GaN MISHEMT device and manufacturing method thereof

Abstract

The present invention discloses a GaN MISHEMT device and a method for manufacturing the same. The manufacturing method comprises: manufacturing an epitaxial structure, the epitaxial structure comprising a channel layer and a barrier layer formed on the channel layer, wherein a two-dimensional electron gas is formed between the AlGaN barrier layer and the channel layer; in-situ epitaxially growing a two-dimensional material passivation layer on the barrier layer; forming a dielectric layer on the two-dimensional material passivation layer; and manufacturing a source, a drain, and a gate, wherein the source and drain are arranged on the barrier layer and electrically connected via the two-dimensional electron gas, and the gate is arranged on the dielectric layer and located between the source and drain. The manufacturing method provided by the present invention comprises in-situ growing a two-dimensional h-BN as a surface passivation layer after growing the GaN HEMT epitaxial structure, and then depositing a dielectric layer for a second time. This can prevent surface damage, shield surface dangling bonds, reduce interface state density, and thereby effectively suppress the current collapse effect, enabling the device to obtain better DC and dynamic characteristics.

Description

Technical Field

[0001] The present invention relates to a HEMT device, in particular to a GaN MISHEMT device and a manufacturing method thereof, and belongs to the technical field of semiconductors. Background Art

[0002] Since the beginning of the 21st century, global warming has become increasingly prominent, environmental pollution has become a serious problem, and the energy crisis has intensified. Achieving efficient and environmentally friendly energy utilization has become the key to addressing these issues. Electricity, as one of humanity's primary energy sources, consumes enormous amounts in society and daily life. Therefore, improving the conversion efficiency of power conversion systems is crucial to reducing energy waste. GaN HEMT devices, with their exceptional properties such as a large bandgap, high breakdown field strength, and high electron saturation drift velocity, are ideally suited for high-frequency, high-temperature, and high-power applications such as wireless communication base stations, radar, automotive electronics, power grid transmission, and the aerospace industry. Despite their numerous advantages, GaN HEMT devices have been limited in their commercial application by reliability issues, gate leakage, and the current collapse effect. The current collapse effect manifests itself as a sharp drop in output current when driven by a high-frequency signal, resulting in a reduction in output power density and power-added efficiency.

[0003] Current research indicates that current collapse is related to traps on the AlGaN surface. The emergence of GaN MISHEMTs (GaN MISHEMTs) reduces gate leakage while increasing the device's gate breakdown voltage. They can also reduce interface trap charge to a certain extent, thereby suppressing the current collapse effect. The dielectric layer materials used in GaN MISHEMT devices are typically SiO2, Si3N4, Al2O3, NiO, and HfO2. The low dielectric constants of traditional SiO2 and Si3N4 dielectric materials make the devices susceptible to DC degradation, resulting in reduced saturation current and transconductance. High-K materials such as Al2O3 and HfO2 are gaining increasing attention. However, the dielectric layers of these GaN MISHEMTs are typically fabricated after the HEMT epitaxial structure is grown and then transferred to other devices for secondary epitaxial growth. This inevitably introduces new interface states between the dielectric layer and the (Al)GaN due to environmental and process influences, making it difficult for the MISHEMT device to effectively suppress the current collapse effect, leading to poor dynamic characteristics.

[0004] See also Figure 1The prior art discloses a technical solution for passivating the surface of a HEMT device by using h-BN as a single dielectric layer or inserting h-BN between AlGaN and a dielectric layer. However, the h-BN in the MISHEMT device disclosed in the prior art is prepared by transfer or secondary deposition after the HEMT epitaxial structure is grown. Due to the two-dimensional characteristics of h-BN, h-BN as a single dielectric layer has poor bonding with GaN and is easily detached during the process, thereby reducing the device yield. In addition, if such a structure is prepared by transfer or secondary deposition, it will inevitably be affected by the environment and process, resulting in new interface states between h-BN and AlGaN, which in turn affects device performance, makes it impossible to effectively suppress the current collapse effect, and deteriorates the dynamic characteristics of the device.

[0005] In addition, some researchers have used in-situ grown SiN to passivate the AlGaN surface, but SiN does not have two-dimensional properties, and the fixed charge at the interface between SiN and h-BN will seriously affect the threshold voltage of the device. Summary of the Invention

[0006] The main purpose of the present invention is to provide a GaN MISHEMT device and a manufacturing method thereof, so as to overcome the deficiencies in the prior art.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a method for manufacturing a GaN MISHEMT device, comprising:

[0009] Providing an epitaxial structure, the epitaxial structure comprising a channel layer and a barrier layer formed on the channel layer, wherein a two-dimensional electron gas is formed between the barrier layer and the channel layer;

[0010] In-situ epitaxial growth of a two-dimensional material passivation layer on the barrier layer;

[0011] forming a dielectric layer on the two-dimensional material passivation layer; and

[0012] A source electrode, a drain electrode and a gate electrode are manufactured, wherein the source electrode and the drain electrode are arranged on the barrier layer and are electrically connected through the two-dimensional electron gas, and the gate electrode is arranged on the dielectric layer and is located between the source electrode and the drain electrode.

[0013] The embodiment of the present invention also provides a GaN MISHEMT device manufactured by the manufacturing method.

[0014] Compared with the prior art, the advantages of the present invention include:

[0015] 1) The present invention provides a method for fabricating a GaN MISHEMT device. By in-situ growing an h-BN passivation layer, the device effectively avoids impurity adsorption on the (Al)GaN surface. The device utilizes the excellent electrical insulation properties, high thermal conductivity, high elastic modulus, lack of dangling bonds, and absence of charged impurities of two-dimensional h-BN to effectively shield AlGaN interface charges.

[0016] 2) An embodiment of the present invention provides a method for fabricating a GaN MISHEMT device. After growing the GaN HEMT epitaxial structure, a two-dimensional h-BN layer is in situ grown as a surface passivation layer, and then a secondary dielectric layer is deposited. This can prevent surface damage, shield surface dangling bonds, reduce interface state density, and effectively suppress the current collapse effect, enabling the device to obtain better DC and dynamic characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the manufacturing process principle of a GaN MISHEMT device in the prior art;

[0018] Figure 2 This is a schematic diagram of the manufacturing process principle of a GaN MISHEMT device provided in a typical embodiment of the present invention;

[0019] Figure 3 1 is a schematic structural diagram of a GaN MISHEMT device provided in a typical embodiment of the present invention;

[0020] Figure 4a-4f The present invention is a schematic diagram of the manufacturing process structure of a GaN MISHEMT device provided in a typical implementation case. DETAILED DESCRIPTION

[0021] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0022] The existing methods for producing h-BN mainly include: solid-phase reaction method, microwave molten salt method and chemical vapor deposition (CVD) method (see Cui Shiqiang, Kan Hongmin, Zhang Ning, and Ru Hongqiang, "Preparation, Application and Research Progress of Hexagonal Boron Nitride," Functional Materials, vol. 51, no. 08, pp. 8072-8077, 2020). People have formed an inherent cognition with inertial thinking and tried to use different methods to prepare h-BN and transfer it to prepare HEMT, but they did not fully realize that the interface states introduced during the transfer process will not only fail to effectively play the role of h-BN, but will affect the reliability of h-BN and a series of device performance.

[0023] The interface state problem of the MIS structure of MISHEMT devices prepared in the prior art has always been a major factor affecting device performance and a problem that researchers have always wanted to solve. Therefore, various secondary deposition methods have been improved, such as pre-deposition plasma treatment (S. Yang et al., "High-Quality Interface in Al2O3 / GaN / AlGaN / GaN MISStructures With In Situ Pre-Gate Plasma Nitridation," IEEE Electron Device Letters, vol. 34, no. 12, pp. 1497-1499, 2013.). Although some researchers have recognized the interface states introduced by secondary deposition and attempted to solve the problem from the source, for example, by in-situ growth of dielectric layers and passivation layers by MOCVD to solve this technical problem (Hu Guizhou, "Research on MIS-HEMT Devices with In-situ Growth of Dielectric Layers," Master's Degree, Xidian University, 2010).

[0024] See also Figure 2 The main purpose of the present invention is to propose a method for fabricating a GaN MISHEMT device using in-situ growth of two-dimensional h-BN as a passivation layer. After the GaN HEMT epitaxial structure is grown, a two-dimensional material such as an h-BN film is continued to be in-situ grown as a passivation layer. The advantages of the two-dimensional h-BN, such as excellent electrical insulation properties, high thermal conductivity, high elastic modulus, no dangling bonds, and no charged impurities, are utilized to shield the (Al)GaN interface charge and prevent the introduction of interface states in subsequent processes. The fabrication method of the GaN MISHEMT device provided by the embodiment of the present invention solves the problem of interface state introduction caused by secondary transfer or deposition by in-situ growing two-dimensional materials such as h-BN film as a passivation layer, thereby greatly reducing the interface state density above the AlGaN, significantly suppressing the current collapse effect, and thus obtaining better DC characteristics and dynamic characteristics. It should be noted that in the fabrication method provided by the present invention, when the epitaxial structure after in-situ h-BN film growth is transferred from the MOCVD system to the dielectric deposition system for growing other structures or dielectric layers, the AlGaN surface is covered by the in-situ grown h-BN film. Therefore, during the sample transfer process, impurities are not adsorbed or introduced, thereby maintaining a low interface state density. An embodiment of the present invention provides a method for fabricating a GaN MISHEMT device, comprising:

[0025] Providing an epitaxial structure, the epitaxial structure comprising a channel layer and a barrier layer formed on the channel layer, wherein a two-dimensional electron gas is formed between the barrier layer and the channel layer;

[0026] In-situ epitaxial growth of a two-dimensional material passivation layer on the barrier layer;

[0027] forming a dielectric layer on the two-dimensional material passivation layer; and

[0028] A source electrode, a drain electrode and a gate electrode are manufactured, wherein the source electrode and the drain electrode are arranged on the barrier layer and are electrically connected through the two-dimensional electron gas, and the gate electrode is arranged on the dielectric layer and is located between the source electrode and the drain electrode.

[0029] Furthermore, the material of the two-dimensional material passivation layer includes any one or a combination of two or more of h-BN, graphene, black phosphorus (BP), graphitic carbon nitride (g-C3N4), transition metal dichalcogenides (TMDs) and layered double hydroxides (LDHs), but is not limited thereto.

[0030] Furthermore, the thickness of the two-dimensional material passivation layer is 1-50 nm.

[0031] Furthermore, the manufacturing method specifically includes: manufacturing the epitaxial structure by vapor phase epitaxial growth, and in-situ growing the two-dimensional material passivation layer on the barrier layer.

[0032] Furthermore, the manufacturing method specifically includes: forming the dielectric layer by atomic layer deposition or chemical vapor deposition.

[0033] Furthermore, the material of the dielectric layer includes Si3N4.

[0034] Furthermore, the thickness of the dielectric layer is greater than 0 and less than or equal to 50 nm.

[0035] Furthermore, the manufacturing method specifically includes: sequentially forming the two-dimensional material passivation layer and the dielectric layer in the area outside the source and drain areas on the barrier layer, and then forming the source and drain electrodes corresponding to the source and drain areas;

[0036] Alternatively, the two-dimensional material passivation layer and the dielectric layer in the source and drain regions are first removed, and then the source and drain electrodes are correspondingly manufactured in the source and drain regions.

[0037] Furthermore, the channel layer and the barrier layer are made of materials including III-V compounds.

[0038] Furthermore, the material of the channel layer includes GaN, and the material of the barrier layer includes AlGaN.

[0039] Furthermore, the channel layer is arranged on the buffer layer, the buffer layer is arranged on the nucleation layer, and the nucleation layer is arranged on the substrate.

[0040] Furthermore, a GaN capping layer is formed on the barrier layer, and the two-dimensional material passivation layer is formed on the GaN capping layer.

[0041] The embodiment of the present invention also provides a GaN MISHEMT device manufactured by the manufacturing method.

[0042] The technical solution, its implementation process and principles will be further explained below with reference to the accompanying drawings.

[0043] In some more specific embodiments, please refer to Figure 3, a GaN MISHEMT device includes a substrate, an AlN nucleation layer, an AlGaN stress control layer, a high-resistance GaN layer, a GaN channel layer, an AlGaN barrier layer, and a GaN cap layer arranged in sequence from bottom to top, a source electrode and a drain electrode are arranged on the GaN cap layer, an h-BN passivation layer and a Si3N4 dielectric layer are stacked in sequence on the GaN cap layer between the source electrode and the drain electrode, and a gate electrode is arranged on the Si3N4 dielectric layer.

[0044] For more specific implementations, see Figure 4a-4f A method for manufacturing a GaN MISHEMT device specifically includes the following steps:

[0045] 1) Provide a Si substrate (other substrates can also be used) and clean the Si substrate:

[0046] First, the Si substrate was ultrasonically cleaned in an acetone solution for 3 minutes, then ultrasonically cleaned in an isopropanol solution for 5 minutes, and then ultrasonically cleaned in ultrapure water for 5 minutes. The residual acetone and isopropanol solution were repeatedly rinsed with ultrapure water to remove the residual acetone and isopropanol solution, and finally dried with nitrogen gas.

[0047] 2) MOCVD growth of HEMT epitaxial structure and h-BN passivation layer:

[0048] A Si substrate was placed in an MOCVD system. A 200nm nucleation layer, a 1μm AlGaN stress control layer, a 500nm high-resistance GaN layer, a 400nm GaN channel layer, a 20nm AlGaN barrier layer, and a 2nm GaN cap layer were first grown on the Si substrate. Subsequently, a 2nm h-BN passivation layer was in situ grown on the GaN cap layer.

[0049] 3) Growth of Si3N4 dielectric layer:

[0050] A 20nm Si3N4 dielectric layer is grown on the h-BN passivation layer by atomic layer deposition (ALD) or chemical vapor deposition;

[0051] 4) Mesa etching isolation:

[0052] The sample was spin-coated using a spin coater at a speed of 3000 rpm for 30 seconds. The sample was then soft-baked at a hot plate temperature of 90°C for 100 seconds. The sample after soft baking was exposed for active area isolation. Finally, the exposed sample was developed in a developer, rinsed repeatedly with ultrapure water, and dried with nitrogen.

[0053] The samples after photolithography development were isolated by mesa etching using an ICP etching device. After etching, the mask was removed by ultrasonic cleaning with acetone solution for 3 minutes, followed by ultrasonic cleaning with isopropyl alcohol solution for 5 minutes, and then repeatedly rinsed with ultrapure water and finally dried with nitrogen gas.

[0054] 5) Preparation of ohmic contact electrodes

[0055] The sample was spin-coated with a coating machine at a speed of 3000 rpm for 30 seconds. The sample was then soft-baked at a hot plate temperature of 90°C for 100 seconds. The source and drain electrode regions of the sample after the soft bake were exposed. Finally, the exposed sample was placed in a developer, repeatedly rinsed with ultrapure water, and blown dry with nitrogen.

[0056] The developed samples were treated with oxygen plasma process to remove the residual photoresist, and the treatment time was 3 min.

[0057] ICP etching equipment is used to etch away the Si3N4 dielectric layer and h-BN passivation layer in the source electrode area and the drain electrode area;

[0058] The etched sample is placed in an electron beam evaporation station, and four layers of metal, Ti / Al / Ni / Au, are sequentially deposited on the source electrode area and drain electrode area not covered by the photoresist to form the source electrode and drain electrode;

[0059] The sample after the source and drain electrode metals were evaporated was soaked in an acetone solution and ultrasonically treated for 10 minutes for stripping. It was then placed in an isopropanol solution and ultrasonically treated for 5 minutes. It was then repeatedly rinsed with ultrapure water and finally dried with nitrogen gas.

[0060] The peeled sample was placed in a rapid annealing furnace and rapidly annealed at 830°C for 30 seconds in a nitrogen atmosphere to form an ohmic contact.

[0061] 6) Preparation of gate electrode:

[0062] First, the sample with ohmic contact was ultrasonically cleaned in acetone solution for 3 minutes, then ultrasonically cleaned in isopropanol solution for 5 minutes, and then ultrasonically cleaned in ultrapure water for 5 minutes. The residual acetone and isopropanol solution were repeatedly rinsed with ultrapure water to remove the residual acetone and isopropanol solution, and finally dried with nitrogen gas.

[0063] The sample was spin-coated using a spin coater at a speed of 3000 rpm for 30 seconds. The sample was then soft-baked at a hot plate temperature of 90°C for 100 seconds. The gate region of the sample after the soft bake was exposed. Finally, the exposed sample was developed in a developer, rinsed repeatedly with ultrapure water, and dried with nitrogen.

[0064] The residual photoresist on the developed samples was removed by oxygen plasma treatment for 3 min.

[0065] The sample after oxygen plasma treatment was placed in an electron beam evaporation station, and two layers of Ni / Au metal were sequentially evaporated on the gate electrode area not covered by the photoresist to form a gate;

[0066] The metal-evaporated sample was soaked in an acetone solution and ultrasonically treated for 10 minutes for peeling, then placed in an isopropanol solution and ultrasonically treated for 5 minutes, then repeatedly rinsed with ultrapure water, and finally blown dry with nitrogen to complete the device fabrication.

[0067] Specifically, two-dimensional materials such as h-BN and (Al)GaN belong to the III-V group of wide-bandgap semiconductor materials. h-BN has gradually attracted attention in the electronics field due to its excellent electrical insulation properties, high thermal conductivity, and high elastic modulus. At the same time, two-dimensional h-BN has a two-dimensional crystal structure similar to graphene, and has no dangling bonds in the direction perpendicular to the two-dimensional plane. Using two-dimensional materials such as h-BN as the passivation layer of GaN HEMT devices can avoid the interface state problems caused by dangling bonds on the device surface.

[0068] An embodiment of the present invention provides a method for fabricating a GaN MISHEMT device. After growing a GaN HEMT epitaxial structure, a two-dimensional h-BN layer is in-situ grown as a surface passivation layer, and then a secondary dielectric layer is deposited. This can prevent surface damage, shield surface dangling bonds, reduce interface state density, and effectively suppress the current collapse effect, enabling the device to obtain better DC and dynamic characteristics.

[0069] An embodiment of the present invention provides a method for fabricating a GaN MISHEMT device. By in-situ growing an h-BN passivation layer, impurity adsorption on the (Al)GaN surface is effectively avoided. The excellent electrical insulation properties, high thermal conductivity, high elastic modulus, absence of dangling bonds, and absence of charged impurities of two-dimensional h-BN can effectively shield the AlGaN interface charge.

[0070] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A method for manufacturing a GaN MISHEMT device, characterized in that include: Fabricating an epitaxial structure, the epitaxial structure comprising a channel layer and a barrier layer formed on the channel layer, wherein a two-dimensional electron gas is formed between the barrier layer and the channel layer; In-situ epitaxial growth of a two-dimensional material passivation layer on the barrier layer, wherein the thickness of the two-dimensional material passivation layer is 1-50 nm and the material of the two-dimensional material passivation layer is h-BN; Forming a dielectric layer on the two-dimensional material passivation layer, wherein the dielectric layer is made of Si3N4 and has a thickness greater than 0 and less than or equal to 50 nm; as well as A source electrode, a drain electrode and a gate electrode are manufactured, wherein the source electrode and the drain electrode are arranged on the barrier layer and are electrically connected through the two-dimensional electron gas, and the gate electrode is arranged on the dielectric layer and is located between the source electrode and the drain electrode.

2. The production method according to claim 1, characterized in that Specifically, the method includes: producing the epitaxial structure by vapor phase epitaxial growth, and in-situ growing the two-dimensional material passivation layer on the barrier layer.

3. The production method according to claim 1, characterized in that Specifically include: The dielectric layer is formed by atomic layer deposition or chemical vapor deposition.

4. The production method according to claim 1, characterized in that Specifically include: The two-dimensional material passivation layer and the dielectric layer are sequentially formed in the area outside the source and drain areas on the barrier layer, and then the source and drain electrodes are correspondingly formed in the source and drain areas; Alternatively, the two-dimensional material passivation layer and the dielectric layer in the source and drain regions are first removed, and then the source and drain electrodes are correspondingly manufactured in the source and drain regions.

5. The production method according to claim 1, characterized in that: The channel layer and the barrier layer are made of materials including III-V compounds.

6. The production method according to claim 5, characterized in that: The material of the channel layer includes GaN, and the material of the barrier layer includes AlGaN.

7. The production method according to claim 1, characterized in that: The channel layer is disposed on a buffer layer, the buffer layer is disposed on a nucleation layer, and the nucleation layer is disposed on a substrate.

8. The production method according to claim 1, characterized in that: A GaN capping layer is further formed on the barrier layer, and the two-dimensional material passivation layer is formed on the GaN capping layer.

9. A GaN MISHEMT device fabricated by the method according to any one of claims 1 to 8.

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