Avalanche diode and detector

Abstract

The invention discloses an avalanche diode and a detector, as one example, the avalanche diode includes a substrate; the first electrode has a first doping type, and the first electrode extends into the substrate from one surface of the substrate; the second electrode has a second doping type, the second electrode extends into the substrate from one surface of the substrate, and the second electrode and the first electrode are arranged at an interval; and the diversion structure is annularly arranged on the outer periphery of the first electrode, and the diversion structure extends into the substrate from the first surface. The avalanche diode of the technical scheme of the invention can improve the detection efficiency and is beneficial to production and preparation.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric detectors, and in particular to an avalanche diode and a detector. Background Art

[0002] A single photon avalanche diode (SPAD) is a semiconductor photodetector with single-photon detection sensitivity. It uses the avalanche effect that occurs when a PN junction operates above the reverse breakdown voltage. It can multiply the carriers generated by the absorbed light and generate a large current that is detected by an external circuit, thereby realizing the photoelectric detection process.

[0003] In the existing photodiode structure, a P region needs to be set on the lower surface, and it usually needs to be prepared using a back ion implantation process. The P regions on both sides also need to use high-energy ion implantation or deep trench implantation processes, which makes the single-photon avalanche diode process complicated and difficult to prepare. Summary of the invention

[0004] The main purpose of the present invention is to provide an avalanche diode, aiming to improve the detection efficiency of the device by achieving edge breakdown.

[0005] To achieve the above object, the avalanche diode proposed by the present invention comprises:

[0006] substrate;

[0007] A first electrode having a first doping type, wherein the first electrode extends from a surface of the substrate to the substrate;

[0008] a second electrode having a second doping type, the second electrode extending from a surface of the substrate into the substrate and spaced apart from the first electrode; and

[0009] The flow-guiding structure is arranged around the outer periphery of the first electrode, and the flow-guiding structure extends from the first surface to the substrate.

[0010] In a possible embodiment of the present application, the depth of the guide structure is greater than the depth of the first electrode.

[0011] In a possible embodiment of the present application, the avalanche diode further includes a first semiconductor region, wherein the first semiconductor region has the second doping type and extends into the substrate in a direction away from the first electrode.

[0012] In a possible embodiment of the present application, the guide structure is a deep trench isolation structure or a shallow trench isolation structure.

[0013] In a possible embodiment of the present application, the avalanche diode further includes a second semiconductor region, wherein the second semiconductor region has the second doping type and extends into the substrate in a direction away from the second electrode.

[0014] In a possible embodiment of the present application, the substrate has a first surface and a second surface opposite to each other;

[0015] The avalanche diode further includes an isolation structure, which extends from the first surface to the second surface. The isolation structure is arranged around the outer periphery of the second electrode and the second semiconductor region, and is arranged adjacent to the second electrode and the second semiconductor region.

[0016] In a possible embodiment of the present application, a passivation layer is formed on the inner wall surface of the flow-guiding structure on one side close to the first electrode;

[0017] And / or, a passivation layer is formed on a contact surface between the isolation structure and the substrate.

[0018] In a possible embodiment of the present application, the second electrode is arranged in a ring shape, and the second electrode is arranged around the outer periphery of the first semiconductor region.

[0019] In a possible embodiment of the present application, the first doping type is N-type, and the second doping type is P-type;

[0020] Alternatively, the first doping type is P type, and the second doping type is N type.

[0021] The present invention also provides a detector, comprising the avalanche diode as described above.

[0022] The avalanche diode of the present invention includes a substrate, a first electrode, a second electrode, and a current-conducting structure. As an example, the substrate is formed with a first surface and a second surface relative to each other. The first electrode and the second electrode are used to play the role of ohmic contact. The current-conducting structure is used as a barrier. Under the forced action of the current-conducting structure, the photogenerated charges are forced to flow through the avalanche region instead of the non-avalanche region when they converge, thereby improving the efficiency of the photogenerated carriers triggering the avalanche. Under the action of the current-conducting structure, the avalanche diode of the present invention can reduce the spacing between the first electrode and the second electrode, and can reduce the spacing between the first electrode and the second electrode. In this way, by reducing the spacing between the two electrodes, a higher detection performance can be maintained even when the device size is smaller, which is conducive to the miniaturization of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0024] Figure 1 A longitudinal cross-sectional view of an embodiment of an avalanche diode of the present invention;

[0025] Figure 2 FIG. 4 is a longitudinal cross-sectional view of another embodiment of an avalanche diode according to the present invention.

[0026] Description of Figure Numbers:

[0027] Label name Label name 1 Avalanche diode 13 Second electrode 11 Substrate 14 Diversion structure 111 First surface 15 The first semiconductor region 112 Second surface 16 The second semiconductor region 12 First electrode 17 Isolation Structure

[0028] The purpose, features and advantages of the present invention will be described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] Single-photon avalanche diodes operate above the breakdown voltage of the PN junction and can be used in highly sensitive photon capture environments. Since the avalanche region of existing avalanche diode devices is usually formed by the concentration control of the N+ / N- region at the lower surface P region, the left and right P regions, and the upper surface P-, a potential gradient can be formed, which can make the photogenerated electrons in the N- region flow to the avalanche region at the N+ / N-, thereby triggering an avalanche and being detected. However, for the P region at the lower surface of the single-photon avalanche diode of this structure, the back ion implantation process is required to be prepared; the P regions on both sides also need to use high-energy ion implantation or deep trench implantation processes, resulting in a complex process for the single-photon avalanche diode and difficult implementation.

[0034] Therefore, the present invention proposes an avalanche diode that can achieve the conduction and aggregation of photogenerated charges, thereby ensuring detection efficiency and being more conducive to the preparation of the device. Figure 1 and Figure 2 In one embodiment of the present invention, the avalanche diode comprises:

[0035] Substrate 11;

[0036] A first electrode 12 having a first doping type, wherein the first electrode 12 extends from a surface of the substrate 11 to the inside of the substrate 11;

[0037] A second electrode 13 having a second doping type, the second electrode 13 extending from a surface of the substrate 11 to the inside of the substrate 11 and spaced apart from the first electrode 12; and

[0038] The flow-guiding structure 14 is disposed around the outer periphery of the first electrode 12 , and the flow-guiding structure 14 extends from the first surface 111 to the substrate 11 .

[0039] In this embodiment, the material of the substrate 11 can be a silicon wafer, of course, it can also be selenium, germanium, etc., which is not limited here. The substrate 11 includes two surfaces arranged opposite to each other. The following embodiments refer to these two surfaces as a first surface 111 and a second surface 112 respectively. The two surfaces can be basically parallel, that is, the two surfaces are arranged in parallel, and the two surfaces may be partially non-parallel due to processing errors. The first surface 111 can be the front side of the substrate 11, and the second surface 112 can be the back side of the substrate 11. Therefore, when the second surface 112 is the light incident surface, the avalanche diode 1 is a back-illuminated structure, which can improve the geometric filling factor and detection efficiency of the device. Of course, the above structure is not limited here. The first electrode 12 has a first doping type, that is, it is formed by doping impurity ions in the substrate 11. For example, the doped ion conductivity type is N-type or P-type. The second electrode 13 has a second doping type, which is different from the doping type of the first electrode 12. For example, when the first doping type is N-type, the second doping type is P-type. Conversely, when the first doping type is P-type, the second doping type is N-type.

[0040] The substrate 11 may be a P-type epitaxial component (P-EPI) or an N-type epitaxial component (N-EPI). This embodiment is described by taking the substrate 11 as a P-type epitaxial component (P-EPI) as an example. That is, P-type ions are grown on the surface of a silicon wafer, and then P-type atoms, such as non-metallic boron (B) atoms, may be lightly doped on the basis of the substrate 11. The first electrode 12 may be formed by doping N-type atoms with a relatively high concentration, such as non-metallic phosphorus (P) or metal arsenic (As), thereby forming an N+ region, i.e., the first electrode 12. The second electrode 13 is formed by doping P-type atoms with a relatively high concentration, such as B atoms, etc., on the basis of the substrate 11, thereby forming a P+ region, i.e., the second electrode 13. The first electrode 12 may be used as the cathode of the device, and the second electrode 13 may be used as the anode of the device, so that the obtained large current can be derived. The carriers generated on both sides of the substrate 11 can drift to the avalanche zone. When photons are incident from the back side (second surface), both sides of the first electrode 12 of the device are drift zones. As an example, the photogenerated carriers generated drift from the second surface 112 to the avalanche zone below the first electrode 12 under the action of the electric field, thereby triggering an avalanche. That is, when light is incident on the structure, photogenerated carrier drift zones can appear on both sides of the device. Under the action of the electric field, the carriers drift to the position below the first electrode 12, triggering avalanche breakdown, thereby realizing efficient detection of single photons by the avalanche diode 1. A circle of guide structure 14 is arranged around the first electrode 12, and a drift ring is introduced to block the converged current from flowing from the side of the first electrode 12 to the first electrode 12, thereby changing the current flow direction and the electric field direction, forcing it to flow from the bottom surface of the first electrode 12 through the avalanche zone, and then there is a certain probability of triggering an avalanche, which greatly improves the photon detection efficiency (PDE) of the device, that is, the ratio of the number of detected photons to the number of incident photons.

[0041] The avalanche diode 1 of the present invention includes a substrate 11, a first electrode 12, a second electrode 13, and a current-conducting structure 14. As an example, the substrate 11 is formed with a first surface 111 and a second surface 112 opposite to each other. The first electrode 12 and the second electrode 13 are used to play the role of ohmic contact. The current-conducting structure 14 is used as a barrier. Under the forced action of the current-conducting structure 14, the photogenerated charges are forced to flow through the avalanche region when they converge, rather than flowing through the non-avalanche region, thereby improving the efficiency of photogenerated carriers triggering avalanches. Under the action of the current-conducting structure 14, the avalanche diode of the present invention can reduce the spacing between the first electrode 12 and the second electrode 13, and can reduce the spacing between the first electrode 12 and the second electrode 13. In this way, by reducing the spacing between the two electrodes, a higher detection performance can be maintained even when the device size is smaller, which is conducive to device miniaturization.

[0042] Please refer to Figure 1 and Figure 2In a possible embodiment of the present application, the depth of the guide structure 14 is greater than the depth of the first electrode 12 .

[0043] In this embodiment, the depth of the guide structure 14 can be set according to the depth of the avalanche zone. Setting the depth of the guide structure 14 to be greater than the depth of the first electrode 12 can block the converged current from flowing from the side of the first electrode 12 to the first electrode 12, and force it to flow through the avalanche zone from the bottom of the first electrode 12, thereby increasing the probability of triggering avalanche and improving the photon detection efficiency of the device.

[0044] Please refer to Figure 2 In a possible embodiment of the present application, the avalanche diode further includes a first semiconductor region 15 , wherein the first semiconductor region 15 has the second doping type and extends in a direction away from the first electrode 12 into the substrate 11 .

[0045] In this embodiment, the first semiconductor region 15 has the same doping type as the substrate 11. The first semiconductor region 15 is a P-type well (P-Well, PW for short). By reasonably designing the peak value and doping concentration of the reverse doping, the appropriate voltage when edge breakdown occurs can be regulated so that the voltage is not too high, thereby making it easier for the photogenerated carriers to drift from the two side edges of the substrate 11 to the bottom position of the first electrode 12. The carriers generated by the photons absorbed at this position have a greater probability of triggering an avalanche. That is, the edge electric field of the first electrode 12 away from the first surface 111 is the strongest, and an avalanche is easily triggered at this position, so it is an avalanche zone. When light is incident on this structure, a photogenerated carrier drift zone may appear on both sides of the device. Under the action of the electric field, the carriers drift to the position where the first electrode 12 is connected to the first semiconductor to trigger an avalanche breakdown. This position is located at the bottom edge of the first electrode 12. By appropriately setting the doping concentration of the first semiconductor region 15, the edge of the first electrode 12 can deplete the first semiconductor region 15 (PW) and expand the depletion region to the low-doped substrate 11 region below the first semiconductor region 15, so that the photogenerated electrons generated at the substrate 11 positions on both sides of the device can drift to the avalanche region at the bottom of the first electrode 12 to trigger an avalanche. By setting the first semiconductor region 15, the flow-guiding structure 14 can be more easily realized, and the breakdown voltage can also be reduced, which can increase the probability of avalanche occurrence, thereby improving the detection efficiency.

[0046] Please refer to Figure 1 and Figure 2 In a possible embodiment of the present application, the guide structure 14 is a deep trench isolation structure 17 or a shallow trench isolation structure 17 .

[0047] In this embodiment, the guide structure 14 can be a shallow trench isolation structure 17STI or a deep trench isolation structure 17DTI of different depths, which can be formed by using a standard CMOS process. As an example, the trench isolation structure 17 is formed in a surface of the substrate 11, and the depth and width of the trench isolation structure 17 can be set according to the actual application, so as to guide the current generated by the convergence of photogenerated charges and flowing to the first electrode 12, so that the current can flow from the bottom surface of the first electrode 12 through the avalanche region, rather than through the non-avalanche region, that is, the side of the first electrode 12, so as to increase the probability of triggering avalanche, thereby improving the photon detection efficiency of the device.

[0048] Please refer to Figure 1 and Figure 2 In a possible embodiment of the present application, the avalanche diode further includes a second semiconductor region 16 , wherein the second semiconductor region 16 has the second doping type and extends in a direction away from the second electrode 13 into the substrate 11 .

[0049] In this embodiment, the second semiconductor region 16 has the same doping type as the substrate 11. For example, when the substrate 11 is a P-type substrate 11, the second semiconductor region 16 is also a P-type well (PW), so that it can serve as a transition structure between the second electrode 13 and the substrate 11, and can guide the anode potential of the device to the bottom of the P-type substrate 11. At the same time, it is also convenient to control the direction of the electric field, so that the electric field is directed toward the edge breakdown area of ​​the first electrode 12, such as N+, which can increase the breakdown probability and improve the sensitivity. The doping concentration of the second semiconductor region 16 can be the same as the doping type and doping concentration of the first semiconductor region 15, or it can be different from it, which is not limited here. Optionally, the second semiconductor region 16 is a shallow P-well type.

[0050] Please refer to Figure 1 and Figure 2 In a possible embodiment of the present application, the substrate 11 has a first surface 111 and a second surface 112 opposite to each other;

[0051] The avalanche diode further includes an isolation structure 17 , which extends from the first surface 111 to the second surface 112 . The isolation structure 17 is disposed around the outer periphery of the second electrode 13 and the second semiconductor region 16 , and is disposed adjacent to the second electrode 13 and the second semiconductor region.

[0052] In this embodiment, in order to achieve the accuracy of the light detected by each device, an isolation structure 17 is also provided at the edge of the substrate 11, so as to isolate two adjacent pixel areas. The isolation structure 17 can be formed by a groove filled with an insulating medium. The isolation structure 17 can be a deep groove or a shallow groove, which is not limited here. In this embodiment, the isolation structure 17 can be optionally set as a deep groove type DTI, and the deep groove type DTI extends from one side surface of the substrate 11 to the other side surface set oppositely, so as to achieve complete isolation between the two pixels. The isolation structure 17DTI is located at the junction of adjacent pixels and runs through the entire PEPI substrate 11, which can effectively prevent optical crosstalk and electrical crosstalk between adjacent pixels to improve the detection performance of the avalanche diode 1.

[0053] Please refer to Figure 1 and Figure 2 In a possible embodiment of the present application, a passivation layer is formed on the inner wall surface of the flow-guiding structure 14 on one side close to the first electrode 12;

[0054] And / or, a passivation layer is formed on the contact surface between the isolation structure 17 and the substrate 11 .

[0055] In this embodiment, since the guide structure 14 is adjacent to the avalanche region, an interface defect will be formed on the substrate 11 during the process of forming the deep groove or shallow groove of the guide structure 14 by using the CMOS process, and non-photogenerated carriers that are easily generated will enter the avalanche region. To this end, in this embodiment, a passivation layer material can be deposited on the substrate 11 to form a passivation layer on the contact surface between the isolation structure 17 and the substrate 11, thereby passivating the interface defects. The passivation layer material can be SiOx / AlOx. By depositing the passivation layer material, a hole-enriched layer can be formed on the silicon surface in contact with the isolation structure 17, thereby effectively passivating the silicon surface, reducing the influence of non-photogenerated carriers on avalanche breakdown, and greatly reducing the dark count (DCR, Dark Count Rate) generated by interface defects, that is, the count rate of the SPAD device in a dark environment). In this embodiment, a passivation material such as SiOx / AlOx, HiK material, etc. containing anions may be deposited at the interface where the substrate 11 contacts the isolation structure 17, and a hole-enriched layer may be formed on the silicon surface to reduce the dark counts generated by interface defects. The second semiconductor region 16 and the isolation structure 17 are arranged adjacent to each other, which can reduce the non-photogenerated carriers generated by the isolation structure 17 from entering the avalanche region, thereby reducing the dark count rate (DCR) of the device and improving the performance of the device.

[0056] Please refer to Figure 1 and Figure 2In a possible embodiment of the present application, the second electrode 13 is arranged in a ring shape, and the second electrode 13 is arranged in a ring around the outer periphery of the first semiconductor region 15.

[0057] In this embodiment, the second electrode 13 is set to be ring-shaped, which can cooperate with the first electrode 12 located in the middle to improve the convenience of ohmic contact. The second electrode 13 is in contact with the outer side of the first semiconductor region 15, thereby increasing the doping concentration, and after the avalanche occurs, the current can be quickly moved from the first electrode 12N+ to the second electrode 13P+, so that it can be derived and detected, thereby improving the derivation efficiency, thereby also improving the detection efficiency. Of course, in other embodiments, the second electrode 13 can also be set in a block structure, with two blocks respectively provided, symmetrically arranged on the outer side of the first electrode 12.

[0058] Please refer to Figure 1 and Figure 2 In a possible embodiment of the present application, the first doping type is N-type, and the second doping type is P-type;

[0059] Alternatively, the first doping type is P type, and the second doping type is N type.

[0060] In this embodiment, the first doping type is N-type, and the second doping type is P-type, then the substrate 11 is a P-type epitaxial component, that is, the avalanche diode proposed in the present invention is a SPAD device with P-EPI as the substrate 11. The first semiconductor region 15 is a P-type well, the first electrode 12 is N+, the second electrode 13 is P+, and the second semiconductor region 16 is also a P-type well, so that when the device is above the avalanche breakdown voltage, the photogenerated carriers drift to the junction region under the action of the electric field. Since the collision ionization rate and mobility of electrons are higher than those of holes, a higher photon detection efficiency can be obtained. In other embodiments, the substrate 11 can also be an N-type epitaxial component, and the avalanche diode proposed in the invention can also be a SPAD device with N-EPI as the substrate 11, and the polarity of the material only needs to be synchronously reversed. In this embodiment, the first doping type is N-type, the first semiconductor region 15 is an N-type well, the first electrode 12 is P+, the second electrode 13 is N+, and the second semiconductor region 16 is also an N-type well. When NEPI is used as the substrate 11, the passivation layer formed on the inner wall surface of the guide structure 14 on the side close to the first electrode 12, and the passivation layer material formed on the contact surface between the isolation structure 17 and the substrate 11 should contain cations, thereby forming an electron-rich area on the N-EPI surface to achieve the purpose of passivating the defects of the N-EPI substrate 11.

[0061] The present invention also discloses a detector, which includes the avalanche diode 1 as mentioned above. The detailed structure of the avalanche diode 1 can be referred to the above embodiment and will not be repeated here. It can be understood that since the above avalanche diode 1 is used in the detector of the present application, the embodiments of the detector of the present application include all technical solutions of all embodiments of the above avalanche diode 1, and the technical effects achieved are also exactly the same, which will not be repeated here.

[0062] The number of avalanche diodes 1 can be multiple, and the multiple avalanche diodes 1 are arranged in an array, and every two avalanche diodes 1 are separated by an isolation structure 17. The substrate 11 of the multiple avalanche diodes 1 can be an integral structure, and the isolation structure 17 is set between two adjacent avalanche diodes 1 to facilitate processing. Of course, the detector can also include an integrated circuit that can be electrically connected to the first electrode 12 and the second electrode 13, so as to serve as a structure for export and back-end processing.

[0063] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An avalanche diode, characterized in that: include: substrate; A first electrode having a first doping type, wherein the first electrode extends from a surface of the substrate to the substrate; a second electrode having a second doping type, the second electrode extending from a surface of the substrate to the substrate and spaced apart from the first electrode; as well as The flow-guiding structure is arranged around the outer periphery of the first electrode, and the flow-guiding structure extends from the first surface to the substrate.

2. The avalanche diode according to claim 1, characterized in that: The depth of the flow-guiding structure is greater than the depth of the first electrode.

3. The avalanche diode according to claim 1, characterized in that: The avalanche diode further includes a first semiconductor region having the second doping type and extending into the substrate in a direction away from the first electrode.

4. The avalanche diode according to claim 1, characterized in that: The guide structure is a deep trench isolation structure or a shallow trench isolation structure.

5. The avalanche diode according to any one of claims 1 to 4, characterized in that: The avalanche diode further includes a second semiconductor region having the second doping type and extending into the substrate in a direction away from the second electrode.

6. The avalanche diode according to claim 5, characterized in that: The substrate has a first surface and a second surface opposite to each other; The avalanche diode further includes an isolation structure, which extends from the first surface to the second surface. The isolation structure is arranged around the outer periphery of the second electrode and the second semiconductor region, and is arranged adjacent to the second electrode and the second semiconductor region.

7. The avalanche diode according to claim 6, characterized in that: The flow-guiding structure has a passivation layer formed on an inner wall surface of a side close to the first electrode; And / or, a passivation layer is formed on a contact surface between the isolation structure and the substrate.

8. The avalanche diode according to any one of claims 1 to 4, characterized in that: The second electrode is arranged in a ring shape, and the second electrode is arranged around the outer periphery of the first semiconductor region.

9. The avalanche diode according to claim 8, characterized in that The first doping type is N-type, and the second doping type is P-type; Alternatively, the first doping type is P type, and the second doping type is N type.

10. A detector, characterized in that: Comprising the avalanche diode according to any one of claims 1 to 9.

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