GaN high resistance layer preparation method and gan hent device preparation method

Abstract

The application discloses a GaN high-resistance layer preparation method and a GaN HEMT device preparation method. The GaN high-resistance layer preparation method is prepared by a MOCVD device and comprises at least one substrate layer, and a GaN high-resistance layer is epitaxially grown based on the substrate layer. The substrate layer at least comprises a pretreatment stage of nucleation and / or epitaxial growth. A Ga source in a reaction gas used when the substrate layer is pretreated is TMGa. When the GaN high-resistance layer is prepared, a C source for doping is independently supplied, and the Ga source in the reaction gas is switched to TEGa. The growth temperature is 900-1100 DEG C. Under the growth temperature, TEGa is less likely to decompose active C atoms beneficial to Ga-C bond formation than TMGa, so as to avoid that the concentration distribution of the C source available for doping is affected by the decomposition reaction of the Ga source. The high-resistance layer provided by the application has a uniform resistivity distribution.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, and in particular to a method for preparing a GaN high-resistivity layer and a method for preparing a GaN HEMT device. Background Technology

[0002] GaN semiconductor materials possess excellent properties such as a large bandgap, high breakdown electric field, high electron saturation drift velocity, strong radiation resistance, and good chemical stability. Moreover, they can form heterojunctions with AlGaN materials. The piezoelectric polarization and spontaneous polarization at the heterojunction interface can generate a high concentration of two-dimensional electron gas (2DEG), making it an excellent choice for manufacturing HEMT (High Electron Mobility Transistor) devices.

[0003] When fabricating HEMT devices on heterogeneous substrates, the general sequence includes a substrate, a high-resistivity buffer layer (high-resistivity layer), a channel layer, a barrier layer, and a device layer. In some special cases, a nucleation layer or buffer layer may be grown between the substrate and the high-resistivity buffer layer to improve lattice fit and the growth rate of the high-resistivity buffer layer. Figure 1 As shown, when growing a high-resistivity buffer layer, TMGa (trimethylgallium) is generally used as the Ga source to form self-doped (unintentional) C, thus economically and conveniently forming a high-C-doped high-resistivity buffer layer. Furthermore, TMGa uses a horizontal gas inlet, with the middle circle referring to the wafer W, and the upper and lower walls referring to the cavity walls 10.

[0004] A horizontal air intake can be a left-to-right intake (e.g., as shown in the image). Figure 1 (The arrows shown indicate the direction of air intake to exhaust). It can also be an air intake that radiates radially from the center.

[0005] Using trimethylgallium (TMGa) as the Ga source, with or without a C source, and employing a horizontal gas inlet method, when preparing a self-doped high-resistivity layer, TMGa decomposes to release a significant amount of active carbon atoms that readily form Ga-C bonds. This leads to an increase in the intrinsic C impurity concentration in the GaN channel layer. Therefore, as GaN deposition progresses, the resulting epitaxial layer is a high-resistivity GaN epitaxial layer (or high-resistivity layer). When growing a GaN high-resistivity layer using TMGa as the source gas, its resistivity change along the wafer diameter is as follows: Figure 2 As shown: When actually testing the growth parameters of a wafer, the resistivity of its high-resistivity layer always fluctuates in the gas inlet direction, that is, the resistivity of the high-resistivity layer usually exhibits a non-uniform phenomenon.

[0006] The change in resistivity of this high-resistivity layer indicates that the C source of trimethylgallium self-doping should come from one or more products of the trimethylgallium decomposition process. Moreover, when the amount of this product reaches a certain level, it is easy to be transformed into other forms of expression that are not suitable for C doping. It is precisely because of this situation that no matter how the flow rate and flow field are adjusted, i.e., the concentration of the reactant gas and the flow intensity are adjusted, it is impossible to prepare a C-doped high-resistivity layer with relatively uniform resistivity.

[0007] In MOCVD equipment, high-resistivity layers prepared using horizontal gas inlet and the commonly used trimethylgallium (TMG) source often exhibit resistivity inhomogeneity due to the influence of the gas supply method and the order of gas reactions. Even adjusting the location of the process zone and the gas supply cannot overcome this inhomogeneity. Consequently, subsequent device fabrication is prone to inconsistent quality. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a GaN high-resistivity layer and a method for preparing a GaN HEMT device, aiming to solve the problem of uneven resistivity of the high-resistivity layer when using TMGa as a Ga source to perform self-doping of a carbon-containing high-resistivity layer during horizontal gas inlet.

[0009] To solve the above problems, the present invention is achieved through the following technical solution:

[0010] A method for preparing a GaN high-resistivity layer, which is prepared using an MOCVD device, includes:

[0011] At least one substrate layer is provided, and the GaN high-resistivity layer is epitaxially grown based on the substrate layer; the substrate layer includes at least a pretreatment stage for nucleation and / or epitaxial growth; the Ga source in the reaction gas used during the pretreatment of the substrate layer is TMGa. During the preparation of the GaN high-resistivity layer, a C source for doping is independently supplied, and the Ga source in the reaction gas is switched to TEGa; the growth temperature is 900-1100℃. At this growth temperature, TEGa is less likely than TMGa to decompose into active C atoms that facilitate Ga-C bond formation, thus avoiding the influence of the Ga source decomposition reaction intensity on the C doping concentration.

[0012] Optionally, the flow rate of TEGa into the reaction chamber of the MOCVD equipment is not less than 1E-3 mol / min, the growth rate is not less than 2 μm / h, and the growth pressure is 30-100 mbar.

[0013] Optionally, the molar ratio of Group V source to Group III source ranges from 500 to 2000.

[0014] Optionally, the C source is any one of ethylene, ethane, and propane.

[0015] Optionally, the flow rate of the C source is controlled to be 100-1000 sccm, and the molar ratio of the C source to the Ga source is not greater than 1.

[0016] Optionally, the MOCVD equipment includes at least one reactor, the reactor including a reaction chamber, the substrate being placed inside the reaction chamber, wherein the reactor supplies reaction gas and carrier gas to the reaction chamber in a manner parallel to the plane of the substrate.

[0017] On the other hand, the present invention also provides a method for fabricating a GaN HEMT device, comprising:

[0018] Step S11: Prepare the GaN high resistivity layer using the GaN high resistivity layer preparation method described above; Step S12: Sequentially form a channel layer, a barrier layer, and a device layer on the GaN high resistivity layer.

[0019] Optionally, the channel layer is an unintentionally doped GaN epitaxial layer, and when forming the channel layer, the Ga source in the reaction gas is switched to TMGa.

[0020] Optionally, the gas pressure is 100-300 mbar during the deposition of the channel layer.

[0021] Optionally, TMGa is used as the Ga source when preparing the barrier layer.

[0022] This invention has at least one of the following technical effects:

[0023] This invention uses a horizontal air intake method to introduce TEGa (triethylgallium) into the MOCVD equipment as a gallium source, and the resulting high-resistivity layer has a uniform resistivity distribution. This effectively solves the problem of uneven resistivity of the high-resistivity layer caused by using TMGa as a Ga source to self-dopat carbon-containing high-resistivity layers when using horizontal air intake.

[0024] Specifically, in the preparation of the GaN high-resistivity layer, a C source for doping is supplied independently, and TEGa is used as the Ga source in the reaction gas. Although TEGa has low source efficiency, the intrinsic C impurity concentration of GaN grown from TEGa is very low. This avoids the concentration distribution of the C source used for doping being affected by the decomposition reaction of the Ga source. When the uniformity of the Ga source gas is not a problem, the uniformity of the deposited C doping concentration will be greatly improved, thereby greatly improving the uniformity of the resistivity of the deposited GaN high-resistivity layer. Attached Figure Description

[0025] Figure 1 A schematic diagram of horizontal air intake during the fabrication of a GaN high-resistivity layer in a HEMT device using an MOCVD apparatus;

[0026] Figure 2 This is a schematic diagram of a reaction model for preparing a GaN high-resistivity layer using TMGa as a Ga source in an MOCVD device.

[0027] Figure 3 This is a schematic diagram of the structure of a GaN HEMT device provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic flowchart of a method for preparing a GaN high-resistivity layer according to an embodiment of the present invention. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for fabricating a GaN high-resistivity layer and a GaN HEMT device based on the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0030] like Figure 4 As shown, this embodiment provides a method for preparing a GaN high-resistivity layer, which is carried out in an MOCVD equipment, including: Step S1, at least one substrate layer, the GaN high-resistivity layer being epitaxially grown based on the substrate layer; the substrate layer includes at least a nucleation and / or epitaxial growth pretreatment stage; the Ga source in the reaction gas used during the pretreatment of the substrate layer is TMGa. Step S2, when preparing the GaN high-resistivity layer, a C source for doping is independently supplied and the Ga source in the reaction gas is switched to TEGa; at this time, the growth temperature is 900-1100℃. At this growth temperature, TEGa is less likely than TMGa to decompose into active C atoms that are conducive to the formation of Ga-C bonds, thereby reducing the generation of certain products in other expression forms that are not suitable for C doping, thereby avoiding the influence of the concentration of independently introduced C doping on the intensity of the Ga source decomposition reaction.

[0031] In this embodiment, during the preparation of the GaN high-resistivity layer, a C source for doping is supplied independently, and TEGa is used as the Ga source in the reaction gas. Although TEGa has low source efficiency, its intrinsic C impurity concentration during GaN growth is relatively low. This avoids the concentration distribution of the C source used for doping being affected by the decomposition reaction of the Ga source. When the uniformity of the Ga source gas is not a problem, the uniformity of the C doping concentration introduced separately will also be greatly improved, thereby forming a stable reaction environment in the reaction chamber and greatly improving the resistivity uniformity of the deposited GaN high-resistivity layer.

[0032] In this embodiment, the flow rate of TEGa into the MOCVD equipment is not less than 3E-3mol / min; the growth pressure is 30-100mbar; and the growth rate of the GaN high-resistivity layer is not less than 2μm / h.

[0033] In this embodiment, the molar ratio of group V source to group III source ranges from 500 to 2000. Group V source refers to group V elements, such as N source. The growth of GaN high-resistivity layer requires both Ga source and N source, and ammonia is generally used as the N source.

[0034] The C source is preferably any one of ethylene, ethane, and propane. In other embodiments, the C source can also be methane, acetylene, benzene, toluene, etc. In this embodiment, when preparing the GaN high-resistivity layer, the flow rate of the independently supplied C source for doping is controlled at 100-1000 sccm, and the molar ratio of the C source to the Ga source (TEGa is selected as the Ga source) is not greater than 1. This achieves C doping at the 1E19-1E20 cm⁻³ level with high reactant gas utilization. The independently supplied C source is the doping source for the GaN high-resistivity layer prepared in this embodiment, which increases the film resistance by forming Ga-C bonds with gallium atoms.

[0035] In this embodiment, the MOCVD equipment includes at least one reactor, the reactor including a reaction chamber, and the substrate layer placed within the reaction chamber. The reactor supplies reactant gas and carrier gas to the reaction chamber in a manner parallel to the plane of the substrate layer. In this embodiment, the MOCVD equipment can be any existing technology, and will not be described in detail here.

[0036] In this embodiment, TEGa (triethylgallium) is introduced into the MOCVD equipment as a gallium source using a horizontal air intake method. The resulting high-resistivity layer has a uniform resistivity distribution, which can effectively solve the problem of uneven resistivity of the high-resistivity layer caused by using TMGa as a Ga source to self-dopat carbon-containing high-resistivity layers when using horizontal air intake.

[0037] On the other hand, please refer to Figure 3As shown, this embodiment also provides a method for fabricating a GaN HEMT device, including: step S11, fabricating the high-resistivity layer 101 as described above; step S12, sequentially forming a channel layer 102, a barrier layer 103, and a device layer 104 on the high-resistivity layer 101.

[0038] In this embodiment, the substrate layer 100 is made of Si; compared with SiC or GaN substrates, using Si substrates can save material costs, and compared with sapphire substrates, it has better thermal conductivity.

[0039] In this embodiment, a nucleation layer and a transition buffer layer are further included, located between the substrate layer 100 and the high-resistivity layer 101. The nucleation layer is made of AlN. The transition buffer layer is made of AlxGa(1-x)N. The transition buffer layer can be an AlxGa(1-x)N graded layer, where x gradually decreases, which can improve the lattice fit. Alternatively, in some other embodiments, the transition buffer layer can also be an AlxGa(1-x)N-GaN alternating growth layer to relieve stress.

[0040] The high-resistivity layer 101 is epitaxially grown with C / Fe-doped GaN to reduce the leakage current of the device buffer layer and improve the device breakdown voltage.

[0041] The channel layer 102 is an unintentionally doped GaN epitaxial layer, forming a heterojunction with the AlxGa(1-x)N material of the barrier layer 103. Piezoelectric polarization and spontaneous polarization at the heterojunction interface generate a high concentration of two-dimensional electron gas (2DEG). During the formation of the channel layer 102, the Ga source in the reaction gas is switched to TMGa. The gas pressure during the deposition of the channel layer 102 is 100-300 mbar, preferably 180-250 mbar, to suppress the self-doping reaction of C.

[0042] In this embodiment or other embodiments, an insertion layer can also be prepared. The material of the insertion layer is AlN, and the material of the barrier layer 103 is AlxGa(1-x)N. The insertion layer is located between the barrier layer 103 and the channel layer 102.

[0043] In this embodiment or other embodiments, a cap layer may also be fabricated between the barrier layer 103 and the device layer 104, and the material of the cap layer is GaN. The device layer 104 is an application layer, including a source, a drain, a gate, and a dielectric layer, etc.

[0044] In this embodiment, trimethylgallium (TMGa) can also be used as the Ga source when preparing the transition buffer layer, channel layer 102 and barrier layer 103.

[0045] After using triethylgallium (TEGa) instead of trimethylgallium as the gallium source in the GaN high-resistivity layer 101, the resistivity of the GaN high-resistivity layer is more uniform, which in turn makes the breakdown resistance of the high-resistivity layer of GaN HEMT devices consistent, and also indirectly improves the yield of GaN HEMT devices.

[0046] In summary, in this embodiment, when fabricating GaN HEMT devices using MOCVD technology, the GaN high-resistivity layer uses triethylgallium as the gallium source and simultaneously introduces a carbon source independently to deposit a highly carbon-doped high-resistivity layer. It can be understood that this is mainly a semiconductor material manufacturing process for HEMT devices, and it improves upon the problem of non-uniform resistivity of the high-resistivity layer under MOCVD.

[0047] Furthermore, in the context of this document, unless otherwise indicated, the term “layer” encompasses both the singular and plural forms.

[0048] In the foregoing description, numerous specific details have been set forth to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid obscuring the invention.

[0049] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0050] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this invention, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0051] Spatial relation terms such as “below,” “under,” “below,” “below,” “under,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then the element or feature described as “below” or “under” or “below” will be oriented “above” the other element or feature. Thus, the exemplary terms “below” and “under” can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly. The terminology used herein is intended only to describe particular embodiments and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprise" and / or "comprising," when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups. When used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0052] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a GaN high-resistivity layer, which is prepared using an MOCVD device, comprising: At least one substrate layer, the GaN high-resistivity layer being epitaxially grown based on the substrate layer; The substrate layer includes at least a pretreatment stage for nucleation and / or epitaxial growth; The Ga source in the reaction gas used during the pretreatment of the substrate layer is TMGa; characterized in that... When preparing the GaN high-resistivity layer, a C source for doping is supplied independently, and the Ga source in the reaction gas is switched to TEGa. The growth temperature is 900-1100℃. At this growth temperature, TEGa is less likely to decompose into active C atoms that are conducive to the formation of Ga-C bonds than TMGa, so as to avoid the uniformity of C doping concentration being affected by the intensity of the Ga source decomposition reaction. The growth pressure of the GaN high-resistivity layer is 30-100 mbar.

2. The method for preparing a GaN high-resistivity layer as described in claim 1, characterized in that, The flow rate of TEGa into the reaction chamber of the MOCVD equipment is not less than 0.001 mol / min, and the growth rate is not less than 2 μm / h.

3. The method for preparing a GaN high-resistivity layer as described in claim 2, characterized in that, The molar ratio of Group V sources to Group III sources ranges from 500 to 2000.

4. The method for preparing a GaN high-resistivity layer as described in claim 3, characterized in that, The C source is ethylene, ethane, or propane.

5. The method for preparing a GaN high-resistivity layer as described in claim 4, characterized in that, The flow rate of the C source is controlled at 100-1000 sccm, and the molar ratio of the C source to the Ga source is not greater than 1.

6. The method for preparing a GaN high-resistivity layer as described in claim 1, characterized in that, The MOCVD equipment includes at least one reactor, the reactor including a reaction chamber, the substrate being placed inside the reaction chamber, wherein the reactor supplies reaction gas and carrier gas to the reaction chamber in a manner parallel to the plane of the substrate.

7. A method for fabricating a GaN HEMT device, characterized in that, include: Step S11: Prepare the GaN high-resistivity layer using the GaN high-resistivity layer preparation method according to any one of claims 1 to 6; Step S12: Form a channel layer, a barrier layer, and a device layer sequentially on the GaN high-resistivity layer.

8. The method for fabricating a GaN HEMT device as described in claim 7, characterized in that, The channel layer is an unintentionally doped GaN epitaxial layer. When the channel layer is formed, the Ga source in the reaction gas is switched to TMGa.

9. The method for fabricating a GaN HEMT device as described in claim 8, characterized in that, The gas pressure during the deposition of the channel layer is 100-300 mbar.

10. The method for fabricating a GaN HEMT device as described in claim 9, characterized in that, TMGa was used as the Ga source when preparing the barrier layer.

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