Nonselective, material-independent, precision plasma delayering of metals and dielectrics

Nonselective, high-precision, plasma-assisted delayering provides a robust means for failure analysis of heterogeneously integrated devices. While chemical mechanical planarization is often used to planarize different materials exposed on the wafer surface, deleterious defects, such as gouging and corrosion, can impact die yield and device performance. To circumvent these issues, in this work, we demonstrate a material-independent, nonselective plasma delayering technique. The etch rate is uniform over the area of interest, requiring only a single dry etching chamber. Ar, CF4, and O2, commonly used in high-volume microchip fabrication, are selected as etchants of W, Ti, and SiO2. These materials are chosen as representative examples of metals and dielectrics found in CMOS devices. We use methyl acetate as an etch retardant to reduce and eventually halt the etching process. The relative methyl acetate mass flow rate provides precise control of the etching of both metals and dielectrics, defining a process window in which all three etch rates begin to converge. Depending on the process need, such as planarizing highly corrugated surface, the uniform etching can also be modified to become more material-dependent and selective to provide precision delayering and achieve a planarized surface.