Composite gate GaN-based HEMT and preparation method and application thereof

Abstract

The application discloses a composite gate GaN-based HEMT and a preparation method and application thereof. The composition of the composite gate GaN-based HEMT comprises a substrate, a GaN buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a passivation layer which are sequentially arranged in layers, and further comprises a source electrode, a composite gate electrode and a drain electrode. The preparation method of the composite gate GaN-based HEMT comprises the following steps: 1) sequentially epitaxially growing the GaN buffer layer, the GaN channel layer, the AlN insertion layer, the AlGaN barrier layer and the passivation layer on the substrate; 2) depositing the source electrode and the drain electrode and then performing annealing treatment; and 3) depositing a comb-shaped gate and a T-shaped gate field plate to obtain the composite gate GaN-based HEMT. The composite gate GaN-based HEMT has the advantages of good withstand voltage performance, high stability and reliability, and the preparation method is simple and feasible, and the composite gate GaN-based HEMT is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a composite gate GaN-based HEMT, its fabrication method, and its applications. Background Technology

[0002] Gallium nitride (GaN) has characteristics such as a large bandgap, high breakdown field strength, and significant polarization effect. GaN-based high electron mobility transistors (HEMTs), represented by AlGaN / GaNHEMT, have advantages such as high electron saturation velocity, high electron mobility, and strong breakdown field (up to 3.4MV / cm), making them particularly suitable for power electronics applications under high temperature and high pressure conditions.

[0003] In industrial applications, the reliability of GaN-based HEMTs is particularly critical, and the breakdown voltage (V) is crucial. br AlN (AlN)-based HEMTs are one of the important indicators for evaluating their reliability. A typical GaN-based HEMT (comprising a substrate, GaN buffer layer, GaN channel layer, AlN insertion layer, AlGaN barrier layer, and passivation layer stacked sequentially, and also including a source, gate, and drain. The source and drain form ohmic contacts with the AlGaN barrier layer, and the gate forms a Schottky contact with the AlGaN barrier layer) is a lateral device. In the off-state with a high drain voltage, the strong polarization charge induces a strong electric field at the edge of the gate near the drain. The presence of the strong electric field peak causes the actual breakdown voltage of the device to be much lower than its theoretical breakdown voltage. Therefore, the application of typical GaN-based HEMTs in high voltage applications is greatly limited.

[0004] Currently, the most common method to improve the breakdown voltage performance of GaN-based HEMTs is to introduce field plate structures such as gate field plates, source field plates, drain field plates, and composite field plates. Wespel et al. reported the relationship between composite field plate structures and breakdown voltage and on-resistance. The use of field plate structures helps to reduce the peak value of the strong electric field on the drain side of the device gate, thereby improving the off-state breakdown voltage of the device (M.Wespel et al.Trapping Effects at the Drain Edge in 600V GaN-on-SiHEMTs[J].in IEEE Transactions on Electron Devices,2016,63(2):598-605). However, the introduction of field plate structures also leads to an increase in the dispersion effect and on-resistance of the device, which significantly weakens the high-power gain efficiency of the device and ultimately leads to the degradation of the frequency characteristics and switching characteristics of the device. In addition, the current fabrication process of composite field plates is relatively complex, requiring multiple depositions of passivation layers and field plate metals. Impurities and other defects introduced during this process will undoubtedly directly affect the reliability of the device.

[0005] Therefore, developing a GaN-based HEMT that combines good pressure resistance, stability, and reliability is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a composite gate GaN-based HEMT, its preparation method, and its application.

[0007] The technical solution adopted in this invention is:

[0008] A composite gate GaN-based HEMT comprises a substrate, a GaN buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a passivation layer stacked sequentially, and further comprises a source, a composite gate, and a drain. The source forms an ohmic contact with the AlGaN barrier layer and is in contact with the passivation layer. The composite gate comprises a comb-shaped gate and a T-shaped gate field plate covering the comb-shaped gate. The comb-shaped gate comprises a plurality of comb teeth arranged parallel in a vertical direction. The comb teeth penetrate the passivation layer and form a Schottky contact with the AlGaN barrier layer. The drain forms an ohmic contact with the AlGaN barrier layer and is in contact with the passivation layer.

[0009] Preferably, the substrate is a Si substrate.

[0010] Preferably, the length of the comb teeth is 0.2μm to 0.9μm, the width is 0.1μm to 1μm, and the spacing between the comb teeth is 0.5μm to 1μm (the spaces between the comb teeth are filled with a passivation layer material).

[0011] Preferably, the length of the T-shaped gate field plate extending toward the source electrode is 1 μm to 5 μm.

[0012] Preferably, the length of the T-shaped gate plate extending toward the drain electrode is 1 μm to 5 μm.

[0013] Preferably, the thickness of the GaN buffer layer is 2μm to 5μm.

[0014] Preferably, the thickness of the GaN channel layer is 0.1 μm to 0.3 μm.

[0015] Preferably, the thickness of the AlN insertion layer is 1 nm to 10 nm.

[0016] Preferably, the mass percentage of Al in the AlGaN barrier layer is 15% to 35%.

[0017] Preferably, the thickness of the AlGaN barrier layer is 15nm to 30nm.

[0018] Preferably, the passivation layer comprises at least one of Si3N4, SiO2, Al2O3, and AlN.

[0019] Preferably, the thickness of the passivation layer is 0.5 μm to 1.3 μm.

[0020] Preferably, the source electrode comprises Ti, Al, Ni and Au.

[0021] Preferably, the comb-shaped grid comprises Ni and Au.

[0022] Preferably, the T-shaped grid plate comprises Ni and Au.

[0023] Preferably, the drain electrode is composed of Ti, Al, Ni and Au.

[0024] A method for preparing a composite gate GaN-based HEMT as described above includes the following steps:

[0025] 1) A GaN buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a passivation layer are epitaxially grown sequentially on the substrate using metal-organic chemical vapor deposition (MOCVD).

[0026] 2) The source and drain fabrication regions are etched on the passivation layer using inductively coupled plasma etching (ICP), and then the source and drain are deposited using electron beam evaporation deposition (PVD), followed by annealing.

[0027] 3) The composite gate fabrication region is etched on the passivation layer using inductively coupled plasma etching, and then a comb gate and a T-type gate field plate are deposited using electron beam evaporation deposition to obtain the composite gate GaN-based HEMT.

[0028] Preferably, the substrate described in step 1) has been cleaned before use.

[0029] Preferably, the cleaning process involves: placing the substrate sequentially in acetone, ethanol, and deionized water for ultrasonic cleaning for 10 to 30 minutes, then removing it and rinsing the surface with deionized water, followed by drying with an N2 gun.

[0030] Preferably, the annealing in step 2) is carried out in an N2 atmosphere, the annealing temperature is 800℃~900℃, and the annealing time is 20s~40s.

[0031] An electronic device comprising the aforementioned composite gate GaN-based HEMT.

[0032] The beneficial effects of the present invention are: the composite gate GaN-based HEMT of the present invention has the advantages of good voltage resistance, high stability and reliability, and its preparation method is simple and feasible, making it suitable for large-scale industrial application.

[0033] Specifically:

[0034] 1) The composite gate GaN-based HEMT of the present invention is provided with a composite gate composed of a comb gate and a T-shaped gate field plate. The multiple gate teeth of the comb gate can disperse the strong polarization charge under a single gate, reduce the charge density effect under the gate, and reduce the strong electric field peak on the gate-drain side under the high drain voltage state in the off state. In addition, the edge of the T-shaped gate field plate introduces another electric field peak, which further reduces the strong electric field peak on the gate-drain side. The two work together to extend the width of the depletion region expansion and significantly improve the breakdown voltage of the device.

[0035] 2) The composite gate in the GaN-based HEMT of the present invention has a simple and feasible fabrication process. Compared with the traditional composite field plate, it simplifies the fabrication process, avoids defects such as impurities introduced by the fabrication of the composite field plate, and has little impact on the on-resistance, resulting in good device stability and reliability. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a composite gate GaN-based HEMT as an example.

[0037] Figure 2 This is a schematic diagram of the structure of a GaN-based HEMT as a comparative example.

[0038] Figure labeling: 10, substrate; 20, GaN buffer layer; 30, GaN channel layer; 40, AlN insertion layer; 50, AlGaN barrier layer; 60, passivation layer; 70, source; 80, composite gate; 801, comb gate; 802, T-type gate field plate; 90, drain; 100, gate.

[0039] Figure 3 The diagram shows a comparison of the electric field distribution of a composite gate GaN-based HEMT used in the example and a GaN-based HEMT used in the comparative example.

[0040] Figure 4 The diagram shows a comparison of the breakdown characteristics of a composite gate GaN-based HEMT used in the embodiment and a GaN-based HEMT used in the comparative example. Detailed Implementation

[0041] The present invention will be further explained and described below with reference to specific embodiments.

[0042] Example:

[0043] A composite gate GaN-based HEMT (structural schematic shown in Figure 1) Figure 1As shown, the structure comprises a substrate 10, a GaN buffer layer 20, a GaN channel layer 30, an AlN insertion layer 40, an AlGaN barrier layer 50, and a passivation layer 60 stacked sequentially, and also includes a source 70, a composite gate 80, and a drain 90; the source 70 forms an ohmic contact with the AlGaN barrier layer 50 and is in contact with the passivation layer 60; the composite gate 80 comprises a comb gate 801 and a T-shaped gate field plate 802 covering the comb gate 801; the comb gate 801 comprises three comb teeth arranged in parallel along the vertical direction; the comb teeth penetrate the passivation layer 60 and form a Schottky contact with the AlGaN barrier layer 50; the drain 90 forms an ohmic contact with the AlGaN barrier layer 50 and is in contact with the passivation layer 60.

[0044] The preparation method of the above-mentioned composite gate GaN-based HEMT includes the following steps:

[0045] 1) The Si substrate was ultrasonically cleaned in acetone, ethanol and deionized water for 20 min in sequence. Then it was taken out and rinsed with deionized water. Then it was dried with an N2 gun. Then, the following layers were epitaxially grown on the Si substrate in sequence using MOCVD: a GaN buffer layer with a thickness of 2 μm, a GaN channel layer with a thickness of 0.1 μm, an AlN insertion layer with a thickness of 2 nm, an AlGaN barrier layer with a thickness of 20 nm (Al mass percentage of 25%) and a passivation layer with a thickness of 0.5 μm (composed of Si3N4).

[0046] 2) The source and drain regions were etched on the passivation layer using the ICP method, and then Ti / Al / Ni / Au metals were deposited sequentially using the PVD method to form the source and drain. The layers were then annealed at 850℃ for 30s in an N2 atmosphere (to form ohmic contacts).

[0047] 3) The composite gate fabrication region is etched on the passivation layer using the ICP method, and then Ni / Au metal is deposited sequentially using the PVD method to form a comb-shaped gate and a T-shaped gate field plate. The length of the comb teeth is 0.3 μm, the width is 1 μm, the spacing between the comb teeth is 1 μm (the space between the comb teeth is filled with Si3N4), the length of the T-shaped gate field plate extending towards the source is 2 μm, and the length of the T-shaped gate field plate extending towards the drain is 2 μm, thus obtaining the composite gate GaN-based HEMT.

[0048] Comparative example:

[0049] A GaN-based HEMT (typical structure; structural schematic shown) Figure 2As shown, the structure comprises a substrate 10, a GaN buffer layer 20, a GaN channel layer 30, an AlN insertion layer 40, an AlGaN barrier layer 50, and a passivation layer 60 stacked sequentially, and also includes a source 70, a gate 100, and a drain 90; the source 70 forms an ohmic contact with the AlGaN barrier layer 50 and is in contact with the passivation layer 60; the gate 100 penetrates the passivation layer 60 and forms a Schottky contact with the AlGaN barrier layer 50; the drain 90 forms an ohmic contact with the AlGaN barrier layer 50 and is in contact with the passivation layer 60.

[0050] The preparation method of the above GaN-based HEMT includes the following steps:

[0051] 1) The Si substrate was ultrasonically cleaned in acetone, ethanol and deionized water for 20 min in sequence. Then it was taken out and rinsed with deionized water. Then it was dried with an N2 gun. Then, the following layers were epitaxially grown on the Si substrate in sequence using MOCVD: a GaN buffer layer with a thickness of 2 μm, a GaN channel layer with a thickness of 0.1 μm, an AlN insertion layer with a thickness of 2 nm, an AlGaN barrier layer with a thickness of 20 nm (Al mass percentage of 25%) and a passivation layer with a thickness of 0.5 μm (composed of Si3N4).

[0052] 2) The source and drain regions were etched on the passivation layer using the ICP method, and then Ti / Al / Ni / Au metals were deposited sequentially using the PVD method to form the source and drain. The layers were then annealed at 850℃ for 30s in an N2 atmosphere (to form ohmic contacts).

[0053] 3) The gate fabrication region is etched on the passivation layer using the ICP method, and then the gate is formed by sequentially depositing metal Ni / Au using the PVD method, thus obtaining GaN-based HEMT.

[0054] Performance testing:

[0055] 1) A comparison of the electric field distributions of the composite gate GaN-based HEMT in the embodiment and the GaN-based HEMT in the comparative example is shown in the figure below. Figure 3 As shown.

[0056] Depend on Figure 3 It can be seen that: in the comparative GaN-based HEMT (typical structure), during off-state breakdown, there is a strong electric field peak on the side of the gate biased towards the drain. This peak exceeds the limiting electric field strength of GaN material, causing the device to break down prematurely. In the composite gate GaN-based HEMT of the embodiment, during off-state breakdown, due to the comb-shaped gate structure with multiple comb teeth, the strong electric field caused by the original single gate charge density effect is dispersed under the gate. In addition, the introduction of the T-shaped gate field plate introduces another electric field peak at the edge of the T-shaped gate field plate, and the two electric field peaks are equal. The combination of the comb-shaped gate structure and the T-shaped gate field plate structure expands the depletion region and effectively increases the breakdown voltage.

[0057] 2) A comparison of the breakdown characteristics of the composite gate GaN-based HEMT in the embodiment and the GaN-based HEMT in the comparative example is shown in the figure below. Figure 4 As shown.

[0058] Depend on Figure 4 It can be seen that when both devices are completely off, the drain voltage corresponding to the drain current of the device reaching 0.0010 A / mm is taken as the breakdown voltage. It can be seen that the breakdown voltage of the composite gate GaN-based HEMT in the embodiment is increased by 302.44% compared with the GaN-based HEMT in the comparative example.

[0059] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A composite gate GaN-based HEMT, characterized in that, The composition includes a substrate, a GaN buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a passivation layer stacked sequentially, and also includes a source, a composite gate, and a drain; the source forms an ohmic contact with the AlGaN barrier layer and is in contact with the passivation layer. The composite gate comprises a comb-shaped gate and a T-shaped gate field plate covering the comb-shaped gate; the comb-shaped gate comprises multiple comb teeth arranged in parallel along the horizontal direction between the source and the drain; the length of the comb teeth is 0.2μm to 0.9μm, the width is 0.1μm to 1μm, and the spacing between the comb teeth is 0.5μm to 1μm; the composition of the comb-shaped gate comprises Ni and Au; the comb teeth penetrate the passivation layer and form a Schottky contact with the AlGaN barrier layer; the drain forms an ohmic contact with the AlGaN barrier layer and is in contact with the passivation layer.

2. The composite gate GaN-based HEMT according to claim 1, characterized in that: The length of the T-shaped gate plate extending towards the source is 1 μm to 5 μm; the length of the T-shaped gate plate extending towards the drain is 1 μm to 5 μm.

3. The composite gate GaN-based HEMT according to claim 1 or 2, characterized in that: The thickness of the GaN buffer layer is 2μm to 5μm; the thickness of the GaN channel layer is 0.1μm to 0.3μm; and the thickness of the AlN insertion layer is 1nm to 10nm.

4. The composite gate GaN-based HEMT according to claim 1 or 2, characterized in that: The Al mass percentage content in the AlGaN barrier layer is 15% to 35%.

5. The composite gate GaN-based HEMT according to claim 4, characterized in that: The thickness of the AlGaN barrier layer is 15nm to 30nm.

6. The composite gate GaN-based HEMT according to claim 1 or 2, characterized in that: The passivation layer comprises at least one of Si3N4, SiO2, Al2O3, and AlN.

7. The composite gate GaN-based HEMT according to claim 6, characterized in that: The thickness of the passivation layer is 0.5 μm to 1.3 μm.

8. A method for preparing a composite gate GaN-based HEMT as described in any one of claims 1 to 7, characterized in that, Includes the following steps: 1) A GaN buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a passivation layer are sequentially epitaxially grown on the substrate using metal-organic chemical vapor deposition. 2) The source and drain fabrication regions are etched on the passivation layer using inductively coupled plasma etching, and then the source and drain are deposited using electron beam evaporation deposition, followed by annealing. 3) The composite gate fabrication region is etched on the passivation layer using inductively coupled plasma etching, and then a comb gate and a T-type gate field plate are deposited using electron beam evaporation deposition to obtain the composite gate GaN-based HEMT.

9. An electronic device, characterized in that, The composition includes the composite gate GaN-based HEMT as described in any one of claims 1 to 7.

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