Optical control for improving near-infrared sensitivity and channel separation

Abstract

This application relates to light control for improving near-infrared sensitivity and channel separation. In one embodiment, an image sensor includes: a plurality of photodiodes arranged in rows and columns of a pixel array; and a filter layer having a plurality of filters disposed above the plurality of photodiodes. The filter layer has a first side facing the plurality of photodiodes and a second side opposite the first side. The image sensor further includes a color filter layer having a plurality of color filters disposed above the plurality of photodiodes. The color filter layer has a first surface facing the second side of the filter layer and a second surface opposite the first side. Individual microlenses are configured to direct incoming light through corresponding filters and color filters to respective photodiodes.

Description

Technical Field

[0001] The present invention generally relates to the counter design of image sensors, and more particularly to image sensors for infrared light. Background Art

[0002] Image sensors have been widely used. Image sensors are widely used in digital still cameras, mobile phones, security cameras, and medical, automotive, and other applications. The technology for manufacturing image sensors has been making rapid progress. For example, the demand for higher image sensor resolution and lower power consumption has led to further miniaturization of image sensors and their integration into digital devices.

[0003] Some image sensors are used for near-infrared (NIR) sensing (also referred to as infrared or IR sensing for simplicity and brevity). IR sensing is generally defined as including light wavelengths from approximately 700 nm to approximately 1000 nm. IR sensing can be used to perform imaging that is otherwise beyond visual perception. When IR light is emitted towards a target and reflected from the target, the IR sensor stores the reflected light. In different applications, IR sensing can measure the target distance, size, position, and recognition features.

[0004] Individual pixels of an image sensor are typically sensitive to multiple light wavelengths. Thus, even when the pixels are optimized to respond primarily to IR light, the presence of other wavelengths can still affect the pixel response, making it difficult for the pixels to resolve the intensity of the IR light. Conversely, in some usage scenarios, the pixels do not receive sufficient IR radiation to provide a meaningful reading. Therefore, the accuracy or applicability of the image sensor can be limited. Summary of the Invention

[0005] One aspect of the present application provides an image sensor, the image sensor comprising: a plurality of photodiodes arranged in rows and columns of a pixel array; a filter layer including a plurality of filters disposed above the plurality of photodiodes, the filter layer having a first side facing the plurality of photodiodes and a second side opposite the first side; a color filter layer including a plurality of color filters disposed above the plurality of photodiodes, the color filter layer having a first surface facing the second side of the filter layer and a second surface opposite the first side of the filter layer; and a plurality of microlenses disposed adjacent to the second surface of the color filter layer, wherein individual microlenses are configured to direct incident light through the corresponding filter and color filter to reach the respective photodiodes. Brief Description of the Drawings

[0006] The non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, in which like reference numerals refer to like parts throughout the various views, unless otherwise specified.

[0007] Figure 1 FIG. is a diagram of an image sensor according to an embodiment of the technology of the present invention.

[0008] Figure 2 FIG. is a cross-sectional view of an exemplary pixel according to an embodiment of the technology of the present invention.

[0009] Figure 3 FIG. shows a cross-sectional view of an exemplary unit deep trench isolation (CDTI) microstructure according to an embodiment of the technology of the present invention.

[0010] Figure 4 FIG. shows a top plan view of an exemplary CDTI microstructure according to an embodiment of the technology of the present invention.

[0011] Figures 5A to 5C FIG. is an exemplary graph of the quantum efficiency (QE) of a channel according to an embodiment of the technology of the present invention.

[0012] Figure 6A FIG. is a diagram of an exemplary layer of an image sensor according to an embodiment of the technology of the present invention.

[0013] Figure 6B FIG. shows a partially exploded perspective view of an image sensor according to an embodiment of the technology of the present invention.

[0014] Figures 7A to 7D FIG. is an exemplary graph of the quantum efficiency (QE) of an image sensor according to an embodiment of the technology of the present invention.

[0015] Figure 8A FIG. is a diagram of an exemplary image sensor according to an embodiment of the technology of the present invention.

[0016] Figure 8B is Figure 8A an exemplary graph of the quantum efficiency (QE) of the image sensor shown in.

[0017] Figure 9A FIG. is a diagram of another exemplary image sensor according to an embodiment of the technology of the present invention.

[0018] Figure 9B is Figure 9A an exemplary graph of the quantum efficiency (QE) of the image sensor shown in.

[0019] Figure 10A FIG. is a diagram of yet another exemplary image sensor according to an embodiment of the technology of the present invention.

[0020] Figure 10B isFigure 10A An exemplary graph of the quantum efficiency (QE) of the image sensor shown in

[0021] Figure 11A FIG. is a diagram of another exemplary image sensor according to an embodiment of the technology of the present invention.

[0022] Figure 11B is Figure 11A An exemplary graph of the quantum efficiency (QE) of the image sensor shown in

[0023] Figure 12A FIG. is a diagram of another exemplary image sensor according to an embodiment of the technology of the present invention.

[0024] Figure 12B is Figure 12A An exemplary graph of the quantum efficiency (QE) of the image sensor shown in

[0025] Throughout several views of the drawings, corresponding reference characters indicate corresponding components. Those skilled in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to facilitate understanding of the various embodiments of the present invention. Additionally, commonly known elements that are useful or necessary in a commercially viable embodiment are often not shown or described in detail so as not to obscure these various embodiments of the present invention. Detailed Description

[0026] An image sensor is disclosed, and more particularly an image sensor with improved sensitivity to IR light is disclosed. In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, those skilled in the art will recognize that the techniques described herein may be practiced without one or more of the specific details, or may be practiced using other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure certain aspects.

[0027] Reference throughout this specification to "one example" or "one embodiment" means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present invention. Thus, the appearances of the phrases "in one example" or "in one embodiment" in various places throughout this specification are not necessarily all referring to the same example. Additionally, the particular features, structures, or characteristics may be combined in any suitable manner in one or more examples.

[0028] For purposes of ease of explanation, spatially relative terms, such as "under", "below", "lower", "above", "upper", etc., may be used in this document to describe the relationship of one element or feature illustrated in the figures to another element or feature. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, an element described as "below" another element or feature will be oriented "above" the other element or feature. Thus, the exemplary terms "under" and "beneath" can encompass both an orientation above and below. The device may have other orientations (rotated 90 degrees or at other orientations) and accordingly the spatially relative descriptors used herein are to be interpreted accordingly. Additionally, it should be understood that when a layer is referred to as being "between two layers", that layer can be the only layer between the two layers or there can also be one or more intervening layers.

[0029] Throughout this specification, several terms are used. These terms will assume their ordinary meaning in the art, unless specifically defined otherwise herein or the context in which they are used clearly implies otherwise. It should be noted that in this document, element names and symbols may be used interchangeably (e.g., Si and silicon); however, both have the same meaning.

[0030] Briefly, examples in accordance with the teachings of the present invention relate to image sensor pixels (also referred to as channels) in which the sensitivity to infrared light is improved (e.g., the quantum efficiency is increased) and the crosstalk between channels is reduced (e.g., the channel separation is improved). In some embodiments, incoming light propagates towards the pixel through two filter layers: one layer has a color bandpass filter (e.g., a green bandpass filter, a blue bandpass filter, a red bandpass filter, or an infrared bandpass filter) and the other layer has a band selection filter (e.g., infrared (IR) pass, IR block, full wavelength block). The two filter layers cooperate to selectively expose the IR channels (pixels) to IR light while filtering out non-IR wavelengths. In some embodiments, the IR channels may absorb IR light from adjacent green channels.

[0031] In some embodiments, a unit deep trench isolation (CDTI) microstructure is added to the semiconductor material of the IR pixel to improve the capture of IR light by guiding the light towards the IR photodiode, thus improving the quantum efficiency (QE) of the IR channel. In some embodiments, the CDTI microstructure may also be added to other channels, such as to the semiconductor material of an adjacent green channel to improve the light guiding towards the IR pixel.

[0032] Figure 1FIG. is a diagram of an exemplary image sensor 10 according to an embodiment of the technology of the present invention. The image sensor 10 includes pixels 11 arranged in rows (R) and columns (C) of a pixel array 12. When the image sensor 10 is exposed to light, individual pixels 11 acquire certain voltage values. After each pixel has acquired its voltage value, a readout circuit system 14 reads out the image data and then transmits it to a functional logic 18.

[0033] The readout circuit system 14 can capture the voltage values of individual pixels (P1 to Pn). For example, a control circuit system 16 can determine a specific row Ri in the pixel array 12 that is coupled to the readout circuit system 14. After capturing the pixel values in row Ri, the control circuit system 16 couples row Ri+1 to the readout circuit system 14 and repeats the process until the voltage values of all pixels in the column have been captured. In other embodiments, the readout circuit system 14 can use various other techniques ( Figure 1 not illustrated herein) to read out the image data, such as serial readout or simultaneous full parallel readout of all pixels. In different embodiments, the readout circuit system 14 can include an amplifier circuit system, an analog-to-digital conversion (“ADC”) circuit system, or other circuit systems. In some embodiments, the pixel values are captured and processed by the functional logic 18. For example, such processing can include image processing, image filtering, image extraction and manipulation, light intensity determination, etc.

[0034] Figure 2 FIG. is a cross-sectional view of an exemplary pixel according to an embodiment of the technology of the present invention. For simplicity, two pixels 110a and 110b are illustrated, but in other embodiments the pixel array 120 can include a greater number of pixels. The illustrated pixels 110a, 110b respectively include photodiodes 280a, 280b disposed in one or more layers of a semiconductor material 29. In some embodiments, the photodiodes 280a, 280b can be n-type photodiodes formed in the semiconductor material 29, and the semiconductor material 29 can be a silicon substrate, a doped silicon substrate, or a P-type epitaxial silicon substrate. However, in some embodiments, the polarities can be reversed. For example, the photodiodes 280a, 280b can be p-type photodiodes formed in an n-type semiconductor material 29 (such as an n-type doped silicon substrate or an n-type epitaxial silicon substrate). In some embodiments, adjacent photodiodes 280a, 280b are at least partially separated by deep trench isolation 30, which can reduce signal crosstalk between adjacent photodiodes 280a, 280b.

[0035] In operation, photodiodes 280a, 280b generate charge in response to receiving incoming light 20. In some embodiments, the incoming light may propagate through a vertical stack having a microlens 22, a color filter layer 260, a filter layer 270, a buffer oxide layer 40 having a plurality of metal grids 32, and a cell deep trench isolation (CDTI) microstructure 26 before reaching the photodiodes 280a, 280b. The color filter 260 may include a plurality of color filters optically arranged to filter the incoming light 20 according to specific light wavelengths, such as a red filter, a blue filter, a green filter, and an infrared (IR) color filter. This vertical stack is used to filter the incoming light 20 and direct the light toward the corresponding photodiodes 280a, 280b. When the filtered light reaches the photodiodes 280a, 280b, corresponding charge is generated and routed away from the pixel array 120 at an appropriate pitch and toward a readout circuitry (e.g., Figure 1 the readout circuitry 14). The buffer oxide layer 40 may include, for example, an oxide material deposited on the back side of the semiconductor material 29 by a chemical vapor deposition (CVD) process. The metal grids 32 may be formed in the buffer oxide layer 40 between adjacent pixels (photodiodes) and may operatively direct the filtered light to the corresponding photodiodes 280a, 280b by reflection and / or refraction, thereby preventing or at least reducing color crosstalk between the photodiodes 280a, 280b.

[0036] Figure 3 A cross-sectional view showing an exemplary CDTI microstructure 26 according to an embodiment of the technology of the present invention. These cross-sectional views correspond to Figure 2 the views shown in Figure 3 Details of the CDTI microstructure 26 are shown. In the depicted embodiment, the CDTI microstructure 26 is disposed in the region of a photodiode (PD) 280 in the path of the incident light. The CDTI microstructure 26 operatively changes the light transmission path within the corresponding photodiode 280 by reflection, refraction, and / or diffraction to enhance the light reception of the corresponding photodiode 280 for IR light having a light wavelength in the range of 700 nm to 1000 nm. In different embodiments, the surface adjacent to the CDTI microstructure 26 may be the front surface of the photodiode (as depicted in Figure 2 ), or may be the back surface (in the case where the incoming light enters from a direction opposite to the direction shown in Figure 2 ).

[0037] In various embodiments, each of the CDTI microstructures 26a through 26f includes a core dielectric material having a refractive index less than that of the semiconductor material. In one example, the semiconductor material is silicon. However, those skilled in the art will appreciate that any Group III element (B, Al, Ga, In, Tl), Group IV element (C, Si, Ge, Sn, Pb), Group V element (N, P, As, Sb, Bi), and suitable combinations of these elements can be used to form the semiconductor material. In some examples, the core dielectric material may include an oxide / nitride, such as silicon oxide (SiO 2 ), hafnium oxide (HfO 2 ), silicon nitride (Si 3 N 4 ), silicon oxynitride (SiO x N y ), tantalum oxide (Ta 2 O 5 ), titanium oxide (TiO 2 ), zirconium oxide (ZrO 2 ), aluminum oxide (Al 2 O 3 ), lanthanum oxide (La 2 O 3 ), praseodymium oxide (Pr 2 O 3 ), cerium oxide (CeO 2 ), neodymium oxide (Nd 2 O 3 ), promethium oxide (Pm 2 O 3 ), samarium oxide (Sm 2 O 3 ), europium oxide (Eu 2 O 3 ), gadolinium oxide (Gd 2 O 3 ), terbium oxide (Tb 2 O 3 ), dysprosium oxide (Dy 2 O 3 ), holmium oxide (Ho 2 O 3 ), erbium oxide (Er 2 O 3 ), thulium oxide (Tm 2 O 3 ), ytterbium oxide (Yb 2 O 3 ), lutetium oxide (Lu 2 O 3 ), yttrium oxide (Y 2 O 3) etc. In addition, those skilled in the relevant art should recognize that according to the teachings of the technology of the present invention, other stoichiometric combinations of the above metals / semiconductors and their oxides / nitrides / nitroxides can be used as long as their refractive index is less than that of the semiconductor material.

[0038] Although Figure 3 not illustrated in, each of the CDTI microstructures 26 may also include a liner material disposed between the photodiode and the core dielectric material. In some embodiments, the liner material may include at least one of a negatively charged high-k dielectric material (e.g., a dielectric material having a dielectric constant greater than 3.9) or a doped semiconductor material. For example, trenches can be etched, and boron, nitrogen, or arsenic can be implanted into the sidewalls of the trenches to form a doped semiconductor material as the liner material. Alternatively, trenches can be etched and hafnium oxide can be deposited in the trenches to form a negatively charged high-k liner material before depositing the core dielectric material into the trenches.

[0039] In different embodiments, the CDTI microstructures 26 can have different shapes. Some examples of these shapes are parallelepipeds, polygons (e.g., triangles, trapezoids, rectangles as seen in cross-sectional views), polyhedrons, cylinders, ellipsoids, hemispheres, and half-spheres. In some embodiments, the CDTI microstructures 26 can include a stack of several geometric shapes, such as the tapered trenches shown as CDTI microstructure 26d. Other configurations can also be used, such as combinations of shapes shown as CDTI microstructures 26a to 26f. In operation, the CDTI microstructures 26 direct light towards the interior of the photodiode.

[0040] Figure 4 A top plan view showing an exemplary CDTI microstructure arrangement according to an embodiment of the technology of the present invention. In different embodiments, one CDTI microstructure ("feature") or multiple CDTI microstructures can be used for a given photodiode. For example, CDTI microstructure 26a includes a single rectangular feature, while CDTI microstructure 26b includes nested rectangular features, and CDTI microstructure 26c includes nested rectangular features and circular features.

[0041] In different embodiments, the CDTI microstructures 26 can be arranged in different spatial distributions. For example, the rectangular CDTI microstructures 26d, 26e, and 26f can be arranged in different arrays with a structure-to-structure distance of H, W. The spatial arrangement of the microstructures 26 and the associated spacings H, W can be configured based on the desired quantum efficiency associated with the specific optical wavelength for the corresponding photodiode. As another non-limiting example, CDTI microstructure 26g includes microstructures with different shapes within a common array. It can also be, for example, by Figure 4The microstructures shown in [the reference] are combined to implement other distributions of the CDTI microstructure 26.

[0042] Figures 5A to 5C is an exemplary graph of the quantum efficiency (QE) of channels according to an embodiment of the technology of the present invention. The horizontal axis of the graph shows the wavelength of the incoming light in nanometers. The vertical axis shows the quantum efficiency (QE) of pixels (channels) in a Bayer pattern (B, Gb, Gr, R). The illustrated pattern includes pixels with a pitch of 1.4 μm and without CDTI ( Figure 5A ), CDTI in four pixels ( Figure 5B ), and CDTI in one pixel ( Figure 5C ). The infrared (IR) spectrum is generally considered to extend from about 700 nm to about 1000 nm, or correspond to a wavelength band centered at about 850 nm. Generally, the higher the QE is preferably, the higher the sensitivity of the pixel to the corresponding light wavelengths associated with the color channels and the IR channel. However, the pixels in the pixel array should also preferably have different QEs for incoming light of different wavelengths to improve the differentiation.

[0043] Now turn attention to Figure 5A , within the IR spectrum (e.g., near 850 nm), the QE of all channels arranged in a Bayer pattern is in the range of about 10% to 20%. This QE level may not be sufficient to achieve high-performance (e.g., high-sensitivity) channels. Additionally, since all channels have similar QEs within the IR spectrum, the illustrated pixel array may not be suitable for determining visible light information, as non-IR pixels have a response comparable to that of IR pixels.

[0044] Now turn attention to Figure 5B , with respect to the IR spectrum (e.g., near 850 nm), the QE of all channels arranged in a Bayer pattern is in the range of about 40% to 50%. In some embodiments, the increase in the QE level compared to Figure 5A is due to the CDTI microstructure guiding more light towards the corresponding photodiodes of the pixels (channels). In some embodiments, this QE level is considered sufficient to achieve high-performance channels. However, all channels are still characterized by having comparable QEs, so the pixel array may not be suitable for sensing the IR spectrum, similar to the scenario described in connection with Figure 5A .

[0045] Now turn attention to Figure 5C, within the IR spectrum, the QE of all channels in the Bayer pattern is in the range of approximately 10% to 30%. The illustrated single-pixel array contains only one CDTI microstructure in one color channel, in contrast to the 4-pixel array (i.e., one CDTI microstructure / pixel) with four CDTI microstructures in all four color channels shown in FIG. 5B. At the same wavelength, the QE values are typically between Figure 5A the QE value of Figure 5B and the QE value of

[0046] . However, the four pixels still feature a comparable QE within the IR spectrum, without showing significant differences. Figures 6A to 7B The comparable QE levels described above may indicate strong crosstalk between pixels. Some embodiments of filtering for improving the QE difference of pixels in the IR spectrum are described below with reference to

[0047] Figure 6A is a diagram of an exemplary layer of an image sensor according to an embodiment of the technology of the present invention. Figure 6B FIG. shows a perspective view of an image sensor according to an embodiment of the technology of the present invention. In some embodiments, the pixel array 120 includes the plurality of photodiodes 280, a color filter layer 260 stacked above the filter layer 270, and the color filter layer 260 is in turn stacked above the plurality of photodiodes 280. The microlens 22, the color filter 260i, the filter 270i, and the corresponding photodiode 280i can together form a unit pixel (e.g., Figure 1 pixel 11).

[0048] In some embodiments, the filter layer 270 has a first side 272 facing the plurality of photodiodes 280 and a second side 274 opposite the first side 272. The color filter layer 260 has a first surface 262 facing the second side 274 of the filter layer 270 and a second surface 264 opposite the first side 272 of the filter layer 270. In other words, the color filter layer 260 is formed on the second side 274 of the filter layer 270. The plurality of microlenses 22 are disposed near the second surface 264 of the color filter layer 270 and direct the incoming light 20 to the corresponding photodiodes 280i.

[0049] In operation, the incoming light 20 propagates through the color filter layer 260 and through the filter layer 270 to reach the photodiodes 280. In some embodiments, the individual fields (regions) 260i of the color filter layer 260 and the individual fields (regions) 270i of the filter layer 270 generally correspond to the individual photodiodes 280i. In other embodiments, the individual fields of the color filter layer 260 and / or the individual fields of the filter layer 270 may cover a plurality of individual photodiodes 280i.

[0050] In some embodiments, the distribution of color filters 260i (e.g., blue (B) filter, green (G) filter, red (R) filter, infrared (IR) filter) corresponds to photodiodes 280i of the photodiode layer 280. Each photodiode 280i operates to generate charge corresponding to the absorption of a specific wavelength filtered by the corresponding color filter. The color filters 260i may be arranged according to a specific color pattern (e.g., the Bayer pattern or mosaic of red filter, green filter, blue filter, and IR filter (e.g., B, G, G, IR or R, G, G, IR)) to transmit blue light, green light, red light, and IR light accordingly. When the incoming light 20 passes through the color filter layer 260, the individual color fields or color regions of the color filters 260i allow light within a specific wavelength bandwidth (e.g., B, G, R, IR) to pass through while significantly rejecting other wavelengths. The incoming light 20 further propagates through the filter layer 270. Here, the fields 270i may be configured to act as a band-reject filter and block the IR wavelength ("Block"), act as a band-pass filter and allow all wavelengths to pass through ("Clear"), or act as a band-pass filter but only allow the IR wavelength to pass through ("Pass") while rejecting light in the visible spectrum. In other words, each of the individual fields 270i in the filter layer 270 is operable to further selectively filter the light wavelength (e.g., allow a specific range of light wavelengths to pass through or reject a specific range of light wavelengths) after the incoming light 20 has been filtered by the corresponding individual color fields or color regions of the color filter.

[0051] For example, analyzing the optical path color filter corresponding to the photodiode 280i (referred to as the IR photodiode) associated with the IR filter in the upper left section (row 2, column 2), the corresponding filter 260i ("IR") allows the incoming IR light to pass through and direct it towards the filter layer 270, and then the filter layer 270 allows all infrared light to pass through towards the corresponding photodiode 280i by means of a "Pass" filter for this area. Thus, the IR illumination of the IR photodiode 280i in the upper left corner is maximized. Additionally, for example, analyzing the light path of the photodiode 280i (referred to as the blue photodiode) associated with the blue filter in the upper left corner (row 1, column 1), the corresponding color filter 260i ("B") allows the incoming blue light to pass through towards the filter layer 270 for this area, and then the filter layer 270 blocks the infrared light and allows visible light (e.g., blue light) to pass through by means of a "Block" filter. Thus, the corresponding blue photodiode 280i has a relatively limited QE, and the IR radiation contributed to the adjacent diagonal IR photodiode 280i is also relatively limited. Further, analyzing the light path of the photodiode 280i (referred to as the green photodiode) associated with the green filter in the upper row (row 1, column 2 or 4) of the photodiode layer, the corresponding color filter 260i ("G") allows the incoming green light to pass through towards the filter layer 270, and the filter layer 270 allows all wavelengths to pass through by means of a "Clear" filter for this area. Thus, the corresponding G photodiode 280i will have a relatively high QE. Additionally, the adjacent lateral IR photodiode 280i can receive additional radiation, which will increase its QE at IR wavelengths, as explained below.

[0052] The "Block" filter of the filter layer 270 is an IR rejection filter that operates to reject infrared light, such as light having a wavelength greater than 850 nm. The "Block" filter of the filter layer 270 can be implemented by a band-reject filter. In one embodiment, the band-reject filter can be formed of a material that blocks IR light and allows visible light to pass through. The "Pass" filter of the filter layer 270 can be implemented by a band-pass filter, and the "Pass" filter allows infrared light (such as light having a wavelength greater than 850 nm) to pass through the corresponding photodiode 280i, such as the photodiode 280i of an IR pixel (channel). In one embodiment, the band-pass filter can be formed of a material that allows IR light to pass through and blocks light in the visible light spectrum. The "Clear" filter of the filter layer 270 can be formed of a transmissive or transparent material and operates to allow all light (such as visible light and infrared light) to pass through toward the corresponding photodiode 280i, such as a green pixel (channel). Those skilled in the art will understand the selection of materials and processes for forming the filter layer 270 that includes a "Block" filter for blocking IR light, a "Pass" filter for allowing IR light to pass through, and a "Clear" filter for allowing all light to pass through. Accordingly, some details are omitted for the sake of brevity and conciseness of the description.

[0053] In some embodiments, the "Pass" filter can be arranged to be located between the ("IR") color filter 260i (IR color filter) and the corresponding photodiode 280i (IR channel). The "Pass" filter can be surrounded by a "clear-through" filter. In some embodiments, the ("G") color filter 260i is disposed adjacent to the side of the ("IR") color filter 260i (IR color filter), and the "Clear" filter is arranged to be located between the ("G") color filter 260i (G color filter) and the corresponding photodiode 280i (G channel). In some embodiments, the ("B") color filter 260i is disposed diagonally with respect to the ("IR") color filter 260i (IR color filter), and the "Block" filter is arranged to be located between the ("B") color filter 260i (G color filter) and the corresponding photodiode 280i (B channel). In some embodiments, the ("R") color filter 260i is disposed diagonally with respect to the ("IR") color filter 260i (IR color filter), and the "Block" filter is arranged to be located between the ("R") color filter 260i (G color filter) and the corresponding photodiode 280i (R channel).

[0054] Figures 7A to 7DIt is a graph of the quantum efficiency (QE) of a channel according to an embodiment of the technology of the present invention. The horizontal axis in each graph shows the optical wavelength in nanometers, and the vertical axis shows the QE. The dashed boxes in each graph mark the wavelength bands of interest within the total IR spectrum.

[0055] Figure 7A Shows the QE of a Bayer arrangement of pixels (channels) without using a CDTI or filter layer. At a wavelength of approximately 850 nm, the QE of all pixels is approximately 25%. In many applications, this QE level is considered insufficient and / or the difference is insufficient.

[0056] Figure 7B Shows the QE of a pixel arrangement including the color filter layer 260 and the filter layer 270 shown in FIG. 6. The blue channel and the red channel have a relatively low QE of approximately 3% at 850 nm, while the green channel and the IR channel have a relatively high QE of approximately 20% within the wavelength band of interest at approximately 850 nm. Therefore, it can be considered that the channel separation is sufficient, but the absolute value of the QE of the IR channel may be too low for some applications.

[0057] Figure 7C Shows the QE of a pixel arrangement including a CDTI microstructure above the green photodiode and the IR photodiode in addition to the color filter layer 260 and the filter layer 270 shown in FIG. 6. In this case, the blue channel and the red channel have a relatively high QE of approximately 20% at 850 nm, while the green channel and the IR channel have a QE of approximately 35% to 40% within the wavelength range of approximately 850 nm. Therefore, the absolute value of the QE of the IR channel may be sufficient for some applications. However, the channel separation between the blue channel and the red channel on one side and the green channel and the IR channel on the other side may be insufficient for some applications. In other words, compared with the green channel and the IR channel, the blue and red channels may have too high a QE to achieve sufficient channel separation.

[0058] Figure 7D Shows the QE of a pixel arrangement including a CDTI microstructure placed in the IR photodiode region in addition to the color filter layer 260 and the filter layer 270 shown in FIG. 6. In this case, Figure 7DCompared with the QE shown in [reference], all channels have slightly lower QE. This result can be attributed to the lack of CDTI structure above the green channel. Therefore, the QE of the red and blue channels at 850 nm is about 7%, while the green and IR channels have a QE of about 25% to 30% at wavelengths close to 850 nm. In some applications, channel separation can be defined as the QE of the blue and red channels at 850 nm being 10% less than the QE of the IR channel. Therefore, the channel separation between the blue and red channels on one side and the green and IR channels on the other side can be sufficient (about a 1:3 ratio), and the absolute value of the QE of the IR channel (25% to 30%) can also be sufficient for some applications. In many embodiments, an IR or NIR image sensor should meet these two requirements: the absolute value of the QE of the IR channel and the channel separation requirement. The following refers to Figures 8A to 12B Describes some combinations of CDTI patterns and color filters and filters.

[0059] Figure 8A FIG. [reference] is a diagram of an example of an image sensor 120 according to an embodiment of the technology of the present invention. The illustrated image sensor 120 includes a CDTI microstructure 26 disposed within a photodiode of an IR channel to redistribute light within the photodiode region to improve IR sensitivity. The illustrated embodiment may include a square array pattern of CDTI microstructures, but other patterns may also be used. In the illustrated embodiment, the square CDTI microstructure 26 may have a square structure in a cross-sectional view. The square CDTI microstructures 26 may be arranged with equal spacing within the respective photodiodes. In some embodiments, the illustrated image sensor 120 may also include a color filter layer 260 and a filter layer 270 as shown in FIG. 6, for example.

[0060] Figure 8B is Figure 8A A graph of the quantum efficiency (QE) of the image sensor shown in [reference]. For the illustrated embodiment, the blue and red channels have a QE of about 7% at 850 nm, while the green and IR channels have a QE of about 25% to 30% within the spectral range of interest close to 850 nm. Therefore, for some applications, the absolute value of the QE of the IR channel and the channel separation between the blue and red channels on one side and the green and IR channels on the other side can be sufficient.

[0061] Figure 9AFIG. is a diagram of another example of an image sensor 120 in accordance with an embodiment of the technology of the present invention. The illustrated image sensor 120 includes CDTI microstructures 26 disposed within the photodiodes of the IR channel and the green channel to improve IR sensitivity by diffracting, reflecting, and / or refracting light within the photodiode region of the IR channel and guiding light toward the IR channel in an adjacent green channel. Without being bound by theory, it is believed that an additional CDTI microstructure pattern located above the green channel or G channel can guide additional light into the IR photodiode toward the adjacent side of the IR channel. The illustrated embodiment includes an 8-square CDTI array pattern, but other patterns may be used depending on the pixel size and the spacing between the square CDTI microstructures 26 to achieve a desired quantum efficiency for the corresponding pixels. In some embodiments, the illustrated image sensor 120 may also include a color filter layer 260 and a filter layer 270 as shown in FIG. 6.

[0062] Figure 9B is Figure 9A A graph of the quantum efficiency (QE) of the image sensor shown in. For the illustrated embodiment, the blue and red channels have a QE of approximately 13% at 850 nm, while the green and IR channels have a QE of approximately 30% within the spectrum of interest near 850 nm. Thus, both the absolute value of the QE of the IR channel (approximately 30%) and the channel separation between the blue and red channels on one side and the green and IR channels on the other side (higher by approximately 10%) may be sufficient for some applications.

[0063] Figure 10A FIG. is a diagram of yet another example of an image sensor 120 in accordance with an embodiment of the technology of the present invention. The illustrated image sensor 120 includes CDTI microstructures 26 within the respective photodiodes associated with the IR channel and the G channel. The illustrated embodiment includes a square CDTI microstructure pattern for the IR channel and a strip pattern located above the green channel. In some embodiments, the illustrated image sensor 120 may also include a color filter layer 260 and a filter layer 270.

[0064] Figure 10B is Figure 10A A graph of the quantum efficiency (QE) of the image sensor shown in. For the illustrated embodiment, the blue and red channels have a QE of approximately 13% at 850 nm, while the green and IR channels have a QE of approximately 32% within the spectrum of interest near 850 nm. Thus, both the absolute value of the QE of the IR channel and the channel separation between the blue and red channels on one side and the green and IR channels on the other side may be sufficient for some applications.

[0065] Figure 11A It is a diagram of another example of the image sensor 120 according to an embodiment of the technology of the present invention. The illustrated image sensor 120 includes CDTI microstructures 26 within corresponding photodiodes associated with the IR channel and the G channel. The illustrated embodiment includes a square CDTI microstructure pattern above the IR channel and a strip-shaped CDTI pattern above the green channel. Figure 11A The strip-shaped CDTI pattern in Figure 10A is longer than the strip-shaped CDTI pattern shown in

[0066] Figure 11B is Figure 11A A graph of the quantum efficiency (QE) of the image sensor shown in Figure 10B For the illustrated embodiment with the longer strip-shaped CDTI microstructure pattern, the blue and red channels have a QE of approximately 10% at 850 nm, which is a smaller QE than the QE shown in

[0067] Figure 12A In at least some embodiments, it may be beneficial to reduce the QE of the blue and red channels. The IR channel has a QE of approximately 40% within the spectrum of interest near 850 nm. Thus, both the absolute value of the QE of the IR channel and the channel separation between the blue and red channels on one side and the IR channel on the other side may be sufficient for some applications.

[0068] Figure 12B It is a diagram of another example of the image sensor 120 according to an embodiment of the technology of the present invention. The illustrated image sensor 120 includes CDTI microstructures 26 above the IR channel and the green channel. The illustrated embodiment includes a square CDTI pattern for the IR channel. The CDTI microstructure pattern arranged within the photodiode associated with the green channel adjacent to the IR channel includes both strips and arcuate members (or curved microstructures) to direct light from the adjacent green channel towards the IR channel to improve IR sensitivity. The curvature of the arcuate member or curved microstructure can be configured based on the desired light guiding requirements (e.g., the amount of light to be guided from the green channel to the IR channel). In some embodiments, the illustrated image sensor 120 may also include a color filter layer 260 and a filter layer 270.Yes Figure 12A is a graph of the quantum efficiency (QE) of the image sensor shown in Figure 12A . Here, the blue and red channels have a QE of approximately 12% at 850 nm, which is slightly higher than the QE shown in Figure 12A . Figure 11B The IR channel has a QE of approximately 40% within the spectrum of interest near 850 nm. Thus, both the absolute value of the QE of the IR channel and the channel separation between the blue and red channels on one side and the IR channel on the other side may be sufficient for some applications.

[0069] Many embodiments of the techniques described above may take the form of computer-executable instructions or controller-executable instructions, including routines executed by a programmable computer or controller. Those skilled in the relevant art will appreciate that the techniques may be practiced on a computer / controller system in addition to the systems shown and described above. The techniques may be included in a special-purpose computer, an application-specific integrated circuit (ASIC), a controller, or a data processor that is specially programmed, configured, or constructed to execute one or more of the computer-executable instructions described above. Of course, any logic or algorithm described herein may be implemented in software or hardware or a combination of software and hardware.

[0070] The description of the examples of the invention illustrated above (including what is described in the abstract of the invention) is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Although specific examples of the invention are described herein for illustrative purposes, those skilled in the relevant art will recognize that various modifications can be made within the scope of the invention.

[0071] Such modifications can be made to the invention in light of the above detailed description. The terms used in the appended claims should not be construed as limiting the invention to the specific examples disclosed in this specification. Rather, the scope of the invention will be determined entirely by the appended claims, which are to be interpreted in accordance with established principles of claim interpretation.

Claims

1. An image sensor, which comprises: a plurality of photodiodes arranged in rows and columns of a pixel array; a filter layer including a plurality of filters disposed above the plurality of photodiodes, the plurality of filters including a blocking filter, a pass-through filter, and a through filter, the filter layer having a first side facing the plurality of photodiodes and a second side opposite the first side; a color filter layer including a plurality of color filters disposed above the plurality of photodiodes, the plurality of color filters including a blue filter, a green filter, a red filter, and an infrared filter, the color filter layer having a first surface facing the second side of the filter layer and a second surface opposite the first side of the filter layer; and a plurality of microlenses disposed adjacent to the second surface of the color filter layer, wherein individual microlenses are configured to direct incoming light through corresponding filters and color filters to respective photodiodes, wherein the pass-through filter is configured to transmit the wavelength of the incoming light, the blocking filter is configured to block incoming infrared light, and the through filter is configured to transmit incoming infrared light.

2. The image sensor according to claim 1, wherein the plurality of photodiodes include an infrared channel, a green channel, a red channel, and a blue channel configured to respond to corresponding wavelengths of the incoming light, wherein the plurality of color filters comprise: the blue filter configured to transmit blue light, the green filter configured to transmit green light, the red filter configured to transmit red light, and the infrared filter configured to transmit infrared light, and wherein the through filter is disposed between the infrared channel and the infrared filter.

3. The image sensor according to claim 2, wherein the green channel is disposed adjacent to a side of the infrared channel, and wherein the pass-through filter is disposed between the green channel and the green filter.

4. The image sensor according to claim 2, wherein the blue channel is disposed diagonally with respect to the infrared channel, and wherein the blocking filter is disposed between the blue channel and the blue filter.

5. The image sensor according to claim 2, wherein the red channel is disposed diagonally with respect to the infrared channel, and wherein the blocking filter is disposed between the red channel and the red filter.

6. The image sensor according to claim 1, wherein an individual photodiode among the plurality of photodiodes includes a microstructure disposed in a semiconductor material of the photodiode.

7. The image sensor according to claim 6, wherein the microstructure is a unit deep trench isolation microstructure.

8. The image sensor according to claim 1, wherein the plurality of photodiodes include an infrared channel, a green channel, a red channel, and a blue channel configured to respond to corresponding wavelengths of the incoming light, and wherein the infrared channel includes a microstructure disposed in a semiconductor material of the infrared channel.

9. The image sensor according to claim 8, wherein the microstructure is a first microstructure, and the image sensor further includes a second microstructure disposed in the semiconductor material of the green channel, wherein the green channel is disposed adjacent to a side of the infrared channel.

10. The image sensor according to claim 9, wherein the second microstructure is configured to direct the incoming light toward the infrared channel.

11. The image sensor according to claim 8, wherein the blue channel is disposed diagonally with respect to the infrared channel, and wherein the semiconductor material of the blue channel does not have a microstructure.

12. The image sensor according to claim 8, wherein the red channel is disposed diagonally with respect to the infrared channel, and wherein the semiconductor material of the red channel does not have a microstructure.

13. The image sensor according to claim 8, wherein the microstructure includes a plurality of unit deep trench isolation microstructures.

14. The image sensor according to claim 13, wherein individual microstructures among the plurality of unit deep trench isolation microstructures have the same shape and size.

15. The image sensor according to claim 13, wherein individual microstructures among the plurality of unit deep trench isolation microstructures have different shapes or sizes.

16. The image sensor according to claim 13, wherein the microstructure includes features extending to different depths within the semiconductor material.

17. The image sensor according to claim 9, wherein the first microstructure and the second microstructure each include a plurality of unit deep trench isolation microstructures.

18. The image sensor according to claim 17, wherein the second microstructure includes a plurality of elongated microstructures parallel to the side of the infrared channel.

19. The image sensor according to claim 18, wherein the second microstructure includes at least one curved microstructure bent toward the side of the infrared channel.

20. The image sensor according to claim 9, wherein the first microstructure includes a plurality of square microstructures, and wherein the second microstructure includes a plurality of elongated microstructures parallel to the side of the infrared channel.

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