Vapor phase growth apparatus

Abstract

This vapor phase growth apparatus supplies to a reactor a raw material gas obtained by making the vapor of an organic metal raw material accompany a carrier gas. The carrier gas is supplied to a container filled with the organic metal raw material, and the vapor of the organic metal raw material is made to accompany the carrier gas to obtain the raw material gas. In a carrier gas supply line upstream of the container, a heater for heating the carrier gas in a line is provided between a mass flow controller for controlling the supply amount of the carrier gas and the container for storing the organic metal raw material. The present invention further comprises a second gas heater that, when a raw material gas dilution line that supplies the carrier gas to the raw material gas supply line downstream of the container is provided, heats the carrier gas in the dilution line downstream of a second mass flow controller that controls the supply amount of the carrier gas in the raw material gas dilution line.

Description

Vapor phase growth equipment

[0001] The present invention relates to a vapor phase growth apparatus.

[0002] Conventionally, in a vapor phase growth apparatus for forming a compound semiconductor thin film on a substrate, a method for supplying a metalorganic raw material to a substrate is generally performed in which nitrogen, hydrogen, or the like is supplied as a carrier gas to a container filled with the metalorganic raw material, and the carrier gas, carrying the vapor of the metalorganic raw material, is discharged from the container filled with the metalorganic raw material and supplied to a reactor (reaction furnace) (see, for example, Patent Document 1).

[0003] In this vapor phase growth apparatus, the following source gas supply device is used to form a compound semiconductor thin film on a substrate in a reactor. This source gas supply device entrains the vapor of an organic metal precursor with a carrier gas to form a source gas, and supplies this source gas to the reactor. In the source gas supply device, nitrogen, hydrogen gas, or the like is supplied as a carrier gas to a container filled with an organic metal precursor. The vapor of the organic metal precursor is entrained in this carrier gas to form a source gas, which is then drawn out of the container and supplied to the reactor.

[0004] When a source gas is supplied to a reactor, its vapor pressure depends on its temperature. To ensure a constant supply of metalorganic precursors, the source temperature must be maintained at a predetermined level. For this reason, for example, a container filled with the metalorganic precursor may be placed in a thermostatic chamber. To ensure a constant supply of metalorganic precursors, it is necessary to maintain not only the temperature but also the flow rate of the carrier gas and the pressure inside the metalorganic precursor container. Therefore, when the vapor pressure of the metalorganic precursor is low or when a large amount of the precursor needs to be supplied, it is necessary to maintain the temperature of the metalorganic precursor at a relatively high level to ensure the supply of the metalorganic precursor.

[0005] For example, one approach would be to heat the carrier gas by installing a heater in a mass flow controller that controls the supply rate of the carrier gas. However, because the mass flow controller is an electronic device, heating it to a high temperature makes it impossible to control the flow rate. Furthermore, if the temperature of the metal-organic source container becomes higher than the heating temperature of the mass flow controller, the following problem arises. That is, a carrier gas at a relatively low temperature is supplied to the metal-organic source container, which is maintained at a high temperature. This causes the temperature inside the container to drop, destabilizing the metal-organic source vapor and resulting in an insufficient supply of the metal-organic source. Furthermore, if the temperature inside the piping downstream of the container drops, the metal-organic source, which has a low vapor pressure, condenses, preventing the appropriate amount from being supplied to the reactor.

[0006] Japanese Patent Application Publication No. 2002-313731

[0007] The present invention provides a vapor phase growth apparatus that can stably supply source gas to a reactor even when the vapor pressure of the metalorganic source is low or when a large amount of the metalorganic source needs to be supplied.

[0008] The vapor phase growth apparatus of the present invention is a vapor phase growth apparatus for forming a compound semiconductor thin film on a substrate in a reactor, and includes the following source gas supply device. The source gas supply device supplies a source gas obtained by entraining vapor of an organic metal precursor with a carrier gas to the reactor. The carrier gas is supplied to a container filled with the organic metal precursor, and the vapor of the organic metal precursor is entrained in the carrier gas to form a source gas. A heater for heating the carrier gas in the carrier gas supply line upstream of the container is provided between the mass flow controller that controls the supply amount of the carrier gas and the container that stores the organic metal precursor. When a source gas dilution line for supplying carrier gas to the source gas supply line downstream of the container is provided, the source gas dilution line further includes a second gas heater downstream of the second mass flow controller that controls the supply amount of the carrier gas for heating the carrier gas in the dilution line.

[0009] According to the vapor phase growth apparatus of the present invention, even when the vapor pressure of the metalorganic raw material is low or when a large amount of the metalorganic raw material needs to be supplied, the source gas can be stably supplied to the reactor.

[0010] Fig. 1 is a schematic diagram showing the configuration of a source gas supply device in a vapor phase growth apparatus of a first embodiment. Fig. 2 is a schematic diagram showing the configuration of a source gas supply device in a vapor phase growth apparatus of a second embodiment. Fig. 3 is a schematic diagram showing the configuration of a comparative example for the first embodiment. Fig. 4 is a schematic diagram showing the configuration of a comparative example for the second embodiment. Fig. 5 is a schematic diagram of a vapor phase growth apparatus.

[0011] FIG. 1 is a schematic diagram showing the configuration of a source gas supply device B1 in a vapor phase growth apparatus A1 of a first embodiment. FIG. 5 is a schematic diagram of a vapor phase growth apparatus A in which the source gas supply device B1 is used. In FIG. 5, the vapor phase growth apparatuses A1 and A2 of the first and second embodiments are collectively referred to as vapor phase growth apparatus A, and the source gas supply devices B1 and B2 are collectively referred to as source gas supply device B. The vapor phase growth apparatus A of the embodiment is a metal-organic chemical vapor deposition apparatus (hereinafter referred to as an MOCVD apparatus) that forms a thin film of a compound semiconductor or the like on a substrate by the MOCVD (Metal Organic Chemical Vapor Deposition) method. In the vapor phase growth apparatus A, a source gas G2 supplied from a source gas supply device B is supplied to a reactor (reaction furnace) C, where a compound semiconductor thin film is formed on a substrate.

[0012] 1 , reference numeral 1 denotes a storage container for an organometallic precursor gas that serves as a supply source of organometallic precursor gas, reference numeral 4 denotes a carrier gas inlet line that introduces a carrier gas G1 such as hydrogen (carrier gas) from a carrier gas inlet outside the apparatus into the container 1, and reference numeral 5 denotes a source gas supply line that introduces a gas containing an organometallic material (organometallic precursor gas) G2 from the container 1 to the outside of the apparatus. The storage container 1 is located within a thermostatic chamber 1a.

[0013] The metal-organic storage vessel 1 serves as a supply source for the metal-organic source gas G2, and the source gas G2 containing the metal-organic source gas, which is a low vapor pressure source, is obtained by bubbling or sublimation using the carrier gas G1 introduced from the carrier gas introduction line 4. The metal material in the vessel 1 is heated to a predetermined temperature (100 to 200°C) in a thermostatic chamber 1a. Note that the above temperature is a representative example, and if the supply of the metal-organic source gas is being considered, including conventional MOCVD methods, a lower temperature such as 0°C is also possible.

[0014] The upstream side of the carrier gas introduction line 4 is composed of two systems of first introduction lines 4a and 4b. After the downstream sides of the two first introduction lines 4a and 4b are joined, the carrier gas introduction line 4 again branches into two systems of second introduction lines 4d and 4e. Each of the first introduction lines 4a and 4b and each of the second introduction lines 4d and 4e is provided with a valve 4c. Each of the second introduction lines 4d and 4e is provided with a mass flow controller 4f, which enables adjustment of the flow rate of the carrier gas G1 introduced into the container 1 through the carrier gas introduction line 4.

[0015] The downstream sides of the two second inlet lines 4d and 4e join together to form a single third inlet line 4g, which is provided with a gas heater 4h for heating the carrier gas G1 to a predetermined temperature and a valve 4j for opening and closing the flow path of the carrier gas G1 immediately upstream of the container 1.

[0016] Here, the distance and internal volume from the mass flow controller 4f to the thermostatic chamber 1a are preferably minimized to maintain good flow rate control responsiveness. While commercially available heaters 4h can be used, the outlet temperature of the heater 4h drops significantly, making it desirable to minimize the piping from the heater 4h to the thermostatic chamber 1a. In other words, the temperature of the carrier gas G1 introduced from the heater 4h into the container 1 should be the same as that of the thermostatic chamber 1a. If the temperature of the carrier gas G1 is lower than that of the thermostatic chamber 1a, the raw material will cool and liquefy. If the temperature of the carrier gas G1 is higher than that of the thermostatic chamber 1a, the raw material will decompose. The set temperature of the heater 4h varies depending on the type of raw material and the conditions of use. The present configuration is suitable for use with raw materials that require high temperatures, such as europium compounds. Examples of organometallic raw materials suitable for the present configuration include scandium compounds.

[0017] The control range of the outlet temperature of the heater 4h is set, for example, in comparison with the temperature of the thermostatic bath 1a (+40 / -0°C). As an example of the current heating temperature, the temperature of the thermostatic bath 1a that heats the europium compound source container is 130°C. The heating temperature of the gas heater 4h provided upstream of this thermostatic bath 1a is 150°C. The heating temperature of the gas heater 4h is preferably in the range from the same temperature as the temperature of the thermostatic bath 1a to about +40°C.

[0018] In the first embodiment, a heater 4h is installed in the carrier gas inlet line 4. The mass flow controller 4f is an electronic device that cannot be heated to high temperatures, and the flowing gas is set to 80°C or less. Therefore, a heater 4h is installed downstream of the mass flow controller 4f in the carrier gas inlet line 4, separate from the mass flow controller 4f. In the first embodiment, a gas heater 4h is installed between the mass flow controller 4f and the metal-organic source vessel 1. Note that the term "gas heater" does not specify the energy of the heater 4h, but rather means "a heater that heats the gas in the piping." The heater 4h may be a gas-powered heater that provides a large amount of heat to the carrier gas G1, but it may also be, for example, an electric heater.

[0019] In the first embodiment, the gas heater 4h is provided not only to heat the carrier gas G1 but also to first provide a large amount of heat to the carrier gas G1, and then a piping heater (not shown) is used to provide a relatively small amount of heat, thereby stably heating the carrier gas G1. Even if the upstream piping and valve are heated with a piping heater, the output of the piping heater is insufficient to stabilize the temperature of the carrier gas G1 when it reaches the raw material container 1, and the raw material cannot be stably supplied to the reactor. In the first embodiment, the gas heater 4h is added to the upstream piping (carrier gas inlet line 4), thereby stabilizing the temperature of the carrier gas G1 supplied to the raw material container 1 and enabling the raw material to be stably supplied to the reactor.

[0020] The source gas supply line 5 downstream of the vessel 1 is equipped with a valve 5b for opening and closing the flow path of the source gas G2 immediately downstream of the vessel 1, a pressure gauge 5c for detecting the pressure of the source gas G2 downstream of the valve 5b, and a valve 5d for adjusting the pressure of the source gas G2. A bypass line 6 having a valve 6a is provided between the third inlet line 4g and the supply line 5, and this allows a portion of the carrier gas G1 to be directly added to the source gas G2. The source gas supply line 5 is supplied to a reactor C (see FIG. 5) in which a compound semiconductor thin film is formed on a substrate.

[0021] In this way, the carrier gas G1 passes through multiple valves 4c and has its flow rate controlled by a mass flow controller 4f. The carrier gas G1 is then heated to a predetermined temperature by a gas heater 4h and supplied to the metal-organic raw material in the vessel 1 via valve 4j. The metal-organic raw material is heated to a predetermined temperature in a thermostatic chamber 1a. Although "multiple valves 4c" are used in the embodiment, the present invention does not necessarily require multiple valves. The source gas G2 obtained by entraining the vapor of the metal-organic raw material in the carrier gas G1 is supplied to the reactor C (see FIG. 5) via valve 5b. At this time, the pressure control valve 5d is controlled so that the pressure measured by the pressure gauge 5c becomes the predetermined pressure.

[0022] As described above, the vapor phase growth apparatus A1 in the first embodiment includes a source gas supply device B1. The source gas supply device B1 supplies a source gas G2 obtained by entraining the vapor of a metalorganic precursor with a carrier gas G1 to the reactor C in order to form a compound semiconductor thin film on a substrate in the reactor C. A carrier gas such as nitrogen or hydrogen is supplied as the carrier gas G1 to the container 1 filled with the metalorganic precursor, and the vapor of the metalorganic precursor is entrained in the carrier gas G1 to produce the source gas G2. The source gas G2 is drawn out of the container 1 and supplied to the reactor C. The carrier gas inlet line 4 upstream of the container 1 in the source gas supply device B1 includes a gas heater 4h for heating the carrier gas G1, located between the mass flow controller 4f that controls the supply rate of the carrier gas G1 and the container 1 storing the metalorganic precursor. With this configuration, the addition of the gas heater 4h to the source gas supply line 5 makes it possible to heat the temperature of the carrier gas G1 supplied to the source container 1 to the same temperature as the source material in the container 1. Therefore, even when the vapor pressure of the metal-organic raw material is low or when a large amount of the metal-organic raw material needs to be supplied, the source gas G2 can be stably supplied to the reactor C.

[0023] 2 is a schematic diagram showing the configuration of a source gas supply device B2 in a vapor phase growth device A2 of the second embodiment. The device A2 shown in the figure differs from the device A1 of the first embodiment in that one of two first inlet lines 4a, 4b branches off from the carrier gas inlet line 4 and becomes a source gas dilution line 7 that is directly connected to the source gas supply line 5. Other components that are the same as those in the first embodiment are given the same reference numerals and detailed description will be omitted.

[0024] The raw material gas dilution line 7 is provided with a second mass flow controller 7a, which makes it possible to adjust the flow rate of the carrier gas G1 supplied to the raw material gas supply line 5 through the raw material gas dilution line 7. The raw material gas dilution line 7 is provided with a second gas heater 7h downstream of the second mass flow controller 7a, which heats the carrier gas G1 to a predetermined temperature.

[0025] If the source gas G2 in the source gas supply line 5 is cooled by the carrier gas G1 supplied from the source gas dilution line 7, there is a risk that the source material in the gas will be liquefied. In the second embodiment, a second gas heater 7h is provided downstream of the second mass flow controller 7a in the source gas dilution line 7 to heat the carrier gas G1 supplied to the source gas supply line 5. This makes it possible to prevent condensation of the metal-organic source material due to cooling of the source gas G2 in the source gas supply line 5.

[0026] The second embodiment differs from the first embodiment in that it further includes a source gas dilution line 7 including a second mass flow controller 7a and a second gas heater 7h. The carrier gas G1 passing through the second gas heater 7h reduces the concentration of the metal-organic precursor in the source gas G2 supplied from the valve 5b of the source gas supply line 5, and can prevent a subsequent shortage of source material due to condensation of the metal-organic precursor. Specifically, when the carrier gas G1 heated to a predetermined temperature by the second gas heater 7h is supplied to the source gas G2 to dilute the source gas G2, condensation of the metal-organic precursor, which occurs when the temperature of the carrier gas G1 is relatively low, can be prevented.

[0027] FIG. 3 is a schematic diagram showing the configuration of a comparative example compared to the first embodiment. FIG. 4 is a schematic diagram showing the configuration of a comparative example compared to the second embodiment. In each comparative example, it is possible to heat the carrier gas G1, for example, using the mass flow controller 4f of the carrier gas inlet line 4 or the second mass flow controller 7a of the second mass flow controller 7a. However, there is a limit to how much the mass flow controllers 4f and 7a can be heated externally, and the heated carrier gas G1 will be at a temperature lower than the predetermined temperature (the same temperature as the raw material in the vessel 1). Therefore, if the carrier gas G1 heated by the mass flow controllers 4f and 7a is introduced into the vessel 1 or merged with the raw material gas G2, it will be difficult to stably supply the raw material to the reactor C.

[0028] In contrast, in the vapor phase growth apparatuses A1 and A2 of the respective embodiments, a gas heater 4h for heating the carrier gas G1 is provided in the source gas supply line 5 between the mass flow controller 4f for controlling the supply rate of the carrier gas G1 and the container 1 for storing the metal-organic source. With this configuration, the addition of the gas heater 4h to the source gas supply line 5 makes it possible to heat the temperature of the carrier gas G1 supplied to the source container 1 to the same temperature as the source material in the container 1, and the source material in the container 1 can be stably supplied to the reactor C.

[0029] Furthermore, the vapor phase growth apparatus A2 of the second embodiment is equipped with a source gas dilution line 7 that directly supplies carrier gas G1 into source gas G2 delivered from vessel 1, thereby making it possible to reduce the metalorganic precursor concentration in source gas G2. The source gas dilution line 7 is equipped with a second gas heater 7h that heats carrier gas G1 in the dilution line. According to this configuration, in the source gas dilution line 7 that joins with the source gas supply line 5 downstream of vessel 1, the second gas heater 7h heats carrier gas G1 to a predetermined temperature, thereby preventing condensation of the metalorganic precursor in the source gas supply line 5 that may occur due to the carrier gas G1 supplied from the source gas dilution line 7.

[0030] The configurations in the above-described embodiments are merely examples of the present invention, and various modifications are possible without departing from the spirit of the present invention, such as replacing the components of the embodiments with well-known components.

[0031] REFERENCE SIGNS LIST 1 Container 1a Thermostatic chamber 4 Carrier gas introduction line 4f Mass flow controller 4h Gas heater (heater) 5 Source gas supply line 7 Source gas dilution line 7a Second mass flow controller 7h Second gas heater (second heater) A, A1, A2 Vapor phase growth apparatus B, B1, B2 Source gas supply apparatus C Reactor G1 Carrier gas (carrier gas) G2 Source gas

Claims

1. In a vapor deposition apparatus for forming a compound semiconductor thin film on a substrate in a reactor, a raw material gas supply device is provided which allows the vapor of an organometallic raw material to be entrained in a carrier gas to form a raw material gas and supplies this raw material gas to the reactor. The raw material gas supply device supplies a carrier gas to a container filled with the organometallic raw material, and allows the vapor of the organometallic raw material to be entrained in this carrier gas to form a raw material gas. A heater for heating the carrier gas in the line is provided between a mass flow controller for controlling the supply amount of the carrier gas and the container in the carrier gas supply line upstream of the container. A vapor deposition apparatus.

2. The vapor deposition apparatus according to claim 1, further comprising a raw material gas dilution line for supplying a carrier gas to the raw material gas supply line downstream of the container, and a second heater for heating the carrier gas in the dilution line is provided downstream of a second mass flow controller for controlling the supply amount of the carrier gas in the raw material gas dilution line.

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