Monolithic Integrated a-Si:H based pin-Diodes with Orthogonal Liquid Light Guidance Structures for Lab-on-Microchip Appl
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0989-A10-04
Monolithic Integrated a-Si:H Based Pin-Diodes with Orthogonal Liquid Light Guidance Structures for Lab-on-Microchip Applications Heiko Sch‰fer, Konstantin Seibel, Lars Schˆler, and Markus Bˆhm Institute for Microsystem Technologies, University of Siegen, Hˆlderlinstr. 3, Siegen, 57076, Germany ABSTRACT We report the fabrication of an amorphous silicon based fluorescence sensor for miniaturized total analysis systems along with experimental results on optical excitation and detection elements. The pin-photodiode exhibits a dynamic range of 110dB and a room temperature dark current of less than 3000 charge carriers per ms according to a detector area of 0.1256mm2. The spectral response is ranging from 320nm to 780nm with a maximum at 600nm @ 80% quantum efficiency. To provide high sensitivity, the excitation light irradiates the fluid orthogonally to the active sensor detection direction by means of specifically designed microfluidic capillaries filled with e.g. methylene iodide or 1,2-o-dibrombenzene. The liquid core, which is enclosed by solid cladding materials, has been calculated to dimensions of a width of 16.75µm or 59.67µm with a height from 15µm to 50µm according to a number of propagating modes inside of 16 or 57, respectively. INTRODUCTION Since the early 90ís, several groups have started to develop optics for microchips used in total analysis systems [1,2,3,4,5]. However, there is still a tremendous need for the development of miniaturized fluorescence detection systems [6,7,8]. Most notably, due to the higher absorption coefficient for visible light and the low dark current, an amorphous silicon detector is more suitable for the detection of fluorescence light than a crystalline silicon detector. In particular, most applied labeling dyes used for chemical and biological analysis emit in the visible part of the light spectrum. The Application specific Lab-on-Microchip (ALM) is a monolithically integrated technology platform, combining microfluidic networks, microoptical components and microelectronic circuits [9]. With its full-fledged monolithic integration onto a standard Application Specific Integrated Circuit (ASIC), the ALM allows for dramatic reductions of sample volumes and analysis times, thus offering vastly improved speed, reliability and efficiency. As a consequence, the ALM is well suited to perform fast and mobile environmental analysis without the need of large and expensive diagnostic instrumentation. In contrast to most of the commonly used architectures that are manufactured by micromechanical procedures on unpatterned silicon or glass substrates combined with polymer materials like poly(dimethylsiloxane) (PDMS) or polymethylmethacrylate (PMMA) the ALM offers a wide range of functional components. Integrated optoelectronic devices and microoptical waveguides can provide a portable, parallel and inexpensive solution for on-chip fluorescence sensing. With regard to cost minimization during the early stages of ALM process development we are using thermal oxidized silicon wafers o
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