Application of Laser Microetching in Formation of Air-Bearing Surface for Magnetic Head Sliders
- PDF / 4,104,714 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 45 Downloads / 141 Views
(Coherent, Innova 90) was used as an excitation source for the wet etching process. The etchant selected for the experiment was a KOH aqueous solution of various concentrations from 0.1 M to 20 M. At the wavelength used in this study, the absorption of the laser beam energy by the KOH etchant layer above the substrate surface (around 2 mm thick) is less than 2 % and therefore is negligible. The laser beam was bent using mirrors and then focused by a laser focusing and monitoring system (D.S. Scanner Co. Ltd.) which has an objective lens (Mitsutoyo 50 x, N.A.=0.42). The laser beam can be focused down to a spot size of 4 pm which is diffraction limited. The samples were fixed by electron wax on the bottom of an irradiation cell which was mounted onto a scanning X-Y stage (Unimotion Controls Pte Ltd). The substrate surface stayed in focus throughout the etching process. A CCD video camera was mounted on top of the optic column, and the video image was sent to a TV monitor for focusing adjustment and real time monitoring. After the laser etching, samples were rinsed in water and cleaned in a supersonic bath by trichloroethylene and acetone. The profiles and dimensions of the etched features were observed by scanning electron microscopy (SEM). RESULTS AND DISCUSSION Preliminary etching experiments were performed in KOH solutions with different concentrations, ranging from 0 to 20 M, to investigate the effect of KOH concentration on the etching behavior of the polycrystalline AI2O3TiC material. Figures 1(a) and l(b) show the SEM micrographs of laser etched grooves on an AI20 3TiC substrate in a KOH solution with different concentrations of 0.1 M and 2 M. The laser power and scan speed are all 960 mW and 3 Am/s respectively. It was found that when the KOH concentration was below 0.25 M, etching was accompanied with bubble'formation in the region of laser irradiation. The etched grooves were rough and irregular as shown in Fig. l(a). This is believed due to the lack of a KOH etchant. When there is not enough KOH etchant to remove the strongly-heated region of the polycrystalline AI2O3TiC surface, the laser incident point will have extremely high local temperature and sharp temperature gradients and produce a fluid streaming which results in strong microstirring of the etchant. The water in the solution is vaporized. A microjet of boiling fluid emanating from the point of laser incidence on the substrate surface can be observed.
Jij
(a) KOH 0.1 M, 960 mW, 3 ftm/s.
(b) KOH 2 M, 960 mW, 3 Frm/s.
Fig. 1. SEM micrographs of laser etched grooves inan AI20 3TiC substrate in KOH solutions with different concentrations.
318
As the KOH concentration exceeded 1 M, the etching process became bubble-free, and walls of etched grooves were well defined and very clean as shown in Fig. 1(b). The grooves are V-shaped with smooth side walls and have no cracks and debris. In the experiment, the etching width and depth are much larger than the laser beam spot size. When the etched groove becomes deeper, the side walls become nearly fla
Data Loading...
