High-sensitivity single photon avalanche detector and manufacturing method thereof

Abstract

The invention discloses a high-sensitivity single-photon avalanche detector and a manufacturing method thereof. The method comprises the following steps: S1, preparing a germanium substrate on an insulator; s2, forming a deep N well region and a deep P well region; s3, deep grooves are sequentially formed around the multiplication area from inside to outside; s4, performing ion implantation in the deep P well region to form an avalanche N + type region and an avalanche P + type region; s5, forming an electrode contact P + + region; s6, forming an electrode contact N + + region; and S7, forming a first metal electrode and a second metal electrode. According to the high-sensitivity single-photon avalanche detector and the manufacturing method thereof, the germanium substrate is adopted to prepare the field effect transistor to serve as a photoelectric detector, the working voltage is low, the detection sensitivity is high, and the low working voltage has important significance in simplifying a bias circuit, expanding the application field of the bias circuit, saving energy and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of detectors, and in particular relates to a high-sensitivity single-photon avalanche detector based on a germanium-on-insulator substrate and a manufacturing method thereof. Background Art

[0002] With the development of modern communications towards quantum technology, the rise of the metaverse, and the realization of autonomous driving technology, higher requirements have been placed on photodetectors, especially the need to detect extremely weak signals. Single-photon detectors have the characteristics of fast response speed, large avalanche gain, high photon detection efficiency, and can detect single photons, making them highly concerned devices in the fields of automotive lidar, mobile phone cameras, etc. Single-photon detection is a method for detecting extremely weak light. The photocurrent intensity of the light it detects is lower than the thermal noise level of the photodetector itself at room temperature (10-14W). The usual DC detection method cannot extract this signal buried in the noise. Single-photon detection has a wide range of applications in high-resolution spectral measurement, non-destructive material analysis, high-speed phenomenon detection, precision analysis, atmospheric pollution measurement, bioluminescence, radiation detection, high-energy physics, astronomical photometry, optical time domain reflectometry, quantum key distribution systems, and other fields.

[0003] The devices currently used in single photon detection mainly include: photomultiplier tube (PMT), avalanche photoelectric diode (APD), superconducting single photon detectors (SSPD) and superconducting transition edge sensor (STES).

[0004] Photomultiplier tube (PMT) is an electric vacuum device that uses the external photoelectric effect to detect light signals. Photomultiplier tube has the advantages of high gain, low noise power and low dark current; but it has the disadvantages of large size, high reverse bias, poor magnetic field resistance, and complex use and maintenance, which greatly limits its application.

[0005] Avalanche photodiode (APD) is a photoelectric device based on the internal photoelectric effect. Avalanche photodiode has internal gain and amplification. One photon can generate 10 to 100 pairs of photogenerated electron-hole pairs, which can generate a large gain inside the device. Avalanche diode has the advantages of high detection sensitivity, high response speed, high gain coefficient, insensitivity to ionizing radiation and magnetic field, low dark current, small size and simple structure.

[0006] Superconducting single photon detector (SSPD) is a superconductor single photon detection technology based on niobium nitride (NbN). Its advantages are ultra-fast response and almost negligible dark count rate, but its low quantum efficiency (currently only about 5% to 10%, while PMT quantum efficiency is 30%, Si-APD quantum efficiency is 60% to 80%, STES quantum efficiency is more than 90%), high price, complex use and maintenance, poor anti-interference ability, etc., which greatly restricts its practical application.

[0007] Superconducting transition edge sensor (SETS) is a device that uses superconducting materials as the photosensitive layer for single photon detection. It has a very high quantum efficiency and an extremely low dark count rate. However, due to the long transition time between the superconducting state and the normal state of the current superconducting material, the sensor repetitive operating frequency is only about 20KHz (the operating frequency of PMT can reach 1MHz, the operating frequency of SiAPD can reach 1MHz, and the operating frequency of SSPD can reach 1000MHz). The extremely low operating frequency is the main reason why STES cannot be widely used at present.

[0008] After years of development, single-photon detection technology has been widely used in avalanche diodes due to their high detection sensitivity, high response speed, high gain coefficient, insensitivity to ionizing radiation and magnetic fields, low dark current, small size, simple structure, etc. However, single-photon avalanche detectors are currently based on silicon substrates. Since silicon is an indirect bandgap semiconductor, it requires a larger voltage to cause avalanche, and the photocurrent is relatively small.

[0009] Therefore, further improvements are made to the above problems. Summary of the invention

[0010] The main purpose of the present invention is to provide a high-sensitivity single-photon avalanche detector based on a germanium-on-insulator substrate and a manufacturing method thereof. A field-effect transistor is prepared using a germanium substrate as a photodetector, which has a low operating voltage and high detection sensitivity. The low operating voltage is of great significance for simplifying bias circuits, expanding their application fields, and saving energy. In addition, the single-photon avalanche detector using a germanium-on-insulator substrate with a low operating voltage has good absorption characteristics in the infrared and near-infrared, and can also be compatible with CMOS process devices, which is conducive to integrated manufacturing with post-circuit.

[0011] In order to achieve the above object, the present invention provides a method for manufacturing a high-sensitivity single-photon avalanche detector, which is characterized by comprising the following steps:

[0012] Step S1: growing a layer of aluminum oxide thin film on a silicon-on-insulator substrate and a germanium substrate respectively to form a first base substrate and a second base substrate respectively, and combining the first base substrate and the second base substrate through a bonding process to form a germanium-on-insulator substrate;

[0013] Step S2: performing deep N-well doping in the silicon region of the germanium-on-insulator substrate to form a deep N-well region, and performing deep P-well doping in the deep N-well region to form a deep P-well region;

[0014] Step S3: forming deep trenches (one on each side, serving as the first deep trench and the second deep trench) around the multiplication region from the inside out, and filling them with isolation material as an isolation layer (the method used is photolithography and dry etching, with a depth of 400 microns);

[0015] Step S4: performing ion implantation in the deep P-well region to form an avalanche N+ type region and an avalanche P+ type region, wherein the avalanche N+ type region and the avalanche P+ type region are used to form a multiplication region for absorbing photons;

[0016] Step S5: performing high doping of the cathode contact region in the germanium region of the germanium-on-insulator substrate, thereby forming an electrode contact P++ region;

[0017] Step S6: low-doping the peripheral region to form an N-type peripheral region, and high-doping the low-doped N-type peripheral region to form an electrode contact N++ region (two regions);

[0018] Step S7: Using photolithography and etching methods, a first metal electrode (absorption region) is formed in the electrode contact P++ region, and a second metal electrode is formed in the electrode contact N++ region, thereby completing the fabrication of a high-sensitivity single-photon avalanche detector.

[0019] As a further preferred technical solution of the above technical solution, in step S1, the growth method is atomic layer vapor deposition, and the thickness of the aluminum oxide film is 5-10 nm.

[0020] As a further preferred technical solution of the above technical solution, in step S2, the doping method of the deep N well is ion implantation, and the doping concentration is 10 13 per cubic centimeter; thickness is 400 microns;

[0021] The deep P-well doping method is thermal diffusion or ion implantation, the thickness is 300 microns, and the doping concentration is 10 13 Per cubic centimeter.

[0022] As a further preferred technical solution of the above technical solution, in step S4, the doping concentration of the avalanche N+ type region and the avalanche P+ type region is 1015 -10 17 Atom / cm 3 ;

[0023] In step S5, the doping concentration is 10 19 -10 21 Atom / cm 3 , thickness is 50nm;

[0024] In step S6, the doping concentration of the N-type peripheral region is 10 15 Atom / cm 3 The doping concentration of the electrode contact N++ region is 10 19 -10 21 Atom / cm 3 , thickness is 50nm.

[0025] As a further preferred technical solution of the above technical solution, the energy of the incident photon is higher than the bandgap width E of the semiconductor material germanium. g When the voltage is 0.66eV, the germanium region of the silicon substrate on the insulator acts as an absorption region, absorbing infrared and near-infrared wavelengths, and the avalanche multiplication region occurs in the silicon region. The photogenerated electrons generated in the absorption region are connected to the avalanche region in the silicon through the first metal electrode, wherein the low doping concentration region is the avalanche multiplication region, generating photogenerated electron-hole pairs, and the higher doping region is the avalanche region;

[0026] (Due to its high doping concentration and narrow depletion layer width, it has a larger electric field.) When a photon enters the SPAD photosensitive area, the photon has a certain probability of being absorbed by the depletion region and generating electron-hole pairs. Under the action of the strong electric field in the depletion region, the electron-hole pairs can quickly generate a large number of carriers through the multiplication effect, triggering an avalanche breakdown.

[0027] The voltage across the PN junction is V = V br +V ex , where V br is the avalanche voltage, V ex Over-bias voltage (the avalanche voltage of the detector is generally 18-25V. If the doping concentration is low, the avalanche voltage is higher, V ex Generally, it is 2-3V). Due to the existence of the external voltage, the generated current is collected by the cathode and the anode (according to the external voltage, the first metal electrode and the second metal electrode act as the cathode / anode); the function of the isolation layer is to isolate the peripheral area and the working avalanche area of ​​the device, reduce the leakage current, and improve the sensitivity of the single-photon avalanche detector.

[0028] In order to achieve the above objectives, the present invention also provides a high-sensitivity single-photon avalanche detector, which is applied to a method for manufacturing the high-sensitivity single-photon avalanche detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure in a silicon-on-insulator substrate and a germanium substrate;

[0030] Figure 2 It is a schematic diagram of the structure in a germanium-on-insulator substrate;

[0031] Figure 3 Schematic diagram of N-type and P-type doping in the deep N-well of a single-photon avalanche detector on a germanium-on-insulator substrate;

[0032] Figure 4 Schematic diagram of the isolation layer in a single-photon avalanche detector on a germanium-on-insulator substrate;

[0033] Figure 5 Schematic diagram of the highly doped P-type contact region in the P-well of a single-photon avalanche detector on a germanium-on-insulator substrate;

[0034] Figure 6 Schematic diagram of the absorption region electrode of the single photon avalanche detector electrode region on a germanium-on-insulator substrate;

[0035] Figure 7 Schematic diagram of the N-type contact area of ​​the electrode region of the single-photon avalanche detector on a germanium-on-insulator substrate;

[0036] Figure 8 Schematic diagram of metal electrodes of single photon avalanche detector on germanium substrate on insulator;

[0037] Fig. 9 This is a structural diagram of a single-photon avalanche detector on a germanium-on-insulator substrate.

[0038] The reference numerals include: silicon-on-insulator substrate 10; aluminum oxide film 11; germanium substrate 12; deep N-well region 20; deep P-well region 21; isolation layer 30; avalanche N+ type region 40; avalanche P+ type region 41; electrode contact P++ region; N-type peripheral region 60; electrode contact N++ region 61; first metal electrode 70; second metal electrodes 71, 72; SPAD photosensitive region 80. DETAILED DESCRIPTION

[0039] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0040] In the preferred embodiment of the present invention, those skilled in the art should note that the silicon substrate and the like involved in the present invention may be regarded as prior art.

[0041] Preferred embodiments.

[0042] The present invention discloses a method for manufacturing a high-sensitivity single-photon avalanche detector, comprising the following steps:

[0043] Step S1: Figure 1-2 As shown, a layer of aluminum oxide thin film is grown on a silicon-on-insulator substrate and a germanium substrate respectively to form a first base substrate and a second base substrate respectively, and the first base substrate and the second base substrate are combined by a bonding process to form a germanium-on-insulator substrate;

[0044] Step S2: Figure 3 As shown, deep N-well doping is performed in the silicon region of the germanium-on-insulator substrate to form a deep N-well region, and deep P-well doping is performed in the deep N-well region to form a deep P-well region (as shown in FIG. Figure 3 As shown, and finally, impurity activation annealing is performed on the deep N-well region 20 and the deep P-well region 21, and the annealing method is thermal annealing, microwave annealing or laser annealing);

[0045] Step S3: Figure 4 As shown, deep trenches are formed around the multiplication region and from the inside to the outside (one on each side, serving as the first deep trench and the second deep trench), and then filled with isolation material as an isolation layer (the method used is photolithography and dry etching, with a depth of 400 microns);

[0046] Step S4: Figure 5 As shown, ion implantation is performed in the deep P-well region to form an avalanche N+ type region and an avalanche P+ type region, and the avalanche N+ type region and the avalanche P+ type region are used to form a multiplication region for absorbing photons;

[0047] Step S5: Figure 6 As shown, a cathode contact region is highly doped in a germanium region of a germanium-on-insulator substrate, thereby forming an electrode contact P++ region;

[0048] Step S6: Figure 7 As shown, the peripheral region is low-doped to form an N-type peripheral region, and the low-doped N-type peripheral region is highly doped to form an electrode contact N++ region (two regions);

[0049] Step S7: Figure 8-9 As shown, a first metal electrode (absorption region) is formed in the electrode contact P++ region, and a second metal electrode is formed in the electrode contact N++ region by using photolithography and etching methods, thereby completing the fabrication of a high-sensitivity single-photon avalanche detector.

[0050] Specifically, in step S1, the growth method is atomic layer vapor deposition, and the thickness of the aluminum oxide film is 5-10 nm.

[0051] More specifically, in step S2, the deep N-well doping method is ion implantation, and the doping concentration is 10 13 per cubic centimeter; thickness is 400 microns;

[0052] The deep P-well doping method is thermal diffusion or ion implantation, the thickness is 300 microns, and the doping concentration is 10 13 Per cubic centimeter.

[0053] Furthermore, in step S4, the doping concentration of the avalanche N+ type region and the avalanche P+ type region is 10 15 -10 17 Atom / cm 3 ;

[0054] In step S5, the doping concentration is 10 19 -10 21 Atom / cm 3 , thickness is 50nm;

[0055] In step S6, the doping concentration of the N-type peripheral region is 10 15 Atom / cm 3 The doping concentration of the electrode contact N++ region is 10 19 -10 21 Atom / cm 3 , thickness is 50nm.

[0056] Furthermore, the energy of the incident photon is higher than the bandgap width E of the semiconductor material germanium. g When the voltage is 0.66eV, the germanium region of the silicon substrate on the insulator acts as an absorption region to absorb infrared and near-infrared wavelengths. The avalanche multiplication region (composed of the avalanche N+ region 40 and the avalanche P+ region 41) occurs in the silicon region. The photogenerated electrons generated in the absorption region pass through the first metal electrode and the avalanche region in the silicon (the avalanche region is a depletion region composed of the avalanche N+ region 40 and the avalanche P+ region 41). Fig. 9 The white dotted box mark shows that the region with low doping concentration is the avalanche multiplication region, where photogenerated electron-hole pairs are generated, and the region with higher doping concentration is the avalanche region;

[0057] (Due to its high doping concentration and narrow depletion layer width, it has a larger electric field.) When a photon enters the SPAD photosensitive region 80, the photon has a certain probability of being absorbed by the depletion region (i.e., the avalanche region) and generating electron-hole pairs. Under the action of the strong electric field in the depletion region, the electron-hole pairs can quickly generate a large number of carriers through the multiplication effect, i.e., trigger an avalanche breakdown.

[0058] The voltage applied across the PN junction (the second metal electrodes 71 and 72) is V = V br +V ex , where V br is the avalanche voltage, V ex Over-bias voltage (the avalanche voltage of the detector is generally 18-25V. If the doping concentration is low, the avalanche voltage is higher, V ex Generally, it is 2-3V). Due to the existence of the external voltage, the generated current is collected by the cathode and the anode (according to the external voltage, the first metal electrode and the second metal electrode act as the cathode / anode); the function of the isolation layer is to isolate the peripheral area and the working avalanche area of ​​the device, reduce the leakage current, and improve the sensitivity of the single-photon avalanche detector.

[0059] A first deep trench is formed between the deep N-well region and the deep P-well region, wherein the first deep trench is filled with an isolation material and serves as isolation between the single photon avalanche diode region and the substrate potential extraction region;

[0060] The germanium region is used to form an absorption region of a single photon avalanche diode mechanism;

[0061] An avalanche N+ type region and an avalanche P+ type region are sequentially connected in the deep N well region, and the avalanche N+ type region and the avalanche P+ type region are used to form an avalanche multiplication region; a second deep trench and a deep N well region (actually a ring if three-dimensional) are sequentially formed around the avalanche multiplication region;

[0062] The second deep trench is filled with an isolation material, which serves as isolation between the anode region and the cathode region of the single photon avalanche diode.

[0063] The deep N-well region is used to form a single photon avalanche diode structure;

[0064] An anode lead-out terminal of an avalanche diode is formed in the deep N-well region.

[0065] A cathode lead-out terminal of an avalanche diode is formed in the avalanche P+ type region.

[0066] The germanium substrate has a thickness of 500 microns, a resistivity of 10-15 Ω·cm, and a crystal orientation of (100).

[0067] The surface protection layer of the deep N-well region and the deep P-well region may be, but is not limited to, silicon oxide or silicon nitride.

[0068] The material of the anode lead-out terminal, the cathode lead-out terminal and the substrate lead-out terminal is metal, which may be but is not limited to gold or copper.

[0069] The invention also discloses a high-sensitivity single-photon avalanche detector, which is applied to a manufacturing method of the high-sensitivity single-photon avalanche detector.

[0070] For the present invention:

[0071] The method uses germanium on insulator material as a substrate, forms a high-quality germanium on insulator substrate by oxidation bonding, forms a deep trench DTI in the substrate by photolithography technology, fills the deep trench with isolation material as isolation by chemical vapor deposition, forms a deep N-well region and a deep P-well region in the substrate by photolithography and ion implantation, grows a protective layer on the entire structure of the surface of the deep N-well region and the deep P-well region by thermal oxidation, forms a photon absorption region in the germanium region by photolithography, forms an N-well multiplication region in the silicon region by photolithography and ion implantation, and forms a photon absorption region in the germanium region by photolithography and ion implantation. + Area and P + Area, P + The region contains a cathode lead terminal; an N-well region required for forming an avalanche diode structure, and an anode lead terminal formed in the N-well region;

[0072] Through photolithography and ion implantation, a P-well region is formed in the deep P-well, and a substrate lead-out terminal is formed in the P-well region. The principle of the present invention is that a single-photon avalanche photodiode is a device based on the internal photoelectric effect, which uses the avalanche ionization process to achieve this purpose. Its essence is a PN junction in a reverse biased state. When the energy of the incident photon is higher than the bandgap width E of the semiconductor material, g When it is absorbed, it will generate electron-hole pairs. If the absorption occurs in the depletion region, due to the existence of the PN junction barrier electric field, the photogenerated electrons and holes will move to both ends of the PN junction under the action of the electric field force, forming a photocurrent. For a PN junction, the electric field strength expression is:

[0073]

[0074] If P + The typical value of the N region and the N region (because the two regions actually have different doping concentrations, N is lower than P, so it is called P+N) is 1×10 19 / cm -3 and 1×10 17 / cm -3 If the external bias voltage is 15V, the maximum electric field can be calculated to be about 6.7×10 5 V / cm, carriers are impact ionized and avalanche multiplied under such a high electric field, which will cause the total number of carriers in the barrier region to increase exponentially, thereby doubling the initial photocurrent and achieving a larger gain. For germanium on insulator materials, which are direct bandgap semiconductors, they can absorb infrared and near-infrared wavelengths and generate a larger photocurrent at the same voltage. Photogenerated carriers can obtain enough energy to collide with bound valence electrons.

[0075] It is worth mentioning that the technical features such as the silicon substrate involved in the patent application of this invention should be regarded as the prior art. The specific structure, working principle and possible control method and spatial arrangement method of these technical features can be selected by conventional methods in the field and should not be regarded as the inventive point of this patent. This patent will not be further elaborated.

[0076] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a high-sensitivity single-photon avalanche detector, characterized in that: The following steps are involved: Step S1: growing a layer of aluminum oxide thin film on a silicon-on-insulator substrate and a germanium substrate respectively to form a first base substrate and a second base substrate respectively, and combining the first base substrate and the second base substrate through a bonding process to form a germanium-on-insulator substrate; Step S2: performing deep N-well doping in the silicon region of the germanium-on-insulator substrate to form a deep N-well region, and performing deep P-well doping in the deep N-well region to form a deep P-well region; Step S3: forming deep trenches from the inside to the outside around the multiplication area, and filling them with isolation materials as isolation layers; Step S4: performing ion implantation in the deep P-well region to form an avalanche N+ type region and an avalanche P+ type region, wherein the avalanche N+ type region and the avalanche P+ type region are used to form a multiplication region for absorbing photons; Step S5: performing high doping of the cathode contact region in the germanium region of the germanium-on-insulator substrate, thereby forming an electrode contact P++ region; Step S6: low-doping the peripheral region to form an N-type peripheral region, and high-doping the low-doped N-type peripheral region to form an electrode contact N++ region; Step S7: using photolithography and etching methods, a first metal electrode is formed in the electrode contact P++ region, and a second metal electrode is formed in the electrode contact N++ region, thereby completing the fabrication of a high-sensitivity single-photon avalanche detector.

2. The method for manufacturing a high-sensitivity single-photon avalanche detector according to claim 1, characterized in that: In step S1, the growth method is atomic layer vapor deposition, and the thickness of the aluminum oxide film is 5-10 nm.

3. The method for manufacturing a high-sensitivity single-photon avalanche detector according to claim 2, characterized in that: In step S2, the deep N well is doped by ion implantation, and the doping concentration is 10 13 per cubic centimeter; thickness is 400 microns; The deep P-well doping method is thermal diffusion or ion implantation, the thickness is 300 microns, and the doping concentration is 10 13 Per cubic centimeter.

4. The method for manufacturing a high-sensitivity single-photon avalanche detector according to claim 3, characterized in that: In step S4, the doping concentration of the avalanche N+ type region and the avalanche P+ type region is 10 15 -10 17 Atom / cm 3 ; In step S5, the doping concentration is 10 19 -10 21 Atom / cm 3 , thickness is 50nm; In step S6, the doping concentration of the N-type peripheral region is 10 15 Atom / cm 3 The doping concentration of the electrode contact N++ region is 10 19 -10 21 Atom / cm 3 , thickness is 50nm.

5. The method for manufacturing a high-sensitivity single-photon avalanche detector according to claim 1, characterized in that: The energy of the incident photon is higher than the bandgap width E of the semiconductor material germanium. g When the germanium region of the silicon substrate on the insulator is used as an absorption region, absorbing infrared and near-infrared wavelengths, the avalanche multiplication region occurs in the silicon region, and the photogenerated electrons generated in the absorption region are connected to the avalanche region in the silicon through the first metal electrode, wherein the low doping concentration region is the avalanche multiplication region, generating photogenerated electron-hole pairs, and the higher doping region is the avalanche region; When a photon enters the SPAD photosensitive area, it has a certain probability of being absorbed by the depletion region and generating electron-hole pairs. Under the action of the strong electric field in the depletion region, the electron-hole pairs can quickly generate a large number of carriers through the multiplication effect, triggering an avalanche breakdown. The voltage across the PN junction is V = V br +V ex , where V br is the avalanche voltage, V ex It is over-biased. Due to the existence of external voltage, the generated current is collected by the cathode and anode; the function of the isolation layer is to isolate the peripheral area and the working avalanche area of ​​the device, reduce leakage current, and improve the sensitivity of the single-photon avalanche detector.

6. A high-sensitivity single-photon avalanche detector, characterized in that: A method for manufacturing a high-sensitivity single-photon avalanche detector as described in any one of claims 1 to 5.

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