Combined short-wavelength infrared and visible light sensor

Abstract

The sensor (200, 500, 700) includes an array of optically active pixels disposed on a semiconductor die (210, 510, 710). The array of optically active pixels includes at least one pixel (P1) configured to detect short wavelength infrared (SWIR) light and at least one pixel (P2) configured to detect visible light incident on the sensor.

Description

[Technical Field]

[0001] Related Applications This application claims priority to and benefit of U.S. Provisional Patent Application No. 63 / 414,182, filed October 7, 2022, which is incorporated herein by reference in its entirety.

[0002] This application is also related to International Application No. PCT / US23 / 75098, filed September 26, 2023, which claims priority to and the benefit of U.S. Provisional Application No. 63 / 377,120, filed September 26, 2022, and which is incorporated herein by reference in its entirety.

[0003] This specification relates to packaging of semiconductor photosensors. [Background technology]

[0004] The optical sensor is configured to convert radiation intensity and wavelength spectrum into an electrical signal. The optical sensor can include a device for detecting light intensity. The optical sensor fabricated on a semiconductor die includes an optically active surface area (OASA) having an array of pixels that serve to convert light and color spectrum into an electrical signal. The optical sensor's OASA can also include, for example, a microlens array to help direct incident light to each pixel (thereby increasing the sensitivity of the image sensor) and / or a color filter array (CFA). Summary of the Invention

[0005] In a general aspect, the sensor includes an array of optically active pixels disposed on a semiconductor die, the array of optically active pixels including at least one pixel configured to detect short wavelength infrared radiation (SWIR) and at least one pixel configured to detect visible light incident on the sensor.

[0006] In a general aspect, an imaging device includes a photosensor die including a semiconductor substrate. At least one device is fabricated in the semiconductor substrate. An array of optically active pixels is disposed on the photosensor die. The array of optically active pixels includes at least one pixel configured to detect short wavelength infrared (SWIR) light and at least one pixel configured to detect visible light incident on the photosensor die.

[0007] In a further aspect, an intermetal dielectric (IMD) layer is disposed on the bottom surface of the semiconductor substrate, the IMD layer including at least a metal level of the redistribution layer of the photosensor die.

[0008] In a general aspect, a method includes forming a photosensor die including a semiconductor substrate, wherein at least one device is fabricated in the semiconductor substrate, and disposing an array of optically active pixels on the photosensor die. The method further includes configuring at least one pixel of the array of optically active pixels to detect short wavelength infrared (SWIR) light incident on the photosensor die, and configuring at least one other pixel of the array of optically active pixels to detect visible light incident on the photosensor die.

[0009] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0010] [Figure 1A] 1 shows an example of a color filter array that includes a mosaic of various color and infrared filter elements. [Figure 1B] 1 shows an example of a color filter array that includes a mosaic of various color and infrared filter elements. [Figure 1C] 1 shows an example of a color filter array that includes a mosaic of various color and infrared filter elements. [Figure 2] FIG. 1 is a cross-sectional view of a combined short-wave infrared (SWIR) and visible light optical sensor assembly configured for surface illumination. [Figure 3] 3 is an exploded view of the photosensor assembly of FIG. 2 showing electrical connections to pixel devices fabricated in the silicon substrate. [Figure 4A] 3 is a cross-sectional view of a portion of the photosensor assembly of FIG. 2 showing the bottom electrode in the SWIR filter element connected to the metal level of the redistribution layer. [Figure 4B] 3 illustrates a cross-sectional view of a portion of the photosensor assembly of FIG. 2 showing the bottom electrode in the SWIR filter element connected to the polysilicon gate of the transistor. [Figure 4C] 3 is a cross-sectional view of a portion of the photosensor assembly of FIG. 2 showing a bottom electrode in a SWIR filter element connected to a source or drain of a transistor. [Figure 5] FIG. 1 is a cross-sectional view of a combined SWIR-visible light photosensor assembly configured for backside illumination. [Figure 6A] 6 is a cross-sectional view of a portion of the photosensor assembly of FIG. 5 showing the bottom electrode in the SWIR filter element connected to the metal level of the redistribution layer. [Figure 6B] 6 is a cross-sectional view of a portion of the photosensor assembly of FIG. 5 showing a bottom electrode in a SWIR filter element connected to a polysilicon gate of a transistor. [Figure 6C] 6 is a cross-sectional view of a portion of the photosensor assembly of FIG. 5 showing a bottom electrode in a SWIR filter element connected to a source of a transistor. [Figure 7]1 is a cross-sectional view of an exemplary combined SWIR-visible light sensor assembly including an infrared sensitivity enhancement feature. [Figure 8] FIG. 1 is a cross-sectional view of a combined SWIR-visible light photosensor assembly in which an IR filter element is disposed in the center of a 2×2 array of color filter elements. [Figure 9] 1A-1C illustrate an exemplary method for fabricating an optical sensor assembly. [Figure 10A] FIG. 1 illustrates the construction of a mosaic of color and SWIR filter elements. [Figure 10B] FIG. 1 illustrates the construction of a mosaic of color and SWIR filter elements. [Figure 10C] FIG. 1 illustrates the construction of a mosaic of color and SWIR filter elements.

[0011] In the drawings, which are not necessarily drawn to scale, like reference symbols or alphanumeric characters may indicate like and / or similar components in different figures. The drawings generally illustrate various implementations discussed in this disclosure, by way of example, but not by way of limitation. A reference symbol shown in one drawing may not be repeated for the same and / or similar elements in associated figures. Reference symbols or alphanumeric identifiers that are repeated in multiple figures may not be specifically discussed with respect to each of those drawings, but are provided for context between the associated figures. Also, where multiple instances of an element are shown, not all of the same elements in the drawings are specifically referred to with a single reference symbol or alphanumeric identifier. DETAILED DESCRIPTION OF THE INVENTION

[0012] A light sensor fabricated on a semiconductor die includes an optically active surface area (OASA) that includes an x-y array of pixel sensors that serve to convert light and color spectrums into electrical signals. In some implementations, the light sensor may include a complementary metal-oxide semiconductor (CMOS) pixel sensor. In some implementations, each pixel sensor in the array of pixel sensors may include, for example, a photodiode or phototransistor that senses incident light and converts it into an electrical signal. The light sensor's OASA may also include a color filter array (CFA). The CFA may be a mosaic of small color filters coupled to the pixel sensors to capture color information. For example, a Bayer RBG color filter or mosaic may include a pattern of red (R), blue (B), and green (G) color filters to capture color information related to R, B, and G colors. The light sensor's OASA may also include a microlens array to help direct incident light to each pixel to increase the sensitivity of the light sensor. In some implementations, the microlens array may be an x-y array of microlenses.

[0013] A pixel may refer to either an individual pixel sensor device, an individual pixel sensor and associated color filter, or collectively an individual pixel sensor, associated color filter, and associated microlens. An individual pixel sensor device may be a photodiode or a phototransistor.

[0014] A short-wavelength infrared (SWIR) imager or sensor assembly is a type of optical sensor configured to capture images with wavelengths of light outside the visible range. An exemplary SWIR imager can detect and capture images in the short-wavelength infrared (SWIR) region of the electromagnetic spectrum, for example, ranging from approximately 900 nm to 2500 nm. In some implementations, images may be captured at a wavelength of 1550 nm. In some implementations, the SWIR imager can be a colloidal quantum dot (CQD) sensor based on a semiconductor material, such as silicon. When a bulk semiconductor material absorbs light, it releases electrons from its chemical bonds, allowing them to move freely through the semiconductor material. The same process occurs in quantum dot structures, where the diameter of the quantum dots can be only a few nanometers. However, unlike bulk semiconductor materials, the released electrons cannot move freely. They are quantum confined by the edges of the quantum dots, which have a limited, finite size. The quantum dots can be, for example, only a few nanometers in diameter. A useful property of quantum dots for imaging is that the light absorbed by them is tunable. In some implementations, quantum dots are tunable such that the color can be continuously tuned to almost any wavelength within the visible and infrared spectrum simply by choosing the right material, the right dot size, and the right bias voltage. In some implementations, the CQD structures described herein may be configured to detect radiation within the SWIR region of the electromagnetic spectrum.

[0015] Newer industrial and consumer applications, such as automotive applications such as advanced driver assistance systems (ADAS) and autonomous driving (AD) systems, can include other circuitry in the same package as the optical sensor die for improved imaging performance. The other circuitry may include an image signal processor (ISP) or an application specific integrated circuit (ASIC). The ISP or ASIC die can be coupled or combined with the optical sensor die in the package.

[0016] The light sensor device may be fabricated in a semiconductor die (light sensor die) by, for example, wafer-level processing and coupled to a circuit such as an ASIC. The ASIC may include, for example, a driver circuit and an A / D converter. The ASIC circuit may be fabricated on the same semiconductor die as the device for detecting light intensity or on a separate ASIC die coupled to the light sensor die.

[0017] In some implementations, the photosensor and associated ASIC circuitry can generate an electrical output. The raw image (RAW) data generated by the photosensor may be in the form of, for example, 0s and 1s for each pixel of the photosensor array. Additionally, the ISP may be a dedicated processor that converts the RAW data generated by the photosensor into a workable image output through various signal conditioning processes. These various signal conditioning processes may include, for example, one or more of noise reduction, lens shading correction, gamma correction, auto-exposure, and / or auto-white balance.

[0018] This disclosure describes an imaging device (sensor assembly) in which visible light detector pixels, infrared detector pixels, and SWIR detector pixels can be fabricated within a single photosensor die.

[0019] The visible light detector and infrared detector may be, for example, photodiodes, and the SWIR detector may be a capacitive detector using a CQD layer as the capacitive material. The color filter array deployed over the pixels in the photosensor die may include a square, rectangular, hexagonal, or any other shaped mosaic of various color filter elements.

[0020] In some implementations, the square or rectangular mosaic may include filter elements corresponding to visible color pixels, e.g., red, green, and blue, and at least one additional filter element corresponding to a SWIR detector pixel. The filter element corresponding to the SWIR detector pixel may be a layer of colloidal quantum dot material disposed between two electrodes forming a SWIR detector capacitor. Due to the longer wavelengths of SWIR radiation than those of visible radiation, the addition of the SWIR pixel to the color pixels can contribute to better resolution of the image output by the ISP, which converts the raw data generated by the photosensor into a workable image output.

[0021] 1A, for example, shows a 2×2 color filter array 100A including filter elements corresponding to SWIR pixels, according to at least one implementation. The color filter array 100A may have an RGB-IR 2×2 format including a total of four pixel elements, including an IR filter element corresponding to the SWIR detector pixel and blue, red, and green filter elements corresponding to three corresponding visible light detector pixels.

[0022] 1B, for example, shows a 4×4 color filter array 100B including four filter elements corresponding to SWIR pixels, according to at least one implementation. The color filter array 100B may have an RGB-IR 4×4 format including two red filter elements, two blue filter elements, eight green filter elements, and four IR filter elements corresponding to SWIR detector pixels.

[0023] In some implementations, the filter elements corresponding to SWIR detector pixels in the filter array may be less than one pixel in size. FIG. 1C , for example, shows a 2×2 color filter array 100C including IR filter elements less than one pixel in size. The color filter array 100C may have an RGB-IR 2×2 format including a total of four pixel elements, including a blue filter element, a red filter element, two green filter elements, and an IR filter element less than one pixel in size. The IR filter elements may be arranged within 2×2 RGGB blocks. In some implementations, the IR filter elements may be arranged at the centers of the 2×2 RGGB blocks.

[0024] The exemplary color filter array described above is based on an RGB color scheme for the color pixels. In some other implementations, other color schemes may be used. For example, any of the various color schemes used in various cameras or image capture devices may be used. For example, the color scheme of the color filter array may be based on red, green, blue, and white. For example, another color scheme of the color filter array may be based on cyan, yellow, and magenta.

[0025] In example implementations, the photosensor die on which both the visible light detector pixels and the SWIR detector pixels are fabricated may be stacked on, bonded to, and / or electrically connected to the ASIC die. In example implementations, the photosensor die may be stacked directly on, bonded to, and / or electrically connected to the ASIC die.

[0026] In some exemplary implementations, the photosensor die may be positioned face-to-face with the ASIC die and directly bonded to the ASIC die. In exemplary implementations, fabrication of the photosensor die, the ASIC die, and bonding the two may involve wafer-level processing. The bonding surfaces of the photosensor die and the ASIC die may include surface regions of dissimilar materials. The dissimilar materials may include, for example, a conductive material such as copper, a passivation material such as an oxide or other insulator, and a semiconductor material such as silicon. Bonding the photosensor die to the ASIC die may include techniques such as hybrid bonding for stacking and electrically connecting the dies together. Hybrid bonding may include, for example, introducing copper pads disposed in an insulator material layer on the surfaces of the two dies. Hybrid bonding may further include stacking the two dies face-to-face and aligning and fusing the copper pads disposed on the opposing surfaces of the dies to each other while bonding the rest of the opposing surfaces to each other. As a result, the two dies in the assembly may be electrically connected using small copper-to-copper connections.

[0027] Copper pads on the surfaces of the ASIC die and the photosensor die may be connected to the metal level of the redistribution layer of the respective die using, for example, metal-filled through-silicon vias (TSVs).

[0028] The assembly of an ASIC die bonded to a photosensor die may be referred to herein as a SWIR-visible light photosensor assembly or simply a photosensor assembly.

[0029] In some example implementations, the SWIR-visible light photosensor assemblies described herein may be configured for SWIR imaging under front side illumination (FSI) of the photosensor assembly. The SWIR-visible light photosensor assemblies may be referred to as front side illuminated because incident light passes through a portion or layer of the SWIR-visible light photosensor assembly, including, for example, a wiring or metal level of a redistribution layer, before passing through a silicon layer that may include SWIR detectors and visible light detector devices such as photodiodes. In the description herein, the top side of an element or structure may be referred to as the side of the element or structure facing the direction of incident radiation or light. The bottom side of the element or structure may be referred to as the side opposite the top side.

[0030] In some implementations, the bottom side of the front-illuminated photosensor die can be hybrid bonded to the top side of the ASIC die with electrical connections between the two dies.

[0031] In some other example implementations, the SWIR-visible light photosensor assemblies described herein may be configured for SWIR imaging under backside illumination (BSI) of the photosensor assembly. A backside-illuminated SWIR-visible light photosensor assembly may include the same elements as a front-illuminated SWIR-visible light photosensor assembly, but a layer containing wiring or a metal level of the redistribution layer is disposed behind the silicon layer such that light incident on the SWIR-visible light photosensor assembly first illuminates the silicon layer before passing through the layer containing wiring or metal level of the redistribution layer.

[0032] 2 illustrates an exemplary SWIR-visible light optical sensor assembly 200 configured for SWIR imaging under front surface illumination (FSI). The cross-sectional view shown is along line AA in FIG. 1B. The direction of front surface illumination is indicated, for example, by an arrow marked FSI at the top of the figure.

[0033] As shown in FIG. 2, in an exemplary implementation, the SWIR-to-visible light photosensor assembly 200 includes an ASIC die 110 disposed below and bonded to a photosensor die 210 .

[0034] The ASIC die 110 may include an ASIC layer 112 fabricated on or in a semiconductor substrate 111. The ASIC layer 112 may include devices and circuits such as diodes and transistors (not shown) for image signal processing. The ASIC die 110 may further include an inter-metal dielectric layer (IMD layer 113) and a passivation layer 113P disposed on the ASIC layer 112. The IMD layer 113 may include redistribution layer metal levels 113M, e.g., metal levels M1-M5, for distributing electrical signals to and from devices and circuits within the ASIC die 110.

[0035] Oxide layer 114 may be disposed on IMD layer 113. A top surface TS of oxide layer 114 may form a bonding surface for bonding ASIC die 110 to photosensor die 210, for example, across a bond line shown as dashed line B in FIG.

[0036] In an example implementation, the metal pads may be embedded in the oxide layer 114 approximately at the top surface TS. In some implementations, the metal pads may be copper pads 115. The top surface TS of the oxide layer 114, including the copper pads 115, may be planarized, for example, by chemical mechanical polishing (CMP), to prepare a bonding surface for bonding the photosensor die 210, for example, across a bond line shown as dashed line B in FIG.

[0037] Copper pad 115 may be electrically connected by metal-filled through-substrate vias to metal levels 113M, e.g., metal levels M1-M5, of the redistribution layer for distributing electrical signals to and from devices and circuits within ASIC die 110. In some implementations, the metal-filled through-substrate vias may be TSVs 115T. In an exemplary implementation, metal levels M1-M5 of the redistribution layer in ASIC die 110 may be made from metals, such as copper and aluminum, or metal alloys.

[0038] 2, the photosensor die 210 may include an inter-metal dielectric layer (IMD layer 213) disposed on a semiconductor substrate (silicon substrate 212). A color filter array (CFA 250) may be disposed on the IMD layer 213. A passivation layer 213P may be disposed between the CFA 250 and the IMD layer 213, for example.

[0039] CFA 250 may include, for example, rows of IR filter elements 252 alternating with green filter elements 254. Filter elements 254 may be filter elements along line AA shown in FIG. 1B. Green filter elements 254, which may be made from an organic material, may allow green light to pass through and interact with a photodetector, such as a photodiode 400 disposed in silicon substrate 212 below green filter elements 254.

[0040] In an exemplary implementation, the IR filter element 252 in the CFA 250 may include, for example, a photosensitive layer of colloidal quantum dots. The layer of colloidal quantum dots may include, for example, semiconductor nanocrystals dispersed in an organic film. The IR filter element 252 may be disposed between a bottom electrode 262 and a top electrode 264. The bottom electrode 262 may be made of, for example, tantalum or copper and may be disposed on a passivation layer 213P above the IMD layer 213. The top electrode 264 may be formed of, for example, a material that is transparent to SWIR and visible light, such as indium tin oxide (ITO) doped with Al and ZnO. The bottom electrode 262, the top electrode 264, and the layer of colloidal semiconductor nanocrystals of the IR filter element 252 may form a capacitive structure that can collect charge generated in the layer of colloidal semiconductor nanocrystals by incident SWIR.

[0041] The colloidal semiconductor nanocrystals in the IR filter element 252 may be, for example, lead sulfide (PbS), indium arsenide (InAs), indium phosphide (InP), lead selenide (PbSe), cadmium sulfide (CdS), cadmium selenide (CdSe), indium gallium arsenide (InxGa 1-x The material may include at least one of lead oxide (PbO), lead mercury telluride (CdHgTe), zinc selenide (ZnSe), lead oxide (PbO), and lead sulfate (PbSO4), or a combination thereof.

[0042] CFA 250 may extend across an array of pixels P. Figure 2, for example, illustrates an exemplary pair of pixels as a rectangle marked with a dashed line. The pixel pair may include pixel P1 and pixel P2. In an exemplary implementation, the number of pixels in the imager may be, for example, hundreds of thousands or even millions.

[0043] As shown in FIG. 2 , the top electrode 264 disposed on the IR filter element 252 may extend across all pixels, including pixels associated with color filter elements, e.g., green filter elements 254. In some implementations, all pixels P may share a common top electrode 264, while each pixel P associated with an IR filter element 252 may have an individual bottom electrode. The individual bottom electrode may include the electrode 262. In exemplary implementations, the top electrode 264 and the bottom electrode 262 may be made of, for example, a metal and / or an at least partially transparent material. Transparent materials may include, for example, indium tin oxide, indium oxide, tungsten oxide, aluminum, gold, platinum, silver, magnesium, copper, and combinations and layer structures thereof. In exemplary implementations, the top electrode 262 may be, for example, an indium tin oxide (ITO) material doped with ZnO and Al. In an exemplary implementation, the bottom electrode 262 may be a patterned layer of metal including, for example, one or more of copper, tantalum, titanium, or tungsten.

[0044] In the photosensor die 210, the inter-metal dielectric layer (IMD layer 213) may include redistribution layer metal levels 213M, such as metal levels M1, M2, M3, and / or M4, for distributing electrical signals to and from the pixel devices 246 in each pixel. The pixel devices 246 may be fabricated, for example, in or on a silicon substrate 212. In example implementations, the pixel devices 246 may include diodes, transistors, and / or amplifiers. The electrical signals distributed across the metal levels 213M may include, for example, the output of the IR filter element 252 in pixel P1 and the output of the photodiode 400 in pixel P2. In example implementations, the pixel devices 246 may be coupled to the output of the IR filter element 252, which includes colloidal quantum dots. In some example implementations, the bottom electrode 262 may be connected to a metal level within the metal level 213M, such as metal level M1. In an example implementation, a metal-filled via 213T through the IMD layer 213 may connect the bottom electrode 262 to metal level M1. In an example implementation, the metal levels M1-M3 of the redistribution layer in the photosensor die 210 may be made from a metal or metal alloy. The metal or metal alloy may include, for example, copper or aluminum. In an example implementation, a tungsten contact 213W may connect metal level M1 to pixel devices 246 fabricated in or on the silicon substrate 212.

[0045] In the photosensor die 210, the silicon substrate 212 may be a thinned silicon substrate. An oxide layer 214 may be disposed on a back surface of the silicon substrate 212. A bottom surface BS of the oxide layer 214 may form a bonding surface for bonding the silicon substrate 212 to the ASIC die 110, for example, across a bond line shown as dashed line B in FIG.

[0046] In an example implementation, copper pad 215 may be embedded in oxide layer 214 near bottom surface BS or near bond line B. The bottom surface BS of oxide layer 214, including copper pad 215, may be planarized, for example, by a chemical mechanical polishing (CMP) process, to prepare a bonding surface for bonding photosensor die 210 to ASIC die 110 across the bond line, shown as dashed line B in FIG.

[0047] Copper pads 215 embedded in oxide layer 214 may be electrically connected by metal-filled through-substrate vias, such as TSVs 215T, to metal levels 213M of a redistribution layer for distributing electrical signals to and from devices and circuits within photosensor die 210. Metal levels 213M may include, for example, metal levels M1-M3.

[0048] In an exemplary implementation, to bond the ASIC die 110 to the photosensor die 210, the surface TS of the oxide layer 114 of the ASIC die 110 and the surface BS of the oxide layer 214 of the photosensor die 210 are positioned opposite each other and bonded together in a hybrid bonding process. Hybrid bonding processes include, for example, oxide-to-oxide and metal-to-metal bonding processes.

[0049] In an exemplary implementation, copper pad 115 in oxide layer 114 and copper pad 215 in oxide layer 214 may be aligned and coupled to one another in a hybrid bonding process. The hybrid bonding process may include low-temperature processing of the bonded assembly, which may result in copper interdiffusion to couple copper pad 115 and copper pad 215 together. The low-temperature processing may include, for example, a temperature of about 200° C. to about 250° C. The coupling of copper pad 115 and copper pad 215 may electrically connect the redistribution layers of the two dies, such as metal levels M1-M5 and metal levels M1-M3, to exchange electrical signals between ASIC die 110 and photosensor die 210.

[0050] Metal levels M1-M3 of photosensor die 210 and metal levels M1-M5 of ASIC die 110 may be fabricated from copper. In an example implementation, the redistribution layer in photosensor die 210 may include an additional metal level M4 disposed within IMD layer 213. Metal level M4 may include aluminum pads 248 accessible through openings O in the top of photosensor die 210, for example, for wirebonding external wire connections to the die.

[0051] In an example implementation, the photosensor die 210 may include a microlens array, e.g., an array 270 of microlenses 272, disposed on the front surface FS of the die to help direct incident light to each pixel P. In an example implementation, as shown in FIG. 3 , the microlenses 272 may be disposed only above the color filter elements, e.g., red, blue, and green color filter elements, in the CFA 250. The microlenses 272 may not be disposed above the IR filter elements in the CFA 250. For example, FIG. 3 illustrates the microlenses 272 disposed only above the color filter elements, such as the green filter element 254, and not above the IR filter element 252 in the CFA 250.

[0052] 3 also shows the bottom electrode 262 of the IR filter element 252 connected to the transistor 282 and the photodiode 400 associated with the color pixel, for example, connected to the transistor 284. The transistor 282 and the transistor 284 may be part of a device 246 formed in or on the silicon substrate 212. In an exemplary implementation, the device 246 may be used to read or clear charge accumulated or induced in the respective pixel by SWIR light or visible light.

[0053] In an exemplary implementation, each pixel P may be associated with a pixel device 246, which may be fabricated in or on the silicon substrate 212. In an exemplary implementation, the device 246 may be a MOSFET device or other transistor fabricated in or on the surface of the silicon substrate 212. As shown in FIGS. 4A-4C , the device 246 may include a polysilicon gate G disposed on the surface of the silicon substrate 212, and heavily doped source and drain regions disposed in or on the surface of the substrate 212. The source region may include a source S, and the drain region may include a drain D.

[0054] In some example implementations, as shown in FIG. 4A , the bottom electrode 262 disposed below the IR filter element 252 in pixel P1 may be connected to a metal level M1 by a metal-filled via 213T and further connected to a polysilicon gate G disposed on the surface of the silicon substrate 212 by a metal-filled via extension 213E of the metal-filled via 213T.

[0055] In some example implementations, as shown in FIG. 4B, the electrode 262 disposed below the IR filter element 252 may be connected only to a polysilicon gate G disposed on the surface of the silicon substrate 212 by a metal-filled via 214T.

[0056] In some example implementations, as shown in FIG. 4C, the bottom electrode 262 disposed below the IR filter element 252 may be connected only to a heavily doped source S disposed in or on the surface of the substrate 212 by a metal-filled via 215T.

[0057] In an exemplary implementation, metal-filled vias 213T, 214T, and 215T may be, for example, Ti / W-filled vias. Electrode 262 may be, for example, made of titanium and tungsten.

[0058] Figure 5 shows an exemplary SWIR-visible light photosensor assembly 500 configured for SWIR imaging under backside illumination (BSI). The cross-sectional view shown in Figure 5 is taken along line AA in Figure 1B. The direction of backside illumination is indicated, for example, by an arrow marked BSI at the top of the figure.

[0059] 5 , in an exemplary implementation, SWIR-visible light photosensor assembly 500 includes a photosensor die 510 including a color filter array, e.g., CFA 250, disposed on an upper surface of a thinned silicon substrate 512. An IMD layer 513 may be disposed below the silicon substrate 512. A passivation layer 513P may be disposed between the silicon substrate 512 and the IMD layer 513. The ASIC die 110 is disposed below the photosensor die 510 and is bonded to the photosensor die 510 using, for example, a hybrid bonding process. This hybrid bonding process may be the same as or similar to the hybrid bonding process described above in connection with SWIR-visible light photosensor assembly 200.

[0060] In the SWIR-visible light photosensor assembly 500 shown in FIG. 5 , a pattern of SWIR detector pixels and visible light detector pixels may be formed in a silicon substrate 512. FIG. 5 shows, for example, a SWIR pixel P1 and a visible light detector pixel P2 formed in the silicon substrate 512. A CFA 250 disposed on the top surface of the silicon substrate 512 may include, for example, a row of IR filter elements 252 alternating with green filter elements 254 similar to the filter elements IR-G-IR-G along line AA shown in FIG. 1B . The IR filter elements 252 may be aligned with SWIR pixels, for example, pixel P1, and the green filter elements 254 may be aligned with visible color pixels, for example, pixel P2. The green filter elements 254, which may be made of an organic material, may allow green light to pass through and interact with a photodetector, such as a photodiode 400 formed in the silicon substrate 512 below the green filter elements 254.

[0061] The CFA 250 may extend across an array of pixels of various color types and patterns. Figure 5, for example, illustrates a pair of adjacent pixels, a SWIR pixel P1 and a visible light detector pixel P2, as adjacent rectangles marked with dashed lines. In an exemplary implementation, the number of pixels in the imager may be, for example, hundreds of thousands or even millions.

[0062] The silicon substrate 512 used in the SWIR-visible light optical sensor assembly 500 is sometimes referred to herein as backside illuminated silicon (BSI silicon).

[0063] In an exemplary implementation, the IR filter element 252 in the CFA 250 may include, for example, a photosensitive layer of colloidal quantum dots. The layer of colloidal quantum dots may include, for example, semiconductor nanocrystals dispersed in an organic film. The IR filter element 252 may be disposed between a bottom electrode 262 and a top electrode 264. The bottom electrode 262 may be made of, for example, tantalum or copper and may be disposed on a passivation layer disposed on the silicon substrate 512. The top electrode 264 may be formed of, for example, a material that is transparent to SWIR and visible light, such as doped indium tin oxide (ITO). The bottom electrode 262, the top electrode 264, and the layer of colloidal semiconductor nanocrystals of the IR filter element 252 may form a capacitive structure that can collect charge generated or induced in the layer of colloidal semiconductor nanocrystals by incident SWIR.

[0064] In some exemplary implementations, the top electrode 264, made of, for example, ITO, may extend over both the SWIR pixel and the visible light pixel, as shown in Figure 5. In some other exemplary implementations, the top electrode 264, made of, for example, ITO, may extend only over the SWIR pixel (P1).

[0065] In an exemplary implementation, deep isolation trenches, e.g., trench 520, may be formed to separate the photodiodes 400 formed in the silicon substrate 512 in the color pixels, e.g., pixel P2, from the BSI silicon in the SWIR pixels, e.g., pixel P1. Although the deep isolation trenches 520 are shown in FIG. 5 as extending only partially through the depth of the silicon substrate 512, they may extend completely through the silicon substrate 512. Also, in an exemplary implementation, the deep isolation trenches may be formed from the front side, or the same side as the IMD layer 513, in which case they may be filled with polysilicon and SiO2 or W metal or any other combination.

[0066] Additionally, a through-silicon via, e.g., TSV 522, may be formed within each SWIR pixel P1 and extend from the top surface of the silicon substrate 512 to a metal level, e.g., metal level M1, within the IMD layer 513 disposed below the silicon substrate 512.

[0067] In an exemplary implementation, the top surface of the silicon substrate 512 (as well as other exposed surfaces, including, for example, the sidewalls of the trenches 520 and the TSVs 522) may be coated with a passivation insulator, including, for example, a high-κ insulator layer 512K and an oxide layer 512D, or other insulator. The high-κ insulator layer 512K may include, for example, a high-κ insulator such as Al2O3 / HfO2 / Ta2O5.

[0068] In an example implementation, the TSV 522 may be lined with oxide 523 and filled with a metal plug 513T to electrically connect the bottom electrode 262 in the SWIR pixel (P1) to the metal level M1. The metal plug 513T may comprise, for example, tungsten, tantalum, or copper.

[0069] The IR filter element 252 may include, for example, colloidal semiconductor nanocrystals dispersed in a film that may be spin-coated as an organic fluid colloid onto the silicon substrate 512. Semiconductor nanocrystals (quantum dot photodetectors) include, for example, PbS, InAs, InP, PbSe, CdS, CdSe, InxGa 1-x The nanocrystals may include at least one of As, (Cd-Hg)Te, ZnSe(PbS), ZnS(CdSe), ZnSe(CdS), PbO(PbS), and PbSO4(PbS) nanocrystals or other semiconductor quantum dots.

[0070] As shown in FIG. 5 , the pixel P1 includes an upper electrode 264 disposed on the CFA 250 and a lower electrode 262 disposed below the IR filter element 252 in each pixel P1. All pixels P1 may share a common upper electrode 264, and each pixel P1 may have an individual lower electrode 262. In an exemplary implementation, the upper electrode 264 and the lower electrode 262 may be made of, for example, a metal and / or an at least partially transparent material. The upper electrode 264 may include, for example, indium tin oxide, indium oxide, tungsten oxide, aluminum, gold, platinum, silver, magnesium, or copper, as well as combinations and layer structures thereof. In an exemplary implementation, the upper electrode may be, for example, an indium tin oxide (ITO) material doped with ZnO and Al. In an exemplary implementation, the lower electrode 262 may be, for example, a patterned layer of metal including one or more of copper, tantalum, titanium, or tungsten.

[0071] In an exemplary implementation, the top electrode 264 and bottom electrode 262 in each pixel P1 may be connected to a metal level, such as metal level M1, in the IMD layer 513 disposed below the silicon substrate 512. This connection may be made, for example, by a metal plug 513T disposed in a TSV 522. The TSV 522 may be filled or lined with an oxide layer 512D and / or oxide 523 for passivation.

[0072] In an exemplary implementation, each pixel contact may be made of, for example, tantalum, titanium nitride, and tungsten (Ta / TiN / W) contacts, including the bottom electrode 262. Each pixel contact may be separated to create a high value capacitor, for example, with a high-κ insulator layer 512K lining the top surface of the silicon substrate 512 and the sidewalls of the TSVs 522. The high-κ insulator layer may include, for example, aluminum oxide, hafnium oxide, and tantalum oxide (Al2O3 / HfO2 / Ta2O5). The high value capacitor may store charge generated in the IR filter element 252 by incident SWIR, for example, for periodic readout.

[0073] In the photosensor die 510, the IMD layer 513 may include a redistribution layer metal level 513M for distributing electrical signals in each pixel P1 and P2 to and from pixel devices that may be fabricated in or on the silicon substrate 512. The metal level 513M may include, for example, metal levels M1 through M3. The fabricated devices (not shown) may include, for example, diodes, transistors, or amplifiers. In some example implementations, tungsten-filled plugs 516 and 517 extending from the metal level M1 into the silicon substrate can establish electrical connection to pixel devices, e.g., transistors, fabricated in or on the silicon substrate 512. For example, the tungsten-filled plugs 516 and 517 extending from the metal level M1 into pixels P2 and P1, respectively, can establish electrical connection to respective pixel devices (e.g., transistors) formed in the silicon substrate.

[0074] In some example implementations, the redistribution layer within the photosensor die 510 may include aluminum pads 548 accessible through openings O in the top of the photosensor die 510, for example, for wire bonding external wire connections to the die.

[0075] In example implementations, photosensor die 510 may include a microlens array, e.g., array 270, disposed on the front surface FS of the die, to help direct incident light to each pixel P. In example implementations, microlenses 272 may be disposed only above color filter elements, e.g., red, green, and blue color filter elements, in CFA 250. In some example implementations, microlenses 272 may not be disposed above IR filter elements 252 in CFA 250.

[0076] 6A , the bottom electrode 262 disposed below the SWIR filter element 252 may first be connected to a metal level M1 by a metal plug 512P disposed in a through-silicon via 513T extending through the silicon substrate 512. Furthermore, the metal level M1 may be independently connected to the polysilicon gate G of the pixel device 546 by a metal-filled via 546V passing through the IMD layer 513.

[0077] In some example implementations, as shown in FIG. 6B , the bottom electrode 262 disposed below the SWIR filter element 252 may be directly connected to the polysilicon gate G of the pixel device by a metal plug 515P disposed in a through-silicon via 515T that extends through the silicon substrate 512 and terminates at the polysilicon gate G of the pixel device.

[0078] 6C , the bottom electrode 262 disposed below the SWIR filter element 252 may be directly connected to the heavily doped source S of the pixel device 546 by a metal plug 516P. The metal plug 516P may be disposed in a through-silicon via 516T extending through the silicon substrate 512. Furthermore, the metal level M1 may also be independently connected to the polysilicon gate G of the pixel device by a metal-filled via 546V extending from the M1 layer through the IMD layer 513 to the polysilicon gate G.

[0079] In some exemplary implementations, the above-described photosensor die 210 and photosensor die 510 may include an infrared sensitivity enhancement mechanism to improve visual images. An exemplary enhancement mechanism may include a diffractive inverted pyramid array (IPA) structure disposed on a silicon substrate within the visible color pixel. The IPA structure may be light trapping and may increase absorption of light incident on the visual color pixel. In exemplary implementations, the IPA structure may be disposed on top of a photodetector within the pixel to detect near-infrared light.

[0080] In an exemplary implementation, the IPA structure can increase the IR sensitivity of the visual image. Additionally, the IPA structure, together with deep trench isolation of the pixels, can reduce the effects of crosstalk between pixels.

[0081] FIG. 7 illustrates an exemplary SWIR-visible light photosensor assembly 700. The SWIR-visible light photosensor assembly 700 may generally have the same structure and characteristics as the SWIR-visible light photosensor assembly 500 illustrated in FIG. 5. However, the SWIR-visible light photosensor assembly 700 illustrated in FIG. 7 further includes an infrared-sensitivity enhancement mechanism. For example, as shown in FIG. 7, an inverted pyramid structure 710 may be formed on the top surface of a photodiode 400 disposed in the silicon substrate 512 below a color filter element, e.g., a green filter element 254. The inverted pyramid structure 710 may trap light by diffraction and increase the absorption of light incident on the photodiode 400, enhancing the IR sensitivity of the sensor.

[0082] 8 shows a cross-sectional view of an exemplary combined SWIR-visible light photosensor assembly 800 configured for SWIR imaging under backside illumination (BSI). The cross-sectional view shown is taken along line CC in FIG. 1C. The direction of backside illumination is indicated, for example, by an arrow marked BSI at the top of the figure.

[0083] The SWIR-visible light photosensor assembly 800 includes an ASIC die 110 disposed below and bonded to a photosensor die 810. The photosensor die 810 may include a pixel array in which an IR filter element is located in the center of a 2x2 RGGB pattern of color filter elements, for example, as shown in FIG. 1C.

[0084] In the combined SWIR-visible light photosensor assembly 800, a CFA 850 is disposed on the top surface of a silicon substrate 512. The CFA 850 may include, for example, an array of IR filter elements 252, each IR filter element being centered in a 2×2 pattern of color filter elements BGGR. The IR filter elements 252 may be aligned with SWIR pixels, e.g., pixel P1. The green filter elements 254 may be aligned with visible light pixels, e.g., pixel P2. The red filter elements 256 may be aligned with visible light pixels, e.g., pixel P3. The blue filter elements in the BGGR pattern may be associated with corresponding blue visible light pixels, although the blue pixels are not visible in the cross-sectional view shown in FIG. 8 . The green filter element 254 and the red filter element 256, which may be made from organic materials, may pass green light and red light, respectively, allowing them to interact with the photodiode 400 disposed in the silicon substrate 512 below the green filter element 254 and the red filter element 256.

[0085] In an exemplary implementation, the IR filter element 252 in the CFA 850 may be surrounded by a backside deep isolation trench (e.g., trench 520) that extends at least partially through the thickness of the silicon substrate 512. The deep trench isolation trench extending through the silicon substrate 512 may also separate the visible light pixels P2 and P3. Although the deep trench is shown as extending partially into the silicon, in an exemplary implementation, the deep trench may extend all the way through the silicon substrate 512. The deep trench may also be formed from the front side, in which case it may be filled with polysilicon and SiO2 or W metal or any other combination of materials.

[0086] Deep trench isolation trenches 520 may consume silicon that would otherwise be part of an adjacent pixel.

[0087] FIG. 9 illustrates an exemplary method 900 for combining SWIR and visible light detection in a single optical sensor.

[0088] The method 900 includes forming 910 a photosensor die including a semiconductor substrate, wherein at least one device is fabricated within the semiconductor substrate.

[0089] Method 900 further includes disposing (920) an array of optically active pixels on the photosensor die, configuring (930) at least one pixel of the array of optically active pixels to detect short wavelength infrared (SWIR) light incident on the photosensor die, and configuring (940) at least one other pixel of the array of optically active pixels to detect visible light incident on the photosensor die.

[0090] In an exemplary implementation of method 900, configuring 930 at least one pixel of the array of optically active pixels to detect SWIR includes disposing a layer of quantum colloidal dots between an upper electrode and a lower electrode in the pixel.

[0091] In an exemplary implementation of method 900, configuring 940 at least one pixel of the array of optically active pixels to detect visible light includes forming a photodiode within the pixel. In an exemplary implementation, method 900 further includes disposing a diffractive inverted pyramid structure on a photodiode formed within the semiconductor die to detect near-infrared light. Example implementations related to steps 930 and 940 are described below in connection with FIGS. 10A-10C.

[0092] In an exemplary implementation, as described below with reference to FIGS. 10A-10C , steps 930 and 940 of method 900 may involve disposing a layer of color photoresist including a pattern of color filter elements, e.g., green filter elements 254, over an array of optically active pixels, e.g., pixels P1 and P2. The layer of color photoresist may then be patterned to define openings, e.g., openings OS, for at least one SWIR filter element, e.g., SWIR filter element 252. A layer of colloidal quantum dot material may then be applied over the layer of color filter elements to fill the openings for at least one SWIR filter element 252. Excess colloidal quantum dot material on the color filter elements may be etched away by a photolithography process or removed by chemical-mechanical polishing (CMP). A layer of ITO may then be applied over the layer of color filter elements and the layer of colloidal quantum dot material. The layer of ITO may form the top electrode 264 for the SWIR filter element 252.

[0093] 10A-10C also illustrate the formation of a mosaic of, for example, color filter elements and SWIR filter elements. Figure 10A illustrates, for example, a stage of construction in which a layer of color photoresist, for example, layer 250, including, for example, green filter element 254, is disposed above an array of optically active pixels, for example, pixels P1 and P2. An opening OS may be created in layer 250 to receive colloidal quantum dot material for at least one SWIR filter element 252 in a subsequent construction stage.

[0094] 10B shows a layer of quantum colloid dots 254 and a layer of ITO 264 applied over the structure to fill the apertures OS and form an IR filter element, such as IR filter element 252. Excess quantum colloid dot material 259 and ITO material 269 may extend outside the area of ​​the array of optically active pixels.

[0095] FIG. 10C shows that excess quantum colloid dot material and ITO material 269, which may extend over areas outside the array of optically active pixels, can be removed by etching.

[0096] In some example implementations, a layer of colloidal quantum dot material may first be disposed over all of the optically active pixels. The layer of colloidal material may then be covered with a protective layer (e.g., SiO or SiN) and then patterned and etched to form openings to receive colored resist for a plurality of visible light color filter elements.

[0097] In an example implementation, the mosaic has filter elements arranged in at least one of the following: A) RGB-IR 2x2 format, including one red filter element, one blue filter element, one green filter element, and one SWIR filter element for a total of four filter elements; B) an RGB-IR 4x4 format, including two red filter elements, two blue filter elements, eight green filter elements, and four SWIR filter elements, for a total of 16 filter elements; or C) RGB 2x2+IR format including one red filter element, one blue filter element, two green filter elements, and one SWIR filter element in the center of a 2x2 RGB square for a total of five filter elements, where the SWIR filter element is less than one pixel in size.

[0098] In an exemplary implementation, the method 900 further includes disposing a diffractive inverted pyramid structure on a photodiode formed in the semiconductor die to detect near-infrared light.

[0099] In an exemplary implementation, the method 900 further includes disposing an array of microlenses at least over the plurality of visible light color filter elements.

[0100] In an exemplary implementation, the method 900 further includes bonding and electrically connecting an application specific integrated circuit (ASIC) die to the semiconductor die.

[0101] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It will therefore be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the implementations. These have been presented by way of example only, and not limitation, and it will be understood that various changes in form and detail may be made. Any portion of the apparatus and / or methods described herein may be combined in any combination except mutually exclusive combinations. The implementations described herein may include various combinations and / or subcombinations of functions, components, and / or features of the different implementations described.

[0102] In the foregoing specification, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled with another element, it will be understood that the element may be directly on, connected to, or coupled with the other element, or that one or more intervening elements may be present. Conversely, when an element is referred to as being directly on, directly connected to, or directly coupled with another element, no intervening elements are present. Throughout the detailed description of the present invention, the terms directly on, directly connected, or directly coupled may not be used, but elements shown as being directly on, directly connected, or directly coupled may be referred to as such. The claims of this application (if included) may be amended to describe the exemplary relationships described herein or shown in the drawings.

[0103] As used herein, the singular can include the plural unless the context clearly dictates otherwise. Spatially relative terms (such as above, above, upper, below, below, under, lower, and the like throughout) are intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the drawings. In some implementations, the relative terms above and below can include vertically above and vertically below, respectively. In some implementations, the term adjacent can include laterally adjacent or horizontally adjacent.

[0104] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "comprises" and variations thereof are used synonymously with the term "comprises" and variations thereof and are open, non-limiting terms. As used herein, the terms "optional" or "optionally" mean that the subsequently described feature, event, or circumstance may or may not occur, and that the description includes both instances when the feature, event, or circumstance occurs and instances when it does not occur. Ranges may be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, the aspect includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant in relation to the other endpoint, and independently of the other endpoint.

[0105] Some implementations may be implemented using various semiconductor processing and / or packaging technologies, such as, but not limited to, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), and / or other types of semiconductor processing technologies associated with semiconductor substrates.

Claims

1. A sensor (200, 500, 700, 800), an array of optically active pixels (P1, P2) disposed on a semiconductor die (210, 510, 810), said array of optically active pixels comprising: at least one pixel (P1) configured to detect short wavelength infrared (SWIR); and at least one pixel (P2) configured to detect visible light.

2. The sensor of claim 1 , wherein the at least one pixel configured to detect SWIR includes a layer of quantum colloidal dots disposed between a top electrode and a bottom electrode.

3. The sensor of claim 1 , wherein the at least one pixel configured to detect visible light includes a photodiode formed within the semiconductor die.

4. The sensor of claim 3 , further comprising a diffractive inverted pyramid structure disposed on the photodiode formed in the semiconductor die for detecting near-infrared light.

5. 10. The sensor of claim 1, further comprising a color filter array disposed above the array of optically active pixels, the color filter array comprising a mosaic of a plurality of visible light color filter elements and at least one SWIR filter element, the at least one SWIR filter element comprising a layer of quantum colloidal dots disposed between an upper electrode and a lower electrode.

6. The sensor of claim 5 , wherein the mosaic has one SWIR filter element in any given 2×2 section.

7. 6. The sensor of claim 5, wherein the mosaic has filter elements arranged in an RGB 2x2+IR format including one red filter element, one blue filter element, two green filter elements, and one SWIR filter element in the center of a 2x2 RGB square for a total of five filter elements, the SWIR filter elements being less than one pixel in size.

8. The sensor of claim 1 , further comprising an array of microlenses disposed above the at least one pixel configured to detect visible light.

9. an optical sensor die (200, 500, 700, 800) including a semiconductor substrate (212, 512, 700, 800) and at least one device (282, 284, 246, 546) fabricated in the semiconductor substrate; an array of optically active pixels (P1, P2, P3) disposed on the photosensor die, the array of optically active pixels including at least one short wavelength infrared (SWIR) pixel (P1) and at least one visible light pixel (P2, P3); an inter-metal dielectric (IMD) layer (513) disposed on a bottom surface of the semiconductor substrate (512), the IMD layer including at least a metal level (M1) of a redistribution layer of the photosensor die.

10. 10. The imaging device of claim 9, wherein the at least one SWIR pixel includes a layer of quantum colloidal dots disposed between an upper electrode and a lower electrode, and the at least one visible light pixel includes a photodiode formed in the semiconductor substrate.

11. The quantum colloid dot layer may be made of PbS, InAs, InP, PbSe, CdS, CdSe, In ｘ Ga １－ｘ As, CdHgTe, ZnSe (PbS), ZnS (CdSe), ZnSe (CdS), PbO (PbS), and PbSO ４ 11. The imaging device of claim 10, comprising colloidal semiconductor nanocrystals made from at least one of: (PbS);

12. The imaging device of claim 10 , further comprising a diffractive inverted pyramid structure disposed on the photodiode formed in the semiconductor substrate for detecting near-infrared light.

13. 10. The imaging device of claim 9, wherein a deep isolation trench etched into the semiconductor substrate separates at least a first pixel from a second pixel in the array of optically active pixels.

14. 10. The imaging device of claim 9, further comprising a color filter array (CFA) disposed above the array of optically active pixels, the CFA comprising a mosaic of a plurality of visible light color filter elements and at least one SWIR filter element, the at least one SWIR filter element comprising a layer of quantum colloidal dots (QCDs) disposed between a top electrode and a bottom electrode.

15. 15. The imaging device of claim 14, further comprising: a layer of passivation material disposed on a top surface of the semiconductor substrate below the CFA, the layer of passivation material comprising at least one of silicon dioxide and a high-κ insulator material.

16. 16. The imaging device of claim 15, wherein the top electrode and the semiconductor substrate above the layer of QCD form a capacitor with the high-κ insulator material therebetween as a capacitive material.

17. The imaging device of claim 14 , wherein the bottom electrode is electrically connected to a metal level in the IMD layer by a metal-filled via that extends through the semiconductor substrate.

18. 15. The imaging device of claim 14, wherein the bottom electrode is electrically connected to a transistor formed in or on the semiconductor substrate by a metal-filled via that extends through the semiconductor substrate.

19. the semiconductor substrate is a first semiconductor substrate, the re-distribution layer is a first re-distribution layer, the IMD layer is a first IMD layer, and the imaging device is an application specific integrated circuit (ASIC) die including a second semiconductor substrate; a second IMD layer disposed on the second semiconductor substrate, the second IMD layer including at least a metal level of a second redistribution layer (RDL) of the ASIC die; 10. The imaging device of claim 9, wherein the photosensor die is stacked above the ASIC die with an insulating layer disposed between the bottom surface of the first semiconductor substrate and a top surface of the second IMD layer, the insulating layer bonding the photosensor die to the ASIC die.

20. 20. The imaging device of claim 19, wherein the insulating layer disposed between the bottom surface of the first semiconductor substrate and the top surface of the second IMD layer includes a pair of copper pads fused together to electrically connect the first RDL of the photosensor die and the second RDL of the ASIC die.

21. Forming a photosensor die (910) including a semiconductor substrate, at least one device fabricated in the semiconductor substrate; disposing an array of optically active pixels on the photosensor die (920); configuring (930) at least one pixel of the array of optically active pixels to detect short wavelength infrared (SWIR) radiation incident on the photosensor die; and configuring (940) at least one other pixel of the array of optically active pixels to detect visible light incident on the photosensor die.

22. 22. The method of claim 21 , wherein configuring at least one pixel of the array of optically active pixels to detect SWIR comprises disposing a layer of quantum colloidal dots between a top electrode and a bottom electrode in the at least one pixel.

23. 22. The method of claim 21, wherein configuring at least one pixel of the array of optically active pixels to detect visible light comprises forming a photodiode within the at least one pixel.

24. 24. The method of claim 23, further comprising disposing a diffractive inverted pyramid structure on the photodiode formed in the at least one pixel for detecting near-infrared light.

Images