Patent Application
20230175168
The present application claims priority to Korean Patent Application No. 10-2021-0172667, filed Dec. 6, 2021 and Korean Patent Application No. 10-2021-0189525, filed Dec. 28, 2021 the entire contents of which is incorporated herein for all purposes by this reference.
The present disclosure relates to a method of manufacturing a high-quality β-Ga2O3 thin film. More particularly, the present disclosure relates to a method and apparatus for manufacturing a high-quality β-Ga2O3 thin film through epitaxial growth, the method and apparatus using a halide vapor phase epitaxy (HVPE) process that enables high-quality epitaxial growth and can improve a production yield by additionally feeding a hydrogen chloride (HCl) gas during the epitaxial growth of a thin film to reduce pre-reaction between precursors and by increasing a movement distance to a susceptor to increase the growth rate and control crystallinity.
A national project supported by government associated with this invention is described below.
Existing Si-based power semiconductor devices have reached limits in performance improvement, compared to technology development, due to inherent physical property limitations. As a result, industrial demands for power semiconductor materials with wide-bandgap (WBG) properties and ultra-wide bandgap (UWB) properties have gradually grown.
UWB β-Ga2O3 materials are used as wafers for next-generation power semiconductors with cost-competitiveness, as the manufacturing costs thereof are approximately 1/3 to 1/5 cheaper than that of GaN materials or SiC materials. β-Ga2O3 epitaxial growth is a technology for growing a single-crystal layer of β-Ga2O3 on a homogeneous substrate of β-Ga2O3, or for growing a single-crystal layer of α-Ga2O3 on a heterogeneous substrate such as sapphire. That is, Ga2O3 epitaxial growth includes technologies for obtaining high-quality single-crystal layers and doping techniques for obtaining n-type doping characteristics.
Ga2O3 materials are present mostly in the form of β-Ga2O3, which is the most stable form, and also can be present in 4 different phases (α, β, δ, ε).
β-Ga2O3 is the most stable form at high-temperature ranges and thus can be easily used to grow ingots. α-Ga2O3 is a relatively stable form at low-temperature ranges of 500° C. or less. The remaining types are meta-stable forms and thus exist unstably.
In the conventional method, during an epitaxial growth process, pre-reactions between GaClx and oxygen generate powders. As shown in
In addition, since such powders are observed on a surface of thin films, there has been a problem in that high-quality epitaxial growth is difficult to achieve.
The present disclosure has been made to provide solutions to the above problems. An objective of the present disclosure is to provide an apparatus and method for manufacturing a high-quality β-Ga2O3 thin film through halide vapor phase epitaxy (HVPE) growth. During the epitaxial growth process of forming the thin film, an additional hydrogen chloride (HCl) gas is supplied to reduce pre-reaction between precursors, and a moving distance to a susceptor is increased to increase the growth rate and control crystallinity, resulting in high-quality epitaxial growth and an increase in production yield.
Another objective of the present disclosure is to provide a method and apparatus for manufacturing a high-quality β-Ga2O3 thin film, using a HVPE growth process capable of reducing a pre-reaction between GaClx and O2 and a pre-reaction between SiH4 and O2 to increase growth rate and doping concentration, respectively.
To accomplish the above objectives, the present disclosure provides an apparatus for manufacturing a high-quality β-Ga2O3 thin film through halide vapor phase epitaxy (HVPE) growth. The apparatus includes: 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-Ga2O3 thin film is to be formed. The additional chlorine-based gas reduces a pre-reaction between the GaClx and oxygen, to facilitate formation of Ga2O3 on a surface of the substrate.
In the present disclosure, a first guide member may be 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.
The first guide member may be curved toward an inlet or outlet of the reaction gas generating unit.
On the other hand, a second guide member may be 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.
The second guide member is characterized to be inclined toward a nozzle of the source tube.
In the present disclosure, the susceptor unit is vertically installed to be spaced from the nozzle of the source tube by a predetermined distance. Preferably, the predetermined distance between the nozzle of the source tube and the susceptor unit is in a range of 5 cm to 11 cm.
In addition, the chlorine-based gas and the additional chlorine-based gas may be HCl gas.
Furthermore, the nozzle of the source tube may have a shower head structure with a plurality of through holes.
On the other hand, in order to accomplish the above objectives, the present disclosure provides a method of manufacturing a high-quality β-Ga2O3 thin film through halide vapor phase epitaxy (HVPE) growth. The manufacturing method includes: 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 Ga2O3 epitaxial layer through a reaction between the GaClx, the oxygen-based gas, and the dopant gas on a substrate.
In this case, in the supplying of the additional chlorine-based gas, HCl gas may be supplied at a flow rate in a range of 50 sccm to 80 sccm.
In addition, the manufacturing method may further include in-situ annealing after the epitaxial growth.
According to the present disclosure as described above, during an epitaxial growth process of a thin film through halide vapor phase epitaxy (HVPE) growth. During the epitaxial growth process of forming the thin film, an additional hydrogen chloride (HCl) gas flow can be supplied to reduce pre-reaction between precursors, and a movement distance to a susceptor can be increased to increase the growth rate and control crystallinity, resulting in high-quality epitaxial growth and an increase in production yield.
In addition, pre-reaction between GaClx and O2 can be reduced to increase the growth rate, and pre-reaction between SiH4 and O2 can be reduced to increase a doping concentration.
Hereinafter, a method of manufacturing a high-quality β-Ga2O3 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.
Referring to
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-Ga2O3 thin film is added to prevent the generation of powder by the pre-reaction between the GaClx and oxygen.
That is, as illustrated in
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.
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.
In the present disclosure, HCl gas is used as the chlorine-based gas and the additional chlorine-based gas. In addition, SiH4 (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 SiH4 can be used.
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.
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.
To this end, as illustrated in
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.
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.
On the other hand, the first guide member 112 may be curved toward an inlet or outlet of the reaction gas generating unit 110.
That is, although the first guide member 112 is illustrated to have a rectangular cross section in
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.
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.
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.
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.
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.
A high-quality β-Ga2O3 thin film manufacturing method using the HVPE-based high-quality β-Ga2O3 thin film manufacturing apparatus structured as described will be described below.
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 Ga2O3 epitaxial thin film on a substrate.
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-Ga2O3 thin film growth.
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.
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.
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.
It is confirmed from
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-Ga2O3 thin film surface has no significant difference from existing β-Ga2O3 thin film surfaces. However, in this case, the growth rate increases, and the generated powder has a small particle size.
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-Ga2O3 thin film due to the excessively high growth rate.
Furthermore, as shown in
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.
On the other hand, in the present disclosure, the method may further include an in-situ annealing step performed after the epitaxial growth step.
In the annealing step, the in-situ annealing is performed in which annealing is performed under a N2 or Ar gas atmosphere without a doping gas immediately after the completion of the formation of the doped layer.
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.
Table 1 shows evaluation results of electrical properties according to in-situ annealing time.
As shown in Table 1, a heat treatment for the in-situ annealing is required to be performed under a N2 atmosphere to activate all of the dopants.
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.
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.
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.
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.
According to the present disclosure described above, the pre-reaction between GaClx and O2 is reduced to increase the growth rate, and the pre-reaction between SiH4 and O2 is reduced to increase a doping concentration.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0172667 | Dec 2021 | KR | national |
| 10-2021-0189525 | Dec 2021 | KR | national |
