First Wafer Effect of Multiple SiO2/SiN Stack Layers Prepared by using Plasma-enhanced Chemical Vapor Deposition

Thickness control of a semiconductor thin film in the multistack layer (MSL) deposition process is important for improving the reliability and the performance of devices based on 3-dimensional stacked layers. The “first wafer effect” refers to the phenomenon where the thickness and the map profile of the first prepared wafer differ from those of the wafer prepared via the continuous process when deposition is started after the plasma deposition process has not been conducted for a certain time. We adopted stack seasoning to eliminate the first wafer effect for the MSL thickness and substantially reduced the effect; we also propose a mechanism based on stable improvement of the environment inside the chamber. Another interesting result is that, in addition to ensuring the reproducibility of the variations in stack layer thickness among wafers, the individual thicknesses of stack layers in the first wafer are reliably improved.