A SiC PIN diode based on AlN and a manufacturing method thereof

Abstract

The present invention provides an AlN-based SiC PIN diode and a manufacturing method thereof. The diode comprises a lower side of an N-type heavily doped semiconductor transmission layer connected to an upper side of an N-type ohmic electrode; a lower side of an N-type lightly doped AlN withstand voltage improvement layer connected to an upper side of the N-type heavily doped semiconductor transmission layer; a lower side of an N-type intrinsic layer connected to an upper side of the N-type lightly doped AlN withstand voltage improvement layer; a lower side of a P-type heavily doped semiconductor transmission layer connected to an upper side of the N-type intrinsic layer; and a lower side of a P-type ohmic electrode connected to an upper side of the P-type heavily doped semiconductor transmission layer, so that the current resistance of the SiC PIN diode is improved, and the thermal conductivity of the AlN material is close to that of the SiC material, and the longitudinal heat distribution of the AlN material in the PIN diode is more uniform, and concentrated hot spots are not likely to occur, and thermal failure of the device is not likely to occur.

Description

Technical Field

[0001] The present invention relates to an AlN-based SiC PIN diode and a manufacturing method thereof. Background Art

[0002] SiC DevicesSiC materials have attracted extensive attention and research due to their superior physical properties. Their high-temperature, high-power electronic devices have the advantages of high input impedance, fast switching speed, high operating frequency, high temperature and high pressure resistance, and have been widely used in switching power supplies, high-frequency heating, automotive electronics, and power amplifiers.

[0003] However, due to the limitations of material properties, the intrinsic breakdown field strength is fixed. The main method currently used to increase the withstand voltage of PIN diodes is to improve the terminal structure and obtain a PIN diode with a higher withstand voltage by optimizing the doping method. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an AlN-based SiC PIN diode and a manufacturing method thereof, so as to improve the current capacity of the SiC PIN diode. The thermal conductivity of the AlN material is close to that of the SiC material, and the longitudinal heat distribution in the PIN diode is more uniform, and concentrated hot spots are not likely to occur, which is not likely to cause thermal failure of the device.

[0005] One of the present inventions is implemented as follows: a high voltage SiC PIN diode based on AlN, comprising:

[0006] An N-type ohmic electrode;

[0007] an N-type heavily doped semiconductor transmission layer, wherein the lower side of the N-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type ohmic electrode;

[0008] An N-type lightly doped AlN withstand voltage improvement layer, wherein the lower side of the N-type lightly doped AlN withstand voltage improvement layer is connected to the upper side of the N-type heavily doped semiconductor transmission layer;

[0009] An N-type intrinsic layer, the lower side of the N-type intrinsic layer is connected to the upper side of the N-type lightly doped AlN withstand voltage improvement layer;

[0010] a P-type heavily doped semiconductor transmission layer, wherein the lower side of the P-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type intrinsic layer;

[0011] and, a P-type ohmic electrode, wherein the lower side of the P-type ohmic electrode is connected to the upper side of the P-type heavily doped semiconductor transmission layer.

[0012] Furthermore, the thickness of the N-type lightly doped AlN voltage-enhancing layer is 2 to 3 micrometers, and the thickness of the N-type intrinsic layer is 3 micrometers.

[0013] Furthermore, the doping concentration of the N-type lightly doped AlN withstand voltage enhancement layer is 1*10 17 cm -3 .

[0014] Furthermore, the doping concentration of the N-type lightly doped AlN withstand voltage improvement layer is twice the doping concentration of the N-type intrinsic layer.

[0015] The second aspect of the present invention is achieved as follows: a method for manufacturing a SiC PIN diode based on AlN, specifically comprising the following steps:

[0016] Step 1, washing the surface of the SiC epitaxial wafer with deionized water, and then soaking it in a heated mixed washing solution for 1 minute to further remove foreign matter on the surface of the SiC epitaxial wafer to form a substrate; the mixed washing solution includes ammonia water, hydrogen peroxide and deionized water;

[0017] Step 2, epitaxially growing an N-type heavily doped semiconductor transmission layer on the surface of the substrate;

[0018] Step 3, epitaxially growing an N-type lightly doped AlN voltage-enhancing layer on the N-type heavily doped semiconductor transport layer;

[0019] Step 4, epitaxially growing an N-type SiC intrinsic layer on the N-type lightly doped AlN withstand voltage improvement layer;

[0020] Step 5, epitaxially growing a P-type heavily doped semiconductor transmission layer on the N-type SiC intrinsic layer;

[0021] Step 6: removing the substrate obtained according to the above steps through a substrate removal process;

[0022] Step 7: evaporate and photolithograph on the N-type heavily doped semiconductor transmission layer to produce an N-type ohmic electrode, and then evaporate and photolithograph on the P-type heavily doped semiconductor transmission layer to produce a P-type ohmic electrode.

[0023] Furthermore, the thickness of the N-type lightly doped AlN voltage-enhancing layer is 3 microns.

[0024] Furthermore, the doping concentration of the N-type lightly doped AlN withstand voltage improvement layer is 1*10 17 cm -3 .

[0025] Furthermore, the N-type lightly doped AlN voltage-enhancing layer is N-type AlN.

[0026] Furthermore, the thickness of the N-type intrinsic layer is 3 microns.

[0027] Furthermore, the thickness of the N-type heavily doped semiconductor transmission layer is 6 microns.

[0028] The advantages of the present invention are as follows: in the present invention, the N-type lightly doped AlN withstand voltage improvement layer is below the N-type intrinsic layer, and the structure does not affect the withstand voltage characteristics of the PN junction formed by the original PN structure. Simply adding a layer of N-type lightly doped AlN withstand voltage improvement layer can greatly improve the withstand voltage of the PIN diode. The thermal conductivity of the AlN material is close to that of the SiC material, and the longitudinal heat distribution in the PIN diode is more uniform, and concentrated hot spots are not likely to occur, which is not likely to cause thermal failure of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0030] Figure 1 This is a flow chart of a method for manufacturing an AlN-based SiC PIN diode according to the present invention;

[0031] Figure 2 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 1 ;

[0032] Figure 3 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 2 ;

[0033] Figure 4 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 3 ;

[0034] Figure 5 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 4 ;

[0035] Figure 6 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 5 ;

[0036] Figure 7 A schematic diagram of a method for manufacturing an AlN-based SiC PIN diode according to the present invention Figure 6 ;

[0037] Figure 8 A schematic diagram of a diode manufactured by a method for manufacturing a SiC PIN diode based on AlN according to the present invention;

[0038] Fig. 9 Schematic diagram of the space charge region during the working process of the diode of the present invention Figure 1 ;

[0039] Fig.10Schematic diagram of the space charge region during the working process of the diode of the present invention Figure 2 . DETAILED DESCRIPTION

[0040] like Figures 1 to 8 As shown, the present invention provides a method for manufacturing an AlN-based SiC PIN diode, which specifically includes the following steps:

[0041] Step 1, washing the surface of the SiC epitaxial wafer with deionized water, and then soaking it in a heated mixed washing solution for 1 minute to further remove foreign matter on the surface of the SiC epitaxial wafer to form a substrate; the mixed washing solution includes ammonia water, hydrogen peroxide and deionized water;

[0042] Step 2, epitaxially growing an N-type heavily doped semiconductor transmission layer on the surface of the substrate;

[0043] Step 3: epitaxially grow an N-type lightly doped AlN voltage-increasing layer on the N-type heavily doped semiconductor transport layer, wherein the thickness of the N-type lightly doped AlN voltage-increasing layer is 3 microns, the N-type lightly doped AlN voltage-increasing layer is N-type AlN, and the doping concentration of the N-type lightly doped AlN voltage-increasing layer is 1*10 17 cm -3 ;

[0044] Step 4, epitaxially growing an N-type SiC intrinsic layer on the N-type lightly doped AlN withstand voltage improvement layer, wherein the thickness of the N-type intrinsic layer is 3 microns;

[0045] Step 5, epitaxially growing a P-type heavily doped semiconductor transmission layer on the N-type SiC intrinsic layer, wherein the thickness of the N-type heavily doped semiconductor transmission layer is 6 microns;

[0046] Step 6: removing the substrate obtained according to the above steps through a substrate removal process;

[0047] Step 7: evaporate and photolithograph on the N-type heavily doped semiconductor transmission layer to produce an N-type ohmic electrode, and then evaporate and photolithograph on the P-type heavily doped semiconductor transmission layer to produce a P-type ohmic electrode.

[0048] like Figure 8 As shown, the present invention provides an AlN-based SiC PIN diode, comprising:

[0049] An N-type ohmic electrode;

[0050] an N-type heavily doped semiconductor transmission layer, wherein the lower side of the N-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type ohmic electrode;

[0051] An N-type lightly doped AlN withstand voltage improvement layer, wherein the lower side of the N-type lightly doped AlN withstand voltage improvement layer is connected to the upper side of the N-type heavily doped semiconductor transmission layer;

[0052] an N-type intrinsic layer, wherein the lower side of the N-type intrinsic layer is connected to the upper side of the N-type lightly doped AlN withstand voltage improvement layer, the thickness of the N-type intrinsic layer is 3 microns (the thickness of the N-type intrinsic layer in the prior art is 6 microns), and the material of the N-type intrinsic layer is SiC;

[0053] a P-type heavily doped semiconductor transmission layer, wherein the lower side of the P-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type intrinsic layer;

[0054] and, a P-type ohmic electrode, wherein the lower side of the P-type ohmic electrode is connected to the upper side of the P-type heavily doped semiconductor transmission layer.

[0055] The doping concentration of the N-type lightly doped AlN withstand voltage improvement layer is 1*10 17 cm -3 .

[0056] The thickness of the N-type lightly doped AlN voltage-resistant improving layer is 3 microns.

[0057] The doping concentration of the N-type lightly doped AlN voltage-enhancing layer is twice the doping concentration of the N-type intrinsic layer.

[0058] The diode of the present invention is a vertical structure and a bipolar device. The diode has extremely high withstand voltage capability. On the original basis, an N-type lightly doped AlN withstand voltage improvement layer is added above the N-type heavily doped semiconductor transmission layer. Since the AlN material has a large band gap of 6.2eV, which is about twice that of the SiC material, it has the characteristic of improving withstand voltage. In addition, the AlN material can be easily lightly doped with N type based on the existing process technology. This characteristic is consistent with the solution of improving withstand voltage, and the withstand voltage characteristic is improved instead of the current characteristic.

[0059] The thermal conductivity of AlN material is 3.19 W / cm / K, which is close to that of SiC material. Its longitudinal heat distribution in the PIN diode is more uniform, and it is less likely to have concentrated hot spots and cause thermal failure of the device.

[0060] The main reason why the PIN diode improves the withstand voltage level of the diode under the same thickness is that a space charge region is formed when the PIN diode is reversely pressurized. The space charge region diffuses from the N-type intrinsic layer to the N-type lightly doped AlN withstand voltage improvement layer. When the space charge region diffuses to the N-type lightly doped AlN withstand voltage improvement layer, because the doping concentration of the N-type lightly doped AlN withstand voltage improvement layer is twice that of the N-type intrinsic layer, at the same voltage, the expansion depth of the space charge region is half of the original. Therefore, under the same thickness, the withstand voltage level is 1.5 times the original. Fig. 9 and 10As shown, the space charge region is divided into two parts. The thickness of the N-type intrinsic region and the N-type lightly doped AlN withstand voltage improvement layer are consistent, but the withstand voltage of the N-type lightly doped AlN withstand voltage improvement layer is twice that of the N-type intrinsic region.

[0061] like Fig. 9 and Fig.10 As shown in the figure, at low voltage, the space charge region diffuses to the N-type intrinsic withstand voltage region. When the voltage is gradually increased, the space charge region diffuses to the AlN region. However, since the doping concentration of AlN is twice that of SiC, the diffusion depth is half at the same voltage. Therefore, under the same thickness, the withstand voltage level is 1.5 times the original.

[0062] The thickness of the PIN diode remains unchanged, that is, the thickness of the N-type lightly doped AlN voltage-resistant improvement layer is 3 microns. When the thickness of the N-type intrinsic layer is 3 microns, the voltage resistance can be increased by 1.5 times and the current can be increased by 2 times. If the thickness of the PIN diode is reduced by 1 micron, the thickness of the N-type lightly doped AlN voltage-resistant improvement layer is 2 microns. When the thickness of the N-type intrinsic layer is 3 microns, the voltage resistance can be the same as that of the prior art, but the current is still improved.

[0063] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A high voltage SiC PIN diode based on AlN, characterized in that: include: An N-type ohmic electrode; an N-type heavily doped semiconductor transmission layer, wherein the lower side of the N-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type ohmic electrode; An N-type lightly doped AlN withstand voltage improvement layer, wherein the lower side of the N-type lightly doped AlN withstand voltage improvement layer is connected to the upper side of the N-type heavily doped semiconductor transmission layer; An N-type intrinsic layer, the lower side of the N-type intrinsic layer is connected to the upper side of the N-type lightly doped AlN withstand voltage improvement layer; a P-type heavily doped semiconductor transmission layer, wherein the lower side of the P-type heavily doped semiconductor transmission layer is connected to the upper side of the N-type intrinsic layer; and, a P-type ohmic electrode, wherein the lower side of the P-type ohmic electrode is connected to the upper side of the P-type heavily doped semiconductor transmission layer.

2. The AlN-based high-voltage SiC PIN diode according to claim 1, characterized in that: The thickness of the N-type lightly doped AlN voltage-resistant improving layer is 2 to 3 microns, and the thickness of the N-type intrinsic layer is 3 microns.

3. The AlN-based high-voltage SiC PIN diode according to claim 1, characterized in that: The doping concentration of the N-type lightly doped AlN voltage-enhancing layer is 1*10 17 cm -3 .

4. The AlN-based high-voltage SiC PIN diode according to claim 1, characterized in that: The doping concentration of the N-type lightly doped AlN voltage-enhancing layer is twice the doping concentration of the N-type intrinsic layer.

5. A method for manufacturing a SiC PIN diode based on AlN, characterized in that: The specific steps include: Step 1, washing the surface of the SiC epitaxial wafer with deionized water, and then soaking it in a heated mixed washing solution for 1 minute to further remove foreign matter on the surface of the SiC epitaxial wafer to form a substrate; the mixed washing solution includes ammonia water, hydrogen peroxide and deionized water; Step 2, epitaxially growing an N-type heavily doped semiconductor transmission layer on the surface of the substrate; Step 3, epitaxially growing an N-type lightly doped AlN voltage-enhancing layer on the N-type heavily doped semiconductor transport layer; Step 4, epitaxially growing an N-type SiC intrinsic layer on the N-type lightly doped AlN withstand voltage improvement layer; Step 5, epitaxially growing a P-type heavily doped semiconductor transmission layer on the N-type SiC intrinsic layer; Step 6: removing the substrate obtained according to the above steps through a substrate removal process; Step 7: evaporate and photolithograph on the N-type heavily doped semiconductor transmission layer to produce an N-type ohmic electrode, and then evaporate and photolithograph on the P-type heavily doped semiconductor transmission layer to produce a P-type ohmic electrode.

6. The method for manufacturing an AlN-based SiC PIN diode according to claim 5, characterized in that: The thickness of the N-type lightly doped AlN voltage-enhancing layer is 2 to 3 micrometers, and the thickness of the N-type SiC intrinsic layer is 3 micrometers.

7. The method for manufacturing an AlN-based SiC PIN diode according to claim 5, characterized in that: The doping concentration of the N-type lightly doped AlN voltage-enhancing layer is 1*10 17 cm -3 .

8. The method for manufacturing an AlN-based SiC PIN diode according to claim 5, characterized in that: The N-type lightly doped AlN voltage-resistant improving layer is N-type AlN.

9. The method for manufacturing an AlN-based SiC PIN diode according to claim 5, characterized in that: The thickness of the N-type heavily doped semiconductor transmission layer is 6 microns.

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