Abstract:
Provided is a barrier seal for an electrostatic chuck in the plasma etching process. The barrier seal comprises multiple sealing portions to block the connecting layer of the electrostatic chuck and the plasma gas. The groove of the electrostatic chuck may be completely filled by the barrier seal. Even one of the multiple sealing portions is destroyed in the plasma etching process by the plasma gas, the barrier seal still prevents leaking of the electrostatic chuck effectively. The barrier seal provides a buffer period for engineers to replace the damaged barrier seal before the leaking occurs. Danger of leaking caused by abrupt breaking of the barrier seal is reduced. Furthermore, the barrier seal facilitates stability and safety of the plasma etching process. The yield of products manufactured by the electrostatic chuck may be improved.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a barrier seal for use with an electrostatic chuck in a plasma etching equipment, and more particularly to a barrier seal that may be mounted into a groove of the electrostatic chuck with multiple sealing portions. 
         [0003]    2. Description of the Related Art 
         [0004]    Conventional plasma etching equipment is shown in  FIG. 9 . The plasma etching equipment comprises an electrostatic chuck  90 . The electrostatic chuck  90  comprises an upper element  91  which is made of dielectric ceramic materials, a bottom element  92 , and a soft connecting layer  93 . The connecting layer  93  connects to the upper element  91  and the bottom element  92 . The electrostatic chuck  90  further comprises an extending element  100  around the electrostatic chuck  90 . There are a gap  110  and a groove  113  between the electrostatic chuck  90  and the extending element  100 . Plasma gas  120  can flow into the space between the electrostatic chuck  90  and the extending element  100  through the gap  110 , and the plasma gas  120  further permeates into the groove  113  and destroys the connecting layer  93  to induce the erosion of the electrostatic chuck  90  and a leaking point in the plasma etching process. The working fluid in the electrostatic chuck  90  may flow out to the exterior of the electrostatic chuck  90  through the leaking point and induce pollution of the environment. 
         [0005]    In order to resolve said problems, disposing epoxy  130  in the groove  113  is a skill in the art as shown in  FIG. 10 . The groove  113  is filled by the epoxy  130  to prevent the damage of the connecting layer  93  by the plasma gas  120 . However, the epoxy  130  is eroded easily and becomes thinner by the plasma gas  120 . After plasma etching for a long term, a leaking point is formed and the epoxy  130  loses its protection function gradually. In addition, the lifetime of the epoxy  130  is hard to estimate. Engineers may not timely block the leaking point before the gas leak happens. 
         [0006]    Another skill in the art provides a replaceable elastomer ring  140  to substitute for the epoxy  130  as shown in  FIG. 11 . The elastomer ring  140  may overcome the above problems of the epoxy  130 . However there is only a sealing portion  150  between the connecting layer  93  and the groove  113 . The size of the groove  113  is very small. It is hard to install the elastomer ring  140  into the groove  113  evenly. As the elastomer ring  140  cannot be disposed in the groove  113  evenly, engineers may hardly estimate the lifetime of the elastomer ring  140 . When the elastomer ring  140  is unable to block the connecting layer  93 , the erosion of the connecting layer  93  and the pollution will be induced. Many problems still exist in sealing the groove  113  of the electrostatic chuck  90  in a plasma etching equipment. 
       SUMMARY OF THE INVENTION 
       [0007]    An objective of the present invention is to provide a barrier seal to be disposed in the groove of the electrostatic chuck with multiple sealing portions. The barrier seal of the present invention may not induce the gas leak caused by partial damages of the barrier seal. Furthermore, the barrier seal provides a buffer period to estimate the lifetime of the barrier seal. Engineers can replace the damaged barrier seal before the leaking occurs. The present invention facilitates stability and safety of the plasma etching process. 
         [0008]    To achieve the foregoing objective, the present invention provides a barrier seal for use with an electrostatic chuck including an upper element, a bottom element, and a connecting layer connecting the upper element and the bottom element, and a groove formed among an outer edge of the connecting layer, the upper element, and the bottom element, and the barrier seal being an elastomer ring and comprising: 
         [0009]    a primary sealing portion comprising at least one edge toward the groove, wherein a side of the at least one edge is a chamfered edge; and 
         [0010]    at least one minor sealing portion protruding away from a side of the primary sealing portion. 
         [0011]    The advantage of the present invention is utilizing the primary sealing portion and the at least one minor sealing portion to construct double sealing portions to protect the connecting layer. If the primary sealing portion is eroded by the plasma gas, the at least one minor sealing portion still blocks between the connecting layer and the plasma gas continuously. The gas leak of the electrostatic chuck does not occur abruptly. The at least one minor sealing portion provides a buffer period to replace the damaged barrier seal for engineers. The present invention prevents induction of the environmental pollution by the working fluid from the electrostatic chuck. The plasma etching process may be safe in the semiconductor industry. The qualities of products manufactured by the electrostatic chuck may be stable. 
         [0012]    Particularly, the cross-section of the barrier seal is in an L shape. A side of the primary sealing portion toward the groove comprises an edge, and the edge is a chamfered edge. The barrier seal comprises a first minor sealing portion. The first minor sealing portion protrudes from an inner side of the primary sealing portion toward the groove. A side of the first minor sealing portion toward the groove comprises two edges, and the two edges are chamfered edges. The advantage of the present invention is utilizing the L-shaped barrier seal to fit with the L-shaped groove of the electrostatic chuck. The chamfered edges of the primary sealing portion and the first minor sealing portion help the elastomer ring to be disposed in the groove easily. Then the groove may be completely filled and sealed by the elastomer ring. The electrostatic chuck is not interrupted from working due to the fact that damages of the elastomer ring occur abruptly. 
         [0013]    More particularly, the barrier seal comprises at least one second minor sealing portion. The at least one second minor sealing portion protrudes from an outer side of the primary sealing portion in a direction away from the groove. The at least one second minor sealing portion comprises a chamfered edge away from the groove. The advantage of the present invention is utilizing the primary sealing portion, the at least one minor sealing portion, and the at least one second minor sealing portion to construct triple sealing portions to protect the connecting layer. The gap between the electrostatic chuck and the extending element may be blocked by the at least one second minor sealing portion. The present invention is more effective to prevent the plasma gas from permeating through the gap into the groove to destroy the connecting layer. 
         [0014]    Particularly, the cross-section of the barrier seal is in a T shape. A side of the primary sealing portion toward the groove comprises two edges, and the two edges are chamfered edges. The barrier seal comprises a first minor sealing portion. The first minor sealing portion protrudes from an inner side of the primary sealing portion toward the groove. A side of the first minor sealing portion toward the groove comprises two edges, and the two edges are chamfered edges. The advantage of the present invention is utilizing the T-shaped barrier seal to fit with the T-shaped groove of the electrostatic chuck. The chamfered edges of the primary sealing portion and the first minor sealing portion help the elastomer ring to be disposed in the groove easily. Then the groove may be completely filled and sealed by the elastomer ring. The electrostatic chuck is not interrupted from working due to the fact that damages of the elastomer ring occur abruptly. 
         [0015]    More particularly, the barrier seal comprises at least one second minor sealing portion. The at least one second minor sealing portion protrudes from an outer side of the primary sealing portion in a direction away from the groove. The at least one second minor sealing portion comprises a chamfered edge away from the groove. The advantage of the present invention is utilizing the primary sealing portion, the at least one minor sealing portion, and the at least one second minor sealing portion to construct triple sealing portions to protect the connecting layer. The gap between the electrostatic chuck and the extending element may be blocked by the at least one second minor sealing portion. The present invention is effective in preventing the plasma gas from permeating through the gap into the groove to destroy the connecting layer. 
         [0016]    Most particularly, the barrier seal further comprises a third minor sealing portion to substitute for the at least one second minor sealing portion. The third minor sealing portion protrudes from an outer side of the primary sealing portion in a direction away from the groove. A height of the third minor sealing portion is larger than a height of the primary sealing portion, and the third minor sealing portion is in contact with the upper element and the bottom element of the electrostatic chuck respectively. 
         [0017]    The advantage of the present invention is utilizing the third minor sealing portion to substitute for the at least one second minor sealing portion first. Furthermore, the advantage of the present invention is also utilizing the primary sealing portion, the at least one minor sealing portion, and the third minor sealing portion to construct triple sealing portions to protect the connecting layer. The gap between the electrostatic chuck and the extending element may be blocked and partially filled by the third minor sealing portion. The present invention is effective in enduring the erosion from the plasma gas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic view of the first embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0019]      FIG. 2  is a schematic view of the second embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0020]      FIG. 3  is a schematic view of the third embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0021]      FIG. 4  is a schematic view of the fourth embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0022]      FIG. 5  is a schematic view of the fifth embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0023]      FIG. 6  is a schematic view of the sixth embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0024]      FIG. 7  is a schematic view of the seventh embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0025]      FIG. 8  is a schematic view of the eighth embodiment of the barrier seal disposed on the groove of an electrostatic chuck in accordance with the present invention; 
           [0026]      FIG. 9  is a schematic view of a conventional electrostatic chuck of an etching equipment with plasma; 
           [0027]      FIG. 10  is a schematic view of filling the groove of a conventional electrostatic chuck with epoxy; 
           [0028]      FIG. 11  is a schematic view of a replaceable elastomer ring disposed on the groove of a conventional electrostatic chuck. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    A barrier seal of the present invention is used for a sidewall of an electrostatic chuck  10 . With reference to  FIG. 1 , the electrostatic chuck  10  comprises an upper element  11 , a connecting layer  12 , and a bottom element  13 . The upper element  11  has a bottom portion  111  and a top portion  112 . A diameter of the bottom portion w is less than a diameter W of the top portion. The connecting layer  12  connects to the bottom portion  111  of the upper element  11  and the bottom element  13 . A groove  14  is formed around an outer surface of the connecting layer  12 . The groove  14  is also between the upper element  11  and the bottom element  13 . 
         [0030]    Before filling the groove  14  by the barrier seal, part of the outer connecting layer  12  is removed to get a depth D and a diameter w′. The diameter w′ of the connecting layer is less than the diameter w of the bottom portion. Then the cross-section of the groove  14  is in an L shape with reference to  FIGS. 1 and 2 . 
         [0031]    With reference to  FIG. 1 , the first embodiment of the barrier seal is an elastomer ring  20 . The cross-section of the elastomer ring  20  is in an L shape, and the elastomer ring  20  is corresponding to the groove  14  in shape. The elastomer ring  20  comprises: a primary sealing portion  21  and a first minor sealing portion  22 . The primary sealing portion  21  toward the groove  14  further comprises an edge  211 . The edge  211  is a chamfered edge. The edge  211  is corresponding to a corner between the bottom portion  111  and the top portion  112  of the upper element  11 . The first minor sealing portion  22  protrudes from an inner side of the primary sealing portion  21  toward the groove  14 . The first minor sealing portion  22  toward the groove  14  comprises two edges  221 . The two edges  221  are also chamfered edges. One of the two edges  221  is corresponding to a corner between the bottom portion  111  of the upper element  11  and the connecting layer  12 . Another one of the two edges  221  is corresponding to a corner between the connecting layer  12  and the bottom element  13 . The chamfered edges help the elastomer ring  20  to be disposed in the groove  14  easily. Then the groove  14  may be completely filled and evenly sealed by the elastomer ring  20 . 
         [0032]    With reference to  FIG. 2 , the electrostatic chuck  10  further comprises an extending element  30  around the sidewall of the electrostatic chuck  10 . There is a gap  31  between the electrostatic chuck  10  and the extending element  30 . The gap  31  connects to the groove  14  directly. Plasma gas  40  may destroy the connecting layer  12  through the gap  31  and the groove  14  in a plasma etching process. The erosion and the leaking occur after the connecting layer  12  is damaged by the plasma gas  40 . 
         [0033]    With reference to  FIG. 2 , the second embodiment of the barrier seal is an elastomer ring  20 A. The cross-section of the elastomer ring  20 A is substantially in an L shape, and the elastomer ring  20 A is corresponding to the groove  14  in shape. The elastomer ring  20 A comprises: a primary sealing portion  21 A, a first minor sealing portion  22 A, and a second minor sealing portion  23 A. The primary sealing portion  21 A toward the groove  14  further comprises an edge  211 A. The edge  211 A is a chamfered edge. The edge  211 A is corresponding to a corner between the bottom portion  111  and the top portion  112  of the upper element  11 . The first minor sealing portion  22 A protrudes from an inner side of the primary sealing portion  21 A toward the groove  14 . The first minor sealing portion  22 A toward the groove  14  comprises two edges  221 A. The two edges  221 A are also chamfered edges. One of the two edges  221 A is corresponding to a corner between the bottom portion  111  of the upper element  11  and the connecting layer  12 . Another one of the two edges  221 A is corresponding to a corner between the connecting layer  12  and the bottom element  13 . The chamfered edges help the elastomer ring  20 A to be disposed in the groove  14  easily. Then the groove  14  may be completely filled and sealed by the elastomer ring  20 A. 
         [0034]    The second minor sealing portion  23 A protrudes from an outer side of the primary sealing portion  21 A in a direction away from the groove  14 . The second minor sealing portion  23 A is very close to an interface between the primary sealing portion  21 A and the top portion  112  of the upper element  11 . The second minor sealing portion  23 A comprises a chamfered edge  231 A away from the groove  14 . The gap  31  between the electrostatic chuck  10  and the extending element  30  may be blocked by the second minor sealing portion  23 A. The second minor sealing portion  23 A may stop the plasma gas  40  from flowing into the gap  31  and the groove  14 . The second minor sealing portion  23 A effectively prevents the damage of the connecting layer  12  caused by the etching of the plasma gas  40 . 
         [0035]    The present invention of the barrier seal is used for a sidewall of another kind of the electrostatic chuck  10 A. With reference to  FIG. 3 , another kind of the electrostatic chuck  10 A comprises an upper element  11 A, a connecting layer  12 A, and a bottom element  13 A. The upper element  11 A has a bottom portion  111 A and a top portion  112 A. A diameter of the bottom portion w 11  is less than a diameter of the top portion W 11 . The bottom element  13 A has a top unit  131 A and a bottom unit  132 A. A diameter w 13  of the top unit  131 A is less than a diameter W 13  of the bottom unit  132 A. The connecting layer  12 A connects to the bottom portion  111 A of the upper element  11 A and the top unit  131 A of the bottom element  13 A. A groove  14 A is formed around an outer surface of the connecting layer  12 A. The groove  14 A is between the upper element  11 A and the bottom element  13 A. 
         [0036]    Before filling the groove  14 A by the barrier seal, part of the outer connecting layer  12 A is removed to get a depth D and a diameter w″. The diameter w″ of the connecting layer is less than the diameter w 11  of the bottom portion and the diameter w 13  of the top unit. Then the cross-section of the groove  14 A is in a T shape with reference to  FIGS. 3, 4 and 5 . 
         [0037]    With reference to  FIG. 3 , the third embodiment of the barrier seal is an elastomer ring  20 B. The cross-section of the elastomer ring  20 B is in a T shape, and the elastomer ring  20 B is corresponding to the groove  14 A in shape. The elastomer ring  20 B comprises: a primary sealing portion  21 B and a first minor sealing portion  22 B. The primary sealing portion  21 B toward the groove  14 A further comprises two edges  211 B. The two edges  211 B are chamfered edges. One of the two edges  211 B is corresponding to a corner between the bottom portion  111 A and the top portion  112 A of the upper element  11 A. Another one of the two edges  211 B is corresponding to a corner between the top unit  131 A and the bottom unit  132 A of the bottom element  13 A. The first minor sealing portion  22 B protrudes from an inner side of the primary sealing portion  21 B toward the groove  14 A. The first minor sealing portion  22 B toward the groove  14 A comprises two edges  221 B. The two edges  221 B are also chamfered edges. One of the two edges  221 B is corresponding to a corner between the bottom portion  111 A of the upper element  11 A and the connecting layer  12 A. Another one of the two edges  221 B is corresponding to a corner between the connecting layer  12 A and the top unit  131 A of the bottom element  13 A. The chamfered edges help the elastomer ring  20 B to be disposed in the groove  14 A more easily. Then the groove  14 A may be completely filled and sealed by the elastomer ring  20 B. 
         [0038]    With reference to  FIG. 4 , the electrostatic chuck  10 A further comprises an extending element  30 A around the sidewall of the electrostatic chuck  10 A. There is a gap  31 A between the electrostatic chuck  10 A and the extending element  30 A. The gap  31 A connects to the groove  14 A directly. Plasma gas  40  may destroy the connecting layer  12 A through the gap  31 A and the groove  14 A in a plasma etching process. The erosion and the leaking occur after the connecting layer  12 A is damaged by the plasma gas  40 . 
         [0039]    With reference to  FIG. 4 , the fourth embodiment of the barrier seal is an elastomer ring  20 C. The cross-section of the elastomer ring  20 C is substantially in a T shape, and the elastomer ring  20 C is corresponding to the groove  14 A in shape. The elastomer ring  20 C comprises: a primary sealing portion  21 C, a first minor sealing portion  22 C, and a second minor sealing portion  23 C. The primary sealing portion  21 C toward the groove  14 A further comprises two edges  211 C. The two edges  211 C are chamfered edges. One of the two edges  211 C is corresponding to a corner between the bottom portion  111 A and the top portion  112 A of the upper element  11 A. Another one of the two edges  211 C is corresponding to a corner between the top unit  131 A and the bottom unit  132 A of the bottom element  13 A. The first minor sealing portion  22 C protrudes from an inner side of the primary sealing portion  21 C toward the groove  14 A. The first minor sealing portion  22 C toward the groove  14 A comprises two edges  221 C. The two edges  221 C are also chamfered edges. One of the two edges  221 C is corresponding to a corner between the bottom portion  111 A of the upper element  11 A and the connecting layer  12 A. Another one of the two edges  221 C is corresponding to a corner between the connecting layer  12 A and the top unit  131 A of the bottom element  13 A. The chamfered edges help the elastomer ring  20 C to be disposed in the groove  14 A easily. Then the groove  14 A may be completely filled and sealed by the elastomer ring  20 C. 
         [0040]    The second minor sealing portion  23 C protrudes from an outer side of the primary sealing portion  21 C in a direction away from the groove  14 A. The second minor sealing portion  23 C is very close to an interface between the primary sealing portion  21 C and the top portion  112 A of the upper element  11 A. The second minor sealing portion  23 C comprises a chamfered edge  231 C away from the groove  14 A. The gap  31 A between the electrostatic chuck  10 A and the extending element  30 A may be blocked by the second minor sealing portion  23 C. The second minor sealing portion  23 C may stop the plasma gas  40  from flowing into the gap  31 A and the groove  14 A. The second minor sealing portion  23 C effectively prevents the damage of the connecting layer  12 A caused by the etching of the plasma gas  40 . 
         [0041]    With reference to  FIG. 5 , the fifth embodiment of the barrier seal is an elastomer ring  20 C′. The cross-section of the elastomer ring  20 C′ is substantially in a T shape, and the elastomer ring  20 C′ is corresponding to the groove  14 A in shape. The elastomer ring  20 C′ comprises: a primary sealing portion  21 C′, a first minor sealing portion  22 C′, and three components of the second minor sealing portion  23 C′. The primary sealing portion  21 C′ toward the groove  14 A further comprises two edges  211 C′. The two edges  211 C′ are chamfered edges. One of the two edges  211 C′ is corresponding to a corner between the bottom portion  111 A and the top portion  112 A of the upper element  11 A. Another one of the two edges  211 C′ is corresponding to a corner between the top unit  131 A and the bottom unit  132 A of the bottom element  13 A. The first minor sealing portion  22 C′ protrudes from an inner side of the primary sealing portion  21 C′ toward the groove  14 A. The first minor sealing portion  22 C′ toward the groove  14 A comprises two edges  221 C′. The two edges  221 C′ are also chamfered edges. One of the two edges  221 C′ is corresponding to a corner between the bottom portion  111 A of the upper element  11 A and the connecting layer  12 A. Another one of the two edges  221 C′ is corresponding to a corner between the connecting layer  12 A and the top unit  131 A of the bottom element  13 A. The chamfered edges help the elastomer ring  20 C′ to be disposed in the groove  14 A easily. Then the groove  14 A may be completely filled and sealed by the elastomer ring  20 C′. 
         [0042]    The three components of the second minor sealing portion  23 C′ protrude from an outer side of the primary sealing portion  21 C′ in a direction away from the groove  14 A. The three components of the second minor sealing portion  23 C′ are formed respectively on a top position, a middle position, and a bottom position of the outer side of the primary sealing portion  21 C′. Each one of the three components of the second minor sealing portion  23 C′ comprises a chamfered edge  231 C′ away from the groove  14 A. The gap  31 A between the electrostatic chuck  10 A and the extending element  30 A may be blocked by the three components of the second minor sealing portion  23 C′. The three components of the second minor sealing portion  23 C′ may stop the plasma gas  40  from flowing into the gap  31 A and the groove  14 A. The three components of the second minor sealing portion  23 C′ effectively prevents the damage of the connecting layer  12 A caused by the etching of the plasma gas  40 . The number of the components on the second minor sealing portion  23 C′ is not limited to three. The mounting positions of the three components on the second minor sealing portion  23 C′ are not limited to the top position, the middle position, and the bottom position on the outer side of the primary sealing portion  21 C′ respectively. Engineers can change the numbers and mounting positions of the components on the second minor sealing portion  23 C′ selectively. 
         [0043]    With reference to  FIG. 6 , the sixth embodiment of the barrier seal is an elastomer ring  20 D. The cross-section of the elastomer ring  20 D is substantially in a T shape. The elastomer ring  20 D comprises: a primary sealing portion  21 D, a first minor sealing portion  22 D, and a third minor sealing portion  24 D. The primary sealing portion  21 D toward the groove  14 A further comprises two edges  211 D. The two edges  211 D are chamfered edges. One of the two edges  211 D is corresponding to a corner between the bottom portion  111 A and the top portion  112 A of the upper element  11 A. Another one of the two edges  211 D is corresponding to a corner between the top unit  131 A and the bottom unit  132 A of the bottom element  13 A. The first minor sealing portion  22 D protrudes from an inner side of the primary sealing portion  21 D toward the groove  14 A. The first minor sealing portion  22 D toward the groove  14 A comprises two edges  221 D. The two edges  221 D are also chamfered edges. One of the two edges  221 D is corresponding to a corner between the bottom portion  111 A of the upper element  11 A and the connecting layer  12 A. Another one of the two edges  221 D is corresponding to a corner between the connecting layer  12 A and the top unit  131 A of the bottom element  13 A. The chamfered edges help the elastomer ring  20 D to be disposed in the groove  14 A easily. Then the groove  14 A may be completely filled and sealed by the elastomer ring  20 D. 
         [0044]    The third minor sealing portion  24 D protrudes from an outer side of the primary sealing portion  21 D in a direction away from the groove  14 A. A height H of the third minor sealing portion  24 D is larger than a height h of the primary sealing portion  21 D, and the third minor sealing portion  24 D is in contact with the top portion  112 A of the upper element  11 A and the bottom unit  132 A of the bottom element  13 A respectively. The gap  31 A between the electrostatic chuck  10 A and the extending element  30 A may be blocked by the third minor sealing portion  24 D. The third minor sealing portion  24 D may stop the plasma gas  40  from flowing into the gap  31 A and the groove  14 A. The third minor sealing portion  24 D effectively prevents the damage of the connecting layer  12 A caused by the etching of the plasma gas  40 . 
         [0045]    With reference to  FIG. 7 , the seventh embodiment of the barrier seal is an elastomer ring  20 E. The cross-section of the elastomer ring  20 E is in the shape of a cap. The elastomer ring  20 E comprises: a primary sealing portion  21 E and a third minor sealing portion  24 E. The primary sealing portion  21 E toward the groove  14 A further comprises two edges  211 E. The two edges  211 E are chamfered edges. One of the two edges  211 E is corresponding to a corner between the bottom portion  111 A and the top portion  112 A of the upper element  11 A. Another one of the two edges  211 E is corresponding to a corner between the top unit  131 A and the bottom unit  132 A of the bottom element  13 A. The third minor sealing portion  24 E protrudes from an outer side of the primary sealing portion  21 E in a direction away from the groove  14 A. A height H 1  of the third minor sealing portion  24 E is larger than a height h 1  of the primary sealing portion  21 E, and the third minor sealing portion  24 E is in contact with the top portion  112 A of the upper element  11 A and the bottom unit  132 A of the bottom element  13 A respectively. The gap  31 A between the electrostatic chuck  10 A and the extending element  30 A may be blocked by the third minor sealing portion  24 E. The third minor sealing portion  24 E may stop the plasma gas  40  from flowing into the gap  31 A and the groove  14 A. The third minor sealing portion  24 E effectively prevents the damage of the connecting layer  12 A caused by the etching of the plasma gas  40 . 
         [0046]    With reference to  FIG. 8 , the eighth embodiment of the barrier seal is an elastomer ring  20 E′. The cross-section of the elastomer ring  20 E′ is substantially in the shape of a cap. The elastomer ring  20 E′ comprises: a primary sealing portion  21 E′ and a third minor sealing portion  24 E′. The primary sealing portion  21 E′ toward the groove  14  further comprises two edges  211 E′. The two edges  211 E′ are chamfered edges. One of the two edges  211 E′ is corresponding to a corner between the bottom portion  111  and the top portion  112  of the upper element  11 . Another one of the two edges  211 E′ is very close to a top surface of the bottom element  13 . The third minor sealing portion  24 E′ protrudes from an outer side of the primary sealing portion  21 E′ in a direction away from the groove  14 . A height H 2  of the third minor sealing portion  24 E′ is larger than a height h 2  of the primary sealing portion  21 E′, and the third minor sealing portion  24 E′ is in contact with the top portion  112  of the upper element  11  and the bottom element  13  respectively. The gap  31  between the electrostatic chuck  10  and the extending element  30  may be blocked by the third minor sealing portion  24 E′. The third minor sealing portion  24 E′ may stop the plasma gas  40  from flowing into the gap  31  and the groove  14 . The third minor sealing portion  24 E′ effectively prevents the damage of the connecting layer  12  caused by the etching of the plasma gas  40 . 
         [0047]    The differences between the elastomer ring  20 E and the elastomer ring  20 E′ are the height h 1 , h 2  of the primary sealing portion and the height H 1 , H 2  of the third minor sealing portion. Different designs of the bottom element  13 ,  13 A may be used with the elastomer ring  20 E′ or the elastomer ring  20 E respectively with reference to  FIGS. 7 and 8 . Engineers may select the appropriate elastomer ring  20 E or the elastomer ring  20 E′ to use with the different electrostatic chucks  10 . 
         [0048]    All kinds of the elastomer rings  20 ,  20 A,  20 B,  20 C,  20 C′,  20 D,  20 E,  20 E′ are made of rubber. The elastic property of the rubber may help the elastomer ring  20 ,  20 A,  20 B,  20 C,  20 C′,  20 D,  20 E,  20 E′ be disposed in the groove  14 ,  14 A evenly and completely. The elastomer ring  20 ,  20 A,  20 B,  20 C,  20 C′,  20 D,  20 E,  20 E′ may effectively prevent the damage of the connecting layer  12 ,  12 A caused by the etching of the plasma gas  40 . 
         [0049]    In summary, the barrier seal for a sidewall of the electrostatic chuck  10  utilizes multiple sealing portions such as double or triple sealing portions to prevent the plasma gas  40  from flowing into the groove  14 ,  14 A or the gaps  31 ,  31 A to damage the connecting layer  12 ,  12 A. Even one of the multiple sealing portions is destroyed by the plasma gas  40 , the gas leak of the electrostatic chuck  10 ,  10 A will not occur. Engineers may timely replace the damaged barrier seal before the leaking. The present invention is beneficial for the development of the semiconductor industry. 
         [0050]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.