Rainer Haspel

Advanced industrial fluorescence metrology used for qualification of high quality optical materials

Schott Glas is developing and producing the optical material for various specialized applications in telecommunication, biomedical, optical, and micro lithography technology. The requirements on quality for optical materials are extremely high and still increasing. For example in micro lithography applications the impurities of the material are specified to be in the low ppb range. Usually the impurities in the lower ppb range are determined using analytical methods like LA ICP-MS and Neutron Activation Analysis. On the other hand absorption and laser resistivity of optical material is qualified with optical methods like precision spectral photometers and in-situ transmission measurements having UV lasers. Analytical methods have the drawback that they are time consuming and rather expensive, whereas the sensitivity for the absorption method will not be sufficient to characterize the future needs (coefficient much below 10-3 cm-1). In order to achieve the current and future quality requirements a Jobin Yvon FLUOROLOG 3.22 fluorescence spectrometer is employed to enable fast and precise qualification and analysis. The main advantage of this setup is the combination of highest sensitivity (more than one order of magnitude higher sensitivity that state of the art UV absorption spectroscopy) and fast measurement and evaluation cycles (several minutes compared to several hours necessary for chemical analytics). An overview is given for spectral characteristics and using specified standards. Moreover correlations to the material qualities are shown. In particular we have investigated the elementary fluorescence and absorption of rare earth element impurities as well as defects induced luminescence originated by impurities.

Fluorescence metrology used for analytics of high-quality optical materials

Optical, glass ceramics and crystals are used for various specialized applications in telecommunication, biomedical, optical, and micro lithography technology. In order to qualify and control the material quality during the research and production processes several specialized ultra trace analytisis methods have to be appliedcs Schott Glas is applied. One focus of our the activities is the determination of impurities ranging in the sub ppb-regime, because such kind of impurity level is required e.g. for pure materials used for microlithography for example. Common analytical techniques for these impurity levels areSuch impurities are determined using analytical methods like LA ICP-MS and or Neutron Activation Analysis for example. On the other hand direct and non-destructive optical analysistic becomes is attractive because it visualizes the requirement of the optical applications additionally. Typical eExamples are absorption and laser resistivity measurements of optical material with optical methods like precision spectral photometers and or in-situ transmission measurements by means ofusing lamps and or UV lasers. Analytical methods have the drawback that they are time consuming and rather expensive, whereas the sensitivity for the absorption method will not be sufficient to characterize the future needs (coefficient much below 10-3 cm-1). For a non-destructive qualification for the current and future quality requirements a Jobin Yvon FLUOROLOG 3.22 fluorescence spectrometery is employed to enable fast and precise qualification and analysis. The main advantage of this setup is the combination of highest sensitivity (more than one order of magnitude higher sensitivity than state of the art UV absorption spectroscopy), fast measurement and evaluation cycles (several minutes compared to several hours necessary for chemical analystics). An overview is given for spectral characteristics using specified standards, which are necessary to establish the analytical system. The elementary fluorescence and absorption of rare earth element impurities as well as crystal defects induced luminescence originated by impurities was investigated. Quantitative numbers are given for the relative quantum yield as well as for the excitation cross section for doped glass and calcium fluoride.

Advanced industrial metrology used for qualification of high-quality optical materials

Schott Glass is producing and developing the optical material for various specialized applications in photonics, optical and microlithography technology. In order to achieve the specifications several of metrology R&D activities have been done and hardware has been installed in the metrology labs. Today special diagnostics are available to qualify materials for the absolute refractive index, the transmissin, radiation durability and inner quality to ensure the quality of the produced materials. Methods used for this qualifications are minimum deviation, precision spectral photometer, in-situ transmission measurements using UV lasers and Rayleigh Scattering. The optical material quality requirements of such materials are extremely high and still increasing. Therefore further development and implementation of diagnostics have been iniatiated, e.g. Raman Scattering, fluorescence and refractive index measurements. We present the status of R&D activities for metrology, which is necessary to visualize the status and the improvement of the optical quality with the help of new and improved metrology.