Abstract:
A method for exposing an object to fluid using principles of the present invention includes the steps of introducing the object into a coanda flow forming passage and directing a coanda jet onto a coanda profile that surrounds the object to cause amplified flow to surround the object and move axially through the passage. An apparatus for exposing an object to fluid utilizing principles of the present invention includes a chamber having an enclosed coanda profile and a fluid inlet such as a coanda slot fluidly coupled to the passage. The passage is proportioned to receive an object to be treated. In one embodiment of the method and apparatus, fluid apertures for focusing an additional fluid onto the object may be positioned within the chamber, and a fluid may be directed from the apertures onto the object to clean the object before the object is dried using the amplified flow through the chamber.

Description:
BACKGROUND OF THE INVENTION 
     In manufacturing processes requiring high levels of cleanliness, it becomes necessary to clean and dry the robotic devices used to handle products undergoing manufacture. One context in which this is extremely important is during the manufacture of semiconductor wafers. For example, during wet processing of wafer substrates robotic end effectors carry the substrates between chemical processing steps, rinse steps, and or drying steps. Between certain of these steps it is important to clean the end effectors so that substances that adhere to the end effectors during wafer transport are not transferred back onto the wafers when the wafers are subsequently retrieved by the same end effectors. For example, droplets or films of chemical solution are likely to be deposited onto an end effector used to transport a wafer away from a chemical process chamber and into a rinsing chamber. It will be important to remove these deposits from the end effector before the end effector retrieves the wafers from the rinsing chamber for transport to a drying chamber—so that the deposits are not transferred back onto the wafer. In other contexts, periodic washing and drying of end effectors may be important towards minimizing particle contamination of the end effectors and wafers. 
     It is desirable to provide a cleaning/drying tool for process end effectors that minimizes process time, process fluid (e.g. cleaning/drying fluids and/or gases) consumption, and footprint size. 
     SUMMARY OF THE INVENTION 
     A method for exposing an object to fluid using principles of the present invention includes the steps of introducing the object into a flow passage and directing a high velocity stream onto a coanda profile that surrounds the object. This causes a cylindrical amplified flow to surround the object and move axially through the passage. An apparatus for exposing an object to fluid utilizing principles of the present invention includes a chamber having an enclosed coanda profile and a fluid inlet coupled to the passage. The passage is proportioned to receive an object to be treated. In one embodiment of the method and apparatus, nozzles for focusing an additional fluid onto the object may be positioned within the chamber, and a fluid may be directed from the nozzles onto the object to clean the object before the object is dried using the amplified flow induced in the chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view showing a pair of wash/dry apparatuses utilizing principles of the present invention, coupled to common drain plumbing. 
     FIG. 2 is an exploded perspective view of one of the wash/dry apparatuses of FIG.  1 . 
     FIG. 3 is a top plan view of the manifold of the wash/dry apparatus of FIG.  2 . 
     FIG. 4 is a side elevation view of the manifold of FIG.  3 . 
     FIG. 5 is a cross-section view of the manifold taken along the plane designated  5 - 5  in FIG.  3 . 
     FIG. 6 is a cross-section view of the manifold taken along the plane designated  6 - 6  in FIG.  4 . 
     FIG. 7 is a cross-section view of the manifold taken along the plane designated  7 - 7  in FIG.  4 . 
     FIG. 8 is a cross-section view of the manifold taken along the plane designated  8 - 8  in FIG.  4 . 
     FIG. 9 is a cross-section view similar to FIG. 5, showing the spray nozzles in place and the cap on the manifold. 
     FIG. 10 is a cross-section view similar to FIG. 9, illustrating use of the apparatus to clean end effectors. 
     FIG. 11 is a perspective view of an alternate embodiment of a manifold and cap assembly. 
     FIG. 12A is a top elevation view of the manifold of FIG. 11; 
     FIG. 12B is a cross-sectional side view of the manifold taken along the plane designated  12 B- 12 B in FIG. 12A; 
     FIG. 12C is a cross-sectional side view of the manifold taken along the plane designated  12 C- 12 C in FIG.  12 A. 
    
    
     DETAILED DESCRIPTION 
     One embodiment of an apparatus for washing and/or drying using a coanda profile is shown in the drawings. This embodiment will be described for use in washing and drying the end effectors of robotic components used to transport semiconductor wafer substrates between processing steps. The embodiment is described this way only for purposes of convenience, as the apparatus and method may be equally suitable for use in treating other articles to be washed, dried, and/or otherwise treated with fluids. 
     Referring to FIG. 1, a coanda washing apparatus  10  includes a manifold  12 , cap  14  attached to manifold  12 , and drain plumbing  16  positioned to receive fluids from manifold  12  and to direct such fluids through system plumbing  17  for disposal or recirculation. The apparatus  10  may be used independently, or two or more such apparatuses  10  may be used side-by-side as a part of a larger assembly as shown in FIG.  1 . The components are preferably made from a material inert to the chemicals that are to be cleaned from the end effectors using the apparatus  10 . For example, in a semiconductor environment PVDF or PFA is desirable for the manifold  12 , cap  14  and associated plumbing. 
     Referring to FIGS. 2 and 9, cap  14  includes a central opening  18  beveled downwardly from the upper surface of the cap. On the underside  20  (FIG. 9) of the cap  14  is a circular cutout  22  that creates a narrow slot between the cap  14  and manifold  12 . A plurality of throughbores  24  are shown for receiving fasteners used to hold the cap  14  on the manifold  12 . 
     Manifold  12  (FIG. 2) includes a central chamber  26  having a diameter that varies from the top to the bottom of the manifold  12  to form a coanda profile (i.e. a profile that will induce coanda flow in the supply fluid), a constricted chamber, and an expansion chamber. The profile is “revolved” in that it extends 360° around the chamber interior to encircle the object for treatment. The revolved profile may be formed using a lathe or other means. 
     Referring to the cross-section view of the chamber  26  in FIG. 8, it can be seen that the upper opening  28  that leads into the chamber  26  has rounded edges  30  that transition from the horizontal plane to the vertical chamber walls. These rounded edges form the coanda profile. Downstream of the rounded edges  30  lies a relatively narrow cylindrical region  32  of the chamber, and downstream of this constricted region  32  is a flared expansion region  34 . A second, larger diameter, cylindrical region  36  lies downstream of flared region  34 . At the lower opening  38  of the chamber  26  is a circular seat  40  proportioned to receive an o-ring  42  (FIG.  1 ), which, when the manifold is coupled to drain plumbing  16  (FIG.  1 ), seals the connection between the manifold and the drain plumbing. 
     Referring to FIGS. 2 and 9, a pair of arcuate grooves  39  are formed in the upper surface of the manifold  12 . Centrally disposed along each groove  39  is a downwardly extending bore  41 . When cap  14  is secured to manifold  12  as shown in FIG. 9, circular cutout  22  on the underside of cap  14  is positioned over the grooves  39  and bores  41  to create a narrow “coanda slot” between them. 
     Side ports  44  (FIG. 2) and  46  (FIG. 4) are positioned on opposite sides of manifold  12 . In one method utilizing principles of the invention, port  44  is a deionized (“DI”) water port, and port  46  is a nitrogen gas port. Elbow fittings  45 ,  47  are mounted to ports  44 , 46  to connect the ports to the appropriate fluid and/or gas sources such as a DI water source  49  and a nitrogen gas source  51 . 
     Referring to FIG. 6, tubular branches  48  extend from DI water port  44  to opposite sides of central chamber  26 . Each tubular branch  48  terminates at a fluid aperture such as interior port  50 . These fluid apertures preferably include spray nozzles  52  which are disposed in the interior ports  50  (as shown in FIG. 9) when the manifold is fully assembled. Thus, DI water introduced into water port  44  travels through the bifurcated flow path formed by branches  48  and is propelled into the central chamber  26  by spray nozzles  52 . 
     As shown in FIG. 7, tubular branches  54  extend from gas port  46 . The branches  54  fluidly intersect with upwardly extending bores  41  (see also FIG.  5 ). Nitrogen gas introduced into gas port  46  passes through branches  54  and bores  41 , and into the narrow coanda slot defined between arcuate grooves  39  and the cutout  22  (FIG. 9) on the undersurface of cap  14 . 
     Drain plumbing  16 , FIG. 1, comprised of standard plumbing components, includes a pipe section  56  having an increased-diameter lip  58  at its upper end. A collar  60  serves to connect pipe section  56  to manifold  12 . Collar  60  is slidably positioned on the exterior surface of pipe section  56  and includes a threaded interior surface. The lower exterior of manifold  12  has a corresponding threaded surface  62 . To assemble the plumbing  16  and manifold  12 , collar  60  is advanced in the direction of the arrow in FIG.  1  and then screwed into engagement with threaded surface  62  of manifold  12 . Lip  58  is proportioned to prevent collar  60  from becoming detached from pipe section  56 . Drain plumbing  16  is further connected to system plumbing  17  that directs fluids draining from manifold  12  away from the manifold for disposal or reconditioning/recirculation. 
     Operation of the system  10  will next be described. With the manifold  12 , cap  14  and plumbing  16  fully assembled, an object such as a process end effector  64  is passed vertically downward through opening  18  in the cap  14  and into the central chamber  26  of manifold  12  as shown in FIG. 10. A cleaning fluid, which may be DI water or a cleaning solution, is introduced into elbow pipe  45  that leads to inlet  44  (FIG.  2 ). The cleaning fluid moves from inlet  44  through tubular branches  48  (FIG. 6) and is focused onto the end effector by spray nozzles  52 , thus cleaning the end effectors as they are passed through the chamber. Rinsing in this method of close proximity requires only minimal rinse fluid. Also, because the chamber  26  has a constricted region  32  positioned above the elevation of the nozzles  52  and expansion chamber  34 , there is minimal mist rise out of the chamber  26  during cleaning. 
     Fluid exits the bottom of the chamber  26  and travels through plumbing  16 ,  17  where it may be disposed of or recirculated for reuse. 
     After cleaning has been performed, flow of cleaning fluid into the chamber  26  is terminated. The end effector or other object is discontinued in its descent and is passed vertically upward for the drying process. An inert drying gas such as nitrogen is introduced into inlet  46  via elbow connector  47  (FIG.  2 ). The gas passes through tubular passages  54  (FIG.  7 ), then moves upwardly through bores  41  and into the arcuate grooves  39  (FIGS. 2,  7  and  10 ), filling the volume of the grooves  39 . From the arcuate grooves  39 , the gas is forced through the narrow slot  22  (FIG. 10) formed in the underside of cap  14 . Passage through the narrow cutout creates a high velocity flow (which is horizontal in FIG. 10) directed toward the central axis of the manifold chamber as indicated by arrows A 1 . Naturally, this high velocity flow can be generated using various other methods known to those skilled in the art. 
     Referring to FIG. 10, the Coanda effect, which is the tendency of fluids (including air or gases) to attach to and follow the curved surface of a wall, causes the coanda jet (the high velocity turbulent gas stream emitted from coanda slot  22  and indicated by arrows A 2 ) to follow the profile of the chamber wall, creating a cylindrical high-speed thin-wall attached flow (i.e. coanda flow) through the chamber. As can be seen in FIG. 10, the Coanda profile subtends an arc from horizontal to vertical, meaning that the gas travels in a horizontal direction (A 1 ) through the coanda slot and then follows the chamber wall into a vertical flow orientation (A 2 ). 
     One effect of the coanda flow is the entrainment of ambient air. Specifically, as it flows into the chamber, the coanda flow entrains ambient air in the region of the cap&#39;s opening  18  and draws the ambient air into the manifold as indicated by arrows A 3 . The ambient air mixes with the drying gas to create a stream of mixed gas, which flows into the manifold as indicated by arrows A 4 . In this manner, the manifold operates as an air amplifier that causes drying to occur using a fraction of the nitrogen or other drying gas that would otherwise be used in the process. In one embodiment, the volumetric flowrate of entrained air may exceed ten times the flow rate of the drying gas used. 
     Because the coanda profile surrounds a central axis, the coanda jet induces cylindrical coanda flow that likewise surrounds the end effectors and promotes unidirectional flow of the entrained air. The velocity of the mixed gas within the chamber  26  is greatest at the constricted section defined by the geometry of wall  32  (FIG.  8 ). Introduction of an end effector into the chamber further constricts the flow path and increases air velocity through the chamber. Very high stream velocities are easily achieved using a revolved horizontal-to-vertical Coanda profile in this manner. For example, introduction of 5 SCFM of nitrogen at 20 psi will entrain over 50 SCFM of ambient air to produce chamber velocities in excess of 75 mph. The high velocity gas stream shears liquid droplets off of the end effectors to dry the end effectors. The dimensions of the coanda slot  22  (FIG. 9,  10 ) and the wall  32  are selected for efficiency of air entrainment and velocity through the chamber. 
     The circumferential shape of the chamber and associated components may be selected according to the dimensions of the object to be treated within the chamber. Thus, although the chamber  26  has a circular shape, alternate shapes may be utilized. 
     For example, the alternative embodiment  10   a  of FIGS. 11 and 12A through  12 C includes a manifold  12   a  having a chamber  26   a  that is elliptical in cross-section. Apparatus  10   a  includes a cap  14   a  having an elliptical central opening  18   a  that is beveled downwardly from the upper surface of the cap. A circular cutout (similar to cutout  22 FIG. 9) is formed in the underside of the cap  14   a  to form the narrow slot between cap  14   a  and manifold  12   a  when assembled. 
     The central chamber  26   a  of manifold  12   a , similar to chamber  26  of manifold  12 , has internal diameter that varies both radially and vertically to form, from top to bottom of manifold  12   a , a coanda profile, constriction chamber, and expansion chamber. This profile is also “revolved” in that it extends 360° around the elliptical shape of the chamber interior to encompass the object for treatment. As with the first embodiment, the upper opening  28   a  that leads into the chamber  26   a  has rounded edges  30   a  to induce coanda flow. Downstream of the coanda profile  30   a  lies a constricted flow region  32   a  of the chamber, and downstream of the constricted region  32   a  is a flared expansion chamber  34   a.    
     A circular groove  39   a  (similar to arcuate grooves  39 ) is formed in the upper surface of the manifold  12   a , and a bore  41   a  extends downwardly from groove  39   a  into the manifold  12   a . When cap  14   a  is secured to manifold  12   a , the circular cutout (not shown but see cutout  22  of FIG. 9) on the underside of cap  14   a  is positioned over the groove  39   a  and bore  41   a  to create a narrow slot between them for fluid passage. 
     Side port  44   a  is a DI water port. As with the first embodiment, tubular side branches (not shown but see branches  48  of FIG. 6) extend from port  44   a  to opposite sides of central chamber and terminate at interior ports  50   a  having spray nozzles (see nozzles  52  of FIG.  2 ). DI water introduced into water port  44   a  travels through the bifurcated flow path formed by the tubular branches and is propelled into the central chamber  26   a  by the spray nozzles. 
     A nitrogen gas port  46   a  is positioned on an opposite side of the manifold  12   a  from DI water port  44   a  Gas port  46   a  fluidly intersects with downwardly extending bore  41   a . Nitrogen gas introduced into gas port  46   a  passes through the bore  41   a , and into the narrow slot defined between circular groove  39   a  and the cutout on the undersurface of cap  14   a . As with the first embodiment, this creates a high velocity horizontal flow of gas towards the center of the chamber opening, after which the gas attaches to and follows the curved coanda profile in a vertical direction. 
     Although two embodiments of the invention have been shown, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Instead, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.