Silicon carbide-based ultraviolet position sensitive detector and preparation method thereof

Abstract

The invention provides a silicon carbide-based ultraviolet position sensitive detector and a preparation method thereof, and belongs to the technical field of position detectors. Comprising an N-type silicon carbide substrate layer, an electrical isolation layer, a high-doping lower drift layer, a low-doping middle drift layer and a high-doping upper drift layer which are arranged from bottom to top, the high-doping lower drift layer is provided with a first pattern region, and the low-doping middle drift layer and the high-doping upper drift layer are located in the first pattern region; first ohmic contact electrodes are arranged on the two opposite sides of the first pattern area in the first direction respectively, two second ohmic contact electrodes are arranged on the top of the highly-doped upper drift layer in a spaced mode in the second direction, the second direction is perpendicular to the first direction, and the conductive characteristics of the highly-doped lower drift layer and the highly-doped upper drift layer are opposite. The technical problems of large detection structure position error and non-ideal measurement precision caused by device structure defects of an ultraviolet position sensitive detector in the prior art can be solved.

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 photoelectric 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, a 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 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 Embodiments of the present invention provide a silicon carbide-based ultraviolet position-sensitive detector and a preparation method thereof. It can solve the technical problems of large position error in the detection structure and unsatisfactory measurement accuracy of the ultraviolet PSD in the prior art due to the device structure defect. The technical solution is as follows: In a first aspect, an embodiment of the present invention provides a silicon carbide-based ultraviolet position-sensitive detector, including 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.

[0005] 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.

[0006] 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 .

[0007] 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.

[0008] Optionally, the ohmic contact area layers under 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.

[0009] 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.

[0010] 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 。

[0011] 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.

[0012] 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.

[0013] 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: 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; 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; Step 3: Deposit SiO 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 2 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.

[0014] The beneficial effects brought by the technical solution provided by the embodiment of the present invention at least include: 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, 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 photo-generated electrons and holes to move in the highly doped upper drift layer and the highly doped lower drift layer respectively under light illumination, reducing the interference between the lateral and longitudinal carrier migrations and the electric field, which helps to improve the linearity of the relationship between the magnitude of the current collected by the electrode structure and the distance from the light illumination point, reduces the mutual interference between the 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 the device structure defects in the existing ultraviolet PSD technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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 be obtained based on these drawings.

[0016] 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 lowly 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; Figure 2 It is a schematic diagram of the steps for etching to form the lowly 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; 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; Figure 4 It is in Figure 3 The schematic diagram of the step of depositing a passivation layer on the device; Figure 5 It is actually in Figure 4 The schematic diagram of the steps for etching and depositing the first ohmic contact electrode and the second ohmic contact electrode on the device; Figure 6 It is a three-dimensional structure schematic diagram of a silicon carbide-based ultraviolet position-sensitive detector provided by the embodiments of the present invention; Figure 7 is Figure 6 The top - view structural schematic diagram of the structure in Figure 8 is Figure 6 The front - view structural schematic diagram of the structure in Figure 9 is Figure 6 The left - view structural schematic diagram of the structure in Figure 10 The three - dimensional structural schematic diagram of another silicon carbide - based ultraviolet position - sensitive detector provided in the embodiment of the present invention; Figure 11 is Figure 10 The top - view structural schematic diagram of the structure in Figure 12 is Figure 10 The left - view structural schematic diagram of the structure in Figure 13 The flowchart of the preparation method provided in the embodiment of the present invention.

[0017] In the figure: 1 - N - type silicon carbide substrate layer; 2 - electrical isolation layer; 2a - second pattern region; 3 - highly doped lower drift layer; 3a - first pattern region; 4 - low - doped middle drift layer; 5 - highly doped upper drift layer; 6 - first ohmic contact electrode; 7 - second ohmic contact electrode; 8 - ohmic contact region layer; 9 - passivation layer. Detailed implementation manners 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.

[0018] Figure 1 The step schematic diagram of growing the N - type silicon carbide substrate layer, electrical isolation layer, highly doped lower drift layer, low - doped middle drift layer and highly doped upper drift layer of the silicon carbide - based ultraviolet position - sensitive detector provided in the embodiment of the present invention; Figure 2 The step schematic diagram of etching to form the low - doped middle drift layer and highly doped upper drift layer in the first pattern region of the silicon carbide - based ultraviolet position - sensitive detector provided in the embodiment of the present invention; Figure 3 The step schematic diagram of etching to form the highly doped lower drift layer in the second pattern region of the silicon carbide - based ultraviolet position - sensitive detector provided in the embodiment of the present invention; Figure 4 is Figure 3 The step schematic diagram of depositing the passivation layer on the device in Figure 5 is actually Figure 4 The step schematic diagram of etching and depositing the first ohmic contact electrode and the second ohmic contact electrode on the device in Figure 6 The three - dimensional structural schematic diagram of a silicon carbide - based ultraviolet position - sensitive detector provided in the embodiment of the present invention; Figure 7 is Figure 6 The top - view structural schematic diagram of the structure inFigure 8 is Figure 6 a front view structural schematic diagram of the structure in Figure 9 is Figure 6 a left view structural schematic diagram of the structure in Figure 10 is a three - dimensional structural schematic diagram of another silicon carbide - based ultraviolet position - sensitive detector provided in an embodiment of the present invention; Figure 11 is Figure 10 a top view structural schematic diagram of the structure in Figure 12 is Figure 10 a left view structural schematic diagram of the structure in

[0019] As Figures 1 to 12 shown, based on the above - mentioned 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 region 3a. The low - doped middle drift layer 4 and the highly doped upper drift layer 5 are located in the first graphic region 3a. First ohmic contact electrodes 6 are respectively arranged on opposite sides of the first graphic region 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.

[0020] In an 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 successively grown thereon. Exemplarily, in an embodiment of the present invention, the electrical isolation layer 2 is an N - type doped silicon nitride layer with a thickness of 0.5μm 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 1μm 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 2μm 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 400nm and a doping concentration of 2.5×10 18 cm -3。In this embodiment, the electrical isolation layer 2 is N-type. Under high doping, the drift layer 3 and the high-doped upper drift layer 5 have P-type and N-type conductive characteristics respectively. The high-doped lower drift layer 3 is P-type doped by epitaxial growth. The high-doped upper drift layer 5 can be N-type doped by epitaxial growth or by ion implantation.

[0021] In another possible implementation manner of the embodiment of the present invention, if the electrical isolation layer 2 is P-type, the high-doped lower drift layer 3 and the high-doped upper drift layer 5 can also have N-type and P-type conductive characteristics respectively. Among them, the high-doped lower drift layer 3 is N-type doped by epitaxial growth, and the high-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 high-doped lower drift layer 3 and the high-doped upper drift layer 5 are opposite.

[0022] Further, referring to Figure 2 , on the top of the device, that is, above the high-doped upper drift layer 5, an Ni metal layer is deposited by evaporation as a mask. Then, an inductively coupled plasma etching (ICP) method is used to etch the high-doped upper drift layer 5 and the low-doped middle drift layer 4 downward 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. The etching depth from the high-doped upper drift layer 5 downward is 2.5 μm. After the high-doped lower drift layer 3 is exposed, the metal mask is removed. The use of an evaporated metal mask as a pre-etching process is considered because silicon carbide materials are 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.

[0023] Further, 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 continuous growth structure, while the area above for detecting the position of the incident light spot is an independent specific area. Therefore, after the previous step, a layer of photoresist is uniformly spin-coated on the high-doped lower drift layer 3 surrounding the first graphic area 3a. After exposure, development, and post-baking, a thick dry-etch photoresist mask is formed. Then, the inductively coupled plasma etching method is also used to etch the high-doped lower drift layer 3 downward 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, and then the photoresist is removed, forming the second stepped structure of the entire device. Referring to Figure 7 or Figure 11, at this time, an overall "hui"-shaped stepped structure is formed above the N-type silicon carbide substrate layer 1 of the device. That is, from the top-down view direction, the high-doped upper drift layer 5 is located in the inner "square" area of the "hui"-shaped area, and the exposed high-doped lower drift layer 3 is located in the area between the inner "square" and the outer "square" of the "hui"-shaped area, while the exposed electrical isolation layer 2 is located outside the outer "square" area of the "hui"-shaped area.

[0024] Further, referring to Figure 4 , after forming a thin sacrificial oxide layer over the entire device through wet and dry oxidation, it is removed with HF solution to repair the damage caused by etching in the previous step. Then, a 10-nm high-quality SiO 2 layer is grown on the surface through high-temperature oxidation, and then 200 nm of SiO 2 is deposited using plasma-enhanced chemical vapor deposition (PECVD) to form the passivation layer 9.

[0025] Further, referring to Figures 6 to 9 , in a possible implementation manner of the embodiment of the present invention, 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 , in order to ensure sufficient conductivity between the high-doped upper drift layer 5 and the high-doped lower drift layer 3 and the electrodes provided above them for receiving carriers, it is necessary to etch the passivation layer 9 above the graphic windows corresponding to the electrodes provided on the high-doped upper drift layer 5 and the high-doped lower drift layer 3, and a pair of mutually parallel long-strip-shaped ohmic contact region layers 8 are formed by ion implantation from the edge. The doping concentration of the long-strip-shaped ohmic region layer 8 needs to be higher than the doping concentrations of the corresponding high-doped upper drift layer 5 and high-doped lower drift layer 3 below, to ensure good ohmic contact between the high-doped upper drift layer 5 and the high-doped lower drift layer 3 and the upper electrodes. Then, along the extending direction of the long-strip-shaped ohmic contact region layer 8, a Ni / Ti / Al / Au metal layer is deposited on the two long-strip-shaped ohmic contact region layers 8 of the high-doped lower drift layer 3, the excess metal is stripped, and high-temperature annealing of the electrodes is performed to form good ohmic contact, and finally two first ohmic contact electrodes 6 arranged in parallel at intervals are formed. Correspondingly, along the extending direction of the long-strip-shaped ohmic contact region layer 8, two second ohmic contact electrodes 7 arranged in parallel at intervals are formed on the two long-strip-shaped ohmic contact region layers 8 of the high-doped upper drift layer 5 using the same process, and the overall fabrication of the silicon carbide-based ultraviolet position-sensitive detector is completed.

[0026] Exemplarily, in an 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 used to receive 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 both strip-shaped. The two ohmic contact region layers 8 on the highly doped upper drift layer 5 and the two ohmic contact region layers 8 on the highly doped lower drift layer 3 are perpendicular to each other. 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, in 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. Exemplarily, in an embodiment of the present invention, the aspect ratio range of the effective photosensitive region layer of the device is 1 to 1.5. This aspect ratio range is determined by comprehensively considering the difficulty of device preparation and the position coordinate distribution of the incident light spot for conventional demand detection. Through experiments, relatively accurate and sensitive measurement results can be obtained within this range. The actual aspect ratio in the embodiment of the present invention is not limited.

[0027] Further, referring to Figure 5 、 Figures 10 to 12 , 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 1×10 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, the method of directly depositing strip-shaped metal electrodes is adopted. After forming the electrode region through photoresist coating, exposure, and development, and 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.

[0028] 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, 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 generated photoelectrons and holes 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 linear degree of the relationship between the magnitude of the current collected by 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 the device structure defects in the prior art ultraviolet PSD.

[0029] Figure 13 It is a flowchart of the preparation method provided by the embodiments of the present invention. As Figure 13 shown, the embodiments of the present invention also provide a preparation method for fabricating the silicon carbide-based ultraviolet position-sensitive detector as Figures 1 to 12 shown, and this method includes the following steps: 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 thereon.

[0030] 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 its doping concentration is 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 the doping concentration is 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 the doping concentration is 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 the doping concentration is 2.5×10 18 cm -3 .

[0031] S2: Evaporate a mask on the top of the highly doped upper drift layer 5, and etch downward the highly doped upper drift layer 5 and the low-doped middle drift layer 4 until the top of the highly doped lower drift layer 3 is exposed to form a first graphic area 3a.

[0032] Specifically, in this step, on top of the device, that is, above the highly doped upper drift layer 5, an Ni metal layer is deposited by evaporation as a mask. Then, an inductively coupled plasma etching (ICP) method is used to etch downward the highly doped upper drift layer 5 and the lightly doped middle drift layer 4 until the top of the highly doped lower drift layer 3 is exposed, so as to form a first patterned area 3a on the highly doped lower drift layer 3. Only the highly doped upper drift layer 5 and the lightly doped middle drift layer 4 within the first patterned area 3a are retained, forming a first stepped structure with the underlying highly doped lower drift layer 3.

[0033] Further, after the above operations, a layer of photoresist is spin-coated uniformly on the highly doped lower drift layer 3 surrounding the first patterned 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 highly 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 patterned area 2a on the electrical isolation layer 2. Then the photoresist is removed to form the second stepped structure of the entire device.

[0034] S3: Deposit SiO on the outer surfaces of the electrical isolation layer 2, the highly doped lower drift layer 3, the lightly doped middle drift layer 4, and the highly doped upper drift layer 5 2 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 patterned windows on the tops of the highly doped lower drift layer 3 and the highly doped upper drift layer 5.

[0035] Specifically, in this step, after forming a thin sacrificial oxide layer above 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 steps. Then, a high-quality 10-nm-thick SiO layer is grown by high-temperature oxidation on the surface, and then 200 nm of SiO is deposited using plasma-enhanced chemical vapor deposition (PECVD) 2 to form the passivation layer 9. 2

[0036] 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 , and 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 an ohmic contact region layer 8. Instead, by directly depositing a strip-shaped metal electrode, an electrode area is formed through photoresist coating, exposure, and development. After etching away the passivation layer 9 at the corresponding patterned 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. ​

[0037] The silicon carbide-based ultraviolet position-sensitive detector provided by the embodiment of the present invention prepared by the above preparation method uses wide-bandgap semiconductor material silicon carbide as the main body of the device for the migration of carriers after receiving light irradiation, and 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 current collected by the electrode structure and the distance from the light-irradiated 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. Thereby solving the technical problems of large detection structure position errors and unsatisfactory measurement accuracy caused by device structure defects in the prior art for ultraviolet PSDs.

[0038] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second" and similar terms used in the specification and claims of this invention patent application do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "an" do not denote a quantity limitation, but mean that there is at least one. The terms "comprising" or "including" and similar words 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. The terms "connected" or "coupled" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" etc. are only used to indicate relative position relationships, and when the absolute position of the object being described changes, the relative position relationships may also change accordingly.

[0039] The above are only optional embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles 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: The invention comprises 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, wherein the highly doped lower drift layer (3) has a first graphic region (3a), the low doped middle drift layer (4) and the highly doped upper drift layer (5) are located in the first graphic region (3a), first ohmic contact electrodes (6) are respectively arranged on opposite sides of the first graphic region (3a) in a first direction, two second ohmic contact electrodes (7) are arranged at intervals on the top of the highly doped upper drift layer (5) along a second direction, the second direction being perpendicular to the first direction, and the highly doped lower drift layer (3) and the highly doped upper drift layer (5) have opposite conductive properties.

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

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

4. The silicon carbide-based ultraviolet position sensitive detector according to claim 3, characterized in that: When the doping concentration of the highly doped lower drift layer (3) and the highly doped upper drift layer (5) is less than or equal to 1×10 18 cm -3 When the first ohmic contact electrode (6) and the highly doped lower drift layer (3) are connected, an ohmic contact region layer (8) is provided between the second ohmic contact electrode (7) and the highly doped upper drift layer (5), and the two are connected via 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 region layers (8) below the two first ohmic contact electrodes (6) and the two second ohmic contact electrodes (7) are both in the shape of long strips, and together surround a rectangular device effective photosensitive region, wherein the aspect ratio of the device effective photosensitive region is in the range of 1 to 1.

5.

6. The silicon carbide-based ultraviolet position sensitive detector according to claim 3, characterized in that: When the doping concentration of the highly doped lower drift layer (3) and the highly doped upper drift layer (5) is greater than 1×10 18 cm -3 When the first ohmic contact electrode (6) is connected to the top of the highly doped lower drift layer (3), the second ohmic contact electrode (7) is connected to the top of the highly 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 opposite conductive properties to the highly doped lower drift layer (3), and the doping concentration of the electrical isolation layer (2) is in the range of 1×10 16 cm -3 Up 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 of the highly doped lower drift layer (3) is in the range of 0.2-10 μm, the thickness of the low doped middle drift layer (4) is greater than 1 μm, the thickness of the highly doped upper drift layer (5) is in the range of 0.2-10 μm, and the thickness of the first ohmic contact electrode (6) and the second ohmic contact electrode (7) is 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 material of the first ohmic contact electrode (6) and the second ohmic contact electrode (7) is at least one of nickel, titanium, aluminum or gold.

10. A preparation method for manufacturing the silicon carbide-based ultraviolet position sensitive detector according to any one of claims 1 to 6, characterized in that: include: Step 1: using the N-type silicon carbide substrate layer (1) as an epitaxial substrate, and sequentially growing thereon 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); Step 2: evaporating a mask on the top of the highly doped upper drift layer (5), and etching downwards the highly doped upper drift layer (5) and the low doped middle drift layer (4) until the top of the highly doped lower drift layer (3) is exposed, so as to form the first pattern region (3a); Step 3: depositing SiO2 on the outer surfaces of 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) to form a passivation layer (9), and etching and depositing the first ohmic contact electrode (6) and the second ohmic contact electrode (7) at corresponding pattern windows on the top of the highly doped lower drift layer (3) and the highly doped upper drift layer (5).

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