Patent ID: 7253011

Claim:
A method of fabrication of a semiconductor integrated circuit device, comprising the steps of: (a) introducing first water into a first water purifying system, and sending out first purified water from the first water purifying system; (b) introducing the first purified water into a second water purifying system having a pure water circulating loop, and sending out second purified water from a first supply point on the pure water circulating loop; and (c) feeding a first wet treatment apparatus with the second purified water, thereby performing the first wet treatment to a wafer in the first wet treatment apparatus; step (b) including the sub-steps of: (b1) removing ions from the first purified water through use of a cation removing filter in the pure water circulating loop, the cation removing filter having a membrane sheet; and (b2) removing foreign particles from the first purified water which has passed through the cation removing filter through use of a heat welded ultrafiltration filter in the pure water circulating loop, wherein, from said second purified water that has been fed to said first wet treatment apparatus, an ionized amine or ionized amine substance has been removed to such an extent as not to affect the characteristics of the semiconductor integrated circuit device to be fabricated using said second purified water.