Patent Publication Number: US-2017368659-A1

Title: Processing apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a processing apparatus which is capable of performing a plurality of processing operations all by itself which include a grinding process, a polishing process, a cutting process with a cutting tool, etc. 
     Description of the Related Art 
     For grinding a workpiece such as a semiconductor wafer or the like to make it thinner, it has been customary in the art for higher quality and productivity to perform a rough-grinding process on the workpiece in the first place and then carry out a finish-grinding process on the workpiece to finish the workpiece to a desired thickness. As disclosed in Japanese Patent Laid-Open No. 2016-010838, there has been known a processing apparatus wherein a grinding wheel for rough grinding and a grinding wheel for finish grinding are juxtaposed and workpieces held on respective chuck tables disposed on a turntable are delivered successively to the grinding wheels upon rotation of the turntable. 
     The applicant of the present invention has proposed a grinding apparatus having two inner and outer grinding wheels that are disposed concentrically with each other for making the grinding apparatus as a processing apparatus small in size, as disclosed in Japanese Patent Laid-Open No. 1988-62650. The grinding wheels have respective vertical movable shafts or spindles, and the rotational drive power of a motor is transmitted by a belt to the spindle of the outer grinding wheel. 
     SUMMARY OF THE INVENTION 
     With the grinding apparatus disclosed in Japanese Patent Laid-Open No. 1988-62650, since the rotational drive power of a motor is transmitted by the belt to the spindle of the outer grinding wheel, the spindle tends to wobble during rotation as it is pulled sideways by the belt. Therefore, the disclosed grinding apparatus may not be able to grind workpieces to a nicety. 
     It is therefore an object of the present invention to provide a processing apparatus which is relatively small in size and which is capable of grinding workpieces highly accurately. 
     In accordance with an aspect of the present invention, there is provided a processing apparatus including a chuck table having a holding surface for holding a workpiece thereon, and processing means for processing the workpiece held on the holding surface of the chuck table, wherein the processing means includes a spindle, a motor for rotating the spindle about its own axis, a wheel mount coupled to an end of the spindle and facing the holding surface of the chuck table, a first tool detachably mounted on a mount surface of the wheel mount, the first tool having a first diameter, a second tool mount nonrotatably and axially movably mounted on the spindle over a rear surface of the wheel mount which is opposite the mount surface of the wheel mount, the second tool mount having a storage region for storing therein the wheel mount and the first tool mounted on the wheel mount, and a second tool mount member surrounding the storage region and having an inside diameter larger than the first diameter, a second tool detachably mounted on the second tool mount and having an inside diameter larger than the first diameter, and moving means for moving the second tool mount in axial directions of the spindle, the moving means positions the second tool mount selectively in a retracted position in which the first tool is kept in contact with, but the second tool is kept out of contact with, the workpiece held on the chuck table and a second tool working position in which the first tool is kept out of contact with, but the second tool is kept in contact with, the workpiece held on the chuck table. 
     Preferably, when the moving means positions the second tool mount in the retracted position, the first tool is exposed out of the storage region of the second tool mount, and fasteners by which the first tool is fastened to the wheel mount are exposed from the rear surface of the wheel mount. 
     The first tool and the second tool are mounted on the same spindle and disposed concentrically with each other. It is not necessary to use a belt for rotating one of the tools, and hence the spindle is prevented from being pulled sideways and from wobbling during rotation. Therefore, the processing apparatus is relatively small in size and is capable of grinding the workpiece to a nicety. 
     The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of a processing unit of the processing apparatus; 
         FIG. 3  is a fragmentary cross-sectional view of the processing unit, depicting the manner in which a second tool mount is in a retracted position and a workpiece is being ground by a first tool; 
         FIG. 4  is a fragmentary cross-sectional view of the processing unit, depicting the manner in which the second tool mount is in a second tool working position and the workpiece is being polished by a second tool; 
         FIG. 5A  is a fragmentary cross-sectional view of the processing unit, depicting the manner in which the first tool is detached; and 
         FIG. 5B  is a fragmentary cross-sectional view of the processing unit, depicting the manner in which the first tool is replaced with a cutting tool and the workpiece is being cut by the cutting tool. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A processing apparatus according to a preferred embodiment of the present invention will be described in detail below with reference to the drawings.  FIG. 1  depicts in perspective the processing apparatus, generally denoted by  2 , according to the preferred embodiment of the present invention. The processing apparatus  2  includes a base  4  with an upstanding column  6  mounted on a rear portion of the base  4 , a pair of vertical guide rails  8  fixed to the column  6 , and a processing unit (processing means)  10  vertically movably mounted on the rails  8 . The processing unit  10  has a spindle housing  12  and a support  14  that supports the spindle housing  12 . The support  14  is mounted on a movable table  16  vertically movably mounted on the rails  8 . 
     As best depicted in  FIG. 2 , the processing unit  10  includes a vertical spindle  18  rotatably housed in the spindle housing  12 , a motor  20  for rotating the spindle  18  about its own axis, a wheel mount  22  fixed to a lower end (distal end) of the spindle  18 , and a grinding wheel  24  as a first tool removably fastened to a lower mount surface  22   a  of the wheel mount  22  by a plurality of screws  26  as fasteners. The grinding wheel  24  includes an annular wheel holder  28  attached to the wheel mount  22  by the screws  26  and an annular array of grinding stones  30  secured to an outer circumferential edge of the lower end of the wheel holder  28 . 
     An air cylinder  32  having an annular chamber  34  defined therein is disposed around and fixed to the spindle  18  in axially facing relation to a rear surface  22   b  of the wheel mount  22  which is opposite the lower mount surface  22   a  thereof. The annular chamber  34  in the air cylinder  32  houses an annular piston  36  slidably inserted therein. A plurality of piston rods  37  movably disposed in the annular chamber  34  have respective upper ends coupled to the lower surface of the piston  36  and respective lower ends fixed to a second tool mount  38  disposed below the air cylinder  32 . 
     The annular chamber  34  in the air cylinder  32  includes a head-end compartment selectively supplied with air under compression through a first air supply passageway  35   a  and a rod-end compartment selectively supplied with air under compression through a second air supply passageway  35   b.  According to the present embodiment, the air cylinder  32 , the piston  36 , and the piston rods  37  jointly make up moving means. 
     The second tool mount  38  has a storage region (storage recess)  40  defined in a lower end face thereof for storing therein the wheel mount  22  and the grinding wheel  24  mounted on the wheel mount  22 . A second tool mount member  38   a  is mounted on the lower end face of the second tool mount  38  in surrounding relation to the storage region  40 . The inside diameter of the second tool mount member  38   a  is larger than the diameter of the grinding wheel  24  as the first tool. 
     The second tool mount  38  is fixed to the lower ends of the piston rods  37  of the air cylinder  32  that is fixed to the spindle  18 . Therefore, the second tool mount  38  is nonrotatably and axially movably mounted on the spindle  18  over the rear surface  22   b  of the wheel mount  22  which is opposite the lower mount surface  22   a  thereof. 
     That the second tool mount  38  is nonrotatably and axially movably mounted on the spindle  18  means that the second tool mount  38  does not rotate relatively to the spindle  18 , but rotates with the spindle  18 , and that the second tool mount  38  is movable in the axial directions of the spindle  18 . A second tool  42  as a polishing pad, whose inside diameter is larger than the diameter of the grinding wheel (first tool)  24 , is detachably fastened to the second tool mount member  38   a  by a plurality of screws  44 . The grinding wheel  24  and the polishing pad  42  are mounted on the same spindle  18  and hence are disposed concentrically with each other. 
     Referring back to  FIG. 1 , the processing apparatus  2  includes a processing unit feed mechanism  52  for moving the processing unit  10  vertically along the guide rails  8 . The processing unit feed mechanism  52  includes a ball screw  48  disposed between and parallel to the guide rails  8  and threaded through a nut on the movable table  16  and a pulse motor  50  connected to an upper end of the ball screw  48 . When the pulse motor  50  is energized, it rotates the ball screw  48  about its own axis, moving the processing unit  10  vertically along the guide rails  8 . 
     The base  4  has a cavity  4   a  defined in an upper surface thereof, and a chuck table mechanism  54  is disposed in the cavity  4   a.  The chuck table mechanism  54  has a chuck table  56  that is movable by a moving mechanism, not depicted, in Y-axis directions between a workpiece loading/unloading position A in front of the processing unit  10  and a processing position B facing the processing unit  10 . The cavity  4   a  is covered with bellows  58  on both sides of the chuck table mechanism  54 . A control panel  60  for the operator of the processing apparatus  2  to enter processing conditions and commands is disposed on the upper surface of a front portion of the base  4  remote from the column  6 . 
     Operation of the processing apparatus  2  thus constructed will be described below. The processing unit  10  depicted in  FIG. 2  uses the grinding wheel  24  as the first tool and the polishing pad  42  as the second tool. The processing unit  10  grinds the surface of a wafer  11  as a workpiece held on an upper holding surface of the chuck table  56  with the grinding wheel  24  as the first tool, and thereafter polishes the ground surface of the wafer  11  with the polishing pad  42  as the second tool. 
     More specifically, the chuck table  56  that is holding the wafer  11  thereon is moved in a Y-axis direction from the workpiece loading/unloading position A to the processing position B in  FIG. 1 . Then, as depicted in  FIG. 3 , the chuck table  56  is positioned such that the grinding stones  30  of the grinding wheel  24  will pass in the vicinity of the center of the wafer  11  held on the chuck table  56 . While the chuck table  56  is rotating about its own axis in the direction indicated by the arrow a at approximately 300 rpm, and the grinding wheel  24  is rotated about its own axis in the direction indicated by the arrow b at approximately 6000 rpm. At the same time, the pulse motor  50  is energized to bring the grinding stones  30  of the grinding wheel  24  downwardly into contact with the wafer  11 . The grinding wheel  24  is fed downwardly at a predetermined grinding feed speed, causing the grinding stones  30  to grind the wafer  11  until the wafer  11  is thinned to a desired thickness. 
     While the grinding wheel  24  is grinding the wafer  11 , air under pressure is supplied through the second air supply passageway  35   b  to the rod-end compartment of the chamber  34 , lifting the piston  36 . Though the grinding wheel  24  as the first tool is held in contact with the wafer  11 , therefore, the second tool mount  38  is kept in a retracted position depicted in  FIG. 3  in which the polishing pad  42  as the second tool is held out of contact with the wafer  11 . 
     When the grinding of the wafer  11  is finished, air under pressure is supplied through the first air supply passageway  35   a  to the head-end compartment of the chamber  34 , lowering the piston  36 . The piston  36  is lowered by a sufficiently large stroke to cause the storage region or recess  40  defined in the second tool mount  38  to store therein the wheel mount  22  and the grinding wheel  24  mounted thereon and also to bring the polishing pad  42  as the second tool into contact with the wafer  11  held on the chuck table  56 , as depicted in  FIG. 4 . 
     Then, the chuck table  56  is rotated about its own axis in the direction indicated by the arrow a, and the polishing pad  42  is rotated about its own axis in the direction indicated by the arrow b, polishing the ground surface of the wafer  11 . When the wafer  11  is thus polished, distortions and irregularities caused on the wafer  11  by the polishing process are removed, bringing the upper surface of the wafer  11  to a mirror finish. 
     With the processing apparatus  2  according to the present embodiment described above, the moving means made up of the air cylinder  32 , the piston  36 , and the piston rods  37  positions the second tool mount  38  selectively in the retracted position (see  FIG. 3 ) in which the first tool  24  is kept in contact with, but the second tool  42  is kept out of contact with, the wafer  11  held on the chuck table  56  and a second tool working position (see  FIG. 4 ) in which the first tool  24  is kept out of contact with, but the second tool  42  is kept in contact with, the wafer  11  held on the chuck table  56 . 
     A process of replacing the grinding wheel  24  as the first tool with another tool will be described below with reference to  FIGS. 5A and 5B . For replacing the grinding wheel  24 , air under pressure is supplied to the head-end compartment of the chamber  34 , bringing the second tool mount  38  into the retracted position as depicted in FIG.  5 A. Then, the screws  26  are removed, and the grinding wheel  24  as the first tool is dislodged from the wheel mount  22 . Then, as depicted in  FIG. 5B , a cutting tool wheel  62  as a first tool is mounted on the wheel mount  22 . The cutting tool wheel  62  includes an annular holder  64  and a cutting tool  66  mounted on the annular holder  64 . 
     For cutting the wafer  11  held on the chuck table  56  with the cutting tool  66  which is being rotated, the cutting tool  66  that has incised into the wafer  11  by a predetermined depth is rotated in the direction indicated by the arrow b, and the chuck table  56  is fed linearly in the direction indicated by the arrow Y 1 . The surface of the wafer  11  held on the chuck table  56  is thus cut into a flat surface by the cutting tool  66 . 
     In the above embodiment, the grinding wheel  24  as the first tool is mounted on the wheel mount  22 , and the polishing pad  42  as the second tool is mounted on the second tool mount  38 . However, the first and second tools are not limited to the illustrated combination, but two of various tools including a grinding wheel, a dry polishing pad, a chemical mechanical polishing (CMP) pad, and a cutting tool wheel, etc. may be combined as the first and second tools. 
     The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.