Sub 10 nm thick amorphous carbon overcoat FOR thin film magnetic media

Takayuki YAMAMOTO and Hiroyuki HYODO

Fujitsu Laboratories Ltd. Atsugi, 243-0197 Japan

Takashi TOYOGUCHI

Yamagata Fujitsu Ltd. Higashine, 999-3701 Japan

Abstract

The areal recording density of hard disk drives has rapidly increased by over 100% per year in the 1990s and is expect to increase further in the 21st century. Such a high rate has required improvement in device components, such as a Giant Magnetoresistive (GMR) head and a low noise medium, mechatronics and signal processing. In addition, the reduction of magnetic spacing has become an imperative for maintaining such a rate. The magnetic spacing is defined by the sum of flying height and thickness of the overcoat in the head and medium. Therefore, there has been a big motivation to reduce the thickness of the overcoat while keeping its high durability and strong corrosion resistance. An overcoat is expected to be on the order of nanometers in an advance recording system.

Nitrogenated or hydrogenated amorphous carbon films by DC magnetron sputtering has been widely used for an overcoat in the thin film medium because they have provided superior performance in tribology and in corrosion resistance. However, as the overcoat thickness approaches to less than 10 nm, the sputtered films may not maintain the performance. Though plasma chemical vapor deposition (pCVD) or ion beam deposition (IBD) appears to be an alternative to the sputtering because it provides films with high hardness and good coverage, it is still a concern whether or not the deposition can continue to provide such good properties when film thickness reduces to a few nanometers.

Filtered Cathodic Arc (FCA) deposition can produce very hard amorphous carbon even at a few nanometers, compared with other methods such as DC sputtering, pCVD and IBD. The amorphous carbon films composed of a tetragonal sp³ bonding that forms a diamond structure, and a trigonal sp² bonding that forms a graphite structure. The film prepared by FCA deposition has an sp³ content higher than those by the other methods. We can obtain smooth and highly dense films. As a result, the FCA film shows the strongest wear resistance among films prepared by other methods, as shown in Figure 1. The FCA film can be a strong candidate for an ultra-thin overcoat of advance media.

This work was supported in part by ASET in the MITI’S R&D program.

Keywords: overcoat, thin film magnetic media, amorphous carbon, FCA, tribology

Takayuki YAMAMOTO

Fujitsu Laboratories Ltd.

10-1 Morinosato-wakamiya

Atsugi 243-0197 Japan

takayui@flab.fujitsu.co.jp

Tel: +81 (46) 249-6695 , Fax: +81 (46) 250-8268