CN105047532B - The method that two-dimensional electron gas is obtained in SiC material - Google Patents

Abstract

The invention provides a method for obtaining two-dimensional electron gas in a SiC material, comprising the following steps: Step 1: take a SiC substrate with a (0001) crystal plane; Step 2: take a SiC substrate with a (0001) crystal plane An AlN layer with a crystal plane of (0001) is fabricated on the bottom. The invention can be used in the manufacture of SiC-based switching devices. Compared with existing SiC-based field effect transistors, the invention improves the mobility of channel carriers, thereby reducing the on-state resistance of devices and reducing power consumption.

Description

A method for obtaining two-dimensional electron gas in SiC materials

technical field

The invention relates to a method for obtaining a two-dimensional electron gas, in particular to a method for obtaining a two-dimensional electron gas for SiC materials.

Background technique

The third-generation semiconductor silicon carbide (SiC) is a wide bandgap semiconductor material with excellent physical and electrical properties. It has the characteristics of wide band gap, high breakdown field strength, high thermal conductivity, etc., so it is very suitable for the development of high temperature, high power, high frequency power electronic devices.

SiC is currently the only compound semiconductor that can be oxidized to form SiO ₂ , but there is a high interface state density at the interface between SiC and SiO ₂ . This is mainly because the device gate oxide is formed by oxidizing SiC. During the oxidation process, the C element in SiC is partially oxidized to form CO and CO ₂ , leaving more interface states between the gate oxide and the SiC substrate, and the remaining Some C elements failed to oxidize, forming C clusters, making the interface quality between gate oxide and SiC substrate not as high as SiO ₂ and SiC. These interface states not only reduce the conductive carriers in the channel of SiC-based MOS devices, but also form scattering centers to further reduce the channel mobility, resulting in high on-resistance and low operating frequency of the device. Even if there are devices such as JFETs to avoid MOS interfaces, since the diffusion coefficient of impurities in SiC is very low, it is often doped by ion implantation, and the activation temperature of implanted ions is quite high, which will cause large crystal damage. Thus the mobility is not high enough. This requires the search for a new SiC-based carrier-conducting interface that enables the generation of high-density, high-mobility channel carriers.

Contents of the invention

The purpose of the present invention is to provide a method for obtaining two-dimensional electron gas in SiC materials, which is aimed at the characteristics of high interface state density and low carrier mobility of traditional SiC-based MOS devices, and proposes to deposit A dielectric with high dielectric constant, high spontaneous polarization, high critical electric field, and lattice matching. A high-density two-dimensional electron gas is generated between the dielectric and SiC through polarization.

The first embodiment of the present invention provides a method for obtaining a two-dimensional electron gas in a SiC material, comprising the following steps:

Step 1: Take a SiC substrate whose crystal plane is (0001);

Step 2: Fabricate an AlN layer with (0001) crystal plane on the SiC substrate with (0001) crystal plane.

The second embodiment of the present invention provides a method for obtaining a two-dimensional electron gas in a SiC material, comprising the following steps:

Step 1: Take a crystal plane as SiC substrate;

Step 2: On the crystal face for An AlN layer with crystal plane (0001) was fabricated on the SiC substrate.

The third embodiment of the present invention provides a method for obtaining a two-dimensional electron gas in a SiC material, comprising the following steps:

Step 1: Take a SiC substrate whose crystal plane is (0001);

Step 2: making an AlN layer with a crystal plane of (0001) on a SiC substrate with a crystal plane of (0001);

Step 3: Fabricate an AlxGa1 _{- xN} layer with a (0001) crystal plane on the AlN layer with a (0001) crystal plane.

The fourth embodiment of the present invention provides a method for obtaining a two-dimensional electron gas in a SiC material, comprising the following steps:

Step 1: Take a SiC substrate whose crystal plane is (0001);

Step 2: Fabricate a crystal plane of (0001) on a SiC substrate with a crystal plane of AlN layer;

Step 3: On the crystal plane for The AlN layer is fabricated on crystal planes as AlxGa1 _{- xN} layer.

The fifth embodiment of the present invention provides a method for obtaining a two-dimensional electron gas in a SiC material, comprising the following steps:

Step 1: Take a crystal plane as SiC substrate;

Step 2: On the crystal face for Fabricate an AlN layer whose crystal plane is (0001) on the SiC substrate;

Step 3: Fabricate an AlxGa1 _{- xN} layer with a (0001) crystal plane on the AlN layer with a (0001) crystal plane.

The invention can be used in the manufacture of SiC-based switching devices. Compared with existing SiC-based field effect transistors, the invention improves the mobility of channel carriers, thereby reducing the on-state resistance of devices and reducing power consumption.

Description of drawings

In order to further illustrate the technical content of the present invention, the present invention is described in further detail below in conjunction with accompanying drawing and embodiment, wherein:

Fig. 1 is the structural representation of embodiment 1 of the present invention;

Fig. 2 is the structural representation of embodiment 2 of the present invention;

Fig. 3 is the structural representation of embodiment 3 of the present invention;

Fig. 4 is the structural representation of embodiment 4 of the present invention;

Fig. 5 is a schematic structural diagram of Embodiment 5 of the present invention.

Detailed ways

(1) There can be the following film combinations on the SiC substrate material: (a) AlN (b) AlN/Al _x Ga _1-x N film. According to the spontaneous polarization and piezoelectric polarization characteristics of the wurtzite structure, the lattice constant of the Al _x Ga _1-x N material is smaller than that of the SiC substrate, that is, the Al _x Ga _1-x N material grown on the SiC material is subjected to compressive stress The piezoelectric polarization opposite to its own spontaneous polarization is generated, and the piezoelectric polarization of the substrate material is 0. The two materials will generate polarization-induced charges at the interface due to the change of polarization intensity, and the calculation formula is as follows:

ρ=-{[P _sp (Al _x Ga _1-x N)+P _pe (Al _x Ga _1-x N)]-[P _sp (SiC)+P _pe (SiC)]}

Psp and Ppe are the spontaneous and piezoelectric polarizations of the corresponding materials, respectively.

(2) According to the calculation formula in (1), positive polarized surface charges need to be formed at the interface of the two materials to attract the two-dimensional electron gas to the potential well of the heterojunction. Due to the polarization direction and The size of the material is different, and the growth of the material needs to meet a certain crystal plane orientation. That is, the Al _x Ga _1-x N material of the Al(Ga) surface is grown on the (0001) SiC substrate; or the Al _x Ga _1-x N material of the N surface with an Al composition less than about 0.6 is grown on the (0001 ) surface SiC substrate; or the Al _x Ga _1-x N material on the Al (Ga) surface with an Al composition greater than 0.6 is grown on on the SiC substrate.

Now in conjunction with accompanying drawing and embodiment the present invention is further stated:

Example 1

Please refer to Fig. 1, the present invention provides a method for obtaining two-dimensional electron gas in SiC material, comprising the following steps:

Step 1: Take a SiC substrate 1 with a crystal plane of (0001), the SiC substrate 1 with a crystal plane of (0001) has a hexagonal wurtzite crystal structure, and the crystal plane is a substrate of (0001) 1 is the crystal plane with zero off angle;

Step 2: Fabricate an AlN layer 2 with a (0001) crystal plane on a SiC substrate 1 with a (0001) crystal plane.

Wherein the SiC substrate 1 is a semi-insulating material with a thickness of 3-10 μm, and the thickness of the AlN layer 2 is 5nm-50nm, which can be properly n-type doped to compensate for the loss of two-dimensional electrons at the interface of the two materials. The growth method adopted for the deposited material may be one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition.

Example 2

Please refer to Fig. 2, the present invention provides a method for obtaining two-dimensional electron gas in SiC material, comprising the following steps:

Step 1: Take a crystal plane as SiC substrate 1, the crystal plane is The SiC substrate 1 has a crystal structure of hexagonal wurtzite, and the crystal planes are The SiC substrate 1 is a crystal plane with zero off-angle;

Step 2: On the crystal face for An AlN layer 2 with a (0001) crystal plane is fabricated on a SiC substrate 1 .

Wherein the SiC substrate 1 is a semi-insulating material with a thickness of 3-10 μm, and the thickness of the AlN layer 2 is 5nm-50nm, which can be properly n-type doped to compensate for the loss of two-dimensional electrons at the interface of the two materials. The growth method adopted for the deposited material may be one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition.

Example 3

Please refer to Fig. 3, the present invention provides a method for obtaining two-dimensional electron gas in SiC material, comprising the following steps:

Step 1: Take a SiC substrate 1 with a crystal plane of (0001), the SiC substrate 1 with a crystal plane of (0001) has a hexagonal wurtzite crystal structure, and the crystal plane is a substrate of (0001) 1 is the crystal plane with zero off angle;

Step 2: making an AlN layer 2 with a (0001) crystal plane on a SiC substrate 1 with a (0001) crystal plane;

Step 3: on the AlN layer 2 with a crystal plane of (0001), make an AlxGa1 _- xN layer 3 with a crystal plane of (0001), the Al _{composition x in} the AlxGa1 _- xN layer 3 is from It varies from 0 to 1, that is, the material represents one of AlN, AlGaN, and GaN, that is, when x is 0, it is a GaN material, when x is 1, it is an AlN material, and if 0<x<1, it is AlGaN.

Wherein the SiC substrate 1 is a semi-insulating material with a thickness of 3-10 μm. The thickness of the AlN insertion layer 2 is 0-2nm, so you can choose not to insert the AlN layer 2, and the thickness of about 1nm is because the AlN layer has a better lattice match with 4H-SiC, so as a buffer layer, it can effectively reduce the impact of the interface state density. The shielding effect of polarized charges increases the concentration and electron mobility of the two-dimensional electron gas. The thickness of the AlxGa1 _{- xN} layer 3 is 15nm-30nm, which can be properly n-type doped to provide enough two-dimensional electrons. The growth method adopted for the deposited material may be one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition.

Example 4

Please refer to Figure 4, the present invention provides a method for obtaining two-dimensional electron gas in SiC materials, including the following steps:

Step 1: Take a SiC substrate 1 with a crystal plane of (0001), the SiC substrate 1 with a crystal plane of (0001) has a hexagonal wurtzite crystal structure, and the crystal plane is a substrate of (0001) 1 is the crystal plane with zero off angle;

Step 2: Fabricate a SiC substrate 1 with a crystal plane of (0001) as AlN layer 2;

Step 3: On the crystal plane for AlN layer 2, on which the crystal plane is fabricated as Al _x Ga _1-x N layer 3, the crystal plane is Al composition _x in the AlxGa1 _- xN layer 3 is less than about 0.6.

Wherein the SiC substrate 1 is a semi-insulating material with a thickness of 3-10 μm. The AlN insertion layer 2 has a thickness of 0-2nm, and the AlxGa1 _{- xN} layer 3 has a thickness of 15nm-30nm, which can be properly n-type doped to provide enough two-dimensional electrons. The growth method adopted for the deposited material may be one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition.

Example 5

Please refer to Fig. 5, the present invention provides a method for obtaining two-dimensional electron gas in SiC material, comprising the following steps:

Step 1: Take a crystal plane as SiC substrate 1, the crystal plane is The SiC substrate 1 has a crystal structure of hexagonal wurtzite, and the crystal planes are The SiC substrate 1 is a crystal plane with zero off-angle;

Step 2: On the crystal face for A SiC substrate 1, on which an AlN layer 2 with a crystal plane of (0001) is fabricated;

Step 3: Fabricate an AlxGa1 _- xN layer 3 with a (0001) crystallographic plane on the AlN layer 2 with a (0001) crystallographic plane, the _{AlxGa1 - xN} layer 3 with a (0001) crystallographic plane The Al composition x in it is greater than about 0.6.

Wherein the SiC substrate 1 is a semi-insulating material with a thickness of 3-10 μm. The AlN insertion layer 2 has a thickness of 0-2nm, and the AlxGa1 _{- xN} layer 3 has a thickness of 15nm-30nm, which can be properly n-type doped to provide enough two-dimensional electrons. The growth method adopted for the deposited material may be one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. a kind of method obtaining two-dimensional electron gas in SiC material, includes the following steps：

Step 1：It is the SiC substrate of (0001) to take a crystal face, and the SiC substrate of (0001) is the crystalline substance for having hexagonal wurtzite Body structure, and be the crystal face at zero bias angle；

Step 2：The AlN layers that crystal face is (0001) are made in the SiC substrate that crystal face is (0001).

2. a kind of method obtaining two-dimensional electron gas in SiC material, includes the following steps：

Step 1：The crystal face is taken to beSiC substrate, the SiC substrate of (0001) is the crystalline substance for having hexagonal wurtzite Body structure, and be the crystal face at zero bias angle；

Step 2：It is in crystal faceSiC substrate on make crystal face be (0001) AlN layers.

3. a kind of method obtaining two-dimensional electron gas in SiC material, includes the following steps：

Step 1：It is the SiC substrate of (0001) to take a crystal face, and the SiC substrate of (0001) is the crystalline substance for having hexagonal wurtzite Body structure, and be the crystal face at zero bias angle；

Step 2：The AlN layers that crystal face is (0001) are made in the SiC substrate that crystal face is (0001)；

Step 3：The Al that crystal face is (0001) is made on the AlN layers that crystal face is (0001)_xGa_1-xN layers, wherein crystal face is (0001) Al_xGa_1-x0 ＜ x ＜ 1 of Al components in N layers.

4. a kind of method obtaining two-dimensional electron gas in SiC material, includes the following steps：

Step 1：It is the SiC substrate of (0001) to take a crystal face, and the SiC substrate of (0001) is the crystalline substance for having hexagonal wurtzite Body structure, and be the crystal face at zero bias angle；

Step 2：Making crystal face in the SiC substrate that crystal face is (0001) isAlN layers；

Step 3：It is in crystal faceAlN layers on make crystal face beAl_xGa_1-xN layers, wherein crystal face is (0001) Al_xGa_1-xAl components x in N layers is less than 0.6.

5. a kind of method obtaining two-dimensional electron gas in SiC material, includes the following steps：

Step 1：The crystal face is taken to beSiC substrate, the SiC substrate of (0001) is the crystalline substance for having hexagonal wurtzite Body structure, and be the crystal face at zero bias angle；

Step 2：It is in crystal faceSiC substrate on make crystal face be (0001) AlN layers；

Step 3：The Al that crystal face is (0001) is made on the AlN layers that crystal face is (0001)_xGa_1-xN layers, wherein crystal face is (0001) Al_xGa_1-xAl components x in N layers is more than 0.6.