High-temperature pin ultraviolet detector and preparation method thereof

Abstract

The invention discloses a high-temperature pin ultraviolet detector, which belongs to the technical field of microelectronics and comprises a 4H-SiC substrate, a 4H-SiC epitaxial layer, a 4H-SiC absorption layer and a 4H-SiC contact layer which are stacked from bottom to top, the two sides of the 4H-SiC contact layer, the 4H-SiC absorption layer and the 4H-SiC epitaxial layer are etched to form inclined mesa structures; a plurality of inverted trapezoidal grooves are etched in the middle of the 4H-SiC contact layer; the whole upper surface of the device is covered with a passivation layer; the P-type ohmic contact metal and the N-type ohmic contact metal are respectively arranged on the lower table top and the upper table top of the inclined table top structure; a metal Pad is arranged above the P-type ohmic contact metal and the N-type ohmic contact metal; a diffusion barrier layer is arranged between the metal Pad and the P / N type ohmic contact metal. According to the structural design, the thermal stability of ohmic contact is improved, the service life of ohmic contact in a high-temperature environment is prolonged, and the device performance is improved.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a high-temperature PIN ultraviolet detector and a preparation method thereof. Background Art

[0002] UV detection is a common analytical technique used in many fields such as optical communications, flame detection, combustion monitoring, chemical analysis, astronomy, etc. Most of these applications require UV instruments that can operate in high temperature and harsh environments. In the past decade, wide bandgap semiconductors have become the most attractive materials in the field of optoelectronics. Their wide bandgap and inherent properties have promoted the development of reliable photodetectors that can selectively detect short wavelengths (i.e., ultraviolet, UV) in high temperature regions (up to 300°C).

[0003] The bandgap of 4H-SiC material is 3.26eV, which directly determines the high-temperature working ability of 4H-SiC devices. Compared with Si and GaAs, 4H-SiC has a wider bandgap, which makes the intrinsic carrier concentration of 4H-SiC lower. Low intrinsic carrier concentration means that 4H-SiC-based devices have lower leakage current when working in high-temperature environments. The maximum operating temperature of 4H-SiC can reach 1000℃.

[0004] Common UV detectors include photoconductive photodetectors, metal-semiconductor-metal photodetectors, Schottky, pn and pin junction photodetectors. Among them, pin is more suitable for high temperature applications due to its simple preparation process and low leakage current. The main driving force for the development of high temperature UV detection instruments is to conduct on-site monitoring of harsh environments and processes that generate UV signals in industrial, automotive, aerospace and energy production systems. Therefore, it is undoubtedly of great significance to study and design high-performance 4H-SiC high temperature UV detectors.

[0005] For device manufacturing, the preparation of ohmic contact is an essential key process. In high temperature environments (>450℃), the thermal stability of ohmic contact is very important, and its degradation will lead to the degradation of the performance of the entire device or even failure. For 4H-SiC devices working under high temperature extreme conditions, a high-temperature resistant ohmic contact is a must for actual devices. If the ohmic contact is not resistant to high temperatures or has poor thermal stability, the high-temperature characteristics of the 4H-SiC material will not be able to be brought into play.

[0006] The existing ohmic contacts mainly include Ni / SiC ohmic contacts, Pt / Ti / SiC ohmic contacts, etc. Among them, Ni / SiC ohmic contact technology is the most mature, and has been widely used in business due to its simple process and low specific contact resistance. High temperature treatment is an inevitable process for forming ohmic contacts, during which part of the C elements in SiC will diffuse into Ni. However, since the C elements diffused into Ni cannot combine with Ni and act as free C, this will bring difficulties to the subsequent wire bonding process. In addition, Ni / SiC ohmic contacts will degrade when working in a high-temperature environment for a long time. The reason why Pt / Ti / SiC ohmic contacts fail rapidly is the severe oxidation of Ti atoms at the metal / SiC interface. For high-temperature resistant devices, the high-temperature environment will cause the surface O atoms to diffuse rapidly toward SiC, causing ohmic contact degradation. Summary of the invention

[0007] In order to solve the problem of device failure caused by ohmic contact degradation at high temperature in the prior art, the present invention provides a high-temperature PIN ultraviolet detector and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0008] In a first aspect, the present invention provides a high-temperature pin ultraviolet detector, comprising a 4H-SiC substrate, a 4H-SiC epitaxial layer, a 4H-SiC absorption layer, a 4H-SiC contact layer, a passivation layer, a P-type ohmic contact metal, an N-type ohmic contact metal, a metal pad, and a diffusion barrier layer;

[0009] The 4H-SiC substrate, the 4H-SiC epitaxial layer, the 4H-SiC absorption layer and the 4H-SiC contact layer are stacked from bottom to top;

[0010] The 4H-SiC contact layer, the 4H-SiC absorption layer and both sides of the 4H-SiC epitaxial layer are etched to form an angled mesa structure; wherein the upper surface of the 4H-SiC contact layer forms an upper mesa of the angled mesa structure, and the sidewalls of the 4H-SiC contact layer, the sidewalls of the 4H-SiC absorption layer and part of the sidewalls of the 4H-SiC epitaxial layer together form inclined sidewalls of the angled mesa structure; the upper surfaces of both sides of the 4H-SiC epitaxial layer form lower mesas of the angled mesa structure;

[0011] A plurality of inverted trapezoidal grooves are etched in the middle of the 4H-SiC contact layer, and the plurality of inverted trapezoidal grooves extend downward from the upper surface of the 4H-SiC contact layer to the inside of the 4H-SiC contact layer;

[0012] The passivation layer covers the entire upper surface of the device;

[0013] The P-type ohmic contact metal is arranged on the lower mesa of the inclined mesa structure, including Ni / W / TaSi stacked in sequence. 2 / Ti / Pt;

[0014] The N-type ohmic contact metal is arranged on the upper mesa of the inclined mesa structure, including Ti / TaSi stacked in sequence. 2 / Ti / Pt;

[0015] The metal pad is arranged above the P-type ohmic contact metal and the N-type ohmic contact metal;

[0016] A diffusion barrier layer is further provided between the metal Pad and the P-type ohmic contact metal and between the metal Pad and the N-type ohmic contact metal. The diffusion barrier layer includes metal Ti / Pt.

[0017] In a second aspect, the present invention provides a method for preparing a high-temperature PIN ultraviolet detector, the preparation method comprising the following steps:

[0018] forming a 4H-SiC epitaxial layer, a 4H-SiC absorption layer and a 4H-SiC contact layer on a 4H-SiC substrate in sequence;

[0019] The 4H-SiC contact layer, the 4H-SiC absorption layer and the 4H-SiC epitaxial layer are etched to form a tilted mesa structure; wherein the upper surface of the 4H-SiC contact layer forms an upper mesa of the tilted mesa structure, and the sidewalls of the 4H-SiC contact layer, the sidewalls of the 4H-SiC absorption layer and part of the sidewalls of the 4H-SiC epitaxial layer together form inclined sidewalls of the tilted mesa structure; and the upper surfaces on both sides of the 4H-SiC epitaxial layer form a lower mesa of the tilted mesa structure;

[0020] Etching the middle position of the 4H-SiC contact layer to form a number of inverted trapezoidal grooves;

[0021] Formation of a passivation layer over the entire sample surface;

[0022] A P-type ohmic contact metal and an N-type ohmic contact metal are respectively prepared on the lower table and the upper table of the inclined table structure; wherein the P-type ohmic contact metal includes Ni / W / TaSi2 / Ti / Pt stacked in sequence, and the N-type ohmic contact metal includes Ti / TaSi stacked in sequence. 2 / Ti / Pt;

[0023] Forming a diffusion barrier layer on the P-type ohmic contact metal and the N-type ohmic contact metal; the diffusion barrier layer metal Ti / Pt;

[0024] A metal pad is formed on the diffusion barrier layer, thereby completing the device fabrication.

[0025] Beneficial effects of the present invention:

[0026] The high temperature PIN ultraviolet detector proposed by the present invention adopts N-type ohmic contact Ti / TaSi2 / Ti / Pt and P-type ohmic contacts Ni / W / TaSi 2 / Ti / Pt, and use Ti / Pt as a diffusion barrier layer; the diffusion barrier layer can effectively prevent the Au and O elements in the metal Pad from migrating into the epitaxial layer, significantly reducing the further diffusion of Au and O through the barrier, and TaSi 2 The layer can also effectively slow down the diffusion rate of O atoms toward SiC, further improving the thermal stability and life of the ohmic contact at high temperatures. At the same time, the introduction of metal Ni can reduce the annealing temperature required for the formation of P-type ohmic contacts. And metal W can combine with C to react with the free C generated by the Ni-based ohmic contact, so that the N-type and P-type specific contact resistances remain basically stable, thereby improving the thermal stability of the ohmic contact and its life in high temperature environments;

[0027] 2. The high-temperature PIN ultraviolet detector proposed in the present invention is designed with a trapezoidal groove structure, which can reduce light reflection while enabling the absorption zone i to absorb more photons, thereby improving the responsiveness of the photodetector and improving the detection rate and performance of the photodetector.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a high-temperature PIN ultraviolet detector provided by an embodiment of the present invention;

[0030] Figure 2 It is a schematic flow chart of a method for preparing a high-temperature PIN ultraviolet detector provided in an embodiment of the present invention;

[0031] Figures 3a-3k It is a schematic diagram of the preparation process of the high-temperature PIN ultraviolet detector provided by an embodiment of the present invention;

[0032] Description of reference numerals:

[0033] 1-4H-SiC substrate, 2-4H-SiC epitaxial layer, 3-4H-SiC absorption layer, 4-4H-SiC contact layer, 5-passivation layer, 6-P-type ohmic contact metal, 7-N-type ohmic contact metal, 8-metal pad, 9-diffusion barrier layer. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] For ohmic contact structures, high temperature environments can cause ohmic contact degradation, which in turn causes device aging. Analysis shows that at high temperatures, over time, ohmic contact degradation of 4H-SiC sensors and electronic devices is driven by two main failure mechanisms: 1. Au and O on the surface migrate to the ohmic contact / SiC interface, resulting in rectification. 2. Mixing between the metals of the diffusion barrier and the potential ohmic contact metallization leads to increased resistance. Degradation of ohmic contacts can lead to device failure.

[0036] Based on this, the first aspect of the present invention proposes a high temperature PIN ultraviolet detector. Figure 1 , Figure 1 1 is a schematic structural diagram of a high-temperature PIN ultraviolet detector provided in an embodiment of the present invention, the device comprises a 4H-SiC substrate 1, a 4H-SiC epitaxial layer 2, a 4H-SiC absorption layer 3, a 4H-SiC contact layer 4, a passivation layer 5, a P-type ohmic contact metal 6, an N-type ohmic contact metal 7, a metal Pad 8 and a diffusion barrier layer 9;

[0037] A 4H-SiC substrate 1, a 4H-SiC epitaxial layer 2, a 4H-SiC absorption layer 3 and a 4H-SiC contact layer 4 are stacked from bottom to top;

[0038] The 4H-SiC contact layer 4, the 4H-SiC absorption layer 3 and both sides of the 4H-SiC epitaxial layer 2 are etched to form an angled mesa structure; wherein the upper surface of the 4H-SiC contact layer 4 forms an upper mesa of the angled mesa structure, and the side walls of the 4H-SiC contact layer 4, the side walls of the 4H-SiC absorption layer 3 and part of the side walls of the 4H-SiC epitaxial layer 2 together form inclined side walls of the angled mesa structure; the upper surfaces of both sides of the 4H-SiC epitaxial layer 2 form lower mesas of the angled mesa structure;

[0039] A plurality of inverted trapezoidal grooves are etched in the middle of the 4H-SiC contact layer 4, and the plurality of inverted trapezoidal grooves extend downward from the upper surface of the 4H-SiC contact layer 4 to the inside of the 4H-SiC contact layer 4;

[0040] The passivation layer 5 covers the upper surface of the entire device;

[0041] The P-type ohmic contact metal 6 is arranged on the lower mesa of the inclined mesa structure, including Ni / W / TaSi stacked in sequence. 2 / Ti / Pt;

[0042] The N-type ohmic contact metal 7 is arranged on the upper mesa of the inclined mesa structure, and includes Ti / TaSi 2 / Ti / Pt;

[0043] The metal Pad 8 is disposed above the P-type ohmic contact metal 6 and the N-type ohmic contact metal 7;

[0044] A diffusion barrier layer 9 is further provided between the metal Pad 8 and the P-type ohmic contact metal 6 and between the metal Pad 8 and the N-type ohmic contact metal 7 . The diffusion barrier layer 9 includes metal Ti / Pt.

[0045] Specifically, in this embodiment, the 4H-SiC substrate 1 is n+ doped; the 4H-SiC epitaxial layer 2 is p+ doped, and the doping concentration is 5×10 18 -5.0×10 19 cm -3 , the doping element is Al; the 4H-SiC absorption layer 3 is n-doped, and the carrier concentration is 1.0×10 15 -1.0×10 16 cm -3 ; 4H-SiC contact layer 4 is n+ doped, with a carrier concentration of 5.0×10 18 -1.0×10 19 cm -3 .

[0046] Optionally, as an implementation, the thickness of the 4H-SiC substrate 1 may be 350 μm, the thickness may be 2 μm, the thickness of the 4H-SiC absorption layer 3 may be 1 μm, and the thickness of the 4H-SiC contact layer 4 may be 0.5 μm.

[0047] Furthermore, the depth of the inverted trapezoidal groove may be 0.2-0.4 μm, and the width may be 1-2 μm;

[0048] Optionally, the passivation layer 5 is made of SiO 2 / SiN x The composite layer has a thickness of 20-30nm.

[0049] Optionally, the material of metal Pad 8 is TaSi 2 / Pt / Au.

[0050] The high temperature PIN ultraviolet detector proposed in the present invention adopts N-type ohmic contact Ti / TaSi2 / Ti / Pt and P-type ohmic contact Ni / W / TaSi 2 / Ti / Pt, and use Ti / Pt as a diffusion barrier layer; the diffusion barrier layer can effectively prevent the Au and O elements in the metal Pad from migrating into the epitaxial layer, significantly reducing the further diffusion of Au and O through the barrier, and TaSi 2The layer can also effectively slow down the diffusion rate of O atoms toward SiC, further improving the thermal stability and life of the ohmic contact at high temperatures. At the same time, the introduction of metal Ni can reduce the annealing temperature required for the formation of P-type ohmic contacts. And metal W can combine with C to react with the free C generated by the Ni-based ohmic contact, so that the N-type and P-type specific contact resistances remain basically stable, thereby improving the thermal stability of the ohmic contact and its life in high temperature environments.

[0051] In addition, the high-temperature PIN ultraviolet detector proposed in the present invention is designed with a trapezoidal groove structure, which can reduce light reflection while enabling the absorption zone i to absorb more photons, thereby improving the responsiveness of the photodetector and improving the detection rate and performance of the photodetector.

[0052] The second aspect of the present invention also provides a method for preparing a high temperature PIN ultraviolet detector, see Figure 2 , Figure 2 1 is a flow chart of a method for preparing a high-temperature PIN ultraviolet detector provided by an embodiment of the present invention, the method specifically comprising the following steps:

[0053] Step 1: forming a 4H-SiC epitaxial layer, a 4H-SiC absorption layer and a 4H-SiC contact layer on a 4H-SiC substrate in sequence.

[0054] First, an n+ type 4H-SiC substrate with a thickness of 350 μm is provided;

[0055] Then, a p+ type 4H-SiC epitaxial layer with a thickness of 2 μm is epitaxially grown on the n+ type 4H-SiC substrate using a conventional CVD (Chemical Vapor Depositio) process;

[0056] Next, an n-type 4H-SiC absorption layer with a thickness of 1 μm is epitaxially grown on the p+ type 4H-SiC epitaxial layer using a CVD process;

[0057] Finally, an n+ type 4H-SiC contact layer with a thickness of 0.5 μm is epitaxially grown on the n-type 4H-SiC absorption layer using a CVD process.

[0058] Step 2: Etching the 4H-SiC contact layer, the 4H-SiC absorption layer and the 4H-SiC epitaxial layer to form a tilted mesa structure.

[0059] The upper surface of the 4H-SiC contact layer forms an upper mesa of the angled mesa structure, and the sidewalls of the 4H-SiC contact layer, the sidewalls of the 4H-SiC absorption layer, and part of the sidewalls of the 4H-SiC epitaxial layer together form inclined sidewalls of the angled mesa structure; the upper surfaces on both sides of the 4H-SiC epitaxial layer form a lower mesa of the angled mesa structure;

[0060] Step 3: Etch the middle position of the 4H-SiC contact layer to form a plurality of inverted trapezoidal grooves.

[0061] Step 4: forming a passivation layer on the entire sample surface.

[0062] Step 5, preparing a P-type ohmic contact metal and an N-type ohmic contact metal on the lower table and the upper table of the inclined table structure respectively;

[0063] Among them, the P-type ohmic contact metal includes Ni / W / TaSi stacked in sequence 2 / Ti / Pt, N-type ohmic contact metal includes Ti / TaSi stacked in sequence 2 / Ti / Pt;

[0064] Specifically, 100nm Ni, 30nm W, and 400nm TaSi can be grown on the lower table of the inclined table structure in sequence by using photolithography, etching, and magnetron sputtering processes. 2 , 100nm Ti, 300nm Pt, forming a P-type ohmic contact metal;

[0065] Accordingly, 100nm Ti, 300nm TaSi and 100nm TiO2 layers can be grown on the upper surface of the tilted table structure by photolithography, etching and magnetron sputtering. 2 , 100nm Ti, 300nm Pt, to form an N-type ohmic contact metal.

[0066] The preparation order of the P-type ohmic contact metal and the N-type ohmic contact metal can be interchanged.

[0067] Step 6: forming a diffusion barrier layer on the P-type ohmic contact metal and the N-type ohmic contact metal; the diffusion barrier layer metal is Ti / Pt.

[0068] Specifically, 100 nm Ti and 300 nm Pt are sequentially grown on the P-type ohmic contact metal and the N-type ohmic contact metal respectively by using magnetron sputtering technology to form a diffusion barrier layer.

[0069] Step 7: forming a metal pad on the diffusion barrier layer, thereby completing device preparation.

[0070] Specifically, 20 nm TaSi2, 100 nm Pt and 1 μm Au may be grown in sequence on the diffusion barrier layer to form a metal Pad.

[0071] The device preparation is now completed.

[0072] The following is a specific example, combined with Figures 3a-3kThe schematic diagram of the preparation process shown in FIG. 1 is a detailed introduction to the preparation process of the high-temperature PIN ultraviolet detector of the present invention.

[0073] S1, providing an n+ type 4H-SiC substrate 1 with a thickness of 350 μm, such as Figure 3a shown.

[0074] S2, epitaxially grow a p+ type 4H-SiC epitaxial layer 2 with a thickness of 2 μm on the n+ type 4H-SiC substrate 1 using a conventional CVD process, as shown in Figure 3b As shown. Among them, the doping concentration of the P+ type 4H-SiC epitaxial layer 2 is 5×10 18 -5.0×10 19 cm -3 , the doping element is Al element.

[0075] S3, epitaxially growing an n-type 4H-SiC absorption layer 3 with a thickness of 1 μm on the p+ type 4H-SiC epitaxial layer 2 by using a CVD process, such as Figure 3c As shown in Figure 2, the carrier concentration of the n-type 4H-SiC absorption layer 3 is 1.0×10 15 -1.0×10 16 cm -3 .

[0076] S4, epitaxially growing an n+ type 4H-SiC contact layer 4 with a thickness of 0.5 μm on the n- type 4H-SiC absorption layer 3 by using a CVD process, such as Figure 3d As shown. Among them, the carrier concentration of the n+ type 4H-SiC contact layer 4 is 5.0×10 18 -1.0×10 19 cm -3 .

[0077] S5. Using photoresist reflow technology and inductively coupled plasma etching (ICP) process, the tilted terrace structure of the device is etched, such as Figure 3e shown.

[0078] S6, etching the surface of the n+ type 4H-SiC contact layer 4 to form an inverted trapezoidal groove with a depth of 0.2-0.4 μm and a width of 1-2 μm, such as Figure 3f shown.

[0079] S7, Growth of SiO by Thermal Oxidation and PECVD 2 / SiN x The composite layer is used as the passivation layer 5, and the thickness of the passivation layer 5 is 20nm-30nm. Figure 3g shown.

[0080] S8, using photolithography, etching and magnetron sputtering processes, 100nmTi, 300nm TaSi are grown on the upper table of the inclined table structure in sequence 2 , 100nm Ti, 300nm Pt, and rapid thermal annealing at 800℃ vacuum for 10s to form N-type ohmic contact metal 7, such as Figure 3h shown.

[0081] S9, using photolithography, etching and magnetron sputtering processes, 100nmNi, 30nmW, 400nmTaSi are grown on the lower table of the inclined table structure in sequence 2 , 100nm Ti, 300nm Pt, and rapid thermal annealing at 800℃ in vacuum for 10s to form a P-type ohmic contact metal 6, such as Figure 3i shown.

[0082] S10, using magnetron sputtering technology to sequentially grow 100nm Ti and 300nm Pt on the P-type ohmic contact metal and the N-type ohmic contact metal, and perform rapid thermal annealing for 10s in a vacuum at 800°C to form a diffusion barrier layer 9, as shown in FIG. Figure 3j shown.

[0083] S11, using photolithography, electron beam evaporation process and etching process magnetron sputtering technology to grow 20nm TaSi on the diffusion barrier layer 2 , 100nm Pt and 1μm Au, and annealed in 700℃ Ar for 30 minutes to form metal Pad8, as shown in Figure 3k shown.

[0084] At this point, the preparation of the high-temperature pin ultraviolet detector has been completed. The n-type 4H-SiC ohmic contact Ti / TaSi 2 The diffusion barrier layers of Ti / Pt and Ti / Pt are very effective in preventing Au and O from migrating into the active epitaxial layer. Ni can reduce the annealing temperature required for the formation of P-type ohmic contacts, and the metal W can combine with C to react with the free C generated by the Ni-based ohmic contact, so that the 4H-SiC sensor and electronic device can work reliably for a certain period of time even at a high temperature of 800°C.

[0085] It should be noted that in the process of preparing high-temperature PIN ultraviolet detectors, the CVD process, photoresist reflow technology, inductively coupled plasma etching process, thermal oxidation process, photolithography, etching and magnetron sputtering process, annealing process, electron beam evaporation process, corrosion process, etc. involved are all existing mature process means. This embodiment only makes a brief description. The detailed implementation process can refer to the existing relevant technology implementation.

[0086] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0087] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0089] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0090] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A high temperature PIN ultraviolet detector, characterized in that: It comprises a 4H-SiC substrate (1), a 4H-SiC epitaxial layer (2), a 4H-SiC absorption layer (3), a 4H-SiC contact layer (4), a passivation layer (5), a P-type ohmic contact metal (6), an N-type ohmic contact metal (7), a metal pad (8) and a diffusion barrier layer (9); The 4H-SiC substrate (1), the 4H-SiC epitaxial layer (2), the 4H-SiC absorption layer (3) and the 4H-SiC contact layer (4) are stacked from bottom to top; The 4H-SiC contact layer (4), the 4H-SiC absorption layer (3) and both sides of the 4H-SiC epitaxial layer (2) are etched to form an angled mesa structure; wherein the upper surface of the 4H-SiC contact layer (4) forms an upper mesa of the angled mesa structure, and the side walls of the 4H-SiC contact layer (4), the side walls of the 4H-SiC absorption layer (3) and part of the side walls of the 4H-SiC epitaxial layer (2) together form inclined side walls of the angled mesa structure; and the upper surfaces of both sides of the 4H-SiC epitaxial layer (2) form a lower mesa of the angled mesa structure; A plurality of inverted trapezoidal grooves are etched in the middle of the 4H-SiC contact layer (4), and the plurality of inverted trapezoidal grooves extend downward from the upper surface of the 4H-SiC contact layer (4) to the interior of the 4H-SiC contact layer (4); The passivation layer (5) covers the upper surface of the entire device; The P-type ohmic contact metal (6) is arranged at the lower table of the tilted table structure, and comprises Ni / W / TaSi2 / Ti / Pt stacked in sequence; The N-type ohmic contact metal (7) is arranged on the upper table surface of the tilted table surface structure, and comprises Ti / TaSi2 / Ti / Pt stacked in sequence; The metal pad (8) is arranged above the P-type ohmic contact metal (6) and the N-type ohmic contact metal (7); A diffusion barrier layer (9) is also provided between the metal Pad (8) and the P-type ohmic contact metal (6), and between the metal Pad (8) and the N-type ohmic contact metal (7), and the diffusion barrier layer (9) comprises metal Ti / Pt.

2. A high temperature PIN ultraviolet detector according to claim 1, characterized in that: The 4H-SiC substrate (1) is n+ doped; The 4H-SiC epitaxial layer (2) is p+ doped, with a doping concentration of 5×10 18 -5.0×10 19 cm -3 , the doping element is Al element; The 4H-SiC absorption layer (3) is n-doped, and the carrier concentration is 1.0×10 15 -1.0×10 16 cm -3 ; The 4H-SiC contact layer (4) is n+ doped, with a carrier concentration of 5.0×10 18 -1.0×10 19 cm -3 .

3. A high temperature PIN ultraviolet detector according to claim 1, characterized in that: The inverted trapezoidal groove has a depth of 0.2-0.4 μm and a width of 1-2 μm.

4. A high temperature PIN ultraviolet detector according to claim 1, characterized in that: The passivation layer (5) is made of SiO2 / SiN x The composite layer has a thickness of 20-30nm.

5. A high temperature PIN ultraviolet detector according to claim 1, characterized in that: The material of the metal Pad (8) is TaSi2 / Pt / Au.

6. A method for preparing a high-temperature PIN ultraviolet detector, characterized in that: The preparation method comprises the following steps: forming a 4H-SiC epitaxial layer, a 4H-SiC absorption layer and a 4H-SiC contact layer on a 4H-SiC substrate in sequence; The 4H-SiC contact layer, the 4H-SiC absorption layer and the 4H-SiC epitaxial layer are etched to form a tilted mesa structure; wherein the upper surface of the 4H-SiC contact layer forms an upper mesa of the tilted mesa structure, and the sidewalls of the 4H-SiC contact layer, the sidewalls of the 4H-SiC absorption layer and part of the sidewalls of the 4H-SiC epitaxial layer together form inclined sidewalls of the tilted mesa structure; the upper surfaces on both sides of the 4H-SiC epitaxial layer form a lower mesa of the tilted mesa structure; Etching the middle position of the 4H-SiC contact layer to form a plurality of inverted trapezoidal grooves; Formation of a passivation layer over the entire sample surface; A P-type ohmic contact metal and an N-type ohmic contact metal are respectively prepared on the lower mesa and the upper mesa of the tilted mesa structure; wherein the P-type ohmic contact metal comprises Ni / W / TaSi2 / Ti / Pt stacked in sequence, and the N-type ohmic contact metal comprises Ti / TaSi2 / Ti / Pt stacked in sequence; Forming a diffusion barrier layer on the P-type ohmic contact metal and the N-type ohmic contact metal; the diffusion barrier layer metal is Ti / Pt; A metal Pad is formed on the diffusion barrier layer, thereby completing device preparation.

7. The method for preparing a high-temperature PIN ultraviolet detector according to claim 6, characterized in that: A 4H-SiC epitaxial layer, a 4H-SiC absorption layer and a 4H-SiC contact layer are sequentially formed on a 4H-SiC substrate, specifically comprising: Providing an n+ type 4H-SiC substrate with a thickness of 350 μm; epitaxially growing a p+ type 4H-SiC epitaxial layer with a thickness of 2 μm on the n+ type 4H-SiC substrate using a conventional CVD process; epitaxially growing an n-type 4H-SiC absorption layer with a thickness of 1 μm on the p+ type 4H-SiC epitaxial layer using a CVD process; An n+ type 4H-SiC contact layer with a thickness of 0.5 μm is epitaxially grown on the n-type 4H-SiC absorption layer by using a CVD process.

8. The method for preparing a high temperature PIN ultraviolet detector according to claim 6, characterized in that: The step of preparing a P-type ohmic contact metal and an N-type ohmic contact metal on the lower mesa and the upper mesa of the tilted mesa structure respectively includes: By using photolithography, etching and magnetron sputtering processes, 100nm Ni, 30nm W, 400nm TaSi2, 100nm Ti and 300nm Pt are sequentially grown on the lower table of the tilted table structure to form a P-type ohmic contact metal; By using photolithography, etching and magnetron sputtering processes, 100nm Ti, 300nm TaSi2, 100nm Ti and 300nm Pt are grown in sequence on the upper table surface of the tilted table structure to form an N-type ohmic contact metal.

9. The method for preparing a high-temperature PIN ultraviolet detector according to claim 6, characterized in that: Forming a diffusion barrier layer on the P-type ohmic contact metal and the N-type ohmic contact metal; comprising: 100 nm Ti and 300 nm Pt are grown sequentially on the P-type ohmic contact metal and the N-type ohmic contact metal respectively by using magnetron sputtering technology to form diffusion barrier layers.

10. The method for preparing a high temperature PIN ultraviolet detector according to claim 6, characterized in that: Forming a metal Pad on the diffusion barrier layer specifically includes: 20 nm TaSi2, 100 nm Pt and 1 μm Au are sequentially grown on the diffusion barrier layer to form a metal Pad.

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