Groove type Schottky barrier diode and manufacturing method thereof

Abstract

The invention provides a groove type Schottky barrier diode and a preparation method thereof. The diode comprises a substrate, the surface of the substrate comprises a device layer, the device layer has a first conductive type, the surface of the device layer further comprises a groove, the groove is arranged on the surface of the device layer, and the groove is filled with an insulating medium; the field plate is arranged in the insulating medium; the bottom inversion layer is arranged at the bottom of the groove and has a second conduction type; the diode further comprises a metal anode layer. According to the technical scheme, the bottom inversion layer is arranged and used for modulating electric field distribution of the device layer, mainly smooth longitudinal electric field distribution, and due to the fact that the bottom inversion layer has the conductivity type different from that of the device layer, it is equivalent to that charge traps of P-N junctions are added to the bottom, and a neutral area is provided; the trend that an electric field is intensively distributed on the surface can be slowed down, and the electric field is more uniformly distributed in the direction perpendicular to the surface of the substrate.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and more particularly to a trench Schottky barrier diode and its fabrication method. Background Technology

[0002] Schottky barrier diodes are made using the characteristics of metal-semiconductor (MS) contacts. Since the current transport in a metal-semiconductor contact mainly relies on majority carriers (electrons), its electron mobility is high. Furthermore, MS junctions can be precisely manufactured at the submicron scale, enabling Schottky barrier diodes to be used in submillimeter-wave and terahertz frequency bands.

[0003] Compared to traditional Schottky barrier diodes, trench MOS structure Schottky diodes (TMBS) exhibit better reverse blocking characteristics and lower reverse leakage current. TMBS devices primarily utilize a thin-layer MOS structure to adjust the electric field distribution in the active region between trenches. This alters the electric field distribution within the depletion layer under a given reverse bias, resulting in higher breakdown voltage and lower leakage current for TMBS devices compared to planar Schottky diodes with the same doping concentration. Therefore, improving the breakdown voltage characteristics of TMBS has been a key focus of TMBS research and development. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a trench Schottky barrier diode and its fabrication method, which can improve the voltage withstand characteristics of the diode.

[0005] To address the aforementioned problems, this invention provides a trench-type Schottky barrier diode, comprising: a substrate, the surface of which includes a device layer having a first conductivity type; the surface of the device layer further including: a trench disposed on the surface of the device layer, the trench being filled with an insulating dielectric; a field plate disposed within the insulating dielectric to modulate the electric field distribution of the device layer; and a bottom inversion layer disposed at the bottom of the trench and having a second conductivity type for modulating the electric field distribution of the device layer; the diode further comprising: a metal anode layer covering the surface of the device layer, forming a Schottky diode with the device layer; and the field plate being electrically connected to the metal anode layer.

[0006] Optionally, the field plate is a stepped field plate, with the gradient direction set to converge downwards from the surface of the substrate.

[0007] Optionally, the field plate is made of polycrystalline silicon.

[0008] Optionally, the insulating medium is made of silicon oxide.

[0009] Optionally, the first conductivity type is N-type, and the second conductivity type is P-type.

[0010] To address the aforementioned problems, this invention provides a method for fabricating a trench-type Schottky barrier diode, comprising the following steps: providing a substrate, the surface of which includes a device layer having a first conductivity type; forming a trench within the device layer; forming a bottom inversion layer at the bottom of the trench, the bottom inversion layer having a second conductivity type for modulating the electric field distribution of the device layer; filling the trench with an insulating dielectric; forming a field plate within the insulating dielectric; forming a metal anode layer on the surface of the device layer, thereby forming a Schottky diode with the device layer, wherein the field plate is in contact with the metal anode layer to modulate the electric field distribution of the device layer.

[0011] Optionally, the field plate is a stepped field plate, with the gradient direction set to converge downwards from the surface of the substrate.

[0012] Optionally, the field plate is made of polycrystalline silicon.

[0013] Optionally, the insulating medium is made of silicon oxide.

[0014] Optionally, the first conductivity type is N-type, and the second conductivity type is P-type.

[0015] The above technical solution sets up a bottom inversion layer to modulate the electric field distribution of the device layer, mainly to smooth the vertical electric field distribution. Since the bottom inversion layer has a different conductivity type than the device layer, it is equivalent to adding a charge trap of the PN junction at the bottom, providing a neutral region, which can reduce the tendency of the electric field to concentrate on the surface and make it more uniformly distributed along the direction perpendicular to the substrate surface. Attached Figure Description

[0016] Appendix Figure 1 The diagram shown is a structural schematic of a trench Schottky barrier diode according to the present invention.

[0017] Appendix Figure 2 The diagram shows the implementation steps of a method for fabricating a slotted Schottky barrier diode according to a specific embodiment of the present invention.

[0018] Appendix Figure 3A To be continued Figure 3F The diagram shown is a process flow chart of the fabrication method of the slotted Schottky barrier diode according to a specific embodiment of the present invention. Detailed Implementation

[0019] The specific embodiments of the trench Schottky barrier diode and its fabrication method provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0020] Appendix Figure 1The diagram shows a structural schematic of a trench Schottky barrier diode according to the present invention, including: a substrate 40, a device layer 10 on the surface of the substrate 30, and a metal anode layer 20.

[0021] The device layer 10 has a first conductivity type. In this specific embodiment, the substrate 40 and the device layer 10 are single-crystal silicon substrates. In other specific embodiments, they can be any common substrate material, including single-crystal silicon, germanium silicon, SOI, SiC, sapphire, GaAs, and GaN. The first conductivity type is N-type, and the second conductivity type is P-type. In other specific embodiments, the first conductivity type can be p-type, and the second conductivity type can be N-type. The device layer 10 is formed on the surface of the substrate 40 using an epitaxial process.

[0022] In this specific embodiment, the device layer 10 includes a trench 11, a field plate 12, and a bottom inversion layer 13.

[0023] The trench 11 is disposed on the surface of the device layer 10, and the trench is filled with an insulating medium 14. In this specific embodiment, the insulating medium 14 is silicon oxide; in other specific embodiments, the insulating medium can be any material including silicon oxide, silicon nitride, silicon oxynitride, etc., or a multilayer composite layer composed of them. The accompanying drawings of this specific embodiment illustrate two trenches as an example. In other specific embodiments, more or fewer trenches connected in parallel should be considered as feasible technical solutions.

[0024] The field plate 12 is disposed within the insulating medium, preferably a stepped field plate, and its material includes, but is not limited to, polycrystalline silicon, or any metal or alloy thereof, including copper, aluminum, tungsten, and titanium. The field plate 12 is in contact with the metal anode layer 20 to modulate the electric field distribution of the device layer 10. This primarily smooths the longitudinal electric field distribution, reducing the tendency for the electric field to concentrate on the surface and making it more uniformly distributed along the direction perpendicular to the substrate surface.

[0025] The bottom inversion layer 13 is disposed at the bottom of the trench 11, preferably made of the same material as the device layer 10, and has a second conductivity type different from that of the device layer 10, for modulating the electric field distribution of the device layer 10. This primarily smooths the longitudinal electric field distribution. Because the bottom inversion layer 13 has a different conductivity type than the device layer 10, it is equivalent to adding a charge trap for the PN junction at the bottom, providing a neutral region that can mitigate the tendency of the electric field to concentrate on the surface, making it more uniformly distributed along the direction perpendicular to the substrate surface.

[0026] The diode further includes a metal anode layer 20, which can be made of any metal, including copper, aluminum, tungsten, and titanium, or an alloy thereof. The metal anode layer 20 covers the surface of the device layer 10, forming a Schottky diode. The field plate 12 is in contact with the metal anode layer 20 to provide an electrical path to the outside. A metal cathode layer 21 is also included on the back side of the substrate, forming the two electrodes of the Schottky diode together with the metal anode layer 20.

[0027] Appendix Figure 2 The diagram illustrates the implementation steps of a method for fabricating a trench-type Schottky barrier diode according to a specific embodiment of the present invention, including: Step S10, providing a substrate, the surface of which includes a device layer having a first conductivity type; Step S11, forming a trench within the device layer; Step S12, forming a bottom inversion layer at the bottom of the trench, the bottom inversion layer having a second conductivity type for modulating the electric field distribution of the device layer; Step S13, filling the trench with an insulating dielectric; Step S14, forming a field plate within the insulating dielectric; Step S15, forming a metal anode layer on the surface of the device layer, forming a Schottky diode with the device layer, the field plate contacting the metal anode layer to modulate the electric field distribution of the device layer.

[0028] Appendix Figure 3A To be continued Figure 3F The diagram shown is a process flow chart of the fabrication method of the slotted Schottky barrier diode according to a specific embodiment of the present invention.

[0029] Appendix Figure 3A As shown, referring to step S10, a substrate 40 is provided. The surface of the substrate includes a device layer 30, which has a first conductivity type. In this specific embodiment, the device layer 30 is a single-crystal silicon substrate; in other embodiments, it can be any common device layer including single-crystal silicon, germanium silicon, SOI, SiC, sapphire, GaAs, and GaN. The first conductivity type is N-type, and the second conductivity type is P-type. In other specific embodiments, the first conductivity type can be p-type, and the second conductivity type can be N-type.

[0030] Appendix Figure 3B As shown, referring to step S11, trenches are formed within the device layer 30. The trenches 31 can be formed by photolithography and etching on the surface of the device layer 30.

[0031] Appendix Figure 3CAs shown, referring to step S12, a bottom inversion layer 33 is formed at the bottom of the trench 31. The bottom inversion layer 33 has a second conductivity type and is used to modulate the electric field distribution of the device layer 30. The bottom inversion layer 33 is disposed at the bottom of the trench 31. Doped regions can be selectively formed at the bottom by ion implantation or diffusion, and then annealed to form an inversion layer with a different conductivity type. The bottom inversion layer 33 has a second conductivity type different from that of the device layer 30 and is used to modulate the electric field distribution of the device layer 30. Here, it mainly smooths the vertical electric field distribution. Since the bottom inversion layer 33 has a different conductivity type than that of the device layer 30, it is equivalent to adding a charge trap of the PN junction at the bottom, providing a neutral region, which can reduce the tendency of the electric field to concentrate on the surface and make it more uniformly distributed along the direction perpendicular to the substrate surface.

[0032] Appendix Figure 3D As shown, referring to step S13, the trench 31 is filled with an insulating medium 34. In this specific embodiment, the insulating medium 34 is silicon oxide; in other specific embodiments, the insulating medium can be any material including silicon oxide, silicon nitride, silicon oxynitride, or a multilayer composite layer composed of them. The formation method can be to form a continuous insulating medium by epitaxial deposition, and to remove the insulating medium on the surface of the device layer 30 by polishing, while retaining the insulating medium 34 in the trench 31.

[0033] Appendix Figure 3E As shown, referring to step S14, a field plate 32 is formed within the insulating medium 34. The field plate 32 is made of materials including, but not limited to, polysilicon, or any metal or alloy thereof, including copper, aluminum, tungsten, and titanium. The field plate 32 is used to modulate the electric field distribution of the device layer 30. Primarily, it smooths the longitudinal electric field distribution, reduces the tendency for the electric field to concentrate on the surface, and makes it more uniformly distributed along the direction perpendicular to the substrate surface. The formation method can first involve etching trenches within the insulating medium, then epitaxially depositing a continuous polysilicon layer, and finally polishing to remove the polysilicon layer on the surface of the device layer 30, leaving the polysilicon layer within the insulating medium 34 to form the field plate 32.

[0034] Appendix Figure 3F As shown, referring to step S15, a metal anode layer 40 is formed on the surface of the device layer 30, forming a Schottky diode with the device layer 30. The field plate 32 is in contact with the metal anode layer to modulate the electric field distribution of the device layer.

[0035] After the above steps are completed, the structure of the obtained trench Schottky barrier diode is shown in the attached figure. Figure 1 As shown.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A trench-type Schottky barrier diode, characterized in that, include: A substrate, the surface of which includes a device layer having a first conductivity type, the surface of which further includes: The trench is disposed on the surface of the device layer and is filled with an insulating medium. An electric field plate is disposed within the insulating medium to modulate the electric field distribution of the device layer; A bottom inversion layer is disposed at the bottom of the trench and has a second conductivity type for modulating the electric field distribution of the device layer; The diode also includes: A metal anode layer covers the surface of the device layer and forms a Schottky diode with the device layer. The field plate is electrically connected to the metal anode layer.

2. The diode according to claim 1, characterized in that, The device layer is formed using an epitaxial process.

3. The diode according to claim 1, characterized in that, The field plate is a stepped field plate, with the gradient direction set to converge downwards from the surface of the substrate.

4. The diode according to claim 1, characterized in that, The field plate is made of polycrystalline silicon.

5. The diode according to claim 1, characterized in that, The insulating medium is made of silicon oxide.

6. The diode according to claim 1, characterized in that, The first conductivity type is N-type, and the second conductivity type is P-type.

7. A method for fabricating a trench Schottky barrier diode, characterized in that, Includes the following steps: A substrate is provided, the surface of which includes a device layer having a first conductivity type; Trenches are formed within the device layer; A bottom inversion layer is formed at the bottom of the trench, the bottom inversion layer having a second conductivity type for modulating the electric field distribution of the device layer; The trench is filled with an insulating medium; A field plate is formed within the insulating medium; A metal anode layer is formed on the surface of the device layer, forming a Schottky diode with the device layer. The field plate is in contact with the metal anode layer to modulate the electric field distribution of the device layer.

8. The method according to claim 7, characterized in that, The field plate is a stepped field plate, with the gradient direction set to converge downwards from the surface of the substrate.

9. The method according to claim 7, characterized in that, The field plate is made of polycrystalline silicon.

10. The method according to claim 7, characterized in that, The insulating medium is made of silicon oxide.

11. The method according to claim 7, characterized in that, The first conductivity type is N-type, and the second conductivity type is P-type.

12. The method according to claim 7, characterized in that, The device layer is formed using an epitaxial process.

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