Patent Publication Number: US-2011056434-A1

Title: Heat treatment apparatus

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Japanese Patent Application Nos. 2009-205031, filed on Sep. 4, 2009, and 2010-157959, filed on Jul. 12, 2010, in the Japanese Patent Office, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat treatment apparatus configured to perform a process such as a thin film forming process, a dopant diffusing process, or an etching process on a substrate such as a silicon wafer, and more particularly, to a heat treatment apparatus configured to grow a silicon carbide (SiC) film on a SiC wafer. 
     2. Description of the Related Art 
     In a conventional heat treatment apparatus, a substrate holding tool such as a boat is loaded into a reaction chamber formed in a reaction tube in a state where a plurality of substrates (wafers) are vertically arranged in multiple stages in the boat, and a susceptor installed around the boat is induction-heated to a predetermined temperature by using an induction coil installed outside the reaction tube, so as to perform a film forming process. 
     At this time, to prevent the reaction tube or a case from being heated by radiation heat from the susceptor, an insulator is installed between the reaction tube and the susceptor. Generally, the insulator is made of carbon because a carbon material is resistant to a high temperature and has a low impurity concentration. Usually, carbon is used in the form of felt for low heat conductivity and high thermal resistance. 
     However, since carbon is conductive, carbon is induction-heated like the susceptor. Thus, less energy is applied to the susceptor, and power loss occurs. In addition, if the insulator installed to block heat is heated, the temperature of the reaction tube disposed outside the insulator is increased, and thus the temperature of the case is also increased by heat radiating from the reaction tube. In this case, a measurement such as water cooling is necessary to decrease the temperature of the case. However, this increases power loss. 
     Furthermore, in the case where an insulator made of carbon felt is used in a vertical type apparatus, a higher reaction tube and a longer insulator are necessary to process more wafers at a time. However, in this case, the strength of carbon felt decreases largely, and it is very difficult to erect and install the carbon felt. Carbon felt can be installed by fixing it with binders. However, in this case, the advantage of carbon material, that is, a low impurity concentration, is weakened. 
     In addition, since carbon is a consumable, it is necessary to replace carbon felt periodically. However, since carbon felt has a fine line shape, if the carbon felt is touched when it is replaced, fine carbon particles may be scattered. This may result in harmful environments. For, if the scattering carbon particles are brought into contact with person&#39;s skin, the person may suffer from itching. 
     Patent document 1 below discloses a semiconductor crystal growing apparatus, in which high-frequency power is applied to an induction heating unit to heat a radiation member by induction and grow epitaxial films on a plurality of substrates. 
     [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2007-95923 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a heat treatment apparatus in which the temperature of an insulator heated by an induction current can be kept low and a susceptor can be efficiently heated. 
     According to an aspect of the present invention, there is provided a heat treatment apparatus for growing silicon carbide single crystal films or silicon carbide polycrystal films on a plurality of silicon carbide substrates, the heat treatment apparatus comprising: a coil installed around an outside of a reaction tube to generate a magnetic field; a susceptor installed in the reaction tube and configured to be heated by an induction current; and an insulator installed between the susceptor and the reaction tube, wherein the insulator is divided into parts in a circumferential direction, and an insulating material is inserted between the divided parts of the insulator 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view illustrating a heat treatment apparatus according to the present invention. 
         FIG. 2  is a vertical sectional view illustrating a reaction furnace used in the heat treatment apparatus according to an embodiment of the present invention. 
         FIG. 3  is a schematic vertical sectional view illustrating a quartz container and an insulator according to a first embodiment of the present invention. 
         FIG. 4A  is a view taken along arrow A-A of  FIG. 3 , and  FIG. 4B  is a view taken along arrow B-B of  FIG. 3 . 
         FIG. 5A  to  FIG. 5C  are views for explaining a method of installing an insulator on a quartz container, and  FIG. 5D  is a view for explaining horizontal sewing with a carbon thread. 
         FIG. 6A  to  FIG. 6D  are views for explaining flows and actions of a high-frequency current and an induction current according to the first embodiment of the present invention, in which  FIG. 6A  and  FIG. 6B  illustrate the case where an insulating material is inserted between divided parts of the insulator, and  FIG. 6C  and  FIG. 6D  illustrate the case where the insulator is not divided. 
         FIG. 7A  to  FIG. 7C  are views illustrating an insulating part according to a second embodiment of the present invention, in which  FIG. 7A  is a schematic vertical sectional view illustrating a quartz container ceiling part and an insulator ceiling part,  FIG. 7B  is a schematic horizontal sectional view which corresponds to a section taken along arrow A-A of  FIG. 3  and illustrates the quartz container ceiling part and the insulator ceiling part, and  FIG. 7C  is a schematic horizontal sectional view which corresponds to a section taken along arrow B-B of  FIG. 3  and illustrates a quartz container body part and an insulator body part. 
         FIG. 8A  to  FIG. 8C  are views illustrating an insulating part according to a modification example of the second embodiment of the present invention, in which  FIG. 8A  is a schematic vertical sectional view illustrating a quartz container ceiling part and an insulator ceiling part,  FIG. 8B  is a schematic horizontal sectional view which corresponds to a section taken along arrow A-A of  FIG. 3  and illustrates the quartz container ceiling part and the insulator ceiling part, and  FIG. 8C  is a schematic horizontal sectional view which corresponds to a section taken along arrow B-B of  FIG. 3  and illustrates a quartz container body part and an insulator body part. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described hereinafter with reference to the attached drawings. 
     First, with reference to  FIG. 1 , an explanation will be given on an example of a heat treatment apparatus according to the present invention. 
     In a heat treatment apparatus  1  of the present invention, wafers  6  are accommodated substrate containers such as cassettes  2  for loading and unloading operations. 
     The heat treatment apparatus  1  includes a case  3 , and a cassette carrying entrance  4  configured to be opened and closed by a front shutter (not shown) is formed in the front wall of the case  3 . In the case  3 , a cassette stage  5  is installed at a position close to the cassette carrying entrance  4 . 
     A cassette  2  is carried on the cassette stage  5  or carried away from the cassette stage  5  by an in-process carrying device (not shown). 
     The cassette  2  carried to the cassette stage  5  by the in-process carrying device is placed on the cassette stage  5  in a state where wafers  6  inside the cassette  6  are vertically positioned and a wafer entrance of the cassette  2  faces upward, and then the cassette stage  5  rotates the cassette  2  so that the wafer entrance of the cassette  2  faces the backside of the case  3 . 
     Near the center part of the case  3  in a front-to-back direction, a cassette shelf (substrate container shelf)  7  is installed. The cassette shelf  7  is configured so that a plurality of cassettes  2  can be stored in multiple rows and columns. At the cassette shelf  7 , a transfer shelf  9  is installed to store cassettes  2  that are carrying objects of a wafer transfer device  8 . In addition, at the upside of the cassette stage  5 , a standby cassette shelf  11  is installed, and the standby cassette shelf  11  is configured to store standby cassettes  2 . 
     Between the cassette stage  5  and the cassette shelf  7 , a cassette carrying device  12  is installed. The cassette carrying device  12  is configured to carry cassettes  2  among the cassette stage  5 , the cassette shelf  7 , and the standby cassette shelf  11 . 
     At the backside of the cassette shelf  7 , the wafer transfer device  8  is installed. The wafer transfer device  8  can rotate horizontally, move back and forth, and ascend and descend while holding wafers  6 , so as to transfer wafers  6  between cassettes  2  placed on the transfer shelf  9  and a substrate holding tool such as a boat  13 . 
     At the upside of the rear part of the case  3 , a process furnace  14  is installed, and a bottom opening (furnace port) of the process furnace  14  is configured to be opened and closed by a furnace port shutter  15 . 
     At the lower side of the process furnace  14 , a boat elevator  16  is installed for moving the boat  13  upward/downward to load/unload the boat  13  into/from the inside of the process furnace  14 . The boat elevator  16  includes an elevating arm  17 , and a cover such as a seal cap  18  is horizontally installed on the elevating arm  17 . The seal cap  18  is configured to support the boat  13  vertically and close and open the furnace port. 
     The boat  13  is made of a heat-resistant material that does not contaminate wafers  6 , such as quartz, and is configured to hold a plurality of wafers  6  (for example, about fifty to about one hundred fifty wafers) in a state where the wafers  6  are horizontally oriented and vertically stacked at predetermined intervals with the centers of the wafers  6  being aligned. 
     At the upside of the cassette shelf  7 , a cleaning unit  19  is installed to supply a purified atmosphere such as clean air. The cleaning unit  19  is configured to circulate clean air in the case  3 . 
     Next, an operation of the heat treatment apparatus  1  will be described. 
     The cassette carrying entrance  4  is opened, and a cassette  2  is supplied to the cassette stage  5 . Then, the cassette  2  is introduced through the cassette carrying entrance  4  and is carried by the cassette carrying device  12  to the cassette shelf  7  or the standby cassette shelf  11  where the cassette  2  is temporarily stored, and the cassette  2  is transferred to the transfer shelf  9  from the cassette shelf  7  or the standby cassette shelf  11  by the cassette carrying device  12 . Alternatively, the cassette  2  may be directly transferred to the transfer shelf  9  from the cassette stage  5 . 
     After the cassette  2  is transferred to the transfer shelf  9 , the wafer transfer device  8  charges wafers  6  from the cassette  2  to the boat  13  which is placed at a lowered position. 
     After a predetermined number of wafers  6  which are not processed are charged into the boat  13 , the bottom side of the process furnace  14  closed by the furnace port shutter  15  is opened by moving the furnace port shutter  15 . Then, the boat elevator  16  lifts the boat  13  so that the boat  13  can be loaded into the process furnace  14 . 
     After the boat  13  is loaded, a predetermined process is performed on the wafers  6  in the process furnace  14 . Thereafter, in the reverse order to the above, the boat  13  is moved down, and the wafer transfer device  8  transfers the processed wafers  6  from the boat  13  to the cassettes  2 . The cassettes  2  in which the processed wafers  6  are charged is carried to the outside of the case  3 . 
     Next, with reference to  FIG. 2  to  FIG. 5D , the process furnace  14  will be described in more detail. 
     A reaction tube  21  is installed to process substrates such as wafers  6 , and at the bottom side of the reaction tube  21 , a manifold  22  made of a material such as stainless steel is hermetically installed. A bottom opening of the manifold  22  forms the furnace port, and the furnace port is selectively closed by one of the furnace port shutter  15  and the seal cap  18 . 
     In the reaction tube  21 , a susceptor  24  having a cylindrical shape with an opened side is erected on the manifold  22  to surround the boat  13  when the boat  13  is loaded, and between the susceptor  24  and the reaction tube  21 , an insulating part  23  having a cylindrical shape with an opened side to surround the susceptor  24  is erected on the manifold  22 . The insulating part  23  includes an insulator  25  made of a material such as carbon felt and disposed at an inner layer side, and a quartz container  26  installed at an outer layer side. The insulator  25  and the quartz container  26  are combined to form a dual structure. 
     At the outside of the reaction tube  21 , an induction coil  27  is installed around the reaction tube  21  to generate a magnetic field. The induction coil  27  is supported by a coil supporting part  28 , and the coil supporting part  28  is surrounded by an insulating part  29 . 
     A reaction chamber  30  is constituted at least by the susceptor  24 , the manifold  22 , and the seal cap  18 . 
     In addition, a gas supply inlet  31  and a gas exhaust outlet  32  are formed in the manifold  22 . The gas supply inlet  31  is connected to a gas supply source (not shown), and the gas exhaust outlet  32  is connected to an exhaust device such as a vacuum pump. 
     Next, explanations will be given on a detailed structure of the insulating part  23 , and a method of installing the insulator  25  on the quartz container  26 . 
     The insulating part  23  has a dual structure in which the insulator  25  and the quartz container  26  are combined. The quartz container  26  has a split structure constituted by a quartz container ceiling part  33 , at least one quartz container body part  34 , and a quartz container lower part  35  (refer to  FIG. 3 ). 
     The quartz container ceiling part  33  has a circular disk shape. In a bottom center part of the quartz container ceiling part  33 , a ceiling part concave part  33   b  is formed so that a ceiling part flange  33   a  can be formed along the circumference of the quartz container ceiling part  33 . A ring-shaped ceiling part cutout part  33   c  is formed along the outer circumference of the ceiling part flange  33   a . The quartz container body part  34  has a cylindrical shape. At the upper outer circumference of the quartz container body part  34 , a ring-shaped body part protrusion  34   a  is formed, which can be engaged with and disengaged from the ceiling part cutout part  33   c . At the lower outer circumference of the quartz container body part  34 , a body part cutout part  34   b  is formed with the same shape with the ceiling part cutout part  33   c , and at the lower inner circumference of the quartz container body part  34 , a body part inner flange  34   c  is formed. In addition, at the upper outer circumference of the quartz container lower part  35 , a lower part protrusion  35   a  is formed with the same shape with the body part protrusion  34   a.    
     The quartz container  26  is assembled in a row by engaging the ceiling part cutout part  33   c  with the body part protrusion  34   a , the body part cutout part  34   b  with the body part protrusion  34   a , and the body part cutout part  34   b  with the lower part protrusion  35   a.    
     The quartz container body parts  34  can be stacked in multiple stages, and the height of the quartz container  26  can be adjusted by increasing or decreasing the number of the stacked quartz container body parts  34   
     In addition, a plurality of thread hook protrusions  36  are extended from the inner wall of the quartz container body part  34 , and holes  37  are vertically formed in the centers of the thread hook protrusions  36 . 
     The insulator  25  includes an insulator ceiling part  38  and insulator body parts  39  stacked in multiple stages. Each of the insulator body parts  39  is divided into predetermined parts in the circumferential direction. In  FIG. 5A  to  FIG. 5D , the insulator body part  39  has a spilt structure divided into four parts. For example, each of the parts is formed by superimposing a plurality of 10-mm thickness carbon felts (three in  FIG. 5A  to  FIG. 5D ) and stitching the superimposed carbon felts with carbon threads  41 . 
     The insulator ceiling part  38  has the same thickness as the depth of the ceiling part concave part  33   b  of the quartz container ceiling part  33 , and a ring-shaped cutout part  38   a  is formed along the lower outer circumference of the insulator ceiling part  38 . The weight of the insulator ceiling part  38  is supported by engaging the insulator ceiling part  38  into the ceiling part concave part  33   b  while deforming the insulator ceiling part  38  and fitting the ceiling part flange  33   a  to the cutout part  38   a  so that the insulator ceiling part  38  does not fall. 
     In addition, the height of the insulator body part  39  is less than the height of the quartz container body part  34  by the height of the body part protrusion  34   a . In the lower outer circumference of the insulator body part  39 , a ring-shaped cutout part  39   a  is formed, and the cutout part  39   a  can be engaged in a row with the body part inner flange  34   c  of the quartz container body part  34 . The weight of the insulator body part  39  is supported by the body part inner flange  34   c  so that the insulator body part  39  does not fall. 
     Like in the case of the quartz container  26 , the height of the insulator  25  can be adjusted by increasing or decreasing the number of the stacked insulator body parts  39 . In addition, the insulator body parts  39  have the same inner diameter as the inner diameter of the quartz container lower part  35 , and when the insulator  25  is installed on the quartz container  26 , the bottom surface of the lowermost insulator body part  39  is placed on the top surface of the quartz container lower part  35 . 
     The insulator ceiling part  38  is divided into the same angular parts. In the drawing, the insulator ceiling part  38  is divided into four quarter-circle parts. The insulator body part  39  is divided into parts in the circumferential direction (four parts in the drawing), and a plurality of thread holes  42  are formed in the insulator body part  39  at predetermined positions. The insulator body part  39  may be divided into any number of parts, for example, two parts or 8 parts. 
     Radially extending gaps are formed between the divided parts of the insulator ceiling part  38 , and insulating and heat-resistive filling materials such as ceiling part zirconium sheets  43  formed by coating quartz members with zirconium layers are inserted in the gaps. Two concave pillar-shaped zirconium sheets that are engaged with each other may be used as the ceiling part zirconium sheets  43 , or a long pillar-shaped zirconium sheet and two short pillar-shaped zirconium sheets that are combined in a cross shape may be used as the ceiling part zirconium sheets  43 . The insulator ceiling part  38  and the ceiling part zirconium sheets  43  form a circular disk shape. 
     The insulator ceiling part  38  and the quartz container ceiling part  33  are fixed to each other by the same method as that used for fixing the insulator body part  39  and the quartz container body part  34  (described later), and the insulator body part  39  is a replaceable part. 
     In addition, pillar-shaped insulating and heat-resistive filling material such as body part zirconium sheets  45 , which are formed by coating quartz members with zirconium layers and have a plurality of thread holes  44  at predetermined positions, are inserted between the divided parts of the insulator body part  39  as filling materials, and the insulator body part  39  and the body part zirconium sheets  45  form a cylindrical shape. The ceiling part zirconium sheets  43  have the same thickness as that of the insulator ceiling part  38 , and the body part zirconium sheets  45  have the thickness as that of the insulator body part  39 . 
     When the insulator  25  is installed on the quartz container  26 , a ceiling part  23   a  is formed by assembling the quartz container ceiling part  33  and the insulator ceiling part  38 ; the body part  23   b  are formed by assembling the quartz container body part  34  and the insulator body part  39 ; and the ceiling part  23   a  and the body part  23   b  are combined as a unit. Then, the insulating part  23  may be assembled by sequentially superimposing the body part  23   b  on the quartz container lower part  35 , another body part  23   b  on the body part  23   b , and the ceiling part  23   a  on the body part  23   b.    
     When the quartz container body part  34  and the insulator body part  39  are assembled, as shown in  FIG. 5A , the insulator body part  39  is fixed to the quartz container body part  34  by passing carbon threads  41  through the holes  37  formed in the thread hook protrusions  36  and passing the carbon threads  41  through thread holes  42  formed in the insulator body part  39 . The carbon threads  41  are prepared for the thread holes  42 , respectively, and as shown in  FIG. 5B , the quartz container body part  34  and the insulator body part  39  are stitched at the holes  37  and the thread holes  42 , respectively. Holes may be formed in the insulator body part  39  to receive the thread hook protrusions  36  for bringing the quartz container body part  34  and the insulator body part  39  into contact with each other. 
     After installing all the divided parts of the insulator body part  39  on the quartz container body part  34  with gaps being formed between the divided parts, as shown in  FIG. 5C , the body part zirconium sheets  45  are inserted in the gaps between the divided parts of the insulator body part  39  and are fixed to the quartz container body part  34  by passing carbon threads  41  through the holes  37  and passing the carbon threads  41  through the thread holes  44  formed in the body part zirconium sheets  45 , so as to assemble the body part  23   b  as a unit. Although not shown, like in the case of the quartz container body part  34 , thread hook protrusions through which holes are formed are extended from the ceiling part concave part  33   b  of the quartz container ceiling part  33 , and thread holes are formed in the insulator ceiling part  38 , so that the insulator ceiling part  38  can be fixed to the quartz container ceiling part  33  by passing carbon threads  41  through the thread holes so as to assemble the ceiling part  23   a  as a unit. 
     At this time, the insulator body part  39  and the body part zirconium sheets  45  inserted between divided parts of the insulator body part  39  are respectively installed on the quartz container body part  34  by the separate carbon threads  41 , so that they can be insulated from each other. The directions of the carbon threads  41  used to fix the insulator body part  39  and the body part zirconium sheets  45  are different from the directions shown in  FIG. 5D  but the carbon threads  41  intersect hi-frequency currents and induction currents (described later), for example, in a perpendicular direction. In addition, the carbon threads  41  are coupled to the thread hook protrusions  36 , respectively, and the boat carbon threads  41  are separated in the circumferential direction, so that a current may not be induced in the carbon threads  41 . 
     Next, body parts  23   b  are stacked unit a desired height is obtained (two stages in  FIG. 3 ), and then the bottom side of the ceiling part  23   a  is engaged with the topside of the uppermost body part  23   b . In this way, the insulator  25  is fixed to the quartz container  26  to form the insulating part  23  as an integrated part. 
     To perform a film forming process, first the boat  13  in which a predetermined number of wafers  6  are held is loaded into the reaction chamber  30 . 
     Next, a process gas such as monosilane and propane is introduced into the reaction chamber  30  through the gas supply inlet  31  from the gas supply source (not shown), and along with this, a high-frequency current  46 , for example, 30-kHz current, is applied to the induction coil  27  to generate an alternating-current magnetic field. By the alternating-current magnetic field, an induction current  47  is generated in the susceptor  24 , and as the induction current  47  is excessively generated, the susceptor  24  is heated by Joule heating. 
     At this time, as shown in  FIG. 6A  to  FIG. 6D , like in the susceptor  24 , an induction current  47  is also generated in the insulator  25  made of a material such as carbon felt in a direction canceling the high-frequency current  46  flowing in the circumferential direction of the induction coil  27 , that is, in a direction opposite to the direction of the high-frequency current  46 . However, as shown in  FIG. 6A  and  FIG. 6B , since the passage of the induction current  47  is cut in small pieces by the body part zirconium sheets  45 , the induction current  47  is not greater than an induction current generating in the case of  FIG. 6C  and  FIG. 6D  where the body part zirconium sheets  45  are not installed. Therefore, the insulator  25  may be less heated. Therefore, more energy can be applied to the susceptor  24 , and the susceptor  24  can be heated with improved energy efficiency. 
     As the susceptor  24  is heated, the boat  13  and the wafers  6  surrounded by the susceptor  24  are heated to a predetermined temperature by radiation heat so that SiC crystal films can be formed on the wafers  6 . If the film forming process is completed, the process gas is exhausted through the gas exhaust outlet  32  by the exhaust device (not shown), and the boat  13  is unloaded from the reaction chamber  30 . 
     During the process, the susceptor  24  is heated to 1500° C. to 1800° C., but heat transfer to parts such as the reaction tube  21  and the quartz container body part  34  can be suppressed because the insulating part  23  and the insulating part  29  block radiation heat from the heated susceptor  24 . Owing to the insulating part  23 , the temperature of the reaction tube  21  may be reduced to 1000° C. or lower, and owing to the insulating part  29 , radiation heat from the reaction tube  21  can be blocked. 
     The heat distribution in the susceptor  24 , which is induction-heated by the high-frequency current  46  applied to the induction coil  27 , is characterized by a higher temperature at an upper part and a lower temperature at a lower part. Similarly, the heat distribution pattern of the insulator  25  is vertical. In this case, the insulator  25  may be aged at a different rate. However, according to the present invention, the insulating part  23  in which the quartz container  26  and the insulator  25  are integrated has a split structure formed by stacking the body parts  23   b  each configured as a unit. Therefore, only an aged unit can be replaced to reduce replacing costs and making the replacing work easy. In addition, manpower can also be reduced. 
     In addition, since the carbon threads  41  used to fix the insulator body part  39  and the body part zirconium sheets  45  are disposed in directions crossing the high-frequency current  46  and the induction current  47 , an induction current is not generated in the carbon threads  41  so that abnormal heating or aging of the carbon threads  41  can be prevented and thus the durability of the carbon threads  41  can be improved. 
     Furthermore, according to the present invention, the insulator  25  is integrated by fixing the insulator  25  to the quartz container  26  by using the carbon threads  41  through the holes  37  and the thread holes  42 . Therefore, when replacing the insulator  25 , it is unnecessary to directly handle the insulator  25 . This prevents scattering of fine carbon particles from the carbon felt of the insulator  25 , and harmful environments. 
     Next, a second embodiment of the present invention will be described with reference to  FIG. 7A  to  FIG. 7C . The basic concept of the second embodiment is the same as that of the first embodiment, and thus a description of the basic concept will not be repeated. Furthermore, in  FIG. 7A  to  FIG. 7C , the same elements as those illustrated in  FIG. 3  to  FIG. 4B  are denoted by the same reference numerals, and descriptions thereof will not be repeated. 
     In the second embodiment, an insulator ceiling part  48  has a circular disk shape, and a cut line  49  penetrates the insulator ceiling part  48  from the upper side to the lower side. The cut line  49  extends from the center to the circumference of the insulator ceiling part  48  (coincident with the radius of the insulator ceiling part  48  in  FIG. 7B ), and the cut line  49  is sloped from a vertical line when viewed in section (refer to  FIG. 7A ). An insulating and heat-resistive filling material having the same shape as the cut line  49 , such as a ceiling part zirconium sheet  51  formed by coating a quartz member with a zirconium layer, is inserted in the cut line  49 . Since the insulator ceiling part  48  is cut in the circumferential direction by the cut line  49 , the insulator ceiling part  48  is discontinuous. 
     In addition, an insulator body part  52  is formed by cutting a cylindrical insulator in a circumferential direction, and for this, a cut line  53  is formed from the upper side to lower side of the insulator body part  52 . The cut line  53  is sloped from a radial direction when viewed in horizontal section, and an insulating and heat-resistive filling material having the same shape as the cut line  53 , such as a body part zirconium sheet  54  formed by coating a quartz member with a zirconium layer, is inserted in the cut line  53 . 
     The insulator ceiling part  48  and the quartz container ceiling part  33  are assembled as follows. The insulator ceiling part  48  is fixed to the quartz container ceiling part  33  by using carbon threads  41  (refer to  FIG. 5A  to  FIG. 5D ); and the ceiling part zirconium sheet  51  is inserted in the cut line  49  and is fixed to the quartz container ceiling part  33  by using carbon threads  41  different from the carbon threads  41 , so that a ceiling part  23   a  (refer to  FIG. 3 ) of an insulating part  23  (refer to  FIG. 3 ) can be formed as a unit. In addition, a ring-shaped cutout part  48   a  formed in the bottom outer circumference of the insulator ceiling part  48  is engaged with the ceiling part flange  33   a  formed on the bottom side of the quartz container ceiling part  33  so that separation of the insulator ceiling part  48  can be prevented and integration of the quartz container ceiling part  33  and the insulator ceiling part  48  can be reinforced. 
     In addition, the insulator body part  52  and the quartz container body part  34  are assembled as follows. The insulator body part  52  is fixed to the quartz container body part  34  by using carbon threads  41 ; and the body part zirconium sheet  54  is inserted in the cut line  53  and is fixed to the quartz container body part  34  by using carbon threads  41  different from the carbon threads  41 , so that a body part  23   b  (refer to  FIG. 3 ) of the insulating part  23  can be formed as a unit. In addition, the insulating part  23  is assembled by sequentially stacking the quartz container lower part  35  (refer to  FIG. 3 ), the body part  23   b , and the ceiling part  23   a.    
     When a film forming process is performed by using the insulating part  23 , an induction current  47  (refer to  FIG. 6A  to  FIG. 6D ) is generated in the insulator  25  in a direction opposite to the direction of a high-frequency current  46  (refer to  FIG. 6A  to  FIG. 6D ) applied to the induction coil  27  (refer to  FIG. 2 ). However, since the passages of the induction current  47  in the insulator ceiling part  48  and the insulator body part  52  are cut in small pieces by the cut line  49  and the cut line  53 , the induction current  47  is small, and thus the insulator  25  can be less heated. 
     Furthermore, in the second embodiment, the cut line  49  is formed at one position of the insulator ceiling part  48 , and the cut line  53  is formed at one position of the insulator body part  52 . That is, each of the insulator ceiling part  48  and the insulator body part  52  has a one-piece structure. Thus, when installing the insulator ceiling part  48  and the insulator body part  52  on the quartz container ceiling part  33  and the quartz container body part  34 , a work such as a position alignment work is not necessary, and thus the workability can be improved. 
     In addition, the cut line  49  is sloped from a vertical direction, and the cut line  53  is sloped from a radial direction. That is, the cut line  49  and the cut line  53  are sloped so that the cut line  49  and the cut line  53  can intersect the direction of radiation heat from the susceptor  24 . Therefore, radiation heat of the susceptor  24  that tends to pass through the cut line  49  and the cut line  53  can be blocked in the middles of the cut line  49  and the cut line  53 , and thus the insulating performance of the insulator  25  can be improved. 
     The cut line  49  and the cut line  53  may have other shapes as long as the passage of an induction current  47  can be cut in small pieces by the cut line  49  and the cut line  53 .  FIG. 8A  to  FIG. 8C  illustrate a modification example of the second embodiment. 
     In the modification example, a bent cut line  55  having a &lt;-shaped vertical section is formed in the insulator ceiling part  48 , and a bent cut line  56  having a &lt;-shaped horizontal section is formed in the insulator body part  52 . 
     A ceiling part zirconium sheet  51  having the same shape as the cut line  55  is inserted in the bent cut line  55 , and a body part zirconium sheet  58  having the same shape as the cut line  56  is inserted in the bent cut line  56 . 
     In the modification example, the cut line  55  and the cut line  56  intersect heat radiated from the susceptor  24  a plurality of times, and thus transfer of radiation heat may be blocked more surely as compared with the case of using the cut line  49  and the cut line  53 . That is, insulating performance can be improved. 
     If the insulator ceiling part  48  and the insulator body part  52  are physically cut into small pieces, it is sufficient to cut the passage of an induction current  47  into small pieces. This is possible by forming only cut lines in the insulator ceiling part  48  and the insulator body part  52 , and by this, the insulator  25  can be less heated and the susceptor  24  can be heated more efficiently. In the second embodiment and the modification example of the second embodiment, insulating and heat-resistant zirconium sheets are inserted in the cut lines to improve insulating performance and energy efficiency much more. 
     Furthermore, in the second embodiment, the cut line  49  is sloped from a vertical direction, and the cut line  53  is sloped from a radial direction. That is, the cut line  49  and the cut line  53  are sloped from a heat radiation direction. However, if radiation heat is negligible, the cut line  49  and the cut line  53  may be formed in the same direction as the direction of radiation heat. 
     According to the present invention, there is provided a heat treatment apparatus configured to grow silicon carbide single crystal films or silicon carbide polycrystal films on a plurality of silicon carbide substrates. In the heat treatment apparatus, a coil is installed around an outside of a reaction tube to generate a magnetic field, a susceptor is installed in the reaction tube so as to be heated by an induction current; an insulator is installed between the susceptor and the reaction tube; the insulator is divided into parts in a circumferential direction, and an insulating material is inserted between the divided parts of the insulator. Therefore, an induction current generating in the insulator by a magnetic field created from the coil can be cut by the insulating material so that the insulator can be less heated, and along with this, the susceptor can be efficiently heated. 
     In addition, according to the present invention, a quartz container is additionally disposed between the reaction tube and the insulator, and the insulator is fixed to the quartz container for integration. Therefore, when the quartz container is installed or replaced, it is unnecessary to touch the insulator. 
     In addition, according to the present invention, the insulator is stitched to the quartz container with carbon threads, and the carbon threads are disposed in directions crossing an induction current. Therefore, an induction current may not be generated in the carbon threads, and thus abnormal heating or thermal aging of the carbon threads can be prevented to increase the durability of the carbon threads. 
     (Supplementary Note) 
     The present invention also includes the following embodiments. 
     (Supplementary Note 1) According to an embodiment of the present invention, there is provided a heat treatment apparatus for growing silicon carbide single crystal films or silicon carbide polycrystal films on a plurality of silicon carbide substrates, the heat treatment apparatus comprising: a coil installed around an outside of a reaction tube to generate a magnetic field; a susceptor installed in the reaction tube and configured to be heated by an induction current; and an insulator installed between the susceptor and the reaction tube, wherein the insulator is divided into parts in a circumferential direction, and an insulating material is inserted between the divided parts of the insulator. 
     (Supplementary Note 2) 
     According to another embodiment of the present invention, there is provided a heat treatment apparatus for growing silicon carbide single crystal films or silicon carbide polycrystal films on a plurality of silicon carbide substrates, the heat treatment apparatus comprising: 
     a coil installed around an outside of a reaction tube to generate a magnetic field; 
     a susceptor installed in the reaction tube and configured to be heated by an induction current; and 
     a disk-shaped insulator ceiling part and a cylindrical insulator body part installed between the susceptor and the reaction tube, 
     wherein cut lines are formed in the insulator ceiling part and the insulator body part in circumferential directions, and insulating materials are inserted in the cut lines. 
     (Supplementary Note 3) 
     The heat treatment apparatus of Supplementary Note 1 or 2 may further comprise a quartz container disposed between the reaction tube and the insulator, wherein the insulator may be fixed to the quartz container for integration. 
     (Supplementary Note 4) 
     In the heat treatment apparatus of Supplementary Note 3, the quartz container may have a split structure that allows vertical multi-layer stacking. 
     (Supplementary Note 5) 
     In the heat treatment apparatus of Supplementary Note 2, the cut line of the insulator ceiling part may be sloped from a vertical direction when viewed in vertical section. 
     (Supplementary Note 6) 
     In the heat treatment apparatus of Supplementary Note 2, the cut line of the insulator body part may be sloped from a radial direction when viewed in horizontal section. 
     (Supplementary Note 7) 
     In the heat treatment apparatus of Supplementary Note 2, the cut line of the insulator ceiling part may be bent in a &lt;-shape when viewed in vertical section. 
     (Supplementary Note 8) 
     In the heat treatment apparatus of Supplementary Note 2, the cut line of the insulator body part may be bent in a &lt;-shape when viewed in horizontal section.