A moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and its preparation method

Abstract

The application discloses moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and a preparation method thereof. y N x The preparation method comprises the following steps: growing a P+ type SiC epitaxial layer with a three-dimensional moth-eye structure on a P+ type SiC substrate by epitaxy, growing an n-type Ga2O3 functional layer and an n+ type Ga2O3 functional layer on the P+ type SiC epitaxial layer by epitaxy in sequence, growing a passivation protective layer at a joint of the three-dimensional moth-eye structure, forming an anode electrode on a surface of the n+ type Ga2O3 functional layer, forming a cathode electrode on a back surface of the P+ type SiC substrate, and forming a back reflection layer on a back surface of the cathode electrode. y N x The ultraviolet detector of the application realizes complementary of material disadvantages of gallium oxide and silicon carbide, widens corresponding wavelength range and performance of the device, and improves optical utilization of the device.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device technology, and relates to a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector and its preparation method. Background Technology

[0002] An ultraviolet detector is a device that converts ultraviolet light signals into electrical signals. Ultraviolet photodetectors 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, and have become a hot topic in the field of photoelectric detection in recent years.

[0003] In the field of ultraviolet detectors, the main semiconductor materials involved 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 heterostructures of multiple materials can integrate the advantages of each material. Furthermore, research has revealed that heterojunction detectors also exhibit the remarkable characteristic of dual-band response peaks.

[0004] However, current single-photon detection capabilities are achieved using avalanche diode designs. Silicon carbide-based single-photon detectors exhibit relatively weak response. Gallium oxide lacks reliable p-type doping, making it impossible to fabricate single-material-based single-photon detectors. Silicon carbide and gallium oxide, as excellent representatives of third-generation semiconductor materials, can shield visible light, and their high breakdown field strength makes them suitable for fabricating single-photon detectors. Therefore, it is extremely important to find ways to complement the material disadvantages of silicon carbide and gallium oxide to develop entirely new ultraviolet detectors. Summary of the Invention

[0005] The purpose of this invention is to provide a moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector and its fabrication method. The technical solution adopted in this invention is as follows:

[0006] A moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector includes:

[0007] P+ type SiC substrate;

[0008] The P+ type SiC epitaxial layer is hemispherical and is spaced apart 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 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 protective layer, the Si y N x A passivation protective layer is disposed on the P+ type SiC substrate and is located between two adjacent n+ type Ga2O3 functional layers;

[0012] An anode electrode is disposed on the n+ type Ga2O3 functional layer;

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

[0014] A back reflective 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 × 10⁻⁶. 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 × 10⁻⁶. 16 cm -3 ~5×10 16 cm -3 .

[0017] A method for fabricating a moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector, comprising:

[0018] S1. Epitaxial growth of a P+ type SiC epitaxial layer on a P+ type SiC substrate;

[0019] S2. Alkali-earth-doped silicon oxide is deposited on the P+ type SiC substrate and the P+ type SiC epitaxial layer using low-pressure chemical vapor deposition to form an alkali-earth-doped silicon oxide etching mask.

[0020] S3. Use photolithography and etching processes to create windows in the alkaline earth-doped silicon oxide etching mask, and the window pattern is circular.

[0021] S4. The alkaline earth-doped silicon oxide etching mask after windowing is annealed using a rapid thermal annealing process to form a moth-eye structure etching mask. The P+ type SiC epitaxial layer is etched into a three-dimensional moth-eye structure using a spherical mask to form a three-dimensional moth-eye structure P+ type SiC epitaxial layer.

[0022] S5. An n-type Ga2O3 functional layer and an n+ type Ga2O3 functional layer are sequentially epitaxially grown on the P+ type SiC epitaxial layer of the three-dimensional moth-eye structure.

[0023] S6. The junction of the three-dimensional moth-eye structure is etched away using photolithography and etching processes, and Si is grown using plasma-enhanced chemical vapor deposition. y N x Passivation protective layer;

[0024] S7. Using photolithography and etching processes, the Si... y N x The passivation protective layer has windows;

[0025] S8. Ti, Ni, and Au metals are sequentially deposited on the n+ type Ga2O3 functional layer, and Ni metal is deposited on the back side of the P+ type SiC substrate. A rapid thermal annealing process is used in an inert atmosphere to form an anode electrode on the surface of the n+ type Ga2O3 functional layer and a cathode electrode on the back side of the P+ type SiC substrate.

[0026] S9. Ti, Ni, and Ag metals are sequentially deposited on the back of the cathode electrode using an electron beam evaporation process to form a back reflection layer, thus obtaining the moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector.

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

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

[0029] In one embodiment of the present invention, in step 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 step S8, the thicknesses of Ti, Ni, and Au metals are 10nm-30nm, 10nm-30nm, and 40nm-60nm, respectively, and the thickness of the Ni metal on the back side is 80nm-120nm; the annealing temperature is 950℃-1050℃, and the annealing time is 2min-5min.

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

[0032] The beneficial effects of this invention are:

[0033] 1. The moth-eye antireflection 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 material disadvantages of gallium oxide and silicon carbide, and adopting a long, moth-eye-like optical antireflection structure to broaden the corresponding wavelength range and performance of the device.

[0034] 2. The method for fabricating a moth-eye antireflective SiC / Ga2O3 heterojunction ultraviolet detector of the present invention can obtain an ultraviolet detector with a moth-eye structure, which has intrinsic optical antireflective capability, requires no additional optical management design, and achieves the complementary material disadvantages of gallium oxide and silicon carbide, thus broadening the corresponding wavelength range and performance of the device. The present invention uses alkaline earth-doped silicon oxide as an etching mask, passivation isolation layer and antireflection and antireflection 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 costs. Moreover, the process scheme uses standard processes and standard equipment, requiring no special equipment, and has universality. Attached Figure Description

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

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

[0037] Figure 3 This is 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 windowing in an alkaline earth-doped silicon oxide etching mask provided in an embodiment of the present invention;

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

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

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

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

[0043] Figure 9 The Si provided for the embodiments of the present invention y N x A schematic diagram of the passivation protective layer growth;

[0044] Figure 10 This is a schematic diagram illustrating the formation of the anode and cathode electrodes provided in an embodiment of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1. P+ type SiC substrate; 2. P+ type SiC epitaxial layer; 3. n- type Ga2O3 functional layer; 4. n+ type Ga2O3 functional layer; 5. Si y N x 6. Passivation protective layer; 7. Anode electrode; 8. Cathode electrode; 9. Back reflector layer. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0048] Example 1:

[0049] The embodiments of the present invention provide a moth-eye antireflection 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, achieving the complementary material disadvantages of gallium oxide and silicon carbide. By adopting a long, moth-eye-like optical antireflection structure, the corresponding wavelength range and performance of the device are broadened.

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

[0051] P+ type SiC substrate 1;

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

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

[0054] n+ type Ga2O3 functional layer 4 is disposed on n- type Ga2O3 functional layer 3. The 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-reflection effect and greatly improve anti-reflection ability.

[0055] Si y N x Passivation protective 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] Anode electrode 6 is disposed on n+ type Ga2O3 functional layer 4;

[0057] Cathode electrode 7 is disposed on the back side of P+ type SiC substrate 1;

[0058] A back reflective layer 8 is disposed on the back side of the cathode electrode 7.

[0059] In an 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 × 10⁻⁶. 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 × 10⁻⁶. 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] Example 2:

[0061] The embodiments of the present invention provide a method for fabricating a moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector, which uses an annealing and reflowing process of an alkaline earth-doped silicon oxide mask to achieve a three-dimensional structure etching mask, thereby realizing a three-dimensional moth-eye antireflection SiC / Ga2O3 heterojunction structure.

[0062] The fabrication method of this moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector includes:

[0063] S1. Epitaxially grow a P+ type SiC epitaxial layer 2 on a P+ type SiC substrate 1, as shown in the attached figure. Figure 2 ;

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

[0065] S3. Use photolithography and etching processes to create windows in the alkaline earth-doped silicon oxide etching mask. The window pattern is circular with a radius of 500nm–1000nm. Refer to the attached document. Figure 4 ;

[0066] S4. Anneal the alkaline earth-doped silicon oxide etching mask after windowing using a rapid thermal annealing process to form a moth-eye structure etching mask. The annealing temperature is 950℃~1050℃, and the time is 2min~5min. Refer to the appendix. Figure 5 A spherical mask was used to etch the P+ type SiC epitaxial layer into a three-dimensional moth-eye structure, forming the three-dimensional moth-eye structure P+ type SiC epitaxial layer 2, as shown in the attached figure. Figure 6 This structure has built-in optical management capabilities, and the size of the arranged structural features is between 500nm and 1000nm, with a period of 500nm to 1000nm.

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

[0068] S6. Using photolithography and etching processes, the joints of the three-dimensional moth-eye structure are etched away, and Si is grown using plasma-enhanced chemical vapor deposition (PECVD). y N x Passivation protective layer 5, see attached diagram. Figure 9 ;

[0069] S7. Using photolithography and etching processes on Si y N x Passivation protective layer 5 windows;

[0070] S8. Ti, Ni, and Au metals are sequentially deposited on the n+ type Ga2O3 functional layer 4, with thicknesses of 10nm–30nm, 10nm–30nm, and 40nm–60nm respectively. Ni metal is deposited on the back side of the P+ type SiC substrate 1, with a thickness of 80nm–120nm. A rapid thermal annealing process is used in an inert atmosphere at a temperature of 950℃–1050℃ for 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. (Refer to Appendix) Figure 10 ;

[0071] S9. Using electron beam evaporation, Ti, Ni, and Ag metals are sequentially deposited on the back side of the cathode electrode 7 to form a back reflective layer 8. The thicknesses of Ti, Ni, and Ag are 150 nm–250 nm, 150 nm–250 nm, and 750 nm–850 nm, respectively. The resulting moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector is shown in the attached diagram. Figure 1 .

[0072] The method for fabricating the moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector of the present invention uses alkaline earth-doped silicon oxide as an etching mask, passivation isolation layer, and antireflection and antireflection structure, essentially a three-in-one function. All three structures are achieved through a single ohmic contact annealing process, simplifying the process, reducing costs, and utilizing standard processes and equipment, eliminating the need for specialized equipment and demonstrating universality. The moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector fabricated by this method improves the optical utilization of the device, while the gallium oxide and silicon carbide bifunctional layer enhances the detector's high response width, thereby improving the device's detection performance.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. All content that does not depart from the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A moth-eye anti-reflection SiC / The Ga2O3 heterojunction ultraviolet detector is characterized by... include: P+ type SiC substrate; The P+ type SiC epitaxial layer is hemispherical and is spaced apart 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 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 protective layer, the Si y N x A passivation protective layer is disposed on the P+ type SiC substrate and is located between two adjacent n+ type Ga2O3 functional layers; An anode electrode is disposed on the n+ type Ga2O3 functional layer; A cathode electrode is disposed on the back side of the P+ type SiC substrate; A back reflective layer is disposed on the back side of the cathode electrode.

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

3. The anti-reflection SiC with moth-eye effect according to claim 1 / The Ga2O3 heterojunction ultraviolet detector is characterized by... The thickness of the P+ type SiC epitaxial layer is 8μm to 10μm, and the doping concentration is 1×10⁻⁶. 16 cm -3 ~5×10 16 cm -3 .

4. A moth-eye anti-reflection SiC / The method for fabricating a Ga2O3 heterojunction ultraviolet detector is characterized by, include: S1. Epitaxial growth of a P+ type SiC epitaxial layer on a P+ type SiC substrate; S2. Alkali-earth-doped silicon oxide is deposited on the P+ type SiC substrate and the P+ type SiC epitaxial layer using low-pressure chemical vapor deposition to form an alkali-earth-doped silicon oxide etching mask. S3. Use photolithography and etching processes to create windows in the alkaline earth-doped silicon oxide etching mask, and the window pattern is circular. S4. The alkaline earth-doped silicon oxide etching mask after windowing is annealed using a rapid thermal annealing process to form a moth-eye structure etching mask. The P+ type SiC epitaxial layer is etched into a three-dimensional moth-eye structure using a spherical mask to form a three-dimensional moth-eye structure P+ type SiC epitaxial layer. S5. An n-type Ga2O3 functional layer and an n+ type Ga2O3 functional layer are sequentially epitaxially grown on the P+ type SiC epitaxial layer of the three-dimensional moth-eye structure. S6. The junction of the three-dimensional moth-eye structure is etched away using photolithography and etching processes, and Si is grown using plasma-enhanced chemical vapor deposition. y N x Passivation protective layer; S7. Using photolithography and etching processes, the Si... y N x The passivation protective layer has windows; S8. Ti, Ni, and Au metals are sequentially deposited on the n+ type Ga2O3 functional layer, and Ni metal is deposited on the back side of the P+ type SiC substrate. A rapid thermal annealing process is used in an inert atmosphere to form an anode electrode on the surface of the n+ type Ga2O3 functional layer and a cathode electrode on the back side of the P+ type SiC substrate. S9. Ti, Ni, and Ag metals are sequentially deposited on the back of the cathode electrode using an electron beam evaporation process to form a back reflection layer, thus obtaining a moth-eye anti-reflection SiC / Ga2O3 heterojunction ultraviolet detector.

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

6. The method for fabricating the moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that, In S3, the radius of the windowed pattern is 500nm to 1000nm.

7. The method for fabricating the moth-eye antireflection SiC / Ga2O3 heterojunction ultraviolet detector according to claim 4, characterized in that, In step S4, the annealing temperature is 950℃~1050℃, and the annealing time is 2min~5min.

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

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

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