Abstract:
A wafer transfer robot for use in multi-chambered semiconductor device manufacturing equipment includes a base, at least one extendable and retractable arm rotatably supported by the base at one side thereof, and a blade coupled to the other side of each arm. The blade includes a plate having an upper surface dedicated to support a wafer, and a wafer guide disposed at the top of the plate. The wafer seats a wafer on the plate and confines the wafer to an orientation in which a flat zone or notch of the wafer faces in a predetermined direction. Therefore, the wafer can be prevented from slipping to an abnormal position on the blade and a pre-alignment of the wafer can be maintained. Thus, the wafer transfer robot helps to sustain the production yield.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to semiconductor device manufacturing equipment. More particularly, the present invention relates to multi-chambered semiconductor device manufacturing equipment and to a wafer transfer robot for transferring a wafer between chambers of the equipment. 
         [0003]    2. Description of the Related Art 
         [0004]    Semiconductor devices are being constantly developed along with the rapid development of information telecommunications technology and the increase in popularity of information processing devices such as personal computers. In this respect, today&#39;s semiconductor devices must operate at high speeds and have the capacity to store large amounts of data. Thus, techniques in the fabricating of semiconductor devices are being studied and developed with an aim toward maximizing the integration density, reliability, and response speed, etc., of the devices. 
         [0005]    In general, a semiconductor device has several thin layers of circuit patterns stacked on a pure silicon wafer. A plurality of individual processes, such as thin film deposition, photolithography, ashing, etching, and ion implantation processes are repetitively and sequentially performed on the wafer to fabricate the circuit patterns. In general, these sequences of processes are performed in two different ways. One way is batch (or multi-wafer) processing in which several wafers are processed at the same time. The other way is single-wafer processing in which wafers are processed one at a time. 
         [0006]    Batch processing provides a high throughput because about up to 50 wafers can be processed at a time. On the other hand, single-wafer processing is generally more time consuming but allows for each process to be carried out very precisely. However, multi-chamber semiconductor device manufacturing equipment has been developed to carry out single-wafer processing with high throughput. 
         [0007]    Typical multi-chamber semiconductor device manufacturing equipment comprises at least one process chamber in which an ion implantation or etching process is performed, a transfer chamber that communicates with the process chamber, a wafer transfer robot disposed in the transfer chamber, a load-lock chamber that is mounted on one side of the transfer chamber and into which a plurality of wafers are loaded and unloaded en bloc, and an alignment chamber that communicates with the transfer chamber and aligns the wafers for their transfer by the transfer robot. 
         [0008]    The wafer transfer robot rapidly and sequentially transfers individual wafers between the load-lock chamber, the alignment chamber, and the process chamber so that the multi-chamber semiconductor device manufacturing equipment can provide a high throughput even though the wafers are each processed one at a time in the process chamber(s), i.e., even though the equipment carries out single-wafer processing. 
         [0009]    The wafer transfer robot of the conventional semiconductor device manufacturing equipment includes a body that is supported on the ground and has a rotary drive unit, an arm coupled on one side thereof to the body so as to be rotated by the rotary drive unit, and at least one blade disposed on the other end of the arm. The arm is made up of links that are articulated such that the arm can be extended and retracted with respect to the body. Thus, the arm moves the blade forward or backward when the arm is extended or retracted. Furthermore, the blade includes a metallic plate oriented to support a wafer horizontally. More specifically, the metallic plate has the shape of a fork comprising at least one prong. The fork is longer than the diameter of the wafer supported by the blade. Accordingly, the blade supports the center of the wafer. 
         [0010]    Furthermore, the blade has an arcuate wafer guide step which extends along part of the outer peripheral edge of the blade and protrudes a predetermined height from the surface of the blade on which the wafer rests. The wafer guide step extends around enough of the wafer to prevent the wafer from sliding in a horizontal direction while the wafer is being transferred. For example, the wafer guide step confronts the outer circumferential surface of the wafer at the side of the blade coupled to the arm and at the distal end of the blade, i.e., at the tip(s) of the prong(s). Furthermore, the wafer guide step has an inclined inner side surface that guides a wafer loaded onto the blade and seats the wafer on the blade. 
         [0011]    However, the wafer mounted on the blade gains inertia when the blade is rapidly rotated or moved forward or backward by the arm. In addition, the coefficient of friction between the wafer and the blade is low because the blade is metallic. Consequently, the wafer slides up along the inclined surface of the wafer guide step when the blade stops rotating or moving, thereby falling off of the blade or assuming an abnormal position on the blade. In either of these cases the wafer can be damaged, which reduces the production yield. 
         [0012]    Furthermore, the wafer guide step has a radius of curvature equal or similar to that of the wafer in order to guide the outer circumferential surface of the wafer and seat the wafer on the blade. However, the wafer can rotate relative to the blade when the blade comes to a stop because, again, the coefficient of friction between the wafer and the blade is low. Thus, the wafer loses its alignment with the site or chuck (wafer support) disposed in the processing chamber to which the wafer is being transferred by the transfer robot. As a result, the wafer can be processed incorrectly, whereby the production yield is reduced. 
       SUMMARY OF THE INVENTION 
       [0013]    Therefore, an object of the present invention is to provide wafer transfer robot that does not adversely affect the production yield of a manufacturing process carried out by equipment that employs the wafer transfer robot. 
         [0014]    A more specific object of the present invention is to provide a wafer transfer robot having a blade that includes a plate on which a wafer being transferred is supported, and which prevents a wafer supported by the blade from falling from the blade or from slipping to an abnormal position on the blade especially when the blade is rapidly rotated or accelerated in forward or backward directions. 
         [0015]    Another object of the present invention is to provide a wafer transfer robot, in which a wafer does not slide or rotate relative to the blade, such that a wafer can be transferred to or from a designated position without its pre-aligned state being altered. 
         [0016]    According to one aspect of the present invention, there is provided a wafer transfer robot which comprises a base, at least one extendable and retractable arm rotatably supported by the base at one side thereof, and a blade coupled to the other side of each said arm, wherein the blade includes a plate having an upper surface dedicated to support a wafer, and a wafer guide disposed at the top of the plate. The wafer guide has at least one guide surface projecting above the upper surface of the plate and which is complimentary to an arcuate edge and to either a flat zone or a notched portion of a wafer. 
         [0017]    According to another aspect of the present invention, there is provided semiconductor device manufacturing equipment which comprises at least one load-lock, a wafer alignment apparatus that aligns wafers, at least one process apparatus, a transfer chamber to which each of the chambers of the load-lock, alignment and process apparatuses are commonly connected, and a wafer transfer robot disposed within the transfer chamber, wherein the wafer transfer robot includes a base, at least one arm coupled to the base at one side thereof, and a blade coupled to the other side of each arm, wherein the blade includes a plate having an upper surface dedicated to support a wafer, and a wafer guide disposed at the top of the plate. The wafer guide has at least one guide surface projecting above the upper surface of the plate and which is complimentary to an arcuate edge and to either a flat zone or a notched portion of a wafer. 
         [0018]    Thus, the wafer guide is configured to confine a wafer supported on the plate to an orientation in which a flat zone or notch of the wafer faces in a predetermined direction. In particular, the wafer guide of the wafer transfer robot may include a wafer guide step having an arcuate vertical guide surface whose radius of curvature corresponds to that of a wafer, and a wafer orientation guide pin having a linear or pointed vertical guide surface that corresponds to a flat zone or notch of a wafer. The wafer orientation guide pin may also be mounted at an end of the plate so as to be rotatable about an axis extending perpendicular to the upper surface of the plate. Furthermore, the wafer orientation guide pin and the wafer guide step may each have an inclined guide surface that guides the wafer onto the plate when the wafer is lowered towards the blade. The blade may also include at least one pad at the upper surface of the plate so as to contact a lower surface of the wafer supported by the pate. The pad is of a material, such as rubber, which will provide a high coefficient of friction with the wafer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above and other objects, features and advantages of the present invention will become more apparent to those of ordinary skill in the art by referring to the following detailed description of the preferred embodiments thereof made with reference to the attached drawings in which: 
           [0020]      FIG. 1  is a schematic plan view of semiconductor device manufacturing equipment according to the present invention; 
           [0021]      FIG. 2  is a perspective view of the wafer transfer robot of the equipment shown in  FIG. 1 , according to the present invention; 
           [0022]      FIG. 3  is a sectional view of the wafer transfer robot; 
           [0023]      FIG. 4  is a broken away perspective view of the rotary driver of the wafer transfer robot; and 
           [0024]      FIG. 5  includes side and plan views of the blade of the wafer transfer robot. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings. Note, like numbers designate like elements throughout the drawings. 
         [0026]    As illustrated in  FIGS. 1 and 2 , semiconductor device manufacturing equipment according to the present invention includes a plurality of load-locks  100  each comprising a chamber accommodating a cassette  104  in which a plurality of wafers  102  are mounted, an alignment apparatus  200  which aligns wafers  102  transferred from the load-lock chambers  100 , at least one process apparatus  300  for performing a semiconductor device manufacturing process, a transfer chamber  400  to which the process apparatus  300 , the alignment apparatus  200 , and the load-locks  100  are commonly connected, and a wafer transfer robot  150  disposed in the transfer chamber  400 . The wafer transfer robot  150  has at least one blade  110  that transfers a wafer  102  between the chambers of the load-lock and process apparatus  100  and  300 . 
         [0027]    For example, the wafer transfer robot  150  may have two blades  110  facing in opposite directions. Such a robot may be referred to hereinafter as a “two-blade wafer transfer robot”. The two-blade wafer transfer robot  150  transfers a wafer  102  aligned in the chamber of the alignment apparatus  200  to the front of a process chamber  300  using one blade  110 , and transfers a wafer  102  that has been processed in a process chamber  300  into the chamber of a load-lock  100  using the other blade  110 . On the other hand, the wafer transfer robot  150  may have only one blade  110 . Such a wafer transfer robot will be referred to hereinafter as a “one-blade transfer robot”. The one-blade wafer transfer robot  150  first unloads a wafer  102  processed in the chamber of a process apparatus  300 , and then transfers a wafer  102  aligned in the chamber of the alignment apparatus  200  to a process chamber  300 . Accordingly, the one-blade wafer transfer robot  150  takes at least twice as long as the two-blade wafer transfer robot  150  to transfer an equal number of wafers  102  throughout corresponding pieces of the semiconductor device manufacturing equipment. Reference will be made with respect to a two-blade transfer robot in the description that follows. 
         [0028]    Referring now to  FIG. 2  and  FIG. 3 , the wafer transfer robot  150  also has a base  140  that is supported on the ground, and a plurality of arms  160 . The base  140  includes a tubular casing  147  and a rotary drive unit  148  disposed at the bottom of the casing  147 . One side of each of the arms  160  is coupled to the body  140  so that the arms  160  can be rotated in their entirety by the rotary drive unit  148 . Also, each of the arms  160  includes a pair of wings  130  having first ends coupled to the rotary drive unit  148 , and a plurality of extenders  120 . The extenders  120  of each arm  160  have first ends that are pivotally connected to second ends of the wings  130  of the arm  160 , respectively. Second ends of the extenders  120  of each arm  160  are pivotally connected to a respective blade  110 . The wings  130  of each arm  160  can be rotated relative to each other by the rotary drive unit  148  to move the blades  110  forward or backward. In particular, the extenders  120  move the blade  110  forward or backward when the wings  130  are rotated in opposite directions by the rotary drive unit  148 . 
         [0029]    For instance, the blades  110  are in a home position when the wings  130  of each arm  160  extend parallel to each other but in opposite directions from the body  140 , as shown in  FIG. 2 . In this case, the blades  110  are moved forward from the home position, i.e., are extended from the body  140 , when the wings  130  of each arm  160  are rotated at the same time toward one another. On the other hand, the blades  110  are moved backward when the wings  130  of each arm  160  are rotated at the same time away from each other. 
         [0030]    Next, the rotary drive unit  148  and its connection to the arms  160  will be described in more detail with reference to  FIGS. 3 and 4 . 
         [0031]    The base  140  of the wafer transfer robot  150  has a plurality of rings  142 , e.g., an upper ring  142   a  and a lower ring  142   b,  disposed one above the other on the base  140 . The first ends of the two wings  130  of each arm  160  are attached to the rings  142   a,    142   b,  respectively. That is, a first wing  130   a  of each arm  160  is attached to the upper ring  142   a,  and a second wing  130   b  of the arm is attached to the lower ring  142   b.  Also, the wings  130  have horizontal portions extending from the second ends thereof that are connected to the extenders  120 . As shown best in  FIG. 3 , the horizontal portions of the wings  130  are situated at the same or similar level as the extenders  120 . Moreover, one of the wings  130  of each arm  160  has a downward bend to account for the difference in height between the rings  142 . 
         [0032]    The rings  142  are supported by bearings  144  so as to be rotatable relative to the casing  147  of the base  140 . The base  140  also includes a first shaft  146   a  for rotating the upper ring  142   a,  and a second shaft  146   b  for rotating the lower ring  142   b.  The second shaft  146   b  surrounds the first shaft  146   a.    
         [0033]    The rotary drive unit  148  includes a reversible upper motor  148   a  connected to the lower portion of the first shaft  146   a  for rotating the first shaft  146   a,  and a reversible lower motor  148   b  connected to the lower portion of the second shaft  146   b  for rotating the second shaft  146   b.  The upper and lower motors  148   a  and  148   b  are supported on a plurality of mounts  149  inside the casing  147 , respectively. Each of the upper and lower motors  148   a  and  148   b  may be a stepping motor. 
         [0034]    In addition, discs  145  are mounted to the first and second shafts  146   a  and  146   b,  respectively. Each disc  145  has permanent magnets spaced at predetermined intervals along the outer circumferential surface thereof. Each ring  142  has permanent magnets spaced along its inner circumferential surface. The inner and outer circumferential surfaces of the discs  145  and the rings  142  face each other, respectively. The magnetic fields of the permanent magnets are established in the rotational direction of the upper and lower rings  142   a  and  142   b.  Thus, the upper and lower rings  142   a  and  142   b  are rotated by magnetic forces when the first and second shafts  146   a  and  146   b  are rotated, respectively. Therefore, the upper and lower motors  142   a  and  142   b  of the wafer transfer robot  150  can be operated to rotate the wings  130  of each arm  160  in the same or different directions, thereby moving the blades  110  forward or backward via the extenders  120 . 
         [0035]    The blades  110  will now be described in more detail with reference to  FIGS. 2 and 5 . Each blade  110  includes a wafer support plate  111  formed of at least one member for supporting a wafer  102 . The plate  111  has an upper (horizontal) surface parallel to the direction in which the extenders  120  and hence, the blades  110 , move forward or backward. Each blade  110  also has a pivot (not shown), such as a pin, connecting the plate  111  to the second end of an extender  120 , and a bearing (also not shown) interposed between the pin and the second end of the extender  120 . Thus, the plate  111  can rotate relative to the second ends of the extenders  120  when the extenders  120  are moved forward or backward. 
         [0036]    The shape of the plate  111  is such as to support the wafer  102  symmetrically about the center of the wafer  102  (the wafer may have a flat zone or notch at or in one side of the wafer  102  and thus, the center of the wafer may not coincide with the geometrical center of the circular outline of the wafer  102 ). For example, the plate  111  can have the shape of a palm that supports the center of the wafer  102 . In this case, there is only a slight possibility that the wafer  102  will slide relative to the plate  111  because of the wide area of contact between the lower surface of the wafer  102  and the plate  111 . Alternatively, the plate  111  can have the shape of a fork having prongs supporting the wafer  102  at both sides of the center of the wafer  102 . In this case, the plate  111  allows the blade  110  to move forward or backward when lift pins (not shown) are used to remove or the wafer from or transfer the wafer onto the blade  110 . Such lift pins are commonly found in the wafer support of a process apparatus. The lift pins can be inserted between the prongs into contact with the lower surface of the wafer  102 . Then, the blade  110  can be moved backward so that the wafer  102  can be transferred from the blade  110  to the lift pins while maintaining its horizontal orientation. The unloading of a wafer  102  from the blade  110 , the loading of a wafer  102  onto the blade  100 , and the transferring of a wafer  102  by the blade  110  can all be carried out stably because the blade supports a wafer with its center located at the geometrical center of the plate  111  of the blade  110 . 
         [0037]    In any case, the wafer transfer robot  150  must be operated below a certain speed if a wafer  102  being transferred is to be stably and accurately in loaded or unloaded into or from a chamber of the equipment. That is, a wafer  102  supported on the blade  110  would attempt to rotate or slide relative to the wafer support plate  111  under its own inertia when the blade  110  accelerates. If this were allowed to occur, the orientation of the wafer would change, i.e., the pre-alignment of the wafer  102  would be ruined. 
         [0038]    However, each blade  110  of the wafer transfer robot  150  according to the present invention has a wafer guide  170  that fixes the wafer  102  in place in a predetermined orientation on the wafer support plate  111 . In particular, the wafer guide  170  cooperates with a flat zone or notch at or in the edge of the wafer  102  prevent the wafer  120  from sliding relative to the wafer support plate  111  and thereby maintain the orientation (alignment) of the wafer. 
         [0039]    The wafer guide  170  will now be described in more detail with reference to  FIGS. 2 and 5 . The wafer guide  170  includes a wafer guide step  112  having a vertical arcuate surface protruding upwardly from the plate  111  around a portion of the wafer  102  to seat the wafer  102  on the plate  111  at a position where the center of the wafer  102  coincides with the center of the plate  111 , and an inclined guide surface extending to the arcuate vertical surface so as to guide the wafer  112  into position on the plate  111 . Furthermore, the wafer guide step  112  prevents the wafer  102  supported on the plate  111  from sliding horizontally relative to the plate  111  while the wafer is being transferred. 
         [0040]    In addition, the blade  110  includes at least one pad  114  disposed on the plate  111  so as to contact the lower surface of a wafer  102  supported on the plate  111 . The at least one pad  114  has a higher coefficient of friction with the wafer  102  than the plate  111 . For example, the pad  114  is formed of rubber. In the embodiment of  FIGS. 2 and 5 , four pads  114  are formed on the prongs of the plate  111  and can prevent the wafer  102  from sliding in any direction relative to the plate  111 . 
         [0041]    Thus, the wafer transfer robot  150  according to the present invention can prevent a wafer  102  supported on the plate  111  from escaping from the blade  110  or resting abnormally on the blade  110  even when the blade  110  is rotated or moved forward or backward rapidly. 
         [0042]    Furthermore, the wafer guide  170  further comprises at least one wafer orientation guide pin  116  disposed on the plate  111 . In the embodiment of  FIGS. 2 and 5 , one portion of the wafer guide step  112  is disposed at the end of one of the prongs of the plate  111 , and a wafer orientation guide pin  116  is disposed at the end of the other prong of the plate  111  across from the wafer guide step  112 . The wafer orientation guide pin  116  is designed for use with a wafer having a flat zone or a notch. More specifically, the wafer orientation guide pin  116  has a linear vertical surface conforming to the flat zone of a wafer or a pointed vertical surface that conforms to a notch in the edge of a wafer. The vertical surface of the wafer orientation guide pin  116  engages the wafer at the flat zone or in the notch of the wafer to orient the wafer such that the flat zone or notch of the wafer  102  faces in one direction. For example, the flat zone of the wafer  102  shown in  FIG. 5  is oriented by the wafer orientation guide pin  116  at an angle of about 45° in a clockwise direction with respect to the direction in which the blade  110  moves forward. In addition, the wafer orientation adjustment guide pin  116  can have an inclined guide surface similar to that of the wafer guide step  112 . Thus, in the case in which the wafer has a notch, the wafer orientation guide pin has a shape similar to that of a three-sided pyramid. In any case, the wafer orientation pin  116  and the wafer guide step  112  cooperate to guide and fix the wafer  102  in place on the plate  111  and thereby maintain the orientation of the wafer. Therefore, the wafer transfer robot  150  according to the present invention can transfer a pre-aligned wafer  102  without the wafer  102  sliding or rotating on the blade  110 . 
         [0043]    Furthermore, the wafer orientation guide pin  116  is rotatably supported by a shaft  118  at the end of the plate  111  of the blade  110 . When the wafer is loaded onto the plate  111 , the wafer orientation guide pin  116  is positioned such that the flat zone or notch of the wafer  102  can be located at basically an arbitrary position on the plate  111 . Then, the wafer orientation guide pin  116  is rotated about the axis of the shaft  118  and brought into engagement with the wafer  102  so that the wafer  102  is fixed in position with the flat zone or notch of the wafer  102  facing in one direction. 
         [0044]    For example, although not illustrated, a push lever is used to move the wafer orientation guide pin  16  into contact with the wafer  102  after the wafer has been loaded onto the plate  111  of the blade  110 . With respect to the embodiment shown in  FIG. 5 , the push lever is used to rotate the wafer orientation guide pin  16  in a clockwise direction about the longitudinal axis of the shaft  118  and thereby bring the wafer orientation guide pin  116  into contact with the flat zone of the wafer  102 . As a result, the wafer  102  is fixed in place as aligned. 
         [0045]    At this time, the wafer orientation adjustment pin  116  pushes the wafer  102 , at the flat zone (or notch as the case may be), against the wafer guide step  112  disposed across from the wafer orientation guide pin  116 . Thus, the wafer  102  is grasped between the wafer orientation guide pin  116  and the wafer guide step  112 . For this reason, external forces can not move the wafer  102  off of the plate  111  of the blade  110 . Furthermore, the wafer transfer robot  150  according to the present invention can transfer the wafer at an inclination in contrast to the conventional wafer transfer robot which is only capable of transferring a wafer  102  horizontally. 
         [0046]    According to the present invention as described above, the wafer transfer robot  150  can transfer a wafer without the wafer escaping from the blade  110  or becoming abnormally positioned on the blade  1100  even when the blade  110  is rapidly rotated or accelerated in forward or backward directions. Furthermore, the wafer transfer robot  105  can transfer a pre-aligned wafer without the alignment of the wafer changing during its transfer. Therefore, the present invention helps to maximize the production yield 
         [0047]    Finally, the invention has been described in connection with the preferred embodiments thereof. However, it is to be understood that the present invention is not limited to the disclosed embodiments. On the contrary, modifications and alternative arrangements of the disclosed embodiments will be apparent to those of ordinary skill in the art. For example, although the wafer orientation guide pin  116  has been described as being disposed at the terminal end of the plate  111  of the blade  110 , the present invention is not so limited. Rather, the wafer orientation guide pin  116  may be disposed at the edge of the plate  111  adjacent to the extenders  120 . Therefore, various changes to the disclosed embodiments are seen to be within the true spirit and scope of the invention as defined by the appended claims.