A semiconductor device

Abstract

The present invention discloses a semiconductor device, including an epitaxial structure, wherein the epitaxial structure includes a high resistance layer, a channel layer and a barrier layer, wherein a plurality of newly added p-GaN layers doped with Mg are arranged between the channel layer and the high resistance layer, and a plurality of newly added channel layers are arranged between the channel layer and the high resistance layer, wherein the newly added p-GaN layers and the newly added channel layers are arranged alternately; the thickness of the barrier layer is greater than or equal to 20nm; and the content of Al component in the barrier layer is greater than or equal to 20%. The semiconductor device of the present invention has an epitaxial structure in which a plurality of P-GaN layers doped with low concentration of Mg are added below the GaN channel layer. On the premise of ensuring that the Vth does not change much or is improved, a thicker barrier layer and a higher Al% component can be used, so as to more effectively suppress the diffusion of Mg in the upper P-GaN layer and better exert the device performance. At the same time, due to the thickening of the barrier layer, its crystal quality is improved, and the gate stability of the device can be further improved, and the device is more reliable.

Description

[0001] This application is a divisional application of the invention patent application with the application date of November 30, 2023, application number 2023116173669, and invention name "An epitaxial structure of a semiconductor device, a preparation method thereof, and a semiconductor device". Technical Field

[0002] The invention belongs to the technical field of microelectronics and third-generation semiconductor materials, and in particular relates to a semiconductor device including an improved epitaxial structure. Background Art

[0003] With the development of high-voltage switches and high-speed RF circuits, gallium nitride high electron mobility transistors (GaN HEMTs) have become the focus of research in this field. Conventional GaN HEMT devices are all depletion-type, with a threshold voltage of <0V, and require a negative turn-on voltage. When designing power, RF and microwave chips, the negative gate voltage power supply design increases the design cost; the threshold voltage of the enhanced HEMT is positive, and only a positive bias is required to make it work or pinch off in actual applications. This can eliminate the circuit design of negative bias, simplify the circuit, reduce the complexity of circuit design and the cost of preparation, which is of great significance for large-scale power microwave RF circuit applications. For power switching circuits, enhanced HEMT devices ensure that the HEMT device is in the off state when the drive circuit fails, thereby providing failure protection for the power switching system.

[0004] There are several methods to realize normally-off HEMT devices, such as fluorine ion implantation, partially or fully recessed AlGaN with MIS gate, p-GaN gate, etc. Among the above methods, p-GaN gate has proven to be the most reliable and is currently being used in commercial products, in thinner (e.g. ) The formation of a p-GaN layer (p-AlGaN or p-InAlN) on top of the AlGaN barrier layer can effectively deplete the two-dimensional electron gas (2DEG), thereby achieving normally-off operation. This two-dimensional electron gas (2DEG) depletion effect depends largely on the thickness of the AlGaN barrier layer, the Al% composition, and the Mg doping concentration in the p-GaN on top of the AlGaN barrier layer, and gradually weakens with the increase of the thickness of the AlGaN barrier layer (>20nm) and / or Al% (>20%). Therefore, to obtain an ideal threshold voltage Vth (e.g., 1~2V), the thickness and Al% of the AlGaN barrier layer must be adjusted simultaneously.

[0005] Therefore, in the existing scheme, a more common method to realize p-GaN-based enhanced HEMT is to design the barrier layer to be 12nm-15nm, and the threshold voltage is about 2V. However, due to the relatively thin thickness of the barrier layer, the Mg atoms in the p-GaN will easily diffuse into the channel layer, thereby increasing the on-resistance of the device and affecting the working efficiency of the HEMT device. In p-GaN-based enhanced HEMT devices, in order to effectively reduce the number of Mg atoms in p-GaN that diffuse into the channel layer, the commonly used method is to thicken the barrier layer. However, the thickening of the barrier layer will weaken the transconductance gate control ability of the p-GaN layer, causing the threshold voltage to move negatively, thereby reducing the threshold voltage, or even turning it negative, thereby losing its normally-off characteristics. Therefore, a balance needs to be struck between the two.

[0006] The main problems of the prior art are: in order to obtain a positive Vth bias (switching voltage of 1 to 2V), it is necessary to reduce the thickness of the barrier layer and simultaneously reduce the Al% component in the barrier layer or increase the Mg doping concentration in the p-GaN layer; but the adjustment brings three problems: 1. The barrier layer thickness becomes thinner, so that the Mg in the p-GaN layer above the barrier layer can easily diffuse into the 2DEG channel layer during the growth process, thereby reducing the concentration of 2DEG, increasing Ron, and reducing device performance; 2. The barrier layer becomes thinner and the Al% component decreases, which reduces the concentration of 2DEG and increases the on-resistance, affecting the device performance of GaN. At the same time, due to the thinning of the thickness, the crystal quality of the material layer deteriorates, and the reliability of the barrier layer also deteriorates; 3. Increasing the Mg concentration in the p-GaN layer will make it easier for Mg to diffuse into the channel layer, thereby affecting the device performance.

[0007] At present, the industry has done a lot of work on the barrier layer, such as using alloy barrier layers (one or more AlN layers) or superlattice barrier layers formed by alternating AlInGaN (Al and In component changes) with different component concentrations. The core idea of ​​the two ideas is to increase the thickness of the barrier layer, but the increase in the thickness of the barrier layer will weaken the transconductance gate control ability of the p-GaN layer, making it difficult to control the electrons in the channel layer, thus forming leakage. That is to say, after the barrier layer becomes thicker, the valence band in the energy band generated by the p-GaN layer is difficult to pull the valence band of GaN in the channel layer higher than the Fermi level. If it is lower than the Fermi level, the performance of the device becomes normally open, that is, the threshold voltage becomes negative.

[0008] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the invention

[0009] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a semiconductor device that can use a thicker barrier layer and a higher Al% component while ensuring that Vth does not change much or is improved, and can more effectively inhibit the diffusion of upper Mg and better exert device performance.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] An epitaxial structure of a semiconductor device comprises a substrate, an AlN layer, a transition layer, a high resistance layer, a channel layer, a barrier layer and a p-GaN layer in sequence, wherein one or more newly added p-GaN layers doped with Mg are arranged between the channel layer and the high resistance layer, and one or more newly added channel layers are arranged between the channel layer and the high resistance layer, wherein the layer closest to the channel layer is the newly added p-GaN layer, and the layer closest to the high resistance layer is the newly added channel layer.

[0012] The epitaxial structure of the semiconductor device of the present invention redesigns the structure below the barrier layer, and adds one or more p-GaN layers doped with low concentration Mg below the GaN channel layer. On the premise of ensuring that Vth does not change much or is improved, a thicker barrier layer (>20nm) and a higher Al% component (>20%) can be used to more effectively inhibit the diffusion of Mg in the upper p-GaN layer and better exert the device performance.

[0013] According to some preferred implementation aspects of the present invention, the thickness of the channel layer is greater than 20 nm.

[0014] According to some preferred implementation aspects of the present invention, a newly added p-GaN layer doped with Mg is provided between the channel layer and the high resistance layer, and a newly added channel layer is provided between the newly added p-GaN layer doped with Mg and the high resistance layer.

[0015] According to some preferred implementation aspects of the present invention, multiple layers of newly added p-GaN layers doped with Mg and multiple layers of newly added channel layers are arranged between the channel layer and the high resistance layer; the newly added p-GaN layers doped with Mg and the newly added channel layers are arranged alternately; and the side closest to the channel layer is the newly added p-GaN layer doped with Mg, and the side closest to the high resistance layer is the newly added channel layer.

[0016] According to some preferred implementation aspects of the present invention, the Mg doping concentration in the newly added p-GaN layer near the high resistance layer is greater than the Mg doping concentration in the newly added p-GaN layer near the channel layer. The main purposes are: 1. Avoiding the formation of excessively high concentrations of Mg near the barrier layer and the possibility of diffusion into the channel layer, thereby affecting the device performance; 2. Multiple layers of p-GaN layers with different concentrations can more effectively attract or deplete electrons in the channel layer, and can also form a built-in PN junction in the epitaxial layer, consuming the charge in the material so that the voltage resistance performance of the epitaxial layer material is better.

[0017] According to some preferred implementation aspects of the present invention, the doping concentration of Mg in the newly added p-GaN layer is 1E17 / cm 3 ~5E18 / cm 3 .

[0018] According to some preferred implementation aspects of the present invention, the thickness of the newly added p-GaN layer close to the high resistance layer is greater than the thickness of the newly added p-GaN layer close to the channel layer.

[0019] According to some preferred implementation aspects of the present invention, the thickness of the newly added p-GaN layer is 10 nm to 20 nm.

[0020] According to some preferred implementation aspects of the present invention, the thickness of the newly added GaN channel layer close to the GaN high resistance layer is greater than the thickness of the newly added GaN channel layer close to the GaN channel layer.

[0021] The present invention also provides a method for preparing the epitaxial structure of the semiconductor device as described above, comprising the following steps:

[0022] An AlN layer, a transition layer, a high resistance layer, one or more layers of newly added p-GaN layers doped with Mg, one or more layers of newly added channel layers, a channel layer, a barrier layer and a p-GaN layer are sequentially grown on a substrate; the newly added p-GaN layers and the newly added channel layers are alternately arranged.

[0023] According to some preferred implementation aspects of the present invention, the preparation parameters for growing the newly added p-GaN layer and the newly added channel layer are: N2 atmosphere, temperature of 900-1000°C, pressure of 100-200 mbar, V / III ratio of 5000-10000. The surface flatness of the prepared GaN is a roughness of less than 0.5 nm. However, it is difficult to achieve a surface roughness of less than 0.5 nm using existing preparation methods; the smaller the surface roughness, the smoother the surface of the epitaxial layer, which also indirectly indicates that the quality of the epitaxial layer has improved, and at the same time, it is of great help to improve the mobility of the 2DEG under the barrier layer.

[0024] The present invention also provides a semiconductor device comprising the epitaxial structure as described above.

[0025] The main principle of the present invention is as follows: In the HEMT device structure, the generation of two-dimensional electron gas is due to the piezoelectric polarization between the barrier layer AlGaN and the GaN channel layer and the spontaneous polarization of the AlGaN layer itself, thereby forming a highly concentrated electron gas (2DEG) in the area of ​​a few nanometers on the upper surface of the GaN channel layer, so that the device is in a conducting state under normal circumstances. By growing a p-GaN layer on top of the barrier layer, a PN junction electric field is formed to attract the electrons in the channel layer, thereby forming the device shutdown. The barrier layer is separated from the PN junction electric field, which means that the barrier layer cannot be too thick and the concentration of the Al% component cannot be too high. If the barrier layer is too thick or the Al% component is too high, the device cannot be turned off. The present invention mainly adopts a new structure below the barrier layer, and adds one or more layers of low-concentration p-GaN (holes) below the GaN channel layer to help the p-GaN above the barrier layer to attract 2DEG electrons, and at the same time can also improve the breakdown voltage of the epitaxial layer. The principle is: the intrinsic GaN channel layer is mainly an N-type material. By introducing a low-concentration Mg-GaN layer into the GaN channel layer, a PN junction can be formed inside the channel layer, reducing the electron concentration in the channel layer, thereby improving the device withstand voltage.

[0026] Due to the adoption of the above technical scheme, compared with the prior art, the advantages of the present invention are as follows: the semiconductor device of the present invention, whose epitaxial structure adds multiple layers of P-GaN layers doped with low concentration of Mg below the GaN channel layer, can use thicker barrier layers and higher Al% components on the premise of ensuring that Vth does not change much or is improved, so as to more effectively inhibit the diffusion of Mg in the upper P-GaN layer and better exert the device performance. At the same time, due to the thickening of the barrier layer, its crystal quality is improved, which can also further improve the gate stability of the device, and the device is more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 is a schematic cross-sectional structural diagram of an epitaxial structure of a semiconductor device in Embodiment 1 of the present invention;

[0029] Figure 2 is a schematic cross-sectional structural diagram of an epitaxial structure of a semiconductor device in Embodiment 2 of the present invention;

[0030] Figure 3It is a schematic diagram of the cross-sectional structure of the epitaxial structure of the semiconductor device in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution 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, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] In response to the existing p-GaN problems, the current traditional method still works on the barrier layer and the p-GaN layer above it, but the problems recorded in the background technology still occur, that is, in order to obtain a positive Vth, the thickness of the barrier layer is reduced while the Al% component in the barrier layer is reduced, which causes Mg to easily diffuse into the 2DEG channel layer, and the device performance and reliability deteriorate. The present invention adopts a solution of inserting one or more additional p-GaN layers between the channel layer and the substrate, so that the electrons in the channel layer and the holes in the p-GaN layer form a PN junction capacitor, thereby attracting the electrons in the channel layer and preventing them from moving freely, thereby consuming the electrons in the channel layer, increasing the threshold voltage, and further improving the vertical leakage performance of the epitaxial layer. At the same time, the present invention also adopts a special growth process and structure to avoid Mg from diffusing upwards. First, after the p-GaN layer is grown, the process adopts low-temperature growth (900-1000°C) to avoid the diffusion of Mg; second, there is a new channel layer between the new p-GaN layers, and the intrinsic MOCVD growth of the new channel layer will be biased towards the N-type layer, thereby attracting Mg and reducing the diffusion of the channel layer toward the barrier layer; third, the thickness of the channel layer close to the barrier layer must be at least 20nm. Through the combination of these three points, the gate control and threshold voltage of the device will not degrade during long-term use, which is closer to actual production application.

[0033] Specifically, the semiconductor device of this embodiment includes an epitaxial structure, which includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high resistance layer, a GaN channel layer, an AlGaN barrier layer and a p-GaN layer (i.e., a Mg-GaN layer), wherein one or more layers of newly added p-GaN layers doped with Mg, i.e., newly added Mg-GaN layers, and one or more layers of newly added GaN channel layers are arranged between the GaN channel layer and the GaN high resistance layer; at the same time, the layer closest to the channel layer is the newly added p-GaN layer, and the layer closest to the high resistance layer is the newly added channel layer.

[0034] Preferably, a newly added p-GaN layer doped with Mg is arranged between the GaN channel layer and the GaN high resistance layer, and a newly added GaN channel layer is arranged between the newly added p-GaN layer doped with Mg and the high resistance layer, that is, the epitaxial structure includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high resistance layer, a newly added GaN channel layer, a newly added p-GaN layer doped with Mg, a GaN channel layer, an AlGaN barrier layer and a p-GaN layer.

[0035] More preferably, multiple layers of newly added p-GaN layers doped with Mg and multiple layers of newly added GaN channel layers are arranged between the GaN channel layer and the GaN high resistance layer; and the newly added p-GaN layers doped with Mg and the newly added GaN channel layers are arranged alternately; and the side closest to the GaN channel layer is the newly added p-GaN layer doped with Mg, and the side closest to the GaN high resistance layer is the newly added GaN channel layer.

[0036] At the same time, the Mg doping concentration in the newly added p-GaN layer close to the GaN high resistance layer is greater than the Mg doping concentration in the newly added p-GaN layer close to the channel layer. The Mg doping concentration in the newly added p-GaN layer is 1E17 / cm 3 ~5E18 / cm 3 .

[0037] The thickness of the newly added p-GaN layer close to the GaN high resistance layer is greater than the thickness of the newly added p-GaN layer close to the GaN channel layer. The thickness of the newly added p-GaN layer is 10nm to 20nm.

[0038] The thickness of the newly added GaN channel layer close to the GaN high resistance layer is greater than the thickness of the newly added GaN channel layer close to the GaN channel layer. The thickness of the newly added GaN channel layer is 20-50nm.

[0039] The thickness of the GaN channel layer closest to the AlGaN barrier layer is greater than 20 nm.

[0040] Example 1

[0041] like Figure 1 As shown in FIG. 1 , the epitaxial structure of the semiconductor device in this embodiment includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high resistance layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a GaN channel layer, an AlGaN barrier layer, and a Mg-GaN layer. The doping concentration of Mg in the newly added Mg-GaN layer is 5E18 / cm 3 , with a thickness of 20nm; the thickness of the newly added GaN channel layer is 20nm, the thickness of the AlGaN barrier layer is 20nm, and the Al component is 20%.

[0042] Example 2

[0043] like Figure 2 As shown, the epitaxial structure of the semiconductor device in this embodiment includes two newly added Mg-GaN layers and two newly added GaN channel layers, and the thickness of the AlGaN barrier layer is increased to 25 nm, and the Al component is increased to 23%.

[0044] Specifically, the epitaxial structure of the semiconductor device in this embodiment includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high resistance layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a GaN channel layer, an AlGaN barrier layer and a Mg-GaN layer.

[0045] The thickness of the GaN channel layer near the AlGaN barrier layer is 20 nm, the thickness of the newly added GaN channel layer near the GaN high resistance layer is 50 nm, and the thickness of the newly added GaN channel layer near the AlGaN barrier layer is 20 nm.

[0046] The thickness of the newly added Mg-GaN layer near the GaN high-resistance layer is 20nm, and the Mg doping concentration is 5E18 / cm 3 The thickness of the newly added Mg-GaN layer near the AlGaN barrier layer is 10nm, and the Mg doping concentration is 1E17 / cm 3 .

[0047] Example 3

[0048] like Figure 3 As shown, the epitaxial structure of the semiconductor device in this embodiment includes three newly added Mg-GaN layers and three newly added GaN channel layers, and the thickness of the AlGaN barrier layer is increased to 28 nm, and the Al component is increased to 26%.

[0049] Specifically, the epitaxial structure of the semiconductor device in this embodiment includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high resistance layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a GaN channel layer, an AlGaN barrier layer and a p-GaN layer.

[0050] The thickness of the GaN channel layer near the AlGaN barrier layer is 20nm. The thickness of the newly added GaN channel layer near the GaN high resistance layer is 50nm, the thickness of the newly added GaN channel layer in the middle is 20nm, and the thickness of the newly added GaN channel layer near the AlGaN barrier layer is 20nm.

[0051] The thickness of the newly added Mg-GaN layer near the GaN high-resistance layer is 20nm, and the Mg doping concentration is 5E18 / cm3 The thickness of the newly added Mg-GaN layer in the middle is 20nm, and the Mg doping concentration is 2E18 / cm 3 The thickness of the newly added Mg-GaN layer near the AlGaN barrier layer is 10nm, and the Mg doping concentration is 1E17 / cm 3 .

[0052] Example 4 Preparation method

[0053] In the existing process, H2 is used as the carrier gas for the p-GaN and GaN channel layers. However, due to the characteristics of Mg, it is particularly easy to form a complex with H2, thereby limiting the P-type characteristics of Mg. In the preparation of the newly added p-GaN and the newly added GaN channel layers in this embodiment, N2 is used as the carrier gas to maximize the characteristics of Mg; at the same time, during the preparation, the temperature is 900-1000°C, the pressure is 100-200mbar, and the V / III ratio is 5000-10000, so as to obtain the newly added p-GaN layer and the newly added GaN layer with good crystal quality, and the surface roughness of the channel layer is less than 0.5nm to ensure the mobility of 2DEG.

[0054] Specifically, the preparation of the p-GaN layer and the GaN layer in this embodiment specifically includes the following steps:

[0055] a. The carrier gas introduced into the MOCVD reaction chamber is switched from H2 to N2, and the pressure of the reaction chamber is adjusted;

[0056] b. Adjust the temperature to 900-1000°C, add NH3, TMGa and Cp2Mg at different flow rates, and sequentially grow a new Mg-GaN layer and a new GaN channel layer on the surface of the high-resistance GaN layer.

[0057] Comparative Example 1

[0058] The epitaxial structure of the semiconductor device in this comparative example includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer, and a Mg-GaN layer, wherein the thickness of the AlGaN barrier layer is 20 nm, and the Al component is 20%. The epitaxial structure of the semiconductor device in this comparative example is a common epitaxial layer structure at present.

[0059] Comparative Example 2

[0060] The epitaxial structure of the semiconductor device in this comparative example includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high-resistance layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a GaN channel layer, an AlGaN barrier layer, and a p-GaN layer. The newly added GaN channel layer and the newly added Mg-GaN layer are prepared by a growth process using H2 as a carrier gas, a pressure of 200 mbar, a V / III ratio of 5000, and a temperature of 1000°C. The doping concentration of Mg in the newly added Mg-GaN layer is 5E18 / cm 3 The thickness of the newly added GaN channel layer is 20nm, the thickness of the AlGaN barrier layer is 20nm, and the Al composition is 20%.

[0061] Comparative Example 3

[0062] The epitaxial structure of the semiconductor device in this comparative example includes, from bottom to top, a Si substrate, an AlN layer, an AlGaN transition layer, a GaN high-resistance layer, a newly added GaN channel layer, a newly added Mg-GaN layer, a GaN channel layer, an AlGaN barrier layer, and a Mg-GaN layer. The newly added GaN channel layer and the newly added Mg-GaN layer are prepared by a growth process using N2 as a carrier gas, a pressure of 200 mbar, a V / III ratio of 5000, and a temperature of 1100°C. The doping concentration of Mg in the newly added Mg-GaN layer is 5E18 / cm 3 The thickness of the newly added GaN channel layer is 20nm, the thickness of the AlGaN barrier layer is 20nm, and the Al composition is 20%.

[0063] Tests and Results

[0064] Relevant performance tests were performed on the epitaxial structures and semiconductor devices in Examples 1-3 and Comparative Examples. The test methods and test results are shown in Table 1.

[0065] Table 1 Test results

[0066]

[0067] The structure of comparative example 1 is a common epitaxial layer structure. In order to more accurately compare the experimental results, the thickness of its barrier layer is set to 20nm (5nm thicker than the current normal thickness), the Al component is 20%, and its threshold voltage is only 0.5V, and the Rsh block resistance is 380 ohms / sq. Compared with comparative example 1, the epitaxial structure of embodiment 1 adds a new Mg-GaN layer (Mg concentration is 5E18 / cm3, thickness is 20nm), and its threshold voltage is significantly improved from 0.5V to 1.8V. At the same time, the leakage current of its epitaxial layer under high voltage becomes smaller, indicating that the new Mg-GaN layer plays a role, but the on-resistance Rsh of the electron gas in the channel layer deteriorates, and its value deteriorates from 380 to 395. It is believed that because the Mg doping concentration in embodiment 1 is too high and too close to the channel layer, part of the Mg easily runs into the channel layer, thereby deteriorating Rsh, but it can still meet the requirements of current products. On the basis of Example 1, the structure was continuously optimized to obtain Example 2 and Example 3. After continuous optimization of the concentration, thickness and growth structure of the newly added p-GaN, the result of Example 3 was finally obtained. Compared with Comparative Example 1, even if the barrier layer adopts a thicker thickness (28nm) and a higher Al component (26%), its threshold voltage is still greatly improved, and the leakage of the epitaxial layer under high voltage is also well controlled, and the high-voltage leakage is reduced from 1.3E-5 in Example 1 to 8.6E-7, which is a great improvement. Through the design of the structure, the concentration of Mg diffusion into the channel layer is also reduced, so that Rsh is better than Comparative Example 1, and the on-resistance of the device is greatly reduced.

[0068] In the experiment of Comparative Example 2 using H2 as the carrier gas, it was found that the threshold voltage was improved, but the increase was not as much as that in Example 1. It is believed that this is because a large amount of H2 enters the growth of the Mg-GaN layer and forms a complex with Mg, thereby limiting the characteristics of Mg. This can also be supported by the data of vertical leakage of the epitaxial layer. The leakage current increase under high pressure is not that high, and its Rsh is also improved compared with Comparative Example 1. The main reason is that the surface roughness in the channel layer has deteriorated. This is because Mg and H2 combine in large quantities in the H2 atmosphere, resulting in more V-pits (V-shaped pits) generated during the growth of Mg-GaN, which in turn affects the quality of the channel layer. The deterioration of the surface roughness of the GaN layer can also support this. At the same time, the results of Comparative Example 3 show that by increasing the temperature during the preparation of the newly added GaN channel layer and the newly added p-GaN layer, the threshold voltage is reduced and the leakage current is increased. The main reason is that due to the excessively high growth temperature, the decomposition rate of the GaN layer is accelerated, resulting in the deterioration of the growth steps on the surface of the GaN layer and a rougher surface. At the same time, due to the excessively high temperature, excessive Mg is doped, making the surface even rougher. These two factors lead to a worse result.

[0069] Through the above experiments and results, it is found that the use of multiple layers of new p-GaN layers with different gradient concentrations can obtain a higher threshold voltage. At the same time, due to the increase in the thickness of the barrier layer and the Al component, the Rsh on-resistance of the device is also reduced, and the voltage resistance performance of the epitaxial layer is further improved.

[0070] The epitaxial structure of the semiconductor device of the present invention redesigns the structure below the barrier layer, and adds one or more layers of p-GaN layers doped with low concentration of Mg below the GaN channel layer. Under the premise of ensuring that Vth does not change much or is improved, a thicker barrier layer (>20nm) and a higher Al% component (>20%) can be used to more effectively inhibit the diffusion of Mg in the upper p-GaN layer and better exert the device performance. The key points of the present invention are: 1. The position of the newly added Mg-doped p-GaN: at a position greater than 20nm below the AlGaN barrier layer; below 20nm, Mg will diffuse into the 2DEG layer, reducing the electron gas concentration and increasing the resistance; 2. The distribution of p-GaN concentration: in the direction away from the 2DEG channel layer, its concentration increases successively, from the position of 20nm, the concentration is 1E17 / cm 3 To 5E18 / cm 3 , can be divided into one or more layers; the thickness and Al% component of the corresponding barrier layer can be thickened by changing the number of layers and concentration. For example: in Example 2, the thickness of the AlGaN barrier layer can be increased from 20nm to 25nm, and the Al component of 20% can be increased to 23%; in Example 3: the thickness of the AlGaN barrier layer can be increased from 20nm to 28nm, and the Al component of 20% can be increased to 26%; 3. Growth method of p-GaN layer and GaN channel layer: The conventional MOCVD method uses H2 as the carrier gas, but due to the characteristics of Mg, the present invention uses N2 atmosphere, the temperature is 900-1000℃, the pressure is 100-200mbar, and the V / III ratio is 5000-10000; the GaN surface flatness is obtained with a roughness of less than 0.5nm. The above three points must be combined to achieve the technical effect of this application.

[0071] The above embodiments prepared by the method of the present invention are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A semiconductor device comprising an epitaxial structure, wherein the epitaxial structure comprises a high resistance layer, a channel layer and a barrier layer, characterized in that: A plurality of newly added p-GaN layers doped with Mg are arranged between the channel layer and the high resistance layer, and a plurality of newly added channel layers are arranged between the channel layer and the high resistance layer, and the newly added p-GaN layers and the newly added channel layers are arranged alternately; the thickness of the barrier layer is greater than or equal to 20 nm; the content of Al component in the barrier layer is greater than or equal to 20%; The newly added p-GaN layer and the newly added channel layer are prepared by the following method: a. The carrier gas introduced into the MOCVD reaction chamber is switched from H2 to N2, and the pressure of the reaction chamber is adjusted; b. Adjust the temperature to 900~1000℃, add NH3, TMGa and Cp2Mg at different flow rates, and grow a new p-GaN layer and a new channel layer on the surface of the high resistance layer in sequence.

2. The semiconductor device according to claim 1, wherein: The surface roughness of the newly added p-GaN layer and the newly added channel layer is less than 0.5 nm.

3. The semiconductor device according to claim 1, wherein: The newly added p-GaN layer closest to the channel layer is arranged at a position greater than 20 nm below the barrier layer.

4. The semiconductor device according to claim 1, wherein: The preparation parameters for growing the newly added p-GaN layer and the newly added channel layer are: N2 atmosphere, temperature of 900-1000°C, pressure of 100-200 mbar, and V / III ratio of 5000-10000.

5. The semiconductor device according to claim 1, wherein: The doping concentration of Mg in the newly added p-GaN layer increases in a direction away from the channel layer.

6. The semiconductor device according to claim 1 or 5, characterized in that: The Mg doping concentration in the newly added p-GaN layer close to the high resistance layer is greater than the Mg doping concentration in the newly added p-GaN layer close to the channel layer; and / or the thickness of the newly added p-GaN layer close to the high resistance layer is greater than the thickness of the newly added p-GaN layer close to the channel layer.

7. The semiconductor device according to claim 1, wherein: The thickness of the newly added p-GaN layer is 10nm~20nm; the thickness of the newly added GaN channel layer is 20~50nm.

8. The semiconductor device according to claim 1, wherein: The method comprises, in sequence, a substrate, an AlN layer, a transition layer, a high resistance layer, the newly added p-GaN layer and the newly added channel layer, a channel layer, a barrier layer and a p-GaN layer which are alternately arranged; and / or, the layer closest to the channel layer is the newly added p-GaN layer, and the layer closest to the high resistance layer is the newly added channel layer.

9. The semiconductor device according to claim 8, characterized in that The substrate is a Si substrate; the transition layer is an AlGaN transition layer; the high resistance layer is a GaN high resistance layer; the channel layer is a GaN channel layer; the barrier layer is an AlGaN barrier layer; and the p-GaN layer is a Mg-GaN layer.

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