Ultrathin (< 5 nm) hard carbon films are of great interest to the magnetic storage industry as the areal density approaches 100 Gbit/in 2 . These films are used as overcoats to protect the magnetic layers on disk media and the active elements of the read-write slider. Tetrahedral amorphous carbon films can be produced by filtered cathodic arc deposition, but the films will only be accepted by the storage industry only if the "macroparticle" issue has been solved. Better plasma filters have been developed over recent years. Emphasis is put on the promising twist filter system -a compact, open structure that operates with pulsed arcs and high magnetic field. Based on corrosion tests it is shown that the macroparticle reduction by the twist filter is satisfactory for this demanding application, while plasma throughput is very high. Ultrathin hard carbon films have been synthesized using Sfilter and twist filter systems. Film properties such as hardness, elastic modulus, wear, and corrosion resistance have been tested. Index Terms: diamond-like carbon, cathodic vacuum arc, macroparticle filtering, magnetic storage, carbon overcoats 3
I. INTRODUCTIONUltrathin (< 5 nm) hard carbon films are used as protective overcoats on hard disks and readwrite heads. The tribological properties of the head-disk interface are not only of mechanical but also of chemical nature: the overcoat should protect the magnetic layers against wear and corrosion [1, 2]. The areal density of information stored in disk drive products increased at an amazing rate of over 65% for many years rate, and continues to accelerate to even greater rates [3]. To accomplish this, the "magnetic spacing" between the magnetic layers of the disk and read/write sensor of the head must continue to decrease. The magnetic spacing includes the overcoats, lubrication, and the fly height. Thinner overcoats allow the read-write head to be closer to the magnetic layer of the disk, and hence, the size of individual bits on the disk to be smaller. As we work toward an areal density of 100 Gbit/in 2 , the magnetic spacing approaches the sub-10-nm regime (pseudo-contact recording) and overcoat thickness must shrink to 1-2 nm. Overcoats currently used are sputtered or ion-beam deposited diamond-like carbon films, typically doped with hydrogen or nitrogen. They cease to provide acceptable levels of corrosion protection when the film thickness is less than 5 nm.Overcoats need to be tough (hard and elastic), chemically inert, pinhole-free, and compatible with the lubricant. The challenge of ultrathin film synthesis is to make the films as thin as possible and still continuous, as opposed to an assembly of islands.Nucleation and growth of ultrathin films is a field of intense research. For carbon, it is well known that films that are rich in sp 3 (diamond) bonds should be grown in a kinetic mode at low temperature (less than 200°C, preferably room temperature), with film-forming carbon atoms or ions having an energy of about 100 eV. This energy is optimized for subplantat...
