Patent ID: 7015119

Claim:
A method of fabrication of a semiconductor integrated circuit device, comprising the steps of: (a) introducing water into a primary pure water purifying system as first raw material water; (b) introducing, as second raw material water, primary pure water which has been obtained by the purification of said first raw material water through use of said primary pure water purifying system, into a secondary pure water purifying system having a secondary pure water circulating loop; and (c) feeding a first wet treatment apparatus with secondary pure water which has been obtained by the purification of said second raw material water through use of said secondary pure water purifying system, thereby subjecting a semiconductor integrated circuit wafer to first wet treatment in the first wet treatment apparatus, step (c) including the sub-steps of: (c1) removing ions from the second raw material water through use of a cation removing filter disposed between a secondary pure water supply point from the secondary pure water circulating loop and a use point in the first wet treatment apparatus, the cation removing filter having a membrane sheet; and (c2) feeding the use point of said first wet treatment apparatus with the secondary pure water which has passed through said cation removing filter.