Paper PS-TuP12
Etch Characteristics of Magnetic Tunneling Junction Materials by Using Noble Gas and Hydrogen

Tuesday, October 23, 2018, 6:30 pm, Room Hall B

As next generation non-volatile memory device, spin transfer torque magnetic random access memory (STT-MRAM) is one of the prospective memory devices. But anisotropic etching of magnetic tunneling junction material (MTJ) is vey difficult especially in nano-scale. Ar ion beam etch (IBE) not only has low etch selectivity but also induces sidewall re-deposition. Even though tilted ion beam can remove deposited materials at sidewall, a shadow effect restricts the effective removal of deposited materials in nano-scale pitch size. Some chemical reactive ion etching (RIE) can improve problems of Ar IBE, but they show other problem such as low selectivity, corrosion and chemical damage to magnetic materials.

In this study, MTJ materials were etched by using H₂, Ne, Ar and Xe inductively coupled plasma (ICP) and observed their etch characteristics. The nano-scale patterned MTJ material sample which is composed of CoPt(10nm), MgO(1nm), CoFeB(10nm) with W hardmask was used for comparing etch profiles with re-deposition. The results show that H₂ and Ne etch showed better etch profile and higher etch selectivity of MTJ materials over W than those with Ar. With Xe, etch selectivity was lower than the other gas, even though Xe showed an anistropic profile. Also using the vibrating sample magnetrometer (VSM), we compared saturated magnetic moments (Ms) to identify magnetic degradation. The patterned sample etched with Ne and Ar showed similar Ms, which means no significant magnetic degradation when using Ne.