The present invention is concerned with semiconductor device manufacturing, and is more particularly concerned with apparatus and methods for diluting a chemical used in connection with semiconductor device manufacturing. This device can be used in other high tech application s such as pharmaceutical or specialty chemical blending applications.
Typical chemical dilution systems use a variety of methods to assure precise measurement of the chemical components that are blended to make up the final chemical solution. Some of these methods include mass based methods which use load cells to measure the weight of the components of chemicals to be mixed. Others use flow meters to measure flow of the components of chemicals to be mixed. In some cases the system uses mass-flow controllers which determine a combination of mass and flow to of the components of chemicals to be mixed. Finally some of these systems use conductivity to determine the concentration of the final mix of chemistry. All of these types of instruments have a certain amount of variation or inaccuracy of the output based on the electrical tolerances of the devices that do not meet some of the tight tolerances or specifications in certain high tech or pharmaceutical applications.
This invention uses precisely calibrated vessels that can be filled to an exact volume every time. This gives an extremely repeatable process that can not be varied by any inaccuracy or variation of instrumentation.
This invention incorporates three main process stages in order to blend or dilute chemicals, a concentrate storage stage which is a storage and transfer process of the concentrated chemistry, a concentrate measuring stage which is a series of precisely calibrated vessels containing concentrated chemical that is used to measure and transfer the concentrated chemical needed for the chemical mixture, a dilution stage which is a precisely calibrated vessel that contains dilution water that is used to measure and transfer the water needed to dilute the chemical mixture.
The invention further includes an auto titration device coupled to the concentrate storage stage that measures the normality of the concentrate chemical. This can also be done by lab analysis prior to the concentrate chemistry being put online.
The invention further includes a Programmable Logic Controller (PLC) or similar device that is programmed to determine a dilution ratio for the final mixed chemical based on the exact calibrated volume of water as it will be mixed with a calculated number of vessel volumes or “shots” from the series of calibrated vessels in the concentrate measuring stage. The controller is further programmed to transfer the precisely calibrated volume of dilution water and concentrated chemicals to the mix vessel using gravity to achieve the dilution ratio to within the desired tolerance. As is understood by those who are skilled in the art, “chemistry” or “a chemistry” refers to any chemical substance, solution and/or mixture.
The invention includes a concentrated chemistry mixing stage which is made up of a series of precisely calibrated vessels that can be added to a chemical mix in predetermined combination s to achieve a precise mixture within a desired tolerance.
The invention includes a qualification stage which includes a storage tank, pumping device, and quality verification analyzer used to verify the final concentration of the mixture to the desired tolerance.
The apparatus and methods of the present invention are well suited to precisely provide a highly dilute chemistry (e.g., a surfactant or other chemical) to a semiconductor device processing apparatus (e.g., photo track or the like) or similar pharmaceutical devices. In addition, the inventive apparatus and methods can be provided cost effectively, and can be arranged to selectively operate so only concentrated chemistry is used without dilution.
Other features, operations, and benefits of the present invention will become more apparent from the detailed description of the invention, the appended claims and the accompanying drawings.
The present invention provides for a chemical dilution or mixing system that utilizes precisely calibrated fixed volume vessels to attain a final mixture within a tight tolerance.
The Concentrate Chemical Storage in
The concentrate chemical is analyzed for concentration either with laboratory analysis or using an on-line titration analyzer (AIT101D). The concentration result is automatically sent to the PLC or entered manually into the control system using the operator interface system.
Once the concentration data is entered in the control system the Programmable Logic Controller (PLC) uses an algorithm to calculate the exact volume of concentrate chemical is needed along with the fixed volume of dilution water to result in the desired final concentration of mixed chemical.
The Dilution Module shown in
The dilution vessel is manufactured to be very close to 20 liters, but the actual volume is measured using a graduated cylinder and recorded in the PLC as the fixed volume.
The Concentrate Chemical Measuring Module in
This series of incrementally smaller chemical measuring vessels allows the ability to add small amounts of concentrated chemical as determined by the variation in concentrate chemical assay as measured by laboratory analysis or online titration analyzer. Multiple volumes or “shots” can be added from any of the chemical measuring vessels as determined by the PLC algorithm.
The Concentrate Chemical Vessel (TT300) is filled with concentrated chemical using pump (P101) and opening inlet valve (V301). The liquid level then overflows into the tube and a sensor (LSH3038) detects liquid in the overflow tube which shuts off the feed valve (V301). Next the overflow tube drain valve (V303) opens and empties the overflow tube of its liquid into a chemical recovery vessel (TR900). This will always provide the same volume of concentrated chemical.
The content of the Dilution Vessel (TT200) is emptied into the mix tank (TM700) by opening outlet valve (V202).
The content of the Concentrate Chemical Vessel (TT300) is emptied into the mix tank (TM700) by opening outlet valve (V302).
The Concentrate Chemical Measuring Vessel (TT300) is then filled again with concentrated chemical using pump (P101) and opening inlet valve (V301). The liquid level then overflows into the tube and a sensor (LSH3038) detects liquid in the overflow tube which shuts off the feed valve (V301). Next the overflow tube drain valve (V303) opens and empties the overflow tube of its liquid into a chemical recovery vessel (TR900).
The Chemical Measuring Vessel (TT300) is mounted at a higher elevation than the Roughing Column (TT400), Fine Tune Column (TT500), and Ultrafine Column (TT600). This allows the Chemical Measuring Vessel (TT300) to be used as a low pressure fill source for the other vessels TT400, TT500, & TT600.
The Chemical Measuring Vessel (TT300) is mounted is then used to fill the Roughing Column (TT400), Fine Tune Column (TT500), and Ultrafine Column (TT600) any number of times based on the algorithm in the PLC that calculates the number of shots needed of each of the various Chemical Measuring vessels to reach the desired endpoint of the final mixed chemical.
Example: The concentrate chemical is 25.08% and the desired final endpoint concentration is 2.38±0.005%. 20 liters of UPW is emptied from the dilution vessel (TT200) into the mix vessel (TM700) and combined with 2 liters of concentrate chemical from the Chemical Measuring Vessel (TT300). In order to reach the desired final endpoint concentration is 2.38 ±0.005%, the PLC would add 4 volumes or “shots” from the Fine Tune Chemical Vessel (TT500) and 7 volumes or “shots” from the Ultra-Fine Tune Chemical Vessel (TT600).
Once the final mix is in the Mix Vessel (TM700) it is re-circulated using the mix module pumps (P702 or P703) through static mixer (SM701), through conductivity sensor (AIT7520) and back to the Mix Vessel (TM701). Level switches (LSH748A & LSL749A) are used on the Mix Vessel (TM700) to prevent tank overflow or low level pump starvation. The conductivity sensor (AIT7520) is used to determine that the solution has reached homogeneous mix equilibrium and is then ready to transfer to the qualification tank (TQ800).
Once in the Qualification tank (T0800) the mixed chemical is re-circulated using the Qualification module pumps (P801 or P802). Several batches from the Chemical Mix Module will ten fill the Qualification module prior to sample and analysis by the online titration analyzer. A sample line from the qualification tank (TQ800) to the auto-titration instrument enables online qualification of the Qualification Tank (TQ800). It may take several minutes for the auto-titration analyzer to sample and analyze, therefore the qualification tank may contain a composite mix of several batches from the mix module.
When the Point of Use requires a fill, the Chemical Mix Module would stop mixing batches and stop transferring batches to the Qualification module. This would allow the auto titrator to sample and analyze the current composite mix in the Qualification tank (TQ800) and verify the quality to transfer to the Point of Use.
Once the transfer to the Point of Use is complete the Chemical Mix Module can begin making batches and filling the Qualification module.
If the Auto titrator determines that the composite mixture is out of tolerance, the Qualification tank can be pumped to a rework tank or tote for future disposition.
A backup tote of dilute material (TD104) is in standby mode to deliver to the Point of Use in case of a out of tolerance mix, or if any system failure in the Chemical mixing system occurs.