The invention discloses a low-cost apparatus for chemical solution preparation with controlled process parameters such as chemical age, temperature, yield of active ingredients at the point of use. In addition, this apparatus provides chamber-to-chamber consistency on these parameters across multiple processing chambers on a single wafer wet-clean system. The invention also discloses a method to use chemical solution mixture resident time to achieve optimal combined effect of temperature, reactivity and yield of active ingredients of chemical solution mixture for best wafer treatment results.