Investigation of carbon void defects on hard disk surfaces

Abstract

A carbon void on a hard disk surface is a defect that occurs during the carbon sputter deposition process for the manufacture of hard disks. Because the carbon overcoat on hard disk surfaces acts as a barrier to corrosion, it is essential to reduce the number and size of carbon voiddefects. In the present study, carbon void defects on hard disk surfaces were studied using various failure analysis tools. The influence of the substrate bias voltage on the number and size of carbon void defects was also investigated. The results of the failure analysis show that there wasa 40–50% loss in recorded magnetic bit signal due to an increase in the gap between a recording head and a hard disk surface with carbon void defects. Removing the bias voltage on the substrate during the sputtering process reduced the carbon void defects significantly. The average numberof carbon void defects per disk surface was reduced from 4 to 0·5. In addition, the average size of the carbon void defect was reduced from 8 μm to 3·8 μm.