DISPERSIVE WHITE-LIGHT INTERFEROMETRY FOR ABSOLUTE DISTANCE MEASUREMENT WITH DIELECTRIC MULTILAYER SYSTEMS ON THE TARGET

We have extended the use of a dispersive white-light interferometer fo r absolute distance measurement to include effects of dielectric multi layer systems on the target. The phase of the reflected wave changes a s a function of wavelength and layer thickness and causes errors in th e interferometric distance measurement. With dispersive white-light in terferometry these effects can be measured in situ, and the correct me chanical distance can be determined. The effects of thin films deposit ed upon the target have been investigated for one and two layers (phot oresist and SiO2 upon Si). Experimental results show that the thicknes ses of these layers can also be determined with an accuracy of the ord er of 10 nm. (C) 1996 Optical Society of America