Hemt device with multi-metal gate structure and method of manufacturing the same

Abstract

The application discloses a HEMT device with a multi-metal gate structure and a preparation method thereof. The device comprises an AlGaN / GaN epitaxial layer, source and drain electrodes connected to two ends of an upper surface of the AlGaN / GaN epitaxial layer, a gate electrode arranged close to the source electrode side of the source and drain electrodes, a first layer metal X of the gate electrode deposited by an electron beam evaporation method, and a second layer metal Y of the gate electrode deposited by a magnetron sputtering method. The work function of the second layer metal Y is higher than that of the first layer metal X. The metal structure in contact with the (Al) GaN after the gate electrode is stripped is Y / X / Y. The multi-metal gate structure is in contact with the (Al) GaN, so that the electric field is redistributed, the electric field peak value of the gate edge close to the drain electrode is reduced, the breakdown voltage of the device is improved, the gate edge electric field peak value is weakened due to the gate injection of electrons to form a virtual gate effect, the current collapse of the device is reduced, and the dynamic performance of the device is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor, in particular to a HEMT device with a multi-metal gate structure and a preparation method thereof. BACKGROUND

[0002] GaN material is widely used in high-frequency power amplifiers and high-voltage power switches due to its high electron mobility, low on-resistance, excellent heat dissipation capacity, and high breakdown voltage. Currently, the breakdown voltage of GaN-based HEMT devices is far from the theoretical limit of GaN material (3.4 MV / cm), and the devices are prone to breakdown between the gate and the drain. How to reduce the high electric field peak near the edge of the gate on the drain side will be beneficial to improve the breakdown voltage of the device. The most common method is to use gate field plates or source field plates to adjust the electric field distribution, thereby reducing the high electric field peak near the edge of the gate on the drain side. On the other hand, the virtual gate effect caused by the gate injection of electrons aggravates the influence on the current collapse of the device, making the device exhibit poor performance under stress conditions. Currently, passivation processes are commonly used to reduce surface states on the barrier layer to suppress current collapse (R. Hao, et al, IEEE Electron Device Lett., 2017, 38(11)); and field plate processes are also reported to modulate the electric field and reduce surface states (H. Hanawa, et al, IEEE International Reliability Physics Symposium Proceedings., 2013). Some scholars (A. K. Visvkarma, et al, Semicond. Sci. Technol., 2019, 34(10)) have achieved a double-layer gate metal process by changing the angle of electron beam deposition, forming a Ni / (Al)GaN and Ti / (Al)GaN gate double-contact interface, changing the gate edge electric field distribution, and improving the breakdown voltage and dynamic performance of the device.

[0003] Currently, the equipment for depositing metal is generally electron beam evaporation or magnetron sputtering. The magnetron sputtering equipment mainly relies on argon ion bombardment of the target material to sputter atoms of the material onto the wafer surface; and the electron beam evaporation equipment mainly relies on heating to melt the material, and when the material reaches the boiling point, the particles of the material will one by one separate from the material surface to the wafer surface. For the magnetron sputtering equipment, the sputtering distance is short, mainly involving collisions between particles, and an average free path of particle motion needs to be considered, similar to a point light source, and the angles between the particles are large, so the area of the material sputtered on the wafer surface will be larger than the defined lithography window; and the cavity of the electron beam evaporation is long, similar to a parallel light source, and the metal material will be vertically evaporated on the wafer surface.

[0004] In summary, the double-gate metal process helps to improve the breakdown voltage and dynamic performance of the device. However, the method of changing the angle of electron beam deposition mentioned above is difficult to control accurately and has poor repeatability. SUMMARY

[0005] The HEMT device with the multi-metal gate structure provided by the application comprises an AlGaN / GaN epitaxial layer, source-drain electrodes and a gate electrode, the two ends of the upper surface of the AlGaN / GaN epitaxial layer are connected with the source-drain electrodes, the gate electrode is connected with the upper surface of the AlGaN / GaN epitaxial layer, the gate electrode comprises a first layer of metal X and a second layer of metal Y, and the metal structure in contact with the (Al) GaN after the gate electrode is peeled off is Y / X / Y.

[0006] The object of the application is achieved at least by one of the following technical solutions.

[0007] The HEMT device with the multi-metal gate structure provided by the application comprises an AlGaN / GaN epitaxial layer, source-drain electrodes and a gate electrode, the two ends of the upper surface of the AlGaN / GaN epitaxial layer are connected with the source-drain electrodes, the gate electrode is connected with the upper surface of the AlGaN / GaN epitaxial layer, the gate electrode comprises a first layer of metal X and a second layer of metal Y, and the metal structure in contact with the (Al) GaN after the gate electrode is peeled off is Y / X / Y.

[0008] The method of combining electron beam with magnetron sputtering is adopted, and the multi-metal gate structure Y / X / Y is realized after the metal is peeled off. The method does not need to change the angle of electron beam deposition, and the electron beam and the magnetron sputtering only need to adopt the conventional deposition method, which has repeatability, and compared with the double-gate metal process mentioned above, the method based on the application realizes a three-layer gate metal process.

[0009] The HEMT device with the multi-metal gate structure provided by the application comprises an AlGaN / GaN epitaxial layer, source-drain electrodes and a gate electrode, the two ends of the upper surface of the AlGaN / GaN epitaxial layer are connected with the source-drain electrodes, the gate electrode is connected with the upper surface of the AlGaN / GaN epitaxial layer, the gate electrode comprises a first layer of metal X and a second layer of metal Y, and the metal structure in contact with the (Al) GaN after the gate electrode is peeled off is Y / X / Y.

[0010] The HEMT device with the multi-metal gate structure provided by the application is an AlGaN / GaN HEMT device.

[0011] Further, the length of the second layer metal Y on both sides of the first layer metal X is 0.5-1 μm.

[0012] Further, the second layer metal Y completely covers the first layer metal X.

[0013] Further, the distance from the gate electrode to the source electrode is less than the distance from the gate electrode to the drain electrode, that is, the gate electrode is arranged close to the source side of the source-drain electrode.

[0014] The application provides a method for preparing the HEMT device with the multi-metal gate structure, comprising the following steps:

[0015] (1) defining a source-drain electrode window on an AlGaN / GaN epitaxial layer, preparing a source-drain electrode and performing annealing to form an ohmic contact;

[0016] (2) defining a gate electrode photolithography window, preparing a multi-metal gate structure Y / X / Y, and obtaining the HEMT device with the multi-metal gate structure.

[0017] Further, the photolithography window of the gate electrode in step (2) is designed to be 1-2 μm.

[0018] Further, in the multi-metal gate structure Y / X / Y in step (2), the first layer metal X is deposited by an electron beam evaporation method, and the second layer metal Y is deposited by a magnetron sputtering method; and the thickness of the second layer metal Y is greater than the thickness of the first layer metal X.

[0019] Further, in the multi-metal gate structure Y / X / Y in step (2), the first layer metal X is one of Ni, Ti, TiN, etc., and the second layer metal Y is one of Cu, W, Ni, etc.

[0020] Compared with the prior art, the application has the following beneficial effects and advantages:

[0021] The multi-metal gate prepared by the electron beam and the magnetron sputtering does not need an additional photolithography step, the second layer metal Y prepared by the magnetron sputtering completely covers the first layer metal X prepared by the electron beam, forming the multi-metal gate structure Y / X / Y; the electric field distribution is adjusted, the electric field peak value of the gate edge close to the drain electrode is reduced, and the breakdown voltage of the device is improved; at the same time, the lower electric field peak value of the gate edge weakens the virtual gate effect formed by the gate injection of electrons, through the C-V characteristic test, the saturation capacitance (158 pF) of the device corresponding to the W / TiN / W structure at a test frequency of 10 KHz is reduced by 13.9% compared with the device (136 pF) of the TiN structure, and the dynamic performance of the device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1A schematic diagram of an epitaxial layer of a GaN-based HEMT device before preparing a source-drain contact electrode for an embodiment;

[0023] Figure 2 A schematic diagram of a device structure after preparing a source-drain contact electrode and annealing to form an ohmic contact for an embodiment;

[0024] Figure 3 A schematic diagram of a device structure after forming a gate electrode for an embodiment;

[0025] Figure 4 A graph of capacitance data of a HEMT device with a multi-metal gate structure and a device with a TiN structure prepared in Example 2;

[0026] In the graph, AlGaN / GaN epitaxial layer 1, source-drain electrode 2, gate electrode 3. DETAILED DESCRIPTION

[0027] The specific implementation of the present application is further described below in conjunction with examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following processes are not specifically described in detail, they can be implemented or understood by those skilled in the art with reference to the prior art.

[0028] Example 1

[0029] The present embodiment provides a HEMT device with a multi-metal gate structure, as shown in Figure 3 The device includes an AlGaN / GaN epitaxial layer 1, and source-drain electrodes 2 connected to both ends of the upper surface of the AlGaN / GaN epitaxial layer. The gate electrode 3 is disposed close to the source electrode side of the source-drain electrode 2. The first layer of metal Ti of the gate electrode 3 is deposited by electron beam evaporation, and the second layer of metal Ni of the gate electrode 3 is deposited by magnetron sputtering without additional photolithography steps. The metal structure in contact with (Al) GaN after peeling off the gate electrode 3 is Ni / Ti / Ni. Figure 3 In the graph, G-1 represents the first layer of metal, and G-2 represents the second layer of metal.

[0030] The present embodiment also provides a method for preparing a HEMT device with a multi-metal gate structure, comprising the following steps:

[0031] (1) Defining a source-drain electrode window on an AlGaN / GaN epitaxial layer (the epitaxial layer before preparing a source-drain contact electrode is shown in Figure 1 ), preparing a source-drain electrode 2 and annealing to form an ohmic contact, as shown in Figure 2 ;

[0032] (2) Defining a gate electrode 3 photolithography window, and preparing a multi-metal gate structure Ni / Ti / Ni, as shown in Figure 3The gate lithography window of the HEMT device is designed as 1 μm, and the length of the second layer metal Ni on both sides of the first layer metal Ti in the metal structure Ni / Ti / Ni formed after the gate electrode is stripped is 0.7 μm, the thickness of the first layer metal Ti is 50 nm, the thickness of the second layer metal Ni is 250 nm, and the second layer metal Ni completely wraps the first layer metal Ti, thereby obtaining the HEMT device with the multi-metal gate structure.

[0033] The HEMT device with the multi-metal gate structure prepared in Example 1 has good dynamic performance and low saturation capacitance, and can refer to Figure 4 .

[0034] Example 2

[0035] The present embodiment provides a HEMT device with a multi-metal gate structure, as shown in Figure 3 , the device comprises an AlGaN / GaN epitaxial layer 1, and source-drain electrodes 2 connected to both ends of the upper surface of the AlGaN / GaN epitaxial layer, a gate electrode 3 disposed close to the source electrode side of the source-drain electrodes 2, a first layer metal TiN of the gate electrode 3 deposited by electron beam evaporation, and a second layer metal W of the gate electrode 3 deposited by magnetron sputtering, without the need for additional photolithography steps, and a metal structure W / TiN / W formed after the gate electrode 3 is stripped and contacts (Al) GaN.

[0036] The present embodiment also provides a method for preparing a HEMT device with a multi-metal gate structure, comprising the following steps:

[0037] (1) Defining a source-drain electrode window on an AlGaN / GaN epitaxial layer 1, preparing source-drain electrodes 2 and performing annealing to form ohmic contact, as shown in Figure 2 .

[0038] (2) Defining a gate electrode 3 lithography window, preparing a multi-metal gate structure W / TiN / W, as shown in Figure 3 ; the gate lithography window of the HEMT device is designed as 1 μm, and the length of the second layer metal W on both sides of the first layer metal TiN in the metal structure W / TiN / W formed after the gate electrode is stripped is 0.5 μm, the thickness of the first layer metal TiN is 50 nm, the thickness of the second layer metal W is 200 nm, and the second layer metal W completely wraps the first layer metal TiN, thereby obtaining the HEMT device with the multi-metal gate structure.

[0039] Figure 4The C-V characteristic comparison chart of the HEMT device with the multi-metal gate structure (W / TiN / W) prepared in Example 2 is shown in FIG. 6, which only shows the corresponding capacitance data at a test frequency of 10 KHz. It can be seen that the device with the W / TiN / W structure has a lower saturated capacitance value than the device with the TiN structure.

[0040] The above examples are only preferred embodiments of the present application, which are used to explain the present application, but not to limit the present application. Any changes, replacements, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present application shall fall within the protection scope of the present application.

Claims

1. A method for fabricating a HEMT device with a multi-metal gate structure, characterized in that, Includes the following steps: (1) Define source and drain electrode windows on AlGaN / GaN epitaxy, prepare source and drain electrodes and anneal them to form ohmic contacts; (2) Define the gate electrode photolithography window, fabricate a multi-metal gate structure Y / X / Y, and obtain the HEMT device with the multi-metal gate structure; in the multi-metal gate structure Y / X / Y, the first metal layer X is deposited by electron beam evaporation, and the second metal layer Y is deposited by magnetron sputtering; and the thickness of the second metal layer Y is greater than the thickness of the first metal layer X; in the multi-metal gate structure Y / X / Y, the first metal layer X is one of Ni, Ti, and TiN, and the second metal layer Y is one of Cu, W, and Ni; The HEMT device with a multi-metal gate structure includes: an AlGaN / GaN epitaxial layer, source / drain electrodes, and a gate electrode; the source / drain electrodes are respectively connected to the two ends of the upper surface of the AlGaN / GaN epitaxial layer; the gate electrode is connected to the upper surface of the AlGaN / GaN epitaxial layer; the gate electrode includes a first metal layer X and a second metal layer Y; the metal structure formed after the gate electrode is stripped and in contact with (Al)GaN is Y / X / Y; the length of the second metal layer Y on both sides of the first metal layer X is 0.5-1 μm; the second metal layer Y completely encapsulates the first metal layer X; the distance from the gate electrode to the source is less than the distance from the gate electrode to the drain.

2. The method for fabricating a HEMT device with a multi-metal gate structure according to claim 1, characterized in that, The photolithographic window of the gate electrode in step (2) is designed to be 1-2 μm.

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