Capacitance based scanner for thickness mapping of thin dielectric films

We have recently developed a technique capable of mapping variations in the thickness of thin dielectric films. This technique is based on accurately recording the capacitance between a spherical probe and the conductive substrate of a dielectric film. Once the capacitance has been recorded, and assuming the dielectric constant is known, the thickness of the film can be readily extracted, with better than 0.2 μm accuracy. In the current experimental configuration, the probe can be raster scanned with respect to the surface of the dielectric film, enabling one to record three-dimensional images and observe any spatial variations in sample thickness. The spatial resolution (i.e., the imaging resolution) of the technique is primarily dictated by the size of the probe and currently rests at ∼200 μm. This technique is applicable to any dielectric film on a conductive substrate, assuming the dielectric constant is known.