Abstract:
Apparatus for processing multiple semiconductor wafers, includes a transfer chamber, a first processing chamber mounted in fixed relation to the transfer chamber and having a first wafer-holding platform with a center, a second processing chamber mounted in adjustable relation to the transfer chamber and to the first chamber and having a second wafer-holding platform with a center, and a robot rotatably mounted within the transfer chamber and having first and second wafer-holding arms spaced parallel to each other for inserting a pair of wafers simultaneously into the first and second chambers and for placing the wafers accurately centered over the respective platforms. The spacing of the platform centers is adjusted relative to the spacing of the robot arms such that the wafers are centered and placed with a preselected degree of accuracy onto the respective platforms for efficient processing of the wafers.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to an apparatus ensuring the accurate placement of semiconductor wafers onto respective platforms (or susceptors) within reaction chambers which are precisely (and adjustably) spaced apart, the apparatus providing compensation for dimensional variations due to mechanical tolerances and reducing the effects of thermal expansion or contraction with changes in temperature.  
         BACKGROUND OF THE INVENTION  
         [0002]    Today&#39;s semiconductor circuits have features such as vias with diameters that are a small fraction of a micron, for example, only about 0.13 micron, with depths of 4 to 5 times the diameter. Such small via diameters and large depth to diameter ratios make it difficult with currently used materials (e.g., aluminum or copper) to properly metalize the vias completely down to their lower ends. Accordingly, a chemical vapor metalizing process using a highly volatile precursor compound of tungsten, such as tungsten hexaflouride (WF 6 ), is advantageously used to metalize the vias. In order to keep the tungsten being deposited on the exposed surface of the wafer from being deposited beyond and/or beneath the edge or rim of the wafer, inert gas, such as argon or argon mixed with helium, is flowed in an annular stream of the gas upward and over the rim. Flowing such a stream of inert gas, termed “edge-purging”, reduces or eliminates tungsten deposition adjacent the edge of the wafer by diluting or physically excluding the WF 6  precursor gas. For edge-purging to be fully effective, however, each wafer should be accurately centered on its respective platform.  
           [0003]    In order to increase manufacturing throughput for a given capital investment, two wafer platforms can be mounted in a processing chamber. However, with previously known apparatus the exact positions of the centers of the platforms can vary because of manufacturing tolerances or because of thermal expansion or contraction of the apparatus caused in turn by changes of temperature. Unless these dimensional variations are properly compensated for they can significantly affect the efficiency of edge-purging because of inaccurate centering of the wafers when placed on their respective platforms. The present invention provides a simple and effective way of overcoming these difficulties.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the invention, in one specific aspect thereof, there is provided an apparatus for processing semiconductor wafers. The apparatus provides for accurate placement of two or more wafers onto respective processing platforms by substantially reducing mechanical tolerance and other variations in the positions of the platforms relative to that of a wafer-handling robot.  
           [0005]    (Claim 1) From a first apparatus aspect, the present invention is an apparatus for processing multiple semiconductor wafers. The apparatus comprises a transfer chamber, first and second processing chamber, and a robot. The first processing chamber is mounted in fixed relation to the transfer chamber and has a first wafer-holding platform with a center. The second processing chamber is mounted in adjustable relation to the transfer chamber and to the master chamber and has a second wafer-holding platform with a center. The robot is rotatably mounted within the transfer chamber and has first and second wafer-holding arms spaced parallel to each other for inserting a pair of wafers simultaneously into the first and second chambers and for placing the wafers accurately centered over the respective platforms. The spacing of the platform centers is adjusted relative to the spacing of the robot arms such that the wafers are centered and placed with a preselected degree of accuracy onto the respective platforms for efficient processing of the wafers.  
           [0006]    (Claim 3) From a second apparatus aspect, the invention is an apparatus for processing multiple semiconductor wafers. The apparatus comprises a transfer chamber, first and second processing chamber, a mechanism for adjustably mounting the second chamber in relation to the first chamber and to the transfer chamber, and a robot. The first processing chamber is mounted in known relation to the transfer chamber and has a first wafer-holding platform with a center. The second processing chamber has a second wafer-holding platform with a center. The mechanism provides a plurality of position adjustments for the second chambers. The robot is rotatably mounted within the transfer chamber and has first and second wafer-holding arms spaced parallel to each other for inserting a pair of wafers simultaneously into the first and second chambers and for placing the wafers accurately centered over the respective platforms. The spacing of the platform centers are adjusted relative to the spacing of the robot arms such that the wafers are centered and placed with a preselected degree of accuracy onto the respective platforms for efficient processing of the wafers.  
           [0007]    (Claim 7) From a third aspect the invention is an apparatus for processing at least two semiconductor wafers simultaneously. The apparatus comprises a transfer chamber, a load-lock chamber adjacent the transfer chamber, first and second processing chambers, adjusting means for adjustably mounting the second chamber in relation to the first chamber and to the transfer chamber, and a robot. The first processing chamber is mounted in known relation to the transfer chamber and has a first wafer-holding platform with a center. The second processing chamber has a second wafer-holding platform with a center. The adjusting means has a bellows assembly positioned between the transfer chamber and the second chamber and provides for relative movement thereof and also provides a wafer passageway between the chambers while maintaining an hermetic seal. The robot is rotatably mounted around a center axis within the transfer chamber and has first and second wafer-holding arms spaced parallel to each other for withdrawing a pair of wafers from the load-lock chamber and inserting the pair of wafers simultaneously into the first and second chambers and for positioning both of the wafers with a preselected degree of accuracy over the respective platforms. The spacing of the platform centers is adjusted to a preselected degree of accuracy by the adjusting means relative to each other and to the spacing of the robot arms and the center axis such that the wafers are centered and placed with the preselected degree of accuracy onto the respective platforms for efficient processing of the wafers.  
           [0008]    (Claim 9) From a fourth aspect the invention is an apparatus for processing a pair of semiconductor wafers simultaneously. The apparatus comprises a transfer chamber, a load-lock chamber adjacent the transfer chamber, first and second processing chambers, mechanical means for adjustably mounting the second chamber in relation to the first chamber and to the transfer chamber, mechanical means for adjustably mounting the second chamber in relation to the first chamber and to the transfer chamber, a slit valve, and a remotely controlled robot. The first processing chamber is mounted in fixed relation to the transfer chamber and has a first wafer-holding platform with a center. The second processing chamber has a second wafer-holding platform with a center. The mechanical means supports the second chamber against the load-lock chamber in cantilever fashion and has a bellows assembly positioned between the transfer chamber and the second chamber to provide for relative movement thereof and to provide a wafer passageway between the respective chambers while maintaining an hermetic seal. The remotely controlled robot is rotatably mounted around a center axis within the transfer chamber and has first and second wafer-holding arms spaced parallel to each other for withdrawing a pair of wafers from the load-lock chamber and inserting the pair of wafers simultaneously into the first and second chambers and for positioning both of the wafers to a preselected degree of accuracy over the respective platforms. The spacing of the platform centers are adjusted by the mechanical means relative to each other and to the spacing of the robot arms and the center axis such that the wafers are centered and placed with the preselected degree of accuracy onto the respective platforms for efficient processing of the wafers.  
           [0009]    A better understanding of the invention will be gained from the following description given in conjunction with the accompanying drawings and claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic plan view, partially broken away, showing portions of an apparatus embodying features of the invention with dual chambers (one fixed and the other adjustable) for accurately processing semiconductor wafers;  
         [0011]    [0011]FIG. 2 is an exploded view in perspective showing a mechanism provided according to the invention for positioning the center of one of the dual chambers with great accuracy relative to the other and to a wafer-handling robot;  
         [0012]    [0012]FIG. 3 is a side section view taken as indicated by a line  3 - 3  in FIG. 1, showing the mechanism of FIG. 2 adjustably coupling one of the chambers of FIG. 1 to a fixed portion of the apparatus;  
         [0013]    [0013]FIG. 4 is a schematic plan view of a portion of the mechanism of FIG. 2 illustrating how a bellows (a central part of the mechanism) can be expanded or contracted to adjust the longitudinal position of the one chamber;  
         [0014]    [0014]FIG. 5 is a schematic plan view of the bellows of FIG. 2 illustrating how the bellows can be compressed at either end to adjust the sideways position of the one chamber; and  
         [0015]    [0015]FIG. 6 is a schematic side view of the bellows of FIG. 2 showing how the bellows can be compressed lengthwise along an edge to adjust the vertical position of the chamber. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Referring now to FIG. 1, there is shown a schematic plan view of an apparatus  10  embodying features of the invention, for accurately processing two or more semiconductor wafers simultaneously. The apparatus  10  comprises a transfer chamber  12 , a wafer-handling robot  14 , a first wafer-processing chamber  16 , a second wafer-processing chamber  18 , a load-lock chamber  20  (shown in dashed outline), and additional wafer-processing chambers  16   a,    18   a,    16   b,  and  18   b  (all shown in dashed outline) which may be identical to the respective chambers  16  and  18 .  
         [0017]    The chamber  16  is attached in fixed relation to an outer side of a wall  22  (one of four) of the transfer chamber  12 . The chamber  18 , on the other hand, is attached to the wall  22  by a mechanism, indicated at  24 , provided by the invention and which permits the chamber to be adjusted in position in the “X”, “Y” and “Z” directions relative to the transfer chamber  12 , and to the robot  14 . The mechanisms  24  will be described in detail hereinafter.  
         [0018]    The chamber  16 , which for convenience is termed the “master” chamber, contains a wafer-supporting platform  26  (shown as a dashed line circle) with a center at  28 , and the chamber  18 , termed the “slave” platform, contains a wafer-supporting platform  30  (shown as a dashed line circle) with a center at  32 . The mechanism  24  permits precise adjustment of the slave chamber  18  and the exact position of the platform center  32  by a small angle indicated at  34  lying in a horizontal plane (i.e., the plane of FIG. 1) and by a small amount longitudinally, indicated by an arrow  36  lying within the horizontal plane. As will be explained hereinafter, the position of the slave chamber  18  may also be adjusted slightly in the vertical direction. Thus, the exact position in the “X”, “Y”, and “Z” directions of the platform center  32  can be precisely set relative to the position of the platform center  28  and the robot  14 . Except for their different modes of attachment to the wall  22  of the transfer chamber  12 , the master and slave chambers  16  and  18  may be identical to each other.  
         [0019]    The robot  14  (well known in the art) has a first horizontal arm  40  which at its outer end holds in precise alignment on the arm a semiconductor wafer  42  having a center  44 . The robot  14  also has a second horizontal arm  46  which holds a second wafer  48  with its center  50  precisely aligned on the arm. As shown in FIG. 1 the robot arms  40  and  46  lie on and are extendable along respective longitudinal, parallel axes  52  and  54 . The axis  52  intersects the platform center  28  and the wafer center  44 . Similarly, the axis  54  intersects the platform center  32  (the position of this center having been adjusted accordingly) and the center  50  of the wafer  48 . Thus when the robot arms  40  and  46  are extended to insert the wafers  42  and  48  into the respective chambers  16  and  18  and onto the platforms  26  and  30 , the center  44  of the wafer  42  will be exactly aligned over the center  28  of the platform  26 , and the center  50  of the wafer  48  will be exactly aligned over the center  32  of the platform  30 .  
         [0020]    After having determined the angular and longitudinal coordinates of the center  28  of the platform  26  relative to the center axis  56  of the robot  14 , which coordinates can be measured with great accuracy, these values are entered as data in a computer (not shown but well known in the art) which controls the robot. Thereafter, whenever the robot  14  is extended, its arm  40  inserts a wafer into the master chamber  16 , and that wafer (i.e., the wafer  42 ) will be positioned over the platform  26  so that the platform center  28  and the wafer center  44  are exactly aligned. Also, by virtue of the present invention, the other arm  46  of the robot  14 , which is simultaneously extended into the slave chamber  18 , positions the respective wafer  48  so that its center  50  is exactly aligned with the center  32  of the platform  30 .  
         [0021]    The robot  14  is rotatable around a vertical center  56  within the transfer chamber  12  so that pairs of wafers can be inserted into or withdrawn from the respective processing chambers and/or the load-lock chamber. The wafers are precisely positioned on their respective robot arms  40  and  46 . The transfer chamber  12  is hermetically sealable by a respective pair of slit valves  60  in each of the walls of the chamber. These valves  60  are remotely operated in conjunction with the robot  14  to permit its arms  40  and  46  to be inserted into selected ones of the load-lock and processing chambers. Some portions of the apparatus  10  (which are well known) are not shown herein. The general construction and operation of the apparatus  10  may be like that shown in U.S. Pat. No. 5,855,681, which is incorporated herein by reference.  
         [0022]    Referring now to FIG. 2, there is shown in exploded relation the mechanism  24  provided in accordance with the invention for adjusting to a preselected degree of accuracy the position of the slave chamber  18  and the center  32  of its platform  30  relative to the center  28  of platform  26  and to the robot  14 . The mechanism  24  comprises a front plate  64 , a center bellows assembly  66 , a rear plate  68 , a pair of springs  70  (only one is shown), set screws  72  (only one of which is shown), and fastening bolts  74  (only one of which is shown). The bellows assembly  66  comprises a front flange  76 , a rear flange  78 , and an accordion-pleated, thin metal bellows  80  (shown here in dashed line) sealed between the front and rear flanges. The flanges  76  and  78  are fastened and sealed to the respective plates  64  and  68  and provide an hermetic seal around a horizontal passage, indicated at  82 , through the plates  64  and  68  via which passage a wafer may be inserted into the slave chamber  18 . The bellows assembly  66 , while maintaining hermetic seal, permits movement of the front plate  64  relative to the rear fixed plate  68 , and thus adjustment of the exact position of the slave chamber  18 , as will further be explained shortly. The top of the front plate  64  has a rear shoulder  84 , which when the mechanism  24  is fastened together, hooks over and bears down upon a top ledge  86  on the rear plate  68 .  
         [0023]    Referring next to FIG. 3, there is shown a cross-section taken generally along the line  3 - 3  in FIG. 1, with portions broken away, showing schematically the mechanism  24  as fastened between the transfer chamber  12  and the slave chamber  18 . The transfer chamber  12  (as illustrated here but not FIG. 1) has a top lid  90 , and the slave chamber  18  has a top lid  92  and a wall  94  with the wafer passage-way  82  extending through it. The transfer chamber  12  is hermetically sealable from the slave chamber  18  by a respective slit valve  60  (shown schematically). The plate  68  of the mechanism  24  is fastened and sealed in fixed relation to the wall  22  of the transfer chamber  12  by bolts and hermetic seals (not otherwise identified). Similarly the plate  64  of the mechanism  24  is fastened and sealed in fixed relation to the wall  94  of the slave chamber  18  by bolts and hermetic seals (not otherwise identified). Lastly, the bellows assembly  66 , with its front and rear flanges  76  and  78  and bellows  80 , is fastened and hermetically sealed between the plates  64  and  68  by bolts and sealing rings (not otherwise identified). Thus the wafer passage-way  82  is hermetically sealed against gas leakage into or out of it even though the plate  64  is moveable relative to the plate  68 .  
         [0024]    As is shown in FIG. 3, the plate  64  has its top shoulder  84  overhanging the top ledge  86  of the plate  68 . Fastened by screws  95  beneath the shoulder  84  is a longitudinal member  96  which rests on the ledge  86  along a horizontal bearing line indicated at  98 . The plate  64 , along with the slave chamber  18 , hangs on the plate  68 , being, in effect, hinged to it along the bearing line  98 . The ledge  86  has a front step  100  which prevents the member  96  from falling off of the ledge  86 . As will be explained in greater detail shortly, by incrementally expanding or contracting the bellows  80 , the slave chamber  18  can be adjusted in the “X”, “Y” and “Z” directions relative to the master chamber  16  (see FIG. 1) and to the transfer chamber  12  and the robot  14 . The “Z” direction may be represented by an arc  102  illustrated in FIG. 3, the arc  102  indicating a slight amount of swinging of the plate  64  toward or away from the plate  68  during adjustment of the position of the slave chamber  18 . Movement along the arc  102  (i.e., the “Z” direction) permits the slave chamber  18  to be leveled and to lie in the same horizontal plane as the master chamber  16 .  
         [0025]    Positioned near the two lower corners of the plates  64  and  68  are respective ones of the compression springs  70  (see also FIG. 2). One of these springs  70  is shown in dotted outline in FIG. 3 and is positioned within a cavity  104  in the plate  64 . A plug  106  screwed through the plate  68  compresses the spring  70  by a desired amount to counterbalance the weight of the slave chamber  18 . An identical plug  106  and spring  70  (not shown) near the opposite corner of the plates  64  and  68  are adjusted so that both springs  70  exert the same balancing forces against the plate  64 .  
         [0026]    Positioned near each spring  70  is a respective one of the set screws  72  (also see FIG. 2). One of these screws  72  is adjusted to bear against the plate  64  so that a desired gap indicated at  108 , between the plates  64  and  68  is established adjacent a corner of the plates. A similar gap (not shown and not necessarily the same width) is likewise established by another set screw  72  (not shown) at the opposite corner of the plates  64  and  68 . The settings of the various set screws  72  establishes the “X”, “Y”, and “Z” dimensional adjustments of the position of the slave chamber  18 . After the set screws  72  have been adjusted, to desired settings, respective ones of the fastening bolts  74 , one of which is shown in dotted outline in FIG. 3, are tightened and the plate  64  held immobile relative to the plate  68 , so that the dimensional adjustments described above remain intact.  
         [0027]    Referring now to FIG. 4 there is shown a plan view schematically illustrating how the mechanism  24  with its bellows  80  can be expanded or contracted, as indicated by the double-headed arrow  36  (see also FIG. 1) to provide dimensional adjustment of what may be conveniently termed the “Y” position of the slave chamber  18 . Here the plates  64 ,  68  are illustrated as parallel to each other.  
         [0028]    Referring now to FIG. 5, there is shown a plan view schematically illustrating how the mechanism  24  with its bellows  80  can be compressed on either end (the right end shown compressed here). This provides for relative angular movement of the plates  64 ,  68  as indicated by the arc  34  (see also FIG. 1). This movement may be conveniently termed an adjustment in the “X”, position of the slave chamber  18 .  
         [0029]    Referring now to FIG. 6, there is shown a side view schematically illustrating how the mechanism  24  with its bellows  80  can be compressed along its length (the length along the bottom of the bellows  80  being shown as compressed here). This provides for relative angular movement of the plates  64 ,  68  as indicated by the arc  102  (see also FIG. 3). This movement may be conveniently termed adjustment in the “Z” position of the slave chamber  18 .  
         [0030]    An apparatus  10 , with it mechanism  24  and master and slave chambers  16  and  18 , has been built and shown to provide a suitably high degree of accuracy in the centering of semiconductor wafers during processing employing “edge purging”. The chambers  16  and  18  easily accommodated wafers of 200 mm size. The slave chamber  18  was adjustable in position by about one-eighth inch (0.125 in.) in each of the “X”, “Y” and “Z” directions. Being physically separate units, the chambers  16  and  18  had respective platform centers not appreciably affected by relative thermal expansion, contrary to the case with a single chamber having dual wafer platforms (as known in prior art).  
         [0031]    The above description is intended in illustration and not in limitation of the invention. Various changes and modifications in the embodiment illustrated may occur to those skilled in the art and can be made without departing from the spirit or scope of the invention as set forth in the accompanying claims. For example, wafers of different sizes from that given may be processed in the apparatus  10 , and the position adjustments of the slave chamber  18  may be different from those given.