Patent Publication Number: US-2005121313-A1

Title: Method and apparatus for executing plural processes on a microelectronic workpiece at a single processing station

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      Not Applicable  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      The fabrication of microelectronic components from a workpiece, such as a semiconductor wafer substrate, polymer substrate, etc., involves a substantial number of processes. There are a number of different processing operations performed on the workpiece to fabricate the microelectronic component(s). Such operations include, for example, material deposition, patterning, doping, chemical mechanical polishing, electropolishing, and heat treatment.  
      Material deposition processing involves depositing thin layers of electronic material to the surface of the workpiece (hereinafter described as, but not limited to, a semiconductor wafer). Patterning provides removal of selected portions of these added layers. Doping of the semiconductor wafer is the process of adding impurities known as “dopants” to the selected portions of the wafer to alter the electrical characteristics of the substrate material. Heat treatment of the semiconductor wafer involves heating and/or cooling the wafer to achieve specific process results. Chemical mechanical polishing involves the removal of material through a combined chemical/mechanical process while electropolishing involves the removal of material from a workpiece surface using electrochemical reactions.  
      Numerous processing devices, known as processing “tools”, have been developed to implement the foregoing processing operations. These tools take on different configurations depending on the type of workpiece used in the fabrication process and the process or processes executed by the tool. One tool configuration, known as the Equinox(R) wet processing tool and available from Semitool, Inc., of Kalispell, Mont., includes one or more workpiece processing stations that utilize a workpiece holder and a process bowl or container for implementing wet processing operations. Such wet processing operations include electroplating, etching, cleaning, electroless deposition, electropolishing, etc.  
      In accordance with one configuration of the foregoing Equinox(R) tool, the workpiece holder and the process bowl are disposed proximate one another and function to bring the semiconductor wafer held by the workpiece holder into contact with a processing fluid disposed in the process bowl and forming a processing chamber.  
      Conventional workpiece processors have utilized various techniques to bring the processing fluid into contact with the surface of the workpiece in a controlled manner. For example, the processing fluid may be brought into contact with the surface of the workpiece using a controlled spray. In other types of processes, such as in partial or full immersion processing, the processing fluid resides in a bath and at least one surface of the workpiece is brought into contact with or below the surface of the processing fluid.  
     BRIEF SUMMARY OF THE INVENTION  
      An apparatus for processing a microelectronic workpiece is set forth. The apparatus comprises a workpiece support adapted to hold the microelectronic workpiece and a processing container adapted to receive the microelectronic workpiece held by the workpiece support. A drive mechanism is connected to drive the processing container and the workpiece support holding the microelectronic workpiece relative to one another so that the microelectronic workpiece may be moved to a plurality of workpiece processing positions. At least two chemical delivery systems are employed. A first chemical delivery system is used to provide at least one processing fluid to the processing container for application to the microelectronic workpiece when the microelectronic workpiece is in a first one of the plurality of workpiece processing positions while a second chemical delivery system is used to provide at least one processing fluid to the processing container for application to the microelectronic workpiece when the microelectronic workpiece is in a second one of the plurality of microelectronic workpiece processing positions. The apparatus also includes at least two chemical collector systems. A first chemical collector system is used to assist in at least partially removing spent processing fluid provided by the first chemical delivery system while the microelectronic workpiece is in the first one of the plurality of workpiece processing positions. Similarly, a second chemical collector system is used to assist in at least partially removing spent processing fluid provided by the second chemical delivery system from the processing container while the microelectronic workpiece is in the second one of the plurality of microelectronic workpiece processing positions. In accordance with one embodiment, the apparatus is particularly adapted to execute an immersion process, such as electroplating, and a spraying process, such as an in-situ rinse.  
    
    
     BRIEF DESCRIPTION-OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a perspective view of a reactor constructed in accordance with one embodiment of the present invention.  
       FIG. 2  is a cross-sectional view of the reactor illustrated in  FIG. 1 .  
       FIG. 3  is a further cross-sectional view of the reactor illustrated in  FIG. 1 .  
       FIGS. 4 and 5  illustrate the orientation of the processing head and corresponding workpiece during a workpiece loading operation.  
       FIGS. 6-9  are cross-sectional views of the reactor of  FIG. 1  illustrating the microelectronic workpiece at various processing positions within the processing container.  
       FIGS. 10 and 11  are cross-sectional views of the reactor of  FIG. 1  illustrating the microelectronic workpiece at various angular positions within the second processing portion of the processing container so as to vary the position of initial contact of a stream of processing fluid with a surface of the microelectronic workpiece.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      With reference to  FIGS. 1-3 , there is shown a reactor assembly  20  for processing a microelectronic workpiece, such as a semiconductor wafer  25  or the like. Generally stated, the reactor assembly  20  is comprised of a reactor head, shown generally at  30 , that includes one or more components used to support the workpiece  25 . Additionally, the reactor assembly  20  includes a corresponding reactor container, shown generally at  35 , that receives one or more processing fluids from one or more chemical delivery systems.  
      The reactor head  30  of the reactor  20  is preferably comprised of a stationary assembly  40  and, optionally, a rotor assembly  45  that is driven by a corresponding rotor motor  47 . Rotor assembly  45  may be configured to receive and carry an associated wafer  25  or like workpiece, position the workpiece in a process-side down orientation within reactor container  35 , and to rotate or spin the workpiece. The rotor assembly  45  and/or reactor head  30  may also be used to elevate the workpiece after initial contact with a processing liquid so that only a meniscus of the processing fluid contacts the side of the workpiece that is to be processed. This also falls within the ambit of an immersion process.  
      The reactor head  30  is mounted on a lift/rotate apparatus  50  which is configured to rotate the reactor head  30  from an upwardly-facing disposition in which it receives the wafer to be plated, to a downwardly facing disposition in which the surface of the wafer to be processed is positioned so that it may be brought into contact with a processing fluid, such as an electroplating solution, in reactor container  35 . A robotic arm (not illustrated), which may include an end effector, is typically employed for placing the workpiece  25  in position on the rotor assembly  45 , and for removing the processed wafer from within the rotor assembly  45  after processing is complete.  
      Lift/rotate apparatus  50  is preferably capable of moving the workpiece  25  to a plurality of positions with respect to reactor container  35 . More particularly, the lift/rotate apparatus  50  may be capable of moving the reactor head  30  and the corresponding workpiece  25  in a vertical fashion toward and away from the reactor container  35 . Such vertical motion may be directed by a programmable control system  55  or the like. Programmable control system  55  may also be used to adjust the spin rate of the rotor motor  47 .  
      Although lift/rotate apparatus  50  of the disclosed embodiment has the ability to rotate reactor head  30  for presentation of the workpiece  25  by a corresponding robot in a process-side up orientation, it will be recognized that apparatus  50  need not have such rotation abilities. Rather, the workpiece  25  may be presented to the reactor head  30  by the corresponding robot in a process-side down orientation. In such instances, rotation of the workpiece to the process-side down orientation may take place on the corresponding robot or another apparatus within the overall processing system.  
      The reactor container  35  includes a first processing portion, shown generally at  60 , that is configured to execute a first process in which one or more processing fluids are delivered to treat at least one surface of the workpiece  25 . In the illustrated embodiment, for exemplary purposes, first processing portion  60  of container  35  is configured to execute an electroplating process. However, the first processing portion  60  of container  35  may be alternatively configured to execute any number of different processes. Such processes include, but are not limited to, immersion processes, vapor processes, spray processes, gaseous processes, etc.  
      Pursuant to executing an electroplating process in the first processing portion  60 , container  35  is configured to provide a flow of an electroplating solution to one or more surfaces of the workpiece  25 . To this end, container  35  includes an interior container  65  having an inlet  70  through which a flow of electroplating solution is provided. The electroplating solution provided through inlet  70  flows through the interior container  65  and overflows therefrom about an upper weir  75  into an exterior overflow region  77 . This type of reactor assembly is particularly suited for effecting electroplating of semiconductor wafers or like workpieces, in which an electrically conductive, thin-film layer of the wafer is electroplated with a blanket or patterned metallic layer while in a process-side down orientation.  
      Within the interior container  65  there is an anode assembly, shown generally at  80 , having one or more anodes  85  that is in the electrical contact with the electroplating solution (although the illustrated embodiment utilizes a single anode  85 ). The one or more anodes  85  are electrically connected to a source of electroplating power (not shown) through one or more electric conductive structures. The anode assembly  80  may be constructed in the manner set forth in PCT Application No. PCT/US99/15430, entitled “REACTOR VESSEL HAVING IMPROVED CUP, ANODE AND CONDUCTOR ASSEMBLY”, filed Jul. 9, 1999 (Attorney Docket No. SEM4492P0200PC; Corporate Docket No. P98-0017PCT), the teachings of which are hereby incorporated by reference. An alternative reactor container suitable for immersion processing is set forth in U.S. Ser. No. 60/143,769, entitled “workpiece processor having improved processing chamber”, filed Jul. 12, 1999 (Attorney Docket No. SEM4492P0831US; Corporate Docket No. P99-0034).  
      In those instances in which the reactor is to be used in an electroplating process, the rotor assembly  45  of head  30  may include one or more cathode contacts that provide electroplating power to the surface of the wafer. In the illustrated embodiment, a cathode contact assembly is shown generally at  90 . This cathode contact assembly may be constructed in accordance with the teachings of PCT Application No. PCT/US99/15847, entitled “METHOD AND APPARATUS FOR COPPER PLATING USING ELECTROLESS PLATING AND ELECTROPLATING”, filed Jul. 12, 1999 (Attorney Docket No. SEM4492P0571PC; Corporate Docket No. P99-0025PCT). Although the various contact configurations illustrated in that patent application provide electroplating power directly to the side of the wafer that is to be processed, it will be recognized that backside contact may be implemented in lieu of front side contact when the substrate is conductive or other means are provided to electrically connect the backside of the workpiece with the process side thereof. The contact assembly  90  may be operated between an open state that allows the wafer to be placed on the rotor assembly  45 , and a closed state that secures the wafer to the rotor assembly and brings the electrically conductive components of the contact assembly  85  into electrical engagement with the surface of the wafer that is to be plated.  
      Processing container  35  also includes a second processing portion, shown generally at  95 , that is adapted to execute a further process on one or more surfaces of the microelectronic workpiece  25 . In the illustrated embodiment, the second processing portion  95  is adapted to execute a process in which a processing fluid is provided at the downward facing surface of the workpiece  25 . To this end, one or more nozzles  100  are provided in the second processing portion  95  and are directed toward the workpiece  25 .  
      It is often desirable to at least partially inhibit mixing of the processing chemicals used in different processing steps. Reactor container  35  therefore includes separate collection systems for collecting spent processing fluids (e.g., processing fluids that have contacted one or more surfaces of the workpiece  25 ). With respect to the illustrated embodiment, the processing fluids used in processes carried out in the first processing portion  60  of reactor container  35  are liquids that overflow the weir  75  of the interior container  65  and enter the overflow region  77 . After entering the overflow region  77 , the processing chemicals are removed through one or more outlets that are in fluid communication with the overflow region  77 . The fluid exiting from the reactor container  35  subsequently undergoes disposal, recycling, constituent dosing, etc.  
      In those instances in which the processing fluid used in the first processing portion  60  is in a gaseous or vapor state, overflow region  77  may be connected to a vacuum source. Spent processing fluid may then be removed as it overflows the weir  75 . As above, process fluid exiting from the reactor container  35  may subsequently undergo disposal, recycling, constituent dosing, etc.  
      A further collection system is used for collecting spent processing fluids employed in processes carried out in the second processing portion  95 . The further collection system, generally designated at  105 , is provided in or proximate the second processing portion  95 . In the illustrated embodiment, the first processing portion  60  of reactor container  35  is disposed vertically below the second processing portion  95  and, further, is open to the second processing portion  95 . These factors complicate the collection process as it is to be executed by the further collection system. For example, if a liquid is used as the processing fluid in the second processing portion  95  and delivered to a surface of the microelectronic workpiece  25 , liquid drops can readily enter and adversely effect the first processing portion  60 . Although small amounts of the liquid may be tolerated in the first processing portion  60 , the substantial amounts of the liquid that are often introduced during spray processing or like can and often will reduce the effectiveness of the processing that takes place in the first processing portion  60 .  
      To overcome the foregoing problems, the further collection system  105  is in the form of one or more fluid channels, shown generally at  110 , that are disposed at the inner periphery of reactor container  35 . As shown, the fluid channels  110  are located in the second processing portion  95  proximate the position of the workpiece  25  as it undergoes processing in the second processing portion  95 . Each fluid channel, as illustrated in  FIGS. 2 and 3 , may be defined by a splash wall  115  and a retainer wall  120 . The splash wall  115  and retainer wall  120  may each be disposed at an angle with respect to horizontal. The manner in which this further collection system functions will become clearer in connection with the operational description below.  
      In operation, the reactor head  30  is elevated and rotated by the lift/rotate apparatus  50  to a loading position, illustrated in  FIG. 4 , that is located above the reactor container  35 . While in this position, a workpiece  25  is placed upon rotor assembly  45  with the side of the workpiece that is to be electroplated facing upward. The contact assembly  90  of the rotor assembly  45  is then actuated to grip the workpiece  25  and secure it therewith. This actuation also causes the contact assembly  90  to make electrical contact with the workpiece  25  to supply power for the electroplating operation. As noted above, however, rotation of the reactor head  30  need not take place in apparatus in which the workpiece  25  is rotated to a process-side down position prior to introduction of the workpiece  25  to the rotor assembly  45 .  
      Once the workpiece  25  has been secured with the rotor assembly  45 , the lift/rotate apparatus  50  is directed by the control system  55  to rotate the reactor head  30  so that the surface of the workpiece that is to be processed is faced downward, as illustrated in  FIG. 5 . With the workpiece  25  in this state, the control system  55  directs the lift/rotate apparatus  50  to drive the rotor assembly  45  and the corresponding workpiece to a first workpiece processing position within the reactor container  35 . This first workpiece processing position may be located in either the first processing portion  60  or the second processing portion  95  of the reactor container  35 . For exemplary purposes, it will be assumed that processing will first take place in the first processing portion  60 . As such, the lift/rotate apparatus  50  is directed by the control system  55  to take the necessary steps to bring the workpiece  25  to the position illustrated in  FIG. 6 . In this position, at least the lower surface of the workpiece  25  is brought into contact with a flow of electroplating solution provided at the upper portion of interior container  65 . Electroplating power is then provided to both the workpiece  25  and the anode  85  to affect electroplating of the surface. During the electroplating process, spent processing fluid is collected within the overflow region  77  and removed from the reactor container  35 .  
      Once electroplating is completed in the first processing portion  60 , the control system  55  directs the lift/rotate apparatus  50  to move the workpiece  25  to an intermediate position, designated generally at  57  of  FIG. 7 . While at this position, the workpiece  25  is spun at a high rotation rate to fling off a bulk portion of any excess electroplating solution. This reduces drag out and waste of the electroplating solution.  
      After the bulk portion of the excess electroplating solution has been flung off, the control system  55  directs the lift/rotate apparatus  50  to move the workpiece  25  to a second processing position. Here, in the exemplary process, the second processing position is located in the second processing portion  95  of the reactor container  35 . The lift/rotate apparatus  50  thus drives the workpiece  25  to the position illustrated in  FIG. 7 . In this position, one or more further processing chemicals are provided from a chemical supply system to contact one or more surfaces of the workpiece  25 . With respect to the specific embodiment disclosed herein, a liquid stream of a processing fluid, such as water that may or may not include additives, is provided through the one or more nozzles  100  to contact the lower surface of the workpiece  25  that has been electroplated. As the liquid stream is directed toward the workpiece surface, the rotor assembly  45  and corresponding workpiece  25  are rotated at a high rotation rate so that the liquid impinging on the workpiece surface is flung radially outward therefrom under the influence of centripetal acceleration. The liquid flung in this manner is collected by the further collection system  105 . More particularly, the liquid flung in this manner contacts the splash wall  115  corresponding to the channel  110  that is immediately adjacent the lower surface of the workpiece  25 , and proceeds downward therealong into the corresponding channel  110 . Retainer wall  120 , being disposed at an angle with respect to horizontal, assists in retaining the accumulated liquid within the corresponding channel  110 . One or more outlets  125  are placed in fluid communication with the channel  110  to allow the spent processing liquid to be removed from the reactor container  35 . As such, the spent processing liquid used in the second processing portion  95  is effectively removed from the reactor container  35  by the further collection system  105 , thereby minimizing the amount of the spent liquid that enters the first processing portion  60 .  
      As can be seen in the FIGUREs, a plurality of collection channels  110  may be used. In accordance with one embodiment of the present invention, all of the plurality of collection channels  110  can be connected to a common drain. Such a configuration is particularly useful in those instances in which a single processing fluid is employed for processing the workpiece when it is in the second processing portion  95 . However, it may be desirable to process the workpiece  25  using more than one type of processing fluid in the second processing portion  95  while collecting the processing fluids separately. To this end, programmable control system  55  directs the lift/rotate apparatus  50  to a plurality of positions within the second processing portion  95 . Here, those positions differ with respect to their vertical position within the reactor container  35 .  
      A unique manner of delivering a fluid stream to the surface of a workpiece is illustrated in connection with  FIGS. 7-9  As illustrated, the workpiece  25  is moved to a plurality of processing positions within the second processing portion  95 . With reference to  FIG. 7 , the reactor head  30  is driven by the control system  55  to place the workpiece  25  at a first processing position within the second processing portion  95 . In this position, nozzle  100  directs a stream of processing fluid  130  toward a central portion of the lower surface of the workpiece  25  at an upward angle. As the stream of processing fluid  130  is provided to the surface of workpiece  25 , the control system  55  directs the reactor head  30  to move the workpiece  25  sequentially through the positions illustrated in  FIGS. 7 through 9 . Such movement through these positions can be executed in accordance with a controlled continuous velocity, a controlled velocity profile, or in discrete steps. As the workpiece  25  is moved to these various processing positions, the stream of processing fluid  130  from nozzle  100  is directed at a substantially fixed point in space. Since the stream  130  is fixed at an acute angle as the workpiece  25  is moved, the radial position at which the stream  130  contacts the workpiece  25  changes and approaches the periphery of the surface of workpiece  25 . This is particularly useful when this apparatus configuration and method of operation are used in connection with electroplating operations, since the stream  130  may be comprised of deionized water and effectively “chase off” electroplating solution from surface of microelectronic workpiece  25 .  
      As can be seen in the foregoing figures, a plurality of channels  110  are employed. Each channel  110  corresponds to one or more processing positions assumed by the workpiece  25  as it is processed in the second processing portion  95 . In those instances in which a single processing fluid is used in the second processing portion  95 , the channels  110  may be connected together and tied to a single outlet  135 . However, it is also possible to provide different processing fluids to the surface of the workpiece  25  at different processing positions within the second processing portion  95 . In such operations, channels  110  may be used to separately collect each of the processing fluids and provide them to separate outlets.  
      An alternative method (or additional method, if used in conjunction with the method described above) of delivering a stream of processing fluid to the downward facing surface of the workpiece  25  is illustrated in  FIGS. 10 and 11 . In accordance with this latter method, reactor head  30  is driven to a fixed position within second processing portion  95  by the lift/rotate apparatus  50  under the direction of control system  55 . A stream of processing fluid is provided through one or more nozzles  100 . Control system  55  directs lift/rotate apparatus  50  to rotate reactor head  30  through a plurality of angles so that the stream of processing fluid  130  makes initial contact with the lower surface of workpiece  25  at a plurality of portions thereof sequentially as a function of time. Again, workpiece  25  may be spun at a high rotation rate to fling off spent processing fluid into the fluid channels  110  of the further collection system  105  as the stream of processing fluid  130  is delivered to the surface of workpiece  25 . Rotation of the reactor head  30  and corresponding workpiece  25  may be executed in accordance with a controlled motion profile, such as a controlled continuous or variable rotation rate, between the starting and ending angular positions. Alternatively, the controlled motion profile may be in the form of discrete angular steps between the starting and ending angular positions.  
       FIGS. 10 and 11  illustrate starting and ending angular positions that may be employed, with  FIG. 10  illustrating the starting angular position and  FIG. 11  illustrating the ending angular position. In this illustrated embodiment, the stream of processing fluid  130  is initially directed to a central portion of the workpiece  25  as in  FIG. 10 . Reactor head  30  and the corresponding workpiece  25  are then rotated through one or more angular positions to reach the ending angular position shown in  FIG. 11  in which the stream of processing fluid  130  is directed for initial contact with a peripheral portion of the workpiece  25 .  
      Although, as noted above, the present invention is suitable for use in a wide range of microelectronic workpiece processes, it is particularly well-suited for use in microelectronic workpiece electroplating. After plating a wafer, the surface of the wafer that has been exposed to the plating solution is wetted with plating solution. The contact assembly and corresponding barrier seal are also wetted at the seal interface with the wafer. This condition is difficult to solve due to conflicting requirements. The wafer needs to remain wetted until the plating solution can be neutralized by deionized water or another neutralizer. The contact seal, on the other hand, needs the residual solution removed or dried to prevent migration of the plating solution to the sealed area, and ultimately behind it, during product removal. Simply trying this residual plating solution is not an option to to the corrosive/oxidizing effect drying has on the plated film. Such problems are addressed by rinsing the wafer and seal interface before the wafer is removed from the reactor. Also, it has been found to be desirable to occasionally rinse the seal and electrical contact in the absence of a wafer to assist in preventing a buildup of copper salts.  
      Numerous modifications may be made to the foregoing system without departing from the basic teachings thereof. Although the present invention has been described in substantial detail with reference to one or more specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.