Patent Publication Number: US-2013233491-A1

Title: Dry etching apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/459,586, pending, which claims the benefit of the Korean Patent Application Nos. P2008-0064236 filed on Jul. 3, 2008, and P2009-0049502 filed on Jun. 4, 2009, which are hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dry etching apparatus, and more particularly, to a dry etching apparatus which is capable of forming a uniform pattern in a substrate surface. 
     2. Discussion of the Related Art 
     A solar cell with a property of semiconductor converts a light energy into an electric energy. 
     A structure and principle of the solar cell according to the related art will be briefly explained as follows. The solar cell is formed in a PN-junction structure where a positive (P)-type semiconductor makes a junction with a negative (N)-type semiconductor. When a solar ray is incident on the solar cell with the PN junction structure, holes (+) and electrons (−) are generated in the semiconductor owing to the energy of the solar ray. By an electric field generated in a PN-junction area, the holes (+) are drifted toward the P-type semiconductor and the electrons (−) are drifted toward the N-type semiconductor, whereby an electric power is produced with an occurrence of electric potential. 
     The solar cell can be largely classified into a wafer type solar cell and a thin film type solar cell. 
     The wafer type solar cell uses a wafer made of a semiconductor material such as silicon. In the meantime, the thin film type solar cell is manufactured by forming a semiconductor in type of a thin film on a glass substrate. 
     The wafer type solar cell is disadvantageous in that the wafer type solar cell is thicker as compared to the thin film type solar cell and the wafer type solar cell is manufactured through the use of a high-priced material. However, with respect to efficiency, the wafer type solar cell is better than the thin film type solar cell. 
     In order to maximize absorption of solar ray in the wafer type solar cell, an uneven structure (or concavo-convex pattern) is formed in a substrate surface of the wafer type solar cell. 
     If using a monocrystalline silicon substrate, a wet etching such as an alkali etching is performed so as to form the uneven structure (or pattern) in a surface of the monocrystalline silicon substrate. Meanwhile, if using a polycrystalline silicon substrate, crystal molecules are arranged at different orientation directions so that it is difficult to form the uneven structure (or pattern) in a surface of the polycrystalline silicon substrate by the alkali etching. 
     Furthermore, if forming the uneven structure (or pattern) by the wet etching, the substrate is decreased in its thickness. In this respect, it is necessary to use the thick substrate when performing the wet etching. Using the thick substrate causes the increase in production cost of the solar cell. 
     Accordingly, there is a need to propose a new method for uniformly forming the uneven structure in the surface of the substrate without regard to the orientation direction of crystal molecules. 
     When the substrate is etched by the wet etching for a process of manufacturing a semiconductor device or flat panel display device, using the thick substrate causes the increase in production cost. In addition, it is difficult to realize the uniform pattern in the substrate. 
     Eventually, there is an increasing requirement for a method of forming the uniform pattern in the substrate when manufacturing the solar cell, the semiconductor device, or the flat panel display device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a dry etching apparatus that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An aspect of the present invention is to provide a dry etching apparatus, which is capable of forming a uniform pattern in a substrate surface. 
     Additional features and aspects of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a dry etching apparatus, for etching at least one substrate through the use of plasma, comprises the at least one substrate placed on a tray inside a chamber; a susceptor, provided inside the chamber while confronting with the at least one substrate, for supplying a high-frequency power to form the plasma; a grounding part provided beneath the susceptor while being untouchable to the susceptor; and an insulating part provided between the susceptor and the grounding part. 
     The grounding part is formed in a rectangular or circular shaped flat panel with a central hole therein. 
     Also, the grounding part includes a mesh portion. 
     The grounding part includes a plurality of openings arranged in a grid configuration. 
     The grounding part is formed in shape of a rectangular or circular frame. 
     The insulating part is formed of a ceramic or Teflon™ (polytetrafluoroethylene [PTFE]) material. 
     The insulating part comprises a first insulator confronting with a central portion of the susceptor; and a plurality of second insulators engaged with the first insulator, wherein the second insulator is bent to be confronting with a lateral surface of the susceptor and the rest of the susceptor except the central portion of the susceptor. 
     Each step-shaped surface is formed at a portion for engaging the first insulator and the second insulator with each other, and a portion for engaging the neighboring second insulators with each other, and wherein the first and second insulators are engaged through the step-shaped surface. 
     Furthermore, the dry etching apparatus additionally comprises a first sealing member provided between the insulating part and the susceptor; and a second sealing member provided between the insulating part and the grounding part. 
     Also, the dry etching apparatus comprises a susceptor supporting member for electrically connecting the susceptor to a rear surface of the substrate by elevating the grounding part; and an electrode rod for supplying the high-frequency power to the susceptor, the electrode rod passing through the susceptor supporting member. 
     The susceptor supporting member comprises a first supporter connected with the susceptor by passing through the chamber, the grounding part, and the insulating part; a second supporter connected with the grounding part by passing through the chamber; and a plate connected with the first and second supporters. 
     Also, the tray for supporting the at least one substrate is electrically connected with the susceptor by elevation of the susceptor. 
     In addition, the dry etching apparatus comprises a bellows provided between the chamber and the plate. 
     The dry etching apparatus further comprises a bellows provided between a bottom surface of the chamber and the grounding part. 
     The grounding part is grounded by the bellows. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  illustrates a dry etching apparatus according to one embodiment of the present invention; 
         FIG. 2  illustrates a perspective view of explaining an insulating part in the dry etching apparatus according to one embodiment of the present invention; 
         FIG. 3  illustrates a perspective view of explaining a grounding part according to the first embodiment of the present invention; 
         FIG. 4  illustrates a perspective view of explaining another grounding part according to the first embodiment of the present invention; 
         FIG. 5  illustrates a dry etching apparatus according to another embodiment of the present invention; 
         FIG. 6  illustrates a perspective view of explaining a grounding part according to the second embodiment of the present invention; 
         FIG. 7  illustrates a perspective view of explaining a grounding part according to the third embodiment of the present invention; 
         FIG. 8  illustrates a perspective view of explaining a grounding part according to the fourth embodiment of the present invention; and 
         FIG. 9(A  and B) illustrates an operation of dry etching apparatus according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Hereinafter, a dry etching apparatus according to the present invention and its operation method will be described with reference to the accompanying drawings. 
       FIG. 1  illustrates a dry etching apparatus according to one embodiment of the present invention. 
     Referring to  FIG. 1 , the dry etching apparatus  100  according to one embodiment of the present invention includes a chamber  110 ; at least one substrate  130  placed inside the chamber  110 ; a susceptor  160  for forming a plasma to etch a surface of the substrate  130 ; a grounding part  162  for preventing an abnormal discharge from occurring beneath the susceptor  160 , the grounding part  162  provided beneath the susceptor  160 ; an insulating part  164  for insulating the susceptor  160  and the grounding part  162  from each other, the insulating part  164  provided therebetween; and an electrode rod  180  for supplying a high-frequency power for the plasma to the susceptor  160 , the electrode rod  180  being electrically connected with the susceptor  160  by passing through the grounding part  162  and the insulating part  164 . 
     The chamber  110  provides a reaction space for a dry etching process (for example, a reactive ion etching process). In front of the chamber  110 , there is a showerhead  120  installed so as to supply a processing gas used for formation of the plasma to the reaction space. For uniformly supplying the processing gas to the inside of the chamber  110 , the showerhead  120  may be provided with a plurality of diffusion members. For example, the showerhead  120  may include a first diffusion member (not shown) for firstly diffusing the processing gas supplied from the external of the reaction space; and a second diffusion member (not shown) including a plurality of shower holes to secondly diffuse the processing gas, firstly diffused by the first diffusion member, into the inside of the reaction space. At this time, at least one of the first and second diffusion members may be rotated. The processing gas may be Cl 2 , SF 6 , NF 3 , HBr, or their mixture. If needed, Ar, O 2 , N 2 , He, or their mixture may be added thereto. 
     The at least one substrate  130  may be positioned in the reaction space between the showerhead  120  and the susceptor  160  in such a way that the at least one substrate  130  confronts with the susceptor  160 . In this case, the at least one substrate  130  may be any one of a substrate or wafer used for manufacturing a solar cell, a substrate or wafer used for manufacturing a semiconductor device, or a substrate or glass substrate used for manufacturing a flat panel display device. 
     The at least one substrate  130  may be positioned inside the chamber  110  while being placed on a tray  140 . The tray  140  may be formed in a rectangular shape or a circle shape, and the tray  140  may be formed of a metal material, for example, aluminum. That is, if the at least one substrate  130  placed on the tray  140  corresponds to the substrate or wafer used for manufacturing the solar cell, or the substrate or wafer used for manufacturing the flat panel display device, the tray  140  may be formed in the rectangular shape. If the at least one substrate  130  placed on the tray  140  corresponds to the substrate or wafer used for manufacturing the semiconductor device, the tray  140  may be formed in the circle shape. 
     In the meantime, if placing the plurality of substrates  130  on the tray  140 , the plurality of substrates  130  may be arranged at fixed intervals in a matrix configuration, but it is not limited to this configuration. 
     The dry etching apparatus  100  according to one embodiment of the present invention may further include a tray supporting member  150  for supporting the tray  140 . 
     The two tray supporting members  150  are respectively provided at both sidewalls of the chamber  110 , wherein the tray supporting members  150  are arranged in parallel. The tray supporting members  150  support the tray  140  transferred to the reaction space through a chamber gate (not shown) by a tray transferring apparatus. At this time, the tray supporting member  150  may be a roller member, and the tray transferring apparatus may be a transferring robot or a conveyor. 
     The susceptor  160  is positioned inside the chamber  110  in such a way that the susceptor  160  confronts with a rear surface of the tray  140 . The susceptor  160  generates the plasma through the use of high-frequency power supplied through the electrode rod  180 , to thereby etch the surface of the substrate  130  placed on the tray  140 . The susceptor  160  is identical in shape to the tray  140 . 
     The insulating part  164  is positioned between the susceptor  160  and the grounding part  162 , so as to electrically insulate the rear and lateral surfaces of the susceptor  160  from the grounding part  162 . For this, as shown in  FIG. 2 , the insulating part  164  may includes a first insulator  220  with a through hole  210 ; and a plurality of second insulators  230  to be engaged with the first insulator  220 . 
     The first insulator  220  is positioned in such a way that the first insulator  220  confronts a central portion of the susceptor  160 . 
     Each of the plurality of second insulators  230  is provided with a horizontal portion confronting with the rest of the susceptor  160  except the central portion of the susceptor  160 ; and a vertical portion confronting with the lateral surface of the susceptor  160 . 
     The horizontal portion in each second insulator  230  is engaged with the neighboring second insulators  230  as well as the first insulator  220 . In this case, at least one step-shaped surface  240  is formed at a portion for engaging the first insulator  220  and the second insulator  230  with each other, and a portion for engaging the neighboring second insulators  230  with each other. This step-shaped surface  240  enables the increase of grounding path between the susceptor  160  and the grounding part  162 , and also enables easiness of engagement. 
     The insulating part  164  may be formed of a ceramic material or Teflon® (PTFE) material which is capable of enhancing a density of the plasma generated in the reaction space, and is also capable of preventing the abnormal discharge. Preferably, the insulating part  164  is formed of Teflon® (PTFE) material, but not necessarily. A dielectric constant of Teflon® (PTFE) material is higher than that of ceramic material. Owing to the high dielectric constant of Teflon® (PTFE) material, even though the insulating part  164  is formed at a small thickness (for example, 40 mm or less), a high insulating efficiency can be realized. Also, since Teflon® (PTFE) material is not reactive on an etching gas, it is possible to minimize a sag in the susceptor  160 . 
     The grounding part  162 , formed in the same shape as that of the susceptor  160 , is electrically grounded by a ground (not shown). In case of a general dry etching apparatus, it is impossible to make a direct grounding in the susceptor  160 , whereby the abnormal discharge is generated beneath the susceptor  160 . Meanwhile, in case of the dry etching apparatus according to the present invention, the grounding part  162  is grounded while being positioned beneath the susceptor  160  so that it is possible to prevent the abnormal discharge from occurring beneath the susceptor  160 . 
     As shown in  FIG. 3 , the grounding part  162  according to the first embodiment of the present invention may be a rectangular-shaped flat panel  310  with a central hole  312 , but it is not limited to this structure. The grounding part  162  may be a circular-shaped flat panel based on the shape of the susceptor  160 . 
     As shown in  FIG. 4 , the grounding part  162  according to the first embodiment of the present invention may further include a plurality of openings  314  arranged in a grid configuration. In this case, each opening  314  may be formed in a rectangular shape or a circular shape. 
     A first sealing member  169   a  is provided between the susceptor  160  and the insulating part  164 , and a second sealing member  169   b  is provided between the grounding part  162  and the insulating part  164 . In this case, the first and second sealing members  169   a  and  169   b  may be respectively O-rings, and the first sealing member  169   a  may be positioned above the first insulator  220 . The first and second sealing members  169   a  and  169   b  separate the reaction space inside the chamber  110  from an external atmospheric space. 
     The susceptor  160 , the grounding part  162 , and the insulating part  164  may be integrated into one body with the first and second sealing members  169   a  and  169   b  positioned in-between by a connection member (not shown). 
     In the meantime, the dry etching apparatus  100  according to one embodiment of the present invention may further include a susceptor supporting member  170  and a high-frequency power supplier  182 . 
     The susceptor supporting member  170  includes a first supporter  172 , a second supporter  174 , and a plate  176 . 
     One end of the first supporter  172  is connected with the central portion of the susceptor  160  by sequentially passing through the bottom surface of the chamber  110 , the central hole  312  of the grounding part  162 , and the through hole  210  of the insulating part  164 ; and the other end of the first supporter  172  supports the rear surface of the susceptor  160  while being connected with the plate  176 . 
     The second supporter  174  supports the rear surface of the grounding part  162  by passing through the bottom surface of the chamber  110 . For this, the second supporter  174  may include an upper supporter  174   a  which is connected to the grounding part  162  with a third sealing member  178  interposed in-between; a lateral supporter  174   b  which is perpendicularly bent from the upper supporter  174   a  being adjacent to the first supporter  172 ; and a lower supporter  174   c  which is bent from the lateral supporter  174   b  while being parallel to the upper supporter  174   a,  and is connected to the plate  176  with a fourth sealing member  179  interposed in-between. At this time, the lateral supporter  174   b  may be provided with a through hole through which the first supporter  172  passes. The third and fourth sealing members  178  and  179  may be respectively O-rings. 
     The plate  176  supports the other end of the first supporter  172  and the lower supporter  174   c  of the second supporter  174 . 
     The aforementioned susceptor supporting member  170  can support the susceptor  160 , and also elevate or lower the susceptor  160  by an elevating apparatus (not shown). At this time, the elevating apparatus elevates the susceptor supporting member  170  to a predetermined height which is suitable for loading or unloading the tray  140  when the tray  140  is loaded on or unloaded from the tray supporting member  150 . After completing the loading or unloading of the tray  140 , the elevating apparatus elevates the susceptor supporting member  170  so that the susceptor  160  is electrically connected with the tray  140 , to thereby carry out an etching process. 
     The high-frequency power supplier  182  supplies high-frequency power to the electrode rod  180  which is electrically connected with the susceptor  160  by passing through the susceptor supporting member  170 . This high-frequency power supplier  182  supplies the high-frequency power to the electrode rod  180  so as to apply the high-frequency power to the tray  140  when the susceptor  160  is electrically connected with the tray  140  by the susceptor supporting member  170 . 
     The electrode rod  180  is electrically connected with the central portion of the susceptor  160  by passing through the plate  176  and the first supporter  172  in the susceptor supporting member  170 . 
     The dry etching apparatus  100  according to one embodiment of the present invention may further include a bellows  190  for protecting the high-frequency power supplier  182  and the susceptor supporting member  170  being exposed to the external of the chamber  110 . 
     The bellows  190  is provided between the lower surface of the chamber  110  and the plate  176  of the susceptor supporting member  170 . This bellows  190  is formed of a flexible material, which is capable of protecting the high-frequency power supplier  182  and the susceptor supporting member  170  being exposed to the external of the chamber  110  by its contraction and expansion. As shown in  FIG. 5 , the bellows  190  may be provided between the internal bottom surface of the chamber  110  and the grounding part  162  of the susceptor  160 . In this case, the third and fourth sealing members  178  and  179  shown in FIG.  1  may be omitted. Thus, the bellows  190  provided inside the chamber  110  enables the decrease in size of the dry etching apparatus  100 . 
     In  FIG. 5 , the grounding part  162  may be grounded to the external ground by the bellows  190 . 
       FIG. 6  illustrates a perspective view for explaining a grounding part according to the second embodiment of the present invention. 
     Referring to  FIG. 6 , the grounding part  162  according to the second embodiment of the present invention may be provided with an external frame  410 , a central frame  420 , and a mesh portion  430 . 
     The external frame  410  is formed in a rectangular shape corresponding to the edge of the susceptor  160 .  FIG. 6  illustrates the rectangular-shaped external frame  410 , but the shape of the external frame  410  is not limited to the rectangular shape. If the susceptor  160  is formed in a circular shape, the external frame  410  may be formed in the circular shape. 
     The central frame  420  is formed in the external frame  410  such that the first supporter  172  passes through the central frame  420 . Then, second and third sealing members  169   b  and  178  may be respectively provided on upper and lower surfaces of the central frame  420  so as to separate the reaction space inside the chamber  110  from the external atmospheric space. 
     The mesh portion  430  is formed in a mesh type to connect the external frame  410  and the central frame  420  with each other. 
       FIG. 7  illustrates a perspective view for explaining a grounding part according to the third embodiment of the present invention. 
     Referring to  FIG. 7 , the grounding part  162  according to the third embodiment of the present invention may be formed in a rectangular-shaped frame to be overlapped with the edge of the susceptor  160 . Then, second and third sealing members  169   b  and  178  may be respectively provided on upper and lower surfaces of the grounding part  162  formed in shape of the rectangular frame so as to separate the reaction space inside the chamber  110  from the external atmospheric space. 
       FIG. 8  illustrates a perspective view for explaining a grounding part according to the fourth embodiment of the present invention. 
     Referring to  FIG. 8 , the grounding part  162  according to the fourth embodiment of the present invention may be formed in a circular-shaped frame to be overlapped with the edge of the susceptor  160 . Then, second and third sealing members  169   b  and  178  may be respectively provided on upper and lower surfaces of the grounding part  162  formed in shape of the circular frame so as to separate the reaction space inside the chamber  110  from the external atmospheric space. 
     An operation of the dry etching apparatus according to the present invention will be explained with reference to  FIG. 9(A  and B). 
     As shown in  FIG. 9(A) , the external tray  140  is loaded on the tray supporting member  150 . According as the elevating apparatus is driven, the susceptor supporting member  170  is lowered so that the susceptor  160  is maintained at a predetermined height. 
     When the tray  140  is supported by the tray supporting member  150 , as shown in  FIG. 9(B) , the susceptor  160  is elevated by elevation of the susceptor supporting member  170  according to an operation of the elevating apparatus, whereby the susceptor  160  is electrically connected with the rear surface of the tray  140 . 
     As the high-frequency power supplied from the high-frequency power supplier  182  to the electrode rod  180  is applied to the tray  140  through the susceptor  160 , and simultaneously the processing gas is supplied to the reaction space from the showerhead  120 , plasma (P) is generated in the reaction space of the chamber  110 , that is, between the showerhead  120  and the tray  140 . Then, ion and radical are generated by collision between the processing gas and electrons accelerated by the plasma (P), and the generated ion and radical enter into the substrate  130  placed on the tray  140 , whereby the etching process is carried out. 
     After completing the etching process, the susceptor  160  is lowered, and the tray  140  supported by the tray supporting member  150  is unloaded. 
     In the dry etching apparatus  100  according to the present invention, the grounding part  162  is provided beneath the susceptor  160  so as to prevent the discharge from occurring beneath the susceptor  160 , so that it is possible to realize the wide processing margin and uniform etching through enhancement of plasma density. 
     In the meantime, the dry etching apparatus  100  according to the present invention may be used for forming an uneven structure (or concavo-convex pattern) in a surface of a substrate so as to maximize absorption of solar ray when manufacturing a wafer type solar cell. Through a dry etching process performed by the dry etching apparatus  100  according to the present invention, the uneven structure can be uniformly formed in the surface of the substrate for the wafer type solar cell without regard to orientation direction of crystal molecules. Accordingly, the dry etching apparatus  100  according to the present invention enables the use of relatively-thin substrate on the process of manufacturing the wafer type solar cell. 
     Furthermore, the dry etching apparatus  100  according to the present invention can be used for a dry etching process when manufacturing a semiconductor device or a flat panel display device. 
     As mentioned above, the dry etching apparatus  100  according to the present invention includes the grounding part  162  provided beneath the susceptor  160 , whereby it is possible to prevent the abnormal discharge from occurring beneath the susceptor  160 , thereby realizing the wide processing margin and uniform etching through enhancement of plasma density. 
     Also, the uneven structure can be uniformly formed in the surface of the substrate for the wafer type solar cell without regard to orientation direction of crystal molecules, through the dry etching process performed by the dry etching apparatus  100  according to the present invention. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.