The control of defects on the wafer is a critical task for nano-scale memory devices to achieve high yields. Even though supercritical CO2 drying technology has been available for more than 10 years, its application in 300mm wafer fabrication process still lacks an effective solution for the control of particles and metallic contaminant generated. To address this, the authors studied the CO2 purification process and found that most of particles on the wafer after supercritical CO2 treatment were found to be organic contaminants from the CO2 raw material. A CO2 purification system with an activated carbon absorber demonstrated superior performance for removing organic contaminants from the CO2. The metallic contaminants, coming from the supercritical chamber’s stainless steel parts, were decreased by aging of the supercritical fluid at a high temperature. A dense metal oxide film generated by aging with IPA-added supercritical CO2 at a high temperature was shown to prevent corrosion of the stainless steel surface. Knowledge and control of contaminations at the nano level will soon enable supercritical CO2 drying in 300mm nano-scale memory manufacturing.