Silicon thin-film UV filter for NADH fluorescence analysis

A new optical detector system for fluorescence analysis in on-chip high-speed screening arrays is described. It consists of a photodiode covered by a re-crystallized silicon film, which acts as a single-film optical filter. The crystalline structure of the silicon film has a strong influence on the optical properties of the filter. The fabrication process and characterization of a polycrystalline Si thin-film on glass are reported. The method is compatible with standard CMOS processes. The optical properties of the designed filter are such that fluorescent light of wavelengths of 420 nm or higher can be measured in the presence of (UV) excitation light (340-360 nm). A selectivity exceeding 35 dB has been demonstrated. The technique has the potential for 50 dB selectivity and higher. NADH concentration measurements in the range 0-1 mMol/l illustrate the application of the system for determination of enzymatic activity of different analytes. (C) 2002 Elsevier Science B.V. All rights reserved.