Gallium oxide device with mesa and U-shaped field plate composite terminal and preparation method thereof

Abstract

The invention relates to a gallium oxide device with a mesa and a U-shaped field plate composite terminal and a preparation method of the gallium oxide device. The gallium oxide substrate is located on the cathode metal; the gallium oxide epitaxial layer is located on part of the surface of the gallium oxide substrate, a groove is formed in one side, and a table top is formed on the other side; the anode metal layer is located on a table top formed by the gallium oxide epitaxial layer; the insulating film layer covers the bottom and the side wall of the groove and part of the surface of the anode metal layer; the organic photosensitive resin insulating medium is filled in the groove and is positioned on the insulating film layer; the metal field plate layer is located in the organic photosensitive resin insulating medium and forms a pit with an arc-shaped side face, one end of the metal field plate layer is connected with the anode metal layer, and the distance between the other end of the metal field plate layer and the table top is larger than that between the bottom of the pit and the table top. According to the device, the reverse voltage endurance capability of the device can be improved under the condition that the terminal length is relatively small, and the terminal efficiency of the gallium oxide device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power semiconductors, and particularly relates to a gallium oxide device with a mesa and U-shaped field plate composite terminal and a preparation method thereof. Background Art

[0002] Gallium oxide is a relatively emerging wide-bandgap semiconductor material. Among them, β-Ga2O3 has attracted more and more attention from the scientific research community and the industrial community in recent years because its single crystal can be prepared by the melting method, which has the potential to continuously reduce the material cost. β-Ga2O3 has a large bandgap width and a high critical breakdown field strength, and has a high Baliga figure of merit, which is about 10 times that of SiC and 4 times that of GaN. It is a semiconductor material very suitable for applications in high-voltage and high-power fields.

[0003] The Schottky diode is a very common semiconductor device, which has the advantages of low conduction voltage drop, fast recovery time, low noise, etc., and is widely used in rectifier circuits, radio frequency mixer rectifiers, detection circuits, etc. The β-Ga2O3 Schottky diode is suitable for applications in high-voltage and high-power electric power fields. At present, there have been many research works on β-Ga2O3 Schottky diodes at home and abroad, but the results are still far from the theoretical performance of β-Ga2O3. For most diode devices, under the reverse breakdown voltage state, the electric field concentration effect at the corners causes the device to break down and the leakage current to increase significantly, which is an unavoidable problem. Therefore, it is very necessary to design a reasonable terminal structure to improve the edge electric field concentration effect and increase the breakdown voltage ability of the diode device.

[0004] In gallium oxide materials, the doping and activation of P-type acceptors are relatively difficult, so the PN junction terminal technologies such as junction termination extension and field limiting ring in previous Si devices are not very applicable to gallium oxide. The terminal scheme of the field plate is currently relatively common in gallium oxide devices, but the lateral area of the field plate is relatively large, which will lead to a relatively large terminal area, thereby increasing the unit area of the device and further increasing its cost. Therefore, optimizing the terminal structure is also very necessary for reducing the cost of the device. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a gallium oxide device with a mesa and U-shaped field plate composite terminal and a preparation method thereof. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0006] An embodiment of the present invention provides a gallium oxide device with a mesa and U-shaped field plate composite terminal, including:

[0007] Cathode metal;

[0008] A gallium oxide substrate located on the cathode metal;

[0009] A gallium oxide epitaxial layer, located on a partial surface of the gallium oxide substrate, with a groove formed on one side and a mesa formed on the other side;

[0010] An anode metal layer, located on the mesa formed by the gallium oxide epitaxial layer;

[0011] An insulating thin film layer, covering the bottom and side walls of the groove, and a partial surface of the anode metal layer;

[0012] An organic photosensitive resin insulating medium, filled in the groove and located on the insulating thin film layer;

[0013] A metal field plate layer, located in the organic photosensitive resin insulating medium and forming a pit with an arc-shaped side surface. One end of the metal field plate layer is connected to the anode metal layer, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa.

[0014] In an embodiment of the present invention, the groove extends from the upper surface of the gallium oxide epitaxial layer to the inside of the gallium oxide epitaxial layer; or, the groove extends from the upper surface of the gallium oxide epitaxial layer to the surface of the gallium oxide substrate; or, the groove extends from the upper surface of the gallium oxide epitaxial layer to the inside of the gallium oxide substrate.

[0015] In an embodiment of the present invention, the depth of the groove is greater than 1 μm.

[0016] In an embodiment of the present invention, the material of the insulating thin film layer includes one or more of SiO2, Al2O3, HfO2, and ZrO2, and the thickness is 50 - 200 nm.

[0017] In an embodiment of the present invention, the organic photosensitive resin insulating medium includes one or more of benzocyclobutene, photosensitive polyimide, photosensitive polybenzoxazole, and photosensitive epoxy resin.

[0018] In an embodiment of the present invention, the thickness of the metal field plate layer is 100 - 300 nm, the lateral width is 5 - 50 μm, and the longitudinal depth extending into the groove is 60% - 80% of the groove depth.

[0019] In an embodiment of the present invention, the material of the gallium oxide substrate includes highly doped n+β-Ga2O3, the doping element includes one or more of Si and Sn, and the doping concentration is 1×10 18 -5×10 19 cm -3 , and the thickness is 300 - 650 μm;

[0020] The material of the gallium oxide epitaxial layer includes low-doped n-β-Ga2O3, and the doping elements include one or more of Si and Sn, and the doping concentration is 1×10 15 -1×10 17 cm -3 , and the thickness is 10-20μm;

[0021] The material of the cathode metal includes one or more of Ti, Au, Ni, and Au;

[0022] The material of the anode metal layer includes one or more of Ni and Au.

[0023] Another embodiment of the present invention provides a method for manufacturing a gallium oxide device with a mesa and U-shaped field plate composite terminal, including the steps of:

[0024] Providing a gallium oxide substrate;

[0025] Growing a gallium oxide epitaxial layer on the gallium oxide substrate;

[0026] Depositing a cathode metal on the back surface of the gallium oxide substrate;

[0027] Fabricating an anode metal layer in the active region of the gallium oxide epitaxial layer;

[0028] Etching the gallium oxide epitaxial layer to form a groove on one side and a mesa on the other side of the gallium oxide epitaxial layer;

[0029] Depositing an insulating thin film layer on the bottom and side walls of the groove and on the surface of the anode metal layer;

[0030] Spin-coating an organic photosensitive resin insulating material in the groove and on the insulating thin film layer, and making the organic photosensitive resin insulating material in the groove form a pit with an arc-shaped side surface;

[0031] Depositing a metal field plate layer on the organic photosensitive resin insulating material, such that one end of the metal field plate layer is connected to the anode metal layer, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa;

[0032] Filling the groove with the organic photosensitive resin insulating material to form an organic photosensitive resin insulating medium;

[0033] Opening holes in the area of the anode metal layer.

[0034] In one embodiment of the present invention, etching the gallium oxide epitaxial layer includes:

[0035] Etching the gallium oxide epitaxial layer using a self-alignment process, and the etching depth is less than the thickness of the gallium oxide epitaxial layer;

[0036] Alternatively, an etching process with self-alignment is used to etch the gallium oxide epitaxial layer, and the etching depth is equal to the thickness of the gallium oxide epitaxial layer;

[0037] Alternatively, an etching process with self-alignment is used to etch the gallium oxide epitaxial layer, and the etching depth is greater than the thickness of the gallium oxide epitaxial layer.

[0038] In one embodiment of the present invention, an organic photosensitive resin insulating material is spin-coated in the groove and on the insulating thin film layer, and the organic photosensitive resin insulating material in the groove forms a pit with an arc-shaped side surface, including:

[0039] Clean the surface of the sample;

[0040] Spin-coat an adhesion promoter in the groove and on the insulating thin film layer;

[0041] Spin-coat an organic photosensitive resin insulating material on the surface of the adhesion promoter;

[0042] Using puddle development technology, pre-bake, expose, develop, and harden the organic photosensitive resin insulating material to form a pit with an arc-shaped side surface in the organic photosensitive resin insulating material at the groove.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] In the gallium oxide device of the present invention, a groove is formed in the gallium oxide epitaxial layer, and an organic photosensitive resin insulating medium is filled in the groove. The metal field plate layer is arranged in the organic photosensitive resin insulating medium. The entire composite terminal is composed of the groove, the organic photosensitive resin insulating medium, and the metal field plate layer. The terminal length mainly depends on the length of the metal field plate layer, and the total terminal length is smaller. In the reverse blocking state, the composite terminal can reduce the intensity of the edge peak electric field and transfer and disperse the position of the edge peak electric field. Therefore, the device can increase the reverse breakdown voltage ability of the device and improve the terminal efficiency of the gallium oxide device under the condition of a smaller terminal length. Description of the Drawings

[0045] Figure 1 It is a schematic structural diagram of a gallium oxide device with a mesa and a U-shaped field plate composite terminal provided by an embodiment of the present invention;

[0046] Figure 2 It is a schematic structural diagram of another gallium oxide device with a mesa and a U-shaped field plate composite terminal provided by an embodiment of the present invention;

[0047] Figure 3 It is a schematic structural diagram of yet another gallium oxide device with a mesa and a U-shaped field plate composite terminal provided by an embodiment of the present invention;

[0048] Figures 4a - 4l isFigure 1 Schematic diagram of the preparation process of a gallium oxide device with a mesa and a U-shaped field plate composite terminal;

[0049] Figures 5a - 5l is Figure 2 Schematic diagram of the preparation process of a gallium oxide device with a mesa and a U-shaped field plate composite terminal;

[0050] Figures 6a - 6l is Figure 3 Schematic diagram of the preparation process of a gallium oxide device with a mesa and a U-shaped field plate composite terminal. Specific embodiments

[0051] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0052] Embodiment 1

[0053] Please refer to Figure 1 , Figure 1 which is a schematic diagram of the structure of a gallium oxide device with a mesa and a U-shaped field plate composite terminal provided by an embodiment of the present invention.

[0054] The gallium oxide device with a mesa and a U-shaped field plate composite terminal in this embodiment is a Schottky diode, which includes, from bottom to top: a cathode metal 3; a gallium oxide substrate 1 located on the cathode metal 3; a gallium oxide epitaxial layer 2 located on a partial surface of the gallium oxide substrate 1, with a groove formed on one side and a mesa formed on the other side; an anode metal layer 4 located on the mesa formed by the gallium oxide epitaxial layer 2; an insulating thin film layer 5 covering the bottom and side walls of the groove and a partial surface of the anode metal layer 4; an organic photosensitive resin insulating medium 6 filled in the groove and located on the insulating thin film layer 5; a metal field plate layer 7 located in the organic photosensitive resin insulating medium 6 and forming a pit with an arc-shaped side surface, one end of the metal field plate layer 7 is connected to the anode metal layer 4, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa.

[0055] Specifically, one side edge of the gallium oxide epitaxial layer 2 is etched away to form a groove, and the unetched gallium oxide epitaxial layer 2 on the other side forms a mesa and serves as the active region. The anode metal layer 4 covers the surface of the active region to form a Schottky contact. The insulating thin film layer 5 covers the side wall and the bottom of the groove; the end of the insulating thin film layer 5 can be located on the surface of the anode metal layer 4 and extend from the surface of the anode metal layer 4 into the groove; the end of the insulating thin film layer 5 can also be located on a part of the mesa of the gallium oxide epitaxial layer 2 and be in contact with the anode metal layer 4, that is, the insulating thin film layer 5 extends from the gallium oxide epitaxial layer 2 into the groove. The organic photosensitive resin insulating medium 6 is located in the insulating thin film layer 5 and fills the groove. One end of the metal field plate layer 7 is connected to the anode metal layer 4, and the other end extends into the organic photosensitive resin insulating medium 6 to form a U-shaped pit in the organic photosensitive resin insulating medium 6. It can be understood that the position of the other end of the metal field plate layer 7 should be higher than the position of the pit to form a U-shaped pit, for example, it can extend to a position slightly higher than the pit, or it can extend to a position flush with the anode metal layer 4. The composite terminal is composed of the groove, the organic photosensitive resin insulating medium 6, and the metal field plate layer 7, and the composite terminal structure is located at the edge of the Schottky diode.

[0056] Specifically, the gallium oxide substrate 1 is a heavily doped n+ substrate, and its material includes highly doped n+ β-Ga2O3. The doping elements include one or more of Si and Sn, and the doping concentration is 1×10 18 -5×10 19 cm -3 , and the thickness is 300 - 650 μm. The material of the gallium oxide epitaxial layer 2 includes lightly doped n-β-Ga2O3. The doping elements include one or more of Si and Sn, and the doping concentration is 1×10 15 -1×10 17 cm -3 , and the thickness is 10 - 20 μm.

[0057] Specifically, the groove extends from the upper surface of the gallium oxide epitaxial layer 2 into the gallium oxide epitaxial layer 2, as Figure 1 shown; it can also extend from the upper surface of the gallium oxide epitaxial layer 2 to the surface of the gallium oxide substrate 1, as Figure 2 shown, Figure 2 which is a schematic structural diagram of another gallium oxide device with a mesa and U-shaped field plate composite terminal provided by an embodiment of the present invention; it can also extend from the upper surface of the gallium oxide epitaxial layer 2 into the gallium oxide substrate 1, as Figure 3 shown, Figure 3 which is a schematic structural diagram of yet another gallium oxide device with a mesa and U-shaped field plate composite terminal provided by an embodiment of the present invention.

[0058] Specifically, the depth of the groove is greater than 1 μm.

[0059] Considering the actual etching engineering situation, if the etching equipment has limited effect, the groove depth can be greater than 1 μm. With the improvement of the equipment effect, the depth can be further increased. For example, the depth is 5 μm, but it is not limited to 5 μm. Even the groove depth can reach the depth of etching away the entire epitaxial layer thickness, or can reach the depth of etching into the gallium oxide substrate 1.

[0060] This embodiment does not limit the width of the groove. In the figure, one side of the groove is represented as a mesa, and the other side is an open area. The width of the groove is determined by the area covered by the photomask, and can be wide or narrow. Exemplarily, the width of the groove is 20 - 100 μm, and of course, it can be further adjusted.

[0061] Specifically, the material of the insulating thin film layer 5 includes one or more of SiO2, Al2O3, HfO2, and ZrO2, and the thickness is 50 - 200 nm.

[0062] The insulating thin film layer 5 bears a large electric field, so the thickness should not be too thin. Therefore, the thickness is selected to be 50 - 200 nm. Exemplarily, the insulating thin film layer 5 is selected to be 50 nm or 100 nm.

[0063] Specifically, the organic photosensitive resin insulating medium 6 includes one or more of benzocyclobutene BCB, photosensitive polyimide, photosensitive polybenzoxazole, and photosensitive epoxy resin. Exemplarily, the organic photosensitive resin insulating medium 6 adopts benzocyclobutene BCB 4026 - 46 of Dow Chemical.

[0064] Specifically, the thickness of the metal field plate layer 7 is 100 - 300 nm, the lateral width is 5 - 50 μm, and the longitudinal depth extending into the groove is 60% - 80% of the groove depth.

[0065] The thickness of the metal field plate layer 7 is generally about 200 nm, and it can be thickened or thinned. It should not be too thick. For example, when it is increased to more than 500 nm, the process needs to be modified. Being too thick will cause the metal to not peel off during metal stripping. It should not be too thin either. For example, when it is below 30 nm, the metal field plate is prone to breakage, or the adhesion is poor and it will fall off, and the field plate will lose its effect. Therefore, overall, the thickness of the metal field plate layer 7 is preferably 100 - 300 nm.

[0066] The longitudinal depth of the metal field plate layer 7 extending into the groove is related to the depth of the groove itself and the depth of the pit developed by "puddle development" of the organic photosensitive resin insulating medium 6. Preferably, the longitudinal depth of the metal field plate layer 7 extending into the groove is 60% - 80% of the entire groove depth. Of course, the longitudinal depth of the metal field plate layer 7 extending into the groove can also be shallower.

[0067] The lateral width of the metal field plate layer 7 is preferably 5 - 50 μm. In order to form a U-shaped pit, the distance from the end of the metal field plate layer 7 located in the organic photosensitive resin insulating medium 6 to the mesa is greater than the distance from the bottom of the pit to the mesa.

[0068] In this embodiment, the distance from the end of the metal field plate layer to the mesa is greater than the distance from the bottom of the pit to the mesa, forming a U-shaped pit. Using the relatively wide width, the electric field is extended towards the edge, and a better electric field distribution can be obtained, achieving higher breakdown voltage.

[0069] Specifically, the material of the cathode metal 3 includes one or more of Ti, Au, Ni, and Au. Exemplarily, the material of the cathode metal 3 is a combination of Ti / Au or Ti / Al / Ni / Au. Among them, the thickness of the Ti / Au metal layer can be a combination of 20 - 60 nm / 120 - 250 nm, and the thickness of the Ti / Al / Ni / Au metal layer can be a combination of 20 / 120 / 50 / 40 nm. The material of the anode metal layer 4 includes one or more of Ni and Au. Exemplarily, the material of the anode metal layer 4 is Ni / Au, and the thickness is 50 / 200 nm.

[0070] The working principle of the gallium oxide device in this embodiment is as follows: When a forward bias voltage is applied, the gallium oxide device enters the on state and has a low turn-on voltage drop; when a reverse bias voltage is applied, due to the existence of the arc-shaped metal field plate layer, the peak electric field at the edge of the mesa terminal located at the edge of the anode metal layer can be weakened and transferred, reducing the intensity of the edge peak electric field, thereby alleviating the problem of overly concentrated edge electric field and premature breakdown. It can improve the reverse breakdown voltage ability of the device under the condition of a smaller terminal length and improve the terminal efficiency of the gallium oxide Schottky barrier diode.

[0071] The gallium oxide device of this embodiment introduces a deep groove and a metal field plate layer with an arc-shaped side pit. In the reverse blocking state, the composite terminal can reduce the intensity of the edge peak electric field and transfer and disperse the position of the edge peak electric field. Compared with some traditional terminals, the terminal length mainly depends on the length of the U-shaped field plate, and the total terminal length is smaller; compared with the traditional structure, the reverse breakdown voltage ability of the device is increased, the terminal efficiency of the gallium oxide Schottky barrier diode can be improved, which provides the possibility of reducing costs in industrial production of the device, and can also promote the application of gallium oxide material devices and give play to their advantages in the high-voltage and high-power fields.

[0072] Embodiment Two

[0073] Based on Embodiment One, this embodiment provides a preparation method for a gallium oxide device with a mesa and U-shaped field plate composite terminal. Please refer to Figure 1 and Figures 4a - 4l , Figures 4a - 4l For Figure 1Schematic diagram of the preparation process of a gallium oxide device with a mesa and a U-shaped field plate composite terminal. The preparation method includes the steps:

[0074] S1. Provide a gallium oxide substrate 1.

[0075] Specifically, the Si- or Sn-doped highly doped n+-Ga2O3 substrate material is cleaned with acetone and isopropyl alcohol, and blown dry with a high-purity N2 gas gun to obtain the highly doped n+-Ga2O3 substrate 1, as Figure 4a shown.

[0076] S2. Grow a gallium oxide epitaxial layer 2 on the gallium oxide substrate 1.

[0077] Specifically, using one of the processes of hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), or metalorganic chemical vapor deposition (MOCVD), grow a low-doped epitaxial layer of about 10 μm on the highly doped n+-Ga2O3 substrate 1, and the doping element is Si or Sn to obtain the n-Ga2O3 epitaxial layer 2, as Figure 4b shown.

[0078] S3. Deposit a cathode metal 3 on the back surface of the gallium oxide substrate 1.

[0079] Specifically, after cleaning with acetone and isopropyl alcohol and drying with N2, clean the gallium oxide substrate 1 with a solution of 98% concentrated H2SO4:H2O2 = 7:3, rinse it with deionized water, dry it with high-purity N2, and then use the electron beam evaporation process to deposit 20 - 60 nm / 50 - 200 nm of Ti / Au on the back surface of the highly doped n+-Ga2O3 substrate 1. Then, perform annealing in a rapid annealing furnace at 300 - 500 °C in an N2 atmosphere for 1 min to obtain the cathode metal 3, as Figure 4c shown.

[0080] S4. Fabricate an anode metal layer 4 in the active region of the gallium oxide epitaxial layer 2.

[0081] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying with N2, use the photolithography and development processes to define the anode region, and then deposit the anode metal Ni / Au by electron beam evaporation with a thickness of 50 / 200 nm. Then, perform lift-off to obtain the anode metal layer 4, as Figure 4d shown.

[0082] S5. Etch the gallium oxide epitaxial layer 2 to form a groove on one side and a mesa on the other side of the gallium oxide epitaxial layer 2.

[0083] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying it with N2, ICP etching using a BCl3 / Ar system is employed to etch the gallium oxide epitaxial layer 2 with a self-alignment process. The etching depth is less than the thickness of the gallium oxide epitaxial layer 2. Exemplarily, the etching depth is 5 μm, thereby forming a groove. The unetched gallium oxide epitaxial layer 2 on one side of the groove forms a mesa, and the anode metal layer 4 is located on the mesa, as Figure 4e shown.

[0084] S6. Deposit an insulating thin film layer 5 on the bottom and side walls of the groove and on the surface of the anode metal layer 4.

[0085] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying it with N2, an insulating thin film layer 5 of about 50 nm is deposited using the ALD process, as Figure 4f shown. The insulating thin film layer 5 can be a relatively dense insulating material, such as SiO2, Al2O3, HfO2, ZrO2, etc.

[0086] S7. Spin-coat an organic photosensitive resin insulating material in the groove and on the insulating thin film layer 5, and make the organic photosensitive resin insulating material in the groove form a pit with an arc-shaped side wall.

[0087] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying it with N2, a photosensitive resin material is spin-coated to fill the etched groove area, and appropriate pre-baking is performed to stabilize the photosensitive resin medium, as Figure 4g shown. Then, using the photosensitive characteristics of the photosensitive resin medium, a matching "puddle development" technique is employed, supplemented by photolithography and development processes, etc., to further process the filled photosensitive resin material in the groove area to obtain a pit, as Figure 4h shown. Taking the organic photosensitive resin insulating material BCB 4026-46 from Dow Chemical as an example, this process includes the following steps:

[0088] 1) Clean the surface of the sample. Clean the surface with organic solvents such as acetone and NMP.

[0089] 2) Spin-coat an adhesion promoter in the groove and on the insulating thin film layer 5. Specifically, the adhesion promoter used is AP3000, and the spin-coating speed can be set above 2000 rpm and below 5000 rpm.

[0090] 3) Spin-coat an organic photosensitive resin insulating material on the surface of the adhesion promoter. Specifically, spin-coat BCB 4026-46, with an initial speed of 1000 rpm for 10 s; then the speed is increased to 8000 rpm for 45 s, and the formed film thickness is about 4.4 μm.

[0091] 4) Using the puddle development technique, pre-bake, expose, develop, and harden the organic photosensitive resin insulating material to form a pit with an arc-shaped side surface in the organic photosensitive resin insulating material at the groove. Specifically, first, perform pre-baking with a hot plate at a pre-baking temperature of 100 °C for 6 min; then perform exposure with a power of 850 mJ / cm 2 ; then perform pre-development baking with an ordinary hot plate at 100 °C for 1 min or 90 °C for 90 s; then perform development. The developer used is DS2100, and spin-coating development is carried out at a spin-coating speed of 50 - 200 rpm. Exemplarily, the spin-coating speed is 100 rpm for 3 min, and it can be rinsed with a photoresist stripper DS2100 using a dropper; then immediately perform hardening with hardening conditions of 100 °C for 1 min; finally, perform post-hardening under the conditions of a protective gas atmosphere, 250 °C, and 1 h to complete the processing of BCB.

[0092] In the above steps, the pre-baking temperature and time, exposure dose, and development time are the parameters that have the greatest impact on the pit depth. By adjusting their combination, the depth of the pit can be adjusted. The rotation speed and development time during development can affect the morphology, opening, etc. of the pit, and this part will have a great impact on the angle of the arc-shaped field plate. It should be noted that the results of the above lithography-like process are not the simple superposition results of single variables. The settings of the entire process, even including the techniques, will be the influencing factors of the results.

[0093] In this embodiment, through a mask aligner and a photomask, by selective exposure, the dissolution degree of the photosensitive resin in the developer is different, thereby realizing the processing of the morphology and obtaining a pit with an arc-shaped side surface.

[0094] S8. Deposit a metal field plate layer 7 on the organic photosensitive resin insulating material, so that one end of the metal field plate layer 7 is connected to the anode metal layer 4, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa.

[0095] Specifically, first, define the via hole area through photolithography and development, and use RIE etching to open the hole to expose the anode metal layer to facilitate the next deposition of the field plate, as Figure 4i shown. Then, define the field plate area through photolithography and development. Here, it should be noted that the length of the field plate needs to be able to form a U-shaped structure. Therefore, the distance from the end of the field plate in the groove to the mesa is greater than the distance from the bottom of the pit to the mesa. Then, deposit the metal field plate layer 7 using electron beam evaporation. The metal field plate layer 7 is connected to the anode metal layer 4, and then stripping is performed to obtain the arc-shaped field metal field plate layer 7, as Figure 4j shown.

[0096] S9, filling the groove with the organic photosensitive resin insulating material to form an organic photosensitive resin insulating medium 6.

[0097] Specifically, the photosensitive resin material is filled in the groove to fill the remaining cavity, and together with the organic photosensitive resin insulating material remaining after photolithography in S7, an organic photosensitive resin insulating medium 6 is formed. Figure 4k shown.

[0098] S10 , opening a hole in the region of the anode metal layer 4 .

[0099] Specifically, the region of the anode metal layer 4 is opened to facilitate subsequent device packaging and use, such as Figure 4l shown.

[0100] The device fabrication is now completed.

[0101] Based on the table terminal, this embodiment first deepens the depth of the groove, and then uses the photosensitivity of the photosensitive resin to process an arc-shaped pit through the development technology, and deposits a field plate metal of appropriate length in the pit to form a U-shaped field plate, and the field plate is connected to the anode metal. The remaining vacant part is then filled to complete the device processing. Not only is the total terminal length smaller and the occupied area smaller, but the reverse voltage withstand capability of the device is increased, and the terminal efficiency of the gallium oxide Schottky barrier diode is improved.

[0102] Embodiment 3

[0103] Based on the first embodiment, this embodiment provides a method for preparing a gallium oxide device with a mesa and a U-shaped field plate composite terminal. Figure 2 and Figures 5a - 5l , Figures 5a - 5l for Figure 2 A schematic diagram of the preparation process of a gallium oxide device having a mesa and a U-shaped field plate composite terminal. The preparation method comprises the steps of:

[0104] S1, providing a gallium oxide substrate 1, such as Figure 5a shown.

[0105] S2, growing a gallium oxide epitaxial layer 2 on the gallium oxide substrate 1, such as Figure 5b shown.

[0106] S3, depositing cathode metal 3 on the back of gallium oxide substrate 1, such as Figure 5c shown.

[0107] S4, forming an anode metal layer 4 in the active region of the gallium oxide epitaxial layer 2, such as Figure 5d shown.

[0108] S5. Etching the gallium oxide epitaxial layer 2 to form a groove on one side of the gallium oxide epitaxial layer 2 and a terrace on the other side.

[0109] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying it with N2, ICP etching of the BCl3 / Ar system is used to etch the gallium oxide epitaxial layer 2 with a self-alignment process, and the etching depth is equal to the thickness of the gallium oxide epitaxial layer 2, thereby forming a groove. The unetched gallium oxide epitaxial layer 2 on one side of the groove forms a mesa, and the anode metal layer 4 is located on the mesa, as Figure 5e shown.

[0110] S6. Deposit an insulating thin film layer 5 on the bottom and side walls of the groove and on the surface of the anode metal layer 4, as Figure 5f shown.

[0111] S7. Spin-coat an organic photosensitive resin insulating material in the groove and on the insulating thin film layer 5, as Figure 5g shown, and make the organic photosensitive resin insulating material in the groove form a pit with an arc-shaped side wall, as Figure 5h shown.

[0112] S8. Deposit a metal field plate layer 7 on the organic photosensitive resin insulating material, such that one end of the metal field plate layer 7 is connected to the anode metal layer 4, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa, as Figure 5i and 5j shown.

[0113] S9. Fill the groove with the organic photosensitive resin insulating material to form an organic photosensitive resin insulating medium 6, as Figure 5k shown.

[0114] S10. Open a hole in the area of the anode metal layer 4, as Figure 5l shown.

[0115] So far, the device fabrication is completed.

[0116] Example 4

[0117] Based on Example 1, this example provides a preparation method for a gallium oxide device with a mesa and U-shaped field plate composite terminal. Please refer to Figure 3 and Figures 6a - 6l , Figures 6a - 6l which Figure 3 is a schematic flow chart of the preparation process of a gallium oxide device with a mesa and U-shaped field plate composite terminal. The preparation method includes the steps:

[0118] S1. Provide a gallium oxide substrate 1, as Figure 6a shown.

[0119] S2. Grow a gallium oxide epitaxial layer 2 on the gallium oxide substrate 1, as Figure 6b shown.

[0120] S3. Deposit a cathode metal 3 on the back of the gallium oxide substrate 1, as Figure 6c shown.

[0121] S4. Fabricate an anode metal layer 4 in the active region of the gallium oxide epitaxial layer 2, as Figure 6d shown.

[0122] S5. Etch the gallium oxide epitaxial layer 2 to form a groove on one side and a mesa on the other side of the gallium oxide epitaxial layer 2.

[0123] Specifically, after cleaning the sample with acetone and isopropyl alcohol and drying it with N2, use ICP etching with a BCl3 / Ar system to etch the gallium oxide epitaxial layer 2 by a self-alignment process. The etching depth is greater than the thickness of the gallium oxide epitaxial layer 2, and the etching region enters the gallium oxide substrate 1 with a penetration depth of 1 μm, thereby forming a groove. The unetched gallium oxide epitaxial layer 2 on one side of the groove forms a mesa, and the anode metal layer 4 is located on the mesa, as Figure 6e shown.

[0124] In this embodiment, the etching depth of the groove is greater than the thickness of the gallium oxide epitaxial layer, and the etching region enters the gallium oxide substrate, which can weaken the influence of the "micro-groove" region introduced during the etching process on the electric field modulation effect.

[0125] S6. Deposit an insulating thin film layer 5 on the bottom and side walls of the groove and on the surface of the anode metal layer 4, as Figure 6f shown.

[0126] S7. Spin-coat an organic photosensitive resin insulating material in the groove and on the insulating thin film layer 5, as Figure 6g shown, and make the organic photosensitive resin insulating material in the groove form a pit with an arc-shaped side wall, as Figure 6h shown.

[0127] S8. Deposit a metal field plate layer 7 on the organic photosensitive resin insulating material, such that one end of the metal field plate layer 7 is connected to the anode metal layer 4, and the distance from the other end to the mesa is greater than the distance from the bottom of the pit to the mesa, as Figure 6i and 6j shown.

[0128] S9. Fill the groove with the organic photosensitive resin insulating material to form an organic photosensitive resin insulating medium 6, as Figure 6k shown.

[0129] S10. Open a hole in the region of the anode metal layer 4, as Figure 6l shown.

[0130] Thus, the device fabrication is completed.

[0131] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as falling within the protection scope of the present invention.

Claims

1. A gallium oxide device having a mesa and a U-shaped field plate composite terminal, characterized in that: include: Cathode metal (3); A gallium oxide substrate (1) located on the cathode metal (3); A gallium oxide epitaxial layer (2) is located on a portion of the surface of the gallium oxide substrate (1), with a groove formed on one side and a terrace formed on the other side; an anode metal layer (4), located on the table formed by the gallium oxide epitaxial layer (2); An insulating film layer (5) covering the bottom and side walls of the groove and a portion of the surface of the anode metal layer (4); An organic photosensitive resin insulating medium (6), filled in the groove and located on the insulating film layer (5); A metal field plate layer (7) is located in the organic photosensitive resin insulating medium (6) and forms a pit with an arc-shaped side surface, one end of the metal field plate layer (7) is connected to the anode metal layer (4), and the distance from the other end to the table surface is greater than the distance from the bottom of the pit to the table surface.

2. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 1, characterized in that: The groove extends from the upper surface of the gallium oxide epitaxial layer (2) to the interior of the gallium oxide epitaxial layer (2); or, the groove extends from the upper surface of the gallium oxide epitaxial layer (2) to the surface of the gallium oxide substrate (1); or, the groove extends from the upper surface of the gallium oxide epitaxial layer (2) to the interior of the gallium oxide substrate (1).

3. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 2, characterized in that: The depth of the groove is greater than 1 μm.

4. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 1, characterized in that: The material of the insulating film layer (5) includes one or more of SiO2, Al2O3, HfO2, and ZrO2, and the thickness is 50-200 nm.

5. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 1, characterized in that: The organic photosensitive resin insulating medium (6) includes one or more of benzocyclobutene, photosensitive polyimide, photosensitive polybenzoxazole, and photosensitive epoxy resin.

6. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 1, characterized in that: The metal field plate layer (7) has a thickness of 100-300 nm, a lateral width of 5-50 μm, and a longitudinal depth extending into the groove of 60%-80% of the groove depth.

7. The gallium oxide device with a mesa and U-shaped field plate composite terminal according to claim 1, characterized in that: The material of the gallium oxide substrate (1) includes highly doped n+β-Ga2O3, the doping elements include one or more of Si and Sn, and the doping concentration is 1×10 18 -5×10 19 cm -3 , thickness is 300-650μm; The material of the gallium oxide epitaxial layer (2) includes low-doped n-β-Ga2O3, and the doping elements include one or more of Si and Sn, with a doping concentration of 1×10 15 -1×10 17 cm -3 , thickness is 10-20 μm; The material of the cathode metal (3) includes one or more of Ti, Au, Ni, and Au; The material of the anode metal layer (4) includes one or more of Ni and Au.

8. A method for preparing a gallium oxide device having a mesa and a U-shaped field plate composite terminal, characterized in that: Includes steps: Providing a gallium oxide substrate (1); Growing a gallium oxide epitaxial layer (2) on the gallium oxide substrate (1); Depositing a cathode metal (3) on the back side of the gallium oxide substrate (1); Producing an anode metal layer (4) in the active region of the gallium oxide epitaxial layer (2); Etching the gallium oxide epitaxial layer (2) to form a groove on one side of the gallium oxide epitaxial layer (2) and a terrace on the other side; Depositing an insulating film layer (5) on the bottom and sidewalls of the groove and on the surface of the anode metal layer (4); Spin coating an organic photosensitive resin insulating material in the groove and on the insulating film layer (5), so that the organic photosensitive resin insulating material in the groove forms a pit with an arc-shaped side surface; Depositing a metal field plate layer (7) on the organic photosensitive resin insulating material, such that one end of the metal field plate layer (7) is connected to the anode metal layer (4), and the distance from the other end to the table is greater than the distance from the bottom of the pit to the table; Filling the groove with the organic photosensitive resin insulating material to form an organic photosensitive resin insulating medium (6); Holes are opened in the region of the anode metal layer (4).

9. The method for preparing a gallium oxide device having a mesa and a U-shaped field plate composite terminal according to claim 8, characterized in that: Etching the gallium oxide epitaxial layer (2) comprises: The gallium oxide epitaxial layer (2) is etched using a self-alignment process, wherein the etching depth is less than the thickness of the gallium oxide epitaxial layer (2); Alternatively, the gallium oxide epitaxial layer (2) is etched using a self-alignment process, with the etching depth being equal to the thickness of the gallium oxide epitaxial layer (2); Alternatively, the gallium oxide epitaxial layer (2) is etched using a self-alignment process, and the etching depth is greater than the thickness of the gallium oxide epitaxial layer (2).

10. The method for preparing a gallium oxide device having a mesa and a U-shaped field plate composite terminal according to claim 8, characterized in that: Spin coating an organic photosensitive resin insulating material in the groove and on the insulating film layer (5), and forming a pit with an arc-shaped side surface by the organic photosensitive resin insulating material in the groove, comprising: Clean the sample surface; Spin coating an adhesive in the groove and on the insulating film layer (5); Spin coating an organic photosensitive resin insulating material on the surface of the adhesive; The organic photosensitive resin insulating material is pre-baked, exposed, developed and hardened by using a puddle development technology to form a pit with an arc-shaped side surface in the organic photosensitive resin insulating material at the groove.

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