The performance of demanding optical layer systems is determined in practice by deviations in the layer thicknesses and the optical constants of the deposited layers. The deviations depend on the system and process. To avoid costly faulty batches, the expected yield is estimated using realistic simulation runs (virtual layers or computational manufacturing), taking into account the specific features of the available depositing technology, prior to the actual layer preparation.
The Fraunhofer IOF has developed a simulation tool which calculates the statistical fluctuations in optical constants and layer thicknesses in their impact on the required specifications of a given design.
These simulations are undertaken for quartz crystal monitoring and optical broad-band monitoring with the OptiMon process photometer as well as for derived hybrid strategies.
In addition to process-specific fluctuations in the shutter response time and deposition rate, the simulation is based on the background level in the optical in-situ spectra as well as in-process fluctuations in the optical constants. These constants can be recorded using a multi-oscillator model.
Fraunhofer Institute for Applied Optics and Precision Engineering IOF