Abstract:
A system for processing a workpiece includes a process head assembly and a base assembly. The process head assembly has a process head and an upper rotor. The base assembly has a base and a lower rotor. The base and lower rotor have magnets wherein the upper rotor is engageable with the lower rotor via a magnetic force created by the magnets. The engaged upper and lower rotors form a process chamber where a semiconductor wafer is positioned for processing. Process fluids for treating the workpiece are introduced into the process chamber, optionally while the processing head spins the workpiece. Additionally, air flow around and through the process chamber is managed to reduce particle adders on the workpiece.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This Application is a Continuation-In-Part of U.S. patent application Ser. No. 10/690,864, filed Oct. 21, 2003 and now U.S. Pat. No. 6,930,046, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/202,074, filed Jul. 23, 2002 and now U.S. Pat. No. 6,794,291, which is a Continuation of U.S. patent application Ser. No. 09/437,711, filed Nov. 10, 1999, now U.S. Pat. No. 6,423,642, which is a Continuation-In-Part and U.S. National Phase of International Patent Application No. PCT/US99/05676, filed Mar. 15, 1999, published in English and designating the United States, and claiming priority to U.S. Patent Application No. 60/116,750, filed Jan. 22, 1999. Priority to these applications is claimed under 35 U.S.C. §§ 119, 120 and/or 365. The above-identified Applications are also incorporated herein by reference. 

   TECHNICAL FIELD 
   The invention relates to surface preparation, cleaning, rinsing and drying of workpieces, such as semiconductor wafers, flat panel displays, rigid disk or optical media, thin film heads or other workpieces formed from a substrate on which microelectronic circuits, data storage elements or layers, or micro-mechanical elements may be formed. These and similar articles are collectively referred to herein as a “wafer” or “workpiece.” Specifically, the present invention relates to a workpiece processor and system for treating semiconductor workpieces. 
   BACKGROUND OF THE INVENTION 
   The semiconductor manufacturing industry is constantly seeking to improve the processes and machines used to manufacture microelectronic circuits and components, such as the manufacture of integrated circuits from wafers. The objectives of many of these improved processes and machines include: decreasing the amount of time required to process a wafer to form the desired integrated circuits; increasing the yield of usable integrated circuits per wafer by, for example, decreasing contamination of the wafer during processing; reducing the number of steps required to create the desired integrated circuits; improving the uniformity and efficiency of processes used to create the desired integrated circuits; and reducing the costs of manufacture. 
   As the semiconductor industry advances particle “adder” specifications, the number and size of the permitted particulate contamination in the manufacture of semiconductor wafers is continuously being reduced. Existing machines are not sufficient for future particle specifications. 
   Further, in the processing of wafers, it is often necessary to subject one or more sides of the wafer to a fluid in liquid, vapor or gaseous form. Such fluids are used to, for example, etch the wafer surface, clean the wafer surface, dry the wafer surface, passivate the wafer surface, deposit films on the wafer surface, remove films or masking materials from the wafer surface, etc. Controlling how the processing fluids are applied to the wafer surfaces, reducing the potential for cross contamination of the processing fluids, and effectively cleaning or rinsing process fluids from process chamber surfaces are often important to the success of the processing operations. 
   SUMMARY OF THE INVENTION 
   A new wafer processing system has been invented that provides significant improvements in manufacturing microelectronic and similar devices. The new system reduces particle contamination. As a result there are fewer defects in the end products. This reduces the total amount of raw materials, process fluids, time, labor and effort required to manufacture microelectronic devices. Accordingly, the new wafer processing system of the present invention significantly increases manufacturing yields. 
   A unique workpiece processor design has been invented that significantly reduces cross contamination of process fluids. The unique design also greatly increases the ability to exhaust vapor or fumes and drain process fluids from the process chamber during processing of a semiconductor wafer. Further, the processor of the present invention utilizes a relatively simple, magnetic rotor engagement mechanism that reduces variability of vibration affects caused by variations in manufacturing techniques from one processor to another. As a result of these design improvements, the effects of wafer processing is more consistent from one workpiece processor to the next, and high manufacturing quality standards and increased efficiencies are achieved. 
   In one embodiment, the wafer processing system of the present invention provides a plurality of workpiece stations for plating, etching, cleaning, passivating, depositing and/or removing films and masking materials from a workpiece surface. The system includes a robot, which is moveable between the workpiece stations and moves the workpiece from one station to another. At least one of the workpiece stations includes a workpiece processor having an upper rotor and a lower rotor engageable to form a workpiece process chamber. A magnetic force between repulsing magnets is utilized to maintain contact between the rotors during operation of the processor. This unique process chamber design reduces vibrations, which have been found to be a major contributor to particulate contamination, and also reduces the chances of process fluids leaking onto the surface of processed wafers, which can result in defects or failure of the microelectronic end products. 
   The wafer processing system of the present invention has also been designed to increase air flow through the workpiece processor during processing. Better air flow management reduces particle contamination and increases overall processing efficiency. As a result, less time, materials and energy is consumed. Particularly, the processor of the present invention has air flow passageways in the process head, which draws ambient air from the mini-environment surrounding the processor, into the process head, and out through the bottom of the processor. Further, annular channels formed in the base and the upper rim of the base relieve pressure build up in the process chamber. During operation, openings in the upper rim of the base receive “blow-by” fluids. The annular channels bleed the “blow-by” fluids off to an exhaust port, relieving pressure build up. Moreover, an air aspirator is connected to an annulus positioned below the motor in the process head. The aspirator sucks any gaseous fluids that may come from the air flow passageways in the process head or the annular channels in the base. Additionally, a central opening in the process head and upper rotor, and a process fluid nozzle in the base which extends upwardly through an opening in the lower rotor and is connected to a snorkel permits air to be drawn directly into the workpiece processor during operation. As a result of these design improvements, air flow in the process chamber is greatly enhanced, and more uniform processing and increased efficiencies are achieved. 
   Other features and advantages of the invention will appear hereinafter. The features of the invention described above can be used separately or together, or in various combinations of one or more of them, with no single feature essential to the invention. The invention resides as well in sub-combinations of the features described. The process chamber can be used alone, or in a system with robotic automation and various other process chambers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a workpiece processing system according to the present invention. 
       FIG. 2  is a top plan view of the workpiece processing system shown in  FIG. 1 , with components removed for purpose of illustration. 
       FIG. 3  is a perspective view of a workpiece processor according to one embodiment of the present invention. 
       FIG. 4  is a top view of the workpiece process chamber shown in  FIG. 3 . 
       FIG. 5  is a cross-sectional view of the workpiece processor shown in  FIG. 4  taken along dashed line A—A. 
       FIG. 6  is a cross-sectional view of the workpiece processor shown in  FIG. 4  taken along dashed line B—B. 
       FIG. 7  is a cross-sectional view of the workpiece processor shown in  FIG. 4  taken along dashed line C—C. 
       FIG. 7A  is an enlarged partial view of the area of the processor designated A in  FIG. 7 . 
       FIG. 8  is a perspective view of a process head assembly according to the present invention. 
       FIG. 9  is a top view of the process head assembly shown in  FIG. 8   
       FIG. 10  is a cross-sectional view of the process head assembly shown in  FIG. 9  taken along dashed line A—A. 
       FIG. 11  is a perspective view of a bottom portion of a process head assembly according to the present invention. 
       FIG. 12  is a perspective view of a top portion of a base assembly according to the present invention. 
       FIG. 13  is a top view of the base assembly shown in  FIG. 12 . 
       FIG. 14  is a cross-sectional view of the base assembly shown in  FIG. 13  taken along dashed line A—A. 
       FIG. 15  is a cross-sectional view of the base assembly shown in  FIG. 13  taken along dashed line B—B. 
       FIG. 16  is a cross-sectional view of the base assembly shown in  FIG. 13  taken along dashed line C—C. 
       FIG. 17A  is a top perspective view of an upper rotor according to one embodiment of the present invention. 
       FIG. 17B  is a cross-sectional view of the upper rotor illustrated in  FIG. 17A . 
       FIG. 17C  is a bottom perspective view of the upper rotor illustrated in  FIGS. 17A and 17B . 
       FIG. 18A  is a top perspective view of a lower rotor according to one embodiment of the present invention. 
       FIG. 18B  is a cross-sectional view of the lower rotor illustrated in  FIG. 18A . 
       FIG. 18C  is a bottom perspective view of the lower rotor illustrated in  FIGS. 18A and 18B . 
       FIG. 19A  is a top perspective view of an upper rotor according to another embodiment of the present invention. 
       FIG. 19B  is a cross-sectional view of the upper rotor illustrated in  FIG. 19A . 
       FIG. 19C  is a bottom perspective view of the upper rotor illustrated in  FIGS. 19A and 19B . 
       FIG. 20A  is a top perspective view of a lower rotor according to another embodiment of the present invention. 
       FIG. 20B  is a cross-sectional view of the lower rotor illustrated in  FIG. 20A . 
       FIG. 20C  is a bottom perspective view of the lower rotor illustrated in  FIGS. 20A and 20B . 
       FIG. 21A  is a top perspective view of a head ring of a process head assembly according to the present invention. 
       FIG. 21B  is a cross-sectional view of the head ring illustrated in  FIG. 21A . 
       FIG. 21C  is an enlarged partial view of the area of the head ring designated A in  FIG. 21B . 
   

   DETAILED DESCRIPTION 
   As shown in  FIGS. 1–3 , a processing system  10  has an enclosure  15 , a control/display  17 , and an input/output station  19  and a plurality of processing stations  14 . Workpieces  24  are removed from carriers  21  at the input/output station  19  and processed within the system  10 . 
   The processing system  10  includes a support structure for a plurality of processing stations  14  within the enclosure  15 . At least one processing station  14  includes a workpiece processor  16  and an actuator  13  for opening and closing processor  16 . The processor  16  of the present invention is designed to be utilized in a processing system  10 , for example, as disclosed in pending U.S. Patent Application Ser. No. 60/476,786, filed Jun. 6, 2003, and U.S. Pat. Nos. 6,900,132 and 6,930,046. 
   These U.S. patents and application are incorporated herein by reference. System  10  may include only a plurality of processors  16  or it may include other processing modules, in addition to one or more processors  16 , such as could be configured to perform a variety of functions including but not limited to electrochemical processing, etching, rinsing, and/or drying. 
   The system  10  in  FIG. 2  is shown having ten process stations  14 , but any desired number of processing stations  14  may be included in the enclosure  15 . The processing station support preferably includes a centrally located, longitudinally oriented platform  18  between the processing stations  14 . One or more robots  26  having one or more end-effectors  31  move within the enclosure  15  for delivering workpieces  24  to and from various processing stations  14 , and to load and unload workpieces  24  into and out of the process stations  14 . In a preferred embodiment, the robot  26  moves linearly along a track  23  in the space  18 . A process fluid source and associated fluid supply conduits may be provided within enclosure  15  below the platform  18  in fluid communication with a workpiece processor  16  (shown in  FIG. 3 ) and other processing stations  14 . 
     FIGS. 3–11  illustrate a workpiece processor  16  according to the present invention. The processor  16  comprises a process head assembly  28  and a base assembly  30 . The head assembly  28  is comprised of a process head  29 , a head ring  33 , an upper rotor  34 , a fluid applicator  32  and a motor  38 . The base assembly  30  is comprised of a mounting base  40 , a lower rotor  36  and a bowl mount  43 . The head assembly  28  can be moved vertically to engage with and separate from the base assembly  30 . The head assembly  28  and the base assembly  30  form a process chamber  37  within which the upper  34  and lower  36  rotors are positioned. 
   Turning specifically to  FIGS. 5–11 , a process fluid applicator  32  extends upwardly from a central portion of the head assembly  28  and extends downwardly through a sleeve  96  into the head assembly. Air inlet  140  and process fluid inlets  92 ,  94  are positioned within the sleeve  96 . The air inlet  140  and the process fluid applicator  32  run downwardly through central openings in the process head  29 , the head ring  33  and the upper rotor  34 . Process fluid supply lines (not shown) are connected to the upwardly extending portion of the process fluid applicator  32  for delivering process fluids into the workpiece process chamber. The motor  38  is positioned in the head  29  and is coupled to the upper rotor  34 . During operation, the motor  38  spins the upper rotor  34 . The head ring  33  mounts the upper rotor  34  and the motor  38  within the head  29 . An automated actuator  13  is attached to the head assembly  28  and moves the process head assembly  28  from an open position, where a workpiece may be loaded into and removed from the process chamber  37  by robot  26 , to a closed position where the workpiece will be processed. As will be explained more fully below, the head assembly  28  has a plurality of air inlets and passageways that contribute to the improved air flow management of the present invention. 
   The base assembly  30  lower rotor  36  has an engagement ring  110  with three tabs  114  which cooperate with a slotted mounting member  144  positioned at the bottom of the base  40  to attach the lower rotor  36  to the base  40 . The tabs  114  of the engagement ring  110  cooperate with the slots of the mounting member  144  to create a bayonet connection. Positioned within the base  40  is at least a first annular magnet  42 . The lower rotor  36  also includes at least one second magnet  44 . It should be understood, that instead of using single annular magnets in the base  40  and lower rotor  36  a plurality of non-annular magnets may also be used. The first  42  and second  44  magnets are adjacent to one another and have a like polarity. By utilizing magnets having a like magnetic field or polarity, the first  42  and second  44  magnets repel one another, causing the lower rotor  36  to be forced upwards from the base  40  by a magnetic force. When the head and base assemblies  28  and  30  are separated, the magnetic force of the magnets  42 ,  44  pushes the lower rotor  36  away from base  40  causing the tabs  114  of the engagement ring  110  to firmly engage the mounting member  144  of the base, thus providing the desired bayonet connection. 
   When the head and base assemblies are to be engaged, the actuator  13  lowers the head assembly  28  until the upper rotor  34  contacts the lower rotor  36 . Upon further force from the actuator  13 , the upper rotor  34  pushes down on the lower rotor  36  and against the repulsion force created by the magnets  42 ,  44  until the head ring  33  seats on the base as shown in  FIG. 7A  at  33 A. When the head ring  33  seats on the base, the contact between the tabs  114  of the engagement ring  110  and the mounting member  144  is broken, and the lower rotor  36  is free to spin with the upper rotor  34 . With the head ring  33  and base  40  in the positions shown in  FIGS. 5–7A , with the lower rotor free to spin with the upper rotor, the repulsion force created by the magnets  42 , 44  maintains the contact between the upper and lower rotors until the head assembly is raised for loading/unloading the processor. 
   Turning to  FIGS. 5–7  and  12 – 16 , the base  40  includes an annular plenum  80  which has several (e.g., four) drains  82 . The drains  82  are pneumatically actuated via a poppet valve  84  and actuator  86 . Each drain  82  is provided with a fitting connector  88  to provide separate paths for conducting processing liquids of different types to appropriate systems (not shown) for storage, disposal, or recirculation. Accordingly, cross contamination of process fluids is minimized. As best shown in  FIGS. 5–7 ,  18 A–C and  20 A–C, the lower rotor  36  has a skirt  48 , which extends downwardly into annular plenum  80  and encourages process fluids to flow into annular plenum  80  and through the drains  82 . 
   Still referring to  FIGS. 5–7 ,  18 A–C and  20 A–C, the lower rotor  36  has a plurality of pins extending upwardly from its surface. First, the lower rotor  36  includes a plurality of stand-off pins  50 . When the workpiece  24  is loaded into the process chamber  37 , the workpiece  24  initially sits on the stand-off pins  50 . The lower rotor  36  also includes a plurality of alignment pins  52 , which align and center the workpiece  24  in the x-y plane when the workpiece  24  is loaded into the process chamber  37 . The alignment pins  52  extend farther away from the surface  150  of the lower rotor  36  than the stand-off pins  50  do, preventing the workpiece  24  from being misaligned in the process chamber  16 . Finally, the lower rotor  36  includes at least one, and preferably a plurality of engagement pins  54 . The engagement pins  54  preferably having a beveled end to enhance coupling with the upper rotor  34  (as explained below) and an annular gasket or O-ring  56  formed from a compressible material to create a flexible contact with the upper rotor  34 . 
   Turning to  FIGS. 5–7 ,  17 A–C and  19 A–C, the upper rotor  34  includes a plurality of stand-off pins  120  and countersunk bores  46 . During operation, and best shown in  FIGS. 5–7 , the workpiece  24  (not shown) is contained between the stand-off pins  120  of the upper rotor  34  and the stand-off pins  50  of the lower rotor  36 . Workpiece process chamber  37  is formed between the inner surface  148  of the upper rotor  34  and an inner surface  150  of the lower rotor  36 . The stand-off pins  50 ,  120  do not clamp the workpiece  24  between them, but instead contain the workpiece within a desired clearance, allowing the workpiece  24  to slightly “clock,” i.e., float within the desired clearance, during processing. This prevents the workpiece  24  from being pinched and accidently damaged and allows a greater surface area of the workpiece  24  to be treated. In a preferred embodiment, there is a 0.02 inch clearance between stand-off pins  50 ,  120 , which permits the workpiece  24  to be “clocked” during processing. This arrangement allows substantially the entire surface of the workpiece  24  to be treated, even the surface area which would otherwise be covered by the stand-off pins  50 ,  120 . 
   Referring specifically to  FIG. 5 , as the upper rotor  34  engages the lower rotor  36 , the beveled end of the engagement pins  54  are inserted into a corresponding one of the plurality of bores  46  (shown in  FIG. 17C ) in the upper rotor  34 . The annular, compressible gasket or O-ring  56  enhances contact between the upper rotor  34  and the lower rotor  36  and acts as a vibration dampener when the process chamber  16  is in use. 
   While the general configuration of the upper  34  and lower  36  rotors is as described above, the specific configuration may vary depending on the desired process to be carried out in the process chamber  16 . For example, FIGS.  17 A–C and  18 A–C show the upper  34  and lower  36  rotors utilized in a process for removing polymer or a masking material from a wafer surface. In this preferred embodiment, the rotor configurations conform to the general description provided above. As shown in  FIGS. 17A–C , however, the upper rotor  34  is segmented or provided with notches  160  to allow process fluids to more freely exit the process chamber  37 . 
   However, it may be preferred to employ slight variations to the rotor configurations described above for a different process. For example, the rotor configurations for a process commonly known as “backside bevel etch” are disclosed in FIGS.  19 A–C and  20 A–C. Generally, in a “backside bevel etch” process, a chemical solution (e.g., hydrofluoric acid) is provided to etch, or selectively remove, metal or oxide layers from the backside and/or peripheral edge, i.e., the bevel edge, of the wafer. During this process, while the backside and bevel are being supplied with the chemical solution, the top side of the wafer is being supplied with an inert gas or deionized water rinse, or an alternate processing solution. After etching, the etched side and preferably both sides of the wafer are supplied with deionized water rinse, spun to remove fluids, and dried with heated nitrogen. A detailed explanation of semiconductor etching processes, including the “backside bevel etch” process is disclosed in U.S. Pat. No. 6,632,292, assigned to the assignee of the present invention, and incorporated herein by reference. 
   In a preferred embodiment, the upper rotor  34  utilized for a “backside bevel etch” process is disclosed in  FIGS. 19A–C . The upper rotor  34  includes a process fluid passageway  108  that communicates with an annulus  146  formed in the inner surface  148  of the upper rotor  34 . Turning to  FIGS. 20A–C , the lower rotor  36  preferred for use in the “backside bevel etch” process includes a sealing member  118  that runs circumferentially around the outer perimeter of the lower rotor  36 . Preferably, the sealing member  118  is formed from a compressible material. When the upper  34  and lower  36  rotors are engaged, the sealing member  118  deforms and creates a contact face seal between the rotors. The contact face seal is not a complete seal. That is, even with the contact face seal, “leaks” are provided to allow draining of the process chamber  37 . The magnetic force from magnets  42 ,  44  keep the lower rotor  36  and upper rotor  34  engaged and the contact seal in place during processing. During the “backside bevel etch” process, the acidic process fluid applied to the backside of the wafer wraps around the periphery or bevel edge of the wafer onto a portion of the top side of the wafer. As a result, the acidic process fluid is forced into the annulus  146  formed in the inner surface  148  of the upper rotor  34  by the inert gas being applied to the top side of the wafer, and is vented out through the process fluid passageway  108  in the upper rotor  34 . 
   Turning to  FIGS. 21A–C , and as shown in  FIG. 7A , the head ring  33  includes a rim  162  and a vertical cylindrical alignment surface  164 . When the head assembly  28  and base assembly  30  are closed, the vertical cylindrical alignment surface  164  aligns the head ring  33  with the base  40  and rim  162  rests on the rim of the base  40  to ensure proper alignment between the upper  34  and lower  36  rotors. 
   The improved air flow and process fluid drainage aspects of the new wafer processing system will now be discussed. 
   First, the head assembly  28  has a multitude of air flow passageways which draw ambient air from the fab environment into the head assembly  28  and out through the base  40  of the process chamber  16 . As shown in  FIG. 6 , an annulus  136  is positioned in the head  29  just below the motor  38 . The annulus  136  is connected to an air aspirator (not shown), which sucks gaseous vapors or particles from the motor  38  out of the head  29 . An aspirator tube (not shown) exits the head  29  via a service conduit attached to support  130 . The negative pressure created by the aspirator  132  also acts to remove any gaseous vapors or fumes that may come from other air passageways in the head assembly  28  or the base  40 . 
   Second, turning to  FIGS. 5–7  and  21 A–C, a plurality of vents holes  60  are formed in the head ring  33 . As specifically shown in  FIGS. 21A–C , the vent holes  60  draw air from the mini-environment within enclosure  15  through air channels  124  into an inner volume or air gap  134  formed by the slanting outer surface of the upper rotor  34  and the head ring  33 . The inner air gap  134  communicates with a channel  137  that wraps around the periphery of both the upper rotor  34  and the lower rotor  36 , and continues down into the annular drain cavity  80  formed in the recess of the base  40 . Eventually, process fluid vapors are vented out through the exhaust ports  82  formed in the annular drain cavity  80 . 
   Third, the process chamber  16  of the present invention is also designed to relieve inherent pressure build up experienced by carrying out operations in a closed process chamber  16 . Referring to  FIGS. 12–14 , a plurality of openings  71  are formed in the upper rim  73  of the base  40 . The openings  71  are connected to exhaust channels  142  formed in a lower portion of base  40 . A pump or the like (not shown) is connected to the exhaust channels  142  via at least one, and preferably two, exhaust ports  72 , creating a negative pressure and a path for exhausting process fluids through the channels  142  (represented by the dashed lines in  FIG. 14 ). Turning now to  FIG. 5 , when the head assembly  28  is lowered and engages the base  40 , an annular plenum  70  formed in the head ring  33  covers the upper rim  73  of the base  40 . The annular plenum  70  in the head ring  33  permits the openings  71  in the upper rim  73  to receive “blow-by” of process fluids during operation. These “blow-by” process fluids are bled off by the negative pressure in the exhaust channels  142 . Again, this process path is represented by dashed lines in  FIG. 5 . Accordingly, unwanted pressure build up in the process chamber  37  is minimized during operation. 
   Fourth, air is introduced directly into the workpiece process chamber through openings in the head assembly  28  and the base assembly  30 . Turning to  FIGS. 12–16 , the base assembly  30  includes a centrally positioned process fluid applicator  62  that extends upwardly from the base  40 . Generally, the processing fluids may be a liquid, vapor or gas or a combination of liquid/vapor/gas. The process fluid applicator  62  in the base assembly  30  includes a back-side vent aperture  64 . In a preferred embodiment, process fluid applicator  62  includes a plurality of back-side vent apertures  64 . The back-side vent apertures  64  communicate via air channel  66  with snorkel  68 . The snorkel  68  is open to the mini-environment inside the enclosure  15 , allowing air to be delivered directly to the backside of the workpiece. Turning to the head assembly  28  and  FIGS. 3–7 , an air inlet  140  is formed in a central portion of the assembly  28 . One end of the air inlet  140  is open to the mini-environment and one end opens into the workpiece process chamber through opening  106  in the upper rotor  34 . Accordingly, air is drawn from the mini-environment into the workpiece process chamber to provide air directly to the top and backsides of the workpiece. 
   During operation, process fluids are applied to the top and backsides of the workpiece. The process fluid applicators of the present invention will now be discussed in more detail. Both the head assembly  28  and the base assembly  30  include process fluid applicators. Referring to  FIG. 13 , the base assembly  30  has a process fluid applicator  62  in the base  40 . The applicator  62  includes a connector  74  for connecting the process fluid applicator to a various process fluid supplies. Accordingly, the applicator  62  includes additional ports; e.g., lateral slotted port  76  and apertures  78 . The ports and apertures in the process fluid applicator  62  direct process fluid upward through opening  112  in the lower rotor  36  towards the backside workpiece surface. For example, in a preferred embodiment, air is supplied through vent apertures  64 , an etchant (e.g., hydrofluoric acid, sulfuric acid, or a mixed acid/oxidizer) is supplied through lateral slotted port  76 , deionized water is supplied through a first aperture  78  and nitrogen and isopropylalcohol are supplied through second aperture  78 . The applicator  62  may also include a purging nozzle for directing a stream of purging gas, such as nitrogen across the workpiece surface. 
   With reference now to  FIGS. 5–11 , and as mentioned above, the head assembly  28  also includes a process fluid applicator  32 . The applicator  32  has a nozzle  35  for directing streams of processing fluids through inlets  92 ,  94  and out into the workpiece process chamber through openings  100  in the head  29  and  106  in the upper rotor  34 , respectively. The processing fluids provided through nozzle  35  and inlets  92 ,  94  may be the same or different fluids. Examples of such processing fluids include air nitrogen, isopropylalcohol, deionized water, hydrogen peroxide, ST-250 (a post-ash residue remover solution), an etchant (e.g., hydrofluoric acid, sulfuric acid), or any combination thereof. The nozzle  35  and inlets  92 ,  94  extend axially downwardly through a sleeve  96  (that includes air inlet  140 ) in the head  29  so as not to interfere with rotation of the upper rotor  34 , which is coupled to motor  38 . 
   Operation of the new wafer processing system will now be explained. With the process head assembly in an open position, robot  26  loads a workpiece  24  into the process chamber  37  where it sits on stand-off pins  50  extending from the lower rotor  36 . Actuator  13  begins to lower the head assembly  28  until it engages base assembly  30 . Axial centering extension  122  of the head ring  33  contacts the chamber assembly first, ensuring that head assembly  28  and the base assembly  30  are axially aligned. The head assembly  28  continues to move downward, until the upper rotor  34  makes contact with the lower rotor  36 . Eventually, the force applied to the lower rotor  36  (from the actuator  13  via upper rotor  34 ) will overcome the magnetic repulsion force between the magnets  42  in the base bowl  40  and the magnets  44  in the lower rotor  36 , relieving engagement ring  110  (of the lower rotor  36 ) from the slotted mounting member  144  (of the base  40 ). Engagement pins  54  of the lower rotor  36  are inserted into the corresponding bores  46  in the upper rotor  34 . It may be necessary to rotate the rotors  34 ,  36  slightly in order to align the engagement pins  54  with the bores  46 . 
   At this point in the operation of processor  16 , the process chamber  37  is in a fully-closed, process position. In this position, the device or top side of the workpiece  24  and the inner surface  148  of upper rotor  34  form a first process chamber  102 . The bottom side or backside of the workpiece  24  and the inner surface  150  of lower rotor  46  form a second process chamber  104 . As discussed above, fluid applicator  32  introduces process fluid to the first process chamber  102 , while fluid applicator  62  introduces process fluid to the second process chamber  104 . In a preferred embodiment, the motor  38  rotates one of either the upper rotor  34  or the lower rotor  36 . Because the rotors  34 ,  36  are engaged, the workpiece  24  is spun while process fluids are applied to the top and backsides of the workpiece  24 . Liquids flow outwardly over the workpiece  24  via centrifugal force. This coats the workpiece  24  with a relatively thin liquid layer. The tight tolerance between the upper and lower rotors  34 ,  36  and the workpiece  24  helps to provide a controlled and uniform liquid flow. Gases, if used, can purge or confine vapors of the liquids, or provide chemical treatment of the workpiece  24  as well. The spinning movement of the rotors  34 ,  36  drives the fluids radially outward over the workpiece  24 , and into the annular plenum  80  formed in the base  40 . From here, the process fluids exit the base  40  via drains  82 . The valves  84  control release of the process fluids through fittings  88 . 
   After processing is complete, the actuator  13  lifts the head assembly  28  away from the base assembly  30  by actuating a motor. In the system  10  shown in  FIG. 2 , the robot  26  moves along the track  23  and uses end-effector  31  to remove the workpiece  24  from the open process chamber  16 . The robot  26  then travels along the linear track  23  for further processing of the workpiece  24 , or to perform a transport operation at the input/output station  19 . 
   While the present invention has been described in terms of concurrently providing different process fluids to the device and bottom sides of the workpiece, multiple sequential processes of a single workpiece can also be performed using two or more processing fluids sequentially provided through a single inlet. For example, a processing fluid, such as a process acid, may be supplied by the lower process fluid applicator  62  to the lower process chamber  104  for processing the lower surface of the workpiece  24 , while an inert fluid, such as nitrogen gas, may be provided to the upper process chamber  102 . As such, the process acid is allowed to react with the lower surface of the workpiece  24  while the upper surface of the workpiece is effectively isolated from hydrofluoric acid reactions. 
   While the process head, process head assembly, chamber assembly, rotors, workpieces and other components are described as having diameters, they can also have non-round shapes. Further, the present invention has been illustrated with respect to a wafer or workpiece. However, it will be recognized that the present invention has a wider range of applicability. By way of example, the present invention is applicable in the processing of flat panel displays, microelectronic masks, and other devices requiring effective and controlled wet chemical processing. 
   While embodiments and applications of the present invention have been shown and described, it will be apparent to one skilled in the art that other modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except by the following claims and their equivalents.