IMAGE SENSOR WITH SIDE-MOUNTED ELECTRONIC CATCHING

Description

Domaine technique

[0001] The present invention relates to image sensors in general, and more particularly, but not exclusively, to image sensors for visible and short wave infrared (SWIR), namely between 900 nm and 1700 nm. Technique antérieure

[0002] SWIR sensors based on crystalline semiconductor materials, such as InGaAs, are known. Such a photosensitive structure is represented very schematically in the diagram. figure 1 .

[0003] Light is absorbed by the semiconductor material (InGaAs) 14, and then the electrons thus generated are transmitted into each pixel of the readout circuit 16 (“Read Out Integrated Circuit”) ROIC ) via electrodes in the form of metallic beads 18 which also ensure the mechanical integrity of the assembly. This is the most common approach in commercial detectors. The principle is identical for other wavelengths and materials (HgCdTe, InSb, etc.)

[0004] A second approach for IR imaging is to replace the semiconductor material 14 with dispersed nanocrystals (quantum dots, more commonly known as "Colloidal Quantum Dots" (CQD)). This potentially offers a solution with lower manufacturing costs, as well as sensitivity to other wavelengths.

[0005] A photosensitive structure operating according to this second approach is illustrated in the figure 2 When light is absorbed, electrons are generated at the CQD 19 in a polymer matrix 15. An electric field E, whose resultant is directed along the normal to the plane of the sensor, is applied by means of an external metallic layer 11 deposited on the polymer matrix 15. This electric field makes it possible to collect the electrons generated at the level of each pixel of the reading circuit 16, all the collection electrodes 18 associated with the pixels being at the same potential.

[0006] US patent applications 2016 / 0181325 and US patent applications 2016 / 119562 describe an image sensor operating according to this second approach.

[0007] The problem with such an architecture is that the metallic layer absorbs and reflects some of the incident light, which reduces the sensitivity of the sensor and complicates manufacturing. Exposé de l'invention

[0008] Therefore, there is a need to further improve image sensors, and in particular to solve this problem.

[0009] The invention aims to address this, according to a first aspect, by means of a method of operating an image sensor according to claim 1, comprising a medium including at least one photosensitive material capable of generating charges by photoelectric effect when the sensor is exposed to incident light, and collection electrodes in contact with said medium, associated with pixel circuits, a method in which at least one electric field having a lateral component is created to collect said charges on at least one of said collection electrodes, allowing their reading by the associated pixel circuit, and in which said electric field is generated by creating at least one potential difference between said collection electrode and at least one other area of ​​the sensor, brought to a different potential, this other area being located between at least two collection electrodes.

[0010] Thanks to the invention and the lateral component of the field created by the potential difference between said collection electrode and said at least one other area of ​​the sensor, it is possible to do without an external electrode in the form of a metallic layer deposited on top of the medium comprising the photosensitive material.

[0011] The invention thus makes it possible to collect more light and improve the sensor's performance, particularly its sensitivity. Furthermore, the sensor's manufacturing process can be simplified, as the aforementioned outer layer deposition step is no longer necessary.

[0012] This other area is another collecting electrode, which is not then used to collect charges during the generation of the electric field, or any other electrode or set of electrodes dedicated to the generation of this field.

[0013] The orientation of the lateral component of the electric field can be sequentially changed to sequentially collect charges on different respective collection electrodes. This allows some of the existing collection electrodes to be used as field electrodes to generate the electric field. Thus, if desired, for example to minimize sensor development costs, the invention can be implemented with a conventional collection electrode arrangement, without the need to integrate additional field electrodes.

[0014] To change the orientation of the lateral component of the resulting electric field, different electrodes can be sequentially subjected to different potentials. This allows the reconstruction, from two consecutive partial images containing information obtained from only some of the pixels, of a complete image with information from all the pixels. Equivalent resolution can thus be achieved by reducing the image acquisition frequency, compared to a conventional sensor where all the collecting electrodes are used to acquire a single image.

[0015] In some implementation examples, at least two adjacent electrodes are alternately subjected to different potentials in order to alternately collect charges on said electrodes. This maximizes the intensity of the field created by taking advantage of the proximity of the electrodes between which this field is generated.

[0016] Charges are preferentially collected at a given collecting electrode using an electric field with a lateral component, generated between this electrode and at least one other electrode at a different potential, preferably at least two other electrodes at different potentials, these two other electrodes being equidistant from the collecting electrode. This allows the charges present in the medium, around the collecting electrode, to be drained towards it. In examples of implementations of the invention, at least one of these other electrodes is subsequently used as the collecting electrode, the electrode previously used as the collecting electrode no longer serving as a collecting electrode but instead being used to generate the electric field.

[0017] The collection electrodes are preferably arranged in a matrix configuration, with different potentials V1, V2, for example, applied to the electrodes in a checkerboard pattern, so as to generate electric fields with a non-zero lateral component. Preferably, the potential of each collection electrode alternates between the first potential V1 and the second V2, and vice versa. Since, for a given pattern of applied potentials V1, V2, only half of the pixels are active, with corresponding electrodes used to collect charges and thus form an image, reversing the checkerboard pattern from one image to the next allows the potentials of the pixel electrodes to be changed, activating the other half of the pixels that were previously inactive. Thus, with two consecutive nested partial images, a complete image can be reconstructed with information from all the pixels.

[0018] Alternatively, at least one dedicated electrode is used exclusively as a field electrode to generate the electric field, without ever being used to collect charges read by the associated pixel circuit. Thus, thanks to these additional dedicated field electrodes, in cases where the collection electrodes are arranged in a matrix configuration, all the collection electrodes can be at the same potential when the pixel circuits allow it.

[0019] In this variant, since all pixels are active when capturing a single image, it is no longer necessary to sequentially subject the collection electrodes to different potentials to act as field electrodes, and the resulting image contains complete information for all pixels. This solution avoids loss of resolution during image acquisition but can make the sensor design more complex due to the addition of these field electrodes.

[0020] Said at least one field electrode, and better each field electrode, is located between at least two collecting electrodes, in particular equidistant from them, a field having a non-zero lateral component being generated between each of these collecting electrodes and the field electrode.

[0021] The field electrodes are preferably arranged uniformly between the collecting electrodes, for example, so that one field electrode is surrounded by four adjacent collecting electrodes. This arrangement allows for uniform charge collection by the collecting electrodes.

[0022] Preferably, this should include at least one field electrode, and ideally each field electrode should have a cross-section smaller than that of the collection electrode when the sensor is viewed from the front. This prevents a loss of resolution at a constant pixel matrix size.

[0023] The electric field generated for charge collection within said medium can exhibit different time profiles, depending, for example, on the intended application.

[0024] The electric field can be pulsed during pixel reading, which can help limit power consumption and heating. In other words, during pixel reading, the field electrode does not maintain the same potential throughout the entire reading process, and its potential exhibits, for example, at least two successive pulses.

[0025] The sensor may include any pixel circuits suitable for reading the charges collected by the collecting electrodes, and in particular common drain amplifier type (“Source Follower”) pixel circuits in linear or logarithmic mode, column charge amplifier type (“Capacitive Trans-Impedance Amplifier” (CTIA)) or direct injection type (“Direct Injection”), these circuits being known in themselves and for example described in the publication “Focal-Plane-Arrays and CMOS Readout Techniques of Infrared Imaging Systems”, IEEE Transactions on circuits and systems for video technology, vol 7, No 4, August 1997.

[0026] Preferably, at least one RESET switch is mounted in parallel with the pixel circuit so that, when closed, it imposes a predefined voltage on the associated electrode to enable it to generate the desired electric field.

[0027] Pixel reading can be done in global shutter mode ("Global Shutter") or rolling shutter mode ("Rolling Shutter").

[0028] At least one of the electrodes used to generate the electric field with a non-zero side component can be biased by applying a constant voltage during the exposure time of the corresponding pixel. The electrode thus biased can be the field electrode or a collecting electrode used as a field electrode. It can also be the collecting electrode itself, when this is compatible with the operation of the pixel circuit, for example, when the pixel circuit is of the CTIA type. It can also be both: both the collecting electrode and the adjacent electrode(s) used to create the field with the collecting electrode.

[0029] This electrode can be biased before the start of the exposure time with a voltage that is the inverse of the bias voltage during the exposure time. This helps to limit any charge remanence by displacing charges trapped in defects. At least one of the electrodes used to generate the electric field with a non-zero side component can be biased by applying a pulsed voltage during the exposure time, as mentioned above. This optimizes energy consumption and reduces sensor heating.

[0030] This electrode can, in particular, be polarized before the start of the exposure time and / or cease to be polarized before the end of the exposure time.

[0031] Preferably, the electrodes, especially the collection electrodes, are metallic.

[0032] The electrodes, especially the collection electrodes, may contain one or more metals chosen from: Al; Al / TiW; In; Au; Ti / Au; Ti / Pt / Au; Cu; Cu / Au; Ni; Ni / Au; Cr; AuSn and their mixtures.

[0033] The electrodes, particularly the collection electrodes, are preferably circular in shape when viewed from the front, notably in the form of beads. Alternatively, the electrodes, particularly the collection electrodes, are in the form of nested structures, notably in the form of combs.

[0034] The electrodes, especially the collection electrodes, are preferentially deposited on a sensor readout circuit comprising the pixel circuits, before the deposition of said medium.

[0035] Electrodes, especially collection electrodes, can be deposited by evaporation, sputtering, machining, electrolytic growth or metal plating.

[0036] The electrodes, especially the collection electrodes, can be formed by a top metallic layer of a sensor readout circuit including the pixel circuits, present at the output of the sensor casting, in particular a top metallic layer protected or not by an open passivation layer at the electrodes.

[0037] The photosensitive material preferably comprises nanocrystals, preferably quantum dots, especially colloidal or graphene, dispersed in the medium.

[0038] The photosensitive material may include an amorphous, crystalline or semi-crystalline semiconductor.

[0039] The photosensitive material can be deposited as one or more stacked layers above the electrodes. Alternatively, the photosensitive material can be arranged as one or more layers extending horizontally between the electrodes. Adding extra layers optimizes performance by improving the transport of photogenerated charge carriers or by reducing the distance electron-hole pairs must travel before dissociating. These additional layers can also enable multispectral operation of the sensor, for example, at two different wavelengths.

[0040] The photosensitive material can still be entangled and arranged in a disorderly manner in said medium.

[0041] The invention also relates, according to another aspect, to an image sensor according to claim 13, in particular for implementing the method according to the invention as defined above, comprising a medium including at least one photosensitive material capable of generating charges by photoelectric effect when the sensor is exposed to incident light, and collection electrodes in contact with said medium, associated with pixel circuits, the medium having a face opposite to that in contact with the collection electrodes which is devoid of a metallic layer, the pixel circuits being configured to create at least one electric field having a lateral component to collect said charges on at least one of said collection electrodes.

[0042] This electric field can notably be created between two electrodes arranged at the level of the pixel circuits, for example between a collection electrode and adjacent collection electrodes, or between a collection electrode and one or more dedicated field electrodes, as detailed above.

[0043] The image sensor may exhibit all or some of the characteristics described above. According to another aspect of the invention, the invention also relates to a photosensitive structure for an image sensor according to the invention, comprising: collection electrodes, and a medium comprising a photosensitive material capable of generating electrical charges by photoelectric effect, having one face in contact with the electrodes and an opposite face exposed to light which is devoid of a metallic layer.

[0044] Such a medium may include nanocrystals, as mentioned above.

[0045] The structure may include dedicated field electrodes, as defined above. The invention also relates, according to another aspect, to a method for manufacturing an image sensor according to the invention, comprising the deposition of said medium on the collection electrodes, this deposition being carried out according to a method chosen from: spin-coating, inkjet printing, spray-coating and drop casting. Brève description des dessins

[0046] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the attached drawing, on which: [ Fig 1 ] there figure 1 , as previously described, schematically represents an early photosensitive structure of a prior art image sensor, [ Fig 2 ] there figure 2 , previously described, schematically illustrates a second photosensitive structure of a prior art image sensor, [ Fig 3 ] there figure 3 schematically represents, in side view, an example of a photosensitive structure according to the invention, [ Fig 4 ] there figure 4 schematically represents, in top view, the photosensitive structure of the figure 3 , having an electrode matrix with a checkerboard pattern of applied potentials, [ Fig 5 ] there figure 5 schematically illustrates, in top view, a photosensitive structure according to the invention, having an electrode matrix with field electrodes, [ Fig 6 ] there figure 6 schematically represents an example of the distribution of RESET transistors in pixel circuits, [ Fig 7 ] there figure 7 schematically represents, in lateral view, a photosensitive structure according to the invention, with layers of semiconductor material stacked above the electrodes, [ Fig 8 ] there figure 8 is a schematic side view of a photosensitive structure according to the invention with layers of semiconductor material extending in the thickness direction between the electrodes, [ Fig 9 ] there figure 9 is a schematic side view of a photosensitive structure according to the invention, with semiconductor material entangled and arranged in a non-ordered manner in said medium, [ Fig 11a ] there figure 11a schematically represents, in top view, a photosensitive structure according to the invention, without the addition of electrodes, [ Fig 11b ] there figure 11b schematically illustrates, in side view, the photosensitive structure of the figure 11a , [ Fig 12a ] there figure 12a schematically represents, in top view, a photosensitive structure according to the invention, with electrodes in the form of beads, [ Fig 12b ] there figure 12b schematically illustrates, in side view, the photosensitive structure of the figure 12a , [ Fig 13a ] there figure 13a schematically represents, in top view, a photosensitive structure according to the invention with electrodes in the form of nested structures, [ Fig 13b ] there figure 13b schematically illustrates, in side view, the photosensitive structure of the figure 13a , [ Fig 14a ] there figure 14a is a first example of a timing diagram illustrating one way to polarize the field electrode, [ Fig 14b ] there figure 14b is a second example of a timing diagram illustrating another way to polarize the field electrode, [ Fig 14c ] there figure 14c is a third example of a timing diagram illustrating one way to polarize the field electrode, [ Fig 14d ] there figure 14d is a fourth example of a timing diagram illustrating another way to polarize the field electrode, [ Fig 14e ] there figure 14e is a fifth example of a timing diagram illustrating another way to polarize the field electrode, and [ Fig 15 ] there figure 15 is a simplified diagram showing the pixel circuits and transistors that allow the electrodes to be placed under a predefined potential. Description détaillée

[0047] There figure 3 schematically represents, in side view, an example of a photosensitive structure according to the invention, comprising a reading circuit 16 having collection electrodes 181 in contact with a medium 15 deposited on the reading circuit 16, and comprising a photosensitive material 19.

[0048] The reading circuit 16 is arranged to generate a potential difference between a first set 181a of said electrodes and a second set 181b of said electrodes, in order to have an electric field E having a non-zero lateral component to collect the charges generated in the medium by the photoelectric effect, and being able to do without a top metallic electrode layer, unlike the prior art described with reference to the figure 2 .

[0049] There figure 4 schematically represents, in top view, the photosensitive structure of the figure 3 , where the collection electrodes 181 are arranged in a matrix arrangement in contact with the medium 15.

[0050] The collection electrodes 181 are connected to respective pixel circuits, allowing the current collected by them to be amplified and thus generating an output signal representative of the illumination of the corresponding pixels.

[0051] The photosensitive material 19 is for example in the form of CQD dispersed in the medium 15, which comprises an electrically insulating polymer.

[0052] To generate the desired electric field, different potentials V1, V2 can be applied to the electrodes 181 in a checkerboard pattern. For example, if the pixel circuits allow it, the electrodes 181a are subjected at the same instant to the same first potential V1 while the electrodes 181b are subjected to the same second potential V2, different from the first.

[0053] For example, the potential difference between V1 and V2 allows the generation of local electric fields in the vicinity of each collecting electrode 181a, having a non-zero lateral component, which displaces the charges generated by the photoelectric effect towards it. The charges 190 generated by the photoelectric effect at the CQDs are then collected by the collecting electrodes 181a. In the case where the charges 190 are electrons, the potential V1 of the electrodes 181a collecting these electrons is then greater than the potential V2 of the electrodes 181b.

[0054] In this example, only half of the collection electrodes 181, namely electrodes 181a, are active at any given time to collect the charges generated by the photoelectric effect. Therefore, to recover the missing information from the other pixels corresponding to electrodes 181b, the potentials V1 and V2 are reversed sequentially from one image to the next; that is, electrodes 181a, to which potential V1 was previously applied, are now subjected to potential V2, and vice versa. Then, electrodes 181a become inactive and the charges are collected by electrodes 181b. Then electrodes 181b again become inactive and the charges are collected by electrodes 181a, and so on.

[0055] Thus, it is possible to reconstruct, from two consecutive less resolved images containing information for only half of the sensor's pixels, a more resolved image with complete information for all pixels.

[0056] Furthermore, it is possible to have voltages V1 and V2 both positive, or both negative, or one positive and the other negative, provided that there is a sufficient potential difference to create a lateral electric field allowing the collection of charges.

[0057] There figure 15 schematically represents an example of a circuit that allows for the reading of pixels and the setting of electrodes to the desired potentials.

[0058] In this figure, the 181a collection electrodes are associated with the pixels " a "and the 181b collection electrodes are associated with the pixels" b "

[0059] Regardless of the architecture of the 500 pixel circuit (common drain amplifier ("Source Follower") in linear or logarithmic mode, capacitive trans-impedance amplifier (CTIA) or direct injection (DI) type), it typically has two inputs: a first input 501 connected to a reference voltage Vref and a second input 502 connected to electrode 181a or 181b via an optional switch RSTa or RSTb. The output 503 of the pixel circuit is labeled "OUT". A switch 505a (RSTPDa) or 505b (RSTPDb), for example a transistor, is connected in parallel with the 500 pixel circuit, connecting electrode 181a or 181b to a voltage line with a predefined potential VRST.

[0060] There figure 6 A top view illustrates an example of connecting 505 switches. All 505a switches associated with 181a collection electrodes can be connected together by parallel connections on the same RSTPDa line, as illustrated in the figure 6 , while the other 505b switches associated with the 181b collection electrodes are connected to another line RSTPDb, by connections that interlock with those of the RSTPDa line. During a first phase, switches 505a and RST-b are open and switches 505-b and RST-a are closed, thus bringing electrodes 181a to a potential lower than VRST, and electrodes 181b to a potential equal to VRST.

[0061] During this phase, pixels b can also be reset while the pixels a are integrated, by closing the RST-b switch.

[0062] During a second phase, switches 505-a and RST-b are closed and switches 505-b and RST-a are open, bringing electrodes 181a to a potential equal to VRST, and electrodes 181b to a potential lower than VRST.

[0063] During this phase, the pixels a can also be reset while the b pixels are integrated, by closing the RST-a switch.

[0064] In a CTIA-type 500 pixel circuit architecture, the reference voltage Vref is fixed and the voltage across the photodiode associated with this circuit, when the corresponding 505 switch is open, becomes VRST-Vref.

[0065] In a 500 pixel circuit architecture of the "Source Follower" type, the voltage across the photodiode gradually stabilizes to tangent to VRST when the corresponding 505 switch is open.

[0066] The aforementioned opening and closing phases of switches 505a and 505b, and vice versa, follow one another to form the aforementioned checkerboard pattern of applied voltages.

[0067] In one variant, only the same part of the electrodes 181 can always be used as active pixels, for example the electrodes 181a, the other part serving permanently as field electrodes.

[0068] In another variant, represented at the figure 5 Dedicated electrodes 183 are used as field electrodes to generate the electric field without collecting charges read by the associated pixel circuits, in addition to the collection electrodes 181. The collection electrodes 181 can then be at the beginning of each exposure at the same potential, which is different from that applied to the field electrodes 183 during reading. The field electrodes 183 are preferably, as illustrated, arranged uniformly between the collection electrodes 181, so that one field electrode 183 is surrounded by four adjacent collection electrodes 181. This arrangement allows for uniform charge collection.

[0069] As shown in this figure, the field electrodes 183 preferably have a smaller cross-section than the collection electrodes, which makes it possible not to harm the resolution of the sensor by increasing the interval between the collection electrodes 181. Various structures of the medium containing the photosensitive material can be used to generate the charges by photoelectric effect.

[0070] THE figures 7 à 9 illustrate variants where the photosensitive material is a semiconductor arranged in different ways within the insulating material.

[0071] There figure 7 schematically represents a photosensitive structure with layers 191 of semiconductor stacked above the collection electrodes 181 deposited on the reading circuit 16.

[0072] There figure 8 illustrates a photosensitive structure with 191 layers of semiconductor extending in the thickness direction between the collecting electrodes 181.

[0073] These 191 semiconductor layers described in relation to the figures 7 And 8 These additional layers optimize performance by improving the transport of photogenerated charges or by reducing the distance electron-hole pairs must travel before dissociating. They can also enable multispectral operation of the sensor, for example, at two different wavelengths.

[0074] There figure 9 schematically represents a photosensitive structure with an entangled semiconductor 191 arranged in a non-ordered manner in the medium 15.

[0075] THE figures 11a , 12a And 13a represent different examples of collection electrodes 181 suitable for a photosensitive structure according to the invention.

[0076] THE figures 11a And 11billustrate a first variant where the collection electrodes 181 are formed by an upper metallic layer of the readout circuit 16, present at the casting output of the sensor. This upper metallic layer may or may not be protected by a passivation layer (not shown), open at the collection electrodes 181.

[0077] THE figures 12a et 12b represent a second variant where the collection electrodes 181 are in the form of beads, presenting a circular outline in front view.

[0078] THE figures 13a et 13b illustrate a third variant where the collection electrodes 181 are in the form of nested structures, for example in the form of nested combs.

[0079] In the second and third variants, the electrodes are deposited for example by evaporation, by sputtering, by machining, by electrolytic growth or by metal plating.

[0080] When the sensor includes field electrodes, these can also be formed by a top metallic layer of the readout circuit 16, by balls or pads, or by comb-like structures, nested with each other or with the collecting electrodes. These field electrodes can be deposited by any conventional technique, for example, one of those mentioned above.

[0081] Various voltage profiles over time can be applied to the electrodes of the sensor used to generate the electric field with a non-zero lateral component, in order to create the desired potential difference between them.

[0082] There figure 14a This diagram presents an example of a timing diagram illustrating one possible way to vary the polarization voltage V of the field electrode over time, as a function of the readout signal R. The readout signal R controls the exposure time. Charge readings occur as long as the readout signal R is high. The duration for which the high level of the signal R is maintained thus determines the exposure time.

[0083] In the example illustrated in the figure 14a Throughout the exposure time texp, the field electrode is polarized at a constant voltage V. As illustrated in the figure 14b , the field electrode voltage is maintained constantly at V including when the readout signal R is at low level, in order to reduce the energy consumption required for switching from high level to low level and vice versa.

[0084] In the example illustrated in the figure 14c , the polarization of the field electrode at voltage V begins just before the exposure of the associated pixel to light and ends just before the end of the exposure.

[0085] In the example illustrated in the figure 14d The field electrode is polarized throughout the exposure time t exp to a voltage in the form of amplitude V pulses. This reduces energy consumption and sensor heating.

[0086] In the example illustrated in the figure 14e The field electrode, in addition to being polarized throughout the exposure time texp to voltage V, is polarized to a voltage of opposite sign V3 just before the start of the exposure. This reduces the remanence of charges by driving out charges trapped in defects. For example, V3 = -V.

[0087] The invention is not limited to the embodiments described above, nor to SWIR sensors. The invention can be used in particular in mid-wavelength infrared (MWIR) or long-wavelength infrared (LWIR) sensors, provided that suitable photosensitive materials are used.

[0088] It is possible, if necessary, to allow adjustment during sensor operation of the time profiles and / or amplitudes of the voltages applied to the field and / or collection electrodes, in order to vary the electric field with a non-zero lateral component. In particular, the sensor can be designed to allow modification, if desired, via software for example, of the potential difference V2-V1 used to generate the electric field with a lateral component, depending, for example, on the « auto-gating » to adapt the voltage according to the intensity in order to avoid pixel saturation, or active multi-pulse imaging by driving the potential difference in a synchronized manner with a laser for a longer exposure time (e.g. Figure 14c ), or by varying the potential difference according to the temperature or exposure time to obtain a homogeneous and unique non-uniformity correction.

Claims

1. Method of operation of an SWIR, MWIR or LWIR image sensor, comprising a medium (15) comprising at least one photosensitive material (19; 191) which is able to generate charges (190) by means of the photoelectric effect when the sensor is exposed to incident light, and collection electrodes (181) in contact with said medium (15), which are associated with pixel circuits (500), the medium (15) having a face opposite the one in contact with the collection electrodes (181) which has no external electrode layer, in which method there is created at least one electrical field with only a lateral component in order to collect said charges (190) on at least one of said collection electrodes (181), making it possible for them to be read by the associated pixel circuit (500), wherein said lateral component of the electrical field is generated by creating at least one potential difference between said collection electrode (181) and at least one other zone of the sensor which is another collection electrode or a field electrode dedicated to generating this field, brought to a different potential, this other zone being situated between at least two collection electrodes (181).

2. Method according to the preceding claim, said at least one other zone being another collection electrode, wherein the orientation of the lateral component of the electrical field is changed sequentially in order to sequentially collect the charges on different respective collection electrodes (181a, 181b), preferably wherein at least two adjacent electrodes (181a, 181b) are alternately subjected to different potentials so as to alternately collect the charges on said electrodes, the charges notably being collected on a given collection electrode (181a) using an electrical field having at least one lateral component and which is generated between it and at least one other electrode (181b) brought to a different potential, preferably two other electrodes (181b) brought to a different potential, these two other electrodes (181b) preferably being equidistant from the collection electrode (181a), at least one of said other electrodes (181b) notably then being used as a collection electrode, the electrode (181a) having been used previously as a collection electrode no longer being used as a collection electrode and being used to generate the electrical field.

3. Method according to one of the two preceding claims, the collection electrodes (181a, 181b) being arranged according to a matrix arrangement, different potentials V1, V2 being applied to the collection electrodes (181a, 181b) according to a draughtboard arrangement, so as to generate electrical fields having at least one non-zero lateral component, the potential of each collection electrode (181a, 181b) preferably alternately switching from the first potential V1 to the second potential V2 and vice versa.

4. Method according to Claim 1, said at least one other zone being a dedicated electrode (183) used exclusively as a field electrode to generate said electrical field without being used to collect charges read by the associated pixel circuit, said field electrode (183) being situated between at least two electrodes (181) collecting the photoelectric charges, the field with a lateral component being generated between each of these collection electrodes (181) and the field electrode (183), the field electrodes (183) being arranged uniformly between the collection electrodes (181), so that a field electrode (183) is surrounded by several, notably four, adjacent collection electrodes (181), the field electrode (183) preferably having a section which is smaller than that of the collection electrode (181).

5. Method according to any one of the preceding claims, the electrical field being pulsed during the reading of a pixel and / or at least one RESET switch (505a; 505b) is connected in parallel with the pixel circuit (500) so as, when closed, to impose a predefined voltage on the associated electrode (181a; 181b).

6. Method according to any one of the preceding claims, at least one of the electrodes being biased by the application of a voltage which is constant during the exposure time, said electrode notably being biased before the start of the exposure time, said electrode preferably ceasing to be biased before the end of the exposure time, said electrode notably being biased before the start of the exposure time with a voltage which is the reverse of that of the biasing during the exposure time.

7. Method according to any one of the preceding claims, the electrodes (181, 183) being metallic, notably comprising one or more metals chosen from among: Al; Al / TiW; In; Au; Ti / Au; Ti / Pt / Au; Cu; Cu / Au; Ni; Ni / Au; Cr; AuSn and mixtures thereof, in particular the electrodes (181, 183) being formed by an upper metallic layer of a read circuit (16) of the sensor comprising the pixel circuits, which is present at the output of the casting of the sensor, notably an upper metallic layer protected or not by a passivation layer which is open at the electrodes.

8. Method according to any one of the preceding claims, the electrodes (181, 183) having a circular outline when seen from the front, notably being in the form of balls or the electrodes (181, 183) being in the form of nested structures, notably in the form of combs.

9. Method according to any one of the preceding claims, the electrodes (181, 183) being deposited on a read circuit (16) of the sensor, comprising the pixel circuits, before said medium is deposited.

10. Method according to Claim 7, the electrodes (181, 183) being formed by an upper metallic layer of a read circuit (16) of the sensor comprising the pixel circuits, which is present at the output of the casting of the sensor, notably an upper metallic layer protected or not by a passivation layer which is open at the electrodes.

11. Method according to any one of the preceding claims, the photosensitive material comprising nanocrystals (19), preferably quantum dots, notably colloidal or graphene quantum dots, dispersed in the medium (15).

12. Method according to any one of Claims 1 to 10, the photosensitive material (191) being deposited in the form of one or more layers stacked on top of the electrodes (181, 183) or the photosensitive material (191) being arranged in the form of one or more layers extending in the thickness direction between the electrodes (181, 183) or the photosensitive material (191) being nested and arranged in an unordered fashion in said medium (15).

13. SWIR, MWIR or LWIR image sensor, notably for implementing the method according to any one of the preceding claims, comprising a medium (15) comprising at least one photosensitive material (19; 191) which is able to generate charges (190) by means of the photoelectric effect when the sensor is exposed to incident light, and collection electrodes (181) in contact with said medium (15), which are associated with pixel circuits, the medium (15) having a face opposite the one in contact with the collection electrodes (181) which has no external electrode layer, the pixel circuits being configured to create at least one electrical field with only a lateral component in order to collect the charges (190) on at least one of the collection electrodes (181), making it possible for them to be read by the pixel circuit (500), the lateral component of the electrical field being generated by creating at least one potential difference between said collection electrode (181) and at least one other zone of the sensor which is another collection electrode or a field electrode dedicated to generating this field, this other zone being situated between at least two collection electrodes (181).