# Patent

## Title
Microbolometer contact systems and methods

## Abstract

Systems and methods are directed to contacts for an infrared detector. For example, an infrared imaging device includes a substrate having a first metal layer and an infrared detector array coupled to the substrate via a plurality of contacts. Each contact includes for an embodiment a plurality of metal studs each having a first end and a second end and each disposed between the first metal layer and a second metal layer, wherein the first end of each metal stud is disposed on a portion of the first metal layer that is at least partially on the surface of the substrate.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No. 14/281,780 filed May 19, 2014 which is a continuation of U.S. patent application Ser. No. 12/576,971 filed Oct. 9, 2009 now U.S. Pat. No. 8,729,474 issued May 20, 2014, both of which are incorporated by reference herein in their entireties.


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 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 formed with two separate contacts, which may or may not be shared with adjacent microbolometers in the array. One contact is used to provide a reference voltage for the microbolometer while the other contact provides a signal path from the microbolometer to the ROIC. A drawback of a conventional contact is that it is too large and/or does not scale proportionally as semiconductor processing technologies transition to smaller dimensions. Consequently, as microbolometer dimensions are reduced, the conventional contact may consume a greater percentage of the area designated for the microbolometer, which reduces the area available for the desired resistive portion of the microbolometer and impacts microbolometer performance. As a result, there is a need for improved techniques for implementing contacts, 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 contacts for an infrared detector. For example, in accordance with an embodiment of the invention, contacts are disclosed, such as for infrared detectors within a focal plane array, that may be more area efficient as compared to conventional contacts. For one or more embodiments, the contact systems and methods disclosed herein may provide certain advantages over conventional contact approaches, especially as semiconductor processing technologies transition to smaller dimensions.
In accordance with one embodiment, an infrared imaging device includes a substrate having a first metal layer; an infrared detector array coupled to the substrate via a plurality of contacts, wherein each contact includes: a second metal layer formed on the first metal layer; a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills an inner portion of the contact; and a first passivation layer formed on the third metal layer.
In accordance with one embodiment, an infrared imaging device includes a substrate having a first metal layer; an infrared detector array coupled to the substrate via a plurality of contacts, wherein each contact includes: a metal stud formed on the first metal layer; a second metal layer formed on the metal stud; a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills an inner portion of the contact; and a first passivation layer formed on the third metal layer.
In accordance with another embodiment, a method of forming a contact on a substrate for an infrared detector array includes applying a polyimide coating on the substrate; applying a passivation layer on the polyimide coating; applying a photoresist pattern on the passivation layer; etching to expose a first metal layer on the substrate; depositing a second metal layer on the first metal layer; applying a photoresist pattern on the second metal layer; depositing a third metal layer on the second metal layer to at least partially fill an inner portion of the contact; applying a first passivation layer on the third metal layer and a portion of the second metal layer; and etching to release and provide the contact.
In accordance with another embodiment, a method of forming a contact on a substrate for an infrared detector array includes applying a polyimide coating on the substrate; applying a photoresist pattern on the polyimide coating; etching the polyimide coating to expose a first metal layer on the substrate; forming a metal stud on the first metal layer; planarizing a surface of the polyimide coating and the metal stud; applying a passivation layer on the polyimide coating and the metal stud; applying a photoresist pattern on the passivation layer; etching to expose the metal stud; depositing a second metal layer on the metal stud; depositing a third metal layer on the second metal layer; applying a first passivation layer on the third metal layer and a portion of the second metal layer; and etching to release and provide the contact.
In accordance with an embodiment, an infrared imaging device is provided that includes: a substrate having a first metal layer disposed at least partially on a surface of the substrate; an infrared detector array coupled to the substrate via a plurality of contacts, wherein each contact includes: a second metal layer; a plurality of metal studs each having a first end and a second end and each disposed between the first metal layer and the second metal layer, wherein the first end of each metal stud is disposed on a portion of the first metal layer that is at least partially on the surface of the substrate; where the second metal layer forms part of a leg metal layer to couple with an infrared detector within the infrared detector array and wherein the second metal layer covers a surface of the second end of each metal stud and wraps around an outer edge of the surface of the second end of each metal stud; where a portion of the second metal layer that wraps around the outer edges of the second ends forms a depression in the second metal layer; a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills the depression in the second metal layer; and a first passivation layer formed on the third metal layer.
In accordance with another embodiment, an infrared imaging device is provided that includes: a substrate having a first metal layer disposed at least partially on a surface of the substrate; an infrared detector array coupled to the substrate via a plurality of contacts, wherein each contact includes: a plurality of metal studs each having a first end and a second end, wherein the first end of each metal stud is formed on the first metal layer on at least a portion disposed on the surface of the substrate; a second metal layer covering a top surface of the second end of each metal stud and extending continuously between the top surfaces of the second ends of the metal studs; a depression in the second metal layer; and a third metal layer formed on the second metal layer, where the third metal layer at least partially fills the depression in the second metal layer.
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 physical layout diagram of a microbolometer array in accordance with an embodiment of the invention.
FIG. 2 shows a top view and a cross-sectional side view of a contact, such as for a contact within the microbolometer array of FIG. 1, in accordance with an embodiment of the invention.
FIGS. 3A through 3R illustrate a processing overview for manufacturing a contact, such as for the contact of FIG. 2, in accordance with an embodiment of the invention.
FIGS. 4A and 4B show physical layout diagrams of microbolometer arrays in accordance with one or more embodiments of the invention.
FIG. 5 shows a top view and a cross-sectional side view of a contact, such as for a contact within the microbolometer array of FIG. 1, 4A or 4B, in accordance with an embodiment of the invention.
FIGS. 6A through 6Q illustrate a processing overview for manufacturing a contact, such as for the contact of FIG. 5, in accordance with one or more embodiments of the invention.
FIGS. 7A through 7P illustrate a processing overview for manufacturing a contact, such as for the contact of FIG. 5, in accordance with one or more embodiments of the invention.
FIG. 8 shows a block diagram illustrating an infrared camera in accordance with one or more embodiments.
FIG. 9 shows a block diagram illustrating another implementation example for an infrared camera in accordance with one or more embodiments.
FIG. 10 shows a perspective view of a contact having multiple studs, in accordance with an embodiment of the invention.
FIGS. 11A through 11U illustrate a processing overview for manufacturing a contact with multiple studs, such as for the contact of FIG. 10, in accordance with one or more embodiments of the invention.



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
FIG. 1 shows a physical layout diagram of a microbolometer array 100 in accordance with an embodiment of the invention. Microbolometer array 100 includes microbolometers 102 and 104, which may be viewed as being arranged as one column of two rows (e.g., where the terms rows and columns are interchangeable, i.e., alternatively viewed as being arranged as one row of two columns). However, it should be understood that microbolometer array 100 is an example of an array (or a portion of an array) having contacts in accordance with one or more embodiments.
Microbolometers 102 and 104 each include a resistive material 106, which may be formed of a high temperature coefficient of resistivity (TCR) material (e.g., vanadium oxide (VOx) or amorphous silicon). Resistive material 106 is suspended on a bridge 108, with resistive material 106 coupled to its contacts 114 via legs 112. Legs 112 attach to resistive material 106 through a resistive material contact 110 (labeled VOx contact, e.g., a leg metal to resistive metal contact).
In general, microbolometers 102 and 104 may represent conventional microbolometers that are constructed in a conventional manner with conventional materials. However, contacts 114 (which are separately referenced as contacts 114(1) through 114(3)) represent novel contacts as disclosed herein in accordance with one or more embodiments.
For example, FIG. 2 shows a top view 202 and a cross-sectional side view 204 of a contact 200, which may represent an example implementation for contact 114 (e.g., contact 114(1), contact 114(2), or contact 114(3)) within the microbolometer array of FIG. 1, in accordance with an embodiment of the invention. Contact 200 may be viewed as forming a basket-shaped contact that is formed on a substrate 206 (e.g., of the ROIC) to contact a metal layer 218 (labeled Metal 5) of substrate 206 (e.g., a silicon substrate). Substrate 206 may have an overglass layer 208 formed thereon.
Contact 200 includes a leg metal layer 212 and a basket fill layer 214. Leg metal layer 212 may be made, for example, of titanium, tungsten, copper, or other known metals, while basket fill layer 214 may be made, for example, of aluminum. Contact 200 may further include a layer 216 (L2) on basket fill layer 214, with layer 216 made, for example, of silicon dioxide. Contact 200 may also further include a partial layer 210 (L1) disposed near a top portion of contact 200, but generally for an embodiment not disposed down to a base portion of contact 200 (e.g., at or near metal layer 218). Partial layer 210 may be made, for example, of silicon nitride. Layer 216 (L2) and partial layer 210 (L1) may function as passivation layers.
Contact 200 in accordance with one or more embodiments may provide certain advantages over conventional forms of contacts. For example, contact 200 does not include a liner layer (e.g., made of nickel-chromium) disposed between metal layer 218 and leg metal layer 212 to support contact 200 as would be required for some conventional approaches. As a further example, contact 200 does not require partial layer 210 (L1) to be disposed down to the base portion to metal layer 218, such as between the liner layer and leg metal layer 212 as would be required for some conventional approaches. Consequently, contact 200 may be more area efficient as semiconductor processing technologies transition to smaller dimensions and may be more easily aligned (e.g., self aligned) with metal layer 218 to form a suitable contact, such as for example for legs 112 (FIG. 1) of a corresponding microbolometer.
FIGS. 3A through 3R illustrate a processing overview (cross-sectional side views) for manufacturing a contact, such as contact 200 of FIG. 2, in accordance with an embodiment of the invention. Substrate 206 with overglass 208 is coated with a photoresist 301, which is exposed and developed using a mask (FIG. 3A), and metal layer 218 is deposited followed by lift-off and removal of photoresist 301 (FIG. 3B).
A polyimide coating 302 is applied (FIG. 3C). Photoresist 301 may optionally be applied, which is exposed and developed using a mask (FIG. 3D), to allow a reticulation (RET) process to optionally be performed (FIG. 3E). Photoresist 301 may again be optionally applied, which is exposed and developed using a mask (FIG. 3F), to allow a reticulation liner (LNR) process to optionally be performed (FIG. 3G). FIGS. 3D to 3G are optional process operations to allow metal layer 218 to be exposed and a metal liner to be provided as is done in some conventional processes. However, in accordance with an embodiment, these steps are optional and not required, which may provide some manufacturing advantages, as would be understood by one skilled in the art.
Partial layer 210 (L1, FIG. 2) is formed by applying a silicon nitride coating (FIG. 3H), followed by photoresist 301, which is exposed and developed using a mask (FIG. 3I), and a via process is performed (through layer 1 (L1) that forms partial layer 210) by etching and removal of photoresist 301 (FIG. 3J). For example, the etching process (e.g., reactive ion etching) may be performed using an isotropic and/or an anisotropic etch process, which may provide a narrower via (hole) above metal layer 218.
Photoresist 301 is optionally applied to areas outside of the contact area, which is exposed and developed using a mask (FIG. 3K), leg metal layer 212 is deposited, lift-off is performed (e.g., no leg metal is lifted off over the contact structure), and photoresist 301 is removed (FIG. 3L). Photoresist 301 is again applied, which is exposed and developed using a mask (FIG. 3M), basket fill layer 214 is deposited, lift-off is performed, and photoresist 301 is removed (FIG. 3N).
Layer 216 (L2, FIG. 2) is formed by applying a silicon dioxide coating (FIG. 3O), followed by photoresist 301, which is exposed and developed using a mask (FIG. 3P). A bridge cut leg process is performed by etching (e.g., reactive ion etching) and ion milling and photoresist 301 is removed (FIG. 3Q). Polyimide coating 302 is then removed to provide contact 200 as a released contact structure. As shown as an example in FIG. 3R, contact 200 may provide a contact width at a top portion of approximately four micrometers, which may be significantly less than conventional contact structures (e.g., six micrometers or more).
FIGS. 4A and 4B show physical layout diagrams of microbolometer arrays 400 and 450, respectively, in accordance with one or more embodiments of the invention. Microbolometer arrays 400 and 450 each illustrate a portion of an array of microbolometers (e.g., an array of any desired size) and may be viewed as being similar to microbolometer array 100 (FIG. 1).
Specifically, microbolometer array 400 includes a number of microbolometers with shared contacts (e.g., contacts 114), as shown in FIG. 4A, while microbolometer array 450 includes a number of microbolometers, with each microbolometer having two contacts (e.g., contacts 114) that are not shared with other microbolometers, as shown in FIG. 4B. As noted similarly for microbolometer array 100, microbolometer arrays 400 and 450 may represent conventional microbolometers that are constructed in a conventional manner with conventional materials. However, contacts 114 represent novel contacts as disclosed herein in accordance with one or more embodiments.
For example for microbolometer arrays 100, 400, and 450, contacts 114 may be implemented as disclosed in reference to contact 200 (FIG. 2) and may be manufactured as set forth in reference to FIGS. 3A through 3R, in accordance with one or more embodiments. Alternatively, contacts 114 within microbolometer arrays 100, 400, and 450 may be implemented as a stud contact (e.g., post/stud contact) as disclosed herein in accordance with one or more embodiments.
For example, FIG. 5 shows a top view 502 and a cross-sectional side view 504 of a contact 500, which may represent an example implementation for contact 114 within the microbolometer array of FIG. 1, 4A, or 4B, in accordance with one or more embodiments of the invention. Contact 500 may be viewed as forming a stud-shaped contact (rather than a basket-shaped contact as disclosed for contact 200) that is formed on substrate 206 (e.g., of the ROIC) to contact metal layer 218 (labeled Metal 5) of substrate 206 (e.g., a silicon substrate that may have overglass layer 208 formed thereon).
As disclosed similarly for contact 200 (FIG. 2), contact 500 includes leg metal layer 212 and basket fill layer 214. Contact 500 may further include layer 216 (L2) on basket fill layer 214 and partial layer 210 (L1) disposed near a top portion of contact 200, but generally for an embodiment not disposed down along leg metal layer 212, as shown in FIG. 5. Contact 500 further includes a stud 506, which is disposed between metal layer 218 and leg metal layer 212. Stud 506 may be made of a metal, such as for example titanium, tungsten, copper, or other known metals.
Contact 500 in accordance with one or more embodiments may provide certain advantages over conventional forms of contacts. For example, contact 500 does not include a liner layer disposed between metal layer 218 and leg metal layer 212 to support contact 500 as would be required for some conventional approaches. Rather, contact 500 utilizes stud 506, which allows a very small contact structure relative to some conventional approaches. As a further example, contact 500 does not require partial layer 210 (L1) to be disposed down along leg metal layer 212, such as between the liner layer and leg metal layer 212 as would be required for some conventional approaches.
Consequently, contact 500 may be more area efficient as semiconductor processing technologies transition to smaller dimensions and may be more easily aligned (e.g., self aligned) with metal layer 218 to form a suitable contact, such as for example for legs 112 (FIG. 1, 4A, or 4B) of a corresponding microbolometer.
FIGS. 6A through 6I illustrate a processing overview (cross-sectional side views) for manufacturing a contact, such as contact 500 of FIG. 5, in accordance with an embodiment of the invention. As shown in FIG. 6A, substrate 206, with metal layer 218, overglass 208, and polyimide coating 302, is coated with photoresist 301 (e.g., a masking layer that has been exposed and developed to prepare to form stud 506). An etching process is performed for polyimide coating 302 (FIG. 6B), photoresist 301 is removed, and a metal deposition process is performed to form stud 506 (FIG. 6C).
A surface planarizing process is performed and partial layer 210 (L1) is deposited (FIG. 6D), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and an etching process is performed to form a contact opening (FIG. 6E).
Photoresist 301 is removed and a metal deposition process is performed to form leg metal layer 212 (FIG. 6F), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and a metal deposition process is performed to form basket fill layer 214 (FIG. 6G). Photoresist 301 is removed and layer 216 (L2) is deposited (FIG. 6H), a portion of which may also serve as a bridge layer (e.g., top portion) of the microbolometer (e.g., bridge 108 of FIG. 1). The bridge portion layers are separated from the contact portion layers (e.g., released by a pattern and etch process) to provide contact 500 as a released contact structure (FIG. 6I). As an example, contact 500 may provide a contact width at a top portion of approximately three micrometers, which may be significantly less than conventional contact structures (e.g., six micrometers or more).
The processing overview as set forth in FIGS. 6a through 6I may be varied in accordance with one or more embodiments. For example in accordance with an embodiment, the process may include an etch-stop formed over stud 506, as illustrated in FIGS. 6J through 6Q. Specifically as an example, after stud 506 is formed (FIG. 6C), a surface planarizing process is performed (FIG. 6J) and an etch-stop 706 (e.g., a basket etch-stop) is patterned and deposited (FIG. 6K). Partial layer 210 (L1) is deposited (FIG. 6L), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and an etching process is performed to form a contact opening (FIG. 6M).
Photoresist 301 is removed and a metal deposition process is performed to form leg metal layer 212 (FIG. 6N), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and a metal deposition process is performed to form basket fill layer 214 (FIG. 6O). Photoresist 301 is removed and layer 216 (L2) is deposited (FIG. 6P), a portion of which may also serve as a bridge layer (e.g., top portion) of the microbolometer (e.g., bridge 108 of FIG. 1). The bridge portion layers are separated from the contact portion layers (e.g., released by a pattern and etch process) to provide contact 500 as a released contact structure (FIG. 6Q).
FIGS. 7A through 7I illustrate an alternative processing overview for manufacturing a contact, such as contact 500 of FIG. 5, in accordance with an embodiment of the invention. In general, stud 506 of FIG. 6I is formed as disclosed by metal deposition, but may alternatively be formed by electroplating as disclosed in reference to FIGS. 7A through 7I.
As shown in FIG. 7A, substrate 206, with metal layer 218, overglass 208, and polyimide coating 302 (e.g., release layer 1), is coated with photoresist 301 (e.g., a masking layer that has been exposed and developed to prepare to form stud 506). An etching process is performed for polyimide coating 302 (FIG. 7B), photoresist 301 is removed, and a metal plating base layer 702 is deposited (FIG. 7C). The metal plating base layer may be made, for example, of nickel chrome.
Photoresist 301 is applied and stud 506 is formed by an electroplating process (FIG. 7D, plated stud). A lap-stop material 704 may optionally be applied over stud 506, as shown in FIG. 7D. Photoresist 301 is removed, metal plating base layer 702 is removed by etching, except for the portion under stud 506 (FIG. 7E), and polyimide coating 302 is removed (FIG. 7F).
Polyimide coating 302 (e.g., release layer 2 or microbolometer release layer) is applied along with lap-stop material 704, as shown in FIG. 7G. A surface planarization process is performed and lap-stop material 704 is removed (FIG. 7H). Partial layer 210 (L1) is deposited (FIG. 7I), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). The process may then proceed as discussed in reference to FIGS. 6E to 6I to form contact 500, but having stud 506 plated as disclosed and as would be understood by one skilled in the art.
The processing overview as set forth in FIG. 7a through 7I may be varied in accordance with one or more embodiments. For example in accordance with an embodiment, the process may include an etch-stop formed over stud 506, as illustrated in FIGS. 7J through 7P. Specifically as an example, after stud 506 is formed, the surface planarization process is performed, and lap-stop material 704 is removed (FIG. 7H), an etch-stop 706 (e.g., a basket etch-stop) is patterned and deposited (FIG. 7J). Partial layer 210 (L1) is deposited (FIG. 7K), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). The process may then proceed as shown in FIGS. 7L through 7P in a similar fashion as discussed in reference to FIGS. 6E to 6I to form contact 500, but having stud 506 plated and having etch-stop 706 as disclosed and as would be understood by one skilled in the art.
Systems and methods are disclosed herein to provide contacts for an infrared detector, in accordance with one or more embodiments. For example, in accordance with an embodiment, contacts are disclosed, such as for infrared detectors within a focal plane array. As an implementation example, FIG. 8 shows a block diagram illustrating a system 800 (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 800 comprises, in one implementation, an image capture component 802, a processing component 804, a control component 806, a memory component 808, and a display component 810. Optionally, system 800 may include a sensing component 812.
System 800 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 801. The system 800 may represent any type of infrared camera that employs infrared detectors having contacts, which may be implemented as disclosed herein. System 800 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 804 distant from and controlling image capture component 802 via the network).
In various embodiments, processing component 804 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 804 may be adapted to interface and communicate with components 802, 806, 808, and 810 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 808 comprises, in one embodiment, one or more memory devices adapted to store data and information, including for example infrared data and information. Memory device 808 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 804 may be adapted to execute software stored in memory component 808 so as to perform method and process steps and/or operations described herein.
Image capture component 802 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 contacts as disclosed herein) for capturing infrared image data (e.g., still image data and/or video data) representative of an image, such as scene 801. In one implementation, the infrared sensors of image capture component 802 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 800). In one or more embodiments, image capture component 802 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 802 may further include temperature sensors (or temperature sensors may be distributed within system 800) to provide temperature information to processing component 804 as to operating temperature of image capture component 802.
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 801. Processing component 804 may be adapted to process the infrared image data (e.g., to provide processed image data), store the infrared image data in memory component 808, and/or retrieve stored infrared image data from memory component 808. For example, processing component 804 may be adapted to process infrared image data stored in memory component 808 to provide processed image data and information (e.g., captured and/or processed infrared image data).
Control component 806 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 804 may be adapted to sense control input signals from a user via control component 806 and respond to any sensed control input signals received therefrom. Processing component 804 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 806 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 800, 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 810 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 804 may be adapted to display image data and information on the display component 810. Processing component 804 may be adapted to retrieve image data and information from memory component 808 and display any retrieved image data and information on display component 810. Display component 810 may comprise display electronics, which may be utilized by processing component 804 to display image data and information (e.g., infrared images). Display component 810 may be adapted to receive image data and information directly from image capture component 802 via the processing component 804, or the image data and information may be transferred from memory component 808 via processing component 804.
Optional sensing component 812 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 812 provide data and/or information to at least processing component 804. In one aspect, processing component 804 may be adapted to communicate with sensing component 812 (e.g., by receiving sensor information from sensing component 812) and with image capture component 802 (e.g., by receiving data and information from image capture component 802 and providing and/or receiving command, control, and/or other information to and/or from one or more other components of system 800).
In various implementations, sensing component 812 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 812 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 802.
In some implementations, optional sensing component 812 (e.g., one or more of sensors) may comprise devices that relay information to processing component 804 via wired and/or wireless communication. For example, optional sensing component 812 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 800 may be combined and/or implemented or not, as desired or depending on the application or requirements, with system 800 representing various functional blocks of a related system. In one example, processing component 804 may be combined with memory component 808, image capture component 802, display component 810, and/or optional sensing component 812. In another example, processing component 804 may be combined with image capture component 802 with only certain functions of processing component 804 performed by circuitry (e.g., a processor, a microprocessor, a logic device, a microcontroller, etc.) within image capture component 802. Furthermore, various components of system 800 may be remote from each other (e.g., image capture component 802 may comprise a remote sensor with processing component 804, etc. representing a computer that may or may not be in communication with image capture component 802).
FIG. 9 shows a block diagram illustrating a specific implementation example for an infrared camera 900 in accordance with one or more embodiments. Infrared camera 900 may represent a specific implementation of system 800 (FIG. 8), as would be understood by one skilled in the art.
Infrared camera 900 (e.g., a microbolometer readout integrated circuit with bias-correction circuitry and interface system electronics) includes a readout integrated circuit (ROIC) 902, which may include the microbolometer unit cell array having one or more contacts 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 904. The A/D converter 904 may be located as part of or separate from ROIC 902.
The output signals from A/D converter 904 are adjusted by a non-uniformity correction circuit (NUC) 906, which applies temperature dependent compensation as would be understood by one skilled in the art. After processing by NUC 906, the output signals are stored in a frame memory 908. The data in frame memory 908 is then available to image display electronics 910 and a data processor 914, which may also have a data processor memory 912. A timing generator 916 provides system timing.
Data processor 914 generates bias-correction data words, which are loaded into a correction coefficient memory 918. A data register load circuit 920 provides the interface to load the correction data into ROIC 902. 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 914 so that the output signals from ROIC 902 are uniform over a wide temperature range.
It should be understood that various functional blocks of infrared camera 900 may be combined and various functional blocks may also not be necessary, depending upon a specific application and specific requirements. For example, data processor 914 may perform various functions of NUC 906, while various memory blocks, such as correction coefficient memory 918 and frame memory 908, may be combined as desired.
Various embodiments have been described in which each contact that couples an infrared detector leg (e.g., a bolometer leg) to a readout integrated circuit (ROTC) substrate includes a single metal stud. However, although it might be expected by one skilled in the art that a single stud of relatively maximal width would provide the most robust contact, in some situations it may be advantageous to be able to provide multiple studs for each contact. For example, it has been determined that a stud contact that includes more than one stud may provide a distributed electrical load, may provide greater mechanical support for the contact, and may provide redundant electrical connections between the detector and the associated readout circuitry. For example, a microbolometer coupled to readout circuitry via a contact having four studs may be able to be operated even if one or more of the studs is damaged (e.g., if one stud suffers damage, the remaining three studs continue to provide support electrical coupling for the contact).
FIG. 10 shows a top perspective of an exemplary four-stud contact 1000, which may represent an example implementation for contact 114 within the microbolometer array FIGS. 1, 4A, and/or 4B, in accordance with one or more embodiments of the invention. As shown in FIG. 10, contact 1000 may be arranged to couple metal layer 218 formed on substrate 206 (e.g., a contact pad that corresponds to a single contact 1000 and that is formed form a contiguous exposed portion of a metal layer 218 on the substrate) to a corresponding leg 112. Leg 112 may run, above and separated from substrate 206 between contact 1000 and resistive material 106 of one or more bolometer bridges as discussed herein.
As shown, contact 1000 may include four metal studs 506 that extend vertically from metal layer 218 to a second metal layer (e.g., a metal layer that forms leg 112 and a portion of contact 1000) such that each metal stud 506 includes a first end and a second end and each is disposed between metal layer 218 and the second metal layer. For example, the first end of each metal stud may be disposed on a portion of metal layer 218 that is at least partially on the surface of the substrate 206.
The second metal layer may form a part of a leg metal layer to couple with an infrared detector within an infrared detector array. As shown in FIG. 10, the second metal layer may cover a surface of the second end of each metal stud and wrap around an outer edge of the surface of the second end of each metal stud such that a portion of the second metal layer that wraps around the outer edges of the second ends forms a depression 1002 in the second metal layer. Depression 1002 may be formed between an outer raised ridge 1008 of the contact that extends around a periphery of the contact and additional raised portions 1004 that cover and wrap around the second ends of studs 506.
A third metal layer may be formed on the second metal layer such that the third metal layer at least partially fills or completely fills the depression in the second metal layer. In the example of FIG. 10, depression 1002 is only partially filled so that the depression and raised portions 1004 remain visually identifiable. In other embodiments, contact 1000 may include an etch stop layer that runs over the top surfaces of the second ends of studs 506 of a single contact upon which the leg metal layer may run over studs 506 and between the top surfaces of the studs. In such an embodiment, depression 1002 may be a substantially planar depression in which no raised portions 1004 are visually identifiable.
Metal studs 506 may be formed from a single conductive material or may be electroplated studs having an electroplating material formed along the sidewalls of each stud and between each stud and metal layer 218. As shown in FIG. 10, each metal stud 506 formed in a multiple-stud contact may have a width of less than about 1 micron. Contact 1000 may, for example, include four metal studs and may have a width (e.g., in a direction parallel to the surface of substrate 206) of less than about 4 microns.
As shown in FIG. 10, a gap may be formed between each of several discrete metal studs that form a single contact. The gap may, for example, be a gas-filled gap, a vacuum gap, or a gap that is partially or completely filled with a material such as an insulating material.
FIGS. 11A through 11N illustrate a processing overview (cross-sectional side views) for manufacturing a contact such as contact 1000 of FIG. 10, in accordance with an embodiment of the invention. As shown in FIG. 11A, substrate 206, with metal layer 218, overglass layer 208, and polyimide coating 302, is coated by a photoresist material 301 (e.g., a masking layer that has been exposed and developed to have a plurality of openings 1115 to prepare to form a corresponding plurality (e.g., four) of studs. Although four openings 1115 are shown in FIG. 11A, it is to be understood that this is merely illustrative and other embodiments may be devised with two studs, three studs, five studs, or more than five studs without departing from the scope of this disclosure. As shown in FIG. 11A, metal layer 218 may include structure (e.g., a plurality of vertically extending conductive portions 1113 that extend from an internal circuitry portion 2181 through overglass 208 to a top metal layer 218T) that corresponds to the structure of the studs to be formed. An etching process is performed for polyimide coating 302 (FIG. 11B) to form openings 1117 in polyimide coating 302 exposing a plurality of portions of metal layer 218 (e.g., portions of top metal layer 218T), photoresist 301 is removed, and a metal plating base layer 702 is deposited in openings 1117 and on the exposed portions of metal layer 218 (FIG. 11C). The metal plating base layer may be made, for example, of nickel chrome.
As shown in FIG. 11C, portions 702S of electroplating base layer 702 may be formed along sidewalls of openings 1117 and bottom portions 702B of electroplating base layer 702 may be formed on the exposed portions of metal layer 218.
Photoresist 301 is applied and stud metal may be provided to form metal studs 506A, 506B, 506C, 506D and metal cap 1001 in an electroplating process (FIG. 11D). As shown, at this stage of production metal cap 1001 may extend over the top of studs 506A, 506B, 506C, 506D. Studs 506A, 506B, 506C, 506D and metal cap 1001 may be made of a metal such as, for example: titanium, tungsten, copper, or other known metals. A lap-stop material 704 may optionally be applied over metal cap 1001, as shown in FIG. 11D. Photoresist 301 is removed, metal plating base layer 702 is removed from the top of the polyimide coating 302 by etching (FIG. 11E), and polyimide coating 302 is removed (FIG. 11F). Although embodiments are discussed in which sidewall portions 702S of electroplating base layer remain along the sidewalls of studs 506A, 506B, 506C, 506D, this is merely illustrative. In other embodiments, side metal plating 702S may be removed.
Polyimide coating 302 (e.g., release layer 2 or microbolometer release layer) is applied along with lap-stop material 1010, as shown in FIG. 11G. A surface planarization process is performed, in which the metal cap 1001, lap-stop material 1010, and lap-stop material 704 are removed (FIG. 11H). Partial layer 210 (L1) is deposited (FIG. 11I), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1).
Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and an etching process is performed to form a contact opening 1121 that extends through partial layer 210 (FIG. 11J). Photoresist 301 is removed and a metal deposition is performed to form leg metal layer 212 (FIG. 11K), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). As shown in FIG. 11K, a depression 1100 may be formed in leg metal layer 212. Depression 1100 may, in an embodiment, include sub-depressions 1102 and/or 1104. Sub-depression 1102 may run around a periphery of the contact (e.g., around raised portions 1004 within outer raised portion 1106 of FIG. 10). Sub-depressions 1104 may be formed between portions of leg metal layer 212 that cover and wrap around top ends of each stud 506. Although sub-depressions 1102 and 1104 appear to be separated in the side view of FIG. 11K, sub-depressions 1102 and 1104 may be portions of a single continuous depression as shown in the perspective view of FIG. 10.
Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and a metal deposition process is performed to form a basket fill layer 214 (FIG. 11L). For example, basket fill material may be deposited over photoresist 301 and an exposed portion of leg metal layer 212 and the portions of the basket fill material formed on photoresist 301 may be lifted off by removing photoresist 301. Basket fill layer 214 may be made, for example, of aluminum. Layer 216 (L2) is deposited (FIG. 11M), a portion of which may also serve as a bridge layer (e.g., top portion) of the microbolometer (e.g., bridge 108 of FIG. 1). Layer 216 may be made, for example, of silicon dioxide. The bridge portion layers are separated from the contact portion layers (e.g., released by a pattern and etch process) to provide contact 1000 as a released contact structure with four studs (FIG. 11N).
The processing overview as set forth in FIGS. 11A through 11N may be varied in accordance with one or more embodiments. For example, in accordance with an embodiment, the process may include an etch-stop formed over studs 506A, 506B, 506C, 506D, as illustrated in FIGS. 11O through 11U. Specifically as an example, after studs 506A, 506B, 506C, 506D are formed (FIG. 11D), a surface planarizing process is performed (see, e.g., FIGS. 11G and 11H) and an etch-stop 706 (e.g., basket etch-stop) may be patterned and deposited (FIG. 11O). As shown in FIG. 11O, the etch-stop layer 706 may be formed partially on polyimide coating 302 and on studs 506A, 506B, 506C, 506D extending continuously between the top surfaces of studs 506A, 506B, 506C, 506D. A partial layer 210 (L1) is deposited (FIG. 11P), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1).
As shown in FIG. 11Q, photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and an etching process is performed to form a contact opening 1109 that extends through partial layer 210 to expose etch-stop 706. Photoresist 301 is removed and a metal deposition is performed to form leg metal layer 212 (FIG. 11R), a portion of which may also serve as a bridge layer of the microbolometer (e.g., bridge 108 of FIG. 1). As shown in FIG. 11R, a depression 1110 may be formed in leg metal layer 212. Depression 1110 may, in an embodiment, be a depression having a substantially planar bottom formed at the top of metal studs 506A, 506B, 506C, 506D.
Photoresist 301 is applied (e.g., exposed and developed to form a masking layer) and a metal deposition process is performed to form a basket fill layer 214 (FIG. 11S). For example, basket fill material may be deposited over photoresist 301 and an exposed portion of etch-stop 706 and the portions of the basket fill material formed on photoresist 301 may be lifted off by removing photoresist 301. Basket fill layer 214 may be made, for example, of aluminum. Layer 216 (L2) is deposited (FIG. 11T), a portion of which may also serve as a bridge layer (e.g., top portion) of the microbolometer (e.g., bridge 108 of FIG. 1). Layer 216 may be made, for example, of silicon dioxide. The bridge portion layers are separated from the contact portion layers (e.g., released by a pattern and etch process) to provide contact 1000 as a released contact structure with four studs (FIG. 11U).
As shown in FIG. 11U, leg metal layer 212 of the resulting contact may be formed on etch-stop 706 and may be formed over the top surfaces of the top ends of each metal stud 506 and may run continuously between the top surfaces to provide conductive contact between leg metal layer 212 and each stud 506 of that contact.
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.

## Claims

1. An infrared imaging device comprising:
a substrate having a plurality of contacts, each contact comprising:
a first metal layer, disposed at least partially on a surface of the substrate,
at least a portion of a second metal layer, and
a plurality of discrete metal studs each having a first end and a second end and each disposed between the first metal layer and the second metal layer, wherein the first end of each metal stud is disposed on a portion of the first metal layer that is at least partially on the surface of the substrate, and wherein the second end of each metal stud is disposed on the second metal layer;

wherein at least a portion of the second metal layer covers a surface of the second end of each metal stud and wraps around an outer edge of the surface of the second end of each metal stud, and wherein the portion of the second metal layer that wraps around the outer edges of the second ends forms a depression in the second metal layer;
an infrared detector array coupled to the substrate via a plurality of legs, wherein each leg is coupled to one of the contacts via the plurality of discrete metal studs, wherein at least a portion of the second metal layer forms part of a leg metal layer to couple with an infrared detector within the infrared detector array, and the infrared detector array comprises:
a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills the depression in the second metal layer, and
a first passivation layer formed on the third metal layer; and

a readout integrated circuit formed within the substrate.

2. The infrared imaging device of claim 1, wherein the infrared detector array comprises a plurality of microbolometers, wherein the leg metal layer couples with a corresponding one of the legs of at least one of the microbolometers, and wherein the third metal layer completely fills the depression in the second metal layer.

3. The infrared imaging device of claim 1, wherein the plurality of metal studs comprises four metal studs.

4. The infrared imaging device of claim 3, wherein the first passivation layer is made of silicon dioxide, and wherein the metal studs are formed by electroplating.

5. The infrared imaging device of claim 4, wherein the second metal layer is formed directly on the first metal layer via the plurality of metal studs with no intervening liner layer between the second metal layer and the first metal layer, wherein the first metal layer forms part of the readout integrated circuit within the substrate, wherein the infrared detector array comprises a plurality of microbolometers, and wherein the second metal layer forms part of the leg metal layer to couple with a corresponding one of the legs of at least one of the microbolometers.

6. The infrared imaging device of claim 1, wherein the infrared detector array comprises a plurality of microbolometers, and wherein each microbolometer comprises:
a resistive material forming a bridge wherein the legs couple the resistive material to the second metal layer, and wherein the first metal layer forms part of the readout integrated circuit within the substrate.

7. A method of forming the contact and at least a portion of one of the legs of claim 1 on the substrate for the infrared detector array, the method comprising:
applying a polyimide coating on the substrate;
applying a photoresist pattern on the polyimide coating;
etching to expose a plurality of portions of the first metal layer on the substrate;
forming the first ends of the plurality of discrete metal studs on a corresponding one of the exposed portions of the first metal layer;
depositing the second metal layer on the second ends of the metal studs so that the second metal layer covers a surface of the second end of each metal stud and wraps around the outer edge of the surface of the second end of each metal stud to form a depression in the second metal layer, wherein the second end of each of the metal studs is disposed opposite the first end of that metal stud;
applying a photoresist pattern on the second metal layer;
depositing the third metal layer on the second metal layer to at least partially fill the depression in the second metal layer;
applying the first passivation layer on the third metal layer and a portion of the second metal layer; and
etching to release and provide the contact.

8. The method of claim 7, further comprising:
applying a photoresist pattern to the substrate;
depositing the first metal layer on the substrate, wherein the first metal layer is coupled to a readout integrated circuit fixated within the substrate; and
wherein the first passivation layer is disposed at a top portion distant from the first metal layer.

9. The method of claim 8, wherein the infrared detector array comprises a plurality of microbolometers, wherein at least a portion of the second metal layer forms part of the leg metal layer to couple with a corresponding leg of at least one of the microbolometers, and wherein the plurality of metal studs are formed by electroplating.

10. The method of claim 7, further comprising:
applying an additional photoresist pattern on the second metal layer before depositing the third metal layer;
wherein the depositing the third metal layer comprises lifting-off a portion of the third metal layer and removing the additional photoresist; and
wherein the etching to release comprises:
applying a further additional photoresist pattern over the first passivation layer,
performing ion milling, and
removing the further additional photoresist pattern remaining.

11. An infrared imaging device comprising:
a substrate having a first metal layer disposed at least partially on a surface of the substrate;
a plurality of metal studs each having a first end and a second end, wherein the first end of each metal stud is formed on the first metal layer on at least a portion disposed on the surface of the substrate;
at least a portion of a second metal layer covering a top surface of the second end of each metal stud and extending continuously between the top surfaces of the second ends of the metal studs, wherein each of the second ends of the plurality of metal studs is disposed on the second metal layer, and wherein at least a portion of the second metal layer covers a surface of the second end of each metal stud and wraps around an outer edge of the surface of the second end of each metal stud;
a depression in the second metal layer formed by at least the portion of the second metal layer that wraps around the outer edges of the second ends;
a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills the depression in the second metal layer;
a readout integrated circuit disposed within the substrate; and
an infrared detector array coupled to the substrate via a plurality of legs and the plurality of metal studs.

12. The infrared imaging device of claim 11, wherein the infrared detector array comprises a plurality of microbolometers, and wherein the second metal layer forms part of a leg metal layer to couple with a corresponding one of the legs of at least one of the microbolometers.

13. The infrared imaging device of claim 11, wherein the third metal layer completely fills the depression in the second metal layer, and wherein each of the legs further comprises a first passivation layer formed on the third metal layer.

14. The infrared imaging device of claim 13, further comprising a second passivation layer formed on the second metal layer on a side opposite of where the third metal layer is formed, wherein the second passivation layer is disposed at a top portion distant from the first metal layer.

15. The infrared imaging device of claim 14, wherein the first passivation layer is made of silicon dioxide, wherein the second passivation layer is made of silicon nitride, and wherein the leg comprises an etch-stop layer disposed between the plurality of metal studs and the second metal layer, with the metal stud formed by electroplating.

16. The infrared imaging device of claim 11, wherein the contact comprises a plating base layer disposed between each metal stud and the first metal layer.

17. The infrared imaging device of claim 11, wherein the infrared detector array comprises a plurality of microbolometers, and wherein each microbolometer comprises:
a resistive material forming a bridge with the legs coupling the resistive material to the second metal layer, wherein the first metal layer forms part of the readout integrated circuit within the substrate.

18. A method of forming the contact and at least a portion of the legs of claim 11 on the substrate for the infrared detector array, the method comprising:
applying a polyimide coating on the substrate;
applying a photoresist pattern on the polyimide coating;
etching the polyimide coating to expose a plurality of portions of the first metal layer on the substrate;
forming the plurality of metal studs on the first metal layer;
removing the polyimide coating and applying an additional polyimide coating;
planarizing a surface of the additional polyimide coating and the plurality of metal studs;
providing an etch stop layer on the additional polyimide coating and the plurality of metal studs;
applying a passivation layer on the polyimide coating and the etch stop layer;
applying a photoresist pattern on the passivation layer;
etching to expose the etch stop layer;
depositing the second metal layer on the passivation layer and the etch stop layer so that the second metal layer covers the second ends of the metal studs and wraps around the outer edge of the surface of the second end of each metal stud to form the depression in the second metal layer; and
depositing the third metal layer on the second metal layer to at least partially fill the depression in the second metal layer.

19. The method of claim 18, comprising:
applying a photoresist pattern to the substrate;
depositing the first metal layer on the substrate, wherein the first metal layer is coupled to a readout integrated circuit formed within the substrate;
applying an additional passivation layer on the third metal layer and a portion of the second metal layer;
etching to release, wherein the additional passivation layer is disposed at a top portion distant from the substrate, and wherein the etching the polyimide coating and the etching to expose the etch stop layer comprises subsequently removing the photoresist pattern remaining.

20. The method of claim 19, wherein the infrared detector array comprises a plurality of microbolometers, and wherein the second metal layer forms part of a leg metal layer to couple with a corresponding leg of at least one of the microbolometers.

21. The method of claim 20, wherein the passivation layer, the additional passivation layer, and the second metal layer portions form part of a bridge of at least one of the microbolometers.

22. The method of claim 18, wherein the forming the plurality of metal studs comprises electroplating a metal and applying a lap-stop material to form the plurality of metal studs.

23. The method of claim 18, wherein the forming the plurality of metal studs comprises:
depositing a plating base on the polyimide coating and the first metal layer;
performing an electroplating process to form the plurality of metal studs over the first metal layer, wherein the plating base is disposed along sidewalls of each metal stud and between each metal stud and the first metal layer;
etching the plating base; and
applying the additional polyimide coating and applying a lap-stop material on the additional polyimide coating prior to the planarizing of the surface which removes the lap-stop material.

24. The method of claim 23, comprising:
applying an additional lap-stop material on a metal cap that extends across the plurality of metal studs prior to the etching of the plating base; and
wherein the providing the etch stop layer comprises depositing the etch-stop layer on the plurality of metal studs prior to depositing the second metal layer.