Scalability of Magnetic Tunnel Junctions Patterned by a Novel Plasma Ribbon Beam Etching Process on 300 mm Wafers

Abstract

The performance of magnetic tunnel junction (MTJ) over its critical dimension (CD) is critical to the application of spin transfer torque magnetic random access memory. To study the CD scaling effects, we designed a series of MTJ CDs and used a novel plasma ribbon beam etching (PRBE) process to pattern the MTJs. PRBE has constant beam density and beam angle distribution across a 300 mm wafer. The MTJs patterned by PRBE demonstrated low tunneling magnetoresistance degradation from 145% on blanket films to $\sim 130$ % for MTJ CDs ranging from 100 to 20 nm. At 20 nm, MTJ switching current was down to 20 $\mu \text{A}$ , and the thermal stability factor was still above 40, demonstrating good device scalability.