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    • 专利摘要:
    The invention relates to a SPAD type photodiode (200) comprising: a semiconductor substrate (201) of a first conductivity type having a front face and a back face; and a first semiconductor region (203) of the second conductivity type extending into the substrate (201) from its front face and towards its back face, the side faces of the first region (203) being in contact with the substrate (201) and the junction between the lateral faces of the first region (203) and the substrate (201) defining an avalanche zone of the photodiode.
    公开号:FR3056019A1
    申请号:FR1658513
    申请日:2016-09-13
    公开日:2018-03-16
    发明作者:Norbert Moussy
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    (54) SPAD TYPE PHOTODIODE.
    The invention relates to a SPAD type photodiode (200) comprising: a semiconductor substrate (201) of a first type of conductivity having a front face and a rear face; and a first semiconductor region (203) of the second type of conductivity extending in the substrate (201) from its front face and in the direction of its rear face, the lateral faces of the first region (203) being in contact with the substrate (201) and the junction between the lateral faces of the first region (203) and the substrate (201) defining an avalanche region of the photodiode.
    B15154 - DD17140JB
    SPAD TYPE PHOTODIODE
    Field
    The present application relates to the field of avalanche photodiodes for the detection of single photons, also called SPAD photodiodes (from the English Single Photon Avalanche Diode).
    Presentation of the prior art
    A SPAD photodiode is essentially constituted by a PN junction polarized in reverse at a voltage greater than its avalanche threshold. When no electric charge is present in the depletion zone or space charge zone of the PN junction, the photodiode is in a pseudo-stable, non-conductive state. When a photogenerated electric charge is injected into the depletion zone, if the speed of movement of this charge in the depletion zone is sufficiently high, that is to say if the electric field in the depletion zone is sufficiently intense , the photodiode is likely to enter an avalanche. A single photon is thus capable of generating a measurable electrical signal, and this with a very short response time. SPAD photodiodes make it possible to detect radiation of very low light intensity, and are used in particular for the detection of single photons and the counting of photons.
    It would be desirable to be able to at least partially improve certain aspects of known SPAD photodiodes.
    B15154 - DD17140JB
    summary
    Thus, one embodiment provides a photodiode of the SPAD type comprising: a semiconductor substrate of a first type of conductivity having a front face and a rear face; and a first semiconductor region of the second type of conductivity extending in the substrate from its front face and towards its rear face, the lateral faces of the first region being in contact with the substrate and the junction between the lateral faces of the first region and the substrate defining an avalanche region of the photodiode.
    According to one embodiment, the photodiode further comprises a first polarization metallization of the substrate, located on the front face of the substrate, and a second polarization metallization of the first region, located on the front face of the first region.
    According to one embodiment, the first region comprises several bars or semiconductor tubes of the second type of conductivity extending in the substrate.
    According to one embodiment, the distance, in cross section, between two neighboring bars or tubes of the first region is less than or equal to 3 μm.
    According to one embodiment, the first region extends in the substrate over a depth of between 5 and 25 μm.
    According to one embodiment, the photodiode further comprises a first semiconductor layer coating the rear face of the substrate, the first region passing entirely through the substrate and interrupting in the first layer, the first layer being doped with the first type of conductivity and doping level lower than that of the substrate, or the first layer being doped with the second type of conductivity and doping level lower than that of the first region.
    According to one embodiment, the photodiode further comprises a second semiconductor layer coating the front face of the substrate, the first region passing entirely through the second
    B15154 - DD17140JB layer, the second layer being doped with the first type of conductivity and doping level lower than that of the substrate.
    According to one embodiment, the photodiode further comprises a localized doped region of the second type of conductivity, of doping level lower than that of the first region, extending in the substrate from its upper face and laterally surrounding the first region.
    According to one embodiment, the substrate is made of silicon, the first region being formed by filling, with polycrystalline silicon of conductivity type opposite to that of the substrate, with a trench formed in the substrate.
    According to one embodiment, the substrate rests, on the side of its rear face, on an insulating layer, and the first region passes entirely through the substrate and is interrupted on the front face of the insulating layer.
    According to one embodiment, the first region is formed by partial filling, with polycrystalline silicon of conductivity type opposite to that of the substrate, with a trench formed in the substrate, the trench then being filled with an insulating material so as to obtain an insulating wall connecting the front face of the insulating layer to the front face of the substrate.
    Brief description of the drawings
    These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments made without implied limitation in relation to the attached figures among which:
    Figure 1 is a schematic and partial side sectional view of an example of a SPAD photodiode;
    Figure 2 is a schematic and partial side sectional view of an example of an embodiment of a SPAD photodiode;
    Figure 3 is a schematic and partial side sectional view of another example of an embodiment of a SPAD photodiode;
    B15154 - DD17140JB Figure 4 is a schematic and partial side sectional view of another example of an embodiment of a SPAD photodiode; and Figures 5, 6 and 7 are schematic and partial cross-section views illustrating examples of SPAD photodiodes according to one embodiment.
    detailed description
    The same elements have been designated by the same references to the different figures and, moreover, the various figures are not drawn to scale. For the sake of clarity, only the elements which are useful for understanding the embodiments described have been shown and are detailed. In particular, a SPAD photodiode generally comprises ancillary circuits, in particular a circuit for biasing its PN junction at a voltage greater than its avalanche threshold, a reading circuit adapted to detect a triggering of an avalanche of the photodiode, thus a quenching circuit whose function is to interrupt the avalanche of the photodiode once it has been triggered. These auxiliary circuits have not been shown in the figures and will not be detailed, the embodiments described being compatible with the auxiliary circuits equipping known SPAD photodiodes. In the following description, when referring to qualifiers of absolute position, such as the terms forward, backward, up, down, left, right, etc., or relative, such as the terms above, below, top , lower, etc., or to orientation qualifiers, such as the terms horizontal, vertical, lateral, etc., reference is made to the orientation of the sectional views of Figures 1, 2, 3 or 4, being it is understood that, in practice, the photodiodes described can be oriented differently. Unless specified otherwise, the expressions approximately, appreciably, and of the order of mean to the nearest 10%, preferably to the nearest 5%, or, when they
    B15154 - DD17140JB relate to absolute or relative angles or angular orientations, to within 10 degrees, and preferably to within 5 degrees.
    A problem which arises in known SPAD photodiodes is that of collecting the photogenerated charges deep into the substrate, at a distance distant from the avalanche zone of the photodiode, that is to say the part of the zone. depletion of the photodiode in which the electric field is strong enough for the avalanche to be triggered by a single charge. Indeed, beyond a certain distance from the PN junction, the electric field resulting from the reverse polarization of the PN junction is canceled out or attenuated strongly, and no longer makes it possible to drive the photogenerated charges towards the avalanche area. Only the random scattering in the substrate is then likely to drive the photogenerated charges towards the avalanche zone, with a non-negligible probability that the photogenerated charges never reach the avalanche zone or reach it with a significant delay. This problem arises in particular when it is desired to collect photogenerated charges under the effect of light radiation of long wavelength, for example radiation of wavelength between 750 and 1200 nm in silicon.
    FIG. 1 is a schematic and partial sectional view of an example of a SPAD 100 photodiode. The photodiode 100 comprises a semiconductor substrate 101, for example made of silicon. In the example shown, the substrate 101 is P-type doped (P-). The photodiode 100 further comprises, in an upper part of the substrate 101, an N-type doped region 103 (N +) extending from the upper face of the substrate, and, under the region 103, a P-type doped region 105 ( P +), with a doping level higher than that of the substrate 101, extending from the underside of the region 103. The region 105 has, in top view, an area smaller than that of the region 103, and is located in look of a central portion 103a of region 103. A peripheral ring region 103b of region 103 therefore extends laterally beyond the periphery of region 105. The face
    B15154 - DD17140JB lower of the central region 103a of the region 103 is in contact with the upper face of the region 105, and the lower face and the lateral face of the peripheral region 103b of the region 103 are in contact with the substrate 101. Thus, the PN junction of the photodiode 100 comprises a central part formed between the region 105 and the central part 103a of the region 103, and a peripheral part formed between the substrate 101 and the peripheral part 103b of the region 103. In the example shown, the photodiode 100 further comprises a passivation layer 107, for example made of silicon oxide, coating the upper face of the substrate 101 at the periphery of the photodiode. In addition, in this example, the photodiode 100 comprises, in a lower part of the substrate 101, a doped region of type P 109 (P +), of doping level higher than that of the substrate, extending into the substrate 101 from its underside over substantially the entire surface of the photodiode.
    By way of example, the thicknesses of regions 103 and 105 are from a few tens to a few hundred nanometers, and the thickness of substrate 101 located under region 105, that is to say between the underside of region 105 and the upper face of the layer 109 in the example shown is from a few micrometers to a few tens of micrometers.
    In operation, the region 103, forming the cathode of the photodiode, is biased at a positive potential V +, and the region 105, forming the anode of the photodiode, is biased at a negative potential V-, so that the cathode voltage -anode of the photodiode is greater than its avalanche voltage. In the example of FIG. 1, the contact terminals making it possible to polarize the photodiode have not been detailed. By way of example, the anode of the photodiode is polarized via the region 109. The cathode of the photodiode can be polarized via a contact metallization located on the front face of the region 103 .
    When the photodiode 100 is reverse biased, an electric field appears at the PN junction of the
    B15154 - DD17140JB photodiode. In Figure 1, there is shown in broken lines the equipotential lines in the substrate 101 when the photodiode 100 is reverse biased. The electric field (not shown) in the photodiode is orthogonal to the equipotential lines, and is all the more intense the closer the equipotential lines are. The space charge area of the PN junction, and the electric field resulting from the reverse bias of the PN junction, extend all the deeper into the substrate 101 as the reverse bias voltage of the photodiode is high, and that the doping levels encountered are low. For a given bias voltage, the electric field generated at the PN junction becomes more intense the higher the doping levels of the P and N type regions forming the junction.
    In practice, the doping levels of the regions 103 and 105 and of the substrate 101 and the bias voltage of the photodiode are chosen so that the electric field at the level of the central part of the PN junction (at the interface between the region 105 and the central part 103a of the region 103) is intense enough for the avalanche to be triggered by a single photogenerated charge, and so that the electric field at the peripheral part of the PN junction (at the interface between the substrate 101 and the peripheral part 103b of the region 103) is sufficiently weak that the avalanche cannot be triggered by a single photogenerated charge. This makes it possible to reduce the risks of parasitic triggering of the avalanche linked to edge effects at the periphery of the PN junction.
    To allow the collection of photogenerated charges deep in the substrate 101, that is to say under the region 105, one solution is to use a substrate 101 of very low doping level, for example less than 5 * 10 ^ ^ atoms / cm-J By way of example, the substrate 101 may be an unintentionally doped semiconductor substrate, that is to say of which the P-type doping results solely from its accidental contamination by
    B15154 - DD17140JB impurities during its manufacture. This allows the electric field generated by the reverse bias of the photodiode to extend deep into the substrate. Under the effect of this electric field, the photogenerated charges in the substrate, in this case electrons, are driven towards the PN junction along a path parallel to the electric field. As a variant, the extension of the electric field in the thickness of the substrate can also be obtained with a substrate with a higher doping level, provided that the reverse bias voltage of the photodiode is significantly increased.
    Another solution (not shown) to allow the collection of photogenerated charges deep in the substrate is to bury the PN junction of the photodiode (that is to say the regions 103 and 105 of FIG. 1) deep in the substrate, so as to shorten the path that photogenerated charges must travel in depth to reach the avalanche zone. In this case, the collection of photogenerated charges towards the avalanche zone may not be assisted by an electric field but result from the random diffusion of the charges in the substrate.
    An object of an embodiment is to provide an alternative solution to the above-mentioned solutions, making it possible to efficiently collect photogenerated charges deep or at the surface in the semiconductor substrate.
    FIG. 2 is a schematic and partial side sectional view of an example of an embodiment of a SPAD 200 photodiode.
    The photodiode 200 comprises a semiconductor substrate 201, for example made of silicon, having, in the orientation of FIG. 2, substantially horizontal upper and lower faces. In this example, the substrate 201 is doped with type P (P). In addition, in this example, the substrate 201 is surmounted by a P-type doped layer 205 (P-), with a doping level lower than that of the substrate, and the lower face of which is in contact with the upper face of the substrate. . In the example
    B15154 - DD17140JB shown, the substrate also rests on a layer 207 doped with type P (P-), of doping level lower than that of the substrate, and the upper face of which is in contact with the lower face of the substrate. In this example, the layer 207 is itself based on a P-type doped layer 209, with a doping level higher than that of the layer 207, and the upper face of which is in contact with the lower face of the layer 207. A By way of example, the layer 209 can be a support substrate, on the upper face of which are formed, by epitaxy, the layer 207, then the substrate 201, then the layer 205. By way of example, the thickness of the substrate 201 is between 1 and 25 μm, and the layers 205 and 207 each have a thickness between 50 nm and 1 μm.
    The photodiode 200 further comprises a localized N-type doped region 203 (N), extending in the substrate 201 from the upper face of the substrate, over only part of the surface of the photodiode. The region 203 extends relatively deep in the substrate 201, typically over a depth of several micrometers, for example over a depth of between 5 and 25 μm. In the example shown, the region 203 extends from the upper face of the layer 205, passes entirely through the layer 205 and the substrate 201, and is interrupted in the layer 207. Thus, in an upper part 203a of the region 203, the lateral faces of the region 203 are in contact with the layer 205, in a central part 203b of the region 203, the lateral faces of the region 203 are in contact with the substrate 201, and in a lower part 203c of the region 203, the lateral faces and the underside of region 203 are in contact with layer 207.
    The substrate 201 forms the anode of the photodiode 200, and the region 203 forms the cathode of the photodiode 200. According to one aspect of the embodiment of FIG. 2, the PN junction formed between the lateral faces of the region 203 and the substrate 201 defines the avalanche zone of photodiode 200. In other words, in the embodiment of FIG. 2, the active part of the PN junction of photodiode 200, that is to say the part of
    B15154 - DD17140JB the PN junction in which the avalanche can be triggered by a single photogenerated charge, extends along a plane not parallel to the upper face of the substrate 201, for example a plane substantially orthogonal to the upper face of the substrate 201. This constitutes a difference compared to the example of FIG. 1 in which the active part of the PN junction is horizontal, that is to say parallel to the upper and lower faces of the substrate.
    The region 203 comprises for example one or more N-type doped silicon fingers, extending in the substrate 201 from its upper face, for example in a substantially vertical direction. As a variant, the region 203 may have the shape of a tube with a substantially vertical central axis, extending in the substrate 201 from its upper face.
    For example, to form the region 203, a trench is first produced, for example by etching, from the upper face of the stack comprising the layers 209 and 207, the substrate 201 and the layer 205, this trench crossing the layer 205 and the substrate 201 and interrupting in the layer 207, then the trench is filled with N-type doped polycrystalline silicon to form the region 203.
    The photodiode 200 of FIG. 2 further comprises an anode contact metallization 211 disposed above the upper face of the substrate 201 and electrically connected to the substrate 201. In the example shown, a localized region of contact making 213 doped type P 213 (P +), with a doping level greater than or equal to that of the substrate, extends into layer 205 from the upper face of layer 205 and extends to the upper face of substrate 201. The metallization 211 is arranged on and in contact with the contacting region 213.
    The photodiode 200 of FIG. 2 further comprises a cathode contact metallization 215 disposed above the upper face of the region 203 and electrically connected to the region 203. In the example shown, the metallization 215 is disposed on and in contact with the upper face of the region
    B15154 - DD17140JB
    203. An N-type doped contact making region (not shown), with a doping level higher than that of region 203, may possibly be provided in the upper part of region 203, the metallization 215 then being placed on and in contact with the upper face of this contacting region.
    In operation, the region 203 forming the cathode of the photodiode is biased to a positive potential V + via the contact metallization 215, and the substrate 201 forming the anode of the photodiode is biased to a negative potential V- by through contact metallization 211, so that the cathode-anode voltage of the photodiode is greater than its avalanche voltage.
    As in the example in FIG. 1, when the photodiode 200 is reverse biased, an electric field appears at the PN junction of the photodiode. In Figure 2, there is shown in broken lines equipotential lines in the semiconductor structure when the photodiode 200 is reverse biased. As shown in the figure, because the doping level of the layers 205 and 207 is lower than the doping level of the substrate 201, the equipotential lines are less tight at the upper parts (at the interface between the layer 205 and the upper part 203a of the region 203) and lower (at the interface between the layer 207 and the lower part 203c of the region 203) of the PN junction of the photodiode than at the level of the central part (at the interface between the substrate 201 and the central part 203b of the region 203) of the PN junction. As a result, the electric field generated at the upper and lower parts of the PN junction is less intense than the electric field generated at the central part of the PN junction.
    The doping levels of the substrate 201, of the layers 205 and 207 and of the region 203, and the bias voltage of the photodiode, are preferably chosen so that the field
    B15154 - DD17140JB electrical at the central part of the PN junction is sufficiently intense that the avalanche can be triggered by a single photogenerated charge, for example is greater than 300 kV / cm over a distance of 100 to 500 nm according to a direction orthogonal to the PN junction, and in such a way that the electric field at the level of the upper part and at the level of the lower part of the PN junction is sufficiently weak that the avalanche cannot be triggered by a single photogenerated charge, for example be less than 300 kV / cm. For example, the reverse breakdown voltage (or avalanche voltage) of the photodiode is between 10 and 50 V, and the reverse bias voltage of the photodiode is greater than its breakdown voltage by value between 0.5 and 10 V. The doping level of the substrate 201 is for example between 5 * 10 ^^ and 7 * 1θ17 atoms / cm ^. The doping level of the region 203 is for example between 1 * 1θ17 and 1 * 10 ^^ atoms / cm ^. The doping level of layers 205 and 207 is for example less than 5 * 10 ^^ atoms / cm ^.
    When a charge is photogenerated in the substrate 201 within a radius of a few micrometers around the PN junction and up to a depth of the order of the depth of the region 203, the charge diffuses laterally in the substrate, and there exists a significant probability that this charge reaches the avalanche zone of the photodiode and causes its triggering. Thus, the photodiode of FIG. 2 makes it possible to efficiently collect photogenerated charges deep in the substrate, like photogenerated charges in an upper part of the substrate. In particular, in the photodiode of FIG. 2, the average time elapsing between the photogeneration of a charge in the substrate 201 and the collection of this charge in the avalanche region of the photodiode is substantially independent of the depth at which charge has been photogenerated in the substrate.
    It will be noted that the photodiode of FIG. 2 is adapted to be lit either on the side of the upper face of the substrate 201, or on the side of the lower face of the substrate 201. In this
    B15154 - DD17140JB last case, thinning or even complete removal of the lower layer 209 may possibly be expected. An advantage of the photodiode of FIG. 2 is that when it is lit by its underside, the anode contact metallization 211 does not lie in the light path and therefore does not reduce the sensitivity of the photodiode .
    In the example of FIG. 2, the upper 205 and lower 207 layers with a lower doping level than the substrate 201 make it possible to reduce the risks of parasitic triggering of the avalanche linked to edge effects at the ends of the PN junction. These layers are however optional, other solutions being able to be provided to control the risks of parasitic triggering linked to edge effects, for example by playing on the shape of the upper and lower terminations of the region 203, or by reducing the level of doping. N type of region 203 at its upper and lower ends. In addition, a similar effect of reducing the risks of parasitic triggering can be obtained by replacing the lower P-type layer 207 by an N-type layer with a lower doping level than that of region 203.
    The PN junction formed between the substrate 201 and the region 203 is preferably reproduced several times so as to increase the chances of capturing photogenerated charges in the substrate. Examples of SPAD photodiodes in which the region 203 is repeated several times are illustrated in FIGS. 5, 6 and 7.
    FIGS. 5, 6 and 7 are cross-sectional views of SPAD photodiodes of the type described in relation to FIG. 2, according to a horizontal section plane X-X (FIG. 2) passing through the substrate 201.
    FIG. 5 illustrates an example of a SPAD photodiode, in which the region 203 comprises a plurality of substantially vertical N-type bars with circular cross section, regularly distributed, in top view, on the surface of the photodiode. Each bar can be topped with metallization
    B15154 - DD17140JB of cathode contact 215 (not visible in Figure 5) contacting the bar. The metallizations 215 surmounting the various bars can be connected together. The anode contact metallization 211 (not visible in FIG. 5) can be a single metallization, for example disposed in a central part of the photodiode, or a distributed metallization comprising several interconnected portions regularly distributed above the upper face of the photodiode.
    FIG. 6 illustrates another example of a SPAD photodiode, which differs from the example of FIG. 5 mainly in that, in the example of FIG. 6, the N-type bars of the region 203 have a cruciform shape in section transverse.
    FIG. 7 illustrates another example of a SPAD photodiode, in which the region 203 comprises a plurality of N-type tubes of substantially vertical central axes, regularly distributed, in top view, on the surface of the photodiode. In the example shown, each type N tube has, in cross section, a square shape with rounded corners. Each N-type tube in region 203 can be surmounted by cathode contact metallization 215 (not visible in FIG. 5), for example an annular metallization, contacting the upper face of the tube. Furthermore, the portion of substrate 201 located inside each N-type tube of region 203 can be surmounted by an anode contact metallization 211 (not visible in FIG. 5), contacting the upper face of the substrate portion. The cathode contact metallizations 215 surmounting the different N-type tubular regions can be connected together. In addition, the anode contact metallizations 211 surmounting the substrate portions 201 contained in the different N-type tubular regions can be connected together.
    In the examples of FIGS. 5, 6 and 7, or, more generally, when the region 203 of the photodiode is repeated several times, the cathode contact metallizations 215 surmounting the different regions 203 can be connected
    B15154 - DD17140JB with each other in groups from several neighboring regions 203, so as to obtain larger detection zones sharing the same electrical connection. Indeed, the light detection zone is for example limited to a few micrometers around each region 203. By grouping several neighboring regions 203 on the same electrical connection, detection pixels of larger dimensions are obtained.
    Furthermore, when the region 203 of the photodiode is repeated several times to increase the surface for collecting photogenerated charges, the distance (in cross section) between two neighboring regions 203 can be chosen so as to maintain a reasonable collection time for photogenerated charges equidistant between two regions 203 neighboring the structure. By way of example, the distance between two regions 203 neighboring the structure is less than 3 μm.
    Figure 3 is a schematic and partial side sectional view of an alternative embodiment of a SPAD 300 photodiode. The SPAD 300 photodiode of Figure 3 includes many structural and functional features common with the SPAD 200 photodiode of Figure 2 These common characteristics will not be described again below. In the following, only the differences compared to the SPAD 200 photodiode will be detailed.
    The SPAD photodiode 300 differs from the SPAD photodiode 200 mainly in that it does not include an upper layer P-type 205 more weakly doped than the substrate 201, surmounting the substrate 201.
    The SPAD photodiode 300 on the other hand comprises, at the upper part 203a of the region 203, a localized region 301 (N-) doped with N type, of doping level lower than that of the region 203, extending in the substrate 201 from the upper face of the substrate and laterally surrounding the region 203. The region 301 extends for example in the substrate 201 over a depth of between 50 and 500 nm. At the top 203a of region 203, the side faces of the region
    B15154 - DD17140JB
    203 are in contact with the region 301. The upper part of the PN junction of the photodiode therefore corresponds to the interface between the region 301 and the substrate 201. Because the level of N-type doping of the region 301 is lower to that of region 203, the electric field generated at the upper part of the PN junction is less intense than the electric field generated at the central part of the PN junction. Thus, the region 301 makes it possible to limit the risks of parasitic triggering of the photodiode linked to the edge effects at the upper end of the region 203. As a variant, the region 301 may have a lateral gradient of doping level, of so that its type N doping level decreases progressively as one moves away from region 203.
    Figure 4 is a schematic and partial side sectional view of an alternative embodiment of a SPAD 400 photodiode. The SPAD 400 photodiode of Figure 4 includes many structural and functional features common with the SPAD 200 photodiode of Figure 2 These common characteristics will not be described again below. In the following, only the differences compared to the SPAD 200 photodiode of FIG. 2 will be detailed.
    In the example of FIG. 4, the photodiode 400 is formed from a substrate of silicon on insulator (SOI) type. The layer 209 corresponds to the support substrate of the SOI stack. An insulating layer 401 (BOX), for example made of a silicon oxide, is placed on and in contact with the upper face of the layer 209. The insulating layer 401 is itself surmounted by the stack of layers 207, 201 and 205. In the example shown, the lower layer 207 is an N-type layer with a doping level lower than that of the region 203, and the upper layer 205 is a P-type layer with a doping level lower than that of the substrate 201.
    In the example of FIG. 4, the region 203 is located at the periphery of a trench extending from the upper face of the layer 205, entirely crossing the layer 205,
    B15154 - DD17140JB the substrate 201 and the layer 207, and emerging on the upper face of the insulating layer 401. After the formation of the trench, N-type doped polycrystalline silicon is deposited on the side walls of the trench so as to fill partially the trench. If necessary, the polycrystalline silicon is removed at the bottom of the trench. The trench is then filled with an insulating material, for example silicon oxide, so as to form an insulating wall 403 connecting the layer 401 to the upper face of the layer 205.
    The configuration of FIG. 4 is of very particular interest in the case where the region 203 has a tubular shape, for example of the type represented in FIG. 7. In fact, in this case, the portion of substrate 201 of type P located at the the interior of the N type tube 203 is entirely isolated from the rest of the substrate 201 by the insulating layer 401 and by the peripheral insulating wall 403. This makes it possible to circumscribe the high-voltage polarization of the substrate 201. This in particular facilitates the integration of other components (not shown) in and on the same substrate 201 as the SPAD photodiode.
    Particular embodiments have been described. Various variants and modifications will appear to those skilled in the art. In particular, the embodiments described are not limited to the numerical examples of dimensions and doping levels mentioned in the description.
    In addition, the advantages described above can be obtained by reversing all the types of conductivity with respect to the examples described in relation to FIGS. 2 to 7.
    B15154 - DD17140JB
    权利要求:
    Claims (11)
    [1" id="c-fr-0001]
    1. SPAD type photodiode (200; 300; 400) comprising:
    a semiconductor substrate (201) of a first type of conductivity having a front face and a rear face; and a first semiconductor region (203) of the second type of conductivity extending in the substrate (201) from its front face and in the direction of its rear face, the lateral faces of the first region (203) being in contact with the substrate (201) and the junction between the lateral faces of the first region (203) and the substrate (201) defining an avalanche region of the photodiode.
    [2" id="c-fr-0002]
    2. Photodiode (200; 300; 400) according to claim 1, further comprising a first metallization (211) of polarization of the substrate (201), located on the front face of the substrate (201), and a second metallization (215) polarization of the first region (203), located on the front face of the first region (203).
    [3" id="c-fr-0003]
    3. Photodiode (200; 300; 400) according to claim 1 or 2, wherein the first region (203) comprises several bars or semiconductor tubes of the second type of conductivity extending in the substrate (201).
    [4" id="c-fr-0004]
    4. Photodiode (200; 300; 400) according to claim 3, wherein the distance, in cross section, between two neighboring bars or tubes of the first region (203) is less than or equal to 3 pm.
    [5" id="c-fr-0005]
    5. Photodiode (200; 300; 400) according to any one of claims 1 to 4, in which the first region (203) extends in the substrate to a depth between 5 and 25 µm.
    [6" id="c-fr-0006]
    6. Photodiode (200; 300; 400) according to any one of claims 1 to 5, further comprising a first semiconductor layer (207) coating the rear face of the substrate (201), the first region (203) entirely passing through the substrate (201) and ending in the first layer (207), the first
    B15154 - DD17140JB layer (207) being doped with the first type of conductivity and doping level lower than that of the substrate (201), or the first layer (207) being doped with the second type of conductivity and doping level lower than that of the first region (203).
    [7" id="c-fr-0007]
    7. Photodiode (200; 400) according to any one of claims 1 to 6, further comprising a second semiconductor layer (205) coating the front face of the substrate (201), the first region (203) entirely passing through the second layer (205), the second layer (205) being doped with the first type of conductivity and with a lower doping level than that of the substrate.
    [8" id="c-fr-0008]
    8. Photodiode (300) according to any one of claims 1 to 6, further comprising a localized region (301) doped with the second type of conductivity, of doping level lower than that of the first region (203), s' extending into the substrate (201) from its upper face and laterally surrounding the first region (203).
    [9" id="c-fr-0009]
    9. Photodiode (200; 300; 400) according to any one of claims 1 to 8, in which the substrate (201) is made of silicon, the first region (203) being formed by filling, with polycrystalline silicon of the type conductivity opposite to that of the substrate, of a trench formed in the substrate (201).
    [10" id="c-fr-0010]
    10. Photodiode (400) according to any one of claims 1 to 9, in which the substrate rests, on the side of its rear face, on an insulating layer (401), and in which the first region (203) passes entirely through the substrate (201) and is interrupted on the front face of the insulating layer (401).
    [11" id="c-fr-0011]
    11. Photodiode (400) according to claim 10, in which the first region (203) is formed by partial filling, with polycrystalline silicon of conductivity type opposite to that of the substrate, with a trench formed in the substrate (201) , the trench then being filled with an insulating material so as to obtain an insulating wall (403) connecting the front face of the insulating layer (401) to the front face of the substrate (201).
    B15154
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    107 103b V + 103a 103 105 103b
    V-
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    引用文献:
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    法律状态:
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1658513|2016-09-13|
    FR1658513A|FR3056019B1|2016-09-13|2016-09-13|PHOTODIODE OF SPAD TYPE|FR1658513A| FR3056019B1|2016-09-13|2016-09-13|PHOTODIODE OF SPAD TYPE|
    CN201780056184.5A| CN109690792A|2016-09-13|2017-09-11|SPAD photodiode|
    PCT/FR2017/052406| WO2018050996A1|2016-09-13|2017-09-11|Spad photodiode|
    US16/325,369| US10651332B2|2016-09-13|2017-09-11|SPAD photodiode|
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