Image sensor

Abstract

Various embodiments of the present disclosure relate to image sensors. The present disclosure relates to an image sensor comprising a plurality of pixels formed in and on a semiconductor substrate and arranged in a matrix having N rows and M columns, where N is an integer greater than or equal to 1 and M is an integer greater than or equal to 2. A plurality of microlenses face the substrate, and each of the microlenses is associated with a corresponding pixel. The microlenses are arranged in a matrix in N rows and M columns, and the pitch of the microlens matrix is greater than the pitch of the pixel matrix in the row direction of the pixel matrix.

Description

Technical Field

[0001] The present disclosure relates generally to the field of image sensors and more particularly to an image sensor comprising a pixel matrix formed in and on a semiconductor substrate and capped by a microlens matrix. Background Art

[0002] An image sensor typically comprises a plurality of pixels formed in and on a semiconductor substrate and arranged in rows and columns in the form of a matrix. Each pixel typically comprises a photosensitive area in which incident light is converted into electron-hole pairs, and one or more control transistors making it possible to read a signal representing the amount of photogenerated charge in the photosensitive area. The photosensitive area of a pixel thus occupies only a portion of the pixel surface. In order to compensate for the loss of collection surface associated with the fill factor of the pixel and to increase the sensitivity of the pixel, it has been proposed to arrange a microlens on each pixel, which extends substantially over the entire surface of the pixel and is configured to focus the incident light on the photosensitive area of the pixel.

[0003] It would be desirable to at least partially improve certain aspects of known image sensors that include a matrix of pixels formed in and on a semiconductor substrate and capped by a matrix of microlenses. Summary of the Invention

[0004] To this end, one embodiment provides an image sensor comprising: a plurality of pixels formed in and on a semiconductor substrate and arranged in a matrix having N rows and M columns, where N is an integer greater than or equal to 1, and M is an integer greater than or equal to 2; and, for each pixel, a microlens associated with the pixel, the microlens facing the substrate, the microlenses being arranged in a matrix in N rows and M columns, wherein, in the direction of the rows of the pixel matrix, a pitch of the microlens matrix is greater than a pitch of the pixel matrix.

[0005] According to one embodiment, the optical axis of each microlens passes through the center of the light-sensitive area of the pixel to which it is associated.

[0006] According to one embodiment, the microlens matrix comprises off-axis microlenses.

[0007] According to one embodiment, N is greater than or equal to 2, and, in the direction of the columns of the pixel matrix, the pitch of the microlens matrix is greater than the pitch of the pixel matrix.

[0008] According to one embodiment, pixels in the plurality of pixels have the same size in a row direction of the pixel matrix and in a column direction of the pixel matrix.

[0009] According to one embodiment, the microlenses in the plurality of microlenses have the same size in the direction of the rows of the pixel matrix and in the direction of the columns of the pixel matrix.

[0010] According to one embodiment, the microlenses of the plurality of microlenses have different sizes in the direction of the rows of the pixel matrix and / or in the direction of the columns of the pixel matrix.

[0011] According to one embodiment, the surface of each microlens is larger when the distance between the central axis of the microlens and the central axis of the pixel associated therewith is large.

[0012] According to one embodiment, the sensor comprises optical spacers arranged between the pixel matrix and the microlens matrix.

[0013] According to one embodiment, the microlenses are refractive microlenses or diffractive microlenses.

[0014] According to one embodiment, the microlenses are diffractive microlenses of the FZP type.

[0015] According to one embodiment, the microlenses are diffractive microlenses of the meta-surface type. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above features and advantages, as well as other features and advantages, are detailed in the following description of specific embodiments, which are given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0017] Figure 1A schematically illustrates a top view of an example of an image sensor; and Figure 1B Schematically shows Figure 1A A cross-sectional view of the image sensor shown;

[0018] Figure 2A schematically illustrates a top view of an example of an image sensor according to one embodiment; and Figure 2B Schematically shows Figure 2A A cross-sectional view of the image sensor shown;

[0019] Figure 3 schematically illustrates an example microlens of the image sensor of FIG2 ;

[0020] Figure 4 illustrates a variation of the image sensor of FIG. 2 ;

[0021] Figure 5 Another embodiment variation of the image sensor of FIG. 2 is shown;

[0022] Figure 6 Shown Figure 5 An exemplary embodiment of a microlens for an image sensor;

[0023] Figure 7 Another embodiment variation of the image sensor of FIG. 2 is shown;

[0024] Figure 8 shows another embodiment variation of the image sensor of FIG. 2 ; and

[0025] Figure 9 Another embodiment variant of the image sensor of FIG. 2 is shown. DETAILED DESCRIPTION

[0026] In the various drawings, the same features have been denoted by the same reference numerals. In particular, structural and / or functional features common to the various embodiments may have the same reference numerals and may have the same structural, dimensional, and material properties.

[0027] For the sake of clarity, only the operations and elements useful for understanding the embodiments described herein are illustrated and described in detail. In particular, the disclosed embodiments of the pixel matrix and peripheral control circuits of the image sensor are not described in detail, as the disclosed embodiments are compatible with conventional embodiments of these elements.

[0028] Unless otherwise specified, when referring to two elements being connected together, this means a direct connection without any intermediate elements other than conductors, and when referring to two elements being coupled together, this means that the two elements may be connected or the two elements may be coupled via one or more other elements.

[0029] In the following disclosure, unless otherwise stated, when reference is made to absolute position qualifiers (such as terms "front", "back", "top", "bottom", "left", "right", etc.) or relative position qualifiers (such as terms "above", "below", "higher than", "lower than", etc.) or directional qualifiers (such as "horizontal", "vertical", etc.), reference is made to the orientation shown in the accompanying drawings, and it should be understood that in practice, the described device may be oriented differently.

[0030] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "approximately" mean within 10%, and in some embodiments, within 5%.

[0031] FIG1 schematically illustrates an example of an image sensor 100. FIG1 more specifically includes a top view of the sensor 100 ( Figure 1A ) and the cross-section along plane BB ( Figure 1B ).

[0032] The sensor 100 includes a plurality of pixels P formed in and on a semiconductor substrate 101, for example, made of silicon. The pixels P have, for example, the same size so as to be dispersed within any processing. For example, in a top view, the pixels P have a square or rectangular shape. In the accompanying drawings, the pixels P are laterally delimited by dotted lines. The pixels P are regularly arranged in a matrix of M columns by N rows, where M and N are integers greater than or equal to 2. In the illustrated example, a matrix of M=4 by N=4 pixels has been shown. In practice, the matrix may include more rows and columns.

[0033] Each pixel includes a photosensitive region PD formed in a substrate 101. Each pixel may also include control elements, such as one or several control transistors (not described in detail in the figure), which are formed in and on the substrate 101, for example, in a peripheral area of the pixel, around the photosensitive region PD of the pixel (in a top view).

[0034] The sensor 100 further includes a peripheral circuit CP (not described in detail in the figure), which is formed in and on the substrate 101 and is arranged in a peripheral area of the sensor, around the pixel matrix P (in a top view). The peripheral circuit CP may include, for example, a power supply, control and / or readout circuits for the pixel matrix P, and / or a metallization layer for connecting the sensor to external devices.

[0035] FIG1 also shows a stack of insulating and conductive layers (not described in detail in the figure) on one side of the upper surface of the substrate 101, also called an interconnect stack, on which traces, vias and metal contacts can be formed for interconnecting the pixels P with the peripheral circuit CP of the sensor. In the example shown, the interconnect stack 103 is arranged on the side of the illumination face of the substrate 101, that is, on the Figure 1B In the orientation of the cross-sectional view of FIG, the interconnect stack 103 is arranged on one side of the upper surface of the substrate 101. This is a so-called front-side illuminated (FSI) sensor. As a variant, the interconnect stack 103 can be arranged on the side opposite to the illuminated side of the substrate 101, that is, on the Figure 1B In the orientation of the cross-sectional view of FIG, the interconnect stack 103 is arranged on one side of the lower surface of the substrate 101. This is a so-called backside illumination (BSI) sensor. Although the examples shown in the drawings and disclosed in this disclosure are all related to FSI type sensors, the disclosed embodiments can of course be configured for BSI type sensors.

[0036] For each pixel P, the sensor 100 further comprises a microlens L, which is arranged on the illumination surface of the pixel, that is, on the Figure 1BIn the cross-sectional view of FIG, the microlenses L are arranged on the upper surface of the pixel. In the illustrated example, each microlens L has a surface substantially equal to the surface of the underlying pixel P, as viewed from above, and is arranged substantially above the underlying pixel P. Thus, the set of microlenses L defines a matrix having M×N microlenses, with the pitch of the microlens matrix L (i.e., the center distance between two adjacent microlenses of the microlens matrix) and the pitch of the pixel matrix P (i.e., the center distance between two adjacent pixels of the pixel matrix) being substantially the same in the row direction, and the pitch of the microlens matrix L and the pitch of the pixel matrix P being substantially the same in the column direction.

[0037] Each microlens L is configured to focus light received on its upper surface toward the photosensitive area PD of the pixel below. In this example, the optical axis AL of each microlens L is substantially orthogonal to the upper surface of the substrate 101 (at Figure 1B The orientation of the cross-sectional view of FIG is vertical), and the optical axis AL passes through the center of the photosensitive area PD of the pixel as seen from above (in this example, coinciding with the center of the pixel).

[0038] In the example of FIG1 , it is assumed that light arrives at the upper surface of the sensor 100 at normal incidence. In the case of a large-sized sensor configured to be placed behind a compact objective lens, for example, in the case of an image sensor embedded in a smartphone, light typically arrives at pixels located near the center of the pixel matrix at normal incidence, but may arrive at pixels located near the edge of the pixel matrix at a relatively strong inclination. In this case, a microlens L having a size slightly smaller than that of the pixel P can be used, and while the offset increases as the microlens moves away from the sensor center, the microlens is offset toward the center of the sensor to compensate for the inclination of the incident light, for example, in the manner described in the article “Microlens design for compact lens system” (Proc. SPIE 5116, Smart Sensors, Actuators, and MEMS, (April 24, 2003)) by H.-J. Hsu, F.-T. Weng, C.-K. Chang, and Y.-K. Hsiao. In this case, the spacing of the microlens matrix L can be smaller than the spacing of the pixel matrix P in both the row and column directions.

[0039] As an example, the microlens L can be formed by resin contact creep, optionally followed by shape transformation, for example, in the manner disclosed in the article “Advanced microlens and color filterprocess technology for the high-efficiency CMOS and CCD image sensors” by Y.-T. Fan, C.-S. Peng and C.-Y. Chu (SPIE, 2000, vol. 4115, p. 263-274) and in the article “A Microlens Reactive Ion Etching Process Study on CMOS Image Sensor-Wen-HaoLo” by P.-C. Huang, C.-H. Ting, K.-F. Huang and T.-S. Tzeng (2018 e-Manufacturing & Design Collaboration Symposium (eMDC), p. 1-3). As a variant, the microlenses L can be formed by nanoprinting, for example, in the manner described in the article "High fidelity fabrication of microlens arrays by nanoimprintusing conformal mold duplication and low-pressure liquid material curing" by C. Peng, X. Liang, Z. Fu and SY Chou (J. Vac. Sci. Technol. B Microelectron. Nanometer Struct., vol. 25, no. 2, p. 410, 2007), or by grayscale lithography, for example, in the manner disclosed in the article "Grayscale lithography process study applied to zero-gap microlenses for sub-2 μm CMOS image sensors" by S. Audran et al. (Proceedings of SPIE, 2010, pp. 763910–763910).

[0040] The method disclosed above results in the formation of a refractive microlens of the planar-convex type, that is to say comprising a substantially flat lower surface or base in contact with the upper surface of the pixel and a convex upper surface. As a variant, the microlens L can be composed of a diffractive structure operating in a limited wavelength range, for example, in the manner disclosed in the article "A MOS Image Sensor With a Digital-Microlens" by K. Onozawa et al. (IEEE Trans. Electron Devices, vol. 55, no 4, p. 986 991, April 2008) or in the article "A 256x256 45 / 65nm 3D-stacked SPAD-based direct TOF image sensor for LiDAR applications with optical polar modulation for up to 18.6dB interference suppression" by A.R. Ximenes, P. Padmanabhan, M.J. Lee, Y. Yamashita, D.N.Yaung and E. Charbon (2018 IEEE International Solid-State Circuits Conference-(ISSCC), 2018, p. 96 98). As a variation, the microlens L is a metasurface lens, as disclosed, for example, in the article “Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmit arrays” by A. Arbabi et al. (Nature Communications, vol. 6, p. 7069, May 2015) or the article “Concept of non-periodic metasurfaces based on positional gradients applied to IR-flat lenses” by M. Gonidec (Opt. Mater. Express 7, 2346-2351 (2017)).

[0041] One limitation of the sensor of FIG. 1 is that the surface occupied by the peripheral circuitry CP is not used to collect light.

[0042] According to one aspect of an embodiment, an image sensor is provided. The image sensor includes: a pixel matrix formed in and on a semiconductor substrate; and a microlens matrix overlying the pixel matrix. The microlenses are larger than the pixels. By utilizing all or part of the surface occupied by circuitry (CP) at the periphery of the pixel matrix as a light-collecting surface, a larger light-collecting surface is obtained for each pixel. Thus, the pitch of the microlens matrix is larger than the pitch of the pixel matrix. Consequently, the sensor has improved sensitivity compared to a sensor in which the microlenses are smaller than or equal to the pixel size.

[0043] FIG2 schematically illustrates an example of an image sensor 200 according to one embodiment. FIG2 more specifically includes a top view of the sensor 200 ( Figure 2A ) and the cross-section along plane BB ( Figure 2B ).

[0044] The main difference between the sensor 200 of FIG. 2 and the sensor 100 of FIG. 1 is the size of its microlens matrix.

[0045] Similar to the example of FIG1 , each pixel P of the sensor 200 includes a microlens L, or M×N microlenses L, which are arranged on one side of the illumination surface of the sensor, that is, on the Figure 2B In the orientation of the cross-sectional view of FIG, the microlens L is arranged on one side of the upper surface of the sensor.

[0046] In the example of FIG2 , in top view, the surface of each microlens L is larger than the surface of the pixel P associated with that microlens L. More specifically, the size of each microlens is larger than the size of the pixel P associated with that microlens in both the row and column directions. Similar to the example of FIG1 , the microlenses L are coplanar, that is, the substantially planar bases of the microlenses L are arranged in the same plane, which in the illustrated example corresponds to the upper surface of the interconnect stack 103. Therefore, in top view, the dimensions of the microlens matrix L are larger than the corresponding dimensions of the pixel matrix P in both the row and column directions, and the pitch of the microlens matrix L is larger than the pitch of the pixel matrix P in both the row and column directions. Consequently, the microlens matrix L extends not only over the entire surface of the pixel matrix P, but also over all or part of the sensor's peripheral surface occupied by the peripheral circuitry CP. This increases the collection surface of each pixel P relative to the example of FIG1 , thereby improving the sensitivity of the sensor. It should be noted that if the circuit CP includes metallization layers on one side of the upper surface of the sensor for connecting the sensor to external devices, these metallization layers should remain accessible and therefore should not be covered by the microlenses. Consequently, the connection metallization layers of the sensor will limit the surface available for expanding the microlens matrix.

[0047] In the example of FIG2 , in a top view, the M×N microlenses L all have substantially the same shape, such as a square or rectangular shape, and have the same size (to avoid any processing dispersion), and are evenly distributed in rows and columns. In other words, the pitch of the microlens matrix L is constant in both the row and column directions.

[0048] Each microlens L of the matrix of M×N microlenses is configured to focus light received on its upper surface with the photosensitive area PD of the pixel P associated therewith (i.e., the pixel P having the same coordinates in the sub-matrix of M×N pixels). In this example, the optical axis AL of each microlens L is substantially orthogonal to the upper surface of the substrate 101 (at Figure 2B The orientation of the cross-sectional view of FIG is vertical), and the optical axis AL passes through the center of the photosensitive area PD of the pixel as seen from above (in this example, coinciding with the center of the pixel).

[0049] In the example of Figure 2, the microlens L is a so-called off-axis microlens, that is, a microlens whose optical axis is not in the center of the lens in a top view, which ensures that: even if the spacing between the pixel matrix and the microlens matrix is different, the light received by each microlens can still be focused in the photosensitive area PD of the corresponding pixel.

[0050] The microlens L is, for example, a refractive microlens formed by nanoprinting or grayscale lithography, or a diffractive lens (also called a metasurface) formed by a diffractive array of nanoelements, for example, by structuring a planar layer.

[0051] Figure 3 Example microlenses of the image sensor of FIG. 2 are schematically shown.

[0052] In this example, the microlenses are diffractive microlenses of the Fresnel zone plate (FZP) type, each consisting of an array of concentric rings or ring segments formed by photolithography and etching of planar layers. Figure 3 In the figure, for the purpose of simplicity and due to the symmetry of the microlens matrix with respect to its horizontal central axis and vertical central axis, only four microlenses L are shown. These four microlenses L correspond to the components of Figure 2A Four microlenses in the upper left quadrant of the microlens matrix in a top view.

[0053] The optical axis of each microlens L coincides with the center of the concentric ring or ring portion forming the microlens. As mentioned above, the microlens L is an off-axis microlens. Figure 3This is obtained in the example of , by the fact that the centers of the concentric rings or ring parts forming each microlens are offset relative to the center of the microlens. For some microlenses L of the sensor, the optical axis of the microlens may not pass through the microlens. Thus, in Figure 3 In the example of FIG. 4 , the microlens consists only of concentric ring portions whose centers are located outside the microlens.

[0054] Figure 4 Is with Figure 2B The cross-sectional view in the same plane as the cross-sectional view, Figure 4 A variation of the image sensor of FIG. 2 is illustrated.

[0055] Figure 4 The difference between the sensor 400 and the sensor 200 of FIG. 2 is that: Figure 4 The sensor 400 further includes an optical spacer 401 in the form of a transparent planar layer between the upper surface of the interconnect stack 103 and the lower surface of the microlens matrix L. The optical spacer 401 has a thickness of, for example, 5 μm to 50 μm, for example, about 10 μm. The spacer 401 makes it possible to limit or eliminate any stray interactions of the incident light with the peripheral circuitry CP of the sensor and / or with the interconnect metallization layers of the pixels P of the sensor.

[0056] It should be noted that the above description of FIG. Figure 4 The disclosed embodiments are particularly advantageous for low-resolution sensors, for example for M and N less than or equal to 100. In practice, in order to maintain a good light collection efficiency, it is preferred that the offset between the optical axis of the microlens and the central axis of the pixel remains limited. Here, X=x*PP denotes the maximum offset allowed between the optical axis of the microlens L of the sensor and the central axis of the corresponding pixel P, wherein x is preferably less than or equal to 2 and PP denotes the pitch of the pixel matrix. The pitch of the microlens matrix is expressed by PL: PL=(M+2*x) / (M-1)*PP. The contribution gain G in the sensitivity is then: G=((M+2*x) / (M-1))2 (in the case of M=N and taking into account that the pixels on the one hand and the microlenses on the other hand have the same size in the direction of rows and in the direction of columns). For x=2 and M=N=100, a gain of G=1.1036, or approximately 10%, can be obtained.

[0057] The embodiments disclosed above are particularly advantageous in sensors comprising a matrix of small SPADs (Single Photon Avalanche Diodes) sharing the same peripheral circuit CP, eg an M×N SPAD matrix with M and N smaller than or equal to 10, eg M=N=4.

[0058] In particular, a small SPAD matrix can be used to form a SiPM (silicon photomultiplier) type sensor. In this case, M×N SPADs are connected in parallel, which makes it possible to increase the dynamics or add time-correlation filters to filter the detected events. For example, when determining the arrival time of a laser pulse, only events generated within a time window limited to the laser pulse width can be considered. The M×N SPAD matrix can then be considered as the spatial resolution element of the image. Therefore, there are no restrictions on the spatial sampling within the image. In this case, the microlenses can have an irregular spatial distribution. In particular, the microlens matrix can include microlenses of different sizes. This makes it possible to compensate for any differences in microlens efficiency that depend on their position in the matrix. In fact, depending on the technology used to manufacture the microlenses, and particularly in the case of diffractive structures, the light collection efficiency of the microlenses may decrease as the offset between the optical axis of the microlenses and their center increases. To compensate for this decrease, the surface of the microlenses can be modified according to the offset of the optical axis of the microlenses relative to their center.

[0059] Figure 5 Is with Figure 2A The top view of the same orientation, Figure 5 A variation of the image sensor of FIG. 2 is illustrated. Figure 5 The main difference between the sensor 500 and the sensor 200 of FIG. 2 lies in the shapes of the M×N microlenses L.

[0060] exist Figure 5 In the example of , the microlenses may have different shapes and / or sizes depending on their position in the microlens matrix, and it will be understood that the total surface area of each microlens is larger than the surface of the pixel with which it is associated. Figure 5 In the example of , the M×N microlenses all have a square or rectangular shape, but when the offset of the optical axis of the microlens relative to the center of the lens is significant, the microlens has a larger surface.

[0061] Figure 6 Schematically shows Figure 5 An example of a microlens L of an image sensor. In this example, Figure 3 Similarly, in the example of , the microlenses L are diffractive microlenses of the FZP type, which consist of concentric rings or ring parts formed by photolithography and etching of planar layers. Figure 6 For the purpose of simplicity, only four micro lenses L are shown. These four micro lenses L correspond to the components Figure 5 The four microlenses in the upper right quadrant of the microlens matrix.

[0062] Figure 7 and Figure 8 Is with Figure 5 Top view in the same orientation, Figure 7 and Figure 8 Pictured Figure 5 Two variants of the sensor. Figure 7 and Figure 8 The sensors 700 and 800 are Figure 5 The sensors 500 differ primarily in the shape of their M×N microlenses L, which are not necessarily rectangular. Figure 7 In the sensor 700, the microlens matrix includes rectangular microlenses and non-rectangular microlenses. Figure 8 In the sensor 800, the microlens matrix includes only non-rectangular microlenses.

[0063] Figure 9 is Figure 2A The top view of the orientation of the top view, Figure 9 Another embodiment variant of the sensor of FIG. 2 is shown. Figure 9 The main difference between the sensor 900 and the sensor of FIG. 2 is that Figure 9 The sensor 900 does not relate to a two-dimensional sensor (M and N greater than or equal to 2), but rather to a linear sensor comprising a stripe with M pixels arranged in a row (M greater than or equal to 2 and N=1).

[0064] Similar to the example of FIG. 2 , in a top view, the surface of each microlens L is larger than the surface of its associated pixel P. More specifically, in the direction in which the pixels are arranged, the size of each microlens is larger than the size of its associated pixel P. Therefore, in the direction in which the pixels P are arranged, the pitch of the microlens strips L is larger than the pitch of the pixel matrix P. This makes it possible to increase the collection surface of each pixel P and, therefore, improve the sensitivity of the sensor.

[0065] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these embodiments may be combined, and those skilled in the art will readily conceive of other variations. In particular, Figure 4 The variant can be Figure 5 、 Figure 7 、 Figure 8 or Figure 9 In addition, Figure 5 、 Figure 7 or Figure 8 A variation of Figure 9 variants.

[0066] Finally, based on the functional description provided above, the actual implementation of the embodiments and variations described herein is within the capabilities of those skilled in the art.

[0067] The various embodiments described above can be combined to provide further embodiments.

[0068] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments claimed by such claims and the full scope of equivalents. Therefore, the claims are not limited by the disclosure.

Claims

1. An image sensor, comprising: semiconductor substrates; a plurality of pixels formed in and on the semiconductor substrate and arranged in a matrix having N rows and M columns, where N is an integer greater than or equal to 1, and M is an integer greater than or equal to 2; as well as a plurality of microlenses facing the substrate, each of the microlenses being associated with a corresponding pixel, and the microlenses being arranged in N rows and M columns in a matrix form, wherein in a row direction of the pixel matrix, a pitch of the microlens matrix is greater than a pitch of the pixel matrix; The microlenses are Fresnel zone plate type diffraction microlenses, each of which is composed of an array of concentric rings or ring parts formed by photolithography and etching of planar layers, and the optical axis of each microlens coincides with the center of the concentric rings or ring parts. 2 . The image sensor of claim 1 , wherein the optical axis of each microlens passes through the center of the photosensitive area of the pixel associated with the microlens.

3. The image sensor of claim 1, wherein the microlens matrix comprises off-axis microlenses.

4. The image sensor of claim 1 , wherein N is greater than or equal to 2, and wherein: In the column direction of the pixel matrix, a pitch of the microlens matrix is greater than a pitch of the pixel matrix. 5 . The image sensor according to claim 1 , wherein pixels in the plurality of pixels have the same size in a row direction of the pixel matrix and in a column direction of the pixel matrix. 6 . The image sensor according to claim 5 , wherein the microlenses in the plurality of microlenses have the same size in a row direction of the pixel matrix and in a column direction of the pixel matrix. 7 . The image sensor according to claim 5 , wherein the microlenses in the plurality of microlenses have different sizes in a row direction of the pixel matrix or in a column direction of the pixel matrix. 8 . The image sensor of claim 7 , wherein the surface area of each microlens corresponds to the distance between a central axis of the microlens and a central axis of the pixel associated with the microlens. 9 . The image sensor according to claim 1 , further comprising an optical spacer disposed between the pixel matrix and the microlens matrix.

10. The image sensor of claim 9, wherein the optical spacer comprises a transparent planar layer.

11. The image sensor of claim 1, wherein the microlens is at least one of a refractive microlens or a diffractive microlens. 12 . The image sensor according to claim 11 , wherein the microlens is a diffractive microlens of the Fresnel zone plate (FZP) type.

13. The image sensor according to claim 11, wherein the microlens is a diffractive microlens of a metasurface type.

14. An image sensor comprising: a substrate comprising a plurality of pixels arranged in a matrix; as well as a plurality of microlenses arranged in a matrix on the substrate and covering the plurality of pixels, each of the microlenses being associated with a corresponding pixel and having a size larger than the associated pixel, the matrix of the microlenses extending outwardly beyond the periphery of the matrix of the pixels; The microlenses are Fresnel zone plate type diffraction microlenses, each of which is composed of an array of concentric rings or ring parts formed by photolithography and etching of planar layers, and the optical axis of each microlens coincides with the center of the concentric rings or ring parts.

15. The image sensor of claim 14, wherein a center of each microlens is offset relative to a center of the associated pixel. 16 . The image sensor according to claim 14 , wherein a pitch of the microlens matrix is greater than a pitch of the pixel matrix along the row direction and the column direction. 17 . The image sensor of claim 14 , wherein the plurality of microlenses include a first microlens having a first shape, and a second microlens laterally surrounding the first microlens, the second microlens having a second shape different from the first shape. 18 . The image sensor according to claim 14 , further comprising a transparent plane layer between the pixel matrix and the microlens matrix, the transparent plane layer having a thickness ranging from 5 μm to 50 μm.

19. A method of manufacturing an image sensor, comprising: forming a plurality of microlenses over and facing a plurality of pixels in a semiconductor substrate, the plurality of pixels being arranged in a matrix having N rows and M columns, where N is an integer greater than or equal to 1, and M is an integer greater than or equal to 2, each of the microlenses being associated with a corresponding pixel, and the microlenses being arranged in the N rows and M columns in a matrix; wherein, in the direction of the rows of the pixel matrix, the pitch of the microlens matrix is greater than the pitch of the pixel matrix; and The microlens is a Fresnel zone plate type diffraction microlens, each of which is composed of an array of concentric rings or ring parts formed by photolithography and etching of a planar layer, and the optical axis of each microlens coincides with the center of the concentric rings or ring parts.

20. The method of manufacturing an image sensor according to claim 19, further comprising: An optical spacer is formed between the pixel matrix and the microlens matrix.

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