Patent ID: 6267894
Filing Date: 2001-07-31
Classification: B01D,Y10S

Abstract:
A method of filtering a liquid disposed in a bath for use in conjunction with the fabrication of semiconductor devices, said liquid containing particles of varying sizes therein which includes the steps of:providing a bath and a pair of independent recirculation routes from said bath and returning to said bath including a bath outflow from said bath to said pair of recirculating routes and a bath inflow from said pair of recirculating routes to said bath:(i) the first of said pair of recirculating routes directly communicating with said bath outflow and said bath inflow and having serially a first controllable valve and a first filter having a relatively large pore size having pores of from about 0.2 to about 2.0 micrometers; and(ii) the second of said pair of recirculating routes directly communicating with said bath outflow and said bath inflow and having serially a second controllable valve and a second filter having a relatively small pore size of from about 0.001 to about 0.2 micrometers;(iii) said first and second routes each providing a return path from each of said first and second filters to said bath inflow passing said liquid from said bath along the associated recirculation route and back to said bath;monitoring the particle count in each of said recirculation routes; andcontrolling said first and second controllable valves individually in response to said particle count.