Patent Publication Number: US-2013240142-A1

Title: Isolation between a baffle plate and a focus adapter

Description:
TECHNICAL FIELD 
     The present disclosure relates to semiconductor wafer fabrication systems. The present disclosure is particularly applicable to ashing systems used in the manufacturing of semiconductor wafers. 
     BACKGROUND 
     Plasma ashing systems have been designed for front-end-of-line (FEOL) and back-end-of-line (BEOL) photoresist removal from semiconductor wafers. In such systems, a plasma source is used to generate a monatomic reactive species which combines with the photoresist to form ash, which is removed with a vacuum pump. An upper chamber of an ashing system includes a quartz focus adapter and an aluminum baffle plate, which are in contact with each other. During wafer processing, the chamber pressure transitions from atmospheric pressure to vacuum and back to atmospheric pressure for each wafer process. The frequent changes in pressure cause the focus adapter to move up and down. The friction from the contact between the focus adapter and the baffle plate during the pressure transitions and the vacuum state generates small particles. Current waferless auto dry clean and idle conditioning can minimize particle generation but cannot prevent the friction between the baffle plate and the focus adapter caused by changes in pressure. Thus, the friction and the particles reduce the mean time between cleans and the lifetime of the baffle plates while increasing yield defect density highlights and costs. 
     A need therefore exists for a method and a device for isolating the focus adapter from the baffle plate during wafer processing. 
     SUMMARY 
     An aspect of the present disclosure is a device that prevents friction between a baffle plate and a focus adapter within an ashing system during wafer processing. 
     Another aspect of the present disclosure is a method to prevent a baffle plate and a focus adapter from contacting during wafer processing. 
     Additional aspects and other features of the present disclosure will be set forth in the description which follows and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present disclosure. The advantages of the present disclosure may be realized and obtained as particularly pointed out in the appended claims. 
     According to the present disclosure, some technical effects may be achieved in part by a device including: a focus adapter; a baffle plate having a plurality of holes positioned around an edge of the baffle plate; and a spacer between the focus adapter and the baffle plate that prevents the focus adapter from contacting the baffle plate. 
     Aspects include the spacer being secured to the baffle plate at each of the plurality of holes. Another aspect includes a housing and a fastener, with the fastener securing a first portion of the spacer between the housing and the baffle plate, and a second portion of the spacer separating the baffle plate from the focus adapter. A further aspect includes the spacer being in the shape of a ring corresponding to a circumference of the baffle plate. A further aspect includes a plurality of spacers positioned around the edge of the baffle plate corresponding to the plurality of the holes. In one aspect, the spacer may be an arc shape. A further aspect includes the spacer having an L-shape. Another aspect includes the thickness of the spacer between the baffle plate and the focus adapter being 0.5 mm. An additional aspect includes the spacer being made of polytetrafluoroethylene, polyether ether ketone, polyoxymethylene, or a polyimide-based plastic. 
     Another aspect includes a method including: placing a spacer on a baffle plate of an ashing system between the baffle plate and a focus adapter, separating the baffle plate from the focus adapter; and securing the spacer to the baffle plate. 
     Aspects of the disclosure include, where the spacer is ring shaped, and the baffle plate and the spacer each have a plurality of holes around a circumference thereof, aligning the holes of the spacer with the holes of the baffle plate, and securing the spacer to the baffle plate by fastening the baffle plate and the spacer to a housing of the ashing system through the holes. An additional aspect includes, where the spacer is arc shaped and has at least one hole therethrough, and the baffle has a plurality of holes, securing the spacer to the baffle plate by fastening the baffle plate and the spacer to a housing of the ashing system through the holes. An additional aspect includes the spacer comprising a neck attached to a flange, and aligning the flange of the spacer between the baffle plate and the focus adapter, and securing the spacer by inserting the neck of the spacer in a hole of the baffle plate, and securing the spacer to the baffle plate by fastening the baffle plate and the spacer to a housing of the ashing system through the hole. Another aspect includes, where the baffle plate comprises a plurality of holes around a circumference thereof, securing the spacer to the baffle plate at each hole, and aligning the flange of each spacer between the baffle plate and the focus adapter. A further aspect includes the spacer being made of polytetrafluoroethylene, polyether ether ketone, polyoxymethylene, or a polyimide-based plastic. An additional aspect includes a thickness of each spacer between the baffle plate and the focus adapter being 0.5 mm. 
     Additional aspects and technical effects of the present disclosure will become readily apparent to those skilled in the art from the following detailed description wherein embodiments of the present disclosure are described simply by way of illustration of the best mode contemplated to carry out the present disclosure. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawing and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  schematically illustrates a cross-section of an upper chamber of an ashing system, in accordance with an exemplary embodiment; 
         FIGS. 2A through 2D  schematically illustrate various shapes of the spacer, in accordance with exemplary embodiments; 
         FIGS. 3A and 3B  schematically illustrate a cross-section of a baffle plate hole area before and after a spacer is inserted, and  FIG. 3C  schematically illustrates a plan view of the spacer, in accordance with an exemplary embodiment; 
         FIGS. 4A through 4C  schematically illustrate a cross-sectional view, a plan view, and a side view of the spacer, in accordance with an exemplary embodiment; and 
         FIGS. 5A and 5B  schematically illustrate a cross-sectional view of the spacer attached to a focus adapter and a plan view of the spacer, respectively, in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments. It should be apparent, however, that exemplary embodiments may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring exemplary embodiments. In addition, unless otherwise indicated, all numbers expressing quantities, ratios, and numerical properties of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” 
     The present disclosure addresses and solves the current problem of contact between a baffle plate and a focus adapter generating particles during wafer processing because of the friction between the baffle plate and the focus adapter. In accordance with embodiments of the present disclosure, a spacer is inserted between the baffle plate and the focus adapter to prevent the baffle plate and the focus adapter from contacting during wafer processing. 
     Embodiments of the present disclosure include a housing, a baffle plate including a plurality of holes, a focus adapter between the housing and the baffle plate, a plurality of spacers aligned with the plurality of holes, and a plurality of fasteners securing the plurality of spacers between the baffle plate and the housing, wherein the plurality of spacers isolate the focus adapter from contacting the baffle plate. 
     Methodology in accordance with embodiments of the present disclosure includes placing a spacer on a baffle plate of an ashing system between the baffle plate and a focus adapter, positioning the spacer such that the spacer prevents the baffle plate from contacting the focus adapter during wafer processing, and securing the spacer to the baffle plate. The spacer may include a neck that is inserted into a hole of the baffle plate, and the spacer may be secured to the baffle plate by fastening the baffle plate and the spacer to a housing of the ashing system through the hole. 
     Still other aspects, features, and technical effects will be readily apparent to those skilled in this art from the following detailed description, wherein preferred embodiments are shown and described, simply by way of illustration of the best mode contemplated. The disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     Adverting to  FIG. 1 , a portion  100  of a cross-section of an upper chamber of an ashing system in accordance with an exemplary embodiment is illustrated. The upper chamber includes a focus adapter housing  101  and a baffle plate  103 . The baffle plate  103  may be made of aluminum. The baffle plate  103  may include one or more holes  111  that allow for one or more fasteners  105  that connect the baffle plate  103  to the housing  101 . The one or more holes  111  may include a seat  111   a  and an inner hole  111   b  that mechanically secure the fastener  105  to the baffle plate  103 . The fasteners  105  may be, for example, screws or other mechanical devices for securing the housing  101  to the baffle plate  103 . Below the housing  101  is a focus adapter  107 , for example made of quartz. According to conventional configurations, the focus adapter  107  comes into contact with the baffle plate  103  during wafer processing causing friction between the focus adapter  107  and the baffle plate  103 . Such friction may generate particles that may contaminate the wafer processing and, for example, reduce the mean time between cleans. However, as illustrated in  FIG. 1 , in accordance with an exemplary embodiment, the setup includes a spacer  109  between the focus adapter  107  and the baffle plate  103 . The spacer  109  prevents friction between the focus adapter  107  and the baffle plate  103  during wafer processing, thereby preventing the generation of particles that may contaminate the wafer and the baffle plate. 
     The spacer  109  may be secured between the housing  101  and the baffle plate  103  by the fastener  105 . The spacer  109  may be made from any material that prevents the focus adapter  107  from contacting with the baffle plate  103 , and that also withstands the conditions within the upper chamber during wafer processing. Such materials may be, for example, polytetrafluoroethylene (PTFE) (e.g., Teflon®), polyether ether ketone (PEEK), polyoxymethylene (POM) (e.g., Delrin®), and polyimide-based plastics (e.g., Vespel®). 
     As illustrated in  FIGS. 2A through 2D , the spacer  109  may come in various shapes as long as the shape of the spacer  109  does not substantially obstruct the plasma and gas flow on a wafer during wafer processing, and the spacer  109  prevents contact between the baffle plate  103  and the focus adapter  107 . As shown in  FIG. 2A , the spacer  109  may be in the shape of a ring  201   a  that lies around the edge of the baffle plate  103 . In such a configuration, the spacer  109  may have holes  203   a  that correspond with the inner holes  111   b  in the baffle plate  103  and the fasteners  105  that secure the baffle plate  103  to the housing  101 . Further, the spacer  109  may be wide enough to be secured between the housing  101  and the baffle plate  103  while still extending far enough towards the center of the baffle plate  103  so as to come into contact with the focus adapter  107  and prevent the focus adapter  107  from contacting the baffle plate  103 . 
     Alternatively, as illustrated in  FIG. 2B , the spacer  109  may be in the shape of an arc  201   b.  Similar to the ring  201   a,  the arc  201   b  may have one or more holes  203   b  to accommodate the fasteners  105  that attach the baffle plate  103  and the spacer  109  to the housing  101 . Also, the arc  201   b  may be secured between the housing  101  and the baffle plate  103  while still wide enough so as to come between the focus adapter  107  and the baffle plate  103  to prevent the focus adapter  107  from contacting the baffle plate  103  during wafer processing. Such arc shaped spacers  109  may be placed around the circumference of the baffle plate  103 , attached to the baffle plate  103  at every inner hole  111   b.    
     Adverting to  FIG. 2C , the spacer  109  may be in the shape of a L-shaped insert  201   c  with a hole  203   c  forming a neck  205  extending from the flat surface  207  of the spacer  109 . The neck  205  may be inserted into the inner holes  111   b  of the baffle plate  103  such that the spacer  109  is seated within the inner holes  111   b  prior to fastening the spacer  109  and the baffle plate  103  to the housing  101 . An L-shaped spacer  109  may be positioned at each inner hole  111   b  around the circumference of the baffle plate. 
     As illustrated in  FIG. 2D , the spacer  109  may be in the shape of a sticker  201   d . The sticker  201   d  may be in any shape, such as the illustrated rectangle. According to this embodiment, the stickers  201   d  may be attached around the rim of the focus adapter  107  to prevent contact between the focus adapter  107  and the baffle plate  103 . The sticker  201   d  may have adhesive on one side that faces the focus adapter  107  such that the sticker  201  d may be positioned along the rim of the focus adapter  107  independently from the positions of the inner holes  111   b  in the baffle plate  103 . 
       FIG. 3A  illustrates the dimensions of the baffle plate  103  and the fastener  105  seated within a hole  111  in the baffle plate  103 , according to an exemplary embodiment. As illustrated, the baffle plate  103  may have a thickness H of 9.80 mm to 10.15 mm, for example 10 mm. The depth H 1  of the seat  111   a  in the hole  111  is 5.4 mm to 6 mm, e.g. 5.5 mm. The thickness H 2  of the baffle plate  103  at the seat  111   a  in the inner hole  111   b  is 4.0 mm to 4.6 mm, for example 4.5 mm. The diameter of the hole  111  above the seat  111   a  may be 6.89 mm to 6.91 mm, e.g., 6.9 mm. The diameter of the inner hole  111   b  below the seat  111   a  may be 3.32 mm to 3.46 mm, for example 3.4 mm. The length L of the fastener  105  (e.g., a screw) may be 8.0 mm to 12.0 mm, e.g. 10 mm such that the fastener  105  may extend 3.0 mm to 7.0 mm, such as 6 mm, beyond the baffle plate  103 . The diameter F of the fastener  105  may be 2.90 mm to 2.93 mm, e.g., 2.92 mm, to fit within the inner hole  111   b.    
     Adverting to  FIG. 3B , the baffle plate  103  may include a frontside surface  301   a  and a backside surface  301   b.  An L-shaped spacer  109 , such as that shown in  FIG. 2C  may be inserted around the fastener  105  such that the neck  205  of the spacer  109  is inserted into the backside surface  301   b  of the inner hole  111   b  of the baffle plate  103  according to the cross-sectional view of the spacer  109   a  in  FIG. 3B . Further,  FIG. 3C  illustrates the plan view  109   b  of the spacer  109  when the spacer  109  is inserted into the hole  111   b  in the baffle plate  103 . The arrow  303  illustrates the direction of the center of the baffle plate  103  relative to the plan view  109   b  of the spacer  109 . 
       FIGS. 4A through 4C  illustrate the various dimensions of an L-shaped insert  201   c  spacer  109 , according to an exemplary embodiment. As illustrated in the cross-sectional view of the spacer  109  in  FIG. 4A , the width W 1  of the spacer  109  may be 7.0 mm to 17.0 mm, for example 13 mm. The width W 2  of the hole  203   c  in the spacer  109  that accepts the fastener  105  may be 2.95 mm to 3.05 mm, e.g. 3 mm, and the width W 3  of the neck  205  of the spacer  109  may be 3.2 mm to 3.35 mm, e.g., 3.3 mm. As discussed above, the hole inner  111   b  in the baffle plate  103  may be 3.32 mm to 3.46 mm, e.g. 3.4 mm, and the diameter F of the fastener  105  may be 2.90 mm to 2.93 mm, e.g. 2.92 mm such that when the spacer  109  and the fastener  105  are inserted into the inner hole  111   b  in the baffle plate  103 , the fastener  105  and the spacer  109  form a tight fit with the inner hole  111   b  in the baffle plate  103 . The thickness T 1  of the spacer  109  may be 0.2 mm to 1.0 mm, for example 0.5 mm. The height D 1  of the spacer  109  may be 4.5 mm to 5 mm, e.g., 5 mm, and the height D 2  of the neck  205  may be 2 mm to 4.8 mm, e.g., 4.5 mm, such that the height D 2  of the neck  205  and the thickness T 1  of the spacer  109  do not exceed the height D 1  of the spacer  109 . The height D 2  of the neck  205  allows the spacer  109  to sit within the inner hole  111   b  in the baffle plate  103 . Further, as illustrated in the plan view of the spacer  109  in  FIG. 4B , the length D 3  of the spacer  109  may be 13.0 mm to 15.25 mm, e.g. 15 mm, and the distance D 4  between the edge closest to the neck  205  and the neck  205  may be 3.8 mm to 4.6 mm, for example 4 mm.  FIG. 4C  illustrates a side view of the spacer  109  illustrating the total height D 1  of the spacer  109 , that accounts for the thickness T 1  of the spacer  109  and the height D 2  of the neck  205 . 
     Adverting to  FIG. 5A ,  FIG. 5A  illustrates a cross-section of the focus adapter  107  including a spacer  109  attached in the form of a sticker  201   d.  The thickness T 2  of the focus adapter  107  may be 6.4 mm to 6.6 mm, e.g., 6.5 mm. The thickness T 3  of the sticker  201   d  may be 0.05 mm to 1.0 mm, e.g., 0.7 mm. In such an embodiment, multiple spacers  109  in the shape of stickers  201   d  may be positioned along the rim of the focus adapter  107  independently from the positions of the inner holes  111   b  in the baffle plate  103 . However, in one embodiment, spacers  109  in the form of stickers  201   d  may be positioned on either side of the holes  111   b  in the baffle plate.  FIG. 5B  illustrates the plan view of the sticker  201   d  in  FIG. 5A . As illustrated, the sticker  201   d  may have a width D 5  of 2.5 mm to 5 mm, e.g., 5 mm, and a length D 6  of 4 mm to 7 mm, e.g., 7 mm. 
     The embodiments of the present disclosure achieve several technical effects, including preventing the focus adapter from contacting the baffle plate during wafer processing, thereby preventing the generation of particles that may contaminate the wafer and the baffle plate. Accordingly, by way of example, the mean time between cleans may be extended, the baffle plates  103  can be reused, particles may not be generated such that there are zero defects, and there are no etch rate issues associated with the baffle plates  103 , thereby reducing costs. Embodiments of the present disclosure enjoy utility in various industrial applications as, for example, producing semiconductor wafers used in microprocessors, smart phones, mobile phones, cellular handsets, set-top boxes, DVD recorders and players, automotive navigation, printers and peripherals, networking and telecom equipment, gaming systems, and digital cameras. The present disclosure therefore enjoys industrial applicability associated with any of various types of semiconductor devices. 
     In the preceding description, the present disclosure is described with reference to specifically exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure, as set forth in the claims. The specification and drawings are, accordingly, to be regarded as illustrative and not as restrictive. It is understood that the present disclosure is capable of using various other combinations and embodiments and is capable of any changes or modifications within the scope of the inventive concept as expressed herein.