Methods and apparatuses for precise trimming of silicon-containing materials are provided. Methods involve oxidizing silicon-containing materials and thermally removing the oxidized silicon-containing materials at particular temperatures for a self-limiting etch process. Methods also involve a surface reaction limited process using a halogen source and modulated temperature and exposure duration to etch small amounts of silicon-containing materials. Apparatuses are capable of flowing multiple oxidizers at particular temperature ranges to precisely etch substrates.

A method of forming features in stack with a silicon containing layer below a mask is provided. Features are etched into the stack. A post etch plasma treatment is provided to reduce surface roughness of sidewalls of the features.

Disclosed are apparatuses and methods for performing atomic layer etching. A method may include supporting and thermally floating a substrate in a processing chamber, modifying one or more surface layers of material on the substrate by chemical adsorption, without using a plasma, while the substrate is maintained at a first temperature, and removing the one or more modified surface layers by desorption, without using a plasma, while the substrate is maintained at a second temperature, the first temperature being different than the second temperature. An apparatus may include a processing chamber and support features configured to support and thermally float a substrate in the chamber, a process gas unit configured to flow a first process gas onto the substrate, a substrate heating unit configured to heat the substrate, and a substrate cooling unit configured to actively cool the substrate.