A gallium nitride transistor device and method of fabrication

Abstract

The application discloses a gallium nitride transistor device and a preparation method, and belongs to the semiconductor field.The gallium nitride HEMT device comprises a substrate 1, a buffer layer 2, a GaN layer 3, an AlGaN layer 4, an in-situ ScN passivation protection layer 5 arranged in sequence from bottom to top, a source electrode 8 and a drain electrode 6 which form ohmic contact with the AlGaN layer 4 through the in-situ ScN passivation protection layer 5, and a gate electrode 7 which forms Schottky contact with the AlGaN layer 4 through the in-situ ScN passivation protection layer 5.The passivation layer is formed by using ScN material, on the one hand, the lattice constant of ScN and AlGaN is more matched, so that the defects on the surface of the device are reduced, on the other hand, the experimental results prove that the application can effectively alleviate the reduction of two-dimensional electron gas, and the problems of current collapse effect and dynamic resistance rise are improved.

Description

Technical Field

[0001] This invention relates to gallium nitride HEMT devices based on in-situ ScN passivation layers and their fabrication methods, belonging to the field of semiconductors. Background Technology

[0002] GaN material is a typical representative of third-generation semiconductors. It has attracted much attention due to its excellent properties such as wide bandgap, strong critical breakdown electric field, high electron mobility, and high temperature resistance. It is very suitable for manufacturing electronic devices with high temperature, high frequency, and high power.

[0003] Compared to other semiconductor materials, AlGaN / GaN heterojunctions can achieve a high concentration of two-dimensional electron gas through spontaneous polarization and piezoelectric polarization effects without additional doping, making them easy to fabricate into HEMT (High Electron Mobility Transistor) devices. In conventional HEMT devices, the AlGaN surface is easily oxidized by oxygen in the air, leading to surface defects. In AlGaN / GaN HEMTs, electrons in the channel are excited by the electric field, tunnel into the device surface, and are trapped by electron traps, forming virtual gates. This depletes the two-dimensional electron gas in the channel, causing performance degradation issues such as current collapse and increased dynamic resistance. Summary of the Invention

[0004] To address issues such as current collapse and dynamic resistance rise, this invention provides a gallium nitride transistor device and its fabrication method, the technical solution of which is as follows:

[0005] The first objective of this invention is to provide a gallium nitride HEMT device, comprising, from bottom to top, a substrate 1, a buffer layer 2, a GaN layer 3, an AlGaN layer 4, and an in-situ ScN passivation protection layer 5, wherein a source 8 and a drain 6 pass through the in-situ ScN passivation protection layer 5 to form an ohmic contact with the AlGaN layer 4, and a gate 7 passes through the in-situ ScN passivation protection layer 5 to form a Schottky contact with the AlGaN layer 4.

[0006] Optionally, the thickness of the in-situ ScN passivation protective layer 5 is 2 to 300 nm.

[0007] Optionally, the substrate 1 is made of AlN grown in a magnetron sputtering apparatus.

[0008] Optionally, the source 8 and drain 6 and the gate 6 are one or more combinations of Ti, Al, Ni and Au.

[0009] Optionally, the material of the buffer layer 2 is one or more combinations of AlN, GaN, AlGaN and InGaN.

[0010] Optionally, the thickness of the buffer layer 2 is 2 to 4 μm.

[0011] Optionally, the thickness of the GaN layer is 1–3 μm.

[0012] Optionally, the thickness of the AlGaN layer is 20–30 nm.

[0013] A second objective of this invention is to provide a method for fabricating a gallium nitride HEMT device, comprising:

[0014] Step 1: Provide a substrate 1;

[0015] Step 2: Grow a buffer layer 2, a GaN layer 3, an AlGaN layer 4, and an in-situ ScN passivation protective layer 5 sequentially on the substrate 1;

[0016] Step 3: Etch the regions corresponding to the drain 6 and source 8 on the ScN passivation protective layer 5. Stop etching when the AlGaN layer 4 is reached.

[0017] Step 4: Deposit the drain 6 and source 8 in the two regions obtained by etching in Step 3, respectively. The drain 6 and source 8 pass through the in-situ ScN passivation protective layer 5 and form ohmic contacts with the AlGaN layer 4.

[0018] Step 5: Etch the region corresponding to the gate 7 on the ScN passivation protection layer 5. Stop etching when the AlGaN layer 4 is reached.

[0019] Step 6: Deposit a gate 7 in the area etched in Step 5. The gate 7 passes through the in-situ ScN passivation protection layer 5 and forms a Schottky contact with the AlGaN layer 4.

[0020] Optionally, step 2 involves growing the in-situ ScN passivation protective layer 5 in a metal-organic chemical vapor deposition (MOCVD) apparatus.

[0021] Optionally, steps 3 and 5 may involve dry etching using Cl2 or BCl3, and incorporating O2 or SF6.

[0022] The beneficial effects of this invention are:

[0023] This invention provides a gallium nitride HEMT device and its fabrication method based on an in-situ ScN passivation protective layer. By using ScN material to form the passivation layer, on the one hand, the lattice constants of ScN and AlGaN are more matched, thereby reducing defects on the device surface. On the other hand, experimental results show that this invention can effectively alleviate the reduction of two-dimensional electron gas and improve the problems of current collapse effect and dynamic resistance increase. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the HEMT device of the present invention.

[0026] Figure 2 This invention presents output characteristic curves of ScN layers grown at different temperatures.

[0027] Figure 3 These are output characteristic curves of devices with ScN layers of different thicknesses according to the present invention.

[0028] Figure 4 These are output characteristic curves of devices with passivation layers made of different materials. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Example 1:

[0031] This embodiment provides a gallium nitride HEMT device based on an in-situ ScN passivation protection layer. See [link to documentation]. Figure 1 The device, from bottom to top, consists of a substrate 1, a buffer layer 2, a GaN layer 3, an AlGaN layer 4, and an ScN passivation layer 5. The drain 6, gate 7, and source 8 penetrate the ScN passivation layer and contact the AlGaN layer. The fabrication method of this device is as follows:

[0032] Step 1: Provide a substrate 1;

[0033] The substrate 1 is made of AlN grown in a magnetron sputtering apparatus.

[0034] Step 2: Grow a buffer layer 2, a GaN layer 3, an AlGaN layer 4, and an in-situ ScN passivation protective layer 5 sequentially on substrate 1;

[0035] Among them, the buffer layer 2 is made of InGaN, with a growth temperature of 900℃ and a thickness of 2μm; the GaN layer has a growth temperature of 900℃ and a thickness of 2μm; the AlGaN layer has a growth temperature of 950℃ and a thickness of 25nm; the in-situ ScN passivation protective layer 5 is grown in a metal-organic chemical vapor deposition (MOCVD) device at a growth temperature of 1000℃ and a thickness of 200nm.

[0036] Step 3: Etch the regions of drain 6, gate 7, and source 8 on the ScN passivation protective layer 5;

[0037] In this embodiment, Cl2 is incorporated into SF6 for dry etching. When etching reaches the AlGaN layer, SF6 reacts with it to form an AlF3 layer, preventing Cl2 from etching further downwards. At this point, the etching is stopped.

[0038] Step 4: Deposit drain 6 and source 8;

[0039] In this embodiment, Ti / Al / Ni / Au (20nm / 160nm / 55nm / 90nm) is deposited in the corresponding etched area, and then rapidly annealed in N2 at 850°C for 1 min to form an ohmic contact, resulting in drain 6 and source 8;

[0040] Step 5: Etch the gate region;

[0041] Dry etching is performed on the ScN passivation layer corresponding to the gate using Cl2 (doped with SF6). When etching reaches the AlGaN layer, SF6 reacts with it to generate an AlF3 layer, preventing Cl2 from etching further down. At this point, etching is stopped.

[0042] Step 6: Deposit gate 7;

[0043] Ni / Au (50nm / 90nm) is deposited in the area corresponding to the etched gate 7 to form a Schottky contact.

[0044] Example 2: The growth temperature of the in-situ ScN passivation protective layer 5 in Example 1 was changed to 800℃, and the rest was the same as in Example 1.

[0045] Example 3: The growth temperature of the in-situ ScN passivation protective layer 5 in Example 1 was changed to 1200℃, and the rest was the same as in Example 1.

[0046] Example 4: The thickness of the in-situ ScN passivation protective layer 5 in Example 1 was changed to 2nm, and the rest was the same as in Example 1.

[0047] Example 5: The thickness of the in-situ ScN passivation protective layer 5 in Example 1 was changed to 100 nm, and the rest was the same as in Example 1.

[0048] Example 6: The thickness of the in-situ ScN passivation protective layer 5 in Example 1 was changed to 300 nm, and the rest was the same as in Example 1.

[0049] Example 7: The in-situ ScN passivation protective layer 5 in Example 1 was replaced with an AlN passivation layer, and the growth temperature was 1300℃.

[0050] Example 8: The in-situ ScN passivation protective layer 5 in Example 1 was replaced with a SiO2 passivation layer, and the growth temperature was 1100℃.

[0051] Example 9: Remove the in-situ ScN passivation protective layer 5 from Example 1.

[0052] To illustrate the beneficial effects of the HEMT device of the present invention, a performance comparison test was conducted on the above embodiments.

[0053] The output characteristics of the gallium nitride transistor devices formed in Examples 1, 2, and 3 were simulated and tested, and the results are as follows: Figure 2 As shown.

[0054] The output characteristics of the gallium nitride transistor devices formed in Examples 1, 4, 5, and 6 were simulated and tested, and the results are as follows: Figure 3 As shown.

[0055] The output characteristics of the gallium nitride transistor devices formed in Examples 1, 7, 8, and 9 were simulated and tested, and the results are as follows: Figure 4 As shown.

[0056] In the figure, the horizontal axis represents the drain voltage, and the vertical axis represents the source-drain current, i.e., the output current. With sufficient input drain voltage, the output current is larger, which means that the current collapse effect is improved. The reciprocal of the slope during the rising phase of the curve is the dynamic resistance. The larger the slope, the better the dynamic resistance rise problem is.

[0057] Figure 2 This indicates that ScN exhibits superior performance at a growth temperature of 1000℃ compared to other growth temperatures. Figure 3 This indicates that the thicker the ScN passivation layer, the better the performance, but the performance improvement becomes less significant when the passivation layer thickness exceeds 200nm. Figure 4 This indicates that adding a passivation layer can indeed improve the current collapse effect and dynamic resistance rise of the device, and the in-situ ScN passivation protection layer of the present invention has superior performance compared with other common materials.

[0058] Some steps in the embodiments of the present invention can be implemented using software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a gallium nitride HEMT device, characterized in that, The gallium nitride HEMT device includes, from bottom to top, a substrate (1), a buffer layer (2), a GaN layer (3), an AlGaN layer (4), and an in-situ ScN passivation protection layer (5). The in-situ ScN passivation protection layer (5) is an ScN layer grown in a metal-organic chemical vapor deposition (MOCVD) device. The source (8) and drain (6) pass through the in-situ ScN passivation protection layer (5) to form an ohmic contact with the AlGaN layer (4), and the gate (7) passes through the in-situ ScN passivation protection layer (5) to form a Schottky contact with the AlGaN layer (4). The substrate (1) is made of AlN grown in a magnetron sputtering apparatus; The source (8) and drain (6) and the gate (7) are one or more combinations of Ti, Al, Ni and Au; The material of the buffer layer (2) is one or more combinations of AlN, GaN, AlGaN and InGaN; The thickness of the buffer layer (2) is 2~4μm; The thickness of the GaN layer is 1–3 μm; The method includes: Step 1: Provide a substrate (1); Step 2: Grow a buffer layer (2), a GaN layer (3), an AlGaN layer (4), and an in-situ ScN passivation protection layer (5) sequentially on the substrate (1). Step 3: Etch the regions corresponding to the drain (6) and source (8) on the ScN passivation protective layer (5). Stop etching when the AlGaN layer (4) is reached. Step 4: Deposit the drain (6) and source (8) in the two regions obtained by etching in Step 3, respectively. The drain (6) and source (8) pass through the in-situ ScN passivation protection layer (5) and form an ohmic contact with the AlGaN layer (4); Step 5: Etch the region corresponding to the gate (7) on the ScN passivation protection layer (5). When etching reaches the AlGaN layer (4), stop etching. Step 6: Deposit a gate (7) in the area etched in Step 5. The gate (7) passes through the in-situ ScN passivation protection layer (5) and forms a Schottky contact with the AlGaN layer (4). In step 2, the in-situ ScN passivation protective layer (5) is grown in a metal-organic chemical vapor deposition (MOCVD) device at a growth temperature of 1000℃ and the thickness of the in-situ ScN passivation protective layer (5) is 200nm. Steps 3 and 5 involve dry etching using Cl2 or BCl3, and incorporating O2 or SF6.

Images