Stacked photon detection device, stacked photon detection sensor and active photon sensing system

Abstract

A stacked photon detection device, including: a first photodetection layer configured to detect photons in a first wavelength range; a second photodetection layer configured to detect photons in a second wavelength range; an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

Description

[0001] STACKED PHOTON DETECTION DEVICE, STACKED PHOTON DETECTION SENSOR AND ACTIVE PHOTON SENSING SYSTEM TECHNICAL FIELD

[0002] The present disclosure generally pertains to a stacked photon detection device, a stacked photon detection sensor and an active photon sensing system.

[0003] TECHNICAL BACKGROUND

[0004] Generally, stacked light sensors or stacked photon detection sensors are known.

[0005] Typically, such stacked photon detection sensors include pixels which include a first photodetection layer and a second photodetection layer which are arranged on each other, and which detect photons in at least partially different spectral regions of the electromagnetic spectrum.

[0006] These stacked photon detection sensors may, for example, be used in multi-spectral imaging applications to capture images of a scene in different spectral regions simultaneously with the same sensor and without parallax between the different images.

[0007] However, both photodetection layers require wiring to read-out an electric signal generated by photoelectric conversion in the respective photodetection layer.

[0008] Due to the stacked structure, the electrical connections for the first photodetection layer may be partially arranged on the second photodetection layer such that a part of the incoming light to be detected by the second photodetection layer - which is thus arranged below the first photodetection layer - may be partially blocked by the electrical connections for the first photodetection layer, thereby reducing the amount of incoming light incident on the second photodetection layer.

[0009] Although there exist techniques for stacked photon detection devices and sensors, it is generally desirable to improve the existing techniques.

[0010] SUMMARY

[0011] According to a first aspect, the disclosure provides a stacked photon detection device, comprising:

[0012] a first photodetection layer configured to detect photons in a first wavelength range; a second photodetection layer configured to detect photons in a second wavelength range;an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0013] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

[0014] According to a second aspect, the disclosure provides a stacked photon detection sensor, comprising:

[0015] an array of stacked photon detection devices, each stacked photon detection device including:

[0016] a first photodetection layer configured to detect photons in a first wavelength range;

[0017] a second photodetection layer configured to detect photons in a second wavelength range;

[0018] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection for photons in the second wavelength range; and

[0019] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

[0020] According to a third aspect, the disclosure provides an active photon sensing system, comprising:

[0021] a stacked photon detection sensor including:

[0022] an array of stacked photon detection devices, each stacked photon detection device including:

[0023] a first photodetection layer configured to detect photons in a first wavelength range;

[0024] a second photodetection layer configured to detect photons in a second wavelength range;

[0025] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0026] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path; andan active light source configured to emit photons in the second wavelength range.

[0027] Further aspects are set forth in the dependent claims, the drawings and the following description.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments are explained by way of example with respect to the accompanying drawings, in which:

[0030] Fig. 1 schematically illustrates in a block diagram a cross-sectional view of an embodiment of a stacked photon detection sensor;

[0031] Fig. 2 schematically illustrates in a block diagram a plan view of an embodiment of a stacked photon detection sensor;

[0032] Fig. 3 A schematically illustrates in a block diagram a cross-sectional view of an embodiment of a stacked photon detection device;

[0033] Fig. 3B schematically illustrates in a block diagram a cross-sectional view of an embodiment of a stacked photon detection device;

[0034] Fig. 4A schematically illustrates in a block diagram a cross-sectional view of an embodiment of a stacked photon detection device;

[0035] Fig. 4B schematically illustrates in a block diagram a cross-sectional view of an embodiment of a stacked photon detection device;

[0036] Fig. 5A schematically illustrates an embodiment of a plasmonic nano-antenna;

[0037] Fig. 5B schematically illustrates an embodiment of a plasmonic nano-antenna;

[0038] Fig. 6 schematically illustrates an embodiment of a maximum ratio of a diameter of a bull’s eye hole of a plasmonic nano-antenna in a stacked photon detection device of an array of stacked photon detection devices and a pixel pitch in the array of stacked photon detection devices; Fig. 7 schematically illustrates in a block diagram a plan view of an embodiment of an arrangement of a plasmonic nano-antenna and metallic connections in an embodiment of a stacked photon detection device; and

[0039] Fig. 8 schematically illustrates in a block diagram an embodiment of an active photon sensing system.DETAILED DESCRIPTION OF EMBODIMENTS

[0040] Before a detailed description of the embodiments under reference of Fig. 4A is given, general explanations are made.

[0041] As mentioned in the outset, generally, stacked light sensors or stacked photon detection sensors are known which may be used, for example, in multi-spectral imaging applications.

[0042] For enhancing the general understanding of the present disclosure, an embodiment of a stacked photon detection sensor 10 is discussed in the following under reference of Figs. 1 and 2, which schematically illustrate the embodiment in a cross-sectional view and in a plan view, respectively, and which also applies to other embodiments of the present disclosure.

[0043] Referring to Fig. 1, the stacked photon detection sensor 10 is depicted in a cross-sectional view, wherein the plane of the cross-section is parallel to a stacking direction SD of the layers of the stacked photon detection sensor 10.

[0044] As depicted in Fig. 1, the stacked photon detection sensor 10 includes a microlens array 11, a color filter 12, an array of stacked photon detection devices 13, a wiring layer 14 and a logic layer 15. Each of the microlens array 11, the color filter 12, the array of stacked photon detection devices 13, the wiring layer 14 and the logic layer 15 may be, for instance, plate-shaped or discshaped, but without limiting the disclosure in this regard.

[0045] The logic layer 15 is arranged at a bottom side of the stacked photon detection sensor 10 and the microlens array 11 is arranged at a top side stacked photon detection sensor 10, wherein, generally, photons enter the stacked photon detection sensor 10 via the top side.

[0046] Thus, with respect to the stacking direction SD, the wiring layer 14 is arranged on or above the logic layer 15, the array of stacked photon detection devices 13 is arranged on or above the wiring layer 14, the color filter 12 is arranged on or above the array of stacked photon detection devices 13, and the microlens array 11 is arranged on or above the color filter 12. In this way, the different layers are stacked along the stacking direction.

[0047] The stacked photon detection sensor 10 may, for example, include a first tier (the top tier) which is connected with a second tier (the bottom tier) via the wiring layer 14. The microlens array 11, the color filter 12 and the array of stacked photon detection devices 13 may be arranged in the first tier and the logic layer 15 may be arranged in the second tier.

[0048] The wiring layer 14 may partially extend into the array of stacked photon detection devices 13.The wiring layer 14 may include wires and Cu-Cu connections to transmit electric signals between the array of stacked photon detection devices 13 and the logic layer 15. The logic layer 15 may include circuits for signal processing of the electric signals received from the array of stacked photon detection devices 13 and may include circuits for generating control signals and may include digital storage for storing, for example, before the data is output by the stacked photon detection sensor 10.

[0049] Each of the microlens array 11, the color filter 12, the array of stacked photon detection devices 13, the wiring layer 14 and the logic layer 15 may be directly in contact with the layer above or below the respective layer, for instance, the wiring layer 14 may be directly in contact in with the logic layer 15 below and the array of stacked photon detection devices 13.

[0050] Hence, a top surface of a layer may be directly in contact with a bottom surface of a higher layer and a bottom surface of the layer may be directly in contact with a top surface of a lower layer. Any surface of the remaining surface of the layer, which is not in contact with a lower or a higher layer, may be referred to as a lateral surface. The entirety of the remaining surfaces of the layer, which are not in contact with a lower or a higher layer, may be referred to as the lateral surface.

[0051] However, there may also be an air gap, a dielectric layer or another functional layer arranged between the different layers.

[0052] Referring now to Fig. 2, where the stacked photon detection sensor 10 is depicted in a plan view which corresponds to a top side plan view (antiparallel to the stacking direction SD), wherein photons enter the stacked photon detection sensor 10 via the top side of the stacked photon detection sensor 10.

[0053] The array of stacked photon detection devices 13 includes a plurality of stacked photon detection devices 100 which are arranged in an array, as depicted in Fig. 2. For the sake of illustration only a 4x4-array is shown, however, the present disclosure is not limited to any particular size of the array or number of stacked photon detection devices 100 provided in the array of stacked photon detection devices 13. The array of stacked photon detection devices 13 may be manufactured by a CMOS (“complementary metal-oxide-semiconductor”) process.

[0054] Each stacked photon detection device 100 may also be referred to, for example, as stacked photon detection pixel or light detection pixel or simply as pixel or image pixel or stacked pixel or stacked image pixel or CMOS pixel or CMOS image pixel or CMOS stacked pixel or CMOS stacked image pixel or CMOS light detection pixel or CMOS stacked photon detection pixel.The plurality of stacked photon detection devices 100 is associated in 2x2-sub-arrays 50 (or 2x2-blocks), as schematically illustrated by the dashed boxes. The color filter 12 of the stacked photon detection sensor 10 may be a Bayer filter array including a plurality of Bayer filters aligned with the 2x2-sub-arrays 50.

[0055] As generally known, a Bayer filter corresponds to a 2x2-arrangement of color filter sections, wherein the 2x2-arrangement includes a blue color filter section (to be understood as being transmissive in the blue part of the visible spectrum) in the top left corner, a first green color filter section (to be understood as being transmissive in the green part of the visible spectrum) in the top right corner, a second green color filter section in the bottom left corner, and a red color filter section (to be understood as being transmissive in the red part of the visible spectrum) in the bottom right corner.

[0056] As schematically depicted in Fig. 2, each Bayer filter is aligned with a different 2x2-sub-array of the array of stacked photon detection devices 13.

[0057] Moreover, each microlens of the microlens array 11 of the stacked photon detection sensor 10 is aligned with a different stacked photon detection device 100. For example, in a top side plan view (antiparallel to the stacking direction SD), the center of the respective microlens overlaps with a center of the respective stacked photon detection device 100.

[0058] Returning to the general explanations, as mentioned above, a stacked photon detection sensor may be used in multi-spectral imaging, for example, using a combination of visible light imaging for which a first photodetection layer is used and near-infrared (“NIR”) or short-wave infrared (“SWIR”) imaging for which a second photodetection layer is used.

[0059] However, both photodetection layers require wiring to read-out an electric signal generated by photoelectric conversion in the respective photodetection layer.

[0060] For further enhancing the general understanding of the present disclosure, an embodiment of a stacked photon detection device 100-1 is discussed in the following under reference of Figs. 3A and 3B, which schematically illustrate the embodiment in a cross-sectional view, and which also applies to other embodiments of the present disclosure.

[0061] The stacked photon detection device 100-1 includes a first photodetection layer 101, a second photodetection layer 102, an interconnection layer 103 and a trench 104.

[0062] The first photodetection layer 101 is configured to detect photons in a first wavelength range, wherein the first wavelength range may correspond to the visible spectrum (i.e. wavelengths in the range of 380-780 nanometers). In other words, the first photodetection layer 101 isconfigured to perform photoelectric conversion when photons in the first wavelength range are incident for generating an electric signal.

[0063] The second photodetection layer 102 is configured to detect photons in a second wavelength range, wherein the second wavelength range may correspond to the NIR spectrum (e.g., wavelengths in the range of 780-1000 nanometers) or the SWIR spectrum (e.g., wavelengths in the range of 1000-3000 nanometers). However, a part of the wavelength range 780-3000 nanometers or the whole wavelength range 780-3000 nanometers may also be referred to as the NIR spectrum or the SWIR spectrum. In other words, the second photodetection layer 102 is configured to perform photoelectric conversion when photons in the second wavelength range are incident for generating an electric signal.

[0064] The interconnection layer 103 provides the electrical connections for the first photodetection layer 101 and may, for example, include one or more metallic connections. The interconnection layer 103 is arranged between the first photodetection layer 101 and the second photodetection layer 102, as depicted in Figs. 3A and 3B.

[0065] The trench 104 surrounds a lateral surface of the first photodetection layer 101 (for example, the trench 104 may entirely surround the lateral surface of the first photodetection layer 101). The trench 104 may further surround the lateral surface of the second photodetection layer 102 (not shown). The trench 104 may also be referred to as pixel separation wall or pixel isolation wall or pixel photon blocking wall. The trench 104 may be a deep trench isolation structure. A deep trench isolation structure may extend into the semiconductor substrate and in some examples the trench isolation structure may define the perimeter of the photodetection layer. Trenches or deep trenches for infrared imaging applications may be particularly important because the infrared light penetration depth in silicon is typically of 10 micrometers compared to about 3 micrometers for visible light.

[0066] The trench 104 may or may not be in direct contact with any or all of the first photodetection layer 101, the second photodetection layer 102 and the interconnection layer 103.

[0067] A color filter section 105 of the color filter 12 is arranged on or above the first photodetection layer 101 and a microlens 106 of the microlens array 11 is arranged on or above the color filter section 105.

[0068] As depicted in Fig. 3A, incoming photons in the visible spectrum 110-1 (example of a first wavelength range) may be subject to photoelectric conversion in the first photodetection layer 101.As depicted in Fig. 3B, incoming photons in the NIR or SWIR spectrum 110-2 (example of a second wavelength range) may not be subject to photoelectric conversion in the first photodetection layer 101, however, may reach the interconnection layer 103 or the second photodetection layer 102 arranged below the first photodetection layer 101.

[0069] As the interconnection layer 103 is arranged between the first photodetection layer 101 and the second photodetection layer 102 it delimits an optical path from the first photodetection layer 101 to the second photodetection layer 102 for photons in the NIR or SWIR

[0070] spectrum 110-2.

[0071] Hence, due to the stacked structure of the photon detection device 100-1, the electrical connections 103 for the first photodetection layer 101 may be partially arranged on or above the second photodetection layer 102 - with respect to the stacking direction SD - such that a part of the incoming photons in the NIR or SWIR spectrum 110-2 to be detected by the second photodetection layer 102 may be blocked by the electrical connections 103 for the first photodetection layer 101, as depicted in Fig. 3B, thereby reducing the amount of incoming light incident on the second photodetection layer 102.

[0072] Returning to the general explanations, it has been recognized that the number of photons in the second wavelength range which reach the second photodetection layer should be increased to improve the detection in the second wavelength range.

[0073] It has been recognized that in a stacked photon device a plasmonic nano-antenna may be used to increase the number of photons in the second wavelength range that reach the second photon detection layer.

[0074] Hence, some embodiments pertain to a stacked photon detection device, wherein the stacked photon detection device includes:

[0075] a first photodetection layer configured to detect photons in a first wavelength range; a second photodetection layer configured to detect photons in a second wavelength range; an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0076] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.The stacked photon detection device may be a pixel which may be manufactured by a CMOS process. The pixel may be a pixel of a stacked photon detection sensor. The manufacturing of the plasmonic nano-antenna may be compatible with the CMOS process. The use of a CMOS process for manufacturing allows to achieve stacked photon detection devices with a small size, for example, the stacked photon detection device may be in the micrometer range (i.e. at least one dimension is in the micrometer range, for instance, in the range of 1-10 micrometers, but without limiting the disclosure in this regard).

[0077] Some embodiments pertain to a stacked photon detection sensor, wherein the stacked photon detection sensor includes:

[0078] an array of stacked photon detection devices, each stacked photon detection device including:

[0079] a first photodetection layer configured to detect photons in a first wavelength range;

[0080] a second photodetection layer configured to detect photons in a second wavelength range;

[0081] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0082] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

[0083] The stacked photon detection sensor or the array of stacked photon detection devices may be manufactured by a CMOS process. The manufacturing of the plasmonic nano-antennas may be compatible with the CMOS process. The stacked photon detection sensor may be a photon detection sensor which includes an array of stacked photon detection devices and wiring and logic for signal processing on the same tier. The stacked photon detection sensor may be a photon detection sensor which includes an array of stacked photon detection devices on a first tier and logic for signal processing on a second tier, wherein the first tier and the second tier are connected by a wiring layer.

[0084] Generally, photons that enter the stacked photon detection sensor are incident on the first photodetection layer of a stacked photon detection device before they are incident on the second photodetection layer of the stacked photon detection device.In this way, a top side and a bottom side of the stacked photon detection sensor may be defined, wherein photons enter the stacked photon detection sensor at the top side which is opposite to the bottom side. A stacking direction may correspond to a direction which points from the top side to the bottom side or vice versa.

[0085] Hence, the first photodetection layer is closer to the top side than the second photodetection layer which is arranged below the first photodetection layer such that incoming photons are incident on the first photodetection layer at first and then on the second photodetection layer.

[0086] In some embodiments, with respect to the stacking direction, the stacked photon detection sensor includes a color filter arranged on or above the array of stacked photon detection devices. The color filter may be transmissive in the first wavelength range (e.g., visible spectrum) and in the second wavelength range (e.g., NIR or SWIR spectrum)

[0087] In some embodiments, the color filter is a Bayer filter array, and each Bayer filter of the Bayer filter array is aligned with a different 2x2-sub-array of the array of stacked photon detection devices.

[0088] In some embodiments, with respect to the stacking direction, the stacked photon detection sensor includes a microlens array arranged on or above the color filter. The microlens array may be made of glass, plastic, etc.

[0089] In some embodiments, each microlens of the microlens array is aligned with a different stacked photon detection device.

[0090] Some embodiments pertain to an active photon sensing system, wherein the active photon sensing system includes:

[0091] a stacked photon detection sensor including:

[0092] an array of stacked photon detection devices, each stacked photon detection device including:

[0093] a first photodetection layer configured to detect photons in a first wavelength range;

[0094] a second photodetection layer configured to detect photons in a second wavelength range;

[0095] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; anda plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path; and

[0096] an active light source configured to emit photons in the second wavelength range.

[0097] The active photon sensing system may be configured to simultaneously capture an image of a scene in the first wavelength range and an image of the scene in the second wavelength range. The active photon sensing system may be configured to simultaneously capture an image of a scene in the first wavelength range (e.g., a grey image or color image such as an RGB image) and perform a time-of-flight measurement using the active light source that emits photons in the second wavelength range to obtain depth information about the scene. In the time-of-flight measurement, the photon emission and the photon detection are synchronized, and the round-trip time of the emitted photons is measured.

[0098] The active light source may be a laser such as a semiconductor laser (e.g., edge-emitting laser or vertical -cavity surface-emitting laser), an addressable array of lasers such that photon emission of each laser can be individually controlled, a light-emitting diode, an addressable array of lightemitting diodes, etc.

[0099] As mentioned above, the first photodetection layer is configured to detect photons in the first wavelength range. The first photodetection layer may be or may include one or more semiconductor layers or regions or semiconductor devices for performing photoelectric conversion in the first wavelength region.

[0100] A semiconductor device may be or may include a photodiode, an avalanche photodiode, a singlephoton avalanche photodiode (“SPAD”), a current-assisted photonic demodulator (“CAPD”), etc.

[0101] Hence, in some embodiments, the first photodetection layer includes a semiconductor material or a combination of semiconductor materials that have a bandgap within the first wavelength range. In some embodiments, the first wavelength range corresponds to a wavelength range in the visible spectrum.

[0102] Thus, for example, the first photodetection layer may include one or more regions of silicon -which may be doped, and which absorbs in the visible spectrum -, for example, the first photodetection layer may include a pn-junction between a p-doped silicon region and an n-doped silicon region.As mentioned above, the second photodetection layer is configured to detect photons in the second wavelength range. The second photodetection layer may be or may include one or more semiconductor layers or regions or semiconductor devices for performing photoelectric conversion in the second wavelength region.

[0103] A semiconductor device may be or may include a photodiode, an avalanche photodiode, a singlephoton avalanche photodiode (“SPAD”), a current-assisted photonic demodulator (“CAPD”), etc.

[0104] Hence, in some embodiments, the second photodetection layer includes a semiconductor material or a combination of semiconductor materials that have a bandgap within the second wavelength range.

[0105] In some embodiments, the second wavelength range corresponds to a wavelength range in the NIR spectrum or the SWIR spectrum.

[0106] In some embodiments, the second wavelength range corresponds at least partially to a lower photon energy than the first wavelength range, for instance, the first wavelength range corresponds to a wavelength range in the visible spectrum and the second wavelength range corresponds to a wavelength range in the NIR or SWIR spectrum.

[0107] Thus, the second photodetection layer may include one or more semiconductor regions - which may be doped - that absorb in the NIR or SWIR spectrum. These semiconductor regions may be, for example, include at least one of germanium, gallium arsenide, indium gallium arsenide, indium phosphide, etc.

[0108] As mentioned above, the stacked photon detection sensor or stacked photon detection device may be used for simultaneous capturing an image of a scene and performing a time-of-flight measurement in different regions of the electromagnetic spectrum.

[0109] Hence, in some embodiments, the second photodetection layer includes a SPAD.

[0110] In some embodiments, the SPAD includes germanium.

[0111] As mentioned above, the interconnection layer is arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range.

[0112] The interconnection layer provides the electrical connections for the first photodetection layer and may, for example, include one or more metallic connections.The interconnection layer has at least one opening through which photons in the second wavelength range can reach the second photodetection layer which may thus correspond to an optical path. The first photodetection layer and the second photodetection layer may or may not be directly in contact with each other.

[0113] However, as discussed under reference of Figs. 3 A and 3B, the interconnection layer may block some of the photons in the second wavelength range.

[0114] It has thus been recognized the number of photons in the second wavelength range which reach the second photodetection layer should be increased to improve the detection in the second wavelength range.

[0115] It has been recognized that in a stacked photon device a plasmonic nana-antenna may be used to increase the number of photons in the second wavelength range that reach the second photon detection layer.

[0116] Hence, as mentioned above, a plasmonic nano-antenna is embedded in the first photodetection layer and is configured to guide photons in the second wavelength range through the interconnection layer via the optical path. The plasmonic nano-antenna may improve a transmission from the first photodetection layer to the second photodetection layer.

[0117] The plasmonic nano-antenna may be made of or include a metal such as gold, silver, etc. The material of the plasmonic nano-antenna is however not limited to metals and may include any conductive material such that the real part of the dielectric function changes the sign across the interface of the first photodetection layer and the plasmonic nano-antenna.

[0118] The plasmonic nano-antenna may be manufactured within the CMOS process of the stacked photon detection device or pixel.

[0119] The plasmonic nano-antenna may be plate-shaped or disc-shaped for example.

[0120] The plasmonic nano-antenna has a structure (and includes a material) which allows photons in the second wavelength range to excite surface plasmons at the interface of the first photodetection layer and the plasmonic nano-antenna.

[0121] The structure may be a periodic modulation of the surface profile or an aperiodic modulation of the surface profile such that the photons can couple to the surface plasmonic resonance(s). A periodic structure at the interface shows properties of an antenna that collects and couples the photons of a given wavelength (in the second wavelength range) into surface plasmons with a given target wavelength, i.e. (surface) plasmonic resonance occurs with the target wavelength.Generally, the periodicity of the spatial variations of the structure of the plasmonic nano-antenna may be adapted in accordance with a given target wavelength of the surface plasmon such that, for example, a wavelength of the active light source in the second wavelength range (without limiting the disclosure in this regard) can excite surface plasmons with the target wavelength. The surface plasmons than travel along the interface and may decay by coupling to a radiative mode.

[0122] Accordingly, the photons that would be blocked by the interconnection layer may excite surface plasmons which travel along the surface of the plasmonic-antenna to a position where they decay radiatively. The position may be a position from which the photons can follow the optical path from the first to the second photodetection layer.

[0123] Hence, the plasmonic nano-antenna guides photons in the second wavelength range through the interconnection layer via the optical path, thereby increasing the number of photons in the second wavelength range that reach the second photon detection layer.

[0124] It has been recognized that the number of photons in the second wavelength that transmit from the first to the second photodetection layer may be increased by providing a central hole or aperture in the plasmonic nano-antenna.

[0125] Hence, in some embodiments, the plasmonic nano-antenna includes a central hole.

[0126] The surface plasmon polaritons may travel along the surface and reach the central hole where high fields above the central hole or aperture are present which may lead to a high transmission efficiency through the central hole or aperture.

[0127] Generally, the dimensions of the optical path through the interconnection layer may be equal to or larger than the diameter of the central hole of the plasmonic nano-antenna. In some embodiments, a distance between different metallic connections of the interconnection layer is equal to or larger than the diameter of the central hole of the plasmonic nano-antenna.

[0128] In some embodiments, the central hole is aligned with the optical path through the interconnection layer.

[0129] In other words, in a plan view along the stacking direction (or antiparallel to the stacking direction), the central hole overlaps with the at least one opening of the interconnection layer. As mentioned above, the plasmonic nano-antenna has a spatially varying surface profile for allowing a coupling of photons to surface plasmons.In some embodiments, the plasmonic nano-antenna includes grooves on a first side. The first side may be oriented away from the second photodetection layer.

[0130] In some embodiments, the grooves on the first side are periodically arranged with a period that satisfies a target wavelength of a plasmonic resonance.

[0131] In other words, the period of the arrangement of the grooves corresponds to the wavelength of the surface plasmon (polariton) which is excited due to a surface plasmonic resonance at the target wavelength.

[0132] In some embodiments, the plasmonic nano-antenna includes grooves on a second side opposite to the first side.

[0133] In some embodiments, the grooves on the second side are periodically arranged with a period that satisfies a target wavelength of a plasmonic resonance.

[0134] In some embodiments, the second side is oriented towards the second photodetection layer. The grooves on the second side may decrease an output divergence, which may further increase throughput of photons via the optical path.

[0135] In some embodiments, the plasmonic nano-antenna is spaced from the interconnection layer. This may further increase throughput of photons via the optical path. The plasmonic nanoantenna may be embedded in the lower half of the first photodetection layer and spaced above the interconnection layer.

[0136] In some embodiments, the plasmonic nano-antenna is a bull’s eye nano-antenna. The bull’s eye structure has a central aperture or hole - which may be in the sub -wavelength range - and the central hole or aperture is surrounded by concentric grooves (and thus also rings).

[0137] Returning to Figs. 4A and 4B, there is schematically illustrated in a block diagram a cross-sectional view of an embodiment of a stacked photon detection device 100-2, which is discussed in the following.

[0138] The embodiment is based on the embodiment of a stacked photon detection device 100-1 as discussed under reference of Figs. 3 A and 3B above.

[0139] Moreover, the stacked photon detection device 100-2 may be used for each stacked photon detection device 100 in the array of stacked photon detection devices 13 in the stacked photon detection sensor 10 as discussed under reference of Figs. 1 and 2 above.

[0140] Here, the array of stacked photon detection devices 13 is manufactured by a CMOS process and, thus, the stacked photon detection device 100-2 is manufactured by a CMOS process as wellsuch that a small size of the stacked photon detection device 100-2 in the micrometer range (e.g. 1-10 micrometers) can be achieved. The stacked photon detection device 100-2 may thus be referred to as pixel or CMOS pixel or the like as also mentioned under reference of Fig. 2 above. A pixel pitch in the array of stacked photon detection devices 13 is accordingly in the micrometer range as well, i.e. a distance between two neighboring stacked photon detection devices 100-2 is in the micrometer range.

[0141] In contrast to the embodiment of Figs 3 A and 3B, the stacked photon detection device 100-2 includes a plasmonic nano-antenna 120 which is embedded in the first photodetection layer 101. In some embodiments, the plasmonic nano-antenna 120 may be integrated with, or interfaces with, the interconnection layer 103, for example, so as to ensure appropriate charge transfer to a floating diffusion node of the stacked photon detection device 100-2.

[0142] Moreover, the second photon detection layer 102 of the stacked photon detection device 100-2 includes a SPAD. The stacked photon detection device 100-2 may thus be used for simultaneous image capturing and time-of-flight detection in different spectral regions, i.e. image capturing in the visible spectrum with the first photodetection layer 101 and time-of-flight detection in the NIR or SWIR spectrum with the second photodetection layer 102.

[0143] As depicted in Fig. 4A and 4B, the plasmonic nano-antenna 120 is arranged above the interconnection layer 103 and is spaced from the interconnection layer 103.

[0144] The plasmonic nano-antenna 120 has grooves on the upper side (first side oriented away from the second photodetection layer 102) and grooves on the lower side (second side oriented towards the second photodetection layer 102) and a central hole. The grooves on the upper side are periodically arranged with a period that satisfies a target wavelength of a plasmonic resonance.

[0145] In this embodiment, the first photodetection layer 101 includes a semiconductor region made of silicon (Si) and the plasmonic nano-antenna 120 is made of gold (Au) and embedded in the silicon semiconductor region.

[0146] The period of the grooves of the plasmonic nano-antenna may be estimated as follows:

[0147] The second photodetection layer 102 detects photons in the NIR or SWIR region, for example, including a wavelength of 1130 nanometers which may be denoted as XQ.

[0148] The wave vector is thus given by:

[0149]

[0150] The target wavelength of the surface plasmon (polariton) is given by:

[0151]

[0152] The period of the grooves then corresponds to XSPP.

[0153] Here, / 3 corresponds to:

[0154]

[0155] Here, smis the dielectric function of the plasmonic nano-antenna 120 at Xf> and sdthe dielectric function of the first photodetection layer 101 at Xf>.

[0156] At Xo = 1130 nanometers, for silicon (Si) it is sd= 11.7 and for gold (Au) it is

[0157] £m= -55.81 + 4.43i such that XSPP= 268 nanometers.

[0158] Referring to Fig. 4A, the detection of the incoming photons in the visible spectrum 110-1 in the stacked photon detection device 100-2 is basically the same as for the stacked photon detection device 100-1 of Figs. 3A and 3B, since most of the photons incoming photons in the visible spectrum 110-1 may be subject to photoelectric conversion in the upper half of the first photodetection layer 101 due to a lower penetration depth.

[0159] Referring now to Fig. 4B, however, for incoming photons in the NIR or SWIR spectrum 110-2, the number of transmitted photons from the first photodetection layer 101 to the second photodetection layer 102 may be increased, since photons that would have been blocked before by the interconnection layer 103 (e.g., a metallic interconnect region) are guided, by the plasmonic nano-antenna 120, through the interconnection layer 103 via the optical path, as schematically illustrated in Fig. 4B.

[0160] Fig. 5A schematically illustrates an embodiment of a plasmonic nano-antenna 120-1, which is discussed in the following.

[0161] The plasmonic nano-antenna 120-1 may be used as the plasmonic nano-antenna 120 of Figs. 4A and 4B.

[0162] The plasmonic nano-antenna 120-1 has a bull’s eye structure - which is schematically shown in a plan view in the upper part of Fig. 5 A - with a central aperture or hole 20 and concentric grooves 21-1 to 21-n.The lower part of Fig. 5 A schematically shows a cross-sectional view taken along the dashed line QS depicted in the upper part of Fig. 5 A.

[0163] The bull’s eye structure of the plasm onic nano-antenna 120-1 has grooves 21-1 to 21 -n on both sides.

[0164] The bull’s eye structure of the plasm onic nano-antenna 120-1 has many structural parameters which can be used to influence a target wavelength of the (surface) plasmonic resonance and the transmission efficiency.

[0165] The structural parameters include a number of grooves (n), a diameter (d) of the central hole, a period (p) of the grooves, a width of the grooves (w), a distance from the center to the first groove (a), a thickness (t), a depth of the grooves (s) and a diameter of the bull’s eye (h) which serves as an estimate for the pixel pitch.

[0166] For example:

[0167] When assuming the values discussed under reference of Figs. 4A and 4B above, the period (p) of the grooves corresponds to p = kspp= 268 nanometers, and the width of the grooves (w) may be estimated to be w = kSpp / 2.

[0168] Fig. 5B schematically illustrates an embodiment of a plasmonic nano-antenna 120-2, which is discussed in the following.

[0169] The plasmonic nano-antenna 120-2 may also be used as the plasmonic nano-antenna 120 of Figs. 4A and 4B instead of using a plasmonic nano-antenna 120 with grooves on both sides. The plasmonic nano-antenna 120-2 is similar to the plasmonic nano-antenna 120-1 of Fig. 5A, however, it has grooves only on one side, for example, the side that is oriented away from the second photodetection layer 102.

[0170] When assuming the values discussed under reference of Figs. 4A and 4B above, the period (p) of the grooves corresponds to p = kspp= 268 nanometers, and the width of the grooves (w) may be estimated to be w = kSpp / 2.

[0171] Fig. 6 schematically illustrates an embodiment of a maximum ratio of a diameter of a bull’s eye hole of a plasmonic nano-antenna in a stacked photon detection device of an array of stacked photon detection devices and a pixel pitch in the array of stacked photon detection devices, which is discussed in the following.

[0172] The plasmonic nano-antenna here corresponds to the bull’s eye plasmonic nano-antenna 120-1 or 120-2 of Figs. 5A and 5B, respectively.The vertical axis in the graph of Fig. 6 corresponds to the diameter (d) of the central hole divided by the diameter of the bull’s eye (h) and the horizontal axis corresponds to the diameter of the bull’s eye (h) as an estimate of the pixel pitch.

[0173] The graph shows a maximum bull’s eye plasmonic nano-antenna hole to pixel pitch for a different number of grooves (n = 3, 4 and 5).

[0174] For example, for a pixel pitch of 4.0 micrometers (h = 4.0 micrometers), to fit 5 grooves (rings) in the plasmonic nano-antenna, the maximum diameter of the central hole (d) may correspond to 27.5 percent of the pixel pitch.

[0175] Fig. 7 schematically illustrates in a block diagram a plan view of an embodiment of an arrangement of a plasmonic nano-antenna 120 and metallic connections 103 in an embodiment of a stacked photon detection device 100-2, which is discussed in the following.

[0176] The stacked photon detection device is the stacked photon detection device 100-2 of Figs. 4A and Fig. 4B.

[0177] The plasmonic nano-antenna 120 may be the plasmonic nano-antenna 120-1 of Fig. 5A or the plasmonic nano-antenna 120-2 of Fig. 5B which is then embedded in the first photodetection layer 101.

[0178] The Fig. 7 shows the stacked photon detection device 100-2 in a top side plan view (antiparallel to the stacking direction SD).

[0179] As depicted in Fig. 7, the central hole 20 overlaps with the optical path through the metallic interconnect region 103 (schematically illustrated as hatched area in Fig. 7) and, thus, the central hole 20 is aligned with the optical path through the interconnection layer 103.

[0180] The dimensions (dmter) of the optical path through the metallic interconnect region 103 are larger than the diameter of the central hole (d) of the plasmonic nano-antenna 120.

[0181] Fig. 8 schematically illustrates in a block diagram an embodiment of an active photon sensing system 200, which is discussed in the following.

[0182] The active photon sensing system 200 includes an active light source 201 such as one or more semiconductor lasers which may be arranged in an array and individually addressable.

[0183] The active photon sensing system 200 includes a stacked photon detection sensor such as the stacked photon detection sensor 10 of Figs. 1 and 2 in which an array of stacked photon devices 100-2 of Figs. 4A and 4B is included.As discussed under reference of Figs. 4A and 4B, the stacked photon detection device 100-2 detects photons in the visible spectrum as the first wavelength range with the first photodetection layer 101 and photons in the NIR or SWIR spectrum as the second wavelength range with the second photodetection layer 102.

[0184] The active light source 201 emits photons in the second wavelength range to perform the time-of-flight measurement.

[0185] Note that the present technology can also be configured as described below.

[0186] (1) A stacked photon detection device, including:

[0187] a first photodetection layer configured to detect photons in a first wavelength range; a second photodetection layer configured to detect photons in a second wavelength range; an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0188] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

[0189] (2) The stacked photon detection device of (1), wherein the second wavelength range corresponds at least partially to a lower photon energy than the first wavelength range.

[0190] (3) The stacked photon detection device of (2), wherein the first wavelength range corresponds to a wavelength range in the visible spectrum and the second wavelength range corresponds to a wavelength range in the near-infrared spectrum or short-wave infrared spectrum.

[0191] (4) The stacked photon detection device of any one of (1) to (3), wherein the second photodetection layer includes a single-photon avalanche diode.

[0192] (5) The stacked photon detection device of (4), wherein the single-photon avalanche diode includes germanium.

[0193] (6) The stacked photon detection device of anyone of (1) to (5), wherein the plasmonic nanoantenna includes a central hole.

[0194] (7) The stacked photon detection device of (6), wherein the central hole is aligned with the optical path through the interconnection layer.(8) The stacked photon detection device of any one of (1) to (7), wherein the plasm onic nano-antenna includes grooves on a first side.

[0195] (9) The stacked photon detection device of (8), wherein the plasmonic nano-antenna includes grooves on a second side opposite to the first side.

[0196] (10) The stacked photon detection device of (9), wherein the second side is oriented towards the second photodetection layer.

[0197] (11) The stacked photon detection device of any one of (8) to (10), wherein the grooves are periodically arranged with a period that satisfies a target wavelength of a plasmonic resonance. (12) The stacked photon detection device of any one of (1) to (11), wherein the plasmonic nano-antenna is spaced from the interconnection layer.

[0198] (13) The stacked photon detection device of any one of (1) to (12), wherein the plasmonic nano-antenna is a bull’s eye nano-antenna.

[0199] (14) The stacked photon detection device of any one of (1) to (13), wherein the plasmonic nano-antenna includes gold.

[0200] (15) The stacked photon detection device of any one of (1) to (14), wherein the stacked photon detection device is manufactured by a CMOS process.

[0201] (16) The stacked photon detection device of (15), wherein the manufacturing of the plasmonic nano-antenna is compatible with the CMOS process.

[0202] (17) A stacked photon detection sensor, including:

[0203] an array of stacked photon detection devices, each stacked photon detection device including:

[0204] a first photodetection layer configured to detect photons in a first wavelength range;

[0205] a second photodetection layer configured to detect photons in a second wavelength range;

[0206] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0207] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.(18) The stacked photon detection sensor of (17), further including a color filter arranged on the array of stacked photon detection devices.

[0208] (19) The stacked photon detection sensor of (18), wherein the color filter is a Bayer filter array, and each Bayer filter of the Bayer filter array is aligned with a different 2x2-sub-array of the array of stacked photon detection devices.

[0209] (20) The stacked photon detection sensor of (18) or (19), further including a microlens array arranged on the color filter.

[0210] (21) The stacked photon detection sensor of (20), wherein each microlens of the microlens array is aligned with a different stacked photon detection device.

[0211] (22) The stacked photon detection sensor of any one of (17) to (21), wherein the array of stacked photon detection device is manufactured by a CMOS process.

[0212] (23) The stacked photon detection sensor of (22), wherein the manufacturing of the plasmonic nano-antennas is compatible with the CMOS process.

[0213] (24) An active photon sensing system, including:

[0214] a stacked photon detection sensor including:

[0215] an array of stacked photon detection devices, each stacked photon detection device including:

[0216] a first photodetection layer configured to detect photons in a first wavelength range;

[0217] a second photodetection layer configured to detect photons in a second wavelength range;

[0218] an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; and

[0219] a plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path; and

[0220] an active light source configured to emit photons in the second wavelength range.

Claims

CLAIMS1. A stacked photon detection device, comprising:a first photodetection layer configured to detect photons in a first wavelength range; a second photodetection layer configured to detect photons in a second wavelength range; an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; anda plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

2. The stacked photon detection device of claim 1, wherein the second wavelength range corresponds at least partially to a lower photon energy than the first wavelength range.

3. The stacked photon detection device of claim 2, wherein the first wavelength range corresponds to a wavelength range in the visible spectrum and the second wavelength range corresponds to a wavelength range in the near-infrared spectrum or short-wave infrared spectrum.

4. The stacked photon detection device of claim 1, wherein the second photodetection layer includes a single-photon avalanche diode.

5. The stacked photon detection device of claim 1, wherein the plasmonic nano-antenna includes a central hole.

6. The stacked photon detection device of claim 5, wherein the central hole is aligned with the optical path through the interconnection layer.

7. The stacked photon detection device of claim 1, wherein the plasmonic nano-antenna includes grooves on a first side.

8. The stacked photon detection device of claim 7, wherein the plasmonic nano-antenna includes grooves on a second side opposite to the first side, wherein the second side is oriented towards the second photodetection layer.

9. The stacked photon detection device of claim 7 or 8, wherein the grooves are periodically arranged with a period that satisfies a target wavelength of a plasmonic resonance.

10. The stacked photon detection device of claim 1, wherein the plasmonic nano-antenna is spaced from the interconnection layer.

11. The stacked photon detection device of claim 1, wherein the plasmonic nano-antenna is a bull’s eye nano-antenna.

12. The stacked photon detection device of claim 1, wherein the plasmonic nano-antenna includes gold.

13. The stacked photon detection device of claim 1, wherein the stacked photon detection device is manufactured by a CMOS process.

14. The stacked photon detection device of claim 13, wherein the manufacturing of the plasmonic nano-antenna is compatible with the CMOS process.

15. A stacked photon detection sensor, comprising:an array of stacked photon detection devices, each stacked photon detection device including:a first photodetection layer configured to detect photons in a first wavelength range;a second photodetection layer configured to detect photons in a second wavelength range;an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; anda plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path.

16. The stacked photon detection sensor of claim 15, further comprising a color filter arranged on the array of stacked photon detection devices.

17. The stacked photon detection sensor of claim 16, wherein the color filter is a Bayer filter array, and each Bayer filter of the Bayer filter array is aligned with a different 2x2-sub-array of the array of stacked photon detection devices.

18. The stacked photon detection sensor of claim 16, further comprising a microlens array arranged on the color filter.

19. The stacked photon detection sensor of claim 18, wherein each microlens of the microlens array is aligned with a different stacked photon detection device.

20. An active photon sensing system, comprising:a stacked photon detection sensor including:an array of stacked photon detection devices, each stacked photon detection device including:a first photodetection layer configured to detect photons in a first wavelength range;a second photodetection layer configured to detect photons in a second wavelength range;an interconnection layer arranged between the first and second photodetection layer which delimits an optical path from the first to the second photodetection layer for photons in the second wavelength range; anda plasmonic nano-antenna embedded in the first photodetection layer and configured to guide photons in the second wavelength range through the interconnection layer via the optical path; andan active light source configured to emit photons in the second wavelength range.

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