Abstract:
In a first aspect, a method is provided for use during plasma processing. The first method includes the steps of (1) placing a substrate on a substrate holder of a plasma chamber; (2) positioning a cover frame adjacent and below a perimeter of the substrate; and (3) employing the cover frame to reduce arcing during plasma processing within the plasma chamber. Numerous other aspects are provided.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to flat panel display and/or semiconductor device manufacturing, and more particularly to methods and apparatus for reducing arcing during plasma processing.  
       BACKGROUND  
       [0002]      FIG. 1  illustrates a conventional apparatus  101  that may be employed during plasma processing. With reference to  FIG. 1 , the conventional apparatus  101  includes a substrate holder  103 , such as a susceptor, for supporting a substrate  105  (e.g., a glass substrate, a polymer substrate, a semiconductor wafer, etc.). The substrate holder  103  may be employed, for example, as a first electrode. The conventional apparatus  101  includes a shadow frame  107  for preventing arcing (e.g., between the substrate holder  103  and a second electrode (not shown)) during plasma processing. A portion  109  (e.g., a lip) of the shadow frame  107  of the conventional apparatus  101  overlies (e.g., contacts) an edge region of the substrate  105  and reduces arcing during plasma processing (as is known in the art), such as thin film deposition. The lip  109  of the shadow frame  107  also prevents film deposition on an outer edge region  111  of the substrate  105 , which is referred to as a film edge exclusion area. While the conventional shadow frame  107  reduces arcing during plasma processing, the shadow frame  107  also disturbs process parameters (e.g., gas flow, electrical field, etc.) in a processing chamber (not shown) which includes the conventional apparatus  101 . Consequently, a film deposited on the substrate  105  (e.g., proximate the lip  109  of the shadow frame  107 ) may not be of a uniform thickness. Improved methods and apparatus for reducing arcing during plasma processing are desirable.  
       SUMMARY OF THE INVENTION  
       [0003]     In a first aspect of the invention, a first method is provided for use during plasma processing. The first method includes the steps of (1) placing a substrate on a substrate holder of a plasma chamber; (2) positioning a cover frame adjacent and below a perimeter of the substrate; and (3) employing the cover frame to reduce arcing during plasma processing within the plasma chamber.  
         [0004]     In a second aspect of the invention, a second method is provided for use during plasma processing. The second method includes the steps of (1) placing a substrate on a substrate holder of a plasma chamber; (2) positioning a cover frame adjacent and below a perimeter of the substrate; (3) positioning a shadow frame adjacent a perimeter of the substrate such that the shadow frame does not contact or overlie the substrate; and (4) employing the cover frame and shadow frame to reduce arcing during plasma processing within the plasma chamber.  
         [0005]     In a third aspect of the invention, a third method is provided for use during plasma processing. The third method includes the steps of (1) placing a substrate on a substrate holder of a plasma chamber; (2) positioning a shadow frame adjacent a perimeter of the substrate such that the shadow frame does not contact or overlie the substrate; and (3) employing the shadow frame to reduce arcing during plasma processing within the plasma chamber. Numerous other aspects are provided, as are systems and apparatus in accordance with these and other aspects of the invention.  
         [0006]     Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0007]      FIG. 1  illustrates a conventional apparatus that may be employed during plasma processing.  
         [0008]      FIG. 2A  illustrates a first exemplary apparatus that may be employed during plasma processing in accordance with an embodiment of the present invention.  
         [0009]      FIG. 2B  illustrates a second exemplary apparatus that may be employed during plasma processing in accordance with an embodiment of the present invention.  
         [0010]      FIG. 3  illustrates a third exemplary apparatus that may be employed during plasma processing in accordance with an embodiment of the present invention.  
         [0011]      FIG. 4  illustrates a top view of a cover frame included in the third exemplary apparatus of  FIG. 3 .  
         [0012]      FIG. 5  illustrates a top view of an alternative cover frame which may be included in the third exemplary apparatus of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION  
       [0013]     Aspects of the present invention may increase the uniformity of film deposited on a substrate (e.g., proximate an edge region of the substrate) during plasma processing, such as plasma enhanced chemical vapor deposition (PECVD). Further, a portion of the substrate upon which no film is deposited, such as a film edge exclusion area, is minimized or eliminated.  
         [0014]      FIG. 2A  illustrates a first exemplary apparatus  201  that may be employed during plasma processing in accordance with an embodiment of the present invention. With reference to  FIG. 2A , the first exemplary apparatus  201  may be included in a plasma chamber  203 . The first exemplary apparatus  201  includes a substrate holder  204 , such as a susceptor, adapted to support a substrate  105  (e.g., a glass substrate, a semiconductor substrate, etc.). The substrate holder  204  may serve as a first electrode (e.g., grounded or powered) during plasma processing. As such, the substrate holder  204  may be susceptible to arcing.  
         [0015]     The first exemplary apparatus  201  includes a cover frame  205  adapted to reduce arcing during plasma processing within the plasma chamber  203 . For example, the cover frame  205  may be formed from aluminum, ceramic or another material that may be maintained at a neutral or floating potential during plasma processing within the plasma chamber  203 . More specifically, the cover frame  205  may be placed upon a surface of the substrate holder  204  such that the cover frame  205  contacts or adjoins one or more surfaces of the substrate holder  204 , thereby preventing portions of the one or more surfaces of the substrate support  204  from contacting a plasma introduced in the plasma chamber  203  during plasma processing.  
         [0016]     As shown in  FIG. 2A , the cover frame  205  may be positioned adjacent and below the perimeter of the substrate  105 . For example, a first end  207  of the cover frame  205  may underlie the substrate  105 . In this manner, the cover frame  205  ensures that portions of one or more surfaces of the substrate holder  204  do not contact the plasma during plasma processing. In one embodiment, at least a 5 mm (preferably a 5-10 mm) portion of the cover frame  205  underlies an edge region  111  of the substrate  105  (e.g., such that the substrate  105  does not need to be perfectly positioned onto the substrate holder  204 ). A larger or smaller portion of the cover frame  205  may underlie the substrate  105 .  
         [0017]     A second end  209  of the cover frame  205  preferably extends at least to the perimeter of the substrate holder  204 . Such an arrangement has been found to increase the uniformity of a film deposited on the substrate  105  (e.g., film deposition uniformity) during plasma processing. For example, use of the cover frame  205  has been found to increase the film deposition uniformity proximate and/or along an edge region  111  of the substrate  105 . The use of the cover frame  205  may also minimize or eliminate a portion of the substrate  105 , such as the edge region  111 , upon which no film is deposited during plasma processing (e.g., an edge exclusion area).  
         [0018]     When the cover frame  205  is employed, the value of at least one process parameter, such as pressure, electrode spacing, RF power and gas flow, within the plasma chamber  203  may be adjusted or tuned from values of the process parameters used during plasma processing in a plasma chamber which includes the convention apparatus  101 . In at least one embodiment, a pressure of 1-3 Torrs (e.g., of Silane, Hydrogen, Nitrogen, Ammonia, etc.), an electrode spacing of about 1000 mils, an RF power of a few kilowatts, and/or a gas flow of about 1000 sccm may be employed. Other values may be employed for the pressure, electrode spacing, RF power and/or gas flow.  
         [0019]     Because the cover frame  205  does not overlie the substrate  105 , the cover frame  205  does not significantly disturb process parameters during plasma processing. Therefore, the uniformity of a film deposited on the substrate  105  (e.g., proximate and/or along an edge region  111  of the substrate  105 ) is increased compared to the uniformity of a film deposited on a substrate using the conventional apparatus  101 . As stated, the cover frame  205  also allows a film to be deposited on all or most of the substrate  105 .  
         [0020]      FIG. 2B  illustrates a second exemplary apparatus that may be employed during plasma processing in accordance with an embodiment of the present invention. With reference to  FIG. 2B , the second exemplary apparatus  210  is similar to the first exemplary apparatus  201 . However, a second end  209  of the cover frame  205  of the second exemplary apparatus  210  may not extend to the perimeter of the substrate holder  204 . Therefore, portions of the substrate holder  204  (e.g., proximate the perimeter of the substrate holder  204 ) are not covered by the cover frame  205  and may be susceptible to arcing. The second exemplary apparatus  210  includes a shadow frame  211  adapted to reduce arcing during plasma processing within the plasma chamber  203 . The shadow frame  211  is placed upon a surface of the cover frame  205  such that the shadow frame  211  overlies one or more surfaces of the substrate holder  204  (e.g., the portions of the substrate holder  204  not covered by the cover frame  205 ). For example, in  FIG. 2B  a portion  213  of the shadow frame  211  overlies the cover frame  205  (e.g., at least a 5 mm (preferably a 5-10 mm) portion of the shadow frame  211  overlies the cover frame  205  in one embodiment, although other values may be used). In this manner, similar to the cover frame  205 , the shadow frame  211  ensures that portions of one or more surfaces of the substrate holder  204  do not contact the plasma during plasma processing.  
         [0021]     The shadow frame  211  may be formed from anodized aluminum, ceramic, or the like. The shadow frame  211  is preferably at a neutral or floating potential to reduce arcing.  
         [0022]     In the embodiment shown, a lip  215  of the shadow frame  211  may be thicker and/or stronger than the lip  109  ( FIG. 1 ) of the shadow frame  107  of the conventional apparatus  101  so as not to deform during shaping as indicated by reference numeral  216 . A remaining portion of the shadow frame  211  that overlies the support holder  204  may be thinner (as indicated by reference numeral  218 ) than a corresponding remaining portion of the conventional shadow frame  107  that overlies the substrate support  103 , for example, to accommodate the cover frame  205 . In at least one embodiment, the lip  215  of the shadow frame  211  may include a bevel of an angle A of about 45° as described further below). The bevel may be of different angles and/or shapes. Such a bevel may regulate the flow of and guide one or more gases over the substrate  105  during plasma processing.  
         [0023]     As shown in  FIG. 2B , the shadow frame  211  is positioned adjacent a perimeter of the substrate  105  such that the shadow frame does not contact or overlie the substrate  105 . Therefore, the shadow frame  211  is a non-contact shadow frame. For example, in one embodiment a portion (e.g., the portion  213  that overlies the cover frame  205 ) of the shadow frame  211  is positioned adjacent the perimeter of the substrate  105  at least a distance  217  of 5 mm (preferably 5-10 mm) from the perimeter of the substrate  105 . Such a spacing reduces the likelihood of contact between the substrate  105  and the shadow frame  211  that might damage (e.g., chip) the substrate  105 . The shadow frame  213  may be positioned a larger or smaller distance from the substrate  105 . As shown in  FIG. 2B , the cover frame  205  preferably covers at least the surface of a substrate holder  204  between the shadow frame  211  and the substrate  105 .  
         [0024]     Embodiments of the present invention that include the shadow frame  211 , may employ a process recipe similar to or the same as the recipe used by the conventional apparatus  101 . Other recipes may be employed. In contrast to the shadow frame  107  of the conventional apparatus  101 , because the shadow frame  211  does not contact or overlie the substrate  105 , the shadow frame  211  does not significantly disturb process parameters during plasma processing. Therefore, the uniformity of a film deposited on the substrate  105  proximate and/or along an edge region  111  of the substrate  105  is generally increased compared to the uniformity of a film deposited on a substrate using the conventional apparatus  101 . Further, the shadow frame  211  does not prevent film deposition onto the edge region  111  of the substrate  105 .  
         [0025]      FIG. 3  illustrates a third exemplary apparatus  301  that may be employed during plasma processing in accordance with an embodiment of the present invention. The third exemplary apparatus  301  is similar to the second exemplary apparatus  210 . In contrast to the second exemplary apparatus  210 , the substrate holder  303  of the third exemplary apparatus  301  includes one or more grooves or slots  305  (e.g., an oval-shaped slot) along an edge region of the substrate holder  303 . For example, the substrate holder  303  may include the one or more grooves or slots  305  proximate a center of each side of the substrate holder  303 . Further, the cover frame  307  includes corresponding grooves or slots  309 . For example, the cover frame  307  may include one or more grooves or slots  309  proximate a center of each side of the cover frame  307 . The third exemplary apparatus  301  may include one or more pins or other kinematic features  311  adapted to couple to a respective groove or slot  305  of the substrate holder  303  and a respective groove or slot  309  of the cover frame  307 . In this manner, the movement of the cover frame  307  on the substrate holder  303  (e.g., due to thermal expansion and/or thermal mismatch between various components) is guided and/or limited. In one or more embodiments, the pins  311  may be cylindrical. Pins of other shapes may be employed. Further, slots of different shapes may be employed. In one embodiment four pins  311  may be employed. Other numbers of pins may be used.  
         [0026]      FIG. 4  illustrates a top view of a cover frame  307  included in the third exemplary apparatus  301 . With reference to  FIG. 4 , the shape of at least an interior perimeter of the cover frame  307  corresponds to the perimeter of the substrate  105  to which the cover frame  307  is adjacently positioned. Cover frames of different shapes may be employed. The cover frame  307  of  FIG. 4  is a single piece cover frame (e.g., formed of anodized aluminum or another suitable material).  
         [0027]      FIG. 5  illustrates a top view of an alternative cover frame  511  which may be included in the third exemplary apparatus  301 . In contrast to the cover frame  307  of  FIG. 4 , the alternative cover frame  511  is formed from multiple pieces. For example, the cover frame  511  includes four pieces  513 - 519  joined together. The cover frame  511  also may include grooves or slots  309  proximate a center of each side of the cover frame  511 . Further, the cover frame  511  may include one or more additional grooves or slots  521  in each side of the cover frame  511  (e.g., to provide additional kinematic features that, for example, may reduce rotation of the cover frame  511  when the cover frame  511  is heated). The additional grooves or slots  521  may be a different shape than the grooves or slots  309  proximate the center of each side of the cover frame  511 . In at least one embodiment, the cover frame  511  may be formed of a ceramic or similar material.  
         [0028]     The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, in one or more embodiments, an apparatus similar to the second exemplary apparatus  210  but which does not include a cover frame  205  may be employed to perform the present methods. The shadow frame (e.g., non-contact shadow frame)  211  of such embodiments is appropriately modified (e.g., dimensioned) to perform the functions of the contact frame  205  of the second exemplary apparatus  210 . During an exemplary method of plasma processing for such embodiments, a substrate is place on a substrate holder of a plasma chamber. The shadow frame is positioned adjacent a perimeter of the substrate such that the shadow frame does not contact or overlie the substrate. Such an arrangement may reduce arcing during plasma processing within the plasma chamber, prevent a surface of the substrate support from contacting a plasma during plasma processing within the plasma chamber, increase film deposition uniformity along an edge region of the substrate, and/or minimize or eliminate edge exclusion.  
         [0029]     Further, in embodiments, such as the second exemplary apparatus  210 , in which the cover frame  205  does not extend to the perimeter of the substrate holder  204 , the cover frame  205  may be adapted to couple to a groove included in the substrate holder. In one or more embodiments the cover frame  205  may be formed from anodized aluminum. An anodized aluminum cover frame may be a one-piece assembly whereas a ceramic cover frame may require a multi-piece assembly joined by appropriate fasteners (e.g., a four-piece assembly joined together by aluminum pins). For at least the above reason, an anodized cover frame may be cheaper to manufacture than a ceramic cover frame, and thermal expansion concerns due to use of multiple components with differing coefficients of thermal expansion may be reduced.  
         [0030]     In one exemplary embodiment, use of the present invention may result in a deposited film non-uniformity of less than approximately 10% across a 1 m×1.2 m glass substrate with an 8 mm edge exclusion.  
         [0031]     Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.