Study of Chromium Hard Mask Formation and Wall Angle Control for Deep Etching Application

AbstractBurnish head is widely used for burnishing process which is one of the critical ways to remove such asperities from the disk surface prior to assembly into hard disk drive. To achieve glide performance for ultra-low flying height, disk media with asperities that exceed the flying height of the magnetic head must be eliminated. One of critical parameter of burnish head is the rail dimension which required very deep etching at > 30 microns. To produce such etching depth, a Cr hard mask is needed. Wet etching process for Cr film was selected to form the Cr hard mask. In this study, the interactions of wet etching condition with the Cr hard mask were investigated in terms of the process impact to the mask wall angle. The chemical reaction was studied and discussed here in term of mass transportation condition. XPS revealed that the etch byproduct was Cr nitrate (Cr(NO3)3) and Cr oxide (Cr2O3). These byproducts passivated the metal surface and limited the fresh etchant arrival onto unetched surface. From the etched topography study, the process is said to be under mass transport control, and the reaction rate was determined to be influenced by the rate of mass transfer of reactants and products to and from the surface

Raman Spectroscopy of DLC/a-Si Bilayer Film Prepared by Pulsed Filtered Cathodic Arc

DLC/a-Si bilayer film was deposited on germanium substrate. The a-Si layer, a seed layer, was firstly deposited on the substrate using DC magnetron sputtering and DLC layer was then deposited on the a-Si layer using pulsed filtered cathodic arc method. The bilayer films were deposited with different DLC/a-Si thickness ratios, including 2/2, 2/6, 4/4, 6/2, and 9/6. The effect of DLC/a-Si thickness ratios on the sp3 content of DLC was analyzed by Raman spectroscopy. The results show that a-Si layer has no effect on the structure of DLC film. Furthermore, the upper shift in G wavenumber and the decrease in ID/IG inform that sp3 content of the film is directly proportional to DLC thickness. The plot modified from the three-stage model informed that the structural characteristics of DLC/a-Si bilayer films are located close to the tetrahedral amorphous carbon. This information may be important for analyzing and developing bilayer protective films for future hard disk drive