Air-bearing surface

Fig. 10—Evolution of head slider and air bearing surface, cited from www.hitachigst.com/hdd/...

Topology Design of Flying Head Air Bearing Surface... 

Fig. 4—The number of CF+ at different positions of the slider surface, (a) air bearing surface (ABS) of magnetic head, (b) CF numbers on different positions of ABS.

Lap and etch air bearing surface, dice row bar into sliders... 

FIGURE 2 Fabrication of heads for HDDs, (a) Thin film inductive and GMR heads are batch fabricated on ceramic wafers, (b) Wafers are sliced into rows. At the row level, the air bearing surface is first lapped to tight flatness specifications, and then lithographically patterned and etched to create air bearing features. Air bearing features are typically 0.1-2 om in height, (c) Finally, rows are parted into individual sliders 1 x 1.25 x 0.3 mm in size. SOURCE IBM. 

X-ray photoelectron spectroscopy (XPS) was done on some of the silicon test samples and on all the sliders. The narrow dimensions of the air bearing surface of the slider are difficult to measure using ellipsometry, while the spot size of the XPS is small enough to measure in these regions. The XPS measurements were done on Surface Science Labs SSX-100 spectrometers (A1 source) at resolution 3 with a 300-pm spot size. These conditions yield an Ag M i2 line width of about 1.13 eV. The anode power was 50 W, and the irradiated area was about 300 x 500 pm because of the 35° angle of incidence. The XPS measurements were performed within 25 min to minimize film thickness erosion due to gradual ablation of the PFOM by the incident x-ray beam. 

FIGURE 4.2 XPS spectra of a 2.4 nm thick film of PFOM on the air bearing surface of a slider. Cls spectrum (a), and Ols spectrum (b). The arrows indicate the binding energies of atoms with different chemical environments. 

Peak Assignments Used in Analysis of the XPS Spectra to Determine PFOM Thickness on the Air Bearing Surface of the Slider... 

Since the air bearing surface of the slider is carbon-overcoated, the same carbon overcoat was placed on some of the silicon strips to evaluate the PFOM film thickness and ellipsometric measurement procedure on carbon- and non-carbon-overcoated substrates. A nominally 12.5-nm-thick layer of sputtered carbon was deposited on silicon strips, and the strips were dip coated with PFOM. The ellipsometric angles A and T were measured. The two-layer model (two films on an absorbing substrate) was used with the optical constants for the materials listed in table 4.6 in calculating the PFOM thickness from A and T on carbon-overcoated silicon. The apparent... 

Since an additional ellipsometric measurement would be needed to determine the carbon-overcoat thickness, the ellipsometric measurement of PFOM thickness directly on non-carbon-overcoated silicon is more straightforward. Silicon strips and wafers were dip coated with PFOM. The PFOM thickness measnred by ellipsometry and the dIX from XPS are listed in table 4.8. The thickness measured by ellipsometry was divided by the dIX from XPS for each sample (last two columns in table 4.8). The experimentally determined average electron mean free path for PFOM film is X = 2.66 nm. Sliders were dip coated with PFOM at the same conditions as the silicon wafers and strips, and dIX was measured on the air bearing surface of each slider by XPS. These dIX were multiplied by A, = 2.66 nm, as determined above, to estimate the PFOM thickness on the air bearing surface. These results are listed in table 4.9. The concentration of the PFOM solution was 650 ppm, and the withdrawal rate was 1.6 mm/s. 

Tests were done to determine the effects of PFOM concentration and withdrawal rate on the PFOM film thickness deposited on the air bearing surface of sliders. The PFOM film thickness was estimated using XPS. The film thickness as a function of PFOM concentration is shown in fig. 4.3a. Run 1 was made in a prototype coating tank using a developmental procedure. Run 2 was made with the coating tank and... 

PFOM Thickness as Estimated from XPS Measurements on the Air Bearing Surface (ABS) of Magnetic Recording Sliders... 

FIGURE 4.3 PFOM thickness estimated from XPS measurements on the air bearing surface of sliders as a function of PFOM concentration at a 1.6 mm/s withdrawal rate (a) and thickness as a function of withdrawal rate at a PFOM concentration of 400 ppm, lx dip (b). 

The electron mean free path of A, = 2.66 nm is within the range of mean free paths reported for polymer thin films on surfaces [8]. Equation (4.4) was used to estimate the PFOM thickness on air bearing surfaces from dIX. The values of dIX and PFOM film thicknesses are given in table 4.9. The PFOM film was 0.5-0.7 nm thicker on the carbon-overcoated air bearing surfaces (table 4.9, column 3) and on the carbon-overcoated rows (table 4.7, columns 3 and 7) than on the silicon wafers (table 4.8, column 3). This is attributed to the difference between the surface chemistry of the SiOj surface of the uncoated silicon and that of the carbon overcoat. 

In conclusion, for the PFOM film thickness measurement, the non-carbon-over-coated silicon wafers can be used to monitor the thickness of PFOM being deposited on the air bearing surface as long as the presence of an offset in the deposited film thickness between the two types of substrates is taken into account. 

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