Plasma enhanced atomic layer etching of high-k layers on WS2

Abstract

The etching of HfO[Formula: see text] and ZrO[Formula: see text] high-k dielectrics is studied using plasma enhanced atomic layer etching. The etching method relies on a continuous argon inductively coupled plasma discharge in which reactive gases are pulsed, followed by substrate biasing; both steps are separated by purge periods. It is found that pure BCl[Formula: see text] is too chemically active while a Cl[Formula: see text]–BCl[Formula: see text] allows a high process synergy; in addition, the latter gives a high selectivity to SiO[Formula: see text]. The optimal etch conditions are applied to high-k layers deposited on top of WS[Formula: see text] transition metal dichalcogenide. Postetch analysis shows negligible tungsten and sulfur depletion as well as negligible change in optical (Raman) response of the 2D layer, indicating that atomic layer etching concepts allows us to prevent WS[Formula: see text] material loss or damage.