A HEMT device and a method of manufacturing the same

Abstract

The application discloses a HEMT device and a preparation method thereof, and relates to the technical field of semiconductors. The HEMT device comprises a substrate and an epitaxial layer arranged on the substrate. A source electrode and a drain electrode are arranged on the epitaxial layer at intervals. A gate electrode is arranged between the source electrode and the drain electrode. Heat conductive members are arranged on the epitaxial layer on both sides of the gate electrode. A ground metal layer is arranged on the side of the substrate away from the epitaxial layer. At least one heat conductive column is arranged outside the active area of the device and penetrates the substrate and the epitaxial layer. The two ends of the heat conductive column are connected with the ground metal layer and the heat conductive members, respectively. The HEMT device and the preparation method thereof increase the side heat dissipation of the HEMT device, thereby improving the heat dissipation effect of the HEMT device.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically, to a HEMT device and its fabrication method. Background Technology

[0002] HEMT (High Electron Mobility Transistor) is a heterojunction field-effect transistor, also known as a modulation-doped field-effect transistor. It uses two materials with different band gaps to form a heterojunction, providing a channel for charge carriers. HEMT devices have high electron saturation velocities, enabling high-power, high-heat-flux-density applications, and are key components in high-performance RF modules and power electronic modules. The performance, reliability, and lifespan of HEMT devices are closely related to their channel temperature during operation. If the channel temperature is too high, leading to excessively high device temperature, it will significantly degrade device performance and drastically reduce lifespan. For example, the local heat flux density of a single GaN HEMT device currently used in RF power amplifiers can reach 1000 W / cm². 2 Heat accumulation causes the junction temperature of the device to rise, which leads to a decrease in output characteristics under high-power operating conditions and affects the lifespan of the device.

[0003] The heat source of GaN HEMT devices is located on the front side, below the gate and near the drain. To dissipate heat effectively, there are two main technical approaches to improve heat dissipation performance in fabrication: one is to add a high thermal conductivity material layer on the front or back of the device; the other is to replace the device substrate with a material with better thermal conductivity. For example, AlN, diamond, or graphene layers can be fabricated on the front side to expand the heat conduction path. However, due to the small size of GaN HEMT devices, simply adding a small area of ​​heat conduction path on the front side cannot completely solve the heat dissipation problem and still limits its power density output. Furthermore, replacing Si or sapphire substrates with substrates made of AlN, copper, SiC, or diamond can further enhance the self-heating capability on the back side of the device. Among these, diamond substrates have the highest thermal conductivity, but their technology is challenging and requires consideration of process compatibility. In addition, the path from the heat source to the heat dissipation substrate still includes interface materials such as epitaxial layers, which have high interface thermal resistance, reducing heat dissipation capacity. Summary of the Invention

[0004] The purpose of this application is to provide a HEMT device and its fabrication method, which increases the side heat dissipation of the HEMT device, thereby improving the heat dissipation effect of the HEMT device.

[0005] One embodiment of this application provides a HEMT device, including a substrate and an epitaxial layer disposed on the substrate. A source and a drain are disposed at a distance on the epitaxial layer, and a gate is disposed between the source and the drain. Thermal conductive elements are also disposed on both sides of the gate on the epitaxial layer. A ground metal layer is disposed on the side of the substrate away from the epitaxial layer. At least one thermally conductive pillar is disposed outside the active region of the device, penetrating the substrate and the epitaxial layer. The two ends of the thermally conductive pillar are respectively connected to the ground metal layer and the thermally conductive pillar of the thermally conductive element.

[0006] As one possible implementation, the thermal conductive element includes annular thermal conductive layers surrounding the source and drain, respectively, and the annular thermal conductive layers are in contact with the gate.

[0007] As one feasible approach, the heat-conducting pillars are respectively located on the side of the source electrode away from the gate and on the side of the drain electrode away from the gate.

[0008] As one feasible approach, the heat-conducting component is made of diamond, and the heat-conducting pillar is made of diamond or graphene.

[0009] As one feasible approach, multiple heat-conducting pillars are respectively arranged in a straight line on both sides of the epitaxial layer.

[0010] As an feasible approach, the diameter of the heat-conducting pillar is between 50-75 μm, and the thickness of the heat-conducting component is between 100-140 nm.

[0011] Another aspect of this application provides a method for fabricating a HEMT device, comprising: fabricating an epitaxial layer on a substrate; forming a source, a gate, a drain, and a thermal conductive element on the epitaxial layer, wherein the thermal conductive element extends outside the active region of the device, the gate is located between the drain and the source, and the thermal conductive element is disposed in the same layer as the gate; etching the epitaxial layer and the substrate from the side of the substrate away from the epitaxial layer to form at least one via, and filling the via with thermally conductive material to form a thermally conductive pillar, the thermally conductive pillar being connected to the thermal conductive element, and the thermally conductive pillar being located outside the active region of the device; depositing a ground metal layer on the side of the substrate away from the epitaxial layer, the ground metal layer being connected to the thermally conductive pillar.

[0012] As one feasible approach, a source, gate, drain, and thermal conductive element are formed on an epitaxial layer, with the thermal conductive element extending beyond the active region of the device. The gate is located between the drain and the source, and the thermal conductive element and the gate are disposed on the same layer. This includes: depositing a first passivation layer on the epitaxial layer; forming a thermal conductive element on the first passivation layer; doping a portion of the epitaxial layer to form a heavily doped region; etching the first passivation layer to expose the heavily doped region, and forming the source and drain on the heavily doped region; forming a second passivation layer on the source and drain, and opening a window on the second passivation layer, with the window located between the drain and the source; evaporating and patterning a first metal on the second passivation layer, with the first metal filling the window to form a T-shaped gate as the gate; etching the first and second passivation layers to expose the source and drain, and depositing a second metal to lead out the source and drain.

[0013] As one feasible method, forming a heat-conducting element on the first passivation layer includes: forming a heat dissipation layer on the first passivation layer by plasma chemical deposition; and forming a heat-conducting element by inductively coupled plasma patterning etching of the heat dissipation layer, wherein the heat-conducting element includes annular heat-conducting layers spaced apart.

[0014] As one feasible approach, before depositing a ground metal layer on the side of the substrate away from the epitaxial layer and connecting the ground metal layer to the heat-conducting pillar, the fabrication method of the HEMT device further includes: etching the substrate and the epitaxial layer from the side of the substrate away from the epitaxial layer to form a ground back hole, the ground back hole penetrating the substrate and the epitaxial layer and connecting to the source, and the ground metal layer covering the surface of the ground back hole.

[0015] As one feasible approach, after forming a source, gate, drain, and thermal conductive element on an epitaxial layer, with the gate located between the drain and the source, and the thermal conductive element disposed on the same layer as the gate, the fabrication method of the HEMT device further includes: forming a dielectric layer on the source, gate, and drain; and forming a field plate at the location corresponding to the gate on the dielectric layer.

[0016] As one feasible approach, at least one via is formed by etching the epitaxial layer from the side of the substrate away from the epitaxial layer, and a thermally conductive material is filled into the via to form a thermally conductive pillar. The thermally conductive pillar is connected to a thermally conductive component and is located outside the active region of the device. This includes: etching the substrate and the epitaxial layer from the side of the substrate away from the epitaxial layer to form multiple vias, with the multiple vias respectively disposed on both sides of the epitaxial layer; filling the multiple vias with thermally conductive material to form thermally conductive pillars, and connecting the thermally conductive pillars to a thermally conductive component.

[0017] The beneficial effects of the embodiments of this application include:

[0018] The HEMT device provided in this application includes a substrate and an epitaxial layer disposed on the substrate. A source and a drain are disposed at intervals on the epitaxial layer, and a gate is disposed between the source and the drain. Thermal conductive elements are also disposed on both sides of the gate on the epitaxial layer, so that the heat generated by the gate can be conducted to the thermal conductive elements in a timely manner. A ground metal layer is disposed on the side of the substrate away from the epitaxial layer. Thermal conductive pillars are disposed outside the active region of the device, penetrating the substrate and the epitaxial layer, and connecting with the ground metal layer and the thermal conductive elements. This makes the thermal conductive pillars, thermal conductive elements and ground metal layer form a three-dimensional thermal conductive structure, thereby expanding the heat dissipation path of the HEMT device and improving the heat dissipation effect of the HEMT device. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a HEMT device provided in an embodiment of this application;

[0021] Figure 2 for Figure 1 Cross-sectional view along AA;

[0022] Figure 3 for Figure 1 Cross-sectional view along BB;

[0023] Figure 4 One of the flowcharts for a method of fabricating a HEMT device provided in this application embodiment;

[0024] Figure 5 This is one of the state diagrams for a method of fabricating a HEMT device provided in an embodiment of this application;

[0025] Figure 6 A second state diagram illustrating a method for fabricating a HEMT device according to an embodiment of this application;

[0026] Figure 7 The third state diagram of a method for fabricating a HEMT device provided in this application embodiment;

[0027] Figure 8 The fourth state diagram of a method for fabricating a HEMT device provided in this application embodiment;

[0028] Figure 9 The fifth state diagram of a method for fabricating a HEMT device provided in the embodiments of this application;

[0029] Figure 10 A sixth state diagram illustrating a method for fabricating a HEMT device according to an embodiment of this application;

[0030] Figure 11 The seventh state diagram of a method for fabricating a HEMT device provided in this application embodiment;

[0031] Figure 12 This is a second flowchart illustrating a method for fabricating a HEMT device according to an embodiment of this application.

[0032] Icons: 10 - HEMT device; 110 - Substrate; 120 - Epitaxial layer; 121 - Nucleation layer; 122 - Buffer layer; 123 - Barrier layer; 200 - First passivation layer; 210 - Second passivation layer; 220 - Dielectric layer; 310 - Source; 320 - Drain; 330 - Gate; 340 - Grounding via; 350 - Grounding metal layer; 360 - Field plate; 410 - Thermal conductive element; 420 - Thermal pillar. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this application, it should be noted that the terms "center," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0038] This application provides a HEMT device 10, such as Figure 1 , Figure 2 and Figure 3 As shown, the device includes a substrate 110 and an epitaxial layer 120 disposed on the substrate 110. A source electrode 310 and a drain electrode 320 are disposed on the epitaxial layer at intervals. A gate electrode 330 is disposed between the source electrode 310 and the drain electrode 320. A heat-conducting element 410 is also disposed on the epitaxial layer 120 on both sides of the gate electrode 330. A ground metal layer 350 is disposed on the side of the substrate 110 away from the epitaxial layer 120. At least one heat-conducting pillar 420 is disposed outside the active region of the device, penetrating the substrate 110 and the epitaxial layer 120. The two ends of the heat-conducting pillar 420 are connected to the ground metal layer 350 and the heat-conducting element 410, respectively.

[0039] The specific structure of the epitaxial layer 120 is not limited in this embodiment, as long as it has the basic structure of the HEMT device 10, i.e., it includes a heterojunction and a two-dimensional electron gas at the heterojunction interface. This embodiment uses a GaN HEMT device as an example for illustration. Specifically, the epitaxial layer 120 of the GaN HEMT device includes an N-type GaN layer and a P-type AlGaN layer sequentially disposed on the substrate 110, wherein the N-type GaN layer serves as a buffer layer 122 and the P-type AlGaN layer serves as a barrier layer 123, forming a two-dimensional electron gas at the interface between the N-type GaN layer and the P-type AlGaN layer. When the HEMT device 10 is working, a corresponding voltage is applied to the gate 330 to form a current between the source 310 and the drain 320, thereby turning on the HEMT device 10. When the HEMT device 10 achieves high-speed switching, a large amount of heat is generated.

[0040] In this embodiment, a heat-conducting element 410, which is on the same layer as the gate 330, is also provided in the active region. A heat-conducting pillar 420 is provided through the substrate 110 and the epitaxial layer 120. The two ends of the heat-conducting pillar 420 are connected to the ground metal layer 350 and the heat-conducting element 410, respectively, so that the ground metal layer 350, the heat-conducting element 410 and the heat-conducting pillar 420 are interconnected. In the subsequent packaging of the HEMT device 10, the ground metal layer 350 serves as the back side of the HEMT device 10 and is connected to the package housing. The gate 330, the source 310, the drain 320 and the heat-conducting element 410 serve as the front side of the HEMT device 10 and are connected to the package housing. This allows heat to be dissipated not only through the front side of the HEMT device 10, but also through the heat-conducting element 410 on the front side and the heat-conducting pillar 420 on the side to the back side and dissipate from the back side, thus expanding the heat dissipation path of the HEMT device 10 and improving the heat dissipation effect of the HEMT device 10.

[0041] In addition, before the epitaxial layer 120 is prepared, it can be done as follows: Figure 2 , Figure 3 As shown, a nucleation layer 121 is first prepared on the substrate 110, and then an N-type GaN layer is formed on the nucleation layer 121. The nucleation layer 121 helps to improve the crystal morphology of the N-type GaN layer, reduce the defect density and residual stress of the N-type GaN layer, and improve the crystal quality of the N-type GaN layer.

[0042] The specific material of the substrate 110 is not limited in this embodiment of the application. For example, it can be silicon carbide, sapphire, or silicon substrate 110. For example, silicon carbide is used in this embodiment of the application.

[0043] It should be understood that the heat-conducting element 410 and the heat-conducting pillar 420 are heat-conducting components and should have a high thermal conductivity. Furthermore, to prevent the heat-conducting element 410 and the heat-conducting pillar 420 from affecting the normal operation of the epitaxial layer 120, they should be made of insulating material. The specific materials of the heat-conducting element 410 and the heat-conducting pillar 420 are not limited in this embodiment, as long as they meet the above two conditions. Those skilled in the art can choose according to the actual situation.

[0044] It should be noted that the embodiments of this application describe the heat-conducting components and heat-conducting pillars using a set of source, gate, and drain electrodes. Those skilled in the art should understand that HEMT devices include multiple sets of source, gate, and drain electrodes arranged side by side. When an HEMT device includes multiple sets of source, gate, and drain electrodes, heat-conducting components and heat-conducting pillars can be provided for each set of source, gate, and drain electrodes respectively.

[0045] The HEMT device 10 provided in this application includes a substrate 110 and an epitaxial layer 120 disposed on the substrate 110. A source 310 and a drain 320 are disposed on the epitaxial layer 120 at a distance from each other. A gate 330 is disposed between the source 310 and the drain 320. A heat-conducting element 410 of the same layer as the gate 330 is also disposed on the epitaxial layer 120. The gate 330 is located between the source 310 and the drain 320, and the heat generated by the gate 330 can be conducted to the heat-conducting element 410 in a timely manner. The heat sink 410 has a ground metal layer 350 on the side of the substrate 110 away from the epitaxial layer 120. A heat-conducting pillar 420 is provided outside the active region of the device, penetrating the substrate 110 and the epitaxial layer 120, and is connected to the ground metal layer 350 and the heat sink 410. This makes the heat sink 420, the heat sink 410 and the ground metal layer 350 form a three-dimensional heat-conducting structure, thereby expanding the heat dissipation path of the HEMT device 10 and improving the heat dissipation effect of the HEMT device 10.

[0046] Optional, such as Figure 2 As shown, the heat-conducting element 410 includes annular heat-conducting layers surrounding the source 310 and the drain 320 respectively, and the annular heat-conducting layers are in contact with the gate 330.

[0047] When HEMT device 10 is working, the heat generated is mainly concentrated in the gate 330. In order to dissipate the heat generated by the gate 330 in a timely manner, the heat conductor 410 is set as two annular heat conductor layers. Both annular heat conductor layers are in contact with the gate 330. The heat generated by the gate 330 can be quickly conducted to the annular heat conductor layers and then transferred to the heat conductor pillar 420 along the annular heat conductor layers.

[0048] In one possible implementation of the embodiments of this application, such as Figure 1 , Figure 3 As shown, the heat-conducting pillars 420 are respectively disposed on the side of the source 310 away from the gate 330 and the side of the drain 320 away from the gate 330.

[0049] By placing the heat-conducting pillar 420 on the side of the source 310 away from the gate 330 and the side of the drain 320 away from the gate 330, the heat-conducting pillar can be kept away from the gate, thus avoiding the heat dissipation efficiency being reduced due to the close proximity of the heat-conducting pillar to the gate and the high temperature near the gate.

[0050] Optionally, the heat-conducting component 410 is made of diamond, and the heat-conducting pillar 420 is made of diamond or graphene.

[0051] As can be seen from the above, the heat-conducting component 410 and the heat-conducting pillar 420, as heat conductors, should have high thermal conductivity and insulation. In view of the above two characteristics, the embodiments of this application select diamond material to prepare the heat-conducting component 410 and select diamond or graphene material to prepare the heat-conducting pillar 420, because diamond, in addition to meeting the above characteristics, also has the advantages of being inexpensive and easy to prepare.

[0052] In one possible implementation of the embodiments of this application, such as Figure 1 , Figure 3 As shown, multiple heat-conducting pillars 420 are respectively arranged in a straight line on both sides of the epitaxial layer.

[0053] By placing multiple heat-conducting pillars 420 in a straight line on both sides of the epitaxial layer, the regularity of the HEMT device 10 can be improved and the fabrication difficulty reduced.

[0054] Optional, such as Figure 2 As shown, the substrate 110 and the epitaxial layer 120 also have a ground back hole 340 extending to the source 310; a dielectric layer 220 is formed on the source 310, the gate 330 and the drain 320, and a field plate 360 ​​is formed on the dielectric layer 220 at the position corresponding to the gate 330.

[0055] The field plate 360 ​​can improve the breakdown field strength and electrostatic discharge protection capability of the HEMT device 10, and also provide support for the gate 330 to prevent the gate 330 from breaking due to being too thin when etching the grounding back via 340. The dielectric layer 220 serves as the capacitor dielectric between the field plate 360 ​​and the gate 330.

[0056] In one possible implementation of this application embodiment, the diameter of the heat-conducting pillar 420 is between 50-75 μm; the thickness of the heat-conducting element 410 is between 100-140 nm.

[0057] To ensure compatibility with existing etching processes for grounding vias, the diameter of the heat-conducting pillar 420 in this embodiment is set between 50-75 μm. Those skilled in the art can also set the diameter and number of heat-conducting pillars 420 according to heat dissipation requirements.

[0058] Among them, such as Figure 2 As shown, when the gate is a T-type gate, the thickness of the heat-conducting component 410 determines the height of the gate foot of the T-type gate. In order to match the height of the gate foot on the T-type in the prior art, the thickness of the heat-conducting component 410 in this embodiment is set between 100-140nm.

[0059] This application also provides a method for fabricating a HEMT device 10, such as... Figure 4 As shown, it includes:

[0060] S10: As Figure 5 As shown, an epitaxial layer is fabricated on substrate 110;

[0061] The specific material of the substrate 110 is not limited in this embodiment. For example, it can be silicon carbide, sapphire, or silicon substrate 110. For example, silicon carbide is used in this embodiment. Furthermore, the specific structure of the epitaxial layer 120 is not limited in this embodiment, as long as it has the basic structure of the HEMT device 10, i.e., it includes a heterojunction and a two-dimensional electron gas exists at the heterojunction interface. This embodiment uses a GaN HEMT device 10 as an example for illustration. Specifically, the epitaxial layer 120 of the GaN HEMT device 10 includes an N-type GaN layer and a P-type AlGaN layer sequentially disposed on the substrate 110, wherein the N-type GaN layer serves as a buffer layer 122 and the P-type AlGaN layer serves as a barrier layer 123, forming a two-dimensional electron gas at the interface between the N-type GaN layer and the P-type AlGaN layer.

[0062] The specific method for preparing the epitaxial layer on the substrate 110 is not limited in the embodiments of this application. For example, chemical deposition can be used.

[0063] S20: As Figures 6 to 8 As shown, a source 310, a gate 330, a drain 320, and a heat conductor 410 are formed on the epitaxial layer. The heat conductor 410 extends outside the active region of the device. The gate 330 is located between the drain 320 and the source 310. The heat conductor 410 and the gate 330 are disposed on the same layer.

[0064] The heat-conducting element 410 is disposed on the same layer as the gate 330, so that the heat generated at the gate 330 can be dissipated through the heat-conducting element 410.

[0065] S30: As Figure 10 As shown, at least one via is formed by etching the epitaxial layer and the substrate 110 on the side of the substrate 110 away from the epitaxial layer, and thermally conductive material is filled in the via to form a thermally conductive pillar 420. The thermally conductive pillar 420 is connected to the thermally conductive component 410 and is located outside the active region of the device.

[0066] The connection between the heat-conducting pillar 420 and the heat-conducting element 410 allows heat on the heat-conducting element 410 to be dissipated through the heat-conducting pillar 420. The heat-conducting material used in this embodiment is not limited, as long as it has high thermal conductivity and insulation properties.

[0067] S40: As Figure 11 As shown, a ground metal layer 350 is deposited on the side of the substrate 110 away from the epitaxial layer, and the ground metal layer 350 is connected to the heat-conducting pillar 420.

[0068] The grounding metal layer 350 serves two purposes: grounding the HEMT device 10 and connecting it to the heat-conducting pillar 420 for rapid heat conduction. Specifically, TiW and Au can be sputtered on the side of the substrate 110 away from the epitaxial layer, followed by electroplating a layer of Ni on the Au.

[0069] The method for fabricating HEMT device 10 provided in this application embodiment can, on the one hand, fabricate HEMT device 10 with good heat dissipation effect, and on the other hand, it is compatible with the existing HEMT device 10 fabrication process, reducing the fabrication process of HEMT device 10 with heat dissipation capability.

[0070] In one possible implementation of the embodiments of this application, such as Figure 12 As shown, a source 310, a gate 330, a drain 320, and a heat conductor 410 are formed on the epitaxial layer. The heat conductor extends outside the active region of the device. The gate 330 is located between the drain 320 and the source 310. The heat conductor 410 and the gate 330 are disposed on the same layer.

[0071] S21: As Figure 5 , Figure 6 As shown, a first passivation layer 200 is deposited on the epitaxial layer;

[0072] S22: A heat-conducting element 410 is formed on the first passivation layer 200;

[0073] The first passivation layer 200 serves as a passivation layer between the gate 330 and the epitaxial layer. Specifically, a 20nm thick silicon nitride layer can be deposited on the epitaxial layer 120 using a low-pressure chemical vapor deposition method as the first passivation layer 200. A heat-conducting element 410 is formed on the first passivation layer 200, such that the heat-conducting element 410 and the gate 330 are located on the same layer.

[0074] S23: Partial doping of the epitaxial layer 120 forms a heavily doped region;

[0075] The heavily doped region serves as the substrate for the source 310 and drain 320, and needs to form an ohmic contact with the metal of the source 310 and drain 320. Specifically, silicon ions are implanted into the epitaxial layer through the first passivation layer 200, followed by annealing to allow the silicon ions to diffuse into the lattice and form the heavily doped region. The annealing temperature is 1130℃. The first passivation layer 200 acts as a barrier layer to prevent damage to the surface of the epitaxial layer during ion implantation.

[0076] In addition, after forming a partially doped region on both sides of the epitaxial layer 120, nitrogen ions can be implanted to form a high-resistivity region to achieve device isolation.

[0077] S24: As Figure 7 As shown, etching the first passivation layer 200 exposes the heavily doped region, and a source 310 and a drain 320 are formed on the heavily doped region.

[0078] The source 310 and drain 320 need to be in contact with the heavily doped regions respectively. At this time, the first passivation layer 200 is first etched at the source 310 and drain 320 to expose the two heavily doped regions. Then, the heavily doped electrode metal is evaporated to form an ohmic contact between the electrode metal and the heavily doped regions, thereby reducing the on-resistance of the source 310 and drain 320.

[0079] Among them, the source 310 and drain 320, as terminals for electrical connection, should have as little resistance as possible, and can be made of Ti / Al / Ti or Ge / Ti / Al / Ni / Au.

[0080] S25: As Figure 8 As shown, a second passivation layer 210 is formed on the source 310 and the drain 320, and a window is opened on the second passivation layer 210, with the window located between the drain 320 and the source 310;

[0081] When HEMT device 10 is working, the gate length is an important parameter affecting the performance of HEMT device 10. The shorter the gate length, the higher the operating frequency. T-gate is currently the most effective process to reduce gate length. In order to form T-gate, a second passivation layer 210 is first formed on the source 310 and drain 320, and the second passivation layer 210 is etched to form a window. The window is located between the source 310 and drain 320 for evaporating the first metal to form gate 330.

[0082] S26: As Figure 8 As shown, a first metal is deposited and patterned on the second passivation layer 210, and the first metal fills the window to form a T-shaped gate as the gate 330.

[0083] A first metal is deposited and patterned on the second passivation layer 210, such that the first metal fills the window to form the gate cap of the T-shaped gate. Since the two annular thermal conductive layers are in contact with the opposite sides of the gate 330, the first metal between the regions of the two annular thermal conductive layers serves as the gate foot of the T-shaped gate.

[0084] After the gate 330 is formed in the first metal-filled window, it is annealed at 400°C to allow the first metal to recrystallize.

[0085] S27: As Figure 10 As shown, the first passivation layer 200 and the second passivation layer 210 are etched to expose the source 310 and the drain 320 and a second metal is deposited to bring out the source 310 and the drain 320.

[0086] In order to interconnect the leads of the source 310 and the drain 320, the first passivation layer 200 and the second passivation layer 210 are etched to expose the source 310 and the drain 320, and a second metal is deposited on the source 310 and the drain 320 respectively, wherein the second metal may be Ti / Pt / Au / Pt / Au / Ti.

[0087] After the source 310 and drain 320 are brought out, a thinner third passivation layer can be deposited on the source 310 and drain 320 to protect the front side of the HEMT device 10. The third passivation layer can be 1.2 μm silicon nitride.

[0088] Optionally, forming a heat-conducting element 410 on the first passivation layer 200 includes:

[0089] S211: A heat dissipation layer is formed on the first passivation layer 200 by plasma chemical deposition;

[0090] S212: The heat-conducting component 410 is formed by inductively coupled plasma patterning etching of the heat dissipation layer, wherein the heat-conducting component 410 includes two annular heat-conducting layers spaced apart.

[0091] Since the heat dissipation layer is made of a thermally conductive and insulating material, inductively coupled plasma etching can be used to etch the insulating material. The specific material of the hard mask is not limited in this application; for example, it can be a metal such as Ti / Ni.

[0092] In one possible embodiment of this application, a ground metal layer 350 is deposited on the side of the substrate 110 away from the epitaxial layer. Before the ground metal layer 350 is connected to the heat-conducting pillar 420, the fabrication method of the HEMT device 10 further includes:

[0093] A grounding back hole 340 is formed by etching the side of the substrate 110 away from the epitaxial layer 120. The grounding back hole 340 penetrates the substrate 110 and the epitaxial layer 120 and is connected to the source 310. The grounding metal layer 350 covers the surface of the grounding back hole 340.

[0094] The grounding back hole 340 grounds the source 310, and the grounding metal layer 350 covers the surface of the grounding back hole 340, so that the grounding metal layer 350 contacts the source 310 to ground the source 310 and at the same time achieve heat dissipation.

[0095] Optional, such as Figure 9 As shown, a source 310, a gate 330, a drain 320, and a heat-conducting element 410 are formed on the active region. The heat-conducting element 410 extends outside the active region. The gate 330 is located between the drain 320 and the source 310. After the heat-conducting element 410 and the gate 330 are disposed on the same layer, the fabrication method of the HEMT device 10 further includes:

[0096] A dielectric layer 220 is formed on the source 310, gate 330 and drain 320; a field plate 360 ​​is formed on the dielectric layer 220 at the position corresponding to the gate 330.

[0097] The field plate 360 ​​can improve the breakdown field strength and electrostatic discharge protection capability of the HEMT device 10, and also provide support for the gate 330 to prevent it from breaking due to the gate 330 being too thin when etching the ground back via 340. The dielectric layer 220 serves as the capacitor dielectric between the field plate 360 ​​and the gate 330. For example, the dielectric layer 220 can be a 200nm thick silicon nitride material.

[0098] In one possible implementation of the embodiments of this application, such as Figure 10 As shown, at least one via is formed by etching the epitaxial layer on the side of the substrate 110 away from the epitaxial layer, and a thermally conductive material is filled into the via to form a thermally conductive pillar 420. The thermally conductive pillar 420 is connected to the thermally conductive element 410 and is located outside the active region of the device, including:

[0099] S31: Multiple vias are formed by etching the substrate 110 and the epitaxial layer from the side of the substrate 110 away from the epitaxial layer, and the multiple vias are respectively disposed on both sides of the epitaxial layer;

[0100] For example, inductively coupled plasma etching can be used to etch multiple vias.

[0101] S32: Thermal conductive material is filled into multiple through holes to form thermal conductive pillars 420, and the thermal conductive pillars 420 are connected to the thermal conductive component 410.

[0102] Multiple through holes form multiple heat-conducting pillars 420. Because the heat-conducting pillars 420 have a large thermal conductivity, they provide multiple heat dissipation channels and improve the heat dissipation effect.

[0103] In addition, before etching the substrate 110 and the epitaxial layer to form multiple vias, the substrate 110 can be thinned to reduce the path of heat dissipation and further improve the heat dissipation performance of the HEMT device 10. Specifically, one side of the epitaxial layer is bonded to the sapphire substrate, and then polished with a grinding wheel until the thickness of the substrate 110 is 100 μm, thereby reducing the thickness of the substrate 110.

[0104] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A HEMT device, characterized by, The device comprises a substrate and an epitaxial layer arranged on the substrate, a source electrode and a drain electrode are arranged on the epitaxial layer in a spaced manner, a gate electrode is arranged between the source electrode and the drain electrode, a heat conduction member is arranged on the epitaxial layer and located on both sides of the gate electrode, a ground metal layer is arranged on the side of the substrate away from the epitaxial layer, at least one heat conduction column is arranged outside the active area of the device and penetrates the substrate and the epitaxial layer, and the two ends of the heat conduction column are connected with the ground metal layer and the heat conduction member respectively. The heat conduction member comprises annular heat conduction layers surrounding the source electrode and the drain electrode respectively, and the annular heat conduction layers are in contact with the gate electrode.

2. The HEMT device of claim 1, wherein, The heat conduction column is arranged on the side of the source electrode away from the gate electrode and the side of the drain electrode away from the gate electrode respectively.

3. The HEMT device of claim 1, wherein, The material of the heat conduction member is diamond, and the material of the heat conduction column is diamond or graphene.

4. The HEMT device of claim 1, wherein, The diameter of the heat conduction column is between 50-75 μm, and the thickness of the heat conduction member is between 100-140 nm.

5. A method of fabricating a HEMT device, characterized by, The device comprises: preparing an epitaxial layer on a substrate; forming a source electrode, a gate electrode, a drain electrode and a heat conduction member on the epitaxial layer, the heat conduction member extending outside the active area of the device, the gate electrode being located between the drain electrode and the source electrode, and the heat conduction member being arranged in the same layer as the gate electrode; forming at least one through hole by etching the epitaxial layer and the substrate from the side of the substrate away from the epitaxial layer, and filling the through hole with a heat conduction material to form a heat conduction column, the heat conduction column being connected with the heat conduction member and located outside the active area of the device; depositing a ground metal layer on the side of the substrate away from the epitaxial layer, the ground metal layer being connected with the heat conduction column; the step of forming a source electrode, a gate electrode, a drain electrode and a heat conduction member on the epitaxial layer, the heat conduction member extending outside the active area of the device, the gate electrode being located between the drain electrode and the source electrode, and the heat conduction member being arranged in the same layer as the gate electrode, comprises: depositing a first passivation layer on the epitaxial layer; forming a heat conduction member on the first passivation layer; doping part of the epitaxial layer to form a heavily doped region; etching the first passivation layer to expose the heavily doped region, and forming the source electrode and the drain electrode on the heavily doped region; forming a second passivation layer on the source electrode and the drain electrode, and opening a window on the second passivation layer, the window being located between the drain electrode and the source electrode; evaporating a first metal on the second passivation layer and patterning, the first metal filling the window to form a T-shaped gate as the gate electrode; etching the first passivation layer and the second passivation layer to expose the source electrode and the drain electrode, and depositing a second metal to lead out the source electrode and the drain electrode; the step of forming a heat conduction member on the first passivation layer, comprises: forming a heat dissipation layer on the first passivation layer by plasma chemical deposition; forming the heat conduction member by inductively coupled plasma patterning etching the heat dissipation layer, wherein the heat conduction member comprises annular heat conduction layers arranged in a spaced manner.

6. The method of claim 5, wherein the method further comprises: Before the step of depositing a ground metal layer on the side of the substrate away from the epitaxial layer, the ground metal layer being connected with the heat conduction column, the method further comprises: etching the substrate from the side of the substrate away from the epitaxial layer to form a ground back hole penetrating the substrate and the epitaxial layer, the ground back hole being connected with the source electrode, and the ground metal layer covering the surface of the ground back hole.

7. The method of claim 5, wherein the method further comprises: The at least one through hole is filled with a heat-conducting material to form a heat-conducting column, the heat-conducting column being connected with the heat-conducting element, and the heat-conducting column being located outside the active region of the device, comprising: etching the substrate and the epitaxial layer from the side of the substrate away from the epitaxial layer to form a plurality of through holes, the plurality of through holes being respectively arranged on both sides of the epitaxial layer; The plurality of through holes are respectively filled with a heat-conducting material to form a plurality of heat-conducting columns, the plurality of heat-conducting columns being connected with the heat-conducting element.

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