Patent Publication Number: US-2015059979-A1

Title: Plasma processing apparatus for vapor phase etching and cleaning

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority of Korean Patent Application No. 10-2013-0102625, filed on Aug. 28, 2013, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a plasma processing apparatus for vapor phase etching and cleaning, and more specifically, to a plasma processing apparatus for vapor phase etching and cleaning, capable of selectively cleaning a surface of a substrate to be processed by causing a direct reaction between a thin film of the surface of the substrate to be processed and high reactive atoms or molecules. 
     BACKGROUND OF THE INVENTION 
     A semiconductor device is an active electronic device having functions of storing, amplifying and switching electrical signals, which is a core part that guides high added values of system and service industries and leads digital information era based on high integration, high performance and low power consumption. 
     The semiconductor manufacturing process can be generally divided into a pre-process (wafer processing process) and a post-process (assembly process and test process), and the market share of pre-process equipments is about 75%. The market share of a wet cleaning apparatus and an apparatus of dry etching called plasma etching is totally 22.6%, forming the second largest market. In the semiconductor manufacturing process, circuits electrically connecting parts are manufactured as one pattern (circuit design) and then drawn on thin films of a plurality of layers in the semiconductor. At this case, an etching process is to remove unnecessary portions on the substrate (wafer) on which the thin films are formed, thereby exposing the circuit pattern. The etching process is divided into a dry etching process that uses plasma and a wet etching process that uses a cleaning solution. 
     The dry etching process is a process in which physical and chemical etching is performed by vertical incident particles of ion flux caused by plasma. Accordingly, as the device design becomes smaller and smaller, there occurs a problem in that the pattern is damaged depending on processes. The wet process is a technology that has been commonly used for a long time, wherein unnecessary portions on the wafer surface are removed by dipping the wafer into a container filled with a cleaning solution or spraying the cleaning solution on the wafer surface while rotating the wafer at a predetermined speed. However, the wet process also has a drawback that there occurs a huge amount of waste water and it is difficult to control the amount of cleaning solution and cleaning uniformity. Further, in case of anisotropic etching, the pattern after cleaning may be larger or smaller compared with the intended design, so that it becomes difficult to process fine patterns. 
     Recently, the size of unit device of the semiconductor chip becomes smaller and smaller as demands for high-speed devices and large-capacity memory devices are increased. Accordingly, the pattern gap formed on the wafer surface becomes narrower and narrower and the thickness of gate insulating film of a device becomes thinner and thinner. Therefore, some problems are emerging, which did not occur in the conventional semiconductor process or were not important. Among them, a typical problem caused by plasma is plasma damage. The plasma damage affects, in property and reliability, devices including transistor in all processes in which the wafer surface is exposed as the semiconductor device becomes miniaturized. Film damage by the electric charge caused by plasma normally occurs in the etching process. The plasma damage is a problem occurring in the dry etching process or the wet etching process, thereby requiring efforts to solve it. 
     SUMMARY OF THE INVENTION 
     In view of the above, the present invention provides a plasma apparatus for vapor phase etching and cleaning, capable of cleaning a substrate surface by causing a direct reaction on a thin film of the surface of the substrate to be processed, whereby there is no plasma damage. 
     According to an aspect of the present invention, there is provided a plasma processing apparatus for vapor phase etching and cleaning, including a reactor body configured to process a substrate to be processed; a direct plasma generation area in the reactor body, info which a process gas is introduced and in which plasma is directly induced to disassociate the process gas; a substrate processing area in the reactor body in which the substrate to be processed is processed by reactive species produced by reacting the disassociated process gas introduced from the direct plasma generation area with a vaporized gas introduced from the outside of the reactor body; a plasma induction assembly configured to induce plasma in the direct plasma generation area; and a gas distribution baffle, which is disposed between the direct plasma generation area and the substrate processing area and has a plurality of through holes that are perforated, through which the disassociated process gas is introduced from the direct plasma generation area to the substrate processing area. 
     Further, the gas distribution baffle may include a plurality of vaporized gas injection holes to inject vaporized gas introduced from the outside to the substrate processing area. 
     Further, the plasma apparatus for vapor phase etching and cleaning according to the present invention may further include one or more gas injection nozzles, each of which directly injects the vaporised gas to the substrate processing area. 
     Further, the plasma induction assembly may include a first electrode and a second electrode that are capacitively coupled with each other. 
     Further, the plasma induction assembly may include a dielectric window that is mounted between the first and second electrodes and the direct plasma generation area. 
     Further, the gas distribution baffle may include a heater to control temperature. 
     Further, the plasma induction assembly may include a cooling channel. 
     Further, the vaporized gas may be vaporized H 2 O. 
     According to another aspect of the present invention, there is provided a plasma processing apparatus for vapor phase etching and cleaning, including a reactor body configured to process a substrate to be processed; a direct plasma generation area in the reactor body, into which a process gas is introduced and in which plasma is directly induced to disassociate the process gas; a reactive area in the reactor body, in which a disassociated process gas introduced from the direct plasma generation area is reacted with a vaporized gas introduced from the outside of the reactor body, thereby forming reactive species; a substrate processing area in the reactor body, in which the substrate to be processed is processed by the reactive species introduced front the reactive area; a plasma induction assembly configured to induce plasma into the direct plasma generation area; a first gas distribution baffle that is disposed between the reactive area and the substrate processing area and that includes a plurality of first through holes that are perforated, through which the reactive species is introduced from the reactive area info the substrate processing area; and a second gas distribution baffle that is disposed between the direct plasma generation area and the reactive area and that includes a second gas distribution baffle having a plurality of second through holes, through which the disassociated process gas is introduced from the direct plasma generation area into the reactive area. 
     Further, the first gas distribution baffle may include a plurality of vaporized gas injection holes to inject the vaporized gas introduced from the outside to the reactive area. 
     Further, the plasma processing apparatus for vapor etching and cleaning according to another aspect of the present invention may further include one or more gas injection nozzles, each of which directly injects the vaporised gas to the reactive area. 
     Further, the plasma induction assembly may include first and second electrodes that are capacitively coupled with each other. 
     Further, the plasma induction assembly may include a dielectric window that is mounted between the first and second electrodes and the direct plasma generation area. 
     Further, the first gas distribution baffle may include a heater to control temperature. 
     Further, the plasma induction assembly may include a cooling channel. 
     Further, the vaporized gas may be vaporized H 2 O. 
     EFFECTS OF THE INVENTION 
     The plasma apparatus for vapor etching and cleaning may clean the substrate to be processed without any plasma damage. Further, it has advantages that there does not occur any residual product and the selectivity is high. Furthermore, the surface of the substrate to be processed may be uniformly cleaned by providing the substrate to be process with the gasified gas for the vapor phase cleaning. The temperature of the gasified gas may be controlled using the heater disposed in the has distribution baffle to inject the gasified gas. Furthermore, the substrate to be processed may be cleaned even in the micro-pattern processing process since there is no plasma damage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a view illustrating a plasma processing apparatus in accordance with a preferred embodiment of the present invention. 
         FIG. 2  is a view illustrating a simplified structure of a capacitively coupled electrode assembly shown in  FIG. 1 . 
         FIG. 3  is a plane view illustrating the top of a first gas distribution baffle shown in  FIG. 1 . 
         FIG. 4  is a plane view illustrating the bottom of a first gas distribution baffle shown in  FIG. 1 . 
         FIG. 5  is a view illustrating a plasma processing apparatus having a cooling channel in a ground electrode. 
         FIG. 6  is a view illustrating another embodiment of a first gas distribution baffle. 
         FIG. 7  is a view illustrating another embodiment of an exhaust baffle. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention can be readily understood by those stilled in the art. The embodiments of the present invention may be modified in a variety of forms and the scope of the present invention should not be construed to be limited to the embodiments described below. The embodiments of the present invention are provided to fully describe them for those skilled in the art. Accordingly, shapes of elements and the like in the drawings may be exaggerated to emphasize a clear explanation. It is noted that the same parts may be identified by the same reference numeral in each drawing. Also, description of well-known functions and constructions are omitted for clarify and conciseness. 
       FIG. 1  is a view illustrating a plasma processing apparatus in accordance with a preferred embodiment of the present invention and  FIG. 2  is a view illustrating a simplified structure of a capacitively coupled electrode assembly shown in  FIG. 1 . 
     Referring to  FIG. 1 , a plasma processing apparatus  10  is comprised of a reactor body  12 , a capacitively coupled electrode assembly  20 , a first gas distribution baffle  50 , a second gas distribution baffle  40  and a power supply  3 . The reactor body  12  includes a substrate support  2  in which a substrate to be processed  1  is disposed. The reactor body  12  has a gas inlet  14  through which a process gas for plasma processing is supplied, on the top of the reactor body  12 , and the process gas supplied from a process gas supply  15  is supplied into the reactor body  12  through the gas inlet  14 . The gas inlet  14  has a gas injection head  30  including a plurality of gas injection holes  32  through which process gas may be supplied into the reactor body  12 . The gas injection head  30  is connected to the gas inlet  14  so that the process gas is injected below a dielectric window  28 . The reactor body  12  has a gas outlet  16  formed on the bottom of the reactor body  12 , the gas outlet  16  being connected to an exhaust pump  17 . The gas outlet  16  is formed at one side of the bottom of the reactor body  12  so that it is not easy for the exhaust gas to be uniformly discharged to the outside of the reactor body  12 . Accordingly, an exhaust ring  70  having an exhaust hole  72  is formed in the lower portion of the reactor body  12 . The exhaust ring  70  is formed to enclose the vicinity of the substrate support  2 , which has a shape having a through hole in the center of it and having an upper portion extended externally. The substrate support  2  is disposed at the through hole in the center of the exhaust ring  70 , and the extended portion of the upper portion is mounted, to contact with a side wail of the internal portion of the reactor body  12 . Here, the circumference of the exhaust ring  70  has the exhaust hole  72  to uniformly discharge the exhaust gas existing in the reactor body  12 . The exhaust hole  72  may have a continuously open shape or be formed of a plurality of through holes. 
     The reactor body  12  may be manufactured of metal material such as aluminum, stainless steel and copper. Further, it may be manufactured of metal coating, for example, anode processed aluminum or nickel plated aluminum. Further, it may be manufactured of refractory metal. As another alternative, it may be possible to totally or partially manufacture the reactor body  12  of electrically insulating material such as quartz and ceramic. As such, the reactor body  12  may be manufactured of any material suitable to perform an intended plasma process. The reactor body  12  may have structures depending on the substrate to be processed  1  and suitable  1   c  generate a uniform plasma, for example, circle structure, square structure and any other structures. 
     The substrate to be processed  1  may be a wafer substrate, a glass substrate and a plastic substrate that are intended to manufacture a variety of apparatus such as a semiconductor device, a display apparatus and a solar cell. The substrate support  2  may be connected to a bias power supply  6 , thereby being biased. Further, two bias power supplies that supply radio-frequency powers different each other are electrically connected to the substrate support  2  through an impedance matcher  7 , thereby biasing the substrate support  2 . Further, the substrate support  2  may be modified and embodied in a structure having zero potential without being supplied with the bias power. The substrate support  2  has lift pins  60  connected to a lift pin driver  62 , the lift pins  60  being used to move the substrate to be processed  1  up and down while supporting the substrate to be processed  1 . The substrate support  2  may have a heater. Further, the substrate support  2  may have an electrostatic chuck. A vacuum chuck is used to keep the substrate to be processed at a constant temperature in the process. Here, the reactor body  12  has a vacuum state therein, thereby causing a limitation of pressure to occur. However, the electrostatic chuck may be used regardless of the limitation of pressure. 
     The capacitively coupled electrode assembly  20  is mounted on the top of the reactor body  12  to form a ceiling of the reactor body  12 . The capacitively coupled electrode assembly  20  is comprised of a first electrode  22  connected to a ground  21  and a second electrode  24  connected to the power supply  3  to be supplied with a frequency power. The first electrode  22  forms a ceiling of the reactor body  12 , which is connected to the ground  21 . The first electrode  22  is formed in a plate shape, and has protrusions  22   a  that are separate one from another at a predetermined gap and formed to be projected to the inside of the reactor body  12 . The first electrode  22  has a gas inlet  14  in the center of it. The second electrode  24  is mounted, between the protrusions  22   a,  which is separated from the first electrode  22  at a predetermined gap. The second electrode  24  is partially inserted into the first electrode  22 , thereby being mounted therein. The second electrode  24  is comprised of a power supply electrode  24   a  connected to the power supply  3  so as to be supplied with a radio frequency power and an insulator  24   b  formed to cover the power supply electrode  24   a  externally. The first and second electrodes  22  and  24  directly generate capacitively coupled plasma into the plasma generation area. While the capacitively coupled electrode assembly  20  is used to induce plasma in the present invention, a radio frequency antenna may also be used in a construction to generate inductively coupled plasma. 
     Referring to  FIG. 2 , the capacitively coupled electrode assembly  20  has the first electrode  22  connected to a ground and the second electrode  24  connected to the power supply  3 , each being helically formed. The protrusion  22   a  of the first electrode  22  and the power supply electrode  24   a  of the second electrode  24  are separated with each other at a predetermined gap, each being formed in a helical shape. The second electrode  24  and the protrusion  22   a  of the first electrode  22  face each other keeping a constant gap therebetween, so that it may be possible to generate uniform, plasma. The capacitively coupled electrode assembly  20  and the second gas distribution baffle  40  have a dielectric window  28  therebetween. The dielectric window  28  is resistant to plasma damage and may be used semipermanently. Here, the first and second electrodes  22  and  24  may also be arranged in parallel. 
     Referring to  FIG. 1  again, the power supply  3  is connected to the second electrode  24  through the impedance matcher  5 , supplying a radio-frequency power. The second electrode  24  may be selectively connected to a direct current power supply  4 . The first gas distribution baffle  50  is a constituent to distribute the vaporized gas to the substrate to be processed  1 , which is disposed over the substrate support  2 . The first gas distribution baffle  50  is comprised of a plurality of first through holes  52  each formed therethrough and a plurality of vaporized gas injection holes  54  formed in the vaporized gas supply route  53  which is disposed inside the first gas distribution baffle  50 . The plasma generated in an area where direct plasma is generated is distributed to an area where the substrate to be processed  1  is processed, that is, under the first gas distribution baffle  50 , through the first through hole  52 . The vaporized gas injection hole  54  is formed in the bottom of the first gas distribution baffle  50 , that is, formed toward the substrate to be processed  1 . The first gas distribution baffle  50  has a vaporized gas supply route  53  used to transfer the vaporized gas therethrough, and the vaporized gas supply route  53  has a plurality of vaporized gas injection holes  54 . The vaporized gas may be directly supplied to a space between the first gas distribution baffle  50  and the substrate support  2  from the vaporized gas supply  56  through a plurality of gas injection nozzles, or may be supplied to the space through the vaporized gas injection hole  54  of the vaporized gas supply route  53 . The plasma and vaporized gas react in an area under the first gas distribution baffle  50  to process the substrate to be processed  1 . The first through hole  52  and vaporized gas injection hole  54  may be formed alternately. 
     The reactor body  12  may further include a second bas distribution baffle  40  to uniformly distribute the plasma. The second gas distribution baffle  40  is disposed between the capacitively coupled electrode assembly  20  and the first gas distribution baffle  50 , which uniformly distributes the plasma through a plurality of second through holes  42  each formed therethrough. The plasma is uniformly distributed through the second gas distribution baffle  40 , and then uniformly distributed through the first gas distribution baffle  50  again. The plasma distributed through the first gas distribution baffle  50  reacts with the vaporized gas injected through the vaporized gas injection hole  54  to form reactive species, and the reactive species are absorbed onto the residual product of the substrate to be processed  1  and then removed in the thermal process. Such cleaning method is called vapor phase etching and cleaning. The vapor phase cleaning is a cleaning method having both merits of wet cleaning and dry etching, which causes a direct reaction between a thin film of the surface of the substrate to be processed  1  and atoms or molecules having high reactivity in a low temperature vacuum chamber, thereby generating selective etching and cleaning. The vapor phase cleaning has merits that its selectivity is high, the amount of cleaning is easily controlled, and there is no plasma damage. Further, the vapor phase cleaning has further merit that it normally does not produce residual products and the residual products may be removed using a simple method compared with that of the wet cleaning, although they are produced. The gas to form the reactive species may be vaporised water (H 2 O). 
     The first gas distribution baffle  50  may further have a heater  51  in its border portion. The heater  51  continues to supply heat to the vaporized water H 2 O passing through the vaporised gas supply route  53  of the first gas distribution baffle  50  so that the vaporized water H 2 O reaches the substrate to be processed  1  in a vapor state without being liquefied. Further, the first gas distribution baffle  50  may further have a sensor to measure a temperature of the vaporized gas. 
       FIG. 3  is a plane view illustrating a top of a first gas distribution baffle shown in  FIG. 1  and  FIG. 4  is a plane view illustrating a bottom of a first gas distribution baffle shown in  FIG. 1 . 
     Referring to  FIGS. 3 and 4 , the first through hole  52  of the first gas distribution baffle  50  is formed through the first gas distribution baffle  50 . On the contrary, the vaporised gas injection hole  54  is formed in a lower portion of the vaporised gas supply route  53  formed inside the first gas distribution baffle  50 , that is, is formed on the bottom of the first gas distribution baffle  50 . Therefore, the first through hole  52  and the vaporized gas injection hole  54  may be identified on the bottom of the first gas distribution baffle  50 , and the first through hole  52  may be identified on the top of the first gas distribution baffle  50 . The first through hole  52  is formed larger than the vaporized gas injection hole  54  in an embodiment of the present invention. The vaporized gas injection hole  54  and the first through hole  52  are uniformly formed throughout the first gas distribution baffle  50 , so that it may be possible to uniformly distribute the plasma and to uniformly inject the vaporized gas. 
       FIG. 5  is a view illustrating a plasma processing apparatus having a cooling channel in a ground electrode. 
     Referring to  FIG. 5 , a plasma processing apparatus  10   a  may include a cooling channel  26  inside a first electrode  22  connected to a ground  21 . The cooling channel  26  may be supplied with a cooling water from a cooling water supply  27  to lower the temperature of an overheated first electrode  22 , keeping if at a constant temperature. 
       FIG. 6  is a view illustrating another embodiment of a first bas distribution baffle. 
     Referring to  FIG. 6 , in a first bas distribution baffle  50   a  of a plasma processing apparatus  10   b,  a vaporized gas injection hole  54   a  is disposed on a top of a first gas distribution baffle  50   a.  Therefore, a vaporized gas is injected above the first gas distribution baffle  50   a  through the vaporized gas injection hole  54   a.  Here, the vaporized gas may be directly supplied to a space between the first gas distribution baffle  50   a  and a second distribution baffle  40  using at least one nozzle. The vaporized gas supplied and the plasma distributed through the second gas distribution baffle  40  are mixed in a space (reactive area) between the first gas distribution baffle  50   a  and the second gas distribution baffle  40  to form reactive species. The reactive species are uniformly distributed toward a substrate to foe processed  1  through a through hole  52  of the first gas distribution hole  50   a.  Since the reactive species are formed in the space between the second gas distribution baffle  40  and the first gas distribution baffle  50   a  and then distributed toward the substrate to be processed  1 , the plasma and vaporized gas may be reacted more efficiently, and the reactive species may be uniformly distributed toward the substrate to be processed  1  through the first through hole  52  of the first gas distribution baffle  50   a.    
       FIG. 7  is a view illustrating another embodiment of an exhaust baffle. 
     Referring to  FIG. 7 , an exhaust ring  70   a  may have a plurality of distribution plates  74  therein. The plurality of distribution plates  74  are a plurality of partition walls, which are alternately disposed on the inner wall of the exhaust ring  70   a  and the inner wall of the reactor body  12 , and make the exhaust gas introduced into the exhaust ring  70   a  through the exhaust hole  72  discharged uniformly while passing through the partition plates disposed alternately. 
     It will be appreciated that the embodiments of the plasma apparatus for vapor phase etching and cleaning in accordance with the present invention are merely exemplary, and various modifications and equivalent other embodiments will be apparent to those skilled in the art. 
     Therefore, it will be clearly understood that the present invention is not limited to shapes mentioned in the detailed description. Accordingly, the true scope of technical protection of the present invention should be defined by the technical ideas of appended claims. Further, it should be understood that the present invention includes all the modifications, equivalences and substitutes within spirits and scopes of the present invention defined by appended claims.