Image sensor apparatus, image sensor device and method for operating an image sensor apparatus - Patents.com

Abstract

The image sensor device (1) comprises a first sensor layer (2) including a first group of pixels (3), each pixel (3) of the first group including a photodiode (14, 15, 16, 17) configured to detect electromagnetic radiation in a first wavelength range. The image sensor device (1) further comprises a second sensor layer (4) including a second group of pixels (5), each pixel (5) of the second group including a photodiode (13) configured to detect electromagnetic radiation in a second wavelength range. The image sensor device (1) further comprises a readout layer (6) including a readout circuit (7) configured to read out electrical signals from the first and second groups of pixels (3, 5). The second sensor layer (4) is disposed between the first sensor layer (2) and the readout layer (6). The second wavelength range is outside the wavelength range detectable by the first sensor layer (2).

Description

[Technical field]

[0001] IMAGE SENSOR UNIT, IMAGE SENSOR DEVICE AND METHOD FOR OPERATING AN IMAGE SENSOR UNIT FIELD OF THE DISCLOSURE The present invention relates to an image sensor unit, an image sensor device and a method for operating an image sensor unit. The image sensor unit is configured to detect electromagnetic radiation in two wavelength ranges. [Background technology]

[0002] CMOS image sensors are used in a wide range of applications, including camera modules and for smartphones, tablet computers, and laptops. Some of these applications, such as photography, rely on sensitivity in the visible light domain, but other applications, such as 3D imaging and authentication, require the image sensor to be sensitive in the infrared (IR) domain. For example, the infrared domain is used in dark environments, or at least in situations where light is limited. The infrared domain can also be used to enhance regular RGB images. The infrared domain provides "texture" because infrared radiation can "see through" certain conditions, such as blur, that the visible wavelength domain cannot see.

[0003] Due to space constraints in modern devices, it is desirable to provide an image sensor device that is sensitive in both the visible and infrared domains. To this end, an image sensor device includes pixels that are sensitive to a particular part of the visible spectrum and pixels that are sensitive to a particular part of the infrared spectrum. Silicon-based photodiodes are a common choice for this connection, since such diodes are sensitive over a wide wavelength range spanning between 190 nm and 1100 nm, thus covering the electromagnetic spectrum in both the visible and near infrared (NIR) domains.

[0004] The pixels for receiving visible light information are typically arranged in the sensor layer according to a two-dimensional array or matrix to obtain sufficient spatial resolution of the image scene. Furthermore, each pixel may include sub-pixels, each sub-pixel configured to detect light of a specific color, for example red, green, and blue (RGB). Typically, the sub-pixels are arranged in a specific pattern, for example according to the so-called Bayer pattern.

[0005] One conventional approach to realizing an image sensor sensitive to both visible and IR light is to place an additional pixel for NIR light on the same (silicon) substrate. Implementing an additional pixel for receiving NIR light information in such an image sensor is typically achieved by sacrificing one of the subpixels, for example one subpixel for sensing green light. However, this comes with several drawbacks, leading to a degradation of image perception and / or loss of spatial resolution, especially in the visible domain.

[0006] Another approach is suggested by Takemoto et al. (see Takemoto et al., "Multiband Imaging CMOS Image Sensor with Multi-Storied Photodiode Structure"). Takemoto et al. disclose a multiband imaging CMOS image sensor with a multi-storey photodiode structure that includes two photodiode arrays for simultaneously capturing visible RGB light and NIR light. An upper silicon substrate has a pixel array for visible RGB light, and a lower silicon substrate has a pixel array for NIR light that passes through the upper substrate. The two substrates each include a wiring layer, and they are bonded face-to-face with each other.

[0007] One major challenge is that the NIR pixels are underneath the visible pixels, so the visible pixels are also exposed to NIR light. This affects the color reconstruction, so that in the digital image the colors receive an NIR contribution equivalent to an amplitude offset. Another drawback is that due to the top first substrate and the wiring layer between the two substrates, the light passing through the first substrate is strongly attenuated by shading or scattering effects. This leads to a lower quantum efficiency (QE) for NIR light. Summary of the Invention [Problem to be solved by the invention]

[0008] The object to be achieved is therefore to provide an image sensor device which overcomes the above mentioned drawbacks, in particular the image sensor device being capable of sensing light in at least two wavelength ranges, leading to improved image perception and quantum efficiency. [Means for solving the problem]

[0009] This object is achieved by the subject matter of the independent claims. Further developments and embodiments are set forth in the dependent claims.

[0010] The improved image sensor device is based on the idea of ​​using two wavelength ranges, a first sensor layer being spectrally responsive to only one of these wavelength ranges and a second sensor layer being spectrally responsive to the other wavelength range. For example, the first wavelength range includes visible light. The second wavelength range can include short-wave infrared (SWIR) light (instead of NIR light). SWIR includes wavelengths from 1.4 μm to 3.0 μm, while NIR includes wavelengths from 780 nm to 1.4 μm. A dedicated SWIR sensor can be placed below the visible light sensor. In contrast to NIR light, SWIR light does not affect the photodiodes of the visible light sensor. That is, the visible light sensor is not sensitive to SWIR light. A general readout circuit can be placed below the second sensor layer and connected in an appropriate manner to the pixels of both sensor layers.

[0011] Here and hereafter, the term pixel refers to a light-receiving element, which may be arranged in a two-dimensional array with other pixels. The pixel may also include circuitry for controlling signals to and from the pixel. The pixel may also include individual wavelength filters for sensing light in a particular wavelength range. A visible light pixel refers to a pixel that can sense light in the visible wavelength range, particularly light in the red, green, and / or blue wavelength ranges. An IR / SWIR pixel refers to a pixel that can sense light in the infrared domain, particularly the short wavelength infrared domain. The term light may generally refer to electromagnetic radiation, including IR radiation, SWIR, and visible light. Thus, green, blue, red, and SWIR light refer to light in distinct wavelength ranges.

[0012] In an embodiment, the image sensor device comprises a first sensor layer including a first group of pixels, each pixel of the first group including a photodiode configured to detect electromagnetic radiation in a first wavelength range. The image sensor device further comprises a second sensor layer including a second group of pixels, each pixel of the second group including a photodiode configured to detect electromagnetic radiation in a second wavelength range. The image sensor device further comprises a readout layer including a readout circuit configured to read out electrical signals from the first and second groups of pixels. The second sensor layer is disposed between the first sensor layer and the readout layer. The second wavelength range is outside the wavelength range detectable by the first sensor layer.

[0013] The first sensor layer has a main extension surface. The first sensor layer includes a main surface and a rear surface. In some embodiments, the wiring of the first group of pixels can be arranged on the main surface of the first sensor layer. The first group of pixels can be arranged as a two-dimensional array or pixel matrix. The first group of pixels can be arranged next to each other in a lateral direction, the lateral direction extending parallel to the main extension surface of the first sensor layer. The first sensor layer includes, for example, at least one million first group of pixels. In at least some embodiments, the first wavelength range includes visible light. The first group of pixels can be configured to sense electromagnetic radiation in the visible wavelength range.

[0014] Alternatively or additionally, the first wavelength range includes NIR light. The first group of pixels can be configured to detect electromagnetic radiation in the NIR wavelength range. This can mean that the first sensor layer includes pixels for detecting visible light and further pixels for detecting NIR light. This can further mean that the first sensor layer includes pixels that can detect light in both the visible and NIR spectrum.

[0015] In some embodiments, each pixel of the first group detects light in the same wavelength range. However, in other embodiments, the pixels of the first group include different subsets of pixels, each subset configured to detect a particular wavelength range within the first wavelength range. According to at least some embodiments, a first subset of pixels detects light in a red (R) wavelength range, a second subset of pixels detects light in a green (G) wavelength range, and a third subset detects light in a blue (B) wavelength range. In this manner, an RGB pixel layer can be formed. The pixels of the different subsets can be arranged according to a particular pattern, for example a Bayer pattern (RGGB). The photodiodes of the pixels of the first group are each configured to convert electromagnetic radiation into an electrical signal. Each photodiode of a pixel can have its own floating diffusion node and / or its own part of a control circuit.

[0016] Each pixel can also include several sub-pixels for sensing light in different wavelength ranges. Each sub-pixel can include a corresponding photodiode. In one embodiment, each pixel includes four sub-pixels arranged in a Bayer pattern (RGGB). Sub-pixels with individual photodiodes can share a common floating diffusion node and / or common parts of a control circuit.

[0017] In an embodiment, the rear surface of the first sensor layer faces the incident electromagnetic radiation. Therefore, in such an embodiment, the rear surface is also called the radiation entrance surface. A configuration in which the wiring of the pixels is arranged on the main surface and the sensor layer is then illuminated from the surface may be called a back-illuminated (BSI) configuration. Thus, the first sensor layer can be in a BSI configuration. However, it is equally possible that the main surface on which the wiring is arranged is illuminated. Such a configuration is called a front-illuminated (FSI) configuration.

[0018] The second sensor layer also has a main extension surface. The main surface of the second sensor layer can be parallel to the main surface of the first sensor layer. The second sensor layer also includes a main surface and a rear surface. In the vertical direction, the second sensor layer is arranged below the first sensor layer. The vertical direction refers to a direction extending perpendicularly to the main extension surfaces of the first and second sensor layers. This can mean that the first sensor layer is arranged between the second sensor layer and the incident electromagnetic radiation. The main surface of the second sensor layer can be arranged to face the first sensor layer or to face the readout layer.

[0019] In an embodiment, the wiring of the second group of pixels can be arranged on a major surface of the second sensor layer. The second group of pixels can be arranged as a two-dimensional array or pixel matrix. The second group of pixels can be arranged laterally next to each other. The second sensor layer includes, for example, at least 1 million second group of pixels. However, the second sensor layer may include fewer than 1 million second group of pixels or fewer second group of pixels than the first group of pixels in the first sensor layer.

[0020] The pixels of the second group may each be configured to detect the same range of electromagnetic radiation within the second wavelength range. However, the pixels of the second group may also be configured to detect different ranges within the second wavelength range. The photodiodes of the pixels of the second group are each configured to convert electromagnetic radiation in the second wavelength range into an electrical signal.

[0021] The second wavelength range is outside the wavelength range detectable by the first sensor layer. This can mean that the first sensor layer includes an exclusive spectral response in the first wavelength range. The first sensor layer may be insensitive in the second wavelength range. This can mean that the first sensor layer does not include a spectral response in the second wavelength range. Electromagnetic radiation in the second wavelength range passes unimpeded through the first sensor layer. This is because the first sensor layer may include a sensor material that exhibits a band gap that is too large for electromagnetic radiation in the second wavelength range. Only photons with sufficient energy to cross the band gap of the material and excite electrons will produce a significant photocurrent. Photon energies in the second wavelength range may be too small to be sensed by the first sensor layer. This can mean that the minimum wavelength of the second wavelength range is greater than the maximum wavelength detectable by the first sensor layer.

[0022] According to at least some embodiments, the second wavelength range includes short wavelength infrared radiation. The second group of pixels can be configured to detect electromagnetic radiation in the SWIR range.

[0023] In one embodiment, the number of pixels in the first group in the first sensor layer matches the number of pixels in the second group in the second sensor layer. This can mean that each pixel in the second group is assigned to one pixel in the first group. In such an embodiment, the spatial resolution of the two corresponding arrays is equal.

[0024] However, it is also possible that the number of pixels in the first group exceeds the number of pixels in the second group, or vice versa. For example, each pixel (e.g., SWIR pixel) in the second group can be allocated to four pixels or sub-pixels (e.g., visible light pixels) in the first group, respectively. For example, each SWIR pixel is allocated to four pixels / sub-pixels of a Bayer pattern (RGGB). This can mean that the pixel area of ​​the SWIR pixel is four times larger than the pixel area of ​​one of the visible light pixels in this example. With a larger pixel area, the pixel is more sensitive because more light can be detected per pixel.

[0025] Similarly, one pixel of the first group can be allocated to two or more pixels of the second group. It is further possible that the number of pixels in the first group does not correlate to the number of pixels in the second group, such that there is no allocation between pixels of different groups.

[0026] The readout layer also has a main extension surface. The main surfaces of the readout layer can be parallel to the main surfaces of the first sensor layer and to the main surfaces of the second sensor layer, respectively. In the vertical direction, the readout layer is arranged below the second sensor layer. This means that the second sensor layer is arranged between the first sensor layer and the readout layer. The readout layer is electrically connected to the first sensor layer and to the second sensor layer. The electrical connection can be established by any suitable means.

[0027] The wiring of the readout circuitry is disposed on a major surface of the readout layer. The readout layer may be disposed such that its major surface faces the second sensor layer. The readout circuitry may be configured to read out electrical signals provided by the photodiodes of the first and second groups of pixels. The readout circuitry may include an input capable of providing the electrical signals of the photodiodes. The readout circuitry may be further configured to operate the pixels.

[0028] The image sensor device can detect light in two separate wavelength ranges, which is beneficial from a cost-effective point of view. For example, the image sensor device can detect visible light and SWIR simultaneously. Compared to other multispectral sensors (e.g., RGB+NIR), there is no trade-off with image quality. There is no need to remove the first group of pixels from the first array, since the second group of pixels are not integrated into the first array, but are in a separate second array below the first array. This means that the spatial resolution of both the first array and the second array can be high. The quantum efficiency (QE) of the first group of pixels (e.g., silicon-based visible light pixels) in the first sensor layer is 0% in the second wavelength range (e.g., SWIR domain). This means that SWIR light does not contribute to color shifts in the visible range. Advantageously, no color correction is required to filter the SWIR component from the visible spectrum. A high image perception can be maintained.

[0029] In an embodiment, the image sensor device comprises a first sensor layer including a first group of pixels, each pixel of the first group including a photodiode configured to detect electromagnetic radiation in the visible wavelength range. The image sensor device further comprises a second sensor layer including a second group of pixels, each pixel of the second group including a photodiode configured to detect electromagnetic radiation in the short wavelength infrared range. The image sensor device further comprises a readout layer including a readout circuit configured to read out electrical signals from the first and second groups of pixels. The second sensor layer is disposed between the first sensor layer and the readout layer.

[0030] In one embodiment of the image sensor device, the first sensor layer is attached to the second sensor layer. According to one aspect of the disclosure, the first sensor layer is attached to the second sensor layer by electrical contacts. The electrical contacts can be formed between the first sensor layer and the second sensor layer. Thus, the pixels of the first group can be electrically connected to the pixels of the second group. This can mean that the wiring of the individual pixels of the first group is electrically connected to the wiring of the individual pixels of the second group by the electrical contacts. The electrical contacts can include metal bumps. For example, the electrical contacts can be formed by hybrid bonding.

[0031] In one embodiment of the image sensor device, the first sensor layer is attached to the second sensor layer by a hybrid bond, and electrical interconnects are formed between the first group of pixels and the second group of pixels.

[0032] Hybrid bonding refers to any bonding technique where a permanent bond is established between two layers, combining a dielectric bond with an embedded metal to form an electrical interconnect. For example, a hybrid bond can be established using an adhesive, which can have metal bumps embedded in it to electrically connect a first sensor layer to a second sensor layer.

[0033] As another example, the dielectric bond can be established by an oxide interface, where the first and second sensor layers each include an individual oxide layer facing each other. Bonding the two oxide layers together can be done by direct bonding or during a fusion bonding process. Copper pads can be fabricated in parallel with the individual oxide layers. In this case, electrical contact can be achieved via metal diffusion bonding during annealing.

[0034] Typically, the first and second sensor layers include a substrate on which the photodiodes and possibly some circuitry are placed. An oxide layer may be placed on top of the substrate, with wiring embedded in the oxide layer to electrically connect the photodiodes and the circuitry. The first and second sensor layers may be placed with the individual oxide layers facing each other for a direct bonding process. The wiring in the oxide layer may be utilized to electrically connect the first group of pixels to the second group of pixels.

[0035] Using permanent bonding, the first and second sensor layers can be aligned with each other. There are no moving parts. An electrical interconnection between the first group of pixels and the second group of pixels can be used to allow the pixels to share a common readout path. The readout path can be a column bus. The electrical signals can be transmitted sequentially to a readout circuit. This configuration is particularly relevant when both groups of pixels operate in a rolling shutter mode. In this case, the readout circuit consumes less space.

[0036] In one embodiment of the image sensor device, the second sensor layer is attached to the readout layer. According to one aspect of the present disclosure, the second sensor layer is attached to the readout layer by electrical contacts. The electrical contacts can be formed between the second sensor layer and the readout layer. Thus, the pixels of the second group can be electrically connected to the readout circuit. This can mean that the wiring of the individual pixels of the second group is electrically connected to the wiring of the readout circuit by the electrical contacts. The electrical contacts can include metal bumps. For example, the electrical contacts can be formed by hybrid bonding.

[0037] In one embodiment of the image sensor device, the second sensor layer is attached to the readout layer by a hybrid bond, thereby forming an electrical interconnect between the second group of pixels and the readout circuitry.

[0038] As mentioned above, hybrid bonding refers to any bonding technique in which a permanent bond is established between two layers, combining a dielectric bond with an embedded metal to form an electrical interconnect. The examples above also apply to this embodiment.

[0039] Typically, the readout layer also includes a substrate on which the readout circuitry is disposed. An oxide layer may be disposed on top of the substrate, with wiring embedded in the oxide layer to electrically connect different parts of the readout circuitry. The second sensor layer and the readout layer may be disposed with the individual oxide layers facing each other for a direct bonding process. The wiring in the oxide layer may be utilized to electrically connect the second group of pixels to parts of the readout layer.

[0040] The second sensor layer can be aligned to the readout layer using permanent bonding. There are no moving parts. The electrical interconnection of the second group of pixels with the readout circuitry allows a separate readout path that is separate from the readout path for the first group of pixels. This configuration is particularly relevant when the first group of pixels operates in a rolling shutter mode and the second group of pixels operates in a global shutter mode. In this case, a global shutter can be used for the second group of pixels, leading to low power consumption due to the short illumination time in the global shutter mode.

[0041] Once the second group of pixels is connected to the readout circuitry via a separate readout path, electrical interconnects to the first group of pixels are no longer necessary. This means that at least some metal layers / metal bumps are not required between the first group of pixels and the second group of pixels. The metal layer shields, scatters and / or reflects electromagnetic radiation. These embodiments therefore have high quantum efficiency, since a large portion of the incident light reaches the second sensor layer without being affected by the metal layer.

[0042] In an embodiment, the image sensor device further includes at least one through-substrate via (TSV) that penetrates the second sensor layer and electrically connects the first group of pixels in the first sensor layer to a readout circuit in the readout layer.

[0043] The TSVs penetrate completely through the second sensor layer. This means that the TSVs reach from the main surface to the rear surface of the second sensor layer. The TSVs can be formed in the second sensor layer by through-holes. In addition, the TSVs can also penetrate completely through the first sensor layer. Thus, through-holes can also be present in the first sensor layer. In this case, the TSVs reach from the radiation entrance surface of the first sensor layer to the rear surface of the second sensor layer. The latter approach can be beneficial from a manufacturing engineering point of view.

[0044] The TSV may include a metallization electrically connecting the wiring of the first sensor layer to the wiring of the readout layer. The TSV may further include an isolation layer isolating the metallization from the second sensor layer and optionally from the first sensor layer. For this purpose, the isolation layer is arranged on the sidewalls of the through-holes. The metallization may be arranged on the isolation layer to form contact areas on the main and rear surfaces of the second and / or first sensor layers. The remaining through-holes may be filled with a filling material. Alternatively, the metallization may completely fill the remaining through-holes.

[0045] The TSVs provide a readout path for reading out the electrical signals of the first group of pixels. In some embodiments, the electrical signals from the second group of pixels are also read out through the TSVs. The electrical signals can be read out sequentially, i.e., one by one, through the TSVs. Thus, the TSVs characterize a readout path for operating the pixels in a rolling shutter mode. A TSV can be electrically connected to only one pixel. A TSV can also be electrically connected to more than one pixel. An image sensor device can include multiple TSVs, with each TSV electrically connected to one or more pixels. For example, each TSV is electrically connected to one row of pixels of an array of pixels. The TSVs can reduce the floor space of the image sensor device without the need for wire bonds. Moreover, the first sensor layer and the second sensor layer can share one common readout layer.

[0046] In some embodiments, the image sensor unit further includes a dual band filter disposed between the first sensor layer and a source of electromagnetic radiation to be sensed, the dual band filter configured to block electromagnetic radiation other than at least a portion of the first wavelength range and at least a portion of the second wavelength range.

[0047] In the vertical direction, the dual-band filter is disposed on or above the first sensor layer, whereby the first sensor layer is disposed between the dual-band filter and the second sensor layer. For example, the dual-band filter includes an organic material. The dual-band filter can also be a dielectric interference filter. The dual-band filter can be attached directly to the first sensor layer or disposed at a predetermined distance from the first sensor layer.

[0048] The dual band filter is provided to adjust the sensitivity to a particular part of the spectrum of the incident electromagnetic radiation. The dual band filter is transparent to at least a part of a first wavelength range and to at least a part of a second wavelength range. Here and hereafter, "transparent" or "semi-transparent" refers to a transparency of at least 80% or at least 90%. This means that the dual band filter transmits electromagnetic radiation in the first and second wavelength ranges towards the first and second sensor layers. The dual band filter blocks electromagnetic radiation of other wavelengths. The first and second wavelength ranges can be distinct from each other by another wavelength range. For example, the dual band filter is transparent to visible light, in particular to the red, green and blue wavelength ranges. Moreover, the dual band filter may be transparent to at least a part of the short-wave infrared range. For example, the dual band filter is transparent in the bands of approximately 1.4 μm, 1.5 μm and / or 1.6 μm. The window of a dual-band filter for SWIR light may be small: for example, the bandwidth of a dual-band filter in the SWIR domain is ±5 nm, ±10 nm, or ±50 nm. In contrast, the dual-band filter may be opaque to the NIR domain, i.e., wavelengths from 780 nm to 1.4 μm.

[0049] If the first sensor layer is based on silicon, the photodiode is sensitive to NIR light. The contribution of NIR light, which degrades the color reconstruction of the digital image, is significantly reduced by the dual-band filter. A dedicated NIR filter is not needed. Moreover, all other undesirable wavelengths can be filtered out from the spectrum. On the other hand, the QE of an RGB pixel (visible light pixel) implemented in silicon is 0% for SWIR light. Therefore, a dual-band filter with a spread in the visible spectrum and a small spread in the SWIR spectrum does not negatively affect the performance of the RGB pixel.

[0050] In an embodiment, instead of a dual band filter, the image sensor device can include a band stop filter arranged between the first sensor layer and the electromagnetic radiation source to be sensed. The band stop filter can be configured to block electromagnetic radiation between a first wavelength range and a second wavelength range. This can mean that the band stop filter is configured to remove a portion of the electromagnetic radiation from the end of the first wavelength range to the second wavelength range. The band stop filter can be opaque at these intermediate wavelengths. Thus, undesired wavelengths can be removed from the optical spectrum to be sensed. The first wavelength range can be the visible range and the second wavelength range can be the SWIR range. In this case, NIR light is removed from the spectrum.

[0051] In an embodiment, the image sensor device further includes a lens or an array of lenses disposed between the first sensor layer and the electromagnetic radiation source to be sensed. The lens or the array of lenses is configured to direct incident light toward the first sensor layer and the second sensor layer. The lens or the array of lenses can be used to direct light through an aperture in a metal layer (e.g., a metal layer composed of pixel wiring or a hybrid junction interface) between the first sensor layer and the second sensor layer. The lens can be a microlens and the array of lenses can be an array of microlenses.

[0052] In an embodiment, the first sensor layer comprises a semiconductor material, in particular silicon.In an embodiment, the readout layer comprises a semiconductor material, in particular silicon.

[0053] Semiconductor materials are ideally suited to processing due to the many available methods. As mentioned above, silicon-based photodiodes are a popular choice, as these diodes are sensitive over a wide wavelength range between 190 nm and 1100 nm, thus covering the relevant part of the electromagnetic spectrum in the visible domain. In addition, due to the wide band gap of silicon, silicon-based photodiodes exhibit superior noise performance compared to other photodiodes, such as germanium-based photodiodes. The electrical and optical properties of silicon are not only suitable for the realization of photodiodes, but also for circuit components.

[0054] In an embodiment, the second sensor layer includes one of germanium, indium gallium arsenide, and a quantum dot layer, or any other material having a band gap suitable for a spectral response to electromagnetic radiation in the second wavelength range.

[0055] Silicon photodiodes are not sensitive to SWIR light. Therefore, sensors for detecting SWIR light must include other materials. Gallium-based photodiodes cover the wavelength range from 400 nm to 1700 nm, while indium gallium arsenide-based photodiodes cover the wavelength range from 800 nm to 2600 nm. Such photodiodes therefore cover at least part of the SWIR wavelength range. Photodiodes based on quantum dot layers can be designed to detect the desired wavelength range. In general, any material can be used that has a suitable band gap and is compatible with the other materials used. Since the main part of the circuit is located in the readout layer, the second sensor layer only needs to include the photodiode and therefore does not need to be designed for good electrical behavior.

[0056] In an embodiment, the first group of pixels and the second group of pixels are configured to be read out in a rolling shutter mode by the readout circuit.

[0057] An image is obtained by converting light into an electronic signal in a photosensitive area. Both the light intensity and the exposure or integration time affect the amount of signal generated. In CMOS image sensors, there are two types of electronic shutter modes: rolling shutter and global shutter. In rolling shutter mode, pixel rows are exposed sequentially under the control of a reset signal, for example starting with the top row and proceeding to the bottom row. During illumination, the pixels are exposed sequentially and read out row by row, whereby the readout process is performed in a repetitive, rolling pattern.

[0058] This means that both the first and second groups of pixels are illuminated during every readout process. The rolling shutter mode allows a high resolution of the image sensor. Thus, the accuracy of the image sensor device is also increased. Moreover, the readout circuit configured for the rolling shutter mode requires less space compared to the readout circuit configured for the global shutter mode.

[0059] In an embodiment, the first group of pixels is configured to be read out by the readout circuit in a rolling shutter mode, and the second group of pixels is configured to be read out by the readout circuit via the transfer unit in a global shutter mode.

[0060] The transfer unit can be understood as a part of the readout circuit. The transfer unit can be arranged next to the readout circuit in the readout layer. The transfer unit and the readout circuit can be integrated in the same substrate. For example, the transfer unit can be arranged below the array of the second group of pixels in the vertical direction. The readout circuit can be arranged around the readout layer. For example, the readout circuit includes an analog-to-digital converter, an output interface, etc. The transfer unit can include a storage capacitor for storing the photoinduced charge carriers. The transfer unit may further include a switch and / or a transistor for controlling the electrical signal to and from the transfer unit.

[0061] In the global shutter mode, all pixels of the pixel matrix are exposed for the same time. After irradiation with electromagnetic radiation, the pixels are read out one by one. The required exposure time is much shorter than that required for the rolling shutter mode. The shorter exposure time can lead to a lower power consumption. Moreover, if the image sensor device consists of an electronic device operated by a user and the infrared light comes from a dedicated light source, the exposure with infrared radiation, especially with SWIR radiation, should be kept short enough to avoid damaging the user's eyes.

[0062] In an embodiment, the first sensor layer further includes control circuitry configured to control an electrical signal to / from each pixel of the first group.

[0063] This means that the first sensor layer also includes circuit parts apart from the photodiodes, in particular each pixel in the first sensor layer can include a transistor for controlling the electrical signal to and from the individual pixel.

[0064] According to some embodiments, each pixel includes a select transistor configured to receive a select signal, thereby allowing individual rows of pixels to be addressed during readout.

[0065] According to some embodiments, each pixel includes at least one transfer transistor configured to receive a transfer signal such that charge carriers generated by the photodiode are transferred to the floating diffusion node of the individual pixel.

[0066] According to some embodiments, each pixel includes a reset transistor configured to receive a reset signal, whereby the floating diffusion node is reset to the pixel supply voltage and excess charge carriers are removed.

[0067] According to some embodiments, each pixel includes a source follower to amplify the photoinduced charge carriers at the floating diffusion node.

[0068] According to some embodiments, the pixel may include an additional transfer transistor that may be configured to receive an additional transfer signal, whereby charge carriers generated by pixels of a second group electrically connected to individual pixels of the first group are transferred to the floating diffusion node.

[0069] By the control circuit, each pixel or each sub-pixel can be individually controlled. This can mean that each pixel / sub-pixel can be controlled to be read by the readout circuit. The control circuit can be small enough to be integrated within the pixel, so that the pixel pitch can be kept small and the photosensitive area covers the main part of each pixel.

[0070] In an embodiment, the wiring of the first group of pixels is arranged on a main surface of the first sensor layer, the main surface facing the second sensor layer and facing away from the radiation entrance surface of the first sensor layer.

[0071] This can mean that the rear surface of the first sensor layer faces the incident electromagnetic radiation. Thus, the image sensor device can have a BSI configuration. As mentioned above, the main surface of the first sensor layer can have an oxide layer in which the wiring is embedded. With the BSI configuration, the wiring is located under the photosensitive pixels, so that the incident light is not blocked or scattered by the wiring and can reach the pixels with the photodiodes unhindered. Thus, the image sensor device has a high QE.

[0072] In one embodiment, the wiring of the second group of pixels is disposed on a major surface of the second sensor layer, the major surface facing the first sensor layer.

[0073] This can mean that the first and second sensor layers can be attached (by hybrid bonding) facing each other, i.e. main surface-to-main surface. As mentioned above, the first and second sensor layers can include a substrate on which the photodiodes are placed. The wiring is embedded in an oxide layer that is placed on top of the respective substrate. The first and second sensor layers can be arranged such that the individual oxide layers face each other for a direct bonding process. The wiring in the oxide layer can be utilized to electrically connect the pixels of the first group to the pixels of the second group. This configuration is advantageous when both groups of pixels are operated in a rolling shutter mode, whereby the pixels can share the same readout path. In this case, the readout circuit consumes less space.

[0074] In one embodiment, the wiring of the second group of pixels is disposed on a major surface of the second sensor layer, the major surface facing the readout layer.

[0075] This can mean that the second sensor layer and the readout layer can be attached (by hybrid bonding) facing each other, i.e. main surface-to-main surface. As mentioned above, the second sensor layer and the readout layer can include a substrate on which the photodiodes or, respectively, the readout circuitry are disposed. The wiring is embedded in an oxide layer disposed on top of the respective substrate. The readout layer and the second sensor layer can be disposed such that the individual oxide layers face each other for a direct bonding process. The wiring in the oxide layer can be utilized to electrically connect the pixels of the second group with parts of the readout layer.

[0076] This configuration is advantageous when the second group of pixels is operated in a global shutter mode, which requires a separate readout path for the second group of pixels. In this case, the illumination time of the second group of pixels can be kept short. Moreover, no hybrid junction interface is required between the first and second sensor layers. This reduces the shadowing and / or scattering effects on the incident light due to wiring and metal layers at the interface.

[0077] Furthermore, there is provided an image sensor device comprising the image sensor arrangement, which means that all features disclosed with respect to the image sensor arrangement are also disclosed and applicable with respect to the image sensor device and vice versa.

[0078] According to at least one embodiment of the image sensor device, the image sensor device further comprises a light source synchronized with the second group of pixels. This can mean that the light source is configured to emit electromagnetic radiation when the second group of pixels is operated to detect electromagnetic radiation. For example, the light source is a SWIR light source that emits light in the short wavelength infrared range. For example, the SWIR light source emits light in a narrow band of approximately 1400 nm, 1500 nm, or 1600 nm. For example, the bandwidth of the emitted light is ±5 nm, ±10 nm, or ±50 nm. The wavelength emitted by the light source may match the transparency of the dual band filter. The light source can illuminate an object, where a portion of the emitted light is reflected. The reflected light can be detected by the second sensor layer.

[0079] In an embodiment, the image sensor may further include a control unit configured to simultaneously control the light source and the second group of pixels. In this manner, the operation of the light source and the second group of pixels are synchronized. By synchronizing the operation of the light source with the second group of pixels, it is possible to minimize the duration of illumination. Thus, the power consumption of the light source is reduced.

[0080] Such image sensors can be conveniently utilized in electronic devices such as smartphones, tablet computers, laptops, or camera modules. For example, the camera modules are configured to operate in the visible domain for photo and / or video capture, and in the infrared domain for 3D imaging and / or authentication purposes. Moreover, image sensors with infrared sensitivity can be used in dark environments where video feeds are required. Such applications range from facial recognition unlocking of mobile phones to driver monitoring systems. Both can be deployed with illumination in the SWIR spectrum, so that the phone user / driver is not dazzled by the light illuminating them.

[0081] Furthermore, a method for operating an image sensor apparatus is provided. The image sensor apparatus may preferably be employed for the method for operating an image sensor apparatus as described herein. This means that all features disclosed with respect to the image sensor apparatus and image sensor device are also disclosed with respect to the method for operating an image sensor apparatus and vice versa.

[0082] According to at least one embodiment of a method for operating an image sensor device, the method includes exposing a first group of pixels of a first sensor layer to electromagnetic radiation, each pixel of the first group including a photodiode configured to detect electromagnetic radiation in a first wavelength range.

[0083] The method further includes transmitting at least a portion of the electromagnetic radiation through the first sensor layer to the second sensor layer. This portion of the electromagnetic radiation corresponds to a second wavelength range that is outside the wavelength range detectable by the first sensor layer. For example, the transmitted portion of the electromagnetic radiation includes at least light in the SWIR domain. The transmission of SWIR light can be achieved by SWIR light that does not interact or only slightly interacts with the sensor material of the first sensor layer.

[0084] The method further includes exposing a second group of pixels of the second sensor layer to a portion of the electromagnetic radiation, each pixel of the second group including a photodiode configured to sense electromagnetic radiation in a second wavelength range.

[0085] The electromagnetic radiation in the second wavelength range can be provided by a light source. The light source can be synchronized with the operation of the second group of pixels. This means, for example, that the light source is operated and emits light only while the photodiodes are operating and sensing the electromagnetic radiation. The light emitted from the light source is reflected by the object, transmitted by the first sensor layer and received by the second sensor layer. The light source can be a SWIR light source.

[0086] The method further includes converting the electromagnetic radiation into an electrical signal with the photodiodes, each of the photodiodes converting the electromagnetic radiation into an electrical signal during operation.

[0087] The method further comprises transferring the electrical signals of the pixels of the first and second groups to a readout layer including a readout circuit. The electrical signals of the pixels can be transferred to the readout circuit one after the other. The electrical signals of the pixels of the first group can be transferred to the readout circuit via the same readout path as the electrical signals of the pixels of the second group. Alternatively, the electrical signals of the pixels of the first group can be transferred to the readout circuit via a separate readout path different from the readout path used for the electrical signals of the pixels of the second group. The readout path can be provided using through-substrate vias and / or a hybrid bond interface.

[0088] Further embodiments of the method will be apparent to those skilled in the art from the above-described embodiments of the image sensor device.

[0089] The following description of the drawings may further illustrate and explain aspects of the improved image sensor device and method of operating the same. Components and portions of the image sensor device that are functionally identical or have the same effect are represented by the same reference numerals. Identical or substantially identical components and portions may only be described with respect to the drawing in which they first appear. Their description is not necessarily repeated in subsequent drawings. [Brief description of the drawings]

[0090] [Figure 1] 1 is a diagram of an example embodiment of an image sensor device; [Diagram 2] FIG. 2 is a diagram of another example embodiment of an image sensor device. [Diagram 3] 1 is a schematic diagram according to one embodiment of an image sensor device; [Figure 4]2 is another schematic diagram of an embodiment of an image sensor device. [Diagram 5] 1 is a schematic diagram of an image sensor device including an image sensor arrangement; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0091] FIG. 1 shows an exemplary embodiment of an image sensor device 1. The image sensor device 1 comprises a first sensor layer 2 including a first group of pixels 3, each pixel 3 of the first group including a photodiode (not shown) configured to detect electromagnetic radiation in a first wavelength range (indicated by an arrow above the image sensor device). The image sensor device 1 further comprises a second sensor layer 4 including a second group of pixels 5, each pixel 5 of the second group including a photodiode (not shown) configured to detect electromagnetic radiation in a second wavelength range. The image sensor device 1 further comprises a readout layer 6 including a readout circuit 7 configured to read out electrical signals from the first and second groups of pixels 3, 5. The second sensor layer 4 is disposed between the first sensor layer 2 and the readout layer 6. The second wavelength range is outside the wavelength range detectable by the first sensor layer 2.

[0092] The first sensor layer 2, the second sensor layer 4, and the readout layer 6 each have a main extension plane. As shown in FIG. 1, the main extension planes can be parallel to each other. The main extension planes can extend in the lateral directions x, y. In the vertical direction z, which points to a direction extending perpendicular to the main extension planes, the first sensor layer 2, the second sensor layer 4, and the readout layer 6 are arranged on top of each other to form a stack. The second sensor layer 4 is arranged on top of the readout layer 6. The first sensor layer 2 is arranged on top of the second sensor layer 4. The first sensor layer 2 is arranged between the second sensor layer 4 and the incident electromagnetic radiation.

[0093] The first sensor layer 2 includes a main surface 2' and a back surface 2". Wiring (not shown) of the first group of pixels may be arranged on the main surface 2' of the first sensor layer 2. In the embodiment shown in FIG. 1, the first sensor layer 2 is arranged such that the back surface 2" faces the electromagnetic radiation source. The main surface 2' of the first sensor layer 2 faces the second sensor layer 4. However, in other embodiments (not shown), the first sensor layer 2 may be arranged in other ways.

[0094] The second sensor layer 4 includes a main surface 4' and a back surface 4". The wiring of the second group of pixels 5 may be arranged on the main surface 4' of the second sensor layer 4. In the embodiment shown in FIG. 1, the second sensor layer 4 is arranged such that the back surface 4" faces the readout layer 6. The main surface 4' of the second sensor layer 4 faces the first sensor layer 2. However, in other embodiments (e.g., as shown in FIG. 2), the second sensor layer 4 may be arranged in other ways.

[0095] The readout layer 6 includes a main surface 6′ and a back surface 6″. Wiring of the readout circuitry 7 may be disposed on the main surface 6′ of the readout layer 6. In the embodiment shown in FIG. 1 , the readout layer 6 is disposed such that its main surface 6′ faces the second sensor layer 4.

[0096] 1 further illustrates a hybrid bond interface 8, by means of which the first sensor layer 2 is attached to the second sensor layer 4. For example, the hybrid bond can be established using an adhesive. In another example, the bond can be made with an oxide layer interface, either directly or during a fusion bonding process.

[0097] The hybrid bonding interface 8 includes electrical interconnects 9, by which the first group of pixels 3 and the second group of pixels 5 can be electrically connected to each other. For example, the electrical interconnects 9 are metal bumps (e.g., solder bumps) embedded in an adhesive. The electrical interconnects 9 can also be metal pads fabricated in parallel with a respective dielectric bonding layer, e.g., an oxide layer. In this case, electrical contact can be achieved via metal diffusion bonding during annealing.

[0098] The implementation of the bonding interface is not limited to the proposed example: in general, any bonding technique can be used that establishes a permanent bond between two layers and combines a dielectric bond with an embedded metal to form the electrical interconnect 9.

[0099] FIG. 1 further illustrates an optical element 10. The optical element 10 may include a dual band filter 11. The dual band filter 11 is arranged between the first sensor layer and the incident electromagnetic radiation to be sensed. This means that in the vertical direction z, the dual band filter 11 is arranged at or above the first sensor layer 2, whereby the first sensor layer 2 is arranged between the dual band filter 11 and the second sensor layer 4. The dual band filter 11 may be attached directly to the first sensor layer 2 or may be arranged at a predetermined distance from the first sensor layer 2, as shown in FIG. 1. The dual band filter 11 is configured to block electromagnetic radiation apart from at least a part of a first wavelength range (e.g. visible light) and at least a part of a second wavelength range (e.g. SWIR light).

[0100] Alternatively or additionally, the optical element 10 includes a lens or an array of lenses. The lens or the array of lenses is configured to direct incident light towards the first sensor layer 2 and the second sensor layer 4. The lens or the array of lenses can be used to direct light through an aperture in a metal layer between the first sensor layer 2 and the second sensor layer 4 (e.g., a metal layer configured with pixel wiring or hybrid junction interface 8). The lens can be a microlens and the array of lenses can be an array of microlenses.

[0101] FIG. 1 further shows two through-substrate vias 12 (TSVs). The TSVs 12 penetrate the second sensor layer 4 and electrically connect the first group of pixels 3 in the first sensor layer 2 to the readout circuitry 7 in the readout layer 6. Each TSV 12 penetrates completely through the second sensor layer. This means that the TSVs 12 reach from the main surface 4′ to the back surface 4″ of the second sensor layer 4.

[0102] In addition, the TSVs 12 may also extend completely through the first sensor layer 2, as shown by the dashed lines. In this case, the TSVs 12 extend from the rear surface 2'' of the first sensor layer to the rear surface 4'' of the second sensor layer 4.

[0103] The TSVs 12 provide a readout path for reading out the electrical signals of the first group of pixels 3. In some embodiments, electrical signals from the second group of pixels 5 are also read out via the TSVs 12. Each TSV 12 may be electrically connected to only one pixel 3. It is also possible for each TSV 12 to be electrically connected to more than one pixel 3. FIG. 1 merely shows two TSVs 12 as an example. However, the image sensor device 1 may include multiple TSVs, with each TSV 12 being electrically connected to one or more pixels 3.

[0104] In Fig. 2 another embodiment of an image sensor device 1 is shown. The embodiment according to Fig. 2 differs from the embodiment of Fig. 1 in that there is no hybrid bond interface 8 between the first sensor layer 2 and the second sensor layer 4. Instead, the hybrid bond interface 8 is between the second sensor layer 4 and the readout layer 6. In particular, a main surface 4' of the second sensor layer 4 is attached to a main surface 6' of the readout layer 6 by a hybrid bond.

[0105] The hybrid bonding interface 8 includes electrical interconnects 9, by which the second group of pixels 5 can be electrically connected to portions of the readout layer 6. As already explained, the electrical interconnects 9 can be metal bumps (e.g. solder bumps) embedded in an adhesive. The electrical interconnects 9 can also be metal pads fabricated in parallel with a respective dielectric bonding layer, e.g. an oxide layer. In this case, the electrical contact can be achieved via a metal diffusion bond during annealing.

[0106] Electrical interconnects 9 provide a separate readout path for the second group of pixels 5 in addition to the readout path for the first group of pixels 3 via TSVs 12 .

[0107] In Fig. 3 a detail of the embodiment according to Fig. 1 is shown in a schematic way. Only the first sensor layer 2 and the second sensor layer 4 are shown, including the hybrid junction interface 8. The readout layer 6 is omitted for illustration purposes. In Fig. 3 it is shown how the second group of pixels 5 (e.g. SWIR pixels) are electrically connected to the first group of pixels 3 (e.g. visible light pixels or RGB pixels). Further pixels 3, 5 can be electrically connected in the same or a similar way.

[0108] In the following, the pixels of the second group will be referred to as SWIR pixels 3, although these pixels may be sensitive to different wavelength ranges, and the pixels of the first group 3 will be referred to as visible light pixels 5. However, it should be noted that the image sensor device 1 is not limited to sensing visible and SWIR light.

[0109] 3, the second sensor layer 4 includes one pixel 5 of a second group, for example, one SWIR pixel 5. The SWIR pixel 5 includes a photodiode 13. For example, the photodiode 13 is a pinned photodiode 13. Except for the photodiode 13 included in the SWIR pixel 5, the second sensor layer 4 may not include a circuit portion such as a transistor.

[0110] The photodiode 13 is configured to detect electromagnetic radiation and convert it into an electrical signal. On its anode side, the photodiode 13 is electrically connected to a potential, for example ground potential. On its cathode side, the photodiode 13 is electrically connected to the first group of pixels 3 via electrical interconnects 9 at the hybrid junction interface 8.

[0111] The visible light pixel 3 in the first sensor layer 2 of the embodiment of FIG. 3 includes four sub-pixels 18-21 with individual photodiodes 14-17. However, other pixel architectures are possible. For example, the visible light pixel 3 may include only one photodiode or may include more photodiodes. Each of the photodiodes may be configured to sense light in the same wavelength range or in different wavelength ranges. As such, the configuration shown in FIG. 3 should be understood as merely an exemplary embodiment.

[0112] The visible light pixel 3 of Figure 3 may include a first subpixel 18 including a photodiode 14 configured to detect and convert electromagnetic radiation in the red wavelength range. The visible light pixel 3 may further include second and third subpixels 19, 20 including respective photodiodes 15, 16 configured to detect and convert electromagnetic radiation in the green wavelength range. The visible light pixel 3 may also include a fourth subpixel 21 including a photodiode 17 configured to detect and convert electromagnetic radiation in the blue wavelength range. Again, the pixels are not limited to RGB and other wavelength ranges are possible.

[0113] Each of the photodiodes 14-17 is electrically connected at their anode side to a potential, for example ground potential. The sub-pixels 18-21 may share a common floating diffusion node 22. At their cathode sides, the photodiodes 14-17 are electrically connected to the floating diffusion node 22 via respective transfer transistors 23 controlled by respective transfer signals TX.

[0114] In the pixel architecture according to Fig. 3, the transfer transistor 23 is included in a control circuit 24. The control circuit 24 further includes a reset transistor 25 arranged to receive a reset signal RST at its gate, whereby the floating diffusion node 22 is reset to the pixel supply voltage VDD and excess charge carriers are removed.

[0115] The control circuit 24 further includes a source follower 26 for amplifying the photo-induced charge carriers at the floating diffusion node 22 .

[0116] The control circuit 24 further includes a select transistor 27 configured to receive a select signal at its gate, thereby allowing the pixel 3 to be addressed during readout. The select transistor 27 is connected on one side to the source follower 26 and on the other side (which includes the TSV 12, as shown in FIG. 1) to a readout path 28.

[0117] 3, the control circuit 24 further comprises a further transfer transistor 29. The further transfer transistor 29 may be configured to receive a further transfer signal TX′, whereby the charge carriers generated by the SWIR pixel 5 electrically connected to the respective visible light pixel 3 are transferred to the floating diffusion node 22. In this way, the SWIR pixel 5 and the visible light pixel 3 share a common floating diffusion node 22 as well as a common readout path 28.

[0118] In Fig. 4 a detail of the embodiment according to Fig. 2 is shown diagrammatically. In Fig. 4 several SWIR pixels 5 of one row of an array of SWIR pixels 5 are shown. Correspondingly several visible pixels 3 of one row of an array of visible light pixels 3 are shown. All rows are indicated with an ellipsis.

[0119] In the embodiment according to Fig. 4, the SWIR pixels 5 are not electrically connected to the visible light pixels 3 via the hybrid bond interface 8. Therefore, the SWIR pixels 5 do not share a common readout path with the visible light pixels 3. Instead, the visible light pixels 3 are read out by the readout circuit 7 via a separate readout path 28, while the SWIR pixels 5 are read out by the readout circuit 7 via a transfer unit 30. Thus, there is an electrical interconnection 9 between the second sensor layer 4 and the readout layer 6 via the hybrid bond interface 8.

[0120] The transfer unit 30 may be arranged next to the readout circuit 7 in the readout layer 6. In the example of FIG. 4, the transfer unit 30 is arranged below the array of SWIR pixels 5. The readout circuit 7 is arranged around the readout layer 6. The transfer unit 30 may be configured such that the SWIR pixels 5 can be read out in a global shutter mode. The transfer unit 30 may include a storage capacitor for storing the photo-induced charge carriers. The transfer unit 30 may further include switches and / or transistors for controlling the electrical signals to and from the transfer unit 30.

[0121] 4 shows an example transfer unit architecture for each SWIR pixel 5. However, the embodiments are not limited to the transfer unit architecture shown and other architectures are possible as well. Each SWIR pixel 5 is assigned to one individual transfer unit 30. The transfer units 30 are connected via a readout path 28' that is connected to the readout circuit 7.

[0122] The photodiode 13 of the SWIR pixel 5 is electrically connected to a floating diffusion node 31 in the readout layer 6 via an optional transfer transistor 32 controlled by a transfer signal TX'. The transfer transistor 32 can also be omitted. The transfer unit 30 further includes a reset transistor 33 configured to receive a reset signal RST', whereby the floating diffusion node 31 is reset to the pixel supply voltage VDD and excess charge carriers are removed. A floating diffusion capacitance 34 stores the charge carriers at the floating diffusion node 31. The transfer unit 30 further includes a first source follower 35 to amplify the photo-induced charge carriers at the floating diffusion node 31.

[0123] The pre-charge transistor 36 acts as a current source load for the first source follower 35. It is also used to pre-charge the sample capacitors 37, 38. The switches 39, 40 together with the first sample capacitor 37 and the second sample capacitor 38 perform the sampling and holding functionality of the SWIR pixel 5. The second source follower 41 buffers the sample signal to the readout path 28'. The row select transistor 42 is also configured to receive a select signal SEL' at its gate, thereby allowing the pixel 5 to be addressed during readout.

[0124] As shown in Figure 4, the architecture of the visible light pixels 3 in this embodiment can be the same as or smaller than that of the embodiment of Figure 3. The visible light pixels 3 in the illustrated row are electrically connected together via readout paths 28. The readout paths 28 are electrically connected to the readout circuitry 7 via the TSVs 12. In this configuration, the visible light pixels 3 can be operated in a rolling shutter mode, while the SWIR pixels 5 can be operated in a global shutter mode.

[0125] 5 shows a schematic diagram of an example embodiment of an image sensor device 43 including the image sensor unit 1 as discussed above. The first group of pixels 3 and the second group of pixels 5 of the image sensor unit 1 can be arranged as an individual two-dimensional array as shown in FIG. 5. The image sensor device 43 further includes a light source 44 synchronized with the second group of pixels 5. For example, the light source emits light in the SWIR range. The image sensor device 43 further includes a control unit 45 configured to control the light source 44 and the second group of pixels 5.

[0126] The embodiments of the image sensor device 1 and method of operating the image sensor device 1 disclosed herein are described for the purpose of familiarizing the reader with novel aspects of the concepts. While preferred embodiments have been shown and described, many variations, modifications, equivalents, and substitutions of the disclosed concepts may be made by those skilled in the art without unduly departing from the scope of the claims.

[0127] It is to be understood that the present disclosure is not limited to the disclosed embodiments and to those specifically shown and described hereinabove. Rather, features described in separate dependent claims or in the specification may be advantageously combined. Moreover, the scope of the present disclosure includes variations and modifications that are obvious to those skilled in the art and that are included within the scope of the appended claims.

[0128] The term "comprising", when used in a claim or the description, does not exclude other elements or steps of the corresponding feature or procedure. In instances where the terms "a" and "an" are used in conjunction with features, these terms do not exclude a plurality of such features. Moreover, any signs in the claims should not be construed as limiting the scope.

[0129] This patent application claims priority from German patent application 102021107730.3, the disclosure of which is incorporated herein by reference. [Explanation of symbols]

[0130] 1. Image sensor device 2 First Sensor Layer 2' Main surface of the first sensor layer 2” Rear surface of the first sensor layer 3 First group of pixels 4 Second Sensor Layer 4' Main surface of second sensor layer 4” Rear surface of second sensor layer 5 Second group of pixels 6 Readout Layer 6' Main surface of readout layer 6” Rear surface of readout layer 7 Readout circuit 8 Joint interface 9 Electrical Interconnects 10 Optical elements 11 Dual Band Filter 12 Through-substrate vias 13~17 Photodiode 18~21 subpixels 22 Floating Diffusion Nodes 23 Transfer transistor 24 Control circuit 25 Reset transistor 26 Source Followers 27 Select transistor 28, 28' read path 29 More transfer transistors 30 Transfer Units 31 Floating Diffusion Nodes 32 Transfer transistor 33 Reset transistor 34 Stray Diffusion Capacitance 35 First Source Follower 36 Precharge transistor 37 First Capacitor 38 Second Capacitor 39 First Switch 40 Second Switch 41 Second Source Follower 42 Select transistor 43 Image Sensor Device 44 Light source 45 Control Unit RST, RST' Reset signal SEL, SEL' Selection signal TX, TX' transmit signal VDD Supply voltage x, y horizontal z vertical direction

Claims

1. a first sensor layer (2) including a first group of pixels (3), each pixel (3) of the first group including a photodiode (14, 15, 16, 17) configured to detect electromagnetic radiation in a first wavelength range; a second sensor layer (4) including a second group of pixels (5), each pixel (5) of the second group including a photodiode (13) configured to detect electromagnetic radiation in a second wavelength range; a readout layer (6) including a readout circuit (7) configured to read out electrical signals from the first group of pixels (3) and the second group of pixels (5), the second sensor layer (4) being disposed between the first sensor layer (2) and the readout layer (6), and the second wavelength range being outside a wavelength range detectable by the first sensor layer (2); a dual-band filter (11) arranged between the first sensor layer (2) and a source of electromagnetic radiation to be sensed, the dual-band filter (11) being configured to block electromagnetic radiation apart from at least a portion of the first wavelength range and at least a portion of the second wavelength range; The image sensor device (1), wherein the first sensor layer (2) is attached to the second sensor layer (4) by hybrid bonding, thereby forming electrical interconnections (9) between the first group of pixels (3) and the second group of pixels (5).

2. 2. The image sensor device (1) of claim 1, wherein the first wavelength range comprises visible light and the second wavelength range comprises short wavelength infrared radiation (SWIR).

3. 2. The image sensor device (1) of claim 1, wherein the first group of pixels (3) and the second group of pixels (5) share a common floating diffusion node (22) and a common readout path (28).

4. 2. The image sensor device (1) of claim 1, wherein the second sensor layer (4) is attached to the readout layer (6) by a hybrid bond, thereby forming an electrical interconnection (9) between the pixels (5) of the second group and the readout circuit (7).

5. 2. The image sensor device (1) of claim 1, further comprising at least one through-substrate via (12) passing through the second sensor layer (4) and electrically connecting the first group of pixels (3) in the first sensor layer (2) to the readout circuit (7) in the readout layer (6).

6. The image sensor device (1) according to claim 1, wherein the first sensor layer (2) and / or the readout layer (6) comprise a semiconductor material.

7. An image sensor device (1) as described in claim 6, wherein the semiconductor material is silicon.

8. 2. The image sensor device (1) of claim 1, wherein the second sensor layer (4) comprises one of germanium, indium gallium arsenide, and a quantum dot layer, or any other material having a band gap suitable for a spectral response to electromagnetic radiation in the second wavelength range.

9. 2. The image sensor device (1) of claim 1, wherein the first group of pixels (3) and the second group of pixels (5) are configured to be read out in a rolling shutter mode by the readout circuit (7).

10. 2. The image sensor device (1) of claim 1, wherein the first group of pixels (3) is configured to be read out by the readout circuit (7) in a rolling shutter mode and the second group of pixels (5) is configured to be read out by the readout circuit (7) in a global shutter mode via a transfer unit (30).

11. 2. The image sensor device (1) of claim 1, wherein the first sensor layer (2) further comprises a control circuit (24), the control circuit (24) being configured to control an electrical signal for each pixel (3) of the first group.

12. 2. The image sensor device (1) of claim 1, wherein the wiring of the first group of pixels (3) is arranged on a main surface (2') of the first sensor layer (2), the main surface (2') facing the second sensor layer (4) and facing away from the radiation entrance surface of the first sensor layer (2).

13. 2. The image sensor device (1) of claim 1, wherein the wiring of the second group of pixels (5) is arranged on a main surface (4') of the second sensor layer (4), the main surface (4') facing the first sensor layer (2).

14. 2. The image sensor device (1) according to claim 1, wherein the wiring of the second group of pixels (5) is arranged on a main surface (4') of the second sensor layer (4), the main surface (4') facing the readout layer (6).

15. An image sensor device (43) comprising an image sensor arrangement (1) according to claim 1 and a light source (44) synchronized with said pixels (5) of said second group.

16. A method for operating an image sensor device (1), comprising: blocking electromagnetic radiation apart from at least a portion of the first wavelength range and at least a portion of the second wavelength range by a dual-band filter (11); exposing a first group of pixels (3) of a first sensor layer (2) to electromagnetic radiation transmitted through said dual-band filter (11), each pixel (3) of said first group comprising a photodiode (14, 15, 16, 17) configured to detect electromagnetic radiation in said first wavelength range; transmitting at least a portion of the electromagnetic radiation transmitted through the dual-band filter (11) through the first sensor layer (2) to a second sensor layer (4), the portion of the electromagnetic radiation corresponding to the second wavelength range outside a wavelength range detectable by the first sensor layer (2); exposing a second group of pixels (5) of the second sensor layer (4) to the portion of the electromagnetic radiation, each pixel (5) of the second group including a photodiode (13) configured to detect electromagnetic radiation in the second wavelength range; converting electromagnetic radiation into an electrical signal by said photodiodes (13, 14, 15, 16, 17); transferring said electrical signals of said first group of pixels (3) and said second group of pixels (5) to a readout layer (6) containing readout circuits (7), The method of claim 1, wherein the first sensor layer (2) is attached to the second sensor layer (4) by hybrid bonding, thereby forming electrical interconnections (9) between the first group of pixels (3) and the second group of pixels (5).

Images