Interdigital radiation-resistant GAN HEMT device structure

Abstract

To provide an interdigital radiation-resistant GaN HEMT device structure that significantly improves the device's radiation resistance, enhances overall electrical performance and radiation performance, improves induced charge extraction capability, and maintains good performance.SOLUTION: A device structure is reflected in the provision of a first Schottky metal layer 10.1 and a second Schottky metal layer 10.2 on the drain side of a gate metal layer 4.2, which are arranged alternately at segment intervals and directly contact a barrier layer 3. An interconnect metal layer 7 on the source is connected to the first Schottky metal layer to form a lateral comb-like structure 7.1. This design can maximally avoid the problem that if all the Schottky metal layers are connected to the second upper metal layer 9, the interconnect metal field plate on the source is to be too short, which to be affect the breakdown capability of the device.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to the field of semiconductor technology, and more particularly to an interdigitated radiation-hard GaN HEMT device structure. [Background technology]

[0002] In recent years, gallium nitride power electronics devices have been gaining widespread application in aerospace, nuclear detection, specialized military equipment, and other fields due to their advantages, including high breakdown voltage, high thermal conductivity, high power quality factor, and excellent radiation resistance. However, devices operating in extreme environments, such as space stations, are susceptible to radiation effects induced by heavy ions, protons, neutrons, X-rays, and gamma rays in space. These radiation effects easily excite electron-hole pairs, generating large numbers of electron-hole pairs. These carriers must be extracted from the device in a timely manner; otherwise, they can accumulate within the device body and easily cause radiation damage, affecting the device's normal operation and, in severe cases, threatening the safe operation of the entire system. To ensure the safe and reliable operation of power systems, devices must be radiation-resistant and able to safely release the electrons and holes induced by the radiation. However, in current mainstream commercial gallium nitride high electron mobility transistors (HEMTs), the gate often adopts a metal (M)-dielectric layer (I)-semiconductor (S) structure, and carriers cannot pass through the insulating dielectric layer to be emitted outside the device. Therefore, the device's radiation resistance is severely limited by the gate structure.

[0003] An existing gallium nitride metal-insulator semiconductor (GaN) high-electron-mobility transistor (HEM) is shown in Figure 1. When the transistor is operating, a positive bias is typically applied to the drain. When the transistor is exposed to radiation and generates electron-hole pairs, the electrons are attracted to the positive voltage on the drain and are released from the drain to the outside of the device. However, the holes cannot pass through the dielectric layer and accumulate in the area near the gate, affecting the normal operation of the transistor and, in severe cases, causing radiation damage to the transistor and even complete burnout.

[0004] Therefore, for the future technological development of gallium nitride metal-insulator-semiconductor (GaN) high-electron-mobility transistors (MIS) devices, it is urgent to solve the problem of hole accumulation in the gate region after irradiation of this type of device, so that the electrons / holes induced by irradiation can be efficiently extracted out of the transistor, improving the device's irradiation resistance and reliability. Summary of the Invention [Problem to be solved by the invention]

[0005] In response to the above-mentioned shortcomings in the prior art, the present invention provides a comb-shaped radiation-resistant GaN HEMT device structure, which effectively solves the problem of radiation damage caused by the accumulation of induced charges due to radiation. [Means for solving the problem]

[0006] To achieve the above objectives, the technical solutions adopted in the present invention are as follows: The comb-shaped radiation-resistant GaN HEMT device structure is a multilayer structure including, from bottom to top, a substrate layer, a gallium nitride layer, a barrier layer, a gate structure, and a second dielectric layer, the thickness direction of the multilayer structure being the z-direction, the gate structure including a first dielectric layer provided on the upper surface of the barrier layer, and a gate metal layer provided on the upper surface of the first dielectric layer, the barrier layer having a source and a drain embedded therein, the gate metal layer (4.2) being sandwiched between the source and the drain, and the three are parallel to each other, the parallel direction being the y-direction, and the direction perpendicular to both the y-direction and the z-direction being the x-direction, and both the source and the drain are provided from bottom to top with an ohmic metal layer, an interconnect metal layer, and a first upper metal layer, a Schottky metal layer in direct contact with the barrier layer between the gate metal layer and the drain, a second upper metal layer on an upper surface of the Schottky metal layer, the Schottky metal layer being composed of first and second Schottky metal layers alternately arranged at intervals along the y direction, an interconnect metal layer on the source extending to the drain to form a comb-like structure 1 along the x direction, an upper surface of the first Schottky metal layer being connected only to a comb tooth I on the comb-like structure 1, and a second upper metal layer having a comb-like structure 2 along the z direction, the second upper metal layer having a comb-like structure 2 along the z direction, and an upper surface of the second Schottky metal layer being connected only to a comb tooth II on the comb-like structure 2.

[0007] Preferably, the number of the first Schottky metal layers is a, the number of the second Schottky metal layers is b, a-1≦b≦a+1, and the length of the first Schottky metal layer in the y direction is l 1a and 10 μm≦l 1a ≦300 μm, the length of the second Schottky metal layer in the y direction is l 2b and 10 μm≦l 2b ≦300 μm, the widths of the first Schottky metal layer and the second Schottky metal layer in the x direction are equal, both being w, and 0.5 μm≦w≦3 μm, the thicknesses of the first Schottky metal layer and the second Schottky metal layer in the z direction are equal, both being t1, and 0.5 μm≦t1≦1 μm, and the distance between the first Schottky metal layer and the second Schottky metal layer is dn and 1 μm ≦ d n ≦20 μm, n=a+b−1, n is a positive integer, and the width of the gate structure in the y direction is W g= Σd n + Σl 1a + Σl 2b where the longitudinal direction of the gate structure is the x-direction, the width direction of the gate structure is the y-direction, and the width direction of the gate structure is the z-direction.

[0008] Preferably, the thickness of the comb tooth I in the z direction is t2, where 0.5 μm≦t2≦3 μm, the length in the y direction of the contact surface between the comb tooth I and the first Schottky metal layer is equal to or less than the length in the y direction of the first Schottky metal layer, the width in the x direction of the contact surface between the comb tooth I and the first Schottky metal layer is equal to or less than the width in the x direction of the first Schottky metal layer, the contact surface between the comb tooth I and the first Schottky metal layer is located in a central region on top of the first Schottky metal layer, and the spacing between adjacent comb teeth I is equal to or greater than the spacing between two adjacent first Schottky metal layers below it.

[0009] Preferably, the distance in the x direction between the gate metal layer and the first Schottky metal layer is c1, and 1 μm≦c1≦5 μm; the distance in the x direction between the end of the comb tooth I facing the drain and the side of the first Schottky metal layer facing the drain is c2, and 2 μm≦c2≦15 μm; the distance in the x direction between the end of the comb tooth I facing the drain and the interconnect metal layer on the drain is c3, and 3 μm≦c3≦8 μm; and the distance in the x direction between the gate metal layer and the drain is L gd = c1+ w + c2+ c3, and w is the width of the first Schottky metal layer in the x-direction.

[0010] Preferably, the length of the comb tooth II in the z direction is l z and 3 μm≦l z≦10 μm, both the width in the y direction and the thickness in the x direction of the comb tooth II are equal to or less than the length in the y direction and the width in the x direction of the second Schottky metal layer thereunder, and the contact surface between the comb tooth II and the second Schottky metal layer is located in a central region of the upper part of the second Schottky metal layer, and the spacing between adjacent comb teeth II is equal to or greater than the spacing between two adjacent second Schottky metal layers thereunder, and there is a strip-shaped metal block extending along the y direction on the upper part of the second upper metal layer, and the metal block has a thickness in the z direction of t s =l z The width in the x direction is the thickness in the x direction of the comb tooth II, and the length in the y direction is equal to the width in the y direction of the gate structure.

[0011] Preferably, the comb tooth structure 1 and the comb tooth structure 2 are not in contact with each other, the distance in the y direction between the comb tooth I and the comb tooth II is equal to or greater than the distance between the first Schottky metal layer and the second Schottky metal layer, the distance in the x direction between the comb tooth I and the comb tooth II is 0.5 to 3 μm, and the distance in the z direction between the comb tooth I and the comb tooth II is 1 μm to 3 μm. z -t2, 1 μm ≦ l z -t2≦5 μm, the comb-tooth structure 1 and the gate metal layer are not in contact with each other, and the gap between them in the z direction is 0.5 to 2 μm.

[0012] Preferably, the number of the comb teeth I and the number of the first Schottky metal layers are the same and both are a, the number of the comb teeth II and the number of the second Schottky metal layers are the same and both are b, and a-1≦b≦a+1.

[0013] Preferably, the distance between the gate metal layer and the source is 1 to 4 μm, the distance between the gate metal layer and the drain is 5 to 25 μm, and the thickness of the first dielectric layer is 50 to 150 nm.

[0014] Preferably, the interdigital structure 2 does not contact the gate structure and drain, but is connected to the shell or substrate layer of the device, thereby dissipating induced charges due to irradiation.

[0015] Preferably, the ohmic metal layer contacts the barrier layer to form an ohmic contact with low resistance characteristics, and the first Schottky metal layer and the second Schottky metal layer contact the barrier layer to form a Schottky contact with unidirectional conductivity.

[0016] The method for fabricating an interdigitated radiation-resistant GaN HEMT device structure includes: Step 1: growing a substrate layer, a gallium nitride layer, a barrier layer, and a first dielectric layer sequentially from bottom to top on an epitaxial wafer; Step 2: etching a portion of the first dielectric layer and the barrier layer to form a deposition area for depositing an ohmic metal layer, and then depositing and forming the ohmic metal layer in the deposition area; Step 3: depositing and forming a gate metal layer on the corresponding gate metal layer deposition area on the first dielectric layer to complete the fabrication of the gate structure; Step 4: etching the first dielectric layer to form a deposition area for depositing the first Schottky metal layer and the second Schottky metal layer, and then depositing and forming the Schottky metal layer in the deposition area; Step 5 includes growing a first second dielectric layer over the entire epitaxial wafer, etching the first second dielectric layer to form a deposition area for depositing an interconnect metal layer, and then depositing and forming the interconnect metal layer in the deposition area to complete the fabrication of the comb-like structure 1; and step 6 of growing a second dielectric layer of the second layer over the entire epitaxial wafer, etching the second dielectric layer of the second layer to form a deposition area for depositing the first upper metal layer and the second upper metal layer, and then depositing and forming the first upper metal layer and the second upper metal layer in the deposition area to complete the fabrication of the drain, source, and comb-like structure 2.

[0017] Preferably, in step 1, the material of the first dielectric layer is any one or a combination of two or more of silicon dioxide, silicon nitride, or aluminum oxide, and in steps 5 and 6, the material of the second dielectric layer is any one or a combination of two or more of silicon dioxide, silicon nitride, or polyimide. [Effects of the Invention]

[0018] Compared with the prior art, the beneficial effects obtained by the present invention are as follows: (1) The innovative structure of the present invention is mainly reflected in the provision of first and second Schottky metal layers alternately arranged at segment intervals on the drain side of the gate metal layer of the transistor, which directly contact the barrier layer. The interconnect metal layer on the source is connected to the first Schottky metal layer to form a horizontal comb-like structure 1. This design maximizes the avoidance of the problem of the interconnect metal field plate on the source being too short, which would affect the breakdown capability of the device, if all the Schottky metal layers were connected to the second upper metal layer. The second upper metal layer is connected to the second Schottky metal layer to form a vertical comb-like structure 2. This design minimizes the problem of excessively large leakage current, which would occur if all the Schottky metal layers were connected to the source. The comb-like structure design helps disperse and absorb the impact energy of high-energy particles, allowing irradiation-induced charges to flow out of the first and second Schottky metal layers and exit the transistor. This prevents radiation damage caused by the accumulation of positive charges, reduces the impact of radiation damage on device performance, and significantly improves the device's radiation tolerance.

[0019] (2) The comb-tooth structure 1 and comb-tooth structure 2 of the present invention, through their precise geometric layout (e.g., the number, size, and spacing of the comb teeth), can help improve the charge distribution near the source, drain, and gate, reduce charge accumulation and hot spot occurrence, and increase charge transfer efficiency, thereby improving the overall electrical performance and irradiation performance of the device, such as breakdown voltage, output current, output power, and irradiation burnout voltage.

[0020] (3) The present invention precisely sets the relative positions (such as the distances in the x, y, and z directions) of the gate metal layer and each part, such as the source, drain, and first Schottky metal layer, thereby enabling more precise adjustment and control of the gate electric field distribution, reducing edge effects and parasitic capacitance, and improving the switching speed and linearity of the device, which is advantageous for maintaining good performance in high-frequency and high-speed application scenarios.

[0021] (4) The present invention provides a solution for improving the radiation-induced charge extraction capability of a gallium nitride metal-insulator semiconductor (GaN) high-electron mobility transistor (HEM) by providing the transistor with the ability to efficiently extract radiation-induced charge while not affecting the normal operation of the transistor, by simplifying the manufacturing process, and by providing a second upper metal layer on the active region, the transistor area is significantly reduced and layout utilization is improved. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view showing the structure principle of a gallium nitride MIS high electron mobility transistor in the prior art; [Figure 2] This is a perspective view of the principle structure of a high-drain, comb-shaped, radiation-resistant GaN HEMT device structure (the Schottky metal layer is connected only to the interconnect metal layer above the source). [Figure 3] This is a perspective view of the structural principle of a comb-shaped, radiation-resistant GaN HEMT device structure with extremely low breakdown voltage (the Schottky metal layer is connected only to the top metal layer). [Figure 4] FIG. 1 is a perspective structural principle diagram of a comb-shaped radiation-resistant GaN HEMT device structure according to the present invention. [Figure 5]5A and 5B are schematic diagrams of a fabrication process for the comb-shaped, radiation-resistant GaN HEMT device structure of the present invention, in which FIG. 5A is a schematic diagram of growing a substrate layer, a gallium nitride layer, a barrier layer, and a first dielectric layer, FIG. 5B is a schematic diagram of etching and depositing an ohmic metal layer, FIG. 5C is a schematic diagram of depositing a gate metal layer, FIG. 5D is a schematic diagram of etching and depositing a Schottky metal layer, FIG. 5E is a schematic diagram of growing a first second dielectric layer and etching and depositing an interconnect metal layer, and FIG. 5F is a schematic diagram of growing a second second dielectric layer and etching and depositing a second top metal layer. DETAILED DESCRIPTION OF THE INVENTION

[0023] In order for those skilled in the art to better understand the technical solutions of the present invention, the following describes preferred embodiments of the present invention in combination with specific examples. It should be understood that the drawings are used for illustrative purposes only and cannot be construed as limiting the present invention. In order to better explain the present embodiment, some components in the drawings may be omitted, enlarged, or reduced in size, and therefore do not represent the actual size of the product. Those skilled in the art can understand that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships shown in the drawings are for illustrative purposes only and cannot be construed as limiting the present invention.

[0024] Example 1 As shown in FIG. 4, the comb-shaped radiation-resistant GaN HEMT device structure is a multilayer structure including, in order from bottom to top, a substrate layer 1, a gallium nitride layer 2, a barrier layer 3, a gate structure 4, and a second dielectric layer 5. The thickness direction of the multilayer structure is the z-direction. The gate structure 4 includes a first dielectric layer 4.1 provided on the upper surface of the barrier layer 3 and a strip-shaped gate metal layer 4.2 provided on the upper surface of the first dielectric layer 4.1. The source and drain are embedded at different intervals in the barrier layer 3 on both sides of the gate metal layer 4.2. The source is closer to the gate metal layer 4.2 and the drain is farther from the gate metal layer 4.2. The gate metal layer 4.2, the source, and the drain are parallel to each other. The parallel direction is the y-direction. The direction perpendicular to both the y-direction and the z-direction is the x-direction. Both the source and the drain are The gate metal layer 4.2 includes an ohmic metal layer 6, an interconnect metal layer 7, and a first upper metal layer 8, which are provided sequentially from bottom to top. The drain-facing side of the gate metal layer 4.2 is provided with a first Schottky metal layer 10.1 and a second Schottky metal layer 10.2, which are spaced apart and alternately arranged, and which are in direct contact with the barrier layer 3. The interconnect metal layer 7 on the source extends to the drain to form a comb-like structure 1 along the x-direction. The top surface of the first Schottky metal layer 10.1 is connected only to comb tooth I7.1 of the comb-like structure 1. The second upper metal layer 9 is provided on the top surface of the second Schottky metal layer 10.2. The second upper metal layer 9 has a comb-like structure 2 along the z-direction. The top surface of the second Schottky metal layer 10.2 is connected only to comb tooth II9.1 on the comb-like structure 2.

[0025] In some examples, the number of first Schottky metal layers 10.1 is a = 3, the number of second Schottky metal layers 10.2 is b = 2, and the length of the first Schottky metal layers 10.1 in the y direction is l 11 =l 12 =l 13 = 50 μm, and the length of the second Schottky metal layer 10.2 in the y direction is l 21 =l 22=50 μm, the first Schottky metal layer and the second Schottky metal layer have equal widths in the x direction, w=2 μm for both, the first Schottky metal layer and the second Schottky metal layer have equal thicknesses in the z direction, t1=0.7 μm for both, the spacing between first Schottky metal layer 10.1 and second Schottky metal layer 10.2 is d1=d2=d3=d4=10 μm, and the width of gate structure 4 in the y direction is W g= Σd n + Σl 1a + Σl 2b =290 μm, where the x direction is the longitudinal direction of the gate structure 4, the y direction is the width direction of the gate structure 4, and the z direction is the thickness direction of the gate structure 4. The three directions x, y, and z correspond to the directions shown in FIG. 4, and so on.

[0026] In some examples, the z-direction thickness of the comb tooth I7.1 is t2 = 1 μm, the y-direction length of the contact surface between the comb tooth I7.1 and the first Schottky metal layer 10.1 is equal to the y-direction length of the first Schottky metal layer 10.1, the x-direction width of the contact surface between the comb tooth I7.1 and the first Schottky metal layer 10.1 is equal to the x-direction width of the first Schottky metal layer 10.1, the contact surface between the comb tooth I7.1 and the first Schottky metal layer 10.1 is located in the central region of the top of the first Schottky metal layer 10.1, and the spacing between adjacent comb teeth I7.1 is equal to the spacing between two adjacent first Schottky metal layers 10.1 below.

[0027] In some examples, the x-direction distance between the gate metal layer 4.2 and the first Schottky metal layer 10.1 is c1=2 μm, the x-direction distance between the drain-facing end of the comb tooth 17.1 and the drain-facing side of the first Schottky metal layer 10.1 is c2=8 μm, the x-direction distance between the drain-facing end of the comb tooth 17.1 and the interconnect metal layer 7 on the drain is c3=6 μm, and the x-direction distance between the gate metal layer 4.2 and the drain is L gd = c1+ w + c2+ c3=18 μm, and w is the width of the first Schottky metal layer in the x-direction.

[0028] In some examples, the length of the tooth II9.1 in the z direction is l z = 5 μm, both the width in the y direction and the thickness in the x direction of the comb tooth II 9.1 are equal to the length in the y direction and the width in the x direction of the underlying second Schottky metal layer 10.2, the contact surface between the comb tooth II 9.1 and the second Schottky metal layer 10.2 is located in the central region of the upper part of the second Schottky metal layer 10.2, the spacing between adjacent comb teeth II 9.1 is equal to the spacing between two adjacent second Schottky metal layers 10.2 therebelow, and there is a strip-shaped metal block 9.2 extending along the y direction on the upper part of the second Schottky metal layer 9.2, and the metal block 9.2 has a thickness in the z direction of l z −t2=4 μm, the width in the x direction is equal to the thickness in the x direction of the comb tooth II 9.1, and the length in the y direction is equal to the width in the y direction of the gate structure 4.

[0029] In some examples, the comb-like structure 1 and the comb-like structure 2 are not in contact with each other, the y-direction spacing between the comb tooth 17.1 and the comb tooth 29.1 is equal to the spacing between the first Schottky metal layer 10.1 and the second Schottky metal layer 10.2, the x-direction spacing between the comb tooth 17.1 and the comb tooth 29.1 is 1.5 μm, and the z-direction spacing between the comb tooth 17.1 and the comb tooth 29.1 is 1.5 μm. z -t2=4 μm, the comb-tooth structure 1 and the gate metal layer 4.2 are not in contact with each other, and the gap between them in the z direction is 0.8 μm. In some examples, the number of comb teeth I 7.1 and the number of first Schottky metal layers 10.1 are the same, and a=3; the number of comb teeth II 9.1 and the number of second Schottky metal layers 10.2 are the same, and b=2.

[0030] In some instances, the interdigitated structure 2 does not contact the gate structure 4 and drain, but is connected to the shell or substrate layer 1 of the device, thereby dissipating induced charges due to irradiation.

[0031] The fabrication of the above interdigital radiation-resistant GaN HEMT device structure includes the following steps, as shown in FIG. Step 1: As shown in Figure 5a, grow a substrate layer 1, a gallium nitride layer 2, a barrier layer 3 and a first dielectric layer 4.1. On the epitaxial wafer, a substrate layer 1 having a thickness of 0.65 mm, a gallium nitride layer 2 having a thickness of 4500 nm, a barrier layer 3 having a thickness of 13 nm, and a first dielectric layer 4.1 having a thickness of 100 nm are grown in this order from bottom to top.

[0032] Step 2: Etch and deposit an ohmic metal layer 6, as shown in Figure 5b. The first dielectric layer 4.1 and a portion of the barrier layer 3 (remaining 0-5 nm after etching) were etched using inductively coupled plasma dry etching and photolithography stripping to form a deposition area for depositing two ohmic metal layers 6. The two ohmic metal layers 6 were then simultaneously deposited within the deposition area. Each ohmic metal layer 6 was formed by sequentially depositing a 100 nm thick Ti layer and a 500 nm thick Al layer. Each ohmic metal layer 6 had a width (x direction) of 3 μm and a length (y direction) of 290 μm. The "simultaneous" deposition refers to the simultaneous deposition of the ohmic metal layers 6 in the source and drain regions. The distance between the ohmic metal layer 6 on the source and the gate metal layer 4.2 was 2 μm, and the distance between the ohmic metal layer 6 on the drain and the gate metal layer 4.2 was 18 μm.

[0033] Step 3: Deposit gate metal layer 4.2, as shown in Figure 5c. By using a photolithography exfoliation method, a gate metal layer 4.2 is deposited and formed in the corresponding deposition area of ​​the first dielectric layer 4.1, completing the fabrication of the gate structure 4. The gate metal layer 4.2 is formed by depositing 150 nm of Ni and 500 nm of Al in that order, and the gate metal layer 4.2 has a width (x direction) of 2 μm and a length (y direction) of 290 μm.

[0034] Therefore, the transistor fabricated in this example has a gate length (x direction) of 2 μm and a gate width (y direction) of 290 μm.

[0035] Step 4: Etch and deposit a Schottky metal layer on the drain side of the gate metal layer 4.2, as shown in Figure 5d. First dielectric layer 4.1 is etched using inductively coupled plasma dry etching and photolithography stripping to form a deposition area for depositing first Schottky metal layer 10.1 and second Schottky metal layer 10.2. Five first Schottky metal layers 10.1 and second Schottky metal layers 10.2, each 50 μm long and spaced 10 μm apart, are then formed within the deposition area. Both first Schottky metal layer 10.1 and second Schottky metal layer 10.2 are formed by sequentially depositing 200 nm thick Ti and 500 nm thick Al.

[0036] Step 5: Grow a second dielectric layer 5 of the first layer, and etch and deposit an interconnect metal layer 7, as shown in Figure 5e. A first second dielectric layer 5 made of silicon nitride is grown to a thickness of 800 nm on the entire epitaxial wafer using plasma-enhanced chemical vapor deposition (PECVD). This is then etched using inductively coupled plasma dry etching (ICP-DPE) to form a deposition area for the interconnect metal layer 7. The interconnect metal layer 7 is then deposited in the deposition area to complete the fabrication of the comb-like structure 1. The interconnect metal layer 7 is formed by sequentially depositing a 300 nm thick Ti layer and a 700 nm thick Al layer.

[0037] Step 6: Grow a second dielectric layer 5, etch and deposit a top metal layer, as shown in Figure 5f. A 4000 nm thick second dielectric layer 5 of silicon nitride material is grown on the entire epitaxial wafer, and then inductively coupled plasma dry etching is used to etch the second dielectric layer 5 to form deposition areas for the first and second upper metal layers 8 and 9. The first and second upper metal layers 8 and 9 are then deposited in the deposition areas to complete the fabrication of the drain, source, and comb-like structures 2. Both the first and second upper metal layers 8 and 9 are deposited with 5000 nm of aluminum metal.

[0038] The photolithography stripping method in each of the above steps first covers the non-feature areas with photoresist, then covers the entire epitaxial wafer with a metal layer, and then uses a stripping method to remove the metal layer in the non-feature areas, and finally leaves the metal layer in the feature areas.

[0039] <Comparative Example 1> As shown in FIG. 1, the device structure includes a substrate layer 1, a gallium nitride layer 2, a barrier layer 3, and a first dielectric layer 4.1, which are arranged in this order from bottom to top. A strip-shaped gate metal layer 4.2 is arranged above the first dielectric layer 4.1. A source and a drain are embedded in the barrier layer 3 on both sides of the gate metal layer 4.2. Both the source and the drain include an ohmic metal layer 6, an interconnect layer 7, and a first upper metal layer 8, which are arranged in this order from bottom to top. The source is close to the gate metal layer 4.2, and the drain is far from the gate metal layer 4.2. A second dielectric layer 5 is filled between the gate metal layer 4.2 and the source and drain. For manufacturing methods and parameters, please refer to the examples and existing standards.

[0040] <Comparative Example 2> The device structure is shown in FIG. 2 , and the fabrication method and parameters refer to Example 1. The difference between this example and Example 1 is that the Schottky metal layer 10 is a continuous strip, and all of the Schottky metal layers 10 are connected only to the interconnect metal layer 7 on the source. This device can drain induced charges due to irradiation from the Schottky metal layer to the outside of the transistor, preventing radiation damage caused by the accumulation of positive charges. However, the inventors discovered that the source of this structure device is directly connected to the right side (drain side) of the gate through the interconnect metal layer 7 and the Schottky metal layer 10, resulting in a very large leakage current of the device because some electrons / holes are not controlled by gate switching.

[0041] <Comparative Example 3> The device structure is shown in FIG. 3 , and the fabrication method and parameters refer to Example 1. The difference between this example and Example 1 is that the Schottky metal layer 10 is a continuous strip, and all of the Schottky metal layers 10 are connected only to the second upper metal layer 9. This device can drain induced charges due to irradiation from the Schottky metal layer 10 to the outside of the transistor, preventing radiation damage caused by the accumulation of positive charges. However, the inventors discovered that in this device structure, the Schottky metal layer 10 is close to the gate and the second upper metal layer 9 is stacked on top of it, which shortens the field plate formed by the source interconnect metal layer 7, resulting in a reduced reverse breakdown capability of the device.

[0042] According to the description and drawings of the present invention, those skilled in the art can easily fabricate the comb-shaped radiation-resistant GaN HEMT device structure of the present invention, easily use the fabrication method thereof, and produce the positive effects described in the present invention.

[0043] Unless otherwise specified, in this invention, the positions and positional relationships of terms such as "length," "vertical," "up" and "down," "base," "back," "right," "left," "vertical," "level," "top," "bottom," "inside" and "outside," "clockwise," "counterclockwise," "axis," "around," "around," and the like are based on the positions and positional relationships as indicated, and are used solely to facilitate and simplify the description of this invention, and do not indicate or suggest that devices or elements must have a specific orientation, be configured, or operate in a specific orientation. Therefore, terms expressing orientations or positional relationships in this invention are used for illustrative purposes only, and should not be understood by those skilled in the art as limitations of the invention. The specific meanings of the above terms can be understood, if necessary, by referring to the drawings.

[0044] Unless otherwise specified or limited, the terms "set," "connect," and "connect" in the present invention should be broadly understood, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection. They may also refer to a direct connection, an indirect connection via an intermediate medium, or an internal connection between two elements. The specific meanings of the above terms in the present invention are often understood by those skilled in the art.

[0045] It should be pointed out that the above is only a preferred embodiment of the present invention, and the above preferred embodiment does not limit the present invention, and the protection scope of the present invention should be in accordance with the scope defined by the claims. Those skilled in the art can make some improvements and modifications without departing from the spirit and scope of the present invention, which should also be considered as the protection scope of the present invention. [Explanation of symbols]

[0046] 1. Board Layer 2 Gallium nitride layer 3 Barrier layer 4-gate structure 4.1 First Dielectric Layer 4.2-Gate Metal Layer 5 Second dielectric layer 6 Ohmic metal layer 7 Interconnect Metal Layers 7.1 Comb Teeth I 8 1st upper metal layer 9 Second upper metal layer 9.1 Comb Teeth II 9.2 Metal Blocks 10 Schottky metal layer 10.1 First Schottky Metal Layer 10.2 Second Schottky Metal Layer

Claims

1. A multilayer structure including, in order from bottom to top, a substrate layer, a gallium nitride layer, a barrier layer, a gate structure, and a second dielectric layer, the thickness direction of the multilayer structure being the z-direction, the gate structure including a first dielectric layer provided on an upper surface of the barrier layer, and a gate metal layer provided on an upper surface of the first dielectric layer, a source and a drain embedded in the barrier layer, the gate metal layer (4.2) being sandwiched between the source and the drain, and the three are parallel to each other, the parallel direction being the y-direction, and the direction perpendicular to both the y-direction and the z-direction being the x-direction, both the source and the drain including, in order from bottom to top, an ohmic metal layer, an interconnect metal layer, and a first upper metal layer, and the gate a Schottky metal layer in direct contact with the barrier layer is provided between the metal layer and the drain; a second upper metal layer is provided on an upper surface of the Schottky metal layer, the Schottky metal layer being composed of first and second Schottky metal layers alternately arranged at intervals along a y direction; the interconnection metal layer on the source extends to the drain to form a comb-tooth structure 1 along an x ​​direction, an upper surface of the first Schottky metal layer being connected only to comb teeth I on the comb-tooth structure 1; the second upper metal layer has a comb-tooth structure 2 along a z direction, and an upper surface of the second Schottky metal layer being connected only to comb teeth II on the comb-tooth structure 2.

2. The number of the first Schottky metal layers is a, the number of the second Schottky metal layers is b, a-1≦b≦a+1, and the length of the first Schottky metal layer in the y direction is l 1a and 10 μm≦l 1a ≦300 μm, and the length of the second Schottky metal layer in the y direction is l 2b and 10 μm≦l 2b ≦300 μm, the widths of the first Schottky metal layer and the second Schottky metal layer in the x direction are equal, both being w, 0.5 μm≦w≦3 μm, the thicknesses of the first Schottky metal layer and the second Schottky metal layer in the z direction are equal, both being t 1 and 0.5 μm≦t 1 ≦1 μm, and the distance between the first Schottky metal layer and the second Schottky metal layer is d n and 1 μm≦d n ≦20 μm, n=a+b−1, n is a positive integer, and the width of the gate structure in the y direction is W g= Σd n + Σl 1a + Σl 2b 2. The comb-shaped radiation-resistant GaN HEMT device structure of claim 1, wherein the longitudinal direction of the gate structure is the x-direction, the width direction of the gate structure is the y-direction, and the width direction of the gate structure is the z-direction.

3. The thickness of the comb tooth I in the z direction is t 2 and 0.5 μm≦t 2 2. The comb-shaped radiation-resistant GaN HEMT device structure of claim 1, wherein a length in a y direction of a contact surface between the comb teeth I and the first Schottky metal layer is equal to or less than a length in the y direction of the first Schottky metal layer, a width in an x ​​direction of a contact surface between the comb teeth I and the first Schottky metal layer is equal to or less than a width in the x direction of the first Schottky metal layer, the contact surface between the comb teeth I and the first Schottky metal layer is located in a central region of an upper part of the first Schottky metal layer, and a spacing between adjacent comb teeth I is equal to or greater than a spacing between two adjacent first Schottky metal layers thereunder.

4. The distance in the x direction between the gate metal layer and the first Schottky metal layer is c 1 and 1 μm≦c 1 ≦5 μm, and the distance in the x direction between the end of the comb tooth I facing the drain and the side of the first Schottky metal layer facing the drain is c 2 and 2 μm≦c 2 ≦15 μm, and the distance in the x direction between the end of the comb tooth I facing the drain and the interconnect metal layer on the drain is c 3 and 3 μm≦c 3 ≦8 μm, and the distance in the x direction between the gate metal layer and the drain is L gd = c 1 + w + c 2 + c 3 2. The interdigitated radiation-resistant GaN HEMT device structure of claim 1, wherein w is the width of the first Schottky metal layer in the x-direction.

5. The length of the comb tooth II in the z direction is l z and 3 μm≦l z ≦10 μm, both the width in the y direction and the thickness in the x direction of the comb tooth II are equal to or less than the length in the y direction and the width in the x direction of the second Schottky metal layer thereunder, and the contact surface between the comb tooth II and the second Schottky metal layer is located in a central region of the upper part of the second Schottky metal layer, and the spacing between adjacent comb teeth II is equal to or greater than the spacing between two adjacent second Schottky metal layers thereunder, and there is a strip-shaped metal block extending along the y direction on the upper part of the second upper metal layer, and the metal block has a thickness in the z direction of t s =l z 2. The comb-like radiation-resistant GaN HEMT device structure according to claim 1, wherein the width in the x direction is the thickness in the x direction of the comb tooth II, and the length in the y direction is equal to the width in the y direction of the gate structure.

6. The comb-tooth structure 1 and the comb-tooth structure 2 are not in contact with each other, the distance in the y direction between the comb teeth I and the comb teeth II is equal to or greater than the distance between the first Schottky metal layer and the second Schottky metal layer, the distance in the x direction between the comb teeth I and the comb teeth II is 0.5 to 3 μm, and the distance in the z direction between the comb teeth I and the comb teeth II is 1 μm. z -t 2 and 1 μm≦l z -t 2 2. The comb-shaped radiation-resistant GaN HEMT device structure according to claim 1, wherein the comb-shaped structure 1 and the gate metal layer are not in contact with each other, and the spacing between them in the z-direction is 0.5-2 μm.

7. 2. The comb-teeth radiation-resistant GaN HEMT device structure according to claim 1, wherein the number of the comb teeth I and the number of the first Schottky metal layers are the same, and both are a; the number of the comb teeth II and the number of the second Schottky metal layers are the same, and both are b, and a-1≦b≦a+1.

8. 2. The comb-shaped radiation-resistant GaN HEMT device structure according to claim 1, wherein the distance between the gate metal layer and the source is 1-4 μm, the distance between the gate metal layer and the drain is 5-25 μm, and the thickness of the first dielectric layer is 50-150 nm.

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