Abstract: Processes for monitoring the levels of oxygen and/or nitrogen in a substantially oxygen and nitrogen-free plasma ashing process generally includes monitoring the plasma using optical emission. An effect produced by the low levels of oxygen and/or nitrogen species present on other species generally abundant in the plasma is monitored and correlated to amounts of oxygen and nitrogen present in the plasma. This so-called “effect detection” process monitors perturbations in the spectra specifically associated with species other than nitrogen and/or oxygen due to the presence of trace amounts of oxygen and/or nitrogen species and is used to quantitatively determine the amount of oxygen and/or nitrogen at a sensitivity on the order of 1 part per million and potentially 1 part per billion.

Abstract: A plasma ashing process for removing photoresist material and post etch residues from a substrate comprising carbon, hydrogen, or a combination of carbon and hydrogen, wherein the substrate comprises a low k dielectric layer, the process comprising forming a plasma from an essentially oxygen free and nitrogen free gas mixture; introducing the plasma into a process chamber, wherein the process chamber comprises a baffle plate assembly in fluid communication with the plasma; flowing the plasma through the baffle plate assembly and removing photoresist material, post etch residues, and volatile byproducts from the substrate; periodically cleaning the process chamber by introducing an oxygen plasma into the process chamber; and cooling the baffle plate assembly by flowing a cooling gas over the baffle plate assembly.