Abstract:
An apparatus for fixing and centering substrates that are each provided with an inner hole is provided. The apparatus has a housing having an axis that extends perpendicular to the plane of a substrate placed on the apparatus. A fixation unit is guided in the housing and is introducible into the inner hole of a substrate. The fixation unit includes an outer element that is moveable along the axis of the housing and relative to the housing, and also includes an inner element that is moveable along the axis of the housing and relative to the housing and to the outer element, which, by way of a relative movement of the inner and outer elements, is expandable for engagement with the inner hole of a substrate.

Description:
BACKGROUND OF INVENTION 
     The present invention relates to an apparatus for fixing in position substrates that each have an inner hole, and includes a housing and an element disposed in the housing and introducible into the inner hole. 
     Such an apparatus can be used, for example, at various stations of an apparatus for the adhesive joining of substrates, as is described, for example, in DE-A-197 18 471, which is not prepublished and which belongs to the Applicant of the present application. In particular, the inventive apparatus is suitable for use with an apparatus for drying substrates, as described in the not prepublished DE-197 21 689, which belongs to the Applicant of the present application. To avoid repetition, the content of the aforementioned applications are incorporated for their content into this application. With the above apparatus, substrates are respectively deposited on a support for specific treatment steps in order, for example, to carry out an adhesive joining of two substrates or a drying of substrates. In this connection, the support surfaces provide no fixing of the substrates that are to be treated and positioned, so that the substrates can slide, especially two substrates that are to be adhesively joined can slide. This in turn affects the treatment process, which can lead to deterioration in the quality of substrates being treated. 
     SUMMARY OF INVENTION 
     DE-A-196 44 158 discloses an apparatus for grasping objects having a through opening. The apparatus has a gripper  12  that comprises a base body  4 , a push member  9  that is axially moveable in the base body  4 , and balls  6  that are disposed in the base body  4  and that, by means of an axial movement of the push member within the main body, can be shifted outwardly beyond the outer periphery of the main body  4 . 
     DE-A-196 18 278 discloses a clamping device for drawing in and clamping a tool holder having a hollow cone shaft in the tool receiving means of a main spindle. With this device, clamping jaws for the securement of the tool holder are spread apart by means of a clamping mechanism that is displaceable relative to the clamping jaws. 
     From the publication “o+p-ölhydraulik und pneumatik-22 (1978) Nr. 1, page 10, there is known an inner hole gripper that fixes a substrate in position by means of a pneumatic expansion of an element that is introduced into an inner hole of the substrate. 
     DE-A-195 29 537 furthermore discloses an apparatus pursuant to the introductory portion of claim  1  . 
     It is therefore an object of the present invention to provide an apparatus of the aforementioned type for fixing in position substrates that are each provided with an inner hole, whereby the apparatus, with straightforward technical means and simple handling of the apparatus, enables a good fixing of the substrates in position in order to enable lower rejection rates and a better quality of the finished substrates. 
     SUMMARY OF THE INVENTION 
     The stated object is inventively realized in that the element that is introducible into the inner hole includes an outer element that is axially moveable relative to the housing, and an inner element that is axially moveable relative to the housing, whereby the outer element can be expanded or spread apart by means of a relative movement of the elements. Due to the expansion of the outer element in the inner hole of a substrate, the substrate is on the one hand fixed in position and is centered relative to the outer element. In particular, with substrates that are to be adhesively interconnected and are yet to be dried, there also results in this connection a good centering of the two substrates relative to one another. Due to the fact that not only the inner element, but also the outer element, are axially moveable relative to the housing, there results a simple possibility for introducing and removing these elements into and out of an inner hole of a substrate. 
     The outer and/or inner element is advantageously cylindrical in order to achieve a straightforward configuration and to be able to reliably come into engagement with the inner hole of the substrate or substrates. 
     In order to provide the expandability of the outer element in a simple manner, slots are provided in an end region of the outer element. The outer element is advantageously elastically expandable, i.e. after the expansion the outer element elastically returns to the non-expanded state and thus releases the engagement with the substrate or substrates. 
     Pursuant to one specific embodiment of the invention, the outer element is provided in the region of the slots with a tapering inner diameter by means of which the ability to expand is achieved during a relative movement of the elements. 
     The outer element can advantageously be axially biased by means of a biasing device so that it is biased in a particular axial position in which the outer element is disposed in an inner hole of a substrate. A particularly suitable biasing device is a spring. 
     Pursuant to one preferred specific embodiment, the inner element has an inclined surface on the outer periphery that is advantageously complementary to the tapering inner diameter of the outer element in order to expand the outer element in a manner that is as free from resistance as possible during a relative movement of the elements. 
     By means of a biasing device, the inner element can advantageously be axially biased into a position that expands the outer element in order to bring the inner element in a simple manner into a position in which the inner element expands the outer element. For this purpose, the biasing device is advantageously a spring. 
     To ensure that at a pressure that is exerted upon the apparatus from the outside prior to a movement of the outer element initially the expansion of the outer element is terminated, the biasing device for the inner element has a smaller spring constant than does the biasing device for the outer element. 
     The outer element preferably has a support surface for the biasing device for the outer and inner elements. 
     Pursuant to a further specific embodiment of the invention, the outer and inner elements can be axially biased by a common biasing device, which is advantageously a spring. By utilizing a common biasing device, the number of components that form the apparatus can be reduced. 
     In order to limit the relative movement of the elements relative to one another, and to prevent the elements from coming apart, the outer element, in a non-expandable end region, is provided with a shoulder in the inner periphery. 
     The inner element advantageously has a projection that can extend out of the outer element in order in a simple manner, by pressure upon the projection, to enable a relative movement between the elements. 
     Pursuant to a further preferred specific embodiment of the invention, the housing that receives the moveable outer and inner elements is stationary in order to form a fixed receiving device. 
     In order to provide a better hold for the fixed substrate or substrates, the housing advantageously has a substrate support surface. 
     At one end the housing advantageously has a base wall in order to form a counter surface for the biasing device that biases the outer and/or inner element. 
     The specification incorporates by reference the disclosure of German priority document 198 18 478.6 of Apr. 24, 1998 and International priority document PCT/DE99/02500 of Apr. 24, 1999. 
    
    
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims. 
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will subsequently be explained with the aid of preferred embodiments with reference to the figures, in which: 
     FIG. 1 shows a schematic illustration of one inventive fixation apparatus in an expanded or spread-apart state, as it is used in a drying apparatus; 
     FIG. 2 shows the inventive fixation apparatus of FIG. 1 in a non-expanded state, whereby for the sake of simplification parts of the drying apparatus have been omitted; 
     FIG. 3 is a schematic illustration of the inventive fixation apparatus of FIG. 1 in a non-expanded and retracted position, whereby again parts of the drawing apparatus have been omitted; 
     FIGS. 4 a  and  b  are a schematic plan view of the inventive apparatus or a schematic sectional view of a housing and an outer element of the inventive fixation apparatus; 
     FIG. 5 is an enlarged schematic illustration of a further embodiment of the inventive fixation apparatus. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 is a schematic illustration of an inventive fixation apparatus  1  as it is utilized in a—at least partially illustrated—drawing apparatus  2  for semiconductor substrates. The drawing apparatus  2  illustrated in FIG. 1 can be of the type disclosed in the not prepublished DE 197 721 689, which belongs to the Applicant of the present application. To avoid repetition, the content of that application is incorporated relative to the subject matter of the present application. 
     The drying apparatus has a lower portion  4  and a non-illustrated upper portion. The lower portion  4  is provided with a supporting plate  5  having a glass support panel  6  upon which a substrate disk  8  is disposed. The supporting plate  5  is rotatable, and is simultaneously guided in its position, by rollers  9  and  10 . Although only two rollers  9 ,  10  are illustrated in FIG. 1, the drawing apparatus generally has three rollers that are respectively angularly offset by 120° relative to one another. 
     The lower portion  4  is furthermore provided with a central guide element  12  for receiving the inventive fixation apparatus  1 . 
     As can be best seen in FIG. 2, the fixation apparatus  1  is provided with a stationary housing  15  that is accommodated in the guide element  12 . The housing  15  has a hollow cylindrical shape with an annular flange  16  at an upper end of the housing. The annular flange  16  projects beyond the outer periphery of the cylindrical housing  15  and forms a substrate support surface  17  on the upper surface. 
     Concentrically disposed within the cylindrical housing  15  is a moveably accommodated outer element  20  having an upper end portion  21  that can expand or spread, and a part  22  that cannot expand. The outer element  20  is again hollow cylindrical, and has an inner periphery  24  that tapers upwardly in the direction of the spreadable portion  21 . As can be best seen in FIG. 4, three slots  23  are provided in the region of the spreadable end portion  21 . 
     The lower end of the non-expandable part  22  is closed off by means of a plug  25  that can be screwed in. 
     The outer element  20  is biased upwardly by means of a spring  27 , which on the one hand is supported against the plug  25  and on the other hand is supported against the guide element  12 . The guide element  12  is provided with a centered guide projection  28  that extends into the spring  27 , which is embodied as a compression spring. In this way, a lateral sliding and tilting of the spring  27  is prevented. 
     Concentrically accommodated in the outer element  20  is an inner element  30  that is displaceable relative to the outer element. The inner element  30  has a hollow cylindrical end portion  32 , a conically tapering central portion  33 , and an end portion  34  that forms a projection. 
     The hollow cylindrical end portion  32  has a hollow receiving chamber  36  in which is accommodated a spring  37 . One end of the spring  37 , which is embodied as a compression spring, is supported against the plug  25 , and the other end of the spring is supported against an inner wall of the inner element in order to bias it upwardly. 
     The conically tapering central portion  33  is provided with an inclined outer peripheral surface  39  that is complimentary to the conically tapering inner circumferential surface of the expandable end portion  21  of the outer element  20 . 
     The cylindrical end portion  34  forms a projection that can extend through the expandable end portion  21 , as illustrated in FIG.  1 . 
     In FIGS. 1 to  3 , a so-called inner hole gripper  40  is illustrated above the inventive fixation apparatus  1 . 
     This inner hole gripper  40  is axially moveable by a non-illustrated mechanism. The inner hole gripper  40  is furthermore provided with a spherically shaped end portion  41  that can be introduced into an inner hole of a substrate  8  and can be spread apart within the inner hole in order to grasp the substrate  8  and possibly transport it. Inner hole grippers of this type are known, and the inner hole gripper will therefore not be further described. 
     The operation of the inventive fixation apparatus  1  will now be explained with the aid of FIGS. 1 to  3 . As can be seen in FIG. 1, the outer element is biased upwardly via the spring  27  within the stationary housing  15 . In so doing, the outer element  20  extends through an inner hole of a substrate  8 . Furthermore, the inner element  30  is biased upwardly by the spring  37  within the outer element  20 . In so doing, the inclined surface  39  comes into contact with the tapered inner periphery  24  of the expandable end portion  21  and spreads the expandable end portion  21  apart. As a result, the outer periphery of the expandable end portion  21  comes securely into engagement with the inner hole of the wafer  8 . The wafer is consequently centered and fixed relative to the fixation apparatus  1 . In the position illustrated in FIG. 1, the cylindrical end portion  34  extends axially out of the expandable end portion  21  of the outer element  20 . 
     In order to release the fixation of the wafer  8 , the spherical head  41  of the inner hole gripper is brought into contact with an upper surface of the cylindrical end portion  34  of the inner element  30 , as can be seen in FIG.  1 . The inner element  21  is then pressed downwardly by the inner hole gripper  40  into the outer element, and in particular against the tension of the spring  37 . Due to the fact that the spring constant of the spring  37  is less than the spring constant of the spring  27 , which biases the outer element upwardly, the outer element  20  initially maintains its position. When the inner element  30  is disposed in the position illustrated in FIG. 2, the inclined surface  39  is no longer in contact with the tapering portion of the inner periphery  24  of the outer element, and the expandable end portion  21  elastically returns to its non-spread apart position. Consequently, the contact with the inner hole of the wafer  8  is released, which is thus no longer fixed. 
     After releasing the fixation, the inner hole gripper  40  is now moved further downwardly, as a result of which the outer element  20  is now also pressed downwardly against the force of the spring  27  out of the inner hole of the wafer  8 . This position is illustrated in FIG.  3 . In this position, the spherical head  41  of the inner hole gripper  40  can be spread apart in order to come into engagement with the inner hole and to grasp the wafer  8 . If the inner hole gripper is now moved upwardly, it takes the wafer  8  along with it. In so doing, the outer element  20  and the inner element  30  return in a reversed manner into the position shown in FIG. 1, whereby this time the outer element merely does not extend through an inner hole of the wafer  8 . 
     The fixation of a wafer with the fixation apparatus  1  is effected in the reverse order. 
     FIG. 5 shows a further specific embodiment of the inventive fixation apparatus. The inventive fixation apparatus pursuant to the second embodiment has a hollow cylindrical housing  45 . An end portion of the hollow cylinder is provided with a radially extending wall  46  that closes off the hollow cylinder. The wall  46  is provided with a centered central projection  47 . 
     Disposed in the housing  45  is an outer element  49  that is axially displaceable within the housing and that has an expandable end portion  51  and a non-expandable part  52 . The outer element  49  is hollow cylindrical and has an inner periphery  54  that tapers in the upper region and forms an inclined surface  55 . Disposed in the region of the non-expandable part  52 , on the inner periphery  54 , is an annular element  56  that is connected to the inner periphery  54  in any suitable manner, for example via a screw connection. 
     Concentrically disposed within the outer element  49  is an inner element  58  that is essentially the same as the inner element  30  of the first embodiment. The inner element is again provided with an essentially hollow cylindrical end portion  60 , a conically tapering central portion  61 , as well as a cylindrical end portion  62 . The hollow cylindrical portion  60  defines a receiving chamber  64  for a spring  65 , which axially upwardly biases the inner element  58 . The spring  65  extends into the receiving chamber  64 , is supported against a wall thereof, and extends from there through the annular element  56  to the radially extending end wall  46  of the housing  45 . The guide projection  47  of the end wall  46  extends into the spring  65 , which is embodied as a compression spring, and guides the same. 
     The radially tapering central portion  61  is again provided with an inclined surface  68  that is complementary to the inclined surface  55 , and in the position shown in FIG. 5 comes into engagement therewith in order to spread the expandable end portion  51  of the outer element  49  apart. The cylindrical portion  62  extends axially outwardly out of the outer element  49 . 
     The manner of operation of the fixation apparatus pursuant to the second embodiment is essentially the same as the operation of the apparatus pursuant to the first embodiment. 
     The essential difference is that only one spring  65  is provided that serves to axially upwardly bias not only the inner element  58  but also the outer element  49 . This occurs in that the spring first axially upwardly biases the inner element  58  and via the inner element  58  indirectly axially upwardly biases the outer element  49 . If via an inner hole gripper the inner element  58  is pressed from above, the inner element moves downwardly relative to the outer element  49 , and in particular against the tension of the spring  65 . In so doing, in the same manner as described in conjunction with the first embodiment, the expansion of the expandable part  51  of the outer element is released. After a further, downwardly directed movement of the inner hole gripper, the inner element  58  comes into engagement with the annular element  56 . After a further, downwardly directed movement of the inner hole gripper, the outer element is now also pressed downwardly. 
     The inventive fixation apparatus was described with the aid of specific embodiments, in particular in conjunction with a drying apparatus  2  for semiconductor substrates. However, embodiments and modifications will be possible for one skilled in the art without thereby departing from the inventive concept. For example, the fixation apparatus can also be used with other apparatus where a substrate having an inner hole must be fixed in position.