In 1965, RCA (Radio Corporation of America) developed a method for cleaning silicon wafers and applied it to the fabrication of RCA components. This cleaning method became the basis for many future wafer cleaning processes.

The RCA cleaning method relies on solvents, acids, surfactants and water to spray, purify, oxidize, etch and dissolve wafer surface contamination, organic and metal ion contamination without destroying the wafer surface features and chemically Wash thoroughly in ultrapure water (UPW) after product.

Common cleaning solutions and their functions:

(1) Ammonium hydroxide/hydrogen peroxide/DI water mixture (APM;  NH4OH/ H2O2/ H2O at 65~ 80"C).

APM is usually called SC1 cleaning solution, its formula is NH4OH: H2O2: H2O = 1: 1: 5~ 1: 2: 7, with oxidation and micro-etching to undercut and remove surface particles, also can remove light organic pollutants and some metalized pollutants. However, surface roughness occurs at the same time as silicon oxidation and etching.

(2) Hydrochloric acid/hydrogen peroxide/DI water mixture (HPM; HC1/ H2O2/H2O at 65~80°C).

HPM is usually called SC2 cleaning solution, its formula is HC1: H2O2: H2O= 1: 1: 6~ 1: 2: 8, which can dissolve alkali metal ions and hydroxides of aluminum, iron and magnesium. In addition, chloride ions in hydrochloric acid undergo complex reactions with residual metal ions to form complexes that are easily soluble in an aqueous solution, which can remove metal contaminants from the bottom layer of silicon.