Abstract

During the last decade, the rapid development and implementation of new concepts in precision laser metrology generated an increased demand for high quality optical component. A special requirement in this field is the production of coatings with lowest losses which is mainly achieved by adapted ion beam sputter processes in the present state of optical thin film technology. For the optimization of an existing ion beam sputter process, a new method of online process monitoring has been installed: In general, ion beam sputter processes are based on high energetic (about 1000eV) inert gas ions which sputter the desired coating material from a high purity target. For the deposition of oxide materials, the target can alternatively consist of the oxide or the corresponding metal, which is oxidized during the process in the residual oxygen atmosphere of the recipient. In the actual process, emission of plasma radiation in front of the metal target can be observed. This radiation is investigated by an online spectrometer for different process parameters in respect to the optical properties of the produced coatings. Silicon, aluminum and tantalum were chosen as target materials and sputtered under different operating conditions of the ion source and selected oxygen flow values. In the present setup, the plasma radiation at the target surface is collected and coupled into a fiber by a convex lens (fig.1). The optical fiber is conducting the light out of the high vacuum chamber into one of two existing monochromators covering the spectral region from 200nm up to 800nm. The power of the light spectrally resolved by the monochromator is measured by a photomultiplier tube, and the corresponding signal is recorded by a standard PC which is also employed for the wavelength control.

© 1998 Optical Society of America