Patent Publication Number: US-2017365492-A1

Title: Wafer processor door interface

Description:
PRIORITY CLAIM 
     This application claims priority to U.S. Provisional Patent Application No. 62/350,809, filed Jun. 16, 2016, and now pending. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is processors, systems, and methods for processing semiconductor material wafers, and similar workpieces or substrates for microelectronic devices. 
     BACKGROUND OF THE INVENTION 
     Microelectronic devices, such as semiconductor devices, are generally fabricated on and/or in silicon or other semiconductor material wafers. Patterned layers are formed on the wafer surface via photolithography. Photoresist used in the photolithography steps is removed by chemical stripping. This may be a relatively time consuming process where the wafers are immersed in a bath of heated solvent, for example in a wet bench or other apparatus. The solvent (or other process liquid) must be removed from the wafers after the chemical stripping step without contaminating the manufacturing environment, and advantageously also without diluting the bath of heated solvent with rinsing or cleaning liquids. 
     Accordingly, engineering challenges remain in providing systems and methods for processing wafers. 
     SUMMARY OF THE INVENTION 
     A wafer processing system includes at least one processor having a tank for holding a process liquid. A clean assembly above the tank is provided with an upper housing having at least one upper housing spray nozzle, and a lower housing having at least one lower housing spray nozzle, with the lower housing below the upper housing. A door between the upper housing and the lower housing is movable via an actuator from an open position wherein a load port through the clean assembly is open, to a closed position wherein the load port is closed off. The door largely prevents liquids used in the upper housing from moving down into the process liquid in the tank, and may also improve gas flow in the system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of processing system. 
         FIG. 2  is a side view of the system shown in  FIG. 1 . 
         FIG. 3  is a perspective view of the tank of the system shown in  FIGS. 1 and 2 . 
         FIG. 4  is a section view taken along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a perspective view of the head shown in  FIGS. 1 and 2 . 
         FIG. 6  is a top perspective view of an alternative clean assembly having a door in the closed position. 
         FIG. 7  is a perspective section view of the clean assembly as shown in  FIG. 6 . 
         FIG. 8  is a side section view of the clean assembly as shown in  FIGS. 6 and 7 . 
         FIG. 9  is a side section view of the clean assembly of  FIGS. 6-7  with the door in the open position. 
         FIG. 10  is a perspective view of an alternative design. 
         FIG. 11  is an enlarged side view of the design of  FIG. 10  with the door in the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , a processing system  20  has first and second wafer processors  28  within an enclosure  22 . The enclosure  22  may have access openings  24  and  26  to allow workpieces, such as semiconductor wafers, to be moved into and out of the processing system  20 , typically via robots. The access openings  24  and  26  may have closures, such as movable panels or windows, for closing off the access openings  24  and  26  during processing, to better contain vapors or gases within the enclosure  22 . The enclosure  22  may also be provided with air inlets and exhaust connections, to provide a controlled flow of air through the enclosure. 
     As shown in  FIGS. 1 and 2 , each processor  28  has a head  50  for loading wafers  100  into and out of a process tank  30 . Depending on the specific process performed, a secondary chamber  48 , such as a spin rinser dryer, may be associated with each processor  28  within the enclosure. 
     Turning now to  FIGS. 3 and 4 , a clean assembly  32  is provided at the top of the process tank  30 . The clean assembly  32 , if used, generally includes clean housing  34  surrounded by a lower or clean housing drain channel  40 , and a rinse housing  36  surrounded by an upper or rinse housing drain channel  38 . The drain channels  38  and  40  are connected to a facility drain and optionally to a vacuum source. The process tank also includes one or more liquid inlets and one or more liquid drains, for filling and draining the process liquid, or providing a flow of process liquid through the process tank. 
     As best shown in  FIG. 4 , a rotor  56  in the process tank  30  has a plurality of arms  58  extending radially outward from a central hub  62 , with a holder  60  at the outer end of each arm  58 . A motor  64  is connected to the rotor  56  for rotating the rotor  56  in the process tank  30 . 
     In use, a process liquid, generally a solvent, for example dimethyl sulfoxide (DMSO), is pumped into the process tank  30  so that the process tank  30  is filled to e.g., 50 to 90% of capacity. The head  50  holding a wafer  100  is lowered down into a load port  54  at the top of the process tank  30 . The head  50  hands the wafer  100  off to a holder  60  on the rotor  56 . The holder  60  engages the backside and/or edge of the wafer  100 , with the front or device side of the wafer  100  facing up. The motor  64  is actuated to rotate the rotor  56  moving the wafer  100  in a circular path through the process liquid in the process tank  30 . With this movement, a subsequent holder  60  moves into the load port  54  to receive a subsequent wafer  100 . 
     The motor  64  rotates the rotor  56  at a rate that allows the wafer  100  to remain submerged in the process liquid for a time interval sufficient to complete processing the wafer, typically 1 to 30 minutes. As the rotor  56  continues to rotate, the processed wafer  100  returns to the load port  54  and is removed from the process tank via the head  50 . Subsequent wafers  100  are similarly processed. 
     Depending on the specific process and process liquid used, the wafer  100  may then be rinsed in the rinse housing  36 , to remove residual process liquid. A first liquid used as a rinse liquid may be sprayed onto the wafer from rinse nozzles in the rinse housing  36 , and/or on the head  50 . Generally the head  50  also spins the wafer  100  to fling off rinse liquid. In an optional second step performed within the clean assembly  32 , the head may lift the wafer  100  up into the clean housing  34  where the wafer is further cleaned via a spray of a second liquid or a cleaning liquid, such as de-ionized water and/or dried. For applications such as photoresist strip where the process liquid is a solvent, the wafer  100  may be further cleaned and dried via the secondary chamber  48  such as a spin rinser dryer. The wafer  100  is then moved out of the enclosure  22  for further handling or processing. Operations of the system  20  and the process tank  30  are typically controlled via computer, to provide more uniform processing. 
       FIG. 5  shows an alternative head  120  similar to the head  50  and having fingers  122  on a head rotor  124  adapted to hold a wafer  100  at a wafer holding position generally shown at  140 , typically several centimeters below the head rotor  124  of the head  120 . A head motor  126  on the head  120  rotates the head rotor  124 . Rinse arms  128  extend out from a rinse hub  130  attached to the frame of the head  120 , which does not rotate. Rinse nozzles  132  on the rinse arms  128  are aimed at the wafer holding position. In use, with a wafer held in the wafer holding position, rinse liquid is pumped through the rinse hub  130  and the rinse arms  128  to the rinse nozzles, to rinse the up-facing front side of the wafer  100 . 
       FIGS. 6-9  show an alternative clean assembly  150  which may be used in place of the clean assembly  32  shown in  FIGS. 3 and 4 . As shown in  FIGS. 6 and 7 , the clean assembly  150  has an upper or first housing  152  on top of a deck plate  154 . A door  158  is movable horizontally in a door housing  156  to open and closed positions via a door actuator  160 . The door  158  may be provided as a rectangular flat plate having a round opening generally matching the diameter of the load port  54  shown in  FIG. 4 . The door  158  may be supported on a linear bearing  164 . If the process liquid in the tank  30  evolves vapors, for example when the process liquid is a solvent heated to 110 to 120° C., an exhaust line  174  from the door housing  156  may connect to a facility exhaust or vacuum source, to draw off the vapors, with a flow rate of e.g., 500 to 900 liters per minute. A short upright leg  159  may be provided at the back end of the door  158  for attaching the door  158  to the door actuator  160 , and/or for directing air flow through the door housing  156 . The door  158  may be spaced vertically apart from the upper and lower surfaces of the door housing  156  to allow air to flow through the door housing  156  both above and below the door  158  when the door is in the open position. 
     A lower housing or a second housing  170  is positioned on top of and attached onto the process tank  30 . The lower housing  170  may have the same size and shape as the upper housing  152 . Both housings  152  and  170  have a conically tapering sidewall, as shown in  FIGS. 7-9 , to guide liquid flung off of the wafer  100  to a drain  168 . Both housings  152  and  170  also have a circular central opening aligned on a common central vertical axis, to allow the head  50  or  120  to move vertically through the clean assembly  150 , to load and unload wafers  100  into and out of the tank  30 . A purge gas line  176  may provide a purge gas, such as nitrogen into the lower housing  170 , for example at a rate of 20 to 40 liters per minute. 
     As shown in  FIG. 7 , an angled rim  162  is provided on the floor of the door housing  156  within the upper housing  152 . The height of the angled rim  162  is greater at the distal side (the right side in  FIGS. 7-9 ) than at the proximal side (the left side in  FIGS. 7-9 ), with the top surface of the angled rim  162  providing an annular angled door seating surface. As shown in  FIG. 9 , the door  158  is oriented at a slight inclination angle (inclined from proximal side to the distal side). With the door in the open position as shown in  FIG. 9 , the angled seating surface provides spacing between the bottom surface of the door  158  and the angled rim  162 . As a result, the door  158  does not slide or scrape against the angled seating surface during door movement. 
     With the door  158  in the closed position, as shown in  FIGS. 7 and 8 , the angled seating surface provides near contact at the end of travel to limit the gap  190  shown in  FIG. 11 , between the door and the angled rim  162  to reduce evaporation from the tank  30  and to reduce egress of ambient air into the tank  30 . The door  158  need not actually seal with the angled rim  162  when in the closed position. In the design shown, the door in the closed position closes off the load port, but does not seal the load port. Rather, when in the closed position the door  158  may fully or partially contact the angled rim  162 , or be spaced apart from the angled rim  162  by a the gap  190  of e.g., 0.5 to 1 mm. As a result, even with the door  158  in the closed position, the exhaust line  174  continues to draw off vapors from the process liquid in the tank  30 , along with purge gas, if used, although at a reduce flow rate in comparison to the flow rate when the door  158  is open. In designs where the door  158  closes off, but does not seal the load port  54 , no resilient seal components such as O-rings, gaskets, etc. are needed, and the door  158  is not positively forced against the angled rim  162  or other surface. Maintenance requirements are therefore reduced, especially wherein the process liquid, e.g., a heated solvent, is chemically reactive. 
     In a typical operation, the door  158  is moved via the door actuator  160  to the open position shown in  FIG. 9 . The head  50  or  120  moves vertically down through the clean assembly  150  and transfers a wafer  100  onto a holder  60  aligned under the load port  54 . The holder  60  may have active actuator driven fingers or other elements for holding the edge of the wafer  100 . Alternatively, the holder  60  may have passive elements which are moved via interaction with the head  50  or  120 , for grasping and holding the wafer. 
     The motor  64  rotates the rotor  56  to move a processed wafer into alignment with the load port  54 , and the head  50  or  120  picks up the processed wafer. The head then moves up to position the processed wafer in the lower housing  170 . The door  158  remains in the open position. A lower spray nozzle  172  in the lower housing  170  sprays a rinse liquid onto the wafer  100  while the head  50  or  120  rotates the wafer  100 , to remove residual process liquid from the wafer. Particles on the wafer  100 , such as pieces of solid photoresist etched off of the wafer  100 , are also removed. The angled side walls and the floor of the lower housing  170  guide and collect liquid flung off of the wafer. If the rinse liquid is the same as the liquid in the tank, then this collected liquid may be allowed to flow back into the tank. If the rinse liquid is different from the liquid in the tank, then this collected liquid may be removed from the lower housing  170  via a lower housing drain line  178  shown in  FIG. 7 , which is connected to a facility drain. 
     During this rinse process with the wafer  100  in the lower housing  170 , if used, purge gas is pumped into the lower housing  170  via the purge gas line  176 , and the exhaust line  174  is also on. As a result, vapors evolved from the process liquid in the tank  30  are removed largely via the exhaust line  174 , and ambient air is prevented from flowing into the tank and reacting with the process liquid, largely via the purge gas flow the combination of the purge gas flow and the small gap  190  between the lid and the top of the lower housing  170 . 
     The head  50  or  120  then moves up to position the wafer  100  in the upper housing  152 . The door actuator  160  closes the door  158 . The purge and exhaust lines, if used, remain on. The upper spray nozzle  166  sprays a cleaning liquid, such as de-ionized water, onto the wafer  100  while the head rotates the wafer. The used cleaning liquid is collected are removed from the upper housing  152  via the drain  168 . As with the clean assembly  32  shown in  FIGS. 3-4 , in using the clean assembly  150 , following the steps described above, the wafer  100  may then be further cleaned and dried via the secondary chamber  48  such as a spin rinser dryer. The wafer  100  is then moved out of the enclosure  22  for further handling or processing. 
     The door in the closed position prevents the cleaning liquid from moving into the tank  30  and may also help to efficiently exhaust vapors from the tank  30  and limit evaporation of the process liquid. Correspondingly, with the system  20  in the idle state, the door  158  is closed and the purge and exhaust lines are on. The door  158  in the closed position also closes off the load port  54 , preventing any access or line of sight into the tank  30 . The head  50  or the rotor  56  may have a diameter 1-6 mm less than the diameter of the load port  54 , so that even with the door open, there is substantially no line of sight into the tank  30  when the head is below the level of the door  158  during the loading/unloading and cleaning steps. 
     The load port  54  of the clean assembly  32  discussed above relative to  FIGS. 3 and 4  may similarly have a load port door movable from a first position wherein the load port door closes off and seals the load port, to a second position wherein the load port is open. 
     In an alternative design shown in  FIGS. 10 and 11 , a first exhaust port  182  is provided near a mid-point of the door housing  156 , and a second exhaust port  184  and a third exhaust port  186  connect into the front end of the door housing  156 . The exhaust ports  184  and  186  may be vertically positioned so that when the door  158  is closed, the exhaust ports  184  and  186  draw in air from above and from the below the door  158 . For example the door  158  may be positioned at the vertical centerline of the exhaust ports  184  and  186 . Also as shown in  FIG. 10 , the purge gas line  176  may intersect into the lower housing  170  at an off-center position to avoid directly impinging purge gas onto a wafer in the lower housing  170 , reducing potential for particle contamination of the wafer. The purge gas line  176  as well as the exhaust ports are located off to one side of the tank  30 , and not directly over the tank  30 , to reduce evaporation from the tank. 
     The processing system  20  described above effectively contains vapors with the door  158  closed, and the head  50  out of the tank  30  or with the head  50  holding a wafer in the upper housing  152 , as well as with the door  158  open with the head  50  out of the tank  30 , or with the head  50  holding a wafer in the lower housing  170  or the with the head in the fully down position for loading or unloading a wafer into or out of the tank  30 . 
     As used here, wafer refers collectively to silicon or other semiconductor material wafers, as well as other substrates on which micro-scale devices are formed. Thus, novel methods and systems have been shown and described. Various changes and substitutions may of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be limited, except by the following claims and their equivalents.