High-voltage-resistance and low-leakage GaN SBD based on regrowth P-GaN

Abstract

The invention provides a high-withstand-voltage low-leakage GaN SBD based on regrowth P-GaN, and belongs to the technical field of semiconductors. The high-withstand-voltage low-leakage GaN SBD comprises a substrate and a nucleating layer arranged above the substrate; a buffer layer disposed over the nucleating layer; the heavily doped layer is arranged above the buffer layer; the cathode is arranged above the heavily doped layer; a drift layer is arranged above the heavily doped layer, and the drift layer is located between the cathodes; 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 among 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. According to the high-withstand-voltage low-leakage GaN SBD based on regrowth P-GaN, side wall leakage and an anode edge peak electric field are effectively relieved, the electric field is flattened, and the reliability of a device is improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a high-voltage and low-leakage GaN SBD based on regrown P-GaN. Background Art

[0002] The lateral GaN Schottky diode based on AlGaN / GaN has certain advantages, but in order to increase the breakdown voltage, the distance between the Schottky anode and cathode must be designed to be very large, even up to 10μm, which will occupy a large wafer area and is therefore not conducive to the production of high-current devices. In addition, as the channel length increases, the on-resistance and peak field strength of the drift layer increase linearly, which restricts each other and limits the performance. The vertical structure Schottky diode can increase the breakdown voltage by increasing the thickness of the drift layer, thereby effectively reducing the active area. Under the same current and breakdown voltage conditions, its device size is smaller. There are two forms of vertical structure GaN SBD, namely full vertical structure and quasi-vertical structure. Compared with the single-sided heat dissipation of the lateral structure, the full vertical structure of the GaN Schottky diode has the characteristics of double-sided heat dissipation, which greatly reduces the self-heating effect and increases the reliability of the device. Due to its use of GaN substrate, the cost is still too expensive, it is difficult to achieve commercialization, and the market competitiveness is insufficient. GaN quasi-vertical SBD has the advantages of both. It can be like a full vertical diode, does not require additional active area to increase the breakdown voltage, and can get rid of the limitations of the substrate.

[0003] The conventional 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. The anode and the drift layer are in Schottky contact, and the cathode and the heavily doped region are in ohmic contact. Figure 1 shown.

[0004] The leakage current of GaN quasi-vertical SBD under reverse bias increases too much with the increase of bias, 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 GaN quasi-vertical SBD, which greatly limits the breakdown voltage of quasi-vertical devices. At the same time, because the peak electric field of the device is concentrated in the edge area of ​​the anode, the device often breaks down prematurely due to the electric field concentration effect before reaching the theoretical breakdown field strength of the device. At the same time, during the high-voltage switching process, its on-resistance will increase significantly 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 pressure or high frequency conditions, which will cause additional conduction loss and heat generation. In some tests, when the temperature rises to 150°C, the dynamic on-resistance of the gallium nitride device may increase by more than 50%, which greatly reduces the efficiency of the system and may even cause thermal runaway, local overheating and device burnout. Summary of the invention

[0005] The purpose of the present invention is to provide a high withstand voltage and low leakage GaN SBD based on regrown P-GaN. By a method of regrowing P-type gallium nitride (P-GaN), P-GaN is grown on the side wall of the SBD and the groove below the anode, so that the side wall leakage is greatly reduced, and the peak electric field at the edge of the anode is relieved, the leakage of the device is effectively reduced and the breakdown voltage of the device is greatly improved. The regrown p-GaN layer can effectively shield the influence of the trap state on the device and improve the dynamic characteristics of the device. At the same time, P-GaN is regrown inside the device to reduce the leakage inside the device, further improve the breakdown voltage, improve the high temperature environment performance of the device, relieve the overheating phenomenon of the device, and improve the high temperature reliability of the device. A metal field limiting ring is added around the anode to reduce the electric field peak at the PN junction below the anode, so that the terminal surface electric field is flattened to prevent the PN junction from breaking down in advance.

[0006] To achieve the above object, the present invention provides a high withstand voltage and low leakage GaN SBD based on regrown P-GaN, comprising a first region, on which a drift layer is disposed;

[0007] An anode is arranged on the top of the drift layer, and a metal field limiting ring is arranged on the outer ring of the anode;

[0008] A P-GaN region is provided between the anode, the metal field limiting ring and the drift layer, and the P-GaN region includes a groove under the anode, an internal P-GaN region and a sidewall P-GaN region;

[0009] The groove under the anode is arranged on the drift layer, the internal P-GaN region is located inside the drift layer, a sidewall P-GaN region is arranged on the outside of the drift layer, one end of the sidewall P-GaN region is located between the groove under the anode and the metal field limiting ring, and the sidewall P-GaN region is also connected to the anode at this end, and the other end of the sidewall P-GaN region is connected to the heavily doped layer.

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

[0011] a nucleation layer disposed above the substrate;

[0012] a buffer layer disposed above the nucleation layer;

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

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

[0015] Preferably, one end of the sidewall P-GaN region is connected to the groove under the anode 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 sidewalls of the drift layer include vertical sidewalls or inclined sidewalls.

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

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

[0024] Preferably, the groove under the anode and the internal P-GaN region are each provided with at least one

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

[0026] By using the regrown P-GaN technology, a P-GaN region is formed inside the device, on the sidewall, and under the anode. The sidewall P-GaN creates a space charge region on the device sidewall, effectively alleviating the sidewall leakage and the peak electric field at the edge of the anode. At the same time, P-GaN is used as a field plate and a metal field limiting ring structure is added. Compared with the existing dielectric field plate, it can more effectively target the electric field at the edge of the anode and flatten the electric field. The internally added P-GaN can reduce the internal leakage of the device, increase the breakdown voltage of the device, and improve the additional conduction loss and heat generated by traditional devices under high temperature, high pressure or high frequency conditions due to leakage, which greatly reduces the system efficiency and may even cause thermal runaway, local overheating and device burnout, thereby improving the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of a conventional GaN quasi-vertical SBD;

[0028] Figure 2 A schematic diagram of a high-voltage, low-leakage GaN SBD based on regrown P-GaN (the sidewalls of the drift layer are vertical sidewalls);

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

[0030] Reference numerals

[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. Groove under the anode; 10. Internal P-GaN region; 11. Metal field limiting ring. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0033] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0034] Embodiment 1

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

[0036] An anode 6 is arranged on the top of the drift layer 5, and the anode 6 is in Schottky contact with the drift layer 5. A metal field limiting ring 11 is arranged on the outer circle 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, and the P-GaN region includes an anode groove 9, an internal P-GaN region 10, and a sidewall P-GaN region 8; the internally added P-GaN can reduce the internal leakage of the device, improve the breakdown voltage of the device, and improve the additional conduction loss and heat generated by traditional devices under high temperature, high pressure or high frequency conditions due to leakage, which greatly reduces the system efficiency and may even cause thermal runaway, local overheating and device burning, thereby improving the device reliability.

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

[0039] The length, width, height, and P-GaN doping concentration of the groove under the anode 9 and the internal P-GaN region 10 can be designed independently. At least one groove under the anode 9 and the internal P-GaN region 10 are provided.

[0040] The groove 9 under the anode and the drift layer 5 form a space charge region below the edge of the anode 6, which alleviates the peak electric field at the edge of the anode 6 and improves the breakdown voltage. The sidewall P-GaN makes the space charge region exist on the sidewall of the device, effectively alleviating the sidewall leakage and the peak electric field at the edge of the anode 6.

[0041] The sidewalls of the drift layer 5 include vertical sidewalls or inclined sidewalls, and the angle of the inclined sidewalls can be adjusted, such as Figure 3 shown.

[0042] The anode 6 is made of a metal that 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 uses a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact.

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

[0045] Provide a substrate 1, soak the substrate in a hydrofluoric acid solution for 1 minute, then sequentially place the substrate in an acetone solution, an anhydrous ethanol solution, and deionized water for ultrasonic cleaning for 10 minutes each to eliminate surface dangling bonds, and place the cleaned and dried substrate in a H 2 The substrate 1 is heat treated at 1050°C in an atmosphere reaction chamber for 10 minutes to remove surface contaminants. Then, the substrate 1 is placed in a metal organic chemical vapor deposition MOCVD system. The parameters of the MOCVD system are set as follows: the reaction chamber pressure is 10 Torr, the temperature is 900°C, and an Al source with a flow rate of 30 sccm, a hydrogen with a flow rate of 1000 sccm, and an ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time. The MOCVD process is used to deposit and grow a 25 nm AlN nucleation layer 2;

[0046] On the nucleation layer 2, a 0.5 μm GaN buffer layer 3 and a 50 nm GaN heavily doped layer 4 are sequentially deposited by MOCVD process. The MOCVD process parameters are: the reaction chamber pressure is 10 Torr, the temperature is 900°C, and a Ga source with a flow rate of 50 μmol / min, a hydrogen with a flow rate of 1000 sccm, and an 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, and the MOCVD process parameters are: the reaction chamber pressure is 10 Torr, the temperature is 900°C, and a Ga source with a flow rate of 80 μmol / min, a hydrogen with a flow rate of 1000 sccm, and an ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber.

[0048] On the heavily doped layer 4, 600nm SiO is deposited by PECVD process. 2 As a mask, the mesa and the internal P-GaN region 10 are then etched using an etching process, and the SiO 2 After cleaning, the lower groove 9 of the anode is etched by etching process.

[0049] Making SiO 2 Mask, use P-GaN regrowth process to grow 3μm P-GaN in the inner P-GaN region 10, and then repeat the above steps (make SiO 2 The mask is used, and 3 μm P-GaN is grown again using the P-GaN regrowth process, and 200 nm P-GaN is grown again in the groove 9 under the anode and the P-GaN region 8 on the sidewall.

[0050] A mask is made on the heavily doped layer 4 to form an ohmic window, and the layer is placed in an E-Beam electron beam evaporation device. Two cathodes 7 are deposited using an electron beam evaporation process, with Ti / Al / Ni / Au metals used as cathodes. The rate of the electron beam evaporation process is 0.1 nm / s, and annealing is performed at 750° C. for 30 seconds, 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] Masks are made of the first drift layer 5, the second drift layer 12 and the sidewall P-GaN region 8 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. Using nickel and gold targets with a purity of 99.999%, metal Ni / Au is deposited as an anode 6 in the gate window using an electron beam evaporation process, wherein the thickness of Ni is 50nm and the thickness of Au is 150nm. If the metal field limiting ring 11 uses a metal different from that of the gate, a mask can be made separately.

[0052] Therefore, the present invention adopts the high withstand voltage and low leakage GaN SBD based on regrown P-GaN to effectively alleviate the side wall leakage and the peak electric field at the edge of the anode, flatten the electric field, and improve the reliability of the device.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A high withstand voltage and low leakage GaN SBD based on regrown P-GaN, characterized in that: comprising a first region, wherein a drift layer is disposed on the first region; An anode is arranged on the top of the drift layer, and a metal field limiting ring is arranged on the outer ring of the anode; A P-GaN region is provided between the anode, the metal field limiting ring and the drift layer, and the P-GaN region includes a groove under the anode, an internal P-GaN region and a sidewall P-GaN region; The groove under the anode is arranged on the drift layer, the internal P-GaN region is located inside the drift layer, a sidewall P-GaN region is arranged on the outside of the drift layer, one end of the sidewall P-GaN region is located between the groove under the anode and the metal field limiting ring, and the sidewall P-GaN region is also connected to the anode at this end, and the other end of the sidewall P-GaN region is connected to the heavily doped layer.

2. A high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The first region includes a substrate, a nucleation layer disposed above the substrate; a buffer layer disposed above the nucleation layer; A heavily doped layer is disposed above the buffer layer, and a cathode is disposed above the heavily doped layer.

3. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The drift layer is located between the cathodes, and the sidewall P-GaN region is located between the drift layer and the cathodes.

4. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: One end of the side wall P-GaN region is connected to the groove under the anode and the metal field limiting ring.

5. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The substrate is one of sapphire, SiC, Si and GaN.

6. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: 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 withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The sidewall of the drift layer includes a vertical sidewall or an inclined sidewall.

8. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The anode is made of a metal that forms 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 withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: The cathode uses a metal combination of Ti / Al / Ni / Au or Ti / Al / Pt / Au to form an ohmic contact.

10. The high withstand voltage and low leakage GaN SBD based on regrown P-GaN according to claim 1, characterized in that: At least one groove under the anode and one internal P-GaN region are provided.

Images