Abstract:
Apparatus, methods, and computer programs for cleaning opposed surfaces of a semiconductor wafer are presented. One apparatus includes first, second, and third valves, and one or more second drains. The first valves are coupled to a supply of rinsing solution and to first throughways that are coupled to an immersion tank above a region in the immersion tank, the region being defined by an area occupied by the substrate when the substrate is disposed vertically on a support within the immersion tank. The second valves are coupled to first drains and to second throughways that are coupled to the immersion tank below the region, and the third valves are coupled to a supply of cleaning solution and to third throughways that are coupled to the immersion tank below the region. Further, the second drains are coupled to fourth throughways that are coupled to the immersion tank above the region.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a Continuation Application under 35 USC §120 and claims priority from U.S. application Ser. No. 11/743,283, entitled “Substrate Cleaning Techniques Employing Multi-Phase Solution,” filed May 2, 2007, which is herein incorporated by reference. 
       CROSS REFERENCE TO RELATED APPLICATIONS 
       [0002]    This application is related to U.S. patent application Ser. No. 10/608,871, filed Jun. 27, 2003, and entitled “Method and Apparatus for Removing a Target Layer from a Substrate Using Reactive Gases”; U.S. Pat. No. 7,441,299, filed on Mar. 31, 2004, and entitled “Apparatuses and Methods for Cleaning a Substrate”; U.S. Pat. No. 7,452,408, filed on Jun. 30, 2005, and entitled “System and Method for Producing Bubble Free Liquids for Nanometer Scale Semiconductor Processing”; U.S. Pat. No. 8,043,441, filed on Jun. 15, 2005, and entitled “Method and Apparatus for Cleaning a Substrate Using Non-Newtonian Fluids”; U.S. Pat. No. 7,416, 370, filed on Jun. 15, 2005, and entitled “Method and Apparatus for Transporting a Substrate Using Non-Newtonian Fluid”; U.S. Pat. No. 8,323,420, filed on Jun. 30, 2005, and entitled “Method for Removing Material from Semiconductor Wafer and Apparatus for Performing the Same”; U.S. Pat. No. 7,568,490, filed on Dec. 23, 2003, and entitled “Method and Apparatus for Cleaning Semiconductor Wafers using Compressed and/or Pressurized Foams, Bubbles, and/or Liquids”; U.S. Pat. No. 7,648,584, filed on Jan. 20, 2006, and entitled “Method and Apparatus for Removing Contamination from Substrate”; U.S. Pat. No. 7,737,097, filed on Feb. 3, 2006, and entitled “Method for Removing Contamination from a Substrate and for Making a Cleaning Solution”; U.S. Pat. No. 7,696,141, filed on Feb. 3, 2006, and entitled “Cleaning Compound and Method and System for Using the Cleaning Compound”; U.S. patent application Ser. No. 11/543,365, filed on Oct. 4, 2006, and entitled “Method and Apparatus for Particle Removal”; and U.S. patent application Ser. No. 11/732,603, filed on Apr. 3, 2007, and entitled “Method for Cleaning Semiconductor Wafer Surfaces by Applying Periodic Shear Stress to the Cleaning Solution”. The disclosure of each of these related applications is incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0003]    There exists a desire to reduce critical dimensions of features in electronic substrate products. As the features decrease in size, the impact of contaminants during processing of the features increases, which may produce defects. Exemplary contaminants are particulates that include polysilicon slivers, photoresist particles, metal oxide particles, metal particles, slurry residue, dust, dirt, as well as various molecules containing atoms such as carbon, hydrogen, and/or oxygen. Particulates frequently adhere to a substrate surface by weak covalent bonds, electrostatic forces, van der Waals forces, hydrogen bonding, coulombic forces, or dipole-dipole interactions, making removal of the particulates difficult. 
         [0004]    Historically, particulate contaminants have been removed by a combination of chemical and mechanical processes. These processes employ cleaning tools and agents that have a probability of introducing additional contaminants during a cleaning process. 
         [0005]    Another technique for cleaning a substrate surface omits the use of chemical agents by exposing the surface to high heat to vaporize contaminants present thereon. The vapors are removed by evacuating a chamber in which the substrate surface is present. The high temperatures required for this process limits its application to post deposition processes not involving material having a structure that varies at temperatures proximate to the vaporization temperature of the contaminants. 
         [0006]    Another cleaning technique is disclosed in U.S. Pat. No. 6,881,687 and employs a laser-clean yield-enabling system. The system incorporates a laser cleaning operation working in conjunction with a defect inspection operation cooperating to feed information regarding the root cause of remaining defects back to earlier process stages, for correction of the root causes, with resultant improvement in yield. In a simplest configuration, the particles remaining after a laser cleaning would be characterized as to their types, sizes, shapes, densities, locations, and chemical compositions in order to deduce the root causes of the presence of those particular particles. This information is used to improve the yield of subsequent product wafers being processed so that their yields are higher than the wafers characterized. It is desired, however, to provide a more robust cleaning process that avoids the presence of particulate contaminants remaining on the surface that has been subjected to a cleaning process. 
         [0007]    Therefore, a need exists to provide improved techniques to clean substrate surfaces. 
       SUMMARY OF THE INVENTION 
       [0008]    A method and system for cleaning opposed surfaces of a semiconductor substrate having contaminants thereon. In one embodiment the method includes concurrently generating relative movement between a plurality substrates and a solution by exposing a cassette having the substrates contained therein to the solution. The solution has coupling elements entrained therein and the relative movement imparts sufficient drag upon a subset of the coupling elements to create movement of the coupling elements of the subset within the solution and impart a quantity of the drag upon the contaminant to cause the contaminant to move with respect to the substrate. 
         [0009]    Another embodiment is directed to a method that includes generating relative movement between a fluid and the substrate. The relative movement is in a direction that is transverse to a normal to one of the opposed surfaces and creates two spaced-apart flows. Each of the flows is adjacent to one of the opposed surfaces that is different from the opposed surface that is adjacent to the remaining flow of the plurality of flows. The fluid has coupling elements entrained therein, and the relative movement is established to impart sufficient drag upon the contaminants with to move the contaminants with respect to the substrate. Other aspects and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the present invention. 
         [0010]    In another embodiment, an apparatus includes first valves, second valves, third valves, and one or more second drains. One apparatus includes first, second, and third valves, and one or more second drains. The first valves are coupled to a supply of rinsing solution and to first throughways that are coupled to an immersion tank above a region in the immersion tank, the region being defined by an area occupied by the substrate when the substrate is disposed vertically on a support within the immersion tank. The second valves are coupled to first drains and to second throughways that are coupled to the immersion tank below the region, and the third valves are coupled to a supply of cleaning solution and to third throughways that are coupled to the immersion tank below the region. Further, the second drains are coupled to fourth throughways that are coupled to the immersion tank above the region. 
         [0011]    In yet another embodiment, a method includes an operation for placing the substrate on a support in an immersion tank without any solution in the immersion tank, and an operation for activating a plurality of first valves to provide a first flow of a rinsing solution to the immersion tank, the rinsing solution entering the immersion tank above the substrate. A plurality of second valves is activated after deactivating the plurality of first valves to drain the rinsing solution, the rinsing solution exiting the immersion tank below the substrate. The method further includes an operation for activating a plurality of third valves to provide a second flow of a cleaning solution to the immersion tank, the cleaning solution entering the immersion tank below the substrate. A pump is activated to drain the cleaning solution, which exits the immersion tank above the substrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, and like reference numerals designate like structural elements. 
           [0013]      FIG. 1  is a plan view of a substrate processing system including the present inventions. 
           [0014]      FIG. 2  is a simplified side view of an exemplary substrate cleaning system in accordance with one embodiment of the present invention. 
           [0015]      FIG. 3  is a side view of an immersion tank shown in  FIG. 2  and substrate transport system taken along lines  3 - 3 . 
           [0016]      FIG. 4  is a plan view showing a liquid employed to remove particulate contaminants from a substrate surface in accordance one embodiment of the present embodiment. 
           [0017]      FIG. 5  is demonstrating the relative cross-sectional areas of malleable regions in the suspension in relation to contaminants in  FIG. 4  in accordance with the present invention. 
           [0018]      FIG. 6  is plan view of a liquid employed shown in  FIG. 4  demonstrating the forces exerted on a particulate in furtherance of removing the particulate contaminant from the wafer surface in accordance with the present invention. 
           [0019]      FIG. 7  is a flow diagram demonstrating a process for cleaning a substrate shown in  FIGS. 2 and 3 . 
           [0020]      FIG. 8  is a cross-section view of the immersion tank shown in  FIG. 4  in accordance with an alternate embodiment. 
           [0021]      FIG. 9  is a plan view showing a liquid employed to remove particulate contaminants from a substrate surface in accordance with another embodiment of the present invention. 
           [0022]      FIG. 10  is a perspective view of a system employed to clean substrates in accordance with an alternate embodiment. 
           [0023]      FIG. 11  is a cross-sectional view of immersion tanks shown in  FIG. 10 . 
           [0024]      FIG. 12  is an alternate embodiment of one of the immersion tanks shown in  FIGS. 10 and 11 . 
           [0025]      FIG. 13  is an alternate embodiment of one of the immersion tank shown in  FIG. 11 . 
           [0026]      FIG. 14  a cross-section of the immersion tank shown in  FIG. 13  with a lid removed. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. 
         [0028]    Referring to  FIG. 1  an embodiment of the present invention is included in a substrate processing system that includes a plurality of processing modules arranged is what is commonly referred to as a cluster tool  10 . Cluster tool  10  is typically positioned within a clean room  12  that is defined, in part, by surrounding walls  14 . The modules of cluster tool  10  typically include one or more load/unload stations, two of which are shown as  16  and  18 . The atmosphere inside of cluster tool  10  is controlled to minimize, if not prevent, exposure of substrate to the ambient of clean room  12  during processing. Stations  16  and  18  facilitate transportation of a substrate  20  between clean room  12  and modules of cluster tool  10 . From one of stations  16  and  18 , substrate  20  is introduced into a lab-ambient controlled module  22  to facilitate wet processing may be performed. 
         [0029]    Access to wet processing modules  24 ,  26  and  28  by substrate  20  is gained through lab-ambient control transfer module  22 . Lab-ambient control transfer module  22  functions to ensure that substrate  20  reaming dry before entry into each of wet processing modules  24 ,  26  and  28 . To that end, each of wet processing modules  24 ,  26  and  28  functions to surfaces of substrate  20  dry upon completion of processing. Access to plasma processing modules  30  and  32 , after cleaning of substrate  20 , is achieved through load lock  34  and vacuum transfer module  36 . 
         [0030]    Vacuum transfer module  36  interfaces with plasma processing modules  30  and  32  that may be any plasma vapor deposition processing systems known that is suitable for depositing films upon semiconductor substrate, e.g., one or more of plasma processing modules may be a plasma enhanced chemical vapor deposition PECVD system. Were substrate  20  to undergo processing in plating/deposition module  38  or etch processing in etch system module  40  before/after or without undergoing plasma processing, a traversal through load lock  42 . After traversing load lock  42 , substrate enters Controlled Ambient Transfer Module  44  that facilitates access to modules  38  and  40  without exposing substrate to the ambient of clean room  12 . 
         [0031]    In fluid and electrical communication with modules  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38 ,  40 ,  42  and  44  is an environmental control system  50  that regulates the operations of each of modules  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38 ,  40 ,  42  and  44  so that the environment present therein is suitable for the processing desired. An example of cluster tool is discussed in U.S. patent application Ser. No. 11/639,752 that is incorporated by reference herein. 
         [0032]    Referring to both  FIGS. 1 and 2 , an embodiment of one or more of wet processing modules  24 ,  26  and  28  of  FIG. 1  includes a body  51  formed from any suitable material such as aluminum, plastic and the like. Body  51  defines an immersion tank  52  that is spaced-apart from an end  53  defining a void  54  therebetween through which conduits  55  pass to place immersion tank  52  in fluid communication with additional systems (not shown). A tank opening  57  is disposed opposite to the closed end  58  of immersion tank  52 . Positioned opposite to opening  57  is a shelving system  60 . One or more bases  61  may be disposed upon shelving system  60 . Shelving system  60  operates to reciprocate between a first position proximate to opening  57  (as shown) and a second position located remotely with respect to opening  57 . To that end, a track  62  is provided along which shelving system  60  moves. In the second position, opening  57  is unobstructed, allowing access to immersion tank  52 . 
         [0033]    Disposed upon base  61  is a substrate cassette  63  that operates to retain substrates, such as semiconductor substrate  64 . To move substrates  64  between cassette  63  and tank  52  a substrate transport system (STS)  65  is positioned proximate to immersion tank  52 . STS  65  includes a robot  66 , with a picker arm  67  coupled thereto. Picker arm  67  has a picker  68  coupled thereto that has end effector  69 . Picker arm  67  is controlled by robot  66  to move and index the picker  68  with respect to immersion tank  52  enable positioning of end effector  69  in immersion tank  52 . To that end, robot  66  may include a stepper motor, a servo motor, or other type of motor to provide precise control of the picker arm  67 . Picker arm  67  is configured to pivot end effector  69  to extend along two transversely orientated planes to facilitate movement of substrates  64  from cassette  63  into cassette  70 , disposed in tank  52 . To that end, end effector  69  is provided with suitable size and functionality to manipulate substrates  64 . 
         [0034]    In the present example STS  65  is shown with picker arm  67  positioned on the exterior of immersion tank  52 . STS  65  facilitates insertion of picker  68  into immersion tank  52  to a level lower than substrates  64  disposed in cassette  70 . As a result, substrates  64  may be processed in immersion tank  52  to remove particulate matter present on the surfaces of substrate  64 . To that end, immersion tank  52  includes a cleaning solution  71  of sufficient quantity to allow most, if not the entire area, of all surfaces of substrates  64  to be covered by the same. 
         [0035]    Referring to  FIGS. 2 ,  3  and  4 , with shelving system  60  in the second position opening  57  is exposed, allowing unobstructed access to introduce, and retain, cassette  70  in tank  52  vis-à-vis hanger  72  that is attached to hanger arm  73 . Hanger arm  73  is coupled to a motor (not shown) to vary a position of cassette  70  in immersion tank  52 . In one embodiment of the present invention, STS  65  is used to move cassette  70  into immersion tank  52  when loaded with multiple substrates  64 . In this fashion, batch processing of substrates  64  may be undertaken during a cleaning process. For example, substrate  64  may have contaminants  75  thereon. Immersion tank may be filled with solution. Picker arm  67  couples to detent  77  on cassette  70  to move the same into and out of immersion tank  52 . The movement of cassette  70  in solution loosens, softens, dislodges, or otherwise enhances the removal of residues, chemicals and particulates, referred to as contaminants  75 , from surfaces of substrates  64 . The speed at which cassette  70  is introduced into immersion tank  52  is established to facilitate removal of contaminants  75  from substrates  64 . Specifically, solution is fabricated to have the appropriate characteristics to interact with contaminants  75  and remove the same from the surfaces of substrate  64 . Similarly, the speed at which cassette  70  is removed from solution  71  also facilitates removal of contaminants from substrate  64 . As a result, it is possible to introduce cassette  70  and substrates into immersion tank  52  before solution  71  is present. After cassette  70  and substrate  64  are present in immersion tank  52 , solution  71  is introduced and the movement of solution  71  with respect to each of substrates  64  facilitates removal of contaminants  75  therefrom. After removal of substrate  64  from immersion tank  52 , the same may be exposed to a rinse process to remove solution  71  and/or loosens contaminants that remain. This may occur, for example, in one of the remaining wet processing modules  24 ,  26  and  28  by inserting the cassette  70  full of substrate  64  into a tank (not shown) into a rinse state having a solution of de-ionized water DIW or a solution of IPA to facilitate a batch rinse. It should be understood that STS  65  may be employed to remove each substrate  64 , individually, from cassette  70  by picker arm  67 , which lifts the same into space  76  where substrate  64  is retrieved by robot  66  for movement to a rinse station that is well known in the art. 
         [0036]    Referring to both  FIGS. 3 and 4 , an exemplary material that may form solution  71  includes a suspension  90  having multiple regions, with differing flow characteristics so that the flow characteristics associated with one of the regions differs from the flow characteristics associated with the remaining regions. In the present example, suspension  90  includes a liquid region  92  and a coupling element  94 . Liquid region  92  has a first viscosity associated therewith. Coupling element  94  may comprise rigid solid bodies, malleable solid bodies or solid bodies having fluidic characteristics, i.e., solid bodies having a viscosity that is much greater than the viscosity associated with liquid region  92 . Coupling elements  94  are entrained throughout a volume of liquid region  92  such that liquid region  92  functions as a transport for coupling elements  94  in furtherance of placing coupling elements  94  proximate to particulate contaminants  75  present on a surface  98  of substrate  64 . 
         [0037]    Coupling elements  94  consist of a material capable of removing contaminants  75  from surface  98  through transfer of forces from suspension  90 , i.e., movement of liquid regions  92 , to contaminant  75  vis-à-vis coupling elements  94 . Thus, it is desired to provide coupling elements  94  with a cross-sectional area sufficient to remove contaminant  75  from surface  98 . Typically, the cross-sectional area of coupling elements  94  is greater than a cross-sectional area of contaminant  75 . In this manner, movement of contaminant  75  in response to a drag force {right arrow over (F)} d  acting upon coupling element  94  is facilitated, with the understanding that drag force {right arrow over (F)} d  includes both a frictional forces {right arrow over (F)} f , and normal forces, with the normal forces including momentum. Drag force {right arrow over (F)} d  is a function of the physical properties and relative velocities associated with liquid region  92  and coupling elements  94 . 
         [0038]    Friction force {right arrow over (F)} f , the tangential component of drag force {right arrow over (F)} d , on the surface of contaminant  75  is a function of the shear stress at the contaminant surface multiplied by the surface area of the contaminant: {right arrow over (F)} f ={right arrow over (τ)}A. The friction force {right arrow over (F)} f  acting upon the coupling element is the shear stress at the coupling element surface multiplied by the surface area of the coupling element: {right arrow over (F)} f ={right arrow over (τ)}A. A coupling element  94  in contact with contamination  96  directly transfers its friction force. Thus, the contaminant experiences an apparent shear stress that is a ratio of the coupling element  94  to contaminant  75  surface areas. Specifically, the apparent shear force {right arrow over (τ)} c  to which contaminant experiences is 
         [0000]    
       
         
           
             
               
                 τ 
                 -&gt; 
               
               c 
             
             = 
             
               
                 τ 
                 -&gt; 
               
                
               
                   
               
                
               
                 A 
                 / 
                 
                   A 
                   c 
                 
               
             
           
         
       
     
         [0039]    Where A is the cross-section area of coupling element  94  and A c  is the cross-sectional area of contaminant  75 . Assume, for example, that an effective diameter, D, of contaminant  75  is less than about 0.1 micron and a width, W, and length, L, of coupling element  94  are each between about 5 microns to about 50 microns. Assuming a thickness, t, of coupling element  94  is between about 1 to about 5 microns, the ratio (or stress multiplier) could range between 2,500 to about 250,000. This number will increase when the normal forces are included in the drag force {right arrow over (F)} d  calculation. Coupling element  94 , shown in  FIG. 5 , is discussed with respect to being a hexahedron for ease of discussion. However, it should be understood that coupling elements are of substantially arbitrary shapes and that the length, L, width, W, and thickness, t, referred to above is the average value for coupling elements  94  in suspension. 
         [0040]    Referring to  FIG. 6 , forces transferred to contaminant  75  vis-à-vis coupling elements  94  occur through coupling of coupling elements  94  to contaminant through one or more various mechanisms. To that end, liquid region  92  exerts a downward force {right arrow over (F)} D  on coupling elements  94  within liquid region  92  such that coupling elements  94  are brought within close proximity or contact with contaminants  75  on surface  98 . When coupling element  94  is moved within proximity to or contact with contaminant  75 , coupling may occur between coupling element  94  and contaminant  75 . The coupling mechanism that results is a function of the materials, and properties thereof, from which coupling elements  94  and contaminant  75  are formed. Interaction between coupling element  94  and contaminant  75  is sufficient to allow the transfer of a force of sufficient magnitude to overcome an adhesive force between contaminant  75  and surface  98 , as well as any repulsive forces between coupling element  94  and contaminant  75 . Thus, upon coupling element  94  moving away from surface  98  by a shear force {right arrow over (τ)} contaminant  75  that is coupled thereto is also moved away from surface  98 , i.e., contaminant  75  is cleaned from surface  98 . 
         [0041]    One such coupling mechanism is mechanical contact between coupling elements  94  and contaminant  75 . To that end, coupling elements  94  may be more or less malleable than contaminant  75 . In an embodiment wherein coupling elements  94  are more malleable than contaminants  75 , the force imparted upon contaminant  75  is reduced due to deformation of coupling elements  94  occurring from impact with contaminant  75 . As a result, contaminant  75  may become imprinted within coupling element  94  and/or entangled in a network of coupling elements  94 . This may produce a mechanical linkage between coupling element  94  and contaminant  75 , fixing the relative position therebetween. Mechanical stresses may be transferred of coupling elements  94  to contaminant  75 , thereby increasing the probability that contaminant  75  is broken free from surface  98 . Additionally, a chemical coupling mechanism, such as adhesion between contaminant  75  and coupling elements  94 , may occur. 
         [0042]    Where coupling elements  94  and contaminant  75  sufficiently rigid, a substantially elastic collision would occur resulting in a significant transfer of energy from coupling elements  94  to contaminant  75 , thereby increasing the probability that contaminant  75  is broken free from surface  98 . However, the chemical coupling mechanism of adhesion between coupling elements  94  and contaminant  75  may be attenuated, which may reduce the probability gained by the collision. 
         [0043]    In addition, to mechanical and chemical coupling mechanisms discussed above, electrostatic coupling may occur. For example, were coupling element  94  and contaminant  75  to have opposite surface charges they will be electrically attracted. It is possible that the electrostatic attraction between coupling element  94  and contaminant  75  can be sufficient to overcome force connecting contaminant  75  to surface  98 . It should be realized that one or more the aforementioned coupling mechanisms may be occurring at any given time with respect to one or more contaminants  75  on surface. In addition, this may occur randomly or be induced by having coupling element  94  formed from different materials and having different shape and hardness. Alternatively, the electrostatic repulsive interaction between the approaching coupling element  94  and the contaminant  75  may be strong enough to dislodge the contaminant  75  from the surface  98 . 
         [0044]    Referring to  FIGS. 2 ,  4  and  7 , interaction of coupling elements  94  with contaminant  75  is achieved, in part, by generating relative movement between substrates  64  and solution  71 . Relative movement between suspension  90  and substrate  64  occurs at a rate to impart sufficient momentum to allow coupling elements  94  to impact with contaminants  75  and impart a sufficient drag force {right arrow over (F)} D  to move contaminant from surface  98  of substrate  64 , as discussed above. In one embodiment of the present invention, relative movement occurs by placing cassette  70  into solution  71  at a requisite velocity to generate the momentum discussed above and without causing so a quantity of momentum that would damage features of substrate  64  should the same impact with coupling elements  94 . This occurs, in part, by filling immersion tank  52  with solution  71  at function  200 . At function  202 , cassette  70 , having a least one substrate  64  with contaminants  75  thereon, is lowered into solution  71 , generating relative movement between solution  71  and substrate  64 . In this manner, two spaced apart flows  100  and  102  are created around substrate  64 . As shown flow  100  is adjacent to a side of substrate  64  that is opposite to the side to which flow  102  is adjacent. The direction of flows  100  and  102  is substantially transverse to a normal, N, to a surface of substrate  64 . Flow  100  and  102  each has coupling elements  94  entrained therein. The relative movement imparts sufficient drag upon a subset of coupling elements  94  in each of flows  100  and  102  to interact with and cause contaminants  75  to move with respect to the substrate  64  and be removed therefrom. Following a sufficient amount of movement substrates may be removed from cassette  70  by the manner discussed above at function  204 . Following removal substrate  64  may be rinsed to as to completely remove contaminants remaining on substrate  64  by, for example, a de-ionized water (DIW) rinse at function  206 . Alternatively, solution  71  may be drained vis-à-vis one of conduits  55 . Thereafter, another one of conduits  55  may be employed for the introduction of DIW to rinse any remaining contaminants from substrates  64 . 
         [0045]    Referring to both  FIGS. 4 and 8 , in another embodiment, cassette  70  is lowered into immersion tank  52  in the absence of solution  71 . Specifically, cassette  70  is placed to rest upon shelf  93  that is supported upon closed  58  by supports  95 . Thereafter, solution  71  is introduced into immersion tank  52  by a showerhead  101 . To that end, showerhead  101 , in fluid communication with a supply  103  of solution  71 , is designed to produce a plurality of flows of solution  71  having coupling elements  94  entrained therein. Concurrently with ingress of solution  71  into immersion tank  52 , conduits  55  may function as drains to remove the same therefrom. Showerhead  101  is configured to generate a curtain of solution  71 , which is flowed over opposed surface of each of substrates  64  for a sufficient amount of time to remove contaminants  75  from the surfaces thereof. In another embodiment of the present invention, conduits  55  may be closed to allow solution  71  exiting showerhead  101  to accumulate in immersion tank  52  and allow substrate  64  to become submerged in solution  71 . This may be undertaken by coupling of a pump system  106  to each of conduits  55  to control the flow rate therethrough. Posts  95  may be configured to allow shelf to reciprocating between position  105  and position  107 . In this manner, relative motion between solution  71  and opposed surfaces of each of substrates  64  may occur along opposing directions. 
         [0046]    Exemplary embodiments of suspension  90  includes a liquid region  92  having a viscosity between about 1 Centipoises (cP) to about 10,000 cP. Moreover, liquid regions  69  may be a Newtonian fluid or a non-Newtonian fluid. Exemplary materials that may be employed as liquid region  92  include de-ionized water (DIW), hydrocarbon, a fluorocarbon, a mineral oil, or an alcohol and the like. Furthermore, suspension  90  may include ionic or non-ionic solvents and other chemical additives. For example, the chemical additives to suspension  90  can include any combination of co-solvents, pH modifiers, chelating agents, polar solvents, surfactants, ammonia hydroxide, hydrogen peroxide, hydrofluoric acid, tetramethylammonium hydroxide, and rheology modifiers such as polymers, particulates, and polypeptides. 
         [0047]    Coupling elements  94  may possess physical properties representing essentially any sub-state such that in addition to the properties set forth above, do not adhere to surface  98  when positioned in close proximity or contact with surface  98 . Additionally, the damage caused to surface  98  by coupling elements  94  should be deminimus, as well as the adhesion between coupling elements  94  and surface  98 . In one embodiment, the hardness of coupling elements  94  is less than the hardness of surface  98 . Moreover, it is desired that coupling element  94  avoiding adherence to surface  98  when positioned in either close proximity to or in contact with surface  98 . Various embodiments coupling elements  94  may be defined as crystalline solids or non-crystalline solids. Examples or non-crystalline solids include aliphatic acids, carboxylic acids, paraffin, wax, polymers, polystyrene, polypeptides, and other visco-elastic materials. To that end, the quantity of coupling elements  94  in suspension  90  should be present at a concentration that exceeds its solubility limit within liquid region  92 . 
         [0048]    It should be understood that the aliphatic acids represent essentially any acid defined by organic compounds in which carbon atoms form open chains. A fatty acid is an example of an aliphatic acid that can be used as coupling element  94  within suspension  90 . Examples of fatty acids that may be used include lauric, palmitic, stearic, oleic, linoleic, linolenic, arachidonic, gadoleic, eurcic, butyric, caproic, caprylic, myristic, margaric, behenic, lignoseric, myristoleic, palmitoleic, nervanic, parinaric, timnodonic, brassic, clupanodonic acid, lignoceric acid, cerotic acid, and mixtures thereof, among others. 
         [0049]    In one embodiment, coupling elements  94  may represent a mixture of fatty acids formed from various carbon chain lengths extending from C-1 to about C-26. Carboxylic acids are defined by essentially any organic acid that includes one or more carboxyl groups (COOH). When used as coupling elements  94 , the carboxylic acids can include mixtures of various carbon chain lengths extending from C-1 through about C-100. Also, the carboxylic acids can include other functional groups such as but not limited to methyl, vinyl, alkyne, amide, primary amine, secondary amine, tertiary amine, azo, nitrile, nitro, nitroso, pyridyl, carboxyl, peroxy, aldehyde, ketone, primary imine, secondary imine, ether, ester, halogen, isocyanate, isothiocyanate, phenyl, benzyl, phosphodiester, sulfhydryl, but still maintaining insolubility in suspension  90 . 
         [0050]    One manner by which to form suspension  90  with regions formed from carboxylic acid components includes presenting liquid regions  69  as a gel that is formed from a concentration of carboxylic acid solids, such as between about 3% to about 50 wt % and preferably between about 4% to about 20 wt %, with De-ionized water (DIW). Ammonium hydroxide may be added to the solution and the mixture heated to between 55° C. to about 85° C., inclusive to facilitate the solids going into solution, i.e., dissolving. Once the solids are dissolved, the cleaning solution can be cooled down. During the cooling down process, solid compounds in the form of needles or plates would precipitates. An exemplary suspension  90  formed in this manner has a viscosity of about 1000 cP at 0.1 per second shear rate and the viscosity falls to about 10 cP when the shear rate increases to 1000 per second, i.e., it is a non-Newtonian fluid. It should be understood that suspension may be formed by carboxylic acid(s) (or salts) in solvents other than water, polar or non-polar solvents, such as alcohol, may be employed. 
         [0051]    Another embodiment of suspension  90  has coupling elements  94  are formed from a hydrolyzed chemical agent, or by including a surfactant. For example, a dispersant material may be included in liquid region  92  to facilitate dispersal of coupling element  94  throughout suspension  90 . To that end, a base can be added to suspension  90  to enable entrainment of coupling elements  94  from materials such as carboxylic acid or stearic acid that are present in less than stoichiometric quantities. An exemplary base is Ammonium Hydroxide, however, any commercially available base may be used with the embodiments described herein. Additionally, the surface functionality of the materials from which coupling elements  94  are formed may be influenced by the inclusion of moieties that are miscible within suspension  90 , such as carboxylate, phosphate, sulfate groups, polyol groups, ethylene oxide, etc. In this manner, it may be possible to disperse coupling elements  94  throughout suspension  90  while avoiding unwanted agglomeration of the same, i.e., form a substantially homogenous suspension  90 . In this manner, avoided may be a situation in which an agglomeration of coupling elements  94  becomes insufficient to couple to and/or remove contaminant  96  from surface  98 . 
         [0052]    Referring to  FIG. 9 , in another alternate embodiment, suspension  190  may include an additional component, referred to as an immiscible component  111  that is entrained in liquid region  192 . Immiscible components include may include a gas phase, a liquid phase, a solid phase of material, or a combination thereof. In the present example, immiscible components  111  are regions comprising entirely of a plurality of spaced-apart gas pockets dispersed throughout liquid region  192  of suspension  190 . The immiscible components comprise from 2% to 99%, inclusive suspension  190  by volume. Exemplary gas phase immiscible components  111  may be formed from the following gases: nitrogen, N 2 , argon, Ar, oxygen, O 2 , ozone, O 3 , peroxide, H 2 O 2 , air, hydrogen, H 2 , ammonium, NH 3 , hydrofluoric acid, HF. 
         [0053]    Liquid phase immiscible components  111  may include a low-molecular weight alkane, such as, pentane, hexane, heptane, octane, nonane, decane, or mineral oil. Alternatively, liquid phase immiscible components  111  may include oil soluble surface modifiers. Referring to both  FIGS. 4 and 9 , suspension  190  functions substantially similar to suspension  90  with respect to removing contaminant  75 , with coupling elements  94  being substantially similar to coupling elements  94  and liquid region  192  being substantially similar to liquid region  92 . In suspension  190 , however, immiscible component  111  is believed to facilitate placing coupling elements  194  in contact with, or close proximity to, contaminant  75 . To that end, one or more of regions in close proximity to, or contact with contaminant  75 , is disposed between contaminant  75  and one or more immiscible components  111 . Having a surface tension associated therewith, immiscible component  111  subjects coupling elements  194  to a force (F) on coupling element  194  in response to forces in liquid region  192 . The force (F) moves coupling element  194  toward surface  98  and, therefore, contaminant  75 . Coupling between coupling element  194  and contaminant  75  may occur in any manner discussed above with respect to coupling elements  94  and contaminant  75 . 
         [0054]    Immiscible components  111  may be entrained in suspension  190  before being disposed on substrate  64 . Alternatively, immiscible components  111  may be entrained in suspension  190  in-situ as suspension is being deposited on surface  98  and/or may be generated by impact of suspension  190  with surface  98  thereby entraining gases, such as air, present in the surrounding ambient, e.g., generating a foam. In one example, immiscible components  111  may be generated from a gas dissolved within liquid region  192  that comes out of solution upon suspension  190  being subjected to a decrease in ambient pressure relative to pressure of suspension  190 . On advantage of this process is that the majority of immiscible components  111  will form proximate to coupling elements  194 , due to coupling elements  194  have moved settled under force gravity toward surface  98 . This increases the probability that coupling elements  194  coupling with contaminant  75 . 
         [0055]    As with bi-state suspension  90 , tri-state suspension  190  may include additional components to modify and improve the coupling mechanism between coupling elements  194  and contaminant. For example, the pH of the liquid medium can be modified to cancel surface charges on one or both of the solid component and contaminant such that electrostatic repulsion is reduced or amplified. Additionally, the temperature cycling of suspension  190  may be employed to control, or change, the properties thereof. For example, coupling elements  94  may be formed from a material, the malleability of which may change proportionally or inversely proportionally with temperature. In this fashion, once coupling elements  94  conform to a shape of contaminant, the temperature of suspension may be changed to reduce the malleability thereof. Additionally, the solubility of suspension  190  and, therefore, the concentration of coupling elements  94  may vary proportionally or inversely proportionally with temperature. 
         [0056]    An exemplary suspension  190  is fabricated by combining Stearic acid solids, heated above 70° Celsius, to DIW heated above 70° Celsius. The quantity of Stearic acid solids combined with the DIW is approximately 0.1% to 10%, inclusive by weight. This combination is sufficiently to disperse/emulsify the Stearic acid components within the DIW. The pH level of the combination is adjusted above 9 to neutralize the stearic acid components. This is achieved by adding a base, such as ammonium hydroxide (NH 4 OH) to provide a concentration of 0.25% and 10%, inclusive by weight. In this manner, an acid-base mixture is formed, which is stirred for 20 minutes to ensure the homogeneity of the mixture. The acid-base mixture is allowed to reach ambient temperature allowing the fatty acid salt to precipitate and form coupling elements  194 . It is desired that coupling elements  194  formed during precipitation reach a size in a range of 0.5 to 5000 micrometers, inclusive. Immiscible component  111  may be formed from entrainment of air within the acid-base mixture as the same is stirred, if desired. 
         [0057]    In another embodiment, suspension  190  is formed by from granular Stearic acid solids milled to a particle size in a range of 0.5 to 5000 micrometers, inclusive. The milled Stearic acid in granular form is added to DIW while agitating the same to form an acid-DIW mixture. Agitation of the DIW may occur by any means known, such as shaking, stirring, rotating and the like. The Stearic acid forms approximately 0.1% to 10%, inclusive, by weight of the acid-DIW mixture. Dissociation of the Stearic acid is achieved by establishing the pH level of the acid-DIW mixture to be approximately 9 by adding a base. An exemplary base includes ammonium hydroxide (NH 4 OH) in a concentration of 0.5% to 10%, inclusive by weight. The base neutralizes the Stearic acid component forming ammonium stearate salt particles. Typically the NH 4 OH is added to the acid-DIW mixture while the same is being agitated to disperse the solidified Stearic acid particles throughout the acid-DIW mixture. The size distribution of these solidified ammonium stearate particles is in a range of 0.5 to 5,000 micrometers, inclusive. 
         [0058]    In yet another embodiment, suspension  190  is formed from a Stearic-palmitic acid mixture dissolved in isopropyl alcohol (IPA) while the IPA is agitated, as discussed above. This provides a concentration of dissolved fatty acids present in the concentration from a range 2% to 20%, inclusive by weight. Heating of the IPA while avoiding boiling of the same and/or adding an organic solvent, such as acetone, benzene or a combination thereof, may improve solubility of the fatty acid. Any solids remaining in the concentration following dissolution may be removed by filtration or centrifugation techniques, producing a solid-free solution. The solid-free solution may be mixed with a liquid that is a non-solvent, to the fatty acid, such as water, to precipitate a fatty-acid solid. The precipitated fatty acid becomes suspended in solution with the size distribution in the range between 0.5 and 5,000 microns, inclusive. The Stearic acid component may be ionized, as discussed above. 
         [0059]    Referring to  FIG. 10  in accordance with another embodiment of the present invention a substrate cleaning system  400  (SCS) includes a plurality of immersion tanks, shown as  402 ,  404  and  406 . Each of immersion tanks  402 ,  404  and  406  may include any one of suspensions mention above, e.g., suspension  90  or  190 . A picker system that includes multiple pickers, shown as  408 ,  410  and  412 . Each of pickers  408 ,  410  and  412  is coupled to reciprocate along a track  414  so that a substrate  64  held by any one of pickers  408 ,  410  and  412  may be placed in any one of immersion tanks  402 ,  404  and  406 . System  400  is operated under control of a processor  416 , which is in data communication with a computer-readable memory  418 . Processor  416  controls operation of system  400  to submerge substrates  64  into immersion tanks  402 ,  404  and  406 . To that end, processor is in data communication with a motor  420  that functions to move pickers  408 ,  410  and  412  along track  414 , as well as move substrate  64  into, and out of, immersion tanks  408 ,  410  and  412 . Processor is also in data communication with fluid supplies  422 ,  424  and  426  to regulate the introduction of fluids into immersion tanks  408 ,  410  and  412 . Additionally, processor  416  is in data communication with immersion tanks  408 ,  410  and  412  to control the operation thereof, e.g., to allow drainage of fluids from immersion tanks  408 ,  410  and  412 . 
         [0060]    Referring to both  FIGS. 10 and 11  in operation, one of pickers  408 ,  410  and  412 , shown as picker  408 , deposits a substrate  64  into one of immersion tanks  402 ,  404  and  406 , shown as being immersion tank  402 . While in immersion tank  402 , substrate  64  rests upon support  428 . Immersion tank  402  is then filled with solution  71 . Solution  71  is introduced into immersion tank  402  under operation of processor  416 , which facilitates pump (not shown) of fluid supply  422  to move solution  71  from there along conduits  430  and into the appropriate immersion tank  402 ,  404  and  406 . To control flow into immersion tanks  402 ,  404  and  406 , each of the same includes a valve  432 ,  434  and  436 , in data communication with, and operated under control of, processor  416 . Valve  432  selectively allows and prevents fluid from progressing from fluid supplies  422 ,  424  and  426  to immersion tank  402 ; valve  434  selectively allows and prevents fluid from progressing from fluid supplies  422 ,  424  and  426  to immersion tank  404 ; and valve  436  selectively allows and prevents fluid from progressing from fluid supplies  422 ,  424  and  426  to immersion tank  406 . Drainage from immersion tanks  402 ,  404  and  406  is regulated by processor  416  controlling pumps  438 ,  440  and  442 , which is in data communication therewith. Specifically, drainage of immersion tank  402  is facilitated or prevented by pump  438 ; drainage of immersion tank  404  is facilitated or prevented by pump  440 ; and drainage of immersion tank  406  is facilitated or prevented by pump  442 . 
         [0061]    During one mode of operation, solution  71  is introduced into immersion tank  402  at outlet  446  to fill upon immersion tank  402 . This may be achieved before or after introducing substrate  62  into immersion tank  402 . Typically, however, substrate  64  is position in immersion tank  402  before introduction of solution  71 . After resting again support  428 , processor  416  introduces solution  71  into immersion tank  402 . As solution  71  is introduced through outlet  446 , processor  416  activates pump  438  to evacuate solution  71  from immersion tank  402 . In this manner, substrate  64  is exposed to a continuous flow of solution  71 . It should be noted that each of immersion tanks  402 ,  404  and  406  may employed concurrently to expose substrate  64  to a continuous flow of solution  71 . To that end, valves  432 ,  434  and  436  would be operated to allow the ingress of solution  71 , from one of supplies  422 ,  424  and  426  into immersion tanks  420 ,  404  and  406 . Alternatively, one or more of immersion tanks  402 ,  404  and  406  may include DIW, supplied from one of supplies  422 ,  424  and  426 . After being exposed to solution  71 , substrate  564  would be rinsed by being exposed to DIW. This may be accomplished by filling one of immersion tanks  420 ,  404  and  406  with DIW and then introducing substrate  64  therein. Alternatively, substrate  64  may be present in one of immersion tanks,  420 ,  404  and  406 , after which time DIW would be introduced into the same. As well, one of immersion tanks  402 ,  404  and  406  may include suspension  90  while one of the remaining immersion tanks  402 ,  404  and  406  may include suspension  190 , with the remaining immersion tanks  402 ,  404  and  406  would contain DIW. In this configuration, substrate  64  would be exposed to both suspensions  90  and  190  before being rinsed with DIW. It is feasible to sequentially expose substrate  64  suspensions  90  and  190  and DIW sequentially in a common immersion tank  402 . If desired, immersion tanks  402 ,  404  and  406  may be sealed after substrate  64  is placed therein, shown by cover  450  sealing immersion tank  406  including a throughway  52  that may be connected to a purge gas supply  454 , such as helium. In this manner immersion tank  406  may be environmentally controlled to reduce, if not avoid, premature drying of substrate  84 . An O-ring is employed to form a hermetically-tight seal between cover  450  and immersion tank  406 . 
         [0062]    Referring to both  FIGS. 10 and 12 , another embodiment of immersion tanks  402 ,  404  and  406  is shown as immersion tank  502  having a lid  503  with an o-ring  505  forming a fluid tight seal with body  507  of immersion tank  502 . Specifically, immersion tank includes a plurality of throughways  540 ,  542 ,  544 ,  546 ,  547 ,  548 ,  550  and  552 . Throughways  540  and  548  are selectively placed in fluid communication with a supply of isopropyl alcohol (IPA) and DIW, and throughways  546  and  552  are selectively placed in fluid communication with a supply of cleaning solution and DIW. Specifically, throughway  540  may be selectively placed in fluid communication with IPA supply  554  and DIW supply  556  vis-à-vis valves  558  and  560 , respectively. Throughway  548  may be selectively placed in fluid communication with IPA supply  562  and DIW supply  564  vis-à-vis valves  566  and  568 , respectively. Throughways  542  and  550  are in fluid communication with drains  570  and  572 , respectively. Throughway  546  may be selectively placed in fluid communication with a supply  574  of cleaning solution  71  and DIW supply  576  vis-à-vis valves  580  and  582 , respectively. Throughway  547  may be selectively placed in fluid communication with drain  549  vis-à-vis a valve  551 . Throughway  552  may be selectively placed in fluid communication with a supply  584  of cleaning solution  71  and DIW supply  586  vis-à-vis valves  588  and  590 , respectively. 
         [0063]    In operation, substrate  64  is placed in immersion tank  502  in the absence of solution  71 . One or both of valves  580  and  588  are activated, under control of processor  416  to generate a flow of solution into immersion tank  502  through throughways  546  and  552 , respectively. As a result, flows  600  and  602  of solution  71  are generated that move in a direction opposite to gravity {right arrow over (g)}; so as to pass adjacent to opposed surfaces  65  and  67  of substrate  64 , with solution exiting immersion tank  502  by passing into throughways  542  and  550  onto drains  570  and  572 , respectively. After exposure to a sufficient quantity of solution  71  surfaces  65  and  67  are rinsed by exposure to one or more of IPA and/or DIW. To that end, valves  580  and  588  are deactivated and valves  582  and  590  are activated. In this fashion, substrate  64  is exposed to DIW from supplies  576  and  586 , with the DIW passing into drains  570  and  572 . Alternatively, valves  551 ,  560  and  568  may be activated to allow flows  610  and  612  of DIW along a path in the direction of gravity {right arrow over (g)} and exit to drain  549  This is undertaken in the absence of a vacuum. After substrate  64  is completely submerged with DIW, pump  570  is activated to remove DIW. In a similar manner, substrate  64  may be rinsed with IPA from supplies by activation of valves  558  and  566 . 
         [0064]    Referring to  FIGS. 12 and 13 , in accordance with another embodiment of the present invention, another embodiment of immersion tank  502  is shown as immersion tank  602  in which a body  607  throughways,  642 ,  644 ,  646 ,  647 ,  650 ,  652 , drains  649 ,  670 ,  672 , supplies  674 ,  676 ,  684 ,  686  and valves  680 ,  682 ,  688  and  649  provide the same functions provided by body  507  throughways  542 ,  544 ,  546 ,  547 ,  550  and  552 , drains  570 ,  572 , supplies  574 ,  576 ,  584 ,  586  and valves  580 ,  582 ,  588  and  549 , respectively. In addition, immersion tank  602  has formed into body  607  two additional throughways  691  and  692  that allow access to immersion tank by IPA from supply  654  and  662 , respectively. Specifically, valve  658  allows selectively access of IPA from supply  654  to immersion tank  602 , valve  666  allows selectively access of IPA from supply  662  to immersion tank  602 . Valve  660  allows selectively access of DIW from supply  656  to immersion tank  602 , and valve  668  allows selectively access of DIW from supply  664  to immersion tank  602 . In addition, a support  693  upon which substrate  64  rests is coupled to a motor  694  to allow varying a distance between substrate  64  and throughway  647 . Lid  603  includes two sets of O-rings  605  and  606 . O-ring  605  functions in the manner as O-ring  605 . O-ring  606 , on the other hand is positioned at an end of a stopper portion  695  of lid  603  positioned between throughways  540 ,  548  and throughways  542  and  550 . In this configuration, throughways  691 ,  692 ,  640  and  648  are isolated from fluid flow exiting throughways  546  and  552  when valve  551  prevents flow to drain  549 , i.e., a fluid-tight seal if formed between both throughways  642  and  650  and the throughways  691 ,  692 ,  640  and  648 . 
         [0065]    Referring to  FIG. 13 , in one manner of operation, substrate  64  is present placed in immersion tank  602  in the absence of solution  71 . One or both of valves  680  and  688  are activated, under control of processor  416  to generate a flow of solution into immersion tank  602  through throughways  646  and  652 , respectively. valve  551  is deactivated to prevent flow of solution  71  into drain  549 . As a result, flows  700  and  702  of solution  71  are generated that move in a direction opposite to gravity {right arrow over (g)} so as to pass adjacent to opposed surfaces  65  and  67  of substrate  64 , with solution exiting immersion tank  602  by passing into throughways  642  and  650  onto drains  670  and  672 , respectively. 
         [0066]    Referring to both  FIGS. 13 and 14 , after exposure to a sufficient quantity of solution  71  surfaces  65  and  67  are rinsed by exposure to one or more of IPA and/or DIW. Specifically lid  601  is removed to place expose throughways  691 ,  692 ,  540  and  548  in fluid communication with throughways  542  and  550 . Valves  658  and  666  are activated to generate a flow of IPA under force of gravity {right arrow over (g)} that results in the formation of a meniscus  700  where solution  71  contacts IPA and air in immersion tank  602 . During the flow of IPA from both throughways  691  and  692  motor  694  operates to move holder  693  and lift substrate  64  out of immersion tank  602 . As a result, solution  71  is removed from substrate  64  as the same exits immersion tank. 
         [0067]    While this invention has been described in terms of several embodiments, it will be appreciated that those skilled in the art upon reading the preceding specifications and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. Therefore, it is intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention. In the claims, elements and/or steps do not imply any particular order of operation, unless explicitly stated in the claims. 
         [0068]    In one embodiment, the memory stores computer-readable instructions to be operated on by the processor, wherein the computer-readable instructions include a first set of code to control said carrier sub-system and place said substrate in the tank and a second set of code to control the solution handling sub-system. 
         [0069]    In one embodiment, the computer-readable instructions further include a first sub-routine to control said solution handling system to terminate said spaced-apart flows and fill said tank with said solution and a second sub-routine to control said carrier sub-system to remove said substrate from said tank. 
         [0070]    In one embodiment, the computer-readable instructions further include a first sub-routine to control said solution handling system to fill said tank with said solution. 
         [0071]    In one embodiment, the computer-readable instructions further include a sub-routine to fill said tank with a quantity of said solution and terminate said spaced-apart flows.