Abstract:
The invention relates to a substrate carrier comprising two vertical plates and two horizontal plates. In order for the substrate during its transport through a sputter unit to be coated uniformly in its margin regions, a lever arrangement is provided between the two vertical plates. The lever arrangement comprises at least one horizontal web which under the effect of heat expands to a lesser degree than the horizontal plates.

Description:
FIELD OF THE INVENTION  
       [0001]     This application claims priority from German Patent application No. 10 2005 045 717.7 filed Sep. 24, 2005, incorporated herein by reference in its entirety.  
         [0002]     The invention relates to a substrate carrier.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0003]     Substrates are often guided in sputter units past a so-called target, from the surface of which particles are sputtered off, which are subsequently deposited on the substrate. As the substrates can be utilized, for example, glass plates, which are transported through an inline sputter unit. These glass plates are set into a frame connected with a transport device.  
         [0004]     A device for the transport of substrates into and through vacuum treatment units, for example, is known, which comprises a bulky foot part composed of two wheel sets correlated with one track and one support bearing (DE 41 39 549 A1). The substrates to be treated are herein held by means of a rectangular substrate holder.  
         [0005]     Furthermore is known an annular substrate holder for the mounting of a round substrate plate, this substrate holder, in turn, being held by four equally distributed holding arms (DE 102 11 827 C1).  
         [0006]     If the substrates held in frames have a coefficient of thermal expansion different from that of the frames, the substrates may be covered at the margins nonuniformly and onesidedly to too high a degree. In the case of wafers this is referred to as “edge exclusion”, i.e. to a peripheral region of the wafer which is not coated.  
         [0007]     The invention therefore addresses the problem of providing a carrier for substrates, in which the substrate are not covered too thickly at the margin and the coverage on both margins is substantially equal.  
         [0008]     This problem is solved according to the present invention, which relates in part to a carrier for a substrate comprising two vertical plates and two horizontal plates. In order for the substrate not to be coated nonuniformly in its margin regions during its transport through a sputter unit, a lever arrangement is provided between the two vertical plates. The lever arrangement comprises at least one horizontal web which expands to a lesser degree under the effect of heat than the horizontal plates.  
         [0009]     The advantage attained with the invention resides in particular therein that with the aid of a lever arrangement, which exploits the effect of the difference in the coefficients of thermal expansion, the substrates to be coated are held symmetrically relative to the carrier frame.  
         [0010]     An embodiment example of the invention is shown in the drawing and will be described in further detail below. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]      FIG. 1  shows a first embodiment of the invention.  
         [0012]      FIG. 2  shows a second embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  depicts a carrier  1  for a substrate  2 , which comprises a frame with two vertical plates  3 ,  4  and two horizontal plates  5 ,  6 . The plates  3 ,  4  are comprised, for example, of titanium, while the plates  5 ,  6  are comprised, for example, of aluminum.  
         [0014]     The left end of the upper aluminum plate  5  is connected with the titanium plate  3  by means of bolts  7 ,  8 ,  9  or other connection elements.  
         [0015]     The right end of the aluminum plate  5  is not directly connected with the titanium plate  4  but rather indirectly via a small aluminum plate  10 . This small aluminum plate  10  is connected with its right end by means of three bolts  11 ,  12 ,  13  or the like with the titanium plate  4 . At ambient temperature there is a gap between the plate  4  and the aluminum plates  5 ,  6 , which is closed at sputter temperatures. Consequently,  FIG. 1  shows a carrier during sputter operation.  
         [0016]     By means of a bolt  14  or the like approximately in the center of the small aluminum plate  10  a rotatable connection is established between the small aluminum plate  10  and the right end of a web  15  of titanium. Instead of a bolt  14 , a pin, stud or the like can be utilized, which holds together two parts and makes possible their relative movement or rotational movement. There is no fixed connection between the small aluminum plate  10  and the large aluminum plate  5 . The aluminum plate  10  is only guided in the aluminum plate  5 . The left end of the titanium web  15  is rotatably connected with the lower end of a perpendicularly extending web  16  by means of a bolt  17  or the like, which does not extend through the aluminum plate  5 . A rotatable connection between this aluminum plate  5  and the upper end of web  16  is established by means of a bolt  18  or the like. The vertical web  16  does not necessarily need to comprise titanium, it can also be produced for example of steel or another metal.  
         [0017]     Via a bolt  19  or the like in the center of vertical web  16  a connection has been established between this web  16  and the right end of a horizontally extending further web  20 , not, however, with plate  5 . The left end of web  20  is directly connected with plate  5  via a bolt  21  or the like. However, a direct connection between plate  3  and web  20  could also be provided.  
         [0018]     Mirror symmetrically to the structural parts located on the upper plate  5  are also disposed the corresponding structural parts on the lower plate. Therefore, bolt  26  corresponds to bolt  14 .  
         [0019]     The small aluminum plates  10 ,  25  can each move horizontally on the large aluminum plates  5 ,  6 , since they only rest in contact on them or are guided in them.  
         [0020]     With the aid of the lever arrangements formed by webs  15 ,  16 ,  20  and  27 ,  31 ,  32 , respectively, it is possible to keep the distance between plates  3 ,  4  constant.  
         [0021]     The manner in which this is specifically achieved will be described in the following.  
         [0022]     If it is assumed that the device depicted in  FIG. 1  is brought from approximately ambient temperature to a temperature increased by approximately 220° C. as is customary during sputtering, all parts comprised of aluminum expand to a high degree, while the parts comprised of titanium expand to a lesser degree.  
         [0023]     Consequently a relative movement between the individual parts occurs, which essentially results in a relative movement between the small aluminum plates  10  and  25  with respect to the large aluminum plates  5 ,  6 . In effect, the small aluminum plates  10  and  25  pull the plate  4  relatively to the left, such that the original distance from plate  3  is maintained.  
         [0024]     With an increase of the temperature the aluminum plates  5 ,  6  expand to a high degree. The gaps previously existing between the aluminum plates  5 ,  6  and plate  4  are hereby closed. Since the horizontal titanium webs  20 ,  32  are connected with the large aluminum plates  5 ,  6  in points  21 ,  33 , these titanium webs  20 ,  32  move with the aluminum plates  5 ,  6  to the right. They therewith would rotate the webs  16 ,  31  about the pivot points  18 ,  30  in the counterclockwise direction or the clockwise direction, which are fixedly connected in these pivot points  18 ,  30  with the aluminum plates  5 ,  6 , if they were to have a coefficient of thermal expansion corresponding to the coefficients of thermal expansion corresponding to the plates  5 ,  6 . Therewith the small aluminum plates  10 ,  25  would be pushed away toward the right via the webs  15 ,  27 , i.e. they would slide over the large aluminum plates  5 ,  6 . However, points  18  and  30  themselves have shifted considerably toward the right, since they are connected with the plates  5 ,  6 . Consequently, the web  16  does not rotate in the counterclockwise direction, but rather in the clockwise direction, since point  19  relative to point  18  is retained in position by titanium web  20 , while point  18  migrates toward the right. The displacement of points  30  and  18  to the right is herein approximately three times as large as that of points  29  or  19 , respectively. In contrast, web  20 ,  32 , since it is comprised of titanium, has expanded only minimally toward the right and retains points  19  or  29  nearly in their original position.  
         [0025]     As a consequence the upper web  16  is not rotated about point  18  in the counterclockwise direction, but rather in the clockwise direction. The lower web  31  conversely is not rotated about point  30  in the clockwise direction, but rather in the counterclockwise direction.  
         [0026]     The small aluminum plates  10 ,  25  are therewith shifted to the left and over plates  5 ,  6 . Since they are coupled with plate  4 , the latter is also shifted to the left. Therewith the gap previously formed between plate  4  and the small aluminum plates  10 ,  25  is closed. With the appropriate layout of the ratios of the lengths between the points  30 ,  29  and  28 , the distance between the titanium plates  3 ,  4  can be kept constant.  
         [0027]      FIG. 2  shows a second variant of the invention, which includes a frame  40  for the transport of a substrate  2 . This frame  40  is comprised of two large horizontal aluminum plates  41 ,  42  and two vertical titanium plates  43 ,  44 . Centrally on the large aluminum plates  41 ,  42  are disposed titanium webs  45 ,  46 , which are connected with these aluminum plates  41 ,  42  by means of connection elements  47 ,  48  in their center. These titanium webs  45 ,  46  are rotatably connected at their ends with levers  53  to  56  via connection elements  49  to  52 . These levers  53  to  56  are, in turn, rotatably connected with plates  43  or  44  via connection elements  57  to  60 . Ends of the aluminum plates  41 ,  42  are also connected with these plates  43 ,  44  via connection elements  61  to  70 .  
         [0028]     When the frame  40  is heated during the sputtering, the parts comprised of aluminum expand to a greater degree than the parts comprised of titanium. This means that the aluminum plates  41 ,  42  expand horizontally to a greater degree than the titanium plates  43 ,  44  or the titanium webs  45 ,  46 .  
         [0029]     The levers  53  to  56  are hereby rotated about points  57  to  60  in the direction toward the substrate  2 . On the one hand, the aluminum plates  41 ,  42  press plates  43 ,  44  apart, on the other hand, the ends of levers  53  to  56  remain in contact on the substrate, since, due to the lesser thermal expansion of webs  45 ,  46 , these levers  53  to  56  are in effect retained in their position in their center and must rotate inwardly about points  57  to  60 .  
         [0030]     In spite of the tendency of the plates  43 ,  44  to move away from each other, the substrate  2  consequently continues to be retained through levers  53  to  56 .  
         [0031]     In the above described embodiment examples the materials titanium and aluminum were discussed. However, other materials can also be utilized. Aluminum is employed since it is relatively cost-effective. Titanium, which is significantly more expensive than aluminum, is employed since it has a lower coefficient of thermal expansion than aluminum.  
         [0032]     It is understood that the terms “vertical’ and “horizontal” can also be interchanged.