Dry Etching Mechanisms of ZrO2 Thin Films in BCl3/Cl2/Ar Plasma

We investigated etching behavior of ZrO2 thin films and selectivity of ZrO2 thin films to SiO2 and Si3N4 by using inductively coupled plasma system. Experimental results have shown that higher etch rate of ZrO2 thin films was achieved by the reactive ion etching using Cl radicals due to the high volatility of BxClyOz. Consequently, the increased chemical effect was caused to the increase in the etch rate of the ZrO2 thin film. Small addition of Cl-2 to the BCl3/Ar mixture increased selectivities of ZrO2 thin films to SiO2 and Si3N4. The surface analysis by x-ray photoelectron spectroscopy (XPS) showed some evidences that Zr and O were reacted with Cl and BCl and formed nonvolatile metal chlorides and volatile boron-oxy-chlorides. This effect can be related to the concurrence of chemical and physical pathways in the ion assisted chemical reaction.