JP7561066B2 - III-V and III-VI semiconductor film forming equipment - Google Patents

Description

The present invention relates to a III-V and III-VI semiconductor film formation device.

Currently, wide-gap semiconductors such as gallium nitride (GaN), aluminum nitride (AlN), and gallium oxide (Ga ₂ O ₃ ) are being actively researched as materials for next-generation semiconductor devices. In addition, research is being conducted on solar cells that use GaAs and InP to achieve ultra-high efficiency and low loss. Metal organic chemical vapor deposition (MOCVD) is mainly used to manufacture these devices, but since the organic metals used as raw materials contain carbon, a certain amount of carbon (10 ¹⁵ cm ^-3 or more) is mixed into the film as an impurity. If the carbon concentration is higher than the n-type impurity, it becomes difficult to control low-concentration n-type conductivity, so it is ideal to use raw materials that do not contain carbon.
In view of this, the hydride vapor phase epitaxy (HVPE) method shown in Patent Document 1 has attracted attention. The HVPE method has an advantage in that the raw material contains almost no carbon (C) since, for example, gallium metal and a chlorine-based gas are reacted to supply gallium monochloride (GaCl) or gallium trichloride (GaCl ₃ ).
The HVPE method is superior in terms of manufacturing cost because the raw materials are inexpensive, but in the current technology, the raw materials GaCl and _GaCl3 must be generated in a furnace, so the method of supplying gallium chloride (or metal chlorides such as _InCl3 or _AlCl3 ) is a major issue in realizing a large-diameter mass-production epitaxial film formation device. There are also devices in which the raw material section is separated and connected to the furnace by piping (Patent Document 2). In this case, the temperature of the piping is heated to a temperature at which the raw material gas does not condense. For example, since the freezing point of gallium trichloride is 201°C, it is heated to a temperature higher than that. On the other hand, the piping requires joints and valves, and some of the components require flexibility in addition to corrosion resistance and heat resistance. If a material that combines these characteristics is selected, for example, the maximum operating temperature of PTFE (polytetrafluoroethylene) is about 300°C. It is also known that stainless steel, which is the piping material, undergoes transformation when it exceeds 400°C, so the temperature of the piping is set to about 300°C or less.
On the other hand, gallium chloride exists in the form of gallium monochloride at high temperatures, but gallium trichloride is stable at low temperatures including room temperature, and gallium monochloride undergoes a disproportionation reaction below 300°C and decomposes into gallium trichloride and gallium metal. Therefore, it is generally produced in a furnace without passing through a pipe. Gallium metal has a melting point of 30°C, but is often liquid even at room temperature in a supercooled state.
Conventionally, the HVPE method using gallium monochloride as a raw material was mainstream, but research using gallium trichloride as a raw material has also progressed, and in the THVPE method, chlorine is added again to gallium monochloride at high temperatures and supplied to the reactor as gallium trichloride. By changing the raw material to gallium trichloride, high-speed growth is expected. In the production of gallium oxide, it is expected to reduce the impurity concentration.
When gallium trichloride is used as a raw material, it is common to use gallium trichloride itself as a raw material, heat it to evaporate it, and send it to a reactor accompanied by a carrier gas. However, gallium trichloride is a synthetic product, is expensive, has hygroscopic properties, and has a low purity of the raw material itself. Therefore, there is a method of obtaining gallium trichloride by reacting metallic gallium with chlorine or hydrogen chloride in the raw material supply section. At this time, the temperature at which the reaction proceeds smoothly is about 600°C, but at this temperature, the ratio of gallium monochloride to the gallium trichloride produced is high. Therefore, there is also a method of introducing it into a separate chamber and reacting it again with chlorine or hydrogen chloride to increase the ratio of gallium trichloride in the semiconductor material gas (Patent Document 3).

JP 2019-196293 A Patent No. 6117169 Patent No. 5787324

In the method described in Patent Document 3, when the semiconductor material gas is passed through the piping, the temperature drops to a low level below 300°C, the heat resistance temperature mentioned above, so gallium trichloride passes through as a gas, but gallium monochloride decomposes into gallium trichloride and metallic gallium through the disproportionation reaction mentioned above. This increases the ratio of gallium trichloride in the composition of the semiconductor material gas, which is advantageous in that it increases the reaction efficiency, but on the other hand, metallic gallium begins to precipitate in the piping, which can leak from joints during maintenance or cause blockages in the piping.

The present invention aims to provide a film formation apparatus for III-V and III-VI semiconductors using metal chlorides as raw materials, which can suppress clogging of the semiconductor material gas supply pipe connecting the semiconductor material gas generation unit and the reactor.

[1] A film forming apparatus for III-V and III-VI semiconductors using metal chlorides as raw materials,
a reactor for reacting a semiconductor material gas on a substrate;
a semiconductor material gas generating unit that is separate and independent from the reactor and generates the semiconductor material gas and supplies it to the reactor;
a semiconductor material gas supply pipe that connects the semiconductor material gas generation unit and the reactor and supplies the semiconductor material gas from the semiconductor material gas generation unit to the reactor;
having
the semiconductor material gas generation unit has a semiconductor material gas generation unit that stores a solid or liquid material in a lower portion of an internal space, supplies a mixed gas of a carrier gas and a raw material gas to an upper portion of the internal space, and generates the semiconductor material gas by in-situ generation of the solid or liquid material and the mixed gas;
the semiconductor material gas supply pipe has a first connection part connected to the semiconductor material gas generation part and a second connection part connected to the reactor, the first connection part is located at a lower position than the second connection part in the vertical direction, the lowest part of the semiconductor material gas supply pipe is located between the first connection part and the second connection part, and a discharge part for discharging the liquefied solid or liquid material is provided at the lowest part;
III-V and III-VI semiconductor deposition equipment.
[2] The III-V and III-VI semiconductor film formation apparatus according to [1], further comprising a trap below the exhaust portion for collecting the liquefied solid or liquid material.
[3] The III-V and III-VI semiconductor film formation apparatus according to [1] or [2], further comprising a baffle plate disposed inside the semiconductor material gas supply pipe for facilitating the liquefied solid or liquid material to fall into a trap disposed below the exhaust portion and for complicating a flow path of the semiconductor material gas.
[4] The III-V and III-VI semiconductor film formation apparatus according to any one of [1] to [3], wherein at least a portion between the lowest portion of the semiconductor material gas supply pipe and the second connection portion is disposed in a vertical direction.
[5] The III-V and III-VI semiconductor film formation apparatus according to any one of [1] to [3], wherein a shape between the first connection part and the second connection part of the semiconductor material gas supply pipe is substantially U-shaped, and a bottom part of the substantially U-shaped shape is the lowest part.
[6] The III-V and III-VI semiconductor film forming apparatus according to any one of [1] to [5], wherein the metal chloride is gallium trichloride.

The present invention provides a III-V and III-VI semiconductor film formation apparatus that uses metal chlorides as raw materials and can suppress clogging of the semiconductor material gas supply pipe that connects the semiconductor material gas generation unit and the reactor.

FIG. 1 is a schematic diagram showing an example of a semiconductor film forming apparatus according to the present invention. FIG. 2 is a schematic diagram showing another example of the semiconductor film forming apparatus of the present invention. FIG. 3 is a schematic diagram showing still another example of the semiconductor film forming apparatus of the present invention. FIG. 4 is a schematic cross-sectional view showing an example of a baffle plate installed inside the semiconductor material gas supply pipe of the semiconductor film forming apparatus of the present invention. FIG. 5 is a schematic cross-sectional view showing another example of a baffle plate installed inside the semiconductor material gas supply pipe of the semiconductor film forming apparatus of the present invention.

III-V semiconductors are semiconductors that use group III and group V elements. Group III elements are group 13 elements in the IUPAC periodic table (https://iupac.org/what-we-do/periodic-table-of-elements/), including aluminum (Al), gallium (Ga), and indium (In). Group V elements are group 15 elements in the IUPAC periodic table, including nitrogen (N), phosphorus (P), arsenic (As), and antimony (Sb).
III-VI semiconductors refer to semiconductors using group III and group VI elements. The group III elements are as described above. The group VI elements are group 16 elements in the IUPAC periodic table, and include oxygen (O), sulfur (S), and selenium (Se).

[III-V and III-VI Group Semiconductor Film Forming Equipment]
The III-V and III-VI semiconductor film formation apparatus of the present invention (hereinafter also simply referred to as the "semiconductor film formation apparatus of the present invention") uses a metal chloride as a raw material and includes a reaction furnace, a semiconductor material gas generation unit, and a semiconductor material gas supply pipe.

In the reactor, semiconductor material gas is supplied onto a heated substrate, and a thin film is deposited and formed by chemical reaction.
For example, in the case of film formation by the HVPE method, a group III element chloride gas (GaCl3 _, etc.) and a group V element hydride gas ( _NH3 , _PH3 , _AsH3 , etc.) are flowed as semiconductor material gases in hydrogen gas to form a semiconductor thin film on a substrate. For the formation of a gallium nitride (GaN) film, gallium trichloride gas and ammonia gas are flowed as semiconductor material gases to form a film. The HVPE method has a faster growth rate than other film formation methods such as metalorganic vapor phase epitaxy using an organic metal as a source of group III elements and molecular beam epitaxy in an ultra-high vacuum, and is suitable for growing a thick GaN layer.

The semiconductor material gas generating section is separate and independent from the reaction furnace, and supplies the semiconductor material gas to the reaction furnace through a semiconductor material gas supply pipe.
The semiconductor material gas generation unit includes a reaction vessel that stores a solid or liquid material in a lower portion of an internal space, supplies a mixed gas of a carrier gas and a raw material gas to an upper portion of the internal space, and generates the semiconductor material gas by in-situ generation of the solid or liquid material and the mixed gas.

For example, in the case of producing gallium trichloride as a semiconductor material gas by the reaction of gallium with chlorine gas, the reaction vessel includes a first reaction chamber in which a first gas containing gallium monochloride gas is produced by the reaction of gallium with chlorine gas, and a second reaction chamber in which a second gas containing gallium trichloride and gallium monochloride as an impurity is produced by the reaction of the first gas with chlorine gas.
The first reaction chamber contains liquid gallium at the bottom, and chlorine gas is supplied to the top, causing the gallium and chlorine gas to react with each other to generate a first gas containing gallium monochloride gas. The first reaction chambers can be connected in series in two or more units, and the first gas generated in the previous reaction chamber can be supplied to the second or subsequent first reaction chambers to increase the contact opportunity between the unreacted chlorine gas in the first gas and gallium, thereby increasing the concentration (molar concentration) of gallium monochloride gas in the first gas. The temperature (first reaction temperature) at which gallium and chlorine gas are reacted in the first reaction chamber is preferably 300 to 1000°C, more preferably 500 to 1000°C, and even more preferably 700 to 900°C.
The second reaction chamber is supplied with the first gas and chlorine gas generated in the first reaction chamber, and a second gas containing gallium trichloride gas is generated. The second gas may contain gallium monochloride gas and unreacted chlorine gas as impurities in addition to gallium trichloride gas. The temperature (second reaction temperature) at which the second gas and chlorine are reacted in the second reaction chamber is preferably 150 to 1000°C, more preferably 500 to 1000°C, even more preferably 600 to 1000°C, and even more preferably 700 to 900°C.
The reaction vessel including the first reaction chamber and the second reaction chamber, as well as a pipe connecting the first reaction chamber and the second reaction chamber, a pipe supplying chlorine gas to the first reaction chamber and the second reaction chamber, and a pipe discharging the second gas from the second reaction chamber, is preferably made of a material that can withstand the first reaction temperature and the second reaction temperature. Examples of such materials include carbon, stainless steel, and quartz glass. From the viewpoint of corrosion resistance, stainless steel may be coated with boron nitride, silica, PTFE/Ni, or the like.
The reaction vessel is preferably housed in a cylindrical quartz glass container and configured to be heated by a heating mechanism such as a mantle heater disposed around the container. The heating mechanism is preferably capable of independently controlling the temperatures of the first reaction chamber and the second reaction chamber.

The semiconductor material gas supply pipe will be described below with reference to FIGS. 1 to 5 as appropriate.
In the III-V and III-VI semiconductor film formation apparatus 100 (101, 200) of the present invention, the semiconductor material gas supply piping 3 connects the semiconductor material gas generation unit 1 and the reaction furnace 2, and supplies the semiconductor material gas from the semiconductor material gas generation unit 1 to the reaction furnace 2.
The semiconductor material gas supply pipe 3 has a first connection part 3 a connected to the semiconductor material gas generation part 1 and a second connection part 3 b connected to the reaction furnace 2 .
In the vertical direction, the first connection portion 3a is located lower than the second connection portion 3b.
The lowest portion 3c of the semiconductor material gas supply pipe 3 is located between the first connection portion 3a and the second connection portion 3b.
The lowest part 3c is provided with a drain 3d for draining the liquefied solid or liquid material.
A trap 4 for collecting the liquefied solid or liquid material is disposed below the discharge portion 3d. The trap 4 is removable and may be removed unless necessary.

FIG. 1 is a diagram showing a schematic configuration of an example of a semiconductor film forming apparatus according to the present invention.
In the III-V and III-VI semiconductor film formation apparatus 100, at least a portion between the lowest portion 3c of the semiconductor source gas supply pipe 3 and the second connection portion 3b is a vertical portion 3e disposed in the vertical direction.
In FIG. 1, the piping between the first connection portion 3a and the lowest portion 3c is substantially horizontal.

FIG. 2 is a diagram showing a schematic configuration of another example of a semiconductor film forming apparatus according to the present invention.
In the III-V and III-VI semiconductor film formation apparatus 101, at least a portion between the lowest portion 3c of the semiconductor source gas supply pipe 3 and the second connection portion 3b is a vertical portion 3e disposed in the vertical direction.
In FIG. 2, the piping between the first connection portion 3a and the lowest portion 3c is inclined so as to become lower from the first connection portion 3a toward the lowest portion 3c.

FIG. 3 is a diagram showing a schematic configuration of still another example of the semiconductor film forming apparatus of the present invention.
In the III-V and III-VI semiconductor film formation apparatus 200, the shape between the first connection portion 3a and the second connection portion 3b of the semiconductor material gas supply pipe 3 is substantially U-shaped. The bottom of the substantially U-shaped portion is the lowest portion 3c.
In FIG. 3, at least a portion between the lowest portion 3c and the second connection portion 3b is a vertical portion 3e that is disposed in the vertical direction.

It is preferable to dispose a baffle plate 3f (3g) protruding into the flow path inside the vertical portion 3e of the semiconductor material gas supply pipe 3 of the III-V and III-VI semiconductor film formation apparatus 100 (101, 200) in order to promote the disproportionation reaction of gallium monochloride in the pipe.
In order to provide the baffle plate 3f protruding from the inner surface of the pipe as shown in FIG. 4 inside the vertical portion 3e, for example, a slit is made obliquely in the circular pipe, the baffle plate is inserted therein, and the baffle plate is welded from the outside of the circular pipe so as to include the baffle plate and to seal the slit. This can be easily manufactured.
Also, as shown in Fig. 5, the central shaft 3h provided with the baffle plate 3g can be prepared and inserted vertically into the vertical section 3e to place the baffle plate 3g inside the vertical section 3e. In this case, it is preferable to provide a baffle plate holding member 3i for holding the central shaft 3h inside the vertical section 3e. In this example, the baffle plate is not fixed inside the pipe, and a separate member made of several semicircular plates welded at intervals to the central shaft 3h is inserted into the pipe. This makes the flow path more complex, allowing both heat exchange and smooth falling of liquefied gallium to be achieved.

The semiconductor material gas supply pipe 3 may be provided with a vacuum and purge line for vacuum replacement during decomposition.
The trap 4 may be connected by a quick coupling or the like via an O-ring or the like for high temperature resistance, and may be removed during maintenance to recover the liquid gallium. A separate valve and piping may be installed below the trap 4, and the valve may be opened to release the liquid gallium.

It is preferable that the semiconductor material gas supply pipe 3 and the trap 4 are heated and controlled to about 150 to 300° C. in accordance with the lowest heat-resistant temperature of the member.
In FIG. 2, the piping between the first connection portion 3 a and the lowest portion 3 c is also inclined, so that the gallium metal generated in the piping can also be collected in the trap 4 .
Furthermore, Fig. 3 shows a simplified shape for cases where the amount of gallium metal generated is small or where the maintenance interval can be shortened. The semiconductor material gas supply pipe 3 is an approximately U-shaped pipe, with a branch of the drip line at the bottom and a valve at the end. In this case, the part that corresponds to the trap is the branched pipe, and if the valve is opened frequently to drip gallium metal, the structure is simplified and costs are reduced.

[Action and Effect]
By using the present invention to make a part or all of the piping between the semiconductor material gas supply unit and the reactor substantially vertical against gravity, solid or liquid material that has undergone a disproportionation reaction in the piping due to a drop in temperature adheres to the piping wall and, being in a liquid state, easily falls due to gravity and is contained in a liquid tank located away from the gas flow path. This prevents clogging in the piping. Furthermore, maintenance can be performed by opening only one location, and by adding an extraction line via a valve and dripping the liquefied solid or liquid material into a container located further below, the ease of maintenance can be improved.

GaN films were grown under the following conditions using the III-V and III-VI semiconductor film-forming apparatus 100 shown in Fig. 1. After 10 growths, the semiconductor source gas supply pipe 3 was disassembled, and a thin layer of gallium metal was found to be attached to the wall surface, but there was no sign of the pipe being clogged. Meanwhile, about 5 mL of metallic gallium was found in the trap 4.
<Growth conditions>
The pressure of the NH ₃ gas was adjusted to 0.4 atm, the pressure of the mixed gas of the NH ₃ gas and the carrier gas was adjusted to 1 atm, and the flow rate of the mixed gas of the NH ₃ gas and the carrier gas was adjusted to 10 slm. Next, the seed substrate was heated to a growth temperature of 1300 ° C. by heating the growth part of the reactor. Next, in the GaCl ₃ gas generating device, Ga in the container was heated to 800 ° C., chlorine and carrier gas were introduced, GaCl ₃ gas was generated, and the mixed gas of the GaCl ₃ gas and the carrier gas was discharged outside the device through the supply pipe. The discharged mixed gas was transported to the GaN crystal film manufacturing device. At this time, in the GaCl ₃ supply pipe, the pressure of the GaCl ₃ gas was adjusted to 3 × 10 ^-2 atm, the pressure of the mixed gas of the GaCl ₃ gas and the carrier gas was adjusted to 1 atm, and the flow rate of the mixed gas of the GaCl ₃ gas and the carrier gas was adjusted to 10 slm. These gases were sprayed onto the seed substrate, and growth was continued for 10 hours.

DESCRIPTION OF SYMBOLS 1...Semiconductor material gas generation section 2...Reaction furnace 3...Semiconductor material gas supply pipe 3a...First connection section 3b...Second connection section 3c...Lowest section 3d...Exhaust section 3e...Vertical section 3f, 3g...Baffle plate 3h...Central axis 3i...Baffle plate holding member 4...Trap 100, 101, 200...III-V and III-VI group semiconductor film formation apparatus V1, V2...Opening and closing valve

Claims (6)

A film forming apparatus for III-V and III-VI semiconductors using metal chlorides as raw materials,
a reactor for reacting a semiconductor material gas on a substrate;
a semiconductor material gas generating unit that is separate and independent from the reactor and generates the semiconductor material gas and supplies it to the reactor;
a semiconductor material gas supply pipe that connects the semiconductor material gas generation unit and the reactor and supplies the semiconductor material gas from the semiconductor material gas generation unit to the reactor;
having
the semiconductor material gas generation unit has a reaction vessel that stores a solid or liquid material in a lower portion of an internal space, supplies a mixed gas of a carrier gas and a raw material gas to an upper portion of the internal space, and generates the semiconductor material gas by in-situ generation of the solid or liquid material and the mixed gas;
the semiconductor material gas supply pipe has a first connection part connected to the semiconductor material gas generation part and a second connection part connected to the reactor, the first connection part is located at a lower position than the second connection part in the vertical direction, the lowest part of the semiconductor material gas supply pipe is located between the first connection part and the second connection part, and a discharge part for discharging the liquefied solid or liquid material is provided at the lowest part;
III-V and III-VI semiconductor deposition equipment. The III-V and III-VI semiconductor film forming apparatus according to claim 1, further comprising a trap below the exhaust section for collecting the liquefied solid or liquid material. The III-V and III-VI semiconductor film formation apparatus according to claim 1 or 2, wherein the semiconductor material gas supply pipe has a baffle inside, which allows the liquefied solid or liquid material to easily fall into a trap arranged below the exhaust section and complicates the flow path of the semiconductor material gas. The III-V and III-VI semiconductor film forming apparatus according to any one of claims 1 to 3, wherein at least a portion between the lowest portion of the semiconductor material gas supply pipe and the second connection portion is arranged vertically. The III-V and III-VI semiconductor film forming apparatus according to any one of claims 1 to 3, wherein the shape between the first connection part and the second connection part of the semiconductor material gas supply pipe is substantially U-shaped, and the bottom of the substantially U-shaped shape is the lowest part. The III-V and III-VI semiconductor film forming apparatus according to any one of claims 1 to 5, wherein the metal chloride is gallium trichloride.

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