Patent Publication Number: US-2007098598-A1

Title: In-line automated fluid dilution

Description:
TECHNICAL FIELD  
      The present invention relates generally to fluid dilution and, more particularly, to a system and method for precise dilution of fluids related to in-line automated chemical analysis.  
     BACKGROUND  
      Automated systems for measuring the concentration of analytes in a sample have been developed using a number of analytical techniques such as ion chromatography or mass spectrometry. In particular, mass spectrometry is often the technique of choice to achieve sensitivity of parts per billion (ppb) or sub-ppb such as parts per trillion (ppt). For example, commonly assigned U.S. patent application Ser. Nos. 10/641,480, 10/094,394, 10/086,025, and 10/004,627 disclose automated analytical apparatuses that measure contaminants present in trace concentrations or liquid bath constituents and are incorporated by reference herein for all purposes.  
      Such automated analytical apparatuses require the use of dilute fluids (e.g., 1% nitric acid) for internal processes and for cleaning component parts between samples or for certain operations such as maintenance. Examples of these component parts include sample preparation apparatus, fluid lines and tubing, pumps, syringes, mixers, and reservoirs. It is noted that the common dilution agent, ultrapure water (UPW), is commonly part of the available piped in fluids in many manufacturing areas and particularly in semiconductor manufacturing plants.  
      In some cases relatively large volumes of dilute acids or other liquid media are required resulting in the need for large reservoirs located at or in the automated analytical tool and/or frequent replenishment of these reservoirs, e.g., &gt;1 liter of dilute nitric acid is required per day for the tools incorporating the inventions referenced above.  
      It is expected that in-line analytical or metrology instrumentation used to monitor and control industrial processes will have minimal routine maintenance requirements. In semiconductor manufacturing applications, clean-room space is costly and storing long term supplies of diluted reagents next to an analytical tool may be impractical. Many of the desirable reagents are hazardous. Anything that reduces the volume of hazardous material and the potential exposure of personnel to hazardous materials is desirable.  
      Diluted reagents used for sample preparation processes or to clean contamination in analytical systems used to detect contamination levels, must have very low contamination levels down to the parts per trillion range. Thus any inadvertent contamination by personnel or the environment degrade analytical results. By having an automated in-situ dilution capability, strong reagents stored in or near to the analytical tool can be prepared at necessary concentrations as they are needed. Elimination of the need for an operator reduces the likelihood of errors and reduces the danger of introducing environmental contamination.  
      Thus, a system and method for providing in-line automated fluid dilution for use with in-line automated analytical tools is highly desirable to improve productivity and the quality of measurements, to reduce storage requirements, and to reduce costs and to reduce maintenance requirements.  
     SUMMARY  
      The present invention provides a system and method for in-line automated fluid dilution to be used in conjunction with a chemical analysis tool.  
      In accordance with the present invention, an automated in-line fluid dilution system is provided. The system includes at least one supply reservoir containing a concentrated fluid. The system also includes a diluent source which provides a source of the diluent fluid. Normally this is ultrapure water that is commonly available in manufacturing areas as in the case of the semiconductor industry. The system further includes a diluted fluid reservoir operably connected through pumps, a fluid control device connected to the concentrated fluid reservoir(s), and the diluent source, respectively.  
      In accordance with an embodiment of the present invention, an automated in-line fluid dilution system is provided, the system including a supply reservoir containing a concentrated fluid, a diluent source including a diluent, a valve to control the supply of diluent, and a diluted fluid reservoir operably coupled to the supply reservoir and the diluent source. The system further includes a fluid level sensor operably coupled to the diluted fluid reservoir, a pump operably coupled between the supply reservoir and the diluted fluid reservoir, and a controller configured to engage the pump based upon signals from the fluid level sensor to pump desired amounts of the concentrated fluid for providing a diluted fluid in the diluted fluid reservoir, said controller also controlling the diluent valve.  
      In accordance with another embodiment of the present invention, an automated in-line fluid dilution system is provided, the system including a supply reservoir including a concentrated fluid, a diluent source including a diluent, a diluted fluid reservoir for holding a diluted fluid, a first fluid level sensor for sensing a high fluid level in the diluted fluid reservoir, and a second fluid level sensor for sensing a low fluid level in the diluted fluid reservoir. The system further includes a pump operably coupled to the supply reservoir, the diluent source, and the diluted fluid reservoir for metering the concentrated fluid and the diluent into a single fluid stream to be delivered to the diluted fluid reservoir. A controller is configured to engage the pump based upon signals from the first and second fluid level sensors.  
      In accordance with yet another embodiment of the present invention, a method of automated in-line fluid dilution is provided, the method comprising signaling a low fluid level in a diluted fluid reservoir, pumping a concentrated fluid into the diluted fluid reservoir, flowing a diluent into the diluted fluid reservoir until a high fluid level is signaled, thereby providing a diluted fluid in the diluted fluid reservoir, and flowing the diluted fluid to a chemical analysis tool.  
      In accordance with yet another embodiment of the present invention, a method of automated in-line fluid dilution is provided, the method comprising signaling a low fluid level in a diluted fluid reservoir, metering a concentrated fluid and a diluent into a single fluid stream, pumping the single fluid stream into the diluted fluid reservoir until a high fluid level is signaled, and flowing the diluted fluid to a chemical analysis tool. This embodiment lends itself to providing on demand, diluted reagents as required and can be controlled by a computer or microprocessor including the one that also controls a fully automated metrology tool or a manually controlled analytical instrument designed for laboratory use.  
      Advantageously, the present invention provides an efficient and automated system and method of bulk fluid dilution for use in various environments, including but not limited to chemical analysis tools and laboratory settings.  
      The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the present invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a diagram of an automated fluid dilution system for automated in-line chemical analysis in accordance with an embodiment of the present invention.  
       FIG. 2  shows a flowchart of automated fluid dilution in accordance with an embodiment of the present invention.  
       FIG. 3  shows a diagram of another automated fluid dilution system for automated in-line chemical analysis in accordance with another embodiment of the present invention.  
       FIG. 4  shows a flowchart of automated fluid dilution in accordance with another embodiment of the present invention. 
    
    
      Embodiments of the present invention and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures. It should also be appreciated that the figures may not be necessarily drawn to scale.  
     DETAILED DESCRIPTION  
      The present invention provides a system and method for automated and in-line fluid dilution related to an automated in-line chemical analysis system. The fluid to be diluted may be one of various fluids, including but not limited to acids (e.g., nitric, sulfuric, hydrochloric), bases, oxidants, reducing reagents, solvents (such as alcohols, esters, ethers, glycols, ketones, amides, amines, or their mixtures), cleaning solutions, photoresists, strippers, developers, mixtures thereof, and other liquids.  
       FIG. 1  shows a diagram of an in-line automated fluid dilution system  100  used in conjunction with an in-line and automated chemical analysis apparatus in accordance with an embodiment of the present invention. Fluid dilution system  100  includes a concentrated fluid reservoir  102 , a pump  104 , a diluted fluid reservoir  108 , a first sensor  110 , a second sensor  112 , and a controller  114 . A power supply  116  is operably coupled to sensors  110  and  112  and a relay  106 , which is operably coupled to pump  104 . Fluid lines  121 ,  123 ,  125 , and  127  are pathways for different fluids as will be described below.  
      Concentrated fluid reservoir  102  is a vessel compatible with various solutions, such as acidic solutions, and may be capable of being pressurized. In one example, with no intent to limit the invention thereby, fluid reservoir  102  is made of Kel-F or Teflon material to provide compatibility with various solutions without leaching of contaminants. However, various reservoirs are applicable such as those that provide storage ability with sufficient venting capability, compatibility with various solutions, and cleanliness.  
      It is noted that lines transporting fluids may comprise piping, fittings, and/or tubing in one example, but any applicable material and structure that allows for the accurate transfer of liquids may be used to operably connect to valves, syringes, reservoirs, and other apparatus in accordance with the present invention. In one example, with no intent to limit the invention thereby, components are connected with tubing made of Teflon® PFA 450 HP fluoropolymer, having 0.062″ O.D.×0.016″ I.D., Part #106-0062016, available from Parker Hannifin of Cleveland, Ohio.  
      Pump  104  is operably coupled between concentrated fluid reservoir  102  and diluted fluid reservoir  108 . Pump  104  is also operably coupled to relay  106 , which is operably coupled to power supply  116  and controller  114 . Pump  104  provides concentrated fluid from concentrated fluid reservoir  102  to diluted fluid reservoir  108  via fluid lines  121  and  123  under the control of controller  114 . In one example, with no intent to limit the invention thereby, pump  104  is a valve pump  15 OSP available from Bio-Chem Valve Inc. of Boonton, N.J.  
      Diluted fluid reservoir  108  is operably coupled to pump  104  via fluid line  123 , a diluent source via fluid line  127  and valve  118  (or other fluid control device; e.g., a pump, or a mass flow controller), an apparatus requiring diluted fluid via fluid line  125 , and a gas source  107  to pressurize the diluted fluid in reservoir  108  for future transport of the diluted fluid to other apparatus as needed. Diluted fluid reservoir  108  is a vessel compatible with various solutions, such as acidic solutions, and may be capable of being pressurized. In one example, with no intent to limit the invention thereby, fluid reservoir  108  is made of Kel-F or Teflon material to provide compatibility with various solutions without leaching of contaminants. However, various reservoirs are applicable such as those that provide storage ability with sufficient venting capability, compatibility with various solutions, and cleanliness.  
      First and second sensors  110  and  112  detect a fluid level, and in this embodiment detect when diluted fluid reservoir  108  is “full” and “empty”, respectively. In one example, with no intent to limit the invention thereby, sensors  110  and  112  are each capacitive sensors, part number 2-101937, available from E&amp;M Electric of Healdsburg, Calif.  
      Controller  114  is operably coupled to relay  106  and sensors  110  and  112  and includes automation logic for controlling operation of pump  104  and diluent valve  118  while reading signals from sensors  110  and  112 . In one embodiment, controller  114  may be used to mix desired volumes of concentrated fluid and diluent to provide diluted fluids at desired concentrations. In one example, with no intent to limit the invention thereby, controller  114  is a “MicroLYNX-4” controller available from Intelligent Motion Systems, Inc. of Marlborough, Connecticut.  
      Referring now to  FIG. 2  in conjunction with  FIG. 1 , a method of automated fluid dilution is shown in accordance with an embodiment of the present invention. At step  202 , sensor  112  detects a low (“empty”) level of diluted fluid in reservoir  108  and sends a signal to controller  114 . At step  204 , controller  114  engages pump  104  via relay  106 , and at step  206 , pump  104  pulls and pumps concentrated fluid from reservoir  102  to reservoir  108  until stopped by controller  114 . Controller  114  may control the amount of concentrated fluid delivered to reservoir  108  based upon a time parameter, a pump stroke parameter, or both, in conjunction with a volume of diluent parameter based upon the desired dilution of the concentrated fluid. Accordingly, at step  208 , controller  114  engages diluent valve  118  to flow a diluent (e.g., ultra pure water (UPW) from a pressurized UPW supply) into reservoir  108  via fluid line  127  until sensor  110  senses a fluid level and sends a signal to controller  114  indicating that diluent flow should be stopped, as shown at steps  210  and  212 . The diluted fluid in reservoir  108  may then be delivered to parts of the analysis tool requiring the diluted fluid via fluid line  125 .  
      In one example, a 20% concentration of nitric acid may be diluted to a 1% concentration of nitric acid. 20% concentrated nitric acid is provided in a reservoir  102 . When sensor  112 , reading about every 2 seconds, detects a low level of diluted acid in reservoir  108 , sensor  112  sends a signal to controller  114  (either a 1 or 0). Controller  114  then engages pump  104  to provide about 50 ml of concentrated nitric acid in a 1 L reservoir  108  (pump  104  may be engaged for about 200 strokes when pump  104  pulls about 0.25 ml/pump stroke, which may take about 1 minute). After about 50 ml of concentrated nitric acid is provided within reservoir  108 , controller  114  engages diluent valve  118  to provide UPW until a signal from sensor  110  tells controller  114  to disengage diluent valve  118 , thereby “filling” reservoir  108  to about 1 L. Accordingly, 20% concentrated nitric acid will have been diluted to about 1% concentrated nitric acid.  
      Referring now to  FIG. 3 , a diagram of an automated fluid dilution system for automated in-line chemical analysis in accordance with another embodiment of the present invention is shown. Similar to fluid dilution system  100  of  FIG. 1 , fluid dilution system  300  includes a concentrated fluid reservoir  302 , a diluted fluid reservoir  308 , a first sensor  310 , a second sensor  312 , and a controller  314 . A power supply (not shown) is operably coupled to sensors  310  and  312 . Fluid lines  321 ,  323 ,  325 , and  327  are pathways for different fluids as will be described below.  
      Similar to concentrated fluid reservoir  102 , concentrated fluid reservoir  302  is a vessel compatible with various solutions, such as acidic solutions, and may be capable of being pressurized. In one example, with no intent to limit the invention thereby, fluid reservoir  302  is made of Kel-F or Teflon material to provide compatibility with various solutions without leaching of contaminants. However, various reservoirs are applicable such as those that provide storage ability with sufficient venting capability, compatibility with various solutions, and cleanliness.  
      It is noted that lines transporting fluids may comprise piping, fittings, and/or tubing in one example, but any applicable material and structure that allows for the accurate transfer of liquids may be used to operably connect to valves, syringes, reservoirs, and other apparatus in accordance with the present invention. In one example, with no intent to limit the invention thereby, components are connected with tubing made of Teflon® PFA 450 HP fluoropolymer, having 0.062″ O.D.×0.016″ I.D., Part #106-0062016, available from Parker Hannifin of Cleveland, Ohio.  
      Diluted fluid reservoir  308  is similar to diluted fluid reservoir  108  in function but is operably coupled to pump  304  via fluid line  325  for receiving a diluted fluid. Diluted fluid reservoir  308  is a vessel compatible with various solutions, such as acidic solutions, and may be capable of being pressurized. In one example, with no intent to limit the invention thereby, fluid reservoir  308  is made of Kel-F or Teflon material to provide compatibility with various solutions without leaching of contaminants. However, various reservoirs are applicable such as those that provide storage ability with sufficient venting capability, compatibility with various solutions, and cleanliness.  
      Similar to first and second sensors  110  and  112 , first and second sensors  310  and  312  detect a fluid level, and in this embodiment detect when diluted fluid reservoir  308  is “full” and “empty”, respectively. In one example, with no intent to limit the invention thereby, sensors  310  and  312  are each capacitive sensors,. part number 2-101937, available from E&amp;M Electric of Healdsburg, Calif.  
      The full signal from sensor  310  can signal the completion of the filling process. Alternatively, if pump  304  has a fixed volume per stroke, filling of the reservoir is determined by counting the number of strokes. Sensor  310  in this case can then provide an overfill signal alerting personnel of the need for maintenance.  
      Pump  304  is operably coupled to concentrated fluid reservoir  302 , a UPW supply, and diluted fluid reservoir  308  via lines  321 ,  323 , and  325 , respectively, for directly pumping a mixture of concentrated fluid and UPW (i.e., diluted fluid) to diluted fluid reservoir  308  under the control of controller  314 . A variety of pumps may be used for proportional metering (e.g., 20:1) of two fluids (e.g., diluent and concentrated solution) into a single fluid stream (e.g., diluted fluid). In one example, with no intent to limit the invention thereby, pump  304  is a “Q” dual pump available from Fluid Metering, Inc. of Long Island, N.Y.  
      Controller  314  is operably coupled to sensors  310  and  312  and includes automation logic for controlling operation of pump  304  while reading signals from sensors  310  and  312 . In one example, with no intent to limit the invention thereby, controller  314  is a “MicroLYNX-4” controller available from Intelligent Motion Systems, Inc. of Marlborough, Conn.  
      Referring now to  FIG. 4  in conjunction with  FIG. 3 , a flowchart of automated fluid dilution is shown in accordance with another embodiment of the present invention. At step  402 , sensor  312  detects a low (“empty”) level of diluted fluid in reservoir  308  and sends a signal to controller  314 . At step  404 , controller  314  engages pump  304  to pull and pump a mixture of concentrated fluid from reservoir  302  and diluent to reservoir  308  until stopped by controller  314 . At step  406 , sensor  310  senses a fluid level and sends a signal to controller  314  indicating that reservoir  308  is full, and at step  408 , controller  314  disengages pump  304  until step  402  occurs again. The diluted fluid in reservoir  308  may then be delivered to parts of the analysis tool requiring the diluted fluid via fluid line  327 .  
      Advantageously, the present invention provides an efficient and automated system and method of bulk fluid dilution for use in conjunction with automated and in-line chemical analysis tools. In one example, the present invention may be used with “TCM” and “CCM” automated chemical analysis apparatus available from Metara, Inc. of Sunnyvale, Calif. Other areas of application include but are not limited to general automated fluid dilution required in laboratory or bench settings.  
      Embodiments described above illustrate but do not limit the invention. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the present invention. For example, various types and sizes of reservoirs, types of fluids, and dilution ratios are within the scope of the present invention. Furthermore, diluted mixtures having more than two components are within the scope of the present invention. Accordingly, the scope of the invention is defined only by the following claims.