Epitaxial structure of semiconductor device and method for manufacturing the same and semiconductor device

Abstract

The application provides an epitaxial structure of a semiconductor device, a preparation method of the epitaxial structure and the semiconductor device. The epitaxial structure comprises a substrate, a nucleation layer and a buffer layer. The nucleation layer is arranged on the substrate. The buffer layer is arranged on the nucleation layer. The corresponding resistivity of the substrate and the corresponding doping concentration of the buffer layer satisfy a preset corresponding relationship between the resistivity and the doping concentration. The epitaxial structure of the semiconductor device can realize the function of a high-resistance buffer layer by optimizing the matching relationship between the resistivity of the substrate and the doping concentration of the epitaxial layer. Meanwhile, the doping concentration is controlled, so that the crystal quality is ensured, and the device can obtain better reliability.

Description

Technical Field

[0001] This application 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] Gallium nitride (GaN) semiconductor materials have become a research hotspot due to their large bandgap, high electron saturation drift velocity, high breakdown field strength, and good thermal conductivity. In GaN high electron mobility transistor (HEMT) structures, a high-resistivity buffer layer is required to obtain better device leakage current and pinch-off characteristics. Achieving high resistance intrinsically from GaN material is extremely difficult in terms of fabrication, but it can be achieved by introducing acceptor impurities during the buffer layer growth process.

[0003] A common compensation method is to introduce acceptor impurities, typically C or Fe atoms. However, introducing too much C impurity leads to a deterioration in crystal quality, which in turn affects the reliability of the final device. Furthermore, the deep-level traps formed by C impurities can easily degrade the output power and other performance characteristics of the final device. On the other hand, excessive Fe doping causes a deterioration in the surface of the epitaxial layer, which also affects the performance of the final device. In other words, the C content required to obtain a high-resistivity GaN buffer leads to a deterioration in crystal quality, while the Fe content required to obtain a high-resistivity GaN buffer affects the performance of the final device. Therefore, ensuring both the crystal quality of the epitaxial layer and the performance of the final device has become a challenge. Summary of the Invention

[0004] The purpose of this application is to provide an epitaxial structure of a semiconductor device, a method for fabricating the same, and the semiconductor device itself. This method can control the doping concentration by means of the relationship between the resistivity of the substrate and the doping concentration of the buffer layer, thereby ensuring crystal quality and improving the reliability of the semiconductor device.

[0005] In a first aspect, embodiments of this application provide an epitaxial structure for a semiconductor device, the epitaxial structure comprising: a substrate, a nucleation layer, and a buffer layer; the nucleation layer is disposed on the substrate; the buffer layer is disposed on the nucleation layer; the resistivity of the substrate and the doping concentration of the buffer layer satisfy a preset correspondence between resistivity and doping concentration.

[0006] In an optional implementation, the above correspondence includes: when the resistivity is less than 1E7 Ohm·cm, the doping concentration is 1E18cm·cm. -3 ~1E20cm -3 Within the range.

[0007] In an optional embodiment, the above correspondence further includes: when the resistivity is in the range of 1E7 Ohm.cm to 1E12 Ohm.cm, the doping concentration is in the range of 1E16cm. -3~1E18cm -3 Within a certain range, and inversely proportional to resistivity and doping concentration.

[0008] In an optional implementation, the inverse relationship between resistivity and doping concentration is as follows:

[0009] Y = K * X + b, K ≈ -10 6 b≈10 18 ;

[0010] Where Y represents the doping concentration of the buffer layer; X represents the resistivity of the substrate.

[0011] In an optional implementation, the above correspondence further includes: when the resistivity is greater than 1E12 Ohm·cm, the doping concentration is less than 1E16cm. -3 .

[0012] In an optional embodiment, the impurity type of the dopant in the buffer layer includes carbon and / or iron.

[0013] In an optional embodiment, the thickness of the buffer layer is in the range of 100nm to 1000nm.

[0014] In an optional embodiment, the above-mentioned epitaxial structure further includes: a channel layer, a barrier layer, and a cap layer; the channel layer is disposed on the buffer layer; the barrier layer is disposed on the channel layer; and the cap layer is disposed on the barrier layer.

[0015] Secondly, embodiments of this application also provide a semiconductor device, which includes the epitaxial structure of the semiconductor device as described in the first aspect.

[0016] Secondly, embodiments of this application also provide a method for fabricating an epitaxial structure of a semiconductor device. The method includes: forming a nucleation layer on a substrate; the substrate having a target resistivity; forming a buffer layer having a target doping concentration on the nucleation layer; wherein the target resistivity and the target doping concentration satisfy a preset correspondence between resistivity and doping concentration; and sequentially forming a channel layer, a barrier layer, and a cap layer on the buffer layer.

[0017] The embodiments of this application bring the following beneficial effects:

[0018] This application provides an epitaxial structure for a semiconductor device, a method for fabricating the same, and the semiconductor device itself. The epitaxial structure includes a substrate, a nucleation layer, and a buffer layer. The nucleation layer is disposed on the substrate. The buffer layer is disposed on the nucleation layer. The target resistivity of the substrate and the target doping concentration of the buffer layer satisfy a preset relationship between resistivity and doping concentration. This epitaxial structure of the semiconductor device can achieve the function of a high-resistivity buffer layer by optimizing the matching relationship between the substrate resistivity and the doping concentration of the epitaxial layer. Simultaneously, by controlling the doping concentration, crystal quality is ensured, thereby enabling the device to achieve better reliability.

[0019] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application are realized and obtained through the structures particularly pointed out in the description, claims and drawings.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the epitaxial structure of a semiconductor device provided in an embodiment of this application;

[0023] Figure 2 A graph showing the relationship between substrate resistivity and epitaxial buffer layer doping concentration, provided for an embodiment of this application;

[0024] Figure 3 A schematic diagram of the epitaxial structure of another semiconductor device provided in an embodiment of this application;

[0025] Figure 4 This is a schematic diagram of the epitaxial structure of another semiconductor device provided in an embodiment of this application. Detailed Implementation

[0026] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Currently, in GaN HEMT structures, in order to obtain better device leakage current and better pinch-off characteristics, a high-resistivity buffer layer is required. This high-resistivity buffer layer can be achieved by introducing acceptor impurities during the growth process. However, the C content required to obtain a high-resistivity buffer layer will lead to a deterioration in crystal quality, while the Fe content required to obtain a high-resistivity buffer layer will affect the performance of the final device. Therefore, how to ensure the crystal quality of the epitaxial layer while ensuring the performance of the final device has become a challenge.

[0028] Based on this, embodiments of this application provide an epitaxial structure for a semiconductor device, a method for fabricating the same, and the semiconductor device itself. The epitaxial structure includes a substrate, a nucleation layer, and a buffer layer. The nucleation layer is disposed on the substrate. The buffer layer is disposed on the nucleation layer. The target resistivity of the substrate and the target doping concentration of the buffer layer satisfy a preset correspondence between resistivity and doping concentration. This epitaxial structure of the semiconductor device can achieve the function of a high-resistivity buffer layer by optimizing the matching relationship between the substrate resistivity and the doping concentration of the epitaxial layer. Simultaneously, by controlling the doping concentration, crystal quality is ensured, thereby enabling the device to achieve better reliability.

[0029] To facilitate understanding of this embodiment, a detailed description of the epitaxial structure of a semiconductor device disclosed in this application embodiment will be provided first.

[0030] This application provides an epitaxial structure for a semiconductor device, such as... Figure 1 As shown, the epitaxial structure includes: a substrate 10, a nucleation layer 20, and a buffer layer 30; the nucleation layer 20 is disposed on the substrate 10; the buffer layer 30 is disposed on the nucleation layer 20; the target resistivity of the substrate 10 and the target doping concentration of the buffer layer 30 satisfy a preset correspondence between resistivity and doping concentration.

[0031] The substrate 10 may be one or more of gallium nitride, aluminum gallium nitride, indium gallium nitride, aluminum indium gallium nitride, indium phosphide, gallium arsenide, silicon carbide, diamond, sapphire, germanium, silicon, or any other material capable of growing group III nitrides.

[0032] A nucleation layer 20 is grown on the substrate 10, and the nucleation layer 20 includes a high-temperature AlN nucleation layer or a low-temperature GaN nucleation layer.

[0033] A buffer layer 30 is formed on the nucleation layer 20. This layer mainly serves to increase resistance and reduce leakage current of the entire buffer layer. The buffer layer 30 can be a GaN buffer layer or a buffer layer made of other materials. The impurity types of the dopant in the buffer layer 30 include carbon and / or iron; and the thickness of the buffer layer 30 is in the range of 100 nm to 1000 nm. If the thickness is less than 100 nm, it will affect the high resistance of the entire buffer layer; if it is greater than 1000 nm, the growth time will be too long, which will affect the growth efficiency. Furthermore, if the Fe-doped buffer layer is grown too thickly, it will affect its crystal quality and surface morphology.

[0034] Given the substrate resistivity, by satisfying the preset relationship between the substrate resistivity and the doping concentration of the epitaxial buffer layer, high resistance and reduced leakage current of the buffer layer can be achieved.

[0035] This application provides an epitaxial structure for a semiconductor device, comprising a substrate, a nucleation layer, and a buffer layer. The nucleation layer is disposed on the substrate; the buffer layer is disposed on the nucleation layer; and the target resistivity of the substrate and the target doping concentration of the buffer layer satisfy a preset correspondence between resistivity and doping concentration. This epitaxial structure of the semiconductor device can function as a high-resistivity buffer layer. Simultaneously, by optimizing the matching relationship between the substrate resistivity and the doping concentration of the epitaxial layer, the doping concentration is controlled, thereby ensuring crystal quality and ultimately enabling the device to achieve better reliability.

[0036] This application also provides another epitaxial structure for a semiconductor device, which is implemented based on the above embodiments; this application focuses on the preset correspondence between the resistivity of the substrate and the doping concentration of the buffer layer.

[0037] See Figure 2 As shown, given the substrate resistivity, the relationship between the substrate resistivity and the doping concentration (C, Fe, or both) of the epitaxial buffer layer must meet the following requirements:

[0038] (1) When the substrate resistivity is less than 1E7 Ohm.cm, the doping concentration of the buffer layer is in the range of 1E18cm-3 to 1E20cm-3.

[0039] When the substrate resistivity is <1E7 Ohm.cm, the doping concentration of the buffer layer can be controlled within the range of 1E18cm-3 to 1E20cm-3. When the doping concentration is >1E18cm-3, high resistance and reduced leakage current of the buffer layer can be achieved.

[0040] (2) When the resistivity is in the range of 1E7 Ohm.cm to 1E12 Ohm.cm, the doping concentration of the buffer layer is in the range of 1E16cm-3 to 1E18cm-3, and is inversely proportional to the resistivity and the doping concentration.

[0041] That is, when the substrate resistivity is in the range of 1E7 to 1E12 Ohm·cm, the doping concentration of the buffer layer can be controlled in the range of 1E16 cm⁻³ to 1E18 cm⁻³, and the substrate resistivity is inversely proportional to the doping concentration, as shown in the following formula:

[0042] Y=K*X+b, K≈-106, b≈1018;

[0043] Where Y represents the doping concentration of the buffer layer; X represents the resistivity of the substrate.

[0044] (3) When the substrate resistivity is greater than 1E12 Ohm.cm, the doping concentration of the buffer layer is less than 1E16cm-3.

[0045] That is, when the substrate resistivity is >1E12 Ohm.cm, the doping concentration of the buffer layer can be controlled to <1E16cm-3. A lower doping concentration can achieve high resistance and reduce the leakage current of the buffer layer.

[0046] like Figure 3 As shown, another epitaxial structure of a semiconductor device provided in this application embodiment includes, in addition to the substrate 10, nucleation layer 20 and buffer layer 30, a channel layer 40, a barrier layer 50 and a cap layer 60.

[0047] The channel layer 40 is disposed on the buffer layer 30, providing a channel for the movement of two-dimensional electron gas. A barrier layer is disposed on the channel layer; the barrier layer is made of an Al-containing III-VI group material, with the Al content controlled between 0 and 1, for example, it can be Al... x Ga 1-x The material is N, with the Al content x controlled between 0 and 1; the barrier layer and the underlying channel layer 40 together form a heterojunction structure. A cap layer is disposed on the barrier layer, which mainly serves as a passivation layer to improve current collapse.

[0048] See Figure 4 As shown, in a preferred embodiment, the buffer layer is a GaN buffer layer, the barrier layer is an AlGaN barrier layer, and the channel layer is a GaN channel layer. These three layers can also be made of other materials. The semiconductor device in this embodiment can be a radio frequency device or a semiconductor device with other functions.

[0049] The epitaxial structure of a semiconductor device provided in this application can optimize the matching between substrate resistivity and epitaxial layer doping concentration by specifically corresponding to the target resistivity of the substrate and the target doping concentration of the buffer layer, thereby controlling the doping concentration and ensuring crystal quality; furthermore, the structure of the semiconductor device is further optimized by the channel layer, barrier layer and cap layer, improving the reliability of the semiconductor device.

[0050] Based on the above-described epitaxial structure embodiments of semiconductor devices, this application also provides a semiconductor device, which includes the epitaxial structure of the semiconductor device described in the above embodiments.

[0051] Based on the above embodiments of the epitaxial structure of semiconductor devices, this application also provides a method for fabricating the epitaxial structure of a semiconductor device, the method comprising the following steps:

[0052] (1) A nucleation layer is formed on a substrate; the substrate has a target resistivity;

[0053] (2) A buffer layer with a target doping concentration is formed on the nucleation layer; wherein the target resistivity and the target doping concentration satisfy a preset correspondence between resistivity and doping concentration.

[0054] In practice, the target resistivity of the substrate and the target doping concentration of the buffer layer can be determined in advance according to the above correspondence. Then, a substrate with the target resistivity is prepared in sequence, a nucleation layer is grown on the substrate, and a buffer layer with the target doping concentration is grown on the nucleation layer.

[0055] Alternatively, a substrate can be prepared first, and its corresponding target resistivity can be detected. Then, based on the target resistivity and the above correspondence, the approximate doping concentration range corresponding to the buffer layer can be determined, and then a buffer layer that conforms to the doping concentration range can be prepared.

[0056] (3) A channel layer, a barrier layer and a cap layer are formed sequentially on the buffer layer.

[0057] The relationship between the resistivity and the doping concentration is as follows:

[0058] (1) When the resistivity is less than 1E7 Ohm.cm, the doping concentration is in the range of 1E18cm-3 to 1E20cm-3;

[0059] (2) When the resistivity is in the range of 1E7 Ohm.cm to 1E12 Ohm.cm, the doping concentration is in the range of 1E16cm-3 to 1E18cm-3, and it is inversely proportional to the resistivity and the doping concentration; the inverse relationship is as follows:

[0060] Y=K*X+b, K≈-106, b≈1018;

[0061] Where Y represents the doping concentration of the buffer layer; X represents the resistivity of the substrate.

[0062] (3) When the resistivity is greater than 1E12 Ohm.cm, the doping concentration is less than 1E16cm-3.

[0063] The specific preparation process is as follows:

[0064] Prepare a substrate 10; the substrate 10 may be one or more of gallium nitride, aluminum gallium nitride, indium gallium nitride, aluminum indium gallium nitride, indium phosphide, gallium arsenide, silicon carbide, diamond, sapphire, germanium, silicon, or any other material capable of growing group III nitrides.

[0065] A high-temperature AlN or low-temperature GaN nucleation layer is grown on substrate 10.

[0066] A buffer layer 30 is formed on the nucleation layer 20. This layer mainly serves to increase resistance and reduce leakage current of the entire buffer layer. It is usually C-doped or Fe-doped.

[0067] A channel layer 40 is grown on top of the buffer layer 30, which provides a channel for the movement of two-dimensional electron gas.

[0068] A barrier layer 50 is grown on the epitaxial layer of the channel layer 40. This barrier layer is Al. x Ga 1-x The material is N, in which the Al content x is controlled between 0 and 1. The barrier layer and the underlying channel layer 40 together form a heterojunction structure.

[0069] A cap layer 60 is grown on the barrier layer 50. This layer mainly serves as a passivation layer to improve current collapse.

[0070] The method for fabricating the epitaxial structure of the semiconductor device provided in this application has the same implementation principle and technical effect as the aforementioned embodiment of the epitaxial structure of the semiconductor device. For the sake of brevity, any parts not mentioned in the embodiment of the method for fabricating the epitaxial structure can be referred to the corresponding content in the aforementioned embodiment of the epitaxial structure of the semiconductor device.

[0071] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0072] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the technical scope disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. An epitaxial structure for a semiconductor device, characterized in that, The epitaxial structure comprises: a substrate, a nucleation layer and a buffer layer; the nucleation layer is arranged on the substrate; the buffer layer is arranged on the nucleation layer; the corresponding resistivity of the substrate and the corresponding doping concentration of the buffer layer satisfy a preset corresponding relationship between resistivity and doping concentration, so as to realize the role of a high-resistance buffer layer while ensuring the crystal quality; the corresponding relationship comprises: when the resistivity is less than 1E7 Ohm.cm, the doping concentration is in the range of 1E18 cm -3 -1E20 cm -3 ; The correspondence also includes: when the resistivity is in the range of 1E7 Ohm.cm to 1E12 Ohm.cm, the doping concentration is in the range of 1E16cm. -3 ~1E18cm -3 Within the range, and inversely proportional to the resistivity and the doping concentration; The correspondence also includes: when the resistivity is greater than 1E12 Ohm.cm, the doping concentration is less than 1E16cm. -3 .

2. The epitaxial structure of the semiconductor device according to claim 1, characterized in that, When the resistivity is in the range of 1E7 Ohm·cm to 1E12 Ohm·cm, the inverse relationship between the resistivity and the doping concentration is as follows: Y=K X+b,K≈-10 6 ,b≈10 18 ; Wherein, Y represents the doping concentration of the buffer layer; and X represents the resistivity of the substrate.

3. The epitaxial structure of the semiconductor device according to claim 1, characterized in that, The impurity types of the dopant in the buffer layer include carbon and / or iron.

4. The epitaxial structure of the semiconductor device according to claim 1, characterized in that, The thickness of the buffer layer is in the range of 100nm to 1000nm.

5. The epitaxial structure of the semiconductor device according to claim 1, characterized in that, The epitaxial structure further includes: a channel layer, a barrier layer, and a cap layer; the channel layer is disposed on the buffer layer; the barrier layer is disposed on the channel layer; and the cap layer is disposed on the barrier layer.

6. A semiconductor device, characterized in that, The semiconductor device includes the epitaxial structure of the semiconductor device as described in any one of claims 1-5.

7. A method for fabricating an epitaxial structure of a semiconductor device, characterized in that, The method includes: A nucleation layer is formed on a substrate; the substrate has a target resistivity. A buffer layer with a target doping concentration is formed on the nucleation layer; wherein the target resistivity and the target doping concentration satisfy a preset correspondence between resistivity and doping concentration, thereby realizing the function of a high-resistivity buffer layer while ensuring crystal quality. A channel layer, a barrier layer, and a cap layer are sequentially formed on the buffer layer; The corresponding relationship includes: when the resistivity is less than 1E7 Ohm·cm, the doping concentration is 1E18 cm⁻¹. -3 ~1E20cm -3 Within the range; The correspondence also includes: when the resistivity is greater than 1E12 Ohm.cm, the doping concentration is less than 1E16cm. -3 ; The correspondence also includes: when the resistivity is in the range of 1E7 Ohm.cm to 1E12 Ohm.cm, the doping concentration is in the range of 1E16cm. -3 ~1E18cm -3 Within the range, and is inversely proportional to the resistivity and the doping concentration.

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