Patent Publication Number: US-2007113923-A1

Title: Apparatus and method for minimizing the generation of particles in ultrapure liquids

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a continuation of U.S. patent application Ser. No. 10/139,185, filed on May 3, 2002 in the name of KELLY, Wayne et al. and entitled, “APPARATUS AND METHOD FOR MINIMIZING THE GENERATION OF PARTICLES IN ULTRAPURE LIQUIDS.” The priority of U.S. patent application Ser. No. 10/139,185 is claimed under the provisions of 35 USC §120.  
      The disclosures of the following patent applications are hereby incorporated herein by reference in their respective entireties: U.S. Pat. No. 6,698,619 of Richard Wertenberger, entitled “BAG-IN-DRUM FLUID STORAGE AND DISPENSING CONTAINER HAVING RECTANGULAR PARALLELEPIPED CONFORMATION, AND INTEGRATED FLUID SUPPLY SYSTEM UTILIZING SAME”; and U.S. patent application Publication No. US2003/0004608 A1 of Kevin T. O&#39;Dougherty and Robert E. Andrews, entitled “LIQUID HANDLING SYSTEM WITH ELECTRONIC INFORMATION STORAGE.” 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates to minimizing the generation of particles in ultra pure liquids. In particular, the present invention relates to minimizing the generation of particles in ultra pure liquids during filling, dispensing, and transport of containers.  
      Numerous industries require that the number and size of particles in ultra pure liquids be controlled to ensure purity. In particular, because ultra pure liquids are used in many aspects of the microelectronic manufacturing process, semiconductor manufacturers have established strict particle concentration specifications for process chemicals and chemical-handling equipment. These specifications continue to become more stringent as manufacturing processes improve. Such specifications are needed, since if the fluids used during the manufacturing process contain high levels of particles, then the particles may be deposited on solid surfaces. This can in turn render the product deficient or even useless for its intended purpose.  
      A general philosophy behind the specifications is that if the fluid is clean, and the fluid handling component is also clean, the fluid passing through the component will remain clean. Alternatively, if a fluid container is clean, and the container is being filled with clean fluid, the fluid will remain clean during the filling process. A clean fluid in a clean container should still be clean upon delivery to the customer. Fluid handling components fresh from the manufacturing operation are often cleaned prior to packaging, and inherent in the cleaning operation is the assumption that the cleaning system itself does not contaminate the cleaning liquid. In contrast, it is also generally recognized that certain fluid handling components, like pumps, will continuously shed particles into the fluid that the pump is delivering.  
      However, it is not generally recognized that particles can appear in fluids to a greater or lesser degree depending upon the manner in which the fluid is passed through a component or is delivered to a container. For example, it has been discovered that if a clean container is partially filled with clean water, capped, and shaken vigorously, the particle concentration in the water will increase dramatically. New steps are required to ensure that particle concentrations in liquids are low enough to meet the stringent industrial specifications.  
      Thus, there is a need in the art for a system that minimizes particle generation in liquids during filling the containers, transporting the filled containers, and dispensing the liquids from the containers.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention relates to systems and methods of filling containers with ultra pure liquids in a manner that minimizes the amount of particles generated in the liquid. The presence of an air-liquid interface in the container has been shown to increase the particle concentration observed in the liquid. The present invention relates to systems and methods that minimize the air-liquid interface when filling, transporting, and dispensing liquids from containers.  
      A first method of reducing particle generation in an ultra pure liquid is to fill containers using a bottom fill method. The bottom fill method is achieved by utilizing a dip tube having a submerged tip from which the liquid enters the container. Submerging the tip of the dip tube below the surface of the liquid during filling of the container allows the liquid to enter the container with reduced splashing, turbulence, and entrainment of air. Avoiding splashing, turbulence, and entrainment of air ensures the air-liquid interface is minimized, and thus reduces the particles generated in the liquid.  
      A second method of reducing particle generation in an ultra pure liquid is to fill containers for the liquid, of the type including a liner and a rigid overpack, by first collapsing the liner, and filling the collapsed liner. Filling the container according to this method removes the air-liquid interface in the liner, and results in a filled container having no headspace air.  
      Other methods of reducing particle generation in an ultra pure liquid include submerging the nozzle in a system that uses a nozzle to either fill a container or as a cleaning jet. Submerging the nozzle below the surface of the liquid reduces the air-liquid interface and results in less particle generation.  
      In addition, in recirculation baths having a weir over which liquid can fall into a sump, particle generation can occur as the liquid falls into the sump, and causes splashing, bubbles, and turbulence. By reducing the overspill distance between the weir and the liquid in the sump, so that the liquid enters the sump with minimal splashing, reduced particle concentration in the liquid is achieved.  
      In siphoning systems, utilizing a smart siphon can also reduce particle concentrations. A smart siphon is one that is controlled to stop the siphoning action before the siphoning action is broken by entrainment of air and causes the remaining liquid in the siphon to fall back into the tank.  
      Finally, ensuring that any head space air is removed from the container before shipping reduces the particle concentration in the liquid in the container. In containers using liners, the head-space can be removed from the liner by pressurizing the container and venting out the head space air. In addition, in rigid containers, an inert bladder can be inserted to remove the head-space. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an illustration of a standard top fill arrangement for filling a container with an ultra pure liquid.  
       FIG. 2  is an illustration of a submerged tube bottom fill method for filling a container.  
       FIG. 3  is an illustration of a container having a collapsible liner.  
       FIG. 4A  is an illustration of a standard top fill arrangement for filling a container.  
       FIG. 4B  is an illustration of dispensing the contents of a container filled as illustrated in  FIG. 4A  so that the dispensed liquid is passed through an optical particle counter and rotometer.  
       FIG. 5A  is an illustration of a submerged tube bottom fill method for filling a container.  
       FIG. 5B  is an illustration of dispensing the contents of a container filled as illustrated in  FIG. 5A  so that the dispensed liquid is passed through an optical particle counter and rotometer.  
       FIGS. 6A-6D  are illustrations of a method of filling a container having a collapsible liner, and then dispensing the liquid from the container.  
       FIGS. 7A-7C  are illustrations of a method of filling a first container, dispensing the contents of the first container to a second container, and dispensing the contents from the second container through an optical particle counter and rotometer.  
       FIG. 8A  is an illustration of the standard method of filling a container using a nozzle.  
       FIG. 8B  is an illustration of a method of filling a container by submerging the fill nozzle.  
       FIG. 9  is a graph illustrating the particle concentration over elapsed time for both submerged nozzles and nozzles above the surface.  
       FIG. 10A  is an illustration of liquid in a recirculation bath overspilling a weir into an overflow sump area.  
       FIG. 10B  is an illustration of liquid in a recirculation bath overspilling a weir into an overflow sump area in a manner, which reduced particle formation in the liquid.  
       FIG. 11  is an illustration of a system in which water spilling from a bath over a weir into the sump for the recirculating pump is tested for particle concentration.  
       FIG. 12  is a graph indicating the particle concentration over an elapsed time of a filter flush up in a recirculating bath test.  
       FIG. 13  is a graph indicating the particle counts over elapsed time for a recirculating bath with a filter bypass.  
       FIG. 14  is an illustration of a siphoning system for filling a tank.  
       FIG. 15  is a graph illustrating the particle counts over elapsed time for a bottom filling smart siphon.  
       FIG. 16  is a graph illustrating the particle counts over elapsed time for a top filling smart siphon.  
       FIG. 17  is a graph illustrating the particle counts over elapsed time for a bottom filling dumb siphon.  
       FIG. 18  is a graph illustrating the particle counts over elapsed time for a top filling, dumb siphon.  
       FIGS. 19A and 19B  are illustrations of a method of filling a container and removing the head space in the filled container.  
       FIGS. 20A and 20B  are illustrations of a method of filling a container and removing the head space using an inert bladder.  
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is an illustration of a standard top fill arrangement for filling a container with an ultra pure liquid. Shown in  FIG. 1  is a container  1 , liquid  2 , spigot  3 , fill line  4 , valve  5 , and ultra pure liquid source  6 . The valve  5  is located on the fill line  4  between the ultra pure liquid source  6  and the spigot  3 . When the valve  5  is open, ultra pure liquid  2  enters the container  1  at the spigot  3 . The spigot is located over an opening at the top of container  1 .  
      As the ultra pure liquid exits the spigot  3 , the liquid  2  falls freely into container  1  causing splashing, bubbling, and entrainment of air. The splashing, bubbling, and entrainment of air increase the surface area of the liquid, thus increasing an air-liquid interface of the liquid in the container. It has been found that filling a container in this manner causes significant particle generation in the liquid  2  stored in the container  1 , resulting in increased particle concentration in the liquid  2 .  
     Bottom Fill Method  
       FIG. 2  illustrates a modification of the fill system of  FIG. 1 , which reduces the particle concentration in the liquid  2 . Shown in  FIG. 2  is a container  7  with spigot  3  connected to fill line  4 , valve  5 , and ultra pure liquid source  6 , similar to the system of  FIG. 1 . However, unlike the system of  FIG. 1 , the fill system of  FIG. 2  further comprises a fill tube  8  connected to the spigot  3 . The fill tube  8  ends in a submerged tip  9  and extends downwardly in the interior volume of the container  7  so that the submerged tip  9  is positioned near the bottom of the container  7 .  
      As the container  7  is filled, the submerged tip  9  is submerged under the surface of the liquid  2  during substantially the entire filling cycle, allowing the liquid flow from the tip  9  to remain contiguous under the liquid surface  2 . As a result, the liquid exits submerged tip  9  without falling into the container  7 . Rather, the introduction of liquid  2  into the container  1  is much more smooth, and causes much less splashing, bubbling, or turbulence.  
      Filling the container using fill tube  8  with a submerged tip  9  has been found to result in lower particle concentration in the liquid  7 . In particular, when compared to the conventional top filling method in  FIG. 1 , the bottom filling method of  FIG. 2  results in a much lower particle generation in the liquid  2 . By submerging the tip  9  of the fill tube  8 , the air-liquid interface is kept less turbulent, and the overall surface area of the liquid is decreased. This decreased air-liquid interface in turn retards particle shedding from container  58 , and minimizes the particle concentration observed in the liquid.  
     Collapse Liner Fill Method  
       FIG. 3  illustrates an alternative type of container used in packaging ultra pure liquids. The container  10  in  FIG. 3  comprises a rigid outer container  12 , a collapsible liner  14 , an intermediate area  16 , a dip tube  18 , and a fitment  20 . A standard method of filling the container  10  is to insert the liner  14  into the rigid outer container  12 . The liner  14  is then inflated until the liner  14  presses against the outer container  12 . Once the liner  14  is inflated, the container  10  can then be filled with liquid in a conventional manner.  
      This method of filling the container in  FIG. 3  can be modified to minimize particle generation during filling. More particularly, the container  10  shown in  FIG. 3  can be filled in a manner that greatly reduces the air-liquid interface during filling of the container.  
      Connected to the container  10  are an ultra pure liquid source  22 , clean, dry air source  24 , vent  26 , dispense line  28 , and liner air vent  30 . A fluid fill and dispense line  32  connects the liquid source  22  to the inside of the liner  14  at the dip tube  18 . The fill and dispense line  32  also connects to the dispense line  28 . A fill valve  34  is located on the fill and dispense line  32  to allow fluid flow from the liquid source  22  to the liner  14 . Similarly, a dispense valve  36  is located on the fill and dispense line  32  to allow fluid flow out of the container  10  to the dispense line  28 .  
      An air supply line  38  connects the clean, dry air source  24  to the intermediate area  16  between the liner  14  and rigid container  12 . Located on the air supply line  38  are an air inlet valve  40  and an air vent valve  42 . The air inlet valve  40  controls the air flow from the air source  24  into the intermediate area  16 . Similarly, the air vent valve  42  allows air in the intermediate area  16  to be vented from the container  10  to the vent  26 .  
      An air vent line  44  connects the inside of the liner  14  to the liner air vent  30 . A liner vent valve  46  is located on the air vent line  44  and allows air from inside the liner  14  to be vented to the liner air vent  30  via air vent line  44 .  
      The fitment  20  connects to a top opening of the rigid container  12 . The collapsible liner  14  is configured to be placed within the rigid container  12  and extend into the fitment  20 . The dip tube  18  is disposed within the collapsible liner  14  and protrudes substantially to the bottom of the lined container  10 . The dip tube  18  is also configured to extend into the fitment  20 , and as described above is exposed to the fluid fill line  32 . The intermediate area  16  is the area between collapsible liner  14  and rigid container  12  and varies in size depending on whether collapsible liner  14  is expanded or compressed.  
      The lined container  10  and the manner in which it is connected to lines  32 ,  38 , and  44  allows the container  10  to be filled so as to minimize the air-liquid interface normally present when a rigid container is filled with liquid. Minimizing the air-liquid interface in turn results in minimizing any particle generation in the liquid.  
      This process of filling the container  10  begins with collapsing the liner  14 . Starting with all valves  34 ,  36 ,  40 ,  42 , and  46  closed, the liner  14  is collapsed by opening the air inlet valve  40  and the liner vent valve  46 . Once opened, the air inlet valve  40  allows clean dry air from air source  24  to flow into intermediate area  16  via air supply line  38 . The source  24  of the clean, dry air can be any suitably configured source, and is connected to the air supply line  38  in a conventional manner. This air flow increases pressure in intermediate area  16  and compresses collapsible liner  14 . The liner vent valve  46  is also open so that as air is forced into the intermediate area  16  to collapse the liner  14 , the air forced out of the inside of the liner  14  can exit the container  10  via air vent line  44  and be vented at the liner air vent  30 . Once substantially all of the air has been vented from inside the liner  14  and it is suitably collapsed, the air inlet valve  40  and liner vent valve  46  are closed.  
      After collapsing the liner  14 , the container  10  can be filled using the dip tube  18 , which remains located inside the collapsed liner  14 . To fill the container  14 , the fill valve  34  is opened, as well as the air vent valve  42 . Opening the fill valve  34  allows liquid to flow from the liquid source  22  into the collapsible liner  14  via the fill and dispense line  32 . As lined container  10  is filled, collapsible liner  14  expands. Having the air vent valve  42  open allows the air in the intermediate area  16  to exit the container  10  at the vent  26  via line  46  as the liner  14  fills with fluid and expands.  
      As a result of removing most of the air from the collapsed liner  14 , when liquid is introduced into the liner  14  via the dip tube  18 , the air-liquid interface is greatly reduced, to thereby correspondingly reduce particle shedding from the container  10 . Filling the container  10  using the collapse liner fill method has been shown to reduce the particle generation in the liquid, providing a purer liquid for industrial use.  
      The liquid in the lined container  10  can also be dispensed in a manner that minimizes particle generation. This is accomplished by opening the air inlet valve  40  to allow clean dry air to flow through the air supply line  38  into the intermediate area  16 . The air flow increases pressure in the intermediate area  16  and can be used to compress the collapsible liner  14 . As the collapsible liner  14  is compressed, the liquid contained within the collapsible liner  14  is forced out of the container  10  via the fill and dispense line  32  through the dispense valve  36  and to the dispense line  28 . Dispensing the contents of the container  10  in this manner prevents the need for pumps, which continuously shed particles into the liquid that the pumps are delivering. In addition, this dispensing method reduces the air-liquid interface during dispensing, which has been shown to reduce particle generation in the liquid.  
      Though the collapsed liner fill method described above includes a dip tube through which liquid is introduced into the container using a bottom fill method, the same benefits can be achieved by using a top fill method that does not include a dip tube. The resulting particle concentrations achieved by using the collapsed liner fill method are much less than conventional fill methods. In particular, it has been demonstrated that a particle concentration less than 2 particles per milliliter for particles at 0.2 microns diameter is consistently realized by such collapsed liner fill method. In fact, the collapsed liner fill method in specific embodiments has achieved particle concentrations of less than 1 particle per milliliter for particles at 0.2 microns diameter. Current industry specifications require less than 50 particles per milliliter for particles at 0.2 microns diameter.  
      Although  FIG. 3  has been described above as having air contained within collapsible liner  14 , the present invention is not intended to be limited to air and collapsible liner may contain other gases, for instance nitrogen, argon, or any other suitable gas or combination of gases. The  FIG. 3  container fill method has also been described as utilizing a clean dry air source  24 . However, the present invention is not intended to be limited to clean dry air, and source  24  may supply any other suitable gas or combination of gases to the system, such as nitrogen, argon, etc. Further, though the above-described systems and those described hereinafter are discussed as using ultra pure water, other fluids in which the particle content is desired to be strictly controlled will benefit from this invention.  
      The extent to which the alternative fill methods illustrated by  FIGS. 2 and 3  improve the particle count in the liquid is illustrated by the following experiments summarized in Table 1 below and described with reference to  FIGS. 4A  to  6 D. Table 1 shows the results of filling containers according to four different methods, and then dispensing the contents of the container through an optical particle counter to measure the resulting concentration of particles in the liquid.  
      The first fill method results in Table 1 are for top filling a container, inverting the container, and obtaining a resulting particle count. The fill and dispense method used to obtain this data is illustrated in  FIGS. 4A and 4B .  FIG. 4A  shows a container  50 , fill tube  52 , fill line  54 , valve  56 , and ultra pure water source  58 . When the valve  56  is opened, ultra pure water from ultra pure water source  58  travels through fill line  54  to container  50 . The ultra pure water enters the container  50  at the fill tube  52 . Because the fill tube  52  is positioned above an opening in the container  50 , as the ultra pure water enters the container, it falls from the top of the container to the bottom, causing splashing, bubbling, and entrainment of air.  
       FIG. 4B  shows the manner in which the ultra pure water in the container  50  was subsequently dispensed.  FIG. 4B  shows the container  50  located in a pressure vessel  60 . Connected to the pressure vessel  60  is a clean dry air source  62 , a regulator valve  64 , and a pressure indicator  66 . In the container  50  is a dispense probe  68 . The dispense probe  68  is connected to dispense line  70 , along which is located a particle counter  72 , rotometer  74 , and valve  76 . The contents of the container  50  can be dispensed by opening the valve  76  on the dispense line  70  and supplying the pressure vessel  60  with clean dry air. The clean dry air is supplied using the clean dry air source  62 , valve  64 , and pressure indicator  66  in the conventional manner.  
      As the ultra pure water is dispensed, it passes by the particle counter  72 , which is configured to obtain a particle concentration of the liquid. One suitable particle counter is a Particle Measuring Systems M-100 optical particle counter. In addition, the rotometer  74  is configured to measure the flow rate at which the ultra pure water is being dispensed.  
      The system illustrated in  FIGS. 4A and 4B  was used to obtain the data for rows 1 and 2 of Table 1. In obtaining the data for row 1, ten containers were filled with ultra pure water to about 90% of fill capacity according the method illustrated in  FIG. 4A . When the desired fill level was reached for each container, each container was capped and slowly inverted once to mix. The cap on the container was then replaced with a dispense probe and the container was placed in a pressure vessel for dispensing, as illustrated in  FIG. 4B . Each container was dispensed at 300 ml/minute through the particle counter.  
      The data for row 2 were obtained in a similar manner. Ten containers were filled to about 90% capacity. However, instead of simply inverting the containers once to mix, the containers were shaken on an orbital shaker at 180 rpm for 10 minutes to simulate transport conditions. The containers were then dispensed as illustrated in  FIG. 4B .  
      A third method of filling a container summarized in Table 1 is illustrated in  FIGS. 5A and 5B . The system shown in  FIG. 5A  comprises a container  80 , dip tube  82 , submerged tip  84 , fill line  86 , valve  88 , and ultra pure water source  90 . Dip tube  82  extends into container  80  and terminates at submerged tip  84 . As the container  80  is filled, the ultra pure water enters the container  80  via the submerged tip  84 . As a result, when the water exits submerged tip  84 , the water enters the container  80  more smoothly and with less splashing, bubbling, and turbulence than the top filling method illustrated in  FIG. 4A .  
       FIG. 5B  shows the manner in which the ultra pure water is then dispensed from the container  80 .  
      The manner is identical to that described above with reference to  FIG. 4B . Thus, a pressure vessel  60  was used to dispense the ultra pure water past a particle counter and rotometer, which allowed for a particle concentration of the water to be determined. Row 3 of Table 1 summarizes the results of filling ten containers according to the method illustrated in  FIG. 5A , and dispensing them according to the method illustrated in  FIG. 5B .  
       FIGS. 6A-6D  illustrate the fourth container fill method tested to obtain data for Table 1.  FIGS. 6A-6D  illustrate the process of filling and dispensing containers having a collapsible lining using the same container and flow circuitry described above with reference to  FIG. 3 . However, unlike the system illustrated in  FIG. 3 , the system shown in  FIGS. 6A-6D  has in addition an optical particle counter  90  and rotometer  92  located on the fill and dispense line  32 . The optical particle counter  90  and rotometer  92  are used to obtain a particle concentration of the ultra pure water as it is dispensed from the container  10 .  
      The method used to fill and dispense the containers began as shown in  FIG. 6A . In  FIG. 6A , the initial step of collapsing collapsible liner  14  is effected by opening air inlet valve  40  and liner vent valve  46 , while keeping the other valves  34 ,  36 , and  42  closed. Opening the inlet valve  40  and liner vent valve  46  collapses liner  14  by allowing clean dry air from clean dry air source  24  into the intermediate area  16  via line  38 . At the same time the intermediate area  16  is being pressurized, the air in the liner  14  is forced out through the liner vent valve  46  to liner air vent  30 . This causes the liner  14  to collapse around the dip tube  18 .  
       FIG. 6B  illustrates an optional next step of measuring a baseline number of particles in the ultra pure water flowing through line  32 . To obtain the baseline sample, the liner vent valve  46  is closed, and fill valve  34  and dispense valve  36  are both opened, as well as the air inlet valve  40 . Opened valves  34  and  36  allow the water to flow from the source  22  through the fill and dispense line  32  directly to the particle counter  90  and rotometer  92  and out through the dispense line  28 . The opened air inlet valve  40  allows air from the clean dry air source  24  in to the air supply line  38 , to keep the liner  14  collapsed and prevent any of the water from source  22  from entering the liner  14 .  
      Once the baseline particle concentration in the water is obtained, the baseline can then be compared to the particle concentration of the water in lined container  10  after the container has been filled. This step also provides the benefit of filling dip tube  18  with water, thereby removing any entrained air that may be present in the tube  18 .  
       FIG. 6C  illustrates the step of filling the container  10  by introducing water into the collapsed liner  14 . To begin filling the container  10 , the fill valve  34  and air vent valve  42  are opened, while all other valves,  36 ,  40 ,  46  are closed. The opened fill valve  34  allows water from the water source  22  to enter the fill and dispense line  32  and begin filling the liner  14  via dip tube  18 . As the water enters collapsible liner  14 , collapsible liner  14  expands, forcing air out of intermediate area  16 . Opened air vent valve  42  allows the air in intermediate area  16  to vent out through line  38  as collapsible liner  14  expands. The fill process continues until collapsible liner  14  is filled to a desired level. Once full, the fill valve  34  is closed.  
       FIG. 6D  illustrates the final step of dispensing the liquid from the lined container  10 . To dispense the water, the dispense valve  36  and air inlet valve  40  are opened, while the other valves  34 ,  42 ,  46  are closed. Opening the air inlet valve  40  allows air to flow from air source  24  into the intermediate area  16 . The air creates pressure on the collapsible liner  14 , which compresses collapsible liner  14  and forces the water out of the collapsible liner  14 . The liquid exits the liner  14  at the dip tube  18  and flows through the dispense line  32 . As the water passes through the dispense line  32 , the particle concentration is measured by the optical particle counter  90 , and the flow rate is measured by the rotometer  92 . Air is forced into the intermediate area  16  until the desired amount (typically all) of the water is removed from within collapsible liner  14 . Dispensing the water in this manner precludes the need for pumps, which are known to shed particles.  
      Table 1 below summarizes the data collected from the four experiments described above. The table contains averaged results of the four experiments. As can be seen from the data, the highest concentration of particles resulted from top filling the container and shaking. In addition, it can be seen that the bottom fill method, and in particular the fill method involving first collapsing the liner and then filling the collapsed liner (the “collapsed liner fill method”) resulted in significantly lower particle concentrations in the liquid.  
               TABLE 1                       Concentration of Particles (#/ml)                                                    Average particle size   0.10 μm   0.15 μm   0.20 μm   0.30 μm       Top Fill/Invert   124   44   12   1.2       Top Fill/Shake   10151   4820   2066   181       Bottom Fill   29   11   4.0   .085       Collapse Liner Fill   5.2   2.5   1.3   0.52                  
 
      The data in Table 1 show that the presence of an air-liquid interface in a container affects the generation of particles in the liquid. Specifically, the results summarized in Table 1 show that when an air-liquid interface was not present during filling, such as during the collapsed liner fill method, the particle generation was virtually non-existent. When an air-liquid interface was present, as it was in the other three fill methods, particle generation was observed.  
      Though discussed in terms of an air-liquid interface, similar results have been obtained for other interfaces, including containers in which a vacuum exists over the liquid surface. Thus, the term air-liquid interface is used in the broadest sense to cover any liquid interface, including air, other gases or combinations of gases, or even a vacuum, in contact with the liquid surface.  
      Two further experiments involving the collapsed liner fill method were conducted. The experiments also showed that the method of dispensing the contents of the container has an effect on the resulting particle generation. Table 2 below compares the results obtained by collapse filling a container according to the method described with reference to  FIG. 3  above, and then dispensing the contents, in two different ways.  
      The first manner of dispensing involved pouring the contents of the collapsed liner filled container (Container A) into a second container (Container B). As illustrated by the data in Table 1 above, filling Container A using the collapsed liner fill method resulted in the water in Container A having a very low concentration of particles. The water from Container A was then poured into an identical container, Container B. Container B was capped with a standard dispense probe and dispensed through a particle counter. As is shown in Table 2 below, the concentration of particles in the water increased dramatically after it was poured into Container B.  
      The second method of dispensing used is illustrated by  FIGS. 7A-7B . The second method involved collapse liner filling the first container, Container A, and then collapsed liner filling the second container, Container B, from Container A.  FIG. 7A  shows the first step in the process, that of filling Container A using the collapsed liner fill method. Similar to the container and flow circuitry illustrated in  FIG. 3 , FIGS.  7 A-C show a lined container  100  having a rigid outer container  102  and an inner lining  104 . The inner lining  104  is connected to ultra pure water source  106  via line  108 . A fill valve  110  controls the passage of liquid from the source  106  to the container  100 .  
      Also shown connected to the first container  100  is a nitrogen source  112 , nitrogen inlet valve  114 , and pressure indicator  116 . The nitrogen source  112  is connected to the intermediate area  118  via nitrogen supply line  120 . Located on the nitrogen supply line  120  are four valves  122 - 128 . The two outer valves  122 ,  128  allow for nitrogen in the line  120  to vent. The two inner valves,  124 ,  126  control the flow of nitrogen so that it can selectively be directed to either the first container  100  or a second container  130 . The second container  130  is connected to the first container  100  by dispense line  132 . Located along dispense line are two valves  134 ,  136 .  
      Similar to the first lined container  100 , the second lined container  132  comprises a rigid container  138  and collapsible liner  140 . An intermediate area  142  between the rigid container  138  and collapsible liner  140  is also connected to the nitrogen source by line  120 . Both the first container  100  and the second container  130  have dip tubes  144  disposed within their respective collapsible liners  104 ,  140 .  
      In  FIG. 7C , a particle counter  150  and rotometer  152  are located along the dispense line  132  between the valves  134 ,  136 . Locating the particle counter  150  and rotometer  152  between the valves  134 ,  136  allows for the contents of the second container  130  to be dispensed past the particle counter  150  and rotometer  152  so that data regarding particle concentration can be collected.  
       FIG. 7A  illustrates the first step of collapsing the liner of the first container  100 , and filling the container according to the method described above with reference to  FIG. 3 . Next, as shown in  FIG. 7B , the liner  140  of the second container  130  was collapsed. Once the liner  140  of the second container  130  was collapsed, the contents of the first container  100  were dispensed into the second container  130 . Thus, the second container  130  was also filled using the collapsed liner fill method. However, instead of being filled with water from a water source, the second container  130  was filled with the water from the first container  100 . This method allowed for filling the second container  130  in a manner that minimized the air-liquid interface.  
      After the second container  130  was filled, the liquid was dispensed from the second container via dispense line  120 , as shown by  FIG. 7C . The water flowing through dispense line  120  flowed through optical particle counter  150  so that the particle concentration in the water could be determined. The water also flowed through the rotometer  152  to determine the water flow rate.  
      Table 2 below shows the resulting particle concentration in the ultra pure water subjected to both methods of dispensing described above. As the data illustrate, a rather high particle generation can result from simply pouring water from one container to another.  
               TABLE 2                       Concentration of Particles (#/ml)                                                    Average particle size   0.10 μm   0.15 μm   0.20 μm   0.30 μm       Collapse fill A, pour A   1070   433   127   50       into B, dispense B       Collapse fill A, collapse   25.1   9.94   3.02   1.85       fill B from A, dispense B                  
 
      In a similar experiment, the same two dispensing methods were duplicated using a standard HDPE reagent bottle. In these experiments, the first container  100  was replaced with the HDPE bottle. The results for this experiment are summarized in Table 3 below.  
      In Table 3, the first row gives the particle concentration for a HDPE reagent bottle filled via a submerged dip tube, according to the method described above with reference to  FIG. 2 . The submerged dip tube fill and dispense method was used to obtain baseline data to which the remaining two fill and dispense methods could be compared. The second row of Table 3 shows the results of simply pouring the contents of the HDPE reagent bottle into a second container (Container B). The last row of Table 3 contains data from a fill and dispense procedure in which the HDPE reagent bottle was filled using a submerged dip tube, and the second container (Container B) was collapse filled from the HDPE reagent bottle using a method similar to that described above in reference to  FIG. 7B .  
               TABLE 3                       Concentration of Particles (#/ml)                                                    Average particle size   0.10 μm   0.15 μm   0.20 μm   0.30 μm       HDPE bottle, fill via   290   138   64.6   27.6       submerged dip tube,       dispense (baseline data)       Pour from HDPE to B,   4700   1930   797   178       dispense B       Collapse fill B from   305   145   75.7   30.6       HDPE, dispense B                  
 
      As shown in Table 3, a significant number of particles were generated in filling the HDPE bottle with a submerged dip tube. Yet, as can be seen from comparing the first and third rows of Table 3, virtually no particles were subsequently generated in dispensing from the HDPE bottle to the collapsed liner container using the collapse fill method. Again it can be observed that when liquid is poured from one container to another in the typical fashion in which an air-liquid interface is present, significant particle generation is observed. When the liquid transfer takes place in such a way that the air-liquid interface is reduced, the particle generation is likewise reduced.  
      Yet another experiment performed to determine the effect of various methods of dispensing liquid from a container and the resulting particle concentration in the liquid is summarized in Table 4 below. To obtain the data for Table 4, a standard 4-liter rigid HDPE reagent bottle was filled with three liters of ultra pure water using a submerged dip tube method, similar to that described above in connection with  FIG. 2 . In the first test, the bottle was pressurized and the water in the bottle was dispensed via the dip tube directly through an optical particle counter. In the second test, the bottle was shaken for one minute prior to dispensing the water through the optical particle counter. The particle concentrations in the water exiting the bottle are shown in Table 4.  
               TABLE 4                       Concentration of Particles (#/ml)                                                    Average particle size   0.10 μm   0.15 μm   0.20 μm   0.30 μm       Fill and Dispense   290   138   64.6   27.6       Fill, Shake, and   15900   7370   3180   739       Dispense                  
 
      The data of Table 4 show that the effect of an air-liquid interface on particle shedding is common to polymeric containers in general. The length of time between shaking the container and measuring the particle concentration in the liquid did not appear to affect the measurement.  
     Submerged Discharge Nozzle  
       FIGS. 8A and 8B  are illustrations comparing two methods of discharging ultra pure liquid using a nozzle  170 . Shown in  FIG. 8A  is a nozzle  170  through which liquid is discharged into a container  172 . The nozzle  170  is connected to a fill line  174 , which is connected to an ultra pure liquid source  176  and is regulated by a valve  178 . The discharge nozzle  170  is located above the container  172  so that as liquid is discharged from the nozzle  170 , the liquid sprays onto an open bath in the container  172 . This results in air entrainment and increases the air-liquid interfacial area in liquid filling of the container  172 .  
       FIG. 8B  illustrates an alternative method of utilizing a nozzle to fill a container, which reduces particle generation in the liquid. Shown in  FIG. 8B  is a nozzle  180  for filling a container  182 . The nozzle is connected to fill line  184 , which is connected to an ultra pure liquid source  186 . The flow of liquid through the fill line  184  is controlled by a valve  188 . The nozzle  180  is located below a surface  190  of the liquid in the container  182 . As a result of submerging the nozzle  180 , the fluid flow into the container is much less turbulent, and has reduced splashing and air entrainment.  
       FIG. 9  highlights the effects of the submerged nozzle on reduction of the particle concentration in the liquid in the bath.  FIG. 9  is a graph illustrating measurements of particle concentrations taken over an elapsed time for both a system having a submerged nozzle and a system having a nozzle located above the liquid surface. To obtain the data for  FIG. 9 , ultra pure water was sprayed through a nozzle into an open bath in a stainless steel container. The spray water was directed at the surface of the water in the bath, and did not strike any solid surfaces. Water from the bath was directed through an optical particle counter to measure particle generation as a result of spraying. Two types of nozzles were used, a high pressure stainless steel nozzle and a Kynar nozzle. Both types of nozzles were first held three inches above liquid surface of the bath, and then were submerged.  
      The y-axis of  FIG. 9  illustrates the concentration of particles, shown as the number of particles per milliliter for particles having a size of less than 0.065 micrometers. The x-axis gives an elapsed time in minutes. The concentration of particles caused by the stainless steel nozzle when it was held above the surface of the liquid are in a first cluster  200 , while the concentration of particles caused by the Kynar nozzle when it was held above the surface of the liquid are shown by a cluster  202 . The particle concentration, which occurred after the nozzles were submerged is shown by clusters  204  and  206 .  
      The results in  FIG. 9  show a dramatic increase in particle generation when the nozzles were held above the surface of the water. Comparatively, when the nozzles were submerged below the surface, the particle concentrations were much lower. These results show that the presence of an increased air-liquid interface, such as that caused by a nozzle located above the liquid surface, is associated with intense particle generation in operating nozzles.  
      Submerged nozzle systems, such as those variously illustrated in the above-described drawings, can be used to deliver liquid or create a liquid jet for cleaning or other purposes. As the results of the above experiments show, regardless of the purpose of the nozzle, i.e., cleaning or filling, to minimize particle generation, the nozzle system should be configured to allow the nozzle to be submerged.  
     Reduction of Weir Overspill Distance  
      Another aspect of the present invention relates to minimizing the generation of particles in a liquid that has overspilled a weir into an overspill area. This can be accomplished by minimizing the distance between the weir and the water level in the overspill area.  FIGS. 10A and 10B  illustrate the concept of reduction of weir overspill distance. Shown in  FIG. 10A  is a recirculation bath  210  having a weir  212  over which liquid spills into an overspill trough or sump  214 . The overspill trough  214  connects to a recirculating pump  218  for recirculating the liquid in the bath system. The recirculating pump  218  pumps the liquid through a filter  220  and back into the recirculation bath  210 .  
      In  FIG. 10A , the level of liquid  222  in the overspill trough  214  is low enough so that when the liquid overspills the weir  212 , the liquid falls into the trough, causing splashing, bubbling, turbulence, and entrainment of air. The system in  FIG. 10B  shows a level of liquid  224  in the overspill trough  214  that is much higher in elevation relative to the top edge of the overflow weir  212 . As a result, the distance the liquid must fall as it overspills the weir  212  is greatly reduced. This allows the liquid to enter the overspill trough  214  in a manner that reduces splashing, bubbling, turbulence, and entrainment of air.  
      Studies were performed to determine the level of particle generation in water spilling from a bath over a weir into a sump.  FIG. 11  is an illustration of the test system used in performing the studies. Shown in  FIG. 11  is a recirculating etch bath  230 , sump  232 , circulation pump  234 , and filter  236 . Located between the bath  230  and the sump  232  is a weir  231  over which water can spill from the bath  230  into the sump  232 . In addition, the system comprises an ultra pure water source  238 , a filter by-pass valve  240 , a drain  242 , and shut-off valves  244  and  244 A. Also connected to the bath  230  is a sample pump  246 , particle counter  248 , and flow meter  250 .  
      The system of  FIG. 11  comprises two flow loops. A main flow loop  252  connects the sump  232  to the circulation pump  234  and filter  236 . One suitable filter  236  used during testing was a 0.2 micrometer rated UPE filter. During testing, the main flow loop  252  was operated at 50 liters per minute through the bath  230 , sump  232 , circulation pump  234 , and filter  236 . The bath  230  was a 60 liter bath constructed of PVDF, and the remainder of the wetted materials in the pump  234 , such as the tubing and filter housing, were Teflon PFA. The flow circuitry and valving  240 ,  244 ,  244 A were configured to allow the filter  236  to be bypassed during some of the tests.  
      The secondary flow loop  254  comprises a secondary flow path, through the sample pump  246 , the particle counter  248 , and the flow meter  250 . The secondary flow loop  254  was operated at a flow rate of 50 ml/minute and was used to determine a particle concentration in the water. The test system illustrated in  FIG. 11  shows that the particle sample was normally taken from the bath  230 . However, the sample could also be taken from the sump  232 . In addition, while the liquid source  238  is described as supplying ultra pure water, the bath could be run with HF, HCl, or any other fluid in which the particle concentration is to be strictly controlled.  
       FIG. 12  is a graph illustrating the results of running the bath  230  overnight after installing a new filter  236 . To obtain the data used to generate the graph of  FIG. 12 , the particle measurement was done in the bath  230  and the filter  236  was brand new. Initially, the water level in the sump  232  was running about an inch below the water level in the bath  230  and there was no evidence of splashing or bubbling as the water from the bath  230  overspilled into the sump  232 . As can be seen on  FIG. 12 , there was a normal “flush-up” curve  260  for the new filter  236  during the first few hours of particle data.  
      Eventually, evaporation caused the level of water in the sump  232  to drop over time, increasing the spill distance over the weir  231 . As this distance increased, the turbulence in the sump  232  due to water spilling over the weir  231  also increased. There was also a gradual increase in the particle concentration in the bath  230  after about 200 minutes. This was attributed not to loss of filter  236  retention, but rather to an increased challenge concentration of particles at the filter  236  inlet due to particle generation in the sump  232 .  
      After 18 hours of operation, evaporation caused a significant drop in the water level of the sump  232 , and the water spilling into the sump  232  caused significant splashing and bubbling. Water was added to the system using the water source  238 . When enough water was added to the bath  230  to raise the level in the sump  232  to the point where the splashing and bubbling activity disappeared, the particle level in the bath  230  decreased dramatically in the two smallest size channels of the particle counter. This effect is shown by the drop off curve  262  in  FIG. 12 .  
      In the system used to obtain the data for  FIG. 12 , particle measurement was made in the bath  230 , downstream of the filter  236 . The particle generation source was concluded to be in the sump  232 , which was located upstream of the filter  236 . Thus, at least some of the generated particles passed through the filter  236 , especially those particles that were significantly smaller than the pore size rating of the filter. The results showed that even with filter protection, and constant recirculation, a large generation of particles in a fluid could be observed, even downstream of a filter  236 . The use of the filter  236  and the size discrimination seen in the data is further evidence that the phenomena being measured by the particle counter  248  was not simply “bubbles” entering the flow cell of the counter  248 .  
      This sequence of events, including the particle flush up from a new filter  236  followed by evaporation of the liquid so that particles are generated in increasing numbers as the spill height over the weir  231  increased, was recorded for numerous and different types of filters  236  placed in the recirculating bath system. It was also seen in situations where dilute concentrations of HF and HCl were used in the bath system.  
      To highlight the effect of the filter  236 , a second test was performed using the system illustrated in  FIG. 11 . During the second test, the main flow loop  252  was run until the system was clean. Next, the valves  244  and  244 A were configured so that the system was put into a “filter bypass mode.” In the filter bypass mode, the system was recirculating water, but the water did not pass through the filter  236 . As a result, there was no removal of any of the particles in the system by the filter  236 .  
       FIG. 13  is a graph illustrating the results of the filter bypass mode test. In  FIG. 13  there are two curves. The first curve  264  indicates the particle counts for water tested when there was splashing as the water overspilled the weir  231 . The second curve  266  indicates the particle counts for water tested when there was no splashing as the water overspilled the weir  231 . As can be seen from the first curve  264 , when the distance between the water level in the bath  230  and the sump  232  was large, there was significant particle generation caused by liquid spilling over the weir  231  and splashing in the sump  232 . The number of particles built up quickly in the bath  230  to a concentration of over 10,000 per milliliter for particles greater than or equal to 0.065 micrometer diameter.  
      During control tests using the same filter bypass method, the same flow rate, and the same pump, the particle concentration remained near 100-200 per milliliter for particles greater than or equal to 0.065 micrometer diameter, during a thirty minute test. The only way the control test differed was that the distance between the water level in the bath  230  and the sump  232  was small, and no splashing was observed in the sump  232  as the water overspilled the weir  231 . Again, the test was repeated in many forms to verify that the results were consistent. The pump used in this system ran relatively cleanly, and contributed very little particle shedding in the system, as shown by the control data.  
     Smart Siphoning  
       FIG. 14  is an illustration of a common method of siphoning. Shown in  FIG. 14  is a tank  270  with a fill tube  272 . Connected to the fill tube  272  is a three way valve  274  that regulates flow into the tank from an ultra pure water supply  276  and diverts water from the water supply  276  to a water reclaim area  278 . Also connected to the tank  270  were a siphon tube  280  and particle sample tube  282 . Finally, a capacitive sensor  284  is located on the tank  270 .  
      Experiments were performed on the siphoning system shown in  FIG. 14  to determine the effect of the siphoning system on particle generation. When performing the experiments, a 15 liter ECTFE fluoropolymer tank  270  was used. The water level in the tank  270  was cycled up and down using the fill tube  272  and the siphon tube  280 . Particle sampling was performed continuously from the tank  270  via the particle sample tube  282  using a gravity feed method. A 30 second averaging/sample interval was chosen for obtaining the particle data.  
      The fill flow rate from the water supply  276  was set at 1 liter per minute. The capacitive level sensor  284  was used to detect a high level on the tank  270 . Once the high level was detected, the sensor  284  activated a PLC (not shown in  FIG. 14 ) to turn on a timing control signal for four minutes. The timing signal was used to activate a siphon connected to the siphon tube  280 , such as by opening a valve, so that water was drawn out of the tank at 2.5 liters per minute by the siphon. In addition to connecting a siphon to the siphon tube  280 , a pump was sometimes substituted.  
      The control signal also activated the three-way valve  274  to divert the ultra pure water supply away from the test tank  270  and to the water reclaim area  278  during the tank  270  draining process. After the four minutes were up, the test tank  270  was then refilled with water for ten minutes at 1 liter per minute, and a new cycle sequence was begun. In this way, the water level in the tank  270  was cycled up and down smoothly on a regular basis.  
      In some of the tests, the high level sensor  284  and control signal were deactivated, and the valve on the siphon tube  280  was held continuously open so that once a high water level was reached, the system would generate a siphon. Once enough water had been siphoned, the water level in the tank  270  would be so low that the siphon would break due to entrained air, letting any of the water in the siphon tube  280  fall back down into the tank  270 . During these tests, the three way valve  274  was overridden so that the one liter per minute water supply  276  was constantly sending water to the tank  270  at all times.  
      Another variable that was adjusted was the height of the fill tube  272  in the tank  270 . Some tests were conducted using a top fill method, with the fill tube  272  positioned in the tank  270  so that water filled from the top of the tank  270 . Other times a bottom filling method was used, wherein the fill tube  272  was positioned near the bottom of the tank  270  so that the fill tube  272  always remained submerged below the water level in the tank  270 .  
       FIG. 15  is a graph illustrating the best case scenario of filling a tank using a siphon. In obtaining the data for the graph of  FIG. 15 , a bottom filling fill tube was used in addition to a “smart” siphon. A smart siphon refers to a siphon system using the high level sensor  284  to create a timing signal that enabled the siphon to be stopped before the fluid level reached the bottom of the siphon tube  280 , and thus before the siphon was allowed to break the siphoning action.  
      Even though the level of water in the tank  270 , and thus the air-liquid interface, was cycled up and down, the resulting particle levels were relatively low. The average particle levels were near 1.2 particles per milliliter for particles having a size less than or equal to 0.10 micrometer diameter. This is not as good as the particle levels seen when measuring the incoming water supply, which had average particle levels of near 0.03 per milliliter for particles having a size less than or equal to 0.10 micrometer diameter.  
      As shown in  FIG. 15 , particle bursts occurred every few hours. However, the maximum particle concentration reached was only about 20 particles per milliliter for particles having a size less than or equal to 0.10 micrometer diameter. The time scale of the testing graphed in  FIG. 15  covered about 15 hours.  
       FIG. 16  is a graph illustrating the data collected from a test system using top filling and a smart siphon. For the data obtained for  FIG. 16 , the fill tube  272  was located above the surface of the water in the tank  270 , so that the water fell into the tank  270 , causing splashing and bubbles. A smart siphon was still implemented during collection of this data. As can be seen by comparing the graph in  FIG. 15  with the graph in  FIG. 16 , the particle levels are about one hundred times higher during top filling than during bottom filling. In addition, the frequency of the tank cycling is visible in the particle data.  
       FIGS. 17 and 18  illustrate data collected using a dumb siphon. A dumb siphon refers to a siphon that is allowed to break the siphoning action by air entrainment.  FIG. 17  illustrates a system using bottom filling with a dumb siphon, while  FIG. 18  illustrates a system using top filling with a dumb siphon.  
      As can be seen in both  FIGS. 17 and 18 , there is a spike in the particle levels just after the siphon breaks, followed by a drop in the particle levels as low particle level water is added to the tank  270 . This cycle repeats itself, with a spike of particles each time the siphoning action breaks, and a drop each time low particle level water is added to the tank  270 . Again, data were collected over 15 hours. There are little or no apparent long-term clean-up trends in the data, and the frequency of the tank cycling sequence is clearly visible in the particle data. Note that the frequency of the tank fill and dispense cycle in  FIGS. 17 and 18  was not held constant. Rather, some cycles were faster while other cycles were slower.  
      Table 5 below is a numerical summary of the results of the experiments shown in  FIGS. 15-18 . The data show that both filling from the top or allowing air entrainment to break the siphoning action  
                       TABLE 5                                      Average Particle Concentration (#/ml)           Average particle size                                     Method   0.10 μm   0.15 μm   0.20 μm   0.30 μm   0.50 μm                                             bottom fill,   1.2   0.51   0.26   0.086   0.019       smart siphon       top fill,   190   81   35   6.9   0.64       smart siphon       bottom fill,   470   150   56   11   1.5       dumb siphon       top fill,   590   220   82   13   1.3       dumb siphon                  
 
     Removal of Head Space  
      When a partially full container is shaken, high particle concentrations are generated in the liquid. This same phenomenon is often observed when the container is shipped. When packaging some liquids, it may be necessary or desirable to leave an amount of head space in the container to allow the liquid in the container to expand. To create this head space, the container is not filled to maximum capacity, but rather is filled to a level so that an amount of air exists between the top of the liquid and the top of the container. As the container is shipped, the liquid in the container may splash and slosh in the container due to this head space. Another method of reducing particle generation is to remove any head space air from a container subsequent to filling so that any air-liquid interface in the container is reduced or eliminated, and particle generation thereby is minimized during shipping and other movement of the container.  
       FIGS. 19A and 19B  illustrate an open fill method, with a removal of head space air. Shown in  FIGS. 19A and 19B  is a lined container  300  similar to that described above with reference to  FIG. 3 . The lined container  300  comprises a rigid outer container  302  with a liner  304  located inside the rigid outer container  302 . Disposed in the liner  304  is a dip tube  306 . The dip tube  306  is connected to a fill line  308  for supplying the container with liquid. The liner  304  is not collapsed before filling.  
       FIG. 19A  illustrates the step of filling lined container  300  with a liquid. Liquid flows from fill line  308 , through dip tube  306 , and into liner  304 . When lined container  300  is filled to a desired level, a head space  310  exists between the level of liquid in the liner  304  and the top of the liner  304 .  
       FIG. 19B  illustrates the step of removing the head space  310  from the container  300 . In  FIG. 19B , an air inlet  312  is shown, in addition to a liner air vent  314  for venting the head space air. The air inlet  312  connects to an intermediate area  316  located between the rigid outer container  302  and the inner liner  304 . To remove the head space  310 , air is supplied to the intermediate area  316  via the air inlet  312 . At the same time, the inside of the inner liner  304  is exposed to the liner air vent  314 . The increased pressure between the rigid container  302  and liner  304  caused by the air from the air inlet  312  compresses the liner  304 . As the liner  304  compresses, the head space air is vented from inside the liner  304  using the liner air vent  314 . The liner  304  is compressed until substantially all the head space air is removed from the liner  304 . The container  300  is capped and the liner  304  can be sealed to prevent air from re-entering.  
      In addition to venting only the air that occupies the head space, it is possible to fill the liner in an amount which is greater than the desired amount of liquid to be held in the container. After over filling the liner, the liner can then be purged by an amount that yields the finished volume desired to be held in the container. In this manner, the presence of any head space air is likewise avoided.  
       FIGS. 20A and 20B  illustrate another method of removing the head space in a container used to transport ultra pure liquids.  FIG. 20A  shows a container  320  filled according to a bottom fill method using a dip tube  322 . To remove the air liquid interface created by a head space  324 , FIG.  20 B shows the insertion of an inert bladder  326  into the remaining head space in the liner. Alternatively, the head space air may be reduced by pressurizing an area between the liner and the rigid container to vent the head space air.  
      The inert bladder serves to occupy the headspace area, and thus isolate the air from the liquid. The removal of head space  324  eliminates the air-liquid interface, which in turn minimizes particle generation in the water caused by shipping.  
      In addition to using the method described above with reference to FIGS.  19 A-B and  20 A-B, it is possible to obtain a liner having zero head space by filling the container using the collapsed liner fill method described more fully above with reference to  FIG. 3 . The collapsed liner fill method, in addition to allowing the container to be filled and dispensed without the presence of an air-liquid interface, also provides a method of filling a container with no remaining head space.  
      The benefits of a zero head space fill method compared to an open fill method are apparent from the data set out in Table 6 below. To obtain the data set out in Table 6, two methods of filling a container were tested. The first method tested was a standard open fill method, in which an inflated liner was filled with particle-free water. As can be seen from Table 6, when the water was subsequently tested for particles, the particle concentration of the water invariably increased. The exact particle concentration varied somewhat from test to test for the same type of liner. In addition, the particle concentration can vary significantly from one liner type to another, as for example a PTFE liner versus a PEPE liner.  
      The second method tested to obtain the data in Table 6 was a zero head space fill method. The zero head space fill method, similar to the collapsed liner fill method, involved first placing a liner in the rigid outer container. Next, the liner was inflated enough to allow the insertion of a dip tube. Attached to the dip tube assembly was a probe. Preferably the probe was configured like a recycle probe, so that the probe had two ports leading into the liner, a fill port and a vent port. The space between the liner and the rigid outer container was pressurized to collapse the liner completely by venting the air in the liner out the vent port. The liner was then filled using the fill port, which was attached to the dip tube. The container was dispensed by likewise using the dip tube.  
      This fill method virtually eliminated the air liquid interface as the liner was filled. As a result, it was observed that particle shedding was significantly reduced during filling. It follows that even during shipping, the removal of the head space ultimately results in reducing the level of particles in the dispensed fluid.  
               TABLE 6                       Concentration of Particles (#/ml)                                                    Average particle size   0.10 μm   0.15 μm   0.20 μm   0.30 μm       Open fill method   56   23   7.6   1.3       Zero head space fill   4.2   1.5   0.77   0.13       method                  
 
      Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In particular, it should be recognized that the particle generation in a container can vary based on the type of container, type of liner, and type of fluid introduced into the container. However, any liquid that has product performance criteria that are dependent on low particle levels will benefit from the above disclosed filling and packaging methods. Such liquids include ultra pure acids and bases used in semiconductor processing, organic solvents used in semiconductor processing, photolithography chemicals, CMP slurries and LCD market chemicals.  
      The features and advantages of the invention are more fully shown with respect to the following example, which is not to be limitingly construed, as regards to the character and scope of the present invention, but is intended merely to illustrate a specific preferred aspect useful in the broad practice of the present invention.  
     EXAMPLE 1  
      From the same lot of Oxide Slurry OS-70KL material (ATMI Materials Lifecycle Solutions, Danbury, Conn.) several different sample vials were made up, containing the OS-70KL material, to simulate behavior of the liquid in a bag in a drum container of the type generally shown and described herein and in U.S. patent application Publication No. US2003/0004608 A1 and U.S. Pat. No. 6,698,619, incorporated herein by reference in their entirety, with varying headspace in the interior volume of the liner.  
      The sample vials were made up with the following differing headspace levels: 0%, 2%, 5% and 10%. Each of the sample vials was vigorously shaken for one minute by hand, and the liquid in the vial was then subjected to analysis in an Accusizer 780 Single Particle Optical Sizer, a size range particle counter commercially available from Sci-Tec Inc. (Santa Barbara, Calif.), which obtains particle counts in particle size ranges that can then be “binned” algorithmically into broad particle distributions. The data obtained in this experiment are shown in Table 1 below. The particle counts are shown for each of the particle sizes 0.57 μm, 0.98 μm, 1.98 μm and 9.99 μm, at the various headspace percentage values of 0%, 2%, 5% and 10% headspace volume (expressed as a percentage of the total interior volume occupied by the air volume above the liquid constituting the headspace void volume).  
               TABLE 7                          Size Range Particle Counts for Varying Headspace Volumes in Sample Vials                                         Initial Particle                       Average   Count   Particle   Particle   Particle   Particle       Particle Size   Before   Count - 0%   Count - 2%   Count - 5%   Count - 10%       for Range   Shaking   Headspace   Headspace   Headspace   Headspace                         Size Range Particle Counts Immediately After Shaking Vial for One Minute                                     0.57 μm   170,617   609,991   134,582   144,703   159,082       0.98 μm   13,726   14,836   22,096   20,294   26,429       1.98 μm   2,704   2,900   5,298   4,397   6,293       9.98 μm   296   321   469   453   529                 Size Range Particle Counts 24 Hours After Shaking Vial for One Minute                                     0.57 μm   110,771   1,198,296   191,188   186,847   182,217       0.98 μm   11,720   18,137   21,349   20,296   24,472       1.98 μm   2,701   2,383   4,658   4,272   5,704       9.98 μm   138   273   544   736   571                  
 
      The particle size analyzer presented the data in terms of large-size particle counts, in units of particles per milliliter&gt;a specific particle size in micrometers (μm). The particle count data has been determined to provide a direct correlation between the magnitude of the particle count and wafer defectivity when the reagent containing such particle concentration is employed for manufacturing microelectronic devices on semiconductor wafers.  
      The data taken immediately after the shaking experiment show some trending toward larger particle counts with increasing headspace values, particularly for particles≧0.98 μm. Data taken 24 hours later show the same trending toward higher particle distributions.  
      The data show that increasing headspace in the vial produced increasing aggregations of large size particles, which are deleterious in semiconductor manufacturing applications and can ruin integrated circuitry or render devices formed on the wafer grossly deficient for their intended purpose.  
      As applied to bag in a drum containers of the type shown and described herein and in U.S. patent application Publication No. US2003/0004608 A1 and U.S. Pat. No. 6,698,619, incorporated herein by reference in their entirety, the results of this Example indicate the value of the preferred zero headspace arrangement. Any significant headspace in the container holding high purity liquid, combined with movement of the container incident to its transport, producing corresponding movement, e.g., sloshing, of the contained liquid, will produce undesirable particle concentrations. Therefore, to minimize the formation of particles in the contained liquid, the headspace should be correspondingly minimized to as close to a zero headspace condition as possible.  
      Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as hereinafter claimed.