In-situ measurement of dielectric thickness during etching or developing processes

A system has been developed which permits the measurement of dielectric film thicknesses in-situ during development or etching processes. This can be extended to growth or deposition processes. Two examples of its uses are presented: the determination of the thickness of phosphosilicate glass layers on silicon dioxide coated silicon wafers by making use of the etch rate differences, and the monitoring of photoresist thickness during development to characterize the photoresist development process.