MANUFACTURING APPARATUS AND METHOD OF HIGH QUALITY ß-Ga2O3 THIN FILM GROWN BY HALIDE VAPOR PHASE EPITAXY GROWTH

Abstract

Proposed is a manufacturing method of a high-quality β-Ga.sub.2O.sub.3 thin film using a high-quality β-Ga.sub.2O.sub.3 thin film manufacturing apparatus based on halide vapor phase epitaxy (HVPE) growth. The apparatus includes a reaction gas generating unit in which a chlorine-based gas and Ga in a source zone react to generate GaClx, a dopant gas supply unit, an additional chlorine-based gas supply unit for supplying an additional chlorine-based gas in a source tube, oxygen-based gas supply units, and a susceptor unit supporting a substrate on which a Ga.sub.2O.sub.3 thin film is to be formed. During the epitaxial growth, the additional hydrogen chloride (HCl) gas is supplied to reduce the pre-reaction between precursors, and a movement distance to the susceptor can is increased to increase growth rate and growth speed to control the crystallinity. Thus, high-quality epitaxial growth and a high production yield can be achieved.

Claims

1. An apparatus for manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film through halide vapor phase epitaxy (HVPE) growth, the apparatus comprising: a reaction gas generating unit configured to produce GaClx through a reaction between a chlorine-based gas and Ga in a source zone; a dopant gas supply unit configured to supply a dopant gas; an additional chlorine-based gas supply unit configured to supply an additional chlorine-based gas in a source tube; oxygen-based gas supply units configured to supply an oxygen-based gas; and a susceptor unit configured to support a substrate on which a β-Ga.sub.2O.sub.3 thin film is to be formed, wherein the additional chlorine-based gas reduces a pre-reaction between the GaClx and oxygen, to facilitate formation of Ga.sub.2O.sub.3 on a surface of the substrate.

2. The apparatus of claim 1, further comprising a first guide member provided to enhance reactivity between the chlorine-based gas and Ga in the source zone by shortening a passage route for the chlorine-based gas in an internal space of the source zone.

3. The apparatus of claim 2, wherein the first guide member is curved toward an inlet or outlet of the reaction gas generating unit.

4. The apparatus of claim 1, further comprising a second guide member provided on an outlet side of the dopant gas supply unit to minimize an influence on a flow of the GaClx generated in the reaction gas generating unit and to prevent direct contact between the dopant gas and the GaClx.

5. The apparatus of claim 4, wherein the second guide member is inclined toward a nozzle of the source tube.

6. The apparatus of claim 1, wherein the susceptor unit is vertically installed to be spaced from the nozzle of the source tube by a predetermined distance.

7. The apparatus of claim 6, wherein the predetermined distance between the nozzle of the source tube and the susceptor unit is in a range of 5 cm to 11 cm.

8. The apparatus of claim 1, wherein the chlorine-based gas and the additional chlorine-based gas are HCl gas.

9. The apparatus of claim 1, wherein the nozzle of the source tube has a shower head structure with a plurality of through holes.

10. A method of manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film through halide vapor phase epitaxy (HVPE) growth, the method comprising: generating GaClx as a reaction gas through a reaction between a chlorine-based gas and Ga in a source zone; supplying a dopant gas through a dopant gas supply unit; supplying an oxygen-based gas through oxygen-based gas supply units; supplying an additional chlorine-based gas in a source tube; and epitaxially growing a doped Ga.sub.2O.sub.3 epitaxial layer through a reaction between the GaClx, oxygen-based gas, and dopant gas on a substrate.

11. The method of claim 10, wherein in the supplying of the additional chlorine-based gas, HCl gas is supplied at a flow rate in a range of 50 sccm to 80 sccm.

12. The method of claim 10, further comprising in-situ annealing performed after the epitaxial growth.

13. The method of claim 10, wherein in the generating of the reaction gas, a first guide member is provided to enhance reactivity between the chlorine-based gas and Ga in the source zone by shortening a passage route for the chlorine-based gas in an internal space of the source zone.

14. The method of claim 10, wherein in the supplying of the dopant gas, a second guide member is formed on an outlet side of the dopant gas supply unit to minimize an influence on a flow of the GaClx generated in the reaction gas generating unit and to prevent direct contact between the dopant gas and the GaClx.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a diagram illustrating the construction of an apparatus for manufacturing a β-Ga.sub.2O.sub.3 thin film in the related art;

[0036] FIG. 2 is a diagram showing problems occurring in the related art;

[0037] FIG. 3 is a diagram showing β-Ga.sub.2O.sub.3 thin film surfaces in the related art;

[0038] FIG. 4 is a diagram of graphs showing intensity and full width at half maximum (FWHM) values of a β-Ga.sub.2O.sub.3 thin film in the related art;

[0039] FIGS. 5 and 6 are diagrams illustrating the construction of an apparatus for manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film and gas flow therein according to the present disclosure;

[0040] FIG. 7 is a flow chart illustrating a method of manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film according to the present disclosure;

[0041] FIG. 8 is a diagram showing β-Ga.sub.2O.sub.3 thin film surfaces, the β-Ga.sub.2O.sub.3 thin films manufactured by a method of manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film according to the present disclosure;

[0042] FIG. 9 is a diagram of graphs showing measurement results of thin film thickness according to HCl gas flow rate in the present disclosure; and

[0043] FIGS. 10 to 12 are diagrams of graphs showing β-Ga.sub.2O.sub.3 thin film properties manufactured by a method of manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film, the properties such as thin film growth rate according to HCl gas flow rate in the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Hereinafter, a method of manufacturing a high-quality β-Ga.sub.2O.sub.3 thin film through halide vapor phase epitaxy (HVPE) growth, according to a preferred embodiment of the present disclosure, will be described in detail with reference to the accompanying drawings.

[0045] FIGS. 5 and 6 are diagrams illustrating the construction of an apparatus for manufacturing the high-quality β-Ga.sub.2O.sub.3 thin film and gas flow therein according to the present disclosure,

[0046] FIG. 7 is a flow chart illustrating the method of manufacturing the high-quality β-Ga.sub.2O.sub.3 thin film according to the present disclosure, and FIG. 8 is a diagram showing β-Ga.sub.2O.sub.3 thin film surfaces, the β-Ga.sub.2O.sub.3 thin films manufactured by the method of manufacturing the high-quality β-Ga.sub.2O.sub.3 thin film according to the present disclosure.

[0047] Referring to FIGS. 5 and 6, a high-quality β-Ga.sub.2O.sub.3 thin film manufacturing apparatus 100 based on HVPE growth includes: a reaction gas generating unit 110 configured to produce GaClx by causing a reaction between a chlorine-based gas and Ga in a source zone; a dopant gas supply unit 130 configured to supply a dopant gas; an additional chlorine-based gas supply unit 140 configured to supply an additional chlorine-based gas in a source tube; oxygen-based gas supply units 120 configured to supply an oxygen-based gas; and a susceptor unit 10 configured to support a substrate on which a β-Ga.sub.2O.sub.3 thin film is to be formed. The additional chlorine-based gas reduces a pre-reaction between the GaClx and oxygen to facilitate formation of Ga.sub.2O.sub.3 on a surface of the substrate.

[0048] The present disclosure features that the additional chlorine-based gas supply unit 140 that supplies the additional chlorine-based gas in the source tube during the growth of the β-Ga.sub.2O.sub.3 thin film is added to prevent the generation of powder by the pre-reaction between the GaClx and oxygen.

[0049] That is, as illustrated in FIGS. 5 and 6, the additional chlorine-based gas supply unit 140 for supplying the additional chlorine-based gas, apart from the chlorine-based gas (HCl) supplied for reaction with Ga in the source zone, is provided inside the source tube to reduce the pre-reaction between the GaClx and oxygen.

[0050] In this case, the additional chlorine-based gas supply unit 140 is a gas inlet passage provided at an upper portion of the source tube. Alternatively, the additional chlorine-based gas supply 140 may be a separate tube. In one embodiment of the present disclosure, a ¼-inch quartz tube is used. The additional chlorine-based gas supply unit 140 has at least one gas inlet positioned in the source tube to facilitate the supply of the additional chlorine-based gas.

[0051] When the additional hydrogen chloride (HCl) gas is introduced during the thin film epitaxial growth as described above, the pre-reaction between the GaClx and oxygen can be reduced. In addition, a movement distance to the susceptor is increased, and thus the growth rate and growth speed of the thin film increase. Furthermore, high-quality epitaxial growth is enabled by inhibiting the generation of powder.

[0052] In the present disclosure, HCl gas is used as the chlorine-based gas and the additional chlorine-based gas. In addition, SiH.sub.4 (at a concentration of 2000 ppm) is used as the dopant gas. It is obvious that various n-type or p-type impurity dopants other than SiH.sub.4 can be used.

[0053] In the present disclosure as described above, the reaction gas generating unit 110 includes a first guide member 112 to enhance reactivity between the chlorine-based gas and Ga in the source zone by shortening a passage route for the chlorine-based gas in an internal space of the source zone.

[0054] The first guide member 112 is a component to facilitate the reaction between the Ga and HCl gas flowing into the source zone. The first guide member 112 reduces the length of the passage route for the HCl gas so that the HCl gas can flow in close proximity to the Ga.

[0055] To this end, as illustrated in FIGS. 5 and 6, the first guide member 112 has a barrier or a projection protruding downward from an upper inner surface of the reaction gas generating unit 110.

[0056] In this case, the height of the first guide member 112 may vary according to the size of the Ga source zone or the size of the reaction gas generating unit 110.

[0057] In addition, a device for adjusting the height of the first guide member 112 may be added to cause the HCl gas flowing into the source zone to be in close contact with the Ga metal according to the amount of Ga metal consumed so that the reaction between the Ga and HCl gas can be facilitated. In this case, it is preferable to install a sensor that measures the remaining amount (or height) of the Ga metal. In addition, it is preferable to adjust the height of the first guide member 112 according to a signal detected by the sensor.

[0058] On the other hand, the first guide member 112 may be curved toward an inlet or outlet of the reaction gas generating unit 110.

[0059] That is, although the first guide member 112 is illustrated to have a rectangular cross section in FIGS. 5 and 6, the cross-sectional shape of the first guide member 112 is not limited thereto. The cross-sectional shape of the first guide member 112 may be curved toward the inlet of the reaction gas generating unit 110 into which the HCl gas is introduced or the outlet of the reaction gas generating unit 110 from which the HCl gas is discharged so that the HCl gas can easily flow.

[0060] On the other hand, the outlet side of the dopant gas supply unit 130 is provided with a second guide member 114 to minimize an influence the GaClx flow formed by the reaction gas generating unit 110 and to prevent direct contact between the dopant gas and the GaClx.

[0061] The second guide member 114 is formed on an exterior surface of the reaction gas generating unit 110 and positioned between the outlet of the dopant gas supply unit 130 and the outlet of the reaction gas generating unit 110 to prevent direct contact between the dopant gas and the GaClx.

[0062] In this case, the second guide member 114 is preferably inclined toward a nozzle of the source tube to facilitate the flow of the dopant gas toward the nozzle of the source tube. That is, when the second guide member 114 vertically extends, the second guide member 114 can serve as a barrier wall that prevents direct contact between the dopant gas and the GaClx but is likely to obstruct the flow of the dopant gas. Therefore, the second guide member 114 is preferably inclined toward the nozzle of the source tube so that the dopant gas can be easily introduced into the nozzle of the source tube along the second guide member 114.

[0063] In the present disclosure, the susceptor unit 10 is vertically installed to be spaced from the nozzle of the source tube by a predetermined distance. Preferably, the distance between the nozzle of the source tube and the susceptor unit 10 is in a range of 5 cm to 11 cm.

[0064] The nozzle of the source tube preferably has a shower head structure with a plurality of through holes so that the GaClx can be uniformly discharged through the nozzle of the source tube.

[0065] A high-quality β-Ga.sub.2O.sub.3 thin film manufacturing method using the HVPE-based high-quality β-Ga.sub.2O.sub.3 thin film manufacturing apparatus structured as described will be described below.

[0066] The manufacturing method includes: a reaction gas generation step S110 in which a chlorine-based gas and Ga in a source zone react to generate GaClx; a dopant gas supply step S120 in which a dopant gas is supplied through a dopant gas supply unit 130; an oxygen-based gas supply step S130 in which an oxygen-based gas is supplied through oxygen-based gas supply units 120; an additional chlorine-based gas supply step S140 in which an additional chlorine-based gas is supplied in a source tube; and an epitaxial growth step S150 in which the generated GaClx, the oxygen-based gas, and the dopant gas react to form a doped Ga.sub.2O.sub.3 epitaxial thin film on a substrate.

[0067] The present disclosure features the additional chlorine-based gas supply step S140 in which the additional chlorine-based gas is supplied to the source tube to prevent the generation of powder by the pre-reaction between the GaClx and the oxygen during the β-Ga.sub.2O.sub.3 thin film growth.

[0068] As described above, the additional chlorine-based gas supply unit 140 capable of supplying the additional chlorine-based gas, apart from the chlorine-based gas (HCl) supplied for reaction with Ga in the source zone, is provided in the source tube to reduce the pre-reaction between the GaClx and oxygen.

[0069] When the additional hydrogen chloride (HCl) gas is supplied during the thin film epitaxial growth process, the pre-reaction between the GaClx and oxygen can be reduced. In addition, a movement distance to the susceptor is increased, and thus the growth rate and growth speed of the thin film increase. Furthermore, high-quality epitaxial growth can be enabled by inhibiting the generation of powder.

[0070] In this case, in the additional chlorine-based gas supply step, the HCl gas is supplied at a flow rate in a range of 20 sccm to 100 sccm. Most preferably, the HCl gas is supplied at a flow rate in the range of 50 sccm to 80 sccm.

[0071] It is confirmed from FIG. 8 that the gas flow rate of the additional HCl gas affects surface texture and the pre-reaction between the GaClx and oxygen.

[0072] Specifically, the surface texture varies significantly according to the flow rate of the additional HCl gas, for example, at 40 sccm, 60 sccm, and 80 sccm. When the additional HCl gas is supplied at a flow rate of 40 sccm, the formed β-Ga.sub.2O.sub.3 thin film surface has no significant difference from existing β-Ga.sub.2O.sub.3 thin film surfaces. However, in this case, the growth rate increases, and the generated powder has a small particle size.

[0073] When the additional HCl gas is supplied at a flow rate of 60 sccm, it is confirmed that almost no powder is observed and the growth rate is high. When the additional HCl gas is supplied at a flow rate of 80 sccm, it is confirmed that cracks occur on the surface of the 13-Ga.sub.2O.sub.3 thin film due to the excessively high growth rate.

[0074] Furthermore, as shown in FIGS. 9 and 10, when the flow rate of the additional HCl gas is increased, the growth rate significantly increases from 200 nm/min to 900 nm/min.

[0075] As shown in the drawings, since the flow rate of the additional HCl gas affects the surface texture and the pre-reactions between GaClx and oxygen, it is preferable to supply the HCl gas at a flow rate in a range of 50 sccm to 80 sccm in the additional chlorine-based gas supply step.

[0076] On the other hand, in the present disclosure, the method may further include an in-situ annealing step performed after the epitaxial growth step.

[0077] In the annealing step, the in-situ annealing is performed in which annealing is performed under a N.sub.2 or Ar gas atmosphere without a doping gas immediately after the completion of the formation of the doped layer.

[0078] In the present disclosure, the in-situ annealing is performed immediately after the completion of the growth of the doped layer to maximize the lattice rearrangement effect in the grown epitaxial layer and the dopant activation effect.

[0079] Table 1 shows evaluation results of electrical properties according to in-situ annealing time.

TABLE-US-00001 TABLE 1 In-situ annealing Carrier concentration Mobility time (min) (/cm.sup.3) (cm.sup.2/V .Math. s) 0 1.54 × 10.sup.17 71.9 5 1.88 × 10.sup.18 70.2 10 1.13 × 10.sup.19 34.0

[0080] As shown in Table 1, a heat treatment for the in-situ annealing is required to be performed under a N.sub.2 atmosphere to activate all of the dopants.

[0081] On the other hand, the inside of the reaction gas generating unit 110 is provided with a first guide member 112 which reduces the passage route for the chlorine-based gas in the source zone and enhances reactivity between the chlorine-based gas and Ga in the source zone.

[0082] The first guide member 112 is a component to facilitate the reaction between the Ga and the HCl gas flowing into the source zone. Due to the reduction in the passage route for the HCl gas, the HCl gas flows in close contact with the Ga.

[0083] Therefore, in the reaction gas generation step, the reactivity between the chlorine-based gas and Ga in the source zone can be enhanced due to the presence of the first guide member 112 that reduces the passage route for the chlorine-based gas in the internal space of the source zone.

[0084] In addition, in the dopant gas supply step, a second guide member 114 is installed at the outlet side of the dopant gas supply unit 130 to minimize an influence on the flow of the GaClx generated in the reaction gas generating unit 110 and to prevent the direct contact between the dopant gas and the GaClx.

[0085] According to the present disclosure described above, the pre-reaction between GaClx and O.sub.2 is reduced to increase the growth rate, and the pre-reaction between SiH.sub.4 and O.sub.2 is reduced to increase a doping concentration.

[0086] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.