ULTRA-LOW FLYING HEIGHT MEASUREMENTS USING MONOCHROMATIC AND PHASE DEMODULATED LASER INTERFEROMETRY

Phase demodulated laser interferometry and three wavelength monochroma tic interferometry are employed to measure the flying height at the sl ider-disk interface in the sub-100 nanometer spacing range. Phase demo dulated laser interferometry measures the relative displacement of the slider using the actual slider and disk, while three wavelength monoc hromatic interferometry measures the absolute flying height of the sli der using a transparent disk and an actual slider. The results from bo th techniques are found to agree down to the ''landing height'', i.e., the height when the slider is ''resting'' on the top of the disk aspe rities. Landing heights are found to follow the peak-to-valley disk su rface roughness.