SiC-based ultraviolet photodiode with self-anti-reflection structure and preparation method of SiC-based ultraviolet photodiode

Abstract

The invention discloses a self-anti-reflection structure SiC-based ultraviolet photodiode and a preparation method thereof, and relates to the technical field of semiconductors, and the self-anti-reflection structure SiC-based ultraviolet photodiode comprises a cathode, an ohmic contact layer, a substrate, an epitaxial layer and a passivation layer which are stacked in sequence; the isolation layer comprises a plurality of isolation units arranged on the upper surface of the passivation layer in an array mode, and the isolation units are in a bulge shape; the Schottky contact layer is located on the upper surface of the passivation layer and located between the adjacent isolation units; the anode is located on the upper surface of the Schottky contact layer; and the protection layer is positioned on the upper surface of a part of the anode and the upper surface of the exposed isolation unit. The photoelectric detection performance of the device can be improved.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a SiC-based ultraviolet photodiode with a self-antireflection structure and a preparation method thereof. Background Art

[0002] Wide bandgap semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN), diamond (C), etc., due to their wide band gap, can detect ultraviolet light in the 200-380nm band under strong visible and infrared backgrounds. They are also resistant to high temperatures, highly efficient, and highly reliable, making them ideal materials for preparing ultraviolet photodetectors. As a new type of third-generation semiconductor material, silicon carbide (SiC) has excellent properties such as large bandgap, high electron drift velocity, high critical breakdown field strength, high thermal conductivity, and high chemical stability, which makes SiC materials have great application potential in high temperature, high power, optoelectronics, and radiation resistance.

[0003] As an important semiconductor optoelectronic device, the improvement of light utilization will greatly improve the working performance of the device. For this reason, various anti-reflection and anti-reflection films are used in optoelectronic semiconductor devices. Limited by the limitations of materials, equipment, and semiconductor processes, traditional anti-reflection and anti-reflection film designs mostly use planar structure films, and use film thickness to control the anti-reflection effect, while assisting with transparent electrodes and mirror reflection layers to reuse light energy; however, the growth cycle of anti-reflection and anti-reflection films is long, the quality improvement results are limited, and additional optical management-related processes will bring additional costs.

[0004] Therefore, it is urgent to provide a photodiode to improve the defect that it is difficult to generate an anti-reflection and anti-reflection film from a material perspective. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a self-antireflective SiC-based ultraviolet photodiode and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a self-antireflective SiC-based ultraviolet photodiode, comprising:

[0007] A cathode, an ohmic contact layer, a substrate, an epitaxial layer and a passivation layer are sequentially stacked;

[0008] An isolation layer, comprising a plurality of isolation units arranged in an array on the upper surface of the passivation layer, the isolation units being in a bulge shape;

[0009] A Schottky contact layer is located on the upper surface of the passivation layer and between adjacent isolation units;

[0010] an anode, located on the upper surface of the Schottky contact layer;

[0011] The protection layer is located on the upper surface of a portion of the anode and on the upper surface of the exposed isolation unit.

[0012] In a second aspect, the present invention further provides a method for preparing a SiC-based ultraviolet photodiode with a self-antireflection structure, which is used to prepare the SiC-based ultraviolet photodiode with a self-antireflection structure provided above, comprising:

[0013] providing a substrate;

[0014] growing an epitaxial layer on the upper surface of the substrate;

[0015] Treating the upper surface of the epitaxial layer using plasma to obtain a passivation layer;

[0016] Depositing an isolation layer on the upper surface of the passivation layer, and opening windows in the isolation layer to obtain a plurality of rectangular structures arranged in arrays on the upper surface of the passivation layer;

[0017] Depositing a first metal on the exposed surface of the rectangular structure and the passivation layer, and depositing a second metal on the surface of the substrate away from the epitaxial layer;

[0018] Annealing the first metal and the second metal so that the first metal forms a Schottky contact layer and the second metal forms an ohmic contact layer, so that the rectangular structure is reflowed to form an isolation unit, and the isolation unit presents a bulge shape; using a ratio liquid to make the ohmic contact layer transparent, and at the same time cleaning the first metal remaining on the isolation unit;

[0019] Depositing a third metal on the exposed upper surface of the Schottky contact layer and the isolation unit, and removing part of the third metal on the upper surface of the isolation unit, so that the remaining third metal on the upper surface of the Schottky contact layer forms an anode;

[0020] Depositing a protective layer on the exposed upper surfaces of the anode and the isolation unit;

[0021] A fourth metal is deposited on the surface of the ohmic contact layer facing away from the substrate to form a cathode.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides a self-antireflection structure SiC-based ultraviolet photodiode and a preparation method thereof, which can simultaneously form a Schottky contact and an ohmic contact; in addition, the isolation unit arranged in the isolation layer has a good light antireflection and anti-transmission function, which is beneficial to improving the photoelectric detection performance of the device.

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1Schematic diagram of a SiC-based ultraviolet photodiode with a self-antireflection structure provided by an embodiment of the present invention;

[0026] Figure 2 It is a flow chart of a method for preparing a SiC-based ultraviolet photodiode with a self-antireflection structure provided by an embodiment of the present invention;

[0027] Figures 3a to 3i It is a schematic diagram of a method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0029] See also Figure 1 , Figure 1 Schematic diagram of a SiC-based ultraviolet photodiode with a self-antireflection structure provided by an embodiment of the present invention. The SiC-based ultraviolet photodiode with a self-antireflection structure provided by the present invention includes:

[0030] A cathode 9, an ohmic contact layer 6, a substrate 1, an epitaxial layer 2 and a passivation layer 3 are stacked in sequence;

[0031] An isolation layer, comprising a plurality of isolation units 4 arranged in an array on the upper surface of the passivation layer 3, wherein the isolation units 4 are in a bulge shape;

[0032] The Schottky contact layer 5 is located on the upper surface of the passivation layer 3 and between adjacent isolation units 4;

[0033] an anode 7, located on the upper surface of the Schottky contact layer 5;

[0034] The protection layer 8 is located on the upper surface of a portion of the anode 7 and on the upper surface of the exposed isolation unit 4 .

[0035] For more details, please see Figure 1 The device provided in this embodiment can form a Schottky contact and an Ohmic contact at the same time; in addition, the isolation unit 4 provided in the isolation layer has a good light anti-reflection and anti-transmission function, which is beneficial to improving the photoelectric detection performance of the device.

[0036] In an optional embodiment of the present invention, the material of the isolation unit 4 includes alkaline earth doped silicon oxide.

[0037] Specifically, in this embodiment, the isolation unit 4 uses alkaline earth-doped silicon oxide, so that when realizing the device structure, a one-step annealing process and a liquid corrosion process can be used to realize Schottky contact and ohmic contact. At the same time, the matrix structure is annealed and reflowed to form a bulge-shaped array, thereby obtaining a light reduction and anti-reflection enhancement function, thereby improving the photoelectric detection performance of the device.

[0038] In an optional embodiment of the present invention, the distance between adjacent isolation units 4 is 500-800 nm;

[0039] Optionally, the distance between adjacent isolation units 4 is 600 nm or 700 nm.

[0040] In an optional embodiment of the present invention, the protective layer 8 comprises a SiyNx anti-reflective surface.

[0041] Based on the same inventive concept, see Figure 2 , Figure 2 1 is a flow chart of a method for preparing a SiC-based ultraviolet photodiode with a self-antireflection structure provided by an embodiment of the present invention. The present invention also provides a method for preparing a SiC-based ultraviolet photodiode with a self-antireflection structure, which is used to prepare the SiC-based ultraviolet photodiode with a self-antireflection structure provided by the above embodiment of the present invention. The embodiment of the diode is referred to above and will not be described in detail here. The preparation method comprises:

[0042] S101, providing a substrate 1;

[0043] S102, growing an epitaxial layer 2 on the upper surface of the substrate 1;

[0044] S103, treating the upper surface of the epitaxial layer 2 with plasma to obtain a passivation layer 3;

[0045] Specifically, the upper surface of the epitaxial layer 2 is treated with oxygen or oxygen-hydrogen mixed plasma to obtain the passivation layer 3 .

[0046] S104, depositing an isolation layer on the upper surface of the passivation layer 3, and opening windows in the isolation layer to obtain a plurality of rectangular structures arranged in an array on the upper surface of the passivation layer 3;

[0047] Specifically, the isolation layer is opened with windows by using photolithography and etching processes to obtain a rectangular structure; wherein the spacing between adjacent rectangular structures is 500-800 nm, and the width of the windows is 500-800 nm.

[0048] S105, depositing a first metal on the exposed surfaces of the rectangular structure and the passivation layer 3, and depositing a second metal on the surface of the substrate 1 facing away from the epitaxial layer 2;

[0049] Specifically, electron beam evaporation or magnetron sputtering is used to deposit tungsten metal on the exposed surface of the rectangular structure and the passivation layer 3, and nickel metal is deposited on the surface of the substrate 1 away from the epitaxial layer 2; wherein the thickness of the tungsten metal and the nickel metal is 60-70 nm.

[0050] S106, annealing the first metal and the second metal so that the first metal forms a Schottky contact layer 5 and the second metal forms an ohmic contact layer 6, so that the rectangular structure is reflowed to form an isolation unit 4, and the isolation unit 4 is in a bulge shape; using a ratio liquid to make the ohmic contact layer 6 transparent, and at the same time, cleaning the first metal remaining on the isolation unit 4;

[0051] Specifically, the first metal and the second metal are annealed using a rapid thermal annealing process, and the annealing conditions include an inert gas atmosphere, a temperature of 900 to 1100° C., and an annealing time of 160 to 190 seconds.

[0052] Specifically, the mixed solution includes nitric acid, buffered oxide etching solution and deionized water, and the volume ratio of nitric acid, buffered oxide etching solution and deionized water is 1:1:5.

[0053] Compared with the traditional device preparation method, in this embodiment, alkaline earth-doped silicon oxide is used as the material of the isolation unit 4, so that after a one-step annealing process and a ratio liquid cleaning process, the functions of the contact image mask located on the rectangular structure, the rectangular structure reflow to form the isolation unit 4 (passivation isolation), and the optical management structure can be simultaneously realized, which greatly simplifies the process, and all processes are standard processes with strong universality.

[0054] S107, depositing a third metal on the exposed upper surface of the Schottky contact layer 5 and the isolation unit 4, and removing part of the third metal on the upper surface of the isolation unit 4, and the remaining third metal on the upper surface of the Schottky contact layer 5 forms the anode 7;

[0055] S108, depositing a protective layer 8 on the exposed upper surfaces of the anode 7 and the isolation unit 4;

[0056] S109 , depositing a fourth metal on the surface of the ohmic contact layer 6 facing away from the substrate 1 to form a cathode 9 .

[0057] In an optional embodiment of the present invention, the preparation of the SiC-based ultraviolet photodiode with a self-antireflective structure is achieved by the following process, specifically:

[0058] S1. Provide a substrate 1.

[0059] Specifically, the substrate 1 is an n+ type SiC substrate 1, the thickness of the substrate 1 is 350 μm, and the doping concentration of the substrate 1 is 5e18 cm -3 .

[0060] S2, preparing epitaxial layer 2, such as Figure 3a shown.

[0061] Specifically, an epitaxial layer 2 is generated on the upper surface of the substrate 1. The epitaxial layer 2 is an n-type epitaxial layer 2 with a thickness of 1.5 to 2 μm and a doping concentration of 1e16 to 2e16 cm -3 .

[0062] S3, prepare a passivation layer 3, such as Figure 3b shown.

[0063] Specifically, the surface of the n-type SiC epitaxial layer 2 is treated with oxygen or oxygen-hydrogen mixed plasma to form the passivation layer 3; the upper surface of the epitaxial layer 2 is treated with plasma to reduce the surface state and dangling bonds of the n-type SiC epitaxial layer 2.

[0064] Optionally, the thickness of the passivation layer 3 is about 5 nm.

[0065] S4, prepare an isolation layer, such as Figure 3c shown.

[0066] Specifically, an alkaline earth doped silicon oxide passivation isolation layer is deposited on the upper surface of the passivation layer 3 using a low pressure chemical vapor deposition (LPCVD) process, and the isolation layer also plays a role in passivation protection.

[0067] Optionally, the thickness of the isolation layer is 500-1000 nm, and 800 nm is selected in this embodiment.

[0068] S5. Prepare a rectangular structure, such as Figure 3d shown.

[0069] Specifically, a photolithography and etching process is used to open windows in the isolation layer, the width of the windows is 500-800nm, and the window interval is 500-800nm; optionally, the window width is 600nm, and the window interval is 600nm.

[0070] It should be noted that the shape of the window can be polygonal or circular. The shape of the window is selected in the actual production process and is not limited here.

[0071] S6, preparing a first metal and a second metal, such as Figure 3e shown.

[0072] Specifically, metal is deposited on the front and back of the device using electron beam evaporation or magnetron sputtering technology, that is, tungsten metal is deposited on the exposed surfaces of the rectangular structure and the passivation layer 3, and nickel metal is deposited on the surface of the substrate 1 away from the epitaxial layer 2. Optionally, the thickness of the tungsten metal and the nickel metal are both 60 to 70 nm. Optionally, the thickness of the tungsten metal and the nickel metal is 65 nm.

[0073] S7, preparing the Schottky contact layer 5 and the ohmic contact layer 6, such as Figure 3f shown.

[0074] Specifically, the first metal and the second metal are annealed using a rapid thermal annealing process to form a Schottky contact metal and an ohmic contact metal, respectively. The isolation unit 4 after the annealing reaction is refluxed to form a bulge-shaped array, and at the same time, a light reduction and anti-reflection enhancement function is obtained to improve the photoelectric detection performance of the device; after annealing, the ohmic contact layer 6 is transparentized using nitric acid, buffered oxide etchant (BOE) and deionized water. At the same time, the first metal remaining on the isolation unit 4 is cleaned off. After cleaning with the liquid medicine, the free Ni element remaining in the alloy will be cleaned by the liquid medicine, and the remaining SiNi related alloy will become transparent.

[0075] Optionally, the annealing condition is annealing at 1000° C. for 180 seconds in an inert gas atmosphere.

[0076] S8, prepare anode 7, such as Figure 3g shown.

[0077] Specifically, electron beam evaporation or magnetron sputtering is used to deposit aluminum metal on the front side of the device, i.e., the exposed upper surface of the Schottky contact layer 5 and the isolation unit 4, with a deposition thickness of 500 to 1000 nm; then, photolithography and corrosion processes are used to etch away part of the aluminum metal remaining on the upper surface of the isolation unit 4, and the aluminum metal remaining on the upper surface of the Schottky contact layer 5 forms the anode 7.

[0078] S9, preparing a protective layer 8, such as Figure 3h shown.

[0079] Specifically, a SiyNx anti-reflection surface passivation protection layer 8 is deposited on the front side of the device, that is, on the exposed upper surfaces of the anode 7 and the isolation unit 4, using a plasma enhanced chemical vapor deposition (PECVD) process.

[0080] S10, preparing cathode 9, such as Figure 3i shown.

[0081] Specifically, a Ti / Ni / Ag cathode 9 is formed on the back side of the device, ie, the side of the ohmic contact layer 6 facing away from the substrate 1, using an electron beam evaporation process; at the same time, the cathode 9 can serve as a back reflection layer to increase the light utilization rate of the device.

[0082] Optionally, the cathode 9 comprises Ti / Ni / Ag with thicknesses of 200nm / 200nm / 1000nm respectively.

[0083] The present invention proposes a novel method for preparing SiC ultraviolet photoelectric devices. The method uses an alkaline earth doped silicon oxide film to form an anti-reflection window through annealing and reflow. The annealing process can directly form a Schottky contact and an ohmic contact. The method saves multiple steps of process while achieving high-performance devices, thereby reducing the preparation cost of the device.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant is intended to cover non-exclusive inclusion, so that the article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the article or device including the elements. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The orientation or position relationship indicated by "up", "down", "left", "right", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0085] 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 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 representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features 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.

[0086] 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 SiC-based ultraviolet photodiode with a self-antireflection structure, characterized in that: include: A cathode, an ohmic contact layer, a substrate, an epitaxial layer and a passivation layer are sequentially stacked; An isolation layer, comprising a plurality of isolation units arranged in an array on the upper surface of the passivation layer, wherein the isolation units are in a bulge shape; A Schottky contact layer, located on the upper surface of the passivation layer and between adjacent isolation units; an anode, located on the upper surface of the Schottky contact layer; The protective layer is located on a portion of the upper surface of the anode and on the exposed upper surface of the isolation unit.

2. The SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 1, characterized in that: The material of the isolation unit includes alkaline earth doped silicon oxide.

3. The SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 1, characterized in that: The distance between adjacent isolation units is 500-800 nm.

4. The SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 1, characterized in that: The protective layer includes Si y N x Anti-reflective surface.

5. A method for preparing a SiC-based ultraviolet photodiode with a self-antireflection structure, used for preparing the SiC-based ultraviolet photodiode with a self-antireflection structure as claimed in any one of claims 1 to 4, characterized in that: include: providing a substrate; growing an epitaxial layer on the upper surface of the substrate; Treating the upper surface of the epitaxial layer using plasma to obtain a passivation layer; Depositing an isolation layer on the upper surface of the passivation layer, and opening windows in the isolation layer to obtain a plurality of rectangular structures arranged in an array on the upper surface of the passivation layer; Depositing a first metal on the exposed surfaces of the rectangular structure and the passivation layer, and depositing a second metal on the surface of the substrate facing away from the epitaxial layer; Annealing the first metal and the second metal so that the first metal forms a Schottky contact layer and the second metal forms an ohmic contact layer, so that the rectangular structure is reflowed to form an isolation unit, and the isolation unit presents a bulge shape; Using a ratio liquid to perform a transparent treatment on the ohmic contact layer, and at the same time, cleaning the first metal remaining on the isolation unit; Depositing a third metal on the exposed upper surfaces of the Schottky contact layer and the isolation unit, and removing part of the third metal on the upper surface of the isolation unit, so that the remaining third metal on the upper surface of the Schottky contact layer forms an anode; Depositing a protective layer on the exposed upper surfaces of the anode and the isolation unit; A fourth metal is deposited on the surface of the ohmic contact layer facing away from the substrate to form a cathode.

6. The method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 5, characterized in that: The upper surface of the epitaxial layer is treated with plasma to obtain a passivation layer, comprising: The upper surface of the epitaxial layer is treated with oxygen or oxygen-hydrogen mixed plasma to obtain a passivation layer.

7. The method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 5, characterized in that: The isolation layer is opened to obtain a plurality of rectangular structures arranged in an array on the upper surface of the passivation layer, including: The isolation layer is opened with windows by using photolithography and etching processes to obtain the rectangular structure; wherein the spacing between adjacent rectangular structures is 500 to 800 nm, and the width of the windows is 500 to 800 nm.

8. The method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 5, characterized in that: Depositing a first metal on the exposed surfaces of the rectangular structure and the passivation layer, and depositing a second metal on the surface of the substrate away from the epitaxial layer, comprising: Using electron beam evaporation or magnetron sputtering technology, tungsten metal is deposited on the exposed surfaces of the rectangular structure and the passivation layer, and nickel metal is deposited on the surface of the substrate away from the epitaxial layer; wherein the thickness of the tungsten metal and the nickel metal is 60-70nm.

9. The method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 5, characterized in that: Annealing the first metal and the second metal comprises: The first metal and the second metal are annealed using a rapid thermal annealing process, wherein the annealing conditions include an inert gas atmosphere, a temperature of 900 to 1100° C., and an annealing time of 160 to 190 seconds.

10. The method for preparing a SiC-based ultraviolet photodiode with a self-antireflective structure according to claim 5, characterized in that: The proportioned solution includes nitric acid, a buffered oxide etching solution and deionized water, and the volume ratio of the nitric acid, the buffered oxide etching solution and the deionized water is 1:1:5.

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