Patent Publication Number: US-2010117279-A1

Title: Supporting system and a method for supporting an object

Description:
FIELD OF THE INVENTION 
     The invention relates to a supporting system and to a method for supporting an object. 
     BACKGROUND OF THE INVENTION 
     Many types of objects need to be supported by chucks. These objects include, for example, semiconductor wafers, glass objects and the like. Chucks are tailored to each type of object. Thus, glass supporting chucks differ from wafer supporting chucks. A typical inspection system can either inspect one type of object or include multiple spaced apart chucks, one chuck for each type of object. 
     There is a growing need to provide multiple purpose inspection systems that can inspect multiple types of objects. There is a growing need to reduce the space allocated for different chucks. 
     SUMMARY OF THE INVENTION 
     A supporting system, the system includes a vertically movable chuck and a stationary chuck; wherein the vertically movable chuck and the stationary chuck are concentric; wherein the vertically movable chuck vertically moves between an upper position and a lower position; wherein when the vertically movable chuck is positioned at the upper position an upper surface of the vertically movable chuck is higher than an upper surface of the stationary chuck and when the vertically movable chuck is positioned at the lower position the upper surface of the vertically movable chuck is lower than the upper surface of the stationary chuck. 
     Conveniently the upper surface of the vertically movable chuck has a circular shape and a lower surface of the stationary chuck has a ring shape. 
     Conveniently a lower surface of the stationary chuck limits a vertical movement of the vertically movable chuck when the vertically movable chuck is positioned at the upper position. 
     Conveniently the stationary chuck defines an aperture that enables a supporting element to move through the aperture. 
     Conveniently the supporting system includes a background element adapted to be positioned on the vertically movable chuck. 
     Conveniently at least one vacuum channel is formed at an upper surface of the vertically movable chuck and wherein at least one vacuum channel is formed at an upper surface of the stationary chuck. 
     Conveniently the upper surface of the vertically movable chuck is smaller than an object to be supported by the vertically movable chuck and wherein an inner edge of the stationary chuck is shaped and sized such as to support the object. 
     Conveniently the supporting system includes an upper position pressure regulator and a lower position pressure regulator; wherein the upper position pressure regulator is adapted to regulate a fluid pressure provided to the vertically movable chuck such as to place the vertically movable chuck at the upper position; and wherein the lower position pressure regulator is adapted to regulate a fluid pressure provided to the vertically movable chuck such as to place the vertically movable chuck at the lower position. 
     Conveniently the supporting system includes calibration targets. 
     A method for supporting an object, the method includes: placing a vertically movable chuck at a lower position, placing the object on a stationary chuck and applying vacuum by the stationary chuck in response to a determination to support the object by the stationary chuck; placing the vertically movable chuck at a lower position, placing the object on the stationary chuck; moving the vertically movable chuck such as to contact the object; applying vacuum by the vertically movable chuck and moving the vertically movable chuck to an upper position in response to a determination to support the object by the vertically movable chuck; wherein the vertically movable chuck and the stationary chuck are concentric; wherein when the vertically movable chuck is positioned at the upper position an upper surface of the vertically movable chuck is higher than an upper surface of the stationary chuck and when the vertically movable chuck is positioned at the lower position the upper surface of the vertically movable chuck is lower than the upper surface of the stationary chuck. 
     Conveniently the upper surface of the vertically movable chuck has a circular shape and a lower surface of the stationary chuck has a ring shape. 
     Conveniently the method includes limiting a vertical movement of the vertically movable chuck by wherein a lower surface of the stationary chuck the vertically movable chuck is positioned at the upper position. 
     Conveniently the method includes receiving the object from a supporting element that moves within an aperture defined in the stationary chuck. 
     Conveniently the method includes placing a background element on the vertically movable chuck, in response to a determination to support the object by the stationary chuck. 
     Conveniently the method includes applying vacuum via at least one vacuum channel formed at an upper surface of the vertically movable chuck and applying vacuum via at least one vacuum channel formed at an upper surface of the stationary chuck. 
     Conveniently the method includes supporting the object by an inner edged of the stationary chuck; and supporting the object by the vertically movable chuck when positioned in the upper position; wherein the upper surface of the vertically movable chuck is smaller than the object. 
     Conveniently the method includes independently regulating a fluid pressure required for maintaining the vertically movable chuck at the lower position and fluid pressure required for maintaining the vertically movable chuck at the upper position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
         FIGS. 1 ,  2 ,  3  and  4  illustrate a supporting system according to an embodiment of the invention; 
         FIGS. 5 ,  6  and  7  illustrate a placement of a background element on a vertically movable chuck according to an embodiment of the invention; 
         FIGS. 8 ,  9 ,  10  and  11  illustrate a placement of an object on a stationary chuck by a supporting element according to an embodiment of the invention; 
         FIG. 12  illustrates an object that is supported by stationary chuck according to an embodiment of the invention; 
         FIGS. 13 and 14  illustrate a placement of a wafer on a vertically movable chuck according to an embodiment of the invention; and 
         FIG. 15  is a flow chart of a method for supporting an object according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     A multi-purpose supporting system is provided. It can effectively support multiple types of objects including transparent objects and non-transparent objects. By utilizing concentric chucks the overall area of the supporting system is reduced. Conveniently, both chucks participate in placement of objects on a vertically movable chuck. 
     It is noted that the various drawings are out of scale. In addition some drawings do not include all the features of the diced wafer adaptor, for simplicity of explanation. 
       FIGS. 1 ,  2 ,  3  and  4  illustrate supporting system  10  according to an embodiment of the invention.  FIGS. 5 ,  6  and  7  illustrate a placement of background element  120  on vertically movable chuck  20  according to an embodiment of the invention.  FIGS. 8 ,  9 ,  10  and  11  illustrate a placement of object  130  on stationary chuck  12  by a supporting element such as end effector  150  according to an embodiment of the invention.  FIG. 12  illustrates object  130  that is supported by stationary chuck  12  according to an embodiment of the invention.  FIGS. 13 and 14  illustrate a placement of wafer  140  on vertically movable chuck  20  according to an embodiment of the invention. 
       FIGS. 1 and 2  illustrates system  10  when vertically movable chuck  20  is positioned at a lower position while  FIGS. 3 and 4  illustrate system  10  when vertically movable chuck  20  is positioned at an upper position. 
     Vertically movable chuck  20  and stationary chuck  12  are concentric.  FIG. 1  illustrates a ring shaped stationary chuck  12  and a circular vertically movable chuck  20 . It is noted that these chucks can have other shapes. 
     As illustrated in  FIGS. 1 ,  2 ,  3  and  4 , vertically movable chuck  20  can vertically moves between an upper position and a lower position. When vertically movable chuck  20  is positioned at the upper position an upper surface of vertically movable chuck  20  is higher than an upper surface of stationary chuck  12 . When vertically movable chuck  20  is positioned at the lower position the upper surface of vertically movable chuck  20  is lower than the upper surface of stationary chuck  12 . It is noted that vertically movable chuck  20  can be placed in one or more additional positions between the upper and lower positions, although this is not necessarily so. 
     Conveniently, vertically movable chuck  20  is placed in the upper position in a very accurate manner, by limiting it from exceeding a predefined height that is defined by stationary chuck  12 . Conveniently, the lower surface of stationary chuck  12  limits a vertical movement of vertically movable chuck  20  when the vertically movable chuck  20  is positioned at the upper position. 
     The upper surface of vertically movable chuck  20  is smaller than an object to be supported by vertically movable chuck  30 . An inner edge of the stationary chuck is shaped and sized such as to support such an object. Accordingly, an object (to be eventually provided to vertically movable chuck  20 ) is first supported by stationary chuck  20  and only after elevating vertically movable chuck  20  it is supported by vertically movable chuck  20 . 
     In order to provide an object to either one of these chucks an object should be transferred from another location (not shown) that can be located at either side of these chucks. In order to simplify the provision of the object, aperture  30  is defined by stationary chuck  12 . Through this aperture a supporting element (that supports the object before the object is supported by either one of the chucks) can move. The movement can include vertical movement and a horizontal movement. As will be further illustrated in  FIGS. 8-11 , aperture  30  simplifies the provision of an object to stationary chuck  12 . It allows a placement of an object on stationary chuck  12  by using commonly used supporting elements that can place the object on stationary chuck  12  while supporting the lower surface of the object. 
       FIG. 8  illustrates supporting element  150  that approaches stationary chuck  12 . Supporting element  150  supports object  130 .  FIG. 9  illustrates a forward and upper position of supporting element  150  after completing a horizontal movement through aperture  30 . At this point supporting element contacts object  130 . Object  130  can be placed on stationary chuck  12  but can be slightly above stationary chuck  12 . Supporting element  150  is then lowered till it is positioned at a forward and lower position. During the lowering process object  130  can be placed on stationary chuck  12  (if it was not placed on stationary chuck  12  during the forward and upper position).  FIG. 10  illustrates the forward and lower position of supporting element  150 . At this point supporting element  150  does not contact object  130 . Supporting element  150  is then moved away from stationary chuck  12 .  FIG. 11  illustrates a lower backward position of supporting element  150 . At this point supporting element  150  is almost entirely out of aperture  30 . 
     It is noted that when supporting element  150  removes object  130  from stationary chuck  130  the order of these mentioned above operations is reversed. For example, supporting element  150  is positioned at the lower backward position, is horizontally moved towards the forward and lower position, lifted to the forward and upper position (to contact object  130  and optionally to list it above stationary chuck  12 ) and then horizontally moved away from stationary chuck  12 . 
     In some cases, and especially when an inspected object includes transparent or partially transparent areas, it is advantageously to have a certain background behind the object. This background can be fully reflective or fully observing (black) but this is not necessarily so as partially reflective backgrounds can also be required. According to an embodiment of the invention a background element having a desired optical characteristic is provided. This background element can be placed on vertically movable chuck  20  and places at a certain distance below an object that is supported by stationary chuck  12 . 
       FIG. 5  illustrates a background element  120  and system  10 .  FIG. 6  illustrates a placement of background element  120  on vertically movable chuck  20  that is positioned at its upper position.  FIG. 7  illustrates background element  120  on vertically movable chuck  20  after being lowered to its lower position. After this sequence of stages an inspected object can be placed on stationary chuck  12 . The background element  120  is thin enough not to block aperture  30  and enable a placement of an object on stationary chuck  12  by supporting element  150 , as illustrated in  FIGS. 8-11 . 
     Referring back to  FIG. 1 , multiple circular and radially extending vacuum channels  90  are formed at the upper surface of vertically movable chuck  20 . Circular vacuum channel  92  is formed at an upper surface of stationary chuck  12 . Three wafer anti-slide silicon caps  82 ,  84  and  86  are formed at the upper surface of stationary chuck  20 . Stationary chuck  12  is connected to common base plate  70  via three posts such as post  40 . The components (not shown) that support (and vertically move) vertically movable chuck  20  are also connected to common base plate  70 . Flow metering valves  112  and  114  provide an indication about the fluid pressure that is provided to actuators of vertically movable chuck  20 . Upper position pressure regulator  62  regulates a fluid pressure provided to vertically movable chuck  20  such as to place vertically movable chuck  20  at the upper position. Lower position pressure regulator  64  is adapted to regulate a fluid pressure provided to vertically movable chuck  20  such as to place vertically movable chuck  20  at the lower position. Vacuum sensors  52  and  54  sense the vacuum level at circular and radially extending vacuum channels  90  and at circular vacuum channel  92  respectively. Targets  72  are positioned in proximity to stationary chuck  12  such as to enable an inspection system to calibrate itself. 
     Conveniently supporting system  10  can be characterized by at least one of the following characteristics: (i) the upper surfaces of stationary chuck  12  and vertically movable chuck  20  are lapped to a flatness of about 5 microns (although other flatness levels can be maintained, (ii) the lower surface of stationary chuck  12  is also lapped to a flatness of few microns, (iii) when in upper position the upper surface of vertically movable chuck  20  is about half a Millimeter above the upper surface of stationary chuck  12 , (iv) common base plate  70  is connected to a saddle  74  for an inspection linear motion stage; (v) a portion of stationary chuck  12  that extends few millimeters from the inner edge of stationary chuck  12  can support an object. 
       FIG. 15  illustrates method  300  for supporting an object, according to an embodiment of the invention. 
     It is assumed that stationary chuck  12  is used for supporting objects of certain types (such as glass or transparent objects) while vertically movable chuck  20  is used to support objects of other types (such as non-transparent objects and especially semiconductor wafers). Additionally or alternatively, stationary chuck  12  can support larger objects than vertically movable chuck  12 , thus the determination can be responsive to the size of the object. 
     Method  300  starts by stage  310  of determining which chuck out of a vertically movable chuck and a stationary chuck should eventually support the object or receiving an indication about such a determination. The vertically movable chuck and the stationary chuck are concentric. 
     Referring to the example set fourth in  FIG. 1 , supporting system  10  is provided with an indication about the chuck that should eventually support the object. 
     If it is determined that the stationary chuck should eventually support the object and there is no need to place a background element below the inspected object (denoted “stationary chuck, not background required”) then stage  310  is followed by stages  320 ,  322  and  324 . 
     Stage  320  includes placing a vertically movable chuck at a lower position so that the upper surface of the vertically movable chuck is lower than the upper surface of the stationary chuck. Stage  320  is followed by stage  322  of placing the object on a stationary chuck. Stage  322  is followed by stage  324  of applying vacuum by the stationary chuck. The vacuum can be applied by one ore more vacuum channels formed at the upper surface of the stationary chuck. 
     If it is determined that the vertically movable chuck should eventually support the object (denoted “vertically movable chuck”) then stage  310  is followed by stages  330 ,  332 ,  334  and  336 . 
     Stage  330  includes placing the vertically movable chuck at a lower position so that the upper surface of the vertically movable chuck is lower than the upper surface of the stationary chuck. Stage  330  is followed by stage  332  of placing the object on a stationary chuck. Stage  332  is followed by stage  334  of moving the vertically movable chuck to an upper position so that an upper surface of the vertically movable chuck is higher than an upper surface of the stationary chuck. During this movement the vertically movable chuck contacts the object and the lifts it above the stationary chuck. Stage  334  is followed by stage  336  of applying vacuum by the vertically movable chuck. The vacuum can be applied by one ore more vacuum channels formed at the upper surface of the vertically movable chuck. 
     Conveniently, the upper surface of the vertically movable chuck has a circular shape and a lower surface of the stationary chuck has a ring shape. 
     Conveniently, stages  322  and  332  include receiving the object from a supporting element that moves within an aperture defined in the stationary chuck. 
     Conveniently, stage  336  includes limiting a vertical movement of the vertically movable chuck by the lower surface of the stationary chuck when the vertically movable chuck is positioned at the upper position. 
     Conveniently, stage  332  includes supporting the object by at least the inner edge of the stationary chuck and stage  338  includes supporting the object by an upper surface of the vertically movable chuck, wherein this upper surface is smaller than the object. 
     According to an embodiment of the invention, method  300  can also include stages  340  and  342 . Stages  340  and  342  follow stage  310  if it is determined that the stationary chuck should eventually support the object and if it is determined that a background element is required (denoted “stationary chuck, background required”). Stage  340  includes positioning the vertically movable chuck at its upper position. Stage  340  is followed by stage  342  of placing a background element having a required background characteristic on the vertically movable chuck. Stage  342  is followed by stage  320 . 
     Conveniently, stage  330  includes regulating a fluid pressure required for maintaining the vertically movable chuck at the lower position and stage  338  includes regulating a fluid pressure required for maintaining the vertically movable chuck at the upper position. These regulations are mutually independent. 
     Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.