SiNx-SiO2 avalanche photodetector preparation method and device

Abstract

The invention provides a SiNx-SiO2 avalanche photodetector preparation method and device, and relates to the technical field of semiconductor device processing, and the method comprises the steps: providing a first doping type substrate with a specific doping concentration, and the substrate comprises an epitaxial layer; performing doping of a second doping type on the epitaxial layer to form a first region; ion implantation of a first doping type is carried out above the first region to form a second region, and the first region and the second region form an avalanche junction region; etching the first region to form a shallow trench isolation region; generating a first dielectric layer on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector; and generating a second dielectric layer above the first dielectric layer. According to the method, the new shallow trench isolation structure is formed, so that dark noise is reduced, and the surface passivation effect is improved. SiNx-SiO2 is arranged on the surface of the non-shallow trench isolation region, so that light reflection is reduced, and the photoelectric detection efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor device technology, and in particular to a method for preparing a SiNx-SiO2 avalanche photodetector and a device. Background Art

[0002] In the field of integrated circuit manufacturing, with the continuous development and maturity of Si material technology, various advanced processes and technologies are widely used in production practice to improve the performance and reliability of integrated circuits. Among them, shallow trench isolation (STI), as an important isolation technology, has been widely used in integrated circuits with process feature sizes of 0.18μm and below.

[0003] The STI isolation structure is a special trench structure that achieves electrical isolation between adjacent components by etching recessed trenches on the chip surface and then filling these trenches with dielectric materials (usually SiO2). This isolation structure not only has a good isolation effect, but also can significantly reduce the size of integrated circuits and improve the integration and performance of chips.

[0004] In the manufacturing process of STI isolation structure, High-Density Plasma Chemical Vapor Deposition (HDP CVD) technology plays a vital role. HDP CVD technology uses active ions and free radicals generated by high-density plasma to achieve fast and high-quality deposition of SiO2 at a lower temperature. This deposition method can not only ensure that SiO2 is filled into the trench structure to form a dense dielectric layer, but also reduce the formation of interface defects and improve the quality of the SiO2-Si interface.

[0005] However, although STI isolation structure and HDP CVD technology have achieved remarkable results in integrated circuit manufacturing, they still face some challenges. Among them, the SiO2-Si interface defect problem is one of the key factors affecting the performance of integrated circuits. Due to the large difference in physical and chemical properties between SiO2 and Si, defects are easily formed at the interface during the etching process. These defects will increase the dark noise of the photodetector and reduce the signal-to-noise ratio and reliability of the integrated circuit.

[0006] In addition, a single layer of SiO2 as a dielectric layer also has certain limitations. Due to the large difference between the refractive index of SiO2 and the refractive index of air or semiconductor materials, light is easily reflected and scattered at the SiO2-air or SiO2-semiconductor interface, resulting in light loss and image blur. Therefore, a single layer of SiO2 cannot achieve the effect of reducing reflection and scattering of light, limiting the application of integrated circuits in fields such as photoelectric detection, image processing and communications.

[0007] Therefore, although STI isolation technology and HDP CVD technology have achieved remarkable results in integrated circuit manufacturing, the SiO2-Si interface defect problem and the limitations of the single-layer SiO2 dielectric layer are still technical problems that need to be solved. Summary of the invention

[0008] The present application provides a method for preparing a SiNx-SiO2 avalanche photodetector and a device, which solves the technical problems in the prior art that SiO2 as an STI dielectric layer is prone to form defects at the interface and the SiO2 dielectric layer cannot reduce the reflection and scattering of light.

[0009] In order to achieve the above-mentioned objectives, in a first aspect, an embodiment of the present application provides a method for preparing a SiNx-SiO2 avalanche photodetector, comprising: providing a first doping type substrate with a specific doping concentration, the substrate comprising an epitaxial layer; doping the epitaxial layer with a second doping type to form a first region; performing ion implantation of the first doping type above the first region to form a second region, the first region and the second region forming an avalanche junction region; etching the first region to form a shallow trench isolation region; generating a first dielectric layer on the surface of the shallow trench isolation region and on the surface of the SiNx-SiO2 avalanche photodetector; and generating a second dielectric layer above the first dielectric layer.

[0010] Optionally, the first dielectric layer is generated by a dry oxygen oxidation method, and the first dielectric layer is a silicon dioxide layer.

[0011] Optionally, the second dielectric layer is generated by a vapor deposition method, and the second dielectric layer is a silicon nitride layer.

[0012] Optionally, the shallow trench isolation interface formed by the first dielectric layer and the second dielectric layer and the surface of the SiNx-SiO2 avalanche photodetector can passivate the shallow trench isolation interface and reduce the reflection of light by the SiNx-SiO2 avalanche photodetector.

[0013] Optionally, a second type of doping is performed on the first region to form an anode of a SiNx-SiO2 avalanche photodetector.

[0014] Optionally, the anode of the SiNx-SiO2 avalanche photodetector is connected to an external circuit via a metal interconnect hole.

[0015] In a second aspect, an embodiment of the present application provides a SiNx-SiO2 avalanche photodetector device, wherein the SiNx-SiO2 avalanche photodetector device is prepared using a SiNx-SiO2 avalanche photodetector preparation method as described in any one of the first aspects, and the SiNx-SiO2 avalanche photodetector device comprises: a first doping type substrate, a first doping type epitaxial layer disposed on the first doping type substrate, a second doping type first region disposed on the epitaxial layer, a first doping type second region disposed above the first region, a shallow trench isolation region disposed in the first region, a first dielectric layer disposed on the surface of the shallow trench isolation region and on the surface of the SiNx-SiO2 avalanche photodetector, and a second dielectric layer disposed on the first dielectric layer.

[0016] Optionally, the first dielectric layer is a silicon dioxide layer.

[0017] Optionally, the second dielectric layer is a silicon nitride layer.

[0018] Optionally, the SiNx-SiO2 avalanche photodetector device further includes an anode of the SiNx-SiO2 avalanche photodetector device disposed in the first region, and the anode of the SiNx-SiO2 avalanche photodetector device is connected to an external circuit via a metal interconnect hole.

[0019] The embodiment of the present application provides a new method for preparing a SiNx-SiO2 avalanche photodetector, which can more effectively passivate STI interface defects through the combined use of SiNx and SiO2 films. The fixed positive charge and free hydrogen atoms of the SiNx film can diffuse to the Si-SiNx interface, combine with the silicon dangling bonds at the interface, and reduce the surface interface state density. The SiO2 film provides good interface performance and passivation effect, further reducing interface defects. The SiNx film has a good anti-reflection function, and its refractive index can be adjusted within a certain range to match the refractive index of the optoelectronic device, thereby reducing the reflectivity. Although the SiO2 film itself does not have an anti-reflection function, when used in combination with the SiNx film, a laminated structure can be formed to further improve the anti-reflection effect. By passivating STI interface defects and reducing light reflection, the STI and surface dielectric layer filled by the SiNx-SiO2 process can significantly improve the detection efficiency of optoelectronic devices. Passivating interface defects reduces the recombination of carriers at the interface, allowing more photogenerated carriers to be collected and converted into electrical signals. Reducing light reflection increases the absorption and utilization of light by photoelectric devices, further improving detection efficiency.

[0020] The SiNx-SiO2 process can reduce the generation of dark noise by passivating interface defects and reducing surface recombination centers. This allows optoelectronic devices to maintain a high signal-to-noise ratio and detection efficiency even under extremely low light conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a process for preparing a SiNx-SiO2 avalanche photodetector provided in an embodiment of the present application;

[0022] Figure 2A-2H All of them are cross-sectional schematic diagrams of a SiNx-SiO2 avalanche photodetector device in a process of preparing a SiNx-SiO2 avalanche photodetector device provided in an embodiment of the present application;

[0023] Figure 3 A cross-sectional schematic diagram of a SiNx-SiO2 avalanche photodetector device provided in an embodiment of the present application;

[0024] Figure 4 A schematic diagram of a passive quenching and passive reset circuit principle of a SiNx avalanche photodetector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, the working principle of the well-known SPAD is omitted to avoid unnecessary details that hinder the description of the present application.

[0026] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "said", "above", and "the" are intended to also include expressions such as "one or more", unless the context clearly indicates otherwise.

[0027] In semiconductor manufacturing processes, SiO2-filled shallow trench isolation technology is widely used for regional isolation between devices. However, the STI structure in the prior art is prone to form interface defects at the interface between silicon and silicon dioxide, which may increase the dark noise of the photodetector, thereby affecting its performance.

[0028] Specifically, shallow trench isolation technology is a method of isolating devices by forming steep trenches between adjacent devices and filling the trenches with oxide (such as SiO2). The STI structure is usually formed by first depositing a silicon nitride layer on a semiconductor substrate, then patterning the silicon nitride layer to form a hard mask, then etching the substrate to form trenches, and finally filling the trenches with oxide.

[0029] In the STI structure, the quality of the silicon and silicon dioxide interface is critical to the performance of the device. However, due to various factors in the manufacturing process, such as plasma damage, damage during etching, and stress when filling oxide, interface defects may be formed. These defects may include vacancies, dangling bonds, impurity atoms, etc., which will form traps at the silicon and silicon dioxide interface, capture charges and generate noise.

[0030] A photodetector is a device that converts light signals into electrical signals. Its performance is affected by many factors, among which dark noise is an important indicator. Dark noise refers to the noise signal output by the detector in the absence of light. Interface defects increase the dark noise of the photodetector because the charges in the traps are randomly released in the absence of light, generating additional current noise. This noise reduces the signal-to-noise ratio of the detector and affects its ability to detect weak light signals.

[0031] That is to say, the SiO2-filled shallow trench isolation technology is of great significance in the semiconductor manufacturing process as a method of regional isolation between devices. However, the formation of interface defects will increase the dark noise of the photodetector and affect its performance. Therefore, it is necessary to take effective methods to reduce the formation of interface defects and improve the quality of STI structure and the performance of photodetectors.

[0032] Therefore, the embodiment of the present application proposes a new method for preparing a SiNx-SiO2 avalanche photodetector, which significantly improves the performance of the photodetector by forming a new shallow trench isolation structure, specifically a SiNx-SiO2 combined structure. This structure not only optimizes the isolation effect between devices, but also shows significant advantages in reducing dark noise, improving surface passivation effect and enhancing optical properties through its unique properties.

[0033] Specifically, the present application uses SiNx (silicon nitride) film as part of the shallow trench isolation structure. Due to its positively charged property, the SiNx film can effectively attract and fix the negative charge at the interface, thereby significantly reducing the number of charge traps at the interface between silicon and silicon dioxide. These charge traps are one of the main reasons for the increase in dark noise of photodetectors. By reducing charge traps, the embodiments of the present application can significantly reduce dark noise, improve the signal-to-noise ratio of the detector, and make it show higher sensitivity in weak light signal detection.

[0034] SiNx film not only has the function of reducing dark noise, but also attracts much attention for its excellent surface passivation effect. It can effectively reduce the dangling bonds and defects on the silicon surface, thereby reducing the surface recombination rate and improving the surface passivation effect of the detector. This improvement helps to reduce the additional noise generated by surface recombination and further improve the performance stability of the detector.

[0035] On the surface of the photodetector, the embodiment of the present application also adopts a SiNx-SiO2 stacked passivation and anti-reflection structure. This structure not only inherits the advantages of the SiNx film in surface passivation, but also achieves optimized regulation of the incident light through the introduction of the SiO2 layer. The SiO2 layer has a suitable refractive index and can form an effective anti-reflection film system with the SiNx layer, reducing the reflection loss of light on the detector surface and improving the transmittance of light. This improvement allows more incident light to enter the interior of the detector and be absorbed by the photoelectric conversion material, thereby improving the photoelectric absorption conversion efficiency.

[0036] Among them, the preparation method of SiNx-SiO2 avalanche photodetector may include: providing a first doping type substrate with a specific doping concentration, the substrate including an epitaxial layer; doping the epitaxial layer with a second doping type to form a first region; performing ion implantation of the first doping type above the first region to form a second region, the first region and the second region forming an avalanche junction region; etching the first region to form a shallow trench isolation region; generating a first dielectric layer on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector; generating a second dielectric layer above the first dielectric layer.

[0037] The following first introduces the method for preparing the SiNx-SiO2 avalanche photodetector provided in the embodiment of the present application, see Figure 1 , Figure 1 A schematic diagram of a method for preparing a SiNx-SiO2 avalanche photodetector provided in an embodiment of the present application. Figure 1 As shown, the method comprises the following steps:

[0038] S101, providing a first doping type substrate with a specific doping concentration, wherein the substrate includes an epitaxial layer.

[0039] Specifically, see Figure 2AIn the semiconductor manufacturing process, a substrate 201 with a first doping type is first provided. This substrate serves as the basis of the entire device, and its doping type is determined according to requirements, for example, it can be P-type or N-type, depending on the functional requirements of the subsequent device. On this basis, the substrate further includes an epitaxial layer 202, which is formed on the surface of the substrate by epitaxial growth technology, and its structure, composition and thickness are precisely controlled to meet specific performance requirements.

[0040] S102 , doping the epitaxial layer with a second doping type to form a first region.

[0041] Specifically, see Figure 2B The epitaxial layer 202 is subjected to a precisely controlled ion implantation process. In this process, a dopant different from the first doping type of the substrate (for example, if the substrate is P-type, an N-type dopant is used) is used, and the dopant is implanted into a certain depth of the epitaxial layer by setting ion beam parameters (such as energy, dose, and angle), thereby forming a first region 203 with a specific doping concentration in the epitaxial layer. In the embodiment of the present application, N-type ion arsenic doping is used to form an N-type region for avalanche.

[0042] S103 , performing ion implantation of a first doping type on the first region to form a second region, wherein the first region and the second region form an avalanche junction region.

[0043] Specifically, see Figure 2C In the process of preparing the SiNx-SiO2 avalanche photodetector, an ion implantation technique is applied to the epitaxial layer 202. This technique aims to form a region with specific doping characteristics in the epitaxial layer by precisely controlling the implantation process of the dopant, so as to construct an avalanche multiplication region.

[0044] Specifically, a dopant that is consistent with the first doping type of the substrate is used. For example, if the substrate is P-type doped, a corresponding P-type dopant is selected for implantation. During the ion implantation process, the depth and concentration of the dopant implantation are controlled by setting the parameters of the ion beam. These parameters include the energy, dose, and angle of incidence of the ion beam. The energy determines the depth to which the dopant ions can penetrate the epitaxial layer, and the dose affects the amount of dopant implanted, thereby determining the doping concentration of the second region 204 that is ultimately formed. Adjustment of the angle of incidence helps to optimize the distribution of the dopant ions in the epitaxial layer, ensuring that they can be implanted evenly and accurately to a predetermined depth.

[0045] Through this ion implantation process, a second region 204 with a specific doping concentration is formed in the epitaxial layer 202. This region and the original first region 203 in the epitaxial layer together constitute the avalanche region of the SiNx-SiO2 avalanche photodetector. In the avalanche region, a strong electric field gradient is formed between the second region 204 and the first region 203, and this electric field gradient is the key to the occurrence of the avalanche multiplication effect. When photogenerated carriers enter the avalanche region, they will obtain sufficient energy under the action of the strong electric field, thereby initiating a collision ionization process, generating additional electron-hole pairs, and realizing the photocurrent multiplication effect.

[0046] It should be noted that a second type of doping is also required in the first region 203 to form the anode of the SiNx-SiO2 avalanche photodetector. Figure 2D As shown in FIG. 2 , the doping concentration of the region 205 forming the anode is greater than the doping concentration of the second region. In the process of manufacturing the SiNx-SiO2 avalanche photodetector, in addition to the previously mentioned precise control of the ion implantation process of the epitaxial layer 202 to form the second region 204, we also need to perform a second type of doping in the first region 203 to form the anode 205 of the detector.

[0047] S104, etching the first region to form a shallow trench isolation region.

[0048] Specifically, see Figure 2E . In the semiconductor manufacturing process, the first area is etched to form a shallow trench isolation area 206 to achieve effective isolation between devices. Specifically, it includes: using photolithography technology to accurately mark the area to be etched on the silicon wafer. This usually involves coating a layer of photoresist on the silicon wafer, and then transferring the design pattern to the photoresist through a photolithography machine. After the photoresist pattern is formed, it serves as a mask to protect the area that does not need to be etched. Depending on the process requirements, the mask material may be photoresist, SiO2, silicon nitride (SiN) or other highly stable materials. Before etching, the silicon wafer must be thoroughly cleaned to remove surface contaminants and residues. This usually involves cleaning with chemical reagents and deionized water, and then drying the silicon wafer. Shallow trench isolation etching usually uses dry etching technology, such as reactive ion etching (RIE) or inductively coupled plasma etching (ICP). These technologies can provide high etching rates and good directional control. According to the required trench depth and width, adjust etching parameters such as RF bias, gas flow, chamber pressure and etching time. These parameters together determine the etching rate and etching morphology. Under the set parameters, the etching equipment is started to allow the plasma or active free radicals to chemically react and physically bombard the silicon wafer surface, thereby removing the material not protected by the mask. After the etching is completed, the photoresist or other mask material needs to be removed. This usually involves dissolving or stripping with chemical reagents.

[0049] The silicon wafer is cleaned again to remove any residues from the etching process. The trench shape, depth, and width are then checked using a microscope or other inspection equipment to ensure they meet design requirements.

[0050] S105, generating a first dielectric layer on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector.

[0051] Specifically, see Figure 2F .like Figure 2F As shown, a first dielectric layer 207 is generated on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector. In the semiconductor manufacturing process, in order to ensure the stable performance of the SiNx-SiO2 avalanche photodetector and achieve effective device isolation, it is necessary to generate a dielectric layer on the surface of the shallow trench isolation region and the surface of the entire detector. In the embodiment of the present application, a dry oxygen oxidation method is selected to generate this dielectric layer, i.e., the first dielectric layer, and the layer is a silicon dioxide (SiO2) layer.

[0052] Before dry oxygen oxidation, the surface of the shallow trench isolation area and the SiNx-SiO2 avalanche photodetector must be pre-treated. This includes using chemical reagents to clean the silicon wafer surface to remove pollutants such as organic matter and metal ions, and then performing a dehydration process to ensure that the silicon wafer surface is dry and free of water.

[0053] The pretreated silicon wafer is placed in a high-temperature oxidation furnace and high-purity dry oxygen (usually oxygen purity is greater than 99.99%) is introduced. At high temperature (generally 800-1200°C), silicon atoms on the surface of the silicon wafer react chemically with oxygen molecules to form a silicon dioxide layer. The rate of dry oxygen oxidation is relatively slow, but the generated silicon dioxide layer is of high quality, good density, and has good electrical properties and chemical stability. In the dry oxygen oxidation process, parameters such as oxidation temperature, oxygen flow rate, and oxidation time need to be precisely controlled. These parameters directly affect the thickness, growth rate, and quality of the silicon dioxide layer. The higher the oxidation temperature, the faster the oxidation rate, but too high a temperature may increase the roughness of the silicon wafer surface, affecting subsequent processes. Therefore, it is necessary to reasonably control the oxidation temperature while ensuring the oxidation rate. The oxygen flow rate also needs to be controlled within a certain range to ensure that oxygen can fully contact and react with the surface of the silicon wafer. After the oxidation is completed, the silicon dioxide layer needs to be cleaned and inspected. The cleaning step is intended to remove impurities and residues that may be generated during the oxidation process to ensure the cleanliness of the surface of the silicon dioxide layer. The inspection step includes using microscopes, electron beam testing and other equipment to evaluate the thickness, uniformity and quality of the silicon dioxide layer to ensure it meets the design requirements.

[0054] As an insulating layer, the silicon dioxide layer can effectively isolate the different parts of the SiNx-SiO2 avalanche photodetector to prevent current leakage and mutual interference. The silicon dioxide layer can protect the detector surface from mechanical damage, chemical corrosion and environmental pollution, improving the reliability and service life of the device.

[0055] S106 , generating a second dielectric layer above the first dielectric layer.

[0056] Specifically, see Figure 2G .like Figure 2G As shown, in the embodiment of the present application, the second dielectric layer 208 is grown by a plasma enhanced chemical vapor deposition (PECVD) method, wherein the second dielectric layer is a silicon nitride layer (SiNx).

[0057] In the embodiment of the present application, in order to further enhance the performance of the SiNx-SiO2 avalanche photodetector, especially its anti-reflection, corrosion resistance and passivation capabilities, it is necessary to prepare and grow a second dielectric layer on the first dielectric layer.

[0058] Before PECVD deposition, the existing structure surface must be pretreated. This includes using chemical reagents or physical methods to clean the surface to remove pollutants such as organic matter, metal ions, and particulate matter to ensure that the surface is clean, flat, and has good adhesion.

[0059] Pretreatment may also include dehydration to remove residual moisture on the surface to prevent bubbles from forming during the PECVD process or affect film quality.

[0060] The pretreated sample is placed in a PECVD reaction chamber, and the temperature and pressure of the reaction chamber are adjusted to conditions suitable for the growth of SiNx films.

[0061] In the SiNx film, a large number of fixed positive charges are formed. These fixed positive charges form a built-in electric field at the surface of the device, which makes the device surface in an inversion state (that is, the charge type at the surface is opposite to the charge type inside the substrate). The inversion state reduces the probability of carriers (electrons and holes) meeting and recombination on the device surface, thereby reducing the surface recombination rate. During the PECVD process, a large number of free hydrogen atoms are also generated. These free hydrogen atoms can diffuse to the Si-SiNx interface and combine with the silicon dangling bonds at the interface. Silicon dangling bonds are unsaturated silicon atoms on the surface, which easily become recombination centers and increase the surface recombination rate. By combining with hydrogen atoms, the silicon dangling bonds are passivated, and the interface state density on the surface is reduced, thereby further reducing the surface recombination rate.

[0062] The refractive index of SiNx film can be controlled by adjusting the flow ratio of the reaction gases silane and ammonia.

[0063] The refractive index range is usually between 1.8 and 3.3, which makes SiNx film an excellent anti-reflection film material. In actual production, by precisely controlling the gas flow rate and deposition time, a SiNx film with matching film thickness and refractive index can be formed. This matching can minimize the reflection of light on the device surface and increase the absorption and utilization of light inside the device. It should be noted that SiNx film has a good passivation effect on N-type silicon surfaces. For P-type silicon surfaces, the passivation effect of SiNx film may not be as significant as that of N-type silicon surfaces. This is because the charge type of the p-type silicon surface is opposite to the fixed positive charge in the SiNx film, which may offset the effect of the built-in electric field to a certain extent.

[0064] Select appropriate reaction gases, usually a mixture of silane (SiH4), ammonia (NH3) and nitrogen (N2), as well as argon (Ar) or hydrogen (H2) as diluent gases. The flow ratio of these gases needs to be precisely controlled according to the specific PECVD equipment and process requirements.

[0065] Radio frequency (RF) or microwave power is applied to excite the reactant gas, forming a plasma. The high-energy electrons in the plasma collide with the reactant gas molecules, causing them to decompose and produce the active species required for the reaction.

[0066] Under the action of plasma, silane molecules decompose to produce silicon atoms or silicon active species, while ammonia molecules decompose to produce nitrogen atoms or nitrogen active species. These active species react chemically on the sample surface to form a silicon nitride film.

[0067] By controlling parameters such as the flow rate, pressure, temperature and power of the reaction gas, the growth rate, thickness, composition and microstructure of the SiNx film can be precisely controlled.

[0068] During the deposition process, it may be necessary to introduce gases such as oxygen (O2) or water vapor to adjust the refractive index, stress and other properties of the film. After deposition, the SiNx film needs to be annealed to eliminate the stress generated during the deposition process and improve the crystallinity and performance of the film. The cleaning step is to remove impurities and residues that may be generated during the deposition process to ensure the cleanliness of the SiNx film surface. The inspection step includes the use of microscopes, electron beam testing, ellipsometers and other equipment to evaluate the thickness, uniformity, refractive index, stress and other properties of the SiNx film to ensure that it meets the design requirements.

[0069] In the process of preparing the SiNx-SiO2 avalanche photodetector, it is also necessary to connect the anode of the SiNx-SiO2 avalanche photodetector to the external circuit through the metal interconnection hole. Figure 2H. During the preparation of the SiNx-SiO2 avalanche photodetector, metal interconnect holes 209 are formed on the first dielectric layer and the second dielectric layer by photolithography and etching processes. The metal interconnect holes 209 are used to connect the electrode contact area of ​​the device area and the external electrode leads. For example, aluminum metal interconnect holes can be used. The formation of metal interconnect holes requires precise control of the position, size and shape of the holes to ensure good electrical connection and mechanical stability. Conductive metals (such as copper, tungsten or aluminum, etc.) can be filled in the metal interconnect holes to form metal electrodes. These metal electrodes are connected to the anode contact area of ​​the device area and are connected to the external circuit through the metal interconnect holes. At the junction of the metal electrode and the external circuit, a layer of metal leads (such as aluminum leads) is usually grown to facilitate reliable connection with the external circuit.

[0070] By optimizing the structure and size of metal interconnect holes and selecting appropriate metal filling materials, the electrical performance of avalanche photodetectors can be improved, such as reducing resistance and increasing current amplification.

[0071] In addition, the interface between the metal and the insulating layer needs to be considered to ensure good electrical contact and stability.

[0072] The following is a detailed introduction to the SiNx-SiO2 avalanche photodetector device provided in the embodiment of the present application. Figure 3 , Figure 3 A cross-sectional schematic diagram of a SiNx-SiO2 avalanche photodetector device provided in an embodiment of the present application. Figure 3As shown, the SiNx-SiO2 avalanche photodetector device may include: a substrate 201 of a first doping type (such as P-type), which is covered with a first epitaxial layer 202 of the same type (P-type), and the epitaxial layer is formed on the surface of the substrate by epitaxial growth technology. A first region of a second doping type is arranged on the epitaxial layer, wherein the first region is formed by a precisely controlled ion implantation process on the epitaxial layer 202. In this process, a dopant different from the first doping type of the substrate (for example, if the substrate is P-type, an N-type dopant is used), and the dopant is implanted into a certain depth of the epitaxial layer by setting ion beam parameters (such as energy, dose and angle), thereby forming a first region 203 with a specific doping concentration in the epitaxial layer. A second region 204 of the first doping type is arranged above the first region, wherein a dopant consistent with the first doping type of the substrate is used, for example, if the substrate is P-type doped, a corresponding P-type dopant is selected for implantation, and a second region 204 with a specific doping concentration is formed in the epitaxial layer 202. This region and the original first region 203 in the epitaxial layer together constitute the avalanche region of the SiNx-SiO2 avalanche photodetector. It should be noted that a second type of doping is also required in the first region 203 to form the anode 205 of the SiNx-SiO2 avalanche photodetector. A shallow trench isolation region is set in the first region, and the first region is etched to form a shallow trench isolation region 206 to achieve effective isolation between devices. A first dielectric layer is set on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector, and a second dielectric layer is set on the first dielectric layer. The dielectric layer, i.e., the first dielectric layer, is generated by a dry oxygen oxidation method, and the layer is a silicon dioxide (SiO2) layer. A second dielectric layer is prepared on the first dielectric layer. In the present application, plasma enhanced chemical vapor deposition technology is selected to prepare the second dielectric layer, and the layer is a silicon nitride film. The SiNx-SiO2 avalanche photodetector device also includes a metal interconnect hole 209. During the preparation of the SiNx-SiO2 avalanche photodetector, a metal interconnection hole 209 is formed on the first dielectric layer and the second dielectric layer by photolithography and etching processes. The metal interconnection hole 209 is used to connect the electrode contact area of ​​the device area and the external electrode lead.

[0073] Figure 4 A schematic diagram of a passive quenching and passive reset circuit principle diagram of a SiNx avalanche photodetector provided in an embodiment of the present application. Of course, the SiNx avalanche photodetector can also use active quenching, which is not specifically limited in the embodiment of the present application. Figure 4 The SiNx avalanche photodetector shown works under a reverse bias voltage. When receiving a light signal of sufficient intensity, an avalanche multiplication effect occurs, generating a large amount of electrical signals.

[0074] The reverse bias voltage (VH and GND) is the voltage provided to the SiNx avalanche photodetector to make it operate in the avalanche multiplication region.

[0075] During the avalanche multiplication process, when the current generated by the SiNx avalanche photodetector reaches a certain threshold, the quenching resistor (R q ) will start to consume current, thereby reducing the gain of the SiNx avalanche photodetector, achieving a quenching effect. This process is "passive" because it does not rely on external control signals.

[0076] After quenching, the reset capacitor provides a short discharge path to restore the output signal of the SiNx avalanche photodetector to its initial state, preparing for the next trigger. This process is also "passive" because it also does not rely on external control signals.

[0077] In summary, the present application embodiment proposes a method for preparing a SiNx-SiO2 avalanche photodetector device, which significantly improves the performance of the photodetector by forming a new shallow trench isolation structure, specifically a SiNx-SiO2 combined structure. This structure not only optimizes the isolation effect between devices, but also shows significant advantages in reducing dark noise, improving surface passivation effect, and enhancing optical properties through its unique properties.

[0078] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0079] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0080] In the embodiments provided in the present application, it should be understood that the disclosed devices / equipment and methods can be implemented in other ways. For example, the device / equipment embodiments described above are merely schematic, for example, the division of the modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0081] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0082] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0083] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0084] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0085] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a SiNx-SiO2 avalanche photodetector, characterized in that: include: Providing a first doping type substrate with a specific doping concentration, the substrate comprising an epitaxial layer; Doping the epitaxial layer with a second doping type to form a first region; Performing ion implantation of a first doping type on the first region to form a second region, wherein the first region and the second region form an avalanche junction region; Etching the first region to form a shallow trench isolation region; Generating a first dielectric layer on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector; A second dielectric layer is generated over the first dielectric layer.

2. The method for preparing a SiNx-SiO2 avalanche photodetector according to claim 1, characterized in that: The first dielectric layer is generated by dry oxygen oxidation, and the first dielectric layer is a silicon dioxide layer.

3. The method for preparing a SiNx-SiO2 avalanche photodetector according to claim 1, characterized in that: The second dielectric layer is formed by a vapor deposition method, and the second dielectric layer is a silicon nitride layer.

4. The method for preparing a SiNx-SiO2 avalanche photodetector according to claim 1, characterized in that: The shallow trench isolation interface formed by the first dielectric layer and the second dielectric layer and the surface of the SiNx-SiO2 avalanche photodetector can passivate the shallow trench isolation interface and reduce the reflection of light by the SiNx-SiO2 avalanche photodetector.

5. The method for preparing a SiNx-SiO2 avalanche photodetector according to claim 1, characterized in that: The first region is subjected to a second type of doping to form an anode of the SiNx-SiO2 avalanche photodetector.

6. The method for preparing a SiNx-SiO2 avalanche photodetector according to claim 6, characterized in that: The anode of the SiNx-SiO2 avalanche photodetector is connected to an external circuit through a metal interconnection hole.

7. A SiNx-SiO2 avalanche photodetector device, characterized in that: The SiNx-SiO2 avalanche photodetector device is prepared using the SiNx-SiO2 avalanche photodetector preparation method as described in any one of claims 1 to 6, and the SiNx-SiO2 avalanche photodetector device includes: a first doping type substrate, a first doping type epitaxial layer arranged on the first doping type substrate, a second doping type first region arranged on the epitaxial layer, a first doping type second region arranged above the first region, a shallow trench isolation region arranged in the first region, a first dielectric layer arranged on the surface of the shallow trench isolation region and the surface of the SiNx-SiO2 avalanche photodetector, and a second dielectric layer arranged on the first dielectric layer.

8. The SiNx-SiO2 avalanche photodetector device according to claim 7, characterized in that: The first dielectric layer is a silicon dioxide layer.

9. The SiNx-SiO2 avalanche photodetector device according to claim 7, characterized in that: The second dielectric layer is a silicon nitride layer.

10. The SiNx-SiO2 avalanche photodetector device according to claim 7, characterized in that: The SiNx-SiO2 avalanche photodetector device also includes an anode of the SiNx-SiO2 avalanche photodetector device arranged in the first region, and the anode of the SiNx-SiO2 avalanche photodetector device is connected to an external circuit through a metal interconnection hole.

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