Gallium nitride HEMT device with embedded electrode structure

Abstract

This invention discloses a gallium nitride (GaN) HEMT device with an embedded electrode structure, comprising an epitaxial structure of the HEMT device. The epitaxial structure includes a GaN channel layer, an AlGaN barrier layer, and a dielectric cap layer, arranged sequentially from bottom to top. An embedded groove is formed on the epitaxial structure, extending into the AlGaN barrier layer. A first titanium layer, an aluminum layer, and a second titanium layer are sequentially deposited within the embedded groove to form a titanium / aluminum / titanium sandwich metal structure for the source and drain. A low-resistance TiN interface layer is formed between the first titanium layer and the AlGaN barrier layer in the epitaxial structure. An aluminum layer is located between the first and second titanium layers, forming a low-resistance current path. The second titanium layer is disposed on the top surface corresponding to the source or drain, forming a diffusion barrier and anti-oxidation structure. Compared with the prior art, the titanium / aluminum / titanium sandwich metal structure of the source and drain in this invention significantly improves the conduction characteristics and effectively suppresses high-temperature diffusion and oxidation of aluminum.

Description

Technical Field

[0001] This utility model relates to the semiconductor field, and more particularly to the embedded electrode structure of gallium nitride HEMT devices. Background Technology

[0002] Gallium nitride high electron mobility transistors (GaN HEMTs) are power devices based on gallium nitride (GaN), a wide-bandgap semiconductor material. Due to their excellent electrical performance, they have shown great potential in high-frequency, high-power, and high-temperature applications.

[0003] GaN HEMT devices possess the following advantages: high electron mobility, high saturation drift velocity, and high breakdown field strength. The high electron mobility and high saturation drift velocity enable GaN HEMTs to operate at higher frequencies and faster switching speeds, withstand higher voltages, making them suitable for high-voltage applications. They also offer smaller chip areas and higher power density, contributing to system miniaturization. Therefore, GaN HEMT devices, with their superior performance, are gradually replacing traditional silicon devices and show great promise in various fields such as communications, power supplies, and automotive.

[0004] GaN HEMTs typically consist of a substrate, a buffer layer, a GaN epitaxial layer, and an AlGaN barrier layer. A two-dimensional electron gas (2DEG) is formed at the AlGaN-GaN interface due to polarization effects, serving as a conductive channel. GaN HEMT electrodes include gate (G), source (S), and drain (D) electrodes. In existing technologies, GaN HEMT source and drain electrodes often employ a Ti / Al / Ni / Au multilayer structure, which suffers from the following drawbacks: high contact resistance; the Ni / Au layer causes current path detours; and the measured contact resistivity (Rc) is typically >1×10⁻⁶. -6 Ω·cm 2 The process is complex and requires the deposition of additional diffusion barrier layers (such as Pt and Mo), which increases the complexity and cost of the deposition and annealing processes.

[0005] Therefore, there is an urgent need for a gallium nitride HEMT device that can solve the above problems. Utility Model Content

[0006] The purpose of this invention is to provide a gallium nitride HEMT device with an embedded electrode structure, wherein the source and drain adopt a titanium / aluminum / titanium sandwich metal structure, which significantly improves the conduction characteristics and can effectively suppress the high-temperature diffusion and oxidation of aluminum.

[0007] To achieve the above objectives, this utility model provides a gallium nitride HEMT device with an embedded electrode structure, including an epitaxial structure of the HEMT device. The epitaxial structure includes a gallium nitride channel layer, an AlGaN barrier layer, and a dielectric cap layer arranged sequentially from bottom to top. An embedded groove is formed on the epitaxial structure, extending into the AlGaN barrier layer. A first titanium layer, an aluminum layer, and a second titanium layer are sequentially deposited in the embedded groove to form a source and drain of a titanium / aluminum / titanium sandwich metal structure. A low-resistance TiN interface layer is formed between the first titanium layer and the AlGaN barrier layer in the epitaxial structure. The aluminum layer is located between the first titanium layer and the second titanium layer to form a low-resistance current path. The second titanium layer is disposed on the top surface corresponding to the source or drain and forms a diffusion barrier and anti-oxidation structure.

[0008] Preferably, the thickness of the first titanium layer is 10-50 nm.

[0009] Preferably, the thickness of the aluminum layer is 300-500 nm.

[0010] Preferably, the thickness of the second titanium layer is 50-100 nm.

[0011] Preferably, the embedded groove has an inverted trapezoidal structure with a small bottom and a large opening, which provides structural stability.

[0012] Preferably, an aluminum nitride insertion layer is further disposed between the gallium nitride channel layer and the AlGaN barrier layer.

[0013] Preferably, the epitaxial structure further includes a high-resistivity gallium nitride layer disposed under the gallium nitride channel layer.

[0014] Preferably, the gallium nitride HEMT device with embedded electrode structure further includes a growth substrate disposed on the underside of the epitaxial structure to support the epitaxial structure, wherein the growth substrate is a gallium nitride substrate, a sapphire substrate, a silicon carbide substrate, or a silicon substrate.

[0015] Preferably, a gate electrode deposited on the dielectric cap layer is further formed on the epitaxial structure. The gate electrode comprises a first titanium layer, an aluminum layer, and a second titanium layer to form a titanium / aluminum / titanium sandwich metal structure. This design allows the source, gate, and drain electrodes to be configured as a single structure, enabling simultaneous deposition and saving process time.

[0016] Preferably, the dielectric cap layer is a gallium nitride cap layer or a silicon nitride cap layer.

[0017] Compared with existing technologies, this invention directly deposits a titanium / aluminum / titanium sandwich metal structure as the source and drain on the AlGaN barrier layer. A low-resistance TiN interface layer is formed between the first titanium layer and the AlGaN barrier layer in the epitaxial structure, and an aluminum layer forms a low-resistance current path in the middle. The second titanium layer is disposed on the top surface corresponding to the source or drain, forming a diffusion barrier and anti-oxidation structure. This not only achieves low-resistance contact, significantly improves conduction characteristics, and enhances device power conversion efficiency, but also simplifies the structure, reduces the metal stack structure, reduces material costs, eliminates the Ni / Au layer, and avoids electromigration problems. Furthermore, by placing the second titanium layer on top as a diffusion barrier and anti-oxidation structure, this invention can effectively suppress the high-temperature diffusion and oxidation of aluminum without the need for additional diffusion barrier layer deposition. In addition, this invention only uses the titanium / aluminum / titanium sandwich metal structure as the source and drain, without setting other metal layers, eliminating the need for high-temperature annealing; low-temperature annealing is sufficient. This prevents the formation of intermetallic compounds or surface roughness caused by Au diffusion between metal layers during high-temperature annealing, resulting in high device reliability. Furthermore, by setting the source and drain as an embedded structure, this invention can effectively reduce current crowding effects and improve high-temperature diffusion and oxidation. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the gallium nitride HEMT device with an embedded electrode structure according to this invention.

[0019] Figure 2 This is a structural diagram of the source and drain of the gallium nitride HEMT device of this utility model. Detailed Implementation

[0020] To explain in detail the technical content, structural features, objectives and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0021] refer to Figure 1 This utility model discloses a gallium nitride HEMT device 100 with an embedded electrode structure, including an epitaxial structure 20 of the HEMT device. The epitaxial structure 20 includes a gallium nitride channel layer 21, an AlGaN barrier layer 22, and a dielectric cap layer 23 arranged sequentially from bottom to top. An embedded groove 30 extending into the AlGaN barrier layer 22 is formed on the epitaxial structure 20. (Reference) Figure 2The embedded groove 30 is sequentially deposited with a first titanium layer 301, an aluminum layer 302, and a second titanium layer 303 to form a titanium / aluminum / titanium sandwich metal structure for the source 31 and drain 32. A low-resistance TiN interface layer is formed between the first titanium layer 301 and the AlGaN barrier layer 22 in the epitaxial structure 20. The aluminum layer 302 is located between the first titanium layer 301 and the second titanium layer 303 to form a low-resistance current path. The second titanium layer 303 is disposed on the top surface corresponding to the source 31 or drain 32 and forms a diffusion barrier and anti-oxidation structure.

[0022] The dielectric cap layer 23 is a gallium nitride cap layer or a silicon nitride cap layer. The gallium nitride channel layer 21 is a u-GaN layer.

[0023] The first titanium layer 301 has a thickness of 10-50 nm. The aluminum layer 302 has a thickness of 300-500 nm. The second titanium layer 303 has a thickness of 50-100 nm.

[0024] refer to Figure 1 and Figure 2 The embedded groove has an inverted trapezoidal structure with a small bottom and a large opening, which makes the structure stable.

[0025] refer to Figure 1 An aluminum nitride insertion layer 24 is further disposed between the gallium nitride channel layer 21 and the AlGaN barrier layer 22. The epitaxial structure 20 also includes a high-resistivity gallium nitride layer 25 disposed beneath the gallium nitride channel layer 21. The high-resistivity gallium nitride layer 25 is a C-doped C-GaN layer, wherein the C doping concentration is 5E18-2E19 cm⁻¹. -3 .

[0026] refer to Figure 1 The gallium nitride HEMT device 100 with an embedded electrode structure also includes a growth substrate 11 disposed below the epitaxial structure to support it. The growth substrate 11 can be a gallium nitride substrate, sapphire substrate, silicon carbide substrate, or silicon substrate, etc. A gallium nitride buffer layer 10 is also disposed on the growth substrate 11. Specifically, an aluminum nitride buffer layer 12 is disposed between the growth substrate 11 and the gallium nitride buffer layer 10.

[0027] refer to Figure 1 The epitaxial structure 20 also has a gate 33 deposited on the dielectric cap layer. The gate 33 includes a first titanium layer 301, an aluminum layer 302, and a second titanium layer 303 to form a titanium / aluminum / titanium sandwich metal structure. This design allows the source, gate, and drain to be set as the same structure, which can be deposited and formed simultaneously, saving process time.

[0028] Specifically, the aluminum nitride buffer layer 10 has a thickness of 23 nm, and the gallium nitride buffer layer 10 has a thickness of 850 nm. The high-resistivity gallium nitride layer 25 has a thickness of 600-1200 nm, preferably 700 nm; the gallium nitride channel layer 21 has a thickness of 200-300 nm, preferably 250 nm; the aluminum nitride insertion layer 24 has a thickness of 1 nm; the AlGaN barrier layer 22 has a thickness of 15-30 nm, preferably 25 nm; and the dielectric cap layer 23 has a thickness of 2 nm.

[0029] In this invention, a titanium / aluminum / titanium sandwich metal structure is used as the source electrode 31 and the drain electrode 32. After deposition, annealing at a temperature of 500-600℃ in an N2 / H2 mixed gas for 30-120 seconds achieves low-resistance contact. The embedded groove 30 is formed by plasma etching, and the deposited titanium / aluminum / titanium sandwich metal structure ensures that the sidewalls of the embedded groove 30 are covered with metal.

[0030] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the scope of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A gallium nitride HEMT device having an embedded electrode structure, characterized by: The epitaxial structure includes a gallium nitride channel layer, an AlGaN barrier layer, and a dielectric cap layer arranged sequentially from bottom to top. An embedded groove is formed on the epitaxial structure that extends into the AlGaN barrier layer. A first titanium layer, an aluminum layer, and a second titanium layer are deposited sequentially in the embedded groove to form a source and drain of a titanium / aluminum / titanium sandwich metal structure. A low-resistivity TiN interface layer is formed between the first titanium layer and the AlGaN barrier layer in the epitaxial structure. The aluminum layer is located between the first titanium layer and the second titanium layer to form a low-resistivity current path. The second titanium layer is disposed on the top surface corresponding to the source or drain and forms a diffusion barrier and anti-oxidation structure.

2. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: The thickness of the first titanium layer is 10-50 nm.

3. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: The thickness of the aluminum layer is 300-500 nm.

4. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: The thickness of the second titanium layer is 50-100 nm.

5. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: the gallium nitride HEMT device is a gallium nitride HEMT device with an embedded gate structure. The embedded groove has an inverted trapezoidal structure with a small bottom and a large opening.

6. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: An aluminum nitride insertion layer is also disposed between the gallium nitride channel layer and the AlGaN barrier layer.

7. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: The epitaxial structure also includes a high-resistivity gallium nitride layer disposed under the gallium nitride channel layer.

8. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: It also includes a growth substrate disposed on the underside of the epitaxial structure to support the epitaxial structure, wherein the growth substrate is a gallium nitride substrate, a sapphire substrate, a silicon carbide substrate or a silicon substrate.

9. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: A gate electrode, deposited on the dielectric cap layer, is also formed on the epitaxial structure. The gate electrode comprises a first titanium layer, an aluminum layer, and a second titanium layer to form a titanium / aluminum / titanium sandwich metal structure.

10. The gallium nitride HEMT device with an embedded electrode structure of claim 1, wherein: The dielectric cap layer is a gallium nitride cap layer or a silicon nitride cap layer.

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