JP2017076561A - Induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating device that can inductively heat plural coils with one power source and contributes to uniformity of the power distribution of all the coils.SOLUTION: Two coils 51 and 52 are individually arranged in coil arrangement areas A1 and A2 partitioned along an axial direction H of a vacuum container 4 on the outside of the vacuum container 4. As an induction heating power source 6 is applied a high-frequency power source for supplying power from a common current type inverter to a parallel resonance series connection circuit in which two parallel resonance circuits are mutually connected to each other in series, the parallel resonance circuit including resonance capacitors connected in parallel for each of heating coils 51, 52 which are arranged individually in respective coil arrangement areas A1, A2. The respective resonance frequencies of the parallel resonance circuits are set to different values, and the drive frequency is changed, whereby the current ratio of each induction heating coil 51, 52 in the parallel resonance series connection circuit can be changed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an induction heating apparatus capable of induction heating an object to be heated by an energized induction heating coil.

  An induction heating apparatus that can heat an object to be heated by energizing an induction heating coil is heated to a predetermined processing temperature as compared with a heating apparatus that uses a general heating wire type heater as a heating source. It is possible to shorten the heating process (high temperature in a short time), and it is used in various fields.

  For example, in a process of manufacturing a semiconductor in which a semiconductor single crystal is formed on a material wafer, recently, a susceptor is disposed in a vacuum container that can be sealed in an airtight state, and a high frequency current is applied to the induction heating coil. An induction heating device configured to heat the susceptor is used. According to such a semiconductor induction heating apparatus, the wafer placed on the susceptor is also heated, and a thin film with a precisely controlled thickness and impurity concentration can be formed on the surface of the wafer. Manufactures silicon carbide (SiC) semiconductors that are attracting attention as devices that can realize small and low-loss semiconductor devices that surpass silicon (Si) semiconductors due to their excellent physical and chemical properties. In this case, a processing temperature up to about 1800 ° C. is necessary, and an apparatus using a heating wire type heater whose processing temperature is limited to about 1200 ° C. at the maximum cannot be applied.

  When manufacturing semiconductors with induction heating equipment that can increase the temperature in such a short time, batch processing is possible by arranging multiple susceptors in multiple stages in a vacuum vessel in order to improve processing efficiency. The constructed induction heating apparatus has also been put into practical use. For example, as shown in FIG. 7, a common induction heating coil 5 (identical from the outside of the vacuum vessel 4 is formed over the entire region in which at least the susceptor 2 (the table on which the wafer W is placed) is arranged in the internal space 4 </ b> S of the vacuum vessel 4. In the area A where the induction heating coil 5 is arranged outside the vacuum vessel 4, the longitudinal direction H of the vacuum vessel 4 (the direction in which the susceptors 5 are arranged) The induction heating coil 5 in which the electric power of the induction heating coil 5 arranged in the central portion and the area in the vicinity thereof is arranged in the areas of both ends in the longitudinal direction (upper and lower ends in the illustrated example) of the vacuum vessel 4. It tends to be relatively higher than the power of 5. In the figure, the arrangement area A of the induction heating coil 5 extending in the longitudinal direction H (axial direction) of the vacuum vessel 4 is arranged in plural (8 in the illustrated example) arrangement area units in the longitudinal direction H of the vacuum vessel 5. When it is assumed that it is divided into Aa, the configuration in which the induction heating coil 5 common to all the arrangement area units Aa is arranged is schematically shown.

  Further, as shown in the figure, an air supply port 41 and an exhaust port 42 for gas G (carrier gas, silicon raw material gas, carbon raw material gas, etc.) are formed at the lower end of the vacuum vessel 4 and supplied from the air supply port 41. In the case where the gas G flowing upward in the vacuum vessel 4S is discharged from the exhaust port 42, when attention is paid to the heat removal in the vacuum vessel 4S, the heat removal amount is the center in the longitudinal direction of the vacuum vessel 4. Since there are relatively many lower ends of the vacuum vessel 4 in which the air supply port 41 and the exhaust port 42 are formed, the temperature distribution in the vacuum vessel 4S also tends to be lower at the lower end in the longitudinal direction than the other portions. Has been confirmed.

  If the heating state of each susceptor cannot be made uniform during the heat treatment by the induction heating device due to the uneven power distribution of the induction heating coil, the processing for each wafer on the susceptor arranged in multiple stages will vary. As a result, the highly uniform processing (thin film formation processing) required for all wafers cannot be performed, and sufficient quality cannot be ensured.

  Therefore, the winding state of the induction heating coil at the central portion in the longitudinal direction of the vacuum vessel is set more densely than the winding state of the induction heating coil at both longitudinal ends of the vacuum vessel, and uniform heating and leveling of the temperature distribution are performed. A configuration has been devised. In this case, it is required to set the density of the wound state with high accuracy.

  There is also known a configuration in which the induction heating coil is divided into a plurality of parts, a dedicated power source is provided for each induction heating coil, and each power source is individually controlled to equalize the temperature and level the temperature distribution. . Since such a configuration requires a plurality of power sources, in addition to incurring high costs, there is a linkage magnetic flux between adjacent induction heating coils, and other adverse effects are adversely affected. Control is required.

  In addition, as an induction heating apparatus that heats a plurality of induction heating coils using a single power source, Japanese Patent Application Laid-Open No. 2004-26883 discloses an induction heating cooker (so-called IH heater) in which an induction heating coil and a resonant capacitor are connected in series. A configuration in which two series resonant circuits are connected in parallel to the same inverter circuit is disclosed. The inverter to which the series resonant circuit is connected is a voltage type inverter that converts a constant voltage into an alternating current.

  Thus, the structure which arrange | positions the "voltage type series resonance circuit" connected to the voltage type inverter in parallel can be used suitably for the induction heating cooking appliance whose power capacity is about 10 kW.

JP 2012-124081 A (Patent No. 5605198)

  However, for example, when a configuration in which a voltage-type series resonance circuit arranged in parallel is connected to the same voltage-type inverter as a large-capacity power source exceeding 1000 kW, switching elements and diodes constituting the voltage-type inverter are large. A snubber circuit is usually installed in parallel to absorb the turn-off loss of the element, but the snubber circuit loss increases and does not employ an extremely complicated circuit configuration. As long as it does not function as a power source, the function is greatly reduced and the entire system (the entire induction heating apparatus) is adversely affected. In addition, when adopting a configuration in which voltage type series resonance circuits arranged in parallel are connected to the same voltage type inverter, in addition to the above-mentioned turn-off loss, in order to match the matching between the power source and the load coil, usually a transformer Insert a transformer or current transformer between them. This is a countermeasure against a large current on the load coil side flowing directly to the power source side because the voltage type inverter is a series resonance system. That is, if it flows directly to the element in the inverter, an element having a large current capacity must be prepared, but usually a large current flows to the secondary side of the transformer installed between the inverter and the resonance circuit. For this reason, in the case of voltage-type series resonance, a device with a large current capacity is required in any case.

  Furthermore, the elements constituting the voltage type series resonance circuit are limited to self-extinguishing elements. In an induction heating device that requires a voltage-type series resonance circuit subject to such restrictions, in order to achieve a configuration that can handle a large capacity exceeding 1000 kW, the cost must be significantly increased and the circuit configuration must be complicated and customized. Inevitable.

  The above-mentioned problems are not limited to a device that induction-heats a plurality of susceptors arranged in a vacuum vessel, but are wound around the outside of a cylindrical partition that partitions an internal space extending in a predetermined axial direction from other spaces. This similarly occurs even in an induction heating apparatus capable of induction heating an object to be heated arranged in the internal space by the arranged induction heating coil.

  The present invention has been made paying attention to such points, and the main object is to be able to induction-heat a plurality of induction heating coils with a single power source, and further along a predetermined axial direction. It is an object of the present invention to provide an induction heating apparatus capable of adjusting the power distribution of the entire induction heating coil arranged and the temperature distribution of the space in which the object to be heated is arranged.

  That is, the present invention is a cylindrical shape that partitions one induction heating power source capable of outputting alternating-current power of an arbitrary frequency to the induction heating coil, and one internal space extending in the axial direction where an object to be heated can be arranged, from another space. The present invention relates to an induction heating apparatus capable of heating an object to be heated by induction heating by applying a high-frequency current to the partition wall and an induction heating coil arranged in a wound state outside the partition wall. Here, the “tubular partition” in the present invention includes both a cylindrical partition and a rectangular tubular partition. Further, the internal space partitioned from the other space by the cylindrical partition wall may be a space in which both ends along the single axial direction communicate with the other space (a space through the cylinder), or a single space. Only one end along the axial direction may communicate with the other space, and the other end may be a space not communicating with the other space, or a space where both ends in the axial direction are closed. . The number of objects to be heated that can be arranged in the internal space in the present invention may be one or plural.

  And the induction heating apparatus which concerns on this invention divides the coil arrangement | positioning area in the outer side of a partition along an axial direction, arrange | positions at least two induction heating coils separately in mutually different coil arrangement | positioning areas, and uses it as an induction heating power supply. A current conversion inverter configured using a forward conversion circuit that converts an output current from an alternating current power source into a direct current, and an inverse conversion circuit that converts an output current from the forward conversion circuit into an alternating current using a switching element, and at least two Applying at least two parallel resonance circuits in which resonance capacitors are individually connected in parallel to the induction heating coil in series, and a parallel resonance series connection circuit to which AC power is supplied from a current type inverter; Set the resonant frequency of each parallel resonant circuit to a different value and set the drive frequency, which is the frequency of the AC power output from the induction heating power supply. It is characterized in that it is capable of changing the current ratio of the induction heating coil by reduction.

  In the induction heating apparatus according to the present invention, the current-type parallel resonance method is adopted for the induction heating coils connected in parallel to the resonance capacitors in at least two parallel resonance circuits constituting a common parallel resonance series connection circuit. Compared with a configuration in which a dedicated power source is provided for each of the plurality of induction heating coils, and each power source is individually controlled, because a high-frequency current can be applied from one induction heating power source and the object to be heated can be heated by induction heating. Thus, complicated control for each power source is not required, and cost increase can be avoided. In addition, in the induction heating device according to the present invention, a current type is connected to a parallel resonance series connection circuit in which at least two induction resonance coils are connected in series with at least two parallel resonance circuits in which resonance capacitors are individually connected in parallel. Since a current-type parallel resonance induction heating power supply that supplies power from an inverter is applied, a voltage-type series power supply in which multiple voltage-type series resonance circuits arranged in parallel are connected to the same voltage-type inverter. Compared with the applied configuration, the switching elements constituting the inverter circuit are not limited to self-extinguishing elements, and it is possible to use non-self-extinguishing elements and reduce switching loss. Can handle large capacity exceeding 1000 kW (for example, 2000 kW to 3000 kW) without being forced to design a complicated circuit configuration. It is a function.

  In the induction heating apparatus according to the present invention, the resonance frequency of each parallel resonance circuit is set to a different value, and the current of each induction heating coil is changed by changing the drive frequency that is the frequency of the AC power output from the induction heating power supply. Since the ratio can be changed, the arrangement area of the induction heating coil divided along the predetermined axial direction can be changed depending on the area in the power distribution, temperature distribution, etc. By controlling the current ratio of the induction heating coils placed individually in the area, the power distribution of the entire induction heating coil placed outside the partition wall can be adjusted, and the temperature distribution of the space where the object to be heated is placed can be adjusted Is possible. As a result, the power distribution of the entire induction heating coil arranged outside the partition wall can be made uniform, and the temperature distribution of the space where the object to be heated is arranged can be leveled. In addition, if it is the induction heating apparatus which concerns on this invention, as above-mentioned, the electric power of the whole induction heating coil arrange | positioned outside a partition by controlling the current ratio of the induction heating coil arrange | positioned separately in each arrangement | positioning area. Since the distribution can be adjusted and the temperature distribution in the space where the object to be heated is arranged can be adjusted, the power distribution of the entire induction heating coil arranged outside the partition wall can be made uneven, Non-leveling of the temperature distribution in the space where the heated object is arranged can also be achieved. In particular, depending on the location of the object to be heated in the space partitioned by the partition wall, the processing content of the object to be heated, etc., the power distribution of the induction heating coil as a whole and the temperature distribution of the space in which the object to be heated are arranged are different. It may be advantageous to ensure a certain state. In the present invention, a configuration in which at least two induction heating coils are individually arranged in mutually different coil arrangement areas is adopted. For example, the arrangement area of the induction heating coils is set to any arbitrary number of three or more along a predetermined axial direction. By dividing the number into different numbers, placing separate induction heating coils in three or more coil placement areas, and setting the resonance frequency of each parallel resonance circuit configured using each induction heating coil to a different value from each other It is also possible to change the current ratio of three or more induction heating coils by changing the drive frequency.

  In addition, as an arrangement area of the induction heating coil suitable for the present invention, for example, when one induction heating coil is arranged along the axial direction (direction in which the internal space extends) outside the cylindrical partition wall, induction is performed. Arrangement area divided along the axial direction according to the area where the power of the heating coil is relatively high and the area where it is relatively low, and the area where the temperature of the internal space is relatively high and the area where it is relatively low The arrangement area divided along the axial direction can be given. If at least two induction heating coils are individually arranged in mutually different arrangement areas, the power distribution of the entire induction heating coil arranged outside the cylindrical partition wall is adjusted, and the space in which the object to be heated is arranged It is possible to adjust the temperature distribution. Specifically, the current ratio of the induction heating coil disposed in the area corresponding to the area where the power of the induction heating coil is relatively low or the temperature of the internal space is relatively low is determined by the power of the induction heating coil. By changing the drive frequency so as to be larger than the current ratio of the induction heating coil arranged in the relatively high area or the arrangement area corresponding to the area where the temperature of the internal space is relatively high, the entire induction heating coil It is possible to make the power distribution uniform and level the temperature distribution of the space where the object to be heated is arranged.

Further, in the present invention, the current flowing in the induction heating coil arranged in the area corresponding to the area where the power of the induction heating coil is relatively low or the temperature of the internal space is relatively low, The induction heating coil as a whole by changing the drive frequency so that it is smaller than the current flowing in the induction heating coil arranged in the relatively high area or in the arrangement area corresponding to the area where the internal space temperature is relatively high It is also possible to deliberately generate variations (level differences) in the power distribution and the temperature distribution of the space in which the object to be heated is arranged. Furthermore, in the present invention, the current flowing through the induction heating coil arranged in the area corresponding to the area where the power of the induction heating coil is relatively low or the temperature of the internal space is relatively low, The time period during which the drive frequency is changed to be smaller than the current flowing in the induction heating coil placed in the placement area corresponding to the relatively high power area or the area where the internal space temperature is relatively high, and induction The current flowing in the induction heating coil arranged in the area corresponding to the area where the power of the heating coil is relatively low or the temperature of the internal space is relatively low, the area where the power of the induction heating coil is relatively high The drive frequency is changed so that the current flows through the induction heating coil arranged in the arrangement area corresponding to the area where the temperature of the internal space is relatively high. By intentionally distinguishing and controlling the time zone, the power zone of the induction heating coil as a whole and the temperature distribution of the space where the object to be heated are distributed (the difference in height) and the entire induction heating coil It is also possible to secure a time zone for equalizing the power distribution and leveling the temperature distribution of the space in which the object to be heated is arranged.

  In the induction heating device according to the present invention, the induction heating coil that can cover the internal space surrounded by the partition wall is divided along the axial direction from the outside of the partition wall that extends in a predetermined axial direction to form a cylindrical shape. Dividing into a plurality of induction heating coils arranged separately in the coil arrangement area, and connecting at least two parallel resonance circuits in which a resonance capacitor is connected in parallel to each induction heating coil in series with the same current type inverter circuit, By setting the resonance frequency of each parallel resonance circuit to a different value and changing the drive frequency to change the current ratio of each induction heating coil, without complicating the circuit configuration, It is possible to increase the capacity of the power source that can supply power to the plurality of divided induction heating coils, adjust the power distribution of the induction heating coil, The temperature distribution of the space to be placed can be adjusted, and the object to be heated is uniformly heated by the entire coil arranged along the predetermined axial direction, or only a specific part of the object to be heated is more aggressive than the other parts. It is possible to provide an induction heating apparatus that can be heated in a state where the temperature is increased.

The typical sectional view of the induction heating device concerning one embodiment of the present invention. The figure which shows typically the relative positional relationship of the susceptor and wafer in the embodiment. The circuit diagram which shows typically the induction heating power supply in the embodiment. The figure which shows typically the change of the current ratio of each induction heating coil by the change of the frequency in the same embodiment. The figure which shows the induction heating apparatus which concerns on one Embodiment of this invention corresponding to FIG. The typical sectional view of the billet heater concerning one embodiment of the present invention. A typical sectional view of a known induction heating device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the induction heating apparatus 1 according to this embodiment includes a susceptor 2 on which a wafer W can be placed, a boat 3 that supports a plurality of susceptors 2 arranged in multiple stages, a susceptor 2, and a boat. 3 can be accommodated in the internal space 4S, an excellent heat resistance vacuum vessel 4, an induction heating coil 5 wound around the vacuum vessel 4, and an AC power of any frequency can be output to the induction heating coil 5. And an induction heating power source 6.

  The susceptor 2 is a carbon susceptor formed from graphite, which is a refractory metal material having a melting point higher than the maximum temperature during induction heat treatment. This susceptor 2 is an object to be heated in the present invention. In this embodiment, the disk-shaped susceptor 2 set to a predetermined thickness is arranged in a horizontal posture. In the present embodiment, the susceptor 2 is made of an anisotropic graphite sheet having a large thermal conductivity in the plane direction (for example, the thermal conductivity in the plane direction is 200 W / m · K or more and the conductivity in the plane direction is 1000 S / cm or more). Is forming. In the present embodiment, the susceptor 2 having a thermal conductivity in the thickness direction of 50 W / m · K or less and an electrical conductivity in the thickness direction of 50 S / cm or less is applied. The susceptor 2 of the present embodiment is formed by stacking a plurality of anisotropic graphite sheets having a large thermal conductivity in such a plane direction. Thereby, the surface of the susceptor 2 can be heated more uniformly. Note that FIG. 1 and FIG. 2 described later show the entire susceptor 2 in which a plurality of graphite sheets are formed in a laminated form, and each graphite sheet is omitted.

  As shown in FIG. 2, the disk-shaped susceptor 2 applied in this embodiment has a radius larger than the radius of the disk-shaped wafer W placed on the susceptor 2 by a predetermined dimension L shown in FIG. It is set. In this embodiment, the value of L is larger than the penetration depth (hereinafter referred to as “penetration depth δ”) generated in the susceptor 2 by the induction heating coil 5 (for example, 1.5 times the penetration depth δ). To 2.0 times).

Here, with respect to the penetration depth, the relationship between the current flowing inside the conductor (heating body) in the portion x from the surface and the penetration depth is:
Ix = Io exp (−x / δ)
However, Ix: current at the depth x from the surface, Io: eddy current flowing through the surface of the conductor, and δ: penetration depth. Therefore, the current flowing at the penetration depth δ is 1 / e = 0.37, and a current attenuated 0.37 times the current flowing on the surface flows. This relationship is the same for magnetic fields.

  Further, the relationship between the frequency f and the penetration depth δ can be expressed by the following formula 1.

  As described above, the susceptor 2 of the present embodiment has a surface conductivity of 1000 S / cm or more and a resistivity of 1000 μ. Since Ω · cm, from Equation 1, if the frequency is 20 kHz, the penetration depth δ is 1.12 cm. This means that when the frequency is 20 kHz, a large amount of magnetic flux enters the region from the outer edge 2E of the susceptor 2 to 1.12 cm toward the center 2S, and that portion is induction-heated. Therefore, the magnetic flux generated from the induction heating coil 5 generates an eddy current in a predetermined region from the edge 2E of the susceptor 2 toward the center 2S and corresponding to the penetration depth δ (region 2A in FIG. 2). The susceptor 2 is heated by Joule loss. From the above, it can be understood that in the susceptor 2, the heating power enters (passes) in the edge vicinity region 2A including the edge 2E.

  In the induction heating apparatus 1 of the present embodiment, such a susceptor 2 is arranged with its center 2S aligned with the center of the vacuum vessel 4, more specifically, the axial center of the internal space 4Sa of the vacuum vessel 4. doing.

  Further, the center WS is matched with the center 2S of the susceptor 2 by setting the radius of the susceptor 2 to be 1.5 to 2 times the penetration depth δ (current penetration depth δ) than the radius of the wafer W. It is possible to ensure that the magnetic flux from the induction heating coil 5 to the susceptor 2 is extremely difficult to pass through the wafer W placed on the susceptor 2 in the posture, and the wafer W is affected by the magnetic field generated from the induction heating coil 5. It is possible to prevent defects that cause damage. On the other hand, by applying the susceptor 2 configured using an anisotropic graphite material having a large thermal conductivity in the surface direction, the surface of the susceptor 2 from the edge vicinity region 2A of the susceptor 2 heated by Joule loss. Heat is transmitted toward the center of the direction (in the direction of the arrow toward the center 2S of the susceptor 2 in FIG. 2), and the susceptor 2 as a whole can be soaked. Therefore, the entire wafer W placed on the susceptor 2 can be heated, and the temperature distribution in the wafer W can be made uniform.

  The boat 3 supports a plurality of susceptors 2 arranged in multiple stages at a predetermined pitch. With such a boat 3, the susceptor 2 on which the wafers W are placed can be stacked in the inner space 4 </ b> S of the vacuum vessel 4 in a multistage manner. Although FIG. 1 schematically illustrates a boat 3 that can support ten susceptors 2, it is also possible to apply a boat that can support several tens of susceptors 2. In addition, the boat 3 and the vacuum vessel 4 can be comprised with the material which is excellent in heat resistance which can endure the process temperature of 1800 degreeC, and has insulation, for example, SiC. Further, when the processing temperature is 1200 ° C. or less, a boat made of quartz or a vacuum vessel 4 may be applied. In the present embodiment, the plurality of susceptors 2 supported by the boat 3 are arranged in an internal space (a hemispherical space 4Sb described later) in the vicinity of the ceiling wall 44 that forms a hollow partial spherical shape in the internal space 4S of the vacuum vessel 4. Is disposed in a space (cylindrical space 4Sa described later).

  The vacuum container 4 is also called a tube because it has a cylindrical shape, and is supplied from the air supply port 41 to the inside 4S of the vacuum container and flows upward (carrier gas, silicon source gas, carbon source gas). Etc.) can be discharged from the exhaust port 42. This vacuum vessel 4 has a cylindrical side wall 43 (corresponding to the “partition wall” of the present invention) that partitions the internal space 4S extending in a predetermined axial direction H (vertical direction or substantially vertical direction in this embodiment) from other spaces. And a hemispherical ceiling wall 44 continuous with the upper end of the side wall 43, and the internal space 4S is opened only downward. In the present embodiment, the air supply port 41 and the exhaust port 42 are formed in the vicinity of the lower end portion of the vacuum vessel 4.

  The internal space 4S of the vacuum vessel 4 is divided into a hollow hemispherical internal space (hemispherical space 4Sb) surrounded by the ceiling wall 44 and a hollow cylindrical internal space (cylindrical space 4Sa) surrounded by the side wall 43. It can be divided roughly. In the vacuum vessel 4 of the present embodiment, the cylindrical space 4Sa is further divided into an inner circumferential space that accommodates the susceptor 2 and the boat 3 and an outer circumferential space that extends in the height direction along the circumferential wall of the vacuum vessel 4. The inner circumferential space and the outer circumferential space are separated from each other via the hemispherical space 4Sb.

  In the present embodiment, the air supply port 41 is formed at a position that directly communicates with the inner space, and the exhaust port 42 is formed at a position that directly communicates with the outer space. Accordingly, the gas G supplied from the air supply port 41 to the inner circumferential side space of the cylindrical space 4Sa is an inner space in which the susceptor 2 and the wafer W are arranged in the cylindrical space 4Sa as shown by arrows in FIG. After passing through the circumferential space, the gas is exhausted from the exhaust port 42 through the outer circumferential space of the cylindrical space 4Sa. That is, the inner circumferential space functions as a gas supply target space to which the gas G is supplied, and the outer circumferential space functions as an exhaust path that is evacuated through the exhaust port 42. Further, the gas supply rate of the gas G passing through the space (cylindrical space 4Sa, heating chamber) in which the susceptor 2 and the wafer W are arranged is adjusted in the supply port 41 by adjusting the supply amount of the gas G to the vacuum vessel 4S. An adjustable gas supply control valve (not shown) is connected, and a pressure adjusting valve (not shown) capable of adjusting the pressure in the vacuum vessel 4S is connected to the exhaust port 42, and a pressure (not shown) connected to each of these valves. Each valve is controlled by the adjusting device to adjust the pressure in the vacuum vessel 4S to a predetermined value. As the vacuum container 4, a water-cooled double structure can be applied.

  As shown in FIG. 1, the induction heating coil 5 is wound around the vacuum vessel 4 at a position away from the side wall 43 by a predetermined distance outside the side wall 43 of the vacuum vessel 4. In the present embodiment, the arrangement area A of the induction heating coil 5 outside the side wall 43 is divided along the axial direction H into a first coil arrangement area A1 and a second coil arrangement area A2, and the induction heating coil 5 is divided into the first The structure divided | segmented into the 1st induction heating coil 51 arrange | positioned in coil arrangement | positioning area A1 and the 2nd induction heating coil 52 arrange | positioned in 2nd coil arrangement | positioning area A2 is employ | adopted. Specifically, the first induction heating coil 51 is arranged in the first coil arrangement area A1 set at a position surrounding the upper and lower ends in the longitudinal direction of the cylindrical space 4Sa, and the longitudinal center of the cylindrical space 4Sa is arranged. The second induction heating coil 52 is arranged in the second coil arrangement area A2 set at a position surrounding the. In FIG. 1, the first coil arrangement area A1 and the second coil arrangement area A2 are shown with mutually different patterns, a portion of the first induction heating coil 51 that is not in a wound state, and the second induction heating. Each portion of the coil 52 that is not in a wound state is a straight line (a relatively thick line is a line indicating the first induction heating coil 51, and a relatively thin line is a line indicating the second induction heating coil 52). This is shown schematically. As can be understood from FIG. 1, the first coil arrangement area A <b> 1 and the second coil arrangement area A <b> 2 are supplied with AC power from a common AC power source 6.

  In FIG. 1, the arrangement area A of the induction heating coil 5 extending in the axial direction H of the vacuum vessel 4 is divided into a plurality of (eight in the illustrated example) arrangement area units Aa in the longitudinal direction of the vacuum vessel 4. In this case, a plurality of arrangement area units Aa (four arrangement area units Aa in the illustrated example) corresponding to the central portion in the longitudinal direction of the cylindrical space 4Sa and its vicinity are set as the second coil arrangement area A2, and the cylinder A plurality of arrangement area units Aa (two arrangement area units Aa in the illustrated example) corresponding to the upper end side in the longitudinal direction of the cylindrical space 4Sa and a plurality of arrangement area units Aa corresponding to the lower end side in the longitudinal direction of the cylindrical space 4Sa (see FIG. In the illustrated example, a case where two arrangement area units Aa) are set as the first coil arrangement area A1 is schematically shown.

  Moreover, the 1st induction heating coil 51 and the 2nd induction heating coil 52 can be grasped | ascertained as the aggregate | assembly of the several coil unit each wound predetermined times and formed in the predetermined cylinder shape. In this case, if a layout in which one coil unit is arranged in one arrangement area unit Aa is adopted, the arrangement location of each coil unit can be easily specified.

  Moreover, in the induction heating apparatus 1 which concerns on this embodiment, the appropriate process that a magnetic coupling of each induction heating coil 51 and 52 weakens is required.

  The first induction heating coil 51 and the second induction heating coil 52 wound in a solenoid shape are connected to a common induction heating power source 6 (high frequency power source) that can output AC power of an arbitrary frequency (driving frequency). An alternating magnetic field is generated around the first induction heating coil 51 and the second induction heating coil 52 by supplying AC power from the induction heating power source 6 to the first induction heating coil 51 and the second induction heating coil 52. Then, this alternating magnetic field is caused to penetrate the susceptor 2 that is a permeation target, and induction heating is performed. In addition, in the induction heating apparatus 1 of this embodiment, the heat insulating material (illustration omitted) which can exhibit the function which interrupts | blocks so that the heat | fever emitted from the susceptor 2 heated with the induction heating coil 5 may not leak outside the vacuum vessel 4 is shown. ) Can be arranged at an appropriate place. Examples of the heat insulating material include those formed of a material having conductivity and heat resistance and having a volume specific resistivity sufficiently higher than that of the susceptor 2 that is a heating element. The heat insulating material and the susceptor 2 may be set in an electrically insulated state by appropriate means.

  The induction heating power source 6 can appropriately change the frequency (drive frequency) of AC power supplied to the first induction heating coil 51 and the second induction heating coil 52. As shown in FIG. 3, the induction heating apparatus 1 according to the present embodiment forms an induction heating power source 6 using a current type inverter 61 and a parallel resonance series connection circuit 62 described later.

  The current type inverter 61 uses a forward conversion circuit 63 that converts three-phase AC power output from an AC power source into DC power, and an inverse conversion circuit 64 that converts an output voltage from the forward conversion circuit 63 into AC power. It is composed.

  In the present embodiment, the forward conversion circuit 63 is configured by using a plurality of rectifying elements 631 (for example, thyristors) and a coil 632 (inductance), and the DC power converted from AC power by the rectifying element 631 is the coil 632 ( It is set to be a constant direct current by filtering by (inductance). Note that the coil 632 of the forward conversion circuit 63 may be a simple coil, or may be a static winding device serving as an inductance element of an electric circuit, that is, a so-called reactor.

  The inverse conversion circuit 64 is configured by using a plurality of transistors 641 which are switching elements, and converts DC power output from the forward conversion circuit 63 into AC power by the transistors 641, and is also referred to as an inverter circuit. It is. The inverse conversion circuit 64 of the present embodiment employs a circuit in which a plurality of series connection circuit units in which a plurality of transistors 641 (switching elements) are connected in series are connected in parallel. The transistor used as the switching element is any switching element such as a self-extinguishing type such as a bipolar transistor, a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), or a thyristor that is not a self-extinguishing type. Also good.

  A parallel resonant series connection circuit 62 is connected to the output side of the inverse conversion circuit 64. As shown in FIG. 3, the parallel resonant series connection circuit 62 includes a first parallel resonant circuit 65 in which a first resonant capacitor C1 and a first induction heating coil 51 are connected in parallel, a second resonant capacitor C2, and a second induction heating. This is a circuit in which second parallel resonant circuits 66 having coils 52 connected in parallel are connected in series.

  In the present embodiment, the first induction heating coil 51 (inductance L1, resistance R1 shown in FIG. 3 corresponds to the first induction heating coil 51) and the first induction heating coil 51 are connected in parallel as described above. A first parallel resonance circuit 65 is constituted by the first resonance capacitor C1 and a second induction heating coil 52 (inductance L2 and resistance R2 shown in the figure corresponds to the second induction heating coil 52) as a load. A second parallel resonance circuit 66 is constituted by the second resonance capacitor C2 connected in parallel to the second induction heating coil 52. Each resonance capacitor (the first resonance capacitor C1 and the second resonance capacitor C2) functions as a matching unit for matching impedance.

  As shown in FIG. 3, the induction heating power source 6 of the present embodiment is reversely connected to a parallel resonance series connection circuit 62 in which the parallel resonance circuits (the first parallel resonance circuit 65 and the second parallel resonance circuit 66) are connected in series with each other. The output side of the conversion circuit 64 is connected, and AC power generated from DC power by the inverse conversion circuit 64 is supplied to the parallel resonant series connection circuit 62. That is, each parallel resonance circuit (first parallel resonance circuit 65, second parallel resonance circuit 66) in the induction heating power source 6 of the present embodiment is combined and then becomes a load of the current type inverter 61, and becomes a current type parallel resonance circuit. Configure.

  In the induction heating apparatus 1 of the present embodiment, the resonance frequencies of the first parallel resonance circuit 65 and the second parallel resonance circuit 66 connected in series with each other are set to values that differ from each other (for example, a difference of about 1 kHz). The drive frequency (operating frequency) is adjusted by adjusting the current-type parallel resonance type induction heating power supply 6 so that the impedances of the parallel resonance circuits (the first parallel resonance circuit 65 and the second parallel resonance circuit 66) overlap each other to some extent. As a variable, the current ratio between the first induction heating coil 51 and the second induction heating coil 52 (relative ratio between “I1” and “I2” shown in FIG. 3) is controllable. Here, FIG. 4 schematically shows changes in the current ratio of the induction heating coils 51 and 52 due to changes in frequency. From this figure, it can be understood that the current ratio between the induction heating coils 51 and 52 changes by changing the drive frequency. In the present embodiment, for example, the first induction is performed such that the power factor is changed within a predetermined range so that the current of the first induction heating coil 51 is larger than the current of the second induction heating coil 52. The current ratio between the heating coil 51 and the second induction heating coil 52 is controlled.

  In this embodiment, since the two induction heating coils 5 (the first induction heating coil 51 and the second induction heating coil 52) that are not electromagnetically coupled to each other are operated at a resonance frequency of, for example, about 20 kHz, the capacitance is 1 μF. A first resonance capacitor C1 having a capacitance of about 4 μF and a second resonance capacitor C2 having a capacitance of about 4 μF are connected in parallel to the first induction heating coil 51 and the second induction heating coil 52, respectively, and are operated by the constant current inverter 61. .

  Next, the procedure and operation for supplying AC power to the induction heating coil 5 (the first induction heating coil 51 and the second induction heating coil 52) by the induction heating power source 6 having such a configuration will be described.

  In the induction heating power source 6 according to this embodiment, when AC power is output from the AC power source to the forward conversion circuit 63, the forward conversion circuit 63 converts the AC power into DC power by the plurality of rectifier elements 631, and then A constant direct current is obtained by filtering with the coil 632 (inductance). Next, the induction heating power source 6 of the present embodiment outputs the DC power smoothed from the forward conversion circuit 63 to the inverse conversion circuit 64, and the inverse conversion circuit 64 performs on / off control of the transistor 641 (switching element 641). To convert DC power into AC power. Specifically, such DC / AC conversion is performed immediately before the voltage of the resonance capacitors (the first resonance capacitor C1 and the second resonance capacitor C2) constituting the matching unit becomes zero, and switching other than being conducted at that time. When the element 641 is turned on (ignited), all the elements are in a conducting state, and a path for short-circuiting the voltages of the resonance capacitors (the first resonance capacitor C1 and the second resonance capacitor C2) is generated. The switching element 641 has a current of zero, and the ignited switching element 641 increases to a constant current value, and the current path changes. This current reversal action (commutation) is performed by detecting the voltage of the resonance capacitors (first resonance capacitor C1, second resonance capacitor C2), that is, the inverter output voltage, thereby causing each parallel resonance circuit (first parallel resonance circuit 65, It will operate at the resonant frequency of the second parallel resonant circuit 66). Due to this characteristic, even a thyristor that is not self-extinguishing can be operated as an inverter and can be used as a large-current power source.

  In this way, the induction heating power source 6 of the present embodiment is configured such that the direct current is rectangular (rectangular wave) by controlling the transistor 641 (switching element 641) of the inverse conversion circuit 64 in the current type inverter 61. Convert to AC current. The output voltage of the current type inverter 61 has a sinusoidal waveform and operates at the same phase as the output current of the current type inverter 61.

  Subsequently, in the induction heating power supply 6 of the present embodiment, the alternating current (“I” shown in FIG. 3) generated by the inverse conversion circuit 64 causes the first parallel resonance circuit 65 and the second parallel resonance circuit 66 to be in series with each other. By being input to the connected parallel resonance series connection circuit 62 and resonating, an alternating current having a substantially sinusoidal shape is generated in each parallel resonance circuit (the first parallel resonance circuit 65 and the second parallel resonance circuit 66).

  Through the above procedure, when AC power is supplied from the induction heating power source 6 to each induction heating coil 51, 52, the susceptor 2 disposed in the vacuum vessel 4 can be induction heated by each induction heating coil 51, 52. it can.

  Although not shown, the induction heating apparatus 1 of the present embodiment is configured such that the first induction heating coil 51 and the second induction are based on the temperature measured by one or more thermometers that measure the internal temperature of the vacuum vessel 4. It can also be configured to control the output and current ratio of the heating coil 52.

  The induction heating apparatus 1 of the present embodiment having the above-described configuration is a hot wall type CVD (Chemical Vapor Deposition) for heating the entire reaction chamber by causing the internal space 4S of the vacuum vessel 4 to function as a reaction chamber. , An epitaxial apparatus, a heat treatment apparatus such as annealing.

  The induction heating apparatus 1 according to the present embodiment supplies AC power from the induction heating power source 6 to the induction heating coils 51 and 52 in a state where the susceptor 2 on which the wafer W is mounted is supported in a multistage manner by the boat 3. By doing so, an alternating magnetic field is generated around the induction heating coil 5, and this alternating magnetic field penetrates into the susceptor 2 made of graphite and induction-heats the susceptor 2. Note that the induction heating coil 5 (the first induction heating coil 51, the second induction heating, etc.) has a configuration in which the heat insulating material is disposed in the vacuum vessel 4S and closer to the peripheral wall side of the vacuum vessel 4 than the susceptor 2. The alternating magnetic field generated around the coil 52) penetrates the susceptor 2 through the heat insulating material.

  The induction heating apparatus 1 according to the present embodiment has a shorter processing time for raising the temperature to a predetermined processing temperature, which is a merit of the induction heating method, compared to a configuration employing a heating method other than induction heating. It is possible to increase the temperature and contribute to shortening the entire processing time. In particular, according to the induction heating apparatus 1 according to this embodiment that employs a configuration in which a plurality of susceptors 2 are arranged in a multistage manner in the vacuum vessel 4S, batch processing that simultaneously performs processing on a plurality of wafers W is performed. Therefore, the processing efficiency can be further improved.

  Further, for example, in the case of a configuration in which one induction heating coil 5 is wound around the entire outside of the vacuum vessel 4 (see, for example, FIG. 7), in the heating state in which AC power is supplied to the induction heating coil 5, the induction heating coil Focusing on the tendency that the power distribution of 5 is higher in the longitudinal center of the cylindrical space 4Sa than in the longitudinal upper end and the lower end of the cylindrical space 4Sa, as described above, the induction heating according to the present embodiment In the apparatus 1, the arrangement area of the first induction heating coil 51 is set to the first coil arrangement area A1 that surrounds the upper and lower ends in the longitudinal direction of the cylindrical space 4Sa outside the vacuum vessel 4, and the second induction heating is performed. The arrangement area of the coil 52 is set to a second coil arrangement area A2 that surrounds the central portion in the longitudinal direction of the cylindrical space 4Sa outside the vacuum vessel 4.

  And in the induction heating apparatus 1 which concerns on this embodiment, the alternating current output from the induction heating power supply 6 so that the coil current which flows into the 1st induction heating coil 51 becomes larger than the coil current which flows into the 2nd induction heating coil 52. By controlling the current ratio between the induction heating coils 51 and 52 using the power drive frequency as a variable, the power distribution of the induction heating coil 5 as a whole can be made uniform or substantially uniform. In this way, by controlling the current ratio of the plurality of induction heating coils 51 and 52 by one induction heating power source 6 which is a high frequency power source, the plurality of induction heating coils 51 and 52 arranged in the longitudinal direction of the vacuum vessel 4 ( Furthermore, it is possible to prevent or suppress the situation where the power distribution varies for each coil unit described above, and it is possible to uniformly inductively heat the susceptors 2 arranged in multiple stages in the internal space 4S. As a result, the induction heating apparatus 1 according to the present embodiment can uniformly heat the wafer W placed on each susceptor 2 to a predetermined target temperature (epitaxial growth temperature, for example, 1800 ° C.). In addition, when it reaches | attains a predetermined process, each induction heating coil 51 and 52 according to the current ratio of each induction heating coil 51 and 52 which can be adjusted with a drive frequency so that the temperature may be hold | maintained so that the temperature may be maintained. The outputs of the coils 51 and 52 are controlled to maintain a high temperature equilibrium state. Further, the gas supply control valve and the pressure adjusting valve are controlled by the pressure adjusting device so that the pressure value in the vacuum vessel 4S becomes a predetermined value.

  The induction heating apparatus 1 according to the present embodiment maintains a high temperature (about 1800 ° C.) equilibrium state through the above processing, and a thin film having a uniform thickness on the surface of the wafer W placed on each susceptor 2. In this embodiment, a single crystal SiC thin film (also referred to as a SiC epi film, hereinafter referred to as “SiC thin film”) can be formed. And since the growth rate of the SiC thin film increases in proportion to the supply amount of the raw material gas G supplied from the air supply port 41 to the inside 4S (gas supply target space, inner space), the gas G is made efficient. High-temperature growth of the SiC thin film can be obtained by sufficiently heating and sufficiently decomposing and supplying the gas G. That is, the induction heating apparatus 1 according to the present embodiment functions as a CVD epitaxial apparatus that realizes epitaxial growth for forming a SiC thin film on the wafer W, and produces an epitaxial wafer W in which a SiC thin film is deposited on the wafer W by epitaxial growth. can do.

  As described above, the induction heating apparatus 1 according to the present embodiment divides the two induction heating coils 51 and 52 along the axial direction H (longitudinal direction) of the vacuum vessel 4 outside the vacuum vessel 4. Respectively arranged in the first coil arrangement area A1 and the second coil arrangement area A2, and as the induction heating power source 6, resonance capacitors C1 and C2 are respectively provided for the induction heating coils 51 and 52 arranged in the respective coil arrangement areas A1 and A2. Is supplied from a common current type inverter 61 to a parallel resonant series connection circuit 62 in which two parallel resonant circuits (first parallel resonant circuit 65 and second parallel resonant circuit 66) connected in parallel are connected in series. While applying the high frequency power supply to be supplied, the resonance frequencies of the parallel resonance circuits 65 and 66 are set to different values from each other, and the drive frequency is changed in parallel. Since the current ratio of the induction heating coils 51 and 52 in the oscillation series connection circuit 62 is configured to be changeable, the induction heating coils 51 and 52 are inducted by only one power source 6 adopting the current type parallel resonance method. Further, the temperature distribution of the space 4S in which the object to be heated is arranged by the entire induction heating coil 5 arranged along the axial direction H of the vacuum vessel 4 to make the power distribution uniform. Can be achieved, and the plurality of susceptors 2 that are the objects to be heated disposed in the internal space 4S of the vacuum vessel 4 along the axial direction H can be uniformly heated.

  The induction heating apparatus 1 according to the present embodiment to which such a configuration is applied is provided with a dedicated power source for each of the plurality of induction heating coils, and each power source is individually controlled to make the coil power distribution uniform and within the vacuum vessel. Compared with a configuration for leveling the temperature distribution, complicated control of the power supply unit is not required, and there is an advantage that an increase in cost can be avoided.

  In addition, the induction heating apparatus 1 according to the present embodiment that performs power control of the plurality of induction heating coils 51 and 52 using only one induction heating power source 6 of a current type parallel resonance method includes a plurality of voltages arranged in parallel. Compared with a configuration in which a type series resonance circuit is connected to the same voltage type inverter, the switching element 641 constituting the inverter circuit is not limited to a self-extinguishing type element, and a non-self-extinguishing type element can be used. Thus, switching loss can be reduced, and there is an advantage that it is possible to cope with a large capacity exceeding 1000 kW without being forced to design a complicated circuit configuration.

  The induction heating apparatus 1 of this embodiment having such merits is a SiC thin film in which the thickness and impurity concentration are precisely controlled on the wafers W respectively placed on the plurality of susceptors 2 by one induction heating process. It is possible to stably supply a high-quality epitaxial wafer having deposited thereon, which contributes to the practical application of SiC semiconductor devices.

  In addition, in the induction heating device 1 according to the present embodiment, the susceptor 2 formed of carbon (graphite material) having anisotropy in the plane direction is applied, so that the outer periphery of the susceptor 2 is obtained by induction heating processing using high frequency. When the portion (edge vicinity region 2A) is heated, the entire susceptor 2 including the central portion can be heated uniformly based on the characteristics of the susceptor 2 having a high thermal conductivity and electrical conductivity in the plane direction. It is also possible to make the temperature distribution in the mounted wafer W uniform.

  In particular, in the induction heating apparatus 1 of the present embodiment, the diameter of the susceptor 2 is set larger than the diameter of the wafer W by a predetermined dimension (specifically, the diameter of the susceptor 2 is set to a penetration depth δ of 1 than that of the wafer W). The size is set to 5 times to 2.0 times), and the susceptor 2 is not configured to place the wafer W in the edge vicinity region 2A, which is a region where the alternating magnetic field penetrates much, but by an eddy current due to the alternating magnetic field. Since the wafer W on the susceptor 2 is not affected or difficult to be affected, and the wafer W is placed in a region where the eddy current due to the alternating magnetic field is minimized, a large amount of magnetic flux is applied to the wafer W. By avoiding the situation of passing through, the entire susceptor 2 can be uniformly heated in a situation where the eddy current does not affect or is difficult to affect the wafer W. As a result, the wafer W can be prevented from being broken or defective.

  In addition, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the first induction heating coil 51 is arranged in the first coil arrangement area A1 set at a position surrounding the upper and lower ends in the longitudinal direction of the cylindrical space 4Sa, and the longitudinal length of the cylindrical space 4Sa is set. The configuration in which the second induction heating coil 52 is arranged in the second coil arrangement area A2 set at a position surrounding the central portion in the direction is illustrated, but the arrangement area of each induction heating coil is not limited to this, and various conditions are considered. And the arrangement | positioning area of each induction heating coil can be set.

  As an example, paying attention to heat removal in the vacuum vessel 4S, in a portion close to the air supply port 41 and the exhaust port 42, that is, in the lower end portion of the vacuum vessel 4 where the air supply port 41 and the exhaust port 42 are formed and in the vicinity thereof. The temperature tends to be relatively low due to the cooling effect of the gas G supplied to and discharged from the vacuum vessel 4S. Therefore, as shown in FIG. 5, the coil arrangement area A that can surround the cylindrical space 4Sa is divided into two areas A1 and A2 in the axial direction H, and the relatively lower area is defined as the first coil arrangement area. The first induction heating coil 51 is arranged in the first coil arrangement area A1, and the relatively upper area is set as the second coil arrangement area A2, and the second coil arrangement area A2 is the second coil arrangement area A2. The drive frequency of the AC power output from the induction heating power supply 6 is arranged so that the coil current flowing through the first induction heating coil 51 is larger than the coil current flowing through the second induction heating coil 52. It is also possible to apply a mode in which the current ratio of each induction heating coil 51, 52 is controlled using as a variable. In addition, each code | symbol and pattern in FIG. 5 are based on each code | symbol etc. which are shown in FIG.

  In the embodiment shown in FIGS. 1 and 5, etc., the current flows through the induction heating coil arranged in an area corresponding to the area where the power of the induction heating coil is relatively low or the temperature of the internal space is relatively low. The drive frequency is changed so that the current is smaller than the current flowing in the induction heating coil arranged in the area corresponding to the area where the power of the induction heating coil is relatively high or the temperature of the internal space is relatively high. By doing so, it is possible to deliberately produce variations (level differences) in the power distribution of the entire induction heating coil and the temperature distribution of the space in which the object to be heated (susceptor 2) is arranged. Furthermore, the current flowing in the induction heating coil disposed in the area corresponding to the area where the power of the induction heating coil is relatively low or the temperature of the internal space is relatively low, the power of the induction heating coil is relative. Time when the drive frequency is changed to be larger than the current flowing in the induction heating coil arranged in the arrangement area corresponding to the area where the temperature of the internal space is relatively high or the temperature of the internal space is relatively high, and the power of the induction heating coil Current flowing in the induction heating coil arranged in the arrangement area corresponding to the area where the temperature of the internal space is relatively low or the area where the temperature of the internal space is relatively low, the area where the power of the induction heating coil is relatively high, A time zone in which the drive frequency is changed to be smaller than the current flowing in the induction heating coil arranged in the arrangement area corresponding to the area where the temperature is relatively high. By distinguishing and controlling graphically, the power distribution of the entire induction heating coil is equalized or the temperature distribution of the space where the object to be heated is leveled is equalized. It is also possible to configure so as to ensure a time zone in which the temperature distribution of the space in which the heated object is arranged is deliberately caused to vary.

  In addition, each induction heating coil that is individually arranged in a plurality of coil arrangement areas divided along the axial direction of the arrangement area of the induction heating coil may be a coiled state that does not have a difference in density, There may be a difference in density in the winding state. For example, as shown in FIGS. 1 and 5, when the coil arrangement areas A1 and A2 in which the induction heating coils 51 and 52 are arranged are further divided into a plurality of arrangement area units Aa in the axial direction H. It is possible to set a difference in density between the winding states of the induction heating coils 51 and 52 for each arrangement area unit Aa.

  In the above-described embodiment, the induction heating apparatus functioning as an apparatus for forming an epitaxially grown film on the wafer by chemical vapor deposition (CVD) has been exemplified. However, the induction heating apparatus of the present invention is configured by chemical vapor deposition (CVD). ) Can also function as an apparatus for creating a useful film other than the epitaxially grown film on the wafer.

  Further, the induction heating device may perform an appropriate treatment using a chemical reaction with respect to a wafer that is a heating target, or may appropriately use a sintering or melting for the heating target. It is also possible to perform the process.

  The susceptor preferably has anisotropy in the plane direction, but may have no anisotropy in the plane direction. When a susceptor having anisotropy in the plane direction is applied, the values of the thermal conductivity in the plane direction and the electrical conductivity in the plane direction are not particularly limited. Furthermore, in the present invention, if the distance from the edge of the wafer to the edge of the susceptor is within a range that does not affect the wafer in a state where the center position of the wafer is placed on the susceptor, the coil can be used as the susceptor. It is possible to set a value larger than 2.0 times the penetration depth of the generated magnetic flux or a value smaller than 1.5 times the penetration depth of the magnetic flux generated in the susceptor by the coil. is there.

  In the above-described embodiment, the induction heating apparatus in which a plurality of susceptors are arranged in a multistage shape in a vacuum vessel and a plurality of wafers can be heated at the same time is illustrated. However, one susceptor is arranged in a vacuum vessel, It may be an induction heating apparatus capable of performing heat treatment on a single wafer placed on the susceptor.

  The susceptor may be formed by using a single block-like or sheet-like graphite material instead of the sheet-like graphite material.

  Furthermore, the susceptor may be obtained by SiC-coating the surface of a graphite material having anisotropy in the plane direction. In this case, it is possible to avoid a situation where the graphite material and the wafer are in direct contact with each other, suppress contamination of the wafer and generation of useless particles, and reduce unintended reaction with the process gas.

  The induction heating device according to the present invention may be a billet heater (an induction heating device before forging) including an induction heating coil. As an example, FIG. 6 shows one induction heating power source X6 capable of outputting AC power of an arbitrary frequency to the induction heating coil X5 (first induction heating coil X51, second induction heating coil X52), and an object to be heated. The billet material X2 is disposed in a wound state on the outside of the peripheral wall X43, and a cylindrical partition wall (the peripheral wall X43 of the casing X4) that partitions the internal space X4S in which the billet material X2 is linearly movable along the axial direction H from other spaces. A billet heater X1 capable of heating the billet material X2 by induction heating by applying a high frequency current to the induction heating coil X5 (first induction heating coil X51, second induction heating coil X52). The peripheral wall X43 of the casing X4 is made of, for example, coil cement having insulating properties. Similarly to the power supply 6 in the above-described embodiment, the induction heating power supply X6 is a parallel resonance series connection circuit in which a current type inverter and two parallel resonance circuits are connected in series to each other and power is supplied from the current type inverter. (Not shown).

  The billet heater X1 according to the present invention is configured such that the current ratio of the induction heating coils X51 and X52 can be changed by setting the resonance frequency of each parallel resonance circuit to a different value and changing the drive frequency of the power source 6. doing.

  The billet heater X1 will be described in detail. The internal space X4S partitioned by the peripheral wall X43 of the cylindrical casing X4 extends in the axial direction H, and both ends in the axial direction H are open. The arrangement area XA of the induction heating coil X5 outside the peripheral wall X43 of the casing X4 is divided into two areas XA1 and XA2 along the axial direction H, and the two induction heating coils X51 and X52 are arranged differently from each other. , XA2 individually. In the illustrated example, of the two divided coil arrangement areas XA1 and XA2, the area on the downstream side in the traveling direction P of the billet X2 rotatably held by the dummy XD is set as the first coil arrangement area XA1. The first induction heating coil X51 is arranged in the coil arrangement area XA1, the area upstream of the billet X2 in the traveling direction P is set as the second coil arrangement area XA2, and the second induction heating coil is arranged in the second coil arrangement area XA2. X52 is arranged. Then, by controlling the current ratio of the induction heating coils X51 and X52 using the drive frequency of the AC power output from the induction heating power supply X6 as a variable, the coil power distribution of the entire induction heating coil X5 and the arrangement space of the billet X2 are controlled. The temperature distribution of X4S can be adjusted to a desired distribution. In FIG. 6, the first coil arrangement area XA1 and the second coil arrangement area XA2 are shown with mutually different patterns, a portion of the first induction heating coil X51 that is not in a wound state, and a second Each portion of the induction heating coil X52 that is not in a wound state is a straight line (a relatively thick line is a line indicating the first induction heating coil X51, and a relatively thin line is a line indicating the second induction heating coil X52). This is schematically shown in FIG.

  In particular, in the embodiment shown in FIG. 6, a die (not shown) is arranged on the downstream side in the traveling direction P of the billet X2, and the end of the billet X2 downstream in the traveling direction P (the tip of the billet X2) is brought into contact with the die. Thus, if the billet heater X1 is configured so that the contact portion can be processed into a thin wire, the tip portion of the billet X2 (the portion in contact with the die) has a lot of heat removal. That is, when the tip of the heated billet X2 comes into contact with an unheated die and heat is taken away, the tip of the billet X2 is cooled and the temperature falls below the processing temperature.

  Therefore, in the billet heater X1 according to the present embodiment, in order to avoid a situation where the tip portion of the billet X2 is cooled to be lower than the processing temperature, a dummy is used to make the vicinity of the tip portion higher than the other portions. The coil current flowing in the first induction heating coil X51 arranged in the first coil arrangement area XA1, which is the area downstream of the billet X2 in the traveling direction P of the billet X2 held rotatably by the XD, is on the upstream side in the traveling direction P of the billet X2. By changing the drive frequency so as to be larger than the current flowing through the second induction heating coil X52 arranged in the second coil arrangement area XA2, which is the area, the power distribution of the entire induction heating coil and the object to be heated are arranged. It is possible to set so that the temperature distribution of the space X4S is intentionally varied (difference in height).

  In addition, in the billet heater X1 as shown in FIG. 6 regardless of the presence or absence of the dice, in an arrangement area corresponding to an area where the power of the induction heating coil is relatively low or an area where the temperature of the internal space X4S is relatively low. The current flowing through the arranged induction heating coil is larger than the current flowing through the induction heating coil arranged in the arrangement area corresponding to the area where the power of the induction heating coil is relatively high or the temperature of the internal space X4S is relatively high. It is also possible to set so that the drive frequency is changed so as to increase and the power distribution of the entire induction heating coil is made uniform and the temperature distribution of the internal space X4S is made uniform. Furthermore, by changing the drive frequency of the induction heating coil arranged in each arrangement area, a time zone for equalizing the power distribution of the entire induction heating coil and leveling the temperature distribution of the internal space X4S, and the induction heating coil It is also possible to set so as to intentionally distinguish and control the time zone in which the overall power distribution and the temperature distribution of the internal space X4S cause a height difference.

  When realizing the induction heating device according to the present invention as a billet heater, the linear movement of the billet in the casing may be a linear movement in only one direction or a reciprocating movement. The billet traveling direction coincides with or substantially coincides with the axial direction (longitudinal direction) of the casing. If the billet is configured to reciprocate in the internal space of the casing, the coil placement area may be divided along the traveling direction on the upstream side and the downstream side in the traveling direction of “bound”.

  Also, in the billet heater, the arrangement area of each induction heating coil divided in the axial direction is not limited to the area shown in FIG. 6, and the arrangement area of each induction heating coil can be set in consideration of various conditions. .

  In the induction heating device according to the present invention, a configuration in which three or more induction heating coils are individually arranged in different coil arrangement areas may be employed. In this case, the parallel resonance series connection circuit of the induction heating power source is obtained by connecting in series three or more parallel resonance circuits in which resonance capacitors are individually connected in parallel to three or more induction heating coils. What is necessary is just to comprise so that the current ratio of three or more induction heating coils can be changed by setting the resonant frequency of a resonant circuit to a different value, and changing a drive frequency.

  Furthermore, the range in which the drive frequency of the induction heating power source is changed (the change width of the drive frequency) is the magnitude relationship (in terms of the ratio) of the current ratio of the induction heating coils individually arranged in each coil arrangement area divided along the axial direction. And the second induction in which the current flowing in the first induction heating coil arranged in the first coil arrangement area is within the range where the relative magnitude of the coil current value is maintained (for example, the first induction heating coil arranged in the first coil arrangement area). It may be within a range that is always larger than the current flowing through the heating coil), or it may be set within a range that includes a drive frequency with a value that reverses the magnitude relationship of the current ratio of each induction heating coil. That is, in the present invention, in order to adjust the power distribution of each induction heating coil divided and arranged, the drive frequency for reversing the magnitude relationship of the current ratio of each induction heating coil temporarily or for a predetermined time is set. A configuration in which AC power is output from the induction heating power source to each induction heating coil can be employed.

  Moreover, although it is preferable that the high frequency used at the time of heat processing in the induction heating apparatus for this invention is 1 kHz or more, it does not restrict | limit in particular.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Induction heating apparatus 2 ... Object to be heated (susceptor)
4 ... Vacuum container 43 ... Partition wall (side wall)
DESCRIPTION OF SYMBOLS 5 ... Induction heating coil 51 ... 1st induction heating coil 52 ... 2nd induction heating coil 6 ... Induction heating power supply 61 ... Current type inverter 62 ... Parallel resonance series connection circuit 65, 66 ... Parallel resonance circuit (1st parallel resonance circuit, Second parallel resonant circuit)
C1, C2 ... Resonance capacitors (first resonance capacitor, second resonance capacitor)

Claims (3)

One induction heating power source capable of outputting alternating-current power of an arbitrary frequency to the induction heating coil, a cylindrical partition wall that partitions an internal space extending in one axial direction in which an object to be heated can be arranged, from the other space; An induction heating device capable of heating the object to be heated by induction heating by applying a high-frequency current to the induction heating coil arranged in a wound state outside the partition;
Dividing the arrangement area of the induction heating coil outside the partition wall along the axial direction, and individually arranging at least two induction heating coils in mutually different arrangement areas;
The induction heating power source is
A current type inverter configured using a forward conversion circuit that converts an output current from an alternating current power source into a direct current, and an inverse conversion circuit that converts the output current from the forward conversion circuit into an alternating current using a switching element;
A parallel resonance series connection circuit in which at least two parallel resonance circuits each having a resonance capacitor individually connected in parallel to at least two induction heating coils are connected in series to each other, and power is supplied from the current type inverter. And
An induction heating apparatus configured to change a current ratio of each induction heating coil by setting a resonance frequency of each parallel resonance circuit to a different value and changing a driving frequency. The arrangement area of the induction heating coil is relatively to the area where the electric power of the single induction heating coil is relatively high when the single induction heating coil is arranged along the axial direction outside the partition wall. The induction heating device according to claim 1, wherein the induction heating device is divided along the axial direction according to an area to be lowered. 2. The induction heating according to claim 1, wherein the arrangement area of the induction heating coil is divided along the axial direction according to an area where the temperature of the internal space is relatively high and an area where the temperature is relatively low. apparatus.

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