Single photon avalanche diode and preparation method, electronic component and detector

Abstract

The present application belongs to the field of avalanche diodes, and specifically discloses a single-photon avalanche diode and a preparation method, an electronic component, and a detector. The present application proposes a P-doped well with a concentration change, and a single-photon avalanche diode with a curved junction structure is prepared in conjunction with the P-doped well. The single-photon avalanche diode can also be used to prepare electronic components and detectors. The single-photon avalanche diode provided by the present application can significantly increase the probability of photogenerated carriers converging to the avalanche region, and ultimately improve the detection efficiency; at the same time, the diffusion movement of carriers in the P-doped well region is utilized to reduce the time for carriers to move to the avalanche region, thereby reducing the time jitter under the same photosensitive area thickness.

Description

Technical Field

[0001] The present invention belongs to the technical field of avalanche diodes, and in particular relates to a single-photon avalanche diode and a preparation method, an electronic component, and a detector. Background Art

[0002] Single Photon Avalanche Diode (SPAD), also known as SPAD, is an avalanche photodiode working in Geiger mode (operating voltage is greater than breakdown voltage). Due to its advantages of high detection efficiency, low power consumption, and fast response speed, it is widely used in spectroscopy, quantum communication, and three-dimensional imaging. The working principle of SPAD is that in Geiger mode, when SPAD absorbs photons, electron-hole pairs are generated in the avalanche region, and avalanche multiplication effect occurs under the action of a strong electric field, forming an avalanche current.

[0003] Silicon manufacturing technology provides a mature processing platform for the integration of SPADs, but the absorption rate of silicon in the near-infrared band is low. In order to optimize the photon detection efficiency (PDE), the existing technology adopts the preparation of a thicker absorption region to increase the absorption rate to improve the PDE. The carriers generated in the absorption region then move toward the peak of the electric field, and then trigger avalanche breakdown. Although this structure improves the PDE to a certain extent, it has problems such as high operating voltage, high bias voltage, and large time jitter. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the prior art and provide a single photon avalanche diode and a preparation method, an electronic component, and a detector, which specifically adopt the following technical solutions:

[0005] On the one hand, the present application provides a single photon avalanche diode, which specifically includes:

[0006] P-type epitaxial layer, N+ layer, N GR layer, P buried layer, P doped well;

[0007] A P-doped well is provided on the light incident side of the P-type epitaxial layer, and the doping concentration in the P-doped well increases in a direction away from the P epitaxial layer;

[0008] An N+ layer is provided on the light-emitting side of the P-type epitaxial layer, a P buried layer is provided between the N+ layer and the P-type epitaxial layer, and an N GR layer surrounds the N+ layer.

[0009] Among them, the N+ layer is the N-type heavily doped layer close to the central area; the N GR layer is the lightly doped layer at the edge of the N area; the Pburied layer is the P-doped buried layer close to the central area. The above abbreviations are common knowledge to those skilled in the art.

[0010] In some preferred implementations, a light trapping structure and a microlens are provided on the light incident side of the P-doped well.

[0011] In some preferred implementations, a cathode electrode, an anode electrode and a metal reflective layer are provided on the light-emitting side of the P-type epitaxial layer; the cathode electrode is connected to the N+ layer through a cathode contact region; the above-mentioned single-photon avalanche diode also includes a P+ well layer, and the anode electrode is connected to the P+ well layer through an anode contact region.

[0012] In some preferred implementations, the P-type epitaxial layer is surrounded by a metal deep trench isolation (FTI) layer on its side.

[0013] In some preferred implementations, the N+ layer, the N GR layer, the P buried layer, and the P+ well layer are all prepared by ion implantation.

[0014] In some preferred implementations, the P-doped well has a doping concentration lower than -1.710×10 14 cm-3; at 7μm-12μm, the doping concentration range is -1.040×10 20 cm -3 to -1.710×10 14 cm -3 between;

[0015] When the doping concentration is expressed as a positive number, it represents N doping, and when the doping concentration is expressed as a negative number, it represents P doping. In this application, the P-doped well belongs to P doping, so the doping concentration is expressed as a negative number.

[0016] On the one hand, the present application also provides a preparation process of the above-mentioned single photon avalanche diode, and the preparation process comprises the following steps:

[0017] Prepare a silicon wafer, on which a first epitaxial wafer is provided; use a metal deep trench isolation layer (FTI) layout to perform photolithography on the first epitaxial wafer, perform P doping, and prepare a metal deep trench isolation layer; then use an N GR layout to perform photolithography, use an ion implantation method to perform n-type doping on the first epitaxial wafer, and prepare a guard ring, namely, an N GR layer; then use an N+ layout to perform photolithography on the first epitaxial wafer, and perform n+ type doping to prepare an N+ layer, the outer surface of the N+ layer is a cathode contact area; then use a P+ layout to perform photolithography, perform p+ and p-type doping, and prepare a P+ well layer, the outer surface of the P+ well layer is an anode contact area; then use a P buried layout to perform photolithography, perform p-type doping, and prepare a P buried layer;

[0018] The various layouts used in the photolithography process are also called mask layouts. Their function is to accurately prepare various pre-designed patterns on the epitaxial wafer during the processing. In the processing process mentioned in this application, since the corresponding structures need to be prepared in multiple steps during the processing, the corresponding layouts need to be used for precision processing during the preparation of each structure. Therefore, multiple corresponding layouts are required here. Figure 1 A process is performed to precisely prepare the corresponding structure, wherein the metal deep trench isolation layer (FTI) layout is the mask layout used to prepare the metal deep trench isolation layer; the N GR layout is the mask layout used to prepare the N GR layer; the N+ layout is the mask layout used to prepare the N+ layer; the P+ layout is the mask layout used to prepare the P+ well layer; and the P buried layout is the mask layout used to prepare the P buried layer.

[0019] A cathode electrode is prepared on the cathode contact area, an anode electrode is prepared on the anode contact area, and then a metal reflective layer is prepared. The first epitaxial wafer is flipped so that the silicon wafer is located on the top layer, the silicon wafer is thinned, and a silicon dioxide layer is deposited. A P-doped well with increasing doping concentration is prepared by ion implantation and laser annealing methods, and then the silicon dioxide layer is removed, and a light trapping structure is prepared by etching, and then a microlens is processed to obtain a single-photon avalanche diode. The single-photon avalanche diode provided in the present application is a single-photon avalanche diode with a curved junction structure.

[0020] In some preferred implementations, the first epitaxial wafer is a P-type epitaxial wafer; the thickness of the silicon wafer after thinning is 10 μm-20 μm; and the thickness of the silicon dioxide layer is 5 nm-10 nm.

[0021] On the one hand, the present application also provides an electronic component including the above-mentioned single photon avalanche diode.

[0022] On the other hand, the present application also provides a detector comprising the above electronic component.

[0023] The beneficial effects of the present application are as follows: the present application provides a single-photon avalanche diode with a curved junction structure including a P-doped well structure with varying concentrations, which can increase the probability of photogenerated carriers converging to the avalanche region. At the same time, the present application can utilize the diffusion movement of carriers in the P-doped well region to reduce the time for carriers to move to the avalanche region, and reduce the time jitter under the same photosensitive area thickness, thereby achieving a high fill factor and small pixel while maintaining a low breakdown voltage, thereby improving detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Shown is a schematic diagram of the structure of a single photon avalanche diode provided by the present application;

[0025] Figure 2 Shown is the electric field intensity distribution diagram of the single photon avalanche diode provided by the present application;

[0026] Figure 3 Shown is a graph showing the variation of doping concentration with depth of the single photon avalanche diode provided by the present application;

[0027] Figure 4 Shown is a doping concentration distribution diagram of the single photon avalanche diode provided by the present application;

[0028] Figure 5 Shown is a comparison diagram of the probability of electrons moving to the avalanche region and the movement time of the single-photon avalanche diode provided by the present application and the comparison diode;

[0029] Figure 6 Shown is a comparison diagram of the detection efficiency of the single photon avalanche diode provided by the present application and the comparative diode in the wavelength range of 800nm-1100nm;

[0030] Figure 7 Shown is a schematic diagram of the stacking of photolithography patterns used in the single-photon avalanche diode preparation method provided in the present application. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0032] It should be noted that all directional indications in this embodiment (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.

[0033] 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" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] 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.

[0035] First, the present application provides a single photon avalanche diode, which includes the following features:

[0036] P-type epitaxial layer, N+ layer, N GR layer, P buried layer, P+ well layer, P doped well;

[0037] A P-doped well is provided on the light incident side of the P-type epitaxial layer, and the doping concentration in the P-doped well increases in a direction away from the P epitaxial layer;

[0038] An N+ layer is provided on the light-emitting side of the P-type epitaxial layer, a P buried layer is provided between the N+ layer and the P-type epitaxial layer, and an N GR layer surrounds the N+ layer. Figure 1 Herein, Metal Reflector is the metal reflective layer mentioned in this application; Anode is the anode electrode mentioned in this application; Cathode is the cathode electrode mentioned in this application; P-epi is the P epitaxial layer mentioned in this application; Retrograde DPW is the P doped well mentioned in this application; Light Traps is the light trapping structure mentioned in this application; Micro Lens is the microlens structure mentioned in this application; FTI is the metal deep trench isolation (FTI) layer mentioned in this application.

[0039] Combination Figure 1 , an N+ layer, an N GR layer, a P buried layer, and a P+ layer are prepared above the P-type epitaxial layer by ion implantation, a cathode electrode is provided above the N+ layer, an anode electrode is provided above the P+ layer, a metal reflective layer is provided above the cathode electrode and the anode electrode, and a circuit for connecting the cathode electrode, the anode electrode and a controller (not shown in the attached figure) is provided on the metal reflective layer; the N GR layer is a guard ring to isolate the P+ layer; a P-doped well with a doping concentration from high to low along the direction from the incident side to the light output side is prepared by multiple doping below the P-type epitaxial layer, and a light trapping structure and a microlens are also provided below the P-type epitaxial layer. The light trapping structure, the microlens structure, and the metal reflective layer are used to increase the light absorption efficiency; a metal deep trench isolation layer is also surrounded on the side of the P-type epitaxial layer, and the metal deep trench isolation layer has an isolation effect between devices to avoid crosstalk between adjacent single-photon avalanche diodes.

[0040] The single-photon avalanche diode provided in the present application has an avalanche region located at the junction of the N+ layer and the P buried layer. At the same time, a non-planar PN junction is prepared between the N+ layer and the P buried layer. This non-planar PN junction structure makes the combination of the N+ layer and the P buried layer closer. The non-planar PN junction greatly increases the contact area, thereby reducing the on-resistance and making it have a more uniform electric field distribution, thereby improving the stability during operation.

[0041] Combination Figure 2 , Figure 2 The figure shows the electric field intensity distribution diagram of the technical solution provided by the present application. The curved junction single-photon avalanche diode provided by the present application has a P-doped well structure with a gradient concentration, so that in the process of the photogenerated carriers in the power plant's line of action converging to the avalanche area through drift motion, the distribution of the electric field distribution associated with the movement process shows a specific effect; in the existing single-photon avalanche diode, after the thickness of the photosensitive area exceeds a certain range, the probability of the carriers generated in the deep area converging to the avalanche area decreases, and the movement time becomes longer. The single-photon avalanche diode provided by the present application is provided with a P-doped well with a concentration gradient from high to low (from the light incident side to the light output side), so that the carriers converge to the avalanche area through diffusion motion. At the same time, by reasonably designing the thickness of the doping layer to avoid affecting the electric field distribution, the carriers in the weaker electric field area mainly diffuse and in the stronger electric field area mainly drift, thereby ultimately increasing the probability of the carriers converging to the avalanche area and thus improving the detection efficiency.

[0042] Combination Figure 3-6 In the present application, a P-doped well with a concentration gradient is prepared on the incident side of light. The doped well is arranged between the P-type epitaxial layer and the incident side of light. The bonding surface between the P-doped well and the P-type epitaxial layer is taken as the zero point. The doping concentration of the P-doped well shows an increasing trend in the direction away from the P-type epitaxial layer. Figure 3 A graph of doping concentration variation with depth in the present application is provided, which shows the variation of the concentration of a P-doped well in a direction away from the P-type epitaxial layer with depth. Figure 4 Provides a doping concentration profile, combined with Figure 3 and Figure 4 It can be seen that when the doping depth of the P-doped well is 1μm-7μm, the doping concentration is lower than -1.710×10 14 cm -3 ; At 7μm-12μm, the doping concentration range is -1.040×10 20 cm -3 to -1.710×10 14 cm -3When the doping concentration is expressed as a positive number, it represents N doping, and when the doping concentration is expressed as a negative number, it represents P doping. In this application, the P-doped well belongs to P doping, and the P doping concentration here is relatively high, so its doping concentration is expressed as a negative number; similarly, in Figure 4 It can be observed that the doping concentration of the part with higher N doping concentration is represented by a positive number.

[0043] The present invention prepares a P-doped well with a specific doping concentration change, so that electrons far away from the central avalanche region can be gathered to the avalanche region through diffusion movement, thereby increasing the probability of electrons moving to the avalanche region at the same thickness. Figure 5 , Figure 5 A comparison chart of the probability of electrons moving to the avalanche region and the movement time under the same test conditions is provided for a single-photon avalanche diode having a P-doped well with a specific concentration change provided by the present application and a single-photon avalanche diode not having a P-doped well with a specific concentration change provided by the present application (i.e., a comparison diode); Figure 5 It can be seen that the single-photon avalanche diode with a P-doped well with a specific concentration variation provided by the present application significantly increases the probability of photogenerated carriers generated in the range of 6μm-12μm moving to the avalanche region, and also significantly reduces the movement time; Figure 6 The detection efficiency of the single-photon avalanche diode with a P-doped well with a specific concentration change provided by the present application and the single-photon avalanche diode without the P-doped well with a specific concentration change provided by the present application (i.e., the comparison diode) in the range of 800nm-1100nm is demonstrated, wherein the red line segment represents the detection efficiency of the single-photon avalanche diode provided by the present application. In the waveband of 800nm-1100nm, the single-photon avalanche diode provided by the present application has a P-doped well with a specific doping concentration change, and therefore has a detection efficiency that is superior to the single-photon avalanche diode prepared without using the technical solution provided by the present application. This indicates that the technical solution provided by the present invention significantly improves the convergence efficiency in the range of 800nm-1100nm, significantly increases the probability of photons moving to the avalanche region, and significantly improves the detection effect; the effect is more significant in the waveband of 800nm-950nm, which is significantly better than the comparison diode.

[0044] Combination Figure 7 The photolithography used in the preparation method of the technical solution provided in this application, and this application also discloses a feasible preparation process of a single-photon avalanche diode:

[0045] Prepare a silicon wafer, on which a first epitaxial wafer is provided; use a metal deep trench isolation layer (FTI) layout to perform photolithography on the first epitaxial wafer, perform p-type doping on the inner side of the groove, and perform metal filling to prepare a metal deep trench isolation layer, then use an N GR layout to perform photolithography, use low-energy ion implantation to perform n-type doping on the first epitaxial wafer, and prepare a guard ring, namely, an N GR layer, then use an N+ layout to perform photolithography on the first epitaxial wafer, and perform n+ type doping, prepare an arc-shaped N-doped area and heavy doping of a metal contact position after annealing, prepare an N+ layer, and the outer surface of the N+ layer is a cathode contact area, then use a P+ layout to perform photolithography, perform p+ and p-type doping, and prepare a P+ well layer, and the outer surface of the P+ well layer is an anode contact area; then use a P buried layout to perform photolithography, perform p-type doping, and prepare a P buried layer;

[0046] A cathode electrode is prepared on the cathode contact area, an anode electrode is prepared on the anode contact area, and then a metal reflective layer is prepared. The first epitaxial wafer is flipped so that the silicon wafer is on the top layer. The silicon wafer is thinned to a thickness of 12um, and a 10nm thick silicon dioxide layer is deposited. Then, a doping concentration gradient is prepared using high-energy ion implantation and laser annealing methods to prepare a P-doped well with increasing doping concentration. The silicon dioxide layer is then removed, and a light trapping structure is etched out. Then, a microlens is processed to obtain a single-photon avalanche diode.

[0047] Figure 7 Shown is a schematic diagram of the stacking of photolithography patterns used in the preparation method of the technical solution provided in this application.

[0048] Although the description of the present invention has been quite detailed and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A single photon avalanche diode, characterized in that: include: P-type epitaxial layer, N+ layer, N GR layer, P buried layer, P doped well; The P-doped well is provided on the light incident side of the P-type epitaxial layer, and the doping concentration in the P-doped well increases along the direction away from the P-type epitaxial layer; Taking the interface between the P-doped well and the P-type epitaxial layer as the zero point, in the direction away from the P-type epitaxial layer, at 7 μm-12 μm, the doping concentration ranges from -1.040×10 20 cm -3 to -1.710×10 14 cm -3 When the doping concentration is expressed as a negative number, it represents P doping; The N+ layer is disposed on the light-emitting side of the P-type epitaxial layer, the Pburied layer is disposed between the N+ layer and the P-type epitaxial layer, and the N+ layer is surrounded by the N GR layer.

2. A single photon avalanche diode according to claim 1, characterized in that: A light trapping structure and a microlens are provided on the light incident side of the P-doped well.

3. A single photon avalanche diode according to claim 1, characterized in that: The light-emitting side of the P-type epitaxial layer is provided with a cathode electrode, an anode electrode and a metal reflective layer; the cathode electrode is connected to the N+ layer through a cathode contact region; the single-photon avalanche diode also includes a P+ well layer, and the anode electrode is connected to the P+ well layer through an anode contact region.

4. A single photon avalanche diode according to claim 1, characterized in that: The side surface of the P-type epitaxial layer is surrounded by a metal deep trench isolation layer.

5. The single photon avalanche diode according to claim 1, characterized in that: The N+ layer, the N GR layer and the P buried layer are all prepared by ion implantation.

6. A method for preparing a single photon avalanche diode as claimed in claim 3, characterized in that: The following steps are involved: Prepare a silicon wafer, on which a first epitaxial wafer is provided; use a metal deep trench isolation layer layout to perform photolithography on the first epitaxial wafer, perform P doping, and prepare the metal deep trench isolation layer; then use an N GR layout to perform photolithography, use an ion implantation method to perform n-type doping on the first epitaxial wafer, and prepare a guard ring, namely the N GR layer; then use an N+ layout to perform photolithography on the first epitaxial wafer, and perform n+ type doping to prepare the N+ layer, the outer surface of the N+ layer is the cathode contact area; then use a P+ layout to perform photolithography, perform p+ and p-type doping, and prepare the P+ well layer, the outer surface of the P+ well layer is the anode contact area; then use a P buried layout to perform photolithography, perform p-type doping, and prepare the P buried layer; The cathode electrode is prepared on the cathode contact area, the anode electrode is prepared on the anode contact area, and then a metal reflective layer is prepared. The first epitaxial wafer is flipped so that the silicon wafer is located on the uppermost layer. The silicon wafer is thinned and a silicon dioxide layer is deposited. The P-doped well with increasing doping concentration is prepared by ion implantation and laser annealing. The silicon dioxide layer is then removed and a light trapping structure is prepared by etching. A microlens is then processed to obtain the single-photon avalanche diode.

7. The method for preparing a single photon avalanche diode according to claim 6, characterized in that: The first epitaxial wafer is a P-type epitaxial wafer; and / or the thickness of the silicon wafer after thinning is 10 μm-20 μm; and / or the thickness of the silicon dioxide layer is 5 nm-10 nm.

8. An electronic component, characterized in that: A single photon avalanche diode comprising any one of claims 1 to 5.

9. A detector, characterized in that: The electronic component comprising the electronic component as claimed in claim 8.

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