An epitaxial structure and preparation method of a gallium nitride device

Abstract

The present invention discloses a gallium nitride epitaxial structure, belonging to the field of semiconductor technology. It includes a silicon substrate, on which a buffer layer is epitaxially grown, and on which a high-impedance layer with a periodic structure is epitaxially grown. The structure of each period of the high-impedance layer is formed by sequentially growing unintentionally doped Al y Ga (1‑y) N, intentionally doped GaN layer, Al x Ga (1‑x) N, where x = 0.2 to 0.4 and y = 0.6 to 0.8. An unintentionally doped gallium nitride layer is epitaxially grown on the high-impedance layer. A barrier layer is epitaxially grown on the unintentionally doped gallium nitride layer. Through the periodic structure of alternating two materials with lattice deviations in the high-impedance layer, dislocations can be bent within this layer, thereby reducing the extension of dislocation defects caused by lattice mismatch to the barrier layer, and effectively alleviating the leakage current and breakdown characteristic problems of the aforementioned device due to more defects.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to an epitaxial structure of a gallium nitride device and a preparation method thereof. Background Art

[0002] In the past few decades, silicon, as an important basic semiconductor material, has played an extremely important role in the development of electronic integrated circuits and discrete devices. However, with the arrival of the Moore's limit of silicon materials, due to the limitations of its material properties, mainly the low bandgap width and electron drift rate, it has restricted its application in higher voltage and higher frequency situations, and it is becoming increasingly difficult to further reduce the circuit size. Under such conditions, gallium nitride, as a third-generation semiconductor material, has a wider bandgap width (gallium nitride Eg = 3.4eV, silicon Eg = 1.12eV) and higher electron drift rate (the electron drift rate of gallium nitride is 2.5 times that of silicon), which ensures that it has a higher breakdown electric field strength, making it suitable for the preparation of high-voltage and high-frequency power devices. It is an ideal material for emerging fields such as electric vehicles, 5G base stations, and satellites.

[0003] Although gallium nitride is an excellent semiconductor material, it is currently difficult to obtain large-scale commercial gallium nitride single crystals due to the difficulty in material preparation. It is also impossible to obtain gallium nitride devices through homogeneous epitaxy. Using silicon material as the substrate for the epitaxial growth of gallium nitride devices for heterogeneous epitaxy is currently the most common practice in the industry. However, the lattice mismatch between silicon material and gallium nitride material is very high, reaching -16.9%. A higher lattice mismatch will cause a higher defect density in the device. The leakage channel formed by the defects will cause device performance failure and affect the breakdown characteristics of the device.

[0004] The structure of a gallium nitride semiconductor device mainly includes a silicon substrate, a buffer layer, a high-impedance layer, an unintentionally doped gallium nitride layer, and a barrier layer. The inventors believe that due to the large lattice mismatch between silicon materials and gallium nitride materials, a large number of dislocation defects will be introduced into the gallium nitride device. The defects extend from the substrate side to the barrier layer to produce more leakage channels, which have a great impact on the working performance of the device. Therefore, it is necessary to design a gallium nitride epitaxial structure, a semiconductor device, and a preparation method.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art. Summary of the invention

[0006] Through research, the inventors found that due to the large lattice mismatch between silicon materials and gallium nitride materials, a large number of dislocation defects will be introduced into the gallium nitride device, especially longitudinally extending dislocation lines. The dislocation defects will extend from the substrate side to the barrier layer to produce more leakage channels, which will have a great impact on the working performance of the device.

[0007] In view of at least one of the above technical problems, the present disclosure provides an epitaxial structure and a preparation method of a gallium nitride device, and the specific technical solution is as follows:

[0008] A gallium nitride epitaxial structure comprises a silicon substrate, a buffer layer is epitaxially grown on the silicon substrate, a high-impedance layer with a periodic structure is epitaxially grown on the buffer layer, and each period of the high-impedance layer is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N are grown in sequence, wherein x=0.2-0.4, y=0.6-0.8; an unintentionally doped gallium nitride layer is epitaxially grown on the high impedance layer; a barrier layer is epitaxially grown on the unintentionally doped gallium nitride layer, and the periodic structure of alternating two materials with deviations in the lattice of the high impedance layer can make dislocations bend in the layer, thereby reducing the extension of dislocation defects caused by lattice mismatch to the barrier layer, which can effectively alleviate the leakage current and breakdown characteristics problems of the aforementioned device due to more defects.

[0009] A method for preparing a gallium nitride semiconductor device, the gallium nitride semiconductor device comprising the gallium nitride epitaxial structure, the preparation method comprising: selecting a silicon substrate as an epitaxial substrate, using a metal organic compound deposition system as an epitaxial growth system, adjusting the reaction chamber temperature of the metal organic compound deposition system to 1000-1100°C, and using hydrogen as an atmosphere gas to perform high-temperature cleaning on the silicon substrate; then pre-passing aluminum on the silicon substrate, the flow rate and time of the aluminum being a certain calculated value, and growing a buffer layer on the silicon substrate after the pre-passing is completed; adjusting the reaction chamber temperature of the metal organic compound deposition system to 900-1050°C, adjusting the pressure in the reaction chamber to 50-100mbar, V / III to 5000-30000, using C2H4 as a carbon dopant, the carbon doping concentration being accurately controlled by a C2H4 flowmeter, and growing a high impedance layer with a periodic structure on the buffer layer; then growing an unintentionally doped gallium nitride layer on the high impedance layer; and then growing a barrier layer on the unintentionally doped gallium nitride layer.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1. The high impedance layer of the present invention is a periodic structure composed of three materials with different lattice constants, which can cause dislocation defects to bend in the high impedance layer, thereby causing the defects to change their original penetration path, developing from a longitudinal path to a transverse path, and finally terminating at a certain position of the high impedance layer, thereby reducing the number of dislocation defects in the barrier layer as the functional area of ​​the device, and reducing the probability of further introducing new dislocation defects. The leakage channels caused by the defects are also reduced, thereby improving the leakage phenomenon of the device, making the device suitable for a higher voltage environment, thereby improving the breakdown characteristics of the device.

[0012] 2. The extension of dislocation defects to the barrier layer and the entire wafer is effectively reduced, and the in-wafer yield of single-wafer GaN RF devices is significantly improved, which can meet the needs of commercial-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of one period in the high impedance layer of Example 1 in the structure of the present invention;

[0014] Figure 2 It is a schematic diagram of the epitaxial structure of Example 1 in the structure of the present invention.

[0015] Explanation of reference numerals in the figure: 101, silicon substrate; 201, buffer layer; 301, high impedance layer; 401, unintentionally doped gallium nitride layer; 501, barrier layer; 601, intentionally doped p-type gallium nitride layer. DETAILED DESCRIPTION

[0016] In order to better understand the purpose, structure and function of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0017] The serial numbers assigned to the components herein are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" mentioned in this disclosure, unless otherwise specified, includes direct and indirect "connections". In the description of this application, it should be understood that the orientation or position relationship indicated by the orientation terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and brief description, and does not indicate or imply that the device or unit referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0018] like Figure 1 to Figure 2As shown, an epitaxial structure of a gallium nitride device is designed, including a silicon substrate 101, the silicon substrate 101 is suitable for gallium nitride wafers with a diameter range of 2-12 inches, a buffer layer 201 is epitaxially grown on the silicon substrate 101, and a high-resistance layer 301 with a periodic structure is epitaxially grown on the buffer layer 201, and each period of the high-resistance layer 301 is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N is grown sequentially, wherein x=0.2-0.4, y=0.6-0.8; an unintentionally doped gallium nitride layer 401 is epitaxially grown on the high impedance layer 301; and a barrier layer 501 is epitaxially grown on the unintentionally doped gallium nitride layer 401.

[0019] A method for preparing an epitaxial structure of a gallium nitride device, wherein the epitaxial structure of the gallium nitride device is as described above, and the preparation method comprises: selecting a silicon substrate 101 as an epitaxial substrate, using a metal organic compound deposition system as an epitaxial growth system, adjusting the reaction chamber temperature of the metal organic compound deposition system to 1000-1100°C, and performing high-temperature cleaning on the silicon substrate 101 using hydrogen as an atmosphere gas; then pre-passing aluminum on the silicon substrate 101, the pre-passing of aluminum is to avoid chemical reaction between ammonia and the silicon substrate, and the first step of the epitaxial process is to grow a thin layer of aluminum material on the silicon substrate by pre-passing trimethylaluminum into the reaction chamber at high temperature, thereby blocking direct contact between ammonia and the silicon substrate during the subsequent growth of a buffer layer, and ammonia will react with the thin layer of aluminum to generate aluminum nitride material, which becomes part of the buffer layer; the flow rate and time of aluminum are A certain calculated value is obtained. After the pre-pass is completed, a buffer layer 201 is grown on the silicon substrate 101; the temperature of the reaction chamber of the metal organic compound deposition system is adjusted to 900-1050° C., the pressure in the reaction chamber is adjusted to 50-100 mbar, and hydrogen, ammonia and an organic metal source are introduced into the silicon substrate in the reaction chamber of the metal organic chemical vapor deposition system, wherein ammonia is used as a V group source material, trimethyl gallium and trimethyl aluminum are used as III group raw materials, V / III is 5000-30000, C2H4 is used as a carbon dopant, and the doping concentration of carbon is accurately controlled by a C2H4 flowmeter, and a high impedance layer 301 with a periodic structure is grown on the buffer layer 201; then, an unintentionally doped gallium nitride layer 401 is grown on the high impedance layer 301; then, a barrier layer 501 is grown on the unintentionally doped gallium nitride layer 401.

[0020] Working principle: The GaN device structure mainly includes a silicon substrate, a buffer layer, a high impedance layer, an unintentionally doped GaN layer, a barrier layer / intentionally doped p-type GaN layer or a barrier layer; the dislocation defects extending from the silicon substrate interface will penetrate the aforementioned structural layers. The high impedance layer with a sandwich-shaped periodic structure provided by the present invention can cause the dislocation defects to bend in the high impedance layer, thereby causing the defects to change the original penetration path, developing from a longitudinal path to a transverse inclined path, and finally ending at a certain position of the high impedance layer, thereby reducing the number of dislocation defects in the barrier layer as the functional area of ​​the GaN device, and adopting the form of Al x Ga (1-x) N / c-GaN / Al y Ga (1-y) The periodic structure of N can reduce the probability of introducing new dislocation defects into the barrier layer, and the leakage channels caused by defects are also reduced, which improves the leakage phenomenon of GaN devices. It not only ensures that the intermediate carbon-doped GaN layer can block the vertical leakage current, but also makes the GaN device suitable for higher voltage environments, thereby improving the breakdown characteristics of GaN devices.

[0021] In the above implementation, three embodiments are listed to implement the above technical solution:

[0022] Example 1

[0023] In this embodiment, a silicon substrate 101 with a crystal orientation of <111> is selected as an epitaxial substrate;

[0024] The resistivity of the silicon substrate is determined by the dosage of the dopant during the single crystal growth process. Generally, the more dosage is used, the lower the resistivity is, which is a linear relationship. The resistivity of the silicon substrate disclosed in the present invention is 1 milliohm centimeter;

[0025] The oxygen concentration of the silicon substrate is determined by the process conditions used in the single crystal growth process, mainly the following equipment process parameters: crystal rod pulling speed, crystal rod rotation speed, crucible rotation speed, furnace temperature gradient, furnace temperature, pressure and oxygen content in Ar atmosphere gas. By accurately controlling the settings of the corresponding parameters, the oxygen concentration of the finally prepared silicon single crystal rod is within the scope of the claims. The oxygen concentration of the present disclosure is 15 ppma.

[0026] The carbon concentration of the silicon substrate is determined by the process conditions during the single crystal growth process, mainly the following equipment process parameters: crucible speed, furnace temperature, and pressure. By accurately controlling the settings of the corresponding parameters, the carbon concentration of the finally prepared silicon single crystal rod is within the scope of the claims. The carbon concentration of the present disclosure is 0.2 ppma.

[0027] The thickness of the silicon substrate is determined by the slicing, grinding and polishing processes, and the corresponding equipment parameters are adjusted to achieve the required final thickness value. The thickness disclosed in the present invention is 1150 μm;

[0028] GaN wafers were grown using a metal organic vapor deposition (MOCVD) system. The BOW measurement showed a warpage of 10μm. The Candela surface measurement showed a wafer edge crack value of 78ea and a long crack value of 1.5mm.

[0029] As the silicon substrate for comparison 1: the silicon substrate used for growing 8-inch silicon-based gallium nitride wafers, the resistivity of the silicon substrate is 12 milliohm centimeters, the oxygen concentration is 8 ppma, the carbon concentration is 0.3 ppma, and the thickness is 1150 μm. Compared with this comparison, the warpage of the silicon substrate of the present disclosure is reduced by more than 90%, and the number of cracks at the edge of the wafer and the length of longcracks are greatly reduced, which can fully meet the requirements of gallium nitride wafers, and its yield is above 95%.

[0030] As the silicon substrate for comparison 2, a silicon substrate used for growing 8-inch silicon-based gallium nitride wafers has a resistivity of 1 milliohm centimeter, an oxygen concentration of 20 ppma, a carbon concentration of 0.2 ppma, and a thickness of 1150 μm. The gallium nitride wafer is also grown by a metal organic compound vapor deposition MOCVD system, and its warpage BOW measurement shows 24 μm. The Candela surface measurement shows a wafer edge crack value of 145 ea and a longcrack value of 3.7 mm. Both the warpage BOW and the wafer edge crack and longcrack data are improved on the basis of comparison 1, but are not as good as the effect of the disclosed solution.

[0031] As the silicon substrate for comparison 3, the silicon substrate used for the growth of 8-inch silicon-based gallium nitride wafers has a resistivity of 1 milliohm centimeter, an oxygen concentration of 24 ppma, a carbon concentration of 0.2 ppma, and a thickness of 1150 μm. The gallium nitride wafer is also grown by a metal organic compound vapor deposition MOCVD system. Through a microscope, it can be clearly seen that there are a large number of cracks on the surface of the wafer using the silicon substrate with an oxygen concentration of 24 ppma. This is because the mechanical strength of the silicon substrate is too high, resulting in lattice relaxation during the epitaxial growth process due to stress release, resulting in cracks, and gallium nitride devices can no longer be prepared;

[0032] As a silicon substrate for comparison 4, a silicon substrate used for growing 8-inch silicon-based gallium nitride wafers has a resistivity of 1 milliohm centimeter, an oxygen concentration of 10 ppma, a carbon concentration of 0.2 ppma, and a thickness of 1150 μm. The BOW measurement of the gallium nitride wafer warpage using a silicon substrate with an oxygen concentration of 10 ppma shows 47 μm, and the Candela surface measurement shows a wafer edge crack value of 170 ea and a longcrack value of 7.9 mm. Both the warpage BOW and the wafer edge crack and longcrack data are improved on the basis of the control example, but are not as good as the effect disclosed in the present invention.

[0033] As a silicon substrate for comparison 5, a silicon substrate used for growing 8-inch silicon-based gallium nitride wafers has a resistivity of 0.3 milliohm-cm, an oxygen concentration of 10 ppma, a carbon concentration of 0.2 ppma, and a thickness of 1150 μm. The gallium nitride wafer is also grown by a metal organic compound vapor deposition MOCVD system. Through a microscope, it can be clearly seen that there are a large number of cracks on the surface of the gallium nitride wafer using a silicon substrate with a resistivity of 0.3 milliohm-cm. This is because the mechanical strength of the silicon substrate is too high, resulting in lattice relaxation during the epitaxial growth process, which leads to cracks. It is no longer possible to prepare gallium nitride devices;

[0034] As a comparison of silicon substrate 6, the silicon substrate used for the growth of 8-inch silicon-based gallium nitride wafers has a resistivity of 10 milliohm-cm, an oxygen concentration of 10 ppma, a carbon concentration of 0.2 ppma, and a thickness of 1150μm. The BOW measurement of the gallium nitride wafer warpage using a silicon substrate with a resistivity of 10 milliohm-cm shows 72μm, and the Candela surface measurement shows a wafer edge crack value of 230ea and a longcrack value of 11.6mm. Both the warpage BOW and the wafer edge crack and longcrack data are improved on the basis of the control example, but are not as good as the effect disclosed in the present invention.

[0035] As a silicon substrate for comparison 7, a silicon substrate used for growing 8-inch silicon-based gallium nitride wafers has a resistivity of 10 milliohm centimeters, an oxygen concentration of 10 ppma, a carbon concentration of 0.5 ppma, and a thickness of 1150 μm. The gallium nitride wafer is also grown by a metal organic compound vapor deposition MOCVD system, and its warpage BOW measurement shows 56 μm. The Candela surface measurement shows a wafer edge crack value of 132 ea and a longcrack value of 5.6 mm. Both the warpage BOW and the wafer edge crack and longcrack data are improved on the basis of the control example, but are not as good as the effect disclosed in the present invention.

[0036] A metal organic chemical vapor deposition system (MOCVD) is used as an epitaxial growth system, the temperature of the reaction chamber of the metal organic chemical vapor deposition system is adjusted to 1000-1100° C., and the silicon substrate 101 is cleaned at high temperature in an environment where hydrogen is used as an ambient gas to remove oxides on the surface of the silicon substrate 101;

[0037] The parameters of the silicon material itself need to meet the above-mentioned limited ranges at the same time. Only in this way can the mechanical strength of the silicon material be within a range that can not only significantly alleviate the problem of excessive warping during the epitaxial growth of GaN caused by lattice mismatch stress and thermal mismatch stress, but also avoid cracking and scrapping during the epitaxial growth process due to excessive mechanical strength, thereby effectively improving the finished product yield of silicon-based GaN epitaxial growth.

[0038] The silicon substrate defined in the present disclosure can be suitable for high-temperature epitaxial growth of gallium nitride devices in terms of mechanical strength, so that the warpage during the growth process is within a reasonable range, thereby not affecting the production yield of the device, and from the perspective of the preparation of the silicon substrate, the production cost of the silicon substrate is not increased, and the processes for preparing the silicon substrate are all mature processes, and only appropriate adjustments need to be made in doping agents and condition control to meet the requirements of preparing the silicon substrate. Through the present invention, the main parameter indicators of the silicon substrate are defined, and a silicon substrate with mechanical strength suitable for the epitaxial growth of gallium nitride wafers of various sizes is provided, so that the warpage of the gallium nitride wafer is within a controllable range, thereby improving the production yield of silicon-based gallium nitride devices.

[0039] Aluminum is pre-passed on the silicon substrate 101, and the flow rate and time of aluminum are certain calculated values. After the pre-passing, a buffer layer is grown on the silicon substrate 101. The chamber temperature is 900-1050° C., the system chamber pressure is adjusted to 50-100 mbar, V / III is 1000-3000, and the buffer layer adopts an AlN / AlGaN composite structure, and the buffer layer thickness is 300 nm;

[0040] A high impedance layer 301 with a periodic structure is epitaxially grown on the buffer layer 201. Each period of the high impedance layer 301 is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N is grown in sequence, where x=0.2, y=0.8, the chamber temperature is 980-1100°C, the system chamber pressure is adjusted to 50-100 mbar, V / III is 5000-30000, C2H4 is used as the carbon dopant, and the carbon doping concentration is accurately controlled by the C2H4 flowmeter to 1E20 / cm 3 The number of pairs in the entire period is 70, the thickness of the GaN layer in the period is 40nm, and the Alx Ga (1-x) The thickness of the N layer is 10nm, and the thickness of the AlyGa (1-y) The thickness of the N layer is 2nm;

[0041] On the high impedance layer, an unintentionally doped gallium nitride layer is grown, the chamber temperature is 1000-1100° C., the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-50000, and the layer thickness is 1000 nm;

[0042] A barrier layer is grown on the unintentionally doped gallium nitride layer, the barrier layer is an AlGaN layer with an Al component of 21%, the temperature is 1000-1060°C, the system chamber pressure is 50-100mbar, V / III is 1000-5000, and the thickness of the barrier layer is 15nm. Since the thickness of the high impedance layer 301 of the periodic structure described in the present disclosure is much greater than the barrier layer 501, and a thick layer of unintentionally doped gallium nitride layer 401 is separated from the barrier layer 501, the barrier layer 501 using AlGaN, AlInGaN or AlN / AlGaN and their composite structures do not affect the effect of the present disclosure, that is, the technical solution of the present disclosure is applicable to different barrier layers 501, and the technical effect achieved is independent of the barrier layer 501 structure.

[0043] A deliberately doped p-type gallium nitride layer is grown on the barrier layer at a temperature of 900-1000° C., a system chamber pressure of 150-300 mbar, a V / III ratio of 30000-50000, a p-type dopant of Cp2Mg, and a thickness of 100 nm.

[0044] The half-peak widths of the GaN (002) and (102) planes were monitored by an XRD system, showing that they were 354 arcsec and 438 arcsec, respectively, which are fully capable of meeting the requirements for the preparation of high-performance GaN semiconductor devices. The monitoring results of the XRD system show that the dislocation defects inside the GaN wafer are less than those in the control example, that is, Example 1 effectively reduces the extension of dislocation defects to the barrier layer and the entire wafer.

[0045] The gallium nitride epitaxial structure disclosed in the present invention is applied to the power supply power conversion device of the vehicle charging module.

[0046] Example 2

[0047] In this embodiment, a silicon substrate 101 with a crystal orientation of <111> is selected as an epitaxial substrate;

[0048] A metal organic chemical vapor deposition system (MOCVD) is used as an epitaxial growth system, the temperature of the reaction chamber of the metal organic chemical vapor deposition system is adjusted to 1000-1100° C., and the silicon substrate 101 is cleaned at high temperature in an environment where hydrogen is used as an ambient gas to remove oxides on the surface of the silicon substrate 101;

[0049] Aluminum is pre-passed on the silicon substrate 101, and the flow rate and time of aluminum are certain calculated values. After the pre-passing, a buffer layer is grown on the silicon substrate 101. The chamber temperature is 900-1050° C., the system chamber pressure is adjusted to 50-100 mbar, V / III is 1000-3000, and the buffer layer adopts an AlN / AlGaN composite structure, and the buffer layer thickness is 100 nm;

[0050] A high impedance layer 301 with a periodic structure is epitaxially grown on the buffer layer 201. Each period of the high impedance layer 301 is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N is grown in sequence, where x=0.4, y=0.6, the chamber temperature is 980-1100°C, the system chamber pressure is adjusted to 50-100 mbar, V / III is 5000-30000, C2H4 is used as the carbon dopant, and the carbon doping concentration is accurately controlled by the C2H4 flowmeter to 1E18 / cm 3 The number of pairs in the entire period is 125, the thickness of the GaN layer in the period is 20nm, and the Al x Ga (1-x) The thickness of the N layer is 5nm, and the thickness of the AlyGa (1-y) The thickness of the N layer is 5 nm;

[0051] On the high impedance layer, an unintentionally doped gallium nitride layer is grown, the chamber temperature is 1000-1100° C., the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-50000, and the layer thickness is 1000 nm;

[0052] A barrier layer is grown on the unintentionally doped gallium nitride layer, the barrier layer is an AlGaN layer with an Al component of 24%, the temperature is 1000-1060°C, the system chamber pressure is 50-100mbar, V / III is 1000-5000, and the thickness of the barrier layer is 14nm. Since the thickness of the high impedance layer 301 of the periodic structure described in the present disclosure is much greater than the barrier layer 501, and a thick layer of unintentionally doped gallium nitride layer 401 is separated from the barrier layer 501, the barrier layer 501 using AlGaN, AlInGaN or AlN / AlGaN and their composite structures do not affect the effect of the present disclosure, that is, the technical solution of the present disclosure is applicable to different barrier layers 501, and the technical effect achieved is independent of the barrier layer 501 structure.

[0053] A deliberately doped p-type gallium nitride layer is grown on the barrier layer at a temperature of 900-1000° C., a system chamber pressure of 150-300 mbar, a V / III ratio of 30000-50000, a p-type dopant of Cp2Mg, and a thickness of 85 nm.

[0054] The half-peak widths of the GaN (002) and (102) planes were monitored by an XRD system, showing that they were 334 arcsec and 422 arcsec, respectively, which are fully capable of meeting the preparation requirements of high-performance GaN semiconductor devices. The monitoring results of the XRD system show that the dislocation defects inside the GaN wafer are less than those in the control example, that is, Example 2 effectively reduces the extension of dislocation defects to the barrier layer and the entire wafer.

[0055] The gallium nitride epitaxial structure disclosed in the present invention is applied to a fast charging power conversion device of a smartphone.

[0056] Example 3

[0057] In this embodiment, a silicon substrate 101 with a crystal orientation of <111> is selected as an epitaxial substrate;

[0058] A metal organic chemical vapor deposition system (MOCVD) is used as an epitaxial growth system, the temperature of the reaction chamber of the metal organic chemical vapor deposition system is adjusted to 1000-1100° C., and the silicon substrate 101 is cleaned at high temperature in an environment where hydrogen is used as an ambient gas to remove oxides on the surface of the silicon substrate 101;

[0059] Aluminum is pre-passed on the silicon substrate 101, and the flow rate and time of aluminum are certain calculated values. After the pre-passing, a buffer layer is grown on the silicon substrate 101. The chamber temperature is 900-1050° C., the system chamber pressure is adjusted to 50-100 mbar, V / III is 1000-3000, and the buffer layer adopts an AlN / AlGaN composite structure, and the buffer layer thickness is 100 nm;

[0060] A high impedance layer 301 with a periodic structure is epitaxially grown on the buffer layer 201. Each period of the high impedance layer 301 is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N is grown in sequence, where x=0.3, y=0.7, the chamber temperature is 980-1100°C, the system chamber pressure is adjusted to 50-100 mbar, V / III is 5000-30000, C2H4 is used as the carbon dopant, and the carbon doping concentration is accurately controlled by the C2H4 flowmeter to 1E19 / cm 3 The number of pairs in the entire period is 125, the thickness of the GaN layer in the period is 20nm, and the Al x Ga (1-x) The thickness of the N layer is 8nm, and the thickness of the AlyGa (1-y) The thickness of the N layer is 2nm;

[0061] On the high impedance layer, an unintentionally doped gallium nitride layer is grown, the chamber temperature is 1000-1100° C., the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-50000, and the layer thickness is 1000 nm;

[0062] A barrier layer is grown on the unintentionally doped gallium nitride layer. The barrier layer is an AlGaN layer with an Al component of 23%. The temperature is 1000-1060° C., the system cavity pressure is 50-100 mbar, V / III is 1000-5000, and the barrier layer thickness is 14 nm.

[0063] The disclosed epitaxial structure is applied to 5G macro base station RF module devices in the gallium nitride RF field.

[0064] Since the thickness of the high impedance layer 301 of the periodic structure described in the present disclosure is much greater than that of the barrier layer 501, and there is a thick layer of unintentionally doped gallium nitride layer 401 between the barrier layer 501, the use of AlGaN, AlInGaN or AlN / AlGaN and their composite structures for the barrier layer 501 does not affect the effect of the present disclosure, that is, the technical solution of the present disclosure is applicable to different barrier layers 501, and the technical effect achieved is independent of the barrier layer 501 structure used.

[0065] The half-peak widths of the GaN (002) and (102) planes were monitored by an XRD system, showing that they were 340 arcsec and 418 arcsec, respectively, which are fully capable of meeting the requirements for the preparation of high-performance GaN semiconductor devices. The monitoring results of the XRD system show that the dislocation defects inside the GaN wafer are less than those in the control example, that is, Example 3 effectively reduces the extension of dislocation defects to the barrier layer and the entire wafer.

[0066] The gallium nitride epitaxial structure disclosed in the present invention can be applied to different semiconductor devices, such as power devices, radio frequency devices, and field effect transistors.

[0067] Comparative Example 1

[0068] This comparative example uses a silicon substrate with a crystal orientation of <111> as the epitaxial substrate;

[0069] A metal organic chemical vapor deposition system (MOCVD) is used as an epitaxial growth system, the temperature of the reaction chamber of the metal organic chemical vapor deposition system is adjusted to 1000-1100° C., and the silicon substrate 101 is cleaned at high temperature in an environment where hydrogen is used as an ambient gas to remove oxides on the surface of the silicon substrate 101;

[0070] Pre-passing Al on the silicon substrate, the flow rate and time of Al are certain calculated values, and then growing a buffer layer, the chamber temperature is 900-1050° C., the system chamber pressure is adjusted to 50-100 mbar, V / III is 1000-3000, and the buffer layer adopts an AlN / AlGaN composite structure with a thickness of 300 nm;

[0071] A conventional intentionally carbon-doped GaN high-impedance layer is grown on the buffer layer, the chamber temperature is 1050-1100°C, the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-40000, C2H4 is used as a carbon dopant, the carbon doping concentration is accurately controlled by a C2H4 flowmeter, and the thickness of the high-impedance layer is 3000nm;

[0072] On the high impedance layer, an unintentionally doped gallium nitride layer is grown, the chamber temperature is 1000-1100° C., the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-50000, and the layer thickness is 1000 nm;

[0073] A barrier layer is grown on the unintentionally doped gallium nitride layer, the barrier layer is an AlGaN layer with an Al component of 23%, the temperature is 1000-1060° C., the system cavity pressure is 50-100 mbar, V / III is 1000-5000, and the barrier layer thickness is 15 nm;

[0074] On the barrier layer, a deliberately doped p-type gallium nitride layer is grown, the temperature is 900-1000° C., the system chamber pressure is 150-300 mbar, V / III is 30000-50000, the p-type dopant is bis(cyclopentadienyl)magnesium (Cp2Mg), and the thickness of the deliberately doped p-type gallium nitride layer is 100 nm;

[0075] The half-width of the control example was monitored by an XRD ray system, showing that the half-widths of the (002) and (102) planes of gallium nitride were 599 arcsec and 870 arcsec, respectively. The data show that gallium nitride wafers have many dislocation defects, and the preparation of gallium nitride devices will inevitably result in more leakage channels caused by defects, thereby affecting the performance of the devices.

[0076] Comparative Example 2

[0077] This comparative example uses a silicon substrate with a crystal orientation of <111> as the epitaxial substrate;

[0078] A metal organic chemical vapor deposition system (MOCVD) is used as an epitaxial growth system, the temperature of the reaction chamber of the metal organic chemical vapor deposition system is adjusted to 1000-1100° C., and the silicon substrate 101 is cleaned at high temperature in an environment where hydrogen is used as an ambient gas to remove oxides on the surface of the silicon substrate 101;

[0079] Pre-passing Al on the silicon substrate, the flow rate and time of Al are certain calculated values, and then growing a buffer layer, the chamber temperature is 900-1050° C., the system chamber pressure is adjusted to 50-100 mbar, V / III is 1000-3000, and the buffer layer adopts an AlN / AlGaN composite structure with a thickness of 300 nm;

[0080] A conventional intentionally carbon-doped GaN high-impedance layer is grown on the buffer layer, the chamber temperature is 1050-1100°C, the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-40000, C2H4 is used as a carbon dopant, the carbon doping concentration is accurately controlled by a C2H4 flowmeter, and the thickness of the high-impedance layer is 3000nm;

[0081] On the high impedance layer, an unintentionally doped gallium nitride layer is grown, the chamber temperature is 1000-1100° C., the system chamber pressure is adjusted to 100-200 mbar, V / III is 30000-50000, and the layer thickness is 1000 nm;

[0082] A barrier layer is grown on the unintentionally doped gallium nitride layer, the barrier layer is an AlGaN layer with an Al component of 23%, the temperature is 1000-1060° C., the system cavity pressure is 50-100 mbar, V / III is 1000-5000, and the barrier layer thickness is 15 nm;

[0083] On the barrier layer, a deliberately doped p-type gallium nitride layer is grown, the temperature is 900-1000° C., the system chamber pressure is 150-300 mbar, V / III is 30000-50000, the p-type dopant is bis(cyclopentadienyl)magnesium (Cp2Mg), and the thickness of the deliberately doped p-type gallium nitride layer is 100 nm;

[0084] The half-width of the control example was monitored by an XRD ray system, showing that the half-widths of the (002) and (102) planes of gallium nitride were 409 arcsec and 570 arcsec, respectively. The data show that the gallium nitride wafer has many dislocation defects, and the preparation of gallium nitride devices will inevitably result in more leakage channels caused by defects, thereby affecting the performance of the device.

[0085] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. An epitaxial structure of a gallium nitride device, comprising a silicon substrate (101), characterized in that: A buffer layer (201) is epitaxially grown on the silicon substrate (101), and a high-impedance layer (301) with a periodic structure is epitaxially grown on the buffer layer (201), wherein each period of the high-impedance layer (301) is composed of unintentionally doped Al y Ga (1-y) N, intentionally doped GaN layer, unintentionally doped Al x Ga (1-x) N is grown in sequence, wherein x=0.2-0.4, y=0.6-0.8; an unintentionally doped gallium nitride layer (401) is epitaxially grown on the high impedance layer (301); and a barrier layer (501) is epitaxially grown on the unintentionally doped gallium nitride layer (401).

2. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: The resistivity of the silicon substrate (101) is 0.5 to 10 milliohm centimeters.

3. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: The oxygen concentration of the silicon substrate (101) is 10-20 ppma.

4. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: The buffer layer (201) is AlN, AlInN or an AlN / AlInN composite structure, or an AlN / AlGaN composite structure, and the thickness of the buffer layer is 100-300 nm.

5. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: The intentionally doped GaN uses carbon as the dopant, with a carbon doping concentration between 1E18 / cm 3 To 1E20 / cm 3 , the periodic structure is Al x Ga (1-x) N / c-GaN / Al y Ga (1-y) N.

6. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: The barrier layer (501) is one of AlGaN, AlInGaN, AlN / AlGaN or a combination thereof.

7. The epitaxial structure of the gallium nitride device according to claim 1, characterized in that: An intentionally doped p-type gallium nitride layer (601) is epitaxially grown on the barrier layer (501).

8. The epitaxial structure of the gallium nitride device according to claim 7, characterized in that: The thickness of the intentionally doped p-type gallium nitride layer (601) is 50-150 nm.

9. A method for preparing an epitaxial structure of a gallium nitride device, characterized in that: The epitaxial structure of the gallium nitride device is as described in any one of claims 1 to 8, and the preparation method comprises: selecting a silicon substrate (101) as an epitaxial substrate, using a metal organic compound deposition system as an epitaxial growth system, adjusting the temperature of the reaction chamber of the metal organic compound deposition system to 1000-1100° C., and using hydrogen as an atmosphere gas to perform high-temperature cleaning on the silicon substrate (101); then pre-passing aluminum on the silicon substrate (101), wherein the flow rate and time of the aluminum are certain calculated values, and after the pre-passing is completed, passing aluminum on the silicon substrate (101) 1) growing a buffer layer (201) on the top; adjusting the reaction chamber temperature of the metal organic compound deposition system to 900-1050° C., adjusting the pressure in the reaction chamber to 50-100 mbar, V / III to 5000-30000, using C2H4 as a carbon dopant, the carbon doping concentration is accurately controlled by a C2H4 flowmeter, growing a high impedance layer (301) with a periodic structure on the buffer layer (201); and then growing an unintentionally doped gallium nitride layer (401) on the high impedance layer (301); Then, a barrier layer (501) is grown on the unintentionally doped gallium nitride layer (401).

10. The method for preparing the epitaxial structure of a gallium nitride device according to claim 9, characterized in that: A deliberately doped p-type gallium nitride layer (601) is grown on the barrier layer (501), and the growth conditions are as follows: the reaction chamber temperature of the metal organic compound deposition system is adjusted to 900-1000°C, the pressure is 150-300 mbar, the V / III is 30000-50000, and the p-type dopant is bis(cyclopentadienyl)magnesium.

Images