Abstract:
Provided is a semiconductor manufacturing system capable of loading a plurality of semiconductor wafers into a vertical reaction tube, and performing a thermal process. The semiconductor manufacturing system includes a first wafer loading boat, a second wafer loading boat, a plate cap, a door plate and a lifting system. The first wafer loading boat is mounted in the reaction tube and includes a plurality of holder supporters that support a wafer holder in a shape of a board, the wafer holder being loaded vertically at a predetermined interval and on which the semiconductor wafer is rested on. The second wafer loading boat is inside or outside the first wafer loading boat and has a wafer supporter that supports the semiconductor wafer. The lifting system moves either the first wafer loading boat or the second wafer loading boat vertically and separates the semiconductor wafer, which is loaded on the wafer holder, from the wafer holder at a predetermined height. The semiconductor manufacturing system makes it possible to easily load or unload the semiconductor wafer in the wafer loading boats without an additional wafer handling structure. The system also enables to control the gap between the semiconductor wafer and the wafer holder statically from the beginning of thermal processing and dynamically during the thermal processing in order to eliminate any mechanical damages to the wafer caused by stress.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a semiconductor manufacturing system, and more particularly, to a semiconductor manufacturing system having a vertical reaction tube by which a plurality of semiconductor wafers can be processed at a time.  
           [0003]    2. Description of the Related Art  
           [0004]    Since a thermal process during semiconductor manufacturing needs considerable time, it is preferable that a plurality of semiconductor wafers be processed at one time. Generally, a wafer loading boat as a wafer loading structure on which a semiconductor wafer can be deposited horizontally and a vertical reaction tube in a pipe shape are used in the semiconductor manufacturing system during the thermal process because the uniformity of the thermal process is affected by the uniformity of the flow of a reaction gas. In the wafer loading boat, slots are formed at vertical interval for supporting the semiconductor wafer, and at least one or two edges of the semiconductor wafer is then fitted in the slots.  
           [0005]    However, in such conventional semiconductor manufacturing system, since the semiconductor wafer is supported on its edges which are placed in the slots, a supporting force is concentrated on the edge area of the semiconductor wafer contacting the slots. In a thermal process at a high temperature, a significant supporting force is concentrated on the edges of the semiconductor wafer, as the gravitational stress due to the weight of the wafer and the thermal stress due to the different thermal expansion are applied to the semiconductor wafer, thereby resulting in final mechanical deformation of the semiconductor wafer such as a form of warp, bow and slip. Such mechanical deformation becomes a more serious problem in a large size semiconductor wafer, a diameter of which is 300 mm (12 inches) and higher, and thus reliability of a process is reduced. In order to prevent such mechanical deformation of the wafer due to high temperature thermal processing and to distribute the gravitational and thermal stresses of the wafer evenly, a wafer loading boat capable of supporting an entire bottom or a portion of surface of the semiconductor wafer is needed. However, a semiconductor manufacturing system having an additional supporting means will be complex and involve still incomplete solution to avoid the mechanical deformation despite higher process cost, and a user will have difficulties in loading and unloading the semiconductor wafer.  
         SUMMARY OF THE INVENTION  
         [0006]    To solve the above-described and related problems, it is an object of the present invention to provide a semiconductor manufacturing system capable of preventing mechanical deformation of a semiconductor wafer having a large diameter during a thermal process, and by which a time of loading and unloading the semiconductor wafer on a plate using a wafer holder can be reduced, thereby reducing costs of manufacturing the semiconductor.  
           [0007]    In an aspect, the present invention provides a semiconductor manufacturing system capable of loading a plurality of semiconductor wafers into a vertical reaction tube, and performing a thermal process comprising a first wafer loading boat which is mounted in the reaction tube and includes a plurality of holder supporters that support a wafer holder in a shape of a board, the wafer holder being loaded vertically at a predetermined interval and on which the semiconductor wafer is rested on, a second wafer loading boat which is inside or outside the first wafer loading boat and has a wafer supporter that is located under the semiconductor wafer to support the semiconductor wafer which will rest on the wafer holder, a plate cap which supports the first wafer loading boat and the second loading boat in their lower portions, a door plate which supports the plate cap in the lower portion of the plate cap, and a lifting system which moves at least one of the first wafer loading boat and the second wafer loading boat vertically and separates the semiconductor wafer, which is resting on the wafer holder, from the wafer holder at a predetermined height.  
           [0008]    The second wafer loading boat is inwardly adjacent to the first wafer loading boat. The first wafer loading boat comprises the first supporting pillars which are arranged to form a receiving space in a shape of a cylinder inside the first wafer loading boat, a first upper board and a first lower board on which both ends of the first supporting pillars are fixed, and holder supporters which are formed on the first supporting pillars at a predetermined vertical interval to support the wafer holder horizontally. The holder supporters are slots formed by grooving the first supporting pillars. The holder supporters are protrusions protruded at a right angle with respect to the first supporting pillars toward a center of the receiving space to a predetermined length.  
           [0009]    The second wafer loading boat comprises the second supporting pillars which are arranged to form an accommodating space in a shape of a cylinder inside the second wafer loading boat, a second upper board and a second lower board at which both ends of supporting pillars are fixed, and wafer supporters which are formed at the second supporting pillars at a predetermined vertical interval to support the semiconductor wafer horizontally. The wafer supporters are protrusions protruded from the second supporting pillars to a predetermined length. The protrusions shall be (or may be) inclined at a predetermined angle.  
           [0010]    The wafer supporters further include supporting protrusions which are extended from the ends of the protrusions upwardly at a predetermined height. The ends of the supporting protrusions are inclined inwardly or outwardly toward the center of the receiving space. The wafer supporters are slots formed by grooving the second supporting pillars. The bottom of the slot on which the semiconductor wafer is resting is inclined downwardly at a predetermined angle. The predetermined angle is inclined in a range of 0.1° to 45° from horizontal level.  
           [0011]    The wafer holder comprises a main board which is a circular board, and opening portions are made at the rim of the circular board to allow the second wafer loading boat and the wafer supporters, protrusions, or pillars to vertically move through freely. The opening portion is extended from a circumference of the main board toward the center of the main board at a predetermined length and shape.  
           [0012]    The plate cap supports lower portions of the first wafer loading boat and the second wafer loading boat.  
           [0013]    The lifting system moves electrically, by a method of fine controlling of a motor, or hydraulically by a fluid pressure. The lifting system is connected to a lower portion of the second wafer loading boat and vertically moves the second wafer loading boat. The lifting system is connected to a lower portion of the first wafer loading boat and vertically moves the first wafer loading boat. The lifting system includes a lifting controller which controls the height at which the first wafer loading boat and the second wafer loading boat move vertically within the pitch of each slot of the holder supporters.  
           [0014]    The second wafer loading boat is adjacent to the first wafer loading boat, and the wafer supporters of the second wafer loading boat are protrusions.  
           [0015]    The semiconductor manufacturing system according to the present invention includes dual boats having a first wafer loading boat in which the wafer holder can be loaded and a second wafer loading boat which is inside or outside of the first wafer loading boat and in which the semiconductor wafer can be loaded in order to lift the semiconductor wafer up to a predetermined height from the wafer holder. Thus, it is possible to load or unload the semiconductor wafer without unloading the wafer holder from the first wafer loading boat. Therefore, loading or unloading the semiconductor wafer can be performed in a shorter time.  
           [0016]    In addition, heat distribution is uniform in the semiconductor wafer due to resting the semiconductor wafer on the wafer holder, which is usually made of heat-conductive material, when loading the semiconductor wafer. Therefore, uniformity in a semiconductor manufacturing process can be improved.  
           [0017]    Further, as a wafer bows during a thermal process at high temperatures, the center of wafer can ideally touch the center of the wafer holder with an optimized contact area to minimize the mechanical deformation by adjusting the gap between the first wafer loading boat and the second wafer loading boat before starting the processing. It is possible to adjust the gap dynamically even during the process.  
           [0018]    Finally, the shape of the wafer holder can be changed to optimize the contact area of the semiconductor wafer with the wafer holder. Thus, any mechanical or physical defects in the contacting area can be prevented from occurring during the thermal process. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The above object and advantages of the present invention will become more apparent by describing in detail-preferred embodiments thereof with reference to the attached drawings in which:  
         [0020]    [0020]FIG. 1 is a sectional view of a semiconductor manufacturing system according to the present invention;  
         [0021]    [0021]FIG. 2A is an enlarged side-sectional view of portion “A” of FIG. 1;  
         [0022]    [0022]FIG. 2B is a side-sectional view of a dual boat mounted in a semiconductor wafer according to an embodiment of the present invention;  
         [0023]    [0023]FIG. 3 is a top view of a dual boat mounted in a semiconductor wafer according to an embodiment of the present invention;  
         [0024]    [0024]FIG. 4 is a top exploded view of the dual boat mounted in a semiconductor wafer according to an embodiment of the present invention;  
         [0025]    [0025]FIG. 5 is a top view of a dual boat mounted in a semiconductor manufacturing system according to an embodiment of the present invention;  
         [0026]    [0026]FIG. 6 is a plan view of a wafer holder used in the embodiment of FIG. 5;  
         [0027]    [0027]FIG. 7 is an enlarged plan view of a dual boat obtained from the embodiment of FIG. 5;  
         [0028]    [0028]FIG. 8 is an enlarged plan view of portion “B” of FIG. 7;  
         [0029]    [0029]FIGS. 9A through 9D are sectional views of a wafer supporter of a second wafer loading boat of a semiconductor manufacturing system, according to an embodiment of the present invention;  
         [0030]    [0030]FIG. 10A is a sectional view a wafer supporter of a second wafer loading boat of a semiconductor manufacturing system, according to an embodiment of the present invention;  
         [0031]    [0031]FIG. 10B is a sectional view showing a warped semiconductor wafer on a wafer supporter of a second wafer loading boat of FIG. 10A after a thermal process at a high temperature;  
         [0032]    [0032]FIG. 11 is a sectional plan view of a dual boat mounted in a semiconductor manufacturing system, according to an embodiment of the present invention;  
         [0033]    [0033]FIG. 12A is a side-sectional view of a dual boat, according to an embodiment of the present invention, mounted in a reaction tube;  
         [0034]    [0034]FIG. 12B is a side-sectional view of a dual boat when loading and unloading a semiconductor wafer; and  
         [0035]    [0035]FIG. 12C is a lateral-sectional view showing the handling of a semiconductor wafer in a dual boat, according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.  
         [0037]    [0037]FIG. 1 is a sectional view of a semiconductor manufacturing system according to the present invention. FIG. 2A is an enlarged-sectional view of portion “A” of FIG. 1. FIG. 2B is a side-sectional view of a dual boat mounted in a semiconductor wafer according to an embodiment of the present invention.  
         [0038]    Referring to FIG. 1, a semiconductor manufacturing system includes a reaction tube  30  during thermal process. A dual boat including a first wafer loading boat  10  and a second wafer loading boat  20 , in which a semiconductor wafer  100  is loaded, are included in the reaction tube  30 . The first wafer loading boat  10  includes a plurality of wafer supporters that are horizontally loaded and a plate cap  40  which supports the lower portion of the dual boat. In addition, the semiconductor manufacturing system includes a door plate  50 , which supports the plate cap  40  thereunder, inserts the dual boat in the reaction tube  30  and pulls the dual boat out from the reaction tube  30 , and a lifting system  50  which moves one plate of the dual boat vertically within a limited height.  
         [0039]    Referring to FIGS. 2A and 2B, the dual boat includes the first wafer loading boat  10  and the second wafer loading boat  20  inside the first wafer loading boat  10 .  
         [0040]    In the first wafer loading boat  10 , a number of at least three first supporting pillars  11  are arranged in parallel to each other so as to form a cylindrical space for accommodating the semiconductor wafer  100 . In this embodiment, a number of four first supporting pillars  11  are provided. A first upper board  12   a  and a first lower board  12   b  for respectively fixing the first supporting pillars  11  at the same level are connected to both ends of the first supporting pillars  11 . Each of the first supporting pillars  11  includes a holder supporter  11   a  in which a slot is formed to a predetermined depth in each of the first supporting pillars  11 , and thus a circular board can be put on the holder supporter  11   a.  The holder supporter  11   a  is formed in a shape of a slot. A wafer holder  25  in a shape of a circular board is put on the holder supporter  11   a.  The holder supporter  11   a  may be a part that is protruded to a predetermined length from the inner center of each of the first supporting pillars  11 . The interval between the holder supporters  11   a  is long enough to allow a wafer loading blade (not shown) to be inserted under the semiconductor wafer  100 .  
         [0041]    In the second wafer loading boat  20 , a number of at least three second supporting pillars  11  are arranged in parallel to each other so as to form a cylindrical space for receiving the semiconductor wafer  100 . A second upper board  22   a  and a second lower board  22   b  for respectively fixing the second supporting pillars  21  at the same level are connected to both ends of the second supporting pillars  21 . In each second supporting pillar  21 , a wafer supporter  20   a  is protruded to a predetermined length from the inner of each of the second supporting pillars  21 , so as to lift both edges of the semiconductor wafer  100 . Here, the wafer supporter  20   a  is located in the lower portion of the wafer holder  25 , and its position changes into a portion between the holder supporters  11   a  when the semiconductor wafer is lifted.  
         [0042]    The first supporting pillars  11  and the second supporting pillars  21  are arranged not to overlap with one another, and thus a case where the wafer supporter  20   a  is penetrated with overlapping with an opening portion  25   a  of a wafer holder  25 , and the semiconductor wafer  100  is not supported by the wafer holder  25  can be prevented.  
         [0043]    The first wafer loading boat  10  and the second wafer loading boat  20  are supported by one plate cap  40  thereunder. The lifting system  70  extended through the plate cap  40  is connected to the lower portion of the first wafer loading boat  10  or the second wafer loading boat  20 , moves one of the first wafer loading boat  10  or the second wafer loading boat  20 , and thus lifts the semiconductor wafer  100  up to a predetermined height from the wafer holder  25 .  
         [0044]    The first wafer loading boat  10  and the second wafer loading boat  20  are formed of quartz or silicon carbide SiC, which have high durability at a high temperature. Likewise, the wafer holder  25  is formed of quartz or silicon carbide SiC. However, it is desirable that the wafer holder  25  is formed by using silicon carbide SiC considering thermal conductivity or thermal absorption. In particular, in a thermal process at very high temperature, it is desirable that the first and the second wafer loading boats and the wafer holder  25  are formed by using silicon carbide SiC.  
         [0045]    [0045]FIG. 3 is a top view of an embodiment of a dual boat mounted in a semiconductor wafer, according to the present invention. FIG. 4 is a top exploded view of the dual boat mounted in a semiconductor wafer, according to an embodiment of the present invention.  
         [0046]    Referring to FIGS. 3 and 4, the first wafer loading boat  10  is mounted as an outmost circle, and the wafer holder  25  is put on the holder supporter  11   a  which is included in the first wafer loading boat  10 .  
         [0047]    The wafer holder  25  includes a main board  25   b  in a shape of a circular board and an opening portion  25   a  which is extended from circumference of the main board  25   b  to the center thereof. The opening portion  25   a  is formed such that the second supporting pillars  21  of the second wafer loading boat  20  vertically lifts a little space through the opening portion  25   a.  The width of the opening portion  25   a  is greater than the size of the wafer supporter  20   a.    
         [0048]    The second wafer loading boat  20  is formed inside of the first wafer loading boat  10 . The semiconductor wafer  100  is formed inside of the second wafer loading boat  20 . A part of the circumference of the semiconductor wafer  100  is supported by the wafer supporter  20   a  of the second wafer loading boat  20 . Thus, the wafer holder  25  is supported only by the holder supporter  11   a  of the first wafer loading boat  10 , and the semiconductor wafer  100  is supported by both the holder supporter  11   a  of the first wafer loading boat  10  and the second wafer loading boat  20 . The semiconductor wafer  100  can be lifted from the wafer holder  25  to a certain height by vertically moving either the first wafer loading boat  10  or the second wafer loading boat  20 . Here, it is preferable that the semiconductor wafer  100  is lifted up to the middle of the interval between the holder supporters  11   a.  Thus, the semiconductor wafer  100  has spaces under and over it and can be loaded and unloaded without contacting adjacent semiconductor wafers.  
         [0049]    [0049]FIG. 5 is a top view of another embodiment of the dual boat mounted in a semiconductor manufacturing system, according to the present invention.  
         [0050]    Referring to FIG. 5, the first supporting pillar  11  has a groove in its center, which faces the center of the accommodating space. The second supporting pillar  21  is arranged in the similar position on the circumference as the first supporting pillar  11 . In the second supporting pillar  21 , a slot as in the wafer supporter  20   a  is formed at a predetermined interval. The holder supporter  11   a  is formed such that the wafer holder  25  is supported by the lower end of the first supporting pillar  11 . Since it is not necessary to arrange the first supporting pillar  11  and the second supporting pillar  21  to cross each other, the structure and manufacture of such dual boat are simple.  
         [0051]    [0051]FIG. 6 is a plan view of a wafer holder used in the embodiment of FIG. 5. Referring to FIG. 6, the opening portion  25   a  is formed in a shape of a square in the area of the main board  25   b  around which the second supporting pillar  21  is located so as to prepare for the case where the first supporting pillar  11  has a section in a shape of a square. It is desirable that the shape of the opening portion  25   a  is the same as the shape of the section of the second supporting pillar  21 .  
         [0052]    [0052]FIG. 7 is a plan view of a dual boat obtained from the embodiment of FIG. 5. FIG. 8 is a plan view of portion “B” of FIG. 7.  
         [0053]    Referring to FIGS. 7 and 8, the first supporting pillar  11  of the first wafer loading boat  10  is similar with that of FIG. 5. However, the wafer supporter  20   a  of the second supporting pillar  21  is in a shape of a protrusion type rather a slot.  
         [0054]    [0054]FIGS. 9A through 9D are sectional views of an embodiment of a wafer supporter of a second wafer loading boat of a semiconductor manufacturing system according to the present invention.  
         [0055]    Referring to FIG. 9A, the wafer supporter  20   a  is protruded horizontally at right angle to the second supporting pillar  21 . The surface of the wafer supporter  20   a,  on which the semiconductor wafer  100  is put, is flat so that the semiconductor wafer  100  can be stably supported. In particular, the top surface of the wafer supporter  20   a  is almost square, and thus the semiconductor wafer  100  can be stably put on the surface of the wafer supporter  20   a.    
         [0056]    [0056]FIGS. 9B through 9D shows changes in the wafer supporter  20   a  of FIG. 9A, wherein the wafer supporter  20   a  has certain angles upwardly or downwardly from its horizontal position. If the wafer supporter  20   a  is inclined upwardly as shown in FIG. 9B, its end on which the semiconductor wafer  100  is put is rounded or flattened so as to prevent scratches occurring in a contact area of the semiconductor wafer  100  with the wafer supporter  20   a.    
         [0057]    Such wafer supporter  20   a  can prevent defects such as a slip or a scratch occurring when the semiconductor wafer  100  contacts the wafer supporter  20   a  by minimizing the contact area of the semiconductor wafer  100  with the wafer supporter  20   a.    
         [0058]    Referring to FIG. 9D, the wafer supporter  20   a  further includes a protrusion supporter  201  which is upwardly protruded from an end of the wafer supporter  20   a.  In such wafer supporter  20   a,  the semiconductor wafer  100  is supported by an end of the protrusion supporter  201   a  rather the surface of the wafer supporter  20   a.  The end of the protrusion supporter  201   a  can be formed horizontally or be inclined upwardly or downwardly. Thus, the protrusion supporter  201   a  having the inclined end can be used during thermal process at a high temperature, and the protrusion supporter  201   a  having the flattened end can be used to the process at a middle range of temperature.  
         [0059]    [0059]FIG. 10A is a sectional view of another embodiment of a wafer supporter of a second wafer loading boat of a semiconductor manufacturing system, according to the present invention. FIG. 10B is a sectional view showing a warped semiconductor wafer on a wafer supporter of a second wafer loading boat of FIG. 10A after a thermal process at a high temperature.  
         [0060]    Referring to FIG. 10A, the wafer supporter  20   a  in a shape of a slot is formed by grooving the second supporting pillar  21 . Here, the lower portion of the wafer supporter  20   a  is inclined downwardly with predetermined angle in a range of 0.10 to 45° so as to minimize the contact area of the semiconductor wafer  100  with the wafer supporter  20   a,  and thus only a small portion of the end of the semiconductor wafer  100  are rested on the wafer supporter  20   a.    
         [0061]    Referring to FIG. 10B, in the thermal process at a high temperature, the semiconductor wafer  100  is heated, and thus the middle portion of the semiconductor wafer  100  is warped downwardly by gravity. Such mechanical deformation causes the edges of the semiconductor wafer  100  to be warped as well, and thus the contact area of the semiconductor wafer  100  with the wafer supporter  20   a  increases. Then, a supporting point moves toward the middle of the semiconductor wafer  100 , and a supporting force of the semiconductor wafer  100  which is warped acts on a surface contact rather than a contact point, thereby reducing stress in the semiconductor wafer  100 .  
         [0062]    [0062]FIG. 11 is a sectional plan view of another embodiment of the dual boat mounted in a semiconductor manufacturing system, according to the present invention.  
         [0063]    Referring to FIG. 11, each of the first supporting pillar  11  has two pillars which are arranged in parallel with each other and are separated from each other by a predetermined interval. The width of the predetermined interval is larger than the width of the section of the second supporting pillar  21 . Thus, a case where opening portion  25   a  of the wafer holder  25  and the hold supporter  11   a  of the first supporting pillar  11  overlap with each other and thus the wafer holder  25  is not supported can be prevented. In addition, such first supporting pillar  11  is advantageous in that the first supporting pillar  11  and the second supporting pillar  21  can be arranged symmetrically. Here, the first and the second supporting pillars  11  and  21  can be formed in shapes of a cylinder, a square or other shapes having a polygonal section.  
         [0064]    [0064]FIG. 12A is a side-sectional view of the dual boat according to an embodiment of the present invention being mounted in a reaction tube. FIG. 12B is a side-sectional view of the dual boat when loading and unloading a semiconductor wafer, according to an embodiment of the present invention.  
         [0065]    Referring to FIG. 12A, when the thermal process is performed while the semiconductor wafer  100  is loaded on to the dual boat, the wafer supporter  20   a  of the second wafer loading boat  20  is arranged in parallel with the holder supporter  11   a  of the first wafer loading boat  10 . Thus, the semiconductor wafer  100  is supported by the wafer holder  25  while contacting the wafer holder  25 . Then, a reaction gas is provided into the reaction tube  30 , and the semiconductor wafer  100  is thermally processed.  
         [0066]    Referring to FIG. 12B, when the semiconductor wafer  100  is loaded or unloaded before or after the thermal process is performed, the door plate  50  in FIG. 1 is lowered, and the dual boat is pulled out from the reaction tube  30  to provide a position in which the semiconductor wafer  100  can be loaded or unloaded. Then, the lifting system  70  lifts either the first wafer loading boat  10  or the second wafer loading boat  20  up to a predetermined height to lift the semiconductor wafer  100  from the wafer holder  25  to a predetermined height. Thus, the semiconductor wafer  100  is located between the holder supporters  11   a  and has spaces under and above it.  
         [0067]    [0067]FIG. 12C shows a phase of unloading the semiconductor wafer  100  from the dual boat using a wafer handler  150 .  
         [0068]    Referring to FIG. 12C, if the semiconductor wafer  100  has empty spaces under and above as shown in FIG. 12B, a blade  151  of the wafer handler  150  is inserted under the semiconductor wafer  100 , and the semiconductor wafer  100  is pulled out from the second wafer loading boat  20  and is loaded in a cassette placed in out space (not shown). The semiconductor wafer  100  may be pulled out from the exterior cassette and be loaded in the wafer supporter  20   a  of the second wafer loading boat  20 .  
         [0069]    The lifting system  70  is mounted in the plate cap  40  and the door plate  50  under the dual boat. The lifting system  70  is in a shape of a cylinder, an end of which is connected to the second lower board  22   b  while other end is supported by the door plate  50 . Thus, the semiconductor wafer  100  is lifted by lifting the second wafer loading boat  20  a little. Here, in order to prevent the semiconductor wafer  100  from bumping into the wafer holder  25 , it is preferable that the width of moving the lifting system  70  is smaller than the width of the spaces between the holder supporters  11   a.  The lifting system  70  can be moved electrically by a method of fine controlling a motor, or fluid hydraulically by pressurized or vacuum pressure which can smoothly provide a huge lifting force.  
         [0070]    The lifting system  70  may be connected to the first lower board  12   b  of the first wafer loading boat  10 . Thus, the semiconductor wafer  100  can be lifted from the wafer holder  25  by moving vertically the first wafer loading boat  10 . In this case, the first wafer loading boat  10  has to move downwardly.  
         [0071]    As described above, the semiconductor manufacturing system according to the present invention includes the dual boat formed by overlapping the first wafer loading boat  10  and the second wafer loading boat  20  and supports the semiconductor wafer  100  by using the wafer holder  25 . Therefore, a semiconductor wafer having a diameter greater than 12 inches, i.e., 300 mm, can be thermally processed without being warped at a high temperature. In addition, the wafer holder  25  under the semiconductor wafer  100  serves as a heat sink in a process of forming a film by thermal oxidation or by chemical vapor deposition (CVD) and an annealing process, and heat is uniformly distributed in the semiconductor wafer  100 . Therefore, uniformity in the semiconductor manufacturing process can be improved.  
         [0072]    In addition, it is possible to directly load or unload the semiconductor wafer  100  in or out of the dual boat without unloading the wafer holder  25  from the dual boat, by configuring the first wafer loading boat  10  and the second wafer loading boat  20  such that they can be lifted at a predetermined height. Thus, the semiconductor wafer  100  can be loaded or unloaded while using the wafer holder  25  in the dual boat.  
         [0073]    Considering safety of the operation, it is preferable that a lighter one of the first wafer loading boat  10  and the second wafer loading boat  20  is lifted when loading or unloading the semiconductor wafer  100 .  
         [0074]    The lifting system  70  can be provided under the plate cap  40  or in the door plate  50  so as to lift the first wafer loading boat  10  or the second wafer loading boat  20 . Without the additional lifting system  70 , the second wafer loading boat  20  can be located in a higher portion than the first wafer loading boat  10  by lowering the door plate  50  out of the reaction tube  30  and resting the door plate  50  on the floor. Then, since the dual boat is affected by gravity, the second wafer loading boat  20  is lifted up to a predetermined height with respect to the first wafer loading boat  10 . Thus, the semiconductor wafer  100  is separated from the wafer holder  25 . Here, in order to accurately control the lifting height, the lifting system  70  includes (not shown) in which a motor for controlling a height such as a step motor is mounted. Thus, the lifting controller (not shown) can accurately control the height at which the semiconductor wafer  100  is lifted from the wafer holder  25 .  
         [0075]    The controller (not shown) is also connected to a central control unit (not shown) of the semiconductor manufacturing system and can be controlled in creating a recipe file for a unit process. Then, it is possible to program the semiconductor manufacturing system to control the height of the semiconductor wafer  100  from the wafer holder  25  during the thermal process.  
         [0076]    In the present invention, the first wafer loading boat  10  is placed outside the second wafer loading boat  20 . However, the second wafer loading boat  20  can be placed outside the first wafer loading boat  10 . In this case, the above embodiments can be applied. However, it is preferable that the wafer supporter  20   a  is in a shape of a protrusion type, which is extended from the second supporting pillar  21  to under the semiconductor wafer  100 , rather than a shape of a slot type, which is formed by grooving the second supporting pillar  21 .  
         [0077]    In the semiconductor manufacturing system according to the present invention, the semiconductor wafer is supported by the wafer holder which is under the semiconductor wafer, and thus the semiconductor wafer having a large diameter can be supported without mechanical deformation of the semiconductor wafer.  
         [0078]    In addition, since the wafer holder serves as a heat sink during a thermal process, temperature can be uniformly controlled, and thus reliability of the process can be improved.  
         [0079]    The semiconductor manufacturing system according to the present invention includes the dual boat having the first wafer loading boat which supports the wafer holder and the second wafer loading boat which lifts the semiconductor wafer from the wafer holder up to a predetermined height. Then, the semiconductor wafer can be loaded or unloaded without unloading the wafer holder. Thus, a time necessary for loading or unloading the semiconductor wafer can be reduced.  
         [0080]    In addition, the shape of the wafer supporter can be changed to minimize the contact area of the semiconductor wafer with the wafer supporter. Thus, any mechanical or physical defect in the contact area can be prevented from occurring during the thermal process.  
         [0081]    While this invention has been particularly described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and equivalents thereof.