A double-sided mesh silicon carbide-based position sensitive detector and a method for manufacturing the same

Abstract

The application discloses a double-sided grid-shaped silicon carbide-based position sensitive detector and a preparation method thereof, and belongs to the technical field of semiconductor photoelectric detection. The detector comprises a silicon carbide substrate, and grid-shaped P-type silicon carbide high-doped epitaxial layers and grid-shaped N-type silicon carbide high-doped epitaxial layers arranged on the front surface and the back surface of the substrate respectively; the high-doped epitaxial layers simultaneously serve as photosensitive areas and ohmic contact areas, form PN junctions with the substrate to realize photoelectric conversion, and can directly form ohmic contact with metal electrodes due to high doping concentration; grid-shaped structures are formed on the high-doped epitaxial layers on the front and back surfaces through selective etching, so that the terminal capacitance of the detector is reduced. The application combines the high linearity advantage of the double-sided structure, the wide band gap and extreme environment resistance of silicon carbide and the low capacitance design of the grid-shaped electrode, realizes nanosecond-level response speed while maintaining high position linearity, and can be widely applied to the fields of laser collimation, industrial precision measurement and control and high-energy physics detection.

Description

Technical Field

[0001] This invention relates to a double-sided grid-like silicon carbide-based position-sensitive detector and its fabrication method, belonging to the field of optoelectronic detection technology for semiconductor devices. Background Technology

[0002] Position-sensitive detectors (PSDs), based on the transverse photoelectric effect, can continuously and accurately calculate the centroid position of an incident light spot according to the proportional relationship of the electrode output current. Due to their advantages in real-time and continuous position detection, PSDs have been widely used in many cutting-edge fields such as laser collimation calibration, precision measurement and control in industrial automation, and high-energy physics detection. However, current traditional PSD technology still faces several key technical bottlenecks in material systems, device structures, and process design, making it difficult to meet the application requirements of extreme working conditions and high-precision, high-speed detection scenarios. These bottlenecks are as follows.

[0003] (1) Material performance limitations: Currently, mainstream PSDs are still mainly based on silicon (Si) materials. With the increasing demand for low-energy and high-reliability detection systems, the poor reliability of traditional Si-based PSDs has become a major obstacle restricting their application in the field of position detection. Specifically, Si materials have a narrow bandgap (about 1.12 eV) and are inherently sensitive to visible light. To suppress white light noise, expensive filters must be used. In addition, silicon has a low critical displacement energy. Under extreme conditions such as high temperature and strong radiation, intrinsic carriers are easily excited in large quantities, leading to a significant increase in dark current and a severe deterioration in signal-to-noise ratio, which significantly restricts the detection stability and environmental adaptability of the device.

[0004] (2) Structural linearity defects: In traditional single-sided PSDs, the tetra-lateral structure is limited by the edge effect of the surface resistive layer and the mutual interference between electrodes, resulting in severe "pincushion" nonlinear distortion and poor position linearity (nonlinear error is usually greater than 2%), which is particularly evident in the edge region of the detection surface. Although theoretically, pincushion PSDs can achieve distortion-free position detection when satisfying Gear's theorem, they are extremely sensitive to the uniformity, consistency, symmetry and process parameters of the resistance of each functional area of ​​the surface. The actual fabrication process window is narrow, making it difficult to stably obtain high linearity devices under large-scale production conditions.

[0005] (3) Response speed bottleneck: Current mainstream PSDs generally adopt a full-surface resistive layer structure, which introduces a large device junction capacitance. At the same time, existing fabrication processes mostly use doping methods such as ion implantation. Due to the limited activation efficiency, the activation rate of doped atoms is low, making it difficult to achieve high conductivity characteristics, resulting in a high sheet resistance of the resistive layer. Under the combined effect of large junction capacitance and high sheet resistance, the RC time constant of the device increases significantly, which seriously restricts the overall response speed and makes it difficult to meet the application requirements of real-time response in high-frequency dynamic detection scenarios. Summary of the Invention

[0006] This invention aims to address the shortcomings of the aforementioned background technology by providing a double-sided grid-like silicon carbide-based position-sensitive detector. This device uses wide-bandgap semiconductor silicon carbide (SiC) as the substrate, combined with a "front-side P..." + / Back N + The device employs a double-sided homogeneous epitaxial structure, incorporating a grid-like selective etching design in both the front and back photosensitive areas. This technical solution aims to reduce device capacitance and sheet resistance while maintaining high positional linearity, thereby achieving nanosecond-level response speeds and enabling stable operation in extreme environments such as high temperatures and strong radiation.

[0007] This invention provides a double-sided grid-like silicon carbide-based position-sensitive detector and its fabrication method to solve the problems of poor reliability, low linearity and slow response speed of existing position-sensitive detectors in extreme environments.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A double-sided grid-like silicon carbide-based position-sensitive detector includes, from bottom to top, an N-type ohmic contact lower electrode, a grid-like N-type silicon carbide highly doped epitaxial layer, a silicon carbide substrate, a grid-like P-type silicon carbide highly doped epitaxial layer, and a P-type ohmic contact upper electrode; the N-type ohmic contact lower electrode and the P-type ohmic contact upper electrode are provided with metal conductive electrodes.

[0010] Optionally, an N-type buffer layer is provided between the grid-like N-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate; a P-type buffer layer is provided between the grid-like P-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate.

[0011] The aforementioned grid-like structure formed by selective etching on N-type and P-type highly doped epitaxial layers is used to reduce the detector terminal capacitance and improve the response speed.

[0012] The aforementioned N-type and P-type highly doped epitaxial layers can simultaneously serve as photosensitive regions and contact regions: on the one hand, the PN junction formed between the highly doped epitaxial layer and the silicon carbide substrate generates a depletion layer under reverse bias, which is used to absorb incident photons and generate photogenerated carriers to achieve photoelectric conversion; on the other hand, the high doping concentration of the highly doped epitaxial layer enables it to form a good ohmic contact with the metal electrode, without the need for an additional ion implantation step to obtain a heavily doped contact region as in traditional PSDs.

[0013] The aforementioned N-type ohmic contact lower electrode and P-type ohmic contact upper electrode are elongated strips, respectively disposed at opposite ends of the device, and are parallel and perpendicular to each other; wherein, the P-type ohmic contact upper electrode is used to extract hole signals, and the N-type ohmic contact lower electrode is used to extract electron signals;

[0014] The aforementioned metal conductive electrodes can effectively improve the current spread and carrier collection capabilities of devices, and are used for packaging wire bonding and testing.

[0015] The principle of the aforementioned silicon carbide-based double-sided grid-like position-sensitive detector is as follows: When the photosensitive surface of the detector is locally irradiated, incident photons enter the active absorption region (mainly located in the high-resistivity substrate region and depletion layer), generating electron-hole pairs. Under the action of a reverse bias voltage, photogenerated electrons drift towards the N-type region, and photogenerated holes drift towards the P-type region. Subsequently, photogenerated charge carriers diffuse laterally to the corresponding elongated ohmic contact electrodes. By reading the current parameters of a pair of elongated electrodes located at both ends of the X-axis, the X-coordinate of the incident light spot is determined; by reading the current parameters of a pair of elongated electrodes located at both ends of the Y-axis, the Y-coordinate of the incident light spot is determined.

[0016] If the geometric midpoint of the position-sensitive detector is taken as the origin, the position of the incident light spot can be determined by reading the current of the four electrodes. The four electrodes are: the first P-type ohmic contact upper electrode (E1) and the second P-type ohmic contact upper electrode (E2) set at both ends of the upper surface along the X-axis, and the first N-type ohmic contact lower electrode (E3) and the second N-type ohmic contact lower electrode (E4) set at both ends of the lower surface along the Y-axis.

[0017] The X-coordinate of the incident light spot centroid (x, y) on the position-sensitive detector is determined by the current ratio of the two electrodes on the upper surface, and the Y-coordinate is determined by the current ratio of the two electrodes on the lower surface, as specifically expressed as:

[0018] Where I1 and I2 are the currents output from the upper electrode of the first P-type ohmic contact and the upper electrode of the second P-type ohmic contact, respectively; I3 and I4 are the currents output from the lower electrode of the first N-type ohmic contact and the lower electrode of the second N-type ohmic contact, respectively; L x L is the length of the photosensitive surface in the X direction.y The length of the photosensitive surface in the Y direction is given.

[0019] This invention proposes a double-sided grid-like position-sensitive detector based on silicon carbide. Building upon the advantages of double-sided PSD structures (separating X and Y positioning functions to the front and back sides, improving linearity) and utilizing the wide bandgap, high thermal conductivity, and radiation resistance of silicon carbide, the core improvement lies in the use of two separate, non-planar epitaxial growth processes to form highly doped P-type and N-type epitaxial layers on the front and back sides of the substrate, respectively. A double-sided grid-like structure is then formed through selective etching. This design effectively reduces the device's terminal capacitance, shortens carrier transit time, and significantly reduces the RC time constant. Compared to the microsecond-level response speed of traditional full-surface resistive layer structures, the theoretical response speed of this invention can be improved to the nanosecond level. Simultaneously, the highly doped epitaxial layers directly serve as the photosensitive and contact regions, forming good ohmic contacts without the need for additional ion implantation steps, effectively avoiding lattice damage and process complexity caused by ion implantation.

[0020] In summary, this invention combines the structural advantages of double-sided PSD, the material advantages of silicon carbide, and the double-sided grid electrode design and heterogeneous epitaxial process to achieve a position-sensitive detector with high linearity, ultra-fast response speed, and adaptability to extreme environments, overcoming the technical bottlenecks of traditional PSD in high-speed, high-temperature, and high-irradiation application scenarios.

[0021] To further improve device performance, the doping concentration of the N-type silicon carbide substrate is less than 1×10⁻⁶. 17 cm -3 More preferably 1×10 14 cm -3 The doping concentration of highly doped N-type or P-type silicon carbide epitaxial layers is higher than 5 × 10⁻⁶. 18 cm -3 More preferably 1×10 19 cm -3 The thickness of the N-type or P-type silicon carbide highly doped epitaxial layer is greater than 10 nm, more preferably 200 nm; the grid linewidth of the grid structure is 0.01 μm to 100 μm, and the grid spacing is 0.01 μm to 100 μm; preferably, the length of the photosensitive surface in the X direction is equal to the length of the photosensitive surface in the Y direction.

[0022] To ensure the overall performance of the device, the material of the upper electrode of the P-type ohmic contact is a mixture of one or more materials such as nickel, titanium, aluminum, and gold in any proportion; the material of the lower electrode of the N-type ohmic contact is a mixture of one or more materials such as nickel, titanium, aluminum, and gold in any proportion; the metal conductive electrode is preferably composed of titanium and gold layers and is located entirely within the P-type or N-type ohmic contact range; the metal conductive electrode can be compatible as the Pad area for wire bonding.

[0023] The fabrication method of the above-mentioned double-sided grid-like silicon carbide-based position-sensitive detector includes the following sequentially connected steps:

[0024] 1) A P-type highly doped silicon carbide epitaxial layer is epitaxially grown on the upper surface of a silicon carbide substrate, and an N-type highly doped silicon carbide epitaxial layer is epitaxially grown on the lower surface of a silicon carbide substrate; preferably, the P-type and N-type highly doped epitaxial layers are epitaxially grown stepwise on the upper and lower surfaces of the substrate using high-temperature chemical vapor deposition (CVD).

[0025] 2) Using a photoresist pattern or patterned medium as a mask, an inductively coupled plasma (ICP) dry etching technique is used to etch a grid-like groove structure stepwise on the surfaces of the P-type and N-type highly doped silicon carbide epitaxial layers, with an etching depth of 100% of the epitaxial layer thickness; after removing the mask, a grid-like P-type and N-type highly doped silicon carbide epitaxial layer is formed.

[0026] 3) Optionally, a passivation layer is deposited on the surface of the P-type silicon carbide highly doped epitaxial layer and the N-type silicon carbide highly doped epitaxial layer; preferably, a high-temperature thermal oxidation method is used to prepare the silicon dioxide passivation layer, and the passivation layer thickness is less than 200 nm, more preferably 60 nm.

[0027] 4) Spin-coat photoresist onto the passivation layer surface and form a photoresist pattern by exposure and development to define the window areas of the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode. Then, remove the passivation layer in the window areas by etching or wet etching to expose the surfaces of the P-type silicon carbide highly doped epitaxial layer and the N-type silicon carbide highly doped epitaxial layer. Preferably, wet etching or reactive ion etching (RIE) is used to etch the electrode window areas.

[0028] 5) P-type ohmic contact metal is deposited on the surface of the exposed grid-like P-type silicon carbide highly doped epitaxial layer, and N-type ohmic contact metal is deposited on the surface of the exposed grid-like N-type silicon carbide highly doped epitaxial layer. Thermal annealing is then performed to form the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode, respectively. Preferably, the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode are deposited using physical vapor deposition (PVD).

[0029] 6) Deposit metal conductive electrodes on the upper electrode of the P-type ohmic contact and the lower electrode of the N-type ohmic contact;

[0030] 7) Splitting: Divide the epitaxial wafer into individual devices to complete the fabrication of a double-sided grid-like silicon carbide-based position-sensitive detector.

[0031] In step 1), optionally, a P-type buffer layer is epitaxially grown between the P-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate; and an N-type buffer layer is epitaxially grown between the N-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate.

[0032] In step 5), the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode are elongated strips, respectively disposed at opposite ends of the device, and are parallel and perpendicular to each other; the materials of the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode are one or more of nickel, titanium, aluminum, gold and other materials in any proportion; the preferred temperature for the heat annealing treatment is 800~850°C, and the preferred time is 2~3 min.

[0033] Any techniques not mentioned in this invention are based on existing technologies.

[0034] This invention relates to a silicon carbide-based position-sensitive detector with a double-sided grid structure. It inherits the structural characteristics of double-sided PSDs, which separate the X and Y positioning functions to the front and back sides, and has high position linearity. At the same time, by introducing a grid structure formed by selective etching on the highly doped epitaxial layers on both sides, the terminal capacitance of the device is effectively reduced, and the response speed is significantly improved. In addition, the highly doped epitaxial layer serves as both the photosensitive region and the contact region, eliminating the need for an additional ion implantation step, simplifying the device structure and fabrication process, and facilitating industrial production.

[0035] This invention proposes a double-sided grid-like position-sensitive detector based on silicon carbide. Building upon the advantages of a double-sided PSD structure (separating X and Y positioning functions to the front and back sides to improve linearity) and utilizing the wide bandgap, high thermal conductivity, and radiation resistance of silicon carbide, the core improvement and innovation of this invention lies in:

[0036] First, the integrated functional design of the highly doped epitaxial layers. In this invention, the N-type and P-type highly doped silicon carbide epitaxial layers simultaneously serve as both photosensitive and contact regions. They participate in the formation of the PN junction to achieve photoelectric conversion and also act as low-resistance channels for lateral carrier transport. Furthermore, the high doping concentration allows them to directly form good ohmic contacts with the metal electrode without the need for additional ion implantation. This integrated design simplifies the device structure and fabrication process, reduces manufacturing costs, minimizes interface defects, and improves device reliability.

[0037] Second, the double-sided mesh structure achieves an ultrafast response speed. This invention forms a mesh structure on both N-type and P-type highly doped epitaxial layers through selective etching, effectively reducing the device's terminal capacitance, shortening carrier transit time, and significantly reducing the RC time constant. Compared to the microsecond-level response speed of traditional full-surface resistive layer structures, the theoretical response speed of this invention can be improved to the nanosecond level.

[0038] In summary, this invention achieves a position-sensitive detector with high linearity, ultrafast response speed, and adaptability to extreme environments through the synergistic innovation of "integrated functional design of highly doped epitaxial layer + double-sided mesh electrode + silicon carbide material", overcoming the technical bottleneck of traditional PSD in high-speed, high-temperature, and high-irradiation application scenarios. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating the fabrication method of a double-sided mesh silicon carbide-based position-sensitive detector in an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the structure of the double-sided mesh silicon carbide-based position-sensitive detector in an embodiment of the present invention;

[0041] Figure 3 This is a top view of the double-sided mesh silicon carbide-based position-sensitive detector in an embodiment of the present invention;

[0042] Figure 4 This is a bottom view of the double-sided mesh silicon carbide-based position-sensitive detector in an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of the method for defining the position electrode of a double-sided mesh silicon carbide-based position-sensitive detector in an embodiment of the present invention;

[0044] Figure 6 This is a simulation diagram comparing the capacitance of a double-sided grid-shaped silicon carbide-based position-sensitive detector with a double-sided gridless PSD and a single-sided grid-shaped PSD in an embodiment of the present invention.

[0045] Figure 7 This is a simulation diagram of the two-dimensional position characteristics of a double-sided grid-like silicon carbide-based position-sensitive detector in an embodiment of the present invention (based on TCAD simulation).

[0046] Figure 2 In the diagram, 1 is a grid-like N-type silicon carbide highly doped epitaxial layer; 2 is a silicon carbide substrate; 3 is a grid-like P-type silicon carbide highly doped epitaxial layer; 4 is a P-type ohmic contact upper electrode; 5 is a P-type conductive electrode; 6 is an N-type ohmic contact lower electrode; and 7 is an N-type conductive electrode.

[0047] Depend on Figure 5 As can be seen, the detector has four discrete position electrodes on its upper and lower surfaces, corresponding to the four output terminals of the detector. By applying a bias voltage to the electrodes between the upper and lower surfaces and measuring their output photocurrent, the centroid coordinates of the incident light spot can be determined based on the current relationship. The symmetrical electrode layout can effectively improve the linearity of position detection.

[0048] Figure 6This is a simulation comparison of capacitance between a double-sided gridded silicon carbide-based position-sensitive detector, a double-sided gridless PSD, and a single-sided gridded PSD, as shown in the embodiments of the present invention. Simulation results show that, under the same device area and bias conditions, the parasitic capacitance between the electrodes of the double-sided gridded structure is significantly lower than that of the double-sided gridless structure, with a reduction of approximately 25%. This capacitance advantage helps to shorten the position signal settling time and improve the detection bandwidth of the detector under high-frequency modulated optical signals. Further research shows that this capacitance reduction is closely related to the grid's duty cycle; by optimizing the duty cycle, the capacitance value can be effectively controlled.

[0049] Figure 7 This is a simulation diagram of the two-dimensional position characteristics of a double-sided gridded silicon carbide-based position-sensitive detector (based on Silvaco) in an embodiment of the present invention. The figure shows the correspondence between the detected position and the actual position of the light spot as the incident light spot moves within the effective area of ​​the detector. The simulation results show that the position response curve has good linearity in the central region of the detector, with a nonlinearity error of less than 1%. Detailed Implementation

[0050] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] 1 is a grid-like N-type silicon carbide highly doped epitaxial layer; 2 is a silicon carbide substrate; 3 is a grid-like P-type silicon carbide highly doped epitaxial layer; 4 is a P-type ohmic contact upper electrode; 5 is a P-type conductive electrode; 6 is an N-type ohmic contact lower electrode; 7 is an N-type conductive electrode.

[0053] like Figure 2 As shown, the double-sided grid-like silicon carbide-based position-sensitive detector includes, from bottom to top, an N-type ohmic contact lower electrode 6, a grid-like N-type silicon carbide highly doped epitaxial layer 1, a P-type conductive electrode 5, an N-type ohmic contact lower electrode 6, and a P-type ohmic contact upper electrode 4; N-type conductive electrodes 7 and P-type conductive electrodes 5 are disposed on the N-type ohmic contact lower electrode 6 and the P-type ohmic contact upper electrode 4. The grid-like N-type silicon carbide highly doped epitaxial layer 1 has a thickness of 200 nm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The silicon carbide substrate 2 has a thickness of 350 μm and a doping concentration of less than 1×10⁻⁶. 14 cm -3 The thickness of electrode 4 in the P-type ohmic contact is 200 nm, and the doping concentration is 1×10⁻⁶. 19 cm -3The P-type conductive electrode 5 is elongated and is disposed at both ends of the upper surface of the device along the X-axis; the grid-like N-type silicon carbide highly doped epitaxial layer 1 is elongated and is disposed at both ends of the lower surface of the device along the Y-axis; the two pairs of electrodes are parallel to each other and perpendicular to each other.

[0054] The fabrication process for the above-mentioned device is as follows:

[0055] Step 101: Provide a silicon carbide substrate 2 with a doping concentration of less than 1×10⁻⁶. 14 cm -3 The thickness is 350 μm. A mesh-like N-type highly doped silicon carbide epitaxial layer 1 is epitaxially grown on the upper surface of the silicon carbide substrate 2 using high-temperature chemical vapor deposition (CVD), with a doping concentration of 1×10⁻⁶. 19 cm -3 A 200 nm thick N-type highly doped silicon carbide epitaxial layer 1 with a doping concentration of 5 × 10⁻⁶ nm is epitaxially grown on the lower surface of a silicon carbide substrate 2. 18 cm -3 The thickness is 200 nm.

[0056] Step 102: Spin-coat photoresist onto the surface of the highly doped P-type silicon carbide epitaxial layer 4, and form a photoresist pattern by photolithography exposure and development to define the front mesh-like etching area.

[0057] Step 103: Using the photoresist pattern as a mask, an inductively coupled plasma (ICP) dry etching technique is employed to etch a grid-like groove structure on the surface of the P-type highly doped silicon carbide epitaxial layer 4. The etching depth is 200 nm (i.e., etching through the entire highly doped epitaxial layer, with an etching depth of 100% of the epitaxial layer thickness). The photoresist is then removed to form the grid-like P-type highly doped silicon carbide epitaxial layer 4. The grid linewidth is 5 μm, and the grid spacing is 15 μm.

[0058] Step 104: Spin-coat photoresist onto the surface of the N-type silicon carbide highly doped epitaxial layer 2, and form a photoresist pattern by photolithography exposure and development to define the back mesh etching area.

[0059] Step 105: Using the photoresist pattern as a mask, an inductively coupled plasma (ICP) dry etching technique is employed to etch a grid-like groove structure on the surface of the P-type highly doped silicon carbide epitaxial layer 4. The etching depth is 200 nm (i.e., etching through the entire highly doped epitaxial layer, with an etching depth of 100% of the epitaxial layer thickness). The photoresist is then removed to form the grid-like P-type highly doped silicon carbide epitaxial layer 4. The grid linewidth is 5 μm, and the grid spacing is 15 μm.

[0060] Step 106: A silicon dioxide passivation layer with a thickness of 60 nm is formed on the surface of the P-type silicon carbide highly doped epitaxial layer 4 and the N-type silicon carbide highly doped epitaxial layer 2 using a high-temperature thermal oxidation method.

[0061] Step 107: Spin-coat photoresist onto the passivation layer surface and form a photoresist pattern by exposure and development to define the window areas of the P-type ohmic contact upper electrode 5 and the N-type ohmic contact lower electrode 1. Remove the passivation layer in the window areas using wet etching or reactive ion etching (RIE) to expose the surfaces of the P-type silicon carbide highly doped epitaxial layer 4 and the N-type silicon carbide highly doped epitaxial layer 2.

[0062] Step 108: A P-type ohmic contact metal (preferably Ni / Au, 200 nm thick) is deposited on the exposed grid-like P-type silicon carbide highly doped epitaxial layer 4 using physical vapor deposition (PVD). An N-type ohmic contact metal (preferably Ni / Ti / Al / Au, with thicknesses of 35 / 50 / 100 / 100 nm respectively) is deposited on the exposed grid-like N-type silicon carbide highly doped epitaxial layer 2. The epitaxial wafer with deposited metal is then placed in an annealing furnace and annealed at 850°C for 3 min under a nitrogen atmosphere to form a P-type ohmic contact upper electrode 5 and an N-type ohmic contact lower electrode 1. The P-type ohmic contact upper electrode 5 is elongated and positioned at both ends of the upper surface of the device along the X-axis; the N-type ohmic contact lower electrode 1 is elongated and positioned at both ends of the lower surface of the device along the Y-axis. The two pairs of electrodes are parallel and perpendicular to each other.

[0063] Step 107: An N-type metal conductive electrode 6 and a P-type metal conductive electrode 7 are deposited on the P-type ohmic contact upper electrode 5 and the N-type ohmic contact lower electrode 1 using a physical vapor deposition (PVD) method. The electrodes are preferably composed of a titanium layer (500 nm) and a gold layer (500 nm) and are located entirely above the ohmic contact electrode area.

[0064] Step 108: Divide the epitaxial wafer into individual devices, wire bond the finished devices, and perform further electro-optical testing. The lower electrode 1 of the N-type ohmic contact is connected to the positive terminal during testing, and the upper electrode 5 of the P-type ohmic contact is connected to the ground terminal.

Claims

1. A double-sided mesh-like silicon carbide-based position-sensitive detector, characterized in that, include: silicon carbide substrate; A grid-like P-type highly doped silicon carbide epitaxial layer located on the front side of the silicon carbide substrate; A grid-like N-type silicon carbide highly doped epitaxial layer located on the back side of the silicon carbide substrate; The P-type ohmic contact electrode disposed on the grid-like P-type silicon carbide highly doped epitaxial layer; and The N-type ohmic contact lower electrode is disposed on the grid-like N-type silicon carbide highly doped epitaxial layer; The grid-shaped P-type silicon carbide highly doped epitaxial layer and the grid-shaped N-type silicon carbide highly doped epitaxial layer are respectively obtained by selective etching of the entire highly doped epitaxial layer to form a grid-shaped groove structure. The grid-shaped structure is used to reduce the terminal capacitance of the detector.

2. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, The upper electrode of the P-type ohmic contact is elongated and disposed at opposite ends on the front of the detector for extracting hole signals; the lower electrode of the N-type ohmic contact is elongated and disposed at opposite ends on the back of the detector for extracting electron signals; the upper electrode of the P-type ohmic contact and the lower electrode of the N-type ohmic contact are parallel to each other and perpendicular to each other.

3. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 2, characterized in that, The detector has a first P-type ohmic contact upper electrode and a second P-type ohmic contact upper electrode at both ends along the X-axis on the front side, and a first N-type ohmic contact lower electrode and a second N-type ohmic contact lower electrode at both ends along the Y-axis on the back side. The centroid coordinates (x, y) of the incident light spot satisfy the following relationship: ； Where I1 and I2 are the currents output from the upper electrode of the first P-type ohmic contact and the upper electrode of the second P-type ohmic contact, respectively; I3 and I4 are the currents output from the lower electrode of the first N-type ohmic contact and the lower electrode of the second N-type ohmic contact, respectively; L x L is the length of the photosensitive surface in the X direction. y The length of the photosensitive surface in the Y direction is given.

4. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, The grid-like P-type silicon carbide highly doped epitaxial layer and the grid-like N-type silicon carbide highly doped epitaxial layer serve as both photosensitive regions and ohmic contact regions; a PN junction is formed between the highly doped epitaxial layer and the silicon carbide substrate to absorb incident photons and generate photogenerated carriers; the high doping concentration of the highly doped epitaxial layer enables it to directly form an ohmic contact with the metal electrode.

5. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, A P-type buffer layer is further disposed between the grid-like P-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate; an N-type buffer layer is further disposed between the grid-like N-type highly doped silicon carbide epitaxial layer and the silicon carbide substrate.

6. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, The doping concentration of the silicon carbide substrate is less than 1×10⁻⁶. 17 cm -3 The doping concentrations of the grid-like P-type silicon carbide highly doped epitaxial layer and the grid-like N-type silicon carbide highly doped epitaxial layer are each independently higher than 5 × 10⁻⁶. 18 cm -3 .

7. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, The thickness of the grid-like P-type silicon carbide highly doped epitaxial layer and the grid-like N-type silicon carbide highly doped epitaxial layer are each independently greater than 10 nm; the grid linewidth of the grid structure is 0.01 μm to 100 μm, and the grid spacing is 0.01 μm to 100 μm.

8. The double-sided mesh silicon carbide-based position-sensitive detector according to claim 1, characterized in that, The materials of the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode are each independently selected from one or more of nickel, titanium, aluminum, and gold in any proportion; the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode are also provided with metal conductive electrodes, which are composed of titanium and gold layers and are used for encapsulation wire bonding and testing.

9. A method for fabricating a double-sided mesh-like silicon carbide-based position-sensitive detector as described in any one of claims 1 to 8, characterized in that, Includes the following steps: 1) A P-type highly doped silicon carbide epitaxial layer is epitaxially grown on the upper surface of a silicon carbide substrate, and an N-type highly doped silicon carbide epitaxial layer is epitaxially grown on the lower surface of the silicon carbide substrate. 2) Using a photoresist pattern or patterned medium as a mask, an inductively coupled plasma dry etching technique is used to etch a grid-like groove structure stepwise on the surfaces of the P-type silicon carbide highly doped epitaxial layer and the N-type silicon carbide highly doped epitaxial layer. The etching depth is 100% of the epitaxial layer thickness. After removing the mask, a grid-like P-type silicon carbide highly doped epitaxial layer and a grid-like N-type silicon carbide highly doped epitaxial layer are formed. 3) P-type ohmic contact metal is deposited on the surface of the grid-like P-type silicon carbide highly doped epitaxial layer, and N-type ohmic contact metal is deposited on the surface of the grid-like N-type silicon carbide highly doped epitaxial layer. The layers are then subjected to thermal annealing to form the P-type ohmic contact upper electrode and the N-type ohmic contact lower electrode, respectively. 4) Deposit metal conductive electrodes on the upper electrode of the P-type ohmic contact and the lower electrode of the N-type ohmic contact; 5) Split the wafer to complete the fabrication of the double-sided mesh silicon carbide-based position-sensitive detector.

10. The preparation method according to claim 9, characterized in that, In step 1), the P-type highly doped silicon carbide epitaxial layer and the N-type highly doped silicon carbide epitaxial layer are epitaxially grown stepwise on the upper and lower surfaces of the silicon carbide substrate using high-temperature chemical vapor deposition. In step 3), before depositing the ohmic contact metal, the method further includes forming a passivation layer on the surface of the grid-like P-type silicon carbide highly doped epitaxial layer and the grid-like N-type silicon carbide highly doped epitaxial layer, and removing the passivation layer in the electrode window region by etching or wet etching. The heat annealing process is performed at a temperature of 800-850°C for 2-3 minutes.

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