Patent Publication Number: US-8974600-B2

Title: Deposit protection cover and plasma processing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Japanese Patent Application No. 2009-175777 filed on Jul. 28, 2009, and U.S. Provisional Application Ser. No. 61/238,266 filed on Aug. 31, 2009, the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to a deposit protection cover and a plasma processing apparatus. 
     BACKGROUND OF THE INVENTION 
     Conventionally, in the field of manufacture of semiconductor devices or the like, there is known a plasma processing apparatus that processes a target substrate such as a semiconductor wafer by generating plasma within a hermetically sealable processing chamber. Further, there is known a plasma etching apparatus as one example of such a plasma processing apparatus. 
     In such a plasma etching apparatus or the like, plasma etching may cause deposits to adhere on the inside of the processing chamber. The deposits may be peeled off from the inside of the processing chamber and, then, the deposits may be dispersed as particles and be adhered to a semiconductor wafer on which an etching process is being performed. To prevent this problem, conventionally, the inside of the processing chamber has been cleaned periodically. 
     Further, a cylindrical liner is installed so as to cover a wall surrounding a plasma generation space in the processing chamber, and, then deposits are removed from the inside of the processing chamber by regularly replacing or cleaning the liner after separating the liner (see, for example, Patent Document 1). 
     Patent Document 1: Japanese Patent Laid-open Publication No. 2008-270595 
     As stated above, conventionally, the cylindrical liner or the like covering the wall surrounding the plasma generation space has been installed and the liner has been regularly replaced or separated and cleaned. 
     However, deposits may be adhered not only to the plasma generation space of the processing chamber but also to a portion originally considered to be unreachable by plasma, such as a portion under a baffle plate configured to surround a mounting table for mounting a target substrate thereon and provided with a through hole, a slit, or the like through which a gas exhaust is performed. If deposits are adhered to such a portion and if it is difficult to separate and clean components of the processing chamber, it has been difficult to completely remove the deposits by performing a cleaning process within the processing chamber. Therefore, there has been a problem that it takes a long time to complete the cleaning process. 
     Furthermore, to install a detachable cover configured to cover such a portion, at least a surface of the cover needs to be made of an insulating material so as to prevent an abnormal electric discharge, and a highly plasma-resistance material should be used for the cover. Therefore, there has been a problem that manufacturing cost is increased. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, in order to solve the above-mentioned problem, the present disclosure provides a deposit protection cover capable of providing a simple solution to deposits adhered to a portion originally considered to be unreachable by plasma without increasing manufacturing cost, and also provides a plasma processing apparatus using the same. 
     In accordance with a first embodiment of the present disclosure, there is provided a deposit protection cover detachably provided within a processing chamber so as to cover a preset portion of the processing chamber that processes a substrate by generating plasma therein. The cover includes an aluminum plate having a surface on which an anodic oxidation process is performed. Further, the anodic oxidation process is performed by using an electrode part protruded from a cover main body, an exposed area of an aluminum base surface is reduced by removing the electrode part after the anodic oxidation process is performed, and a cut surface formed after removing the electrode part is positioned at a region that is not directly exposed to the plasma within the processing chamber. 
     In accordance with a second embodiment of the present disclosure, there is provided a plasma processing apparatus including a processing chamber and processing a substrate by generating plasma therein. The apparatus includes a deposit protection cover made of an aluminum plate having a surface on which an anodic oxidation process is performed, and the cover is detachably provided within the processing chamber so as to cover a preset portion of the processing chamber. Further, the anodic oxidation process is performed by using an electrode part protruded from a cover main body, an exposed area of an aluminum base surface is reduced by removing the electrode part after the anodic oxidation process is performed, and a cut surface formed after removing the electrode part is positioned at a processing chamber&#39;s portion a region that is not directly exposed to the plasma within the processing chamber. 
     In accordance with the above-mentioned present disclosure, there are provided a deposit protection cover and a plasma processing apparatus capable of providing a simple solution to deposits adhered to the portion originally considered to be unreachable by plasma without increasing manufacturing cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure may best be understood by reference to the following description taken in conjunction with the following figures: 
         FIGS. 1A and 1B  are schematic diagrams illustrating a configuration of a deposit protection cover in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a schematic diagram illustrating a configuration of a plasma etching apparatus in accordance with an embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram illustrating a configuration of major parts of the plasma etching apparatus of  FIG. 2 ; 
         FIG. 4  is a schematic diagram illustrating a configuration of major parts of the plasma etching apparatus of  FIG. 2 ; and 
         FIGS. 5A and 5B  are diagrams for describing usage states of the deposit protection cover of  FIGS. 1A and 1B . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. 
       FIGS. 1A and 1B  are diagrams for describing a configuration of a deposit protection cover  110  in accordance with an embodiment of the present disclosure. The deposit protection cover  110  shown in  FIGS. 1A and 1B  is made of an aluminum plate in a predetermined shape. 
     As illustrated in  FIG. 1A , the deposit protection cover  110  in the middle of manufacture is provided with an electrode part  112  protruding from a cover main body  111  so as to be used when an anodic oxidation process is performed. An anodically oxidized film is formed on the cover main body  111  of the deposit protection cover  110  by performing the anodic oxidation process. Meanwhile, since the electrode part  112  is used as an electrode when the anodic oxidation process is performed, anodically oxidized film is not formed on its surface, and an aluminum base surface is just exposed. 
     Accordingly, in the embodiment shown in  FIG. 1B , the electrode part  112  is removed after the anodic oxidation process is performed on the cover main body  111  of the deposit protection cover  110 , and the deposit protection cover  110  is used without the electrode part  112 . 
     Accordingly, in a state shown in  FIG. 1B , an aluminum base surface is exposed only at a cut surface  112   a  formed after the electrode part  112  is removed. As compared to a state before the removal of the electrode part  112  of  FIG. 1A , an exposed area of the aluminum base surface is reduced. Further, the cut surface  112   a  is formed so as to be positioned at a portion which is not directly exposed to plasma when the deposit protection cover  110  is provided within a processing chamber of a plasma etching apparatus or the like, as will be described later. By the deposit protection cover  110  in such a state, a risk of an abnormal electric discharge can be reduced. 
     Furthermore, by using the aluminum plate of which surface is anodically oxidized as state above, manufacturing cost can be reduced as compared to, e.g., a case of forming highly plasma-resistant fine ceramics on an entire metal plate by thermal spraying. 
     Referring to  FIG. 2 , a configuration of a plasma processing apparatus (plasma etching apparatus in the present embodiment) in which the deposit protection cover  110  having the above-described configuration is provided will now be explained. The plasma etching apparatus includes a substantially cylindrical processing chamber  2  made of, e.g., aluminum of which surface is anodically oxidized. The processing chamber  2  is grounded. 
     A substantially cylindrical susceptor support  4  configured to mount a semiconductor wafer W thereon is installed at a bottom portion of the processing chamber  2  via an insulating plate  3  made of, e.g., ceramics. A susceptor (mounting table)  5  serving as a lower electrode is installed on the susceptor support  4 . A high pass filter (HPF)  6  is connected with the susceptor  5 . 
     A coolant path  7  is provided within the susceptor support  4 , and a coolant is circulated through the coolant path  7  after introduced to a coolant introduction line  8  and is discharged through a coolant discharge line  9 . A cold heat is transferred to the semiconductor wafer W via the susceptor  5 , and, thus the semiconductor wafer W may be adjusted to a desired temperature. 
     The susceptor  5  is formed in a circular plate shape having a protruded upper central portion, and a circular electrostatic chuck  11  having the substantially same diameter as that of the semiconductor wafer W is provided on the protruded upper central portion of the susceptor  5 . The electrostatic chuck  11  includes an electrode  12  embedded in an insulating material. Further, a DC voltage of, e.g., about 1.5 kV is applied to the electrode  12  from a DC power supply  13 , and, thus, the semiconductor wafer W can be electrostactically attracted and held by, e.g., Coulomb force. 
     A gas passage  14  for supplying a heat transfer medium (for example, a He gas) to a rear surface of the semiconductor wafer W is formed through the insulating plate  3 , the susceptor support  4 , the susceptor  5 , and the electrostatic chuck  11 . Cold heat of the susceptor  5  is transferred to the semiconductor wafer W through the heat transfer medium, and, thus, the semiconductor wafer W can be maintained at a preset temperature. 
     An annular focus ring  15  is provided at an upper peripheral portion of the susceptor  5  so as to surround the semiconductor wafer W mounted on the electrostatic chuck  11 . The focus ring  15  is made of a conductive material such as silicon and can improve etching uniformity. 
     An upper electrode  21  is provided above the susceptor  5 , facing the susceptor  5  in parallel. The upper electrode  21  is held on an upper portion of the processing chamber  2  via an insulating member  22 . The upper electrode  21  includes an electrode plate  24 ; and an electrode support  25  made of a conductive material and configured to hold the electrode plate  24 . The electrode plate  24  is made of a semiconductor or a conductor, such as Si or SiC, and has a plurality of discharge holes  23 . The electrode plate  24  forms a facing surface toward the susceptor  5 . 
     A gas inlet port  26  is provided in a center of the electrode support  25  of the upper electrode  21 , and a gas feed pipe  27  is coupled to the gas inlet port  26 . Further, the gas feed pipe  27  is connected with a processing gas feed source  30  via a valve  28  and a mass flow controller  29 . The processing gas feed source  30  feeds an etching gas for a plasma etching process. 
     An exhaust pipe  31  is coupled to a bottom portion of the processing chamber  2 , and the exhaust pipe  31  is connected with an exhaust unit  35 . The exhaust unit  35  includes a vacuum pump such as a turbo-molecular pump and serves to evacuate the inside of the processing chamber  2  to a preset pressure of, e.g., about 1 Pa or less. Therefore, the exhaust unit  35  can create a preset depressurized atmosphere within the processing chamber  2 . Further, a gate valve  32  is provided at a side wall of the processing chamber  2 . After the gate valve  32  is opened, the semiconductor wafer W may be transferred to/from an adjacent load-lock chamber (not illustrated). 
     The upper electrode  21  is coupled to a first high frequency power supply  40  via a matching unit  41 . Further, the upper electrode  21  is also connected with a low pass filter (LPF)  42 . The first high frequency power supply  40  has a frequency ranging from about 27 MHz to about 150 MHz. By applying a high frequency power in such a high frequency range, high-density plasma in a desirable dissociation state can be generated within the processing chamber  2 . 
     The susceptor  5  serving as a lower electrode is coupled to a second high frequency power supply  50  via a matching unit  51 . The second high frequency power supply  50  has a frequency lower than that of the first high frequency power supply  40 . By applying a high frequency power in such a frequency range, an appropriate ionic action can occur without inflicting damage on the semiconductor wafer W serving as a target substrate. Desirably, the frequency of the second high frequency power supply  50  may be in the range of, e.g., about 1 MHz to about 20 MHz. 
     Further, a deposit shield  80  may be detachably provided along an inner wall of the processing chamber  2  so as to prevent adhesion of an etching by-product (deposits) to the processing chamber  2 . That is, the deposit shield  80  may form a processing chamber wall. The deposit shield  80  may be also provided at outer peripheral portions of the susceptor support  4  and the susceptor  5 . Furthermore, in the vicinity of a bottom portion of the processing chamber  2 , a baffle plate (exhaust plate)  83  may be provided between the deposit shield  80  on the processing chamber wall and the deposit shield  80  on the susceptor support  4 . The deposit shields  80  and the baffle plate  83  can be fabricated by coating an aluminum material with ceramics such as Y 2 O 3 . The baffle plate  83  is provided with through holes or slits for gas exhaust. The baffle plate  83  can uniformly exhaust gas through a circular ring-shaped region around the susceptor  5  and be configured to suppress reaching of plasma into a downstream of the baffle plate  83 . 
     In the present embodiment, a deposit protection cover  110  is provided so as to cover a certain portion below the baffle plate  83 . That is, as shown in  FIG. 3 , besides exhaust path portions provided with exhaust paths  120 , non-exhaust-path portions  121 ,  122  and  123  provided without exhaust path  120  exist below the ring-shaped baffle plate  83  due to structural restriction. The deposit protection covers  110  having shapes corresponding to the shapes of the non-exhaust-path portions  121 ,  122  and  123  are detachably installed at the respective non-exhaust-path portions  121 ,  122  and  123 . Furthermore,  FIG. 4  is a partial vertical sectional perspective view illustrating the processing chamber  2 &#39;s part shown in  FIG. 3 . 
     As shown in  FIG. 5A , depending on a process performed in the processing chamber  2 , deposits may be adhered to the non-exhaust-path portions  121 ,  122  and  123  by, e.g., plasma that reaches the non-exhaust-path portions through the through holes of the baffle plate  83 . Since, however, plasma typically does not reach the portions below the baffle plate  83 , those portions have not been considered to be portions to which deposits are adhered. Thus, if deposits  130  are adhered to such portions, those portions cannot be separated to be cleaned. Therefore, when those portions in the narrow processing chamber  2  need be cleaned, it may take a long time to complete the cleaning and the deposits may not be completely removed. 
     Meanwhile, in the present embodiment, as shown in  FIG. 5B , since the non-exhaust-path portions  121 ,  122  and  123  are covered with the deposit protection covers  110 , deposits, if any, may be adhered to the deposit protection covers  110 , and the deposit protection covers  110  can be replaced or cleaned easily after separated. 
     The overall operation of the plasma etching apparatus configured as described above is controlled by a control unit  60 . The control unit  60  includes a process controller  61  having a CPU for controlling each component of the plasma etching apparatus; a user interface  62 ; and a storage unit  63 . 
     The user interface  62  includes a keyboard with which a process manager inputs commands to manage the plasma etching apparatus; and a display on which an operational status of the plasma etching apparatus is visually displayed. 
     The storage unit  63  stores therein control programs (software) for executing various processes in the plasma etching apparatus under the control of the process controller  61 ; and recipes including processing condition data or the like. A necessary recipe may be retrieved from the storage unit  63  and executed by the process controller  61  in response to an instruction from the user interface  62 , and, thus, a desired process may be performed in the plasma etching apparatus under the control of the process controller  61 . Furthermore, the control programs or the recipes including the processing condition data or the like can be retrieved from a computer-readable storage medium (e.g., a hard disk, a CD, a flexible disk, or a semiconductor memory), or can be used on-line by being transmitted from another apparatus via, e.g., a dedicated line, whenever necessary. 
     Before plasma etching is performed on a semiconductor wafer W by the plasma etching apparatus having the above-described configuration, the gate valve  32  is opened. Then, the semiconductor wafer W is loaded into the processing chamber  2  from a load-lock chamber (not shown) and mounted on the electrostatic chuck  11 . Thereafter, a DC voltage is applied from the DC power supply  13 , and, thus, the semiconductor wafer W is electrostatically attracted and held on the electrostatic chuck  11 . Subsequently, the gate valve  32  is closed, and the inside of the processing chamber  2  is evacuated by the exhaust unit  35  to a preset vacuum pressure level. 
     Thereafter, the valve  28  is opened, and a preset etching gas is fed into a central portion of the upper electrode  21  through the gas feed pipe  27  and the gas inlet port  26  from the processing gas feed source  30  while its flow rate is controlled by the mass flow controller  29  and is uniformly discharged toward the semiconductor wafer W through the discharge holes  23  of the electrode plate  24 , as indicated by arrows in  FIG. 2 . 
     Then, the inside of the processing chamber  2  is maintained at a preset pressure. Thereafter, a high frequency power of a preset frequency is applied to the upper electrode  21  from the first high frequency power supply  40 . As a result, a high frequency electric field is generated between the upper electrode  21  and the susceptor  5  as the lower electrode, and the etching gas is dissociated and excited into plasma. 
     Meanwhile, a high frequency power of a frequency lower than that of the first high frequency power supply  40  is applied to the susceptor  5  serving as the lower electrode from the second high frequency power supply  50 . As a result, ions in the plasma can be attracted toward the susceptor  5 , so that etching anisotropy can be improved by ion assist. 
     Upon completing the plasma etching process, the supply of the high frequency power and the processing gas is stopped, and the semiconductor wafer W is unloaded from the processing chamber  2  in the reverse sequence as described above. 
     Although the embodiment of the present disclosure has been described in the above, the present disclosure is not limited to the above-stated embodiment but can be modified in various ways. For example, the plasma etching apparatus is not limited to the parallel plate type apparatus that applies dual frequency powers to the upper and lower electrodes as illustrated in  FIG. 2 . For example, the present disclosure is applicable to various kinds of plasma etching apparatuses such as a type that applies dual high frequency powers to a lower electrode or a type that applies a single high frequency power to a lower electrode, or applicable to various kinds of other plasma processing apparatuses.