Abstract:
Fluid separation assembly that allows easy and fast change-out and minimizes or eliminates leakage during change-out. A fluid separation unit having a housing containing separation means, the housing having an inlet and an outlet spaced from the inlet, each including a fitting for attachment of the housing to a manifold or other device allowing fluid communication through the separation means to a point of use is provided. The fittings are designed for quick connect/disconnect, and for minimal or no leakage. The fittings may be on opposite ends, with top and bottom fittings of different configurations, thereby ensuring proper installation of the assembly. The particular medium to be separated is not particularly limited, and can include slurries, fluids including water, and pre-loaded chromatography columns. A one-way self-sealing valve is used to allow flow from the inlet to the outlet upon application of a pressure differential to one side of the valve. Application of a pressure differential to the opposite side of the valve does not allow flow, thereby preventing leakage.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Fluid separation units with fittings may be installed in small spaces that make it very difficult to change out the filter unit. In addition, conventional disposable fluid separation devices can leak during change-out. Since the chemicals used in a particular process may be hazardous, any leakage is undesirable, both from an environmental standpoint, operator safety, and potential damage of equipment components and products. Similarly, tubing associated with the device can leak or drip during change-out, also potentially resulting in a hazardous condition.  
           [0002]    Chemical Mechanical Planarization (CMP) of wafers is dependent on the quality and uniformity of the slurry running through the system. Typically, slurry enters the system after it flows through a housing packed with media. The media is designed to filter the slurry in order to ensure the quality of the slurry so as to minimize the chance of defects on the wafers. The slurry consists of very fine particles in an aqueous solution.  
           [0003]    Once the filter exhibits a predetermined increase in differential pressure, the operator knows that the filtration media has reached the end of its effective life, and the filter must be removed from the CMP tool and replaced. Since the filter is typically vertically oriented, once the filter is removed, gravity will force any residual slurry in the housing out the inlet that is located at the bottom of the housing. This can damage the tool and/or the wafer being processed, and pose a hazardous condition.  
           [0004]    It is therefore an object of the present invention to provide a fluid separation assembly that can be installed inside a CMP tool, the assembly minimizing or eliminating flow of fluid out of the assembly upon removal.  
           [0005]    It is yet a further object of the present invention to provide a separation assembly that includes dripless connections, minimizing or preventing leakage during change-out.  
         SUMMARY OF THE INVENTION  
         [0006]    The problems of the prior art have been overcome by the present invention, which provides a fluid separation assembly that includes one or more no-drip valves, thereby minimizing or eliminating leakage during change-out. In addition, in view of the minimization or absence of leakage, the assembly is adapted to be installed in the CMP tool rather than outside of the tool. According to a preferred embodiment of the present invention, a fluid separation unit having a housing containing separation media, the housing having a first end and a second end spaced from the first end, each of said first and second ends including a fitting for attachment of the housing to a manifold or other device allowing fluid communication through the separation means to a point of use is provided. The fittings are designed for minimal or no leakage. The top and bottom fittings may be of the same or different configurations. Each or only one may contain a valve. The particular medium to be separated is not particularly limited, and can include slurries and fluids including aqueous fluids. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a schematic representation of the flow layout of a filter housing used in a Chemical Mechanical Planarization process;  
         [0008]    [0008]FIG. 2 is a cross-sectional representation of a valve and coupling in accordance with a first embodiment of the present invention;  
         [0009]    [0009]FIG. 3 is a perspective view of the valve and coupling of FIG. 2;  
         [0010]    [0010]FIG. 4 is a cross-sectional exploded view of a valve and coupling in accordance with a second embodiment of the present invention;  
         [0011]    [0011]FIG. 5 is a perspective exploded view of the valve and coupling of FIG. 4;  
         [0012]    [0012]FIG. 6 is a cross-sectional view of a valve and coupling in accordance with a third embodiment of the present invention;  
         [0013]    [0013]FIG. 7 is a perspective exploded view of the valve and coupling of FIG. 6;  
         [0014]    [0014]FIG. 8 is a cross-sectional view of a valve and coupling in accordance with a fourth embodiment of the present invention;  
         [0015]    [0015]FIG. 9 is a perspective exploded view of the valve and coupling of FIG. 8;  
         [0016]    [0016]FIG. 10 is a perspective view of the valve of FIG. 8 in the normally closed position; and  
         [0017]    [0017]FIG. 11 is a perspective view of the valve of FIG. 8 in the open position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIG. 1 shows a schematic layout of a conventional fluid separation system in which the present invention may be applied. Those skilled in the art will appreciate that the separation systems of the present invention include filters, purifiers, concentrators and contactors (e.g., degassers and ozonators). For purposes of illustration, the separations systems will be exemplified with filters, although the present invention is not to be limited thereto.  
         [0019]    A filter  12  is shown having an inlet end  90  and an outlet end  100  (these could be reversed), each for respective connection to lower and upper manifolds or the like. The filter units  12  may be completely disposable, or may comprise a reusable housing having a disposable inner cartridge. In the embodiment shown in FIG. 1, the first (top) end of each filter unit  12  has a male fitting or coupling  20  forming part of end cap  8 , the coupling  20  preferably being centrally located (with respect to the housing of said filter  12 ) and preferably cylindrical, for attachment to an upper manifold or the like. Similarly, the second (bottom) end of each filter unit  12 , which is spaced from and preferably opposing the first end, has a fitting or coupling  21  forming part of end cap  9 , the coupling  21  also preferably being centrally located, for attachment to a lower manifold or the like. Slurry flows into the filter housing  12  from the bottom inlet  90  and out of the filter housing  12  through the outlet  20 , where it enters the stream for CMP processing. The nature of the slurry is not particularly limited, but typically in CMP applications is comprised of 0.1-0.2 μm diameter clay-like particles such as silica or alumina oxide. Each end cap  8 ,  9  seals in the filter unit  12 .  
         [0020]    Turning now to FIGS. 2 and 3, there is shown a first embodiment of the no-drip valve in accordance with the present invention. The design allows the valve to be molded from an elastomeric material, although other manufacturing techniques can be used. The coupling  21  on end cap  9  includes a spherical or ball-shaped member  15  having an annular slot  16  adapted to receive an O-ring or the like to seal the inlet such as in a corresponding recess in a manifold. A central inlet  17  is formed in the spherical member  15 . The inlet  17  narrows at shoulder  19  into passageway  18  and is in fluid communication with the interior of the housing via passageway  18  (when valve  25  is open as discussed below). Those skilled in the art will appreciate that the difference in diameter between inlet  17  and passageway  18  is not for functional purposes; it is the result of two core pins of different diameters mating, for tooling purposes (i.e., ease of manufacture).  
         [0021]    Valve  25  seats in bore  26  formed in the coupling and in fluid communication with passageway  18  as shown. The valve  25  can be composed of a resiliently flexible material, such as melt processable rubber, a thermoplastic elastomer, silicone, or a urethane. It should have a low durometer and a low compression set, and should be inert to the fluids used in the application. The valve  25  preferably includes a central dome  28  extending from a substantially planar annular base  29  with an outer annular lip  30  rising above the substantially planar base. The dome  28  of the valve  25  has one or more slits which are normally closed (i.e., are in close contact so as to prevent the flow of fluid through them). Upon the influence of a pressure differential on opposite sides of the dome  28  caused by fluid flowing from inlet  17  into passageway  18  and bore  26 , the slits separate and thereby provide fluid communication into the interior of the housing to which the coupling  21  is attached. Upon elimination of the pressure differential, the slits assume their normally closed position. The valve  25  is thus self-sealing. Because of the shape of the dome  28 , a pressure differential on opposite sides of the dome  28  caused by the force of fluid head height in the direction from the housing towards the inlet  17  does not cause the slits to separate, and thus does not provide fluid communication from the interior of the housing to the passageway  18  or inlet  17  even upon mild impact of the housing (unless that pressure differential is sufficient to invert the dome and cause the slits to separate, such as during a backwashing procedure).  
         [0022]    A retainer ring  19  (FIG. 3) is donut-shaped and has a central bore  32  configured to receive dome  28 . The retainer ring  19  is positioned in bore  26  over the valve  25  to hold the valve  25  in place. The retainer ring  19  is preferably rigid, and can be made of a polyolefin, copolymers or a metal. Preferably it is dimensioned so that an interference fit or snap fit is formed when placed in bore  26 .  
         [0023]    Although the valve  25  is illustrated as being positioned in the bottom fitting of the housing, a valve also could be used in the top fitting of the housing, or valves could be used in both the top and bottom fittings.  
         [0024]    Turning now to FIGS. 4 and 5, an alternative embodiment of the present invention is illustrated. Coupling  21  is similar to the embodiment of FIG. 2, with a spherical member  15  and a slot  16  adapted to receive an O-ring or the like to seal the coupling in the receiving manifold. In this embodiment, the valve and O-ring assembly  40  form one integral piece. The assembly  40  includes annular O-ring  42  and valve  125 , which is domed and positioned over aperture  45  in cover cap  41 . The dome has one or more slits as in the embodiment of FIG. 2. The valve  125  attaches to annular O-ring via a thin webbing  43  to form a semi-circular integral assembly as shown. Cover cap  41  assembles to the exterior of the spherical member  15  such as by a snap fit. This embodiment places the valve  125  close to the aperture  45 , thereby reducing the hold-up volume in the coupling, further minimizing leakage through the aperture  45 . Again, the bottom fitting is illustrated by way of example only; a valve could be located in the top fitting or in both the top and bottom fittings.  
         [0025]    [0025]FIGS. 6 and 7 illustrate another embodiment of the present invention that is a modification of the embodiment of FIG. 4. Spherical member  15  is composed of three separate elements as best seen in FIG. 7. First semi-spherical element  50  includes face  55  having a centrally located aperture  53  providing fluid communication to the interior of the housing to which the member  15  is attached. Also provided are a plurality of receiving apertures  56  (four shown). The second element is an integral valve and O-ring assembly  400 . The integral assembly  400  includes annular O-ring  441 , a plurality of apertures  456  shaped and positioned to align with apertures  56  in first semi-spherical element  50 , and a centrally located dome  428  that forms the valve. The dome  428  includes one or more slits as in the previous embodiments. The third element is a second semi-spherical member  60  having an aperture opening  61 . The side of the second spherical member  60  opposite the aperture opening  61  includes a plurality of legs  62  adapted to be received by apertures  456  in assembly  500  and apertures  56  in first semi-spherical member  50 . Accordingly, the number of legs  62  should correspond to the number of apertures  456  and  56 , and the location of the legs should be such that each aligns with a respective aperture  456  and  56  when in the assembled condition of FIG. 6. Preferably the legs  62  form a snap fit in apertures  56 .  
         [0026]    In the assembled condition of FIG. 6, the integral assembly  400  is sandwiched between the first and second semi-spherical elements in a fluid-sealed condition. The annular O-ring  441  allows for fluid sealing of the member  15  in a manifold or other apparatus. Dome  428  of the valve aligns with aperture opening  61  and includes one or more slits to form the self-sealing valve in the same manner as in the previous embodiments.  
         [0027]    [0027]FIGS. 8, 9,  10  and  11  illustrate a preferred embodiment of the present invention. Spherical member  15  is similar to that shown in FIG. 2, and includes annular slot  16  adapted to house an O-ring or the like to seal the spherical member in a corresponding recess in a manifold, for example. Counter bore  117  is in fluid communication with passageway  18  as shown, with passageway  18  preferably having a smaller diameter than bore  117 . Housed in bore  117  is valve  525 , again preferably made of a resiliently flexible material such as rubber, a thermoplastic elastomer, silicone or urethane, with melt processable rubber being particularly preferred. The location of the valve  525  in this embodiment advantageously minimizes hold-up volume in the filter.  
         [0028]    The valve  525  is substantially cylindrical, with a lower portion  526 , an angled shoulder  529  and an upper portion  572 . The lower portion  526  has an outer diameter greater than the outer diameter of the upper portion  527 . The outer diameter of the lower potion  526  is equal to or preferably slightly greater than the inner diameter of the bore  117 , so that an interference or press fit is created when the valve  525  is inserted into the inlet  17  as shown in FIG. 8. The outer diameter of the upper portion  527  is slightly less than the inner diameter of the bore  117 . The height “H” of the valve  525 , measured from the flat marginal portion  530  of the top face  531  of the valve  525 , corresponds to the height of the bore  117 , so that annular marginal portion  530  of the valve  525  intimately contacts shoulder  19  of the spherical member  15  that separates bore  117  from passageway  18 . Dome  525 , centrally located on the top face  531 , sits in passageway  18  as shown. The valve  525  has a central bore  520  leading to the dome  528 .  
         [0029]    [0029]FIG. 10 illustrates slits  535 ,  536  in the dome  528  in the normally closed position, where the slits are in intimate contact. Upon application of a pressure differential between the outer side of the top face  531  and the inner side of the top face  531  so that a higher pressure is applied to the inner side of the top face, the slits separate as shown in FIG. 11 and allow fluid to flow into passageway  18  from bore  117 . A pressure differential applied in the opposite direction would not cause the slits  535 ,  536  to separate (unless the amount of pressure used exceeds that typical during normal operating conditions, such as during a backwash procedure), and thus the valve  525  prevents fluid from flowing in the opposite direction. For example, when the filter is removed from the process, an insufficient pressure differential is present on the dome  528 , and any fluid remaining in the filter is prevented from leaking past the valve  525  and out the inlet  17 . Those skilled in the art will appreciate that although two slits are illustrated, dividing the dome into four sections, fewer or more could be used.  
         [0030]    The valves of the various embodiments exhibit excellent recovery, allowing for steady, constant flow of fluid in the open position even after multiple openings and closings.  
         [0031]    The valves are particularly suited for fluid pass-through applications where replacing displaced fluid with air (venting) is not necessary, such as typical CMP processes. In a typical CMP process, fluid flow is initiated for about 15 minutes at 100-250 ml/min. to prime the system. The cycle is then started, and is on for 1 to 1.5 minutes and then off for 2 to 2.5 minutes (the distribution loop is 20-30 psi or less). The valve assembly must survive a typical run which may be continuous for 1-3 weeks. Similarly, the apparatus may be idle for maintenance or other reason. Typical differential pressures across a clean filter can range from 4 to 7 psi.