A silicon carbide-based ultraviolet position-sensitive detector and its preparation method

Abstract

The present invention provides a silicon carbide-based ultraviolet position-sensitive detector and a preparation method thereof, belonging to the technical field of position detectors. It includes an N-type silicon carbide substrate layer, an electrical isolation layer, a highly doped lower drift layer, a lowly doped middle drift layer, and a highly doped upper drift layer arranged from bottom to top. A first graphic area is provided on the highly doped lower drift layer, and the lowly doped middle drift layer and the highly doped upper drift layer are located in the first graphic area. First ohmic contact electrodes are respectively arranged on opposite sides of the first graphic area in a first direction. Two second ohmic contact electrodes are arranged at intervals along a second direction on the top of the highly doped upper drift layer, and the second direction is perpendicular to the first direction. The conductive characteristics of the highly doped lower drift layer and the highly doped upper drift layer are opposite. It can solve the technical problems of large detection structure position error and unsatisfactory measurement accuracy caused by device structure defects in the existing ultraviolet position-sensitive detectors.

Description

Technical Field

[0001] The present invention relates to the technical field of position detectors, and particularly relates to a silicon carbide-based ultraviolet position-sensitive detector and a preparation method thereof. Background Art

[0002] Ultraviolet PSD (Position Sensitive Detector) has been widely used in the new generation of information technology and has broad application prospects in the fields of motion tracking, vibration monitoring, space optical communication, biosensing, etc. The working principle of PSD is based on the lateral photovoltaic effect. For a common P-I-N structure PSD, when the device surface is irradiated by light, electron-hole pairs are generated at the position of the light spot. These carriers flow through the lateral resistance layer and generate photocurrents on several electrodes arranged at the edges of the lateral resistance layer respectively. Since the resistance of the lateral resistance layer is uniform, the photocurrent output by the electrode is inversely proportional to the distance between the incident light spot position and each electrode, thereby realizing position detection.

[0003] In the related art, commercial PSDs are mainly silicon-based devices. Among them, the wide-bandgap semiconductor material silicon carbide has excellent properties such as a large bandgap width, a high critical displacement energy, a high electron mobility, and a high thermal conductivity coefficient. Silicon carbide-based ultraviolet position-sensitive detectors often have the advantages of good anti-irradiation performance, low noise level, and high temperature stability.

[0004] However, for the existing silicon carbide-based ultraviolet two-dimensional PSD, in order to measure the two-dimensional coordinate position of the incident light spot, two sets of electrodes spaced apart from each other need to be set. Four electrodes are usually arranged in a quadrilateral shape on the same surface of the device. During the detection process, there are mutual interferences in the two-way carrier migration process and the interference of the electric field between adjacent electrodes in different directions, resulting in a large position error in the detection result and reducing the measurement accuracy. Summary of the Invention

[0005] Embodiments of the present invention provide a silicon carbide-based ultraviolet position-sensitive detector and a preparation method thereof. It can solve the technical problem that the detection structure position error of the ultraviolet PSD in the prior art is large and the measurement accuracy is not ideal due to the device structure defect. The technical solution is as follows:

[0006] In a first aspect, an embodiment of the present invention provides a silicon carbide-based ultraviolet position-sensitive detector, which includes an N-type silicon carbide substrate layer, an electrical isolation layer, a highly doped lower drift layer, a lowly doped middle drift layer, and a highly doped upper drift layer. A first graphic area is provided on the highly doped lower drift layer, and the lowly doped middle drift layer and the highly doped upper drift layer are located in the first graphic area. First ohmic contact electrodes are respectively arranged on opposite sides of the first graphic area in a first direction. Two second ohmic contact electrodes are arranged at intervals along a second direction on the top of the highly doped upper drift layer, and the second direction is perpendicular to the first direction. The conductive characteristics of the highly doped lower drift layer and the highly doped upper drift layer are opposite.

[0007] Optionally, a second graphic area is provided on the electrical isolation layer, and the highly doped lower drift layer is located in the second graphic area.

[0008] Optionally, the doping concentration range of the highly doped lower drift layer is 1×10 17 cm -3 to 1×10 21 cm -3 ; the doping concentration range of the highly doped upper drift layer is 1×10 17 cm -3 to 1×10 21 cm -3 .

[0009] Optionally, when the doping concentrations of the highly doped lower drift layer and the highly doped upper drift layer are less than or equal to 1×10 18 cm -3 , an ohmic contact area layer is provided between the first ohmic contact electrode and the highly doped lower drift layer, and between the second ohmic contact electrode and the highly doped upper drift layer, and they are connected through the ohmic contact area layer.

[0010] Optionally, the ohmic contact area layers below the two first ohmic contact electrodes and the two second ohmic contact electrodes are all strip-shaped, and jointly surround to form a rectangular effective photosensitive area of the device. The aspect ratio range of the length and width of the effective photosensitive area of the device is 1 to 1.5.

[0011] Optionally, when the doping concentrations of the highly doped lower drift layer and the highly doped upper drift layer are greater than 1×10 18 cm -3 , the first ohmic contact electrode is connected to the top of the highly doped lower drift layer, and the second ohmic contact electrode is connected to the top of the highly doped upper drift layer.

[0012] Optionally, the conductive characteristics of the electrical isolation layer and the highly doped lower drift layer are opposite. The doping concentration range of the electrical isolation layer is 1×10 16cm -3 to 1×10 21 cm -3 。

[0013] Optionally, the thickness range of the highly doped lower drift layer is 0.2 - 10 μm, the thickness of the lowly doped middle drift layer is greater than 1 μm, the thickness range of the highly doped upper drift layer is 0.2 - 10 μm, and the thicknesses of the first ohmic contact electrode and the second ohmic contact electrode are greater than 0.5 μm.

[0014] Optionally, the materials of the first ohmic contact electrode and the second ohmic contact electrode are at least one of nickel, titanium, aluminum, or gold.

[0015] In a second aspect, an embodiment of the present invention provides a preparation method for manufacturing the silicon carbide-based ultraviolet position-sensitive detector described in the first aspect above, including:

[0016] Step 1: Using the N-type silicon carbide substrate layer as an epitaxial substrate, sequentially grow an electrical isolation layer, a highly doped lower drift layer, a lowly doped middle drift layer, and a highly doped upper drift layer thereon;

[0017] Step 2: Evaporate a mask on the top of the highly doped upper drift layer, and etch downward the highly doped upper drift layer and the lowly doped middle drift layer until the top of the highly doped lower drift layer is exposed to form the first graphic area;

[0018] Step 3: Deposit SiO2 on the outer surfaces of the electrical isolation layer, the highly doped lower drift layer, the lowly doped middle drift layer, and the highly doped upper drift layer to form a passivation layer, and etch and deposit the first ohmic contact electrode and the second ohmic contact electrode at the corresponding graphic windows on the tops of the highly doped lower drift layer and the highly doped upper drift layer.

[0019] The beneficial effects brought by the technical solution provided by the embodiment of the present invention at least include:

[0020] Using the silicon carbide-based ultraviolet position-sensitive detector provided by the embodiments of the present invention, which uses the wide-bandgap semiconductor material silicon carbide as the main body of the device for the migration of carriers after receiving light irradiation, it has excellent characteristics such as a large bandgap width, a high critical displacement energy, a high electron mobility, and a high thermal conductivity coefficient. At the same time, on the device structure, the first ohmic contact electrode and the second ohmic contact electrode for receiving bidirectional carriers are respectively arranged on the surfaces of the highly doped lower drift layer and the highly doped upper drift layer at different height levels. Using this double-sided electrode structure enables the generated photoelectrons and holes under light irradiation to move in the highly doped upper drift layer and the highly doped lower drift layer respectively, reducing the interference between lateral and longitudinal carrier migration and the electric field, which helps to improve the linearity of the relationship between the magnitude of the collected current of the electrode structure and the distance of the light irradiation point, reduces the mutual interference between electrode structures in different directions, reduces the noise level of the ultraviolet PSD, and significantly improves the position resolution and measurement accuracy. Thus, it solves the technical problems of large detection structure position errors and unsatisfactory measurement accuracy caused by device structure defects in the existing ultraviolet PSD technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the steps for growing an N-type silicon carbide substrate layer, an electrical isolation layer, a highly doped lower drift layer, a low-doped middle drift layer, and a highly doped upper drift layer of the silicon carbide-based ultraviolet position-sensitive detector provided by the embodiments of the present invention;

[0023] Figure 2 It is a schematic diagram of the steps for etching to form the low-doped middle drift layer and the highly doped upper drift layer in the first graphic area of the silicon carbide-based ultraviolet position-sensitive detector provided by the embodiments of the present invention;

[0024] Figure 3 It is a schematic diagram of the steps for etching to form the highly doped lower drift layer in the second graphic area of the silicon carbide-based ultraviolet position-sensitive detector provided by the embodiments of the present invention;

[0025] Figure 4 It is during Figure 3 a step schematic diagram of depositing a passivation layer on the device;

[0026] Figure 5 It is actually during Figure 4 a step schematic diagram of etching and depositing the first ohmic contact electrode and the second ohmic contact electrode on the device;

[0027] Figure 6 It is a schematic three-dimensional structure diagram of a silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention;

[0028] Figure 7 is Figure 6 a schematic top view structure diagram of the structure in

[0029] Figure 8 is Figure 6 a schematic front view structure diagram of the structure in

[0030] Figure 9 is Figure 6 a schematic left view structure diagram of the structure in

[0031] Figure 10 It is a schematic three-dimensional structure diagram of another silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention;

[0032] Figure 11 is Figure 10 a schematic top view structure diagram of the structure in

[0033] Figure 12 is Figure 10 a schematic left view structure diagram of the structure in

[0034] Figure 13 It is a flowchart of the preparation method provided in an embodiment of the present invention.

[0035] In the figure: 1 - N-type silicon carbide substrate layer; 2 - electrical isolation layer; 2a - second pattern area; 3 - highly doped lower drift layer; 3a - first pattern area; 4 - lowly doped middle drift layer; 5 - highly doped upper drift layer; 6 - first ohmic contact electrode; 7 - second ohmic contact electrode; 8 - ohmic contact area layer; 9 - passivation layer. Detailed implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Figure 1 It is a schematic diagram of the steps of growing an N-type silicon carbide substrate layer, an electrical isolation layer, a highly doped lower drift layer, a lowly doped middle drift layer and a highly doped upper drift layer of a silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention; Figure 2 It is a schematic diagram of the steps of etching to form a lowly doped middle drift layer and a highly doped upper drift layer in the first pattern area of a silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention; Figure 3 It is a schematic diagram of the steps of etching to form a highly doped lower drift layer in the second pattern area of a silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention; Figure 4 is in Figure 3Schematic diagram of the step of depositing a passivation layer on the device; Figure 5 is real Figure 4 Schematic diagram of the steps of etching and depositing the first ohmic contact electrode and the second ohmic contact electrode on the device; Figure 6 Schematic three-dimensional structure diagram of a silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention; Figure 7 is Figure 6 Top view structure diagram of the structure in Figure 8 is Figure 6 Front view structure diagram of the structure in Figure 9 is Figure 6 Left view structure diagram of the structure in Figure 10 Schematic three-dimensional structure diagram of another silicon carbide-based ultraviolet position-sensitive detector provided in an embodiment of the present invention; Figure 11 is Figure 10 Top view structure diagram of the structure in Figure 12 is Figure 10 Left view structure diagram of the structure in

[0038] As Figures 1 to 12 shown, based on the above defects, an embodiment of the present invention provides a silicon carbide-based ultraviolet position-sensitive detector, including an N-type silicon carbide substrate layer 1, an electrical isolation layer 2, a highly doped lower drift layer 3, a low-doped middle drift layer 4, and a highly doped upper drift layer 5 arranged from bottom to top. The highly doped lower drift layer 3 has a first graphic area 3a, and the low-doped middle drift layer 4 and the highly doped upper drift layer 5 are located in the first graphic area 3a. First ohmic contact electrodes 6 are respectively arranged on opposite sides of the first graphic area 3a in a first direction. Two second ohmic contact electrodes 7 are arranged at intervals along a second direction on the top of the highly doped upper drift layer 5. The second direction is perpendicular to the first direction, and the conductive characteristics of the highly doped lower drift layer 3 and the highly doped upper drift layer 5 are opposite.

[0039] In the embodiment of the present invention, when preparing the silicon carbide-based ultraviolet position-sensitive detector, referring to Figure 1 , using the N-type silicon carbide substrate layer 1 as an epitaxial substrate, the electrical isolation layer 2, the highly doped lower drift layer 3, the low-doped middle drift layer 4, and the highly doped upper drift layer 5 are sequentially grown thereon. Exemplarily, in the embodiment of the present invention, the electrical isolation layer 2 is an N-type doped silicon nitride layer with a thickness of 0.5 μm and a doping concentration of 1×10 16 cm -3 . The highly doped lower drift layer 3 above the electrical isolation layer 2 is a P-type doped silicon carbide layer with a thickness of 1 μm and a doping concentration of 1×10 19 cm -3 . The low-doped middle drift layer 4 above the highly doped lower drift layer 3 is an N-type doped silicon nitride layer with a thickness of 2 μm and a doping concentration of 5×10 14 cm -3。The highly doped upper drift layer 5 above the low-doped middle drift layer 4 is an N-type doped silicon nitride layer with a thickness of 400 nm and a doping concentration of 2.5×10 18 cm -3 。In this embodiment, the electrical isolation layer 2 is N-type, and the highly doped lower drift layer 3 and the highly doped upper drift layer 5 have P-type and N-type conductive characteristics respectively. The highly doped lower drift layer 3 is P-type doped by epitaxial growth, and the highly doped upper drift layer 5 can be N-type doped by epitaxial growth or by ion implantation.

[0040] In another possible implementation manner of the embodiment of the present invention, if the electrical isolation layer 2 is P-type, the highly doped lower drift layer 3 and the highly doped upper drift layer 5 can also have N-type and P-type conductive characteristics respectively, where the highly doped lower drift layer 3 is N-type doped by epitaxial growth, and the highly doped upper drift layer 5 can be P-type doped by epitaxial growth or by ion implantation. As long as the conductive characteristics of the highly doped lower drift layer 3 and the highly doped upper drift layer 5 are opposite.

[0041] Furthermore, referring to Figure 2 , on the top of the device, that is, above the highly doped upper drift layer 5, an Ni metal layer is evaporated as a mask, and then an inductively coupled plasma etching (ICP) method is used to etch the highly doped upper drift layer 5 and the low-doped middle drift layer 4 downward until the top of the highly doped lower drift layer 3 is exposed, so as to form a first graphic region 3a on the highly doped lower drift layer 3, and only the highly doped upper drift layer 5 and the low-doped middle drift layer 4 within the first graphic region 3a are retained, forming a first stepped structure with the highly doped lower drift layer 3 below. The etching depth from the highly doped upper drift layer 5 downward is 2.5 μm, and the metal mask is removed after the highly doped lower drift layer 3 is exposed. The use of an evaporated metal mask as a process before etching is considered because silicon carbide material is difficult to etch, and using a conventional photoresist as an etching mask is prone to problems of insufficient blocking ability, while using a metal film layer as a "hard mask" can effectively solve this problem.

[0042] Furthermore, referring to Figure 3, since when preparing the device structure, the underlying N-type silicon carbide substrate layer 1 and the electrical isolation layer 2 are usually in a continuously grown structure, while the region above for detecting the position of the incident light spot is an independent specific region. Therefore, after the previous step, a layer of photoresist is uniformly spin-coated on the highly doped lower drift layer 3 around the first graphic region 3a, and after exposure, development, and post-baking, a dry-etching thick photoresist mask is formed. Then, the inductively coupled plasma etching method is also used to etch the highly doped lower drift layer 3 downward according to the preset range, with an etching depth of 1.1 μm until the electrical isolation layer 2 is exposed, so as to form a second graphic region 2a on the electrical isolation layer 2, and then the photoresist is removed to form the second stepped structure of the entire device. Refer to Figure 7 or Figure 11 , at this time, the overall structure above the N-type silicon carbide substrate layer 1 of the device is in a "hui"-shaped stepped structure, that is, from the top-down view direction, the inner "square" region in the "hui"-shaped region is the highly doped upper drift layer 5, the region between the inner "square" and the outer "square" in the "hui"-shaped region is the exposed highly doped lower drift layer 3, and the region outside the outer "square" region in the "hui"-shaped region is the exposed electrical isolation layer 2.

[0043] Further, refer to Figure 4 , after forming a thin sacrificial oxide layer on the entire device by wet and dry oxidation and then removing it with an HF solution to repair the damage caused by etching in the previous step. Then, a 10-nm high-quality SiO2 layer is grown on the surface by high-temperature oxidation, and a 200-nm SiO2 passivation layer 9 is deposited using plasma-enhanced chemical vapor deposition (PECVD).

[0044] Further, refer to Figures 6 to 9 , in a possible implementation manner of the embodiment of the present invention, when the doping concentrations of the highly doped lower drift layer 3 and the highly doped upper drift layer 5 are less than or equal to 1×10 18 cm -3When it is time to ensure that the highly doped upper drift layer 5 and the highly doped lower drift layer 3 have sufficient conductivity with the electrodes for receiving carriers disposed above them respectively, it is necessary to etch the passivation layer 9 above the graphic windows corresponding to the electrodes on the highly doped upper drift layer 5 and the highly doped lower drift layer 3, and form a pair of mutually parallel strip-shaped ohmic contact region layers 8 by ion implantation from the edge. The doping concentration of the strip-shaped ohmic region layer 8 needs to be higher than the doping concentration of the corresponding highly doped upper drift layer 5 and highly doped lower drift layer 3 below to ensure good ohmic contact between the highly doped upper drift layer 5 and the highly doped lower drift layer 3 and the upper electrodes. Then, along the extension direction of the strip-shaped ohmic contact region layer 8, deposit a Ni / Ti / Al / Au metal layer on the two strip-shaped ohmic contact region layers 8 of the highly doped lower drift layer 3, strip the excess metal, and perform high-temperature annealing of the electrodes to form good ohmic contact, and finally form two first ohmic contact electrodes 6 arranged in parallel at intervals. Correspondingly, along the extension direction of the strip-shaped ohmic contact region layer 8, use the same process to form two second ohmic contact electrodes 7 arranged in parallel at intervals on the two strip-shaped ohmic contact region layers 8 of the highly doped upper drift layer 5, and complete the overall fabrication of the silicon carbide-based ultraviolet position-sensitive detector.

[0045] Exemplarily, in the embodiment of the present invention, both the first ohmic contact electrode 6 and the second ohmic contact electrode 7 adopt a strip-shaped structure similar to the electrodes for receiving carriers to generate photocurrent on a conventional ultraviolet PSD. And from a top view angle, the ohmic contact region layers 8 below the two first ohmic contact electrodes 6 and the two second ohmic contact electrodes 7 are all strip-shaped. The two ohmic contact region layers 8 on the highly doped upper drift layer 5 are perpendicular to the two ohmic contact region layers 8 of the highly doped lower drift layer 3. The inner sides of the 4 ohmic contact region layers 8 jointly surround to form a rectangular effective photosensitive region of the device. That is to say, within this region, when irradiated by ultraviolet light, carriers with mutually perpendicular migration directions can be generated in the highly doped upper drift layer 5 and the highly doped lower drift layer 3 respectively, and contact with the first ohmic contact electrode 6 or the second ohmic contact electrode 7 on both sides respectively to generate photocurrent, realizing two-dimensional coordinate double-sided detection of the upper and lower surfaces.

[0046] Exemplarily, in the embodiment of the present invention, the aspect ratio range of the effective photosensitive region layer of the device is 1 to 1.5. Its aspect ratio range is determined by comprehensively considering the difficulty of device preparation and the position coordinate distribution of the incident light spots for conventional demand detection. Through experiments, relatively accurate and sensitive measurement results can be obtained within this range. The embodiment of the present invention does not limit the actual aspect ratio.

[0047] Further, referring to Figure 5 、 Figures 10 to 12 , and in another possible implementation manner of the embodiment of the present invention, when the doping concentrations of the highly doped upper drift layer 5 and the highly doped lower drift layer 3 in the device are both greater than 1×1018 cm -3 When the thickness is 18 cm and -3 , the conductivity between the highly doped upper drift layer 5 and the highly doped lower drift layer 3 and the electrodes for receiving carriers provided above them is sufficient. Therefore, there is no need to first perform ion implantation to fabricate the ohmic contact region layer 8. Instead, by directly depositing a strip-shaped metal electrode, the electrode region is formed through photoresist coating, exposure, and development. After etching away the passivation layer 9 at the corresponding graphic window, the first ohmic contact electrode 6 and the second ohmic contact electrode 7 can be directly deposited, which can effectively reduce the preparation difficulty and improve the preparation efficiency.

[0048] For the silicon carbide-based ultraviolet position-sensitive detector provided by the embodiment of the present invention, the wide-bandgap semiconductor material silicon carbide is used as the main body of the device for the carriers to migrate after receiving light irradiation. It has excellent characteristics such as a large bandgap width, a high critical displacement energy, a high electron mobility, and a high thermal conductivity coefficient. At the same time, on the device structure, the first ohmic contact electrode 6 and the second ohmic contact electrode 7 for receiving bidirectional carriers are respectively arranged on the surfaces of the highly doped lower drift layer 3 and the highly doped upper drift layer 5 at different height levels. Using this double-sided electrode structure enables the photo-generated electrons and holes generated under light irradiation to move in the highly doped upper drift layer 5 and the highly doped lower drift layer 3 respectively, reducing the interference between the lateral and longitudinal carrier migrations and the electric field, contributing to improving the linearity of the relationship between the magnitude of the collected current of the electrode structure and the distance of the light irradiation point, reducing the mutual interference between the electrode structures in different directions, reducing the noise level of the ultraviolet PSD, and significantly improving the position resolution and measurement accuracy. Thus, it solves the technical problems of large detection structure position errors and unsatisfactory measurement accuracy caused by device structure defects in the existing ultraviolet PSD.

[0049] Figure 13 is the flowchart of the preparation method provided by the embodiment of the present invention. As Figure 13 shown, the embodiment of the present invention also provides a preparation method for fabricating the silicon carbide-based ultraviolet position-sensitive detector as Figures 1 to 12 shown. This method includes the following steps:

[0050] S1: Using the N-type silicon carbide substrate layer 1 as the epitaxial substrate, sequentially grow an electrical isolation layer 2, a highly doped lower drift layer 3, a low-doped middle drift layer 4, and a highly doped upper drift layer 5 on it.

[0051] Specifically, in this step, the electrical isolation layer 2 is an N-type doped silicon nitride layer with a thickness of 0.5 μm and a doping concentration of 1×10 16 cm -3 . The highly doped lower drift layer 3 above the electrical isolation layer 2 is a P-type doped silicon carbide layer with a thickness of 1 μm and a doping concentration of 1×10 19 cm -3。The low-doped middle drift layer 4 above the drift layer 3 under high doping is an N-type doped silicon nitride layer with a thickness of 2 μm and a doping concentration of 5×10 14 cm -3 。The high-doped upper drift layer 5 above the low-doped middle drift layer 4 is an N-type doped silicon nitride layer with a thickness of 400 nm and a doping concentration of 2.5×10 18 cm -3 。

[0052] S2: Evaporate a mask on the top of the high-doped upper drift layer 5, and etch downward the high-doped upper drift layer 5 and the low-doped middle drift layer 4 until the top of the high-doped lower drift layer 3 is exposed, so as to form a first graphic area 3a.

[0053] Specifically, in this step, on the top of the device, that is, above the high-doped upper drift layer 5, an Ni metal layer is evaporated as a mask by evaporation. Then, the inductively coupled plasma etching (ICP) method is used to etch downward the high-doped upper drift layer 5 and the low-doped middle drift layer 4 until the top of the high-doped lower drift layer 3 is exposed, so as to form a first graphic area 3a on the high-doped lower drift layer 3. Only the high-doped upper drift layer 5 and the low-doped middle drift layer 4 within the first graphic area 3a are retained, forming a first stepped structure with the underlying high-doped lower drift layer 3.

[0054] Further, after the above operation, a layer of photoresist is spin-coated uniformly on the high-doped lower drift layer 3 surrounding the first graphic area 3a. After exposure, development and post-baking, a dry-etching thick photoresist mask is formed. Then, the inductively coupled plasma etching method is also used to etch downward the high-doped lower drift layer 3 according to a preset range, with an etching depth of 1.1 μm, until the electrical isolation layer 2 is exposed, so as to form a second graphic area 2a on the electrical isolation layer 2. Then the photoresist is removed to form the second stepped structure of the whole device.

[0055] S3: Deposit SiO2 on the outer surfaces of the electrical isolation layer 2, the high-doped lower drift layer 3, the low-doped middle drift layer 4 and the high-doped upper drift layer 5 to form a passivation layer 9, and etch and deposit a first ohmic contact electrode 6 and a second ohmic contact electrode 7 at the corresponding graphic windows on the tops of the high-doped lower drift layer 3 and the high-doped upper drift layer 5.

[0056] Specifically, in this step, after forming a thin sacrificial oxide layer above the whole device by wet and dry oxidation and then removing it with an HF solution to repair the damage caused by etching in the previous step. Then, a high-quality SiO2 layer with a thickness of 10 nm is grown by high-temperature oxidation on the surface, and 200 nm of SiO2 is deposited by plasma-enhanced chemical vapor deposition (PECVD) to form the passivation layer 9.

[0057] Further, in a preferred implementation manner of the embodiment of the present invention, the doping concentrations of the highly doped upper drift layer 5 and the highly doped lower drift layer 3 in the device are both greater than 1×10 18 cm -3 . The conductivity between the highly doped upper drift layer 5 and the highly doped lower drift layer 3 and the electrodes provided above them for receiving carriers is sufficient. Therefore, there is no need to first perform ion implantation to fabricate the ohmic contact region layer 8. Instead, by directly depositing a strip-shaped metal electrode, the electrode region is formed through photoresist coating, exposure, and development. After etching away the passivation layer 9 at the corresponding graphic window, the first ohmic contact electrode 6 and the second ohmic contact electrode 7 can be directly deposited, which can effectively reduce the preparation difficulty and improve the preparation efficiency.

[0058] The silicon carbide-based ultraviolet position-sensitive detector provided by the embodiment of the present invention prepared by the above preparation method uses the wide-bandgap semiconductor material silicon carbide as the main body of the device for the migration of carriers after receiving light irradiation. It has excellent characteristics such as a large bandgap width, a high critical displacement energy, a high electron mobility, and a high thermal conductivity coefficient. At the same time, on the device structure, the first ohmic contact electrode 6 and the second ohmic contact electrode 7 for receiving bidirectional carriers are respectively arranged on the surfaces of the highly doped lower drift layer 3 and the highly doped upper drift layer 5 at different height levels. Using this double-sided electrode structure enables the photo-generated electrons and holes generated under light illumination to move in the highly doped upper drift layer 5 and the highly doped lower drift layer 3 respectively, reducing the interference between the lateral and longitudinal carrier migrations and the electric field, helping to improve the linear degree of the relationship between the magnitude of the collected current of the electrode structure and the distance of the illumination point, reducing the mutual interference between the electrode structures in different directions, reducing the noise level of the ultraviolet PSD, and significantly improving the position resolution and measurement accuracy. Thus, it solves the technical problems of large detection structure position errors and unsatisfactory measurement accuracy caused by device structure defects in the existing ultraviolet PSD.

[0059] Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which this invention pertains. The terms "first", "second" and similar terms used in the description and claims of this patent application for invention do not denote any order, quantity or importance, but are merely used to distinguish different components. Similarly, terms such as "a" or "an" do not denote a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalents, and do not exclude other elements or items. Terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper", "lower", "left" and "right" are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationships may also change accordingly.

[0060] The above are only optional embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A silicon carbide-based ultraviolet position-sensitive detector, characterized in that, It includes an N-type silicon carbide substrate layer (1) arranged from bottom to top, an electrical isolation layer (2), a highly doped lower drift layer (3), a lowly doped middle drift layer (4), and a highly doped upper drift layer (5). A first graphic area (3a) is provided on the highly doped lower drift layer (3). The lowly doped middle drift layer (4) and the highly doped upper drift layer (5) are located in the first graphic area (3a). First ohmic contact electrodes (6) are respectively arranged on opposite sides of the first graphic area (3a) in a first direction. Two second ohmic contact electrodes (7) are arranged at intervals along a second direction on the top of the highly doped upper drift layer (5). The second direction is perpendicular to the first direction. The conductive characteristics of the highly doped lower drift layer (3) and the highly doped upper drift layer (5) are opposite.

2. The silicon carbide-based ultraviolet position-sensitive detector according to claim 1, wherein A second graphic area (2a) is provided on the electrical isolation layer (2). The highly doped lower drift layer (3) is located in the second graphic area (2a).

3. The silicon carbide-based ultraviolet position-sensitive detector according to claim 1, characterized in that, The doping concentration range of the high-doped drift layer (3) is 1×10 17 cm -3 to 1×10 21 cm -3 ; the doping concentration range of the high-doped upper drift layer (5) is 1×10 17 cm -3 to 1×10 21 cm -3 .

4. The silicon carbide-based ultraviolet position-sensitive detector according to claim 3, wherein When the doping concentrations of the high-doped lower drift layer (3) and the high-doped upper drift layer (5) are less than or equal to 1×10 18 cm -3 , an ohmic contact region layer (8) is provided between the first ohmic contact electrode (6) and the high-doped lower drift layer (3), and between the second ohmic contact electrode (7) and the high-doped upper drift layer (5), and they are connected through the ohmic contact region layer (8).

5. The silicon carbide-based ultraviolet position-sensitive detector according to claim 4, characterized in that, The ohmic contact area layers (8) below the two first ohmic contact electrodes (6) and the two second ohmic contact electrodes (7) are all strip-shaped and jointly surround to form a rectangular effective photosensitive area of the device. The aspect ratio range of the effective photosensitive area of the device is 1 to 1.

5.

6. The silicon carbide-based ultraviolet position-sensitive detector according to claim 3, characterized in that When the doping concentrations of the high-doped lower drift layer (3) and the high-doped upper drift layer (5) are greater than 1×10 18 cm -3 , the first ohmic contact electrode (6) is connected to the top of the high-doped lower drift layer (3), and the second ohmic contact electrode (7) is connected to the top of the high-doped upper drift layer (5).

7. The silicon carbide-based ultraviolet position-sensitive detector according to any one of claims 1 to 6, characterized in that, The electrical isolation layer (2) has a conductivity characteristic opposite to that of the highly doped bottom drift layer (3), and the doping concentration range of the electrical isolation layer (2) is 1×10 16 cm -3 to 1×10 21 cm -3 .

8. The silicon carbide-based ultraviolet position-sensitive detector according to any one of claims 1 to 6, characterized in that, The thickness range of the highly doped lower drift layer (3) is 0.2 - 10 μm, the thickness of the lowly doped middle drift layer (4) is greater than 1 μm, the thickness range of the highly doped upper drift layer (5) is 0.2 - 10 μm, and the thicknesses of the first ohmic contact electrode (6) and the second ohmic contact electrode (7) are greater than 0.5 μm.

9. The silicon carbide-based ultraviolet position-sensitive detector according to any one of claims 1 to 6, characterized in that, The materials of the first ohmic contact electrode (6) and the second ohmic contact electrode (7) are at least one of nickel, titanium, aluminum, or gold.

10. A preparation method for fabricating a silicon carbide-based ultraviolet position-sensitive detector as described in any one of claims 1 to 6, characterized in that, It includes: Step 1: Using the N-type silicon carbide substrate layer (1) as an epitaxial substrate, growing an electrical isolation layer (2), a highly doped lower drift layer (3), a lowly doped middle drift layer (4), and a highly doped upper drift layer (5) on it in sequence; Step 2: Evaporating a mask on the top of the highly doped upper drift layer (5) and etching down the highly doped upper drift layer (5) and the lowly doped middle drift layer (4) until the top of the highly doped lower drift layer (3) is exposed to form the first graphic area (3a); Step 3: Depositing SiO2 on the outer surfaces of the electrical isolation layer (2), the highly doped lower drift layer (3), the lowly doped middle drift layer (4), and the highly doped upper drift layer (5) to form a passivation layer (9), and etching and depositing the first ohmic contact electrode (6) and the second ohmic contact electrode (7) at the corresponding graphic windows on the tops of the highly doped lower drift layer (3) and the highly doped upper drift layer (5).

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