Challenges and promises in the fabrication of bit patterned media

Bit patterned media (BPM) is one of the promising technologies for ultra-high density storage in future hard disk drives. However, there are many challenges in fabricating BPM. In particular, applications with area density much greater than 1 Tbit/in2 require magnetic bits to be at sub-10 nm dimensions. Etching at these scales is difficult to achieve with conventional ion milling techniques. Instead, reactive ion etching (RIE) techniques must be developed to meet the challenge. In this work, research is presented on the development of a methanol based RIE scheme for fabricating BPM at ultra-high area densities. The paper will discuss the ability of methanol RIE to etch magnetic and nonmagnetic films in both the parallel plate and inductively coupled plasma (ICP) RIE configurations, as well as the advantages of both configurations over Ar ion milling, including enhanced selectivity, minimal redeposition, and less etch induced damage or erosion. We demonstrate the ability to etch sub-20 nm features in commercially available CoCrPt based perpendicular recording media and NiFe with selectivity greater than 10:1 relative to mask materials, such as Ta, TaNx, Ti, and SiNx. These results, the promises of such a technique, and the feasibility of sub-10 nm scale etching are discussed in detail.

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