Avoiding Oxygen Plasma Damage During Hard Mask Etching in Magnetic Tunnel Junction (MTJ) Fabrication Process

摘要

An etch process flow for forming magnetic tunnel junction (MTJ) cells with enhanced throughput that also increases the magnetoresistive ratio and decreases critical dimension (CD) variation is disclosed. A photoresist pattern is formed on a dielectric antireflective coating (DARC), which contacts a top surface of a hard mask (HM) that is an uppermost MTJ layer. After a first ion beam etch (IBE) or reactive ion etch (RIE) transfers the pattern through the DARC, a second etch is used to transfer the pattern through the HM. The second etch includes an oxidant to passivate the pattern sidewalls and completely removes the photoresist layer because of one or both of a thicker DARC and thicker HM than in conventional processing. Accordingly, an oxygen etch typically used to remove the photoresist after the HM etch is avoided and thereby provides improved MTJ performance, especially for CDs60 nm.