Abstract: An apparatus for wet processing of substrates in a controlled environment. It is a single-substrate processing apparatus which is capable of carrying out etching, rinsing, and drying processes all in a single apparatus and in a controlled environment. A closed processing chamber is provided for processing a substrate in a closed environment. Processing liquids and gases are introduced into the chamber and the chamber is rotated with the substrate. Temperature inside the chamber is controlled by heating the gases. Humidity is controlled by varying the proportion of water vapor. The rotation of the chamber with the substrate creates a stable environment where processing parameters are more easily controlled.