JP2018160487A - Method and device for forming gallium nitride film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for forming a gallium nitride film, reducing the burden of cleaning, capable of achieving high productivity, and capable of suppressing contamination of a film due to oxygen.SOLUTION: Gallium nitride is vapor-phase grown on a surface of each of a plurality of substrates to be processed by: arranging the plurality of substrates to be processed in a processing chamber while the substrates are arranged in a horizontal position in a vertical direction and allowing the processing chamber to form a sealed space; adjusting the temperature of the substrates to be processed to 850-930°C and the pressure in the processing chamber to 0.5-1.8 Torr; supplying gallium-containing gas into the processing chamber via a gallium-containing gas introduction member; and supplying nitrogen-containing gas into the processing chamber via a nitrogen-containing gas introduction member.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a gallium nitride film forming method and a film forming apparatus.

  In a compound semiconductor, a semiconductor using nitrogen (N) as a group V element is called a nitride semiconductor. Aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and the like are typical examples of nitride semiconductors.

  Among them, gallium nitride has been put into practical use as a blue light emitting element in optical application fields, and has been put into practical use as a high electron mobility transistor (HEMT) used in communication fields and the like in electronic device application fields. ing.

  Further, gallium nitride is a wide-gap semiconductor and has characteristics that antagonize silicon carbide (SiC) and has high-frequency characteristics and dielectric breakdown voltage with potential higher than that of silicon carbide. For this reason, research has been actively conducted for further practical application, for example, realization of new devices capable of covering a wide range of high frequency, high speed, and high power at a time.

As a method for forming gallium nitride, metal organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE) (Halide Vapor Phase) have been conventionally used. Also known as Epitaxy). A typical HVPE method generates gallium trichloride gas (GaCl ₃ ) by reacting hydrogen chloride gas (HCl) with metallic gallium (Ga) in a high temperature environment at normal pressure and at a temperature of 1000 ° C. or higher. By reacting gallium trichloride gas with ammonia gas (NH ₃ ), a gallium nitride crystal is vapor-phase grown on a sapphire substrate (for example, Patent Document 1).

  On the other hand, recently, there is an increasing demand for throughput improvement, and vertical batch type film forming apparatuses capable of processing a plurality of substrates to be processed at a time by arranging a plurality of substrates to be processed in the height direction have attracted attention. . In the formation of a compound semiconductor film typified by a gallium nitride film, conversion to a vertical batch type film forming apparatus is being sought, and Patent Documents 2 and 3 disclose a vertical type for forming a gallium nitride film. A batch type film forming apparatus is disclosed.

  In addition, a technique for forming a film of GaN at high vacuum and low temperature (600 to 900 ° C.) by molecular beam epitaxy (MBE) has been proposed.

JP 2008-66490 A JP 2014-33112 A Japanese Patent No. 6026351

  By the way, in conventional MOCVD and HVPE, the parts in the processing vessel are formed of SiC having high heat resistance. However, since gallium nitride is deposited on SiC, the adhered gallium nitride becomes a particle source, A great amount of downtime occurs when cleaning the parts in the processing container.

  The apparatuses of Patent Documents 2 and 3 are basically hot wall type apparatuses using quartz as a processing container and parts as in the case of a normal vertical batch film forming apparatus. C. is exemplified. Quartz used as a processing vessel or part has the property that gallium nitride is not formed, so there is a possibility that the generation of particles and the need for cleaning can be reduced by selective film formation on the substrate. When the film is formed, there is a risk that quartz is reduced and oxygen is mixed into the film. Further, when the GaN film is formed at a temperature of 1000 ° C. or higher, the sapphire substrate is formed by nitriding, and the obtained GaN is N-plane GaN, but Ga-plane GaN is preferable.

  Furthermore, the technique of forming a GaN film by MBE has a drawback that the productivity is very poor.

  Therefore, the present invention reduces the burden of cleaning, obtains high productivity, suppresses contamination of the film by oxygen, and can obtain Ga-plane gallium nitride film formation method. Another object is to provide a film formation apparatus.

  In order to solve the above-mentioned problems, a first aspect of the present invention is to define a processing chamber, and a processing container made of quartz in which a plurality of substrates to be processed are arranged in a horizontal orientation in a vertical position. A gallium-containing gas introducing member made of quartz for introducing a gallium-containing gas into the processing chamber, a nitrogen-containing gas introducing member made of quartz for introducing a nitrogen-containing gas into the processing chamber, and an exhaust section for exhausting the processing chamber And a film forming apparatus having a heating apparatus that heats a substrate to be processed disposed in the processing chamber, and forming a gallium nitride film using the film forming apparatus, A process substrate is disposed in a horizontal posture in a state of being arranged in a vertical direction, and a process chamber is set as a sealed space, a temperature of the process substrate is 850 to 930 ° C., and a pressure in the process container is 0.5 to Adjusting to 1.8 Torr; A step of supplying a gallium-containing gas to the processing chamber via the gallium-containing gas introducing member, and a step of supplying a nitrogen-containing gas to the processing chamber via the nitrogen-containing gas introducing member. Provided is a method for forming a gallium nitride film, characterized by vapor-phase growth of gallium nitride on the surface of a substrate.

  According to a second aspect of the present invention, a processing chamber is defined, and a processing vessel made of quartz in which a plurality of substrates to be processed are arranged in a horizontal posture and arranged in a vertical direction, and a gallium-containing gas are provided. A gallium-containing gas introducing member made of quartz introduced into the processing chamber, a nitrogen-containing gas introducing member made of quartz introducing nitrogen-containing gas into the processing chamber, and the gallium into the processing chamber via the gallium-containing gas introducing member A gas supply mechanism that supplies a gas, supplies the nitrogen-containing gas to the processing chamber via the nitrogen-containing gas introduction member, and supplies a purge gas to the processing chamber; an exhaust unit that exhausts the processing chamber; An exhaust device that exhausts the processing chamber through the exhaust unit, a heating device that heats the substrate to be processed disposed in the processing chamber, and a temperature of the substrate to be processed is 850 to 930 ° C., Pressure The vapor deposition of the gallium nitride film on the substrate to be processed by controlling the supply amount of the gallium-containing gas and the nitrogen-containing gas to the processing chamber so that the gallium nitride film is 0.5 to 1.8 Torr. A gallium nitride film deposition apparatus comprising the gas supply mechanism, the exhaust device, and a control unit for controlling the heating device is provided.

  The gallium-containing gas is a gallium chloride gas, the nitrogen-containing gas is a hydride gas containing nitrogen, and it is preferable to form a gallium nitride film by HVPE. The nitrogen-containing hydride gas is preferably ammonia.

  The plurality of substrates to be processed can be inserted into the processing chamber while being held by a substrate holding member made of quartz. A sapphire substrate can be suitably used as the substrate to be processed.

  In the first aspect, after the film formation of the gallium nitride film is repeated a predetermined number of times, a chlorine-containing gas is introduced into the processing chamber through the gallium-containing gas introduction member and the nitrogen-containing gas introduction member, and the gallium You may have the process of cleaning the containing gas introduction member, the nitrogen-containing gas introduction member, and the processing container.

  In the second aspect, a chlorine-containing gas is introduced into the processing chamber via the gallium-containing gas introduction member and the nitrogen-containing gas introduction member, the gallium-containing gas introduction member, the nitrogen-containing gas introduction member, You may further have the cleaning gas supply mechanism which cleans a process container.

  The gallium-containing gas introduction member discharges the gallium-containing gas toward the processing chamber along the height direction of the diffusion space and a gas diffusion space formed along the height direction of the processing chamber. A plurality of gas discharge holes, a plurality of gas discharge holes connected in the height direction of the gas diffusion space, and a gallium-containing gas introduction pipe extending in the horizontal direction, wherein the nitrogen-containing gas introduction member is disposed below the processing chamber. It is preferable to have a nitrogen-containing gas introduction pipe that is inserted and extends to the upper part of the processing chamber and has a plurality of gas discharge holes for discharging a nitrogen-containing gas toward the plurality of substrates to be processed.

  According to the present invention, the temperature of the substrate to be processed is set to 850 to 930 ° C., and the pressure in the processing container is set to 0.5 to 1.8 Torr, thereby reducing the burden of cleaning and obtaining high productivity. Thus, the gallium nitride film can be formed while suppressing contamination of the film by oxygen.

It is sectional drawing which shows schematic structure of the batch type vertical film-forming apparatus with which this invention is applied. It is a horizontal sectional view by the II-II line of the film-forming apparatus of FIG. It is sectional drawing which expands and shows the 1st and 2nd gas introduction pipe | tube which introduce | transduces a gallium chloride gas into a process chamber. It is a figure which shows the relationship between film-forming temperature and the quantity of oxygen (O), hydrogen (H), and carbon (C) which are the impurities in a film | membrane. 875-930 is a SEM photograph showing the film forming property of the GaN film due to the difference in base at ° C., illustrates a case where the base is to form a SiO ₂ mask on the right side in GaN. It is a figure which shows the temperature range and pressure range which can perform suitable GaN film-forming.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<Background to the Present Invention>
First, the background to the present invention will be described.
Conventionally, MOCVD apparatus and HVPE apparatus used as mass production machines for vapor phase growth of gallium nitride (GaN) films are basically single-wafer type cold wall type apparatuses. In such an apparatus, since high-temperature processing at 1000 ° C. or higher is performed at normal pressure, SiC having high heat resistance is used as a part in the processing container. However, since gallium nitride is deposited on SiC, the adhered GaN becomes a particle source, and a great downtime occurs in cleaning parts in the processing container.

  On the other hand, vapor phase growth of a GaN film by MBE forms a GaN film at a high vacuum and a low temperature (600 to 900 ° C.), but there is a problem that productivity is poor.

  On the other hand, the vertical batch type film forming apparatus, which is a hot wall type apparatus using quartz as a processing container or a part, has high productivity and does not deposit GaN on quartz under a predetermined condition. There is a possibility that selective film formation can be performed and the necessity of particle generation and cleaning can be reduced. For this reason, a vertical batch type film forming apparatus has been studied as a film forming apparatus for a GaN film. Even in the vertical batch type film forming apparatus, as in Patent Document 2, the film forming temperature is 1000 ° C. or higher as in the mass production machine, and the film forming conditions are searched.

However, in the case of a vertical batch type film forming apparatus, it has been found that when the film forming temperature reaches 1000 ° C. or higher, there is a risk that quartz (SiO ₂ ) is reduced and oxygen is mixed into the film. Conventionally, GaN is formed by forming a sapphire substrate and forming a film at a film forming temperature of 1000 ° C. or higher, and the obtained GaN is N-plane GaN, and Ga is actually formed. Planar GaN was not obtained.

  On the other hand, it has been found that GaN is deposited on quartz in a region where the deposition temperature is low, and selective deposition cannot be performed. It has also been found that such film formation properties and film formation selectivity are also related to the pressure during the film formation process.

  Therefore, as a result of repeated studies, by optimizing the film forming temperature and pressure in the vertical batch type film forming apparatus, it is possible to suppress the contamination of the film with oxygen while maintaining the original high productivity, In addition, it has been found that selective film formation in which GaN is not formed on quartz can reduce the need for particle generation and cleaning, and can be Ga-face GaN.

<Deposition system>
Next, a schematic configuration of a film forming apparatus configured as a batch type vertical heat treatment apparatus to which the present invention is applied will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a batch type vertical film forming apparatus to which the present invention is applied, and FIG. 2 is a horizontal cross-sectional view taken along the line II-II in FIG. Note that the longitudinal section shown in FIG. 1 is taken along the line II in FIG.
It is.

  As shown in FIG. 1, a vertical batch-type film forming apparatus (hereinafter referred to as a film forming apparatus) 100 is provided with a cylindrical outer tube 101 having a ceiling and an inner side of the outer tube 101. And an inner tube 102. The outer tube 101 and the inner tube 102 are made of quartz, and these function as processing containers. A plurality of sapphire substrates 1 that are substrates to be processed are accommodated inside the inner tube 102, and a GaN film that is a group III-V compound semiconductor film is collectively formed on the accommodated plurality of sapphire substrates 1. A processing chamber 103 is formed.

  One side wall of the inner tube 102 is provided with a gas introduction part 104 for introducing gallium chloride gas as a film forming source gas into the processing chamber 103. The gas introduction unit 104 includes a gas diffusion space 105 a formed along the height direction of the processing chamber 103, and a gas discharge hole 105 b that discharges gas toward the processing chamber 103 is formed in the gas diffusion space 105 a in the height direction. A plurality of diffusion plates 105c are attached along the line.

  Two gas introduction pipes 106 are arranged inside the inner pipe 102 in order to introduce a hydride gas containing nitrogen discharged from the gas discharge holes 105 b into the processing chamber 103. The gas introduction pipe 106 stands vertically from the lower part of the inner pipe 102. A plurality of gas discharge holes 106 a (see FIG. 2) for discharging gas toward the processing chamber 103 are also formed in the gas introduction pipe 106 along the height direction. Furthermore, in addition to the gas introduction pipe 106, a temperature controller 107 is provided inside the inner pipe 102 (see FIG. 2). The temperature controller 107 monitors the temperature inside the processing chamber 103. The temperature controller 107 also stands vertically from the lower part of the inner tube 102.

  An exhaust port for exhausting the inside of the processing chamber 103 is formed on the other side wall of the inner tube 102. For example, the exhaust port is provided for each zone of the processing chamber 103. In this example, three exhaust ports, an upper zone exhaust port 108a, a middle zone exhaust port 108b, and a lower zone exhaust port 108c are provided. There may be four or more zones.

  The exhaust ports 108a to 108c communicate with a space defined by the outer tube 101 and the inner tube 102, respectively. The space functions as an exhaust space 109, and the exhaust space 109 is connected through an exhaust pipe 110 to an exhaust device 111 that exhausts the inside of the processing chamber 103. The exhaust device 111 exhausts the atmosphere inside the processing chamber 103. The exhaust device 111 includes a pressure regulator (not shown) such as APC, and exhausts the inside of the processing chamber 103 while adjusting the pressure inside the processing chamber 103 to a pressure required for processing. It is possible to do.

  The outer tube 101 and the inner tube 102 are inserted into the opening 112 a of the base member 112. The base member 112 is provided with a heating device 113 so as to surround the periphery of the outer wall of the outer tube 101. The heating device 113 heats the plurality of sapphire substrates 1 accommodated in the processing chamber 103.

  An opening 114 is provided below the processing chamber 103. A boat 115 which is a substrate placing jig is taken in and out of the processing chamber 103 through an opening 114. The boat 115 is made of quartz and has a plurality of columns 116 made of quartz. A plurality of grooves (not shown) are formed in the support column 116, and a plurality of, for example, 50 to 150 sapphire substrates 1 are collectively supported by these grooves. As described above, the boat 115 on which the plurality of sapphire substrates 1 are placed is inserted into the processing chamber 103, whereby the plurality of sapphire substrates 1 are accommodated in the processing chamber 103.

  The boat 115 is placed on the table 118 via a quartz heat insulating cylinder 117. The table 118 is supported on a rotating shaft 120 that penetrates a lid portion 119 made of, for example, stainless steel. During film formation, the rotating shaft 120 rotates to rotate the boat 115.

  The lid 119 opens and closes the opening 114. For example, a magnetic fluid seal 121 is provided in the penetrating portion of the lid portion 119 and supports the rotary shaft 120 so as to be rotatable while hermetically sealing. In addition, a sealing member 122 made of, for example, an O-ring is interposed between the peripheral portion of the lid portion 119 and the lower end portion of the inner tube 102, for example, to maintain the sealing performance inside the processing chamber 103. Yes. The rotating shaft 120 is attached to the tip of an arm 123 supported by an elevating mechanism (not shown) such as a boat elevator, for example. Accordingly, the boat 115, the lid portion 119, and the like are integrally moved up and down in the height direction and inserted into and removed from the processing chamber 103.

  The film forming apparatus 100 includes a processing gas supply mechanism 130. The processing gas supply mechanism 130 has gas supply paths 124 a to 124 d communicating with the inside of the processing chamber 103, and supplies gas used for processing into the processing chamber 103 via the gas supply paths 124 a to 124 d. . The gas supply paths 124a to 124c are branched from one gas supply path 124e.

  The processing gas supply mechanism 130 includes a hydride gas supply source 131a for supplying hydride (hydride) gas containing nitrogen (N), a carrier gas supply source 131b for supplying carrier gas, and a gallium chloride gas supply source for supplying gallium chloride. 131c is included.

The hydride gas supply source 131a is connected to the gas introduction pipe 106 via a flow rate controller (MFC) 132a and an on-off valve 133a by a gas supply path 124d. The gas introduction pipe 106 constitutes a gas supply path 124 d for supplying hydride gas inside the processing chamber 103. The hydride gas supply source 131 a supplies ammonia (NH ₃ ) gas into the processing chamber 103 as a hydride gas containing N via two gas introduction pipes 106.

A gas flow path 124f is connected to the carrier gas supply source 131b, and the gas flow path 124f is connected to a gallium chloride gas supply source 131c via a flow rate controller (MFC) 132b and an on-off valve 133b. As the carrier gas, an inert gas such as N ₂ gas or Ar gas can be used.

  An end of a gas supply path 124e is connected to the gallium chloride gas supply source 131c, and the gas supply path 124e is connected to an on-off valve 133f on the gallium chloride gas supply source 131c side and gas supply paths 124a to 124c. An opening / closing valve 133d on the branching portion side to be branched is connected. The on-off valves 133b and 133f are provided in the vicinity of the gallium chloride gas supply source 131c, and the gas passage gas passages 124f and 124e are provided above the on-off valves 133b and 133f of the gas passages 124f and 124e, respectively. A bypass opening / closing valve 133c is provided between the two.

The gallium chloride gas supply source 131 c includes a thermostatic chamber 134 and a heater 135 that heats the thermostatic chamber 134. The thermostat 134 contains gallium trichloride (GaCl ₃ ), which is a solid chloride at room temperature, as gallium chloride. Gas supply paths 124f and 124e are inserted into the thermostatic chamber 134.

When solid GaCl ₃ is accommodated in the thermostatic chamber 134 and heated to about 85 ° C. using the heater 135, the solid GaCl ₃ is vaporized and GaCl ₃ vapor (GaCl ₃ gas) is generated. The GaCl ₃ gas opens the on-off valve 133b, introduces the carrier gas into the thermostatic chamber 134, and opens the on-off valves 133f and 133d, thereby supplying the carrier gas together with the gas supply path 124e and the gas supply paths 124a to 124c. It is introduced into the gas introduction unit 104. GaCl ₃ gas is supplied into the processing chamber 103 via the gas introduction unit 104.

  As described above, a gas containing Ga in the GaN film to be formed is formed from the gas introduction unit 104, and a plurality of gases containing N are arranged in the processing chamber 103 from the gas introduction pipe 106. It is supplied along the film formation surface of the substrate 1.

FIG. 3 shows an enlarged example of the gas supply paths 124a to 124c.
As shown in FIG. 3, the gas supply paths 124 a to 124 c include a first gas introduction pipe 125 and a second gas introduction pipe 126 connected to the first gas introduction pipe 125. The first gas introduction pipe 125 is made of quartz. The first gas introduction pipe 125 is provided in the horizontal direction. One end of the first gas introduction pipe 125 is connected to the gas diffusion space 105a of the gas introduction unit 104 through a slit 113a (see FIG. 2) provided in the heating device 113. The other end of the first gas introduction pipe 125 is connected to the base 127. The base 127 serves to close the other end of the first gas introduction pipe 125 and to insert the second gas introduction pipe 126 into the first gas introduction pipe 125. In this example, the second gas introduction pipe 126 is inserted into the first gas introduction pipe 125 through the central portion of the base 127. Thereby, one end of the second gas introduction pipe 126 communicates with the inside of the first gas introduction pipe 125, and the other end is connected to a pipe constituting the gas supply path 124e. The diameter of the second gas introduction pipe 126 is smaller than the diameter of the first gas introduction pipe 125, and the outer surface of the second gas introduction pipe 126 and the first gas are formed inside the first gas introduction pipe 125. There is a gap between the inner surface of the introduction pipe 125.

  A gas supply path 124g branches from a portion of the gas supply path 124f extending from the carrier gas supply source 131b downstream of the flow rate controller (MFC) 132b, and extends from the hydride gas supply source 131a via the on-off valve 133e. It is connected to the gas supply path 124d.

The inert gas supplied from the carrier gas supply source 131b serves as a carrier gas that picks up and carries gallium chloride gas (GaCl ₃ gas), closes the on-off valve 133b, and bypasses the on-off valve 133c and the on-off valve 133d, And / or by opening the on-off valve 133e, it is also used as a purge gas for purging the inside of the gas supply paths 124a to 124d, the inside of the gas introduction unit 104, the inside of the gas introduction pipes 106a and 106b, and the inside of the processing chamber 103. be able to.

  For example, when the on-off valve 133b is closed and the bypass on-off valve 133c, the on-off valve 133d, and the on-off valve 133e are opened, gas is supplied to both the gas introduction unit 104 and the gas introduction pipe 106 via the gas supply paths 124a to 124d. Then, the inside of the gas supply paths 124a to 124d, the inside of the gas introduction unit 104, the inside of the gas introduction pipe 106, and the inside of the processing chamber 103 can be purged.

  Further, when the on-off valves 133b and 133e are closed and the bypass on-off valve 133c and the on-off valve 133d are opened, gas is supplied to the gas supply paths 124a to 124c and the gas introduction unit 104, and the inside of the gas supply paths 124a to 124c, The inside of the gas introduction unit 104 and the inside of the processing chamber 103 can be purged.

  Further, when the on-off valves 133b and 133c are closed and the on-off valve 133e is opened, gas is supplied to the gas supply passage 124d and the gas introduction pipe 106, and the inside of the gas supply passage 124d, the inside of the gas introduction pipe 106, and the processing chamber. The interior of 103 can be purged.

  The film forming apparatus 100 further includes a cleaning gas supply mechanism 140. The cleaning gas supply mechanism 140 includes a cleaning gas supply source 141. The cleaning gas supply source 141 is connected to the gas supply paths 124a to 124c via the cleaning gas supply path 144a, and is connected to the gas supply path 124d via the cleaning gas supply path 144b. The cleaning gas supply path 144a is provided with a flow rate controller 142a and an on-off valve 143a, and the cleaning gas supply path 144b is provided with a flow rate controller 142b and an on-off valve 143b. As a result, the cleaning gas used for the cleaning process can be supplied into the processing chamber 103 via the gas supply paths 124 a to 124 c and the gas introduction unit 104, and the gas supply path 124 d and the gas introduction pipe 106. It is also possible to supply the inside of the processing chamber 103 via

As the cleaning gas, a chlorine-containing gas that can etch GaN and hardly etch quartz can be used. In particular, chlorine gas (Cl ₂ gas) is preferable because it hardly etches quartz. For this reason, the cleaning gas supply mechanism 140 can in-situ clean the inner wall of the inner tube 102 as a processing container, the parts in the processing chamber 103, piping, and the like.

  The film forming apparatus 100 further includes a control unit 150. The control unit 150 controls each component of the film forming apparatus 100, such as valves, a mass flow controller that is a flow rate controller, a driving mechanism such as a lifting mechanism, a heater power source, and the like. The control unit 150 includes a CPU (computer), and includes a main control unit that controls each of the above components, an input device, an output device, a display device, and a storage device. In the storage device, a program for controlling processing executed by the film forming apparatus 100, that is, a storage medium storing a processing recipe is set, and the main control unit stores a predetermined processing recipe stored in the storage medium. The film forming apparatus 100 performs control so that a predetermined film forming process is performed based on the processing recipe.

<GaN deposition method>
Next, a method for forming a GaN film according to the present invention, which is performed by the film forming apparatus shown in FIG. 1, will be described. The following processing operations are executed based on the processing recipe stored in the storage medium of the storage unit in the control unit 150.

  First, a plurality of, for example, 50 to 150, sapphire substrates 1, which are substrates to be processed, are mounted on the boat 115, the boat 115 is placed on the table 118 via the heat retaining cylinder 117, and the arm 123 is raised by the lifting mechanism. Thus, the boat 115 is inserted into the processing chamber 103 from the lower opening, the opening 114 is sealed by the lid 119, and the processing chamber 103 is set as a sealed space.

  Then, while supplying the carrier gas as the purge gas into the processing chamber 103, the pressure in the processing chamber 103 is controlled to a predetermined range, and the temperature of the plurality of sapphire substrates 1 accommodated in the processing chamber 103 by the heating device 113 is controlled. Is controlled within a predetermined range.

Thereafter, GaCl ₃ gas which is gallium chloride and NH ₃ gas which is a hydride gas containing N are supplied into the processing chamber 103.

When supplying the GaCl ₃ gas which is gallium chloride, the solid GaCl ₃ contained in the thermostatic chamber 134 of the gallium chloride gas supply source 131c is vaporized by the heater 135, and the carrier gas is introduced into the thermostatic chamber 134 from the carrier gas supply source 131b. At the same time, the on-off valves 133f and 133d are opened. Thus, the GaCl ₃ gas is introduced into the gas introduction unit 104 through the gas supply path 124e and the gas supply paths 124a to 124c together with the carrier gas, and is uniformly supplied from the gas introduction part 104 to the processing chamber 103.

Further, when supplying NH ₃ gas which is hydride gas containing N, NH ₃ gas is uniformly supplied from the hydride gas supply source 131 a to the processing chamber 103 through the gas supply path 124 d and the gas discharge hole 106 a of the gas introduction pipe 106. To be supplied.

At the time of vapor phase growth of the GaN film, an atomic layer deposition method (Atomic Layer Deposition) in which GaCl ₃ gas and NH ₃ gas are alternately supplied with a purge in the processing chamber 103 interposed therebetween can be suitably used. GaCl ₃ gas and NH ₃ gas may be supplied simultaneously. By forming the film in this way, a GaN film having a thickness of about 1 to 10 μm is vapor-phase grown (epitaxial growth).

  In such vapor phase growth of the GaN film, the pressure in the processing chamber 103 and the temperature in the processing chamber 103 (substrate temperature) are controlled to be optimum.

In the case of a vertical batch type film forming apparatus using quartz as in the present embodiment, there are advantages such that it is difficult to form a GaN film on quartz by selecting conditions, and that productivity is high. At a high temperature of 1000 ° C. or higher used in MOCVD apparatus and HVPE apparatus that are mass production machines, there is a risk that quartz (SiO ₂ ) is reduced and oxygen is mixed into the film.

  First, the relationship between oxygen and other impurities and temperature was investigated. FIG. 4 is a diagram illustrating the relationship between the film formation temperature and the amounts of oxygen (O), hydrogen (H), and carbon (C) that are impurities in the film. As shown in FIG. 4, the amount of C does not change greatly with temperature, but the amounts of O and H increase rapidly at 940 ° C. or higher.

  Therefore, in order to effectively suppress impurities such as oxygen in the film, the film forming temperature is set to 930 ° C. or lower. Moreover, a Ga-plane GaN film is obtained at such a low temperature. In order to obtain good productivity (growth film formation rate) at a temperature of 930 ° C. or lower, the pressure in the processing chamber 103 is preferably 1.8 Torr (240 Pa) or lower. By setting the temperature and pressure within this range, a film formation rate of 1 to 8 μm / h can be obtained.

GaN has selectivity with respect to quartz (SiO ₂ ). That is, GaN has a property that it is not formed on quartz. Such selectivity is exhibited at 930 ° C. or lower where impurities such as oxygen can be suppressed, and the need for particle generation and cleaning can be reduced. FIG. 5 is an SEM photograph showing the film forming properties of the GaN film depending on the base at 875 to 930 ° C., and shows the case where the base is GaN and a SiO ₂ mask having a thickness of 50 nm is formed on the right side. However, since the SiO ₂ mask is thin, it is not visible in FIG. As shown in FIG. 5, GaN film only covers the physical on SiO ₂ mask, it can be seen that not deposited on the SiO ₂ mask. This confirms that the GaN film has selectivity so that it is not formed on quartz. However, when the film forming temperature is lower than 850 ° C., selectivity with quartz is hardly exhibited, and a GaN film is formed on quartz. Therefore, the temperature (substrate temperature) in the processing chamber 103 is set to 850 ° C. or more from the viewpoint of reducing the need for particle generation and cleaning.

  On the other hand, as described above, in the temperature range of 850 to 930 ° C., a good film forming speed can be obtained when the pressure in the processing chamber 103 is 1.8 Torr (240 Pa) or less, but the pressure is 0.5 Torr (66. If it is lower than 7 Pa), almost no film is formed on the substrate.

  As described above, by setting the temperature in the range of 850 to 930 ° C. and the pressure in the range of 0.5 to 1.8 Torr (66.7 to 240 Pa), the original high productivity of the vertical batch type film forming apparatus. The Ga-face GaN film can be obtained while suppressing the contamination of the film with oxygen, and the selective film formation with no GaN film on quartz can reduce the need for particle generation and cleaning. it can.

  More preferable ranges of temperature and pressure are 900 to 930 ° C. and 0.5 to 1.0 Torr (66.5 to 133 Pa). Within this range, it is possible to further increase the selectivity with which a GaN film does not grow on quartz constituting the processing container and the like, and it is possible to maintain high-quality film formation without contamination.

  Note that when the pressure in the processing chamber 103 exceeds 15 Torr (2000 Pa), quartz becomes cloudy or no film is formed. On the other hand, when the temperature exceeds 950 ° C., Ga-plane GaN is not formed.

  FIG. 6 shows a summary of the film formation state at the above temperature and pressure.

In addition, as the gas flow rate during film formation,
Carrier gas (N ₂ gas): 50-100 sccm
(GaCl ₃ : equivalent to 5-10 sccm)
NH ₃ gas: 3-5 slm
It can be.

  In addition, the film forming apparatus 100 according to the present embodiment includes the inner tube 102, the outer tube 101, and the boat 115, the gas introduction unit 104, and the gas that are present in the processing chamber and in the vicinity thereof. Since all of the introduction pipe 106 and the like are made of quartz, the cleaning gas supply mechanism 140 can perform in-situ cleaning using a chlorine-containing gas.

At the time of cleaning, a chlorine-containing gas, preferably Cl ₂ gas, is supplied as a cleaning gas from the cleaning gas supply source 141 of the cleaning gas supply mechanism 140 to the gas supply paths 124a to 124c via the cleaning gas supply path 144a. Then, the gas is supplied to the gas supply path 124d through the cleaning gas supply path 144b. Accordingly, the cleaning gas is supplied from the gas supply paths 124 a to 124 c to the inside of the processing chamber 103 through the gas introduction unit 104, and is supplied from the gas supply path 124 d to the inside of the processing chamber 103 through the gas introduction pipe 106. And perform cleaning.

  The in-situ cleaning of the vertical batch type film forming apparatus is described in detail in Patent Document 3 (Japanese Patent No. 6026351), and the description thereof is also included in this specification.

  In the present embodiment, as described above, since the GaN film is formed under the condition that the adhesion of the GaN film to the quartz is suppressed, the generation of particles and the necessity for cleaning are low. In addition, the attached GaN film can be easily removed by in-situ cleaning by the cleaning gas supply mechanism 140, and high maintainability can be ensured.

Moreover, since the thermal decomposition temperature of GaCl ₃ is as low as 700 ° C. and requires a relatively large amount, if a conventional vertical gas introduction tube is used, the GaN film is formed at a temperature within the processing chamber 103. There is a possibility that the material cannot be sufficiently supplied to the sapphire substrate due to thermal decomposition before reaching the sapphire substrate 1. For this reason, in this embodiment, the first gas introduction pipe 125 is disposed in the horizontal direction, thereby shortening the run distance of the GaCl ₃ gas, and the inside of the first gas introduction pipe 125, the gas introduction part 104. Thermal decomposition in the inside of the processing chamber 103 and inside the processing chamber 103 can be suppressed and supplied into the processing chamber 103 while maintaining high activity. As a result, GaCl ₃ gas can be more efficiently supplied to the sapphire substrate 1 and contribute to the formation of the GaN film. Further, a plurality of first gas introduction pipes 125 arranged horizontally are arranged in the vertical direction, diffused in the gas diffusion space 105a of the gas introduction unit 104, and supplied to the processing chamber 103, thereby making the GaCl ₃ gas more uniform. Can be supplied.

In contrast, for a gas that requires high activation energy, such as NH ₃ gas used as a hydride gas containing N, the running distance is increased. In this example, NH ₃ gas is run through two gas introduction pipes 106 standing vertically from the lower part of the inner pipe 102 in a vertically long processing chamber 103. By increasing the run-up distance, the thermal energy can be further added to the NH ₃ gas, and the advantage that the activity can be further improved can be obtained. Accordingly, for example, NH ₃ gas can be supplied into the processing chamber 103 with higher activity, and ammonia gas can be more efficiently contributed to the formation of a GaN film that is a compound semiconductor film. .

In the present embodiment, the GaCl ₃ gas that is desired to suppress thermal decomposition and the NH ₃ gas that is thermally activated are separately supplied by a supply method suitable for each in the above-described temperature range. An optimum reaction can be caused on the surface of the sapphire substrate 1 in the substrate 103.

<Other applications>
While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, an example in which a GaN film is formed by HVPE using GaCl ₃ gas that is gallium chloride as the Ga-containing gas and NH ₃ gas that is a hydride gas containing N as the N-containing gas. Although shown, other Ga-containing gases and other N-containing gases may be used. For example, a GaN film may be formed by MOCVD using an organometallic raw material such as trimethylgallium as a Ga-containing gas. However, when a gas having a lower thermal decomposition temperature than GaCl ₃ such as trimethylgallium is used as the Ga raw material, it is necessary to devise measures such as lowering the film forming temperature and further shortening the running distance. Moreover, hydrazine can also be used as the N-containing gas.

  Moreover, although the case where the GaN film was vapor-phase grown with the Ga-containing gas and the N-containing gas was shown in the above embodiment, GaN may be doped with other elements. Furthermore, in the above-described embodiment, an example in which a sapphire substrate is used as a substrate has been shown, but other substrates may be used as long as GaN can be epitaxially grown.

1: Sapphire substrate (substrate)
DESCRIPTION OF SYMBOLS 100; Film-forming apparatus 101; Outer tube 102; Inner tube 103; Processing chamber 104; Gas introduction part 106; Gas introduction pipe 111; Exhaust device 113; Heating device 115; Boat 124a-124g; Gas introduction pipe 126; second gas introduction pipe 130; processing gas supply mechanism 140; cleaning gas supply mechanism 150; control device

Claims (12)

A processing chamber made of quartz, in which a processing chamber is defined, and a plurality of substrates to be processed are arranged in a state of being arranged vertically in a horizontal posture;
A gallium-containing gas introduction member made of quartz for introducing a gallium-containing gas into the processing chamber;
A nitrogen-containing gas introduction member made of quartz for introducing a nitrogen-containing gas into the processing chamber;
An exhaust section for exhausting the processing chamber;
A gallium nitride film forming method for forming a gallium nitride film using a film forming apparatus having a heating apparatus for heating a substrate to be processed disposed in the processing chamber,
Arranging a plurality of substrates to be processed in the processing chamber in a state of being arranged in the vertical direction in a horizontal posture, and making the processing chamber a sealed space;
Adjusting the temperature of the substrate to be processed to 850 to 930 ° C., and adjusting the pressure in the processing container to 0.5 to 1.8 Torr;
Supplying a gallium-containing gas to the processing chamber via the gallium-containing gas introduction member;
A step of supplying a nitrogen-containing gas to the processing chamber through the nitrogen-containing gas introduction member, and vapor-phase-growing gallium nitride on the surface of the substrate to be processed. Method.   The gallium nitride film according to claim 1, wherein the gallium-containing gas is a gallium chloride gas, the nitrogen-containing gas is a hydride gas containing nitrogen, and the gallium nitride film is formed by HVPE. Method.   The method for forming a gallium nitride film according to claim 2, wherein the hydride gas containing nitrogen is ammonia.   4. The gallium nitride film according to claim 1, wherein the plurality of substrates to be processed are inserted into the processing chamber in a state of being held by a substrate holding member made of quartz. 5. The film forming method.   The method for forming a gallium nitride film according to any one of claims 1 to 4, wherein the substrate to be processed is a sapphire substrate.   After repeating the film formation of the gallium nitride film a predetermined number of times, a chlorine-containing gas is introduced into the processing chamber via the gallium-containing gas introduction member and the nitrogen-containing gas introduction member, and the gallium-containing gas introduction member, the nitrogen The method for forming a gallium nitride film according to claim 1, further comprising a step of cleaning the contained gas introduction member and the processing container. A processing chamber made of quartz, in which a processing chamber is defined, and a plurality of substrates to be processed are arranged in a state of being arranged vertically in a horizontal posture;
A gallium-containing gas introduction member made of quartz for introducing a gallium-containing gas into the processing chamber;
A nitrogen-containing gas introduction member made of quartz for introducing a nitrogen-containing gas into the processing chamber;
The gallium-containing gas is supplied to the processing chamber via the gallium-containing gas introducing member, the nitrogen-containing gas is supplied to the processing chamber via the nitrogen-containing gas introducing member, and a purge gas is supplied to the processing chamber. A gas supply mechanism;
An exhaust section for exhausting the processing chamber;
An exhaust device for exhausting the processing chamber through the exhaust unit;
A heating device for heating the substrate to be processed disposed in the processing chamber;
The supply amount of the gallium-containing gas and the nitrogen-containing gas to the processing chamber is controlled so that the temperature of the substrate to be processed is 850 to 930 ° C. and the pressure in the processing container is 0.5 to 1.8 Torr. And a control unit that controls the gas supply mechanism, the exhaust device, and the heating device so that the gallium nitride film is vapor-phase grown on the substrate to be processed. apparatus.   The gallium nitride film according to claim 7, wherein the gallium-containing gas is a gallium chloride gas, the nitrogen-containing gas is a hydride gas containing nitrogen, and the gallium nitride film is formed by HVPE. apparatus.   The gallium nitride film forming apparatus according to claim 8, wherein the hydride gas containing nitrogen is ammonia.   10. The gallium nitride film according to claim 7, wherein the plurality of substrates to be processed are inserted into the processing chamber in a state of being held by a substrate holding member made of quartz. 11. Film forming equipment.   A cleaning gas supply for introducing a chlorine-containing gas into the processing chamber via the gallium-containing gas introducing member and the nitrogen-containing gas introducing member, and cleaning the gallium-containing gas introducing member, the nitrogen-containing gas introducing member, and the processing container. The gallium nitride film deposition apparatus according to claim 7, further comprising a mechanism. The gallium-containing gas introduction member includes a gas diffusion space formed over the height direction of the processing chamber, and a plurality of gallium-containing gas discharges toward the processing chamber along the height direction of the diffusion space. A plurality of gas discharge holes, and a plurality of gallium-containing gas introduction pipes connected in the height direction of the gas diffusion space and extending in the horizontal direction,
The nitrogen-containing gas introduction member is inserted below the processing chamber, extends to an upper portion of the processing chamber, and has a plurality of gas discharge holes for discharging nitrogen-containing gas toward the plurality of substrates to be processed. The apparatus for forming a gallium nitride film according to any one of claims 7 to 11, further comprising an introduction pipe.