Plasma atomic layer etching (ALE) for SiO2 and Si3N4 and reactive ion etching (RIE) for SiO2 with hole-patterns were developed using C4F8 and the low global warming potential gases of perfluoroisopropyl vinyl ether (PIPVE) and perfluoropropyl vinyl ether (PPVE). The ALE windows of SiO2 and Si3N4 were in the range of 50.0-57.5 V for all precursors. Etch per cycle of SiO2 was determined to be 5.5Å /cycle (C4F8), 3.3Å /cycle (PIPVE), and 5.4Å /cycle (PPVE), all lower than that of Si3N4. PPVE reduced global warming emissions by 49%, demonstrating better vertical etch profiles in RIE compared to C4F8.
In this work, plasma ALE process was developed for ruthenium that involves plasma fluorination with C4F8 or CHF3 plasma and ion bombardment with Ar plasma in an inductively coupled plasma (ICP) reactor. Chemical sputtering threshold of C4F8 plasma is lower than that of CHF3 plasma owing to the higher F1s/C1s ratio fluorocarbon layers. The ALE window was confirmed with bias voltage of 150~210V. The etch per cycle (EPC) of ruthenium was determined to be 1.5 nm/cycle for C4F8 and 0.6 nm/cycle for CHF3. The EPC of ruthenium was self-limited with increasing Ar plasma etch time.
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