Diode Radiation Sensor

Abstract

a substrate (3; 103; 203; 303), a first layer (8) of semiconductor material doped with a first type of doping and formed on a front side (4) of the substrate (3; 103; 203; 303), and a second layer (9) of semiconductor material doped with a second type of doping of electrically opposite sign to the first type and formed at a first depth in the substrate (3; 103; 203; 303), thereby forming a high electric field region (10) between the first layer (8) and the second layer (9); A diode radiation sensor comprising a third layer (12) of semiconductor material doped with a second type of doping and formed in the substrate (3; 103; 203; 303) at a second depth deeper than the first depth, and a first insulating region (15; 315) formed on the periphery of the substrate (3; 103; 203; 303) and extending in depth into the substrate (3; 103; 203; 303) to an intermediate region between the front face (4) and the rear face (5; 105; 205) of the substrate (3; 103; 203; 303). A passivation layer (18; 118; 218; 318) is interposed between the sidewalls of the first insulating region (8) and the substrate (3; 103; 203; 303).

Description

[Technical field]

[0001] definition In this patent, by passivation layer in a device is meant a layer of semiconductor material, the non-depleted passivation layer being obtained because the passivation layer contains a sufficiently high concentration of majority carriers of the same type as are present in the substrate on which the passivation layer is formed during normal operation of the device.

[0002] The invention is applicable in the field of radiation sensors, in particular in the field of diode radiation sensors.

[0003] More particularly, the present invention relates to sensors having one or more charge multiplication diodes. [Background technology]

[0004] Radiation sensors include single photon avalanche diodes (SPADs). A single SPAD consists of a charge multiplying diode polarized to operate in Geiger mode. A sensor can consist of a single SPAD or a set of SPADs, also called a microcell or pixel. Sensors consisting of multiple SPADs include silicon photomultiplier sensors, also called SiPMs, which generally consist of SPADs connected in parallel.

[0005] Generally, as shown in Figure 1, the microcell M is formed in a substrate S of semiconductor material, generally epitaxial. In such substrate S, a first layer P1 of doped semiconductor material is identified as being of a first type of conductor (which may be, without difference, n-type or p-type, but of opposite sign to the doping of the substrate S). Such first layer P1 is formed on the front side of the substrate S.

[0006] Then there is a second layer P2 of semiconductor material doped with the opposite sign to the first layer P1, this second layer P2 being formed in the substrate S in the depth direction. The substrate is generally doped with the same sign as P2, but with a smaller amount. Then there is a bottom layer PF, generally doped with the same sign as P2. A diode source is generally, but not necessarily, between the first layer P1 and the bottom layer PF, and depending on the source, an empty region is formed between the first layer P1 and the second layer P2 or between the first layer P1 and the bottom layer PF. In either case, a region with a high electric field E is formed between the first layer P1 and the second layer P2 to produce a diode charge multiplication effect in the presence of a suitable polarization.

[0007] For each SPAD, at least one of the two poles or two electrical contacts must be functionally isolated from its neighbours in order to operate correctly as envisaged. For such reasons, a generally electrical, and possibly optical, isolation region R is usually formed between them. In fact, optical isolation between adjacent cells is not essential, but is desirable to reduce the noise associated with optical crosstalk.

[0008] However, this means that part of the volume of the device is dedicated to insulating regions R.

[0009] Furthermore, the second layer P2 must be spaced away from such region R in order to substantially obtain a guard ring, which may be of the virtual guard ring type (VGR), i.e. to prevent excessively high electric fields at the edges of the active region.

[0010] Thus, in a SiPM, the sensitive area of ​​each SPAD is significantly smaller than its total area due to the insulating region R and the guard ring VGR, which results in the formation of a so-called dead edge of the cell. By defining the fill factor of the cell as the ratio of the sensitive area to the total area of ​​the microcell, it is clear that the higher this number, the more efficient the single cell. Moreover, it is clear that the smaller the microcell, the more detrimental the raised dead edge is.

[0011] Thus, with respect to what has been described thus far, the fill factor of a microcell is affected firstly by the space lost due to the formation of the insulating regions, and secondly by the required spacing to form the virtual guard ring.

[0012] However, insulating regions also have a further downside for SiPMs or similar types of optical sensors.

[0013] First, the insulating regions affect the continuity of both the front and rear surfaces of the substrate: since one of these two surfaces is used as the photon entrance surface, it is clear that the presence of such regions creates a physical discontinuity on such surface.

[0014] Furthermore, discontinuities on the surface of the substrate result in changes in the surface topography, which in turn creates problems for the support arrangement of further elements or for substrate surface processing. Summary of the Invention [Problem to be solved by the invention]

[0015] The object of the present invention is to at least partially overcome the above-mentioned drawbacks and to provide a radiation sensor having improved performance with respect to comparable sensors in terms of the ability of an incident photon to trigger with the greatest possible probability the charge multiplying effect of the diode forming the sensor itself.

[0016] In particular, it is an object of the present invention to provide a diode radiation sensor in which the fill factor of the microcell is improved relative to comparable sensors of the prior art without significantly (or excessively) increasing the dark count rate.

[0017] More specifically, it is an object of the present invention to provide a charge multiplication diode radiation sensor (generally an avalanche diode) in which the insulating regions have a lower incidence on the substrate, reducing if not substantially cancelling their contribution to the occurrence of the so-called dead edge.

[0018] Another object of the present invention is to provide a diode-type radiation sensor that transports charges generated in the substrate to a high electric field region and effectively triggers the charge multiplication effect.

[0019] A final, but important, objective is to provide a diode radiation sensor in which the insulating regions have a limited, if not zero, effect on the plane of incidence of photons with respect to what occurs in known optical sensors. [Means for solving the problem]

[0020] Such objects, as well as others which will become more apparent hereinafter, are achieved by a diode radiation sensor according to the following claims, which should be considered an integral part of the present disclosure.

[0021] In particular, a diode radiation sensor typically, but not necessarily, consists of one or more charge multiplying diodes polarized to operate in Geiger mode. As such, the sensor comprises a substrate made of a semiconductor material and having two surfaces, a front surface and a rear surface opposite the front surface.

[0022] At least near the front surface is at least a first layer of semiconductor material that is doped with a first type of doping, whether n-type or p-type, such first layer being formed over at least a first central region of the front surface of the substrate.

[0023] There is also at least a second layer of semiconductor material doped with a second type of doping of electrically opposite sign to the first type. Such second layer is formed at a first depth in the substrate and extends substantially parallel to the first layer to affect a second region that, in the presence of a suitable polarization of the sensor, identifies a region with a high electric field between the two layers. In other words, the two layers form a charge multiplication region of such a type of diode whose operating area, and therefore whose charge multiplication level, is determined by the power supply of the same diode.

[0024] According to an aspect of the invention, the radiation sensor also comprises at least a third layer of semiconductor material doped with a second type of doping and formed in the substrate at a second depth deeper than the first depth, in particular the third layer being lateral in planar projection and affecting at most a third region overlapping the second region.

[0025] From the above, the third layer can be simplified by claiming that the third layer can partially overlap the second layer, but that it substantially forms a frame for the high electric field region and is located between the second layer and the region of the substrate where the collection of charges occurs due to the incidence of radiation. In this sense, the third layer preferably prevents the charges generated in the substrate from being directed towards the virtual guard ring and focuses the charges towards the high electric field region. In other words, the third layer substantially performs a funnel function with respect to the charges generated in the substrate and thus directed towards the high electric field region. Preferably, this applies regardless of the extension of such region.

[0026] With the above implementation, the relevant part of the voltage drop of the sensor is generally located between the first and second layers, since the first layer is the region with the highest electric field. Approximately the same voltage drop is also identified between the first and third layers, since the third layer is generally at the same potential as the second layer. In order to avoid avalanche buildup above the third layer, it is important that the voltage drop between the third and first layers is generated over a path significantly longer than the voltage drop between the first and second layers. The implementation of the third layer deeper than the second layer advantageously allows the aforementioned path to be built up, limiting, if not cancelling, the additional charge multiplication.

[0027] According to another aspect of the invention, the radiation sensor comprises at least a first insulating region formed on the periphery of the substrate and extending in depth from the front surface to an intermediate region between the front and rear surfaces in the same substrate. In particular, such a first insulating region is laterally disposed on at least the first and second layers. In the figure, it is observed that the first insulating region is much more extensive, but this should not be considered as limiting the invention.

[0028] There is therefore electrical, and generally optical, insulation between the surface layers of the charge multiplication diodes forming the sensor. However, preferably, the parts of the substrate that are not laterally affected by the insulating regions are not adversely affected by the insulating regions, increasing the fill factor value of the radiation sensor of the invention. In other words, it can be seen that the insulating regions can be limited to isolating only the regions of the diode where charge multiplication occurs, and not the underlying substrate, thus avoiding its inflow.

[0029] Moreover, it is further advantageous that such insulating regions, which in fact form trenches, do not affect both surfaces, but only the front surface, which is particularly advantageous in the case of sensors intended to be illuminated on the rear surface, since the rear surface is continuous and unaffected and therefore there are no elements present that can affect the correct incidence of the radiation or in any case reduce its sensitive surface.

[0030] Furthermore, there are no discontinuities in the rear surface that could adversely affect the creation of additional surface layers or the placement of additional elements such as microlenses.

[0031] Even more advantageously, for the same volume of photon collection area, the sensor of the present invention has a much smaller high electric field region, thus reducing the noise generated in this region, which typically forms a significant portion of the dark noise of the sensor.

[0032] According to another aspect of the invention, at least one passivation layer is interposed between the sidewalls of the first insulating region and the substrate, at least from the second depth of the third layer towards the rear surface of the substrate, in particular the layer containing a sufficiently high concentration of majority carriers of the same type as those of the substrate during normal operation of the device so as not to become empty.

[0033] Therefore, preferably there is a passivation of at least one lateral portion of the insulating region starting from the third layer towards the bottom of the substrate, thereby avoiding the generation of electromagnetic fields that may hinder or otherwise adversely affect charge collection by diverting the charges from their optimal path across the high electric field region. This is particularly advantageous when the insulating region is deeper than the charge multiplication diode.

[0034] More preferably, the passivation layer prevents the passivation layer from being implanted into collection regions of charged elements created at the interface between the first insulating region and the substrate.

[0035] More preferably, if the passivation layer is polarized by an electrical contact, it can contribute to the ability to focus the charge generated by radiation incident on the substrate towards the high electric field region. Moreover, it is still advantageously observed that, if the insulating region is particularly deep in the substrate relative to the third layer, its lateral passivation contribution to the aforementioned charge transport action is clearly significant. Further features and advantages of the invention will become more apparent in the light of the detailed description of preferred but non-exclusive embodiments of an optical sensor according to the invention, given by way of non-limiting example with the aid of the accompanying drawings, in which: [Brief description of the drawings]

[0036] [Figure 1] 1 shows a schematic diagram of a radiation sensor according to the state of the art; [Diagram 2] 1 shows a schematic diagram of a radiation sensor according to the invention; [Diagram 3] 3 shows a variant of the embodiment of the radiation sensor of FIG. 2. [Figure 4] 3 shows a variant of the embodiment of the radiation sensor of FIG. 2. [Diagram 5] 3 shows a variant of the embodiment of the radiation sensor of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] With reference to the cited figures, and in particular to Figure 2, a radiation sensor 1 is generally, but not necessarily, described as having one or more charge multiplying diodes 2 polarized to operate in Geiger mode. For ease of explanation, the sensor 1 shown in the figure comprises a single diode 2, but it will be clear that such an embodiment should not be considered as limiting the invention.

[0038] More specifically, the charge multiplication diode 2 is generally of the avalanche type due to the impact ionization mechanism.

[0039] The sensor 1 thus comprises a substrate 3 made from a semiconductor material and having two surfaces: a front surface 4 and a rear surface 5 opposite the front surface 4 .

[0040] On the front side 4 there is a first layer 8 of semiconductor material doped with a first type of doping. In the figures, such doping is n-type, but this aspect should not be considered as limiting the invention either. Indeed, the inversion of the types of doping cited in the present text would not make any difference for the purposes of this patent.

[0041] The thickness of the first layer 8 can also be any thickness according to the design parameters of the sensor 1. In general, regardless of what can be deduced from the drawings, all layer thicknesses shown in this patent are specified to be in accordance with the design parameters of the radiation sensor without any limitation to the present invention.

[0042] The location of the first layer 8 on the front surface of the substrate 3 is also a feature that is considered non-limiting for the present invention, since there are embodiment variants not shown here in which the same first layer is formed deeper in the substrate (but closer to the front surface) and connected to the front surface by electrical contacts.

[0043] A first layer 8 is formed covering a first central region of the front surface 4 of the substrate 3 .

[0044] There is also a second layer 9 of semiconductor material doped with a second type of doping of opposite electrical sign to the first type. Typically, the substrate 3 is also doped with the second type of doping, but at a lower doping level than the doping level of the second layer. Similarly, typically, on the rear face 5 of the substrate there is a further layer 40 doped with the second type of doping, typically at a higher doping relative to the doping of the substrate. In the figures, it can be seen that such further doped layer 40 covers the entire rear face 5, but such an aspect should not be considered as limiting different embodiments of the invention in which the further doped layer covers only a portion of the rear face of the substrate.

[0045] The second layer 9 is formed at a first depth within the substrate 3 and extends substantially parallel to the first layer 8 so as to affect a second region. Furthermore, between the second layer 9 and the first layer 8 a high electric field region 10 is detectable for generating charge multiplication in the presence of a suitable polarization of the sensor 1.

[0046] At the periphery of the first layer 8 and the second layer 9 there is a separation space from the edge of the cell which serves a similar function, essentially a virtual guard ring 11, i.e. the virtual guard ring has the function of preventing high electric fields at the edge of the active region.

[0047] According to one aspect of the invention, the optical sensor 1 comprises a third layer 12 of semiconductor material doped with a second type of doping (hence matching the doping of the second layer 9) and formed in the substrate 3 at a second depth deeper than the first depth, i.e. this third layer is at a deep depth in the substrate 3 relative to the depth of the second layer 9. In particular, the third layer 12 influences a third region that is laterally of the second region in a planar projection.

[0048] That is, the third layer 12 essentially forms a frame for the charge multiplication diode 2, as previously described. In this sense, the third layer preferably prevents charges generated in the substrate 3 from moving towards the virtual guard ring 11, focusing these charges in the high electric field region 10 where multiplication by impact ionization takes place.

[0049] We have already mentioned the substantial funnel effect, since it effectively, albeit crudely, demonstrates the function of transporting the charges generated in the substrate 3 by the incidence of radiation into the high electric field region 10, where a charge multiplication effect is obtained.

[0050] Advantageously, due to such transport similar to an efficient focusing mechanism of charge, the size of at least the second layer 9 and the high field layer 10 can be reduced, if not the size of the first layer 8, thereby providing the following advantages: There is potentially more space for a virtual guard ring 11.

[0051] This is important in general, but is fundamental for the small size of the cell: the minimum size required for the virtual guard ring 11 to be effective uses the full width of the cell, without leaving space for the first layer 8 and second layer 9. The capacitance of diode 2 is reduced, which makes it possible to build microcells with faster charging times, especially in the case of the passive charge multiplication quenching mechanisms provided by the so-called "quench resistance" typically used in analog SiPMs. A lower cathode capacitance also corresponds to a lower gain derived from the charge multiplication effect, defined as the average number of charges passing through the high field layer 10 for each detected photon. The overall lower gain allows less noise to be associated.

[0052] However, the focusing effect performed by the third layer of semiconductor material 12 also allows the use of further constructive measures.

[0053] According to another aspect of the invention, the radiation sensor 1 comprises a first insulating region 15, which is formed on the periphery of the substrate 3 and extends in depth direction within the same substrate 3 starting from the front surface 4 to an intermediate region between the front surface and the rear surface 5. In particular, the figure shows that such a first insulating region 15 is arranged laterally at least in the first layer 8, the second layer 9 and the third layer 12. However, such an aspect should not be considered as limiting different embodiments of the invention, for example, where the insulating region is only adjacent to the first two layers or is deeper than the third layer. However, further embodiment variants are described below.

[0054] Typically, the insulating regions 15 are formed by etching the substrate 3 and inserting into the grooves thus obtained one or more materials that are typically, but not necessarily, isolators (typically, oxides of the semiconductor material of which the same substrate 3 is formed), but such an embodiment should not be considered as limiting the invention either, the material may be any and the insulating regions can be obtained in a different way to that described. Still applicable in the above case, typically, but not necessarily, the semiconductor material is silicon and therefore the oxide is silicon.

[0055] In any case, the function of the insulating regions 15 is at least the functional separation between surface portions of adjacent cells forming the sensor 1. As mentioned above, since the insulating regions 15 may generate electric or electromagnetic fields that may impede or otherwise adversely affect the collection of charges that are then directed towards the high field regions 10, the substrate portions 3 that are not laterally affected by the insulating regions 15 are not subject to such possible adverse effects, increasing the fill factor value of the radiation sensor 1 of the present invention.

[0056] Moreover, preferably, such insulating region 15, which in fact forms a trench, does not affect both faces, but only the front face 4. This is particularly advantageous in the case of a radiation sensor 1 intended to be illuminated at the rear face 5, since the rear face 5 is continuous and unaffected and therefore free of elements that can affect the incidence of photons.

[0057] Yet, as previously mentioned, there are no discontinuities on the rear surface that could adversely affect the creation of additional surface layers or the positioning of additional elements such as lenses.

[0058] According to another aspect of the invention, a passivation layer 18 is interposed between the sidewalls of the first insulating region 15 and the substrate 3, starting from the second depth relative to the third layer 12.

[0059] According to some embodiments of the invention, the passivation layer comprises a layer of semiconductor material doped with a second type of doping. According to other embodiments of the invention, the passivation layer is formed by inducing appropriate charges in portions of the substrate adjacent to the first insulating region by appropriately polarizing portions of interest in the first insulating region. Thus, the manner in which the aforementioned passivation layer is formed is not a limiting feature of the invention.

[0060] In either case, it can be seen in the drawings that a passivation layer 18 is interposed between the entire first insulating region 15 and the substrate 3, but such an embodiment should not be considered as limiting the invention.

[0061] Therefore, preferably, said sidewalls of the insulating region 15 are passivated at the edges to reduce the injection of heat-generated carriers at the interface between the substrate 3 and the first insulating region 15, i.e. to reduce the dark current of the sensor 1. Furthermore, the same passivation avoids the generation of electromagnetic fields that would hinder the collection of charges from the substrate 3.

[0062] It can further be seen in the figure that the third region affected by the third layer 12 is in contact with the passivation layer 18 on a first side, but extends on the opposite side over a length that substantially corresponds to the distance between the second layer 9 and the passivation layer 18.

[0063] Preferably, the third layer 12 and the passivation layer 18 have the same type of polarity, so that their electrical contacts make it possible to power them together, if deemed necessary, for example by electrical contacts connected to the passivation layer 18. Such a single power supply therefore enhances the ability to focus the charges generated by photons incident on the substrate 3 towards the high electric field region 10.

[0064] Obviously, such features should not be considered as limiting the invention. In fact, both the third layer and the passivation layer do not have to be provided, or even provided together, just as the third layer and the passivation layer do not have to be in contact with each other. Also, the fact that the opposite third layer extends over a length that substantially corresponds to the distance between the second layer and the passivation layer is not a feature that should be considered as limiting the invention, and the extension of the third layer can be so large that in planar projection the third layer partially overlaps the second layer.

[0065] Furthermore, although in the figures it can be seen that the third layer 12 extends parallel to the surface of the sensor 1, such an aspect should also not be considered as limiting the invention, and the third layer may have a substantially oblique extension or any other.

[0066] However, it is still found that, preferably, when the insulating region 15 is deeper in the substrate 3 than the third layer 12, the passivation layer 18 actively cooperates in the aforementioned charge transport function performed by the third layer 12.

[0067] If the passivation layer 18 is appropriately polarized according to the third layer 12, such contribution is also advantageously increased.

[0068] It should also be noted that, more preferably, if the insulating region 15 is particularly deeper in the substrate 3 than the third layer 12, the contribution of the passivation layer 18 to the aforementioned charge transport action is certainly relevant.

[0069] The cooperation with such a third layer 12 is not limited to what has just been mentioned: in fact, in the absence of the passivation layer 18, the insulating regions 15 may prevent the collection of charges in the substrate 3 by undesired electric fields.

[0070] In the figure, it can be seen that the first layer 8 of semiconductor material is not intrinsic. In practice, a fourth layer 20 of semiconductor material, always doped with a first type of doping, is formed on the front surface 4 of the substrate 3 above the first layer 8. In particular, the doping of the fourth layer 20 is greater than that of the first layer 8. Thereby, in effect, the first layer 8 is patterned, i.e. the first layer 8 preferably has a doping gradation that allows to model the electric field involved therein, especially at the edges. Furthermore, different doping species can be used in the fourth layer 20 and the first layer 8 in order to further model the doping gradient. In either case, this enhances the effect of the virtual guard ring 11. Potentially, the extension of such a virtual guard ring 11 can therefore be reduced.

[0071] The latter aspect is in fact related to the efficiency of the radiation sensor 1. In the aforementioned case, in fact the distance between the periphery of the first region and the passivation layer 18 (i.e. between the first layer 8 and the passivation layer 18) is predefined, as is the distance between the second region (and therefore the second layer 9) and the same passivation layer 18. However, according to a variant of the embodiment not shown here, the first region is in contact with an insulating region that covers substantially the entire front surface of the substrate. It is clear that in such a case the passivation layer covers the insulating region only from a certain depth.

[0072] The location of the fourth layer 20 on the front surface of the substrate 3 is also a feature that is considered non-limiting for the present invention, since there are embodiment variants not shown here in which the same fourth layer is formed in the depth direction of the substrate (but close to the front surface and in any case at least partially interposed between the front surface and the first layer) and connected to the front surface by electrical contacts. However, in other embodiment variants, the same fourth layer is molded and provided with the aforementioned electrical contacts.

[0073] It has previously been said that one of the advantages of the present invention is that the insulating region 15 does not affect the rear face 5 of the substrate 3. However, in certain circumstances it may be necessary for there to be an isolation which generally affects the coupling between adjacent diodes 2 and the substrate 3.

[0074] According to a variant of the embodiment shown in Fig. 3, the sensor 100 comprises a fifth layer 130 of semiconductor material, doped with a second type of doping, interposed between the passivation layer 118 and the rear face 105 of the substrate 103. Such a fifth layer 130 advantageously makes it possible to increase the functional isolation between adjacent cells of the sensor 100.

[0075] Furthermore, the fifth layer 130 is in contact with the rear face 105, which generally has a further doped layer 140 of the same type. Such a further layer 140, which covers the photon entrance window in the backlit sensor 100, must be powered. Preferably, such a power supply can have electrical contacts arranged via the fifth layer 130 and the passivation layer 118, and thus on the front face of the sensor 100. This makes it possible to avoid metallization of the rear face of the sensor 100.

[0076] However, such an insulation may be considered to be insufficient, especially at the optical level, according to a further embodiment variant shown in Figure 1, in which the radiation sensor 200 comprises a second insulating region 232 made on the periphery of the substrate 203 and extending in the depth direction from the rear face 205, as shown in Figure 4. Advantageously, the functional insulation between adjacent cells can thus be properly calibrated.

[0077] A sixth layer 233 of doped semiconductor material, again having the same advantages as the passivation layer 218, but with a second type of doping and with a thickness according to design parameters, is interposed between the second insulating region 232 and the substrate 203. However, such an aspect should also not be considered as limiting the invention, and the sixth layer may not be present in different embodiment variants.

[0078] The depth of the second insulating region 232 is also not a limitation of the present invention. In other words, it is not necessary for the second insulating region 232 to contact the passivation layer 218. First, in fact, according to different embodiment variants not shown here, the second insulating region contacts the first insulating region in the same way that the sixth layer contacts the passivation layer.

[0079] According to a further embodiment variant shown in Figure 5, the first insulating region 315 and the second insulating region 332 remain spaced apart, as do the passivation layer 318 and the sixth layer 333. To ensure functional isolation between adjacent cells, a seventh layer 335 of doped semiconductor material with a second type of doping is interposed between them.

[0080] In light of the above, it will be seen that the radiation sensor of the present invention achieves all its preset objectives.

[0081] In particular, the improved fill factor of the microcells provides improved performance over comparable sensors.

[0082] More specifically, the insulating regions have a lower incidence on the substrate and the presence of a special doping layer covering them reduces, if not substantially cancels, their contribution to the occurrence of the so-called dead edge.

[0083] The third layer and the passivation layer improve the transport of charges generated in the substrate to the high electric field layer, making it possible to effectively induce the charge multiplication effect.

[0084] The present invention may be subject to many modifications and variations, all of which are within the scope of the appended claims. Moreover, all details may further be replaced by other technically equivalent elements, and materials may be varied as necessary, without departing from the scope of protection of the invention defined by the appended claims.

Claims

1. In a diode radiation sensor having one or more charge multiplication diodes (2), the diode radiation sensor (1; 100; 200; 300) a substrate (3; 103; 203; 303) made of a semiconductor material, having a front surface (4) and a rear surface (5; 105; 205) opposite said front surface (4); at least one first layer (8) of semiconductor material doped with a first type of doping and formed at least close to said front surface (4) of said substrate (3; 103; 203; 303) so as to cover at least a first central area of ​​said front surface (4) of said substrate (3; 103; 203; 303); at least one second layer (9) of semiconductor material doped with a second type of doping of electrically opposite sign to said first type and formed at a first depth in said substrate (3; 103; 203; 303), the second layer (9) is substantially parallel to the first layer (8) so as to affect a second region between the first layer (8) and the second layer (9); a second layer (9), the second region generating a high electric field region (10) for producing a charge multiplication effect by polarization of the diode radiation sensor (1; 100; 200; 300); at least one third layer (12) of semiconductor material doped with said second type of doping and formed in said substrate (3; 103; 203; 303) at a second depth deeper than said first depth, a third layer (12) which influences a third region which is lateral in a planar projection and at most overlaps the second region; at least one first insulating region (15; 315) formed around the periphery of said substrate (3; 103; 203; 303) and extending in depth within said substrate (3; 103; 203; 303) from said front surface (4) to an intermediate region between said front surface (4) and said rear surface (5; 105; 205) so as to be arranged laterally at least with respect to said first layer (8) and said second layer (9); a passivation layer (18; 118; 218; 318) interposed between at least a sidewall portion of the first insulating region (8) and the substrate (3; 103; 203; 303) from at least the second depth of the third layer (12) towards the rear face (5; 105; 205); 1. A diode radiation sensor comprising:

2. at least one fourth layer (20) of semiconductor material doped with said first type of doping and formed at least close to said front surface (4) of said substrate (3; 103; 203; 303) above said first layer (8), 2. The radiation sensor according to claim 1, wherein the doping of the fourth layer (20) is greater than the doping of the first layer (8) so as to obtain a conductivity of the fourth layer (20) greater than a conductivity of the first layer (8).

3. 2. The radiation sensor of claim 1, wherein each point of the periphery of the second region is spaced apart from the passivation layer (18; 118; 218; 318) by at least one predetermined distance.

4. said third region influenced by said third layer (12) on a first side is in contact with said passivation layer (18; 118; 218; 318), The radiation sensor of claim 3 , extending in opposite directions over a length at least equal to said predetermined distance.

5. 2. The radiation sensor of claim 1, further comprising at least one fifth layer (130) of semiconductor material doped with the second type of doping and interposed between the passivation layer (118) and the rear face (105) of the substrate (103).

6. 2. The radiation sensor according to claim 1, comprising at least one second insulating region (232; 332) formed on the periphery of the substrate (203; 303) and extending depthwise into the substrate (203; 303) starting from the rear face (205).

7. 7. The radiation sensor of claim 6, further comprising a sixth layer (233; 333) of at least one tool of semiconductor material doped with the second type of doping, the sixth layer (233; 333) being interposed between the second insulating region (232; 332) and the substrate (203; 303).

8. 8. The radiation sensor of claim 7, comprising at least one seventh layer (335) of semiconductor material doped with the second type of doping and interposed between the passivation layer (318) and the sixth layer (333).

9. 2. The radiation sensor according to claim 1, wherein the insulating region (15; 232; 332) is formed from an oxide of the semiconductor material.

10. 2. Radiation sensor according to claim 1, comprising a further layer (40; 140) on the rear face of the substrate, doped with the second type of doping.

Images