A vertical single photon avalanche diode device and a method of manufacturing the same

Abstract

The application provides a vertical single photon avalanche diode device and a preparation method thereof. The SPAD device comprises a plurality of SPAD units. Each SPAD unit comprises, in a longitudinal section, a substrate and an epitaxial layer arranged on the upper surface of the substrate, a deep trench extending longitudinally is arranged in the epitaxial layer; a filling layer is arranged in the deep trench, and the filling layer is used as a first electrode contact of the SPAD unit; a first well region and a second well region are sequentially arranged on both sides of the deep trench in the epitaxial layer, and the first well region and the second well region are different in doping type; a PN junction is formed between the first well region and the second well region, and the upper surface of the PN junction is the second well region; and a heavily doped region is arranged on the top of the second well region on both sides of the deep trench, and the heavily doped region is used as a second electrode contact of the SPAD unit. By arranging the deep trench in the SPAD structure, the volume of the avalanche region of the SPAD is increased, and the photon detection efficiency of the SPAD is improved.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a vertical single-photon avalanche diode device and its fabrication method. Background Technology

[0002] A single-photon avalanche diode (SPAD) is an avalanche photodiode operating in Geiger mode (i.e., operating voltage greater than breakdown voltage). It can be used for single-photon detection, enabling the detection of extremely weak light signals. In operation, a high reverse bias voltage is applied across the cathode (N+) and anode (P+) of the SPAD, causing the PN junction of the diode to be reverse biased and operating in Geiger mode. When a photon enters the photosensitive region of the SPAD, it has a certain probability of being absorbed by the depletion region, generating electron-hole pairs. These electron-hole pairs, under the influence of the strong electric field in the depletion region, can rapidly generate a large number of charge carriers through a multiplication effect, thus triggering avalanche breakdown. Because SPADs can detect single photons, they have enormous application potential in quantum communication, fluorescence lifetime imaging, and 3D imaging technologies.

[0003] Currently, the most commonly used single-photon avalanche diode structures include the Goetzberger diffused guard ring structure, see [link to relevant documentation]. Figure 1 The cross-sectional schematic diagram of the Gertzberger diffused grounding electrode structure shown includes a P-type substrate, an N+ doped region, and an N-type grounding electrode. The N+ doped region is located at the center of the top of the P-type substrate, and the N-type grounding electrode is positioned around the N+ doped region. The P-type electrode extends from the back of the substrate. For the single-photon avalanche diode with the above structure, the light absorption length is short, resulting in low photon detection efficiency (PDE). Increasing the substrate depth to improve photon detection efficiency leads to significant timing jitter. Furthermore, the PN junction of the above single-photon avalanche diode is horizontal, which, due to its inherent structural limitations, makes miniaturization design difficult. Summary of the Invention

[0004] To address this, the present invention provides a vertical single-photon avalanche diode device structure and its fabrication method, which can be used to solve the technical problems of low photon detection efficiency (PDE) and high difficulty in miniaturization design of conventional single-photon avalanche diode structures.

[0005] In a first aspect, embodiments of this application provide a vertical single-photon avalanche diode device, the single-photon avalanche diode device comprising a plurality of single-photon avalanche diode units, each single-photon avalanche diode unit comprising, in a longitudinal section: a substrate and an epitaxial layer disposed on the upper surface of the substrate, wherein a longitudinally extending deep trench is formed in the epitaxial layer; a filling layer is disposed in the deep trench, the filling layer serving as a first electrode contact of the single-photon avalanche diode unit; a first well region and a second well region are sequentially disposed in the epitaxial layer and on both sides of the deep trench, wherein the first well region and the second well region have different doping types; a PN junction is formed between the first well region and the second well region, the top surface of the PN junction being the second well region between the top surface of the epitaxial layer; a heavily doped region is disposed on the top of the second well region located on both sides of the deep trench, serving as a second electrode contact of the single-photon avalanche diode unit.

[0006] In some embodiments, the single-photon avalanche diode unit further includes: a first insulating layer located on the inner surface of the deep trench, the first insulating layer being used to isolate the filling layer and the first well region; and a second insulating layer located on the upper surface of the epitaxial layer, wherein the second insulating layer has a first opening and a second opening corresponding to the upper surface of the deep trench and the heavily doped region.

[0007] In some embodiments, the filling layer is made of doped polycrystalline silicon or metal.

[0008] In some embodiments, the substrate is made of any one of the following semiconductor materials: silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide.

[0009] In some embodiments, the lower surfaces of the first well region and the second well region are flush and not lower than the bottom of the deep trench.

[0010] In some embodiments, the lower surface of the deep trench is lower than the lower surface of the first well region, and the lower surface of the first well region is lower than the lower surface of the second well region.

[0011] In some embodiments, the single-photon avalanche diode device further includes a deep isolation trench structure located around each of the single-photon avalanche diode units, the deep isolation trench structure extending through the epitaxial layer and the substrate.

[0012] In some embodiments, the single-photon avalanche diode device further includes a protective ring located around the single-photon avalanche diode device on top of the epitaxial layer.

[0013] Secondly, embodiments of this application provide a method for fabricating a vertical single-photon avalanche diode unit. The method includes: depositing an epitaxial layer on a substrate; forming a deep trench in the epitaxial layer; depositing a first insulating layer on the inner surface of the deep trench; and depositing a filling layer on the surface of the first insulating layer; depositing a second insulating layer on the upper surface of the epitaxial layer; sequentially forming a first well region and a second well region in the epitaxial layer on both sides of the deep trench, wherein the upper surface of the second well region is flush with the upper surface of the epitaxial layer and higher than the upper surface of the first well region; wherein the first well region and the second well region have different doping types to form a PN junction between the first well region and the second well region; forming a heavily doped region on top of the second well region located on both sides of the deep trench; etching a first opening and a second opening in the second insulating layer, in the deep trench, and in the heavily doped region, respectively; and setting a first electrode and a second electrode at the first opening and the second opening, respectively.

[0014] Thirdly, embodiments of this application provide a method for fabricating a vertical single-photon avalanche diode device, wherein the single-photon avalanche diode device includes a plurality of single-photon avalanche diode units obtained by the above-described fabrication method, the method comprising: etching around each of the vertical single-photon avalanche diode units to form a deep isolation trench structure penetrating the epitaxial layer and the substrate; and etching the epitaxial layer located around the single-photon avalanche diode device to form a protective ring surrounding the single-photon avalanche diode device.

[0015] The vertical single-photon avalanche diode device provided by this invention features a deep trench formed in the epitaxial layer, increasing the depth of the avalanche region of the single-photon avalanche diode and thus improving the breakdown voltage (PDE). A first well region and a second well region are formed by doping on both sides of the deep trench, resulting in a vertical PN junction. This improves the breakdown voltage V of the vertical single-photon avalanche diode device of this invention. bd The scope is controllable. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the Gertzberg diffused grounding electrode structure in related technologies;

[0017] Figure 2 This is a schematic diagram of the longitudinal section structure of the single-photon avalanche diode unit provided in Embodiment 1 of this application;

[0018] Figure 3 A circuit diagram of a vertical single-photon avalanche diode device provided in an embodiment of this application;

[0019] Figure 4 This is a schematic diagram of the longitudinal section structure of the single-photon avalanche diode unit provided in Embodiment 2 of this application;

[0020] Figure 5 This is a top view of the vertical single-photon avalanche diode device provided in Embodiment 2 of this application;

[0021] Figure 6 This is a schematic diagram of the longitudinal section structure of the single-photon avalanche diode unit provided in Embodiment 3 of this application;

[0022] Figure 7 This is a top view of the vertical single-photon avalanche diode device provided in Embodiment 3 of this application;

[0023] Figures 8 to 14 This is a schematic diagram illustrating the fabrication process of the vertical single-photon avalanche diode device provided in Embodiment 4 of this application. Detailed Implementation

[0024] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0025] Example 1

[0026] Embodiment 1 of this application provides a vertical single-photon avalanche diode device, which includes multiple single-photon avalanche diode units. Figure 2 This is a schematic diagram of the longitudinal section of the single-photon avalanche diode unit 30 provided in Embodiment 1 of this application, as shown below. Figure 2 As shown, the single-photon avalanche diode unit 30 includes the following in its longitudinal section:

[0027] The substrate 1 and the epitaxial layer 2 disposed on the upper surface of the substrate 1, wherein a longitudinally extending deep trench 3 is formed in the epitaxial layer 2; here, the substrate 1 can be a P-type substrate or an N-type substrate, and the material of the substrate 1 can be any one of the semiconductor materials selected from silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide. Correspondingly, the epitaxial layer 2 on the upper surface of the substrate 1 can be a P-type epitaxial layer or an N-type epitaxial layer. A filling layer 4 is disposed in the deep trench 3, and the filling layer 4 serves as the first electrode contact of the single-photon avalanche diode unit 30; the deep trench 3 extends longitudinally in the epitaxial layer, and the depth of the deep trench 3 is less than the depth of the epitaxial layer. Here, the material of the filling layer 4 is doped polycrystalline silicon or metal, and the doping type of the doped polycrystalline silicon can be P-type or N-type, depending on its doping type. The filling layer 4 serves as a cathode contact or an anode contact.

[0028] In this embodiment, a deep trench 3 is formed in the epitaxial layer 2 to increase the depth of the avalanche region of the single-photon avalanche diode, thereby improving the PDE of the single-photon avalanche diode. The material of the filling layer 4 can be doped polysilicon, such as N+ type polysilicon, or it can be a metal material, such as tungsten.

[0029] In the epitaxial layer 2, a first well region 5 and a second well region 6 are sequentially disposed on both sides of the deep trench 3, wherein the first well region 5 and the second well region 6 have different doping types. Here, the first well region 5 and the second well region 6 are formed in the epitaxial layer 2 by doping and annealing, respectively. The depths of the first well region 5 and the second well region 6 are both less than the depth of the epitaxial layer 2. The upper surface of the second well region 6 is flush with the upper surface of the epitaxial layer 2, and the upper surface of the first well region 5 is lower than the upper surface of the epitaxial layer 2. The doping type of the first well region 5 can be P-type or N-type, and the corresponding doping type of the second well region 6 can be N-type or P-type, so as to form a PN junction between the first well region 5 and the second well region 6. The second well region 6 is located between the upper surface of the PN junction and the upper surface of the epitaxial layer. In this way, when the PN junction is in avalanche mode, leakage current at the upper surface of the epitaxial layer can be avoided. It is understood that the PN junction in this embodiment is a vertical PN junction perpendicular to the surface of the epitaxial layer.

[0030] By forming a first well region 5 and a second well region 6 in the epitaxial layer through doping, the doping dose of the P-well or N-well can be adjusted during the doping process to control the breakdown voltage V of the single-photon avalanche diode device. bd .

[0031] A heavily doped region 7 is disposed on the top of the second well region 6 located on both sides of the deep trench 3, serving as the second electrode contact of the single-photon avalanche diode unit 30. Exemplarily, the upper surface of the heavily doped region 7 is flush with the upper surface of the epitaxial layer 2. In this embodiment, the doping concentration of the heavily doped region 7 is greater than that of the second well region 6. The heavily doped region can be P+ type, in which case it can serve as the anode contact of the single-photon avalanche diode; the heavily doped region can be N+ type, in which case it serves as the cathode contact of the single-photon avalanche diode.

[0032] In this embodiment, the single-photon avalanche diode unit 30 further includes: a first insulating layer 8 located on the inner surface of the deep trench 3, the first insulating layer 8 serving to isolate the filling layer 4 from the first well region 5; and a second insulating layer 9 located on the upper surface of the epitaxial layer 2, wherein a first opening 10 and a second opening 11 are correspondingly formed on the upper surface of the deep trench 3 and at the heavily doped region 7. Here, the first opening 10 is used to expose a first electrode contact for connecting a first electrode 12 at the first opening 10, and the second opening 11 is used to expose a second electrode contact for connecting a second electrode 13 at the second opening 11, wherein the first electrode 12 and the second electrode 13 are of opposite types.

[0033] In this embodiment, the single-photon avalanche diode device further includes a deep isolation trench structure (DTI, not shown) surrounding each of the single-photon avalanche diode cells 30, the DTI extending through the epitaxial layer and the substrate. The DTI acts as a shield between SPADs, preventing signals from one SPAD from entering adjacent SPADs to reduce crosstalk. In some embodiments, the DTI is shared by SPADs on either side of a given edge. In embodiments where the DTI is shared, the epitaxial layer on one side of the DTI is part of the SPAD on that side, and the epitaxial layer on the other side of the DTI is part of the SPAD on the other side.

[0034] The single-photon avalanche diode device further includes a guard ring (not shown in the figure) located around the single-photon avalanche diode device on top of the epitaxial layer. The guard ring serves as the ground electrode contact of the single-photon avalanche diode device and is used to connect an external ground electrode. The ground electrode is of the same type as the first electrode 12. The guard ring can be a P+ type guard ring or an N+ type guard ring, used to prevent edge breakdown and avoid avalanche effects at the edge of the PN junction perpendicular to the SPAD surface.

[0035] In some embodiments, the SPAD unit 30 described above can be manufactured in both FSI (front illumination) and BSI (back illumination) modes.

[0036] Figure 3 The circuit diagram of the vertical single-photon avalanche diode device provided in the embodiments of this application is as follows: Figure 3 As shown, the SPAD includes a reverse-biased PN junction 301, which has a reverse bias voltage V. bd This reverse bias voltage generates a relatively high electric field, causing individual charge carriers injected into the depletion layer to trigger self-sustaining avalanches through impact ionization. A P-type MOSFET 302 connected in series with PN junction 301 is used to reset PN junction 301, and a correction voltage V is set at the other end of the P-type MOSFET 302. 过载 A quenching voltage V is applied to the gate of MOSFET 302. 淬灭 , to act as a resistor with relatively high resistance.

[0037] The vertical single-photon avalanche diode device provided in this application features a deep trench formed in the epitaxial layer, increasing the depth of the avalanche region in the single-photon avalanche diode unit, thereby improving the PDE of the single-photon avalanche diode unit. A first well region and a second well region are formed by doping on both sides of the deep trench, resulting in a vertical PN junction. By adjusting the doping concentration and injection energy of the first and second well regions, the Vo of the vertical single-photon avalanche diode device of this invention is improved. bdThe range is controllable, and the bandwidth of the depletion layer of the PN junction can also be adjusted, solving the technical problem that the PDE range of single-photon avalanche diodes is limited by pixel miniaturization design.

[0038] Example 2

[0039] Embodiment 2 of this application provides a vertical single-photon avalanche diode device, which includes multiple single-photon avalanche diode units. Figure 4 This is a schematic diagram of the longitudinal section of the single-photon avalanche diode unit 30A provided in Embodiment 2 of this application. Figure 5 This is a top view of the vertical single-photon avalanche diode device 200A provided in Embodiment 2 of this application, as shown below. Figure 4 As shown, the single-photon avalanche diode unit 30A includes the following in its longitudinal section:

[0040] The substrate 1 and the epitaxial layer 2 disposed on the upper surface of the substrate 1, wherein a longitudinally extending deep trench 3 is formed in the epitaxial layer 2; here, the substrate 1 can be a P-type substrate or an N-type substrate, and the material of the substrate 1 can be any one of the semiconductor materials selected from silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide. Correspondingly, the epitaxial layer 2 on the upper surface of the substrate 1 can be a P-type epitaxial layer or an N-type epitaxial layer. A filling layer 4 is disposed in the deep trench 3, and the filling layer 4 serves as the first electrode contact of the single-photon avalanche diode unit 30A; the deep trench 3 extends longitudinally in the epitaxial layer, and the depth of the deep trench 3 is less than the depth of the epitaxial layer. Here, the material of the filling layer 4 is doped polycrystalline silicon or metal, and the doping type of the doped polycrystalline silicon can be P-type or N-type, depending on its doping type. The filling layer 4 serves as a cathode contact or an anode contact.

[0041] In the epitaxial layer 2, a first well region 5 and a second well region 6 are sequentially disposed on both sides of the deep trench 3, wherein the first well region 5 and the second well region 6 have different doping types; the depth of the first well region 5 and the second well region 6 is less than the depth of the epitaxial layer 2. Here, the first well region 5 and the second well region 6 are formed in the epitaxial layer 2 by doping and annealing, respectively. The upper surface of the second well region 6 is flush with the upper surface of the epitaxial layer 2, and the upper surface of the first well region 5 is lower than the upper surface of the epitaxial layer 2. The lower surfaces of the first well region 5 and the second well region 6 are flush with each other and are not lower than the bottom of the deep trench 3. It should be understood that the position of the lower surfaces of the first well region 5 and the second well region 6 in the epitaxial layer does not exceed the bottom of the deep trench 3. That is to say, the distance L1 from the bottom of the deep trench 3 to the lower surface of the epitaxial layer 2 is less than the distance L2 from the lower surface of the first well region 5 to the lower surface of the epitaxial layer. It is easy to understand that, in space, the first well region 5 and the second well region 6 form a ring structure around the outer periphery of the deep trench 3, ensuring that the depth of the bottom of the deep trench 3 is greater than the bottom of the first well region 5 and the second well region 6. The doping type of the first well region 5 can be P-type or N-type, and the doping type of the corresponding second well region 6 can be N-type or P-type, so as to form a PN junction between the first well region 5 and the second well region 6. The upper surface of the PN junction is lower than the upper surface of the epitaxial layer, and the second well region 6 is between the PN junction and the upper surface of the epitaxial layer. In this way, when the PN junction is in avalanche mode, leakage current at the upper surface of the epitaxial layer can be avoided. The lower surface of the PN junction is higher than the bottom of the deep trench 3, that is, the depth of the PN junction does not exceed the depth of the filler 4, so that the filler 4 can control the electric field of the PN junction region.

[0042] A heavily doped region 7 is disposed on the top of the second well region 6 located on both sides of the deep trench 3, serving as the second electrode contact of the single-photon avalanche diode unit 30A. Exemplarily, the upper surface of the heavily doped region 7 is flush with the upper surface of the epitaxial layer 2. In this embodiment, the doping concentration of the heavily doped region 7 is greater than that of the second well region 6. The heavily doped region can be P+ type, in which case it can serve as the anode contact of the single-photon avalanche diode unit; the heavily doped region can be N+ type, in which case it serves as the cathode contact of the single-photon avalanche diode unit.

[0043] In this embodiment, the single-photon avalanche diode unit 30A further includes: a first insulating layer 8 located on the inner surface of the deep trench 3, the first insulating layer 8 serving to isolate the filling layer 4 from the first well region 5; and a second insulating layer 9 located on the upper surface of the epitaxial layer 2, the second insulating layer 9 having a first opening 10 and a second opening 11 respectively on the upper surface of the deep trench 3 and at the heavily doped region 7. Here, the first opening 10 is used to expose a first electrode contact for connecting a first electrode 12, and the second opening 11 is used to expose a second electrode contact for connecting a second electrode 13.

[0044] In this embodiment, the single-photon avalanche diode device 200A further includes a deep isolation trench structure 14 located around each of the single-photon avalanche diode units 30A, the deep isolation trench structure 14 penetrating the epitaxial layer 2 and the substrate 1. The DTI 14 serves to shield between SPADs, preventing signals from one SPAD from entering adjacent SPADs to reduce crosstalk. In some embodiments, the DTI is shared by SPADs on either side of a given edge. In embodiments where the DTI is shared, the epitaxial layer on one side of the DTI is part of the SPAD on that side, while the epitaxial layer on the other side of the DTI is part of the SPAD on the other side.

[0045] like Figure 5 As shown, the single-photon avalanche diode device 200A includes four single-photon avalanche diode units 30A. In some embodiments, the single-photon avalanche diode device 200A includes multiple single-photon avalanche diode units 30A. In this embodiment, the single-photon avalanche diode device 200A includes a deep isolation trench structure 14 located around each of the single-photon avalanche diode units 30A, the deep isolation trench structure 14 penetrating the epitaxial layer 2 and the substrate 1. The DTI 14 is used to shield between SPADs, preventing signals in one SPAD from entering adjacent SPADs to reduce crosstalk. It should be understood that in this embodiment, the DTI will be shared by SPADs on either side of its edge along a given edge; that is, the epitaxial layer on one side of the DTI is part of the SPAD on that side, and the epitaxial layer on the other side of the DTI is part of the SPAD on the other side.

[0046] The single-photon avalanche diode device 200A further includes a protective ring 15 located around the single-photon avalanche diode device on top of the epitaxial layer 2.

[0047] In some embodiments, the SPAD unit described above can be manufactured in both FSI (front illumination) and BSI (back illumination) modes.

[0048] Example 3

[0049] Embodiment 3 of this application provides a vertical single-photon avalanche diode device, which includes multiple single-photon avalanche diode units. Figure 6 This is a schematic diagram of the longitudinal section of the single-photon avalanche diode unit 30B provided in Embodiment 3 of this application. Figure 7 This is a top view of the vertical single-photon avalanche diode device 200B provided in Embodiment 3 of this application, as shown below. Figure 6 As shown, the single-photon avalanche diode unit 30B includes the following in its longitudinal section:

[0050] A substrate 1 and an epitaxial layer 2 disposed on the upper surface of the substrate 1 are provided. A longitudinally extending deep trench 3 is formed in the epitaxial layer 2. Here, the substrate 1 can be a P-type substrate or an N-type substrate, and the material of the substrate 1 can be any one of the semiconductor materials selected from silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide. Correspondingly, the epitaxial layer 2 on the upper surface of the substrate 1 can be a P-type epitaxial layer or an N-type epitaxial layer. A filling layer 4 is disposed in the deep trench 3, and the filling layer 4 serves as the first electrode contact of the single-photon avalanche diode unit 30B. The deep trench 3 extends longitudinally in the epitaxial layer, and the depth of the deep trench 3 is less than the depth of the epitaxial layer. Here, the material of the filling layer 4 is doped polycrystalline silicon or metal. The doping type of the doped polycrystalline silicon can be P-type or N-type, depending on its doping type. The filling layer 4 serves as a cathode contact or an anode contact.

[0051] In the epitaxial layer 2, a first well region 5 and a second well region 6 are sequentially disposed on both sides of the deep trench 3. The first well region 5 and the second well region 6 have different doping types. Here, the first well region 5 and the second well region 6 are formed in the epitaxial layer 2 by doping and annealing, respectively. The upper surface of the second well region 6 is flush with the upper surface of the epitaxial layer 2, and the upper surface of the first well region 5 is lower than the upper surface of the epitaxial layer 2. The lower surface of the first well region 5 is lower than the bottom of the deep trench 3, and the lower surface of the second well region 6 is lower than the lower surface of the first well region 5. The lower surface of the second well region 6 is higher than the lower surface of the epitaxial layer 2. That is, the depth of the first well region 5 is greater than the depth of the deep trench 3, and the depth of the second well region 6 is greater than the depth of the first well region 5. It can be understood that in this embodiment, the first well region 5 and the second well region 6 are not only distributed on both sides of the deep trench 3, but also distributed at the bottom of the deep trench 3. That is, the first well region 5 and the second well region 6 form a cup-shaped structure in space surrounding the outer periphery and bottom of the deep trench 3, respectively. The first well region 5 can be doped with P-type or N-type, and the corresponding second well region 6 can be doped with N-type or P-type, so as to form a PN junction between the first well region 5 and the second well region 6. The upper surface of the PN junction is lower than the upper surface of the epitaxial layer, and the second well region 6 is between the PN junction and the upper surface of the epitaxial layer. In this way, when the PN junction is in avalanche mode, leakage current at the upper surface of the epitaxial layer can be avoided. The lower surface of the PN junction is surrounded by the first well region 5 and the second well region 6 in sequence, so that the filling layer 4 can control the electric field of the entire PN junction region.

[0052] A heavily doped region 7 is provided on top of the second well region 6 located on both sides of the deep trench 3, serving as the second electrode contact of the single-photon avalanche diode unit 30B. Exemplarily, the upper surface of the heavily doped region 7 is flush with the upper surface of the epitaxial layer 2. In this embodiment, the doping concentration of the heavily doped region 7 is greater than that of the second well region 6. The heavily doped region 7 can be P+ type, in which case it can serve as the anode contact of the single-photon avalanche diode unit; or it can be N+ type, in which case it serves as the cathode contact of the single-photon avalanche diode unit.

[0053] In this embodiment, the single-photon avalanche diode unit 30B further includes: a first insulating layer 8 located on the inner surface of the deep trench 3, the first insulating layer 8 serving to isolate the filling layer 4 from the first well region 5; and a second insulating layer 9 located on the upper surface of the epitaxial layer 2, the second insulating layer 9 having a first opening 10 and a second opening 11 respectively on the upper surface of the deep trench 3 and at the heavily doped region 7. Here, the first opening 10 is used to expose a first electrode contact for connecting a first electrode 12, and the second opening 11 is used to expose a second electrode contact for connecting a second electrode 13.

[0054] In this embodiment, the single-photon avalanche diode unit 30B further includes a deep isolation trench structure 14 located around the single-photon avalanche diode unit 30B, the deep isolation trench structure 14 penetrating the epitaxial layer 2 and the substrate 1. The deep isolation trench structure 14 serves to shield between SPADs, preventing signals from one SPAD from entering adjacent SPADs, thereby reducing crosstalk.

[0055] like Figure 7 As shown, the single-photon avalanche diode device 200B includes four single-photon avalanche diode units 30B. In some embodiments, the single-photon avalanche diode device 300 includes multiple single-photon avalanche diode units 30B. The single-photon avalanche diode device 200B further includes a deep isolation trench structure 14 located around each of the single-photon avalanche diode units 30B, the deep isolation trench structure 14 penetrating the epitaxial layer 2 and the substrate 1. It should be understood that in this embodiment, the DTI will be shared by SPADs on either side of its edge along a given edge; that is, the epitaxial layer on one side of the DTI is part of the SPAD on that side, while the epitaxial layer on the other side of the DTI is part of the SPAD on the other side.

[0056] The single-photon avalanche diode device 200B further includes a protective ring 15 located around the single-photon avalanche diode device on top of the epitaxial layer.

[0057] In some embodiments, the SPAD unit described above can be manufactured in both FSI (front illumination) and BSI (back illumination) modes.

[0058] Example 4

[0059] Embodiment 4 of this application provides a method for fabricating a vertical single-photon avalanche diode unit. Figures 8 to 13 This is a schematic diagram of the fabrication process of the vertical single-photon avalanche diode unit 30 provided in Embodiment 4 of this application. The fabrication method includes:

[0060] Step S1, as follows Figure 8 As shown, an epitaxial layer is deposited on a substrate, and deep trenches are formed in the epitaxial layer. A first insulating layer is deposited on the inner surface of each deep trench, and a filling layer is deposited on the surface of the first insulating layer. The substrate 1 can be a P-type substrate or an N-type substrate, and the material of the substrate 1 can be any semiconductor material selected from silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide. The epitaxial layer 2 deposited on the substrate 1 can be a P-type or N-type epitaxial layer with the same doping type as the substrate 1. An etching pattern is formed on the upper surface of the epitaxial layer 2 using a mask. Deep trenches 3 are etched in the epitaxial layer 2 by exposure and development, with an etching depth less than the depth of the epitaxial layer 2. Subsequently, a first insulating layer 8 is formed on the inner surface of the deep trench 3, and a filling layer 4 is formed by filling the surface of the first insulating layer 8 with doped polycrystalline silicon or tungsten. The filling layer 4 serves as the first electrode contact of the single-photon avalanche diode device.

[0061] Step S2, as follows Figure 9 As shown, a second insulating layer 9 is deposited on the upper surface of the epitaxial layer 2. Here, the materials of the first insulating layer 8 and the second insulating layer 9 can be oxides. The first insulating layer 8 is used to isolate the filling layer 4 and the first well region 5. The second insulating layer 9 covers the entire upper surface of the epitaxial layer 2, including the voids on the upper surface of the filling layer 4, and is used to protect the wafer surface during subsequent doping and annealing processes.

[0062] Step S3: A first well region and a second well region are formed sequentially in the epitaxial layer on both sides of the deep trench through first doping and second doping, respectively. The upper surface of the second well region is flush with the upper surface of the epitaxial layer and higher than the upper surface of the first well region; wherein the first well region and the second well region have different doping types to form a PN junction between the first well region and the second well region; Figure 10As shown, a first well region 5 is formed in the epitaxial layer 2 on both sides of the deep trench 3 through a first doping process. A second well region 6 is formed on both sides of the first well region 5 through a second doping process. The doping types of the first well region 5 and the second well region 6 are opposite, and their doping concentrations are both lower than those of the fill layer 4. Next, a substrate annealing process is performed to activate the doping of the first well region 5 and the second well region 6. The annealing temperature is between 850℃ and 1050℃, and the annealing time is determined by process requirements, such as one hour.

[0063] Step S4: Form a heavily doped region on top of the second well region located on both sides of the deep trench; as shown Figure 11 As shown, a heavily doped region 7 is formed on top of the second well region 6 located on both sides of the deep trench 3 through a third doping process. The doping concentration of the heavily doped region 7 is higher than that of the first well region 5, and the doping type can be P+ or N+. The width of the heavily doped region 7 is smaller than that of the second well region 6. The heavily doped region 7 serves as the second electrode contact of the single-photon avalanche diode device. Next, a rapid substrate annealing process is performed to activate the doping of the heavily doped region 7 while reducing the damage to the device structure caused by prolonged annealing at high temperatures. The rapid annealing temperature is between 850℃ and 1050℃, and the specific annealing time is determined by process requirements, such as a few seconds.

[0064] Step S5: In the second insulating layer 9, the deep trench 3 and the heavily doped region 7 are respectively etched to form the first opening 10 and the second opening 11, as shown below. Figure 12 As shown.

[0065] Step S6, as follows Figure 13 As shown, a first electrode 12 is disposed at the first opening 10, and a second electrode 13 is disposed at the second opening 11. Here, the first electrode and the second electrode can be arbitrarily cathodes or anodes, depending on the doping type of the heavily doped region and the filling layer.

[0066] The above steps yield the vertical single-photon avalanche diode unit 30.

[0067] This application provides a method for fabricating a vertical single-photon avalanche diode device 200. Figure 14 This is a schematic diagram of the structure of the single-photon avalanche diode device 200 provided in the embodiments of this application, as shown below. Figure 14 As shown, the single-photon avalanche diode device 200 includes a plurality of single-photon avalanche diode units 30 prepared by the method described above, the method including:

[0068] The periphery of each vertical single-photon avalanche diode unit 30 is etched to form a deep isolation trench structure 14 that penetrates the epitaxial layer 2 and the substrate 1.

[0069] The epitaxial layer surrounding the single-photon avalanche diode device is etched to form a guard ring 15 around the single-photon avalanche diode device 200. The guard ring 15 serves as a ground electrode contact, and a grounding wire is led out from it.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any person skilled in the art can make various changes, modifications, substitutions and variations to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A vertical single-photon avalanche diode device, characterized in that, The single-photon avalanche diode device includes multiple single-photon avalanche diode units, each of which comprises, in a longitudinal section: A substrate and an epitaxial layer disposed on the upper surface of the substrate, wherein a longitudinally extending deep trench is formed in the epitaxial layer; A filling layer is provided in the deep trench, and the filling layer serves as the first electrode contact of the single-photon avalanche diode unit. In the epitaxial layer, a first well region and a second well region are sequentially arranged laterally on both sides of the deep trench; the first well region is disposed between the second well region and the deep trench, and a portion of the second well region extends upward to the space between the upper surface of the first well region and the upper surface of the epitaxial layer, wherein the first well region and the second well region have different doping types; A PN junction is formed between the first well region and the second well region, and the second well region is located between the upper surface of the PN junction and the upper surface of the epitaxial layer. A heavily doped region is provided on top of the second well region located on both sides of the deep trench, serving as the second electrode contact of the single-photon avalanche diode unit.

2. The single-photon avalanche diode device according to claim 1, characterized in that, The single-photon avalanche diode unit also includes: A first insulating layer is located on the inner surface of the deep trench, the first insulating layer being used to isolate the filling layer and the first well region; A second insulating layer is located on the upper surface of the epitaxial layer, and a first opening and a second opening are respectively formed in the second insulating layer at the upper surface of the deep trench and at the heavily doped region.

3. The single-photon avalanche diode device according to claim 2, characterized in that, The filling layer is made of doped polycrystalline silicon or metal.

4. The single-photon avalanche diode device according to claim 3, characterized in that, The substrate is made of any one of the following semiconductor materials: silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide.

5. The single-photon avalanche diode device according to claim 4, characterized in that, The lower surfaces of the first well region and the second well region are flush and not lower than the bottom of the deep trench.

6. The single-photon avalanche diode device according to claim 4, characterized in that, The lower surface of the deep trench is lower than the lower surface of the first well region, and the lower surface of the first well region is lower than the lower surface of the second well region.

7. The single-photon avalanche diode device according to claim 5 or claim 6, characterized in that, The single-photon avalanche diode device also includes: A deep isolation trench structure is located around each of the single-photon avalanche diode units, and the deep isolation trench structure extends through the epitaxial layer and the substrate.

8. The single-photon avalanche diode device according to claim 7, characterized in that, The single-photon avalanche diode device also includes: A protective ring is located on top of the epitaxial layer, surrounding the single-photon avalanche diode device.

9. A method for fabricating a vertical single-photon avalanche diode unit, characterized in that, The method includes: An epitaxial layer is deposited on a substrate, a deep trench is formed in the epitaxial layer, a first insulating layer is deposited on the inner surface of the deep trench, and a filling layer is deposited on the surface of the first insulating layer. A second insulating layer is deposited on the upper surface of the epitaxial layer; In the epitaxial layers on both sides of the deep trench, a second well region is sequentially formed in the epitaxial layer, and a first well region is formed between the second well region and the deep trench; wherein, the second well region is laterally adjacent to the first well region, and the second well region is formed to cover the side of the first well region near the upper surface of the epitaxial layer, such that a portion of the second well region is located between the first well region and the upper surface of the epitaxial layer; wherein the first well region and the second well region have different doping types to form a PN junction between the first well region and the second well region; A heavily doped region is formed on top of the second well region located on both sides of the deep trench; In the second insulating layer, a first opening and a second opening are respectively etched in the deep trench and the heavily doped region; A first electrode and a second electrode are respectively provided at the first opening and the second opening.

10. A method for fabricating a vertical single-photon avalanche diode device, wherein, The single-photon avalanche diode device comprises a plurality of single-photon avalanche diode units obtained by the fabrication method as described in claim 9, characterized in that the method comprises: Etch around each of the vertical single-photon avalanche diode units to form a deep isolation trench structure that penetrates the epitaxial layer and the substrate; The epitaxial layer surrounding the single-photon avalanche diode device is etched to form a protective ring around the single-photon avalanche diode device.

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