Semiconductor photodetector

Abstract

Semiconductor photodetector The present description relates to a semiconductor photodetector (200) comprising:- an active region (210) made of a doped semiconductor material of a first conductivity type, said active region being adapted to convert light radiation into charge carriers and to store said charge carriers;- at least one repulsion element (230) adapted to repel charge carriers stored in the active region, said repulsion element being positioned within the active region. Figure for abstract: Fig. 2

Description

Title of the invention: Semiconductor photodetector Technical field

[0001] The present description relates generally to electronic components and more specifically to semiconductor photodetectors.

[0002] The present description relates for example to photodiodes, vertical pinned photodiodes, or vertical photogates.

[0003] The present description also relates to electronic devices, such as image sensors, comprising photodetectors. Prior art

[0004] An image sensor may comprise several pixels organized in a network, for example in a matrix, each pixel comprising one (or more) photodetector(s) adapted to capture light radiation (photons) and to convert them into charge carriers, i.e. electrons and / or holes. We can thus speak of photoconversion, or photoelectric conversion. The generated charge carriers can be transferred into one (or more) circuit(s), such as a reading circuit, adapted to convert them into electrical signals. The pixel network is generally associated with different control, reading, power supply circuits, etc.

[0005] Several photodetectors can be integrated in and on the same semiconductor layer, for example a silicon layer. The photodetectors can be isolated from each other by insulators, for example insulating trenches which extend in all or part of the thickness of the semiconductor layer. For example, each photodetector comprises a photosensitive region integrated in the semiconductor layer, which can be designated by the term "active zone" or "active region". This active region corresponds to a region in which the charge carriers are generated by conversion of light radiation, and stored. The active region can be a depletion region, or depletion (from the English "depletion"), of the semiconductor layer, which can be designated by the term "well".

[0006] A photodetector may be a photodiode, which is a semiconductor component having a PN junction, generally formed by a junction between an N-type semiconductor region and a P-type semiconductor region. In operation, the photodiode is in reverse bias mode. When the reverse biased photodiode is exposed to photons, electron-hole pairs may be generated around the PN junction of the photodiode.

[0007] In particular, the photodiode may be a pinned photodiode. A pinned photodiode may be defined as a photodiode in which the active region comprises an N-type or P-type semiconductor region, respectively, surrounded by one or more P-type or N-type semiconductor regions. In this type of photodiode, the N-type active region is generally entirely depleted by heavily P-doped semiconductor regions. Thus, the electrons generated by conversion of light radiation are stored in the depleted N-type active region while the holes are evacuated in the heavily P-doped semiconductor regions. In the case of a P-type active region, depleted by heavily N-doped semiconductor regions, the holes are stored in the active region, while the electrons are evacuated in the heavily N-doped semiconductor regions.

[0008] A photodetector may be a photogate. A photogate may be defined as a photodetector in which the active region comprises an N-type semiconductor region and / or a P-type semiconductor region, in contact with a metal-oxide-semiconductor (MOS) trench region forming a polarization gate. For example, in the case of an N-doped active region, the gate is negatively biased so that the active region is depleted in its volume to be able to store electrons, while the surface in contact with the gate oxide is in inversion in order to evacuate the photogenerated holes.

[0009] It may be sought to improve the performance of the photodetectors, for example, to improve the signal-to-noise ratio (SNR), to increase the dynamic range (DR), and / or to reduce the dark current, for example by increasing the storage capacity of the charge carriers in the active region of the photodetector, which may be referred to in English as "full well capacity", or FWC. Summary of the invention

[0010] One embodiment overcomes all or part of the drawbacks of known photodetectors.

[0011] One embodiment provides a semiconductor photodetector comprising: - an active region made of a doped semiconductor material of a first conductivity type, said active region being adapted to convert light radiation into charge carriers and to store said charge carriers; and - at least one repulsion element adapted to repel charge carriers stored in the active region, said repulsion element being positioned within the active region.

[0012] One embodiment provides a method of manufacturing a semiconductor photodetector, the method comprising: - forming an active region in a doped semiconductor material of a first conductivity type, said active region being adapted to convert light radiation into charge carriers and to store said charge carriers; and - forming at least one repulsion element adapted to repel charge carriers stored in the active region, said repulsion element being formed within the active region.

[0013] According to one embodiment, the at least one repulsion element is arranged in the active region such that it does not divide said active region into several distinct volumes.

[0014] According to one embodiment, the at least one repulsion element is surrounded by the active region in at least one plane.

[0015] According to one embodiment, the at least one repulsion element comprises several repulsion elements, for example several repulsion elements regularly distributed in the active region, for example several repulsion elements substantially equidistant from one another.

[0016] According to one embodiment, the at least one repulsion element is oriented in a longitudinal direction of the photodetector.

[0017] According to one embodiment, the at least one repulsion element is oriented in a transverse direction of the photodetector.

[0018] According to one embodiment, the at least one repulsion element has the shape of a continuous pillar, for example a pillar of polygonal, rectangular, square, oval or circular section.

[0019] According to one embodiment, the at least one repulsion element comprises several implant points separated from each other by portions of the active region, forming for example a discontinuous pillar.

[0020] According to one embodiment, the at least one repulsion element extends from a first face of the active region to a non-zero distance from a second face of the active region opposite the first face, a portion of the active region located between said at least one repulsion element and said second face being for example heavily doped with the first conductivity type.

[0021] According to one embodiment, the at least one repulsion element comprises, for example, an internal capacitive deep trench, preferably adapted to be polarized so as to repel the stored charge carriers.

[0022] According to one embodiment, the at least one repulsion element comprises, for example, an implant region doped with the second conductivity type opposite to the first conductivity type.

[0023] According to one embodiment, the photodetector further comprises a lateral insulating trench configured to laterally isolate said photodetector, for example from other photodetectors.

[0024] According to one embodiment, the insulating trench contains a conductive or semiconductive element, the insulating trench and the conductive or semiconductive element forming a deep lateral capacitive trench.

[0025] According to one embodiment, the photodetector further comprises a lateral implant region between the lateral insulating trench and the active region, the lateral implant region being doped with the second conductivity type opposite to the first conductivity type.

[0026] According to one embodiment, the active region has non-homogeneous doping, for example in one or more transverse directions of the photodetector.

[0027] One embodiment provides an image sensor comprising a plurality of pixels, each pixel comprising at least one photodetector as described above. Brief Description of the Drawings

[0028] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0029] [Fig.1A] represents, by a simplified perspective view, an example of a photodetector;

[0030] [Fig.1B] represents, by a simplified perspective view, an example of a pixel with photodetectors;

[0031] [Fig.2] represents, in a perspective view, a photodetector according to one embodiment;

[0032] [Fig.3A] represents, by a top view in section, a photodetector according to another embodiment;

[0033] [Fig.3B] represents, by a cross-sectional view, the photodetector of [Fig.3A];

[0034] [Fig.4A] represents, by a top view in section, a photodetector according to yet another embodiment;

[0035] [Fig.4B] represents, by a cross-sectional view, the photodetector of [Fig.4A];

[0036] [Fig.5A] represents, by a top view in section, a photodetector according to yet another embodiment;

[0037] [Fig.5B] represents, by a cross-sectional view, the photodetector of [Fig.5A];

[0038] [Fig.6A] represents, by a top view in section, a photodetector according to yet another embodiment;

[0039] [Fig.6B] represents, by a cross-sectional view, the photodetector of [Fig.6A];

[0040] [Fig.7A] represents, by a top view in section, a photodetector according to yet another embodiment;

[0041] [Fig.7B] represents, by a cross-sectional view, the photodetector of [Fig.7A];

[0042] [Fig.8A] represents, in a top sectional view, a photodetector according to yet another embodiment;

[0043] [Fig.8B] represents, by a cross-sectional view, the photodetector of [Fig.8A];

[0044] [Fig.9A] represents, by a top view in section, a photodetector according to yet another embodiment;

[0045] [Fig.9B] represents, by a cross-sectional view, the photodetector of [Fig.9A];

[0046] [Fig. 10A] represents, in a top sectional view, a photodetector according to yet another embodiment;

[0047] [Fig. 10B] represents, by a cross-sectional view, the photodetector of [Fig. 10A];

[0048] [Fig. 11A], [Fig. 11B], [Fig. 11C], [Fig. 11D] and [Fig. 11E] represent, by sectional top views, photodetectors according to other embodiments;

[0049] [Fig.l2A], [Fig.l2B], [Fig.l2C], [Fig.l2D], [Fig.l2E], [Fig.l2F] and [Fig.l2G] represent, by cross-sectional views, steps of an exemplary method of manufacturing a photodetector according to an embodiment;

[0050] [Fig. 13A], [Fig. 13B], [Fig. 13C], [Fig. 13D] and [Fig. 13E] represent, by cross-sectional views, steps of another example of a method of manufacturing a photodetector according to another embodiment; and

[0051] [Fig.l4A], [Fig.l4B], [Fig.l4C], [Fig.l4D] and [Fig.l4E] show curves representing different characteristics of photodetector pixels according to embodiments in comparison with subdivision photodetector pixels of the type of [Fig.lB]. Description of the embodiments

[0052] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0053] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, not all the circuits of a photodetector, for example a memory and / or a reading circuit, are detailed, the embodiments being compatible with all or most photodetector circuits, possibly subject to adaptations within the scope of the person skilled in the art upon reading the present description. In addition, mainly a photodetector has been shown, knowing that this photodetector can be integrated into an electronic device, for example in an image sensor pixel, and a pixel can comprise one or more photodetectors. Furthermore, not all the applications of the photodetectors are detailed.

[0054] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0055] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or to a photodetector in a normal position of use.

[0056] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0057] In the following description, a height or a depth corresponds to a dimension taken in the Z direction, corresponding to the longitudinal or lateral direction of the photodetector, which may be a vertical direction, a length corresponds to a dimension taken in the Y direction, corresponding to a first transverse direction of the photodetector, which may be a first horizontal direction, and a width corresponds to a dimension taken in the X direction, perpendicular to the Y direction, corresponding to a second transverse direction of the photodetector, which may be a second horizontal direction.

[0058] In the following description, when a region is referred to, unless otherwise specified, it is a semiconductor region. In the following description, when a charge is referred to, unless otherwise specified, it is a charge carrier, i.e., an electron or a hole.

[0059] In the following description, the expression "active region" of a photodetector designates a region from which the majority of the light radiation is captured. received by the photodetector and / or a region from which the majority of the light radiation provided by the photodetector is emitted.

[0060] In the examples given below, it is considered that the first conductivity type is of type N and that the second conductivity type is of type P, but the examples can also be applied if the conductivity types are reversed, i.e. that the first conductivity type is of type P and that the second conductivity type is of type N with, for example, appropriate reversals of voltages applied to the CDTIs.

[0061] The present description relates to photodetectors. Particular attention is paid to photodiodes, for example pinched photodiodes, and to photogates, in particular vertical pinched photodiodes and vertical photogates.

[0062] [Fig.1A] represents, by a simplified perspective view, an example of a photodetector 110, which may be a photogate of a pixel. In this example, the photodetector 110 comprises an N-doped active region 111, surrounded by a capacitive deep trench isolation (CDTI) 112. The capacitive deep trench is typically an insulating trench filled with a conductive or semiconductive element, such as metal or polysilicon, which can be polarized, thus forming a polarization grid. The capacitive deep trench 112 also makes it possible to isolate the photodetector, for example from other photodetectors. The active region 111 may correspond to a region of a semiconductive layer (not shown), for example silicon. With an N-doped active region, the bias applied to the CDTI is preferably negative in order to deplete the active region.

[0063] To improve the performance of such a photodetector, for example improving the signal-to-noise ratio (SNR), increasing the dynamic range (DR), and / or reducing the dark current (dark noise), one may seek to increase the storage capacity of the charge carriers in the active region of the photodetector, which may be referred to in English as "full well capacity", or FWC.

[0064] A known solution to increase the storage capacity (FWC) is to increase the doping in the active region. A problem with increasing the doping is that this leads to reducing the depletion effect and therefore requires increasing the bias of the capacitive deep trench to be able to deplete the active region, causing for example an increase in the consumption of an image sensor comprising these photodetectors.

[0065] We can then seek to reduce the size of the photodetector, at the same time as increasing the doping, to reduce the polarization of the CDTI, and increase the resolution of the photodetector, but this then reduces the storage capacity. This is generally referred to as pixel size reduction.

[0066] A solution to increase the performance of the photodetector may then consist of dividing the pixel into several sub-pixels, each sub-pixel corresponding to a photodetector having an active region surrounded by a deep capacitive trench, then grouping the charges of several adjacent sub-pixels. This technique is known as pixel binning, which can be defined as a technique for combining the charges of adjacent pixels, for example by adding or averaging these charges, using multiple pixel readings.

[0067] [Fig.lB] represents, by a simplified perspective view, an example of a pixel with photodetectors 120. [Fig.lB] illustrates the solution described above.

[0068] The photodetector pixel 120 comprises in this example four active regions 121A, 121B, 121C, 121D each surrounded by a CDTI 122A, 122B, 122C, 122D. For example, each active region surrounded by a CDTI forms a photodetector 120A, 120B, 120C, 120D, or sub-pixel.

[0069] This solution makes it possible to improve the storage capacity of the charge carriers of the equivalent pixel, corresponding to the grouped adjacent sub-pixels, without having to increase the polarization of the CDTIs, but this is achieved at the cost of more complex technology, in particular in powering the CDTIs, as well as in reading and processing the signals. For example, if the equivalent pixel corresponds to n adjacent sub-pixels, it is necessary to read and process n signals instead of just one if the pixel had not been divided. In addition, this has the consequence of reducing the evolution of the signal-to-noise ratio which evolves as the square root of the number of sub-pixels.

[0070] There is a need to increase the charge carrier storage capacity of a photodetector, without having to increase the polarization of the active region, and / or without having to increase the number of charge readings.

[0071] The inventors propose photodetectors making it possible to meet the improvement needs described above, and to overcome all or part of the drawbacks of the photodetectors described above.

[0072] Embodiments of photodetectors will be described below. The embodiments described are non-limiting and various variants will become apparent to those skilled in the art from the indications of the present description.

[0073] [Fig.2] represents, in a perspective view, a photodetector 200 according to one embodiment.

[0074] The photodetector 200 comprises, similarly to the photodetector 110 of [Fig.lA], an active region 210 of type N, for example doped N, surrounded by a lateral capacitive deep trench (CDTI) 220, or external CDTI, but it is mainly distinguished in that it further comprises a repulsion element 230 for the charges stored in the active region 210, this repulsion element being positioned within the active region 210. In the example shown, the repulsion element 230 is arranged substantially in the center of the active region, where the electrostatic control by the external CDTI is generally the weakest, but variants are possible.

[0075] In the case of an N-doped active region, the repulsion element is an element for repelling the electrons photogenerated and stored in the active region. In the case of a P-doped active region, the repulsion element is an element for repelling the holes photogenerated and stored in the active region.

[0076] This element is defined as a repulsion element in that it allows for improved depletion of the active region and for repelling a type of photogenerated charge carrier towards the active region.

[0077] The active region 210 is for example an N-doped portion of a silicon (Si) layer, for example an epitaxial silicon layer.

[0078] In the example of [Fig.2], the lateral capacitive deep trench 220 forms a square-section crown around the active region 210 which is parallelepipedal, but other shapes and configurations will appear to the person skilled in the art. For example, there could be several external CDTIs.

[0079] As can be seen in more detail in [Fig.3B] for example, the lateral capacitive deep trench 220 comprises an insulating trench 221, for example made of silicon dioxide (SiO2), filled with a conductive or semiconductive element 222, such as metal or polysilicon, which can be polarized, thus forming a polarization grid. The lateral capacitive deep trench 220 can also laterally isolate the photodetector, for example from other photodetectors, in particular by the presence of the insulating trench 221. The capacitive deep trench is said to be lateral insofar as it extends in a direction substantially parallel to the longitudinal direction of the photodetector, at the lateral edges of the photodetector.

[0080] With an N-doped active region, the bias applied to the lateral CDTI 220 is preferably negative. Alternatively, if the active region were P-doped, the bias applied to the lateral CDTI would preferably be positive.

[0081] In the example of [Fig. 2], the repulsion element 230 is represented in the form of a P-doped implant region, for example heavily P-doped, which has the shape of a pillar of substantially square cross-section. Other pillar cross-sections may be envisaged for the implant region, for example a rectangular cross-section or another polygonal cross-section, an oval cross-section, a circular cross-section, or even other shapes than a pillar. The P-doped implant region may be made of silicon, for example correspond to a P-doped portion of a silicon (Si) layer in which the active region 210 is formed.

[0082] The implant region may be polarized to control its potential, or connected to a floating potential, for example if it is heavily doped, particularly in the case of implant points as described later in another embodiment.

[0083] Alternatively, instead of an implant region, the repulsion element 230 may be an internal capacitive deep trench (CDTI) inserted within the active region 210, for example disposed substantially in the center of the active region.

[0084] In the example of [Fig.2], the repulsion element 230 extends in the Z direction, which is here a vertical direction. As described later in another embodiment, one or more repulsion elements may be in another direction, for example a horizontal direction.

[0085] The repulsion element does not divide the photodetector into several distinct volumes, or several smaller photodetectors, unlike the photodetector pixel of [Fig.lB].

[0086] For example, the repulsion element contacts the upper and lower faces of the active region over a portion of the width or length of the active region, but not over the entire width or length of the active region. For example, the repulsion element does not contact either of the upper and lower faces of the active region.

[0087] For example, the repulsion element is surrounded by the active region in a plane, for example an XY plane in the example shown, but it may be another plane, for example a YZ plane in the embodiment of Figures 10A and 10B. In other words, in the sectional views parallel to this plane, it can be seen that the repulsion element is surrounded by the active region.

[0088] By being positioned within the active region which is of type N (first type of conductivity), and by being doped P (second type of conductivity opposite to the first type of conductivity) in the case of an implant region, or for example negatively polarized in the case of an internal CDTI, the repulsion element makes it possible to locally deplete the active region, typically at the junction between the active region and the repulsion element, with the aim of avoiding the presence of neutral regions in the active region. For example, the repulsion element completes the lateral CDTI 220, thus making it possible not to have to apply too high a polarization in this lateral CDTI, even when the active region 210 is heavily doped. This also avoids increasing the number of readings of the pixel or sub-pixel charges, since the binning technique is not applied.This is because the repulsion element does not divide the photodetector into several smaller photodetectors, as shown above.

[0089] [Fig.2] shows a single repulsion element, but the photodetector may advantageously comprise several repulsion elements within the active region, as described in the embodiments which follow. The repulsion elements are arranged so that they do not divide the photodetector into several distinct volumes, or photodetector sub-elements. For example, each repulsion element is surrounded by the active region in at least one plane.

[0090] [Fig.3A] represents, by a top sectional view, a photodetector 300 according to another embodiment. [Fig.3B] represents, by a cross-sectional view, the photodetector of [Fig.3A]. The sectional view of [Fig.3B] is produced along the sectional plane AA of [Fig.3A]. The sectional view of [Fig.3A] is produced along the sectional plane BB of [Fig.3B].

[0091] The photodetector 300 comprises, similarly to the photodetector 200 of [Fig. 2], an active region 210 of type N, for example doped N, surrounded by a lateral capacitive deep trench 220 (or external CDTI), but it is distinguished therefrom mainly in that, instead of having a single repulsion element, it comprises several repulsion elements 330, four in the example, within the active region 210. Furthermore, each repulsion element 330 is in the form of an internal capacitive deep trench (CDTI).

[0092] Having capacitive deep trenches as repulsion elements allows for better electrostatic control over implant regions. It may further be possible to reuse masks used to form the lateral capacitive deep trench 220.

[0093] Each internal capacitive deep trench 330 comprises an insulating trench 331, for example made of SiO2, filled with a conductive or semiconductive element 332, such as metal or polysilicon, which can be polarized, thus forming a polarization grid. With an N-doped active region, the bias applied to each internal CDTI is preferably negative. Alternatively, if the active region were P-doped, the bias applied to each internal CDTI would preferably be positive.

[0094] In the example of Figures 3A and 3B, the internal capacitive deep trenches 330 are substantially regularly distributed within the active region 210, but other configurations will appear to those skilled in the art.

[0095] In the example of Figures 3A and 3B, each internal capacitive deep trench 330 is represented in the form of a pillar of substantially square section. Other pillar sections may be envisaged, for example a rectangular section or another polygonal section, an oval section, a circular section, or even other shapes than a pillar.

[0096] The photodetector 300 further comprises a P-doped region 301 at the upper face 210A of the active region 210, as well as extraction grids 302 (or transfer gates) passing through the P-doped region 301. An N-type conductive channel may form in a portion of the P-doped region 301 when the extraction gates 302 are biased, to extract the charges. The lower face 210B of the active region is insulated by an insulating region 303 (Ox), for example a SiO2 layer.

[0097] [Fig.4A] represents, by a top sectional view, a photodetector 400 according to yet another embodiment. [Fig.4B] represents, by a cross-sectional view, the photodetector of [Fig.4A]. The sectional view of [Fig.4B] is produced along the sectional plane AA of [Fig.4A]. The sectional view of [Fig.4A] is produced along the sectional plane BB of [Fig.4B].

[0098] The photodetector 400 comprises, similarly to the photodetector 300 of FIGS. 3A and 3B, an active region 410 of type N, for example N-doped, surrounded by a deep lateral capacitive trench 220, a P-doped region 301 at the upper face 410A of the active region 410, extraction gates 302, and an insulating region 303 (Ox) at the lower face 410B of the active region 410, but it is distinguished therefrom mainly in that the repulsion elements 430 are P-doped implant regions, for example heavily P-doped (P+), in the form of pillars (implant pillars). The implant region features described in connection with [Fig. 2], as well as variations thereof, may be applied to the repulsion elements 430 of Figures 4A and 4B.

[0099] In the example of Figures 4A and 4B, the implant pillars 430 extend in the vertical direction Z from the lower face 410B (first face) of the active region 410, and more precisely from a heavily P-doped region 404 (P+) located at the lower face 410B of the active region 410 on the insulating region 303, but they do not extend to the upper face 410A (second face) of the active region 410. The heavily P-doped region 404 makes it possible to connect the implant regions 430 to each other, for example in an equipotential manner. The fact that the implant pillars 430 do not reach the upper face of the active region, more generally that the implant regions or the repulsive elements do not reach one or more faces of the active region, can make it possible to eliminate problems of potential barriers which can cause charge remanences.

[0100] According to an alternative embodiment shown in dotted lines, a heavily N-doped portion 415 (N+) of the active region 410 can advantageously be provided between the P-doped region 301 and the implant pillars 430. Such an alternative allows better collection of charges on the upper face of the photodetector, for example by eliminating the problem of charge remanence.

[0101] [Fig.5A] represents, by a top view in section, a photodetector 500 according to yet another embodiment. [Fig.5B] represents, by a view in section transverse, the photodetector of [Fig.5A]. The sectional view of [Fig.5B] is made along the sectional plane AA of [Fig.5A]. The sectional view of [Fig.5A] is made along the sectional plane BB of [Fig.5B].

[0102] The photodetector 500 of FIGS. 5A and 5B differs from the photodetector of FIGS. 4A and 4B mainly in that the repulsion elements 530 in the form of implant pillars extend in the vertical direction Z from the lower face 210B to the upper face 210A of the active region 210, and that there is no heavily N-doped region between the P-doped region 301 and the implant pillars 530. In addition, no heavily P-doped region (P+) has been shown at the lower face 210B of the active region 210 on the insulating region 303, but this may be provided.

[0103] Having implant regions as repulsion elements allows for greater flexibility in the dimensions and shapes of the repulsion elements compared to internal CDTIs, and to be able to collect holes, for example via the application of a contact at the top of the pillar. In addition, the implementation of implant regions may be simpler to manufacture than CDTIs.

[0104] [Fig.6A] represents, by a top sectional view, a photodetector 600 according to yet another embodiment. [Fig.6B] represents, by a cross-sectional view, the photodetector of [Fig.6A]. The sectional view of [Fig.6B] is produced along the sectional plane AA of [Fig.6A]. The sectional view of [Fig.6A] is produced along the sectional plane BB of [Fig.6B].

[0105] The photodetector 600 of FIGS. 6A and 6B differs from the photodetector of FIGS. 5A and 5B mainly in that each implant region 630 does not form a continuous pillar, but forms a discontinuous pillar comprising several implant points 631, 632, 633 separated from each other by portions of the active region 210, for example N-doped Si portions, and extending one above the other in the vertical direction Z.

[0106] Having implant points as repulsion elements allows for an increase in charge carrier storage capacity (FWC) compared to continuous pillars. Indeed, the volume between two successive implant points can serve as a storage area, thereby maximizing the volume of depleted active region.

[0107] The photodetectors of Figures 3A, 3B, 5A and 5B may correspond to photogrids, or photogates.

[0108] [Fig.7A] represents, by a top sectional view, a photodetector 700 according to yet another embodiment. [Fig.7B] represents, by a cross-sectional view, the photodetector of [Fig.7A]. The sectional view of [Fig.7B] is produced along the sectional plane AA of [Fig.7A]. The sectional view of [Fig.7A] is produced along the sectional plane BB of [Fig.7B].

[0109] The photodetector 700 of Figures 7A and 7B differs from the photodetector of Figures 4A and 4B mainly in that the lateral CDTI 220 is replaced by a P-doped, for example heavily P-doped (P+) lateral implant region 722, this lateral implant region 722 being isolated from other photodetectors by an insulating trench 721, for example a deep trench isolation (DTI). The implementation of implant regions may be simpler to manufacture than the CDTIs.

[0110] In the example of Figures 7A and 7B, the lateral implant region 722 forms a square-section crown around the active region 410 which is parallelepipedal, but other shapes and configurations will appear to those skilled in the art. For example, there could be several lateral implant regions.

[0111] Similar to the photodetector 400 of FIGS. 4A and 4B, the repulsion elements of the photodetector 700 are P-doped implant regions 430, for example heavily P-doped (P+), in the form of continuous pillars which extend in the vertical direction Z from the lower face 410B (first face) of the active region 410, and more precisely from a heavily P-doped region 404 (P+) located at the lower face 410B of the active region 410 on an insulating region 303, but which do not extend to the upper face 410A (second face) of the active region 410.

[0112] Further, similar to photodetector 400 of Figures 4A and 4B, a heavily N-doped portion 415 (N+) of active region 410 may be provided between P-doped region 301 and implant pillars 430.

[0113] [Fig.8A] represents, by a top sectional view, a photodetector 800 according to yet another embodiment. [Fig.8B] represents, by a cross-sectional view, the photodetector of [Fig.8A]. The sectional view of [Fig.8B] is produced along the sectional plane AA of [Fig.8A]. The sectional view of [Fig.8A] is produced along the sectional plane BB of [Fig.8B].

[0114] The photodetector 800 of Figures 8A and 8B differs from the photodetector of Figures 5A and 5B mainly in that, similarly to the photodetector of Figures 7A and 7B, the lateral CDTI 220 is replaced by a P-doped, for example heavily P-doped (P+) lateral implant region 722, this lateral implant region being isolated from other photodetectors by an insulating trench 721, for example a deep trench insulator (DTI). The photodetector 800 comprises a heavily P-doped region 404 (P+) at the lower face 210B of the active region 210. Similar to the photodetector 500 of FIGS. 5A and 5B, the repulsion elements of the photodetector 800 are P-doped, for example heavily P-doped (P+), implant regions 530 in the form of continuous pillars that extend in the vertical direction Z from the lower face 210B to the upper face 210A of the active region 210. The lower face 210B of the active region 210 is insulated by an insulating region 303 (Ox).

[0115] [Fig.9A] represents, by a top sectional view, a photodetector 900 according to yet another embodiment. [Fig.9B] represents, by a cross-sectional view, the photodetector of [Fig.9A]. The sectional view of [Fig.9B] is produced along the sectional plane AA of [Fig.9A]. The sectional view of [Fig.9A] is produced along the sectional plane BB of [Fig.9B].

[0116] The photodetector 900 of Figures 9A and 9B differs from the photodetector of Figures 6A and 6B mainly in that, similarly to the photodetector of Figures 7A and 7B, the lateral CDTI 220 is replaced by a P-doped, for example heavily P-doped (P+) lateral implant region 722, this lateral implant region being isolated from other photodetectors by an insulating trench 721, for example a deep trench insulator (DTI). 6A and 6B, the repulsion elements of the photodetector 900 are P-doped or heavily P-doped implant regions 630, in the form of discontinuous pillars each comprising several P-doped or heavily P-doped (P+) implant points 631, 632, 633, separated from each other by portions of the active region 210. The lower face 210B of the active region 210 is isolated by an insulating region 303. The photodetector 900 may comprise a heavily P-doped region 404 (P+) on the insulating region 303.

[0117] [Fig. 10A] represents, by a top sectional view, a photodetector 1000 according to yet another embodiment. [Fig.lOB] represents, by a cross-sectional view, the photodetector of [Fig.lOA]. The sectional view of [Fig.lOB] is produced along the sectional plane AA of [Fig.lOA]. The sectional view of [Fig.lOA] is produced along the sectional plane BB of [Fig.lOB].

[0118] The photodetector 1000 of FIGS. 10A and 10B differs from the previous photodetectors mainly in that the repulsion elements 1030 extend in a horizontal direction X instead of the vertical direction Z. The repulsion elements 1030 are for example six in number, but this is not limiting, and are separated from each other by a non-zero distance in the vertical direction Z, the space between two repulsion elements being filled by portions of the active region 1010, for example N-doped silicon, which can be formed by epitaxy.

[0119] Similar to the photodetectors of Figures 3A to 6B, the photodetector 1000 includes a lateral CDTI 220 (external CDTI) around the active region 1010. Alternatively, the lateral CDTI could be replaced by a P-doped, for example heavily P-doped, lateral implant region, similar to the photodetectors of Figures 7A to 9B.

[0120] Similar to the photodetectors of Figures 3A to 6B, the repulsion elements 1030 of the photodetector 1000 are implant regions in the form of pillars, the pillars 1030 being oriented horizontally instead of vertically, and the photodetector comprises an insulating region 303 at the lower face 1010B of the active region 1010. The photodetector 1000 further comprises a lower P-doped region 1004 located at the lower face 1010B of the active region 1010 on the insulating region 303, an upper P-doped region 1005 located at the upper face 1010A of the active region 1010, and a heavily N-doped portion 1015 (N+) of the active region between the upper P-doped region 1005 and the upper pillar 1030A.

[0121] In the example shown, the repulsion elements 1030 start from a first lateral face 1010C (the left edge in [Fig.10A]) of the active region 1010 but do not extend to a second lateral face 1010D opposite the first lateral face (the right edge in [Fig.10A]) of the active region 1010, the space between the repulsion elements 1030 and the second lateral face comprising a heavily N-doped region 1016 (N+) of the active region 1010. This is a non-limiting example and other variants may be envisaged by those skilled in the art.

[0122] The embodiment with horizontal repulsion elements can make it possible to increase the storage capacity of the active region, even when the latter has a significant height to width ratio, for example small width for a large height.

[0123] The various embodiments described show that numerous variants of photodetectors with repulsion elements in the active region can be envisaged, thus allowing great adaptability to different types and different dimensions of photodetectors, and thus of pixels.

[0124] More generally than the examples of Figures 4A, 4B, 7A, 7B, 10A, 10B, the active region may have a non-homogeneous N doping (or P in the case of a P-type active region) in the vertical direction Z and / or in a horizontal direction. This may make it possible to avoid residual charges due to potential barriers, and / or make it possible to improve the storage of charge carriers, for example at the edges of the photodetector, for example by exploiting the fact that the electrostatic control on the edges of the photodetector is better due to the distribution of the electric field lines and may therefore make it possible to deplete a more heavily doped area locally.

[0125] [Fig. 11A], [Fig. 11B], [Fig. 11C], [Fig. 11D] and [Fig. 11E] represent, by means of sectional top views, photodetectors according to other embodiments. These figures show in particular other configurations of insertion elements in the active region and other examples of non-homogeneous doping of the active region.

[0126] The photodetector 1101 of [Fig. 11 A] differs from the photodetector 400 of FIGS. 4A and 4B mainly in that the active region 1110 has non-homogeneous doping. In this example, the active region 1110 comprises first heavily N-doped (N+) strips 1112 extending in the X direction between the adjacent implant pillars 430 in this X direction and on either side of these adjacent implant pillars to the lateral edges of the active region 1110 which are opposite in this X direction, and second heavily N-doped (N+) strips 1113 extending in the Y direction between the adjacent implant pillars 430 in this Y direction and on either side of these adjacent pillars to the lateral edges of the active region 1110 which are opposite in this Y direction. The remainder of the active region 1110, which is not in the form of heavily N-doped strips 1112, 1113, corresponds to less heavily N-doped portions 1111 of the active region 1110.

[0127] The photodetector 1102 of [Fig. 1 IB] differs from the photodetector 400 of FIGS. 4A and 4B mainly in that the active region 1120 has non-homogeneous doping. In this example, the active region 1120 comprises very heavily N-doped (N++) corner portions 1124 in the corners of the active region 1120 each encompassing an implant abutment 430, a first heavily N-doped (N+) band 1122 in the X direction between the corner portions 1124 up to the side edges of the active region 1120 which are opposite in this X direction, a second heavily N-doped (N+) band 1123 in the Y direction between the corner regions up to the side edges of the active region 1120 which are opposite in this Y direction, and a less N-doped (N) central portion 1121 which corresponds to the intersection between the first and second bands 1122, 1123.

[0128] The photodetector 1103 of [Fig. 1 IC] is similar to the photodetector of [Fig. 1 IA], but with nine implant pillars 430 regularly distributed in the active region 1110 instead of four in [Fig. 11 A] and thus three first heavily N-doped (N+) 1112 bands extending in the X direction, and three second heavily N-doped (N+) 1113 bands extending in the Y direction. The remainder of the active region 1110, which is not in the form of heavily N-doped 1112, 1113 bands, corresponds to less heavily N-doped 1111 portions of the active region 1110.

[0129] The photodetector 1104 of [Fig. 11D] is similar to the photodetector of [Fig. 11B], but with nine implant pillars 430 regularly distributed in the active region 1120 instead of four in [Fig. 11B], the very heavily N-doped (N++) corner portions 1124 of the active region 1120 encompassing the four most eccentric implant pillars, the first and second bands 1122, 1123 encompassing the four implant pillars positioned between the most eccentric implant pillars in each of the X and Y directions, and the central portion 1121 encompassing a central implant pillar.

[0130] The examples of Figures 1 1A and 1 1C make it possible, for example, to remove local potential barriers, for example linked to a smaller distance between two neighboring pillars. The examples of Figures 1 1B and 11D make it possible, for example, to increase the stored charges by improving the homogeneity of the charges: since it is easier to deplete the active region in the corners, the doping is stronger in these corner regions.

[0131] The photodetector 1105 of [Fig. 11E] is distinguished from all other embodiments in that the implant regions are pillars 1130 of circular cross-section and that most of the pillars are arranged substantially equidistant from each other in the active region 210. This configuration can make it possible to reduce the local potential barriers in the active region.

[0132] Other configurations than those presented in Figures 1 1A to 11E may be envisaged by the person skilled in the art, for example depending on the number of repulsion elements, for example vertical implant pillars, and / or depending on the desired effect (for example removing or minimizing potential barriers or increasing charge homogeneity). Furthermore, instead of one (or more) external CDTI(s), the photodetectors of Figures 11A to 11E could comprise one (or more) P-doped lateral implant region(s), for example heavily P-doped, isolated from other photodetectors by one (or more) insulating trench(es).

[0133] The photodetectors of Figures 1 1A to 11E may correspond to photogrids.

[0134] [Fig.l2A], [Fig.l2B], [Fig.l2C], [Fig.l2D], [Fig.l2E], [Fig. 12F] and [Fig.l2G] represent, by cross-sectional views, steps of an exemplary method of manufacturing a photodetector according to one embodiment. The manufactured photodetector may be similar to the photodetector 500 of Figures 5A and 5B.

[0135] [Fig.12A] represents a starting structure comprising a silicon substrate 1201, surmounted by an N-doped epitaxial silicon layer 1202. A first etching mask 1203 is positioned on the upper face 1202A of the epitaxial silicon layer 1202. The etching mask 1203 comprises first openings 1204.

[0136] [Fig.12B] represents a structure obtained at the end of the etching of the epitaxial silicon layer 1202 from its upper face 1202A and through the first openings 1204 of the first etching mask 1203, so as to form first trenches 1205 in the epitaxial silicon layer 1202. In the example shown, the first trenches 1205 do not extend throughout the entire thickness of this epitaxial silicon layer 1202. Alternatively, the first trenches 1205 could extend throughout the entire thickness of the epitaxial silicon layer 1202 as far as the substrate 1201.

[0137] [Fig.l2C] represents a structure obtained after filling the first trenches 1205 by epitaxial growth with heavily P-doped silicon (P+), or even very heavily P-doped silicon, and removing the first etching mask 1203. Thus, heavily P-doped implant regions 1206 are formed in the form of vertical pillars in an N-doped active region formed by the epitaxial silicon layer 1202.

[0138] [Fig. 12D] represents a structure obtained after the formation of a second etching mask 1207 on the upper face 1202A of the epitaxial silicon layer 1202, this second etching mask comprising second openings 1208, then the formation of second trenches 1209 in the epitaxial silicon layer 1202 by etching from its upper face 1202A and through the second openings 1208 of the second etching mask 1207. In the example shown, the second trenches 1209 do not extend throughout the entire thickness of this epitaxial silicon layer 1202, and extend substantially at the same level as the first trenches 1205 and as well as the implant regions 1206. Alternatively, the second trenches 1209 could extend throughout the thickness of the epitaxial silicon layer 1202 up to the substrate 1201.

[0139] [Fig.l2E] shows a structure obtained after forming capacitive deep trenches (CDTI) 1210 in the second trenches 1209. For example, the second trenches 1209 may be isolated from the epitaxial silicon layer 1202 by an insulator, for example SiO2, then filled with a conductive or semiconductive material, such as a metal or polysilicon, to form the capacitive deep trenches 1210.

[0140] [Fig. 12F] represents a structure obtained after removing the second etching mask 1207, forming extraction gates 1211, a heavily N-doped region 1212 (N+) in the epitaxial silicon layer 1202 from the upper face 1202A of this layer, above the vertical implant pillars 1206, and a P-doped region 1213 on the heavily N-doped region 1212.

[0141] Alternatively, the second etching mask 1207 may be removed before the formation of the CDTIs 1210.

[0142] [Fig.l2G] represents a structure obtained after removing the substrate 1201, oxidizing a lower portion of the epitaxial silicon layer 1202 so as to form an insulating region 1214 on the lower face 1202B of the epitaxial silicon layer 1202, under the vertical implant pillars 1206, and assembling an interconnection substrate 1215 on the upper face 1202A of the epitaxial silicon layer 1202, on the P-doped layer 1213.

[0143] [Fig.l3A], [Fig.l3B], [Fig.l3C], [Fig.l3D] and [Fig.l3E] represent, by cross-sectional views, steps of another example of a method of manufacturing a photodetector according to another embodiment. The manufactured photodetector may be similar to the photodetector 1000 of Figures 10A and 10B.

[0144] [Fig.l3A] shows a starting structure comprising a silicon substrate 1301, topped with an N-doped epitaxial silicon layer 1302, in which first trenches 1303 filled by epitaxial growth with heavily N-doped silicon have been formed so as to form heavily N-doped regions 1304 (N+) in the epitaxial silicon layer 1302. The first trenches 1303 can be formed using a first etching mask, similarly to the first mask 1203 with the first openings 1204 of [Fig.l2A]. In the example shown, the heavily N-doped regions 1304 do not extend throughout the entire thickness of this epitaxial silicon layer 1302. Alternatively, the heavily N-doped regions 1304 could extend throughout the entire thickness of the epitaxial silicon layer 1302 up to the substrate 1301.

[0145] [Fig.13B] represents a structure obtained after the formation of a second etching mask 1305 on the upper face 1302A of the epitaxial silicon layer 1302, this second etching mask comprising second openings 1306, then the formation of second trenches 1307 in the epitaxial silicon layer 1302 by etching from its upper face 1302A and through the second openings 1306 of the second etching mask 1305. In the example shown, the second trenches 1307 do not extend throughout the entire thickness of the epitaxial silicon layer 1302, and extend substantially at the same level as the first trenches 1303 and as well as the heavily N-doped regions 1304. Alternatively, the second trenches 1307 could extend throughout the entire thickness of the epitaxial silicon layer 1302. the thickness of the epitaxial silicon layer 1302 up to the substrate 1301.

[0146] [Fig. 13C] represents a structure obtained following the formation by epitaxial growth with heavily P-doped silicon (P+), or even very heavily P-doped silicon, in the second trenches 1307, of heavily P-doped implant regions 1308 (P+) in the form of horizontal pillars alternating with N-doped silicon regions 1309 also formed by epitaxial growth.

[0147] [Fig. 13D] represents a structure obtained after the formation of a third etching mask 1310 on the upper face 1302A of the epitaxial silicon layer 1302, this third etching mask comprising third openings 1311, then the formation of third trenches 1312 in the epitaxial silicon layer 1302 by etching from its upper face 1302A and through the third openings 1311 of the third etching mask 1310. In the example shown, the third trenches 1312 do not extend throughout the thickness of the epitaxial silicon layer 1302, and extend substantially at the same level as the first and second trenches 1303, 1307. Alternatively, the third trenches could extend throughout the thickness of the epitaxial silicon layer 1302 to the substrate 1301.

[0148] [Fig.13E] shows a structure obtained after forming capacitive deep trenches 1313 in the third trenches 1312. For example, the third trenches 1312 may be isolated from the epitaxial silicon layer 1302 by an insulator, for example SiO2, then filled with a conductive or semiconductive material, such as a metal or polysilicon, to form the capacitive deep trenches 1313.

[0149] Then, similarly to what is described in relation to FIGS. 12F and 12G, the third etching mask 1310 can be removed, extraction gates can be formed on the upper face 1302A of the epitaxial silicon layer 1302, the substrate 1301 can be removed, a lower portion of the epitaxial silicon layer 1302 can be oxidized so as to form an insulating region on the lower face of the epitaxial silicon layer 1302, and an interconnect substrate can be assembled on the upper face of the epitaxial silicon layer 1302.

[0150] [Fig.l4A], [Fig.l4B], [Fig.l4C], [Fig.l4D] and [Fig.l4E] show curves representing different characteristics of photodetector pixels according to embodiments (pillar) in comparison with subdivision photodetector pixels of the type of [Fig.lB] (binning).

[0151] [Fig. 14A] shows curves giving the dark current (Dark Current of summed pixels) as a function of the pixel size (pixel pitch) in a given direction for photodetector pixels of the type in [Fig. 1B] (curve 1401) in comparison with photodetector pixels according to embodiments (curve 1402).

[0152] The circled points correspond to the number n of subdivisions in the given direction for curve 1401 (or to the number p of wall(s) separating the pixel into n subdivisions in the given direction) and to the number p of pillars in the given direction for curve 1402. The curves show that the dark current is lower for the photodetectors according to the embodiments compared to the photodetectors with binning type subdivisions, regardless of the number of subdivisions / walls. The embodiments therefore make it possible to reduce the dark current.

[0153] [Fig.l4B] shows curves giving the storage capacity (FWC of summed pixels) as a function of the pixel size (pixel pitch) in the given direction for pixels with photodetectors of the type in [Fig.lB] (curve 1403) in comparison with pixels with photodetectors according to embodiments (curve 1404). The curves show that one can benefit from an equivalent, or even slightly higher, storage capacity for the photodetectors according to the embodiments compared to binning-type subdivision photodetectors, regardless of the number of subdivisions / walls, and without the disadvantages of binning-type subdivision photodetectors indicated above.

[0154] [Fig.l4C] shows curves giving the dynamic range (DR) as a function of the pixel size (pixel pitch) in the given direction for pixels with photodetectors of the type of [Fig.lB] (curve 1405) in comparison with pixels with photodetectors according to embodiments (curve 1406). The curves show that the dynamic range is greater for photodetectors according to the embodiments compared to photodetectors with binning subdivisions, regardless of the number of subdivisions / walls. The embodiments therefore make it possible to increase the dynamic range.

[0155] [Fig.l4D] shows curves giving the charge to voltage conversion factor (CVF) as a function of pixel pitch in the given direction for pixels with photodetectors of the type of [Fig.lB] (curve 1407) in comparison with pixels with photodetectors according to embodiments (curve 1408). The curves show that an equivalent conversion factor can be benefited from for photodetectors according to the embodiments compared to photodetectors with binning subdivisions, regardless of the number of subdivisions / walls, and without the disadvantages indicated above for photodetectors with binning subdivisions.

[0156] [Fig.l4E] shows curves giving the equivalent noise (Read noise of summed pixels) as a function of the pixel size (pixel pitch) in a given direction for pixels with photodetectors of the type in [Fig.lB] (curve 1409) in comparison with pixels with photodetectors according to embodiments (curve 1410). The curves show that the equivalent noise is lower for the photodetectors according to the embodiments compared to the photodetectors with subdivisions of the binning type, regardless of the number of subdivisions / walls. The embodiments therefore make it possible to reduce the equivalent noise, and thus to increase the signal-to-noise ratio.

[0157] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the active region is N-type in the examples described, the implant regions being P-type, and the CDTIs being, for example, configured to be negatively biased (electron extraction). Alternatively, the active region may be P-type, the implant regions then being N-type, and the CDTIs being, for example, configured to be positively biased (hole extraction).

[0158] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. A semiconductor photodetector (200; 300; 400; 500; 600; 700; 800; 900; 1000; 1101-1105) comprising: - an active region (210; 410; 1010; 1110; 1120) made of a doped semiconductor material of a first conductivity type, said active region being adapted to convert light radiation into charge carriers and to store said charge carriers; and - at least one repulsion element (230; 330; 430; 530; 630; 1030; 1130) adapted to repel charge carriers stored in the active region, said repulsion element being positioned within the active region.

2. A method of manufacturing a semiconductor photodetector, the method comprising: - forming an active region (210; 410; 1010; 1110; 1120) of a doped semiconductor material of a first conductivity type, said active region being adapted to convert light radiation into charge carriers and to store said charge carriers; and - forming at least one repulsion element (230; 330; 430; 530; 630; 1030; 1130) adapted to repel charge carriers stored in the active region, said repulsion element being formed within the active region.

3. A photodetector according to claim 1, wherein the at least one repulsion element is arranged in the active region such that it does not divide said active region into several distinct volumes.

4. A photodetector according to claim 1 or 3, wherein the at least one repulsion element is surrounded by the active region in at least one plane.

5. Photodetector (300; 400; 500; 600; 700; 800; 900; 1000; 1101-1105) according to any one of claims 1, 3, 4, wherein the at least one repulsion element comprises several repulsion elements (330; 430; 530; 630; 1030; 1130), for example several repulsion elements regularly distributed in the active region (210; 410), for example several repulsion elements substantially equidistant from each other.

6. Photodetector (200; 300; 400; 500; 600; 700; 800; 900; 1101-1105) according to any one of claims 1, 3 to 5, wherein the at least one repulsion element (230; 330; 430; 530; 630; 1130) is oriented in a longitudinal direction (Z) of the photodetector.

7. A photodetector (1000) according to any one of claims 1, 3 to 5, wherein the at least one repulsion element (1030) is oriented in a transverse direction (X) of the photodetector.

8. Photodetector (200; 300; 400; 500; 700; 800; 1000; 1101-1105) according to any one of claims 1, 3 to 7, wherein the at least one repulsion element (230; 330; 430; 530; 1030; 1130) has the shape of a continuous pillar, for example a pillar of polygonal, rectangular, square, oval or circular section.

9. Photodetector (600; 900) according to any one of claims 1, 3 to 8, wherein the at least one repulsion element (630) comprises several implant points (631, 632, 633) separated from each other by portions of the active region (210), forming for example a discontinuous pillar.

10. Photodetector (400; 600; 700; 900; 1000) according to any one of claims 1, 3 to 9, wherein the at least one repulsion element (430; 630; 1030) extends from a first face (210B; 410B; 1010C) of the active region (210; 410; 1010) to a non-zero distance from a second face (210A; 410A; 1010D) of the active region opposite the first face, a portion (415; 1016) of the active region located between said at least one repulsion element and said second face being for example heavily doped with the first conductivity type.

11. A photodetector (200; 300) according to any one of claims 1, 3 to 10, wherein the at least one repulsion element (230; 330) comprises, for example, an internal capacitive deep trench, preferably adapted to be biased so as to repel stored charge carriers.

12. A photodetector (200; 400; 500; 600; 700; 800; 900; 1000; 1101-1105) according to any one of claims 1, 3 to 11, wherein the at least one repulsion element (230; 430; 530; 630; 1030; 1130) comprises, for example, an implant region doped with the second conductivity type opposite to the first conductivity type.

13. A photodetector according to any one of claims 1, 3 to 12, further comprising a lateral insulating trench (221; 721) configured to laterally isolate said photodetector, for example from other photodetectors.

14. A photodetector (300; 400; 500; 600; 1000; 1101-1105) according to claim 13, wherein the insulating trench (221) contains a conductive or semiconductive element (222), the insulating trench and the conductive or semiconductive element forming a lateral capacitive deep trench (220).

15. A photodetector (700; 800; 900) according to claim 13 or 14, comprising a lateral implant region (722) between the lateral insulating trench (721) and the active region (210; 410), the lateral implant region being doped with the second conductivity type opposite to the first conductivity type.

16. Photodetector according to any one of claims 1, 3 to 15, in which the active region (410; 1010; 1110; 1120) has non-homogeneous doping, for example in one or more transverse directions of the photodetector.

17. An image sensor comprising a plurality of pixels, each pixel comprising at least one photodetector according to any one of claims 1, 3 to 16.

Images