Gallium oxide hetero epitaxy substrate and manufacturing method of the same

Abstract

The present invention relates to a gallium oxide heteroepitaxy substrate and a method for manufacturing the same. According to one aspect of the present invention, the gallium oxide heteroepitaxy substrate of the present invention comprises a sapphire substrate and a beta gallium oxide (β-Ga2O3) thin film on the sapphire substrate, wherein the thickness of the beta gallium oxide thin film is varied between a first side and a second side opposite to the first side.

Description

Technology Field

[0001] The present invention relates to a gallium oxide heteroepitaxy substrate and a method for manufacturing the same. More specifically, it relates to a gallium oxide heteroepitaxy substrate applicable to wide bandgap devices and a method for manufacturing the same.

[0002] This project (result) is the outcome of the Regional Innovation-Centered University Support System (RISE), carried out with funding from the Ministry of Education and the Busan Metropolitan City and supported by the Busan RISE Innovation Center in 2025. (2025-RISE-02-001-003)

[0003] delete

[0004] delete

[0005] delete Background Technology

[0006] Since semiconductor substrates have a significant impact on the performance of semiconductor devices, much research is underway to manufacture semiconductor substrates with excellent electrical properties.

[0007] In particular, there is increasing demand for semiconductor substrates with a wide band gap that possess superior electrical characteristics compared to conventional silicon-based semiconductor substrates.

[0008] Compound semiconductor substrates such as silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3) are gaining attention as semiconductor substrates with wide bandgap characteristics. Among these, gallium oxide has a wide bandgap characteristic of about 4.8 eV and a high breakdown electric field of 8 MV / cm, and shows a Baliga figure of merit (FOM) that is about 4 times that of gallium nitride and about 10 times that of silicon carbide, and is attracting attention as a next-generation semiconductor substrate that can be applied to various electronic devices.

[0009] Gallium oxide is a material with various crystal phases—alpha (α), beta (β), gamma (γ), delta (δ), and epsilon (ε)—each possessing a different band gap depending on the phase. Among these, beta gallium oxide (β-Ga2O3) is the most thermodynamically stable, making it the subject of much research.

[0010] One method for manufacturing beta gallium oxide in the form of a substrate is to grow a beta gallium oxide single crystal and then process the grown ingot to produce a beta gallium oxide substrate (e.g., Japanese Registered Patent JP 6402079 B2).

[0011] However, it is difficult to grow beta gallium oxide into a single crystal, and due to the cleavage properties of gallium oxide, even if it is grown into a single crystal, it is difficult to process it into a substrate, so the substrate is distributed at a very high price.

[0012] Meanwhile, a technology for manufacturing gallium oxide thin films by heteroepitaxy growth of gallium oxide thin films on a heterogeneous substrate (e.g., a sapphire substrate) is being studied (e.g., Japanese Registered Patent JP 7391290 B2). While this technology can provide gallium oxide substrates at a relatively low cost, there is a problem in that the crystallinity of the gallium oxide thin film is degraded due to a mismatch in lattice matching between the crystals of the heterogeneous substrate and the gallium oxide thin film. Furthermore, heteroepitaxy growth using a sapphire substrate can mainly result in the growth of alpha gallium oxide (α-Ga2O3) thin films with a corundum structure, making it difficult to grow beta gallium oxide thin films. Accordingly, research is required on a heteroepitaxy growth technology capable of obtaining beta gallium oxide thin films.

[0013] Due to the limitations of the aforementioned single-crystal substrate manufacturing technology or thin-film growth technology, beta gallium oxide is applied only to very limited fields, such as power semiconductors, despite its high stability and excellent properties, and is unable to sufficiently replace existing semiconductor devices.

[0014] In particular, beta gallium oxide exhibits excellent photoresponse characteristics in the ultraviolet (UV) band and superior blocking selectivity for visible light and UV wavelengths contained in sunlight, giving it excellent potential as a deep UV photodetector; however, commercialization is difficult due to the high cost of the substrate. Furthermore, even when heteroepitaxy growth technology is applied, it is difficult to grow beta gallium oxide thin films. Even if a beta gallium oxide thin film is grown, the large bandgap variation across the entire film surface results in non-uniform UV reception characteristics, which acts as an obstacle to utilizing gallium oxide thin films as UV photodetectors. Moreover, doping is required to improve the optoelectric properties of UV photodetectors, but there is a problem where the bandgap variation of the beta gallium oxide thin film increases further upon doping.

[0015] Accordingly, there is a need for the development of technology that can resolve the high cost issue of beta gallium oxide substrates while minimizing bandgap deviations of beta gallium oxide, thereby enabling uniform photoresponse characteristics.

[0016] Meanwhile, the aforementioned background technology is technical information that the inventor possessed for the derivation of the present invention or acquired during the process of deriving the present invention, and it cannot be considered as prior art disclosed to the general public prior to the filing of the present invention. Prior art literature

[0017] Japanese Patent JP 6402079 B2 “Method for manufacturing a β-Ga2O3-based single-crystal substrate” Japanese Patent JP 7391290 B2 “Crystalline oxide semiconductor film and semiconductor device” Korean Patent KR 2716283 B2 “Method for growing a single crystal” The problem to be solved

[0018] One embodiment of the present invention aims to provide a gallium oxide heteroepitaxy substrate capable of providing a high-quality beta gallium oxide thin film at a low cost and a method for manufacturing the same.

[0019] One embodiment of the present invention aims to provide a gallium oxide heteroepitaxy substrate and a method for manufacturing the same, which can provide a beta gallium oxide thin film at a low cost while simultaneously providing uniform photoresponse characteristics. means of solving the problem

[0020] As a technical means for achieving the technical problem described above, according to one aspect of the present invention, the gallium oxide heteroepitaxy substrate of the present invention comprises a sapphire substrate and a beta gallium oxide (β-Ga2O3) thin film on the sapphire substrate, wherein the thickness of the beta gallium oxide thin film is varied between a first side and a second side opposite to the first side.

[0021] According to another aspect of the present invention, the beta gallium oxide thin film can satisfy the following [Equation 1].

[0022] [Mathematical Formula 1]

[0023] FR / TR ≤ 0.5

[0024] Provided that TR = (Tmax - Tmin) / Tmin and FR = (Fmax - Fmin) / Fmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, and Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side. Fmax represents the maximum value of the full width at half maximum (FWHM) of the X-ray Diffraction (XRD) omega scan for the (-201) plane between the first side and the second side, and Fmin represents the minimum value of the FWHM between the first side and the second side.

[0025] According to another aspect of the present invention, the beta gallium oxide thin film may comprise tin (Sn) doped at 4 at% or less relative to the gallium element.

[0026] According to another aspect of the present invention, the sapphire substrate may include an inclined surface having an inclination angle of 1° or more.

[0027] According to another aspect of the present invention, the Tmax-Tmin of the beta gallium oxide thin film may be 700 nm or less.

[0028] According to another aspect of the present invention, the Fmax - Fmin of the beta gallium oxide thin film may be 1000 arcsec or less.

[0029] According to another aspect of the present invention, the growth plane of the beta gallium oxide thin film may be a (-201) plane.

[0030] According to another aspect of the present invention, the beta gallium oxide thin film can satisfy the following [Equation 2].

[0031] [Mathematical Formula 2]

[0032] RR / TR ≤ 7

[0033] Provided that TR = (Tmax - Tmin) / Tmin and RR = (Rmax - Rmin) / Rmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Rmax represents the maximum value of the RMS (Root mean square) value of the surface roughness of the beta gallium oxide thin film between the first side and the second side, and Rmin represents the minimum value of the RMS value measured between the first point and the second point.

[0034] According to another aspect of the present invention, the Rmax - Rmin of the beta gallium oxide thin film may be 320 nm or less.

[0035] According to another aspect of the present invention, the deviation of the band gap of the beta gallium oxide thin film measured between the first side and the second side of the beta gallium oxide thin film may be within 0.13 eV.

[0036] According to another aspect of the present invention, the gallium oxide heteroepitaxy substrate may be provided for a photodetector that detects light having a wavelength of 245 nm to 265 nm.

[0037] As a technical means for achieving the technical problem described above, according to another aspect of the present invention, a method for manufacturing a gallium oxide heteroepitaxy substrate of the present invention comprises the steps of providing a sapphire substrate including an inclined surface and growing a beta gallium oxide thin film on the sapphire substrate, wherein in the step of growing the beta gallium oxide thin film, the beta gallium oxide thin film is grown such that its thickness varies between a first side and a second side opposite to the first side.

[0038] According to another aspect of the present invention, the beta gallium oxide thin film can satisfy the following [Equation 1].

[0039] [Mathematical Formula 1]

[0040] FR / TR ≤ 0.4

[0041] Provided that TR = (Tmax - Tmin) / Tmin and FR = (Fmax - Fmin) / Fmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Fmax represents the maximum value of the full width at half maximum (FWHM) of the X-ray Diffraction (XRD) omega scan for the (-201) plane between the first side and the second side, and Fmin represents the minimum value of the FWHM between the first side and the second side.

[0042] According to another aspect of the present invention, the beta gallium oxide thin film can satisfy the following [Equation 2].

[0043] [Mathematical Formula 2]

[0044] RR / TR ≤ 7

[0045] However, TR = (Tmax - Tmin) / Tmin and RR = (Rmax - Rmin) / Rmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Rmax represents the maximum value of the RMS (Root mean square) value of the surface roughness of the beta gallium oxide thin film between the first side and the second side, and Rmin represents the minimum value of the RMS measured between the first point and the second point.

[0046] According to another aspect of the present invention, the step of growing the beta gallium oxide thin film may include a mist providing step of providing a gallium-containing mist on the sapphire substrate. Effects of the invention

[0047] According to any one of the means for solving the problem of the present invention described above, the gallium oxide heteroepitaxy substrate of the present invention comprises a beta gallium oxide thin film having a variable thickness between a first side and a second side, and the thickness variation between the first side and the second side, and the FWHM variation or surface roughness variation with respect to the growth surface satisfy predetermined conditions. In this case, the bandgap variation of the beta gallium oxide thin film can be reduced across the entire surface of the gallium oxide heteroepitaxy substrate, and in particular, the bandgap variation can be minimized even if a dopant such as Sn is doped. Accordingly, a substrate with excellent light reception characteristics for a specific wavelength range can be provided.

[0048] According to any one of the means for solving the problem of the present invention described above, the method for manufacturing a gallium oxide heteroepitaxy substrate of the present invention is manufactured by growing a beta gallium oxide thin film on a sapphire substrate. In particular, the method for manufacturing a gallium oxide heteroepitaxy substrate of the present invention is characterized by controlling the growth such that the thickness variation between the first side and the second side of the beta gallium oxide, the FWHM variation or surface roughness variation with respect to the growth surface, during the growth of the beta gallium oxide thin film satisfy predetermined conditions. In this case, a gallium oxide thin film in the beta phase, rather than the alpha phase, can be uniformly grown on a sapphire substrate having a corundum structure, and a high-value beta gallium oxide thin film can be obtained using an inexpensive sapphire substrate.

[0049] In addition, the method for manufacturing a gallium oxide heteroepitaxy substrate according to the present invention is characterized by controlling the growth of a gallium beta oxide thin film on a sapphire substrate having an inclined surface such that the thickness variation between the first side and the second side of the gallium beta oxide, the FWHM variation or the surface roughness variation with respect to the growth surface satisfy predetermined conditions. In this case, stable beta phase growth is induced across the entire surface of the substrate, and in particular, even if a dopant such as Sn is doped, the aggregation of Sn is suppressed and the influx of heterogeneous phases can be minimized. Accordingly, high-concentration doping of Sn can be achieved, the degree of freedom for doping is secured, and the light reception wavelength range of the gallium beta oxide thin film can be diversified.

[0050] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0051] FIG. 1 is a plan view of a gallium oxide heteroepitaxy substrate according to one embodiment of the present invention. Figure 2 is a cross-sectional view of II-II' of Figure 1. FIG. 3 is a flowchart illustrating a method for manufacturing a gallium oxide heteroepitaxy substrate according to one embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the method of manufacturing the gallium oxide heteroepitaxy substrate of FIG. 3. FIGS. 5a and 5b are X-ray Diffraction (XRD) omega scan graphs for each region (-201) plane of the gallium oxide heteroepitaxy substrate according to Manufacturing Examples 1 and 3 of the present invention. Figures 6a and 6b are XRD omega scan graphs for the (-201) plane of each region of the gallium oxide heteroepitaxy substrate according to Manufacturing Examples 2 and 4 of the present invention. Figures 7a and 7b are the surface roughness measurement results for each region of the gallium oxide heteroepitaxy substrates of Manufacturing Examples 1 and 3 of the present invention. Figures 8a and 8b are the results of surface roughness measurements for each region of a gallium oxide heteroepitaxy substrate according to Manufacturing Examples 2 and 4 of the present invention. Figures 9a and 9b are the results of UV-vis (ultraviolet-visible) spectroscopic analysis for each region of the gallium oxide heteroepitaxy substrates according to Manufacturing Examples 1 and 3 of the present invention. Figures 10a and 10b are the results of UV-vis spectroscopic analysis of each region of the gallium oxide heteroepitaxy substrate according to Preparation Examples 2 and 4 of the present invention. Specific details for implementing the invention

[0052] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0053] Throughout the specification, when a part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members or elements interposed between them. Furthermore, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0054] The gallium oxide (Ga2O3) heteroepitaxy substrate of the present invention may refer to a stacked structure comprising a gallium oxide single-crystal thin film. In this case, the gallium oxide may be composed of an alpha (α) phase, a beta (β) phase, a gamma (γ) phase, a delta (δ) phase, or an epsilon (ε) phase. Preferably, the gallium oxide may be the beta phase, which is the thermodynamically most stable phase.

[0055] The gallium oxide heteroepitaxial substrate of the present invention can be used as a substrate for various semiconductor devices requiring wide band gap characteristics. For example, it can be applied to power semiconductor devices for controlling high-voltage power, applied to ultraviolet (UV) photodetectors, applied as a substrate for transparent electronic devices, used as a device for nano- or micro-mechanical resonators (NEMS or MEMS) used in extreme environments, or applied as a substrate for a light source such as a laser. Preferably, the gallium oxide heteroepitaxial substrate of the present invention can be applied as a substrate for a UV photodetector having solar blind characteristics.

[0056] The present invention will be described in detail below with reference to the attached drawings.

[0057] FIG. 1 is a plan view of a gallium oxide heteroepitaxy substrate according to one embodiment of the present invention.

[0058] Figure 2 is a cross-sectional view of II-II' of Figure 1.

[0059] Referring to FIGS. 1 and 2, the gallium oxide heteroepitaxy substrate of the present invention (hereinafter referred to as ‘epi substrate’) (100) comprises a sapphire substrate (110) and a beta gallium oxide thin film (120).

[0060] As shown in FIG. 1, the epi substrate (100) of the present invention may be a disc shape with a portion of the edge cut off on a flat surface. In this case, the epi substrate (100) may be divided into an upper region (T), a central region (M), and a lower region (B) along a direction perpendicular to the cut surface based on the cut surface. For convenience of explanation below, the direction in which the upper region (T), the central region (M), and the lower region (B) are arranged is defined as the vertical direction of the epi substrate (100). Additionally, the direction perpendicular to the vertical direction on the flat surface of the epi substrate (100) is defined as the horizontal direction of the epi substrate (100). Although the upper region (T), central region (M), and lower region (B) of the epi substrate (100) are defined by dividing the vertical direction of the epi substrate (100) into three equal parts, these regions are merely regions separated to more easily explain the features of the present invention, and the epi substrate (100) may not be provided divided into three regions as in FIG. 1.

[0061] Referring to FIG. 2, the sapphire substrate (110) serves as a base substrate for the epitaxial substrate (100) and provides a growth base surface for growing a beta gallium oxide thin film (120). The sapphire substrate (110) is composed mainly of sapphire (α-Al2O3), but may contain other impurities in addition to sapphire.

[0062] The growth base surface of the sapphire substrate (110) is the surface where the growth of the beta gallium oxide thin film (120) begins, and may correspond to the upper surface of the sapphire substrate (110). The growth base surface of the sapphire substrate (110) may be at least one of the c-surface (0001), a-surface (11-20), m-surface (10-10), or r-surface (1-102).

[0063] The upper surface of the sapphire substrate (110) may be an inclined surface as shown in FIG. 2. For example, the sapphire substrate (110) may include an inclined surface of 1 degree (°) or more. Preferably, the sapphire substrate (110) may include an inclined surface of 6 degrees (°) or more, and more preferably, an inclined surface of 7 degrees (°) to 10 degrees (°).

[0064] The beta gallium oxide thin film (120) is disposed on a sapphire substrate (110) and may be a thin film grown from the upper surface of the sapphire substrate (110). The beta gallium oxide thin film (120) may be a thin film containing beta-phase gallium oxide as a main component. In this specification, the meaning of “containing as a main component” may mean a state in which the proportion of beta-phase gallium oxide among the constituent crystal phases of the gallium oxide thin film (120) is 70% or more, preferably 85% or more of the total.

[0065] The thickness of the beta gallium oxide thin film (120) varies between the first side and the second side opposite to the first side. Here, the first side may refer to the upper side of the upper region (T) with respect to FIG. 1, and the second side may refer to the lower side of the lower region (B) with respect to FIG. 1. That is, as shown in FIG. 2, the thickness (H1) of the first side of the upper region (T) of the beta gallium oxide thin film (120) and the thickness (H3) of the second side of the lower region (B) of the beta gallium oxide thin film (120) are different, and the beta gallium oxide thin film (120) may be configured so that its thickness varies in each of the upper region (T), the central region (M), and the lower region (B). For example, the beta gallium oxide thin film (120) may be configured such that the thickness (H2) in the central region (M) is greater than the thickness (H1) in the first side of the upper region (T), and the thickness (H3) in the second side of the lower region (B) is greater than the thickness (H2) in the central region (M).

[0066] In this case, the difference (Fmax-Fmin) between the maximum thickness (Tmax) and minimum thickness (Tmin) of the beta gallium oxide thin film (120) may be 700 nm or less. Additionally, the difference (Fmax-Fmin) between the maximum thickness (Tmax) and minimum thickness (Tmin) of the beta gallium oxide thin film (120) may be 400 nm or more. Preferably, the difference between the maximum thickness (Tmax) and minimum thickness (Tmin) of the beta gallium oxide thin film (120) may be 500 nm to 700 nm. The existence of a difference in the thickness of the beta gallium oxide thin film (120) may mean that the growth rate of beta gallium oxide on the sapphire substrate (110) varies by region, and specifically, it may mean that the growth mode of beta gallium oxide may vary by region.

[0067] Meanwhile, the thickness variation of the beta gallium oxide thin film (120) may differ from the thickness variation of the sapphire substrate (110). In other words, the angle of inclination between the lower surface and the upper surface of the beta gallium oxide thin film (120) may differ from the angle of inclination between the lower surface and the upper surface of the sapphire substrate (110). For example, as shown in FIG. 2, the angle of inclination between the lower surface and the upper surface of the beta gallium oxide thin film (120) may be smaller than the angle of inclination between the lower surface and the upper surface of the sapphire substrate (110). This may mean that the thickness variation of the beta gallium oxide thin film (120) is smaller compared to the thickness variation of the sapphire substrate (110).

[0068] The growth surface of the beta gallium oxide thin film (120) can be configured in various ways. Here, the growth surface refers to the reference surface on which the beta gallium oxide thin film (120) is grown. The growth surface of the beta gallium oxide thin film (120) can be composed of surfaces such as (100), (010), (001), (-201), etc. Preferably, the growth surface of the beta gallium oxide thin film (120) can be the (-201) surface.

[0069] The Full Width at Half Maximum (FWHM) of the X-ray Diffraction (XRD) omega scan of the growth plane of the beta gallium oxide thin film (120) satisfies a predetermined condition. Specifically, the difference between the maximum value (Fmax) and the minimum value (Fmin) of the FWHM of the growth plane of the beta gallium oxide thin film (120) in the longitudinal direction of the epitaxial substrate (100) may be 1,100 arcsec or less, preferably 1,000 arcsec or less, and more preferably 700 arcsec or less.

[0070] The beta gallium oxide thin film (120) can be doped with a specific element. For example, the beta gallium oxide thin film (120) can be doped with an n-type dopant. Specifically, the beta gallium oxide thin film (120) can be doped with an n-type dopant such as silicon (Si), tin (Sn), Ge (germanium), niobium (Nb), zirconium (Zr), hafnium (Hf), and tantalum (Ta). Preferably, the beta gallium oxide thin film (120) of the present invention can be doped with Sn. Meanwhile, the above-described doping can be performed at 5 at% or less. Preferably, it can be performed at 4 at% or less, and more preferably, it can be doped at 1 to 4 at%. If Sn is doped in excess of 4 at%, the excessively doped Sn may form a heterogeneous phase within the beta gallium oxide single crystal, and the crystallinity of the beta gallium oxide single crystal may be reduced. Meanwhile, doping can be performed at a level suitable for achieving the appropriate carrier density and mobility required for the beta gallium oxide thin film (120), and the lower limit of the doping level is not particularly limited.

[0071] The beta gallium oxide thin film (120) of the present invention has the characteristic that the FWHM deviation in the longitudinal direction of the epitaxial substrate (100) and the height deviation satisfy a predetermined ratio. Specifically, the beta gallium oxide thin film (120) of the present invention satisfies the condition of [Equation 1] below.

[0072]

[0073] Here, FR means (Fmax-Fmin) / Fmin, and TR means (Tmax-Tmin) / Tmin.

[0074] Fmax is the maximum value of FWHM for the growth plane of the beta gallium oxide thin film (120) measured between the first side and the second side of the epitaxial substrate (100), and Fmin is the minimum value.

[0075] Tmax is the maximum value of the thickness of the beta gallium oxide thin film (120) measured between the first side and the second side of the epitaxial substrate (100), and Tmin is the minimum value.

[0076] That is, in the above [Equation 1], FR represents the normalized FWHM deviation for the growth plane of the beta gallium oxide thin film (120), and TR represents the normalized thickness deviation of the beta gallium oxide thin film (120).

[0077] Additionally, the surface roughness of the beta gallium oxide thin film (120) satisfies a predetermined range. Specifically, the surface roughness of the beta gallium oxide thin film (120) in the upper region (T), the surface roughness of the beta gallium oxide thin film (120) in the central region (M), and the surface roughness of the beta gallium oxide thin film (120) in the lower region (B) have different values. Here, surface roughness refers to the surface roughness value immediately after growing the beta gallium oxide thin film (120) (i.e., in the As grown state), and may refer to the RMS (Root mean square) value among the surface roughness values ​​measured through an AFM (Atomic Force Microscope). For the beta gallium oxide thin film (120) of the present invention, the difference between the maximum value (Rmax) and the minimum value (Rmin) among the surface roughness values ​​measured between the first side and the second side of the epitaxial substrate (100) may be 400 nm or less. Preferably, it may be 320 nm or less. More preferably, it may be 320 nm or less.

[0078] Meanwhile, the beta gallium oxide thin film (120) of the present invention has the characteristic that the deviation in surface roughness and the deviation in height in the longitudinal direction of the epitaxial substrate (100) satisfy a predetermined ratio. Specifically, the beta gallium oxide thin film (120) of the present invention satisfies the condition of [Equation 2] below.

[0079]

[0080] Here, RR means (Rmax-Rmin) / Rmin and TR means (Tmax-Tmin) / Tmin.

[0081] Rmax is the maximum value of the surface roughness of the beta gallium oxide thin film (120) measured between the first side and the second side of the epitaxial substrate (100), and Rmin is the minimum value.

[0082] Tmax is the maximum value of the thickness of the beta gallium oxide thin film (120) measured between the first side and the second side of the epitaxial substrate (100), and Tmin is the minimum value.

[0083] That is, in the above [Equation 2], RR represents the deviation of the normalized surface roughness in the As grown state of the beta gallium oxide thin film (120), and TR represents the deviation of the normalized thickness of the beta gallium oxide thin film (120).

[0084] As the beta gallium oxide thin film (120) of the present invention has the above-described features, the bandgap deviation of the epitaxial substrate (100) of the present invention can be reduced across regions of the substrate. In particular, the bandgap deviation in the longitudinal direction of the epitaxial substrate (100) can be reduced. Specifically, the beta gallium oxide thin film (120) of the present invention may have a bandgap deviation between the first side and the second side in the longitudinal direction of the epitaxial substrate (100) within 0.15 eV, and preferably within 0.13 eV.

[0085] The inventors of the present invention have discovered that when the thickness variation in a specific direction of the beta gallium oxide thin film (120) and the FWHM variation with respect to the growth plane satisfy specific conditions, the bandgap variation of the beta gallium oxide thin film (120) can be reduced, thereby improving the bandgap uniformity of the epitaxial substrate (100).

[0086] Specifically, since the sapphire substrate (110) has a corundum crystal structure, when gallium oxide is grown on the sapphire substrate (110), the alpha phase gallium oxide is predominantly grown. However, when gallium oxide is grown on the sapphire substrate (110) having a predetermined inclined surface, the gallium oxide can grow into the beta phase. In this case, if the thickness variation of the beta gallium oxide thin film (120) grown on the inclined surface of the sapphire substrate (110) is controlled under specific conditions, the growth of the gallium beta phase can be further promoted across the entire growth base surface of the sapphire substrate (110). That is, if gallium oxide growth is induced relatively quickly in one region and gallium oxide growth is induced relatively slowly in another region, it is believed that the mode of gallium oxide growth is diversified, and the growth of the beta phase gallium oxide can be induced more predominantly. For example, if the thickness difference (Tmax-Tmin) between the first side and the second side of the beta gallium oxide thin film (120) is controlled to a level of 500 nm to 700 nm, a beta gallium oxide thin film (120) having uniform crystal quality across the entire surface can be obtained. This result deviates from the general common sense that the thickness of the gallium oxide thin film must be uniform across the substrate for excellent crystallinity.

[0087] In particular, when the thickness deviation and FWHM deviation in a specific direction of the beta gallium oxide thin film (120) are controlled to meet specific conditions (e.g., the conditions of [Equation 1]), the crystal uniformity of the gallium oxide beta phase across the entire surface of the substrate can be improved, and the bandgap uniformity of the beta gallium oxide thin film (120) can be improved. That is, the bandgap deviation of the beta gallium oxide thin film (120) may be caused by more heterogeneous phases (e.g., alpha, gamma, delta, epsilon, etc.) being introduced into a specific region during the growth process of the beta gallium oxide. However, as in the present invention, when the growth of the beta gallium oxide thin film (120) is controlled such that the thickness variation and FWHM variation of the beta gallium oxide thin film (120) satisfy predetermined conditions, the gallium oxide growth rate is controlled differently for each region, and the growth of the beta phase gallium oxide is promoted according to various growth modes, thereby minimizing the inflow of heterogeneous phases across the entire growth surface and enabling the growth of a beta gallium oxide thin film (120) having a uniform band gap.

[0088] The aforementioned bandgap homogenization characteristic may be further emphasized when growing a doped beta gallium oxide thin film (120). Specifically, the beta gallium oxide thin film (120) may be doped with a dopant such as Sn. If doping is performed in an excessive amount, Sn may form a heterogeneous phase within the gallium oxide crystal, thereby degrading the crystallinity of the beta gallium oxide thin film (120). To suppress this, Sn doping may be performed in a small amount, preferably less than 5 at%, and preferably less than 4 at%. However, even if Sn is doped at less than 4 at% and does not form a heterogeneous phase within the gallium oxide crystal, a phenomenon of Sn clustering in a specific region may occur. These Sn clusters can suppress the beta phase growth of the gallium oxide crystal and change the growth behavior of the gallium oxide to induce growth into a heterogeneous phase. However, as in the present invention, when the thickness variation and FWHM variation of the beta gallium oxide thin film (120) are controlled to satisfy predetermined conditions, it is believed that the Sn clustering phenomenon during the growth process of gallium oxide can be suppressed and the beta phase growth of gallium oxide can be further promoted.

[0089] In addition, when the thickness variation and surface roughness variation of the beta gallium oxide thin film (120) satisfy a predetermined condition (e.g., when the condition of [Equation 2] is satisfied), the band gap variation of the beta gallium oxide thin film (120) can be reduced as described above.

[0090] Meanwhile, as the bandgap deviation across the entire growth surface of the beta gallium oxide thin film (120) of the present invention is reduced, the epitaxial substrate (100) of the present invention can have uniform UV selectivity. For example, the beta gallium oxide thin film (120) of the present invention may have a bandgap capable of selectively receiving light of wavelengths of 245 to 255 nm across the entire growth surface when undoped. This is a deep ultraviolet (Deep UV) wavelength band that does not overlap with the UV wavelength band caused by sunlight, which means that it can be utilized as a UV light receiving device with excellent solar blind characteristics. Furthermore, even if Sn doping is performed, the beta gallium oxide thin film (120) of the present invention can be free from the problem of Sn density, and the bandgap deviation can be reduced. Accordingly, the light receiving wavelength can be varied to the level of 265 nm through Sn doping, and the epitaxial substrate (100) of the present invention can be utilized as a light receiving device of various wavelengths by controlling selectivity for a specific wavelength.

[0091] In addition, the beta gallium oxide thin film (120) of the present invention is grown from a relatively inexpensive sapphire substrate (110). In particular, in the conventional case, since the substrate had to be manufactured by processing a beta gallium oxide single crystal to manufacture a beta gallium oxide substrate, there was a disadvantage that the manufacturing cost of the beta gallium oxide substrate was high. To overcome this, a technology for growing a beta gallium oxide thin film on a heterogeneous substrate was studied, but there was a problem that it was difficult to manufacture a beta gallium oxide substrate because it was difficult to grow the beta gallium oxide thin film with good quality. However, the beta gallium oxide thin film (120) of the present invention has the advantage of being able to provide the beta gallium oxide thin film (120) at a low cost, as it can promote the growth of the beta phase even though it is grown from an inexpensive sapphire substrate (110).

[0092] As described above, the epitaxial substrate (100) of the present invention includes a beta gallium oxide thin film (120) whose thickness varies between a first side and a second side. Additionally, if the thickness variation of the beta gallium oxide thin film (120) measured between the first side and the second side and the FWHM variation with respect to the growth surface are controlled to satisfy a predetermined condition (e.g., the condition of [Equation 1]), or if the thickness variation of the beta gallium oxide thin film (120) measured between the first side and the second side and the surface roughness variation of the growth surface are controlled to satisfy a predetermined condition (e.g., the condition of [Equation 2]), the bandgap variation of the beta gallium oxide thin film (120) is reduced, and an epitaxial substrate (100) having uniform bandgap characteristics can be provided.

[0093] Meanwhile, the conditions for FWHM deviation regarding the thickness deviation of the beta gallium oxide thin film (120) and the conditions for surface roughness deviation regarding the thickness deviation can be controlled by controlling the growth conditions of the beta gallium oxide thin film (120) described below.

[0094] Hereinafter, a method for manufacturing an epitaxial substrate (100) of the present invention will be described with reference to FIGS. 3 and FIGS. 4.

[0095] FIG. 3 is a flowchart illustrating a method for manufacturing a gallium oxide heteroepitaxy substrate according to one embodiment of the present invention.

[0096] FIG. 4 is a schematic diagram for explaining the method of manufacturing the gallium oxide heteroepitaxy substrate of FIG. 3.

[0097] Referring to FIG. 3, a method for manufacturing a gallium oxide heteroepitaxy substrate (hereinafter referred to as the 'method for manufacturing an epitaxial substrate') first provides a sapphire substrate (S310).

[0098] The method for manufacturing an epitaxial substrate according to the present invention may include various methods capable of epitaxially growing a gallium oxide single crystal. For example, the method for manufacturing an epitaxial substrate according to the present invention may include at least one method among mist chemical vapor deposition (Mist-CVD), hydride vapor phase epitaxy (HVPE), metal-organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). Preferably, the method for manufacturing an epitaxial substrate according to the present invention may include the Mist-CVD method. Hereinafter, the method for manufacturing an epitaxial substrate using the Mist-CVD method will be described based on the method.

[0099] Referring to FIG. 4, the Mist-CVD device may include a raw material storage unit (431), a raw material supply unit (433), a reactor (440), a susceptor (470), a heating unit (460), a discharge unit (483), and an exhaust device (481).

[0100] To briefly describe each component, the raw material storage unit (431) stores a liquid gallium oxide raw material. In this case, the liquid gallium oxide raw material is a gallium-containing solution and may include, for example, Ga(acac)3 or GaCl3. In some embodiments, the raw material storage unit (431) may further include a dopant. The dopant may be an n-type dopant such as Si, Sn, Ge, Nb, Zr, Hf, Ta, etc. The dopant may be weighed in an appropriate amount according to the degree of doping of the beta gallium oxide thin film (120) to be finally manufactured and mixed into the gallium oxide raw material.

[0101] The raw material supply unit (433) is a tube that supplies gallium-containing mist to the reactor (440) and connects the reactor (440) and the raw material storage unit (431). In this case, the gallium-containing mist can be provided by atomizing the gallium oxide raw material through a spray device provided in the raw material storage unit (431) and spraying it into the air. The spray device can be configured to atomize the gallium oxide raw material into micron-sized fine droplets and spray them.

[0102] Meanwhile, the gallium-containing mist sprayed through the spraying device can flow together with the flow of the carrier gas and be supplied to the reactor (440). Air, nitrogen (N2), or oxygen (O2) gas can be used as the carrier gas, and a flow control unit is connected to a raw material supply unit (433) to control the flow rate or velocity of the carrier gas in real time.

[0103] The reactor (440) creates a reaction environment to chemically vapor deposit a gallium-containing mist onto a sapphire substrate (110). The reactor (440) may be made of a material with excellent heat resistance and chemical resistance, for example, a quartz material.

[0104] Although the reactor (440) is arranged in a horizontal direction in FIG. 4, the reactor (440) may also be arranged in a vertical direction.

[0105] The susceptor (470) supports the sapphire substrate (110). The susceptor (470) may include an inclined surface that is inclined to support the sapphire substrate (110). In this case, the angle (θ) formed between the inclined surface of the susceptor (470) and the horizontal plane may be appropriately set within an angle range of less than 90 degrees (°).

[0106] In some embodiments, the susceptor (470) may include at least one of a lifting / lowering means and a tilting means. The lifting / lowering means can control the height of the sapphire substrate (110) by adjusting the fine height of the susceptor (470) within the reactor (440), and the tilting means can control the angle of the sapphire substrate (110) by adjusting the tilt angle (θ) of the susceptor (470). The above-described lifting / lowering means and tilting means are each electrically connected to a control unit, and the degree of lifting / lowering and tilting can be controlled in real time according to a control signal from the control unit.

[0107] The heating unit (460) is configured to heat the reactor (440) and may include a heater and an insulating material. The heating unit (460) may be blocked by zones of the reactor (440), and the control unit can finely control the temperature of the gallium-containing mist within the reactor (440) by individually controlling the temperature for each zone of the heating unit (460).

[0108] The discharge section (483) is configured to discharge residual gas after the reaction is completed and is connected to the reactor (440). The exhaust device (481) is configured to exhaust dry gas from which impurities have been removed from the residual gas.

[0109] Referring to FIG. 4, the step of providing the sapphire substrate (110) is described as follows: the sapphire substrate (110) is placed on the susceptor (470) so that the growth base surface on which the beta gallium oxide thin film (120) is to be grown is exposed.

[0110] In this case, the upper region (T) of the sapphire substrate (110) may be positioned to correspond to the upper part of the susceptor (470), and the lower region (B) of the sapphire substrate (110) may be positioned to correspond to the lower part of the susceptor (470). That is, the first side of the upper region (T) of the sapphire substrate (110) may correspond to the upper part of the susceptor (470), and the second side of the lower region (B) of the sapphire substrate (110) may be positioned to correspond to the lower part of the susceptor (470).

[0111] The upper surface of the sapphire substrate (110) that is not supported by the susceptor (470) and is exposed may correspond to a growth base surface. As described above, the growth base surface of the sapphire substrate (110) may be at least one of the c-plane (0001), a-plane (11-20), m-plane (10-10), or r-plane (1-102). Additionally, the growth base surface of the sapphire substrate (110) may include an inclined surface, and the inclination angle of the inclined surface may be 1 degree (°) or more, preferably 6 degrees (°) or more, and more preferably 7 degrees (°) to 10 degrees (°).

[0112] Referring again to FIG. 3, after a sapphire substrate is provided, a beta gallium oxide thin film is grown on the sapphire substrate (S320).

[0113] Referring again to FIG. 4, a gallium-containing mist generated through a spray device is introduced into a reactor (440) along with a carrier gas, and a beta gallium oxide thin film (120) is grown by chemical vapor deposition on the growth base surface of a sapphire substrate (110).

[0114] In this case, the injection flow rate or flow rate of the carrier gas is controlled by the flow rate control unit, and the supply flow rate and flow rate of the gallium-containing mist can be controlled.

[0115] In addition, the reactor (440) can be heated to a predetermined temperature by the heating unit (460) so that the epitaxial growth temperature of gallium oxide can be controlled.

[0116] A beta gallium oxide thin film (120) can be grown by the method described above.

[0117] Meanwhile, the beta gallium oxide thin film (120) is grown such that its thickness varies between the first side and the second side, and in particular, the thickness of the beta gallium oxide thin film between the first side and the second side and the FWHM of the growth surface can be grown to satisfy a predetermined condition (e.g., the condition of [Equation 1] above).

[0118] In addition, the thickness between the first side and the second side of the beta gallium oxide thin film (120) and the surface roughness value in the As grown state can be grown to satisfy a predetermined condition (e.g., the condition of [Equation 2] above).

[0119] A beta gallium oxide thin film (120) satisfying the above-described conditions can be manufactured by controlling various process variables. Here, the process variables may include at least one of the inclination angle of the base growth surface of the sapphire substrate (110), the angle (θ) of the inclined surface of the susceptor (470), the height of the susceptor (470) in the reactor (440), the flow rate of the gallium-containing mist, and the temperature of the reactor (440). For example, if the angle (θ) of the inclined surface of the susceptor (470) is set to a high angle of 45 degrees (°) or more and the flow rate of the gallium-containing mist is controlled rapidly, the thickness deviation between the first side and the second side of the beta gallium oxide thin film (120) can be increased, and the FWHM deviation of the growth surface between the first side and the second side can also be increased. Additionally, if the angle (θ) of the inclined surface of the susceptor (470) is set to a low angle of less than 45 degrees (°) and the flow rate of the gallium-containing mist is controlled to be slow, the thickness deviation between the first side and the second side of the beta gallium oxide thin film (120) can be reduced, and the FWHM deviation can also be reduced. Meanwhile, if the angle of the inclined surface of the growth base plane of the sapphire substrate (110) is reduced, the thickness deviation between the first side and the second side can be reduced, and the FWHM deviation can be increased. The above-described process variable control method is merely an example of one of various control methods for the thickness deviation and FWHM deviation of the beta gallium oxide thin film (120), and the method of controlling the growth conditions of the beta gallium oxide thin film (120) of the present invention can be performed by combining the above-described process variables in various ways.

[0120] In some embodiments, the step of growing a beta gallium oxide thin film (120) may include a step of evaluating whether the thickness and FWHM conditions of the beta gallium oxide thin film (120) satisfy the conditions of [Equation 1] described above, or a step of evaluating whether the thickness and surface roughness conditions of the beta gallium oxide thin film (120) satisfy the conditions of [Equation 2] described above.

[0121] Additionally, the step of growing the beta gallium oxide thin film (120) may further include, if the condition of the beta gallium oxide thin film (120) evaluated in the middle does not satisfy the condition of [Equation 1] or [Equation 2] described above, a step of controlling process variables including at least one of the inclination angle of the base growth surface of the sapphire substrate (110), the angle (θ) of the inclination surface of the susceptor (470), the height of the susceptor (470) in the reactor (440), the flow rate of the gallium-containing mist, and the temperature of the reactor (440) so that the condition of the beta gallium oxide thin film (120) satisfies the condition of [Equation 1] or [Equation 2] described above.

[0122] When the beta gallium oxide thin film (120) is grown while being controlled to satisfy the conditions described above, the beta phase growth of gallium oxide can be uniformly achieved across the entire surface, and the influx of heterogeneous phases can be minimized so that the beta gallium oxide thin film (120) can have a uniform band gap overall. In particular, even when doping with a dopant such as Sn, the concentration of the dopant is suppressed and the growth of the beta phase gallium oxide is promoted, so that the band gap deviation due to the influx of heterogeneous phases can be further minimized.

[0123] Accordingly, the epitaxial substrate (100) can have overall uniform light reception characteristics, and its value as a light-receiving device with excellent UV selectivity in the 245nm to 265nm wavelength range can be increased.

[0124] In the following, the advantages of the present invention described above will be explained in more detail through the following experimental examples.

[0126] <Manufacturing Example> Manufacturing of an epitaxial substrate

[0127] A total of four types of epitaxial substrates were manufactured using the Mist-CVD apparatus described with reference to Fig. 4.

[0128] Specifically, a sapphire substrate with a diameter of 2 inches was prepared.

[0129] After loading the sapphire substrate into the susceptor so that the growth base plane of the sapphire substrate was set to plane c (0001) and the growth base plane was exposed to the upper surface of the susceptor, a gallium beta oxide thin film was grown so that plane (-201) became the growth plane. In this case, four types of epitaxial substrates were manufactured by controlling the process variables as shown in [Table 1] below.

[0130] division Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Sapphire substrate slope angle 7° 0° 7° 0° doping elements - - Sn Sn Doping level - - 4at% 4at% Susceptor angle 45° 43° 45° 43° Carrier gas flow rate 5L 4.8L 5L 4.8L Reactor temperature 760℃ 760℃ 760℃ 760℃ Growth time 3h 3h 3h 3h

[0132] <Experimental Example 1> Measurement of Beta Gallium Oxide Thin Film Thickness

[0133] The longitudinal thickness of the beta gallium oxide thin film on the epitaxial substrate manufactured according to the above-described manufacturing example was measured.

[0134] Here, the vertical direction refers to the same direction as the inclined surface of the susceptor, and the point corresponding to the top of the susceptor is defined as the first side, and the point corresponding to the bottom of the susceptor is defined as the second side.

[0135] In addition, as shown in FIG. 1, a total of nine regions were defined by dividing the epitaxial substrate into three equal parts in the vertical and horizontal directions, respectively, and the three regions divided in the vertical direction were defined as the upper region (T), the central region (M), and the lower region (B), respectively.

[0136] The thickness of the beta gallium oxide thin film was measured along the right boundary line of the upper region (T), the central region (M), and the lower region (B), and the thickness of each region was calculated as the average of the results measured in the three regions of the top, center, and bottom of each region.

[0137] The thickness was measured using a Scanning Electron Microscope (SEM).

[0138] Each measured thickness value is as shown in [Table 2] below.

[0139] division Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 thickness T 825nm 793nm 825nm 793nm M 841nm 968nm 841nm 968nm B 1490nm 1240nm 1490nm 1240nm TR 0.806 0.564 0.806 0.564 FWHM T 2000arcsec 3770arcsec 2464arcsec 2620arcsec M 1650arcsec 3770arcsec 1870arcsec 3370arcsec B 1700arcsec 2600arcsec 1830arcsec 5320arcsec FR 0.212 0.450 0.346 1.031 FR / TR 0.263 0.798 0.430 1.828 RMS T 27.4nm 20.9nm 65.7nm 39.9nm M 22.4nm 159nm 55.6nm 267nm B 76.0nm 429nm 367nm 429nm RR 2.393 19.526 5.601 9.752 RR / TR 2.969 34.641 6.948 17.300

[0141] Meanwhile, in [Table 2] above, TR represents the normalized deviation ((Tmax-Tmin) / Tmin) of the maximum value (Tmax) and minimum value (Tmin) of thickness measured between the first side and the second side. Additionally, FR represents the normalized deviation ((Fmax-Fmin) / Fmin) of the maximum value (Fmax) and minimum value (Fmin) of FWHM for the growth surface measured between the first side and the second side. Additionally, RR represents the normalized deviation ((Rmax-Rmin) / Rmin) of the maximum value (Rmax) and minimum value (Rmin) of the RMS value of surface roughness measured between the first side and the second side.

[0142] Referring to [Table 2] above, it can be seen that the deviation (Tmax-Tmin) between the maximum value (Tmax) and minimum value (Tmin) of the beta gallium oxide thin film thickness between the first side and the second side of Preparation Examples 1 and 3 is 665 nm, and the deviation between the maximum thickness and minimum thickness of Preparation Examples 2 and 4 is 447 nm. Accordingly, it can be confirmed that the thickness deviation (Tmax-Tmin) between the first side and the second side of the beta gallium oxide thin films of Preparation Examples 1 and 3 is within the range of 500 nm to 700 nm.

[0144] <Experimental Example 2> Measurement of FWHM of Beta Gallium Oxide Thin Film

[0145] XRD analysis was performed on the beta gallium oxide thin films of the epitaxial substrates of Preparation Examples 1 to 4, and an omega scan was performed on the (-201) plane. Specifically, an omega scan was performed on the upper region (T), central region (M), and lower region (B) of the epitaxial substrate.

[0146] The results are as shown in [Table 2] and Figures 5a to 6b above.

[0147] Figures 5a and 5b are X-ray diffraction (XRD) omega scan graphs for each region (-201) plane of the gallium oxide heteroepitaxy substrate according to Manufacturing Examples 1 and 3 of the present invention.

[0148] Figures 6a and 6b are XRD omega scan graphs for the (-201) plane of each region of the gallium oxide heteroepitaxy substrate according to Manufacturing Examples 2 and 4 of the present invention.

[0149] Referring to [Table 2] and Fig. 5a, it can be seen that the deviation (Fmax-Fmin) of the maximum value (Fmax) and minimum value (Fmin) of the FWHM for the (-201) plane between the first side and the second side of the beta gallium oxide thin film of Preparation Example 1 was measured to be 350 arcsec.

[0150] On the other hand, referring to [Table 2] and Fig. 6a, the deviation (Fmax-Fmin) of the maximum value (Fmax) and minimum value (Fmin) of the FWHM for the (-201) plane between the first side and the second side of the beta gallium oxide thin film of Preparation Example 2 was measured to be 1170 arcsec, indicating that the deviation is relatively large.

[0151] In addition, referring to [Table 2] and Fig. 5b, it can be seen that the deviation (Fmax-Fmin) of the maximum value (Fmax) and minimum value (Fmin) of the FWHM for the (-201) plane between the first side and the second side of the beta gallium oxide thin film of Preparation Example 3 doped with 4 at% Sn was measured to be 634 arcsec.

[0152] In addition, referring to [Table 2] and Fig. 6b, it can be seen that the deviation (Fmax-Fmin) of the maximum value (Fmax) and minimum value (Fmin) of the FWHM for the (-201) plane between the first and second sides of the beta gallium oxide thin film of Preparation Example 4, which is doped with 4 at% Sn in the same way as Preparation Example 3, is measured to be 2700 arcsec, indicating the largest deviation.

[0153] Meanwhile, as can be seen by referring to [Table 2], the ratio of the normalized FWHM deviation (FR) to the normalized thickness deviation (TR) (FR / TR) of the beta gallium oxide thin films of Preparation Examples 1 and 3 is 0.263 and 0.430, respectively, satisfying the condition of 0.5 or less. That is, the beta gallium oxide thin films of Preparation Examples 1 and 3 satisfy the condition of [Equation 1] above.

[0154] On the other hand, it can be seen that the ratio of the normalized FWHM deviation (FR) to the normalized thickness deviation (TR) (FR / TR) of the beta gallium oxide thin films of Preparation Examples 2 and 4 is 0.798 and 1.828, respectively, both exceeding 0.5. That is, it can be seen that the beta gallium oxide thin films of Preparation Examples 2 and 4 do not satisfy the conditions of [Equation 1].

[0156] <Experimental Example 3> Measurement of Surface Roughness of Beta Gallium Oxide Thin Film

[0157] The surface roughness of the beta gallium oxide thin films of the epitaxial substrates of Preparation Examples 1 to 4 was measured. Specifically, the RMS values ​​of surface roughness were measured using AFM for the upper region (T), central region (M), and lower region (B) of the epitaxial substrate. In this case, the projected area of ​​each region was 1.0 μm 2 It was. The results are as shown in [Table 2] and Figures 7a to 8b above.

[0158] Figures 7a and 7b are the surface roughness measurement results for each region of the gallium oxide heteroepitaxy substrates of Manufacturing Examples 1 and 3 of the present invention.

[0159] Figures 8a and 8b are the results of surface roughness measurements for each region of a gallium oxide heteroepitaxy substrate according to Manufacturing Examples 2 and 4 of the present invention.

[0160] Referring to [Table 2] and Fig. 7a, it can be seen that the deviation (Rmax-Rmin) between the maximum value (Rmax) and minimum value (Rmin) of surface roughness between the first side and the second side of the beta gallium oxide thin film of Preparation Example 1 is 53.6 nm.

[0161] On the other hand, referring to [Table 2] and Fig. 8a, the deviation (Rmax-Rmin) of the maximum value (Rmax) and minimum value (Rmin) of surface roughness between the first side and the second side of the beta gallium oxide thin film of Preparation Example 2 was measured to be 408.1 nm, indicating that the deviation of surface roughness is relatively large.

[0162] In addition, referring to [Table 2] and Fig. 7b, it can be seen that the deviation (Rmax-Rmin) between the first and second sides of the beta gallium oxide thin film of Preparation Example 3, which is doped with 4 at% Sn, was measured to be 311.4 nm.

[0163] In addition, referring to [Table 2] and Fig. 8b, the deviation (Rmax-Rmin) of the maximum (Rmax) and minimum (Rmin) values ​​of surface roughness between the first and second sides of the beta gallium oxide thin film of Preparation Example 4, which is doped with 4 at% Sn in the same way as Preparation Example 3, was measured to be 389.1 nm, indicating a large deviation.

[0164] Meanwhile, as can be seen by referring to [Table 2], the ratio of normalized surface roughness deviation (RR) to normalized thickness deviation (TR) (RR / TR) of the beta gallium oxide thin films of Preparation Examples 1 and 3 is 2.696 and 6.948, respectively, satisfying the condition of 7 or less. That is, the beta gallium oxide thin films of Preparation Examples 1 and 3 satisfy the condition of [Equation 2] above.

[0165] On the other hand, it can be seen that the ratio of normalized surface roughness deviation (RR) to normalized thickness deviation (TR) (RR / TR) of the beta gallium oxide thin films of Preparation Examples 2 and 4 is 34.641 and 17.300, respectively, both exceeding 7. That is, it can be seen that the beta gallium oxide thin films of Preparation Examples 2 and 4 do not satisfy the conditions of [Equation 2].

[0167] <Experimental Example 4> Measurement of Bandgap of Beta Gallium Oxide Thin Film

[0168] UV-vis (ultraviolet-visible) spectroscopic analysis was performed on the beta gallium oxide thin films of the epitaxial substrates of Preparation Examples 1 to 4. Specifically, UV-vis spectroscopic analysis was performed on the upper region (T), middle region (M), and lower region (B) of the epitaxial substrate, and the band gap for each region was calculated using the Tauc relationship. The results are shown in FIGS. 9a to 10b.

[0169] Figures 9a and 9b are the results of UV-vis (ultraviolet-visible) spectroscopic analysis for each region of the gallium oxide heteroepitaxy substrates according to Manufacturing Examples 1 and 3 of the present invention.

[0170] Figures 10a and 10b are the results of UV-vis spectroscopic analysis of each region of the gallium oxide heteroepitaxy substrate according to Preparation Examples 2 and 4 of the present invention.

[0171] Referring to FIG. 9a, it can be seen that the band gap between the first side and the second side of the beta gallium oxide thin film of Preparation Example 1 is 4.89 eV to 5.02 eV, and the deviation is at the level of 0.13 eV. Through this, it can be seen that the beta gallium oxide thin film of Preparation Example 1 is capable of UV detection in the wavelength range of approximately 247 nm to 253 nm.

[0172] Referring to FIG. 10a, it can be seen that the band gap between the first side and the second side of the beta gallium oxide thin film of Preparation Example 2 is 4.77 eV to 4.87 eV, and the deviation is at the level of 0.10 eV. Through this, it can be seen that the beta gallium oxide thin film of Preparation Example 2 is capable of UV detection in the wavelength range of approximately 254 nm to 259 nm.

[0173] It can be seen that both Preparation Examples 1 and 2 have a bandgap deviation of 0.1 eV, indicating a good bandgap deviation. Meanwhile, considering that the UV wavelength range irradiated from sunlight is 250 nm or higher, it can be seen that the beta gallium oxide thin film of Preparation Example 1 has better solar blind characteristics compared to Preparation Example 2.

[0174] In addition, referring to FIG. 9b, it can be seen that the band gap between the first and second sides of the beta gallium oxide thin film of Preparation Example 3, which is doped with 4 at% Sn, is 4.69 eV to 4.77 eV, and through this, it can be seen that the beta gallium oxide thin film of Preparation Example 3 is capable of UV detection in the wavelength range of approximately 259 nm to 264 nm. Meanwhile, it can be seen that the band gap deviation of the beta gallium oxide thin film of Preparation Example 3 is at the level of 0.08 eV.

[0175] Referring to FIG. 10b, the band gap between the first and second sides of the beta gallium oxide thin film of Preparation Example 4, which is doped with 4 at% Sn, is 4.42 eV to 4.66 eV. This indicates that the beta gallium oxide thin film of Preparation Example 4 can detect UV in the wavelength range of 266 nm to 280 nm. Since the above wavelength range is the wavelength range of solar UV, it can be seen that the solar blind characteristics of the beta gallium oxide thin film of Preparation Example 4 are relatively low. Meanwhile, it can be seen that the band gap deviation of the beta gallium oxide thin film of Preparation Example 4 is large at the level of 0.24 eV. According to reports that the epsilon phase gallium oxide has a band gap of approximately 4.48 eV, it can be seen that the beta gallium oxide thin film of Preparation Example 4 has a significant influx of heterogeneous phases.

[0176] Through this, it can be seen that the beta gallium oxide thin film of Preparation Example 3, which satisfies the conditions of [Equation 1] or [Equation 2] above, has a band gap variation of 0.08 eV across the entire surface of the substrate, and through this, it can be inferred that even if Sn is doped at a relatively high concentration of 4%, Sn aggregation is suppressed and the influx of heterogeneous phases is minimized.

[0177] Therefore, in the case of the epitaxial substrate of the present invention, dopant concentration due to doping and the resulting inhibition of beta phase growth can be minimized, and a gallium beta oxide thin film can be grown stably despite doping, thereby improving the degree of doping freedom. Accordingly, the epitaxial substrate of the present invention can be easily applied to various electronic devices requiring doping, and in particular, since the epitaxial substrate of the present invention exhibits excellent UV selectivity in the wavelength range of 255 nm to 270 nm across the entire substrate, it has high potential for use as a UV device.

[0178] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0179] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0180] 100: Epi substrate 110: Sapphire substrate 120: Beta gallium oxide thin film 431: Raw Material Storage Unit 433: Raw Material Supply Unit 440: Reactor 460: Heating part 470: Susceptor 481: Exhaust system 483: Discharge section T: Upper area M: Central area B: Sub-region

Claims

Claim 1 Sapphire substrate; A gallium oxide heteroepitaxy substrate comprising a beta gallium oxide (β-Ga2O3) thin film on the sapphire substrate, wherein the thickness of the beta gallium oxide thin film varies between a first side and a second side opposite to the first side, and the beta gallium oxide thin film satisfies the following [Equation 1]. [Equation 1] FR / TR ≤ 0.5, TR = (Tmax - Tmin) / Tmin, and FR = (Fmax - Fmin) / Fmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Fmax represents the maximum value of the full width at half maximum (FWHM) of the XRD (X-ray Diffraction) omega scan for the (-201) plane between the first side and the second side, and Fmin represents the first side and the It means the minimum value of the above FWHM between the second side. Claim 2 delete Claim 3 The gallium oxide heteroepitaxy substrate according to claim 1, wherein the beta gallium oxide thin film comprises tin (Sn) doped at 4 at% or less relative to the gallium element. Claim 4 A gallium oxide heteroepitaxy substrate according to claim 1, wherein the sapphire substrate comprises an inclined surface having an inclination angle of 1° or more. Claim 5 A gallium oxide heteroepitaxy substrate according to claim 4, wherein the Tmax-Tmin of the beta gallium oxide thin film is 700 nm or less. Claim 6 A gallium oxide heteroepitaxy substrate according to claim 4, wherein the Fmax - Fmin of the beta gallium oxide thin film is 1000 arcsec or less. Claim 7 A gallium oxide heteroepitaxy substrate according to claim 4, wherein the growth plane of the beta gallium oxide thin film is a (-201) plane. Claim 8 In claim 1, the beta gallium oxide thin film is a gallium oxide heteroepitaxy substrate satisfying the following [Equation 2]. [Equation 2] RR / TR ≤ 7, TR = (Tmax - Tmin) / Tmin, and RR = (Rmax - Rmin) / Rmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Rmax represents the maximum value of the RMS (Root mean square) value of the surface roughness of the beta gallium oxide thin film between the first side and the second side, and Rmin represents the minimum value of the RMS value measured between the first side and the second side. Claim 9 A gallium oxide heteroepitaxy substrate according to claim 8, wherein the Rmax - Rmin of the beta gallium oxide thin film is 320 nm or less. Claim 10 A gallium oxide heteroepitaxy substrate according to claim 1, wherein the deviation of the band gap of the beta gallium oxide thin film measured between the first side and the second side of the beta gallium oxide thin film is within 0.13 eV. Claim 11 In claim 10, the gallium oxide heteroepitaxy substrate is provided for a photodetector that detects light having a wavelength of 245 nm to 265 nm. Claim 12 A step of providing a sapphire substrate including an inclined surface; A method for manufacturing a gallium oxide heteroepitaxy substrate, comprising the step of growing a beta gallium oxide thin film on the sapphire substrate, wherein in the step of growing the beta gallium oxide thin film, the beta gallium oxide thin film is grown such that its thickness varies between a first side and a second side opposite to the first side, and the beta gallium oxide thin film satisfies the following [Equation 1]. [Equation 1] FR / TR ≤ 0.4, TR = (Tmax - Tmin) / Tmin, and FR = (Fmax - Fmin) / Fmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, and Fmax represents the maximum value of the full width at half maximum (FWHM) of the XRD (X-ray Diffraction) omega scan for the (-201) plane between the first side and the second side. Fmin means the minimum value of the FWHM between the first side and the second side. Claim 13 delete Claim 14 In claim 12, the method for manufacturing a gallium oxide heteroepitaxy substrate, wherein the beta gallium oxide thin film satisfies the following [Equation 2]. [Equation 2] RR / TR ≤ 7 stages, TR = (Tmax - Tmin) / Tmin, and RR = (Rmax - Rmin) / Rmin, where Tmax represents the maximum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Tmin represents the minimum value among the thicknesses of the beta gallium oxide thin film measured between the first side and the second side, Rmax represents the maximum value of the RMS (Root mean square) value of the surface roughness of the beta gallium oxide thin film between the first side and the second side, and Rmin represents the minimum value of the RMS measured between the first side and the second side. Claim 15 A method for manufacturing a gallium oxide heteroepitaxy substrate according to claim 12, wherein the step of growing the beta gallium oxide thin film comprises a mist providing step of providing a gallium-containing mist on the sapphire substrate.

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