Andrea, You may be able to find an FTIR microscope. Using this you could use the etalon to calculate the thickness. Good Luck. Rob MacDonald Shearwater Scientific 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