Pixel

Abstract

The invention relates to a pixel. The pixel includes, on the first face, first trenches extending parallel to the first direction and regularly spaced in a second direction (orthogonal to the first direction) and second trenches extending parallel to the second direction and regularly spaced in the first direction. The first trenches include first notches, each first notch extending from the first trench and aligned with a respective second trench. The second trench includes second notches, each second notch extending from the second trench and aligned with a respective first trench.

Description

[0001] Priority claim

[0002] This application claims priority to European Patent Application No. 23306169.6 filed on July 10, 2023, the entire contents of which are incorporated herein by reference to the maximum extent permitted by law. Technical Field

[0003] The present disclosure generally relates to electronic circuits, such as integrated electronic circuits. The present disclosure more particularly relates to integrated circuit pixels, such as pixels (circuits) implemented in a matrix of identical pixels (circuits) in a light sensor, such as a time-of-flight (TOF) sensor. Background Art

[0004] In order to increase the optical path in the silicon of a photodetector of a pixel, such as a single photon avalanche diode (SPAD), it is known to add diffractive structures on the face of the pixel intended for receiving light.

[0005] Figure 1 An example of a face 100 of a silicon photodetector of a pixel Pix1 is shown, which face 100 is used to receive light and is provided with such a diffractive structure. More specifically, Figure 1 is a top view of the structured surface 100 . Figure 1 It is the U.S. patent application publication No. 2022 / 0085084 (corresponding to French patent No. 3114190B1) Figure 2 A simplified reproduction of is incorporated herein by reference.

[0006] Face 100 has two opposite sides (side edges) 102 and 104 parallel to each other and to direction Y, and two opposite sides (side edges) 106 and 108 parallel to each other and to direction X. Direction X is perpendicular to direction Y. In the top view of pixel Pix1, face 100 has a square shape.

[0007] The face 100 is a face of the silicon portion forming the photodetector of the pixel Pix1. The photodetector of the pixel Pix1 is laterally delimited, for example, by an insulating structure 110. The structure 110 is, for example, a capacitive deep trench insulation (CDTI).

[0008] The pixel Pix1 includes a plurality of grooves 112 extending in length along a direction X and a plurality of grooves 114 extending in length along a direction Y. Figure 1 In FIG. 1 , only some of the grooves 112 and 114 are marked with reference numerals in order not to overload the figure. Figure 1 In FIG. 1 , grooves 112 and 114 are indicated by hatching.

[0009] A first portion of groove 112 extends from side 102 to side 104, and a second portion of groove 112 extends from side 104 to side 102. Similarly, a first portion of groove 114 extends from side 106 to side 108, and a second portion of groove 114 extends from side 108 to side 106. Grooves 112 of the first portion of grooves 112 do not join grooves 112 of the second portion of grooves 112. Similarly, grooves 114 of the first portion of grooves 114 do not join grooves 114 of the second portion of grooves 114. Furthermore, grooves 112 do not cross grooves 114.

[0010] U.S. Patent Application Publication No. 2022 / 0085084 (corresponding to French Patent No. 3114190 B1) also discloses other examples of a face of a silicon photodetector of a pixel having first and second trenches, wherein the first trench is perpendicular to the second trench and the first trench does not intersect the second trench.

[0011] These first and second trenches allow increasing the optical path in the silicon of the photodetector, thereby increasing the quantum efficiency of the pixel. Increasing the optical path is particularly important, for example, when the light received and sensed by the pixel is infrared light, for example with a wavelength comprised between 750 nm and 1400 nm, for example equal to about 950 nm, preferably equal to 950 nm.

[0012] Other examples of pixels with photodetectors in silicon are known, wherein the face of the silicon portion corresponding to the photodetector is provided with a first trench and a second trench perpendicular to the first trench.

[0013] Compared to known pixels having the above-described first and second trenches, the optical path in the silicon of the photodetector of the pixel needs to be increased.

[0014] There is a need in the art to address all or some of the disadvantages of known pixels having first and second trenches as described above. Summary of the invention

[0015] In an embodiment, a pixel includes: a silicon portion having a first face, the first face being configured to receive light, such as infrared light; a first groove, the first groove being parallel to a first direction and being regularly spaced apart in a second direction perpendicular to the first direction, the first groove penetrating from the first face into the silicon portion; and a second groove, the second groove being parallel to the second direction and being regularly spaced apart in the first direction, the second groove penetrating from the first face into the silicon portion. In a central region of the first face, the first groove includes a first notch, each first notch penetrating from the first face into the silicon, extending from the first groove including the notch to an adjacent first groove without reaching the adjacent first groove, and aligned with a corresponding second groove. In a central region, the second groove includes a second notch, each second notch penetrating from the first face into the silicon, extending from the second groove including the notch to an adjacent second groove without reaching the adjacent second groove, and aligned with a corresponding first groove.

[0016] According to one embodiment, the first face has two first sides parallel to the first direction and two second sides parallel to the second direction.

[0017] According to one embodiment, the first surface includes: a first area extending from a first one of the first sides toward the central area, the first area only including the second groove; a second area extending from a second one of the first sides toward the central area, the second area only including the second groove; a third area extending from a first one of the second sides toward the central area, the third area only including the first groove; and a fourth area extending from a second one of the second sides toward the central area, the fourth area only including the first groove.

[0018] According to one embodiment, the first and second grooves have no notches outside the central area.

[0019] According to one embodiment, at least one V-shaped pattern made of one first groove and one second groove is arranged in each corner of the first face, outside the central area.

[0020] According to one embodiment, in each corner of the first surface, the at least one V-shaped pattern arranged in the corner is symmetrical with respect to a diagonal line of the first surface extending from the corner, and its apex faces toward the center of the first surface.

[0021] According to one embodiment, for each corner of the first surface: the pixel includes a plurality of V-shaped patterns, each V-shaped pattern having a first groove and a second groove, the V-shaped patterns are continuously and regularly arranged from the corner toward the center of the first surface, the vertex of each of the V-shaped patterns faces the center of the first surface, each of the V-shaped patterns is symmetrical with respect to a diagonal line extending from the corner, and the first grooves of these V-shaped patterns include a first notch in the center area and / or the second grooves of these V-shaped patterns include a second notch in the center area.

[0022] According to one embodiment, in the center region, the first grooves are aligned on first lines of the grid pattern and the second grooves are aligned on second lines of the grid pattern, the first notches are aligned on the second lines of the grid pattern, and the second notches are aligned with the first lines.

[0023] According to one embodiment, in the first direction the central area has a length comprised between 50% and 70% of the length of each first side, and in the second direction the central area has a length comprised between 50% and 70% of the length of each first side.

[0024] According to one embodiment, in the central region, the first and second grooves together with the first and second recesses form a pattern similar to a grid pattern.

[0025] According to one embodiment, the first and second grooves together with the first and second recesses form a pattern having a 90° rotational symmetry with respect to the center of the first face.

[0026] According to one embodiment, the first trenches are arranged at a first pitch in the second direction and the second trenches are arranged at a second pitch in the first direction, the first and second pitches being equal to each other and for example comprised between 300 and 600 nm, preferably equal to about 450 nm.

[0027] According to one embodiment, the length of the first notch in the second direction and the length of the second notch in the first direction are comprised between 40% and 60% of the first and second pitches.

[0028] According to one embodiment, the width of the first trench is equal to the width of the second trench, the widths of the first and second trenches being comprised between 150 and 250 nm, for example approximately equal to 200 nm.

[0029] One embodiment provides a method for manufacturing the above-mentioned pixel, which includes: forming a hard mask on a first surface of the pixel; forming a photoresist mask on the hard mask; patterning the photoresist mask to form a first opening therein, wherein the first opening exposes the hard mask at each position of the first groove, each position of the second groove, each position of the first recess, and each position of the second recess; etching a second opening in the hard mask through the first opening; and etching the first and second grooves and the first and second recesses in the silicon portion through the second opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing features and advantages and other features and advantages will be presented by way of illustration and not limitation in the following description of specific embodiments with reference to the accompanying drawings, in which:

[0031] Figure 1 , described above, is a schematic top view of the face of a silicon photodetector of a pixel;

[0032] Figure 2 is a schematic top view of an idealized embodiment of a face of a silicon photodetector of a pixel;

[0033] Figure 3 is a schematic top view of an embodiment of a face of a silicon photodetector of a pixel;

[0034] Figure 4 is a schematic top view of another embodiment of a face of a silicon photodetector of a pixel;

[0035] Figure 5 is a schematic top view of yet another embodiment of a face of a silicon photodetector of a pixel; and

[0036] Figure 6 is a schematic top view of yet another embodiment of a face of a silicon photodetector of a pixel. DETAILED DESCRIPTION

[0037] In the various drawings, the same features are represented by the same reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals and may be provided with the same structure, dimensions and material properties.

[0038] For the sake of clarity, only the operations and elements useful for understanding the embodiments described herein are described in detail and described. In particular, the implementation of the pixel in an optical sensor (e.g., a time-of-flight sensor) including at least one such pixel, such as a pixel matrix identical to one such pixel, is not described, and the implementation of such a sensor is within the capabilities of those skilled in the art.

[0039] 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 the two elements may be connected or they may be coupled via one or more other elements.

[0040] In the following disclosure, unless otherwise stated, when referring to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or when referring to relative position qualifiers, such as the terms "above", "below", "higher", "lower", etc., or when referring to orientation qualifiers, such as "horizontal", "vertical", etc., it refers to the orientation shown in the figure.

[0041] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "on the order of" mean within 10%, preferably within 5%.

[0042] In the following disclosure, pixels configured to operate at one or several wavelengths in the near infrared (i.e., in the range of 750 nm to 1400 nm), for example pixels configured to operate at a wavelength substantially equal to 940 nm, are considered as examples. The photodiode of the pixel is also considered to be made of silicon, which has poor light absorption for these wavelengths. As an example, further consider that the pixel is configured so that its photodiode operates in a single photon avalanche mode, or in other words, the pixel includes a single photon avalanche diode or SPAD.

[0043] Embodiments herein propose to increase the quantum efficiency of the photodiode of a pixel by providing a structure for dispersing the light reaching the photodiode outside the normal incidence angle. As a result, the optical path length in the photodiode increases, which leads to an increase in quantum efficiency.

[0044] Figure 2 is a schematic top view of an idealized embodiment of a face 200 of a silicon photodetector of pixel Pix2.

[0045] The surface 200 is used to receive light and has a structure (eg, a diffractive structure) formed by grooves 202 and 204 .

[0046] The face 200 has two opposite sides 206 and 208 parallel to each other and to the direction Y, and two opposite sides 210 and 212 parallel to each other and to the direction X. The direction X is perpendicular to the direction Y. The face 200 preferably has a square shape.

[0047] Plane 200 is a plane of silicon part forming the photodetector of pixel Pix2. The photodetector of pixel Pix2 is laterally bounded, for example, by an insulating structure 214. Structure 214 is, for example, a capacitive deep trench insulation (CDTI). In an alternative embodiment, structure 214 is a deep trench insulation (DTI).

[0048] The groove 202 extends in the length of the Y direction, and the groove 204 extends in the length of the X direction. Figure 2 In FIG. 1 , only some of the grooves 202 and 204 are marked with reference numerals in order not to overload the figure. Figure 2 In FIG. 2 , grooves 202 and 204 are indicated by hatching.

[0049] The grooves 202 are regularly spaced apart in the X direction. In other words, the grooves 202 are arranged at a pitch P1. Similarly, the grooves 204 are regularly spaced apart in the Y direction. In other words, the grooves 204 are arranged at a pitch P2. The pitch P1 is equal to the pitch P2.

[0050] For example, for received light in the infrared, the pitches P1 and P2 are comprised between 300 and 600 nm, for example equal to approximately 450 nm, preferably equal to 450 nm.

[0051] For example, the width of the trench 202 (measured along direction X) is equal to the width of the trench 204 (measured along direction Y). For example, for received light in the infrared, the widths of the trenches 202 and 204 are comprised between 150 and 250 nm, for example approximately equal to 200 nm.

[0052] Although this Figure 2 , but the trenches 202 and 204 penetrate into the silicon of the photodetector from the face 200. For example, for light received in the infrared, the trenches 202 and 204 penetrate into the silicon at a depth comprised between 200 and 300 nm, for example a depth equal to approximately 250 nm.

[0053] Surface 200 includes a central region 216, which is Figure 2 The region 216 has a length measured in the direction X, which is included between 50% and 70% of the length of the sides 206 and 208, and the region 216 has a length measured in the direction Y, which is included between 50% and 70% of the length of the sides 210 and 212. Preferably, the central region 216 is square.

[0054] exist Figure 2In an ideal embodiment, the grooves 202 and the grooves 204 intersect in the central region 216 to form a grid pattern throughout the central region 216. In other words, in the central region 216, the grooves 202 are aligned on a first line of the grid pattern and the grooves 204 are aligned on a second line of the grid pattern, the first line being orthogonal to the second line and parallel to the direction Y.

[0055] exist Figure 2 In an ideal embodiment, the pixel Pix2 includes an area extending from the side 206 to the central area 216, preferably extending all the way to the central area 216, and the area includes only the groove 204, or in other words, the area does not have the groove 202. The pixel Pix2 also includes an area extending from the side 208 to the central area 216, preferably extending all the way to the central area 216, and the area includes only the groove 204, or in other words, the area does not have the groove 202. The pixel Pix2 includes an area extending from the side 210 to the central area 216, preferably extending all the way to the central area 216, and the area includes only the groove 202, or in other words, the area does not have the groove 204. The pixel Pix2 also includes an area extending from the side 212 to the central area 216, preferably extending all the way to the central area 216, and the area includes only the groove 202, or in other words, the area does not have the groove 204.

[0056] exist Figure 2 In an ideal embodiment, the pixel Pix2 includes a V-shaped pattern consisting of a groove 202 and a groove 204 at each corner of the surface 200. In each corner, the apex of the V-shaped pattern turns toward the center O of the surface 200. Preferably, in each corner of the surface 200, the V-shaped pattern arranged in the corner is symmetrical with respect to the diagonal line of the surface 200 extending from the corner.

[0057] Through simulation, it has been found that Figure 2 The pixel Pix2 has an optimized pattern of grooves 202 and 204 for use with respect to a similar photodetector but with respect to Figure 1 A pixel having trenches 112 and 114 of the type described improves light absorption in the photodetector of Pix2.

[0058] However, considering the size of the grooves 202 and 204 and their pitches P1 and P2, the pixel Pix2 may not be manufactured using a conventional microelectronics manufacturing process. For example, when using a mask made of a photoresist patterned with openings at the locations of the grooves 202 and 204, the portions of the photoresist remaining between these openings may not adhere sufficiently and be peeled off, which is similar to the case with respect to Figure 2The described comparison results in defects in the pattern of the grooves 202 and 204. This is more particularly the case when the dimensions of the grooves 202 and 204 and their pitches P1 and P2 are, for example, selected or optimized for the received infrared light.

[0059] Therefore, instead of Figure 2 As shown, grooves 202 and 204 are provided to form a grid pattern in the central area 216 of pixel Pix2. A pixel Pix3 similar to pixel Pix2 is proposed herein, but wherein grooves 202 and 204 are replaced by similar grooves 302 and 304, respectively, which include recesses 320 and 322 in the central area 316 of pixel Pix3.

[0060] More specifically, the groove 302 is parallel to the direction Y, and the groove 304 is parallel to the direction 306. In addition, in the central region 316, the groove 302 includes notches 320, each of which extends from the corresponding groove 302 to the adjacent groove 302 along the X direction but does not reach the adjacent groove 302, and the notches 320 are aligned with the groove 304 along the X direction. Similarly, the groove 304 includes notches 322 in the central region 316, each of which extends from the corresponding groove 304 to the adjacent groove 304 along the Y direction but does not reach the adjacent groove 304, and the notches 322 are aligned with the groove 302 along the Y direction.

[0061] Thus, in the central region 316, the pattern formed by the grooves 302 and 304 and the recesses 320 and 322 is similar to a grid pattern, but is not identical to a grid pattern (i.e., the pattern is grid-like). This allows the absorption in the photodetector of the pixel Pix3 to be improved in a manner similar to the grid pattern of the pixel Pix2, and at the same time, this allows the pixel Pix3 to be manufactured using conventional steps of a microelectronics manufacturing process.

[0062] Figure 3 An embodiment of a pixel Pix3 is shown. More specifically, Figure 3 is a schematic top view of an embodiment of a face 300 of a silicon photodetector of pixel Pix3.

[0063] The surface 300 is used to receive light and has a structure (eg, a diffractive structure) formed by grooves 302 and 304 .

[0064] The face 300 has two opposite sides 306 and 308 parallel to each other and to the direction Y, and two opposite sides 310 and 312 parallel to each other and to the direction X. The direction X is perpendicular to the direction Y. The face 300 preferably has a square shape.

[0065] Face 300 is a face of a silicon portion forming a photodetector of pixel Pix3. The photodetector of pixel Pix3 is laterally bounded, for example, by an insulating structure 314. Structure 314 is, for example, a capacitive deep trench insulation (CDTI). In an alternative embodiment, structure 314 is a deep trench insulation (DTI).

[0066] Groove 302 extends in length in the Y direction, while groove 304 extends in length in the X direction. Figure 3 In FIG. 1 , only some of the grooves 302 and 304 are marked with reference numerals in order not to overload the figure. Figure 3 In FIG. 1 , grooves 302 and 304 are hatched.

[0067] Grooves 302 and 304 are similar to previously described grooves 202 and 204, respectively, except that grooves 302 and 304 do not form a complete grid pattern in the central region 316 of pixel Pix3. Therefore, unless otherwise specified, everything that has been indicated for grooves 202 and 204 applies to grooves 302 and 304, respectively. In addition, in pixel Pix3, the central region 316 of face 300 (represented by Figure 3 2 (defined by the dashed line in FIG. 2 ) is similar to central region 216 of face 200 of pixel Pix2. Therefore, unless otherwise noted, all descriptions of region 216 apply to central region 316. Specifically, the dimensions of region 316 relative to sides 306, 308, 310, and 312 are the same as the dimensions of region 216 relative to sides 206, 208, 210, and 212, respectively.

[0068] As shown previously and Figure 3 As shown, in the central region 316, the groove 302 includes a notch 320 and the groove 304 includes a notch 322. In order not to overload the figure, Figure 3 , only a few notches 320 and 322 are cited. Thus, in the central region, the grooves 302 and notches 322 are aligned on a first line of the grid pattern, and the grooves 304 and notches 324 are aligned on a second line of the grid pattern, the first line being parallel to the direction Y and the second line being aligned with the direction X. Preferably, there are no notches 322 that are not aligned with a corresponding groove 302, and there are no notches 324 that are not aligned with a corresponding groove 304.

[0069] The notches 320 and 322 penetrate from the surface 300 into the silicon of the pixel Pix3. Preferably, the notches 320 and 322 penetrate the silicon of the photodetector of the pixel Pix3 to the same depth as the trenches 302 and 304.

[0070] Preferably, the width of the notch 322 (measured in direction X) is equal to the width of the groove 302 , and the width of the notch 324 (measured in direction Y) is equal to the width of the groove 304 .

[0071] Preferably, the length of notch 322 (measured along direction Y) and the length of notch 324 (measured along direction X) are respectively comprised between 40% and 60% of pitch P2 of groove 304 and pitch P1 of groove 302, pitches P1 and P2 being preferably equal to each other.

[0072] Preferably, similar to pixel Pix2, pixel Pix3 includes: a first region, which extends from the side 306 toward the central region 316, preferably up to the central region 316, and the first region only includes the groove 304, or in other words, the first region has no groove 302; a second region, which extends from the side 308 toward the central region 316, preferably up to the central region 316, and the second region only includes multiple grooves 304, or in other words, the second region has no groove 302; a third region, which extends from the side 310 toward the central region 316, preferably up to the central region 316, and only includes the groove 302, or in other words, it has no groove 304; and a fourth region, which extends from the side 312 toward the central region 316, preferably up to the central region 316, and only includes the groove 302, or in other words, it has no groove 304.

[0073] Preferably, as in pixel Pix2, the grid pattern is located only on the central region 216 of face 200, and because notches 320 and 322 help provide a simulated Figure 2 The grid pattern shown is a grid pattern such that the trenches 302 and 304 are free of notches 320 and 322 in the defined first, second, third, and fourth regions.

[0074] For pixel Pix2, pixel Pix3 preferably includes one or more V-shaped patterns in each corner of the face 300, each V-shaped pattern consisting of one groove 302 and one groove 304. In each corner, the vertex of each V-shaped pattern arranged in the corner turns toward the center O of the face 300. Preferably, in each corner of the face 300, each V-shaped pattern arranged in the corner is symmetrical with respect to the diagonal line of the face 300 extending from the corner.

[0075] exist Figure 3 In the example of FIG. 4 , the pixel Pix3 includes only one V-shaped pattern in each corner.

[0076] Preferably, as in pixel Pix2, the grid pattern is located only on the central region 216 of face 200, and the notches 320 and 322 help to simulate Figure 2 In the grid pattern shown, the grooves 302 and 304 of the V-shaped pattern are arranged in the corners of the face 300, which are outside the central area and are free of the notches 322 and 324.

[0077] Preferably, the groove 302 includes the notch 320 only in the central region 316 , and the groove 304 includes the notch 322 only in the central region 316 .

[0078] Preferably, as in Figure 3 In the case of the embodiment, for each corner of the surface 300: the pixel Pix3 includes a plurality of V-shaped patterns, each V-shaped pattern consisting of a groove 302 and a groove 304; the V-shaped patterns are continuously and regularly arranged from the corner toward the center O of the surface 300; the vertex of each V-shaped pattern turns toward the center O of the pixel; and each V-shaped pattern is symmetrical with respect to the diagonal line extending from the corner.

[0079] Preferably, if Figure 3 In the embodiment of , independent of the fact that the grooves 302 and 304 are arranged in a V-shaped pattern, for each groove 302 , the notches 320 are arranged along the groove 302 at a pitch P2 of the groove 304 , and for each groove 304 , the notches 322 are arranged along the groove 304 at a pitch P1 of the groove 302 .

[0080] Preferably, as in Figure 3 In the embodiment of the present invention, independently of the fact that the notches 320 are arranged at a pitch P2 and the notches 322 are arranged at a pitch P1, and independently of the fact that the grooves 302 and 304 are arranged in a V-shaped pattern, for each groove 302, the notches 320 of this groove 302 are arranged on the same side of the groove 302, and for each groove 304, the notches 322 of this groove 304 are arranged on the same side of the groove 304.

[0081] exist Figure 3 In the embodiment of the present invention, preferably, each groove 302 and each groove 322 belongs to a corresponding V-shaped pattern. In other words, there are no grooves 302 or 304 that do not belong to a V-shaped pattern. Specifically, there are no pairs of grooves 302 and grooves 304, wherein the grooves 302 and 304 cross each other and form an X-shaped pattern.

[0082] Preferably, if Figure 3 As is the case in the embodiment of , independently of the fact that the grooves 302 and 304 are arranged in a V-shaped pattern and the pitch of the notches 320 and 322, the pattern formed by the grooves 302 and 304 has a rotational symmetry of 90° with respect to the center O of the face 300. Due to this rotational symmetry, the pixel Pix3 is insensitive to the polarization of the incident light.

[0083] According to an embodiment, a process for manufacturing pixel Pix3 includes the following consecutive steps: forming a hard mask on surface 300; forming a photoresist mask on the hard mask; patterning the photoresist mask to form a first opening therein, which exposes the hard mask at each position of groove 302, each position of groove 304, each position of recess 320, and each position of recess 322; etching the hard mask through the first opening to form a second opening therein; and etching the silicon of the photodetector of pixel Pix3 through the second opening to form grooves 302 and 304 and recesses 320 and 322 therein.

[0084] Using the above process, it may not be possible to manufacture Figure 2 Pixel Pix2 is manufactured because most of the photoresist mask remaining between the first openings between etching the hard mask has small dimensions in the X and Y directions and each forms a small square. In contrast, the above process can be used to manufacture pixel Pix3 because the portion of the photoresist mask remaining in place before etching the hard mask has larger dimensions in the X and Y directions and each forms a strip, for example. Therefore, this portion of the photoresist mask adheres better to the hard mask.

[0085] Figure 4 is a schematic top view of another embodiment of a face 300 of a silicon photodetector of pixel Pix3.

[0086] Figure 3 and Figure 4 The pixel Pix3 of FIG. 1 has many common elements, and only the differences between the two pixels will be described in detail. In particular, unless otherwise noted, all references to Figure 3 The pixels Pix3 points out are applicable to Figure 4 Pixel Pix3.

[0087] Specifically, Figure 3 Compared with the Pix3, Figure 4 In the pixel Pix3 , the grooves 302 and 304 are arranged not only in a V-shaped pattern but also in at least one square pattern, which is preferably arranged in the central area 316 .

[0088] For example, Figure 4 As shown in the example of FIG. 1 , the first trench 302 and the second trench 302 spaced apart from each other by a distance D in the X direction intersect the first trench 304 and the second trench 304 spaced apart from each other by the same distance D. Preferably, the distance D is at least twice the pitches P1 and P2.

[0089] Preferably, the square pattern formed by the intersection of these four grooves 302 and 304 is centered on the center O of the face 300 .

[0090] Despite Figure 4 In the example, there is only one square pattern formed by two grooves 302 and two grooves 304, but in other examples where the pixel Pix3 includes more than one square pattern, preferably, the sides of each square pattern are longer than the pitches P1 and P2, and / or each square pattern is centered on the center O of the surface 300.

[0091] and Figure 3 Compared to pixel Pix3, pixel Pix3 does not have any rotational symmetry with respect to the center O of pixel Pix3.

[0092] Figure 5 is a schematic top view of another embodiment of a face 300 of a silicon photodetector of pixel Pix3.

[0093] Figure 5 and Figure 4 The pixel Pix3 of FIG. 1 has many common elements, and only the differences between the two pixels will be described in detail. In particular, unless otherwise noted, all references to Figure 4 The pixels Pix3 points out are applicable to Figure 5 Pixel Pix3.

[0094] Specifically, Figure 4 Compared with the Pix3, Figure 5 In the pixel Pix3, there are more than one square pattern formed by two grooves 302 and two grooves 304. For example, in Figure 5 In FIG. 1 , there are two square patterns, each of which is formed by two grooves 302 and two grooves 304 .

[0095] For example, Figure 5 In the example of FIG. 3 , the pixel Pix3 does not include any V-shaped pattern consisting of one groove 302 and one groove 304 in the central area 316. In other words, Figure 5 In the example of FIG. 4 , the pixel Pix3 does not include any V-shaped pattern formed by the groove 302 including the notch 320 and the groove 304 including the notch 322 .

[0096] For example, as in Figure 5As in the example of , Pix3 includes more than one V-shaped pattern formed by one groove 302 and one groove 304 in each corner outside the central area 316, which are arranged outside the central area and do not have the notches 320 and 322. In addition, the apex of each of these V-shaped patterns turns toward the center O of the face 300. In addition, in each corner of the face 300, the V-shaped patterns arranged in the corner are continuously and regularly arranged from the corner toward the center O of the face 300. In addition, in each corner of the face 300, each V-shaped pattern arranged in the corner is symmetrical with respect to the diagonal line of the face 300 extending from the corner.

[0097] exist Figure 5 In the example of , in each corner of the face 300 , the pixel Pix3 includes two continuous V-shaped patterns without the notches 320 and 322 .

[0098] In addition, as in Figure 5 In the example of FIG. 316, at least some of the grooves 302, preferably all of the grooves 302, each include a notch 320 on both sides of the groove 302 (taken along the length of the groove 302), and similarly, at least some of the grooves 304, preferably all of the grooves 304, each include a notch 322 on both sides of the groove 304 (taken along the length of the groove 304). Although not shown, in other examples, each groove 302 includes a notch 320 on only one side of the groove 302 in the central region 316, and / or each groove 304 includes a notch 322 on only one side of the groove 304 in the central region 316.

[0099] Figure 6 is a schematic top view of another embodiment of a face 300 of a silicon photodetector of pixel Pix3.

[0100] Figure 4 and Figure 6 The pixel Pix3 of FIG. 1 has many common elements, and only the differences between the two pixels will be described in detail. In particular, unless otherwise noted, all references to Figure 4 The pixels Pix3 points out are applicable to Figure 6 Pixel Pix3.

[0101] Specifically, Figure 4 Compared with the Pix3, Figure 5 In the pixel Pix3, the central area 316 of the pixel Pix3 is smaller.

[0102] Furthermore, independent of the fact that area 316 is smaller, there is no V-shaped pattern whose grooves 302 and 304 include notches 320 and 322, respectively.

[0103] Furthermore, independent of the fact that the area 316 is smaller and that there is no V-shaped pattern in which the grooves 302 and 304 include the notches 320 and 322, respectively, Figure 6 In the pixel Pix3, in the central region 316, the groove 304 includes the notch 322, but the groove 302 does not have the notch 320 in the central region. Although not shown, the opposite is also possible, which means that in other examples, in the central region 316, the groove 302 includes the notch 320, but the groove 304 does not have the notch 322.

[0104] Simulations have shown that for light received in the infrared and for a photodetector having a portion of epitaxial silicon with a thickness of 10 μm, Figure 3 The Pix3 pixel exhibits a 3.4% improvement in absorption relative to the similar Pix1 pixel, Figure 4 The Pix3 pixel exhibits a 3.8% improvement in absorption relative to the similar Pix1 pixel, Figure 5 The pixel Pix3 exhibits a 3.0% improvement in absorption relative to the similar pixel Pix1, and Figure 6 The pixel Pix3 exhibits a 3.4% improvement in absorption relative to the similar pixel Pix1.

[0105] Preferably, in pixel Pix3, as previously described with respect to Figure 3 , Figure 4 , Figure 5 and Figure 6 In all the described embodiments, there is no square pattern formed by the intersection of two grooves 302 and two corresponding grooves 304, the side lengths of which are equal to the pitches P1 and P2. In other words, there is no square pattern formed by the intersection of two consecutive (or adjacent) grooves 302 and two consecutive (or adjacent) grooves 304.

[0106] Preferably, in pixel Pix3, as previously described, Figure 3 , Figure 4 , Figure 5 and Figure 6 In all of the described embodiments shown, outside of the central region 316, the grooves 302 and 304 do not include any notches 320 and 322, respectively.

[0107] Although not explicitly indicated previously, in pixel Pix3, each trench 302 including a portion outside the region 316 and a portion inside the region 316 has no notch 320 on the portion outside the region 316 thereof, and may include a notch 322 on the portion inside the region 316 thereof. Similarly, in pixel Pix3, each trench 304 including a portion outside the region 316 and a portion inside the region 316 has no notch 322 on the portion outside the region 316 thereof, and may include a notch 322 on the portion inside the region 316 thereof.

[0108] 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.

[0109] Finally, actual implementation of the embodiments and variations described herein is within the capabilities of those skilled in the art, based on the functional description provided above.

Claims

1. A pixel comprising: a silicon portion having a first face configured to receive light; first trenches penetrating from the first face into the silicon portion, wherein the first trenches extend parallel to a first direction and are regularly spaced apart in a second direction perpendicular to the first direction; as well as second trenches penetrating from the first face into the silicon portion, wherein the second trenches extend parallel to the second direction and are regularly spaced apart in the first direction; as well as In the central area of ​​the first side: The first trenches include first notches penetrating from the first face into the silicon, wherein each first notch extends from a first trench toward an adjacent first trench without reaching the adjacent first trench, and wherein each first notch is aligned with a corresponding second trench.

2. The pixel according to claim 1, wherein in the central area of ​​the first face: The second trenches include second recesses penetrating from the first face into the silicon, wherein each second recess extends from the second trench toward an adjacent second trench without reaching the adjacent second trench, and wherein each second recess is aligned with a corresponding first trench. 3 . The pixel according to claim 2 , wherein the first face has two first sides parallel to the first direction and two second sides parallel to the second direction.

4. The pixel of claim 3, wherein the first side comprises: a first region extending from a first one of the first sides toward the central region, the first region including only the second grooves; a second region extending from a second one of the first sides toward the central region, the second region including only second grooves; a third region extending from a first one of the second sides toward the central region, the third region including only the first groove; A fourth region extends from a second one of the second sides toward the central region, and the fourth region includes only the first grooves. 5 . The pixel of claim 4 , wherein there is no notch on the first trench in the first region and the third region. 6 . The pixel of claim 4 , wherein there is no notch on the second groove in the second region and the fourth region. 7 . The pixel according to claim 3 , further comprising at least one V-shaped pattern composed of one first groove connected to one second groove, wherein the at least one V-shaped pattern is arranged in a corner of the first face outside the central area.

8. The pixel according to claim 7, wherein in the corner of the first face, the at least one V-shaped pattern is arranged symmetrically with respect to a diagonal line of the first face extending from the corner, and wherein the at least one V-shaped pattern has a vertex turned toward the center of the first face. 9 . The pixel according to claim 3 , further comprising a plurality of V-shaped patterns, each V-shaped pattern being composed of one first groove, wherein the plurality of V-shaped patterns are arranged in corners of the first face outside the central area.

10. The pixel of claim 9, wherein the plurality of V-shaped patterns are continuously and regularly arranged from the corner toward the center of the first face, each of the V-shaped patterns has a vertex turned toward the center of the first face, and each of the V-shaped patterns is symmetrical with respect to a diagonal line extending from the corner. 11 . The pixel of claim 10 , wherein the first grooves of the plurality of V-shaped patterns include a first notch in the central region, and / or wherein the second grooves of the plurality of V-shaped patterns include a second notch in the central region.

12. A pixel according to claim 3, wherein in the first direction, the central area has a length included between 50% and 70% of the length of each first side, and in the second direction, the central area has a length included between 50% and 70% of the length of each first side.

13. The pixel of claim 2, wherein in the central area, the first grooves are aligned on first lines of a grid pattern and the second grooves are aligned on second lines of the grid pattern, the first notches are aligned on the second lines of the grid pattern and the second notches are aligned with the first lines. 14 . The pixel of claim 2 , wherein in the central region, the first and second grooves form a grid pattern together with the first and second recesses. 15 . The pixel according to claim 2 , wherein the first and second grooves together with the first and second recesses form a pattern having 90° rotational symmetry with respect to the center of the first face. 16 . The pixel of claim 2 , wherein the first trenches are arranged at a first pitch in the second direction, and the second trenches are arranged at a second pitch in the first direction, the first pitch and the second pitch being equal to each other and included between 300 nm and 600 nm. 17 . The pixel of claim 15 , wherein a length of the first notch in the second direction and a length of the second notch in the first direction are comprised between 40% and 60% of the first pitch and the second pitch. 18 . The pixel of claim 1 , wherein a width of the first trench is equal to a width of the second trench, the widths of the first trench and the second trench being comprised between 150 nm and 250 nm.

19. The pixel of claim 1, wherein the light is infrared light.

20. A method of manufacturing the pixel according to claim 2, comprising: forming a hard mask on a first side of the pixel; forming a photoresist mask on the hard mask; patterning the photoresist mask to form a first opening therein, the first opening exposing the hard mask at each location of the first trench, each location of the second trench, each location of the first recess, and each location of the second recess; etching a second opening in the hard mask through the first opening; as well as The first and second trenches and the first and second recesses are etched in the silicon portion through the second opening.

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