Fabricating method of gallium oxide thin film, gallium oxide thin film and photo-detecting device

Abstract

A method for manufacturing a gallium oxide thin film, a gallium oxide thin film, and a photodetector are disclosed. The method for manufacturing a gallium oxide thin film may include a first step of depositing a thin film containing a precursor of β-Ga2O3 on a substrate; and a second step of irradiating the thin film with a CW laser.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a gallium oxide thin film, a gallium oxide thin film, and a photodetector. Background Technology

[0002] There is increasing demand for power semiconductors that can reduce energy loss by efficiently utilizing high power. Gallium oxide (Ga2O3), a wide energy bandgap material, is a material receiving attention and research due to its superior electrical properties compared to other materials in fields such as power devices, UV photodetectors, and gas sensors. It possesses excellent electrical characteristics, including an energy bandgap of 4.7 to 4.9 eV, high transmittance in the UV region, and high dielectric breakdown voltage.

[0003] For mobility to be applied within future digital twin-based smart cities, autonomous driving technology is required to ensure safe driving, prevent collisions between vehicles, and utilize energy efficiently. In this context, the transmission and reception system, a fundamental technology of autonomous driving, is a critical element; thus, the development of photodetectors capable of exchanging signals between vehicles and receiving signals across various optical ranges is required. Photodetectors made of gallium oxide can be applied to these transmission and reception systems. Due to its wide energy bandgap and high transmittance for ultraviolet light, it facilitates the fabrication of efficient photodetectors. Furthermore, RF magnetron sputtering, a physical vapor deposition method, can be applied to fabricate these gallium oxide thin films. To deposit highly crystalline gallium oxide (β-Ga2O3) thin films, high thermal energy required for crystallization must be transferred to the film, such as by raising the substrate temperature to approximately 800°C or undergoing an annealing process at 900–1000°C after the process. Therefore, a laser-based annealing method that is energy-efficient and reduces processing time is required. In the case of laser annealing, heat treatment can be performed at room temperature, and a process time of less than 1 minute is required compared to the 2 hours required for heat treatment using a conventional electric furnace. Furthermore, heat treatment within the thin film is possible through repeated laser irradiation, and this treatment reduces point defects within the film, such as grain boundaries, micro-strain, and dislocation density, thereby enabling the fabrication of thin films with good crystallinity. The problem to be solved

[0004] One objective of the present invention is to provide a method for manufacturing a gallium oxide thin film having improved crystal size, dislocation density, and microdisplacement.

[0005] Another objective of the present invention is to provide a gallium oxide thin film manufactured by the above-described method for manufacturing a gallium oxide thin film.

[0006] Another objective of the present invention is to provide a photodetector element comprising the gallium oxide thin film. means of solving the problem

[0007] In one aspect, the present invention provides a method for manufacturing a gallium oxide thin film, comprising: a first step of depositing a thin film containing a precursor of β-Ga2O3 on a substrate; and a second step of irradiating the thin film with a CW laser.

[0008] In one embodiment, the CW laser can be irradiated for about 30 to 60 seconds.

[0009] In one embodiment, the substrate may include a sapphire substrate.

[0010] In one embodiment, the precursor of β-Ga2O3 can be deposited by RF magnetron sputtering.

[0011] In one embodiment, the RF magnetron sputtering can be performed at a substrate temperature of about 250 to 350 ℃.

[0012] In one embodiment, the RF magnetron sputtering can be performed for about 20 to 40 minutes at a power of about 250 to 350 W and a working pressure of about 1 to 5 mTorr.

[0013] In one embodiment, the CW laser may be a CO2CW laser.

[0014] In another aspect, the present invention provides a gallium oxide thin film manufactured by the above-described method for manufacturing a gallium oxide thin film.

[0015] In one embodiment, the gallium oxide thin film may have a grain size of about 17 to 24 nm.

[0016] In one embodiment, the gallium oxide thin film is about 1.3 × 10⁻³ to 2.1 × 10⁻³ -3 lines / nm-2 It can have a dislocation density.

[0017] In one embodiment, the gallium oxide thin film is approximately 1.4 × 10⁻⁶ -2 Up to 2.0 × 10 -2 It can have micro strain.

[0018] In another aspect, the present invention provides a photodetector element comprising a gallium oxide thin film according to the above. Effects of the invention

[0019] The method for manufacturing a gallium oxide thin film according to an embodiment of the present invention enables the production of a gallium oxide thin film having improved crystal size, dislocation density, and fine displacement.

[0020] The gallium oxide thin film according to an embodiment of the present invention has improved crystal size, dislocation density, and microdisplacement.

[0021] A photodetector according to an embodiment of the present invention may include a gallium oxide thin film according to an embodiment of the present invention. Brief explanation of the drawing

[0022] FIG. 1 is a flowchart illustrating a method for manufacturing a gallium oxide thin film according to an embodiment of the present invention. Figure 2 shows the temperature measured according to the CW laser irradiation time in the method for manufacturing a gallium oxide thin film according to an embodiment of the present invention. Figure 3 shows the results of X-ray diffraction analysis of a crystalline gallium oxide thin film after CO2 laser annealing. Figure 4 is a graph showing the crystal size, dislocation density, and microdisplacement calculated based on XRD analysis data of a gallium oxide thin film. Figure 5 is a graph showing the transmittance of a β-Ga2O3 thin film according to CO2 laser annealing time. Figure 6 is a graph showing the absorbance of a β-Ga2O3 thin film according to CO2 laser annealing time. Figure 7 is a Tauc plot graph of the band gap obtained through the transmittance absorption band of a β-Ga2O3 thin film according to CO2 laser annealing time. Figure 8 is a graph showing the photoluminescence and Gaussian fitting peaks of a β-Ga2O3 thin film according to CO2 laser annealing time. Specific details for implementing the invention

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. Similar reference numerals have been used for similar components in the description of each drawing. In the attached drawings, the dimensions of the structures are shown enlarged compared to the actual dimensions for the clarity of the present invention.

[0024] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, or combinations thereof.

[0025] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0026] FIG. 1 is a flowchart illustrating a method for manufacturing a gallium oxide thin film according to an embodiment of the present invention.

[0027] Referring to FIG. 1, a method (100) for manufacturing a gallium oxide thin film according to an embodiment of the present invention may include: a first step (S110) of depositing a thin film containing a precursor of β-Ga2O3 on a substrate; and a second step (S120) of irradiating the thin film with a CW laser.

[0028] The first step (S110) above is a step of depositing a thin film of a gallium oxide precursor on a substrate. For the purpose of manufacturing a gallium oxide thin film according to an embodiment of the present invention, a thin film of a precursor that can be converted into gallium oxide may be formed. In a subsequent process, all or part of the gallium oxide precursor may be converted into gallium oxide. The type of the precursor is not particularly limited, but non-limiting examples include gallium nitrate hydrate.

[0029] In the context of this specification, the terms “gallium oxide precursor” or “gallium oxide” refer to gallium oxide, which is not particularly limited as long as it is an oxide of gallium. Non-limiting examples of such gallium oxide include β-Ga2O3. Where the terms “gallium oxide precursor” or “gallium oxide” are used in this specification, gallium oxide may be understood as a term that can be used interchangeably with β-Ga2O3.

[0030] The above substrate is a material on which a gallium oxide precursor is deposited. The type of the substrate is not particularly limited, as long as it does not cause alteration to the physical and chemical properties of the gallium oxide precursor deposited on the substrate or cause structural instability. In one embodiment, the substrate may include a sapphire substrate.

[0031] The method of depositing the above gallium oxide precursor is not particularly limited. The practitioner may determine the method of depositing the above gallium oxide precursor depending on the type of substrate, the type of gallium oxide precursor, the structure and properties of the desired thin film, etc. In one embodiment, the gallium oxide precursor may be deposited by RF magnetron sputtering.

[0032] The process variables for performing the above RF magnetron sputtering are not particularly limited. The operator may select parameters defining the above RF magnetron sputtering process according to the type of substrate, the type of gallium oxide precursor, the structure and properties of the desired thin film, etc. In one embodiment, the above RF magnetron sputtering may be performed at a substrate temperature of about 250 to 350 °C. In one embodiment, the above RF magnetron sputtering may be performed for about 20 to 40 minutes at a power of about 250 to 350 W and a working pressure of about 1 to 5 mTorr.

[0033] The second step (S120) above is a step of converting the deposited gallium oxide precursor into gallium oxide. The method of converting the gallium oxide is not particularly limited, but a non-limiting example includes irradiating with a CW laser. In the context of this specification, a CW laser may mean a Continuous Wave laser. The type of the CW laser is not particularly limited, but may be a CO2CW laser.

[0034] The time for irradiating the CW laser is not particularly limited as long as the gallium oxide precursor can be converted into gallium oxide. The present invention is at least based on the discovery of an irradiation time capable of converting the gallium oxide precursor into gallium oxide depending on the time for irradiating the CW laser. In one embodiment, the CW laser may be irradiated for about 30 seconds or more. Meanwhile, the present invention is at least based on the discovery that there is an upper limit of the irradiation time that improves the performance of the thin film when the gallium oxide precursor is converted into gallium oxide depending on the time for irradiating the CW laser. In one embodiment, the CW laser may be irradiated for about 60 seconds or less. In one embodiment, the CW laser may be irradiated for about 30 to 60 seconds.

[0035] Meanwhile, the gallium oxide thin film according to an embodiment of the present invention can be manufactured by the gallium oxide thin film manufacturing method.

[0036] The description regarding the gallium oxide thin film according to the embodiment of the present invention above may be applied identically or similarly to the description regarding the method for manufacturing a gallium oxide thin film according to the embodiment of the present invention. Furthermore, the gallium oxide thin film is manufactured by the gallium oxide thin film manufacturing method, and its physical, chemical, and structural properties may be determined by the selection of materials and / or process variables of the gallium oxide thin film manufacturing method. In one embodiment, the gallium oxide thin film may have a grain size of about 17 to 24 nm. In one embodiment, the gallium oxide thin film is about 1.3 × 10⁻⁶ -3 Up to 2.1 × 10 -3 lines / nm -2 It may have a dislocation density. In the context of this specification, "dislocation density" refers to the length (mm) of dislocations per unit volume (mm³) that are misaligned within the structure and may mean the number of defects within the material. In one embodiment, the gallium oxide thin film is approximately 1.4 × 10⁻⁶ -2 Up to 2.0 × 10 -2 It may have micro strain. In the context of this specification, "micro strain" may mean a change in length (mm / mm) due to stress, which is an important factor attributable to lattice distortion caused by a deficiency of atoms.

[0037] Meanwhile, the photodetector according to an embodiment of the present invention may include the gallium oxide thin film.

[0038] The description of the photodetector element according to the embodiment of the present invention may be applied in the same or similar manner to the description of the gallium oxide thin film according to the embodiment of the present invention and / or the description of the method for manufacturing a gallium oxide thin film according to the embodiment of the present invention.

[0039] In the context of this specification, "photodetector" or "photodetector element" means a property or a member having such a property, wherein specific physical and / or chemical properties are manifested or changed when light of a specific wavelength or light including a specific wavelength is irradiated, and the presence or absence of light irradiation or the intensity of light irradiation can be detected by measuring such properties.

[0040] The embodiments of the present invention are described in detail below. However, the embodiments described below are merely partial embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments.

[0041] Preparation Example

[0042] Sputtering process and thin film formation

[0043] A sapphire (Al2O3) substrate to be used for deposition was cleaned in acetone, ethanol, and deionized water (DI Water) for 5 minutes each using an ultrasonic cleaner, dried with nitrogen (N2) gas, and mounted in a sputtering chamber. A thin film was deposited using a Ga2O3 target with 99.99% purity. Initially, the chamber was maintained at a high vacuum of less than 1×10⁻⁶ Torr, and the flow rates of argon (Ar) gas and oxygen (O2) gas were set to 10 sccm and 2 sccm, respectively. The argon (Ar) gas and oxygen (O2) gas flow rates were controlled using a mass flow controller. To remove foreign substances from the target surface and stabilize the RF power and working pressure, pre-sputtering was performed at 50 W for 10 minutes prior to deposition.

[0044] After completing the above pre-sputtering, the substrate temperature is 300℃, the sputtering power is 300W, and the working pressure is 3×10 -3 The setting was set to Torr and deposition was performed for 30 minutes.

[0045] Post-heat treatment

[0046] Repetitive irradiation was performed using a CO2 laser. The laser output power was adjusted to 30W, the frequency to 5 kHz, the mark speed to 2000 mm / s, and the process time to 35 to 45 seconds to measure the results.

[0047] Experimental Example

[0048] Figure 2 shows the temperature measured according to the CW laser irradiation time in a method for manufacturing a gallium oxide thin film according to an embodiment of the present invention. Theoretically, crystallization of the gallium oxide precursor can proceed at 700 to 900 ℃. Referring to Figure 2, it can be confirmed that crystallization occurs only when the CW laser irradiation time is about 30 seconds or more.

[0049] Figure 3 shows the X-ray diffraction (XRD) analysis results of a crystalline gallium oxide thin film after CO2 laser annealing. Generally, a heat treatment process of 2 hours in a temperature atmosphere of 700°C or higher is required for the growth of β-phase Ga2O3 crystals, but it can be confirmed that the growth of β-phase Ga2O3 crystals was achieved in a short time through the CO2 laser annealing. As shown in Figure 2, β-Ga2O3XRD peaks of (-201), (400), (111), (-402), (-313), and (-603) can be observed.

[0050] FIG. 4 is a graph showing the grain size, dislocation density, and micro strain calculated based on XRD analysis data of a gallium oxide thin film manufactured by the method for manufacturing a gallium oxide thin film according to an embodiment of the present invention. The grain size, dislocation density, and micro strain can be calculated through the following process.

[0051] The crystal size is calculated from the full width at half maximum (FWHM) of the XRD analysis data using the following equation (1).

[0052] (1)

[0053] Here, L is the size of the crystal (nm), θ is the value obtained by dividing 2 from the XRD analysis result represented as 2θ (°), K is the Boltzmann constant (k), and λ is the wavelength used in the XRD analysis (Å).

[0054] That is, the size of the decision can be derived by the following equation (2).

[0055] (2)

[0056] Here, β is the full width at half maximum (FWHM).

[0057] Once the crystal size is determined by the above equations (1) and (2), the potential density can be derived through the following equation (3).

[0058] (3)

[0059] Here, δ is the dislocation density (mm²) -2 )am.

[0060] In addition, the fine displacement of the thin film can be derived from the half-width using the following equation (4).

[0061] (4)

[0062] Here, ε is the microdisplacement (μm) of the thin film.

[0063] Referring further to Figure 4, it can be seen that when the CO2CW laser irradiation time exceeds 60 seconds, the crystal size decreases rapidly, and the dislocation density and micro-displacement increase rapidly. Therefore, it can be confirmed that it is desirable for the CO2CW laser irradiation time to be 60 seconds or less in order to manufacture a gallium oxide thin film with improved performance.

[0064] Figure 5 is a graph showing the transmittance of β-Ga2O3 thin films according to CO2 laser annealing time. Referring to Figure 5, all samples show a high transmittance of 85% on average in the visible light region (400 nm to 700 nm), and as the CO2 laser irradiation time increases, they show a low transmittance in the ultraviolet region (100 nm to 400 nm region). This confirms that light in the corresponding wavelength range is absorbed.

[0065] Figure 6 is a graph showing the absorbance of β-Ga2O3 thin films according to CO2 laser annealing time. Referring to Figure 6, it can be seen that all samples absorb light in the wavelength range of 270 nm to 276 nm (4.48 eV to 4.60 eV). This matches the band gap of crystalline gallium oxide (β-Ga2O3).

[0066] Figure 7 is a Tauc plot graph of the band gap obtained through the transmittance absorption band of the β-Ga2O3 thin film according to the CO2 laser annealing time. Referring to Figures 6 and 7, it can be confirmed that a crystalline gallium oxide (β-Ga2O3) thin film having a band gap of about 4.5 eV was formed through CO2 laser annealing.

[0067] Figure 8 is a graph showing the photoluminescence (PL) and Gaussian fitting peaks of β-Ga2O3 thin films according to CO2 laser annealing time ((a) photoluminescence graph according to laser annealing time, (b) CO2 annealing 35s, (c) CO2 annealing, (d) CO2 annealing 45s). Referring to Figure 8, it can be seen that the photoluminescence (PL) spectra of all β-Ga2O3 thin films are emitted in the UV, Blue, and Green regions. In thin films that are not crystallized, there are many non-radiative recombinations. It can be seen that as the temperature increases through CO2 laser annealing, the crystallinity of the thin film improves, which reduces non-radiative recombinations and increases radiative recombinations, thereby improving the photoluminescence (PL) intensity.

[0068] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims. Explanation of the symbols

[0069] 100: Method for manufacturing a gallium oxide thin film

Claims

Claim 1 A method for manufacturing a gallium oxide thin film, comprising: a first step of depositing a thin film containing a precursor of β-Ga2O3 on a substrate; and a second step of irradiating the thin film with a CW laser, wherein the CW laser is irradiated for 60 seconds at a power of 30 W and a frequency of 5 kHz, the precursor of β-Ga2O3 is deposited by RF magnetron sputtering, the RF magnetron sputtering is performed at a substrate temperature of 250 to 350 ℃, and the RF magnetron sputtering is performed for 20 to 40 minutes at a power of 250 to 350 W and a working pressure of 1 to 5 mTorr. Claim 2 delete Claim 3 A method for manufacturing a gallium oxide thin film according to claim 1, wherein the substrate comprises a sapphire substrate. Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 A method for manufacturing a gallium oxide thin film according to claim 1, wherein the CW laser is a CO2CW laser. Claim 8 A gallium oxide thin film manufactured by a method for manufacturing a gallium oxide thin film, comprising: a first step of depositing a thin film containing a precursor of β-Ga2O3 on a substrate; and a second step of irradiating the thin film with a CW laser, wherein the CW laser is irradiated for 60 seconds at a power of 30 W and a frequency of 5 kHz, the precursor of β-Ga2O3 is deposited by RF magnetron sputtering, the RF magnetron sputtering is performed at a substrate temperature of 250 to 350 ℃, and the RF magnetron sputtering is performed for 20 to 40 minutes at a power of 250 to 350 W and a working pressure of 1 to 5 mTorr. Claim 9 In claim 8, the gallium oxide thin film is a gallium oxide thin film having a grain size of 17 to 24 nm. Claim 10 In claim 8, the gallium oxide thin film is 1.3 × 10 -3 Up to 2.1 × 10 -3 lines / nm -2 Gallium oxide thin film having a dislocation density. Claim 11 In claim 8, the gallium oxide thin film is 1.4 × 10 -2 Up to 2.0 × 10 -2 Gallium oxide thin film having micro strain. Claim 12 delete

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