Optimized ellipsometric analysis of computer disk structures

Sputtered media computer disks contain several materials layers, such as chromium, CoNi (or similar magnetic alloys), amorphous carbon(or other dielectric), and fluorocarbon lubricant. Control of the thickness and physical properties of each layer in these disk structures during manufacturing is extremely important. Recently, variable angle spectroscopic ellipsometry (VASE) was used to characterize multilayer disk structures, including layer thicknesses, surface and interfacial roughness, and lateral homogeneity. In this paper we extend the usefulness of the VASE technique by presenting the results of calculations of the sensitivity(as a function of wavelength and angle of incidence) of the ellipsometric measurement to the determination of disk parameters such as layer thicknesses and film interfacial roughness. As a result of these calculations, the user of ellipsometry will know the optimum wavelengths and angles to use for the effective monitor and control of disk production. The technique is applicable to any thin film or multilayer production process.