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In-situ spectroscopic reflectance measurements for OLED process monitoring

: Eritt, M.; Uredat, S.; May, C.; Leo, K.

TU Dresden:
ICEL 7, 7th International Conference on Electroluminescence of Molecular Materials and Related Phenomena : September 02-06, 2008, Dresden
Dresden, 2008
International Conference on Electroluminescence of Molecular Materials and Related Phenomena (ICEL) <7, 2008, Dresden>
Conference Paper
Fraunhofer IPMS ()

A method for in-situ thickness monitoring by spectroscopic reflectance measurement in an OLED-inline deposition tool is presented. The measurements were done on thin organic films deposited by vacuum thermal evaporation. The substrates were bare glass covered with an opaque aluminum layer. The reflectance spectra of different organic materials and thicknesses were recorded and analyzed.
The analysis was done with the knowledge of refraction index and extinction coefficient provided by ex-situ ellipsometry analysis. The reflectance spectra of different materials were shown and discussed. The method will be compared with the ex-situ ellipsometry for analyzing the layer thickness and the results were shown. Spectroscopic reflectance measurement can be used to determine thicknesses of multi-layer stacks also which is presented in this paper by an example of a two layer alpha-NPD and Alq3 stack.
The reproducibility of the measurement system was investigated and gives an excellent feedback of the usability for reflectance measurement equipment inside production tools. The adaption to vacuum deposition tools is straightforward by the usage of only one viewport.
The advantage of reflectance measurement is the in-situ monitoring of optical properties of organic layers which can be sensitive against oxygen and moisture and will allow a reproducible detection of layer reflectance. The spectroscopic reflectance measurement is non-destructive and an efficient method to extract the layer thickness out of an organic layer in excellent accordance to ex-situ data.