An epitaxial structure of a semiconductor device and a method for manufacturing the same, and a semiconductor device

Abstract

The application discloses an epitaxial structure of a semiconductor device, a preparation method of the epitaxial structure and the semiconductor device, and the epitaxial structure comprises a substrate, a transition layer and a gallium nitride epitaxial layer; the transition layer is located on one side of the substrate; the gallium nitride epitaxial layer is located on a side, away from the substrate, of the transition layer; wherein the thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy: Y=c-(X-b)*a; X+Y<c+b; in the formula, c represents an initial thickness reference value of the gallium nitride epitaxial layer, Y<c; b represents an initial thickness reference value of the transition layer, X>b; the units of X, Y, c and b are all nanometers; a is a first coefficient, and is unitless, 1<a<=10. The scheme can guarantee the performance of the device, reduce the thickness of the epitaxial structure of the device, reduce the cost, and improve the production capacity of a production line.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to an epitaxial structure of a semiconductor device, a method for fabricating the same, and the semiconductor device itself. Background Technology

[0002] Group III nitride materials (such as GaN) have unique advantages in realizing optoelectronic devices and high electron mobility transistors, and have broad application prospects in fields such as communications, radar, sensing, and automation.

[0003] Due to the lack of homogeneous substrates, GaN often needs to be grown on heterogeneous substrates, such as silicon and SiC substrates. Influenced by the properties of different materials, GaN cannot usually be grown directly on heterogeneous substrates. Therefore, the industry typically grows a transition layer, such as AlN, on the substrate first, and then grows the GaN epitaxial layer on the transition layer. Considering that the transition layer only needs to serve a transition function, and taking cost into account, the thickness of the transition layer is usually quite thin, generally less than 100 nm. However, the transition layer is also a heterogeneous material relative to GaN, causing defects in the GaN epitaxial layer that result in conductivity, leading to poor device breakdown and breakdown voltage characteristics.

[0004] To address this issue, existing technologies typically compensate for electrons introduced by defects by optimizing the growth conditions of the GaN epitaxial layer. Simultaneously, they improve the breakdown and breakdown voltage characteristics of the device by increasing the thickness of the GaN epitaxial layer (generally, the thickness of the GaN epitaxial layer needs to be greater than or equal to 1500 nm, or even 2000 nm, to meet basic breakdown and breakdown voltage requirements). However, increasing the thickness of the GaN epitaxial layer increases both the consumption of raw materials, leading to higher costs, and the increase in production time, resulting in reduced production line capacity. Summary of the Invention

[0005] This invention provides an epitaxial structure of a semiconductor device and a method for fabricating the same, as well as the semiconductor device itself, to reduce the thickness of the epitaxial structure, lower costs, and increase production line capacity while ensuring device performance.

[0006] According to one aspect of the present invention, an epitaxial structure for a semiconductor device is provided, comprising:

[0007] Substrate;

[0008] A transition layer, located on one side of the substrate;

[0009] The gallium nitride epitaxial layer is located on the side of the transition layer away from the substrate;

[0010] The thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy the following:

[0011] Y = c - (Xb) * a; X + Y < c + b;

[0012] In the formula, c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c and b are all nanometers; a is the first coefficient, which has no unit, 1 < a ≤ 10.

[0013] Optionally, 100nm < X < 1000nm, Y > 1nm.

[0014] Optionally, the gallium nitride epitaxial layer includes a buffer layer and a channel layer, wherein the buffer layer is located on the side of the transition layer away from the substrate, and the channel layer is located on the side of the buffer layer away from the substrate.

[0015] Optionally, the thickness of the buffer layer is Y1, and the thickness of the channel layer is Y2, where Y = Y1 + Y2;

[0016] The initial thickness reference value of the buffer layer is c1, and the initial thickness reference value of the channel layer is c2, where c = c1 + c2;

[0017] Where Y1 < c1; and / or, Y2 < c2.

[0018] Optionally, the transition layer may be made of AlN.

[0019] According to another aspect of the present invention, a method for fabricating an epitaxial structure of a semiconductor device is provided, comprising:

[0020] Provide substrate;

[0021] A transition layer is formed on one side of the substrate;

[0022] A gallium nitride epitaxial layer is formed on the side of the transition layer away from the substrate;

[0023] The thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy the following:

[0024] Y = c - (Xb) * a; X + Y < c + b;

[0025] In the formula, c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c and b are all nanometers; a is the first coefficient, which has no unit, 1 < a ≤ 10.

[0026] Optionally, the preparation method further includes:

[0027] Before fabricating the epitaxial structure, the equipment cavity is cleaned.

[0028] Optionally, after forming a transition layer on one side of the substrate and before forming a gallium nitride epitaxial layer on the side of the transition layer away from the substrate, the fabrication method further includes:

[0029] Remove the current epitaxial wafer from the equipment cavity, clean the equipment cavity, and then put the current epitaxial wafer back into the cleaned equipment cavity.

[0030] Optionally, a transition layer is formed on one side of the substrate, comprising:

[0031] At the target growth temperature and target growth pressure of the transition layer, the target gas is periodically supplied to form the transition layer;

[0032] The transition layer is made of AlN, and the target gases include ammonia and trimethylaluminum; the target gases are provided periodically, including:

[0033] Ammonia is supplied periodically, while trimethylaluminum is continuously supplied; or,

[0034] Trimethylaluminum is supplied periodically, and ammonia is continuously supplied; or,

[0035] Ammonia and trimethylaluminum are supplied alternately periodically.

[0036] According to another aspect of the present invention, a semiconductor device is provided, comprising the epitaxial structure provided in any embodiment of the present invention;

[0037] The semiconductor device also includes a gate, a source, and a drain located on the side of the gallium nitride epitaxial layer away from the substrate, with the gate located between the source and the drain.

[0038] The technical solution of this invention, as summarized above, increases the thickness of the transition layer, allowing the transition layer to share the breakdown voltage. This reduces the thickness of the gallium nitride epitaxial layer while ensuring the device's withstand voltage and breakdown characteristics. Based on the research finding the relationship between the thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer (Y = c - (Xb) * a), the reduction in the thickness of the gallium nitride epitaxial layer is greater than the increase in the thickness of the transition layer. This reduces the total thickness of the gallium nitride epitaxial layer and the transition layer, thereby reducing the overall thickness of the epitaxial structure, achieving cost savings and increased production capacity.

[0039] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the epitaxial structure of a semiconductor device provided in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the epitaxial structure of another semiconductor device provided in an embodiment of the present invention;

[0043] Figure 3 This is a schematic flowchart of a method for fabricating an epitaxial structure of a semiconductor device according to an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the gas output state during the transition layer growth stage provided in an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the gas output state during another transition layer growth stage provided in an embodiment of the present invention;

[0046] Figure 6 This is a schematic diagram of the gas output state during another transition layer growth stage provided in an embodiment of the present invention;

[0047] Figure 7 This is a schematic flowchart of another method for fabricating the epitaxial structure of a semiconductor device provided in an embodiment of the present invention;

[0048] Figure 8 This is a schematic diagram of the structure of a semiconductor device provided in an embodiment of the present invention. Detailed Implementation

[0049] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0050] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in this application can be combined with each other without contradiction.

[0051] First, it should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "comprising" and similar terms mean that the element or object preceding the word encompasses the element or object listed after the word and its equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes. Furthermore, the shapes and sizes of the components in the accompanying drawings do not reflect actual proportions and are only intended to illustrate the content of this invention.

[0052] Figure 1 This is a schematic diagram of the epitaxial structure of a semiconductor device provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the epitaxial structure 10 includes a substrate 11, a transition layer 12, and a gallium nitride epitaxial layer 13; the transition layer 12 is located on one side of the substrate 11; the gallium nitride epitaxial layer 13 is located on the side of the transition layer 12 away from the substrate 11; wherein, the thickness X of the transition layer 12 and the thickness Y of the gallium nitride epitaxial layer 13 satisfy: Y = c - (Xb) * a; X + Y < c + b; where c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c, and b are all nanometers; a is a first coefficient, which has no unit, 1 < a ≤ 10.

[0053] The initial thickness reference value c of the gallium nitride epitaxial layer can be understood as the thickness of the gallium nitride epitaxial layer in the prior art, such as that described in the background art, where the thickness of the gallium nitride epitaxial layer is usually greater than or equal to 1500nm or even 2000nm.

[0054] The initial thickness reference value b of the transition layer can be understood as the thickness of the transition layer in the prior art. For example, as mentioned in the background art, considering the role of the transition layer and cost issues, the thickness of the transition layer is usually very thin, generally less than 100nm.

[0055] In this embodiment, the thickness of the transition layer 12 is X, and the thickness of the gallium nitride epitaxial layer 13 is Y, where X > b, Y < c, and X + Y < c + b. In general, this embodiment of the invention achieves a reduction in the overall thickness of the epitaxial structure while maintaining device performance by adjusting the thickness of the transition layer and the gallium nitride epitaxial layer—that is, increasing the thickness of the transition layer and decreasing the thickness of the gallium nitride epitaxial layer. The specific principle is as follows:

[0056] The inventors discovered that, with the gallium nitride epitaxial layer thickness remaining constant, increasing the thickness of the transition layer can further improve the device's breakdown voltage characteristics. This indicates that the transition layer can also share the breakdown voltage. Therefore, without weakening device performance, increasing the thickness of the transition layer allows for a suitable reduction in the thickness of the gallium nitride epitaxial layer. Through further research, the inventors concluded that when the thickness X of the transition layer 12 and the thickness Y of the gallium nitride epitaxial layer 13 satisfy Y = c - (Xb) * a, device performance can be guaranteed not to be weakened.

[0057] Furthermore, according to Y = c - (Xb)*a, we can obtain cY = (Xb)*a; since 1 < a ≤ 10 and X > b, therefore, (Xb)*a > Xb, that is, cY > Xb.

[0058] Understandably, cY represents the reduction in thickness Y of the gallium nitride epitaxial layer in this embodiment compared to the thickness c of the gallium nitride epitaxial layer in the prior art, and Xb represents the increase in thickness X of the transition layer in this embodiment compared to the thickness b of the transition layer in the prior art.

[0059] Therefore, according to cY > Xb, the reduction in the thickness of the gallium nitride epitaxial layer is greater than the increase in the thickness of the transition layer. In other words, by slightly increasing the thickness of the transition layer, the thickness of the gallium nitride epitaxial layer can be reduced to a greater extent, while ensuring that the performance of the device is not weakened.

[0060] More intuitively, according to cY > Xb, we can conclude that X + Y < c + b. This means that the total thickness of the gallium nitride epitaxial layer and transition layer in this embodiment is less than that in the prior art, while still ensuring that the device's breakdown voltage and breakdown characteristics meet the standards. Furthermore, in this embodiment, the reduced total thickness of the gallium nitride epitaxial layer and transition layer leads to a smaller epitaxial structure thickness, thereby saving raw materials, reducing costs, shortening production time, and increasing production line capacity.

[0061] For example, as described above, assuming the initial thickness reference value of the transition layer is 100nm (i.e., b = 100) and the initial thickness reference value of the gallium nitride epitaxial layer is 2000nm (i.e., c = 2000), the total thickness of the two is 2100nm, and the first coefficient a = 2. When the thickness of the transition layer in this embodiment increases to 900nm (i.e., X = 900), according to Y = c - (Xb) * a, we can obtain Y = 400, that is, the thickness of the gallium nitride epitaxial layer can be reduced to 400nm, and the total thickness of the transition layer and the gallium nitride epitaxial layer is 1300nm, which is significantly reduced compared to the prior art. Thus, while ensuring device performance, it can save raw materials, reduce costs, shorten production time, and increase production capacity.

[0062] It should be noted that the above numerical examples are for illustrative purposes only and do not constitute a limitation of the present invention. The magnitude of the first coefficient is affected by the actual process technology. It is understood that the larger the first coefficient, the greater the thinning of the gallium nitride epitaxial layer can be achieved when the thickness of the transition layer is increased by the same amount. The specific value of the first coefficient is not limited in the embodiments of the present invention.

[0063] In summary, the technical solution of this invention increases the thickness of the transition layer, allowing the transition layer to share the breakdown voltage. This reduces the thickness of the gallium nitride epitaxial layer while ensuring the device's withstand voltage and breakdown characteristics. Based on the research findings of the relationship between the thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer, Y = c - (Xb) * a, it is found that the reduction in the thickness of the gallium nitride epitaxial layer is greater than the increase in the thickness of the transition layer. This reduces the total thickness of the gallium nitride epitaxial layer and the transition layer, thereby reducing the overall thickness of the epitaxial structure and achieving cost savings and increased production capacity.

[0064] Based on the above embodiments, referring to Figure 1 Optionally, 100nm < X < 1000nm, Y > 1nm.

[0065] Specifically, while ensuring device performance, the thickness of the transition layer can be increased as much as possible to further reduce the thickness of the gallium nitride epitaxial layer, thereby reducing the overall thickness of the epitaxial structure, saving costs, and increasing production capacity.

[0066] Reference Figure 1 Optionally, the material of the transition layer 12 includes AlN.

[0067] Reference Figure 1 Optionally, the material of the gallium nitride epitaxial layer 13 includes at least one of GaN, AlGaN and InGaN.

[0068] Figure 2 This is a schematic diagram of the epitaxial structure of another semiconductor device provided in an embodiment of the present invention, as shown below. Figure 2As shown, optionally, the film layer in the epitaxial structure 10 located on the side of the transition layer 12 away from the substrate 11 includes a buffer layer 131, a channel layer 132, a spacer layer 14, a barrier layer 15, and a capping layer 16. The buffer layer 131 is located on the side of the transition layer 12 away from the substrate 11, the channel layer 132 is located on the side of the buffer layer 131 away from the substrate 11, the spacer layer 14 is located on the side of the gallium nitride epitaxial layer 13 away from the substrate 11, the barrier layer 15 is located on the side of the spacer layer 14 away from the substrate 11, and the capping layer 16 is located on the side of the barrier layer 15 away from the substrate 11. Optionally, the gallium nitride epitaxial layer 13 includes a buffer layer 131 and a channel layer 132.

[0069] The buffer layer 131 serves to improve the quality of the subsequent semiconductor material layers to be grown. Optionally, the material of the buffer layer 131 includes at least one of GaN, AlGaN, and InGaN.

[0070] The channel layer 132 provides a better two-dimensional electron gas interface, reduces interface scattering, and improves mobility and two-dimensional electron gas concentration. Optionally, the channel layer 132 can be made of GaN.

[0071] Reference Figure 2 The thickness of the buffer layer is Y1, the thickness of the channel layer is Y2, and Y = Y1 + Y2; the initial thickness reference value of the buffer layer is c1, the initial thickness reference value of the channel layer is c2, and c = c1 + c2; optionally, Y1 < c1; and / or, Y2 < c2.

[0072] Specifically, the thickness of the gallium nitride epitaxial layer is the total thickness of the buffer layer and the channel layer, i.e., Y = Y1 + Y2. When the thickness of the transition layer 12 is increased compared to the prior art, the thickness of at least one of the buffer layer and the channel layer can be reduced, as long as the final total thickness (Y) of the buffer layer and the channel layer and the thickness X of the transition layer satisfy the above relationship Y = c - (Xb) * a. This embodiment of the present invention does not limit this. Specifically, the thickness of the transition layer can be increased, the thickness of the buffer layer can be decreased, and the thickness of the channel layer can remain unchanged; the thickness of the transition layer can also be increased, the thickness of the channel layer can be decreased, and the thickness of the buffer layer can remain unchanged; the thickness of the transition layer can also be increased, the thickness of the buffer layer can be decreased, and the thickness of the channel layer can also be decreased.

[0073] Reference Figure 2 The spacer layer 14 can raise the potential barrier, increase the confinement of the two-dimensional electron gas, reduce alloy scattering, and improve mobility. Optionally, the spacer layer is made of AlN.

[0074] It should be noted that the setting of the spacer layer 14 can be selected according to actual needs, and the embodiments of the present invention do not limit this.

[0075] Reference Figure 2The barrier layer 15, together with the channel layer 132, forms a heterojunction structure, enabling the channel layer 132 to provide a channel for the movement of two-dimensional electron gas. Optionally, the material of the barrier layer 15 includes, but is not limited to, AlGaN.

[0076] Reference Figure 2 The main function of the capping layer 16 is to reduce surface states, reduce surface leakage current in subsequent devices, and suppress current collapse, thereby improving device performance and reliability. Optionally, the material of the capping layer 16 includes, but is not limited to, AlN, GaN, and SiN.

[0077] It should be noted that the inclusion of the cover layer 16 can be selected according to actual needs, and this embodiment of the invention does not limit this.

[0078] Based on the same inventive concept, embodiments of the present invention also provide a method for fabricating the epitaxial structure of a semiconductor device. Figure 3 This is a schematic flowchart of a method for fabricating an epitaxial structure of a semiconductor device according to an embodiment of the present invention, as shown below. Figure 3 As shown, the preparation method includes:

[0079] S101, Provide substrate.

[0080] S102, A transition layer is formed on one side of the substrate.

[0081] S103. A gallium nitride epitaxial layer is formed on the side of the transition layer away from the substrate.

[0082] The thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy the following formula: Y = c - (Xb) * a; X + Y < c + b; where c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c and b are all nanometers; a is the first coefficient, which has no unit, 1 < a ≤ 10.

[0083] As described above, the method for fabricating the epitaxial structure of the semiconductor device provided in this embodiment of the invention can reduce the overall thickness of the epitaxial structure while ensuring device performance by adjusting the thickness of the transition layer and the gallium nitride epitaxial layer, thereby saving costs and increasing production capacity. The specific principle will not be elaborated here.

[0084] Based on the above embodiments, referring to Figure 1 Optionally, the material of the transition layer 12 includes AlN.

[0085] Reference Figure 1 Optionally, the material of the gallium nitride epitaxial layer 13 includes at least one of GaN, AlGaN and InGaN.

[0086] Reference Figure 2Optionally, the gallium nitride epitaxial layer 13 includes a buffer layer 131 and a channel layer 132.

[0087] Optionally, the material of the buffer layer 131 includes at least one of GaN, AlGaN, and InGaN.

[0088] Optionally, the channel layer 132 can be made of GaN.

[0089] Reference Figure 2 The thickness of the buffer layer is Y1, the thickness of the channel layer is Y2, and Y = Y1 + Y2; the initial thickness reference value of the buffer layer is c1, the initial thickness reference value of the channel layer is c2, and c = c1 + c2; optionally, Y1 < c1; and / or, Y2 < c2.

[0090] Reference Figure 2 Optionally, after forming the gallium nitride epitaxial layer on the side of the transition layer away from the substrate, the fabrication method further includes: forming a spacer layer 14 on the side of the gallium nitride epitaxial layer 13 away from the substrate 11, forming a barrier layer 15 on the side of the spacer layer 14 away from the substrate 11, and forming a capping layer 16 on the side of the barrier layer 15 away from the substrate 11.

[0091] Optionally, the spacer layer 14 is made of AlN.

[0092] Optionally, the material of the barrier layer 15 may include, but is not limited to, AlGaN.

[0093] Optionally, the material of the capping layer 16 includes, but is not limited to, AlN, GaN, and SiN.

[0094] Optionally, a transition layer is formed on one side of the substrate, including: periodically supplying a target gas at a target growth temperature and a target growth pressure to form the transition layer.

[0095] The target gas is the gas source used to grow the transition layer. The target growth temperature and target growth pressure can be set by the user, and this embodiment of the invention does not limit them.

[0096] In this embodiment, since the transition layer is relatively thick, the periodic supply of target gas can achieve pulse growth, which is beneficial to improve the quality of the transition layer, further improve the withstand voltage of the transition layer, and thus reduce the thickness of the gallium nitride epitaxial layer to a greater extent, thereby reducing the overall thickness of the epitaxial structure.

[0097] When the transition layer material is AlN, the target gas can be either ammonia or trimethylaluminum. The target gas can be provided periodically in any of the following three ways: ammonia is provided periodically while trimethylaluminum is provided continuously; or trimethylaluminum is provided periodically while ammonia is provided continuously; or ammonia and trimethylaluminum are provided periodically alternately.

[0098] For example, Figure 4 This is a schematic diagram of the gas output state during the transition layer growth stage provided in an embodiment of the present invention, as shown below. Figure 4 As shown, a transition layer can be formed by periodically supplying ammonia gas and continuously supplying trimethylaluminum gas at the target growth temperature and target growth pressure of the transition layer.

[0099] For example, Figure 5 This is a schematic diagram of the gas output state during another transition layer growth stage provided in an embodiment of the present invention, as shown below. Figure 5 As shown, a transition layer can be formed by periodically supplying trimethylaluminum and continuously supplying ammonia gas under the target growth temperature and target growth pressure of the transition layer.

[0100] For example, Figure 6 This is a schematic diagram of the gas output state during another transition layer growth stage provided in an embodiment of the present invention, as shown below. Figure 6 As shown, a transition layer can be formed by periodically and alternately supplying ammonia and trimethylaluminum at the target growth temperature and target growth pressure of the transition layer.

[0101] Figures 4-6 In the middle, the high-level stage can be understood as the gas output stage, and the low-level stage can be understood as the no-gas output stage.

[0102] In some embodiments, the transition layer can also be grown in a continuous growth manner, in which case ammonia and trimethylaluminum can be continuously supplied simultaneously to form the transition layer.

[0103] Optionally, the transition layer can be grown by MOCVD, or by MBE or other equipment, or by a combination of two or more of the above equipment. For example, a certain thickness of AlN can be grown by MBE and then the remaining AlN can be grown by MOCVD.

[0104] Understandably, the growth of the epitaxial structure is carried out in an epitaxial growth apparatus. Specifically, the substrate is first placed into the apparatus cavity, and then the aforementioned transition layer, gallium nitride epitaxial layer, spacer layer, barrier layer, and capping layer are grown sequentially to obtain the epitaxial structure. It should be noted that the growth conditions for each film layer are not specifically limited in this embodiment of the invention.

[0105] Figure 7 This is a schematic flowchart of another method for fabricating the epitaxial structure of a semiconductor device according to an embodiment of the present invention, which optimizes the fabrication method based on the above embodiment. For example... Figure 7 As shown, the preparation method includes:

[0106] S201. Clean the equipment cavity.

[0107] S202. Place the substrate into the device cavity.

[0108] S203, A transition layer is formed on one side of the substrate.

[0109] S204. A gallium nitride epitaxial layer is formed on the side of the transition layer away from the substrate.

[0110] Specifically, in this embodiment, before fabricating the epitaxial structure, specifically before placing the substrate into the device cavity, the device cavity is first cleaned.

[0111] AlN, the material of the transition layer in epitaxial structures, is very stable and difficult to remove completely. This is one of the reasons why the transition layer is very thin in traditional epitaxial structures. Because the transition layer is thin, it has little impact on the equipment and other epitaxial processes. Therefore, in traditional fabrication processes, the cavity of the equipment used to grow epitaxial structures is often not cleaned, or only cleaned once in a very long time. However, in this embodiment of the invention, because the transition layer in the epitaxial structure is relatively thick, in order to avoid shortening the equipment maintenance cycle and affecting the quality of other epitaxial layers due to the accumulation of residual AlN, the cavity can be cleaned before the fabrication of the epitaxial structure, that is, before the substrate is placed into the equipment cavity, to remove the AlN and other residues formed in the fabrication of the previous batch of epitaxial structures, and then the fabrication of the current batch of epitaxial structures can be carried out.

[0112] Specifically, the equipment cavity can be cleaned before each batch (each furnace) of epitaxial structure is prepared, or the equipment cavity can be cleaned after several batches of epitaxial structure preparations are completed, and then a new epitaxial structure can be prepared.

[0113] Regarding the cleaning of the device cavity, in other embodiments, optionally, after forming a transition layer on one side of the substrate and before forming a gallium nitride epitaxial layer on the side of the transition layer away from the substrate, the preparation method further includes: removing the current epitaxial wafer from the device cavity, cleaning the device cavity, and then putting the current epitaxial wafer back into the cleaned device cavity.

[0114] Among them, the current epitaxial wafer refers to the epitaxial wafer that has completed the preparation of the transition layer but has not yet carried out the preparation of the gallium nitride epitaxial layer.

[0115] Specifically, in this embodiment, after forming a transition layer on one side of the substrate, the current epitaxial wafer is first removed from the equipment cavity, the equipment cavity is cleaned, and then the current epitaxial wafer is placed back into the cleaned equipment cavity. Then, a gallium nitride epitaxial layer is formed on the side of the transition layer away from the substrate. In this way, the equipment cavity can be cleaned immediately after the transition layer is formed during each epitaxial structure fabrication process, ensuring that there is absolutely no residual AlN in the cavity during subsequent epitaxial processes. This further guarantees the quality of the epitaxial structure and also prevents AlN from accumulating, extending equipment maintenance cycles, and reducing costs.

[0116] For example, the removal and placement of the epitaxial wafer can be done manually or automatically by a robotic arm, and this embodiment of the invention does not limit this.

[0117] Optionally, the in-situ cleaning function of the epitaxial growth equipment can be used to clean the equipment cavity. Specifically, after activating the in-situ cleaning function, corrosive gases can be released into the cavity to clean away residues, resulting in high cleaning efficiency.

[0118] In some embodiments, if the production line does not have the capability to thoroughly clean the cavity, the preparation of the transition layer and the gallium nitride epitaxial layer can be considered in different equipment cavities.

[0119] Based on the same inventive concept, embodiments of the present invention also provide a semiconductor device. For example, Figure 8 This is a schematic diagram of the structure of a semiconductor device provided in an embodiment of the present invention, such as... Figure 8 As shown, the semiconductor device 100 provided in this embodiment of the invention includes the epitaxial structure 10 provided in any of the above embodiments, and further includes a gate 20, a source 30, and a drain 40 located on the side of the gallium nitride epitaxial layer 13 away from the substrate 11, with the gate 20 located between the source 30 and the drain 40. Since the semiconductor device provided in this embodiment of the invention includes the epitaxial structure provided in any of the above embodiments, it possesses the same beneficial effects as the aforementioned epitaxial structure-related embodiments, as detailed above, and will not be repeated here.

[0120] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An epitaxial structure for a semiconductor device, characterized in that, include: Substrate; A transition layer is located on one side of the substrate; A gallium nitride epitaxial layer is located on the side of the transition layer away from the substrate; Wherein, the thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy the following: Y = c - (Xb) * a; X + Y < c + b; In the formula, c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c and b are all nanometers; a is the first coefficient, which has no unit, 1 < a ≤ 10.

2. The epitaxial structure according to claim 1, characterized in that, 100nm<X<1000nm, Y>1nm.

3. The epitaxial structure according to claim 1, characterized in that, The gallium nitride epitaxial layer includes a buffer layer and a channel layer. The buffer layer is located on the side of the transition layer away from the substrate, and the channel layer is located on the side of the buffer layer away from the substrate.

4. The epitaxial structure according to claim 3, characterized in that, The thickness of the buffer layer is Y1, and the thickness of the channel layer is Y2, where Y = Y1 + Y2; The initial thickness reference value of the buffer layer is c1, and the initial thickness reference value of the channel layer is c2, where c = c1 + c2; Where Y1 < c1; and / or, Y2 < c2.

5. The epitaxial structure according to claim 1, characterized in that, The material of the transition layer includes AlN.

6. A method for fabricating an epitaxial structure of a semiconductor device, characterized in that, include: Provide substrate; A transition layer is formed on one side of the substrate; A gallium nitride epitaxial layer is formed on the side of the transition layer away from the substrate; Wherein, the thickness X of the transition layer and the thickness Y of the gallium nitride epitaxial layer satisfy the following: Y = c - (Xb) * a; X + Y < c + b; In the formula, c represents the initial thickness reference value of the gallium nitride epitaxial layer, Y < c; b represents the initial thickness reference value of the transition layer, X > b; the units of X, Y, c and b are all nanometers; a is the first coefficient, which has no unit, 1 < a ≤ 10.

7. The preparation method according to claim 6, characterized in that, The preparation method further includes: Before fabricating the epitaxial structure, the equipment cavity is cleaned.

8. The preparation method according to claim 6, characterized in that, After forming a transition layer on one side of the substrate, and before forming a gallium nitride epitaxial layer on the side of the transition layer away from the substrate, the fabrication method further includes: The current epitaxial wafer is removed from the equipment cavity, the equipment cavity is cleaned, and then the current epitaxial wafer is put back into the cleaned equipment cavity.

9. The preparation method according to claim 6, characterized in that, The formation of a transition layer on one side of the substrate includes: At the target growth temperature and target growth pressure of the transition layer, the target gas is periodically supplied to form the transition layer; The transition layer is made of AlN, and the target gas includes ammonia and trimethylaluminum; the periodic provision of the target gas includes: Ammonia is supplied periodically, while trimethylaluminum is continuously supplied; or, Trimethylaluminum is supplied periodically, and ammonia is continuously supplied; or, Ammonia and trimethylaluminum are supplied alternately periodically.

10. A semiconductor device, characterized in that, Includes the epitaxial structure as described in any one of claims 1-5; The semiconductor device further includes a gate, a source, and a drain located on the side of the gallium nitride epitaxial layer away from the substrate, with the gate located between the source and the drain.

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