Mechanistic study of ultralow k-compatible carbon dioxide in situ photoresist ashing processes. II. Interaction with preceding fluorocarbon plasma ultralow k etching processes

Process interactions between fluorocarbon (FC) plasma ultralow k (ULK) dielectrics etching followed by carbon dioxide (CO2) in situ photoresist (PR) ashing on ULK damage have been studied in a dual frequency, capacitively coupled plasma reactor. Introduction of ULK trench/via sidewall damage was simulated employing blanket ULK films by exposing them in a non-line-of-sight fashion in a small gap structure to the plasma environment. ULK damage was quantified using the dilute hydrofluoric acid (0.5%/15 s) selective etching method. CO2 in situ ashing processes showed a chamber memory effect due to prior FC plasma etching, significantly increasing damage of pristine ULK films. For ULK plasma etching/PR ashing process sequences, ULK material surfaces were modified by FC plasma etching prior to the CO2 plasma exposure. X-ray photoelectron spectroscopy studies showed that the modifications consisted primarily of 1–2 nm FC coverage of the ULK. This FC deposit remained on the ULK surfaces during in situ CO2 process...