Multi-purpose optical profiler for characterization of materials, film stacks and for absolute topography measurement

We have developed a scanning white-light interference microscope that offers two complementary modes of operation on a common metrology platform. The first mode measures the topography and the second mode measures the complex reflectivity of an object surface over a range of wavelengths, angles of incidence and polarization states. This second mode characterizes material optical properties and determines film thickness in multi-layer film stacks with an effective measurement spot size typically smaller than 10 μm. These data compensate for material and film effects in the surface topography data collected in the first mode. We illustrate the application of this dual-mode technology for post-CMP production-line metrology for the data storage industry. Our tool concurrently measures critical layer thickness and step height for this application. The accuracy of the latter measurement is confirmed by correlation to AFM measurements.