INTERFEROMETRIC MEASUREMENT OF DISK SLIDER SPACING - THE EFFECT OF PHASE-SHIFT ON REFLECTION/

In an interferometric system for measurement of spacing between a tran sparent disk end a slider, the effect of phase shift on reflection off the slider surface must be considered to obtain an accurate measureme nt. In this paper we describe a theoretical treatment of the problem a nd provide typical measurements of phase shift on reflection for sever al types of slider materials in use today. The technique used to measu re phase shift utilizes an ellipsometric measurement of the slider's c omplex index of refraction from which the phase shift on reflection is calculated. Monochromatic interferometric theory is used to show that assuming the slider to behave as a dielectric with a phase shift on r eflection of pi can result in flying height measurement errors on the order of 12 nm. The magnitude of the phase-shift effect is investigate d for different slider materials. In addition, the variation in phase shift as a function of the wavelength of light is investigated.