Moth eye antireflective SiC / Ga2O3 heterojunction ultraviolet detector and preparation method thereof

Abstract

The invention discloses a moth eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and a preparation method thereof. The ultraviolet detector comprises a P + type SiC substrate, a P + type SiC epitaxial layer, an n-type Ga2O3 functional layer, an n + type Ga2O3 functional layer, a SiyNx passivation protection layer, an anode electrode, a cathode electrode and a back reflection layer, the preparation method comprises the following steps: epitaxially growing a P + type SiC epitaxial layer with a three-dimensional moth-eye structure on a P + type SiC substrate, sequentially epitaxially growing an n-type Ga2O3 functional layer and an n + type Ga2O3 functional layer on the P + type SiC epitaxial layer, growing a SiyNx passivation protection layer at the joint of the three-dimensional moth-eye structure, forming an anode electrode on the surface of the n + type Ga2O3 functional layer, forming a cathode electrode on the back surface of the P + type SiC substrate, and forming a SiyNx passivation protection layer on the back surface of the SiyNx passivation protection layer. And forming a back reflecting layer on the back surface of the cathode electrode. The ultraviolet detector provided by the invention realizes the material disadvantage complementation of gallium oxide and silicon carbide, broadens the corresponding wavelength range and performance of the device, and improves the optical utilization rate of the device.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic devices and relates to a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and a preparation method thereof. Background Art

[0002] An ultraviolet detector is a device that can convert ultraviolet light signals into electrical signals. Ultraviolet photoelectric detectors have broad prospects in national defense, ultraviolet astronomy, environmental monitoring, fire detection, turbine engine combustion efficiency monitoring, combustible gas composition analysis, and biological cell cancer detection. It has become a hot topic in the field of photoelectric detection internationally in recent years.

[0003] The main semiconductor materials involved in the field of ultraviolet detectors include SiC, GaN, Ga2O3, ZnO and AlN. Due to the differences in the material properties of these semiconductors, single-material devices often have shortcomings, while heterojunction structures of multiple materials can integrate the advantages of materials. At the same time, the study found that heterojunction detectors also have the amazing characteristic of dual-band response peaks.

[0004] However, avalanche diode designs are currently used to achieve single-photon detection capabilities. Single-photon detection devices based on silicon carbide have weak device response capabilities. Gallium oxide has no reliable p-type doping, and single-photon detectors based on a single material cannot be prepared. As excellent representatives of the third-generation semiconductor materials, silicon carbide and gallium oxide can shield visible light, and their high breakdown field strength makes them suitable for the preparation of single-photon detection devices. Therefore, it is extremely important to complement the material disadvantages of silicon carbide and gallium oxide to develop a new ultraviolet detector. Summary of the invention

[0005] The purpose of the present invention is to provide a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and a preparation method thereof. The technical solution adopted by the present invention is:

[0006] A moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, comprising:

[0007] P+ type SiC substrate;

[0008] A P+ type SiC epitaxial layer, wherein the P+ type SiC epitaxial layer is hemispherical and is spaced and distributed on the P+ type SiC substrate;

[0009] An n-type Ga2O3 functional layer, wherein the n-type Ga2O3 functional layer is disposed on the P+ type SiC epitaxial layer;

[0010] An n+ type Ga2O3 functional layer, wherein the n+ type Ga2O3 functional layer is disposed on the n- type Ga2O3 functional layer, and the p+ type SiC epitaxial layer, the n- type Ga2O3 functional layer and the n+ type Ga2O3 functional layer form a moth-eye structure;

[0011] Si y N x Passivation protection layer, the Si y N x The passivation protection layer is arranged on the P+ type SiC substrate and is located between two adjacent n+ type Ga2O3 functional layers;

[0012] an anode electrode, the anode electrode being disposed on the n+ type Ga2O3 functional layer;

[0013] A cathode electrode, wherein the cathode electrode is disposed on the back side of the P+ type SiC substrate;

[0014] A back reflection layer is disposed on the back side of the cathode electrode.

[0015] In one embodiment of the present invention, the thickness of the P+ type SiC substrate is 300 μm to 400 μm, and the doping concentration is 4×10 18 cm -3 ~6×10 18 cm -3 .

[0016] In one embodiment of the present invention, the thickness of the P+ type SiC epitaxial layer is 8 μm to 10 μm, and the doping concentration is 1×10 16 cm -3 ~5×10 16 cm -3 .

[0017] A method for preparing a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, comprising:

[0018] S1. epitaxially growing a P+ type SiC epitaxial layer on a P+ type SiC substrate;

[0019] S2, using low pressure chemical vapor deposition to deposit alkaline earth doped silicon oxide on the P+ type SiC substrate and the P+ type SiC epitaxial layer to form an alkaline earth doped silicon oxide etching mask;

[0020] S3, using photolithography and etching processes to open a window on the alkaline earth-doped silicon oxide etching mask, wherein the window pattern is circular;

[0021] S4, annealing the alkaline earth-doped silicon oxide etching mask after the window is opened by using a rapid thermal annealing process to form a moth-eye structure etching mask, and etching the P+ type SiC epitaxial layer into a three-dimensional moth-eye structure by using a spherical mask to form a P+ type SiC epitaxial layer of the three-dimensional moth-eye structure;

[0022] S5, epitaxially growing an n-type Ga2O3 functional layer and an n+ type Ga2O3 functional layer in sequence on the P+ type SiC epitaxial layer of the three-dimensional moth-eye structure;

[0023] S6, using photolithography and etching processes to etch away the joints of the three-dimensional moth-eye structure, and using plasma enhanced chemical vapor deposition to grow Si y N x Passivation protective layer;

[0024] S7, using photolithography and etching process to y N x Passivation protective layer window opening;

[0025] S8, depositing Ti, Ni, and Au metals in sequence on the n+ type Ga2O3 functional layer, depositing Ni metal on the back side of the P+ type SiC substrate, using a rapid thermal annealing process in an inert atmosphere to form an anode electrode on the surface of the n+ type Ga2O3 functional layer, and forming a cathode electrode on the back side of the P+ type SiC substrate;

[0026] S9. Use electron beam evaporation technology to deposit Ti, Ni, and Ag metals in sequence on the back side of the cathode electrode to form a back reflection layer, and the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector is prepared.

[0027] In one embodiment of the present invention, in S2, the thickness of the alkaline earth doped silicon oxide etching mask is 1900nm-2100nm.

[0028] In one embodiment of the present invention, in S3, the radius of the window pattern is 500nm-1000nm.

[0029] In one embodiment of the present invention, in S4, the annealing temperature is 950° C. to 1050° C., and the annealing time is 2 min to 5 min.

[0030] In one embodiment of the present invention, in S8, the thicknesses of Ti, Ni and Au metals are 10nm-30nm, 10nm-30nm and 40nm-60nm, and the thickness of the Ni metal on the back is 80nm-120nm; the annealing temperature is 950°C-1050°C, and the annealing time is 2min-5min.

[0031] In one embodiment of the present invention, in S9, the thicknesses of Ti, Ni and Ag in the back reflection layer are 150nm-250nm, 150nm-250nm and 750nm-850nm respectively.

[0032] Beneficial effects of the present invention:

[0033] 1. The moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector of the present invention forms a heterojunction between the P+ type SiC epitaxial layer and the n-type Ga2O3 functional layer, realizing the complementary material disadvantages of gallium oxide and silicon carbide, and adopts an optical anti-reflection structure that looks like a moth-eye, which broadens the corresponding wavelength range and performance of the device;

[0034] 2. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector of the present invention can obtain an ultraviolet detector with a moth-eye structure, which has intrinsic optical anti-reflection capability, does not require additional optical management design, and realizes the complementary material disadvantages of gallium oxide and silicon carbide, broadening the corresponding wavelength range and performance of the device; the present invention adopts alkaline earth-doped silicon oxide as an etching mask, a passivation isolation layer and an anti-reflection and anti-transmittance structure, which is equivalent to a three-in-one function, and completes the three structures through a one-time ohmic contact annealing process, simplifies the process, reduces the cost, and the process scheme uses standard processes and standard equipment, does not require special equipment, and is universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector provided in an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of epitaxial growth of a P+ type SiC epitaxial layer provided in an embodiment of the present invention;

[0037] Figure 3 A schematic diagram of the growth of an alkaline earth-doped silicon oxide etching mask provided in an embodiment of the present invention;

[0038] Figure 4 A schematic diagram of an alkaline earth doped silicon oxide etching mask window opening provided in an embodiment of the present invention;

[0039] Figure 5 A schematic diagram of annealing an alkaline earth doped silicon oxide etching mask provided in an embodiment of the present invention;

[0040] Figure 6 A schematic diagram of etching a P+ type SiC epitaxial layer provided in an embodiment of the present invention;

[0041] Figure 7 A schematic diagram of epitaxial growth of an n-type Ga2O3 functional layer provided in an embodiment of the present invention;

[0042] Figure 8 A schematic diagram of epitaxial growth of an n+ type Ga2O3 functional layer provided in an embodiment of the present invention;

[0043] Fig. 9 The Si provided in the embodiment of the present invention y N x Schematic diagram of the growth of the passivation protection layer;

[0044] Fig.10 A schematic diagram of the formation of an anode electrode and a cathode electrode provided in an embodiment of the present invention.

[0045] Description of reference numerals:

[0046] 1. P+ SiC substrate; 2. P+ SiC epitaxial layer; 3. n- Ga2O3 functional layer; 4. n+ Ga2O3 functional layer; 5. Si y N x Passivation protective layer; 6. Anode electrode; 7. Cathode electrode; 8. Back reflection layer. DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Embodiment 1:

[0049] An embodiment of the present invention provides a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, in which a heterojunction is formed between a P+ type SiC epitaxial layer and an n-type Ga2O3 functional layer, thereby achieving complementary material disadvantages of gallium oxide and silicon carbide, and adopting an optical anti-reflection structure that looks like a moth-eye, thereby broadening the corresponding wavelength range and performance of the device.

[0050] See attached Figure 1 The moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector includes:

[0051] P+ type SiC substrate 1;

[0052] A P+ type SiC epitaxial layer 2, the P+ type SiC epitaxial layer is hemispherical, and the P+ type SiC epitaxial layer is distributed on the P+ type SiC substrate 1 at intervals;

[0053] n-type Ga2O3 functional layer 3, the n-type Ga2O3 functional layer 3 is arranged on the P+ type SiC epitaxial layer 2;

[0054] n+ type Ga2O3 functional layer 4, n+ type Ga2O3 functional layer 4 is arranged on n- type Ga2O3 functional layer 3, p+ type SiC epitaxial layer, n- type Ga2O3 functional layer and n+ type Ga2O3 functional layer form a moth-eye structure, which can achieve anti-reflection and anti-transmission effect and greatly improve anti-reflection ability;

[0055] Si y N x Passivation protection layer 5, Si y N x The passivation protection layer 5 is disposed on the P+ type SiC substrate 1 and is located between two adjacent n+ type Ga2O3 functional layers 3;

[0056] An anode electrode 6, wherein the anode electrode 6 is disposed on the n+ type Ga2O3 functional layer 4;

[0057] A cathode electrode 7, wherein the cathode electrode 7 is disposed on the back side of the P+ type SiC substrate 1;

[0058] The back reflection layer 8 is provided on the back side of the cathode electrode 7 .

[0059] In the embodiment of the present invention, the thickness of the P+ type SiC substrate 1 is 300 μm to 400 μm, and the doping concentration is 4×10 18 cm -3 ~6×10 18 cm -3 The thickness of the P+ type SiC epitaxial layer 2 is 8 μm to 10 μm, and the doping concentration is 1×10 16 cm -3 ~5×10 16 cm -3 The thickness and doping concentration here are optimal values ​​and can be selected according to actual needs.

[0060] Embodiment 2:

[0061] An embodiment of the present invention provides a method for preparing a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, which uses an annealing reflow process technology of an alkaline earth-doped silicon oxide mask to realize a three-dimensional structure etching mask, thereby realizing a three-dimensional moth-eye anti-reflection SiC / Ga2O3 heterojunction structure.

[0062] The preparation method of the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector comprises:

[0063] S1. epitaxially grow a P+ type SiC epitaxial layer 2 on a P+ type SiC substrate 1. Figure 2 ;

[0064] S2. Alkaline earth doped silicon oxide is deposited on the P+ type SiC substrate 1 and the P+ type SiC epitaxial layer 2 by low pressure chemical vapor deposition (LPCVD) to form an alkaline earth doped silicon oxide etching mask. The thickness of the alkaline earth doped silicon oxide etching mask is 1900nm to 2100nm. Figure 3 ;

[0065] S3. Use photolithography and etching process to open windows in the alkaline earth doped silicon oxide etching mask. The window pattern is circular with a radius of 500nm to 1000nm. Figure 4 ;

[0066] S4. Use a rapid thermal annealing process to anneal the alkaline earth doped silicon oxide etching mask after the window is opened to form a moth-eye structure etching mask. The annealing temperature is 950°C to 1050°C and the time is 2min to 5min. Figure 5 , the P+ type SiC epitaxial layer is etched into a three-dimensional moth-eye structure using a spherical mask to form a P+ type SiC epitaxial layer 2 of a three-dimensional moth-eye structure, referring to the attached Figure 6 , the structure has its own optical management capability, the structural feature size of the arrangement is 500nm~1000nm, and the period is also 500nm~1000nm;

[0067] S5. On the P+ SiC epitaxial layer 2 of the three-dimensional moth-eye structure, an n-type Ga2O3 functional layer 3 and an n+ Ga2O3 functional layer 4 are sequentially epitaxially grown. Figure 7 and attached Figure 8 ;

[0068] S6, using photolithography and etching process to etch away the joints of the three-dimensional moth-eye structure, and using plasma enhanced chemical vapor deposition (PECVD) to grow Si y N x Passivation protection layer 5, see attached Fig. 9 ;

[0069] S7, using photolithography and etching process to Si y N x The passivation protection layer 5 has windows;

[0070] S8. Ti, Ni and Au metals are sequentially deposited on the n+ type Ga2O3 functional layer 4, with the thickness of Ti, Ni and Au metals being 10nm-30nm, 10nm-30nm and 40nm-60nm, respectively. Ni metal is deposited on the back side of the P+ type SiC substrate 1, with the thickness of Ni metal being 80nm-120nm. A rapid thermal annealing process is used in an inert atmosphere, with the annealing temperature being 950℃-1050℃ and the time being 2min-5min. An anode electrode 6 is formed on the surface of the n+ type Ga2O3 functional layer 4, and a cathode electrode 7 is formed on the back side of the P+ type SiC substrate 1. See the attached drawings. Fig.10 ;

[0071] S9, using electron beam evaporation process to deposit Ti, Ni, and Ag metals on the back of the cathode electrode 7 in sequence to form a back reflection layer 8, wherein the thicknesses of Ti, Ni, and Ag are 150nm-250nm, 150nm-250nm, and 750nm-850nm, respectively, to complete the preparation of the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, refer to the attached Figure 1 .

[0072] The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector of the present invention uses alkaline earth-doped silicon oxide as an etching mask, a passivation isolation layer, and an anti-reflection and anti-transmittance structure, which is equivalent to a three-in-one function. The three structures are completed through a single ohmic contact annealing process, which simplifies the process and reduces the cost. The process scheme uses standard processes and standard equipment, does not require special equipment, and has universal applicability. The moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector prepared by this method improves the optical utilization rate of the device, and the gallium oxide and silicon carbide dual functional layers improve the high response width of the detector and improve the detection performance of the device.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. All contents that do not deviate from the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector, characterized in that, include: P+ type SiC substrate; A P+ type SiC epitaxial layer, wherein the P+ type SiC epitaxial layer is hemispherical and is spaced and distributed on the P+ type SiC substrate; An n-type Ga2O3 functional layer, wherein the n-type Ga2O3 functional layer is disposed on the P+ type SiC epitaxial layer; An n+ type Ga2O3 functional layer, wherein the n+ type Ga2O3 functional layer is disposed on the n- type Ga2O3 functional layer, and the p+ type SiC epitaxial layer, the n- type Ga2O3 functional layer and the n+ type Ga2O3 functional layer form a moth-eye structure; Si y N x Passivation protection layer, the Si y N x The passivation protection layer is arranged on the P+ type SiC substrate and is located between two adjacent n+ type Ga2O3 functional layers; an anode electrode, the anode electrode being disposed on the n+ type Ga2O3 functional layer; A cathode electrode, the cathode electrode being disposed on the back side of the P+ type SiC substrate; A back reflection layer is disposed on the back side of the cathode electrode.

2. The moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 1, characterized in that: The thickness of the P+ type SiC substrate is 300 μm to 400 μm, and the doping concentration is 4×10 18 cm -3 ~6×10 18 cm -3 .

3. The moth-eye anti-reflection SiC according to claim 1 / Ga2O3 heterojunction ultraviolet detector, characterized in that, The thickness of the P+ type SiC epitaxial layer is 8 μm to 10 μm, and the doping concentration is 1×10 16 cm -3 ~5×10 16 cm -3 .

4. A moth-eye anti-reflection SiC / The method for preparing a Ga2O3 heterojunction ultraviolet detector is characterized in that: include: S1. epitaxially growing a P+ type SiC epitaxial layer on a P+ type SiC substrate; S2, using a low pressure chemical vapor deposition method to deposit alkaline earth doped silicon oxide on the P+ type SiC substrate and the P+ type SiC epitaxial layer to form an alkaline earth doped silicon oxide etching mask; S3, using photolithography and etching processes to open a window on the alkaline earth-doped silicon oxide etching mask, wherein the window pattern is circular; S4, annealing the alkaline earth-doped silicon oxide etching mask after the window is opened by using a rapid thermal annealing process to form a moth-eye structure etching mask, and etching the P+ type SiC epitaxial layer into a three-dimensional moth-eye structure by using a spherical mask to form a P+ type SiC epitaxial layer of the three-dimensional moth-eye structure; S5, epitaxially growing an n-type Ga2O3 functional layer and an n+ type Ga2O3 functional layer in sequence on the P+ type SiC epitaxial layer of the three-dimensional moth-eye structure; S6, using photolithography and etching processes to etch away the joints of the three-dimensional moth-eye structure, and using plasma enhanced chemical vapor deposition to grow Si y N x Passivation protective layer; S7, using photolithography and etching process to y N x Passivation protective layer window opening; S8, depositing Ti, Ni, and Au metals in sequence on the n+ type Ga2O3 functional layer, depositing Ni metal on the back side of the P+ type SiC substrate, using a rapid thermal annealing process in an inert atmosphere to form an anode electrode on the surface of the n+ type Ga2O3 functional layer, and forming a cathode electrode on the back side of the P+ type SiC substrate; S9. Use electron beam evaporation technology to deposit Ti, Ni, and Ag metals in sequence on the back side of the cathode electrode to form a back reflection layer, and the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector is prepared.

5. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that: In the above S2, the thickness of the alkaline earth doped silicon oxide etching mask is 1900nm to 2100nm.

6. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that: In the above S3, the radius of the window pattern is 500nm to 1000nm.

7. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that: In the step S4, the annealing temperature is 950° C. to 1050° C., and the annealing time is 2 min to 5 min.

8. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that: In the S8, the thicknesses of Ti, Ni and Au metals are 10nm-30nm, 10nm-30nm and 40nm-60nm, and the thickness of the Ni metal on the back is 80nm-120nm; the annealing temperature is 950°C-1050°C, and the annealing time is 2min-5min.

9. The method for preparing the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that: In the S9, the thicknesses of Ti, Ni and Ag in the back reflection layer are 150nm-250nm, 150nm-250nm and 750nm-850nm respectively.

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