RCA clean is used to remove organic residues from silicon wafers. In the process, it
oxidizes the silicon and leaves a thin oxide on the surface of the wafer. The general
recipe is for RCA-1 cleanser is: 5 parts water (H2O), 1 part 27% ammonium hydroxide
(NH4oH), 1 part 30%hydrogen peroxide (H2O2). Here is how to prepare it.
325 ml DI water
65 ml NH4OH (27%)
65ml H2O3 (30%)
Put 325 ml DI water in a Pyrex beaker, add 65 ml NH4OH (27%) and then heat to 70 + /-
5 deg C on hot plate. Remove from hot plate and add 65 ml H2O2 (30%). Solution will
bubble vigorously after 1-2 minutes, indicating that it is ready for use. Soak the silicon
wafer in the solution for 15 minutes. When finished, transfer the wafer to a container with
overflowing DI water from a tap to rinse the solution. After several water changes,
remove the wafer under flowing water. (Still water surface can contain organic residue
that will redeposit on the water surface when removing wafer.) To dispose of the RCA-1
solution, dilute with cold water then pour down the drain with plenty of cold water to
flush. Old RCA-1 cleaning solution cannot be used since it loses its effectiveness in 24
hours at room temperature (30 minutes at 70 deg. C).