Patent Publication Number: US-2021183667-A1

Title: Substrate chuck and substrate bonding system including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/203,486, filed Jul. 6, 2016, which itself claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2015-0183959 filed on Dec. 22, 2015, the disclosures of both which are hereby incorporated by reference in their entireties. 
    
    
     FIELD 
     Embodiments of the inventive concept relate to a substrate chuck used in a process of bonding two substrates, and a substrate bonding system including the substrate chuck. 
     BACKGROUND 
     In order to form semiconductor components and/or CMOS image sensor (CIS) products, a wafer bonding process for bonding two semiconductor wafers may be used. During the process for bonding the semiconductor wafers, various types of process defects may be generated. For example, void defects in which a void is formed between two bonded semiconductor wafers, overlay defects formed between two wafers, or the like may be generated. 
     SUMMARY 
     Embodiments of the inventive concept provide a substrate chuck used in a substrate bonding process. 
     Other embodiments of the inventive concept provide a substrate bonding system including a substrate chuck used in a substrate bonding process. 
     Other embodiments of the inventive concept provide a substrate chuck in which defects can be prevented from being generated in a substrate bonding process, and a substrate bonding system including the substrate chuck. 
     The technical objectives of the inventive concept are not limited to the above disclosure; other objectives may become apparent to those of ordinary skill in the art based on the following descriptions. 
     In accordance with an aspect of the inventive concept, a substrate chuck includes a base, a plurality of support pins disposed on the base, and a dam portion which is disposed on the base and surrounds the plurality of support pins. The plurality of support pins include first support pins disposed on a first region of the base and second support pins disposed on a second region of the base. The first support pins have upper surfaces located in the same plane, and the dam portion has an upper surface located at a lower level than the upper surfaces of the first support pins. 
     In an embodiment, the second region may surround the first region and the dam portion may surround the second region. 
     In an embodiment, a width of the first region may be greater than a distance between the dam portion and the first region. 
     In an embodiment, the second support pins may be located at a lower level than the first support pins and a higher level than the dam portion. 
     In an embodiment, each of the second support pins may have a height decreasing for pins closer to the dam portion. 
     In an embodiment, upper surfaces of each of the second support pins may have a descending gradient closer to the dam portion. 
     In an embodiment, the substrate chuck may further include lift holes vertically passing through the base, and lift guard rings which are disposed on the first region of the base, and expose the lift holes and surround the lift holes. The lift guard rings may have upper surfaces disposed in the same plane as the upper surfaces of the first support pins. 
     In an embodiment, the substrate chuck may further include a vacuum channel disposed in the base. 
     In an embodiment, heights of the first support pins may be greater than distances between the plurality of adjacent support pins. 
     In an embodiment, the plurality of support pins may include a third support pin which overlaps a border between the first region and the second region. An upper surface of the third support pin may include a flat portion and an inclined portion. 
     In accordance with an aspect of the inventive concept, a substrate bonding system includes a lower substrate chuck and an upper substrate chuck disposed on the lower substrate chuck. The lower substrate chuck has a non-flat lower substrate contact surface, and the upper substrate chuck has a flat upper substrate contact surface. 
     In an embodiment, the lower substrate chuck may include a lower base, a plurality of support pins which protrude from an upper surface of the lower base, and a dam portion which protrudes from the upper surface of the lower base and surrounds the plurality of support pins. The lower substrate contact surface of the lower substrate chuck may include upper surfaces of the plurality of support pins and an upper surface of the dam portion, and the upper surfaces of the plurality of support pins may be located at a higher level than the upper surface of the dam portion. 
     In an embodiment, the plurality of support pins may include first support pins disposed on the first region of the lower base and second support pins disposed on the second region of the lower base and having lower heights than the first support pins. The first support pins may have upper surfaces located in the same plane, and the second support pins may have inclined upper surfaces. 
     In an embodiment, the substrate bonding system may further include a lower vacuum channel disposed in the lower base, lower lift holes passing through the lower base, and lower lift guard rings which are disposed on the lower base and expose the lower lift holes. The lift guard rings may be disposed between the first support pins and disposed with the same height as the first support pins. 
     In an embodiment, the upper substrate chuck may include an upper base, an upper through hole passing through a center portion of the upper base, an upper vacuum channel disposed at an edge portion of the upper base, and upper lift holes passing through the upper base disposed between the upper through hole and the upper vacuum channel, and the lower substrate chuck may include a lower base, a plurality of support pins disposed on the lower base, a dam portion which is disposed on the lower base and surrounds the plurality of support pins, lower lift holes passing through the lower base and disposed between the plurality of support pins, and lower guard rings which are disposed on the lower base and expose the lower lift holes. 
     In accordance with an aspect of the inventive concept, a substrate chuck includes a base, a plurality of support pins disposed on the base, a dam portion which is disposed on the base and surrounds the plurality of support pins, a vacuum channel disposed in the base, lift holes vertically passing through the base, and lift guard rings which are disposed on the base and expose the lift holes. The plurality of support pins include first support pins disposed on the first region of the base and second support pins disposed on the second region of the base. The first support pins have upper surfaces disposed in the same plane. The first support pins have the upper surfaces located at a level higher than the dam portion. 
     In an embodiment, the second region of the base may surround the first region of the base. 
     In an embodiment, the second support pins may have inclined upper surfaces. 
     In an embodiment, the vacuum channel may pass through the base. An upper vacuum hole of the vacuum channel may be disposed between the first support pin, and a lower vacuum hole of the vacuum channel may not overlap the upper vacuum hole and may be located closer to an outer edge of the base than the upper vacuum hole. 
     In an embodiment, the base may be formed of a SiC material. 
     Details of other embodiments are included in detailed descriptions and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features and advantages of the inventive concepts will be apparent from the more particular description of preferred embodiments of the inventive concepts, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the inventive concepts. In the drawings: 
         FIG. 1  is a conceptual diagram illustrating a substrate bonding system according to an embodiment of the inventive concept; 
         FIG. 2  is a view schematically illustrating a first facility of a substrate bonding system according to an embodiment of the inventive concept; 
         FIG. 3  is a cross-sectional view illustrating an example of a first substrate chuck of a first facility of a substrate bonding system according to an embodiment of the inventive concept; 
         FIG. 4  is a top view illustrating an example of a first substrate chuck of a first facility of a substrate bonding system according to an embodiment of the inventive concept; 
         FIGS. 5, 6A, and 6B  are cross-sectional views illustrating a portion of a first substrate chuck of a first facility of a substrate bonding system according to an embodiment of the inventive concept; 
         FIG. 7  is a cross-sectional view illustrating another example of a first substrate chuck of a first facility of a substrate bonding system according to an embodiment of the inventive concept; 
         FIG. 8  is a cross-sectional view illustrating an example of a second substrate chuck of a first facility of a substrate bonding system according to an embodiment of the inventive concept; and 
         FIGS. 9 to 14  are views for describing a substrate bonding system according to an embodiment of the inventive concept, and a substrate bonding process performed using the substrate bonding system. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Advantages and features of the inventive concept and methods of accomplishing them will be made apparent with reference to the accompanying drawings and some embodiments to be described below. The inventive concept may, however, be embodied in various different forms and should be construed as limited only by the accompanying claims, not by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough and complete and fully conveys the inventive concept to those skilled in the art. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present inventive concept. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Like reference numerals throughout this specification denote like elements. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description in describing one element&#39;s or feature&#39;s relationship to another/other element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both orientations above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly. 
     The exemplary embodiments of the invention will be described with reference to cross-sectional views and/or plan views which are ideal exemplary views. Thicknesses of layers and areas are exaggerated for effective description of the technical contents in the drawings. Forms of the embodiments may be modified by the manufacturing technology and/or tolerance. Therefore, the embodiments of the invention are not intended to be limited to illustrated specific forms and include modifications of forms generated according to manufacturing processes. For example, an illustrated etching area at a right angle corner may be rounded or have a predetermined curvature. Therefore, areas illustrated in the drawings have schematic properties, and shapes of the areas are illustrated special forms of the areas of a device and are not intended to limit the scope of the invention. 
     Like numbers refer to like elements throughout. Thus, the same or similar numbers may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, elements that are not denoted by reference numbers may be described with reference to other drawings. 
       FIG. 1  is a conceptual diagram illustrating a substrate bonding system according to an embodiment of the inventive concept. 
     Referring to  FIG. 1 , a substrate bonding system  1  according to an embodiment of the inventive concept may include a first facility  100  and a second facility  200 . 
     The first facility  100  may be a bonding facility capable of bonding two substrates, and the second facility  200  may be a heat treatment facility capable of increasing the bonding strength between two bonded substrates. For example, the first facility  100  may be a facility in which two substrates are in contact with each other to be bonded, and the second facility  200  may be a heat treatment facility in which the bonding strength between the two bonded substrates in contact with each other may be increased by performing a heat treatment process (i.e., an annealing process). 
       FIG. 2  is a view schematically illustrating the first facility  100 . 
     Referring to  FIGS. 1 and 2 , the first facility  100  may include a loading port  3  capable of loading and unloading a first substrate and a second substrate which are bonding targets, a transfer space  6  in which the first and second substrates are moved using a transferring device  9  in the first facility  100 , a plasma chamber  12  in which a plasma treatment is performed on the second substrate, a cleaning unit  15  capable of cleaning the first and second substrates, and a bonding unit  24  capable of bonding the first and second substrates. 
     The bonding unit  24  may include a first portion  18  and a second portion  21 . The first portion  18  may be closer to the transfer device  9  than the second portion  21 .The first portion  18  may be a portion on which the first and second substrates transferred by the transferring device  9  are mounted. The second portion  21  may be a portion in which a bonding process is performed on the first and second substrates. 
     The bonding unit  24  may include a first substrate chuck  90  in which the second substrate is mounted, a plate  35  on which the first substrate chuck  90  is placed, and a rail system  30  capable of reciprocating movement for the plate  35  between the first portion  18  and the second portion  21 . Further, the bonding unit  24  may include a second substrate chuck disposed on the first substrate chuck  90  and capable of facing the first substrate chuck  90 . 
     An example of the first substrate chuck  90  will be described with reference to  FIGS. 3, 4, 5, 6A, and 6B .  FIG. 3  is a cross-sectional view illustrating the example of the first substrate chuck  90 ,  FIG. 4  is a top view illustrating the example of the first substrate chuck  90 ,  FIG. 5  is a cross-sectional view illustrating a portion of the example of the first substrate chuck  90  (i.e., C of  FIG. 3 ), and  FIGS. 6A and 6B  are cross-sectional views each illustrating the portion of the example of the first substrate chuck  90 . 
     First, referring to  FIGS. 3 and 4 , the first substrate chuck  90  may include a first base  43 , a dam portion  46 , a plurality of support pins  55 , lower lift holes  57 , lower lift guard rings  58 , and lower vacuum channels  61 . The first substrate chuck  90  may be referred to as a lower substrate chuck, and the first base  43  may be referred to as a lower base. 
     The first base  43  may have a first region A 1  and a second region A 2 . The first base  43  may be formed of a SiC material. The dam portion  46  may be disposed on an upper surface  43   a  of the first base  43  to circumferentially surround (i.e., extending circumferentially around) the first and second regions A 1  and A 2 , as illustrated. The first region A 1  may be located at a center portion of the first base  43  and may have a circular shape. The second region A 2  may have a donut shape which surrounds the first region A 1 . A width or diameter of the first region A 1  may be greater than a width of the second region A 2 . Here, the width of the second region A 2  may be a distance between the first region A 1  and the dam portion  46 . Therefore, the width or diameter of the first region A 1  may be greater than the distance between the first region A 1  and the dam portion  46 . 
     The dam portion  46  may protrude from the upper surface  43   a  of the first base  43 . The dam portion  46  may have a flat upper surface. In a top view, the dam portion  46  may have a ring shape. The dam portion  46  may be spaced apart from an outer corner of the first base  43 . In the first base  43 , an edge region  43 e between the outer corner and the dam portion  46  may be flat and located at a level lower than the upper surface of the dam portion  46 . 
     The lower lift holes  57  may pass through the first base  43 . The lower lift holes  57  may pass through the first base  43  in the first region A 1 . 
     The lower lift guard rings  58  may be disposed on (i.e., extend outwardly from) the upper surface  43   a  of the first base  43 . The lower lift guard rings  58  may respectively correspond to the lower lift holes  57  and expose the lower lift holes  57 . For example, the lower lift guard rings  58  may be formed to have a hollow pipe shape, and empty portions of the lower lift guard rings  58  may overlap the lower lift holes  57  and expose the lower lift holes  57 . 
     The lower vacuum channels  61  may pass through the first base  43 . One end of the lower vacuum channel  61  located on the upper surface  43   a  of the first base  43 , that is, for example, an upper vacuum hole  61   a,  may be disposed in the first region A 1  of the first base  43 . The other end of the lower vacuum channel  61  located on a lower surface  43   b  of the first base  43 , that is, for example, a lower vacuum hole  61   b,  may not overlap the upper vacuum hole  61   a.  The lower vacuum hole  61   b  may be located at an outer side relative to the upper vacuum hole  61   a.  In other words, the upper vacuum hole  61   a  may be located on the upper surface  43   a  of the first base  43  in the first region A 1 , and the lower vacuum hole  61   b  may be located on the lower surface  43   b  of the first base  43  in the edge region  43   e.    
     The plurality of support pins  55  may include first support pins  49 , second support pins  51 , and third support pins  53 . 
     The first support pins  49  may be disposed on (i.e., extend outwardly from) the first region A 1  of the first base  43 . The first support pins  49  may protrude from the upper surface  43   a  of the first base  43  and may be disposed at the same height (i.e., may each have the same height). The first support pins  49  may have the same height as the lower lift guard rings  58 . The lower lift guard rings  58  may be disposed between the first support pins  49 . 
     The second support pins  51  may be disposed on (i.e., extend outwardly from) the second region A 2  of the first base  43 . The second support pins  51  may protrude from the upper surface  43   a  of the first base  43  and may be formed with a height lower than the first support pins  49  and the lower lift guard rings  58  (i.e., a height of the second support pins  51  may be lower than a height of the first support pins  49  and the lower lift guard rings  58 ). 
     The first support pins  49  and the second support pins  51  will be described with reference to  FIGS. 3, 4, and 5 . 
     Referring to  FIGS. 3, 4, and 5 , the first support pins  49  may have flat upper surfaces disposed in the same plane and may protrude from the upper surface  43   a  of the first base  43  by a first height ΔH 1 . 
     The dam portion  46  may be formed to have a second height ΔH 2  lower than the first height ΔH 1 . The upper surface of the dam portion  46  may be formed at a level lower than upper surfaces of the first support pins  49 . A width of the dam portion  46  may be greater than a width of an upper surface of each of the plurality of support pins  55 . Here, the dam portion  46  may be formed to have a ring shape of a predetermined width, and the width of the ring shape may be defined as the width of the dam portion  46 . 
     Each of the second support pins  51  may be formed to have a height between the first height ΔH 1  and the second height ΔH 2 . Regarding the second support pins  51 , the heights of pins near the dam portion  46  may be smaller than the heights of pins near the first support pins  49 . The heights of the second support pins  51  may decrease toward the dam portion  46  as illustrated in  FIG. 5  (i.e., in a radially outward direction). The heights of the second support pins  51  may gradually decrease toward the dam portion  46 . Upper surfaces of the second support pins  51  may be inclined at a predetermined angle θ. The angle θ may be greater than 0 degree and smaller than 90 degrees. Each of the second support pins  51  may have an inclined upper surface and a portion thereof facing the dam portion  46  may be low. In other words, the upper surface of each second support pin  51  may taper downwardly toward the dam portion  46  (i.e., in a radially outward direction). 
     Adjacent pins among the plurality of support pins  55  may be spaced apart from each other by a first distance ΔL. The plurality of support pins  55  may have the same width ΔW 1 . The dam portion  46  may have a second width ΔW 2  greater than a first width ΔW 1 . 
     In an embodiment, the second width ΔW 2  of the dam portion  46  may be greater than the first distance ΔL. 
     The plurality of support pins  55  and a border B between the first and second regions A 1  and A 2  will be described with reference to  FIGS. 6A and 6B . 
     Referring to  FIGS. 6A and 6B , the border B between the first and second regions A 1  and A 2 . The border B between the first and second regions A 1  and A 2  may have a portion which passes between the first support pins  49  and the second support pins  51  and/or a portion which overlaps some pins of the plurality of support pins  55 . 
     In an embodiment, as illustrated in  FIG. 6A , the border B between the first and second regions A 1  and A 2  may pass between the first support pins  49  and the second support pins  51 . 
     In an embodiment, as illustrated in  FIG. 6B , a portion of the border B between the first and second regions A 1  and A 2  may overlap some pins of the plurality of support pins  55 . In this manner, the pins among the plurality of support pins  55  which overlap the border B between the first and second regions A 1  and A 2  may be referred to as the third support pins  53 . 
     Each of the third support pins  53  may have a flat first upper surface  53   a  and an inclined second upper surface  53   b.    
     The first upper surfaces  53   a  of the third support pins  53  may be disposed with the same height as the upper surfaces of the first support pins  49 . The second upper surfaces  53   b  of the third support pins  53  may be inclined at the same angle θ as the upper surfaces of the second support pins  51 . The second upper surfaces  53   b  of the third support pins  53  may be inclined in the same manner as the upper surfaces of the second support pins  51  so as to become lower going toward the dam portion  46 . In other words, the second upper surfaces  53   b  taper downwardly toward the dam portion  46 . 
     In an embodiment, the second support pins  51  may have inclined upper surfaces. However, the inventive concept is not limited thereto. For example, as illustrated in  FIG. 7 , the second support pins  51 ′ may have flat upper surfaces of different heights. The second support pins  51 ′ having the flat upper surfaces may have lower heights than the first support pins  49  and the heights thereof may be gradually decreased toward the dam portion  46 . 
     A second substrate chuck  190  facing the first substrate chuck  90  will be described with reference to  FIG. 8 . 
     Referring to  FIG. 8 , the second substrate chuck  190  may include an upper base  115 , upper through holes  145 , upper lift holes  125 , and upper vacuum channels  135 . 
     The upper through holes  145  may pass through a center portion of the second substrate chuck  190 . The upper vacuum channels  135  may be disposed at edge portions of the second substrate chuck  190 . The upper lift holes  125  may pass through the upper base  115  between the upper through holes  145  and the upper vacuum channel  135 . 
     Hereinafter, a substrate bonding system  1  according to an embodiment of the inventive concept and a substrate bonding process performed using the substrate bonding system  1  will be described with reference to  FIGS. 9 to 14 . In  FIGS. 9 to 14 ,  FIG. 9  is a view illustrating a configuration in which a first substrate  300  is mounted on a first substrate chuck  90  and a second substrate  400  is mounted on a second substrate chuck  190 ,  FIG. 10  is a view for describing the first and second substrates  300  and  400 ,  FIG. 11  is a cross-sectional view illustrating lift pins  92  and  192  of the substrate bonding system  1 ,  FIG. 12  is a view illustrating a shape in which the first and second substrates  300  and  400  are starting to be bonded,  FIG. 13  is a view illustrating a configuration in which the first and second substrates  300  and  400  are bonded on the first substrate chuck  90 , and  FIG. 14  is a view illustrating a heat treatment process performed in the second facility  200 . 
     First, referring to  FIGS. 1, 2, and 9 , the substrate bonding system  1  may include the first substrate chuck  90  and the second substrate chuck  190  facing each other. The first substrate chuck  90  may be referred to as a lower substrate chuck, and the second substrate chuck  190  disposed on the first substrate chuck  90  may be referred to as an upper substrate chuck. 
     The first substrate chuck  90  may be the same as that described with reference to  FIGS. 3 to 6B . The second substrate chuck  190  may be the same as that described with reference to  FIG. 8 . 
     The first substrate  300  may be located on the first substrate chuck  90 . The second substrate  400  may be located under the second substrate chuck  190 . Hereinafter, the first substrate  300  is to be referred to as a lower substrate, and the second substrate  400  is to be referred to as an upper substrate. 
     An example of the lower substrate  300  and upper substrate  400  will be described with reference to  FIG. 10 . 
     Referring to  FIG. 10 , the lower substrate  300  may include a lower semiconductor wafer  310  and a lower insulating structure  320  which is disposed on the lower semiconductor wafer  310  and covers internal circuits and/or internal interconnections  315 . 
     The upper substrate  400  may include an upper semiconductor wafer  410  and an upper insulating layer  420  disposed on the upper semiconductor wafer  410 . The upper semiconductor wafer  410  may be a bare semiconductor wafer, and the upper insulating layer  420  may be formed in the plasma chamber  12  of the first facility  100 . 
     Referring again to  FIGS. 1, 2, 3, and 9 , locating the lower substrate  300  on the first substrate chuck  90  may include moving the lower substrate  300  to a cleaning unit  15  from the loading port  3  using the transferring device  9 , cleaning the lower substrate  300 , and moving the cleaned lower substrate  300  onto the first substrate chuck  90  located on a first portion  18  of a bonding unit  24 . 
     The first portion  18  of the bonding unit  24  of the first facility  100  may include lower lift pins  92  and upper lift pins  192 . The lower lift pins  92  and the upper lift pins  192  may make vertically reciprocating movements. Each of the lower lift pins  92  and the upper lift pins  192  may have a suction channel therein. For example, as illustrated in  FIG. 11 , each of the lower lift pins  92  and the upper lift pins  192  may have a suction channel  94  using a vacuum. 
     The lower lift pins  92  disposed under the first substrate chuck  90  may be lifted to pass through the lower lift holes  57  of the first substrate chuck  90  and to be moved higher than the first support pins  49  of the first substrate chuck  90 . The lower lift pins  92  may be in contact with the lower substrate  300  to fix or adsorb the lower substrate  300  using the suction channels  94  of the lower lift pins  92 . 
     Next, the lower lift pins  92  are moved downward, and thus the lower substrate  300  may be in contact with the first support pins  49  of the first substrate chuck  90 . Then, the lower substrate  300  is bent and may come in contact with the second and third support pins  51  and  53  and the dam portion  46  of the first substrate chuck  90 . In this case, the lower substrate  300  may be fixed to the first substrate chuck  90  due to the suction force by the lower vacuum channels  61  of the first substrate chuck  90 . 
     Therefore, the lower substrate  300  may be in contact with the upper surfaces of the plurality of support pins  55  and the upper surface of the dam portion  46  on the first substrate chuck  90 , and a portion thereof may become bent. 
     In the lower substrate  300 , a first portion  300   a  which overlaps the first region A 1  of the first substrate chuck  90  may be flat, a second portion  300   b  which overlaps the second region A 2  of the first substrate chuck  90  may be inclined to have a gradient decreased toward an outer side, and a third portion  300   c  which overlaps the dam portion  46  may be flat and located at a lower level than the first portion  300   a.    
     In the first substrate chuck  90 , the portion in contact with the lower substrate  300  may be referred to as a lower substrate contact surface. Therefore, in the first substrate chuck  90 , the upper surfaces of the plurality of support pins  55  and the upper surface of the dam portion  46  may be the lower substrate contact surfaces. 
     In the plasma chamber  12 , the upper substrate  400  on which the upper insulating layer  420  is formed may be cleaned in the cleaning unit  15 . The cleaned upper substrate  400  may be transferred to the bonding unit  24 . The upper lift pins  192  disposed on the second substrate chuck  190  are lowered, pass through the upper lift holes  125  of the second substrate chuck  190 , are moved under the second substrate chuck  190 , and may fix or adsorb the upper substrate  400  transferred to the bonding unit  24  using the suction channels  94  of the upper lift pins  192 . 
     Next, the upper lift pins  192  are lifted, and the upper substrate  400  may come in contact with a lower surface of the second substrate chuck  190 . The upper substrate  400  may be adsorbed and/or fixed to the second substrate chuck  190  due to the suction force by the upper vacuum channels  135  of the second substrate chuck  190 . The upper substrate  400  mounted under the second substrate chuck  190  may be flat. 
     The lower surface of the second substrate chuck  190  in contact with the upper substrate  400 , that is, the upper substrate contact surface may be flat. The lower substrate contact surface of the first substrate chuck  90  in contact with the lower substrate  300  may be the upper surfaces of the plurality of support pins  55  and the upper surface of the dam portion  46 , and the lower substrate contact surface may not be flat. 
     Each of the first and second substrate chucks  90  and  190  located on the first portion  18  in the bonding unit  24  may be moved to the second portion  21 . 
     The first and second substrate chucks  90  and  190  respectively moved to the second portion  21  may be spaced apart from each other. Further, the lower and upper substrates  300  and  400  may also be spaced apart from each other. 
     The second portion  21  of the bonding unit  24  may include an upper pin  155 . The upper pin  155  may make vertically reciprocating movements. The upper pin  155  passes through the upper through holes  145  of the second substrate chuck  190  and applies pressure to the upper substrate  400  to bend the upper substrate  400 . 
     In the upper substrate  400 , portions in which the upper vacuum channels  135  of the second substrate chuck  190  are located may be in contact with the upper substrate  400  due to the suction force of the upper vacuum channels  135 , and the upper substrate  400  may become bent from a portion in contact with the upper pin  155  while the upper pin  155  of the second substrate chuck  190  is gradually lowered. When the upper substrate  400  is in contact with the lower substrate  300 , the upper pin  155  may stop being lowered. 
     Referring to  FIG. 13 , the suction force of the upper vacuum channels  135  of the second substrate chuck  190  may be removed. At a moment the suction force of the upper vacuum channels  135  is removed, the upper substrate  400  may be in contact with and bonded to the lower substrate  300  while edge portions in contact with the second substrate chuck  190  by the upper vacuum channels  135  are moved downward due to restoring force and gravity. 
     Since surfaces  320  and  420  facing each other of the lower substrate  300  and the upper substrate  400  are formed of an oxide material and moisture is present on the surfaces  320  and  420 , the lower substrate  300  and the upper substrate  400  may be bonded to each other. The moisture in the facing surfaces  320  and  420  of the lower substrate  300  and the upper substrate  400  may be provided in the cleaning unit  15  of the first facility  100 . For example, the lower substrate  300  and the upper substrate  400  are cleansed in the cleaning unit  15  and then may be moved to the bonding unit  24  with moisture on a surface thereof. 
     The bonded lower and upper substrates  300  and  400  may be referred to as a bonding substrate  500 . 
     Next, the upper pin  155  (illustrated in  FIG. 12 ) may be moved upward. Next, the first substrate chuck  90  on which the bonding substrate  500  is placed may be moved to the first portion  18  of the bonding unit  24 . 
     Referring to  FIG. 14 , the bonding substrate  500  may be moved to the second facility  200  from the first substrate chuck  90  (illustrated in  FIG. 13 ). The bonding strength between the lower substrates  300  and  400  of the bonding substrate  500  may be increased by performing a heat treatment process  510  in the second facility  200 . 
     The first substrate chuck  90  according to various embodiments of the inventive concept may include the plurality of support pins  55  disposed on the lower base  43 . The plurality of support pins  55  of the first substrate chuck  90  may be in contact with the first substrate that can be located on the first substrate chuck  90 , that is, the lower substrate  300 . Therefore, the plurality of support pins  55  of the first substrate chuck  90  may be in contact with a lower surface of the lower substrate  300 . Foreign materials that are generated when the bonding process is repeated may not be located on the substrate contact surfaces of support pins  55  and dam portion  46  of the first substrate chuck  90 , and the foreign materials are highly likely to be located between the plurality of support pins  55 . Since the foreign materials located between the plurality of support pins  55  do not affect the contact between the first substrate chuck  90  and the lower substrate  300 , bonding process defects due to the foreign materials may be prevented. 
     Since the first substrate chuck  90  according to various embodiments of the inventive concept is formed of a rigid material, for example, SiC material, the deformation caused by the foreign materials and environment may be minimized. 
     In the substrate bonding system  1  using the first substrate chuck  90  according to various embodiments of the inventive concept, since the plurality of support pins  55  of the first substrate chuck  90  are in contact with the lower substrate  300 , the contact area between the first substrate chuck  90  and the lower substrate  300  may be minimized. Therefore, while the contact area between the first substrate chuck  90  and the lower substrate  300  is decreased, since the force transmitted to the lower substrate  300  due to the vacuum of the first substrate chuck  90  is minimized, overlay defects may be prevented from being generated. 
     The substrate bonding system  1  according to various embodiments of the inventive concept may include the first substrate chuck  90  having non-flat substrate contact surfaces  55  and  46  and the second substrate chuck  190  having a flat substrate contact surface. During the bonding process, as the upper substrate  400  that can be disposed under the second substrate chuck  190  becomes bent, the upper substrate  400  may start to be bonded to the lower substrate  300  disposed on the first substrate chuck  90 . Since the substrate contact surfaces defined by the support pins  55  and dam portion  46  of the first substrate chuck  90  are not flat, the lower substrate  300  may be placed on the first substrate chuck  90  in a bent state. Therefore, the bent upper substrate  400  may be bonded to the bent lower substrate  300 . The inventors have found that overlay defects are decreased in the lower and upper substrates  300  and  400  bonded in this manner. 
     The first substrate chuck according to various embodiments of the inventive concept may include the plurality of support pins disposed on the lower base. The plurality of support pins of the first substrate chuck may be in contact with the lower substrate that can be located on the first substrate chuck. Foreign materials that are generated when the bonding process is repeated may not be located on the substrate contact surface of the first substrate chuck, and the foreign materials are highly likely to be located between the plurality of support pins. Since the foreign materials located between the plurality of support pins do not affect the contact between the first substrate chuck and the lower substrate, bonding process defects due to the foreign materials can be prevented. 
     Since the first substrate chuck according to various embodiments of the inventive concept is formed of a rigid material, for example, a SiC material, the deformation caused by the foreign materials and environment can be minimized. 
     In the substrate bonding system using the first substrate chuck according to various embodiments of the inventive concept, since the plurality of support pins of the first substrate chuck are in contact with the lower substrate, the contact area between the first substrate chuck and the lower substrate can be minimized. Therefore, as the contact area between the first substrate chuck and the lower substrate is decreased and since the force transmitted to the lower substrate due to the vacuum of the first substrate chuck is minimized, overlay defects can be prevented from being generated. 
     The substrate bonding system according to various embodiments of the inventive concept may include a first substrate chuck having non-flat substrate contact surfaces, and a second substrate chuck having a flat substrate contact surface. During the bonding process, as the upper substrate that can be disposed under the second substrate chuck becomes bent, the upper substrate can start to be bonded to the lower substrate  300  disposed on the first substrate chuck  90 . Since the substrate contact surface of the first substrate chuck is not flat, the lower substrate may be placed on the first substrate chuck in a bent state. Therefore, the bent upper substrate can be bonded to the bent lower substrate. The inventors have found that overlay defects are decreased in the lower and upper substrates bonded in this manner. 
     Although a few embodiments have been described with reference to the accompanying drawings, those skilled in the art will readily appreciate that many modifications are possible in embodiments without departing from the scope of the inventive concept and without changing essential features. Therefore, the above-described embodiments should be considered in a descriptive sense only and not for purposes of limitation.