Abstract:
A semiconductor manufacturing apparatus and a wafer loading/unloading method thereof increase productivity. The semiconductor manufacturing apparatus includes a first boat and a second boat having a plurality of first slots and a plurality of second slots, respectively, and disposed such that the first slots and the second slots alternate each other, the first boat mounting a plurality of first wafers in the first slots to direct front faces of the first wafers in a predetermined direction, the second boat mounting a plurality of second wafers in the second slots to direct back faces of the second wafers in the predetermined direction; a reaction tube having an opening and containing the first and second boats mounting the first and second wafers; a plate sealing up the opening of the reaction tube containing the first boat and the second boat; a reaction gas supplier supplying reaction gas into the sealed reaction tube for a predetermined process; and a reaction gas exhauster exhausting the reaction gas from the reaction tube to the external of the reaction tube after the predetermined process.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 from Korean Patent Application 10-2008-0002411, filed on Jan. 9, 2008, the disclosure of which are hereby incorporated by reference in their entirety for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to semiconductor device manufacturing apparatuses, and more particularly, to a semiconductor device manufacturing apparatus for performing diffusion and deposition processes and to a wafer loading/unloading method thereof. 
     2. Description 
     A semiconductor device is generally manufactured through selective and repeated processes such as, for example, a photo, etching, diffusion, chemical vapor deposition, ion implantation, metal deposition on a wafer. 
     In the above-mentioned diffusion process, a process of diffusing impurity of a desired conductive type is performed on a wafer in a high-temperature atmosphere. 
     A semiconductor manufacturing apparatus performing the diffusion process may be employed to thermally diffuse conductive impurity such as, for example, phosphorus into a single crystal silicon or polysilicon at about 700° C. or more, or to heat the wafer in an oxygen atmosphere, thereby obtaining a thermal oxide layer, or to perform annealing and baking etc. Further, the semiconductor manufacturing apparatus may be used to get a deposition layer such as, for example, polysilicon layer and silicon nitride layer through a deposition process. 
     Such semiconductor manufacturing apparatuses undergoing diffusion and deposition processes are almost used as a batch type to process a plurality of wafers once in view of productivity. In the batch-type semiconductor manufacturing apparatus, relatively more wafers should be loaded within one reaction tube to cut down on production costs. 
     A semiconductor manufacturing apparatus according to the conventional art is described as follows, referring to the accompanied drawings. 
       FIG. 1  is a sectional view schematically illustrating a semiconductor manufacturing apparatus according to the conventional art. 
     With reference to  FIG. 1 , a conventional semiconductor manufacturing apparatus includes a reaction tube  10  having a bell shape, a heater  20  adapted surrounding the external part of reaction tube  10  to heat the interior of the reaction tube  10 , a plate  30  raised from a lower part of the reaction tube  10  to seal up the reaction tube  10 , and a boat  40  for loading with an equal interval a plurality of wafers  12  in an upper center part of the plate  30 . 
     The semiconductor manufacturing apparatus may further include a reaction gas supplier for supplying reaction gas into the reaction tube  10 , and an exhauster for exhausting gas after completing a corresponding process within the reaction tube  10 . 
     In the boat  40 , a plurality of slots  42  are formed to support with an equal interval, back faces  12   b  of the plurality of wafers  12  so that front faces  12   a  of the plurality wafers  12  are directed upward. The slot  42  is formed in a flute shape into which an outer circumference face of the wafer  12  is inserted, at a position that a gravity center of the wafer  12  corresponds to a center of the boat  40  within the boat  40 , or in a shape the back face  12   b  of an edge of the wafer  12  can be loaded. The back faces  12   b  of the wafers  12  are supported by the plurality slots  42 . For example, the wafer  12  may be supported by the plurality of slots  42  formed with an azimuth of about 120° within the boat  40 . 
     That is, the boat  40  is formed as a single individual having plurality slots  42  in which a plurality of wafers  12  are inserted or loaded with a uniform interval in a stack structure. For example, the boat  40  is formed to load the wafers  12  of about 70 to about 150 sheets with a uniform interval therebetween, the wafer  12  having a diameter of 300 mm. 
     However, here the plurality of wafers  12  are stacked in one direction. Thus, for example, when the wafers are stacked below an appropriate interval, an error in corresponding diffusion and deposition processes may be caused or an error in a wafer loading/unloading operation may be caused. When a plurality of wafers  12  are loaded into the boat  40  with an interval of about 7.5 mm or below, it may be difficult to provide uniformity in the deposition process. Further, when the interval between the plurality of wafers  12  is lessened to 7.5 mm or below, an alignment margin between the wafers  12  and a blade of transfer robot loading/unloading the wafers  12  may not increase, thereby causing damage or scratches on the wafers  12 . 
     In other words, in a semiconductor manufacturing apparatus according to the conventional art, a diffusion layer or deposition layer of given thickness can be formed on front faces  12   a  and back faces  12   b  of the plurality wafers  12  by loading with the same interval the plurality of wafers  12  having horizontal level within the boat  40  in which a plurality of slots  42  are formed with the same interval therebetween. 
     As described above, a semiconductor manufacturing apparatus according to the conventional art may have the following difficulties. 
     First, relatively more wafers  12  may not be loaded as the wafers  12  should be loaded limited within the boat  40  having a plurality of slots  42  formed to support back faces  12   b  of plurality wafers  12 , thereby decreasing productivity. 
     Secondly, when an interval between plurality wafers  12  loaded in the boat  40  is reduced to below a proper level, damage and scratches on the wafers  12  may be caused due to a collision between a blade of transfer robot and the wafers  12 , thereby decreasing a production yield. 
     SUMMARY 
     Exemplary embodiments of the invention provide a semiconductor manufacturing apparatus and a wafer loading/unloading method thereof, which can increase the number of wafers capable of being simultaneously processed so as to increase productivity. In addition, damage and scratches on wafers causable by a collision between a blade of transfer robot and wafers can be prevented even when an interval between a plurality of wafers is reduced to a given level or below, thereby increasing production yield. 
     In accordance with an exemplary embodiment of the invention, a semiconductor manufacturing apparatus is provided. The semiconductor manufacturing apparatus includes a first boat and a second boat having a plurality of first slots and a plurality of second slots, respectively, and disposed such that the first slots and the second slots alternate each other, the first boat mounting a plurality of first wafers in the first slots to direct front faces of the first wafers in a predetermined direction, the second boat mounting a plurality of second wafers in the second slots to direct back faces of the second wafers in the predetermined direction; a reaction tube having an opening and containing the first and second boats mounting the first and second wafers; a plate sealing up the opening of the reaction tube containing the first boat and the second boat; a reaction gas supplier supplying reaction gas into the sealed reaction tube for a predetermined process; and a reaction gas exhauster exhausting the reaction gas from the reaction tube to the external of the reaction tube after the predetermined process. 
     In accordance with an exemplary embodiment of the invention, a semiconductor manufacturing apparatus is provided. The semiconductor manufacturing apparatus includes a first boat and a second boat having a plurality of first slots and a plurality of second slots, respectively, and disposed such that the first slots and the second slots alternate each other; a transfer robot holding a plurality of first wafers with a plurality of blades, loading the first wafers into the first slots to direct front faces of the first wafers in a predetermined direction, holding a plurality of second wafers with the plurality of blades, and loading the second wafers into the second slots to direct back faces of the second wafers in the predetermined direction; a reaction tube having an opening and containing the first and second boats mounting the first and second wafers; a plate sealing up the opening of the reaction tube containing the first boat and the second boat; a reaction gas supplier supplying reaction gas into the sealed reaction tube for a predetermined process; a reaction gas exhauster exhausting the reaction gas from the reaction tube to the external of the reaction tube after the predetermined process. 
     In accordance with an exemplary embodiment of the invention, a wafer loading/unloading method is provided for use in a semiconductor manufacturing apparatus including a first boat and a second boat which have a plurality of first slots and a plurality of second slots, respectively, and are disposed such that the first slots and the second slots alternate each other. The method includes: loading a plurality of first wafers into the first slots to direct front faces of the first wafers in a predetermined direction; loading a plurality of second wafers into the second slots to direct back faces of the second wafers in the predetermined direction; making the distance between facing front faces of neighboring first and second wafers larger than the distance between facing back faces of neighboring first and second wafers; performing a predetermined process on the front faces of the first and second wafers; and unloading the first and second wafers from the first and second slots. 
     As described above, according to some exemplary embodiments of the invention, a plurality of wafers can be loaded with relatively greater numbers by using first and second boats provided to make back faces of wafers mutually approximate and make front faces of wafers mutually distanced, thereby increasing productivity. 
     Damage and scratches in wafers caused by a collision between a blade of transfer robot and wafers can be prevented by using first and second boats that are provided to alternately support a plurality of wafers and control an interval between the plurality of wafers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention can be understood in more detail from the following description taken in conjunction with the attached drawings in which: 
         FIG. 1  is a sectional view schematically illustrating a semiconductor manufacturing apparatus according to the conventional art; 
         FIG. 2  is a sectional view schematically illustrating a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention; 
         FIG. 3  is a sectional view illustrating first and second boats of  FIG. 2 ; 
         FIG. 4  provides a plan view of  FIG. 3 ; 
         FIGS. 5A and 5B  are sectional views illustrating a plurality of blades for sucking in vacuum the back faces of the plurality of wafers; 
         FIGS. 6A and 6B  are sectional views of transfer robot for rotating the wafers by reducing a distance between blades; and 
         FIGS. 7A through 7I  are sectional views providing the sequence of the wafer loading/unloading method in a semiconductor manufacturing apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention now will be described more fully hereinafter with reference to  FIGS. 2 to 7 , in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Exemplary embodiments of the present invention are more fully described below with reference to  FIGS. 2 to 7 . This invention may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein; rather, these exemplary embodiments are provided so that this disclosure is thorough and complete, and conveys the concept of the invention to those skilled in the art. For purposes of clarity, a detailed description of known functions and systems has been omitted. 
       FIG. 2  is a sectional view schematically illustrating a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention.  FIG. 3  is a sectional view illustrating first and second boats  140  and  150  of  FIG. 2 .  FIG. 4  provides a plan view of  FIG. 3 . 
     As shown in  FIGS. 2 to 4 , a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention includes a reaction tube  110  having, for example, a bell shape, a heater  120  surrounding an external part of the reaction tube  110 , a plate  130  raised from a lower part of the reaction tube  110  and which seals up the inside of the reaction tube  110 , and a first boat  140  and a second boat  150  for loading with an unequal interval a plurality of wafers  112  in a center upper part of the plate  130 . 
     The semiconductor manufacturing apparatus may further include a reaction gas supplier for supplying reaction gas into the reaction tube  110 , and an exhauster for exhausting gas after a completion of corresponding diffusion process or deposition process in the reaction tube  110 . 
     Here, the directions of the first and second boats  140  and  150  supporting the plurality of wafers  112  are different from each other. For example, the first boat  140  supports the back face  112   b  of the wafers  112 , and the second boat  150  supports the front face  112   a  of the wafers  112 . The first boat  140  includes a plurality of first slots  142  supporting an edge portion of back face  112   b  of the wafers  112 , and the second boat  150  includes a plurality of second slots  152  supporting an edge portion of front face  112   a  of the wafers  112 . Here it may be configured, of course, such that the first boat  140  supports the front face  112   a  of the wafers  112  and the second boat  150  supports the back face  112   b  of the wafers  112 . 
     The plurality of wafers  112  loaded in the first and second boats  140  and  150  are positioned crossed so that respective front faces  112  of the wafers  112  are opposed to each other and respective back faces  112   b  thereof are opposed to each other. The distance between the back faces of the wafers  112  is shorter than the distance between the front faces  112   a  of the wafers  112 . This is why a thin film obtained through a diffusion or deposition process is selectively required only on the face  112   a  of the wafer  112 . For example, the distance between the front faces  112   a  of the wafers  112  may be about 7.5 millimeters (mm) or more, and the distance between the back faces  112   b  may be to about 0 in theory. That is, that plurality of wafers  112  loaded in the first and second boats  140  and  150  may be positioned such that the back faces  112   b  are face to face and approximated to each other and the front faces  112   a  are face to face and are distanced from each other. 
     Therefore, in a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention, a plurality of wafers  112  can be loaded by using the first and second boats  140  and  150  such that the back faces  112   b  of the wafers  112  become approximate to each other and the front faces  112   a  of the wafers  112  become distanced from each other, thereby substantially increasing productivity. 
     For example, within the first and second boats  140  and  150  positioned such that the back faces  112   b  of the wafers  112  become approximate to each other and the front faces  112   a  of the wafers  112  become face to face with a distance of about 7.5 mm, about 150 to 200 sheets of wafers  112  can be loaded. As compared with a conventional single boat  140  in which about 100 to about 150 sheets of wafers  112  can be loaded with a distance of about 7.5 mm, in a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention the wafers  112  of about 1.5 times can be more loaded therein in performing the diffusion or deposition process. 
     When the first and second boats  140  and  150  are provided into the reaction tube  110 , reaction gas supplied from the reaction gas supplier flows on the front faces  112   a  of the wafers  112  positioned face to face, thereby selectively forming a diffusion layer or deposition layer on the front faces  112   a  of the wafers  112 . Before supplying the reaction gas to the reaction tube  110 , the plate  130  is raised by an elevator adapted in a lower part thereof, so as to seal up the reaction tube  110 . 
     The reaction gas supplier includes a spraying tube  114  for spraying reaction gas in a given spraying pressure from a side face of the plurality of wafers  112  loaded in the first and second boats  140  and  150 . At this time, reaction gas sprayed from the spraying tube  114  flows in a gaseous state of high temperature, and to prevent the reaction gas from condensing on the surface of wafers  112 , the heater  120  can heat the inside of reaction tube  110 . In addition, a heater block heating in a lower part of the plurality of wafers  112  loaded above the plate  130  may be further provided. 
     The reaction tube  110  is called a tube, and may be formed of, for example, a monolithic single tube according to the conditions required in the process of forming impurity diffusion layer and thermal oxide layer, or may be formed of, for example, an external tube and an internal tube based on a separation type according to the conditions required in the process of forming polysilicon layer and silicon nitride layer. At this time, the conditions required in respective processes have a difference in the vacuum level and process temperature inside the reaction tube  110 . For example, reaction tube  110  of the separation type is mainly used in a deposition process sensitive to the vacuum level by buffering the flow of reaction gas between the internal and external tubes. On the other hand, monolithic reaction tube  110  is mainly used in a diffusion and thermal process of a simple heating scheme insensitive to the vacuum level. 
     The exhauster can maintain a uniform vacuum level inside the reaction tube  110  by pumping the reaction gas supplied into the reaction tube  110  and gas provided after the reaction. For example, the exhauster is provided including a dry pump or rotary pump for pumping the reaction gas and gas provided after the reaction through an exhaust line  116  coupled to one side of the reaction tube  110  so as to maintain in a low vacuum of about 1×10 3  Torr the inside of the reaction tube  110 . 
     On the other hand, the first and second boats  140  and  150  are designed to control an interval between the plurality of wafers  112  loaded in the boats. For example, the first boat  140  is a movable boat that is raised/lowered with a given distance, supporting the back faces  112   b  of the plurality of wafers  112 , and the second boat  150  is a fixed boat fixed supporting the front faces  112   a  of the plurality of wafers  112 . In addition, a precision elevator for raising and lowering the first boat  140  is provided in a lower part of the first boat  140 . 
     To sequentially load the plurality of wafers  112  in the first and second boats  140  and  150 , a previously loaded wafer  112  should be spaced by a given distance from an upper part of corresponding wafer  112 . This is why a sufficient space between an antecedently loaded wafer  112  and a subsequently loaded wafer  112  should be obtained. 
     To load wafer  112  in a first slot  142  of the first boat  140 , the distance from a second slot  152  provided below the first slot  142  should be reduced, and the distance from the second slot  152  provided above the first slot  142  should be increased. Similarly, to load wafer  112  in the second slot  152  of the second boat  150 , the distance from the first slot  142  provided below the second slot  152  should be reduced, and the distance from the first slot  142  provided above the second slot  152  should be increased. 
     Therefore, in a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention, the breaking and scratching of a wafer  112  caused by a collision between a blade  160  of transfer robot and the wafer  112  can be prevented by using the first and second boats  140  and  150  that are provided to alternately support the plurality of wafers  112  and control an interval between the plurality of wafers  112 , thereby increasing a production yield. 
     Here the first slot  142  and the second slot  152  are formed in the structure to respectively support the wafers  112  loaded therein, with a substantially lessened mutual interference, and to simultaneously protect the wafers  112 . For example, the first and second slots  142  and  152  have a tilted support face of a given angle supporting the wafer  112 . Thus, when the first boat  140  moves for the second boat  150  and so the first and second slots  142  and  152  become near, a given margin between the wafer  112  supported by the tilted support face and each slot  142  can be obtained, thereby substantially lessening damage to the wafer  112 . 
     As described above, the second boat  150  is normally positioned supporting the front face  112   a  of the wafer  112  by the second slot  152  of the second boat  150  so that the back face  112   b  of the wafer  112  is directed upward. On the other hand, the first boat  140  is positioned, supporting the back face  112   b  of the wafer  112  by the first slot  142  of the first boat  140  so that the front face  112   a  of the wafer  112  is directed upward. Thus, the transfer robot should load and unload the plurality of wafers  112  loaded in a wafer cassette, into the first and second boats  140  and  150 , in mutually opposite directions of the first and second boats  140  and  150 . Further, the transfer robot moves once in a given unit the plurality of wafers  112  in the movement between the first and second boats  140  and  150  and the wafer cassette. This is why when moving the plurality of wafers  112  one sheet by one sheet, the productivity decreases through the transfer of wafers  112 . 
     When the transfer robot horizontally moves the plurality of wafers  112  from the wafer cassette to the first slot  142  of the first boat  140 , the plurality of wafers  112  should rotate about 180 degrees and move from the wafer cassette to the second slot  152  of the second boat  150 . There may be several methods for rotating the plurality of wafers  112  through the transfer robot. First, the transfer robot may perform the rotation by, for example, sucking in by a vacuum the back faces of the plurality of wafers  112 . Also the plurality of wafers  112  may be rotated by, for example, lessening the distance between blades  160  inserted into between the plurality of wafers  112 . And the rotation may be performed by, for example, clamping the outer circumference face of the plurality of wafers through a mechanical force. 
       FIGS. 5A and 5B  are sectional views illustrating a plurality of blades  160  for sucking in by a vacuum the back faces of the plurality of wafers  112 . When vacuum pressure is generated through a vacuum line  162  provided within the plurality of blades  160  supporting the back faces  112   b  of the plurality of wafers  112 , the plurality of wafers  112  rotate. Here, the plurality of blades  160  are provided so that the plurality of wafers  112  are loaded into the first slot  142  of the first boat  140  or into the second slot  152  of the second boat  150 . For example, the plurality of blades  160  are configured to load the plurality of wafers  112  with an interval of about 15 mm and move the wafers and then load the wafers  112  into the first slot  142  or second slot  152 . That is, the plurality of blades  160  are provided to rotate at an end part of transfer robot arm and so suck in by a vacuum the plurality of wafers  112  with a given interval. Moreover, a vacuum pump for pumping air from the vacuum line  162  may provide a given vacuum pressure through the vacuum line  162  provided within the plurality blades  160 . 
       FIGS. 6A and 6B  are sectional views of transfer robot for rotating the wafers  112  by reducing the distance between the blades  160 . The transfer robot can reduce the distance between the blades so as to prevent the wafers  112  from moving or deviating from the blades during rotating, and then rotate the wafers  112 . Here the blade  160  is configured with a structure to stably support the wafers  112  of a circular shape. Further, a guide  164  is formed protruding with a given height at a position approximate to an outer circumference face of the wafer  112  so as to prevent the wafer  112  from being separated in a horizontal direction. The guides  164  are symmetrically provided not only on an upper part of the blade  160  but on a lower part of the blade  160 . This is why the guide  164  can provide the structure of reducing the distance between the blades  160  to rotate the wafer  112  and so surrounding the wafer  112 . Here, centering on the wafer  112 , the thickness of a plurality of guides  164  provided on the blades  160  provided in upper and lower parts of the wafer  112  is thicker than the thickness of wafer  112 . 
     In addition, for example, when the guide  164  is selectively formed only on the blade  160 , the protruded level of the guide  164  should be larger than the thickness of wafer  112 . 
     Therefore, in a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention, the plurality of wafers  112  are loaded into the first and second boats  140  and  150  so that the back faces  112   b  and the front faces  112   a  of the wafers are supported respectively and alternately by the boats, and further the interval between the plurality of wafers  112  is controlled, thereby enhancing the productivity in the diffusion or deposition process. 
     With the configuration described above, a wafer loading/unloading method for use in a semiconductor manufacturing apparatus according to an exemplary embodiment of the invention is described as follows. 
       FIGS. 7A through 7I  are sectional views providing the sequence of the wafer loading/unloading method in a semiconductor manufacturing apparatus. 
     As shown in  FIG. 7A , the first boat  140  is lowered so that the second slot  152  of the second boat  150  becomes approximate to a lower part of the first slot  142  of the first boat  140 . Here, initially, the first and second slots  142  and  152  are positioned to have a given interval in a vertical direction so that the plurality of wafers  112  are loaded with the same interval therebetween. Thus, the distance of the second slot  152  from an upper part of the first slot  142  should have a given interval so that the wafer  112  can be safely loaded in the first slot  142  in a subsequent step. For example, the first boat  140  can be lowered so that the first slot  142  is distanced about 4.75 mm from the second slot  152  provided above the first slot  142 , and so that the first slot  142  becomes approximate about 0.75 mm to the second slot  152  provided in a lower part of the first slot  142 . 
     With reference to  FIG. 7B , the plurality of wafers  112  whose back faces  112   b  supported and transferred by the blade  160  of the transfer robot, are stably loaded into the first slots  142  of the first boat  140 . That is, transfer robot can transfer the plurality of wafers  112  stored in wafer cassette to the first slot  142  of the first boat  140  in a state that the back faces  112   b  of the plurality of wafers  112  are supported by the plurality of blades  160 . The plurality of blades  160  supporting the plurality of wafers  112  horizontally move to upper parts of the first slots  142 , and then vertically move to load the plurality of wafers  112  in the first slots  142 . 
     As illustrated in  FIG. 7C , the first boat  140  is raised so that the first slots  142  storing the plurality of wafers  112  become approximate to the second slot  152  positioned above the first slot  142 . Here the plurality of wafers  112  stored in the first slots  142  are raised a given height by a movement of the first boat  140 , thereby substantially reducing the interference between the plurality of wafers  112  stored in the first slots  142  and the plurality of wafers  112  to be loaded on the second slots  152 . For example, the first slot  142  may be raised to a height level of about 4 mm. The raised distance of the first slot  142  may become a space where the plurality of wafers  112  to be subsequently loaded in the second slots  152  horizontally move and then vertically move by the blade  160  of the transfer robot. Thus, the plurality of wafers  112  subsequently inserted between the plurality of wafers  112  loaded in the first slots  142  of the first boat  140  can be loaded in the second slots  152  of the second boat  150  without a collision. 
     As shown in  FIG. 7D , the transfer robot rotates about 180 degrees the plurality of wafers  112 , and loads the wafers so that the front faces  112   a  of the plurality of wafers  112  are loaded in the second slots  152 . That is, the transfer robot horizontally moves the plurality of wafers  112  from wafer cassette in a state that the back faces  112   b  of the wafers  112  are supported by the plurality of blades  160 . Then, the plurality of wafers  112  rotate about 180 degrees by sucking in by a vacuum the back faces  112   b  of the plurality of wafers  112 . And then, the front faces  112   a  of the plurality of wafers  112  are loaded in the second slots  152 . 
     As shown in  FIG. 7E , the first boat  140  is lowered so that the first slots  142  supporting the back faces  112   b  of the plurality of wafers  112  become approximate to the second slots  152 , and a subsequent diffusion or deposition process for the plurality of wafers  112  is performed. Here, the first boat  140  is lowered so that the first slot  142  is approximated to the second slot  152  provided in a lower part of the first slot  142 . For example, the first slot  142  is lowered to a height level of about 4 mm so that the back faces  112   b  of the plurality of wafers  112  supported by the first and second slots  142  and  152  are approximated and the front faces  112   a  of the plurality of wafers  112  are distanced from each other. 
     Further, in the diffusion or deposition process, a reaction gas supplied from reaction gas supplier into the reaction tube  110  flows on the front faces  112   a  of the wafers  112 , thereby selectively forming a diffusion layer or deposition layer on the front faces  112   a  of the plurality of wafers  112 . Therefore, a reaction gas flows on the front faces  112   a  of the wafers  112  supported by the first and second slots  142  and  152 , thereby forming the diffusion layer or deposition layer thereon. For example, the distance between front faces  112   a  of the wafers  112  is about 5 mm to 6.5 mm. Then, after a completion of diffusion or deposition process, an unloading operation of the plurality of wafers  112  may be performed in a sequence opposite to the loading sequence of the plurality of wafers  112 . 
     As shown in  FIG. 7F , when the diffusion or deposition process for the plurality of wafers  112  is completed, the first boat  140  is raised so that the first slot  142  supporting the back face  112   b  of the wafers  112  is distanced from the second slot  152  provided in a lower part of the first slot  142 . Here, when the first boat  140  is raised, blade  160  is inserted into between the first slot  142  and second slot  152  provided in a lower part of the first slot  142  in a subsequent process, and the plurality of wafers  112  supported by the second slot  152  are sucked in by a vacuum and unloaded. For example, the first boat  140  raises the first slot  142  by a height of about 4 mm. 
     With reference to  FIG. 7G , the plurality of wafers  112  supported by the second slot  152  are unloaded by using the transfer robot and then rotate about 180 degrees and are stored in wafer cassette. Here the blade  160  of transfer robot sucks in by a vacuum the back face of the wafers  112  whose front face  112   a  is supported by the second slot  152 , and unload the plurality of wafers  112  from the inside of first and second boats  140  and  150 . Then, the plurality of wafers  112  rotate about 180 degrees to be loaded within the wafer cassette. 
     As shown in  FIG. 7H , the first boat  140  is lower so that the first slot  142  supporting the back face  112   b  of the wafers  112  is approximated to the second slot  152  provided in a lower part of the first slot  142 . For example, the first boat  140  moves to lower about 4 mm the first slot  142 . Subsequently, the plurality of wafers  112  supported by the first slots  142  vertically float by the blades  160 , thereby preventing a collision between the second slot  152  provided above the first slot  142  and the plurality of wafers  112 . 
     As shown in  FIG. 7I , the plurality of wafers  112  supported by the first slot  142  are unloaded by using transfer robot, and then are stored in the wafer cassette. Here the blade  160  of transfer robot horizontally moves, supporting the back face  112   b  of the wafers  112  supported by the first slots  142  and then loads the plurality of wafers  112  in the wafer cassette. 
     In addition, the first boat  140  may be raised to have a uniform interval of vertical direction between the first slot  142  and the second slot  152 . 
     Consequently, in a wafer loading/unloading method for use in a semiconductor manufacturing apparatus, front faces  112   a  of a plurality of wafers  112  are positioned face to face with a given interval therebetween, and back faces  112   b  of the plurality of wafers  112  are positioned face to face with becoming approximately to each other, thereby storing a relatively greater number of wafers  112  within reaction tube  110  in performing a diffusion or deposition process and so increasing productivity. 
     It does not matter herein to change the direction of a plurality of wafers  112  loaded in the first and second boats  140  and  150 . For example, the plurality of wafers  112  may be loaded so that the front face  112   a  of each wafer  112  is supported by the first slot  142  of the first boat  140  and the back face  112   b  of each wafer  112  is supported by the second slot  152  of the second boat  150 . Additionally, the distance between back faces  112   b  of the plurality of wafers  112  loaded in the first and second boats  140  and  150  should be relatively short, and the distance between front faces  112   a  thereof should be relatively wider. Having described the exemplary embodiments of the present invention, it is further noted that it is readily apparent to those of reasonable skill in the art that various modifications may be made without departing from the spirit and scope of the invention which is defined by the metes and bounds of the appended claims.