FTIR or spectroscopic ellipsometer will work, but only if the wavelength is long enough. In my experience, most spectroscopic ellipsometers do not suffice, because their wavelength range is 190-1000 nm. I have used a two-sided laser profilometer, with precision alignment, to measure membrane thicknesses in this range to better than 0.1 um. Cyber-Scan used to make a product, but I'm not sure if they're in business anymore. A single-sided profilometer has the problems outlined by others, in terms of error due to unknown reference distance or length. A micro-caliber could work, but I am not familiar with it. Al On Tue, Jan 5, 2010 at 1:38 PM, Andrea Mazzolariwrote: > Hi All, > > i need to realize silicon membranes of thickness 14 and 29 um in (100) > silicon. > > I need to measure membrane thickness with a tollerance of 0.5um. > > Any suggestion about a way to measure membrane thickness with a so good > resolution ? > > Best regards, > Andrea