Point of use recycling system for cmp slurry

Abstract

The present invention generally relates to apparatus and method for recycling both polishing slurry and rinse water from CMP processes. The present invention also relates to rheology measurements and agglomeration prevention using centrifugal pumps.

1 . An apparatus for recycling, comprising:
 a separation unit comprising:
 an inlet configured to receive a mixture of used polishing slurry, rinsing fluid, and polishing waste; 
 a water outlet configured to output a first stream for waste or water recycling; and 
 a slurry outlet configured to output a second stream for slurry recycling polishing; and 
   a slurry filtration unit comprising:
 an inlet connected with the slurry outlet of the separation unit; 
 one or more filtering media configured for filtration or removal of ions and organics; and 
 a pump disposed upstream of the one or more filtering media and configured to press a stream of fluid through the one or more membranes. 
 a product outlet configured to output a stream of concentrated and recycled polishing slurry; and 
 a water outlet for water recycling or waste. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the separation unit comprises a diverter valve selectively connecting the inlet to the water outlet and the slurry outlet. 
     
     
         3 . The apparatus of  claim 2 , wherein the pump of the slurry filtration unit is one of a piston pump, a diaphragm pump, a bellow pump, a peristaltic pump, a magnetically levitated centrifugal pump, and a device for fluid transfer by vacuum draw or pressurization. 
     
     
         4 . The apparatus of  claim 2 , wherein the filtering media of the slurry filtration unit and the is a spiral membrane, a hollow fiber membrane, a tubular membrane, a plate and frame membrane operated in a dead-end filtration methods, a back flushable filtration method, a cross flow filtration method, or a filtering media operated by depth filtration. 
     
     
         5 . The apparatus of  claim 2 , wherein the slurry filtration unit comprises one or more of a microfiltration membrane, a nanofiltration membrane, and an ultrafiltration membrane. 
     
     
         6 . The apparatus of  claim 5 , wherein the slurry filtration unit further comprises a backwash or cross flow clean capability. 
     
     
         7 . The apparatus of  claim 2 , further comprising a UV (ultra violet) unit configured to reduce bacteria and organic contamination from fluid passing through, wherein the UV unit comprises:
 an inlet connected with the water outlet of the separation unit and/or the water outlet of the slurry filtration unit; and   an outlet configured to output a stream of sanitized fluid.   
     
     
         8 . The apparatus of  claim 7 , further comprising a water treatment unit configured to purify the sanitized fluid by removing trace of chemicals, wherein the treatment unit comprises:
 an inlet connected to the outlet of the UV unit; and   an outlet configured to output a stream of purified fluid.   
     
     
         9 . The apparatus of  claim 2 , further comprising a dosing unit connected to the slurry filtration unit for dosing conditioning chemicals during processing in the slurry filtration unit. 
     
     
         10 . The apparatus of  claim 1 , wherein the separation unit is a filtration unit comprising:
 a filtering media comprising:
 a microfiltration membrane; and 
 a nanofiltration membrane disposed downstream to the microfiltration membrane; and 
   a pump disposed upstream of the microfiltration membrane and configured to press a stream of fluid through the filtering media, wherein the slurry outlet is disposed between the microfiltration membrane and the nanofiltration membrane, and the water outlet of the separation unit is disposed downstream to the filtration media.   
     
     
         11 . The apparatus of  claim 1 , further comprising a centrifugal separator configured to separate polymeric or large particles, wherein the centrifugal separator is disposed upstream or downstream of the separation unit. 
     
     
         12 . A method for recycling polishing fluid, comprising:
 generating a waste water stream and a concentration stream from a mixture of used polishing slurry, rinsing fluid and polishing waste;   filtering the concentration stream through a slurry filtration unit to separate a stream of reusable polishing slurry from a water stream;   flowing the stream of reusable polishing slurry to a polishing slurry source for a polishing station; and   flowing the water stream to a recycled water source.   
     
     
         13 . The method of  claim 12 , wherein generating the waste water stream and the concentration stream comprises filtering the mixture through a filtering unit having multiple membranes or using a diverter valve to selectively direct the mixture to a slurry outlet and a water outlet. 
     
     
         14 . The method of  claim 13 , further comprising measuring one or more characteristics of the reusable polishing slurry before flowing the stream of reusable polishing slurry to a polishing slurry source for a polishing station, wherein the one or more characteristics of the reusable polishing slurry comprises one or more of zeta potential, density, particle size, and particle distribution. 
     
     
         15 . The method of  claim 14 , further comprising supplying the reusable polishing slurry to perform a bulk polishing process in the polishing station. 
     
     
         16 . The method of  claim 13 , further comprising:
 sanitizing the water stream to remove organic species from the water stream prior to flowing the water stream to the recycled water source;   purifying the sanitized water stream by a reversed osmosis process through a treatment unit; and   deionizing the purified water stream by one of a continuous electrodeionization (CEDI) process, ion exchange, or ion removal prior to flowing the water stream to the recycled water source.   
     
     
         17 . The method of  claim 16 , further comprising
 supplying rinsing water from the recycled water source to perform one or more initial rinses in a polishing station; and   supplying virgin ultra purified water to perform final rinses in the polishing station.   
     
     
         18 . A polishing slurry unit for a polishing system, comprising:
 a slurry reservoir having a reservoir pump, wherein the slurry reservoir is connected to a virgin slurry source;   a recycling unit comprising one or more filtration units, wherein the one or more filtration unit comprises a filtration pump, and the recycling unit is connected to the slurry reservoir and is configured to receive used polishing slurry, pump the used slurry through the one or more filtration units and provide filtered polishing slurry to the slurry reservoir; and   a controller connected to at least one of the reservoir pump and the filtration pump, wherein the controller is configured to monitor and/or adjust characteristics of the polishing slurry according to process parameters of the at least one pump connected thereto.   
     
     
         19 . The polishing slurry unit of  claim 18 , wherein the filtration pump is a magnetically levitated centrifugal pump. 
     
     
         20 . The polishing slurry unit of  claim 19 , wherein the recycling unit comprises a valve system configured to divert excessive polishing slurry during polishing to a slurry recycling unit and rinse fluid during rinse to a rinse water recycling unit.