Si composite substrate for GAN growth and method for producing same

Abstract

The present invention relates to a Si composite substrate for GaN growth and a method for producing same, in which AlN layers for suppressing the melt-back etching phenomenon are configured as multiple layers each formed in a different manner, thus making it possible for the AlN layers and an AlGaN transition layer to be thinner and the crystal quality of a GaN layer to be improved.

Description

SI composite substrate for GAN growth and its manufacturing method

[0001] The present invention relates to a Si composite substrate for GaN growth and a method for manufacturing the same, and more particularly, to a Si composite substrate for GaN growth and a method for manufacturing the same, which can form thinner AlN layers and AlGaN transition layers while improving the crystal quality of the GaN layer by configuring an AlN layer as a multilayer formed in different ways to suppress the melt-back etching phenomenon.

[0002] In a GaN material-based power semiconductor (HEMT, High Electron Mobility Transistor) device with a horizontal channel structure based on a technology that directly grows GaN material on top of a conventional Si single crystal growth substrate, a design that suppresses the leakage current of the power semiconductor device through a high-quality epitaxial thin film growth technology with high breakdown voltage and high reliability characteristics is essential in order for the device to be operated stably at high temperatures with high voltage and / or high-speed switching functions.

[0003] Figure 1 illustrates a Si composite substrate for GaN growth according to the prior art.

[0004] As illustrated in FIG. 1, a conventional Si composite substrate for GaN growth and a power semiconductor device structure using the same have a structure in which a Si single crystal growth substrate (11) having high electrical resistance characteristics, a melt-back etching prevention layer (12) including an AlN material system (nitride or nitride oxide including an Al composition) for suppressing a melt-back etching phenomenon through a high-temperature reaction with a surface layer of the Si single crystal growth substrate, an AlGaN transition layer (13) composed of multiple layers including an AlGaN material system for controlling strain, and a power semiconductor active layer (14) including a GaN material system are sequentially laminated.

[0005] That is, in the group III nitride power semiconductor HEMT device structure in which the GaN material system is grown directly on top of the conventional Si single crystal growth substrate, a high-resistance Si single crystal growth substrate wafer must be applied along with the formation of a high-resistance GaN buffer layer under the GaN channel layer, but there are the following problems.

[0006] In the conventional group III nitride power semiconductor HEMT device structure, a process of directly growing a GaN material single crystal thin film and a power semiconductor device structure on top of a Si single crystal wafer for group III nitride power semiconductor growth substrate using MOCVD (metal organic chemical vapor deposition) equipment is performed, and a high temperature of around 1100℃ and a reducing atmosphere (H2, H + , NH3, radical ions) is basically performed in a single crystal thin film growth (film formation) process of GaN material system containing Ga atoms. At this time, a Si-Ga metallic eutectic reaction actively occurs with relatively small energy between the surface layer of the Si single crystal wafer and the Ga atoms, which lowers the melting point to below 1000℃. However, when GaN grown at 1100℃ or higher is grown on a Si growth substrate, damage occurs to the substrate, so an AlN material-based melt-back etching prevention layer area is absolutely necessary to block this.

[0007] However, when introducing a melt-back etching prevention layer based on such AlN material system, if GaN is grown directly on the AlN melt-back etching prevention layer, strong tensile stress is generated due to the difference in lattice constant (LC) and coefficient of thermal expansion (CTE) of AlN and GaN, which causes cracks. Therefore, to prevent such cracks, multi-layer AlGaN transfer layers with different Al compositions are stacked between the AlN melt-back etching prevention layer and GaN to control the tensile stress.

[0008] In addition, if the above-described melt-back etching prevention layer is too thin, the Ga atoms of the AlGaN transition layer grown thereon may back-diffuse due to defects and pits that occur between the Si growth substrate and the melt-back etching prevention layer, thereby damaging the Si growth substrate. Therefore, the melt-back etching prevention layer is usually thick, about 200 nm. This causes a problem in that the crystal quality of the GaN layer deteriorates due to stress within the epitaxy, and in order to compensate for the stress caused by the thick AlN layer, the AlGaN transition layer must also become thicker.

[0009] The purpose of the present invention is to solve the above-described conventional problems, and to provide a Si composite substrate for GaN growth and a method for manufacturing the same, which enables thinner AlN layers and AlGaN transition layers while improving the crystal quality of the GaN layer by configuring the AlN layer as a multilayer formed in different ways to suppress the melt-back etching phenomenon.

[0010] The above object is achieved by a Si composite substrate for GaN growth, according to the present invention, comprising: a Si growth substrate; a first AlN layer formed on the Si growth substrate; a second AlN layer formed on the first AlN layer; a third AlN layer formed on the second AlN layer; and an AlGaN transition layer formed on the third AlN layer.

[0011] In addition, the present invention may further include a GaN layer grown on the AlGaN transition layer.

[0012] In addition, the first AlN layer and the third AlN layer can be formed by growing through MOCVD (metal organic chemical vapor deposition), and the second AlN layer can be formed by depositing through sputtering.

[0013] Additionally, the first AlN layer and the third AlN layer may be grown as a single crystal, and the second AlN layer may be deposited as a polycrystal.

[0014] The above object is achieved by a method for manufacturing a Si composite substrate for GaN growth, comprising the steps of: preparing a Si growth substrate; forming a first AlN layer on the Si growth substrate; forming a second AlN layer on the first AlN layer; forming a third AlN layer on the second AlN layer; and forming an AlGaN transition layer on the third AlN layer, according to the present invention.

[0015] According to the present invention, since the AlN layer for suppressing the melt-back etching phenomenon is formed as a multilayer in different ways, a thinner AlN layer and an AlGaN transition layer are possible, and thus the crystal quality of the GaN layer can be significantly improved.

[0016] In addition, according to the present invention, since the pit density can be reduced by depositing an AlN layer having a small grain size through sputtering on defects and pits that occur between the Si growth substrate and the AlN layer, back diffusion of Ga atoms in the AlGaN transition layer can be effectively prevented even when a thin AlN layer is used.

[0017] Meanwhile, the effects of the present invention are not limited to the effects mentioned above, and various effects may be included within a range obvious to those skilled in the art from the contents described below.

[0018] Figure 1 illustrates a Si composite substrate for GaN growth according to the prior art.

[0019] FIG. 2 illustrates a Si composite substrate for GaN growth according to one embodiment of the present invention.

[0020] FIG. 3 illustrates a GaN layer grown on a Si composite substrate for GaN growth according to one embodiment of the present invention.

[0021] Figure 4 is a flowchart of a method for manufacturing a Si composite substrate for GaN growth according to one embodiment of the present invention.

[0022] FIG. 5 illustrates a process for manufacturing a Si composite substrate for GaN growth according to a method for manufacturing a Si composite substrate for GaN growth according to one embodiment of the present invention.

[0023] Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. When designating components in each drawing, it should be noted that, where possible, identical components are given the same reference numerals, even if they appear in different drawings.

[0024] In addition, when describing an embodiment of the present invention, if a detailed description of a related known configuration or function is judged to hinder understanding of the embodiment of the present invention, the detailed description is omitted.

[0025] Additionally, when describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by the terms.

[0026]

[0027] From now on, with reference to the attached drawings, a Si composite substrate (100) for GaN growth according to one embodiment of the present invention will be described in detail.

[0028] FIG. 2 illustrates a Si composite substrate (100) for GaN growth according to one embodiment of the present invention, and FIG. 3 illustrates a GaN layer (160) grown on a Si composite substrate (100) for GaN growth according to one embodiment of the present invention.

[0029] As illustrated in FIGS. 2 and 3, a Si composite substrate (100) for GaN growth according to one embodiment of the present invention includes a Si growth substrate (110), a first AlN layer (120), a second AlN layer (130), a third AlN layer (140), an AlGaN transition layer (150), and a GaN layer (160).

[0030] The Si growth substrate (110) has high resistivity and can be formed of Si having a (111) crystal plane to enable the growth of a high-quality group III nitride semiconductor thin film on the upper portion, and can also be formed of Si having a (100) or (110) crystal plane.

[0031] The first AlN layer (120) is a layer to prevent melt-back etching and is formed on the Si growth substrate (110).

[0032] More specifically, this first AlN layer (120) can be grown into a single crystal at a high temperature (HT) in the range of 900°C to 1100°C through MOCVD (metal organic chemical vapor deposition), and can be formed to a thickness of about 70 nm or less, which is thinner than a conventional melt-back etching prevention layer for stress control, and preferably can be formed to a thickness of 30 nm to 70 nm.

[0033] The second AlN layer (130) is a layer to prevent back diffusion of Ga atoms of the AlGaN transition layer (150) described later, and is formed on the first AlN layer (120).

[0034] More specifically, this second AlN layer (130) can be formed by growing the first AlN layer (120) through MOCVD (metal organic chemical vapor deposition), and then deposited as a polycrystal at a high temperature (HT) in the range of 300°C to 600°C through PVD (physical vapor deposition) such as sputtering ex-situ, and can be formed to a thickness of about 20 nm or less for stress control, and preferably can be formed to a thickness of 5 nm to 20 nm. Meanwhile, the second AlN layer (130) can include a small amount of oxygen atoms during the PVD process.

[0035] The third AlN layer (140) is a layer to prevent melt-back etching and is formed on the second AlN layer (130).

[0036] More specifically, this third AlN layer (140) can be formed by depositing the second AlN layer (130) through sputtering, and then grown into a single crystal at a high temperature (HT) in the range of 900°C to 1100°C through MOCVD (metal organic chemical vapor deposition), and can be formed to a thickness of about 70 nm or less, which is thinner than a conventional melt-back etching prevention layer, for stress control, and preferably can be formed to a thickness of 30 nm to 70 nm.

[0037] The AlGaN transition layer (150) is a layer for alleviating stress due to the difference in lattice constant (LC) between AlN and GaN, and is composed of a multilayer in which multiple layers having different Al compositions are stacked, and is formed on the third AlN layer (140).

[0038] Such an AlGaN transition layer (150) may include, for example, a first AlGaN transition layer (150) formed at 1150°C with a 75% Al composition, a second AlGaN transition layer (150) formed at 1100°C with a 50% Al composition, and / or a third AlGaN transition layer (150) formed at 1050°C with a 25% Al composition, and each layer may have a thickness of 500 nm or less.

[0039] The GaN layer (160) is a layer grown after stress is released through the AlGaN transition layer (150), and is grown on the AlGaN transition layer (150). This GaN layer (160) may be a channel layer in which a 2DEG is formed in a high-frequency and switching power semiconductor device structure such as a HEMT, or a high-resistance layer doped with carbon or Fe, but is not limited thereto.

[0040] According to the Si composite substrate for GaN growth of the present invention having an AlN layer of a multilayer structure as described above, there is an effect of reducing the pit density (defect density) between the Si growth substrate (110) and the AlN by the second AlN layer (130) formed by sputtering to have a small grain size.

[0041] In addition, as the pit density is reduced in this way, even when a thin AlN layer is used, back diffusion of Ga atoms of the AlGaN transition layer (150) to the interface of the Si growth substrate (110) can be effectively prevented.

[0042] In addition, since the present invention can use a relatively thin AlN layer without melt-back etching, the stress within the epitaxy can be reduced, and accordingly, even if a relatively thin AlGaN transition layer (150) is used, there is an advantage in that the crystallinity of the GaN layer (160) can be increased.

[0043] Meanwhile, the table below shows the results of experiments on pit densities in cases where the AlN layer was grown as a single layer of 120 nm through MOCVD only at a high temperature of 1050°C, in cases where it was grown as a double layer through the same MOCVD and sputtering at a high temperature of 600°C, but in three layers of 50 nm (MOCVD), 20 nm (HT-sputtered), and 50 nm (MOCVD), and in cases where it was grown as a double layer through the same MOCVD and sputtering at a low temperature of 300°C, but in three layers of 50 nm (MOCVD), 20 nm (LT-sputtered), and 50 nm (MOCVD).

[0044]

[0045] Capping structureEtch pits(1 / mm 2)RMS roughness(mm)MOCVD1482.31.47MOCVD, HT sputtered71.24MOCVD, RT sputtered261.58

[0046] As shown in the table above, it can be confirmed that the case in which the AlN layer was grown in a double layer through MOCVD and sputtering at a high temperature of 600°C has the lowest pit density and the lowest RMS roughness (root mean square roughness).

[0047]

[0048] From now on, with reference to the attached drawings, a method (S100) for manufacturing a Si composite substrate for GaN growth according to one embodiment of the present invention will be described in detail.

[0049] FIG. 4 is a flowchart of a method (S100) for manufacturing a Si composite substrate for GaN growth according to an embodiment of the present invention, and FIG. 5 illustrates a process for manufacturing a Si composite substrate for GaN growth according to a method (S100) for manufacturing a Si composite substrate for GaN growth according to an embodiment of the present invention.

[0050] As illustrated in FIGS. 4 and 5, a method for manufacturing a Si composite substrate for GaN growth according to an embodiment of the present invention (S100) includes a step of preparing a Si growth substrate (110) (step S110), a step of forming a first AlN layer (120) on the Si growth substrate (110) (step S120), a step of forming a second AlN layer (130) on the first AlN layer (120) (step S130), a step of forming a third AlN layer (140) on the second AlN layer (130), a step of forming an AlGaN transition layer (150) on the third AlN layer (140) (step S150), and a step of growing a GaN layer (160) on the AlGaN transition layer (150).

[0051] Step S110 is the step of preparing a Si growth substrate (110).

[0052] The Si growth substrate (110) has high resistivity and can be formed of Si having a (111) crystal plane to enable the growth of a high-quality group III nitride semiconductor thin film on the upper portion, and can also be formed of Si having a (100) or (110) crystal plane.

[0053] Step S120 is a step of forming a first AlN layer (120) on a Si growth substrate (110).

[0054] The first AlN layer (120) is a layer for preventing melt-back etching. More specifically, the first AlN layer (120) can be grown into a single crystal at a high temperature (HT) in the range of 900°C to 1100°C through MOCVD (metal organic chemical vapor deposition), and can be formed to a thickness of about 70 nm or less, which is thinner than a conventional melt-back etching prevention layer, for stress control, and preferably can be formed to a thickness of 30 nm to 70 nm.

[0055] Step S130 is a step of forming a second AlN layer (130) on the first AlN layer (120).

[0056] The second AlN layer (130) is a layer for preventing back diffusion of Ga atoms of the AlGaN transition layer (150) described later. More specifically, the second AlN layer (130) is formed by growing the first AlN layer (120) through MOCVD (metal organic chemical vapor deposition), and then can be deposited as a polycrystal at a high temperature (HT) in the range of 300°C to 600°C through PVD (physical vapor deposition) such as sputtering ex-situ. The second AlN layer (130) can be formed to a thickness of about 20 nm or less for stress control, and preferably can be formed to a thickness of 5 nm to 20 nm. Meanwhile, the second AlN layer (130) can include a small amount of oxygen atoms during the PVD process.

[0057] Step S140 is a step of forming a third AlN layer (140) on the second AlN layer (130).

[0058] The third AlN layer (140) is a layer for preventing Melt-back Etching. More specifically, the third AlN layer (140) is formed by depositing the second AlN layer (130) through sputtering, and then can be grown into a single crystal at a high temperature (HT) in the range of 900°C to 1100°C through MOCVD (metal organic chemical vapor deposition). In order to control stress, the third AlN layer (140) can be formed to a thickness of about 70 nm or less, which is thinner than a conventional Melt-back Etching prevention layer, and preferably, can be formed to a thickness of 30 nm to 70 nm.

[0059] Step S150 is a step of forming an AlGaN transition layer (150) on the third AlN layer (140).

[0060] The AlGaN transition layer (150) is a layer for alleviating stress due to the difference in lattice constant (LC) between AlN and GaN, and is composed of a multilayer in which a plurality of layers having different Al compositions are stacked. This AlGaN transition layer (150) may include, for example, a first AlGaN transition layer (150) formed with a 75% Al composition at 1150°C, a second AlGaN transition layer (150) formed with a 50% Al composition at 1100°C, and / or a third AlGaN transition layer (150) formed with a 25% Al composition at 1050°C, and each layer may have a thickness of 500 nm or less.

[0061] Step S160 is a step of growing a GaN layer (160) on an AlGaN transition layer (150).

[0062] The GaN layer (160) is a layer grown after stress is released through the AlGaN transition layer (150). This GaN layer (160) may be a channel layer in which a 2DEG is formed in a high-frequency and switching power semiconductor device structure such as a HEMT, or a high-resistance layer doped with carbon or Fe, but is not limited thereto.

[0063] According to the method for manufacturing a Si composite substrate for GaN growth of the present invention having an AlN layer of a multilayer structure as described above, there is an effect of reducing the pit density (defect density) between the Si growth substrate (110) and AlN by the second AlN layer (130) formed by sputtering to have a small grain size.

[0064] In addition, as the pit density is reduced in this way, even when a thin AlN layer is used, back diffusion of Ga atoms of the AlGaN transition layer (150) to the interface of the Si growth substrate (110) can be effectively prevented.

[0065] In addition, since the present invention can use a relatively thin AlN layer without melt-back etching, the stress within the epitaxy can be reduced, and accordingly, even if a relatively thin AlGaN transition layer (150) is used, there is an advantage in that the crystallinity of the GaN layer (160) can be increased.

[0066]

[0067] Although all components constituting the embodiments of the present invention have been described as being combined or operating in combination as one, the present invention is not necessarily limited to such embodiments. That is, within the scope of the present invention, all of the components may be selectively combined and operated in one or more combinations.

[0068] Furthermore, terms such as "include," "comprise," or "have" described above, unless specifically stated otherwise, imply that the corresponding component may be present, and therefore should be interpreted to include other components rather than excluding other components. All terms, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains, unless otherwise defined. Commonly used terms, such as terms defined in dictionaries, should be interpreted to be consistent with the contextual meaning of the relevant technology, and shall not be interpreted in an ideal or overly formal sense, unless explicitly defined in the present invention.

[0069] The above description is merely an example of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention.

[0070] Accordingly, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical concepts within the scope equivalent thereto should be construed as being included within the scope of the present invention.

Claims

1. Si growth substrate; A first AlN layer formed on the Si growth substrate; A second AlN layer formed on the first AlN layer; A third AlN layer formed on the second AlN layer; and A Si composite substrate for GaN growth, comprising an AlGaN transition layer formed on the third AlN layer.

2. In claim 1, A Si composite substrate for GaN growth, further comprising a GaN layer grown on the AlGaN transition layer.

3. In claim 1, The first AlN layer and the third AlN layer are, It is formed by growing through MOCVD (metal organic chemical vapor deposition), The above second AlN layer is, A Si composite substrate for GaN growth, characterized in that it is formed by deposition through sputtering.

4. In claim 3, The first AlN layer and the third AlN layer are, It is grown as a single crystal, The above second AlN layer is, A Si composite substrate for GaN growth, characterized by being deposited as a polycrystal.

5. Step of preparing Si growth substrate; A step of forming a first AlN layer on the Si growth substrate; A step of forming a second AlN layer on the first AlN layer; A step of forming a third AlN layer on the second AlN layer; and A method for manufacturing a Si composite substrate for GaN growth, comprising the step of forming an AlGaN transition layer on the third AlN layer.

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