Abstract:
A magnetic particle trapper for use in a sputtering system includes a roller cover plate having a plurality of openings arranged and dimensioned to accommodate a plurality of rollers associated with a mechanical transport mechanism of the sputtering system, and a plurality of magnets to trap magnetic particles, the plurality of magnets being attached to the roller cover plate in locations proximate to the plurality of openings.

Description:
BACKGROUND 
     A variety of equipment may be used in the manufacture of disk drive media to form the different magnetic and non-magnetic layers. In a typical process, a glass or aluminum substrate travels sequentially through a number of stations at which different materials are deposited under different conditions. For example, one or more sputtering systems may be used to sputter magnetic and/or non-magnetic materials onto the media. 
     In conventional sputtering processes, active sputtering stations for the media must be separated by finite distances. Without such separation, electromagnetic interference might occur between the stations and result in inhomogeneous sputtering or even equipment failure. Thus, the sputtering stations are physically separated, or, if closely situated, the sputtering stations may not be not used concurrently. Indeed, in some sputtering systems, sputtering components may be shared between adjacent sputtering stations and may be moved back and forth between them as the active sputtering station changes. 
     Anelva Corporation of Fuchu, Japan produces equipment that may be used to manufacture magnetic recording media such as hard-disks. Anelva supplies a unit designated as the C-3040. The unit includes a main chamber, entrance and output load locks, substrate load and unload stages and a plurality of processing stations. Disks are fed into the system, transported and treated in processing stations, and then are fed from the system as disks ready for use as hard disks in computer applications. Patents describing this system are U.S. Pat. Nos. 6,740,209, 6,027,618, 6,228,439 B1 and 6,251,232 B1. 
     U.S. Pat. No. 6,740,209 describes an apparatus to be used in manufacturing magnetic recording media.  FIG. 1  is a schematic side cross sectional view of the apparatus.  FIG. 1  comprises a deposition chamber  1 , a substrate holder  90  to locate at least one substrate  9  at a required position in the deposition chamber  1 , and multiple cathode units  3  for sputtering discharge. 
     The deposition chamber  1  is an air-tight vacuum chamber comprising an opening (not shown) for transfer-in-and-out of the substrate  9 . The opening is shut and opened by a gate valve (not shown). The deposition chamber  1  comprises a gas introduction line  12  to introduce an argon gas for the sputtering discharge into the inside. 
     The substrate holder  90  holds the substrate  9  in a vertical position. The substrate holder  90  is capable of holding multiple substrates  9  on the same vertical plane, and at the same height. 
       FIG. 2  (front view) and  FIG. 3  (side view) show schematic views of the substrate holder  90  in the apparatus shown in  FIG. 1 . As shown in  FIG. 2 , the substrate holder  90  comprises multiple small “holder magnets”  96  at the bottom. Each holder magnet  96  has a magnetic pole on the top and the bottom. The magnetic poles of the holder magnets  96  are alternatively opposite in the array direction. 
     Beneath the substrate holder  90 , a magnetic-coupling roller  81  is provided, interposing a partition wall  83 . The magnetic-coupling roller  81  is a cylinder, on which two spirally elongated magnets  82  are provided as shown in  FIG. 2 . These magnets  82  are hereinafter called “roller magnets”. The surface pole of each roller magnet  82  is opposite to each other. The magnetic-coupling roller  81  has a so-called double-helix structure. The magnetic-coupling roller  81  is provided at a position where the roller magnets  82  face to the holder magnet  96  through the partition wall  83 . The partition wall  83  is formed of material that would not disturb the magnetic field, e.g. non-magnetic material. The holder magnets  96  and the roller magnets  82  are magnetically coupled with each other. The magnetic-coupling roller  81  is provided along the transfer line of the substrates  9 . 
     Multiple main pulleys  84  that are rotated around horizontal axes are provided along the transfer line. As shown in  FIG. 3 , the substrate holder  90  rides on the main pulleys  84 . A couple of sub-pulleys  85 ,  85  are in contact with the lower margin of the substrate holder  90 . The sub-pulleys  85 ,  85  pinch the lower margin of the substrate holder  90  to prevent the substrate holder  90  from falling. The multiple sub-pulleys  85 ,  85  are provided along the transfer line as well. 
     As shown in  FIG. 3 , a drive rod  86  is connected with the magnetic-coupling roller  81  through a bevel gear. A motor  87  is connected with the drive rod  86  so that the magnetic-coupling roller  81  can be rotated around its center axis by driving force transferred from the motor  87  through the drive rode  86 . When the magnetic-coupling roller  81  is rotated, the double-helix roller magnets  82  shown in  FIG. 2  are also rotated. When the roller magnets  82  are rotated the plural aligned small magnets of which poles are alternately opposite move simultaneously along the aligning direction. Therefore, the holder magnets  96  magnetically coupled with the roller magnets  82  also move linearly as the roller magnets  82  are rotated, resulting in the substrate holder  90  moving linearly as well. During this liner movement, the main pulleys  84  and the sub-pulleys  85 ,  85  shown in  FIG. 3  are driven to rotate, following the movement. 
     Unfortunately, physical or temporal separation of processing stations results in having to transport disks using such above described mechanical transport systems including disk carrying devices. Such mechanical transport systems are susceptible to mechanical wear which in turn produces contamination byproducts. The friction coefficient in a drive mechanism can be large and a lubricant cannot be used due to the vacuum requirements. For example, the main pulleys  84  and the sub-pulleys  85  shown in  FIG. 3  are susceptible to mechanical wear and produce contamination byproducts. 
     The contamination byproducts may take on the form of magnetic metal debris or ferrous metal debris (magnetic particles). These magnetic particles cause contamination of target materials and cause voids in the deposited films which can lower the yield and throughput in the manufacturing of magnetic media. An object of the present invention is to provide a magnetic particle trapper device to capture the magnetic particles to reduce the target contamination and reduce the voids in the depositing films from such magnetic particles. There is therefore a need for an improved mechanical transport system having at least one magnetic particle trapper device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional, schematic view illustrating an prior art sputtering system including a substrate holder and mechanical drive system. 
         FIG. 2  is a front, schematic view illustrating a prior art substrate holder and mechanical drive system. 
         FIG. 3  is a side, schematic view illustrating a prior art substrate holder and mechanical drive system. 
         FIG. 4  is a schematic view illustrating an exemplary disk transport system, according to one embodiment. 
         FIG. 5  is an exploded view of the disk transport system of  FIG. 4 , according to one embodiment. 
         FIG. 6  is a schematic view illustrating a guide roller and sub-rollers arrangement of an exemplary disk transport system, according to one embodiment. 
         FIG. 7  is a schematic view illustrating a multiple piece magnetic particle trapper, according to one embodiment. 
         FIG. 8  is a schematic view illustrating an alternative two piece magnetic particle trapper, according to one embodiment. 
         FIG. 9  is a schematic view illustrating an alternative one piece magnetic particle trapper, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are directed to a magnetic particle trapper. The function of the magnetic particle trapper is to trap contamination byproducts that may take on the form of magnetic metal debris or ferrous metal debris (magnetic particles) generated by a disk transport system used in a sputtering system. 
     Referring to  FIGS. 4 ,  5 , and  6 , an exemplary disk transport system  100  is illustrated, according to one embodiment. The purpose of the disk transport system  100  is to transport disks  109  held in substrate holders  190  in a linear direction along a horizontal transfer line. A plurality of disk transport systems  100  may be used in a sputtering system to transport disks  109 . 
     The disk transport system  100  includes a pair of substrate holders  190 , a substrate holder support panel  180 , a plurality of holder magnets  196  coupled to the bottom side of the substrate holder support panel  180 , a plurality of main guide rollers  184  and a plurality of sub-rollers  185  coupled to a roller support panel  186 , a magnetic drive unit  190 , and a magnetic particle trapper  150 . 
     The magnetic particle trapper  150  need not be restricted to use in disk transport systems utilizing magnetic drive units. The magnetic particle trapper  150 , and versions thereof, can also be used in any disk transport systems that utilize moving mechanical parts, pulleys, sub-pulleys, guide rollers, sub-rollers, gears, rack and pinion, rails, guides, etc., that are subject to mechanical wear and produce contamination byproducts that may take on the form of magnetic metal debris or ferrous metal debris (magnetic particles). 
     Referring to  FIG. 7 , in the illustrated embodiment, the magnetic particle trapper  150  may include a roller cover plate  152 , a plurality of roller shields  154 , and a plurality of permanent magnets  155 . In this embodiment, permanent magnets  155  are attached to roller cover plate  152 , and roller shields  154  are mounted to roller cover plate  152  to cover permanent magnets  155 . 
     The roller cover plate  152  is removeably mounted to the disk transport system  100  having the plurality of main guide rollers  184 . The roller cover plate  152  may be shaped like an inverted capital letter “L”. The roller cover plate  152  length (L) is greater than the height (H), and the height (H) is greater the width (W). The roller cover plate  152  may have seven semi-circular or semi-oval openings to accommodate the seven main guide rollers  184  associated with the disk transport system  100  of the sputtering system. 
     The magnetic particle trapper  150  utilizes the plurality of permanent magnets  155  to trap magnetic metal debris or ferrous metal debris (magnetic particles). The permanent magnets  155  of magnetic particle trapper  150  are strategically located in proximity to the plurality of main guide rollers  184  and the plurality of sub-rollers  185  coupled to the roller support panel  186 . The plurality of main guide rollers  184  and the plurality of sub-rollers  185  are believed to be a primary source of magnetic metal debris or ferrous metal debris (magnetic particles). 
     A second embodiment of the invention is illustrated in  FIG. 8 , the magnetic particle trapper  150  may include roller shields that are integral to a roller cover plate  152 , a bottom shield  156 , and a plurality of permanent magnets  155 . In this embodiment, permanent magnets  155  are inserted into roller cover plate  152 . Bottom shield  156  is then attached to the bottom of roller cover plate  152 . 
     A third embodiment of the invention is illustrated in  FIG. 9 , the magnetic particle trapper  150  may include roller shields that are integral to a roller cover plate  152 . In this embodiment, a plurality of permanent magnets  155  are inserted into roller cover plate  152 . The permanent magnets  155  are rectangular shaped to increase the effective magnetic field produced by the magnets. As illustrated, the upper row of magnets are mounted such that the south pole faces outward while the lower row of magnets are mounted such that the north pole faces outward. This arrangement allows the magnetic field to loop from the north pole to the south pole of adjacent magnet pairs. The looping magnetic field attracts and collects stray magnetic particles produced by the main guide rollers  184  and the sub-rollers  185 . One purpose of the specific magnetic orientation of the magnets is to minimize eddy currents that may affect the sputtering process. 
     The permanent magnets  155  for all embodiments may be made from magnetic alloys including at least one metal from the group consisting of Neodymium, Iron, Boron, Samarium, and Cobalt. 
     The permanent magnets  155  could each be a simple magnet, stacked magnets or any format of the combinations. The material of magnets is preferably, but not limited to, a Samarium and Cobalt alloy (Sm—Co). The material of the roller cover plate  152  and the roller shields  154  is preferably, but not limited, aluminum. The material of the roller bottom shield  156  is preferably, but not limited, 400 series stainless steel. 
     Disk transport system  100  is utilized to transport disks  109  held in substrate holders  190  in a linear direction along a horizontal transfer line. As shown in  FIGS. 4 ,  5 , and  6 , the substrate holder support panel  180  includes an array of multiple small permanent holder magnets  196  mounted along a bottom surface thereof. Each permanent holder magnet  96  has a magnetic pole on the top and the bottom surfaces. The magnetic poles of the holder magnets  96  are alternatively oppositely directed in the array direction (horizontal transfer line). For example, the first magnet in the magnet array  196  (depicted at the far left of  FIG. 4 ) may be oriented north up and south down, the second magnet may be oriented south up and north down, etc. 
     Beneath the substrate holder support panel  180  resides the magnetic drive unit  190 . Various magnetic drive units for use in disk transport systems are described in the prior art. Magnetic drive unit  190  is similar to the magnetic drive unit disclosed in U.S. Pat. No. 6,740,209. Referring to  FIG. 6 , the magnetic drive unit  190  further includes a motor (not shown), and a magnetic-coupling roller  191 . The magnetic-coupling roller  191  may be provided within a partition cylinder  193  of the magnetic drive unit  190 . The magnetic-coupling roller  191  is a cylinder, on which roller magnets  192  are provided. The surface pole of each of roller magnets  192  are opposite to each other. The magnetic-coupling roller  191  may have a so-called double-helix structure. The magnetic-coupling roller  191  is provided at a position where the roller magnets  192  face towards the holder magnets  196  through the partition cylinder  193  of the magnetic drive unit  190 . The partition cylinder  193  is formed of a material that would not disturb the magnetic field, e.g. non-magnetic material. The holder magnets  196  and the roller magnets  192  are magnetically coupled with each other. The magnetic-coupling roller  191  is provided along the horizontal transfer line of the substrates  9  parallel to the holder magnets  196  attached to the bottom surface of the substrate holder support panel  180 . 
     As shown in  FIGS. 4 and 5 , a plurality of main guide rollers  184  are coupled to a roller support panel  186 . Main guide rollers  184  rotate around horizontal axes and are provided along the horizontal transfer line. Referring to  FIG. 6 , a V-shaped rail  187  attached to a lower surface of the substrate holder support panel  180  makes contact with the plurality of main guide rollers  184  as the substrate holder support panel  180  and substrate holders  190  ride on the main guide rollers  184 . A plurality of sub-rollers  185  are in contact with the lower margin of the substrate holder support panel  180 . The sub-rollers  185  pinch the lower margin of the substrate holder support panel  180  to prevent the substrate holder support panel  180  and substrate holders  190  from deviating from a substantially vertical position. The multiple sub-rollers  185  are provided along the horizontal transfer line as well. 
     The motor is connected to the magnetic-coupling roller  191  so that the magnetic-coupling roller  191  can be rotated around its center axis by driving force transferred from the motor. When the magnetic-coupling roller  191  is rotated, the roller magnets  192  are also rotated. When the roller magnets  192  are rotated the plural aligned holder magnets  196  of which poles are alternately opposite move simultaneously along the aligning direction. Therefore, the holder magnets  196  magnetically coupled with the roller magnets  192  also move linearly as the roller magnets  192  are rotated, resulting in the substrate holder support panel  180  and substrate holders  190  moving linearly together as well. During this liner movement, the main rollers  184  and the sub-rollers  185  shown in  FIGS. 4 ,  5 , and  6  are driven to rotate, following the movement. The main rollers  184  and the sub-rollers  185  are believed to be a primary source of magnetic metal debris or ferrous metal debris (magnetic particles). 
     The magnetic particle trapper  150  as shown in  FIGS. 7-9  utilize magnetic fields generated by the plurality of permanent magnets  155  to trap magnetic metal debris or ferrous metal debris (magnetic particles). The permanent magnets  155  of magnetic particle trapper  150  are strategically located in proximity to the plurality of main guide rollers  184  and the plurality of sub-rollers  185  coupled to the roller support panel  186 . 
     The magnetic particle trapper  150  need not be restricted to use in disk transport systems utilizing magnetic drive units. The magnetic particle trapper  150 , and versions thereof, can also be used in any disk transport systems that utilize moving mechanical parts, pulleys, sub-pulleys, guide rollers, sub-rollers, gears, rack and pinion, rails, guides, etc., that are subject to mechanical wear and produce contamination byproducts that may take on the form of magnetic metal debris or ferrous metal debris (magnetic particles). 
     It should be appreciated by those with skill in this art that, although embodiments of the invention have been previously described with reference to particular disk transport systems, that the embodiments of the invention may be utilized with a wide variety of differing types of disk transport systems having different types of moving mechanical parts, pulleys, sub-pulleys, guide rollers, sub-rollers, gears, rack and pinion, etc., and that the details disclosed in describing the embodiments of the invention are not intended to limit the scope of the invention as set forth in the appended claims. 
     In the foregoing specification, embodiments of the invention have been described with reference to specific exemplary features 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 invention as set forth in the appended claims. The specification and figures are, accordingly, to be regarded in an illustrative rather than a restrictive sense.