation layer  812  that is at least partially disposed between the bridge  302  and the contact  310  so that openings  804  have vertical sidewalls  805  at various locations between bridge  302  and contact  310 . As shown, sidewalls  805  may be formed from a portion of sacrificial layer  800  and passivation layer  812 . 
     A metal layer such as a leg metal layer  808  may then be deposited (e.g., over contact  310 , on portions of the top surface of passivation layer  812 , on sidewalls  805  in contact with both sacrificial layer  800  and passivation layer  812 , on portions of sacrificial layer  800  in openings  804 , and on bridge  302 ) before a dielectric layer  810  is deposited (e.g., over metal layer  808 ) and then metal layer  808 , dielectric layer  810 , and passivation layer  812  may be patterned (e.g., in a masked spacer etch process) so that metal layer  808  remains on some of the sidewalls of openings  804 , as shown in  FIG. 8B . In this way, a metal leg may be formed vertically on some of the sidewalls of openings  804  and horizontal portions  818  having metal layer  808  interposed between passivation layer  812  and dielectric layer  810  may also remain on sacrificial layer  800 . 
     Dielectric layer  810  may be formed from, as examples, silicon dioxide or a silicon nitride. Metal layer  808  may be a single metal layer formed form a homogeneous film of a single material or may include multiple materials (e.g., multiple layers of the same or different materials formed in multiple deposition operations). For example, metal layer  808  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     As shown in  FIG. 8C , sacrificial layer  800  may then be removed to release bridge  302  and vertical legs  308  with horizontal portions  818 . As shown, vertical legs  308  including horizontal portions  818  remain suspended above the ROIC with a space  820  interposed between the vertical legs and the ROIC. Vertical legs having some horizontal portions such as those shown in  FIG. 8C  may be less prone to movement and/or damage than legs having only vertical portions. Vertical legs  308  including horizontal portions  818  may form a continuous conductive path between bridge contact  306  and contact  310  via legs  308 . 
     Vertical legs  308  of  FIG. 8C  may include at least a portion that runs non-perpendicularly to a plane defined by the surface  899  of substrate  802 . For example, vertical legs  308  may run along a path that is parallel to the surface  899 . In another example, vertical legs  308  may run along a path that includes a portion that is parallel to surface  899  and an additional portion that bends downward toward surface  899  at a non-perpendicular angle. 
     It will be appreciated that the processes described above in connection with  FIGS. 6A-8C  can be modified, rearranged, and/or omitted to form vertical bolometer legs having various shapes, sizes, orientations, and arrangements as desired for various purposes.  FIGS. 9, 10, 11, 12, 13A-13Q, 14, and 15  show various arrangements of vertical legs and associated contacts or bridges that can be formed for microbolometer arrays. In particular,  FIGS. 9 and 10  show portions of a microbolometer array (prior to release by removal of a sacrificial layer) having vertical legs formed below the plane of the bridge in the vicinity of a contact and a bridge, respectively, of a microbolometer, according to one embodiment.  FIGS. 11 and 12  show portions of a microbolometer array having vertical legs formed below the plane of the bridge in the vicinity of a contact and a bridge, respectively, of a microbolometer, according to another embodiment.  FIGS. 13A-13Q  show various arrangements of metal and insulation for vertical legs for a microbolometer.  FIGS. 14 and 15  show portions of a microbolometer array having vertical legs formed at or above the plane of the bridge in the vicinity of a contact and a bridge, respectively, of a microbolometer, according to another embodiment. 
     As shown in  FIG. 9 , at a particular stage of production, a portion of metal layer  714  may be formed on sacrificial layer  700  and a portion of dielectric layer  706  may extend over the portion of metal layer  714  that is formed on the sacrificial layer, over a vertical portion of metal layer  714  that is formed on stud  708 , and over a horizontal portion of metal layer  714  that is formed on top of stud  708  such that the portion of dielectric layer  706  that is disposed above the top surface of sacrificial layer  700  is symmetric on multiple sides of stud  708 . Sacrificial layer  700  may then be removed. 
     A process that results in the structure of  FIG. 9  for contact  310  may also form a bridge as shown in  FIG. 10  according to an embodiment. As shown in  FIG. 10 , bridge  302  may include bridge dielectric layers  1000  and  1002  disposed on opposing sides of sensor layer  606 . Dielectric layer  706  may extend vertically from a vertical leg structure  308  and over a portion of bridge dielectric  1002 . Metal layer  710  may cover the portion of dielectric layer  706  that extends vertically from the vertical leg structure  308  and over the portion of bridge dielectric  1002  and the metal layer may extend through bridge dielectric  1002  and leg dielectric  706  to contact sensor layer  606 . 
     In an alternative embodiment, as shown in  FIG. 11 , metal layer  710  may be asymmetric about the top of stud  708  so that metal layer  710  remains in contact with metal layer  714  of contact  310  on the side of stud  708  on which the vertical legs  308  are formed, thereby increasing the contact area between layers  710  and  714 . Following formation of the structures of  FIG. 11  as shown, sacrificial layer  700  may be removed. 
     A process that results in the structure of  FIG. 11  for contact  310  may also form a bridge as shown in  FIG. 12  according to an embodiment. As shown in  FIG. 12 , a portion of metal layer  710  may be formed directly on a portion of bridge dielectric  1002  so that metal layer  710  passes over the portion of bridge dielectric  1002  and through bridge dielectric  1002  to contact sensor layer  606 . 
       FIGS. 13A-13Q  each show a cross sectional view of an exemplary implementation of a vertical bolometer leg such as vertical legs  308  as described herein. As shown in  FIG. 13A , a vertical bolometer leg may include a substantially vertical conductive (e.g., metal) layer  1300  that is disposed between first and second substantially vertical dielectric layers  1302  and  1304  that have a common height H with the vertical conductive layer  1300 . In the configuration of  FIG. 13A , the vertical leg may have a width that is substantially the same along the height of the vertical leg and substantially equal to the sum of the widths of the layers  1300 ,  1302 , and  1304 . 
     In general, a vertical bolometer leg may have a first dimension (e.g., a height H) that extends in a direction that is perpendicular to a plane defined by the associated bolometer bridge and/or a substrate, a second dimension (e.g., a width W) that extends in a direction that is parallel to the plane of the bridge and/or the substrate, and a third dimension that extends along and defines a signal path, where the path may include a portion that extends in a direction parallel to the plane of the bridge and/or the substrate, and where the second dimension is substantially smaller than the first dimension. 
     As shown in  FIG. 13B , in one embodiment, dielectric layer  1302  may extend above the top of conductive layer  1300  and run horizontally over the top of conductive layer  1300  and dielectric layer  1304 . As shown in  FIG. 13C , in one embodiment, conductive layer  1300  may have a height that is shorter than the height of dielectric layer  1302  and dielectric layer  1302  may run underneath the bottom of conductive layer  1300  and dielectric layer  1304 . 
     As shown in  FIG. 13D , in one embodiment, dielectric layer  1302  may extend above the top of conductive layer  1300  and run horizontally over the top of conductive layer  1300  and dielectric layer  1304  and conductive layer  1300  may have a height that is shorter than the height of dielectric layer  1302  and dielectric layer  1304  may run underneath the bottom of conductive layer  1300  to dielectric layer  1302 . As shown in  FIG. 13E , in one embodiment, conductive layer  1300  may have a height that is shorter than the height of dielectric layer  1302 , dielectric layer  1304  may run underneath the bottom of conductive layer  1300  to dielectric layer  1302 , and a horizontal dielectric layer  1306  may cover the top of layers  1300 ,  1302 , and  1304 . 
     As shown in  FIG. 13F , in one embodiment, conductive layer  1300  and dielectric layers  1302  and  1304  may have a common height and a horizontal dielectric layer  1306  may cover the top of layers  1300 ,  1302 , and  1304 . As shown in  FIG. 13G , in one embodiment, conductive layer  1300  may have a vertical portion and a horizontal portion such that conductive layer has, in cross section, an “L” shape. In the configuration of  FIG. 13G , dielectric layer  1304  runs vertically along the vertical portion of conductive layer  1300  and horizontally under the vertical and horizontal portions of conductive layer  1300  and dielectric layer  1302  runs vertically along the vertical portion of conductive layer  1300 , horizontally over the top of the horizontal portion of conductive layer  1300 , and vertically past the horizontal portion of conductive layer  1300  to the bottom of the vertical leg. 
     As shown in  FIG. 1311 , in one embodiment, conductive layer  1300  may be free of any surrounding dielectric material. As shown in  FIG. 131 , in one embodiment, conductive layer  1300  may have one side covered by dielectric layer  1304  and an opposing side that is free of dielectric material. As shown in  FIG. 13J , in one embodiment, a conductive layer  1300  that has one side covered by dielectric layer  1302  and an opposing side that is free of dielectric material may have a height that is shorter than the height of the vertical leg and dielectric layer  1302  may run underneath the bottom of conductive layer  1300 . As shown in  FIG. 13K , in one embodiment, a conductive layer  1300  that has one side covered by dielectric layer  1302  and an opposing side that is free of dielectric material may have a vertical portion and a horizontal portion that runs over the top of dielectric layer  1302 . 
     As shown in  FIG. 13L , in one embodiment, a conductive layer  1300  that has one side covered by dielectric layer  1304  and an opposing side that is free of dielectric material may have a first vertical portion, a horizontal portion that runs over the top of dielectric layer  1304 , and a second vertical portion that is offset from the first vertical portion. In the configuration of  FIG. 13L , dielectric layer  1304  may have a vertical portion that runs along the first vertical portion of conductive layer  1300  and a horizontal portion that runs under the first vertical portion of conductive layer  1300  to the second vertical portion of conductive layer  1300 . 
     As shown in  FIG. 13M , conductive layer  1300  may include a vertical portion and a horizontal portion  1308  that extends horizontally from the bottom of the vertical portion of conductive layer  1300  so that conductive layer  1300  and horizontal portion  1308  form an “L” shape. In the example of  FIG. 13M , conductive layer  1300  is covered on a first side by dielectric (insulating) layer  1302 , on another side by dielectric (insulating) layer  1304 , and along a bottom surface of horizontal portion  1308  by insulating (dielectric layer  1312 ). 
     As shown in  FIG. 13N , in one embodiment, horizontal portion  1308  and the part of the vertical portion that is below the top surface of the vertical portion may be substantially surrounded by one or more dielectric layers such as dielectric layers  1302 ,  1304 , and  1312  so that the top end of the vertical portion of conductive layer  1300  is free of dielectric material. 
     As shown in  FIG. 13O , in one embodiment, conductive portion  1300  may have a vertical portion, a first horizontal portion that extends in a first direction from the top of the vertical portion, a second horizontal portion that extends in an opposing second direction from the bottom of the vertical portion, and an additional portion that fills the space beneath a horizontal dielectric layer  1304  formed under the first horizontal portion. In the configuration of  FIG. 13O , the first horizontal portion, the vertical portion and top of the second horizontal portion of conductive layer  1300  are covered on one side by dielectric layer  1302 . 
     As shown in  FIG. 13P , in one embodiment, conductive layer  1300  may have a vertical portion, a first horizontal portion that extends in a first direction from the top of the vertical portion, and a second horizontal portion that extends in an opposing second direction from the bottom of the vertical portion. In the configuration of  FIG. 13P , the first horizontal portion, the vertical portion and top of the second horizontal portion of conductive layer  1300  are covered on one side by dielectric layer  1302  and dielectric layer  1304  runs under and fills the space under the first horizontal portion of conductive layer  1300 . As shown in  FIG. 13Q , a conductive layer having a vertical portion, a first horizontal portion that extends in a first direction from the top of the vertical portion, and a second horizontal portion that extends in an opposing second direction from the bottom of the vertical portion may be substantially surrounded by an insulating material  1312 . 
     As shown in  FIG. 14 , at a particular stage of production for vertical bolometer legs formed above and perpendicular to surface  603  of a sacrificial layer such as sacrificial layer  600  (e.g., the sacrificial layer upon which the bridge structures for one or more microbolometers are formed), a portion of metal layer  614  may be formed on sacrificial layer  600  and a portion of dielectric layer  624  may extend over the portion of metal layer  614  that is formed on the sacrificial layer, over a vertical portion of metal layer  614  that is formed on stud  608 , and over a horizontal portion of metal layer  614  that is formed on top of stud  608 . Dielectric layer  624 , leg metal layer  626 , and dielectric layer  628  may form a horizontal portion  1400  that extends horizontally from contact  310  and turns perpendicularly to form vertical leg portion  308 . Sacrificial layer  600  may then be removed. 
     A process that results in the structure of  FIG. 14  for contact  310  may also form a bridge as shown in  FIG. 15  according to an embodiment. As shown in  FIG. 15 , bridge  302  may include bridge dielectric layers  1500  and  1502  disposed on opposing sides of sensor layer  606 . Dielectric layer  624 , metal layer  626 , and dielectric layer  628  may form a stack that includes vertical leg portions  308  and a portion  1504  that extends horizontally from a vertical leg portion  308  to bridge  302 . As shown, metal layer  626  may cover a portion of dielectric layer  624  that extends horizontally from the vertical leg structure  308  and over a portion of bridge dielectric  1502  and may pass through bridge dielectric  1502  and leg dielectric  624  to contact sensor layer  606 . 
       FIG. 16  shows a top view of a portion of a vertical leg  308  in a bend region  312 .  FIGS. 17 and 18  show cross sectional side views of exemplary implementations of the bend region  312  taken along the line x-x of  FIG. 16 . As shown in  FIG. 17 , according to one embodiment, bend region  312  may include a pad  1700  formed at the bottom of a vertical conductive layer  1702  that is interposed between vertical dielectric layers  1704  and  1706  of the vertical leg. Pad  1700  may be formed from metal, dielectric materials, or a combination of metal and dielectric materials (as examples). As shown in  FIG. 18 , according to one embodiment, bend region  312  may include a metal pad  1800  formed over the top of vertical conductive layer  1702  and vertical dielectric layers  1704  and  1706  of the vertical leg. Pad  1800  may be formed from metal, dielectric materials, or a combination of metal and dielectric materials (as examples). 
       FIG. 19  is a cross sectional side view of a portion of a microbolometer array at a particular stage of production showing how, in one embodiment, at least a portion of a vertical leg structure may be formed beneath the bridge  302  of a microbolometer. As shown in  FIG. 19 , bridge  302  may include a sensor layer  606  disposed between bridge dielectric layers  1908  and  1910 . Bridge dielectric layer  1910  may be formed on a first sacrificial layer  1904  that is interposed between bridge dielectric layer  1910  and a vertical leg structure  1906  that runs beneath the bridge dielectric layer  1910  and overglass  1902  of an ROIC for the microbolometer array. At the stage of production shown in  FIG. 19 , a second sacrificial layer  1900  may be disposed between the vertical leg structure  1906  and overglass  1902 . 
     In the configuration shown in  FIG. 19 , sensor layer  606  of bridge  302  includes a vertical portion that runs downward from the bridge  302  and turns horizontally to form a portion of bridge contact  306 . As shown, a conductive layer such as conductive layer  1911  may couple sensor material  606  in bridge contact region  306  to the vertical leg structure  1906 . Vertical leg structure  1906  may extend to a contact such as a stud contact or basket contact that couples the vertical leg structure  1906  to a contact on the ROIC (e.g., a contact formed partially or completely within overglass layer  1902 ). Vertical leg structure  1906  may couple to a dedicated contact structure for the bridge  302  underneath which it is formed and/or may be coupled to a shared contact with an adjacent microbolometer. 
       FIG. 20  is a flowchart of illustrative operations that may be performed for forming vertical microbolometer legs for coupling a microbolometer bridge to a ROIC contact structure according to an embodiment. 
     At block  2000 , an imaging device having contact structures and bolometer bridge structures such as microbolometer bridge structures may be provided. The imaging device may include a partially fabricated focal plane array on which a sacrificial layer such as a polyimide layer is formed on a substrate such as a readout integrated circuit and the bridge structures are formed on the sacrificial layer. In some embodiments, an etch stop layer may be formed on the sacrificial layer. However, in other embodiments, the sacrificial layer may be free of any etch stop material. The contact structures may include an electrical contact on the readout integrated circuit and, if desired conductive elements that extend from the electrical contact on the ROIC through some or all of the sacrificial layer. The conductive elements may include a stud or a basket contact and, if desired, one or more additional structures such as passivation layers, metal layers, and/or dielectric layers formed over the conductive elements. 
     At block  2002 , an additional sacrificial layer may be deposited and patterned over or on the sacrificial layer. In embodiments, in which an etch stop layer is provided on the sacrificial layer, the additional sacrificial layer may be deposited on the etch stop layer so that portions of the etch stop layer are formed between the sacrificial layer and the additional sacrificial layer. Patterning the additional sacrificial layer may include etching the additional sacrificial layer to form openings in the additional sacrificial layer at least partially between the bridge structures and the contact structures. 
     At block  2004 , a first leg dielectric material may be formed at least on sidewalls of the openings in the patterned additional sacrificial layer. Forming the first leg dielectric material on the sidewalls of the openings may include depositing the first leg dielectric layer and performing a spacer etch of the first leg dielectric layer. The etch may also leave portions of the first leg dielectric layer on portions of the contact structures and/or the bridge structures as desired. 
     At block  2006 , one or more conductive layers such as a leg metal layer may be deposited (e.g., using a blanket metal deposition) and patterned on the first leg dielectric material on the sidewalls of the openings and over at least some of the contact structures and the bridge structures. The leg metal layer may be formed in contact with a metal layer of the contact structures and with a sensor layer of the bridge structures. 
     At block  2008 , a second leg dielectric layer may be deposited and patterned on the metal layer. Patterning the second leg dielectric layer may include depositing the second leg dielectric layer over the leg metal layer prior to patterning the leg metal layer and performing an in-situ dielectric and metal etch of the leg metal layer and the second leg dielectric layer. 
     At block  2010 , the sacrificial layer and the additional sacrificial layer may be removed to release the bridge structures and the vertical leg structures formed from the first and second leg dielectric layers and the leg metal layers so that the bridge and legs are suspended above the readout integrated circuit and the contact structures are coupled to the bridge structures by the vertical leg structures. In embodiments, in which an etch stop layer is provided on the sacrificial layer, portions of the etch stop layer may also be removed. 
       FIG. 21  is a flowchart of illustrative operations that may be performed for forming vertical microbolometer legs for coupling a microbolometer bridge to a ROIC contact structure according to another embodiment. 
     At block  2100 , an imaging device having contact structures and bolometer bridge structures such as microbolometer bridge structures may be provided. The imaging device may include a partially fabricated focal plane array on which a sacrificial layer such as a polyimide layer is formed on a readout integrated circuit and the bridge structures are formed on the sacrificial layer. The contact structures may include an electrical contact on the readout integrated circuit and, if desired conductive elements that extend from the electrical contact on the ROIC through some or all of the sacrificial layer. The conductive elements may include a stud or a basket contact and, if desired, one or more additional structures such as passivation layers, metal layers, and/or dielectric layers formed over the conductive elements. 
     At block  2102 , the sacrificial layer may be etched to form openings in the sacrificial layer at least partially between the bridge structures and the contact structures. 
     At block  2104 , a first leg dielectric material may be formed at least on sidewalls of the openings in the sacrificial layer. Forming the first leg dielectric material on the sidewalls of the openings may include depositing the first leg dielectric layer and performing a spacer etch of the first leg dielectric layer. The etch may also be performed to leave portions of the first leg dielectric layer on portions of the contact structures and/or the bridge structures as desired. 
     At block  2106 , openings may be formed in a dielectric layer of the contact structures and the bridge structures. Forming the openings in the dielectric layer of the contact structures and the bridge structures may expose portions of a metal layer of the contact structures and/or a sensor layer of the bridge structures. 
     At block  2108 , one or more conductive layers such as a leg metal layer may be deposited (e.g., using a blanket metal deposition) and patterned on the first leg dielectric material on the sidewalls of the openings and over at least some of the contact structures and the bridge structures. The leg metal layer may be formed in contact with the exposed portions of the metal layer of the contact structures and the sensor layer of the bridge structures. 
     At block  2110 , a second leg dielectric layer may be deposited and patterned on the metal layer. Patterning the second leg dielectric layer may include depositing the second leg dielectric layer over the leg metal layer prior to patterning the leg metal layer and performing an in-situ dielectric and metal etch of the leg metal layer and the second leg dielectric layer. 
     At block  2112 , the sacrificial layer may be removed to release the bridge structures and the vertical leg structures formed from the first and second leg dielectric layers and the leg metal layers so that the bridge and legs are suspended above the readout integrated circuit and the contact structures are coupled to the bridge structures by the vertical leg structures. 
       FIG. 22  is a flowchart of illustrative operations that may be performed for forming vertical microbolometer legs for coupling a microbolometer bridge to a ROIC contact structure according to another embodiment. 
     At block  2200 , an imaging device having contact structures and bolometer bridge structures such as microbolometer bridge structures may be provided. The imaging device may include a partially fabricated focal plane array on which a sacrificial layer such as a polyimide layer is formed on a readout integrated circuit, a passivation layer is formed on at least a portion of the sacrificial layer and the bridge structures are formed on the sacrificial layer. The contact structures may include an electrical contact on the readout integrated circuit and, if desired conductive elements that extend from the electrical contact on the ROIC through some or all of the sacrificial layer. The conductive elements may include a stud or a basket contact and, if desired, one or more additional structures such a portion of the passivation layer, metal layers, and/or dielectric layers formed over the conductive elements. 
     At block  2202 , the sacrificial layer and the passivation layer may be etched to form openings in the sacrificial layer and the passivation layer at least partially between the bridge structures and the contact structures. 
     At block  2204 , one or more conductive layers such as a leg metal layer may be deposited (e.g., using a blanket metal deposition) and patterned on the sidewalls of the openings and over at least some of the contact structures, the bridge structures, and portions of the passivation layer on the sacrificial layer. 
     At block  2206 , a leg dielectric layer may be deposited and patterned on the metal layer. Patterning the leg dielectric layer may include depositing the leg dielectric layer over the leg metal layer prior to patterning the leg metal layer and performing an in-situ dielectric and metal etch of the leg metal layer and the second leg dielectric layer. 
     At block  2208 , the sacrificial layer may be removed to release the bridge structures and the vertical leg structures formed from portions of the passivation layer, the leg dielectric layer and the leg metal layer so that the bridge and legs are suspended above the readout integrated circuit and the contact structures are coupled to the bridge structures by the vertical leg structures. 
     The process described above for forming vertical microbolometer legs are merely illustrative. According to various embodiments, vertical legs for a microbolometer array may be formed using other processes. For example, in one embodiment, a process such as the process shown in  FIGS. 23A-23F  may be performed to form vertical legs using an etch stop layer. 
       FIGS. 23A-23F  show cross sectional side views of a portion of a microbolometer array at various stages during production of microbolometer legs for the microbolometer array. 
     Turning now to  FIG. 23A , a portion  2398  of a microbolometer array is shown having a contact  310  and a bridge  302 . As shown, bridge  302  includes a sensor layer (e.g., a layer of temperature sensitive resistive material such as VOx)  2306  and one or more additional layers  2304  such as absorber layers. As shown, contact  310  may be formed from a vertical conductive portion such as metal stud  2308  and one or more layers such as a metal contact layer  2314  in contact with metal stud  2308 . Contact  310  may include additional layers such as a passivation layer  2316  disposed under portions of metal layer  2314 . As shown, an additional layer such as an etch stop layer  2303  (e.g., a layer of dielectric material) may be formed on sacrificial layer  2300  and may extend to form a portion of bridge  302  and/or contact  310 . 
     Sacrificial layer  2300  may be formed from, for example, polyimide. Layers  2303  and  2316  may be formed from, as examples, silicon dioxide or silicon nitride. Metal layer  2314  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     Metal stud  2308  may be conductively coupled to a conductive contact such as contact  2310  of a substrate such as a readout integrated circuit (ROIC) substrate such as a complementary metal-oxide-semiconductor (CMOS) ROIC. In the example of  FIG. 23A , contact  2310  is disposed in an overglass layer  2302  (e.g., a CMOS overglass layer) of the ROIC. Prior to forming vertical legs between the bridge  302  and the contact  310 , bridge  302  may be disposed on sacrificial layer  2300  so that sacrificial layer  2300  fills a gap between bridges of the microbolometer array and the ROIC and runs continuously between the bridges and contacts of the microbolometer array. 
     According to one embodiment, a process for forming vertical legs between bridge  302  and contact  310  may include depositing and patterning an additional sacrificial layer  2320  on etch stop layer  2303  as shown in  FIG. 23B . Patterning the additional sacrificial layer  2320  may include forming openings  2322  in the additional sacrificial layer (e.g., at least partially between the bridge  302  and the contact  310 ) so that remaining portions of additional sacrificial layer  2320  have vertical sidewalls  2325 . Openings  2322  may extend to the top surface  2301  of etch stop layer  2303 . 
     Following the deposition and patterning of additional sacrificial layer  2320 , a dielectric layer  2324  may be deposited and patterned so that portions of the dielectric layer  2324  remain on sidewalls  2325  of additional sacrificial layer  2320  in openings  2322  as shown in  FIG. 23C . A metal layer such as a leg metal layer  2326  may then be deposited over contact  310 , portions of etch stop layer  2303 , dielectric layer  2324  on sidewalls  2325 , portions of additional sacrificial layer  2320 , and bridge  302  as shown in  FIG. 23D . If desired, openings may be formed in portions of etch stop layer  2303  that are disposed over contact  310  and bridge  302  to expose portions of metal layer  2314  and sensor layer  2306  so that metal layer  2326  can be deposited in contact with metal layer  2314  and sensor layer  2306 . Metal layer  2326  may be deposited in a blanket deposition process. 
     As shown in  FIG. 23E , an additional dielectric layer  2328  may be deposited over metal layer  2326  and then metal layer  2326  and additional dielectric layer  2328  may be etched (e.g., in a masked spacer etch process) to remove portions of metal layer  2326  and additional dielectric layer  2328  from etch stop layer  2303  and additional sacrificial layer  2320 . In this way, a dielectric-metal-dielectric stack may be formed vertically on sidewalls  2325  of openings  2322 . Portions of the dielectric-metal-dielectric stack that are continuously coupled with the portions on sidewalls  2325  may also remain on contact  310  and bridge  302 , thereby forming bridge contact  306  and a leg metal contact with metal layer  2314  of contact  310 . 
     Dielectric layers  2324  and  2328  may be formed from, as examples, silicon dioxide or a silicon nitride. Metal layer  2326  may be a single metal layer formed form a homogeneous film of a single material or may include multiple materials (e.g., multiple layers of the same or different materials formed in multiple deposition operations). For example, metal layer  2326  may be formed from titanium, tungsten, copper, aluminum and/or other known metals. 
     As shown in  FIG. 23F , sacrificial layers  2300  and  2320  and portions of etch stop layer  2303  may then be removed to release bridge  302  and vertical legs  308  which remain suspended above the ROIC with a space  2350  interposed between the vertical legs and the ROIC. Vertical legs  308  of  FIG. 23F  may include at least a portion that runs non-perpendicularly to a plane defined by the surface  2399  of substrate  2302 . For example, vertical legs  308  may run along a path that is parallel to the surface  2399 . In another example, vertical legs  308  may run along a path that includes a portion that is parallel to surface  2399  and an additional portion that bends downward toward surface  2399  at a non-perpendicular angle. 
       FIG. 24  shows a cross-sectional side view of a microbolometer bridge that is coupled to legs formed beneath the bridge, according to an embodiment. In the example of  FIG. 24 , bridge  302  includes a sensor layer  2400  formed substantially between bridge dielectric layers  2402  and  2404 . Sensor layer  240  (e.g., a temperature sensitive resistive material, such as VOx) may include one or more horizontal portions that extend in a plane that is parallel to the surface of a substrate over which bridge  302  is formed and may include portions  2406  that extend downward from the horizontal portions in the direction of the substrate (e.g., perpendicularly to the surface of the substrate. Portions  2406  may extend to contact one or more legs such as legs  2420  formed beneath the bridge  302  (e.g., disposed at least partially between bridge  302  and the substrate over which the bridge is disposed). 
     As shown in  FIG. 24 , legs  2420  are formed form a conductive material having a horizontal portion  2408  in contact with sensor layer  2306  and a vertical portion  2410  that extends perpendicularly to horizontal portion  2408 . However, this is merely illustrative. In various embodiments, legs  2420  may include vertical and/or horizontal portions and/or may be covered partially or completely in an insulating material as in, for example, any of the examples described herein. 
     Illustrative operations that may be performed to form a bridge of the type shown in  FIG. 24  are shown in  FIG. 25 . 
     At block  2500 , an imaging device having contact structures that are formed on and/or in a sacrificial layer may be provided. The imaging device may include a partially fabricated focal plane array on which a sacrificial layer such as a polyimide layer is formed on a substrate such as a readout integrated circuit substrate. The contact structures may include an electrical contact on the substrate and, if desired conductive elements that extend from the electrical contact on the ROIC through some or all of the sacrificial layer. The conductive elements may include a stud or a basket contact and, if desired, one or more additional structures such as passivation layers, metal layers, and/or dielectric layers formed over the conductive elements. 
     At block  2502 , openings may be formed in the sacrificial layer. 
     At block  2504 , a first leg dielectric material may be formed at least on sidewalls of the openings in the sacrificial layer. Forming the first leg dielectric material on the sidewalls of the openings may include depositing the first leg dielectric layer and performing a spacer etch of the first leg dielectric layer. 
     At block  2506 , one or more conductive layers such as a leg metal layer may be deposited (e.g., using a blanket metal deposition) and patterned on the first leg dielectric material that is on the sidewalls of the openings and over at least some of the contact structures. The leg metal layer may be formed in contact with a metal layer of the contact structures. 
     At block  2508 , a second leg dielectric layer may be deposited and patterned on the leg metal layer. Patterning the second leg dielectric layer may include depositing the second leg dielectric layer over the leg metal layer prior to patterning the leg metal layer and performing an in-situ dielectric and metal etch of the leg metal layer and the second leg dielectric layer. 
     At block  2510 , an additional sacrificial layer may be deposited on the sacrificial layer. 
     At block  2512 , one or more bolometer bridge contacts may be formed in the second sacrificial layer. 
     At block  2514 , a first bridge dielectric layer may be deposited. 
     At block  2516 , one or more contacts may be formed in the first bridge dielectric layer and the underlying second leg dielectric layer on the leg metal layer for connection to the leg metal layer. 
     At block  2518 , a bolometer resistive sensing material (e.g., a temperature sensitive resistive material such as VOx) may be deposited and patterned to form sensor layers of the bolometer bridges. 
     At block  2520 , as second bridge dielectric material may be deposited and patterned, thereby defining a bridge area of each microbolometer formed over at least portions of the underlying leg materials. 
     At block  2522 , the sacrificial layer and the additional sacrificial layer may be removed to release the bridge structures and the vertical leg structures so that the bridge and legs that are formed beneath the bridge are suspended above the substrate and the contact structures are coupled to the bridge structures by the vertical leg structures. 
     Where applicable, various embodiments of the invention may be implemented using hardware, software, or various combinations of hardware and software. Where applicable, various hardware components and/or software components set forth herein may be combined into composite components comprising software, hardware, and/or both without departing from the scope and functionality of the invention. Where applicable, various hardware components and/or software components set forth herein may be separated into subcomponents having software, hardware, and/or both without departing from the scope and functionality of the invention. Where applicable, it is contemplated that software components may be implemented as hardware components and vice-versa. 
     Software, in accordance with the invention, such as program code and/or data, may be stored on one or more computer readable mediums. It is also contemplated that software identified herein may be implemented using one or more general purpose or specific purpose computers and/or computer systems, networked and/or otherwise. Where applicable, ordering of various steps described herein may be changed, combined into composite steps, and/or separated into sub-steps to provide features described herein. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.