A high-voltage low-leakage GaN SBD based on regrown P-GaN

Abstract

The application provides a high-voltage and low-leakage GaN SBD based on regrown P-GaN, and belongs to the technical field of semiconductors. The GaN SBD comprises a substrate, a nucleation layer arranged above the substrate, a buffer layer arranged above the nucleation layer, a heavily doped layer arranged above the buffer layer, a cathode arranged above the heavily doped layer, a drift layer arranged above the heavily doped layer, the drift layer being located between the cathodes, an anode arranged at the top end of the drift layer, a metal field limiting ring arranged at the outer ring of the anode, a P-GaN region arranged between the anode, the metal field limiting ring and the drift layer, and the P-GaN region comprising an anode lower groove, an internal P-GaN region and a sidewall P-GaN region. The GaN SBD based on the regrown P-GaN can effectively relieve sidewall leakage and anode edge peak electric field, make the electric field flat, and improve the reliability of the device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to a high-voltage and low-leakage GaN SBD based on regrown P-GaN. BACKGROUND

[0002] The AlGaN / GaN-based lateral GaN Schottky diode has certain advantages, but in order to improve the breakdown voltage, the distance between the Schottky anode and the cathode must be designed to be very large, even up to 10 microns, which will occupy a large wafer area, and thus is not conducive to the production of high-current devices. In addition, with the increase of the channel length, the on-resistance and the peak field strength of the drift layer are linearly increased, thereby restricting each other and limiting the performance. The longitudinal structure Schottky diode can improve the breakdown voltage by increasing the thickness of the drift layer, thereby effectively reducing the active area, and under the same current and breakdown voltage conditions, the device size is smaller. The GaN SBD of the longitudinal structure has two forms, namely, a full vertical structure and a quasi-vertical structure. Compared with the single-face heat dissipation of the lateral structure, the full vertical structure of the GaN Schottky diode has the characteristics of double-face heat dissipation, greatly reduces the self-heating effect, and increases the reliability of the device. Since the GaN substrate is used, the cost is still too high, and it is difficult to realize commercialization, and the market competitiveness is not enough. The GaN quasi-vertical SBD has the advantages of both, and can not only like the full vertical diode, but also does not need additional active area to improve the breakdown voltage, and can get rid of the limitation of the substrate.

[0003] The traditional GaN quasi-vertical SBD includes a substrate, a nucleation layer, a buffer layer, a heavily doped region, a drift layer, an anode and a cathode, and the anode is in Schottky contact with the drift layer, and the cathode is in ohmic contact with the heavily doped region, as shown in Figure 1 .

[0004] The leakage current of the GaN quasi-vertical SBD increases too much with the increase of the reverse bias voltage, which eventually leads to soft breakdown of the device due to excessive leakage, and the leakage current along the sidewall is one of the main leakage paths of the GaN quasi-vertical SBD, which greatly limits the breakdown voltage of the quasi-vertical device. At the same time, since the peak electric field of the device is concentrated in the anode edge region, the device often breaks down in advance due to the electric field concentration effect before the theoretical breakdown field strength of the device is reached. At the same time, in the high-voltage switching process, the on-resistance will be significantly increased due to the trap charge effect, such as charge capture in the buffer layer or surface state. This phenomenon is more obvious under high temperature, high voltage or high frequency conditions, which will cause additional on-resistance and heat. In some tests, when the temperature rises to 150 DEG C, the dynamic on-resistance of the gallium nitride device may increase by more than 50%, which greatly reduces the system efficiency, and even may cause thermal runaway, and local overheating leads to the burning of the device. SUMMARY

[0005] The application aims to provide a high-voltage and low-leakage GaN SBD based on regrown P-GaN, which grows P-GaN in the sidewall and the recess under the anode of the SBD through a regrown P-type gallium nitride (P-GaN) mode, so that the sidewall leakage is greatly reduced, the anode edge peak electric field is relieved, the device leakage is effectively reduced, the device breakdown voltage is greatly improved, the regrown P-GaN layer can effectively shield the influence of trap states on the device, and the dynamic characteristics of the device are improved. At the same time, the P-GaN is regrown in the device, the internal leakage of the device is reduced, the breakdown voltage is further improved, the high-temperature performance of the device is improved, the overheating phenomenon of the device is relieved, the high-temperature reliability of the device is improved, and the metal field limiting ring is added around the anode to reduce the electric field peak at the PN junction under the anode, so that the terminal surface electric field is flattened, and the PN junction is prevented from breaking down in advance.

[0006] To achieve the above-mentioned purpose, the application provides a high-voltage and low-leakage GaN SBD based on regrown P-GaN, which comprises a first region, and a drift layer is arranged on the first region.

[0007] A top end of the drift layer is provided with an anode, and an outer ring of the anode is provided with a metal field limiting ring.

[0008] A P-GaN region is arranged between the anode, the metal field limiting ring and the drift layer, and the P-GaN region comprises an anode recess, an internal P-GaN region and a sidewall P-GaN region.

[0009] The anode recess is arranged on the drift layer, the internal P-GaN region is located in the drift layer, the outer side of the drift layer is provided with the sidewall P-GaN region, one end of the sidewall P-GaN region is located between the anode recess and the metal field limiting ring, the sidewall P-GaN region is further connected with the anode at the end, and the other end of the sidewall P-GaN region is connected with a heavily doped layer.

[0010] Preferably, the first region comprises a substrate,

[0011] A nucleation layer is arranged above the substrate;

[0012] A buffer layer is arranged above the nucleation layer;

[0013] A heavily doped layer is arranged above the buffer layer, and a cathode is arranged above the heavily doped layer.

[0014] Preferably, the drift layer is located between the cathodes, and the sidewall P-GaN region is located between the drift layer and the cathodes.

[0015] Preferably, one end of the sidewall P-GaN region is connected with the anode recess and the metal field limiting ring.

[0016] Preferably, the substrate is one of sapphire, SiC, Si and GaN.

[0017] Preferably, the nucleation layer is one of GaN, AlN and AlGaN.

[0018] The buffer layer is one or more of GaN, AlN and AlGaN.

[0019] The heavily doped layer is one of GaN, AlN and AlGaN.

[0020] The material of the drift layer is one of GaN, AlN and AlGaN.

[0021] Preferably, the sidewall of the drift layer comprises vertical sidewall or inclined sidewall.

[0022] Preferably, the anode is a metal forming a Schottky contact with the drift layer, and the material of the metal field limiting ring is the same as that of the anode.

[0023] Preferably, the cathode adopts a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact.

[0024] Preferably, at least one of the anode recess and the internal P-GaN region is provided.

[0025] Therefore, the application adopts the above-mentioned high-voltage low-leakage GaN SBD based on regrown P-GaN, and the technical effects are as follows:

[0026] By using the regrown P-GaN technology, the P-GaN region is formed in the device, the sidewall and the anode, the sidewall P-GaN makes the sidewall of the device exist a space charge region, effectively alleviates the sidewall leakage and the peak electric field at the edge of the anode, and at the same time, the P-GaN as a field plate and adding a metal field limiting ring structure can more effectively target the anode edge electric field compared with the existing dielectric field plate, so as to flatten the electric field. The internal added P-GaN can reduce the internal leakage of the device, improve the breakdown voltage of the device, and at the same time, improve the additional conduction loss and heating under the condition of high temperature, high pressure or high frequency due to the leakage of the traditional device, so that the system efficiency is greatly reduced, and even the heat runaway may be triggered, the local overheating leads to the burning of the device, and the reliability of the device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of a traditional GaN quasi-vertical SBD.

[0028] Figure 2 It is a schematic diagram of a high-voltage low-leakage GaN SBD based on regrown P-GaN (the sidewall of the drift layer is vertical sidewall).

[0029] Figure 3 This is a schematic diagram of a high-voltage, low-leakage GaN SBD based on regenerated P-GaN (the sidewalls of the drift layer are inclined).

[0030] Figure Labels

[0031] 1. Substrate; 2. Nucleation layer; 3. Buffer layer; 4. Heavily doped layer; 5. Drift layer; 6. Anode; 7. Cathode; 8. Sidewall P-GaN region; 9. Anode under-groove; 10. Internal P-GaN region; 11. Metal field confinement ring. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0034] Example 1

[0035] like Figure 2 As shown, a high-voltage, low-leakage GaN SBD based on regenerated P-GaN includes a substrate 1, a nucleation layer 2 disposed above the substrate 1, a buffer layer 3 disposed above the nucleation layer 2, a heavily doped layer 4 disposed above the buffer layer 3, and a cathode 7 disposed above the heavily doped layer 4, wherein the cathode 7 and the heavily doped layer 4 are in ohmic contact; a drift layer 5 is disposed above the heavily doped layer, and the drift layer 5 is located between the cathodes 7.

[0036] An anode 6 is provided at the top of the drift layer 5. The anode 6 and the drift layer 5 are in Schottky contact. A metal field limiting ring 11 is provided on the outer ring of the anode 6. P-GaN is used as a field plate and the metal field limiting ring 11 structure is added. Compared with the existing dielectric field plate, it can more effectively target the electric field at the edge of the anode 6 and flatten the electric field.

[0037] A P-GaN region is provided between the anode 6, the metal field limiting ring 11, and the drift layer 5. The P-GaN region includes the anode under-groove 9, the internal P-GaN region 10, and the sidewall P-GaN region 8. The internally added P-GaN can reduce internal leakage current of the device and improve the breakdown voltage of the device. At the same time, it can improve the situation where traditional devices generate additional conduction losses and heat under high temperature, high voltage or high frequency conditions due to leakage current, which can significantly reduce system efficiency and may even cause thermal runaway, local overheating and device burnout, thus improving device reliability.

[0038] The anode lower groove 9 is arranged on the drift layer 5, the internal P-GaN region 10 is located inside the drift layer 5, the outer side of the drift layer 5 is provided with the side wall P-GaN region 8, one end of the side wall P-GaN region 8 is located between the anode lower groove 9 and the metal field limiting ring 11, and the side wall P-GaN region 8 is also connected with the anode 6 at the end, and the other end of the side wall P-GaN region 8 is connected with the heavily doped layer 4.

[0039] The length, width and height of the anode lower groove 9 and the internal P-GaN region 10 and the P-GaN doping concentration can be designed individually.

[0040] The anode lower groove 9 and the drift layer 5 form a space charge region below the edge of the anode 6, which relieves the peak electric field of the edge of the anode 6 and improves the breakdown voltage. The side wall P-GaN makes the space charge region exist in the side wall of the device, which effectively relieves the side wall leakage and the peak electric field of the edge of the anode 6.

[0041] The side wall of the drift layer 5 includes a vertical side wall or an inclined side wall, and the angle of the inclined side wall can be adjusted, as shown in Figure 3

[0042] The anode 6 is a metal which forms a Schottky contact with the drift layer 5, and the metal field limiting ring 11 is made of the same material as the anode 6.

[0043] The cathode 7 adopts a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact.

[0044] A preparation method of a high-voltage and low-leakage GaN SBD based on regrown P-GaN, comprising the following steps:

[0045] A substrate 1 is provided, the substrate is soaked in a hydrofluoric acid solution for 1 min, and then sequentially ultrasonically cleaned in an acetone solution, an anhydrous ethanol solution and deionized water for 10 min respectively to eliminate surface dangling bonds, the substrate after being blown dry is subjected to heat treatment at a temperature of 1050 DEG C in an H2 atmosphere reaction chamber for 10 minutes to remove surface contaminants, and then the substrate 1 is placed in a metal organic chemical vapor deposition (MOCVD) system, parameters of the MOCVD system are set as follows: a reaction chamber pressure is 10 Torr, a temperature is 900 DEG C, an Al source with a flow rate of 30 sccm, hydrogen with a flow rate of 1000 sccm and ammonia with a flow rate of 3000 sccm are simultaneously introduced into the reaction chamber, and an MOCVD process is adopted to deposit and grow an AlN nucleation layer 2 with a thickness of 25 nm;

[0046] ​On the nucleation layer 2, a 0.5 μm GaN buffer layer 3 and a 50 nm GaN heavily doped layer 4 are deposited in sequence by MOCVD process, the MOCVD process parameters are: the pressure in the reaction chamber is 10 Torr, the temperature is 900 °C, the Ga source with a flow rate of 50 μmol / min, hydrogen with a flow rate of 1000 sccm and ammonia with a flow rate of 3000 sccm are simultaneously introduced into the reaction chamber;

[0047] On the heavily doped layer 4, a drift layer is deposited by MOCVD process, the MOCVD process parameters are: the pressure in the reaction chamber is 10 Torr, the temperature is 900 °C, the Ga source with a flow rate of 80 μmol / min, hydrogen with a flow rate of 1000 sccm and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber.

[0048] On the heavily doped layer 4, a 600 nm SiO2 is deposited as a mask by PECVD process, then the mesa and the internal P-GaN region 10 are etched by etching process, after the SiO2 is cleaned by hydrofluoric acid, the anode recess 9 is etched by etching process.

[0049] The SiO2 mask is made, 3 μm P-GaN is regrown in the internal P-GaN region 10 by P-GaN regrowth process, then the above steps (making SiO2 mask, regrowing 3 μm P-GaN by P-GaN regrowth process) are repeated, 200 nm P-GaN is regrown in the anode recess 9 and the sidewall P-GaN region 8.

[0050] The mask is made on the heavily doped layer 4 to form an ohmic window, the sample is put into an E-Beam electron beam evaporation device, two cathodes 7 are deposited by electron beam evaporation process, Ti / Al / Ni / Au metal is used as the cathode, the rate of the electron beam evaporation process is 0.1 nm / s, and annealing is performed at 750 °C for 30 s, wherein the thickness of Ti is 20 nm, the thickness of Al is 120 nm, the thickness of Ni is 40 nm, and the thickness of Au is 50 nm;

[0051] The first drift layer 5, the second drift layer 12 and the sidewall P-GaN region 8 are masked to form an anode window and a metal field limiting ring window, the sample with the formed window is placed in an electron beam evaporation reaction chamber, nickel and gold targets with a purity of 99.999% are used to deposit metal Ni / Au as the anode 6 in the gate window by electron beam evaporation process, wherein the thickness of Ni is 50 nm and the thickness of Au is 150 nm; if the metal field limiting ring 11 uses a different metal from the gate, a mask can be made separately.

[0052] Therefore, the application adopts the high-voltage and low-leakage GaN SBD based on the regrown P-GaN to effectively relieve the sidewall leakage and the anode edge peak electric field, to make the electric field flat, and to improve the device reliability.

[0053] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A high-voltage low-leakage GaN SBD based on regrown P-GaN, characterized in that, The first region is provided with a drift layer; The top end of the drift layer is provided with an anode, and the outer ring of the anode is provided with a metal field limiting ring; A P-GaN region is arranged between the anode, the metal field limiting ring and the drift layer, and the P-GaN region comprises an anode lower groove, an internal P-GaN region and a side wall P-GaN region. The anode lower groove is arranged on the drift layer, the internal P-GaN region is located inside the drift layer, the side wall P-GaN region is arranged on the outer side of the drift layer, one end of the side wall P-GaN region is located between the anode lower groove and the metal field limiting ring, and the other end of the side wall P-GaN region is connected with the anode. 2.The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, The first region comprises a substrate, a nucleation layer arranged above the substrate, a buffer layer arranged above the nucleation layer, a heavily doped layer arranged above the buffer layer, and a cathode arranged above the heavily doped layer. 3.The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, The drift layer is located between the cathodes, and the side wall P-GaN region is located between the drift layer and the cathodes. 4.The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, One end of the side wall P-GaN region is connected with the anode lower groove and the metal field limiting ring.

5. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 2, wherein, The substrate is one of sapphire, SiC, Si and GaN.

6. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 2, wherein, The nucleation layer is one of GaN, AlN and AlGaN. The buffer layer is one or more of GaN, AlN and AlGaN. The heavily doped layer is one of GaN, AlN and AlGaN. The material of the drift layer is one of GaN, AlN and AlGaN.

7. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, The side wall of the drift layer comprises a vertical side wall or an inclined side wall.

8. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, The anode is a metal forming a Schottky contact with the drift layer, and the metal field limiting ring is made of the same material as the anode.

9. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 2, wherein, The cathode adopts a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact.

10. The high-voltage low-leakage GaN SBD based on regrown P-GaN of claim 1, wherein, The anode lower groove and the internal P-GaN region are each provided with at least one.

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