Gallium nitride Schottky diode and preparation method thereof
By using an N-type SiC substrate and Mg-H structure in GaN Schottky diodes, combined with gradient activation of a patterned hydrogen diffusion barrier layer, the problems of high cost and poor heat dissipation of GaN substrates are solved, the breakdown voltage capability of the device is improved, and it is suitable for high-frequency, high-power and high-voltage applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI XINWEI SEMICON CO LTD
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-01
AI Technical Summary
Existing GaN Schottky diodes suffer from high GaN substrate costs, poor heat dissipation, and insufficient device voltage withstand capability, which limits their widespread use in high-frequency, high-power, and high-voltage applications.
An N-type SiC substrate is used, and a Mg-H structure with Mg and H bonding is formed in a P-type GaN layer. Gradual activation of Mg is achieved through a patterned hydrogen diffusion barrier layer, forming an electric field control region. The doping concentration distribution is optimized to alleviate electric field concentration and improve the breakdown voltage capability.
It effectively reduces manufacturing costs, improves heat dissipation performance, and alleviates electric field concentration through gradual doping concentration distribution, thereby enhancing the device's withstand voltage capability.
Smart Images
Figure CN121968604A_ABST
Abstract
Description
Gallium nitride Schottky diode and its fabrication method Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a gallium nitride Schottky diode and its fabrication method. Background Technology
[0002] With the rapid development of electronic technology, the demand for high-performance semiconductor devices is constantly increasing, especially in high-frequency, high-power, and high-voltage applications. Gallium nitride (GaN), as a wide-bandgap semiconductor material, has become one of the ideal materials for manufacturing high-frequency, high-power, and high-voltage semiconductor devices due to its excellent electrical properties, such as high electron saturation velocity, high electron mobility, and good thermal stability. It is widely used in 5G communications, new energy vehicles, fast charging, and other fields.
[0003] However, existing vertical GaN Schottky diodes (SBDs) still face several challenges in practical applications. Traditional GaN-on-GaN SBDs typically use GaN substrates for fabrication, but the high cost of GaN substrates hinders large-scale commercial applications, making it difficult to meet market demands for low-cost, high-performance devices. Furthermore, the relatively low thermal conductivity of GaN leads to poor heat dissipation during operation, especially in high-power applications. Heat dissipation issues severely impact device stability and reliability, limiting their use in high-power scenarios. Additionally, GaN SBDs must withstand reverse voltage when not in operation, resulting in a highly concentrated electric field at the anode metal edge, leading to insufficient voltage withstand capability and increasing the risk of device failure. Summary of the Invention
[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a gallium nitride Schottky diode and its fabrication method, so as to solve the problems of high cost of GaN substrate, poor heat dissipation and insufficient voltage withstand capability of GaN Schottky diodes in the prior art.
[0005] To achieve the above and other related objectives, the present invention provides a method for fabricating a gallium nitride Schottky diode, the method comprising:
[0006] An N-type SiC substrate is provided, on which an N-type GaN layer is formed;
[0007] An in-situ Mg-doped P-type GaN layer is formed on the N-type GaN layer, and a Mg-H structure with Mg and H bonds is formed in the P-type GaN layer.
[0008] The P-type GaN layer includes a preset anode metal region and an electric field control region surrounding the preset anode metal region. A patterned hydrogen diffusion barrier layer is formed on the P-type GaN layer. The patterned hydrogen diffusion barrier layer covers the preset anode metal region, and the patterned hydrogen diffusion barrier layer has a plurality of annealing windows in the electric field control region. The planar size of the annealing windows gradually increases from the preset anode metal region toward the electric field control region.
[0009] The P-type GaN layer is annealed based on the patterned hydrogen diffusion barrier layer to activate the Mg in the Mg-H structure of the P-type GaN layer not covered by the patterned hydrogen diffusion barrier layer, thereby gradually increasing the activation rate of Mg in the electric field control region from the preset anode metal region to the electric field control region.
[0010] Remove the patterned hydrogen diffusion barrier layer;
[0011] The P-type GaN layer in the predetermined anode metal region is etched away to expose the N-type GaN layer;
[0012] An anode metal layer is formed on the exposed N-type GaN layer.
[0013] Optionally, an island-shaped nucleation layer is formed on the N-type SiC substrate, and the N-type GaN layer is formed on the N-type SiC substrate and the nucleation layer.
[0014] Furthermore, the material of the nucleation layer includes AlN.
[0015] Optionally, the patterned hydrogen diffusion barrier layer may be made of silicon nitride or silicon oxide.
[0016] Optionally, the anode metal layer is formed on the N-type GaN layer in the preset anode metal region and extends to the P-type GaN layer in a portion of the electric field control region near the preset anode metal region.
[0017] Optionally, after forming the anode metal layer on the exposed N-type GaN layer, the method further includes the step of thinning the lower surface of the N-type SiC substrate and forming a cathode metal layer on the lower surface of the N-type SiC substrate.
[0018] The present invention also provides a gallium nitride Schottky diode, the gallium nitride Schottky diode comprising:
[0019] N-type SiC substrate;
[0020] An N-type GaN layer is formed on the N-type SiC substrate; the N-type GaN layer includes a predetermined anode metal region and an electric field modulation region located around the predetermined anode metal region;
[0021] A Mg-doped P-type GaN layer is formed on the N-type GaN layer in the electric field control region, wherein the Mg doping rate in the P-type GaN layer gradually increases from the preset anode metal region toward the electric field control region;
[0022] An anode metal layer formed on the N-type GaN layer in the preset anode metal region.
[0023] Optionally, an island-shaped nucleation layer is formed on the N-type SiC substrate, and the N-type GaN layer is formed on the N-type SiC substrate and the nucleation layer. The material of the nucleation layer includes AlN.
[0024] Optionally, the gallium nitride Schottky diode further includes a cathode metal layer formed on the lower surface of the N-type SiC substrate.
[0025] Optionally, the anode metal layer is formed on the N-type GaN layer in the preset anode metal region and extends to the P-type GaN layer in a portion of the electric field control region near the preset anode metal region.
[0026] As described above, the gallium nitride Schottky diode and its fabrication method of the present invention have the following beneficial effects: The fabrication cost of the device is effectively reduced by using an N-type SiC substrate, and the high thermal conductivity of SiC material improves the heat dissipation performance of the device. Because a Mg-H structure with Mg and H bonds is formed in the P-type GaN layer, the gradual activation of Mg is achieved through a patterned hydrogen diffusion barrier layer, causing the activation rate of Mg in the electric field control region to gradually increase from the anode metal region to the periphery. In the prior art, during reverse breakdown, a negative voltage is applied to the anode and a high voltage is applied to the cathode, often resulting in voltage concentration at the edge of the anode metal. In this structure, the Mg activation doping concentration in the P-type GaN layer is gradually distributed. In regions with higher Mg activation doping concentration, holes recombine more with electrons in the N-type GaN layer, preferentially depleting electrons. This leads to a decrease in electron concentration in the N-type GaN layer from the anode metal edge to both sides, increasing resistance. Consequently, the device preferentially withstands voltage in regions with higher resistance, effectively alleviating the electric field concentration phenomenon at the anode metal edge and improving the device's breakdown voltage capability. Attached Figure Description
[0027] Figure 1 shows a schematic flowchart of the method for fabricating the gallium nitride Schottky diode of the present invention.
[0028] Figures 2 to 6 show schematic cross-sectional views of each step in the fabrication method of the gallium nitride Schottky diode of the present invention.
[0029] Component labeling explanation: 10 N-type SiC substrate, 11 nucleation layer, 12 N-type GaN layer, 13 P-type GaN layer, 131 Mg-H structure, 132 activated Mg, 14 patterned hydrogen diffusion barrier layer, 141 annealing window, 15 anode metal layer, 16 cathode metal layer, 17 electrons, 21 preset anode metal region, 22 electric field control region, steps S1~S7. Detailed Implementation
[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0031] Please refer to Figures 1 to 6. It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0032] This embodiment provides a method for fabricating a gallium nitride Schottky diode, as shown in Figure 1. The fabrication method includes:
[0033] S1, providing an N-type SiC substrate, on which an N-type GaN layer is formed;
[0034] S2, an in-situ Mg-doped P-type GaN layer is formed on the N-type GaN layer, and a Mg-H structure with Mg and H bonds is formed in the P-type GaN layer;
[0035] S3, the P-type GaN layer includes a preset anode metal region and an electric field control region surrounding the preset anode metal region. A patterned hydrogen diffusion barrier layer is formed on the P-type GaN layer. The patterned hydrogen diffusion barrier layer covers the preset anode metal region, and the patterned hydrogen diffusion barrier layer has a plurality of annealing windows in the electric field control region. The planar size of the annealing windows gradually increases from the preset anode metal region toward the electric field control region.
[0036] S4, the P-type GaN layer is annealed based on the patterned hydrogen diffusion barrier layer so that the Mg in the Mg-H structure in the P-type GaN layer not covered by the patterned hydrogen diffusion barrier layer is activated, thereby gradually increasing the activation rate of Mg in the electric field control region from the preset anode metal region to the electric field control region.
[0037] S5, Remove the patterned hydrogen diffusion barrier layer;
[0038] S6, etch away the P-type GaN layer in the preset anode metal region to expose the N-type GaN layer;
[0039] S7, an anode metal layer is formed on the exposed N-type GaN layer.
[0040] The gallium nitride Schottky diode fabrication method of this embodiment effectively reduces the device fabrication cost by using an N-type SiC substrate and improves the device's heat dissipation performance by utilizing the high thermal conductivity of SiC material. Due to the formation of a Mg-H structure with Mg-H bonds in the P-type GaN layer, the gradual activation of Mg is achieved through a patterned hydrogen diffusion barrier layer, causing the activation rate of Mg in the electric field control region to gradually increase from the anode metal region to the periphery. In existing technologies, during reverse breakdown, a negative voltage is applied to the anode and a high voltage to the cathode, often resulting in voltage concentration at the anode metal edge. In this structure, the Mg activation doping concentration in the P-type GaN layer is gradually distributed. In regions with higher Mg activation doping concentration, more holes recombine with electrons in the N-type GaN layer, preferentially depleting electrons. This leads to a decrease in electron concentration in the N-type GaN layer from the anode metal edge to both sides, increasing resistance. Consequently, the device preferentially withstands voltage in regions with higher resistance, effectively alleviating the electric field concentration phenomenon at the anode metal edge and improving the device's breakdown voltage capability.
[0041] The fabrication method of the gallium nitride Schottky diode in this embodiment will be described in detail below with reference to the specific accompanying drawings.
[0042] As shown in Figure 2, step S1 is performed first, providing an N-type SiC substrate 10, on which an N-type GaN layer 12 is formed.
[0043] As a preferred example, an island-shaped nucleation layer 11 is formed on the N-type SiC substrate 10, and an N-type GaN layer 12 is formed on the N-type SiC substrate 10 and the nucleation layer 11. The material of the nucleation layer 11 includes, but is not limited to, aluminum nitride (AlN). The island-shaped nucleation layer 11 allows current to flow through the gaps between the islands, thereby avoiding the obstruction of the vertical Schottky diode current in this embodiment by conventional continuous nucleation layers.
[0044] As shown in Figure 2, step S2 is then performed, in-situ doped magnesium (Mg) P-type GaN layer 13 is formed on the N-type GaN layer 12, and a Mg-H structure 131 with Mg and H bonding is formed in the P-type GaN layer 13.
[0045] Specifically, during the epitaxial growth of the P-type GaN layer 13, byproduct hydrogen (H) atoms from ammonia or hydrogen gas form bonds with the dopant Mg to form the Mg-H structure 131, causing the Mg in the Mg-H structure 131 to lose its activity and not participate in the formation of holes by doping GaN.
[0046] As shown in Figure 3, step S3 is then performed. The P-type GaN layer 13 includes a preset anode metal region 21 and an electric field control region 22 located around the preset anode metal region 21. A patterned hydrogen diffusion barrier layer 14 is formed on the P-type GaN layer 13. The patterned hydrogen diffusion barrier layer 14 covers the preset anode metal region 21, and the patterned hydrogen diffusion barrier layer 14 forms a plurality of annealing windows 141 in the electric field control region 22. The planar size of the annealing windows 141 gradually increases from the preset anode metal region 21 toward the electric field control region 22.
[0047] As an example, the material of the patterned hydrogen diffusion barrier layer 14 includes, but is not limited to, silicon nitride or silicon oxide.
[0048] As shown in Figure 3, step S4 is then performed, in which the P-type GaN layer 13 is annealed based on the patterned hydrogen diffusion barrier layer 14, so that the Mg in the Mg-H structure 131 in the P-type GaN layer 13 not covered by the patterned hydrogen diffusion barrier layer 14 is activated to form activated Mg132, thereby causing the activation rate of Mg in the electric field control region 22 to gradually increase from the preset anode metal region 21 to the electric field control region 22.
[0049] Specifically, step S4 is a selective annealing process, where the patterned hydrogen diffusion barrier layer 14 selects an activation annealing region and anneals the P-type GaN layer 13 exposed by the annealing window 141. After annealing, the Mg-H structure 131 effectively reduces and releases hydrogen, resulting in activated Mg132. The activated Mg132 acts as a dopant to dope the P-type GaN layer 13, forming holes. The activation rate of Mg in the electric field control region 22 gradually increases from the preset anode metal region 21 towards the electric field control region 22, causing the hole concentration in the P-type GaN layer 13 to also gradually increase from the preset anode metal region 21 towards the electric field control region 22.
[0050] As shown in Figure 4, step S5 is then performed to remove the patterned hydrogen diffusion barrier layer 14.
[0051] As shown in Figure 4, step S6 is then performed to etch away the P-type GaN layer 13 of the preset anode metal region 21 to expose the N-type GaN layer 12.
[0052] As shown in Figure 5, step S7 is then performed to form an anode metal layer 15 on the exposed N-type GaN layer 12.
[0053] Specifically, referring to Figure 6, during reverse breakdown, a negative voltage is applied to the anode and a high voltage is applied to the cathode. The voltage will concentrate at the edge of the anode metal layer 15. In this embodiment, the electrons 17 in the P-type GaN layer 13 are depleted by recombination between the holes in the P-type GaN layer 13 and the electrons 17 in the N-type GaN layer 12. The gradually distributed activated Mg132 reduces the concentration of electrons 17 in the N-type GaN layer 12 from the edge of the anode metal layer 15 to both sides. Consequently, the resistance of the N-type GaN layer 12 gradually increases, thus preferentially achieving breakdown in the region with higher resistance. This effectively alleviates the electric field concentration phenomenon at the edge of the anode metal layer 15 and improves the breakdown voltage capability of the device.
[0054] As an example, the anode metal layer 15 is formed on the N-type GaN layer 12 of the preset anode metal region 21 and extends to the P-type GaN layer 13 of the electric field control region 22 near the preset anode metal region 21, so as to simplify the process.
[0055] As an example, after forming the anode metal layer 15 on the exposed N-type GaN layer 12, the method further includes the step of thinning the lower surface of the N-type SiC substrate 10 and forming a cathode metal layer 16 on the lower surface of the N-type SiC substrate 10.
[0056] Thus, as shown in Figure 6, the fabrication of the gallium nitride Schottky diode in this embodiment is complete.
[0057] This embodiment also provides a gallium nitride Schottky diode. Referring to Figures 2 to 6, the gallium nitride Schottky diode includes:
[0058] 10. N-type SiC substrate;
[0059] An N-type GaN layer 12 is formed on the N-type SiC substrate 10; the N-type GaN layer 12 includes a preset anode metal region 21 and an electric field modulation region 22 located around the preset anode metal region 21.
[0060] A Mg-doped P-type GaN layer 13 is formed on the N-type GaN layer 12 in the electric field control region 22, wherein the Mg doping rate in the P-type GaN layer 13 gradually increases from the preset anode metal region 21 toward the electric field control region 22.
[0061] An anode metal layer 15 is formed on the N-type GaN layer 12 in the preset anode metal region 21.
[0062] The gallium nitride Schottky diode can be prepared using the above-described method, but it is not limited to this method. Other suitable preparation methods are also possible, and their beneficial effects can be found in the specific description of the preparation method, which will not be repeated here.
[0063] Specifically, as a preferred example, an island-shaped nucleation layer 11 is formed on the N-type SiC substrate 10, and an N-type GaN layer 12 is formed on the N-type SiC substrate 10 and the nucleation layer 11. The material of the nucleation layer 11 includes, but is not limited to, AlN. The island-shaped nucleation layer 11 allows current to flow through the gaps between the islands, thereby avoiding the obstruction of the vertical Schottky diode current in this embodiment by conventional continuous nucleation layers.
[0064] As an example, the gallium nitride Schottky diode also includes a cathode metal layer 16 formed on the lower surface of the N-type SiC substrate 10.
[0065] As an example, the anode metal layer 15 is formed on the N-type GaN layer 12 of the preset anode metal region 21 and extends to the P-type GaN layer 13 of the electric field modulation region 22 near the preset anode metal region 21. No excessive limitation is placed on the size of its extension.
[0066] In summary, the gallium nitride Schottky diode and its fabrication method of the present invention effectively reduce the fabrication cost of the device by using an N-type SiC substrate and improve the heat dissipation performance of the device by utilizing the high thermal conductivity of SiC material. Due to the formation of a Mg-H structure with Mg-H bonds in the P-type GaN layer, the gradual activation of Mg is achieved through a patterned hydrogen diffusion barrier layer, resulting in a gradual increase in the activation rate of Mg from the anode metal region towards the periphery in the electric field control region. In existing technologies, during reverse breakdown, a negative voltage is applied to the anode and a high voltage to the cathode, often concentrating the voltage at the edge of the anode metal. In this structure, the Mg activation doping concentration in the P-type GaN layer is gradually distributed. In regions with higher Mg activation doping concentration, holes recombine more with electrons in the N-type GaN layer, preferentially depleting electrons. This leads to a decrease in electron concentration in the N-type GaN layer from the anode metal edge towards both sides, increasing resistance. Regions with higher resistance preferentially withstand voltage, effectively alleviating the electric field concentration phenomenon at the anode metal edge and improving the device's breakdown voltage capability. Therefore, the present invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.
[0067] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for fabricating a gallium nitride Schottky diode, characterized in that, The fabrication method includes: providing an N-type SiC substrate, on which an N-type GaN layer is formed; forming an in-situ Mg-doped P-type GaN layer on the N-type GaN layer, wherein a Mg-H structure with Mg and H bonds is formed in the P-type GaN layer; the P-type GaN layer includes a predetermined anode metal region and an electric field control region surrounding the predetermined anode metal region; forming a patterned hydrogen diffusion barrier layer on the P-type GaN layer, the patterned hydrogen diffusion barrier layer covering the predetermined anode metal region, and the patterned hydrogen diffusion barrier layer forming a plurality of annealing windows in the electric field control region, wherein the annealing windows are flat The surface size gradually increases from the preset anode metal region toward the electric field control region; the P-type GaN layer is annealed based on the patterned hydrogen diffusion barrier layer to activate the Mg in the Mg-H structure of the P-type GaN layer not covered by the patterned hydrogen diffusion barrier layer, thereby gradually increasing the activation rate of Mg in the electric field control region from the preset anode metal region toward the electric field control region; the patterned hydrogen diffusion barrier layer is removed; the P-type GaN layer in the preset anode metal region is etched away to expose the N-type GaN layer; an anode metal layer is formed on the exposed N-type GaN layer.
2. The method for fabricating a gallium nitride Schottky diode according to claim 1, characterized in that: An island-shaped nucleation layer is formed on the N-type SiC substrate, and the N-type GaN layer is formed on the N-type SiC substrate and the nucleation layer.
3. The method for fabricating a gallium nitride Schottky diode according to claim 2, characterized in that: The material of the nucleation layer includes AlN.
4. The method for fabricating a gallium nitride Schottky diode according to claim 1, characterized in that: The patterned hydrogen diffusion barrier layer is made of silicon nitride or silicon oxide.
5. The method for fabricating a gallium nitride Schottky diode according to claim 1, characterized in that: The anode metal layer is formed on the N-type GaN layer in the preset anode metal region and extends to the P-type GaN layer in a portion of the electric field control region near the preset anode metal region.
6. The method for fabricating a gallium nitride Schottky diode according to claim 1, characterized in that: After forming the anode metal layer on the exposed N-type GaN layer, the method further includes the step of thinning the lower surface of the N-type SiC substrate and forming a cathode metal layer on the lower surface of the N-type SiC substrate.
7. A gallium nitride Schottky diode, characterized in that, The gallium nitride Schottky diode includes: an N-type SiC substrate; an N-type GaN layer formed on the N-type SiC substrate; the N-type GaN layer including a preset anode metal region and an electric field control region surrounding the preset anode metal region; a Mg-doped P-type GaN layer formed on the N-type GaN layer in the electric field control region, wherein the Mg doping rate in the P-type GaN layer gradually increases from the preset anode metal region toward the electric field control region; and an anode metal layer formed on the N-type GaN layer in the preset anode metal region.
8. The gallium nitride Schottky diode according to claim 7, characterized in that: An island-shaped nucleation layer is formed on the N-type SiC substrate, and an N-type GaN layer is formed on the N-type SiC substrate and the nucleation layer. The material of the nucleation layer includes AlN.
9. The gallium nitride Schottky diode according to claim 7, characterized in that: The gallium nitride Schottky diode also includes a cathode metal layer formed on the lower surface of the N-type SiC substrate.
10. The gallium nitride Schottky diode according to claim 7, characterized in that: The anode metal layer is formed on the N-type GaN layer in the preset anode metal region and extends to the P-type GaN layer in a portion of the electric field control region near the preset anode metal region.