T-type P-GaN gate GaN radio frequency HEMT device and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor devices, and particularly discloses a T-type P-GaN gate GaN radio frequency HEMT device and a preparation method thereof, the device structure sequentially comprises a substrate, a composite buffer layer, a channel layer, an isolation layer, a barrier layer and a P-GaN cap layer from bottom to top, and Mg is doped in the P-GaN cap layer. The method comprises the following steps of: depositing gate electrode metal above a P-GaN cap layer, etching a part of the P-GaN cap layer between a gate electrode and a source electrode and between the gate electrode and a drain electrode, performing H injection on the P-GaN cap layer, re-passivating Mg impurities in the P-GaN cap layer, and changing P-GaN into high resistance, thereby realizing a T-type P-GaN gate electrode and preparing a P-GaN gate GaN radio frequency HEMT (High Electron Mobility Transistor). According to the scheme, a smaller P-GaN gate pin length can be realized, the frequency characteristic of the device is improved, in addition, the problem of surface damage to the surface of the barrier layer when the P-GaN is completely removed is also avoided, and the power performance and the reliability of the device are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a T-type P-GaN gate GaN radio frequency HEMT device and a preparation method thereof. Background Art

[0002] As a typical material of the third-generation semiconductor, GaN has the advantages of large bandgap (3.4eV), high electron mobility, and high electron saturation velocity, so it has broad application potential in the fields of next-generation radio frequency devices, power and electrical devices, etc. Due to the unique polarization effect of the III-GalN heterojunction structure, even when the material is not intentionally doped, a two-dimensional electron gas (2DEG) with high concentration and high electron mobility can be formed at the junction interface. Therefore, the high electron mobility transistor (HEMT) prepared based on the GaN heterojunction structure has the characteristics of high breakdown voltage, low on-resistance, high switching frequency, and small size, making it the preferred solution for the research and development of high-performance, low-power, and low-cost microwave devices, especially in the fields of wireless charging, lidar, electric vehicles, and intelligent transportation.

[0003] Since the concentration of two-dimensional electron gas at the interface of nitride heterojunction is very high and has been formed when the heterojunction structure is formed, traditional GaN-based HEMT devices often behave as depletion mode because they cannot completely deplete the two-dimensional electron gas under the gate, that is, the threshold voltage is negative, and a negative bias voltage needs to be designed to turn off the device, which is very inconvenient for the safe operation of the device and the simplification of circuit design. Enhancement-mode devices can avoid the risk of false start-up and reduce the complexity of gate drive, which has greater advantages. P-GaN gate technology in enhancement-mode devices has gained widespread attention because it can obtain advantages such as stable threshold voltage, strong process controllability, and suitability for large-scale production and commercial use. It is called the most promising method for preparing enhancement-mode HEMT devices. However, this technology still has shortcomings, because direct etching of the P-GaN cap layer between the gate source and the gate drain will cause surface damage to the surface of the barrier layer. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a T-type P-GaN gate GaN radio frequency HEMT device and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] One of the purposes of the present invention is to provide a T-type P-GaN gate GaN radio frequency HEMT device, which comprises a substrate, a composite buffer layer, a channel layer, an isolation layer, a barrier layer and a P-GaN gate in order from bottom to top; the barrier layer, the channel layer and the composite buffer layer are made of group III nitride semiconductors, namely GaN, AlN, InN or a multi-component compound composed of two or more of them; a two-dimensional electron gas is formed at the interface between the channel layer and the barrier layer, which serves as a channel of the GaN radio frequency HEMT device; the P-GaN gate is formed by high-temperature annealing and activation of a Mg-doped GaN cap layer, and has a T-shaped shape; a gate electrode metal is arranged above the P-GaN gate; a source electrode and a drain electrode are arranged on both sides of the P-GaN gate, and the source electrode and the drain electrode form an ohmic contact with the two-dimensional electron gas; a high resistance layer is provided between the source electrode and the P-GaN gate, and between the drain electrode and the P-GaN gate, and the high resistance layer is formed by H injection and annealing of the P-GaN cap layer.

[0007] Preferably, the substrate is one of silicon, silicon carbide, sapphire and diamond.

[0008] Furthermore, the composite buffer layer is composed of a nucleation layer, a transition layer and a buffer layer arranged from bottom to top; the material of the nucleation layer is AlN or GaN, with a thickness of 100-300nm; the material of the transition layer is AlGaN, with a thickness of 200-1500nm; the material of the buffer layer is AlGaN or GaN, with a thickness of 100-5000nm.

[0009] Preferably, the material of the channel layer is GaN or InGaN, and the thickness is 50-500 nm.

[0010] Preferably, the barrier layer is made of one of AlGaN, InGaN, AlN and InAlGaN, and has a thickness of 5-40 nm.

[0011] Preferably, the isolation layer is made of AlN and has a thickness of 0.5-2 nm.

[0012] Preferably, the material of the gate electrode metal layer is one of Ni / Au / Ni alloy, Ti / Au / Ni alloy and TiN / Au / Ni alloy.

[0013] Preferably, the material of the source electrode and the drain electrode is one of Ti / Al / Ni / Au alloy, Ta / Al / W alloy, Ti / Al / Ti / TiN alloy and Ta / Al / Ni / Au alloy.

[0014] Preferably, the concentration of Mg in the P-GaN gate is 1×10 18 -1×10 20 cm -3The height of the P-GaN gate is 10-150nm; the high resistance layer is formed by injecting H into the P-GaN cap layer and annealing it, and the thickness is 2-100nm.

[0015] The second object of the present invention is to provide a method for preparing a T-type P-GaN gate GaN radio frequency HEMT device, comprising the following steps:

[0016] Step 1: Cleaning the substrate surface;

[0017] Step 2: sequentially growing a composite buffer layer, a channel layer, an isolation layer, a barrier layer and a Mg-doped GaN cap layer on the substrate;

[0018] Step 3: annealing the Mg-doped GaN cap layer at high temperature so that Mg is activated to form a P-GaN cap layer;

[0019] Step 4: Isolate the countertop;

[0020] Step 5: Using a photoresist mask and photolithography process, the P-GaN cap layer is etched in some areas, the source electrode and the drain electrode are deposited, and annealed to form an ohmic contact with the two-dimensional electron gas;

[0021] Step 6: Using a photoresist mask and a photolithography process, a gate electrode metal layer is deposited on the surface of the P-GaN cap layer;

[0022] Step 7: Using the gate electrode metal layer as a mask, the P-GaN cap layer between the gate electrode metal layer and the source electrode and between the gate electrode metal layer and the drain electrode is etched, H is injected, and annealing is performed. The Mg impurities in the P-GaN cap layer between the gate electrode metal layer and the source electrode and between the gate electrode metal layer and the drain electrode, as well as the P-GaN cap layer under the gate electrode metal layer are passivated and converted into a high resistance layer, thereby finally forming a T-shaped P-GaN gate.

[0023] Compared with the prior art, the present invention adopts H injection into the P-GaN cap layer under the P-GaN gate. At this time, part of the P-GaN cap layer will become high-resistance GaN, thereby solving the problem of surface damage caused by direct etching; at the same time, due to H diffusion, a smaller P-GaN gate foot length can be achieved, thereby improving the frequency characteristics of the HEMT device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a T-type P-GaN gate GaN radio frequency HEMT device of the present invention.

[0025] Figure 2 This is a flow chart of the method for preparing a T-type P-GaN gate GaN radio frequency HEMT device of the present invention: (a)-(g) are the manufacturing steps in sequence.

[0026] Reference numerals in the figure: 1-substrate; 2-composite buffer layer; 3-channel layer; 4-isolation layer; 5-barrier layer; 6-P-GaN cap layer; 61-P-GaN gate; 62-high resistance layer; 7-source electrode; 8-drain electrode; 9-gate electrode. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0028] like Figure 1 As shown, this embodiment exemplarily shows a T-type P-GaN gate GaN RF HEMT device, which includes a substrate 1, a composite buffer layer 2, a channel layer 3, an isolation layer 4, a barrier layer 5 and a P-GaN gate 61 from bottom to top; the barrier layer 5, the channel layer 3, and the composite buffer layer 2 are made of group III nitride semiconductors, namely GaN, AlN, InN or a multi-component compound composed of two or more of them; a two-dimensional electron gas is formed at the interface between the channel layer 3 and the barrier layer 5, which serves as the channel of the GaN RF HEMT device; the P-GaN gate 61 is formed by high-temperature annealing activation of the Mg-doped GaN cap layer 6, and has a T-shaped shape; a gate electrode metal 9 is arranged above the P-GaN gate 61; a source electrode 7 and a drain electrode 8 are arranged on both sides of the P-GaN gate 61, and the source electrode 7 and the drain electrode 8 form an ohmic contact with the two-dimensional electron gas. A high resistance layer 62 is provided between the source electrode 7 and the P-GaN gate 61 and between the drain electrode 8 and the P-GaN gate 61 . The high resistance layer 62 is formed by H implantation and annealing of the P-GaN cap layer 6 .

[0029] In this embodiment, the substrate 1 is made of one of silicon, silicon carbide, sapphire and diamond.

[0030] In this embodiment, the composite buffer layer 2 includes three layers, namely, a nucleation layer 21, a transition layer 22, and a buffer layer 23 from bottom to top. The material of the nucleation layer is AlN or GaN with a thickness of 100-300nm; the material of the transition layer is AlGaN with a thickness of 200-1500nm; the material of the buffer layer is AlGaN or GaN with a thickness of 100-5000nm.

[0031] In this embodiment, the channel layer 3 is made of GaN or InGaN, and has a thickness of 50-500 nm.

[0032] In this embodiment, the isolation layer 4 is made of AlN with a thickness of 0.5-2 nm, which can reduce the direct interaction and defect generation between the channel layer and the barrier layer and play a buffering role.

[0033] In this embodiment, the barrier layer 5 is made of one of AlGaN, InGaN, AlN, and InAlGaN, and has a thickness of 5-40 nm. It forms a heterojunction with the channel layer, and forms a two-dimensional electron gas channel on one side of the channel layer due to the polarization effect.

[0034] In this embodiment, the metal layer of the gate electrode 6 is Ni / Au / Ni, Ti / Au / Ni, or TiN / Au / Ni;

[0035] In this embodiment, the metal layer of the source electrode 7 and the drain electrode 8 is any one of Ti / Al / Ni / Au, Ta / Al / W, Ti / Al / Ti / TiN, and Ta / Al / Ni / Au.

[0036] In this embodiment, the P-GaN gate 61 is formed by annealing and activating the Mg-doped GaN cap layer 6 at high temperature, wherein the concentration of Mg is 1×10 18 -1×10 20 cm -3 , the shape is T-shaped and the height is 10-150nm.

[0037] In this embodiment, the high resistance layer 62 is formed by H implantation and annealing of the P-GaN cap layer 6, and has a thickness of 2-100 nm.

[0038] Example 1

[0039] In this embodiment, the substrate 1 is made of P-type silicon with a thickness of 1000 μm; the composite buffer layer 2 is divided into three parts, namely, a 200 nm AlN nucleation layer 21, an 800 nm AlGaN transition layer 22 (the Al component is gradually changed from 0.75 to 0.15), and a 3000 nm GaN buffer layer 23; the material of the channel layer 3 is GaN with a thickness of 200 nm; the isolation layer 4 is made of AlN with a thickness of 0.5 nm; the barrier layer 5 is made of AlGaN, in which the aluminum component is 0.21, and the thickness of the barrier layer 5 is 15 nm; the thickness of the P-GaN cap layer 6 is 70 nm, and the doping impurity is Mg, and the doping concentration is 2.5×10 19 cm -3 ; The source electrode 7 and the drain electrode 8 are both made of Ti / Al / Ni / Au alloy, and the gate electrode metal layer 9 is made of Ni / Au / Ni alloy.

[0040] Reference Figure 2 , the specific preparation process is as follows:

[0041] Step 1: The P-type silicon substrate 1 is selected for surface cleaning, such as Figure 2 As shown in (a) in .

[0042] At a high temperature of 1000° C., hydrogen is introduced into the reaction chamber to remove pollutants on the surface of the substrate 1 and to form a microscopic step structure on the surface of the substrate 1 so as to facilitate the subsequent epitaxial growth of various epitaxial layers.

[0043] Step 2: On the substrate 1, a composite buffer layer 2, a channel layer 3, an isolation layer 4, a barrier layer 5, and a P-GaN cap layer 6 are sequentially grown by metal organic chemical vapor deposition. Figure 2 As shown in (b) in .

[0044] The composite buffer layer 2 includes three layers. First, a 200nm AlN nucleation layer 21 is grown on the substrate by MOCVD method at a low temperature of 600°C, then the temperature is raised to 1000°C, and an 800nm ​​transition layer 22 is grown on the nucleation layer by MOCVD method, and finally a 3000nm GaN buffer layer 23 is grown on the transition layer 22.

[0045] Step 3: Grow a 200 nm GaN channel layer 3 on the composite buffer layer 2 by MOCVD at 1000°C.

[0046] Then, an isolation layer 4 with a thickness of 0.5 nm is epitaxially grown on the channel layer 3 , and an AlGaN barrier layer 5 with a thickness of 15 nm is epitaxially grown on the isolation layer 4 .

[0047] Step 4: Then, a GaN cap layer 6 is grown on the barrier layer and doped with Mg at a concentration of 2.5×10 19 cm -3 , and annealing is performed to form a P-GaN cap layer 6.

[0048] Step 5: Clean the epitaxial wafer. The work mainly includes cleaning organic and inorganic substances. Use acetone solution to ultrasonically clean the sample for 5 minutes, then put the sample into isopropanol solution for ultrasonic cleaning for 2 minutes to remove the residual acetone solution on the surface of the sample. Finally, blow dry with a nitrogen gun.

[0049] Step 6: Isolate the countertop, such as Figure 2 As shown in (c) in .

[0050] Specifically, the inductively coupled plasma etching technology (ICP) is used to etch away the entire P-GaN cap layer 6, the AlGaN barrier layer 5, the AlN isolation layer 4, and part of the GaN channel layer 3. The etching depth is 180nm, and the terrace should have neat edges and steep side walls.

[0051] Step 7: Use photolithography to make a photoresist mask, and use reactive ion etching equipment and technology (RIE) to etch away the P-GaN cap layer 6 without photoresist shielding, and etch into a table with neat edges and steep side walls.

[0052] Step 8: The source electrode 7 and the drain electrode 8 are made by electron beam evaporation. The multilayer metal used is Ti / Al / Ni / Au with a thickness of 20 / 120 / 40 / 50nm. Finally, a rapid annealing is performed in a nitrogen atmosphere at 850°C for 30s to make the source electrode 7 and the drain electrode 8 form an ohmic contact with the barrier layer, such as Figure 2 As shown in (d) in .

[0053] Step 9: Use a photolithography process to make a photoresist mask to expose the area where the gate electrode metal layer 9 needs to be made.

[0054] Then, the gate electrode metal layer 9 of Ni / Au / Ni combination is prepared by electron beam evaporation technology, wherein the thickness of Ni / Au / Ni is 50 / 300 / 10 nm, and the gate electrode metal layer 9 is formed after stripping. Figure 2 As shown in (e) in .

[0055] Step 10: Using the prepared gate electrode metal layer 9, source electrode 7 and drain electrode 8 as masks, the gate electrode metal layer 9, source electrode 7, and the P-GaN cap layer 6 between the gate electrode metal layer 9 and the drain electrode 8 are etched by reactive ion etching equipment and technology (RIE) to a depth of 40nm. Figure 2 As shown in (f) in .

[0056] Step 11: H is injected into the etched area and annealed to partially passivate it into high-resistance GaN 62. Due to the annealing process, H will diffuse and the actual effective gate length will be reduced, thus realizing the preparation of T-type P-GaN gate GaN RF HEMT, such as Figure 2 As shown in (g) in .

[0057] Example 2

[0058] like Figure 2 As shown, a T-type P-GaN gate GaN RF HEMT device is prepared by the same method as in Example 1, except that: a silicon carbide material is selected as the substrate 1, which is P-type doped and has a thickness of 300 μm; the composite buffer layer 2 is divided into three parts, namely, a 200 nm GaN nucleation layer 21, a 500 nm Al 0.55 Ga 0.25 N transition layer 22, 1000nm Al 0.05 Ga 0.25 N buffer layer 23; channel layer 3 is made of GaN with a thickness of 300nm; isolation layer 4 is made of AlN with a thickness of 1.5nm; barrier layer 5 is made of Al 0.15 GaN, in which the aluminum content is 0.15 and the thickness is 15nm; the thickness of the P-GaN cap layer 6 is 60nm, and the doping impurity is Mg, and the doping concentration is 5×10 19 cm -3; The source electrode 7 and the drain electrode 8 are both Ta / Al / Ni / Au alloys, and the gate electrode metal layer 9 is Ti / Au / Ni alloy.

[0059] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A T-type P-GaN gate GaN RF HEMT device, characterized in that: The device comprises, from bottom to top, a substrate (1), a composite buffer layer (2), a channel layer (3), an isolation layer (4), a barrier layer (5) and a P-GaN gate (61); the barrier layer (5), the channel layer (3) and the composite buffer layer (2) are made of group III nitride semiconductors, namely GaN, AlN, InN or a multi-component compound composed of two or more thereof; a two-dimensional electron gas is formed at the interface between the channel layer (3) and the barrier layer (5) as a channel of the GaN radio frequency HEMT device; the P-GaN gate (61) is a GaN cap doped with Mg. The layer (6) is formed by high-temperature annealing activation and has a T-shaped shape; a gate electrode metal (9) is arranged above the P-GaN gate (61); a source electrode (7) and a drain electrode (8) are arranged on both sides of the P-GaN gate (61), and the source electrode (7) and the drain electrode (8) form an ohmic contact with the two-dimensional electron gas; a high resistance layer (62) is provided between the source electrode (7) and the P-GaN gate (61) and between the drain electrode (8) and the P-GaN gate (61), and the high resistance layer (62) is formed by H injection into the P-GaN cap layer (6) and annealing.

2. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The substrate (1) is one of silicon, silicon carbide, sapphire and diamond.

3. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The composite buffer layer (2) is composed of a nucleation layer (21), a transition layer (22) and a buffer layer (23) arranged from bottom to top; the material of the nucleation layer (21) is AlN or GaN, with a thickness of 100-300 nm; the material of the transition layer (22) is AlGaN, with a thickness of 200-1500 nm; the material of the buffer layer (23) is AlGaN or GaN, with a thickness of 100-5000 nm.

4. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The material of the channel layer (3) is GaN or InGaN, and the thickness is 50-500nm.

5. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The material of the barrier layer (5) is one of AlGaN, InGaN, AlN and InAlGaN, and has a thickness of 5-40 nm.

6. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The material of the isolation layer (4) is AlN, and the thickness is 0.5-2 nm.

7. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The material of the gate electrode metal layer (9) is one of Ni / Au / Ni alloy, Ti / Au / Ni alloy and TiN / Au / Ni alloy.

8. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The material of the source electrode (7) and the drain electrode (8) is one of a Ti / Al / Ni / Au alloy, a Ta / Al / W alloy, a Ti / Al / Ti / TiN alloy, and a Ta / Al / Ni / Au alloy.

9. The T-type P-GaN gate GaN RF HEMT device according to claim 1, characterized in that: The concentration of Mg in the P-GaN gate (61) is 1×10 18 -1×10 20 cm -3 The height of the P-GaN gate (61) is 10-150 nm; the high resistance layer (62) is formed by H implantation and annealing of the P-GaN cap layer (6), and has a thickness of 2-100 nm.

10. A method for preparing a T-type P-GaN gate GaN RF HEMT device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Cleaning the surface of the substrate (1); Step 2: sequentially growing a composite buffer layer (2), a channel layer (3), an isolation layer (4), a barrier layer (5) and a Mg-doped GaN cap layer (6) on the substrate (1); Step 3: performing high temperature annealing on the Mg-doped GaN cap layer (6) so that Mg is activated to form a P-GaN cap layer (6); Step 4: Isolate the countertop; Step 5: using a photoresist mask and a photolithography process, etching the P-GaN cap layer (6) in a partial area, depositing a source electrode and a drain electrode, annealing, and forming an ohmic contact with the two-dimensional electron gas; Step 6: using a photoresist mask and a photolithography process, depositing a gate electrode metal layer (9) on the surface of the P-GaN cap layer (6); Step 7: Using the gate electrode metal layer (9) as a mask, the P-GaN cap layer (6) between the gate electrode metal layer (9) and the source electrode (7) and between the gate electrode metal layer (9) and the drain electrode (8) is etched, H is injected, and annealing is performed. The Mg impurities in the P-GaN cap layer (6) between the gate electrode metal layer (9) and the source electrode (7) and between the gate electrode metal layer (9) and the drain electrode (8), as well as the P-GaN cap layer (6) below the gate electrode metal layer (9) are passivated and converted into a high resistance layer (62), and finally a T-shaped P-GaN gate (61) is formed.

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