HK1063761A - Pressure vessel systems and methods for dispensing liquid chemical compositions - Google Patents

Description

Pressure vessel system and method for dispensing liquid chemical compositions

Background

1. Field of the invention

The present invention relates to chemical composition delivery systems and methods, and more particularly to chemical delivery systems for electronic technology specific chemical compositions, including CMP slurries for wafer polishing.

2. Correlation technique

Process chemicals for semiconductor manufacturing are typically delivered from bulk containers to a user's workstation using a so-called chemical delivery system. High pressure inert gases, such as nitrogen, have been commonly used to drive chemical compositions from chemical containers to user workstations. The use of high pressure inert gas for chemical delivery has several advantages over delivery systems with pumps: can be transmitted from a long distance and is smooth without pulse, thus avoiding the separation of impurities from the components of the transmission system.

While the advantages of such chemical delivery methods have been realized and the methods have been implemented over a wide range, there are concerns and problems that can occur when chemical compositions of certain semiconductor processes are delivered using such delivery systems. For example, inert gases such as nitrogen, can readily dissolve in certain of these process chemicals during pressurization, resulting in the formation of dry spots on the wafer. These dry spots become manufacturing defects that severely reduce the yield of semiconductor manufacturing. To avoid and eliminate the problem of gas dissolution in the chemical composition, a new delivery system has been devised which incorporates a bladder within a pressure vessel and which is filled with high pressure nitrogen gas to pressurize the chemical composition outside the bladder. Since the chemical composition and the nitrogen gas are not in direct contact, dissolution of the nitrogen gas into the chemical can be avoided. In addition, the chemical composition is not altered by chemical dehydration evaporation during the assay.

When a high pressure inert gas is directly contacted with a chemical composition by delivering the chemical composition containing water, such as a paste composition for polishing a wafer surface, using a method of direct contact with the inert gas, water and other compounds in the chemical composition on the surface of the composition and residues of the composition on the surface of a container rapidly disappear in the inert gas. This is because the inert gas is usually very dry and pure. The amount of compounds such as water within the chemical composition will change due to evaporation. This change in the chemical composition may cause the chemical composition to function improperly when used in a semiconductor manufacturing process. When water evaporates into the inert gas, a dry film or a dry residue may form with little water and less volatile, more concentrated components. In the ointment composition, this dry film or dry residue will be in the form of larger-sized agglomerated particles. These agglomerated particles eventually travel with the chemical composition to the user station and create scratches on the wafer surface. This problem can be solved using the bladder technique described above without direct contact of the nitrogen with the chemical composition. With this technique, a thin, flexible material must be carefully selected for the bladder that can accommodate the chemical composition.

To overcome the evaporation of water into the inert gas, the nitrogen may be humidified by a warmer prior to entering the pressurized chemical composition in the high pressure vessel as described in U.S. patent No. 6,076,541. When the humidified nitrogen gas is contacted with the chemical composition, mass transfer of water between the nitrogen gas and the chemical composition may be significantly reduced or completely eliminated. And therefore no or very little dry residue or dry film will form within the pressure vessel. There are some drawbacks to doing so. First, more space is required to accommodate the humidifier close to the pressure vessel. This can be a serious problem because space is often limited at the semiconductor manufacturing site. Adding equipment to occupy space is not always permissible nor available. Second, the humidified nitrogen can cause problems in system operation. Because the humid nitrogen can flow through a long pipeline to the pressure vessel, the moisture in the nitrogen can condense in the pipeline due to changes in physical conditions. This condensate can clog and cause malfunction of the valve. This condensed water can be further entrained into the pressure vessel to dilute the chemical composition. This is not allowed because the composition of the chemical composition must be precisely controlled to meet the customer specification requirements. In addition, certain chemical components, such as hydrogen peroxide in the chemical composition, may still evaporate into the high purity inert gas even if the inert gas is humidified. Thus, when chemical compositions are delivered in this way, the chemical composition changes, which is clearly not a serious problem at times.

It would therefore be advantageous and an advance in chemical delivery technology if a chemical delivery system could be designed that reduced or even eliminated the above-described disadvantages.

Summary of the invention

The novel and simple apparatus and method according to the present invention reduces or eliminates the problems of dry residue and dry film when using a pressure vessel to deliver liquid chemical compositions, as well as the problems associated with known wetting systems. Herein, the terms "system" and "device" are used interchangeably.

Herein, "liquid chemical composition" means:

a fluid capable of flowing under pressure, gravity, or a combination of both, which may be a newtonian fluid or a non-newtonian fluid; a fluid that may be aqueous, non-aqueous, or a combination of both; combinations of various components (liquid, solid and gas) are possible.

The liquid chemical compositions that may benefit from the present invention contain substantially moisture. Newtonian fluids having various combinations of constituents include, in certain embodiments, one or more organic compounds, such as reactive diluents, non-reactive diluents, solvents, co-solvents, coupling agents, and the like, and abrasive materials, such as distributed within individual particles, or within agglomerates of individual particles. Chemical-mechanical planarization (planarization) pastes and chemical-mechanical polishing pastes are two preferred liquid chemical compositions. Suitable organic solvents may include, for example, organic alcohols, ketones, acids, and the like, and isopropyl alcohol.

A first aspect of the invention is an apparatus for dispensing a liquid chemical composition. A first apparatus embodiment comprises:

a) a pressure vessel having an inlet and an outlet for the liquid chemical composition and a vapor space adapted to contain therein the liquid chemical composition having a vaporizable portion (preferably a major portion of water);

b) means for contacting a dry, preferably highly pure, inert gas, preferably with the formation of bubbles, with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable portion from the chemical composition to the inert gas, thereby forming a humidified inert gas in the vapor space; and

c) means for pressurizing the chemical composition with a wet, high purity inert gas and allowing it to exit the vessel.

The apparatus in this embodiment preferably has a T-shaped connecting tube with two limbs connected to the inlet and outlet respectively and the remaining limb connected to the pressure vessel. It is also preferred that the dry, high purity inert gas is suitably sparged into the pressure vessel near the bottom of the vessel through an inert gas inlet pipe having a discharge end, preferably with a sparging device attached thereto.

The term "dry" as used herein means that the inert gas suitably has a moisture content of less than 10% Relative Humidity (RH), preferably less than 1% RH. The term "high purity" as used herein with respect to the inert gas means that the inert gas contains less than 10 parts per million (ppm) total impurities (inorganic and organic compounds), preferably less than 5 ppm. The term "ultra-high purity" as used herein with respect to the inert gas means that the inert gas contains less than one part per billion total impurities (inorganic and organic compounds). A preferred dry inert gas is C3.29-96 in the Semiconductor Equipment and Materials International (SEMI) Standard (1999), the Standard for Nitrogen, the bulk gas, 99.9995% by mass, which specification is incorporated herein by reference. The term "wet" means that the composition of the gas has a composition selected from the group consisting of water vapor, organic vapor, inorganic vapor, and combinations thereof.

A second apparatus embodiment of the present invention for dispensing a liquid chemical composition comprises:

a) a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) the first compartment being connected to the entry conduit for the wet composition and having a waste conduit for the wet composition to drain to waste, the dividing element acting to establish a level of the wet composition in the first compartment, the first compartment further having an entry conduit for a dry, preferably highly pure, inert gas, the end of which is positioned (preferably suitably submerged in the liquid chemical composition to be discharged to waste) so that the inert gas and the wet composition can contact in the first compartment to form the wet inert gas, the first compartment further providing a discharge for the gas;

c) the discharge port of the humidified inert gas is connected to the second compartment by a humidified inert gas pipe;

d) the second compartment is connected to the inlet and outlet pipes for the liquid chemical composition and to a vapor space which is connected to the first compartment by a humidified inert gas pipe. It is preferred in the apparatus of the second embodiment that the conduit forms part of the means for monitoring the level of the liquid chemical composition in the second compartment. It is also preferred that the humidified inert gas pipe includes a means for removing liquid droplets from the humidified inert gas, the means being selected from the group consisting of: screens, sieves, de-misters, coalescers, absorbent materials, molecular sieves, zeolites, filters, heat exchangers, condensers, cryocoolers, and the like.

A third apparatus embodiment for dispensing a liquid chemical composition comprises:

a) a pressure vessel having a first compartment and a second compartment separated by a dividing element;

b) the first compartment being connected to a wetting composition inlet conduit for spraying the wetting composition into the first compartment and to a waste conduit for allowing the wetting composition to be discharged to waste, the inlet conduit terminating in a means for spraying the wetting composition into the first compartment, the dividing element serving to establish a level of the wetting composition in the first compartment, the first compartment being further connected to a gas inlet conduit for a dry, preferably highly pure, inert gas, having a terminal end positioned (preferably above the level of the sprayed portion of the liquid chemical composition to be discharged to waste) so that the inert gas and the wetting composition can contact within the first compartment to form a wetted inert gas, the first compartment further having a discharge for this wetted inert gas;

c) the discharge port of the humidified inert gas is connected to the second compartment by a humidified inert gas pipe;

d) the second compartment has an inlet pipe and an outlet pipe for the liquid chemical composition, and a vapor space connected to the first compartment by a wet inert gas pipe.

A fourth apparatus embodiment of the present invention for dispensing a liquid chemical composition comprises:

a) a pressure vessel having a first compartment and a second compartment separated by a dividing element;

b) the first compartment being connected to the inlet conduit for spraying the moist composition into a chamber formed by the housing and to a waste conduit for discharging the moist composition to waste, the inlet conduit terminating in a means for spraying the moist composition into the chamber (the dividing element preferably having the function of establishing a level of the moist composition in the chamber), the housing being further connected to a dry, preferably high purity, inert gas inlet conduit, the gas inlet conduit and the housing being adapted to bring the inert gas and the moist composition into contact in the chamber, the housing further having means for moving the moist inert gas into the first compartment;

c) the dividing element having means for passing said humidified inert gas from the first compartment to the second compartment;

d) the second compartment is connected to the inlet and outlet pipes of the liquid chemical composition and to a vapor space which is in fluid communication with the first compartment by means of the means which are allowed to pass through in the dividing element.

A fifth apparatus embodiment is a slight modification of the fourth embodiment and includes the detail that the housing has one or more means for enabling the wetted composition to pass laterally through the housing and into the second compartment after contact with the dry inert gas. Preferably, the means for passing the wetting composition laterally through the housing is located at a position selected from the group consisting of the bottom of the housing, the side walls of the housing, or both.

It should be understood that it is also within the scope of the present invention to have multiple housings in the first compartment, each housing having a gas inlet pipe and a conduit for spraying a wetting composition into each of the housings.

A second aspect of the invention includes a method of delivering a liquid chemical composition. A first preferred method embodiment comprises:

a) filling a pressure vessel with a liquid chemical composition having a vaporizable component (preferably comprising water), the pressure vessel having a vapor space and being adapted to contain the liquid chemical composition;

b) contacting (preferably bubbling) a dry, preferably highly pure, inert gas with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable component from the liquid chemical composition to the dry inert gas to form a humidified inert gas in the vapor space; and

c) the liquid chemical composition is forced out of the pressure vessel using an inert gas humidified in a vapor space.

A second method embodiment of dispensing a liquid chemical composition includes the following process steps:

a) providing a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) at least partially filling the first compartment with a wetting composition, the separation element acting to establish a level of the wetting composition within the first compartment;

c) flowing dry, preferably high purity, inert gas into the first compartment and contacting it with the wet composition to form a wet inert gas, the first compartment being further connected to a wet inert gas discharge line;

d) flowing a humidified inert gas through a conduit into the second compartment; and

e) the second compartment is substantially filled with the liquid chemical composition leaving a vapor space, the second compartment being connected to the first compartment by a conduit.

A third method embodiment of delivering a liquid chemical composition includes the following steps:

a) providing a pressure vessel having a first compartment and a second compartment, the compartments being separated by a dividing element;

b) spraying a wetting composition into the first compartment, the dividing element acting to establish a level of the wetting composition in the first compartment;

c) flowing a dry, preferably high purity, inert gas into the first compartment (preferably above the surface of the wet composition) and contacting it with the wet composition to form a wet inert gas;

d) flowing a humidified inert gas from the first compartment to the second compartment through a conduit; and

e) the second compartment is substantially filled with the liquid chemical composition leaving a vapor space, the second compartment being connected to the first compartment by a conduit.

A fourth method embodiment of delivering a chemical composition includes the following steps:

a) providing a pressure vessel having a first compartment and a second compartment, the compartments being separated by a dividing element, the first compartment having a chamber defined by a housing;

b) spraying the wetting composition into the chamber, the dividing element acting to establish a level of the wetting composition within the chamber;

c) flowing a dry, preferably high purity, inert gas into the chamber to contact the wetted composition to form a wetted inert gas;

d) flowing a humidified inert gas through a conduit into the second compartment; and

e) the second compartment is substantially filled with the liquid chemical composition, leaving a vapor space that is connected to the first compartment by a conduit.

The first apparatus embodiment of the present invention allows dry, preferably highly pure, inert gas to be contacted with the wet composition, which is the liquid chemical composition to be dispensed. The contacting occurs in a pressure vessel, and upon contacting, a moist inert gas is formed, which gas is then used to pressurize the liquid chemical composition and drive it out of the pressure vessel. Thus, there is no need to add space to an external humidifier as in previous apparatus and methods. Because it is better to have only a minimal amount of vapor to saturate the dry inert gas, assay verification may be substantially unaffected when the wetting composition is a dispensed liquid chemical composition. The vapour content of the humidified inert gas can also be easily controlled, in the first embodiment only by carefully flowing the dry inert gas through the liquid chemical composition.

A preferred embodiment of the invention is characterized by the use of two compartments in the unitary pressure vessel, the liquid chemical composition to be dispensed being supplied to one compartment, a smaller amount of the wetting composition (which may be the liquid chemical composition to be dispensed if desired) and dry inert gas being supplied to the other compartment so that they are in contact with each other. The two compartments are in communication with each other through the facilities described herein. Thus, the liquid chemical composition may be driven by a humidified inert gas having a chemical vapor, preferably water vapor, therein, but not limited thereto. The problem of the liquid chemical composition disappearing in the dry inert gas can thus be prevented, while the problem of dry residues can be eliminated at the same time.

In a preferred embodiment, the two compartments are interconnected by a conduit, allowing the flow of the humidified inert gas into and out of the compartments.

In another preferred embodiment, the interconnection of the two compartments is accomplished by a series of means, preferably small openings, such as holes, louvers, channels, etc., provided in the separating means separating the two compartments.

All embodiments of the present invention are provided with the necessary control and isolation valves for discharging and reloading the liquid chemical composition into the pressure vessel, introducing and discharging the liquid chemical composition, and filling and releasing the inert gas. Preferred embodiments of the pressure vessel may utilize one or more parallel pressure vessels for the operation of dispensing the liquid chemical composition. Two or more pressure vessels are generally mounted parallel to each other for continuous delivery of the liquid chemical composition, and may also be arranged in a string for reloading the liquid chemical composition from one pressure vessel to another.

The advantages and aspects of the invention will be elucidated with reference to the drawings and to a preferred embodiment without limitation.

Brief description of the drawings

Fig. 1 to 4 are each a side elevation view schematically showing the process.

FIG. 1 is a preferred embodiment of an apparatus and method for humidifying inert gas by bubbling through a chemical composition;

FIG. 2 is a preferred embodiment of the method and apparatus having two compartments and external piping interconnecting them;

FIG. 3 is another compartment arrangement of FIG. 2;

fig. 4 is another preferred embodiment of the apparatus and method, with two compartments and an internal communication arrangement.

Description of The Preferred Embodiment

Although the method and apparatus of the present invention are most dedicated to CMP apparatus for delivering slurry to semiconductor wafers, the method and apparatus of the present invention can be used in any situation where inert gas is used to pressurize a compartment and moisture loss is a problem. For example, in the production of certain abrasive articles, ointments are used to produce "structured abrasives". U.S. patent No. 5,368,619 to Culler, which is incorporated herein by reference, may be referred to generally. The principles of the present invention may be applied when an inert gas is used to move the paste as it is being hardened into the abrasive coating. Since the main benefit of the present invention is the reduction of space required to humidify the inert gas, the following discussion will focus on the semiconductor industry, although it should be appreciated that the present invention is not limited to any particular use.

Chemical compositions have been used for a variety of purposes in the fabrication of integrated circuits. Aqueous compositions such as silica powder and other necessary chemical compositions are used to polish or planarize the wafer surface (planarizing). This process is often referred to as chemical mechanical polishing or Chemical Mechanical Planarization (CMP) in semiconductor manufacturing processes. In order to ensure the quality of the planarization process, the CMP paste preferably controls the chemical additives and particle size distribution within a specified range. The concentration of chemical additives is typically monitored and adjusted on-line in order to meet their specification requirements. Particle size is preferably monitored and controlled by filtering unwanted particles larger than a few microns in diameter that may form during coalescence, since large particles can scratch the surface of the wafer. It is therefore desirable to avoid the formation of large size particles during the delivery of the chemical composition.

Such chemical compositions are typically delivered by a pressure vessel system through the necessary dispensing conduits. Fig. 1 shows a preferred embodiment of the apparatus 10 for dispensing chemical compositions of the present invention. The pressure vessel 31 contains the chemical composition 32 to be delivered. A chemical composition inlet pipe 20 and a control valve 21 coupled to the container 31 are used to supply the chemical composition into the pressure container 31. A chemical composition discharge pipe 22 and a control valve 23 coupled to the container enable the chemical composition to be sent to a user workstation or other container. The pipes 20 and 22 are alternately connected to the pressure vessel 31, respectively. Both conduits 20 and 22 may be constructed of any material that can withstand the chemical composition. Preferred materials include metals such as stainless steel, and plastics such as Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), high density polyethylene, and polypropylene. The diameter of the conduits 20 and 22 is preferably in the range of 0.125 inches (0.32cm) to about 1.0 inches (2.54 cm).

A side pipe 50 is joined at one end 52 thereof to the pressure vessel 31 near the top and at the other end thereof to the bottom so as to communicate the top and bottom inside the pressure vessel 31.

Level sensors 51a, 51b, 51c and 51d are preferably mounted on the side pipes to monitor the chemically-composed liquid level within the pressure vessel 31. The side tube 50 may be made of the same or different material as the tubes 20 and 22, but preferably has an inside diameter of 0.5 inches (1.3cm) and greater. The level sensors 51a, 51b, 51c and 51d are preferably selected from optical or capacitive types as is well known in the art of level measurement. Other types of level sensors, such as ultrasonic, may also be used for level measurement, in which case they may be attached directly to the pressure vessel at various locations. In this case, the side tube 50 is not necessarily required.

A conduit 45 for high pressure inert gas extends through the pressure vessel 31 near the bottom wall and is connected to the diffuser 40, along with a control valve 46 and a check valve 47. The conduit 45 may also be made of the same material as the conduits 20 and 22. The diffuser 40 is preferably a membrane cartridge similar to the filter cartridge that allows the inert gas to flow through. The diffuser 40 may also have one or more tubes with a number of holes to allow the inert gas to flow through. In any practical configuration, the diffuser 40 is preferably made of a material that can withstand the chemical composition to be dispensed.

A further line 43 is connected to the pressure vessel 31 together with a control valve 42 in order to vent the pressure vessel 31 when required. A pressure relief valve 60 is connected to the pressure vessel 31 by a conduit 61 to release gas once the pressure within the pressure vessel 31 is above a predetermined pressure. The control valve is preferably a pneumatic valve made of a material capable of withstanding chemical compositions such as stainless steel, PTFE, PFA, high density polyethylene or polypropylene.

In operation, the chemical composition is filled into the pressure vessel 31 through the conduit 20. The amount of chemical composition within the pressure vessel 31 is monitored by the level sensors 51 a-d. Once the level of the composition reaches the high level monitored by level sensor 51b, control valve 21 is closed. An ultra-high purity inert gas, preferably at high pressure, such as nitrogen, is then introduced through line 46 as a result of the opening of control valve 46. The inert gas flows through the diffuser 40 and forms small bubbles 30 within the chemical composition 32. The size of the vapor bubble is dependent on the size of the hole in the diffuser 40. Suitably, the diffuser produces pores of diameter less than 50mm, preferably less than about 5 mm. The gas flow is preferably controlled as: the flow rate is from about 1 standard liter per minute (slpm) to about 100slpm and the pressure is from about 0.5 atmosphere to 5 atmosphere. The bubbles rise through the chemical composition and collect some of the vapor during its rise. The inert gas fills vapor space 62 above chemical composition 32, and vapor space 62 in turn pressurizes the chemical composition.

The height of the pressure vessel 31, or more suitably the depth of the chemical composition, is critical for the bubbles to collect sufficient vapor. The height of the pressure vessel 31 is preferably at least 1 meter and the depth 32 of the chemical composition within the pressure vessel 31 is preferably at least 0.5 meter at its high level as monitored by the level sensor 51 b.

The amount of steam (preferably water vapor) in the inert gas, i.e., relative humidity, is suitably in the range of about 50% to 100%, preferably about 80% to about 95%, while the concentration of other chemical vapors, which may or may not be present, may be in the range of parts per million.

When the chemical composition is to be delivered to one or more user stations, control valve 23 may be opened to allow the chemical composition to flow out of pressure vessel 31 through conduit 22 under the pressure of the inert gas containing steam. At this time, an inert gas containing steam is supplied into the steam space 62 to fill the space left by the removed chemical composition. Thus, the pressure within the pressure vessel 31 may be kept constant and the chemical composition may be delivered at a steady pressure and flow rate. The inert gas is preferably high-purity nitrogen gas because it can be widely supplied and is less expensive than any other inert gas. When the composition reaches a low level as monitored by level sensor 51c, control valves 23 and 21 are closed. The high pressure inert gas in the pressure vessel 31 is then released as a result of the control valve 42 being opened. At this stage, the chemical composition may fill the pressure vessel 31 as a result of the control valve 21 being opened. The chemical composition may be refilled into the pressure vessel 31 and discharged for periodic delivery as needed. Two or more such pressure vessels may be operated in parallel. While one of the pressure vessels is in a refilled state, the other may be in a discharged state, such that the chemical composition may be continuously delivered to one or more user workstations.

The pressure vessel 31 is preferably made of metal or plastic such as stainless steel, PTFE, PFA, high density polyethylene, polypropylene, glass, and steel coated on the inside surface with one of plastic or glass materials. The pressure vessel 31 must have sufficient material properties and wall thickness to withstand pressures of up to about 10 atmospheres. The capacity of the pressure vessel is suitably from about 1 to about 5000 litres, preferably in the range of about 20 to 500 litres.

Since the inert gas has received a portion of the chemical composition from which at least a portion can evaporate after contact with the chemical composition, vapor molecules in the top layer of the chemical composition and in the droplets of composition that remain on the inner wall of the pressure vessel 31 will no longer disappear into the inert gas. And thus no dry film or dry residue is formed. With this preferred embodiment, it is not necessary to have a warmer to humidify the inert gas as in known systems. An advantage with this preferred embodiment is that space can be saved for the user and cost-efficiency. Another advantage is that the entire transmission system can be operated more easily than previously known systems, since some components have been omitted.

The bubbles of inert gas may produce droplets of the chemical composition after bursting at the top of the chemical composition surface. These droplets can be splattered onto the inner surface of the pressure vessel wall and eventually fall back into the composition. These droplets will no longer form any dry residue because the inert nitrogen gas has been saturated with steam. The inert gas is preferably insoluble in the chemical composition. This is because the equilibrium between the dissolved and gaseous inert gases of the chemical composition used in semiconductor manufacturing during manufacturing and packaging is generally well established. The added decomposition due to the high pressure of the inert gas is negligible because inert gases such as nitrogen have only very low solubility in aqueous chemical compositions. If the preferred ultra-high purity inert gas is used for this purpose, it is clear that the inert gas does not cause any contamination of the chemical composition. Under normal operating conditions (about 20 c), the partial pressure of the chemical composition in nitrogen will be low. Thus, the preferred ultra-high purity nitrogen gas will not significantly alter the assay of the chemical composition when bubbled through the chemical composition. For example, the change in water concentration is negligible since only a very small amount of water is required to saturate the nitrogen. For example, 35 liters of nitrogen, at room temperature (about 20 deg.C) and a pressure of 30psig, requires only 0.37 milliliters (ml) of water to become saturated.

In an alternative method, a chemical composition may be used to provide steam to the inert gas. Fig. 2 shows another preferred apparatus 100 of the present invention having a pressure vessel 31 for holding a chemical composition. The chemical composition inlet pipe 20 and the control valve 21 are connected to the bottom of the pressure vessel 31 in the chemical composition compartment 29 to supply the chemical composition to be delivered. A chemical composition discharge pipe 22 and a control valve 23 are connected to the bottom of the pressure vessel 31 in order to send the chemical composition. In this embodiment there is a wet chemical composition inlet line 150 and a control valve 151 for supplying a small portion of the wet chemical composition into the inert gas compartment 135 of the pressure vessel. The control valve may optionally be a three-way valve, one of which allows the wet composition to flow into the inert gas compartment 135 and the other of which allows the wet composition waste to flow out of the compartment 135. The wet composition discharge pipe 153 is preferably connected to the three-way valve 151 for discharging the wet composition.

An inert gas inlet line 45 and a control valve 46 are provided for supplying inert gas, preferably at high pressure and high purity, into the inert gas compartment 135, and an exhaust line 42 and a control valve 43 are provided for exhausting. There is a side pipe 143 having one end connected to the bottom of the pressure vessel 31 and the other end connected to the exhaust pipe 42. An additional control valve 138 is provided between the connection to the side pipe 143 on the exhaust pipe 42 and the pressure vessel 31. Preferably, there is a tube 50, one end of which is connected to the side tube 143 and the other end of which is connected to the top side wall of the pressure vessel 31. As with the preferred embodiment shown in FIG. 1, four level sensors 51a-51d are preferably mounted on the side tube 143 to monitor the level of the chemical composition within the pressure vessel 31. A mist eliminator 139 is preferably provided to remove any mist carried over by the chemical composition.

The conduit and control valve are preferably made of a material that can withstand the chemical composition to be dispensed. It is preferable to use a metal material such as stainless steel, a plastic such as PTFE, PFA, high density polyethylene, polypropylene, and the like. The control valve is preferably pneumatic. The mist eliminator can be of any commercially available form made of plastic fibers or film.

The pressure vessel 31 is preferably of similar material and dimensions as the pressure vessel in fig. 1. In order to contain the chemical composition 32 and the wetting composition 134 (preferably deionized water) to be dispensed, the pressure vessel 31 is divided into two separate compartments by a dividing means 133. An inert gas compartment 135 is located in the upper portion of the pressure vessel 31 for containing a wetting composition such as deionized water or a composition to be dispensed. The chemical composition compartment is located in the lower portion of the pressure vessel 31 for containing the chemical composition to be dispensed. The two compartments are in communication with each other through a portion of the exhaust pipe 137, the side pipes 140 and 143, and the duct 50. Preferably, a valve is included in the conduit 50 to allow the humidified inert gas to flow through the conduit 143, thereby bubbling the humidified gas through the liquid chemical composition.

In operation of the apparatus 100, a chemical composition is first introduced into the composition compartment 29 through the composition inlet conduit 20. At this time, the control valve 21 is opened, the control valve 23 is closed, the inert gas control valve 138 is closed, and the exhaust control valve 43 is opened. When the composition in compartment 29 reaches a high level as monitored by level sensor 51b, control valve 21 closes and the filling stops. A wetting composition such as deionized water or a diluted chemical composition is fed into the inert gas compartment 135 to a controlled depth and the three-way valve to the composition supply side is closed. The depth of the composition is preferably at least 2 inches (5cm) so that the end of the inert gas inlet pipe 154 is buried within the composition, but this is not strictly necessary. The three-way valve is intermittently opened to supply the wetting composition to the compartment to maintain a controlled level of the composition. When it is desired to discharge the used composition in compartment 135, the three-way valve may be turned to a "composition out" position. The inert gas supply control valve 46 is preferably always open to allow inert gas to fill the compartment 135 at a controlled pressure. An inert gas, preferably high purity nitrogen, is bubbled through the wetted composition in the gas compartment. The chemicals or water in the wet composition then evaporate into the inert gas. When the composition in compartment 29 is to be delivered to the user station, vent valve 43 may be closed, and control valve 138 opened. Inert gas with a relative humidity of about 50 to 100% flows through the mist eliminator 139, conduits 137, 140, and 50 into the top of the chemical composition compartment 29 along with steam and/or water vapor. The chemical composition to be delivered to the end user is then pressurized with a high pressure inert gas. When the composition discharge control valve 23 is opened, the chemical composition can flow through the discharge pipe 22 and a series of pipes and control devices to one or more user stations. The transmission can be stopped at any time by closing the control valve 23 and can be resumed by opening this control valve. When the composition in the pressure vessel 31 reaches the low liquid level monitored by the liquid level sensor 51c, the control valve 23 is closed and the transmission is stopped. At which time the inert gas control valve 138 is also closed and the exhaust control valve 43 is opened to release the pressure in the pressure vessel. The chemical composition compartment 29 of the pressure vessel 31 can then be refilled. This refilling and draining may be repeated for several cycles. Two or more such pressure vessels may be operated in parallel with one in a delivery state and the other in a refill state for continuous delivery of the chemical composition to a user workstation.

Two additional level sensors 51a are used to monitor the high-high and low-low levels of the chemical composition within the compartment of the pressure vessel 31. The signals from these two sensors are primarily for safety reasons. A warning will occur once the level reaches a high-high level or a low-low level and the system will shut down for a predetermined period of time.

The wet composition or diluted chemical composition may be supplied into the gas compartment 135 through a conduit having a showerhead 210 located within the compartment 135 as shown in figure 3. Spraying the wetting composition with a showerhead will generate droplets 211. Inert gas is supplied into the gas compartment 135 through the conduit 45. The conduit 45 preferably extends nearly its entire length to near the bottom of the gas compartment 135. The inert gas contacts the droplets 211 and steam and/or water vapor is transferred to the inert gas so that the wet inert gas can flow through the mist eliminator 139, the control valve 138, the conduits 137, 140, and 50 into the chemical composition compartment 29 to pressurize the chemical composition as needed. The droplets of composition will be collected on the dividing element 133, which element functions as the floor of the gas compartment 135 and establishes a level of the wetting composition thereon, and then discharged through the conduit 153 provided with the control valve 151.

Fig. 4 shows another preferred apparatus embodiment 500 of the present invention. In contrast to the embodiment of fig. 2 and 3, the embodiment of fig. 4 has a housing 158 within the gas compartment 135. The conduit 150 and valve 156 deliver the wetting composition through the showerhead 210, the showerhead 210 serving to spray the wetting composition within the housing 158. Inert gas is also supplied into the housing 158 through the conduit 45, the valve 46 and the conduit 154. Means 157 are provided to allow the inert gas and chemical vapors and/or water vapor to flow out of the housing 158. The facilities 157 are preferably selected from: holes, louvers, blisters, and the like. To remove any droplets in the inert gas, a defogging material such as plastic fibers may be installed on the device 157. Preferably, there is an annular passage between the housing 158 and the inner wall of the pressure vessel 31 to allow the passage of the humidified inert gas therethrough. Preferably, a plurality of apertures 160 or the like are provided in the separation means 133 between the gas compartment 135 and the chemical composition compartment 29 to allow communication between the two compartments. The humid inert gas may flow through the holes or other means from the gas compartment 135 into the compartment 29 to pressurize the chemical composition to be delivered.

In operation, as in the embodiment of fig. 1-3, a chemical composition is input into the chemical composition compartment 29 of the pressure vessel 31 through the chemical composition supply line 20 and the control valve 21. When the liquid level of the composition reaches the high liquid level monitored by the liquid level sensor 51b, the control valve 21 is closed, and the control valve 43 for exhaust is closed. The control valve 46 is opened to supply inert gas into the housing 158. The wetting composition may be continuously sprayed with the showerhead 210 to generate droplets. The inert gas contacts the droplets and then flows into vapor space 136 of gas compartment 135, further through apertures 160 into space 141 pressurizing the chemical composition. Once the chemical composition is required to be delivered to the user workstation, the control valve 23 may be opened and the chemical composition may flow through conduit 22 to any required external conduits and controls to the user workstation. Keeping the control valve 156 open allows for continuous spraying of the wetting composition, and the control valve 151 in the composition discharge line can also be kept open for continuous discharge.

Fig. 4a shows a fifth apparatus embodiment, which is slightly modified from the embodiment in fig. 4. As can be seen from fig. 4a, openings are provided near and/or at the bottom of the housing 158, which function to enable the wetting composition to drip into the liquid chemical composition to be dispensed.

The preferred embodiment described above is preferably automated using a computer control system or a PLC (power load control) system. The control valve is preferably pneumatically operated and controlled by an automatic control system. The signals from the monitoring devices, such as the level sensors, are sent to a computer or PLC for processing and sending the necessary operating signals to the system.

The advantages of the present invention will be immediately apparent from the above description of the preferred embodiments. Firstly this preferred apparatus is easy to operate. First, it concentrates all the preferred actions into one preferred overall device. The chemical composition can be loaded into or unloaded from the pressure vessel by operating only a plurality of control valves. At the same time high pressure inert gas, preferably also a wetting composition, is supplied to the pressure vessel in order to evaporate the chemicals and/or water into the inert gas and pressurize the chemical composition to be delivered. Thus, no external device is required to provide steam to the inert gas. The assay of the chemical composition to be delivered does not change significantly due to evaporation. The device is also easy to automate. Secondly, very valuable space is saved, since no additional external humidifier is needed to humidify the high pressure inert gas. Third, the overall cost of the pressure system is significantly reduced, since the same objective can be achieved with fewer devices than with known apparatus and methods.

While the above description is representative of the invention, it is in no way intended to limit the scope of the invention as defined in the claims.

Claims (31)

1. An apparatus for delivering a chemical composition, comprising:

a) a pressure vessel having an inlet and an outlet for the liquid chemical composition and a vapor space, the pressure vessel adapted to contain the liquid chemical composition, the liquid chemical composition having a vaporizable portion therein;

b) means for contacting the dry inert gas with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable portion of the chemical composition into the inert gas to form a humidified inert gas in the vapor space; and

c) means for forcing the chemical composition out of the container using a humidified inert gas.

2. The apparatus of claim 1 wherein the inlet and outlet are two limbs of a T-joint, the remaining limb of the T-joint being connected to the pressure vessel.

3. The apparatus of claim 1, wherein the dry inert gas is suitably sprayed into the pressure vessel near the bottom of the vessel through an inert gas inlet pipe. The inert gas inlet pipe has an outlet end.

4. Apparatus according to claim 3, wherein the outlet end of the inert gas inlet pipe has a spray device attached thereto.

5. Device according to claim 1, characterized in that the means for contacting are means for foaming.

6. The apparatus of claim 1 wherein two of said pressure vessels are connected in series.

7. The apparatus of claim 1 wherein two of said pressure vessels are connected together in parallel.

8. An apparatus for delivering a chemical composition, comprising:

a) a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) a first compartment connected to the wet composition inlet conduit and the waste conduit for discharging the wet composition as waste, the dividing element acting to establish a level of the wet composition in the first compartment, the first compartment further having a dry inert gas with one end positioned so that the inert gas in the first compartment can contact the wet composition to form a wet inert gas, the first compartment further having an outlet for the wet inert gas;

c) an outlet for the humidified inert gas connected to the second compartment by a humidified inert gas pipe; and

d) a second compartment connected to the inlet and outlet pipes of the liquid chemical composition, the second compartment having a vapor space connected to the first compartment by a humidified inert gas pipe.

9. The apparatus of claim 8, wherein said wet inert gas line is part of a means for monitoring the level of said liquid chemical composition in said second compartment of said pressure vessel.

10. The apparatus of claim 8 wherein said humidified inert gas pipe comprises a mist eliminator for removing liquid droplets in the humidified inert gas.

11. The apparatus of claim 8 wherein two of said pressure vessels are connected in series.

12. The apparatus of claim 8 wherein two of said pressure vessels are connected together in parallel.

13. The apparatus of claim 8, wherein the height of said pressure vessel is at least about 1 meter.

14. The apparatus of claim 8, wherein said dry inert gas inlet tube end is adapted to be submerged in the wet composition to be delivered to the waste stream.

15. An apparatus for delivering a chemical composition, comprising:

a) a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) a first compartment connected to an inlet pipe for spraying the moist composition into the first compartment and a waste pipe for discharging the moist composition to waste, the inlet pipe terminating in a means for spraying the moist composition into the first compartment, the dividing element acting to establish a level of the moist composition in the first compartment, the first compartment further being connected to an inlet pipe for dry inert gas, the gas inlet pipe terminating in a location such that inert gas can contact the moist composition in the first compartment to form moist inert gas, the first compartment further being provided with an outlet for the moist inert gas;

c) an outlet for the humidified inert gas connected to the second compartment by a humidified inert gas pipe; and

d) a second compartment having an inlet and an outlet for the liquid chemical composition and a vapor space connected to the first compartment by a humidified inert gas pipe.

16. The apparatus of claim 15, wherein said humidified inert gas line is part of a means for monitoring the level of said liquid chemical composition within the pressure vessel.

17. The apparatus of claim 15 wherein said humidified inert gas pipe comprises a mist eliminator for removing liquid droplets from the humidified inert gas.

18. The apparatus of claim 15 wherein two of said pressure vessels are connected in series.

19. The apparatus of claim 15 wherein two of said pressure vessels are connected together in parallel.

20. The apparatus of claim 15 wherein said dry inert gas tube end is adapted to be submerged in a wet composition to be discharged to waste.

21. An apparatus for delivering a chemical composition, comprising:

a) a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) a first compartment connected to an inlet pipe for spraying the moist composition into a chamber formed by the housing and a waste pipe for allowing the moist composition to be discharged to waste, the inlet pipe terminating in a means for spraying the moist composition into the chamber, the housing further being connected to a dry inert gas inlet pipe, the pipes and housing being adapted to allow dry inert gas to contact the moist composition in the chamber so that the moist inert gas is formed, the housing further having means for allowing the moist inert gas to move into the first compartment;

c) a separation element having means for allowing said humidified inert gas to pass from the first compartment to the second compartment; and

d) the second compartment, connected to the inlet and outlet pipes of the liquid chemical composition, also has a vapor space which, thanks to the provision of the passage through the separation element, is in fluid communication with the first compartment.

22. The apparatus of claim 21 wherein said conduit includes a mist eliminator for removing liquid droplets from the inert gas.

23. The apparatus of claim 21 wherein two of said pressure vessels are connected in series.

24. The apparatus of claim 21 wherein two of said pressure vessels are connected together in parallel.

25. Apparatus according to claim 21, wherein the dividing element is operative to establish a level of the wetting composition in the chamber.

26. A method of delivering a chemical composition, comprising the steps of:

a) filling a pressure vessel with a liquid chemical composition having a vaporizable component, the pressure vessel having a vapor space and being adapted to contain the liquid chemical composition;

b) contacting the dry inert gas with at least a portion of the liquid chemical composition in the pressure vessel to transfer at least a portion of the vaporizable component from the liquid chemical composition into the dry inert gas to form a humidified inert gas in the vapor space; and

c) the liquid chemical composition is forced out of the pressure vessel using a humidified inert gas in the vapor space.

27. A method of delivering a chemical composition, comprising the steps of:

a) providing a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) at least partially filling the first compartment with a wetting composition, the function of the dividing element being to establish a level of the wetting composition in the first compartment;

c) flowing dry inert gas into the first compartment so that they can come into contact with the wet composition, thus forming a wet inert gas, the first compartment being further connected to a discharge pipe for this wet inert gas;

d) flowing a humidified inert gas through a conduit into the second compartment; and

e) the second compartment is substantially filled with the liquid chemical composition leaving a vapor space, the second compartment being connected to the first compartment by a conduit.

28. A method of delivering a chemical composition, comprising the steps of:

a) providing a pressure vessel having a first compartment and a second compartment, the two compartments being separated by a dividing element;

b) spraying a wetting composition into the first compartment, the dividing element acting to establish a level of the wetting composition in the first compartment;

c) flowing dry inert gas into the first compartment and contacting it with the wet composition, thereby forming a wet inert gas;

d) flowing a humidified inert gas from the first compartment into the second compartment through the conduit; and

e) the second compartment is substantially filled with the liquid chemical composition leaving a vapor space, the second compartment being connected to the first compartment by a conduit.

29. A method of delivering a chemical composition, comprising the steps of:

a) providing a pressure vessel having a first compartment and a second compartment, the compartments being separated by a dividing element, the first compartment having a chamber defined by a housing;

b) spraying the wetting composition into the chamber, the dividing element acting to establish a level of the wetting composition within the chamber;

c) flowing a dry inert gas into the chamber and contacting it with the wet composition, thereby forming a wet inert gas;

d) flowing a humidified inert gas through the conduit into the second compartment; and

e) the second compartment is substantially filled with the liquid chemical composition, leaving a vapor space that is connected to the first compartment by a conduit.

30. A method according to claim 29, wherein the dividing element is operative to establish a level of the wetting composition in the chamber.

31. A method according to claim 29, wherein the dividing element has means for enabling the wetting composition to flow from the first compartment to the second compartment.