Abrasive recovery method and abrasive recovery device

Abstract

There is provided an abrasive recovery device and an abrasive recovery method capable of recovering a slurry which is condensed until a concentration of its abrasive becomes high while suppressing an increase in pressure loss and a great decrease in a recovery ratio ascribable to membrane clogging. The abrasive recovery device is a device 1 which recovers an abrasive from a used polishing slurry which has been used in a CMP process, the device including a separation membrane 41 having a cylindrical hole passage to which the used polishing slurry is led, wherein an effective filtration part of the hole passage of the separation membrane 41 has a 0.8 m length or less, and the abrasive recovery device 1 condenses the used polishing slurry until a concentration of the abrasive becomes 10 mass % or more.

What is claimed is: 
     
         1 . An abrasive recovery device, comprising;
 a first separation membrane having a first cylindrical hole passage to lead a used polishing slurry in a CMP process, the first cylindrical hole passage having a first effective filtration part,   a second separation membrane provided on a subsequent stage of the first separation membrane,   the second separation membrane having a second cylindrical hole passage to lead a condensate from the first separation membrane,   the second cylindrical hole passage having a second effective filtration part shorter than the first effective filtration part in length,   the second effective filtration part being not longer than 0.8 m,   circulation mechanism configured to pass the condensate from the first separation membrane through the second separation membrane sequentially and condense the used polishing slurry until a concentration of the abrasive becomes 10 mass % or more and recover an abrasive from the used polishing slurry.   
     
     
         2 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of hollow portions of the first separation membrane and the second separation membrane is passed through by the used polishing slurry in a cross-flow method.   
     
     
         3 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of the first separation membrane and the second separation membrane is provided in a membrane separation unit of an internal-pressure type.   
     
     
         4 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of the first separation membrane and the second separation membrane is a hollow-fiber membrane.   
     
     
         5 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of inside diameters of the first separation membrane and the second separation membrane is not less than 0.1 mm nor more than 0.8 mm.   
     
     
         6 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of molecular cut-off of the first separation membrane and the second separation membrane is 3,000 to 30,000.   
     
     
         7 . The abrasive recovery device according to  claim 1 ,
 wherein at least one of the first separation membrane and the second separation membrane is made of any one of polyethylene, tetrafluoroethylene, polyvinylidene difluoride, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, and polyethersulfone.   
     
     
         8 . The abrasive recovery device according to  claim 1 ,
 wherein a length L 1  of the first effective filtration part is 0.8 to 1.5 m, and a length L 2  of the second effective filtration part is 0.2 to 0.8 m.   
     
     
         9 . An abrasive recovery method comprising:
 a first filtration step of passing the used polishing slurry in the CMP process through a first separation membrane having a first cylindrical hole passage, to condense the used polishing slurry, the first cylindrical hole passage having a first effective filtration part; and   a second filtration step of passing a condensate from the first separation membrane through a second separation membrane provided on a subsequent stage of the first separation membrane,   the second separation membrane having a second cylindrical hole passage,   the second cylindrical hole passage having a second effective filtration part shorter than the first effective filtration part in length,   the second effective filtration part being not longer than 0.8 m, to condense the condensate until a concentration of an abrasive of the condensate becomes 10 mass % or more.   
     
     
         10 . The abrasive recovery method according to  claim 9 ,
 wherein at least one of hollow portions of the first separation membrane and the second separation membrane is passed through by the used polishing slurry in a cross-flow method.   
     
     
         11 . The abrasive recovery method according to  claim 9 ,
 wherein at least one of inside diameters of the first separation membrane and the second separation membrane is not less than 0.1 mm nor more than 0.8 mm.   
     
     
         12 . The abrasive recovery method according to  claim 9 ,
 wherein a circulation flow rate of water to be treated in at least one of the effective filtration parts of the first separation membrane and the second separation membrane is 0.5 to 2 m/sec.   
     
     
         13 . The abrasive recovery method according to  claim 9 ,
 wherein, in the first filtration step, the used polishing slurry is condensed to 13 mass % at the maximum by the filtration, and in the second filtration step, the condensate obtained in the first filtration step is condensed up to 26 mass % at the maximum by the filtration.   
     
     
         14 . The abrasive recovery method according to  claim 9 ,
 wherein an abrasive concentration of the used polishing slurry led to the first separation membrane is 0.02 to 5 mass %.   
     
     
         15 . The abrasive recovery method according to  claim 9 ,
 wherein an average particle size of abrasive particles contained in the used polishing slurry is 0.01 to 1 μm.   
     
     
         16 . The abrasive recovery method according to  claim 9 ,
 wherein a circulation flow rate of water to be treated in the first effective filtration part is 0.55 to 1.5 m/sec.   
     
     
         17 . The abrasive recovery method according to  claim 9 ,
 wherein a circulation flow rate of water to be treated in the second effective filtration part is 0.6 to 1 m/sec.