High-voltage schottky diode with vertical algan / gan heterojunction and method of manufacturing the same
By employing a vertical AlGaN/GaN heterojunction structure in the Schottky diode, a two-dimensional electron gas and PN junction are formed, solving the problems of low withstand voltage, large reverse leakage current, and small forward current, thus achieving high forward current and high breakdown voltage in the high-voltage Schottky diode.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU CHIPPORT SEMICON CO LTD
- Filing Date
- 2023-03-24
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies for fabricating vertical junction barrier Schottky diodes suffer from low breakdown voltage, high reverse leakage current, and low forward current.
A structure with a vertical AlGaN/GaN heterojunction is adopted. By etching grooves on the N+-GaN layer and P-GaN layer, and growing AlGaN layer and N--GaN layer on them, a two-dimensional electron gas and PN junction are formed to improve the forward current and uniformly disperse the electric field.
It improves the forward current density and breakdown voltage of the diode, reduces reverse leakage current, and improves the electric field concentration effect.
Smart Images
Figure CN116206976B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microelectronic device technology and relates to a GaN-based Schottky diode and its fabrication method, specifically to a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction and its fabrication method. Background Technology
[0002] The semiconductor industry has developed to the point where its product technologies have played an indispensable role in driving social development and progress. Especially with the gradual maturation of semiconductor technology, third-generation semiconductor materials, represented by GaN, SiC, and semiconductor diamond, have emerged and gradually become a research hotspot in the semiconductor industry due to their significant advantages over the previous two generations. In the more than two decades since GaN materials were first proposed, they have experienced rapid development, and related third-generation semiconductor devices have been widely used.
[0003] Third-generation wide-bandgap semiconductor materials, represented by gallium nitride (GaN), are gradually emerging. Compared with traditional semiconductor materials, GaN has good chemical stability, high breakdown voltage, low on-resistance, and high operating temperature. These advantages greatly compensate for the inherent shortcomings of traditional semiconductor materials. Therefore, GaN devices can operate in high-temperature, high-power, and high-frequency environments.
[0004] Currently, Schottky diodes are being developed towards higher breakdown voltage, higher on-state ratio, and lower on-resistance. A high breakdown voltage ensures device stability under high voltage conditions; a high on-state ratio ensures better switching performance; and low on-resistance results in lower turn-on losses.
[0005] To address the low breakdown voltage issue of gallium nitride (GaN) Schottky barrier diodes (SBDs), using a vertically structured SBD can effectively improve the breakdown voltage compared to using a laterally structured SBD. However, existing technologies for fabricating vertically junction barrier Schottky diodes still suffer from problems such as low breakdown voltage, high reverse leakage current, and low forward current.
[0006] In view of the above-mentioned technical defects of the prior art, there is a need to provide an improved high-voltage Schottky diode and its fabrication method to overcome the above defects. Summary of the Invention
[0007] To overcome the shortcomings of existing technologies, this invention proposes a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction and its fabrication method, which can solve the problems of low withstand voltage, large reverse leakage current, and small forward current of vertical junction barrier Schottky diodes fabricated by existing technologies.
[0008] To achieve the above objectives, the present invention provides the following technical solution:
[0009] A method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction, characterized by comprising the following steps:
[0010] 1) In N with a thickness of 1-4 μm + A P-GaN layer with a thickness of 3 to 9 μm is grown on the front side of the GaN layer;
[0011] 2) In the N + Trenches are etched on the N-GaN and P-GaN layers, the width of which is 3-5 μm and the depth of which is such that the N-GaN layer is filled with N-GaN. + - The GaN layer was etched away by 100-500 nm;
[0012] 3) Grow a layer of N with a thickness of 100-500 nm. - -GaN layer;
[0013] 4) In the N - - An AlGaN layer with a thickness of 10-30 nm is grown on top of the GaN layer;
[0014] 5) In the N + - The cathode is fabricated on the bottom surface of the GaN layer;
[0015] 6) Deposit a dielectric layer with a thickness of 0.2–1 μm on the AlGaN layer;
[0016] 7) Etch away a portion of the N located above the P-GaN layer. - -GaN layer, AlGaN layer and dielectric layer, exposing the top surface of the P-GaN layer;
[0017] 8) An anode groove is etched on the top surface of the exposed P-GaN layer, the depth of which is 300-900 nm;
[0018] 9) An anode is fabricated within the anode groove, on the remaining dielectric layer, and on a portion of the P-GaN layer.
[0019] Preferably, the Al composition of the AlGaN layer is 15% to 40%.
[0020] Preferably, the dielectric layer is an Al2O3 layer, a SiN layer, or a SiO2 layer.
[0021] Preferably, the AlGaN layer and the N - - A two-dimensional electron gas is formed between GaN layers in the vertical direction, but not in the horizontal direction.
[0022] Preferably, the N - A PN junction is formed between the -GaN layer and the P-GaN layer.
[0023] Preferably, the cathode is composed of a Ti layer, an Al layer, a Ni layer and an Au layer stacked together, wherein the thickness of the Ti layer is 20 nm, the thickness of the Al layer is 160 nm, the thickness of the Ni layer is 55 nm and the thickness of the Au layer is 45 nm.
[0024] Preferably, after step 5), a rapid metal annealing process is performed first, followed by step 6), wherein the rapid metal annealing process is a rapid thermal annealing at 870°C in a N2 atmosphere for 30 seconds.
[0025] Preferably, the anode is composed of a Ni layer and an Au layer stacked together, wherein the Ni layer has a thickness of 45 nm and the Au layer has a thickness of 200 nm.
[0026] Furthermore, the present invention also provides a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction, characterized in that it is prepared using the above-described preparation method.
[0027] Compared with the prior art, the high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction and its fabrication method of the present invention have one or more of the following beneficial technical effects:
[0028] 1. The high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction prepared in this invention has a regrown AlGaN layer and a regrown N-type N-type heterojunction in the regrown groove. - - The GaN layer forms an AlGaN / GaN heterojunction in the vertical direction, generating a 2DEG at the heterojunction interface, which can improve the forward current of the diode.
[0029] 2. The high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction prepared in this invention, with regrown N in the regrowing groove. - A PN junction is formed between the GaN layer and the P-GaN layer, which can uniformly disperse the peak electric field, improve the electric field concentration effect, and increase the breakdown voltage. At the same time, in reverse, the PN junction can more effectively reduce reverse leakage current compared to the Schottky junction. Attached Figure Description
[0030] Figure 1 It is N + -Schematic diagram of the GaN layer structure.
[0031] Figure 2 Is Figure 1 This is a schematic diagram of the structure after a P-GaN layer has been grown on top of the existing structure.
[0032] Figure 3 Is Figure 2 The diagram shows the structure after the grooves were etched.
[0033] Figure 4 Is Figure 3 N was grown on the basis - -Schematic diagram of the structure behind the GaN layer.
[0034] Figure 5 Is Figure 4 This is a schematic diagram of the structure after an AlGaN layer has been grown on top of the existing structure.
[0035] Figure 6 Is Figure 5 Based on this, a schematic diagram of the structure after the cathode was created.
[0036] Figure 7 Is Figure 6 This is a schematic diagram of the structure after a medium layer has been grown on top of the existing structure.
[0037] Figure 8 Is Figure 7 Based on this, part of the dielectric layer, AlGaN layer and N were etched away. - -Schematic diagram of the structure behind the GaN layer.
[0038] Figure 9 Is Figure 8 The diagram shows the structure after etching the anode groove.
[0039] Figure 10 Is Figure 9 Based on this, a schematic diagram of the structure after anode was created. Detailed Implementation
[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments. The content of the embodiments is not intended to limit the scope of protection of the present invention.
[0041] This invention relates to a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction and its fabrication method, which can solve the problems of low withstand voltage, large reverse leakage current and small forward current of vertical junction barrier Schottky diodes fabricated by existing technology.
[0042] The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to the present invention includes the following steps:
[0043] I. For example Figure 1 As shown, provide an N + -GaN layer 1.
[0044] In this invention, the N + -GaN layer 1 serves as the substrate. Preferably, the N... + - The thickness of GaN layer 1 is 1 to 4 μm.
[0045] II. Figure 2 As shown, in the N + A P-GaN layer with a thickness of 3 to 9 μm is grown on the front side of the GaN layer.
[0046] Similar to existing technologies, in this invention, the P-GaN layer 2 can be grown using an MOCVD (metal-organic chemical vapor deposition) process.
[0047] III. Figure 3 As shown, in the N + Grooves a are etched on GaN layer 1 and P-GaN layer 2.
[0048] In this invention, the groove a can be etched using ICP (inductively coupled plasma) etching technology.
[0049] During etching, the width of the groove a is set to 3–5 μm. Furthermore, the depth of the groove a is set such that the N... + - The GaN layer 1 is etched away by 100-500 nm, that is, after etching away the P-GaN layer 2, a portion of the N layer thickness is then etched away. + -GaN layer 1, and make the N + The etching thickness of GaN layer 1 is 100-500 nm.
[0050] IV. Figure 4 As shown, an N-GaN layer with a thickness of 100-500 nm is grown as a whole.
[0051] In this invention, the N-GaN layer 3 can also be grown using MOCVD (metal-organic chemical vapor deposition) technology. The N-GaN layer 3 should cover the P-GaN layer 2 and the bottom and sides of the groove a.
[0052] V. For example Figure 5 As shown, an AlGaN layer 4 with a thickness of 10-40 nm is grown on the N-GaN layer 3.
[0053] In this invention, the AlGaN layer 4 can also be grown using MOCVD (metal-organic chemical vapor deposition) process.
[0054] Preferably, during growth, the Al composition of the AlGaN layer 4 is controlled to be 15% to 40%.
[0055] In this invention, an AlGaN / GaN heterojunction is formed by regrowing the AlGaN layer 4, and the AlGaN4 and the N - -GaN layer 3 forms 2DEG (two-dimensional electron gas) b in the vertical direction, but not in the horizontal direction. This reduces the N... - The equivalent resistance of the GaN layer 3 increases the forward current density of the diode. Simultaneously, the higher electron mobility of 2DEG results in better frequency characteristics for the diode.
[0056] VI. For example Figure 6 As shown, in the N + A cathode 5 is fabricated on the bottom surface of GaN layer 1.
[0057] In this invention, preferably, the cathode 5 is composed of a Ti layer, an Al layer, a Ni layer and an Au layer stacked together, wherein the thickness of the Ti layer is 20 nm, the thickness of the Al layer is 160 nm, the thickness of the Ni layer is 55 nm and the thickness of the Au layer is 45 nm.
[0058] More preferably, after the cathode 5 is fabricated, a rapid metal annealing process is performed. This rapid metal annealing process involves rapid thermal annealing at 870°C in a N2 atmosphere for 30 seconds. Through this rapid metal annealing process, the ohmic contact metal used to fabricate the cathode 5 can be alloyed, facilitating the fabrication of the cathode 5.
[0059] VII. For example Figure 7 As shown, a dielectric layer 6 with a thickness of 0.2 to 1 μm is deposited on the AlGaN layer 4.
[0060] In this invention, the dielectric layer 6 can be an Al2O3 layer, a SiN layer, or a SiO2 layer.
[0061] Furthermore, PECVD (plasma-enhanced chemical vapor deposition) process can be used when depositing the dielectric layer 6.
[0062] 8. For example Figure 8 As shown, a portion of the N-type ... - -GaN layer 3, AlGaN layer 4 and dielectric layer 6, exposing the top surface of the P-GaN layer 2.
[0063] In this invention, ICP (inductively coupled plasma) etching technology can also be used for etching.
[0064] IX. For example Figure 9 As shown, an anode groove c is etched on the top surface of the exposed P-GaN layer 2.
[0065] In this invention, the anode groove c can also be etched using ICP (inductively coupled plasma) etching technology.
[0066] Preferably, the depth of the anode groove c is 300-900 nm and the width is 3-6 μm.
[0067] 10. For example Figure 10 As shown, an anode 7 is fabricated within the anode groove c, on the remaining dielectric layer 6, and on a portion of the P-GaN layer 2.
[0068] Preferably, the anode 7 is formed by stacking a Ni layer and an Au layer. The Ni layer has a thickness of 45 nm, and the Au layer has a thickness of 200 nm.
[0069] The present invention is described in more detail below with reference to several specific embodiments, so that those skilled in the art can implement the fabrication of the high-voltage Schottky diode having a vertical AlGaN / GaN heterojunction according to the description of the present invention.
[0070] The following examples have N with different thicknesses - -GaN layers, AlGaN layers of different thicknesses, and dielectric layers of different materials and thicknesses are all identical in other respects.
[0071]
Example 1
[0072] In this embodiment, the N - The thickness of GaN layer 3 is 100 nm, the thickness of AlGaN layer 4 is 10 nm and the Al composition is 15%, and the dielectric layer is a SiN dielectric layer with a thickness of 200 nm.
[0073] Therefore, the fabrication method of the high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction in this embodiment includes the following steps:
[0074] Step 1. Epitaxial material growth.
[0075] In N with a thickness of 3μm + On top of GaN layer 1, a P-GaN layer 2 with a thickness of 7 μm is grown using MOCVD process.
[0076] Step 2. Creation of regrowth grooves and regrowth.
[0077] 2.1) Fabrication of regeneration grooves
[0078] First, a spin coater is used to spin the photoresist at a speed of 3000 rpm. The photoresist used is AZ6130. Then, an NSR1755I7A lithography machine is used for exposure to form the mask pattern of the regrowth groove a region.
[0079] Then, the substrate with the mask prepared was etched with an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s to etch the regroove a groove a, with an etching depth of 7.3 μm.
[0080] 2.2) Regeneration of N - -GaN layer 3
[0081] A 100 nm thick N-GaN layer was deposited using MOCVD deposition equipment.
[0082] 2.3) Regeneration of AlGaN layer 4
[0083] An AlGaN layer 4 with a thickness of 10 nm and an Al composition of 15% was deposited using an MOCVD deposition equipment.
[0084] Step 3. Fabrication of cathode 5.
[0085] First, the photoresist was spun at a speed of 5000 rpm using a spin coater to obtain a photoresist mask with a thickness of 0.8 μm.
[0086] Next, it is baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form a cathode region mask pattern.
[0087] Then, the cathode was fabricated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The ohmic metals were Ti / Al / Ni / Au in sequence, with Ti having a thickness of 20 nm, Al having a thickness of 160 nm, Ni having a thickness of 55 nm, and Au having a thickness of 45 nm. After the ohmic contact metal of the cathode was evaporated, the metal was stripped to obtain a complete cathode 5.
[0088] Finally, the ohmic contact metal is alloyed by rapidly annealing in an N2 atmosphere at 870°C for 30 seconds using an RTP500 rapid thermal annealing furnace to complete the fabrication of cathode 5.
[0089] Step 4. Growth of dielectric layer 6.
[0090] A 200 nm thick SiN dielectric layer was deposited using MOCVD deposition equipment.
[0091] Step 5. Anode fabrication.
[0092] 5.1) Etching away a portion of the top surface of the P-GaN layer 2 to allow for the regeneration of N. — GaN layer 3, regrown AlGaN layer 4 and dielectric layer 6;
[0093] First, a spin coater is used to spin the coating at a speed of 3500 rpm, and then an NSR1755I7A lithography machine is used for exposure to form a partial mask pattern on the top surface of P-GaN layer 2.
[0094] Then, the masked substrate was etched using an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s, with an etching depth of 310 nm.
[0095] 5.2) Fabrication of the anode groove c;
[0096] The photoresist was spun onto the surface of the epitaxial material at a speed of 5000 rpm to obtain a photoresist mask with a thickness of 0.8 μm. It was then baked in a high-temperature oven at 80℃ for 10 min. Finally, it was exposed using an NSR1755I7A lithography machine to obtain the photoresist mask of the anode groove c and the development was completed.
[0097] Next, an ICP98c inductively coupled plasma etching machine was used to etch and remove the 500nm thick P-GaN layer 2 in Cl2 plasma at an etching rate of 0.5nm / s, forming the anode groove c.
[0098] 5.3) Fabrication of Anode 7
[0099] First, a photoresist mask with a thickness of 0.8 μm was obtained by spinning the photoresist mask at a speed of 5000 rpm.
[0100] Next, it is baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form a mask pattern for the anode region.
[0101] Finally, the anode metal was evaporated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The anode metals were Ni / Au, with a Ni thickness of 45 nm and an Au thickness of 200 nm. After evaporation, the metal was stripped to obtain a complete anode 7.
[0102]
Example 2
[0103] In this embodiment, the N - The thickness of GaN layer 3 is 300 nm, the thickness of AlGaN layer 4 is 20 nm and the Al composition is 30%, and the dielectric layer is a SiO2 dielectric layer with a thickness of 1 μm.
[0104] Therefore, the fabrication method of the high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction in this embodiment includes the following steps:
[0105] Step 1. Epitaxial material growth.
[0106] In N with a thickness of 3μm + On top of GaN layer 1, a 7 μm thick P-GaN layer 2 is grown using MOCVD technology.
[0107] Step 2. Creation of regrowth grooves and regrowth.
[0108] 2.1) Fabrication of regrowth groove a
[0109] First, a spin coater is used to spin the photoresist at a speed of 3000 rpm. The photoresist used is AZ6130. Then, an NSR1755I7A lithography machine is used for exposure to form the mask pattern of the regrowth groove a region.
[0110] Then, the substrate with the mask prepared was etched with an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s to etch the regroove a groove a, with an etching depth of 7.3 μm.
[0111] 2.2) Regeneration of N - -GaN layer 3
[0112] An N2 layer with a thickness of 300 nm was deposited using an MOCVD deposition system. - -GaN layer 3.
[0113] 2.3) Regeneration of AlGaN layer 4
[0114] A 20 nm thick AlGaN layer 4 with an Al composition of 30% was deposited using MOCVD deposition equipment.
[0115] Step 3. Fabrication of cathode 5.
[0116] First, the photoresist was spun at a speed of 5000 rpm using a spin coater to obtain a photoresist mask with a thickness of 0.8 μm.
[0117] Next, it was baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form the area mask pattern of cathode 5.
[0118] Then, the cathode was fabricated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The ohmic metals were Ti / Al / Ni / Au in sequence, with Ti having a thickness of 20 nm, Al having a thickness of 160 nm, Ni having a thickness of 55 nm, and Au having a thickness of 45 nm. After the ohmic contact metal of the cathode was evaporated, the metal was stripped to obtain a complete cathode 5.
[0119] Finally, the ohmic contact metal is alloyed by rapidly annealing in an N2 atmosphere at 870°C for 30 seconds using an RTP500 rapid thermal annealing furnace to complete the fabrication of cathode 5.
[0120] Step 4. Growth of dielectric layer 6.
[0121] A SiO2 dielectric layer with a thickness of 1 μm was deposited using an MOCVD deposition equipment.
[0122] Step 5. Anode 7 fabrication.
[0123] 5.1) Regrowing N in a portion of the top surface of the P-GaN layer 2 by etching. - -GaN layer 3, regrown AlGaN layer 4 and dielectric layer 6
[0124] First, a spin coater is used to spin the coating at a speed of 3500 rpm, and then an NSR1755I7A lithography machine is used for exposure to form a partial mask pattern on the top surface of P-GaN layer 2.
[0125] The masked substrate was then etched using an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s, with an etching depth of 1.32 μm.
[0126] 5.2) Fabrication of the anode groove c
[0127] The photoresist mask was spun onto the surface of the epitaxial material at a speed of 5000 rpm to obtain a thickness of 0.8 μm. It was then baked in a high-temperature oven at 80℃ for 10 min. Finally, it was exposed using an NSR1755I7A lithography machine to obtain the anode groove c photoresist mask and complete the development.
[0128] Next, an ICP98c inductively coupled plasma etching machine was used to etch and remove the 500nm thick P-GaN layer 2 in Cl2 plasma at an etching rate of 0.5nm / s, forming the anode groove c.
[0129] 5.3) Fabrication of Anode 7
[0130] First, a photoresist mask with a thickness of 0.8 μm was obtained by spinning the photoresist mask at a speed of 5000 rpm.
[0131] Next, it is baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form a mask pattern for the anode region.
[0132] Finally, the anode metal was evaporated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The anode metals were Ni / Au, with a Ni thickness of 45 nm and an Au thickness of 200 nm. After evaporation, the metal was stripped to obtain a complete anode 7.
[0133]
Example 3
[0134] In this embodiment, the N - The thickness of GaN layer 3 is 500 nm, the thickness of AlGaN layer 4 is 30 nm and the Al composition is 40%, and the dielectric layer is an Al2O3 dielectric layer with a thickness of 700 nm.
[0135] Therefore, the fabrication method of the high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction in this embodiment includes the following steps:
[0136] Step 1. Epitaxial material growth.
[0137] In N with a thickness of 3μm + On top of GaN layer 1, a P-GaN layer 2 with a thickness of 7 μm is grown using MOCVD process.
[0138] Step 2. Creation of regrowth grooves and regrowth.
[0139] 2.1) Fabrication of regrowth groove a
[0140] First, a spin coater is used to spin the photoresist at a speed of 3000 rpm. The photoresist used is AZ6130. Then, an NSR1755I7A lithography machine is used for exposure to form the area mask pattern of the regrowth groove a.
[0141] Then, the substrate with the mask prepared was etched with an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s to etch the regroove a groove a, with an etching depth of 7.3 μm.
[0142] 2.2) Regeneration of N-GaN layer 3
[0143] A 500 nm thick N-GaN layer was deposited using MOCVD deposition equipment.
[0144] 2.3) Regeneration of AlGaN layer 4
[0145] An AlGaN layer 4 with a thickness of 30 nm and an Al composition of 40% was deposited using an MOCVD deposition equipment.
[0146] Step 3. Fabrication of cathode 5.
[0147] First, the photoresist was spun at a speed of 5000 rpm using a spin coater to obtain a photoresist mask with a thickness of 0.8 μm.
[0148] Next, it was baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form the area mask pattern of cathode 4.
[0149] Then, the cathode was fabricated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The ohmic metals were Ti / Al / Ni / Au in sequence, with Ti having a thickness of 20 nm, Al having a thickness of 160 nm, Ni having a thickness of 55 nm, and Au having a thickness of 45 nm. After the ohmic contact metal of the cathode was evaporated, the metal was stripped to obtain a complete cathode 5.
[0150] Finally, the ohmic contact metal is alloyed by rapidly annealing in an N2 atmosphere at 870°C for 30 seconds using an RTP500 rapid thermal annealing furnace to complete the fabrication of cathode 5.
[0151] Step 4. Growth of dielectric layer 6.
[0152] An Al2O3 dielectric layer with a thickness of 700 nm was deposited using an MOCVD deposition equipment.
[0153] Step 5. Anode 7 fabrication.
[0154] 5.1) Etch away a portion of the top surface of the P-GaN layer 2 and regenerate the N-GaN layer 3, the AlGaN layer 4, and the dielectric layer 6;
[0155] First, a spin coater is used to spin the coating at a speed of 3500 rpm, and then an NSR1755I7A lithography machine is used for exposure to form a partial mask pattern on the top surface of P-GaN layer 2.
[0156] The masked substrate was then etched using an ICP98c inductively coupled plasma etching machine in Cl2 plasma at an etching rate of 1 nm / s, with an etching depth of 1.23 μm.
[0157] 5.2) Fabrication of the anode groove
[0158] The photoresist was spun onto the surface of the epitaxial material at a speed of 5000 rpm to obtain a photoresist mask with a thickness of 0.8 μm. It was then baked in a high-temperature oven at 80℃ for 10 min. Finally, it was exposed using an NSR1755I7A lithography machine to obtain the photoresist mask of the anode groove c and the development was completed.
[0159] Next, an ICP98c inductively coupled plasma etching machine was used to etch and remove the 500nm thick P-GaN layer 2 in Cl2 plasma at an etching rate of 0.5nm / s, forming the anode groove c.
[0160] 5.3) Anode fabrication
[0161] First, a photoresist mask with a thickness of 0.8 μm was obtained by spinning the photoresist mask at a speed of 5000 rpm.
[0162] Next, it was baked in a high-temperature oven at 80°C for 10 minutes, and then exposed using an NSR1755I7A lithography machine to form the area mask pattern of anode 7;
[0163] Finally, the anode metal was evaporated using an Ohmiker-50 electron beam evaporation stage at an evaporation rate of 0.1 nm / s. The anode metals were Ni / Au, with a Ni thickness of 45 nm and an Au thickness of 200 nm. After evaporation, the metal was stripped to obtain a complete anode 7.
[0164] The high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction fabricated in this invention forms an AlGaN / GaN heterojunction with the regrown AlGaN layer and the regrown N-GaN layer in the regrowing groove in the vertical direction, generating a 2DEG at the heterojunction interface, which can improve the forward current of the diode. Simultaneously, the high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction fabricated in this invention, with the regrown N-GaN layer in the regrowing groove... - A PN junction is formed between the GaN layer and the P-GaN layer, which can uniformly disperse the peak electric field, improve the electric field concentration effect, and increase the breakdown voltage. At the same time, in reverse, the PN junction can more effectively reduce reverse leakage current compared to the Schottky junction.
[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction, characterized in that, Includes the following steps: 1) In N with a thickness of 1-4 μm + A P-GaN layer (2) with a thickness of 3 to 9 μm is grown on the front side of the GaN layer (1); 2) In the N + Grooves (a) are etched on the N-GaN layer (1) and the P-GaN layer (2), wherein the width of the groove (a) is 3-5 μm and the depth is such that the N-GaN layer is etched into the P-GaN layer (2). + - The GaN layer (1) is etched away by 100-500 nm; 3) Grow a layer of N with a thickness of 100-500 nm. - -GaN layer(3); 4) In the N - - An AlGaN layer (4) with a thickness of 10-30 nm is grown on the GaN layer (3); 5) In the N + - A cathode (5) is fabricated on the bottom surface of the GaN layer (1); 6) Deposit a dielectric layer (6) with a thickness of 0.2 to 1 μm on the AlGaN layer (4); 7) Etch away a portion of the N located on the P-GaN layer (2). - -GaN layer (3), AlGaN layer (4) and dielectric layer (6), exposing the top surface of the P-GaN layer (2); 8) An anode groove (c) is etched on the top surface of the exposed P-GaN layer (2), the depth of which is 300-900 nm; 9) An anode (7) is fabricated in the anode groove (c), on the remaining dielectric layer (6) and on part of the P-GaN layer (2).
2. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 1, characterized in that, The Al composition of the AlGaN layer (4) is 15% to 40%.
3. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 2, characterized in that, The dielectric layer (6) is an Al2O3 layer, a SiN layer, or a SiO2 layer.
4. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 3, characterized in that, The AlGaN layer (4) and the N - - A two-dimensional electron gas (b) is formed between the GaN layers (3) in the vertical direction, but no two-dimensional electron gas is formed in the horizontal direction.
5. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 4, characterized in that, The N - A PN junction is formed between the -GaN layer (3) and the P-GaN layer (2).
6. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 5, characterized in that, The cathode (5) is composed of a Ti layer, an Al layer, a Ni layer and an Au layer stacked together, wherein the thickness of the Ti layer is 20 nm, the thickness of the Al layer is 160 nm, the thickness of the Ni layer is 55 nm and the thickness of the Au layer is 45 nm.
7. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 6, characterized in that, After step 5), a rapid metal annealing process is performed first, followed by step 6). The rapid metal annealing process is a rapid thermal annealing at 870°C in a N2 atmosphere for 30 seconds.
8. The method for fabricating a high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction according to claim 7, characterized in that, The anode (7) is composed of a Ni layer and an Au layer stacked together, wherein the thickness of the Ni layer is 45 nm and the thickness of the Au layer is 200 nm.
9. A high-voltage Schottky diode with a vertical AlGaN / GaN heterojunction, characterized in that, It is prepared using the preparation method described in any one of claims 1-8.