Capacity considerations Ultrapure water

relationship between ultrapure water flow , wafer size

capacity plays important role in engineering decisions upw system configuration , sizing. example, polish systems of older , smaller size electronic systems designed minimum flow velocity criteria of 2 ft per second @ end of pipe avoid bacterial contamination. larger fabs required larger size upw systems. figure below illustrates increasing consumption driven larger size of wafer manufactured in newer fabs. however, larger pipe (driven higher consumption) 2 ft per second criteria meant extremely high consumption , oversized polishing system. industry responded issue , through extensive investigation, choice of higher purity materials, , optimized distribution design able reduce design criteria minimum flow, using reynolds number criteria.

the figure on right illustrates interesting coincidence largest diameter of main supply line of upw equal size of wafer in production (this relation known klaiber s law). growing size of piping system overall requires new approaches space management , process optimization. result, newer upw systems rather alike, in contrast smaller upw systems have less optimized design due lower impact of inefficiency on cost , space management.

another capacity consideration related operability of system. small lab scale (a few gallons-per-minute-capacities) systems not typically involve operators, while large scale systems operate 24x7 trained operators. result, smaller systems designed no use of chemicals , lower water , energy efficiency larger systems.