Gallium nitride-based vertical structure and growth method
By alternately growing the PGaN layer and GaN layer on the n-GaN drift layer of the gallium nitride-based vertical structure, the problems of increased on-resistance and reduced device reliability caused by magnesium diffusion are solved, and more efficient device performance is achieved.
Patent Information
- Application Number
- CN202411834245.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-03-21
AI Technical Summary
In the existing gallium nitride-based vertical structure, magnesium in the P-type GaN layer is prone to diffuse to the drift layer, resulting in an increase in on-resistance, reducing device operation efficiency, and affecting device reliability.
Instead of growing a complete PGaN layer, the diffusion of magnesium is inhibited by alternating growth of the PGaN layer.
The spaced GaN layer can improve the on-resistance of the device, improve the working efficiency, and enhance the reliability of the device.
Smart Images
Figure CN119677153A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and in particular to a gallium nitride-based vertical structure and a growth method. Background Art
[0002] Wide bandgap semiconductor gallium nitride (GaN) can break through the theoretical performance limits of traditional silicon (Si) devices due to its excellent material properties such as high breakdown voltage, low on-resistance and low switching loss, and is used in many semiconductor fields;
[0003] For example, for existing vertical GaN power devices, compared with traditional silicon-based power devices and emerging pure silicon carbide power devices, GaN devices have lower on-resistance at a specific breakdown voltage; or for GaN junction PIN diodes, due to their fast response speed, low on-resistance and high shallow state density, they can play an important role in high-power power amplifiers, laser diodes, high-voltage switches and other fields.
[0004] The existing GaN-based vertical structure includes a stacked structure of a drift layer and a P-type GaN layer from bottom to top, wherein the P-type GaN layer is relatively thick, generally exceeding 100 nm, and the P-type GaN layer contains highly doped magnesium.
[0005] The existing gallium nitride-based vertical structure has the following problems:
[0006] 1. With the increase of Mg doping amount, the Mg impurities in the epitaxial layer increase, and the crystal quality deteriorates accordingly. When the Mg impurities increase to a Mg concentration exceeding 7e19cm-3, the epitaxial layer growth begins to coarsen, and the surface roughness increases accordingly. Therefore, the crystal quality of the entire P-type GaN layer is poor and the surface is rough.
[0007] Second, the magnesium in the P-type GaN layer easily diffuses into the drift layer to form defects, which increases the on-resistance, reduces the working efficiency of the device, and affects the reliability of the device. Summary of the invention
[0008] In view of the shortcomings of the background technology, the present invention provides a gallium nitride-based vertical structure and a growth method. The technical problem to be solved is that the magnesium in the P-type GaN layer in the existing gallium nitride-based vertical structure is easy to diffuse into the drift layer, which will increase the on-resistance, reduce the device working efficiency, and affect the device reliability.
[0009] In order to solve the above technical problems, in the first aspect, the present invention provides the following technical solutions: a gallium nitride-based vertical structure, comprising a substrate, an AlN nucleation layer, an AlGaN buffer layer, a uGaN layer, an n-GaN layer and an n-GaN drift layer stacked in sequence from bottom to top;
[0010] At least two stacked superlattice layers are arranged upward from the top surface of the n-GaN drift layer, and each superlattice layer includes a PGaN layer and a GaN layer arranged in sequence from bottom to top.
[0011] In certain embodiments of the first aspect, the substrate is sapphire, silicon or silicon carbide.
[0012] In certain embodiments of the first aspect, the thickness of the AlN nucleation layer is between 150 nm and 250 nm;
[0013] The thickness of the AlGaN buffer layer is between 500nm and 1000nm;
[0014] The thickness of the uGaN layer is between 1um and 2um;
[0015] The thickness of the n-GaN layer is between 500nm and 1000nm;
[0016] The thickness of the n-GaN drift layer is between 5um and 10um;
[0017] The thickness of the PGaN layer is between 70nm and 90nm;
[0018] The thickness of the GaN layer is between 5nm and 10nm.
[0019] In a certain embodiment of the first aspect, the Al component in the AlGaN buffer layer is between 15% and 45%;
[0020] The doping concentration of silicon in the n-GaN drift layer is between 1e16 cm-3 and 2e16 cm-3.
[0021] In certain embodiments of the first aspect, the number of the superlattice layers is between 2 and 6; and the total thickness of all superlattice layers is between 150 nm and 600 nm.
[0022] In a second aspect, the present invention provides a method for growing a gallium nitride-based vertical structure, comprising the following steps:
[0023] S1: In an MOCVD reactor, an AlN nucleation layer, an AlGaN buffer layer, a uGaN layer, an n-GaN layer and an n-GaN drift layer are sequentially grown on the top surface of the substrate;
[0024] S2: In an MOCVD reactor, alternately growing PGaN layers and GaN layers on the top surface of the n-GaN drift layer; wherein the number of the PGaN layers is the same as the number of the GaN layers, and both are greater than or equal to 2.
[0025] In certain implementation manner of the first aspect, the material of the substrate in step S1 is sapphire, silicon or silicon carbide.
[0026] In a certain implementation of the first aspect, the thickness of the AlGaN buffer layer produced in step S1 is between 500nm and 1000nm;
[0027] The thickness of the uGaN layer produced in step S1 is between 1um and 2um;
[0028] The thickness of the n-GaN layer produced in step S1 is between 500nm and 1000nm;
[0029] The thickness of the n-GaN drift layer produced in step S1 is between 5um and 10um;
[0030] The thickness of the PGaN layer produced in step S2 is between 70nm and 90nm;
[0031] The thickness of the GaN layer produced in step S2 is between 5nm and 10nm.
[0032] In a certain embodiment of the first aspect, the Al component in the AlGaN buffer layer is between 15% and 45%;
[0033] The doping concentration of silicon in the n-GaN drift layer is between 1e16 cm-3 and 2e16 cm-3.
[0034] In certain embodiments of the first aspect, the number of PGaN layers is between 2 and 6; and the total thickness of all PGaN layers and GaN layers is between 150 nm and 600 nm.
[0035] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides an alternately distributed PGaN layer and a GaN layer on the n-GaN drift layer, instead of providing a whole PGaN layer on the n-GaN drift layer, so that the diffusion of magnesium in the PGaN layer to the n-GaN drift layer can be suppressed by the alternately distributed GaN layer, thereby improving the on-resistance of the device and improving the working efficiency;
[0036] In addition, superlattice growth is equivalent to growing a better quality GaN layer (undoped) on top of a poorer quality PGaN layer, and then growing a poorer quality PGaN layer on top of a better quality GaN layer. This repeated growth of multiple layers has many more GaN interface layers than simple PGaN growth. The existence of these interface layers will reduce the total number of defects in the entire P-type GaN layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1is a schematic structural diagram of the gallium nitride-based vertical structure in Example 1;
[0038] Figure 2 Flowchart of the growth method in the embodiment. DETAILED DESCRIPTION
[0039] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.
[0040] Embodiment 1
[0041] like Figure 1 As shown, a gallium nitride-based vertical structure includes a substrate 1, an AlN nucleation layer 2, an AlGaN buffer layer 3, a uGaN layer 4, an n-GaN layer 5 and an n-GaN drift layer 6 which are stacked in sequence from bottom to top;
[0042] At least two stacked superlattice layers 7 are disposed upward from the top surface of the n-GaN drift layer 6 , and each superlattice layer 7 includes a PGaN layer 70 and a GaN layer 71 disposed in sequence from bottom to top.
[0043] In actual use, the present invention arranges alternately distributed PGaN layers 70 and GaN layers 71 on the n-GaN drift layer 6, rather than arranging a whole PGaN layer 70 on the n-GaN drift layer 6. In this way, the staggered GaN layers 71 can inhibit the diffusion of magnesium in the PGaN layer 70 into the n-GaN drift layer 6, thereby improving the on-resistance of the device and improving the working efficiency.
[0044] Specifically, in this embodiment, the substrate 1 is sapphire, silicon or silicon carbide. The size of the substrate 1 can be 4 inches, 6 inches or 8 inches.
[0045] Specifically, in this embodiment, the thickness value and function of each layer of the gallium nitride-based vertical structure are as follows:
[0046] The thickness of the AlN nucleation layer 2 is between 150nm and 250nm;
[0047] The thickness of the AlGaN buffer layer 3 is between 500nm and 1000nm;
[0048] In actual use, the AlN nucleation layer 2 and the AlGaN buffer layer 3 of the above thickness can firstly ensure that the AlN nucleation layer 2 and the AlGaN buffer layer 3 and the entire structure have good crystal quality. Secondly, the AlN nucleation layer 2 of the above thickness can isolate the oxygen, silicon and other impurities from the substrate 1 from diffusing into the vertical structure to the maximum extent, avoiding affecting the electrical performance of the device. Finally, it can provide a mechanical stress basis, regulate stress and improve wafer warpage and surface cracks.
[0049] The thickness of the uGaN layer 4 is between 1um and 2um;
[0050] In actual use, the above-mentioned thickness of the uGaN layer 4 can ensure that the subsequent working areas such as the n-GaN layer 5, the n-GaN drift layer 6 and the PGaN layer 70 are grown on a GaN layer material with good quality and a flat surface;
[0051] The thickness of the n-GaN layer 5 is between 500nm and 1000nm;
[0052] The thickness of the n-GaN drift layer 6 is between 5um and 10um;
[0053] The thickness of the PGaN layer 70 is between 70 nm and 90 nm;
[0054] The thickness of the GaN layer 71 is between 5 nm and 10 nm.
[0055] Exemplarily, in one embodiment, the thickness of the AlN nucleation layer 2 may be 180nm; the thickness of the AlGaN buffer layer 3 may be 600nm; the thickness of the uGaN layer 4 may be 1.2um; the thickness of the n-GaN layer 5 may be 600nm; the thickness of the n-GaN drift layer 6 may be 6um; the thickness of the PGaN layer 70 may be 80nm; and the thickness of the GaN layer 71 may be 6nm.
[0056] Exemplarily, in another embodiment, the thickness of the AlN nucleation layer 2 may be 200nm; the thickness of the AlGaN buffer layer 3 may be 800nm; the thickness of the uGaN layer 4 may be 1.6um; the thickness of the n-GaN layer 5 may be 800nm; the thickness of the n-GaN drift layer 6 may be 8um; the thickness of the PGaN layer 70 may be 85nm; and the thickness of the GaN layer 71 may be 8nm.
[0057] Exemplarily, in some embodiments, the thickness of the AlN nucleation layer 2 may be 230 nm; the thickness of the AlGaN buffer layer 3 may be 900 nm; the thickness of the uGaN layer 4 may be 1.8 um; the thickness of the n-GaN layer 5 may be 900 nm; the thickness of the n-GaN drift layer 6 may be 9 um; the thickness of the PGaN layer 70 may be 88 nm; and the thickness of the GaN layer 71 may be 9 nm.
[0058] Specifically, in this embodiment, the Al component in the AlGaN buffer layer 3 is between 15% and 45%; illustratively, the Al component in the AlGaN buffer layer 3 can be 20%, 25%, 30% or 35%; in actual use, by setting the Al component in the AlGaN buffer layer 3 between 15% and 45%, the crystal quality of the entire vertical structure can be higher, and the surface roughness will not be too bad, so that the uGaN layer 4 can be better connected on the AlN layer 2.
[0059] In addition, the doping concentration of silicon in the n-GaN drift layer 6 is between 1e16cm-3 and 2e16cm-3. This doping concentration can ensure a certain carrier concentration on the basis of achieving high withstand voltage and maintain a low on-resistance of the drift layer; the exemplary doping concentration of silicon in the n-GaN drift layer 6 can be 1.2e16cm-3, 1.4e16cm-3 or 1.8e16cm-3.
[0060] Specifically, in this embodiment, the number of superlattice layers 7 is between 2 and 6; and the total thickness of all superlattice layers 7 is between 150 nm and 600 nm.
[0061] Embodiment 2
[0062] like Figure 2 As shown, the present invention provides a method for growing a gallium nitride-based vertical structure, comprising the following steps:
[0063] S1: In an MOCVD reactor, an AlN nucleation layer 2, an AlGaN buffer layer 3, a uGaN layer 4, an n-GaN layer 5 and an n-GaN drift layer 6 are sequentially grown on the top surface of a substrate 1;
[0064] S2: In an MOCVD reactor, PGaN layers 70 and GaN layers 71 are alternately grown on the top surface of the n-GaN drift layer 6; wherein the number of the PGaN layers 70 and the number of the GaN layers 71 are the same and both are greater than or equal to 2; wherein the structural schematic diagram of the device finally manufactured is as shown in Figure 1 shown.
[0065] Specifically, in this embodiment, the material of the substrate 1 in step S1 is sapphire, silicon or silicon carbide. In addition, the size of the substrate 1 can be 4 inches, 6 inches or 8 inches.
[0066] Specifically, in this embodiment,
[0067] The thickness of the AlN nucleation layer 2 produced in step S1 is between 150nm and 250nm;
[0068] The thickness of the AlGaN buffer layer 3 produced in step S1 is between 500nm and 1000nm;
[0069] The thickness of the uGaN layer 4 produced in step S1 is between 1um and 2um;
[0070] The thickness of the n-GaN layer 5 produced in step S1 is between 500nm and 1000nm;
[0071] The thickness of the n-GaN drift layer 6 produced in step S1 is between 5um and 10um;
[0072] The thickness of the PGaN layer 70 produced in step S2 is between 70nm and 90nm;
[0073] The thickness of the GaN layer 71 fabricated in step S2 is between 5 nm and 10 nm.
[0074] Exemplarily, the thickness of the AlN nucleation layer 2 can be 180nm; the thickness of the AlGaN buffer layer 3 can be 600nm; the thickness of the uGaN layer 4 can be 1.2um; the thickness of the n-GaN layer 5 can be 600nm; the thickness of the n-GaN drift layer 6 can be 6um; the thickness of the PGaN layer 70 can be 80nm; and the thickness of the GaN layer 71 can be 6nm.
[0075] Alternatively, the thickness of the AlN nucleation layer 2 can be 200nm; the thickness of the AlGaN buffer layer 3 can be 800nm; the thickness of the uGaN layer 4 can be 1.6um; the thickness of the n-GaN layer 5 can be 800nm; the thickness of the n-GaN drift layer 6 can be 8um; the thickness of the PGaN layer 70 can be 85nm; and the thickness of the GaN layer 71 can be 8nm.
[0076] Alternatively, the thickness of the AlN nucleation layer 2 can be 230nm; the thickness of the AlGaN buffer layer 3 can be 900nm; the thickness of the uGaN layer 4 can be 1.8um; the thickness of the n-GaN layer 5 can be 900nm; the thickness of the n-GaN drift layer 6 can be 9um; the thickness of the PGaN layer 70 can be 88nm; and the thickness of the GaN layer 71 can be 9nm.
[0077] Specifically, in this embodiment, the Al component in the AlGaN buffer layer 3 is between 15% and 45%; illustratively, the Al component in the AlGaN buffer layer 3 may be 20%, 25%, 30% or 35%;
[0078] In addition, the doping concentration of silicon in the n-GaN drift layer 6 is between 1e16 cm-3 and 2e16 cm-3; the exemplary doping concentration of silicon in the n-GaN drift layer 6 may be 1.2e16 cm-3, 1.4e16 cm-3 or 1.8e16 cm-3.
[0079] Specifically, in this embodiment, the number of superlattice layers 7 is between 2 and 6; and the total thickness of all superlattice layers 7 is between 150 nm and 600 nm.
[0080] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A gallium nitride-based vertical structure, characterized in that: It includes a substrate, an AlN nucleation layer, an AlGaN buffer layer, a uGaN layer, an n-GaN layer and an n-GaN drift layer which are stacked in sequence from bottom to top; At least two stacked superlattice layers are arranged upward from the top surface of the n-GaN drift layer, and each superlattice layer includes a PGaN layer and a GaN layer arranged in sequence from bottom to top.
2. A gallium nitride-based vertical structure according to claim 1, characterized in that: The substrate is sapphire, silicon or silicon carbide.
3. The gallium nitride-based vertical structure according to claim 1, characterized in that: The thickness of the AlN nucleation layer is between 150nm and 250nm; The thickness of the AlGaN buffer layer is between 500nm and 1000nm; The thickness of the uGaN layer is between 1um and 2um; The thickness of the n-GaN layer is between 500nm and 1000nm; The thickness of the n-GaN drift layer is between 5um and 10um; The thickness of the PGaN layer is between 70nm and 90nm; The thickness of the GaN layer is between 5nm and 10nm.
4. The gallium nitride-based vertical structure according to claim 3, characterized in that: The Al component in the AlGaN buffer layer is between 15% and 45%; The doping concentration of silicon in the n-GaN drift layer is between 1e16 cm-3 and 2e16 cm-3.
5. A gallium nitride-based vertical structure according to any one of claims 1 to 5, characterized in that: The number of the superlattice layers is between 2 and 6; the total thickness of all superlattice layers is between 150 nm and 600 nm.
6. A method for growing a gallium nitride-based vertical structure, characterized in that: The following steps are involved: S1: In an MOCVD reactor, an AlN nucleation layer, an AlGaN buffer layer, a uGaN layer, an n-GaN layer and an n-GaN drift layer are sequentially grown on the top surface of the substrate; S2: In an MOCVD reactor, alternately growing PGaN layers and GaN layers on the top surface of the n-GaN drift layer; wherein the number of the PGaN layers is the same as the number of the GaN layers, and both are greater than or equal to 2.
7. The method for growing a gallium nitride-based vertical structure according to claim 6, characterized in that: The material of the substrate in step S1 is sapphire, silicon or silicon carbide.
8. The method for growing a gallium nitride-based vertical structure according to claim 6, characterized in that: The thickness of the AlGaN buffer layer produced in step S1 is between 500nm and 1000nm; The thickness of the uGaN layer produced in step S1 is between 1um and 2um; The thickness of the n-GaN layer produced in step S1 is between 500nm and 1000nm; The thickness of the n-GaN drift layer produced in step S1 is between 5um and 10um; The thickness of the PGaN layer produced in step S2 is between 70nm and 90nm; The thickness of the GaN layer produced in step S2 is between 5nm and 10nm.
9. The method for growing a gallium nitride-based vertical structure according to claim 7, characterized in that: The Al component in the AlGaN buffer layer is between 15% and 45%; The doping concentration of silicon in the n-GaN drift layer is between 1e16 cm-3 and 2e16 cm-3.
10. The method for growing a gallium nitride-based vertical structure according to claim 6, characterized in that: The number of PGaN layers is between 2 and 6; the total thickness of all PGaN layers and GaN layers is between 150 nm and 600 nm.