HEMT device, manufacturing method thereof and radio frequency module

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to an HEMT (High Electron Mobility Transistor) device, a manufacturing method thereof and a radio frequency module. The manufacturing method comprises the following steps: providing a substrate; growing an epitaxial structure on the substrate; depositing a passivation dielectric layer on the epitaxial structure; performing ion implantation from the surface of the epitaxial structure to the substrate to form an ion implantation region; forming a third groove extending to at least part of the epitaxial structure in the ion implantation region; the area of the bottom of the third groove is larger than the orthographic projection area of the bottom of the third groove on the substrate; the orthographic projection area of the ion implantation region on the substrate is greater than the orthographic projection area of the bottom of the third groove on the substrate; and depositing a metal layer on the third groove to form ohmic contact. Through the steps, the ohmic contact resistance is further reduced while the excellent performance is ensured, and the electrical property of the HEMT is improved.

Description

HEMT device, manufacturing method thereof and radio frequency module TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a HEMT device, a manufacturing method thereof and a radio frequency module. BACKGROUND

[0002] High Electron Mobility Transistor (HEMT) has the advantages of high frequency, high voltage, high temperature and the like, and is the future development direction of solid-state microwave power devices and power electronic devices. The performance of ohmic contact has a great influence on the performance of the HEMT device, and how to reduce the ohmic contact resistance of the HEMT device is crucial to improve the performance of the HEMT device. Since the GaN material in the HEMT device has high stability and is not easy to react chemically, it is not easy to form an ohmic base.

[0003] Therefore, how to provide a HEMT device with excellent performance and low ohmic contact resistance is a problem that those skilled in the art need to solve at present. TECHNICAL SOLUTION

[0004] The present application provides a HEMT device, which can solve at least one problem in the background art to effectively reduce the ohmic contact resistance and improve the electrical characteristics of the HEMT.

[0005] In a first aspect, the present application provides a manufacturing method of a HEMT device, which at least comprises the following steps: providing a substrate; growing an epitaxial structure on the substrate; depositing a passivation medium layer on the epitaxial structure; performing ion implantation from the surface of the epitaxial structure to the substrate direction to form an ion implantation area; forming a third trench extending to at least part of the epitaxial structure in the ion implantation area; the area of the bottom of the third trench is greater than the area of the orthographic projection of the bottom of the third trench on the substrate; the orthographic projection area of the ion implantation area on the substrate is greater than the orthographic projection area of the bottom of the third trench on the substrate; depositing a metal layer on the third trench to form an ohmic contact.

[0006] Further, in the manufacturing method, the step of forming a third trench extending to at least part of the epitaxial structure in the ion implantation area comprises the following steps: forming a photoresist layer on the passivation medium layer; and patterning part of the photoresist layer located above the ion implantation area to form a first trench; etching the passivation medium layer located below the first trench to form a second trench; etching the epitaxial structure located below the second trench to form a third trench.

[0007] Further, in the manufacturing method, a difference between a maximum depth and a minimum depth of the first trench is h1, and h1 is between 44nm and 225nm; the photoresist layer has a thickness H, and H is greater than or equal to 5*h1.

[0008] Further, in the manufacturing method, a difference between a maximum depth and a minimum depth of the second trench is h2, and h2 = h1 / A, A represents an etching selectivity ratio of the passivation medium layer to the photoresist layer, and A is between 2.5 and 4.

[0009] Further, in the manufacturing method, a difference between a maximum depth and a minimum depth of the third trench is h3, and h3 = h1 / (A*B), A represents an etching selectivity ratio of the passivation medium layer to the photoresist layer, and A is between 2.5 and 4; B represents an etching selectivity ratio of the passivation medium layer to the epitaxial structure, and B is between 1.2 and 2.

[0010] Further, in the manufacturing method, a difference between a maximum depth and a minimum depth of the third trench is h3, and h3 is between 10nm and 50nm.

[0011] Further, in the manufacturing method, the epitaxial structure at least includes a GaN layer on the substrate and a barrier layer on the GaN layer; and the third trench is formed by etching the epitaxial structure until the GaN layer is exposed.

[0012] Further, in the manufacturing method, an ion concentration of the ion implantation region increases first and then decreases from the surface of the epitaxial structure to the substrate, and the ion implantation region has a high-concentration area; an ion concentration in the high-concentration area is greater than a preset high-concentration value; the third trench is etched to the high-concentration area; and the preset high-concentration value is greater than or equal to 80% of a peak value of the ion concentration of the ion implantation region.

[0013] Further, in the manufacturing method, at least part of a surface of the bottom of the first trench is one or more of an inclined plane, an arc surface, and a concave-convex surface, and / or at least part of a surface of the bottom of the second trench is one or more of an inclined plane, an arc surface, and a concave-convex surface, and / or at least part of a surface of the bottom of the third trench is one or more of an inclined plane, an arc surface, and a concave-convex surface.

[0014] In a second aspect, the present application further provides a HEMT device, comprising: a substrate; an epitaxial structure on the substrate; a passivation dielectric layer on the epitaxial structure; an ion implantation region extending from the surface of the epitaxial structure towards the substrate; a third trench in the ion implantation region and extending from the surface of the epitaxial structure towards the substrate to at least part of the epitaxial structure; the area of the bottom of the third trench is greater than the area of the orthographic projection of the bottom of the third trench on the substrate; the area of the orthographic projection of the ion implantation region on the substrate is greater than the area of the orthographic projection of the bottom of the third trench on the substrate; and a metal layer on the third trench and forming an ohmic contact.

[0015] Further, in the HEMT device, the epitaxial structure comprises at least a GaN layer on the substrate and a barrier layer on the GaN layer; and the third trench extends from the surface of the epitaxial structure towards the substrate to the GaN layer.

[0016] Further, in the HEMT device, the ion implantation region has a high concentration region; the ion concentration in the high concentration region is greater than a preset high concentration value, the preset high concentration value is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region; and the bottom of the third trench is in contact with the high concentration region.

[0017] Further, in the HEMT device, the difference between the maximum depth and the minimum depth of the third trench is h3, and h3 is between 10-50 nm.

[0018] Further, in the HEMT device, at least part of the surface of the bottom of the third trench is one or more of an inclined plane, an arc surface, and a concave-convex surface.

[0019] Further, in the HEMT device, when the bottom of the third trench is an inclined plane, the inclination angle α of the inclined plane is in the range of 5-10°.

[0020] In a third aspect, the present application further provides a radio frequency module comprising the HEMT device described above. Advantages

[0021] The manufacturing method of the HEMT device provided by the present application can effectively reduce the ohmic contact resistance between the source, the drain and the epitaxial structure, and improve the electrical characteristics of the HEMT by designing the ion implantation region and the third trench.

[0022] Other features and advantages of the present application will be illustrated in the following description, and some will become apparent from the description, or will be understood through implementation of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0024] Fig. 1 is a step flow chart of a method for manufacturing a HEMT device according to an embodiment of the present application;

[0025] Fig. 2 is a process flow chart of steps S10-S40 of a method for manufacturing a HEMT device according to an embodiment of the present application;

[0026] Fig. 3 is a schematic diagram of a partial structure of a HEMT device according to an embodiment of the present application;

[0027] Figs. 4-6 are process flow charts of steps S50-S70 of a method for manufacturing a HEMT device according to an embodiment of the present application;

[0028] Figs. 7-9 are schematic diagrams of structures of a HEMT device according to an embodiment of the present application;

[0029] Fig. 10 is a schematic diagram of a partial top view structure of a HEMT device according to an embodiment of the present application.

[0030] Reference signs:

[0031] 10 - substrate; 20 - epitaxial structure; 20a - ion implantation region; 21 - GaN layer; 22 - barrier layer; 30 - passivation dielectric layer; 40 - photoresist layer; 51 - first trench; 51a - first trench bottom; 52 - second trench; 52a - second trench bottom; 53 - third trench; 53a - third trench bottom; 61 - source; 62 - drain; 63 - gate; 70 - passivation protection layer. Embodiments of the present application

[0032] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will describe the technical solutions in the embodiments of the present application clearly and completely with reference to the drawings in the embodiments of the present application. The technical features designed in different embodiments of the present application can be combined with each other as long as they do not conflict with each other.

[0033] At present, the source ohmic contact and the drain ohmic contact of a GaN-based HEMT device are usually realized by high-temperature alloying, ion implantation or secondary epitaxy to achieve low source ohmic contact resistance and drain ohmic contact resistance.

[0034] However, the high-temperature alloy is usually made by rapid annealing of the metal layer at high temperature to form the electrode, and there are quality defects such as rough surface morphology and uneven edge of the electrode, and thus the electrical breakdown phenomenon is prone to occur, the device reliability is reduced, and the like. Since the peak of the ion implantation concentration is not on the surface, the minimum ohmic contact resistance cannot be achieved by directly manufacturing the electrode on the surface. If the etching process is used, the etching depth is difficult to control, so that the ohmic contact resistance obtained by production cannot reach the minimum. If a high-doped GaN layer is prepared by a secondary epitaxy process, there are problems such as complicated manufacturing process, high difficulty, high cost, and inability to realize large-scale and large-size wafer production.

[0035] Therefore, in view of the problems of the HEMT device with low ohmic contact resistance, the purpose of the present application is to provide a HEMT device and a manufacturing method, which can further reduce the ohmic contact resistance while ensuring excellent performance and improve the electrical characteristics of the HEMT.

[0036] In a first aspect, the present application provides a manufacturing method of a HEMT device, which comprises at least the following steps:

[0037] providing a substrate 10;

[0038] growing an epitaxial structure 20 on the substrate 10; the epitaxial structure 20 comprises a heterojunction interface formed by a channel layer and a barrier layer, and a two-dimensional electron gas is generated by polarization.

[0039] depositing a passivation medium layer 30 on the epitaxial structure 20;

[0040] performing ion implantation from the surface of the epitaxial structure 20 to the substrate 10 direction to form an ion implantation region 20a;

[0041] forming a third groove 53 extending to at least part of the epitaxial structure 20 in the ion implantation region 20a, the area of the bottom 53a of the third groove is greater than the area of the orthographic projection of the bottom 53a of the third groove on the substrate 10; the orthographic projection area of the ion implantation region 20a on the substrate 10 is greater than the orthographic projection area of the bottom 53a of the third groove on the substrate 10;

[0042] depositing a metal layer on the third groove 53 to form an ohmic contact.

[0043] Through the above arrangement, the ohmic contact area can be effectively increased, the metal layer is in contact with the region with a larger ion implantation concentration, the ohmic contact resistance between the metal layer and the epitaxial structure 20 is reduced, the etching precision and etching difficulty requirement are reduced, and the electrical characteristics of the HEMT are effectively improved.

[0044] In an embodiment, the forming the third trench 53 extending to at least part of the epitaxial structure 20 in the ion implantation region 20a comprises the following steps:

[0045] forming a photoresist layer 40 on the passivation dielectric layer 30; and patterning part of the photoresist layer 40 above the ion implantation region 20a to form a first trench 51;

[0046] etching the passivation dielectric layer 30 under the first trench 51 to form a second trench 52;

[0047] etching the epitaxial structure 20 under the second trench 52 to form a third trench 53.

[0048] In an embodiment, the difference between the maximum depth and the minimum depth of the first trench 51 is h1, and h1 is between 44nm and 225nm, so as to avoid the influence of the subsequent process of the second trench 52 and the third trench 53 caused by too large or too small h1.

[0049] In an embodiment, the photoresist layer 40 has a thickness H, and H≥5*h1, so as to ensure that the photoresist layer 40 has sufficient thickness for patterning.

[0050] In an embodiment, the difference between the maximum depth and the minimum depth of the second trench 52 is h2, and h2=h1 / A, where A represents the etching selectivity ratio of the passivation dielectric layer 30 and the photoresist layer 40, and A is between 2.5 and 4.

[0051] In an embodiment, the difference between the maximum depth and the minimum depth of the third trench 53 is h3, and h3=h1 / (A*B), where A represents the etching selectivity ratio of the passivation dielectric layer 30 and the photoresist layer 40, and A is between 2.5 and 4; and B represents the etching selectivity ratio of the passivation dielectric layer 30 and the epitaxial structure 20, and B is between 1.2 and 2.

[0052] In an embodiment, the difference between the maximum depth and the minimum depth of the third trench 53 is h3, and h3 is between 10nm and 50nm, for example, h3 can be 10nm, 15nm, 20nm, 20nm, 30nm, 40nm, 50nm, etc., so as to ensure that the third trench bottom 53a is in contact with the region with higher ion concentration. The width W of the third trench bottom 53a in the horizontal direction is between 10μm and 50μm.

[0053] In an embodiment, the epitaxial structure 20 at least comprises a GaN layer 21 on the substrate 10 and a barrier layer 22 on the GaN layer 21; the third trench 53 is formed by etching the second trench 52 towards the epitaxial structure 20 until the GaN layer 21 is exposed. By this arrangement, the metal layer on the third trench 53 can form a good ohmic contact with the GaN layer 21 and the barrier layer 22, thereby ensuring the electrical performance of the HEMT.

[0054] In an embodiment, the ion implantation region 20a has a high concentration region in which the ion concentration first increases and then decreases from the surface of the epitaxial structure 20 towards the substrate 10; the ion concentration in the high concentration region exceeds a preset high concentration value; the third trench 53 is etched into the high concentration region; and the preset high concentration value is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region 20a. By this arrangement, the metal layer on the third trench 53 can be in contact with the high concentration region, thereby significantly reducing the resistance of the ohmic contact.

[0055] In an embodiment, the implantation energy of the ion implantation first increases and then decreases when the ion implantation is performed to form the ion implantation region 20a.

[0056] In an embodiment, at least part of the surface of the first trench bottom 51a is one or more of an inclined plane, an arc surface, and a concave-convex surface; at least part of the surface of the second trench bottom 52a is one or more of an inclined plane, an arc surface, and a concave-convex surface; and / or at least part of the surface of the third trench bottom 53a is one or more of an inclined plane, an arc surface, and a concave-convex surface. The specific arrangement can be made according to actual needs, and is not limited herein.

[0057] In an embodiment, when the third trench bottom 53a is an inclined plane, the inclination angle a of the inclined plane is in the range of 5° to 10°. In this range, the ion concentration of the implanted ions is relatively high, which can effectively ensure that the inclined plane is in complete contact with the high-concentration ions, thereby reducing the contact resistance.

[0058] In an embodiment, the method further comprises the following steps: fabricating a gate 63 on the passivation dielectric layer 30, the gate 63 being in electrical contact with the epitaxial structure 20 through a via hole formed in the passivation dielectric layer 30; and depositing a passivation protective layer 70 on the passivation dielectric layer 30.

[0059] In a second aspect, the application further provides a HEMT device, which at least comprises a substrate 10, an epitaxial structure 20, an ion implantation region 20a, a third trench 53, and a metal layer.

[0060] The epitaxial structure 20 is located on the substrate 10; the passivation dielectric layer 30 is located on the epitaxial structure 20; the ion implantation region 20a extends from the surface of the epitaxial structure 20 to the substrate 10; the third trench 53 is located in the ion implantation region 20a and extends from the surface of the epitaxial structure 20 to the substrate 10 to at least part of the epitaxial structure 20; the area of the bottom 53a of the third trench is greater than the area of the orthographic projection of the bottom 53a of the third trench on the substrate 10; the area of the orthographic projection of the ion implantation region 20a on the substrate 10 is greater than the area of the orthographic projection of the bottom 53a of the third trench on the substrate; and a metal layer is located on the third trench 53 and forms an ohmic contact.

[0061] In an embodiment, the epitaxial structure 20 at least includes a GaN layer 21 located on the substrate 10 and a barrier layer 22 located on the GaN layer 21; and the third trench 53 extends from the surface of the epitaxial structure 20 to the GaN layer 21.

[0062] In an embodiment, the ion implantation region 20a has a high-concentration region; the ion concentration in the high-concentration region exceeds a preset high-concentration value, which is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region 20a; and the bottom 53a of the third trench is in contact with the high-concentration region.

[0063] In an embodiment, the difference between the maximum depth and the minimum depth of the bottom 53a of the third trench is h3, which is between 10 nm and 50 nm; and the width W of the bottom 53a of the third trench in the horizontal direction is between 10 μm and 50 μm.

[0064] In an embodiment, at least part of the surface of the bottom 53a of the third trench is one or more of an inclined plane, a curved surface, and a concave-convex surface.

[0065] In an embodiment, when the bottom 53a of the third trench is an inclined plane, the inclination angle α of the inclined plane is between 5° and 10°.

[0066] In an embodiment, the HEMT device further includes a gate 63 and a passivation protection layer 70; the gate 63 is located above the passivation dielectric layer 30 and is in electrical contact with the epitaxial structure 20 through a via hole formed in the passivation dielectric layer 30; and the passivation protection layer 70 covers the passivation dielectric layer 30.

[0067] Next, the technical solutions of the present application are described and explained in detail through various specific embodiments in combination with the accompanying drawings.

[0068] Embodiment One

[0069] Please refer to FIG. 1-3, FIG. 1 is a step flow chart of the method for manufacturing the HEMT device according to an embodiment of the present application.

[0070] Step S10: providing a substrate 10. The substrate 10 can be a base material for carrying semiconductor integrated circuit components, which is well known to those skilled in the art, and is not limited herein, and is typically a silicon (Si), silicon carbide (SiC), sapphire (Saphhire), gallium nitride (GaN), or the like.

[0071] Step S20: growing an epitaxial structure 20 on the substrate 10. The epitaxial structure 20 can be grown on the substrate 10 by a chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD) process, which is not limited in the present embodiment and can be selected as needed. Specifically, referring to FIG. 3, the epitaxial structure 20 includes at least a GaN layer 21 and a barrier layer 22; a heterojunction is formed between the GaN layer 21 and the barrier layer 22 to form a two-dimensional electron gas. The barrier layer 22 can be one or a stack of AlGaN, aluminum nitride, aluminum indium nitride, aluminum gallium nitride, indium gallium nitride, or aluminum indium gallium nitride, and the thickness of the barrier layer 22 is in the range of 10-30 nm.

[0072] It should be noted that, according to the actual needs of the HEMT device, the epitaxial structure 20 can also be provided as at least one of a nucleation layer, a transition layer, a buffer layer, an insertion layer, or the like (not shown in the figure), which is not limited herein.

[0073] For example, an AlN insertion layer is provided between the GaN layer 21 and the barrier layer 22. The thickness of the AlN insertion layer can be in the range of 0.5-2 nm, and the AlN insertion layer can improve the channel electron density and electron mobility, and improve the effect of the heterojunction interface.

[0074] For example, a nucleation layer and a buffer layer are provided between the substrate 10 and the GaN layer 21. The nucleation layer is made of AlN and has a thickness of 10-50 nm. The nucleation layer can release the mismatch stress generated by the lattice mismatch between the buffer layer and the substrate 10, and the thermal stress generated by the thermal expansion coefficient, and optimize the flatness of the nucleation layer surface to make the growth defects of the epitaxial layer lower. The buffer layer includes one or a combination of AlN, AlGaN, and GaN to alleviate the lattice mismatch and thermal expansion coefficient mismatch between the substrate 10 and the GaN layer 21. Preferably, the buffer layer is a GaN buffer layer.

[0075] Step S30: depositing a passivation medium layer 30 on the epitaxial structure 20; the material of the passivation medium layer 30 can be one or a combination of SiO2, SiN, Al2O3, SiON, which is not limited in the embodiments of the present application. Through the design of the passivation medium layer 30, the influence of external charged particles or impurities on the normal work of the HEMT can be effectively avoided.

[0076] Please refer to FIG. 2 and FIG. 3, step S40: ion implantation is performed from the surface of the epitaxial structure 20 to the substrate 10 to form an ion implantation region 20a; wherein the ion implantation region 20a is formed in the epitaxial structure 20 below the metal layer to be formed into ohmic contact. In the embodiments, the HEMT device includes a source 61 and a drain 62, and the ion implantation region 20a includes a source ion implantation region and a drain ion implantation region respectively. The source ion implantation region is above the source 61 to realize low-resistance ohmic contact. The drain ion implantation region is above the drain to realize low-resistance ohmic contact. The ion implantation can be silicon ion implantation; the angle of ion implantation from the surface of the epitaxial structure 20 can be vertical implantation or implantation at a certain angle, which is designed according to actual needs and is not limited herein. It should be noted that the surface of the epitaxial structure 20 refers to the surface of the epitaxial structure 20 far away from the substrate 10.

[0077] Preferably, when the ion implantation is performed to form the ion implantation region 20a, the implantation energy of the ion implantation decreases from large to small, i.e. high-energy implantation first and then low-energy implantation. For example, through multiple ion implantations. In specific implementation, for example, twice ion implantation, the energy of the first ion implantation is greater than the energy of the second ion implantation, and preferably, the energy of the first ion implantation is preferably 60-75 Kev, and the energy of the second ion implantation is preferably 35-50 Kev. Specifically, high-energy implantation is first performed to make the implanted ion concentration and concentration distribution deep, so as to not constitute a blocking effect for subsequent low-energy implantation, thereby achieving the required preset implantation depth and avoiding the hindering of the ion of low-energy implantation to the ion of subsequent high-energy implantation.

[0078] In a preferred embodiment, the ion implantation region 20a has a concentration of ions that increases first and then decreases from the surface of the epitaxial structure 20 to the substrate 10, and has a high concentration region; the ion concentration in the high concentration region exceeds a preset high concentration value; the third trench 53 is etched into the high concentration region; and the preset high concentration value is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region. That is, the position of the third trench 53 can be ensured to be within the high concentration region where the ion concentration exceeds 80% of the peak value of the ion concentration. In a specific embodiment of the present application, the ion concentration in the high concentration region exceeds 85% of the peak value of the ion concentration. The peak value of the ion concentration refers to the maximum value of the ion concentration in the ion implantation region 20a. For example, in the ion implantation region 20a of FIGS. 7-9, the region of the relatively dense dots represents the high concentration region, and the bottom 53a of the third trench is located within the high concentration region.

[0079] In combination with the above-mentioned limitations on the implantation energy and ion concentration of ion implantation, the epitaxial structure 20 can be accurately formed with a high concentration region having a relatively high concentration, thereby reducing the precision requirement for etching the trench, ensuring the contact of the metal layer with the high concentration region without the etching depth reaching the peak depth, and further significantly reducing the resistance of the ohmic contact.

[0080] It should be noted that the concentration and energy of ion implantation can be selected according to the depth and amount of doping required, and are not limited herein.

[0081] Preferably, the distance from the surface of the epitaxial structure 20 near the passivation medium layer 30 to the position of the peak value of the ion concentration is between 10-50 nm, so that the peak value of the ion concentration is located in the GaN layer 21 or the barrier layer 22 or between the two. For example, when the thickness of the barrier layer 22 is 10-30 nm, the depth of the peak value of the ion concentration is ensured to exceed the thickness of the barrier layer 22 in the epitaxial structure by controlling the ion implantation process. For example, when the thickness of the barrier layer 22 is 10 nm, the depth of the peak value of the ion concentration is 13 nm, i.e., the peak value of the ion concentration is located at a position 13 nm deep from the surface of the epitaxial structure 20 to the substrate 10; similarly, when the thickness of the barrier layer is 20 nm, the depth of the peak value of the ion concentration is 25 nm; and when the thickness of the barrier layer is 25 nm, the depth of the peak value of the ion concentration is 32 nm. The specific depth requirement of the peak value of the ion concentration can be reasonably designed according to the actual device requirements, and is not limited herein. Through the above setting, the peak value of the ion concentration is ensured to be located in the GaN layer 21, so that the metal layer produced subsequently can be in contact with the GaN having a relatively high ion implantation concentration, and the ohmic contact resistance is reduced.

[0082] Referring to FIGS. 4-6, at step S50, a third trench 53 extending to at least part of the epitaxial structure 20 is formed in the ion implantation region 20a, and the area of the bottom 53a of the third trench is greater than the area of the orthogonal projection of the bottom 53a of the third trench onto the substrate 10; and the area of the orthogonal projection of the ion implantation region 20a onto the substrate 10 is greater than the area of the orthogonal projection of the bottom 53a of the third trench onto the substrate 10.

[0083] Through the above limitations of the ion implantation region 20a and the third trench 53, the requirements for etching precision and etching depth can be effectively reduced, and the problem of deviation in ion implantation and etching depth between different batches of products can be reduced, thereby ensuring the consistency of the small ohmic contact resistance.

[0084] As a preferred embodiment, in the present embodiment, the step of forming the third trench 53 extending to at least part of the epitaxial structure 20 in the ion implantation region 20a includes the following steps:

[0085] At step S51, a photoresist layer 40 is formed on the passivation dielectric layer 30, and part of the photoresist layer 40 above the ion implantation region 20a is patterned to form a first trench 51. When the photoresist layer 40 is patterned, the photoresist layer 40 can be patterned into different shapes by changing the exposure energy and the exposure dose. That is,

[0086] The area of the bottom 51a of the first trench is greater than the area of the orthogonal projection of the bottom 51a of the first trench onto the substrate 10, or in other words, the bottom 51a of the first trench can be a surface that is not horizontal or not completely horizontal. The specific shape of the bottom 51a of the first trench can be reasonably designed according to actual needs, and is not limited herein. As an example, at least part of the surface of the bottom 51a of the first trench can be an inclined plane, a curved surface, or a concave-convex surface. When the bottom 51a of the first trench is an inclined plane, the inclination angle of the inclined plane is in the range of 5°-10°, so that the etching of the bottom 52a of the second trench and the bottom 53a of the third trench can also be in the same range, thereby effectively ensuring that the inclined plane of the bottom 53a of the third trench is in complete contact with the high-concentration ions, thereby reducing the contact resistance.

[0087] Preferably, as shown in FIGS. 4-6, the first trench 51 has a maximum depth h1max and a minimum depth h1min in the thickness direction of the epitaxial structure 20, and the difference between h1max and h1min is the depth difference h1 of the first trench bottom 51a, h1 is between 44-225 nm, for example, h1 can be 50 nm, 100 nm, 120 nm, 150 nm, 200 nm, etc. It should be noted that in the present embodiment, the thickness direction of the epitaxial structure 20 refers to the vertical direction perpendicular to the horizontal plane of the epitaxial structure 20, i.e., the direction indicated by the arrow Z in the figure. Since the first trench bottom 51a is a non-horizontal surface, the first trench 51 has a maximum depth h1max and a minimum depth h1min, wherein the maximum depth h1max of the first trench 51 refers to the distance from the surface of the photoresist layer 40 away from the passivation medium layer 30 to the deepest position of the first trench bottom 51a; the minimum depth h1min of the first trench 51 refers to the distance from the surface of the photoresist layer 40 away from the passivation medium layer 30 to the shallowest position of the first trench bottom 51a. By limiting h1 as described above, it is beneficial for subsequent etching of the second trench 52 and the third trench 53, avoiding that h1 is too large or too small to affect the high ohmic contact resistance finally formed.

[0088] In an optional embodiment, referring to FIGS. 4-6, the photoresist layer 40 has a thickness H, wherein H≥5*h1, so as to ensure that the photoresist layer 40 has sufficient thickness for patterning. As an example, the thickness H of the photoresist layer 40 is between 1-2 μm. In the present embodiment, the maximum depth of the first trench 51 can extend to the surface of the passivation medium layer 30 or can not exceed the surface of the passivation medium layer 30. That is, the maximum depth h1max of the first trench 51 can be equal to the thickness H of the photoresist layer or can be less than the thickness H of the photoresist layer.

[0089] Step S52: etching the passivation medium layer 30 located below the first trench 51 to form a second trench 52; when etching the passivation medium layer 30, the material of the passivation medium layer 30 can be SiN, and F-based gas is used to etch SiN. The etching selectivity ratio of the photoresist layer 40 to the passivation medium layer 30 is preferably 3:1.

[0090] Preferably, the area of the second trench bottom 52a is greater than the orthographic projection area of the second trench bottom 52a on the substrate 10. In the present embodiment, the shape of the second trench bottom 52a is consistent with the shape of the first trench bottom 51a, i.e., the shape of the second trench bottom 52a is formed based on the patterned photoresist topography. Therefore, referring to FIGS. 4-6, at least part of the surface of the second trench bottom 52a can also be, for example, an inclined plane, a curved surface, or a concave-convex surface.

[0091] Further, a difference between a maximum depth and a minimum depth of the second trench 52 in a thickness direction of the epitaxial structure 20 is h2, where h2 = h1 / A, A represents an etching selectivity ratio of the passivation medium layer 30 and the photoresist layer 40, and A is in a range of 2.5-4. That is, h2 depends on the etching rate of the passivation medium layer 30 and the shape of the first trench bottom 51a. The specific difference parameter can be reasonably designed according to actual needs, and is not limited herein. It should be noted that the second trench 52 has a maximum depth h2max and a minimum depth h2min, where the maximum depth h2max of the second trench 52 refers to a distance from a surface of the passivation medium layer 30 away from the epitaxial structure 20 to a deepest position of the second trench bottom 52a, and the minimum depth h2min of the second trench 52 refers to a distance from the surface of the passivation medium layer 30 away from the epitaxial structure 20 to a shallowest position of the second trench bottom 52a, and a difference between h2max and h2min is a depth difference h2 of the second trench bottom 52a. By limiting h2, the subsequent etching of the third trench 53 is facilitated, and a high ohmic contact resistance is avoided due to a large or small difference of h2.

[0092] Step S53: etching the epitaxial structure 20 located below the second trench 52 to form a third trench 53, where an area of the third trench bottom 53a is greater than a normal projection area of the third trench bottom 53a on the substrate 10. That is, the third trench bottom 53a can be a non-horizontal or non-completely horizontal surface. The specific shape can be reasonably designed according to actual needs or based on the shape of the second trench bottom 52a or the first trench bottom 51a, and is not limited herein. Specifically, after the first trench 51 with a bottom is formed in the patterned photoresist layer 40, the second trench 52 and the third trench 53 formed by etching the passivation medium layer 30 and the epitaxial structure 20 will form the second trench bottom 52a and the third trench bottom 53a which are consistent with the shape of the first trench bottom 51a under the influence of the first trench bottom 51a.

[0093] As an example, at least part of the surface of the third trench bottom 53a can be, for example, an inclined plane, a curved surface or a concave-convex surface. For example, the third trench bottom 53a in FIG. 4 is an inclined plane, the third trench bottom 53a in FIG. 5 is a concave-convex surface, and the third trench bottom 53a in FIG. 6 is a curved surface. As shown in FIG. 4, when the third trench bottom 53a is an inclined plane, an inclination angle a of the inclined plane is in a range of 5°-10°, and in specific embodiments, for example, a is 5°, 7.5° or 9°. A higher ion concentration in this range can effectively ensure that the inclined plane is completely in contact with the high-concentration ions, thereby reducing the ohmic contact resistance. When the inclination angle a is higher than 10°, the metal layer will not fall in the high-concentration region of ion implantation; and when the inclination angle a is less than 5°, the etching process precision requirement will be increased.

[0094] Preferably, please continue to refer to FIG. 4-6, the third groove 53 in the epitaxial structure 20 thickness direction of the maximum depth and the minimum depth difference is h3, wherein h3=h1 / A*B, A represents the etching selectivity of the passivation layer 30 and the photoresist layer 40, the value range of A is between 2.5-4; B represents the etching selectivity of the passivation layer 30 and the epitaxial structure 20, the value range of B is between 1.2-2.0. It should be noted that the third groove 53 has a maximum depth h3max and a minimum depth h3min, wherein the maximum depth h3max of the third groove 53 refers to the distance from the surface of the epitaxial structure 20 close to the passivation layer 30 side to the deepest position of the third groove bottom 53a; the minimum depth h3min of the third groove 53 refers to the distance from the surface of the epitaxial structure 20 close to the passivation layer 30 side to the shallowest position of the third groove bottom 53a; the difference between h3max and h3min is the depth difference h3 of the third groove bottom 53a. The embodiment limits h3, effectively ensures the contact effect of the metal layer and the ion implantation area, and avoids the high ohmic contact resistance caused by the too large or too small difference of h3.

[0095] In other optional embodiments, the third groove 53 in the epitaxial structure 20 thickness direction of the maximum depth and the minimum depth difference is h3, the thickness difference h3 is between 10-50 nm, for example, h3 can take the value of 10 nm, 15 nm, 20 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc. Further, the width W of the third groove bottom 53a in the horizontal direction is between 10-50 μm. As shown in FIG. 4-6, the horizontal direction is defined as the direction indicated by the arrow X in the figure, and the horizontal direction is perpendicular to the vertical direction of the epitaxial structure 20 (the direction indicated by the arrow Z). The width of the third groove bottom 53a in the horizontal direction can be adjusted according to the actual device, and the width W of the third groove bottom 53a in the horizontal direction at the source 61 and the width W of the third groove bottom 53a in the horizontal direction at the drain 62 can be set the same or different, preferably, the width W of the third groove bottom 53a in the horizontal direction at the drain 62 is greater than the width W of the third groove bottom 53a in the horizontal direction at the source 61.

[0096] When the epitaxial structure 20 at least comprises a GaN layer 21 on the substrate 10 and a barrier layer 22 on the GaN layer 21, as an example, the third trench 53 is formed by etching the second trench 52 towards the epitaxial structure 20 until the GaN layer 21 is exposed, so that the subsequently formed metal layer (i.e. the source 61 and the drain 62) can be in direct contact with the GaN layer 21, while preventing the third trench 53 from not being able to completely penetrate the barrier layer 22, thereby ensuring the ohmic contact effect of the metal layer and the barrier layer 22 and greatly reducing the ohmic contact resistance.

[0097] Referring to FIGS. 7-10, in step S60, a metal layer is deposited on the third trench 53 to form an ohmic contact. Specifically, the metal layer can be deposited by an evaporation process, for example, a Ti / Pt / Au / Ti metal stack, without high-temperature annealing, so as to avoid the problem of poor quality of the source 61 or the drain 62 caused by high temperature. The metal layer can be a single-layer metal or a single-layer alloy or a multi-layer metal or a multi-layer alloy. In the embodiment, the metal layer comprises the source 61 and the drain 62, i.e. the source 61 and the drain 62 are formed by the evaporation process, wherein the source 61 and the drain 62 are isolated from each other.

[0098] It should be noted that in the embodiment, the ion implantation region 20a comprises a source ion implantation region and a drain ion implantation region arranged at intervals; a third trench 53 is formed in the source ion implantation region, and a source is deposited on the third trench 53; another third trench 53 is formed in the drain ion implantation region, and a drain is deposited on the third trench 53.

[0099] The material of the source 61 and the drain 62 can be a metal such as nickel, gold, titanium, aluminum, platinum, chromium or an alloy or a stack thereof, for example, a Ti / Au metal stack, so as to form an ohmic contact with the epitaxial structure 20. Among them, the source 61 and the drain 62 formed by the evaporation process have better quality, i.e. the metal surface is uniform and the edge is neat, which is beneficial to improve the reliability of the device and avoid electrical breakdown.

[0100] In the embodiment, by the above-mentioned method of first ion implantation and then etching, the source 61 and the drain 62 can be effectively ensured to be in contact with the high-concentration region with high ion concentration, thereby further reducing the ohmic contact resistance while reducing the etching requirement.

[0101] In a preferred embodiment, the method for manufacturing the HEMT device further comprises the following steps:

[0102] A gate 63 is formed on the passivation dielectric layer 30, and the gate 63 is in electrical contact with the epitaxial structure 20 through a via hole formed in the passivation dielectric layer 30. The gate 63 can be designed into a T-shaped gate or a recessed gate according to requirements to effectively reduce the short channel effect of the device, and the specific structure is not limited here. The material of the gate 63 can be a metal such as Ni, Ag, Cu, Co, Pu, Ni, Pt, Au, or an alloy or a stack thereof, and is generally formed by electrochemical deposition, electron beam evaporation or sputtering process, and the Schottky contact is not annealed. The Schottky contact is formed after the gate 63 is formed.

[0103] A passivation protective layer 70 is deposited on the passivation dielectric layer 30 to protect the gate 63, the drain 62 and the source 61. The passivation protective layer 70 is preferably a SiN layer to isolate water vapor and protect the device. According to requirements, other passivation structures can also be provided outside the passivation protective layer 70. It should be noted that the step of removing the photoresist layer 40 before forming the gate 63 is included, that is, the photoresist on the HEMT device is stripped by using an organic solution, and then the metal layer is formed.

[0104] Through the above method design of the HEMT device, the ohmic contact area can be effectively increased, and the ohmic contact resistance can be reduced. At the same time, the etching precision and etching depth are low, and the applicability is high. Even if the injection conditions change, the metal layer can still be in contact with the high-concentration region with high concentration, avoiding the problem of deviation due to different batches of products ion injection and different etching depths, effectively ensuring the consistency of the process, and thereby improving the performance of the HEMT device.

[0105] Embodiment Two

[0106] Please refer to FIGS. 7-9, which are structural schematic diagrams of a plurality of embodiments of the HEMT device provided by the present application. In order to achieve at least one of the advantages or other advantages, the second embodiment discloses a HEMT device at least comprising a substrate 10, an epitaxial structure 20, an ion implantation region 20a, a third trench 53, and a metal layer.

[0107] The epitaxial structure 20 is located on the substrate 10. The substrate 10 can be a base material well known to those skilled in the art for carrying semiconductor integrated circuit components, such as silicon (Si), silicon carbide (SiC), sapphire (Saphhire), gallium nitride (GaN), etc. The epitaxial structure 20 at least includes a GaN layer 21 located on the substrate 10 and a barrier layer 22 located on the GaN layer 21; a heterojunction is formed between the GaN layer 21 and the barrier layer 22 to form a two-dimensional electron gas. As an example, the barrier layer 22 can be one or a stack of AlGaN, aluminum nitride, aluminum indium nitride, aluminum gallium nitride, indium gallium nitride, or aluminum indium gallium nitride. Of course, according to actual needs of the HEMT device, the epitaxial structure 20 can also be provided as at least one of a core layer, a transition layer, a buffer layer, an intercalation layer, etc. (not shown in the figure), which is not limited herein.

[0108] The passivation dielectric layer 30 is located on the epitaxial structure 20 to achieve electrical isolation. The material of the passivation dielectric layer 30 can be one or a combination of SiO2, SiN, Al2O3, SiON, which is not limited by the embodiments of the present application.

[0109] The ion implantation region 20a extends from the surface of the epitaxial structure 20 to the substrate 10; wherein the ion implantation can be silicon ion implantation. The angle of ion implantation can be vertical implantation or implantation at an angle, which is specifically designed according to actual needs. Preferably, when ion implantation is performed to form the ion implantation region 20a, the implantation energy of ion implantation decreases from high to low. That is, the implantation energy is first implanted at a high energy and then implanted at a low energy. Specifically, the high-energy implantation is first used to make the implanted ion concentration deep and the concentration distribution deep, so as to not constitute a blocking effect for subsequent low-energy implantation, thereby achieving the required preset implantation depth and avoiding the ion of low-energy implantation from hindering the ion of subsequent high-energy implantation.

[0110] The third trench 53 is located in the ion implantation region 20a and extends from the surface of the epitaxial structure 20 to the substrate 10 and extends to at least part of the epitaxial structure 20. Preferably, the third trench 53 extends from the surface of the epitaxial structure 20 to the GaN layer 21 in the direction of the substrate 10.

[0111] The area of the third trench bottom 53a is greater than the area of the orthogonal projection of the third trench bottom 53a on the substrate 10. That is, the third trench bottom 53a can be a surface that is not horizontal or not completely horizontal. The specific shape thereof can be reasonably designed according to actual needs. As an example, at least part of the surface of the third trench bottom 53a is one or more of an inclined plane, a curved surface, and a concave-convex surface; when the third trench bottom 53a is an inclined plane, the inclination angle a of the inclined plane is in the range of 5°-10°, and the ion concentration injected in this range is higher, which can effectively ensure that the inclined plane is completely in contact with the high-concentration ions, thereby reducing the ohmic contact resistance.

[0112] Further, the area of the orthogonal projection of the ion implantation region 20a on the substrate 10 is greater than the area of the orthogonal projection of the third trench bottom 53a on the substrate, so as to ensure that the metal layer on the third trench 53 can effectively contact the ion implantation region 20a, avoid deviations in the process due to different ion implantation and etching depths in different batches of products, and ensure the consistency of the ohmic contact effect.

[0113] Preferably, the difference between the maximum depth and the minimum depth of the third trench bottom 53a in the thickness direction of the epitaxial structure 20 is h3, and h3 is in the range of 10-50 nm. Further, the width W of the third trench bottom 53a in the horizontal direction is in the range of 10-50 μm.

[0114] In an embodiment, the third trench bottom 53a is in contact with the high-concentration region of the ion implantation region 20a, that is, the third trench bottom 53a is located in the high-concentration region of the ion implantation region 20a with a higher ion concentration. Specifically, the ion implantation region 20a has a high-concentration region; the ion concentration in the high-concentration region exceeds a preset high-concentration value, and the preset high-concentration value is greater than or equal to 80% of the ion concentration peak value of the ion implantation region 20a. By arranging the third trench bottom 53a in the high-concentration region, the contact between the metal layer and the high-concentration region can be ensured, thereby significantly reducing the resistance of the ohmic contact. Preferably, the distance from the surface of the epitaxial structure 20 close to the passivation dielectric layer 30 to the position of the ion concentration peak value is in the range of 10-50 nm, so that the ion concentration peak value is located between the GaN layer 21 and the barrier layer 22 or between the GaN layer 21.

[0115] Referring to FIG. 10, a metal layer is formed on the third trench 53 to form an ohmic contact. In the embodiment, the metal layer of the HEMT device includes a source electrode 61 and a drain electrode 62. The source electrode 61 and the drain electrode 62 are formed on the third trench 53 by an evaporation process and are separated from each other. It should be noted that in the embodiment, the ion implantation region includes a source ion implantation region and a drain ion implantation region which are arranged in a spaced manner. A third trench 53 is formed in the source ion implantation region, and the source electrode 61 is formed on the third trench 53. Another third trench 53 is formed in the drain ion implantation region, and the drain electrode 62 is formed on the third trench 53. It should be noted that the ion concentration, implantation energy, and implantation depth of the source ion implantation region and the drain ion implantation region can be the same or different. The structure and size of the third trench 53 on the source ion implantation region and the third trench 53 on the drain ion implantation region can be the same or different. The structure, size, and material of the source electrode 61 and the drain electrode 62 can be the same or different, and are set according to actual working requirements, which are not limited herein.

[0116] For example, the material of the source electrode 61 and the drain electrode 62 can be a metal such as nickel, gold, titanium, aluminum, platinum, chromium, or an alloy or a stack thereof, for example, a Ti / Au metal stack, to form an ohmic contact with the epitaxial structure 20. The source electrode 61 and the drain electrode 62 formed by the evaporation process have a uniform metal surface and a neat edge, which is beneficial to improve the reliability of the device and avoid electrical breakdown.

[0117] In an optional embodiment, the HEMT device further includes a gate electrode 63 and a passivation layer 70. The gate electrode 63 is located above the passivation dielectric layer 30 and is in electrical contact with the epitaxial structure 20 through a through hole formed in the passivation dielectric layer 30. The gate electrode 63 can be designed in a T-shaped gate or a recessed gate according to requirements to effectively reduce the short channel effect of the device, and the specific structure is not limited herein. The passivation layer 70 covers the passivation dielectric layer 30 to isolate water vapor and protect the device.

[0118] It should be noted that the manufacturing method of the HEMT device and other structures, functions, and effects of the embodiment can be referred to the description of the first embodiment, which is not repeated herein.

[0119] In summary, the HEMT device and the manufacturing method thereof provided by the embodiments of the present application can increase the ohmic contact area, especially the area of the third groove bottom, by the ion implantation and the groove etching scheme, increase the contact area between the ohmic metal and the high-concentration ion implantation area, make the metal layer contact with the high-concentration ion implantation area, reduce the ohmic contact resistance, and the scheme has low requirements for etching precision and etching depth, and even if the implantation conditions change, the metal layer of the source area and the drain area can still make ohmic contact with the high-concentration area, and meanwhile, the scheme can avoid the problem of deviation due to different ion implantation requirements and etching depths in the process of different batches of products, and ensure the consistency of the ohmic contact effect.

[0120] Embodiment three

[0121] The present application also provides a radio frequency module comprising the HEMT device. The radio frequency module can be applied to a base station, a mobile phone and other communication terminal equipment. The HEMT device is a gallium nitride HEMT device, which is the same as the HEMT device in Embodiment one and Embodiment two, and the present application will not be described here.

[0122] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of fabricating a HEMT device, characterized by, The method comprises the following steps: providing a substrate; growing an epitaxial structure on the substrate; depositing a passivation medium layer on the epitaxial structure; performing ion implantation from the surface of the epitaxial structure to the substrate to form an ion implantation region; forming a third trench extending to at least part of the epitaxial structure in the ion implantation region; the area of the bottom of the third trench is greater than the area of the orthographic projection of the bottom of the third trench on the substrate; the area of the orthographic projection of the ion implantation region on the substrate is greater than the area of the orthographic projection of the bottom of the third trench on the substrate; depositing a metal layer on the third trench to form an ohmic contact.

2. The method of fabricating a HEMT device of claim 1, wherein: The method of forming a third trench extending to at least part of the epitaxial structure in the ion implantation region comprises the following steps: forming a photoresist layer on the passivation medium layer; and patterning part of the photoresist layer located above the ion implantation region to form a first trench; etching the passivation medium layer located below the first trench to form a second trench; etching the epitaxial structure located below the second trench to form a third trench.

3. The method of fabricating a HEMT device of claim 2, wherein: The difference between the maximum depth and the minimum depth of the first trench is h1, and h1 is between 44 nm and 225 nm; the photoresist layer has a thickness H, wherein H≥5*h1.

4. The method of making a HEMT device of claim 2, wherein: The difference between the maximum depth and the minimum depth of the second trench is h2, wherein h2=h1 / A, and A represents the etching selectivity ratio of the passivation medium layer to the photoresist layer, and A is between 2.5 and 4.

5. The method of making a HEMT device of claim 2, wherein: The difference between the maximum depth and the minimum depth of the third trench is h3, wherein h3=h1 / (A*B), A represents the etching selectivity ratio of the passivation medium layer to the photoresist layer, and A is between 2.5 and 4; B represents the etching selectivity ratio of the passivation medium layer to the epitaxial structure, and B is between 1.2 and 2.

6. The method of making a HEMT device of claim 1, wherein: The difference between the maximum depth and the minimum depth of the third trench is h3, and h3 is between 10 nm and 50 nm.

7. The method of making a HEMT device of claim 1, wherein: The epitaxial structure at least comprises a GaN layer located on the substrate and a barrier layer located on the GaN layer; and the third trench is etched from the epitaxial structure until the GaN layer is exposed.

8. The method of making a HEMT device of claim 1, wherein: The ion concentration of the ion implantation region distributed from the surface of the epitaxial structure to the substrate direction first increases and then decreases, and has a high concentration region; the ion concentration in the high concentration region exceeds a preset high concentration value; the third trench is etched into the high concentration region; and the preset high concentration value is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region.

9. The method of making a HEMT device of claim 2, wherein: At least part of the surface of the bottom of the first trench is one or more of an inclined plane, a curved surface, and a concave-convex surface, and / or at least part of the surface of the bottom of the second trench is one or more of an inclined plane, a curved surface, and a concave-convex surface, and / or at least part of the surface of the bottom of the third trench is one or more of an inclined plane, a curved surface, and a concave-convex surface.

10. A HEMT device, characterized by The HEMT device comprises: a substrate; an epitaxial structure located on the substrate; a passivation medium layer located on the epitaxial structure; an ion implantation region extending from the surface of the epitaxial structure to the substrate; a third trench located in the ion implantation region and extending from the surface of the epitaxial structure to at least part of the epitaxial structure in the direction of the substrate; the area of the bottom of the third trench is greater than the area of the orthogonal projection of the bottom of the third trench on the substrate; the area of the orthogonal projection of the ion implantation region on the substrate is greater than the area of the orthogonal projection of the bottom of the third trench on the substrate; a metal layer located on the third trench and forming an ohmic contact.

11. The HEMT device of claim 10, wherein: The epitaxial structure comprises at least a GaN layer located on the substrate and a barrier layer located on the GaN layer; the third trench extends from the surface of the epitaxial structure to the GaN layer in the direction of the substrate.

12. The HEMT device of claim 10, wherein: The ion implantation region has a high-concentration region; the ion concentration in the high-concentration region exceeds a preset high-concentration value, and the preset high-concentration value is greater than or equal to 80% of the peak value of the ion concentration of the ion implantation region; the bottom of the third trench is in contact with the high-concentration region.

13. The HEMT device of claim 10, wherein: The difference between the maximum depth and the minimum depth of the third trench is h3, and h3 is between 10 nm and 50 nm.

14. The HEMT device of claim 10, wherein: At least part of the surface of the bottom of the third trench is one or more of an inclined plane, a curved surface, and a concave-convex surface.

15. The HEMT device of claim 14, wherein: When the bottom of the third trench is an inclined plane, the inclination angle α of the inclined plane is in the range of 5° to 10°.

16. A radio frequency module, characterized by: The HEMT device of any one of claims 10-15.

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