Abstract:
Improved durability and longevity of spin chucks is achieved by using a composite support pin structure in which a pin body of a chemically inert plastic includes a hollow cavity containing an insert formed from a material whose Young&#39;s modulus is greater than that of the inert plastic.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to devices for processing wafer shaped articles, and more particularly to such devices having pin constructions. The invention also relates to pin constructions for use in such devices. 
         [0003]    2. Description of Related Art 
         [0004]    Devices for processing wafer shaped articles often include pins that support the articles either from below or laterally about the edge of the wafer. 
         [0005]    Examples of such devices are described in the commonly-owned U.S. Pat. Nos. 4,903,717; 5,513,668; and 6,435,200, the entirety of which patents is hereby expressly incorporated by reference. 
         [0006]    Devices such as these are often used in practice as spin chucks positioned in the process chamber of a single wafer wet processing apparatus, used in the processing of semiconductor wafers and the manufacture of semiconductor devices on such wafers. As these chucks are subjected to highly corrosive chemicals in use, they are typically formed from chemically relatively inert plastics such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). 
       SUMMARY OF THE INVENTION 
       [0007]    The inventor has discovered that the support pins conventionally used in devices for processing wafer shaped articles are subjected to considerable stresses during use, which can serve to impair the reliability of the device and/or shorten its overall service life. As the capital investment in such devices is substantial, new constructions that improve the reliability of such devices and/or extend their service life can be of considerable value. 
         [0008]    According to the invention a device for processing wafer shaped articles is equipped with support pins having a body formed of a chemically inert bulk material and defining a hollow cavity containing a different material whose Young&#39;s modulus is greater than that of the bulk material. 
         [0009]    Devices equipped with such pins can endure a much higher number of processing cycles without failing than conventional devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Other objects, features and advantages of the invention will become more apparent after reading the following detailed description of preferred embodiments of the invention, given with reference to the accompanying drawings, in which: 
           [0011]      FIG. 1  is a side view, partly in vertical section, of a device for treating wafer shaped articles according to an embodiment of the invention; 
           [0012]      FIG. 2   a  is a view in perspective and partly in section illustrating an embodiment of a pin module for use in the chuck of  FIG. 1 ; 
           [0013]      FIG. 2   b  is a sectional view of the pin module of  FIG. 2   a ; and 
           [0014]      FIG. 2   c  is a perspective view of the pin module of  FIG. 2   a.    
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0015]    In  FIG. 1 , a support  1 , intended for holding a wafer-shaped article, especially while the latter is treated with a treatment fluid (for etching of silicon wafers), is mounted on a hollow supporting shaft  2  and can be set into rotation about its axis  11  by this shaft; for this purpose, a rotary drive mechanism  3  is provided (compare U.S. Pat. No. 4,903,717). 
         [0016]    The rotary drive mechanism  3  includes a drive motor  4 , the output pinion  5  of which is coupled by way of a toothed belt  6  with a gear wheel  7  fixedly attached to the supporting shaft  2 . 
         [0017]    In order to feed gas under pressure to the hollow supporting shaft  2 , its lower end is accommodated in a cup-shaped member  8  to which is connected a compressed gas conduit  9  for the supply of a gas (for example nitrogen); this cup-shaped member  8  is sealed by a labyrinth seal  10  with respect to the lower end of the supporting shaft  2 . 
         [0018]    The support  1  includes a base member  20  having approximately the shape of a cup, an annular member  21 , and a central member  22  of a substantially plate-shaped structure. 
         [0019]    The annular member  21  is seated via an annular rib  23  at its outer periphery on the outer rim of the cup-shaped member  20 . Furthermore, the annular member  21  is supported by way of, for example, circular-arc-shaped projections  24  on a surface  25  of the base member  20 . 
         [0020]    The central member  22  has a shoulder  26  resting on a step  27  of the annular member  21 . The central member  22  is attached to the base member  20  by several clamping bolts  30 . The annular member  21  is clamped in place between the base member  20  and the central member  22 . 
         [0021]    A space  31  is provided between the base member  20  and the central member  22 , this space  31  being defined in the downward direction by the surface  25  of the base member  20  and in the upward direction by the surface  32  of the central member  22 . A gap-shaped space  33  emanates from this space  31 ; this space  33  is defined by mutually facing surfaces  34  and  35  of the base member  20  and, respectively, of the annular member  21 . 
         [0022]    A gear rim  40  is accommodated in the space  31  and in the gap-shaped space  33 , this gear rim  40  being coupled with the upper end  41  of the supporting shaft  2  and meshing with its radially outwardly extending peripheral teeth  42  with gear wheels  43  on shafts  44  which latter are received rotatably in bores in the annular member  21 . Each shaft  44  carries a pin  45  arranged eccentrically to its axis of rotation. By turning the shafts  44  with the aid of the gear rim  40 , the radial distance of the pins  45  from the axis of rotation  11  of the support  1  can be varied. The pins  45  serve as stops for the lateral retention of a wafer-shaped article (e.g. a silicon wafer) (not shown) held on the support  1 . 
         [0023]    The gear rim  40  is supported and guided by sliding blocks  6  inserted in the base member  20  in an annular distribution. These sliding blocks  46  are formed, for example, from polytetrafluoroethylene. 
         [0024]    It should furthermore be noted that recesses, not shown, are arranged in the gear rim  40 , the projections  24  of the annular member  21  and the clamping bolts  30  extending through these recesses. These recesses are dimensioned so that the gear rim  40  can be rotated with respect to the annular member  21  and thus the support  1  to such an extent that the pins  45  can be adjusted to the desired degree. 
         [0025]    During the radial turning of the pins  45  by adjustment of the shafts  44 , the base member  20  is braked by a braking device not illustrated in detail, which can be designed, for example, as described in U.S. Pat. No. 4,903,717, namely as a hose brake, and the supporting shaft  2  is rotated with respect to the support  1 . By this relative motion between the support  1  and its supporting shaft  2 , the shafts  44  of the pins  45  are likewise turned. 
         [0026]    In place of the hose brake known from U.S. Pat. No. 4,903,717, the base member  22  can also be associated with a shoe brake. 
         [0027]    A blind hole  50  is arranged in the central member  22  of the support  1 ; the supporting shaft  2  is received in this blind hole  50  with its upper end where the bore  51  in the supporting shaft  2  terminates. The upper end of the supporting shaft  2  is sealed with respect to the central member  22  by a gasket  52 . The gas exiting from the bore  51  in the supporting shaft  2  and entering the space formed by the blind hole  50  flows via several radial bores  53  into an annular space  54  and from there to the nozzle  12  through which the gas leaves the support  1 . 
         [0028]    The annular space  54  is defined by mutually facing surfaces  55  and  56  of the central member  22  and, respectively, of the annular member  21 . 
         [0029]    It can be seen that the space  31  and the gap-shaped space  33  wherein the rotary drive mechanism for the eccentric pins  45  is housed are separated and sealed (by gasket  52 ) from the flow path of the compressed gas through the support (blind hole  50 , bores  53 , annular space  54 ) to the nozzle  12 . 
         [0030]    The pins  45  are made of bulk material that is relatively inert to the highly corrosive chemicals used in wafer wet processing, and are preferably a plastic such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), polyphenylenesulfide (PPS), polyetheretherketone (PEEK), polystyrene/polyethylstyrene (PS/PES), ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), homopolymer of chlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), or ethylene chlorotrifluoroethylene (ECTFE). PTFE and PVDF are particularly preferred. 
         [0031]    As shown in  FIGS. 2   a ,  2   b  and  2   c , the pins  45  may take the form of pin modules  201 , which include gripping parts ( 213 ) that contact a wafer-shaped article either from below or laterally along the edge of the wafer. The construction of pins  45  described above is used for lateral contact with the edge of a wafer-shaped article, as for example is used in spin chucks that operate on the Bernoulli principle, where the wafer is held on a cushion of air but still should be constrained from lateral displacement. 
         [0032]    As used herein the term “pins” also encompasses pin modules as depicted in  FIGS. 2   a ,  2   b  and  2   c . Pin module ( 201 ) comprises a tooth gear ( 207 ), shaft ( 204 ) and gripping part ( 213 ), all preferably formed of the above-described inert bulk material. The gripping parts ( 213 ) may be entirely cylindrical or may have a radially-inwardly facing scalloped surface part to assist in lifting the wafer from its edge, as is sometimes done to aid in expelling liquid between processing stages. In practice, the diameter of the gripping parts ( 213 ) is typically in the range of about 1 to about 5 mm, and most usually about 3 mm. When closing the pin modules ( 201 ) the gripping parts ( 213 ) grip the wafer and thus suffer a stress. 
         [0033]    However, pin module ( 201 ) also includes a cavity ( 202 ) formed in shaft ( 204 ), for example a narrow hole that is drilled into the shaft ( 204 ) from a side that is not in liquid communication during a liquid treatment process carried out on a wafer when being gripped by the gripping parts ( 213 ) of the pins. 
         [0034]    The cavity ( 202 ) is filled in this embodiment by a thin rod ( 210 ) that is preferably pressed into the cavity ( 202 ) so that almost no gap is left between the rod and the bulk material. In order to secure the rod ( 210 ) within the cavity ( 202 ), the cavity ( 202 ) is closed with a setscrew ( 216 ) is used. As the cavity ( 202 ) is a blind bore in this embodiment, the rod ( 210 ) is entirely covered by the bulk inert material on all surfaces within the gripping part ( 213 ). 
         [0035]    The thin rod ( 210 ) has a higher Young&#39;s modulus (E) (or modulus or elasticity) than such a rod would have when made of the surrounding inert bulk material. Preferably the rod material is made of a carbon fiber reinforced composite; however, other materials are possible (e.g. stainless steel or titanium) depending on the process to be carried out on the wafer that is held by the pins. 
         [0036]    The material occupying the cavity ( 202 ), whether a thin rod or some other type of insert or integrated material, preferably has a Young&#39;s modulus at least one order of magnitude greater than that of the surrounding bulk inert material (when expressed as N/mm 2 ), and more preferably has a Young&#39;s modulus that is at least two orders of magnitude greater than that of the surrounding bulk inert material, expressed as N/mm 2 . 
         [0037]    For example, PVDF has a Young&#39;s modulus of about 1.1 kN/mm 2  as measured by the ASTM D638 standard test method, whereas carbon fiber-reinforced plastic has a Young&#39;s modulus of about 124 kN/mm 2  to 152 kN/mm 2 . 
         [0000]    The hole ( 202 ) accommodating the rod ( 210 ) is preferably parallel to the axis of the shaft ( 204 ) and in the center of the gripping part ( 213 ) of the pin. However the hole might be slanted drilled, which is sufficient as long as the upper part of the hole is within the gripping part ( 213 ) of the pin. 
         [0038]    The composite structure of the pins according to the invention provides enhanced durability and longevity to a chuck that incorporates them. For example, a chuck that would fail due to pin breakage after having gripped  100 , 000  wafers now lasts 1,000,000 wafers. 
         [0039]    While the present invention has been described in connection with various preferred embodiments thereof, it is to be understood that those embodiments are provided merely to illustrate the invention, and should not be used as a pretext to limit the scope of protection conferred by the true scope and spirit of the appended claims.