A high surge multi-stage trench schottky diode and a preparation method thereof

Abstract

The application belongs to the technical field of semiconductor devices, and provides a high-surge multi-stage trench Schottky diode and a preparation method thereof. The Schottky diode comprises an anode, an epitaxial wafer and a cathode arranged in sequence. The epitaxial wafer comprises a semiconductor substrate and an epitaxial layer. The epitaxial layer is provided with a plurality of deep trenches on a side in contact with the anode; each deep trench comprises n sub-trenches, the width of each sub-trench gradually decreases in a direction pointing to the bottom along the opening of the deep trench, and n is a positive integer greater than 1. The inner wall and the bottom of each deep trench are provided with a hetero-barrier layer, and a field plate dielectric is further provided in contact with the hetero-barrier layer; and the opening of the deep trench is surrounded by the hetero-barrier layer. The deep trench is filled with a filling structure. The high-surge multi-stage trench Schottky diode has a better electric field shielding effect in a reverse blocking state, can further reduce the electric field of the metal-semiconductor interface, and improve the breakdown voltage of the device, the surge capacity and the long-term working reliability.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, and particularly relates to the field of Schottky diode technology, specifically to a high-surge multi-level trench Schottky diode and its fabrication method. Background Technology

[0002] In recent years, ultra-wide bandgap semiconductor materials with band gaps larger than SiC and GaN have become a new research area of ​​widespread interest due to their superior optical and electrical properties. The larger band gap allows devices to be used in many extreme and harsh environments. For example, in the context of geothermal energy production and oil and gas extraction, they enable higher drilling speeds and lower failure rates. In high-temperature environments, they allow for higher operating temperatures in aluminum plants, steel mills, and coal-fired and gas-fired power plants controlled by electronic sensors, thereby improving the energy efficiency of these industrial processes.

[0003] Baliga's figure-of-merit (BFOM) is an indicator used to represent the suitability of semiconductor materials for power electronics applications. It is expressed as: BFOM = εμE 3 Where ε is the dielectric constant, μ is the mobility, and E is the breakdown field strength of the semiconductor. The BFOM value is approximately equal to the bandgap width E. g The bandgap is positively correlated with the sixth power of the voltage; therefore, a larger bandgap semiconductor means lower power loss and higher conversion efficiency in power device applications, leading to superior and more ideal power electronics applications. Among wide bandgap semiconductor materials, Ga2O3 has a bandgap of 4.8 eV, an ideal breakdown electric field strength of 8 MV / cm, and a BFOM value as high as 3400, approximately four times that of GaN and ten times that of SiC. Therefore, in today's power electronics applications with higher power density and lower power consumption requirements, Ga2O3 material has greater research significance and broader market application prospects.

[0004] However, p-type doped Ga2O3 is difficult to achieve due to various constraints. First, it is difficult to find acceptor impurities with low activation energies. Second, theoretical calculations show that the valence band maximum dispersion of Ga2O3 is small, resulting in a very large effective mass, causing free holes to be almost locally distributed with small μ values. Finally, theoretical predictions specifically for Ga2O3 indicate that due to local lattice distortion, the local self-trapping energy of free holes in the volume is very large, leading to the formation of small poles, which undoubtedly prohibits the conduction of effective holes. These constraints limit the application of Ga2O3 in bipolar power devices.

[0005] The maximum electric field in a gallium oxide Schottky diode occurs at the metal-semiconductor interface. The resulting image force lowers the Schottky barrier height, increases reverse leakage current, and degrades device reliability. Existing technologies introduce p-type oxide barrier layers such as NiO to reduce the electric field at the metal-semiconductor interface. However, because the p-type oxide barrier layer is located on the epitaxial surface, the depletion region expansion is insufficient in the reverse blocking state, resulting in limited electric field shielding. The electric field at the metal-semiconductor interface remains strong, and the leakage current increases significantly with increasing reverse voltage, severely affecting the stability of the Schottky contact and significantly impacting the long-term reliability of the device. Furthermore, because the p-type oxide barrier layer cannot provide hole injection to the drift region (HVPE n) under high forward current,... - The conductivity is modulated using Ga2O3 (10μm), so its surge resistance is relatively weak. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a high-surge multi-level trench Schottky diode, which achieves better electric field shielding in reverse blocking mode, further reduces the electric field at the metal-semiconductor interface, improves the device's breakdown voltage and long-term operational reliability, and enhances surge capability.

[0007] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0008] A high-surge multi-level trench Schottky diode includes an anode, an epitaxial wafer, and a cathode arranged sequentially. The epitaxial wafer includes a semiconductor substrate and an epitaxial layer located on the surface of the semiconductor substrate. The cathode is in contact with the side of the semiconductor substrate opposite to the epitaxial layer, and the anode is in contact with the side of the epitaxial layer opposite to the semiconductor substrate. A plurality of deep trenches are provided on the side of the epitaxial layer in contact with the anode. Each deep trench includes n sub-trenches, and the width of each sub-trench gradually decreases along a first direction, where n is a positive integer greater than 1. The first direction is the direction in which the opening of the deep trench points to the bottom. A heterogeneous barrier layer is provided on the inner wall and bottom of each deep trench, and a field plate dielectric is provided in contact with the heterogeneous barrier layer. The opening of the deep trench is surrounded by the heterogeneous barrier layer. The deep trench is filled with a filling structure.

[0009] In an alternative embodiment, the field plate medium surrounds the opening of the deep trench, and the field plate medium is located between the anode and the heterogeneous barrier layer.

[0010] In an optional embodiment, at least one of the deep trenches has an ohmic contact metal layer at its bottom.

[0011] In an optional implementation, each of the deep trenches has a stepped cross-section along the first direction.

[0012] In an optional embodiment, the filling structure is an anode metal.

[0013] In an optional embodiment, the filling structure is a single dielectric filling structure, wherein the single dielectric is one of silicon oxide, silicon nitride, or polycrystalline silicon.

[0014] In an optional embodiment, the filling structure includes at least two of a first filling medium, a second filling medium, and a third filling medium, wherein the first filling medium is LPTEOS and / or ALD-Al2O3, the second filling medium is BPSG and / or polyimide, and the third filling medium is silicon oxide and / or silicon nitride.

[0015] Preferably, the first filling medium, the second filling medium, and the third filling medium are sequentially filled into the deep trench from the bottom toward the opening direction.

[0016] In an optional embodiment, the anode comprises at least one metal selected from nickel, gold, titanium, titanium tungsten, molybdenum, and aluminum.

[0017] In an optional embodiment, the cathode comprises at least one metal selected from titanium, gold, aluminum, and nickel.

[0018] This invention also provides a method for fabricating the above-mentioned high-surge multi-level trench Schottky diode, comprising the following steps:

[0019] S1. Prepare an epitaxial wafer, the epitaxial wafer comprising a semiconductor substrate and an epitaxial layer located on the surface of the semiconductor substrate;

[0020] The epitaxial wafer is made of a wide bandgap semiconductor or an ultra-wide bandgap semiconductor, such as GaN, Ga2O3, AlN, diamond, etc.; preferably, the semiconductor substrate and the epitaxial layer are doped with the same type, and the semiconductor substrate has a higher doping concentration.

[0021] S2. Deposit cathode metal on the side of the semiconductor substrate away from the epitaxial layer; preferably, the deposition method includes evaporation or sputtering, and the deposition thickness is 100-300 nm.

[0022] S3. Etch the side of the epitaxial layer away from the semiconductor substrate to form a plurality of deep trenches; preferably, the deep trenches are fabricated by ICP, RIE, or laser ablation process; n sub-trenches are correspondingly fabricated by n etching steps; more preferably, the etching process uses a mixture of a chlorine-containing gas (e.g., one or more of Cl2, BCl3, and SiCl4) and at least one of oxygen, nitrogen, and argon to etch the epitaxial layer;

[0023] S4. Deposit the heterogeneous barrier layer on the bottom and inner wall of each deep trench, and extend the heterogeneous barrier layer to the periphery of the opening of the deep trench; preferably, the heterogeneous barrier layer is deposited by magnetron sputtering; preferably, the material of the heterogeneous barrier layer includes an oxide of at least one element selected from Pt, Ni, Au, and Cu; preferably, the thickness of the heterogeneous barrier layer is 100–300 nm; preferably, the patterning of the heterogeneous barrier layer is performed using one of dry etching, wet etching, or stripping processes, wherein the dry etching uses one or more gases selected from Cl2, BCl3, and SiCl4, and the wet etching uses nitric acid or hydrochloric acid;

[0024] S5. The field plate dielectric is deposited and etched on the surface of the heterogeneous barrier layer at the bottom and inner wall of the deep trench to form the field plate dielectric; preferably, the field plate dielectric includes at least one of Al2O3, HfO2, silicon oxide, and silicon nitride; preferably, the field plate dielectric is deposited using the ALD method; preferably, the etching of the field plate dielectric is performed using a mixed gas of at least one of CF4, CHF3, CH2F2, and C4F8 with at least one of oxygen, nitrogen, and argon;

[0025] S6. An anode is deposited on the side of the epitaxial layer away from the semiconductor substrate, and the filling structure is filled inside the deep trench to obtain the high surge multi-level trench Schottky diode.

[0026] The anode forms a Schottky contact with the side of the epitaxial layer opposite to the semiconductor substrate, and the anode forms an ohmic contact with the heterogeneous barrier layer surrounding the deep trench opening.

[0027] Preferably, in step S5, the field plate medium extends to the periphery of the opening of the deep trench, such that both the field plate medium and the heterogeneous barrier layer surround the opening of the deep trench, and the field plate medium is located on the surface of the heterogeneous barrier layer.

[0028] Preferably, in step S5, an ohmic contact metal layer is deposited on the surface of the heterogeneous barrier layer at the bottom center of the deep trench; the ohmic contact metal layer is deposited by magnetron sputtering or vapor deposition; more preferably, the ohmic contact metal layer includes at least one metal selected from Ni, Au, Ti, TiW, Mo, and Al.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The high surge multi-level trench Schottky diode in the present invention can extend the heterogeneous barrier layer into the drift region, and the electric field shielding effect is better in the reverse blocking state, which can further reduce the electric field at the metal-semiconductor contact interface and improve the breakdown voltage and long-term reliability of the device. (2) The multi-level trench structure can make the thickness of p-type oxides such as NiO on the trench surface more uniform, and will not break down prematurely in the thinner part of the heterogeneous barrier layer, resulting in good reverse characteristics; at the same time, the downward current path is larger, the JFET effect is weakened, the series resistance is reduced, and thus the forward characteristics are also better. (3) The ohmic contact is made in the p-type oxide barrier layer, which is equivalent to integrating a heterojunction PiN diode. The turn-on voltage of the heterojunction PiN diode is larger than that of the Schottky diode, and it will only turn on when there is a large forward current; when the forward current is too large, the high surge structure can inject holes through the integrated heterojunction PiN diode to block the drift region (e.g., HVPE n). - (4) The field plate dielectric in the multi-level trench forms a multi-level fin field plate, which can modulate the electric field in the JFET region, making the electric field distribution more gentle, reducing the electric field concentration effect at the bottom of the trench, and reducing the reverse leakage current of the device. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the high-surge multi-level trench Schottky diode according to Embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the high-surge multi-level trench Schottky diode according to Embodiment 2 of the present invention;

[0032] Figure 3 This is a schematic diagram of the high surge multi-level trench Schottky diode of Embodiment 3 of the present invention.

[0033] In the figure: 1. Cathode; 2. Epitaxial wafer; 21. Semiconductor substrate; 22. Epitaxial layer; 3. Anode; 4. Heterogeneous barrier layer; 5. Field plate dielectric; 6. Ohmic contact metal layer; 7. Filling structure. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, any equivalent changes or substitutions made by those skilled in the art according to the following implementation methods without creative effort shall fall within the protection scope of the present invention.

[0035] Unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides a high-surge multi-level trench Schottky diode, including an anode 3, an epitaxial wafer 2, and a cathode 1. The epitaxial wafer 2 includes a semiconductor substrate 21 and an epitaxial layer 22, with the epitaxial layer 22 located on the surface of the semiconductor substrate 21. In this embodiment, the semiconductor substrate 21 is N+-doped (heavily doped N-type) gallium oxide, and the epitaxial layer 22 is N-doped (lightly doped N-type) gallium oxide; the anode is a nickel-gold alloy, and the cathode is a titanium-gold alloy. The side of the semiconductor substrate 21 facing away from the epitaxial layer 22 contacts the cathode 1, and the side of the epitaxial layer 22 facing away from the semiconductor substrate 21 contacts the anode 3. Multiple deep trenches are formed on the side of the epitaxial layer 22 that contacts the anode 3 (i.e., the side of the epitaxial layer 22 facing away from the semiconductor substrate 21), each deep trench including n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The first direction is the direction in which the opening of the deep trench points to the bottom (i.e.,...). Figure 1 (From top to bottom). In this embodiment, the cross-section of each deep trench along the first direction is stepped. The inner wall and bottom of each deep trench are covered with a heterogeneous barrier layer 4, which extends to the side of the epitaxial layer 22 that contacts the anode 3 and surrounds the opening of the deep trench. A field plate dielectric 5 is also covered on the heterogeneous barrier layer 4 on the inner wall and bottom of the deep trench. A filling structure 7 is filled inside each deep trench. In this embodiment, the heterogeneous barrier layer 4 is a p-type oxide NiO, the field plate dielectric 5 is Al2O3, and the filling structure 7 is an anode metal.

[0038] The fabrication method of the high-surge multi-level trench Schottky diode includes the following steps:

[0039] S1. Prepare a gallium oxide epitaxial wafer 2, the epitaxial wafer 2 including a semiconductor substrate 21 and an epitaxial layer 22 located on the surface of the semiconductor substrate 21.

[0040] S2. A titanium / gold alloy is deposited as a cathode 1 on the side of the semiconductor substrate 21 opposite to the epitaxial layer 22 by vapor deposition, with a deposition thickness of 200 nm.

[0041] S3. The epitaxial layer 22 is etched on the side opposite to the semiconductor substrate 21 using ICP (Inductively Coupled Plasma) etching to form multiple deep trenches. Each deep trench contains n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The n sub-trenches are fabricated through n etching steps. The etching gas used in the ICP etching process is a mixture of chlorine and nitrogen.

[0042] S4. A p-type NiO oxide layer 4 is deposited as a heterogeneous barrier layer 4 at the bottom and inner wall of each deep trench, and the heterogeneous barrier layer 4 is extended to surround the opening of the deep trench so that the heterogeneous barrier layer surrounds the opening of the deep trench. The NiO film is deposited by direct growth using magnetron sputtering, and a NiO film with a thickness of 200 nm is finally obtained. It is then annealed at 300 °C for 300 s in an O2 atmosphere. The NiO film is patterned by dry etching with chlorine gas.

[0043] S5. The field plate medium 5 is deposited and etched on the surface of the heterogeneous barrier layer 4 at the bottom and inner wall of the deep trench. The deposition is performed using ALD (atomic layer deposition) and the etching is performed using a mixture of CF4 and oxygen.

[0044] S6. A nickel / gold alloy is deposited as an anode on the side of the epitaxial layer 22 away from the semiconductor substrate 21, and the anode metal is filled in the deep trench. The anode 3 forms a Schottky contact with the side of the epitaxial layer 22 away from the semiconductor substrate 21, and the metal of the anode 3 forms an ohmic contact with the heterogeneous barrier layer 4 surrounding the opening of the deep trench, thus obtaining the high surge multilevel trench Schottky diode.

[0045] Example 2

[0046] like Figure 2 As shown, this embodiment provides a high-surge multi-level trench Schottky diode, including an anode 3, an epitaxial wafer 2, and a cathode 1. The epitaxial wafer 2 includes a semiconductor substrate 21 and an epitaxial layer 22, with the epitaxial layer 22 located on the surface of the semiconductor substrate 21. In this embodiment, the semiconductor substrate 21 is N+ type doped diamond, and the epitaxial layer 22 is N- type doped diamond; the anode is metallic titanium, and the cathode is metallic nickel. The side of the semiconductor substrate 21 facing away from the epitaxial layer 22 is in contact with the cathode 1, and the side of the epitaxial layer 22 facing away from the semiconductor substrate 21 is in contact with the anode 3. Multiple deep trenches are formed on the side of the epitaxial layer 22 that contacts the anode 3 (i.e., the side of the epitaxial layer 22 facing away from the semiconductor substrate 21), each deep trench including n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The first direction is the direction in which the opening of the deep trench points to the bottom (i.e.,...). Figure 1(From top to bottom). In this embodiment, the cross-section of each deep trench along the first direction is stepped. The inner wall and bottom of each deep trench are covered with a heterogeneous barrier layer 4, which extends to the side of the epitaxial layer 22 that contacts the anode 3 and surrounds the opening of the deep trench. A field plate dielectric 5 is also covered on the heterogeneous barrier layer 4 on the inner wall and bottom of the deep trench, which extends from the inside of the deep trench to the side of the heterogeneous barrier layer 4 that contacts the anode 3 and surrounds the opening of the deep trench (i.e., the field plate dielectric 5 is located between the heterogeneous barrier layer 4 and the anode 3). A filling structure 7 is filled inside each deep trench. In this embodiment, the filling structure 7 is a single dielectric filling structure, such as any one of silicon oxide, silicon nitride, or polycrystalline silicon; the field plate dielectric 5 is silicon oxide, and the heterogeneous barrier layer 4 is p-type oxide PtO2.

[0047] The fabrication method of the high-surge multi-level trench Schottky diode includes the following steps:

[0048] S1. Prepare a diamond epitaxial wafer 2, the epitaxial wafer 2 comprising a semiconductor substrate 21 and an epitaxial layer 22 located on the surface of the semiconductor substrate 21.

[0049] S2. On the side of the semiconductor substrate 21 away from the epitaxial layer 22, metallic nickel is deposited as a cathode 1 by sputtering, with a deposition thickness of 100 nm.

[0050] S3. The epitaxial layer 22 is etched on the side opposite to the semiconductor substrate 21 using RIE (Reactive Ion Etching) technology to form multiple deep trenches. Each deep trench contains n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The n sub-trenches are fabricated through n etching processes. The etching gas used in the RIE process is a mixture of BCl3 and oxygen.

[0051] S4. A p-type oxide PtO2 is deposited as a heterogeneous barrier layer 4 at the bottom and inner wall of each deep trench, and the heterogeneous barrier layer 4 is extended to surround the opening of the deep trench, thus enclosing the opening of the deep trench. During PtO2 film deposition, a layer of Pt metal is first sputtered, followed by high-temperature oxidation growth at 600°C for 10 min, ultimately obtaining a PtO2 film with a thickness of 100 nm. The film is then annealed at 300°C for 300 s in an O2 atmosphere. PtO2 film patterning is performed using dry etching with BCl3.

[0052] S5. The field plate medium 5 is deposited and etched on the surface of the heterogeneous barrier layer 4 at the bottom and inner wall of the deep trench. The deposition is carried out using ALD (atomic layer deposition) method, and the etching is carried out using a mixed gas of CHF3, CH2F2 and nitrogen.

[0053] S6. Deposit titanium metal as an anode on the side of the epitaxial layer 22 away from the semiconductor substrate 21, and fill the deep trench with any one of silicon oxide, silicon nitride, or polysilicon as a single filling medium; the anode 3 forms a Schottky contact with the side of the epitaxial layer 22 away from the semiconductor substrate 21, and the anode 3 forms an ohmic contact with the heterogeneous barrier layer 4 surrounding the opening of the deep trench, thus obtaining the high surge multilevel trench Schottky diode.

[0054] Example 3

[0055] like Figure 3 As shown, this embodiment provides a high-surge multi-level trench Schottky diode, including an anode 3, an epitaxial wafer 2, and a cathode 1. The epitaxial wafer 2 includes a semiconductor substrate 21 and an epitaxial layer 22, with the epitaxial layer 22 located on the surface of the semiconductor substrate 21. In this embodiment, the semiconductor substrate 21 is N+-type doped aluminum nitride (AlN), and the epitaxial layer 22 is N-type doped aluminum nitride; the anode is titanium tungsten carbide (TiW), and the cathode is metallic aluminum. The side of the semiconductor substrate 21 facing away from the epitaxial layer 22 is in contact with the cathode 1, and the side of the epitaxial layer 22 facing away from the semiconductor substrate 21 is in contact with the anode 3. Multiple deep trenches are provided on the side of the epitaxial layer 22 that contacts the anode 3 (i.e., the side of the epitaxial layer 22 facing away from the semiconductor substrate 21), each deep trench including n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The first direction is the direction in which the opening of the deep trench points to the bottom (i.e.,...). Figure 1 (From top to bottom). In this embodiment, the cross-section of each deep trench along the first direction is stepped. The inner wall and bottom of each deep trench are covered with a heterogeneous barrier layer 4, which extends to the side of the epitaxial layer 22 that contacts the anode 3 and surrounds the opening of the deep trench. A field plate dielectric 5 is also covered on the heterogeneous barrier layer 4 on the inner wall of the deep trench. In this embodiment, the heterogeneous barrier layer 4 is p-type oxide Au2O3, and the field plate dielectric 5 is silicon nitride. A field plate dielectric 5 is covered on the heterogeneous barrier layer 4 near the inner wall at the bottom of at least one deep trench, and an ohmic contact metal layer 6 is covered on the heterogeneous barrier layer 4 at the very center of the bottom of the deep trench. In this embodiment, the ohmic contact metal layer 6 is metallic nickel. Each deep trench is filled with a filling structure 7. In this embodiment, the filling structure 7 contains multiple filling media. From the opening of the deep trench to the bottom (i.e., the first direction), the third filling medium silicon nitride, the second filling medium polyimide, and the first filling medium LPTEOS (low-pressure tetraethyl silicate vapor-deposited silicon oxide) are filled in sequence.

[0056] It should be noted that the first filling medium can also be ALD-Al2O3 (atomic layer deposited alumina) or a mixture of LPTEOS and ALD-Al2O3, the second filling medium can also be BPSG (borophosphosilicate glass) or a mixture of polyimide and BPSG, and the third filling medium can also be silicon oxide or a mixture of silicon oxide and silicon nitride.

[0057] The fabrication method of the high-surge multi-level trench Schottky diode includes the following steps:

[0058] S1. Prepare an aluminum nitride epitaxial wafer 2, the epitaxial wafer 2 comprising a semiconductor substrate 21 and an epitaxial layer 22 located on the surface of the semiconductor substrate 21.

[0059] S2. On the side of the semiconductor substrate 21 away from the epitaxial layer 22, metallic aluminum is deposited as cathode 1 by vapor deposition, with a deposition thickness of 300nm.

[0060] S3. The epitaxial layer 22 is etched on the side opposite to the semiconductor substrate 21 using a laser ablation process to form multiple deep trenches. Each deep trench contains n sub-trenches (n is a positive integer ≥ 2), and the width of each sub-trench gradually decreases along a first direction. The n sub-trenches are correspondingly created through n etching steps. The etching gas used in the laser ablation process is a mixture of SiCl4 and argon.

[0061] S4. A p-type oxide Au₂O₃ is deposited as a heterogeneous barrier layer 4 at the bottom and inner wall of each deep trench, and the heterogeneous barrier layer 4 is extended to surround the opening of the deep trench, thus enclosing the opening of the deep trench. Magnetron sputtering is used to deposit the Au₂O₃ film, resulting in a 300 nm thick Au₂O₃ film, which is then annealed at 300 °C for 300 s in an O₂ atmosphere. The Au₂O₃ film is patterned using dry etching with SiCl₄.

[0062] S5. A field plate dielectric 5 is deposited and etched on the surface of the heterogeneous barrier layer 4 at the bottom and inner wall of the deep trench. An ohmic contact metal layer 6 is deposited on the surface of the heterogeneous barrier layer 4 at the middle position of the bottom of the deep trench. The deposition of the field plate dielectric 5 is performed using ALD (atomic layer deposition), and the etching is performed using a mixture of C4F8 and argon gas. The ohmic contact metal layer is deposited using magnetron sputtering or vapor deposition.

[0063] S6. Deposit TiW as an anode on the side of the epitaxial layer 22 away from the semiconductor substrate 21. Sequentially fill the deep trench with a third filling medium, silicon nitride, a second filling medium, polyimide, and a first filling medium, LPTEOS, along the first direction. The anode 3 forms a Schottky contact with the side of the epitaxial layer 22 away from the semiconductor substrate 21. The metal of the anode 3 forms an ohmic contact with the heterogeneous barrier layer 4 surrounding the opening of the deep trench, thus obtaining the high-surge multilevel trench Schottky diode.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Various modifications and variations can be made to the present invention by any person skilled in the art. Any simple equivalent changes and modifications made based on the scope of protection of the present invention and the content of the specification should be included within the scope of protection of the present invention.

Claims

1. A high-surge multi-level trench Schottky diode, characterized in that, The device includes an anode, an epitaxial wafer, and a cathode arranged sequentially. The epitaxial wafer includes a semiconductor substrate and an epitaxial layer located on the surface of the semiconductor substrate. The cathode is in contact with the side of the semiconductor substrate facing away from the epitaxial layer, and the anode is in contact with the side of the epitaxial layer facing away from the semiconductor substrate. A plurality of deep trenches are provided on the side of the epitaxial layer in contact with the anode. Each deep trench includes n sub-trenches, and the width of each sub-trench gradually decreases along a first direction, where n is a positive integer greater than 1. The first direction is the direction in which the opening of the deep trench points to the bottom. A heterogeneous barrier layer is provided on the inner wall and bottom of each deep trench, and a field plate dielectric is provided in contact with the heterogeneous barrier layer. The field plate medium surrounds the opening of the deep trench, and the field plate medium is located between the anode and the heterogeneous barrier layer; the opening of the deep trench is surrounded by the heterogeneous barrier layer; the deep trench is filled with a filling structure; an ohmic contact metal layer is disposed on the surface of the heterogeneous barrier layer at the bottom of at least one of the deep trenches; the material of the heterogeneous barrier layer is a p-type oxide of at least one element selected from Pt, Ni, Au, and Cu.

2. The high-surge multi-level trench Schottky diode according to claim 1, characterized in that, Each of the deep trenches has a stepped cross-section along the first direction.

3. The high-surge multi-level trench Schottky diode according to claim 1, characterized in that, The filling structure is an anode metal.

4. The high-surge multi-level trench Schottky diode according to claim 1, characterized in that, The filling structure is a single dielectric filling structure, and the single dielectric is one of silicon oxide, silicon nitride or polycrystalline silicon.

5. The high-surge multi-level trench Schottky diode according to claim 1, characterized in that, The filling structure includes at least two of a first filling medium, a second filling medium, and a third filling medium, wherein the first filling medium is LPTEOS or / and ALD-Al2O3, the second filling medium is BPSG or / and polyimide, and the third filling medium is silicon oxide or / and silicon nitride.

6. The high-surge multi-level trench Schottky diode according to claim 1, characterized in that, The anode comprises at least one metal selected from nickel, gold, titanium, titanium tungsten, molybdenum, and aluminum; and / or the cathode comprises at least one metal selected from titanium, gold, aluminum, and nickel.

7. The method for fabricating a high-surge multi-level trench Schottky diode according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Prepare an epitaxial wafer, the epitaxial wafer comprising a semiconductor substrate and an epitaxial layer located on the surface of the semiconductor substrate; S2. Deposit cathode metal on the side of the semiconductor substrate away from the epitaxial layer; S3. Etch the side of the epitaxial layer away from the semiconductor substrate to form a plurality of deep trenches; S4. Deposit the heterogeneous barrier layer on the bottom and inner wall of each of the deep trenches, and extend the heterogeneous barrier layer to the periphery of the opening of the deep trench; S5. Deposit and etch the field plate medium on the surface of the heterogeneous barrier layer at the bottom and inner wall of the deep trench; the field plate medium extends to the area around the opening of the deep trench; An ohmic contact metal layer is deposited on the surface of the heterogeneous barrier layer at the bottom center of the deep trench; S6. An anode is deposited on the side of the epitaxial layer away from the semiconductor substrate, and the filling structure is filled inside the deep trench to obtain the high surge multi-level trench Schottky diode.

Images