A thin barrier GaN HEMT device with reverse blocking capability

Abstract

This invention belongs to the field of semiconductor technology and relates to a thin-barrier GaNHEMT device with reverse blocking capability. The drain of the device in this invention is divided into two parts: one part is an ohmic contact structure for forward current conduction, and the other part is a MIS structure to achieve reverse blocking and reduce reverse leakage current. This invention uses a 3-6nm thin AlGaN barrier layer, avoiding the etching damage caused by etching the AlGaN barrier layer to achieve zero bias voltage depletion in conventional barriers. Simultaneously, a charge recovery layer is introduced to restore the channel 2DEG density in the thin barrier structure, giving the device better current capability. The thin-barrier GaNHEMT device with reverse blocking capability proposed in this invention has advantages such as simple fabrication, low reverse leakage current, and high withstand voltage.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor devices, specifically relating to a thin barrier GaN HEMT device with reverse blocking capability. Background Technology

[0002] GaN-based high electron mobility transistors (HEMTs) have great potential for application in radio frequency and power electronics due to their superior device performance. However, the performance of current GaN-based devices still falls short of theoretical performance. While much research focuses on improving the blocking performance of GaN HEMTs in the forward turn-off state, the reverse blocking capability is also crucial in many cases. A major application of high electron mobility transistors with reverse blocking capability is bidirectional switching. Due to the inherent properties of GaN material, bidirectional switches constructed using GaN HEMTs with reverse blocking capability offer higher power density, faster switching speeds, lower conduction losses, and smaller circuit area.

[0003] Currently, there is relatively little research on this topic both domestically and internationally. The reported GaN RB-MISHEMT (GaN-based reverse blocking metal–insulator–semiconductor high electron mobility transistor) achieves reverse blocking by adding a MIS drain near the ohmic drain. This structure has advantages such as simple fabrication, low reverse leakage current, and high breakdown voltage. However, in order to properly deplete the two-dimensional electron gas in the channel below the MIS gate and MIS drain at zero bias, the AlGaN barrier layer under the MIS gate and MIS drain needs to be etched to below 6nm. However, the poor repeatability of the AlGaN etching process can also introduce new interface states.

[0004] To address the obstacles hindering the development of GaN devices and to better balance the various performance aspects of GaN HEMT devices with reverse blocking capabilities, further structural optimization is essential. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a thin-barrier GaN HEMT device with reverse blocking capability. Reverse blocking is achieved through MIS drain, and a thin barrier structure is used to avoid etching of the AlGaN barrier layer. Then, a charge recovery layer is introduced to restore the channel 2DEG density in the thin barrier structure.

[0006] The technical solution adopted by this invention to solve the above problems is: a thin barrier GaN HEMT device with reverse blocking capability, such as... Figure 6As shown, from bottom to top, the structure includes a substrate 01, a GaN buffer layer 02 above the substrate 01, a GaN channel layer 03 above the GaN buffer layer 02, and an AlGaN barrier layer 04 above the GaN channel layer 03. The GaN channel layer 03 and the AlGaN barrier layer 04 form a heterojunction, generating a two-dimensional electron gas at the heterojunction interface. A charge recovery layer 05 is deposited on the AlGaN barrier layer 04, and the required gate trenches and drain trenches are etched on the charge recovery layer 05. A dielectric layer 06 is deposited on the bottom and sidewalls of the two trenches and on the upper surface of the charge recovery layer 05. A drain ohmplate is located at one end of the upper surface of the GaN channel layer 03. In the GaN channel layer 03, a drain ohmic metal 07 has its side surface in contact with the AlGaN barrier layer 04 and the dielectric layer 06. A drain trench is adjacent to the drain ohmic metal 07 but separated by the dielectric layer 06. At the left end of the GaN channel layer 03, there is a source ohmic metal 08. The side surface of the source ohmic metal 08 is in contact with the AlGaN barrier layer 04, the charge recovery layer 05, and the dielectric layer 06. A drain trench is adjacent to the source ohmic metal 08 but separated by the charge recovery layer 05 and the dielectric layer 06. A MIS drain metal 10 is deposited in the drain trench, and one end of the MIS drain metal 10 extends to cover the upper surface of the drain ohmic metal 07. A gate metal 09 is deposited in the gate trench.

[0007] Furthermore, the substrate 01 can be one of sapphire, Si, SiC, and GaN.

[0008] Furthermore, the AlGaN barrier layer 04 is a thin barrier layer with a thickness of 3-6 nm.

[0009] Furthermore, the charge recovery layer 05 is LPCVD SiN or in-situ SiN.

[0010] Furthermore, the dielectric layer 06 can be Al2O3, HfO2, etc.

[0011] Furthermore, the material of the MIS drain metal 10 can be W, Cu / W, or Ni / Au.

[0012] Furthermore, the MIS drain metal 10 is directly short-circuited with the drain ohmic metal 07.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a novel GaN HEMT structure with reverse blocking capability. This structure introduces a MIS drain to achieve reverse blocking and reduce reverse leakage current. It also uses a thin barrier structure to reduce the complexity of the process and avoid etching damage caused by etching the AlGaN barrier layer. Then, the channel 2DEG density in the thin barrier structure is restored through a charge recovery layer. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the device proposed in this invention after the growth of a thin barrier 04.

[0015] Figure 2 This is a schematic diagram of the structure of the device proposed in this invention after the deposition of charge recovery layer 05.

[0016] Figure 3 This is a schematic diagram of the structure of the device proposed in this invention after the gate trench and drain trench have been etched.

[0017] Figure 4 This is a schematic diagram of the structure of the device proposed in this invention after the deposition of dielectric layer 06.

[0018] Figure 5 This is a schematic diagram of the structure of the device proposed in this invention after the deposition of drain-source ohmic metal.

[0019] Figure 6 This is a schematic diagram of the complete structure of the thin barrier GaN HEMT device with reverse blocking capability proposed in this invention.

[0020] Figure 7 This is the equivalent circuit of the thin barrier GaN HEMT device with reverse blocking capability proposed in this invention.

[0021] Figure 8 The transfer characteristic curve (logarithmic) of the thin barrier GaN HEMT device with reverse blocking capability proposed in this invention.

[0022] Figure 9 The output characteristic curves of the thin barrier GaN HEMT device with reverse blocking capability proposed in this invention are shown.

[0023] Figure 10 The thin barrier GaN HEMT device with reverse blocking capability proposed in this invention is in V GS 5V, V DS The variation of reverse leakage current from -50V to -100V.

[0024] Figure 11 This is the breakdown characteristic curve of the thin barrier GaN HEMT device with reverse blocking capability proposed in this invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] The thin barrier GaN HEMT device with reverse blocking capability proposed in this invention is as follows: Figure 6As shown, its structure from bottom to top includes: a substrate 01; a GaN buffer layer 02 above the substrate 01; a GaN channel layer 03 above the GaN buffer layer 02; a 3-6nm AlGaN barrier layer 04 above the GaN channel layer 03; a charge recovery layer 05 covering the AlGaN barrier layer 04, on which the required gate trenches and drain trenches are etched; a dielectric layer 06 is deposited on the bottom, sidewalls, and upper surface of the charge recovery layer 05 of the two trenches; a drain ohmic metal 07 is located at the right end of the GaN channel layer 03, and a source ohmic metal 08 is located at the left end; a MIS drain metal 10 is deposited on the dielectric 06 in the trench next to the drain ohmic metal 07, and a gate metal 09 is deposited on the dielectric 06 in the other trench.

[0027] The working principle of the thin barrier GaN HEMT with reverse blocking capability proposed in this invention is as follows:

[0028] When a typical GaN HEMT device is reverse biased, the gate will turn on in the forward direction as the reverse voltage of the drain and source increases, and the resulting large gate current can easily burn out the device. Figure 6 and Figure 7 These are a schematic diagram and an equivalent circuit of the present invention. The device introduces a MIS structure drain near the ohmic drain electrode. This structure can block reverse current when the gate is on and the drain-source is reverse biased. The embodiments of the present invention provide breakdown characteristic curves as shown below. Figure 11 As shown, the device possesses reverse withstand voltage capability. Furthermore, the MIS structure offers advantages such as simple manufacturing, low reverse leakage current, and high withstand voltage. For example... Figure 10 As shown, the device is in V GS 5V, V DS The reverse leakage current remains at 10 when the voltage is between -50V and -100V. -9 The order of magnitude is on the order of A / mm.

[0029] For GaN MISHEMTs with conventional barriers, to deplete the 2DEG beneath the MIS structure at zero bias, the AlGaN barrier layer needs to be etched to below 6 nm. However, the repeatability of AlGaN etching processes is not good and can introduce new interface state traps. The thin barrier structure used in this invention completely avoids these problems. The thin barrier weakens the piezoelectric polarization effect between the AlGaN barrier layer and the GaN channel, significantly reducing the 2DEG density. Figure 2 As shown, by depositing a charge recovery layer of a certain thickness on the AlGaN barrier layer, the channel 2DEG density can be restored, the device on-resistance reduced, and the device given better current capability. Then, by removing part of the charge recovery layer and etching out gate and drain trenches, the 2DEG beneath the MIS gate and drain is depleted at zero bias, as shown in the diagram. Figure 3 As shown.

Claims

1. A thin barrier GaN HEMT device with reverse blocking capability, comprising, from bottom to top, a substrate (01), a GaN buffer layer (02) above the substrate (01), a GaN channel layer (03) above the GaN buffer layer (02), and an AlGaN barrier layer (04) above the GaN channel layer (03); the GaN channel layer (03) and the AlGaN barrier layer (04) form a heterojunction, and a 2DEG is formed at the heterojunction interface; a charge recovery layer (05) is deposited on the AlGaN barrier layer (04), and the required gate trench and drain trench are etched on the charge recovery layer (05); then a dielectric layer (06) is deposited, the dielectric layer (06) covering the bottom and sidewalls of the two trenches and the entire upper surface of the charge recovery layer (05); a right end of the upper surface of the GaN channel layer (03) has A drain ohmic metal (07) is provided, the side of which is in contact with the AlGaN barrier layer (04) and the dielectric layer (06). A drain trench is adjacent to the drain ohmic metal (07) but separated by the dielectric layer (06). A source ohmic metal (08) is provided at the left end of the GaN channel layer (03), the side of which is in contact with the AlGaN barrier layer (04), the charge recovery layer (05) and the dielectric layer (06). A drain trench is adjacent to the source ohmic metal (08) but separated by the charge recovery layer (05) and the dielectric layer (06). A MIS drain metal (10) is deposited in the drain trench, and one end of the MIS drain metal (10) extends to cover the upper surface of the drain ohmic metal (07). A gate metal (09) is deposited in the gate trench.

2. The thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The thickness of the AlGaN barrier layer (04) is 3-6 nm.

3. A thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The charge recovery layer (05) is LPCVD SiN or in-situ SiN.

4. A thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The dielectric layer (06) is Al2O3 or HfO2.

5. A thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The material used for the MIS drain metal (10) is W, Cu / W or Ni / Au.

6. A thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The drain metal (10) of the MIS is directly short-circuited with the drain ohmic metal (07).

7. A thin barrier GaN HEMT device with reverse blocking capability according to claim 1, characterized in that, The MIS structure formed by the drain metal (10), dielectric layer (06), and heterojunction acts as a reverse blocking diode when a reverse voltage is applied to the drain source.

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