|Abstract: ||本論文主要研究應用於生醫螢光檢測之矽光二極體及讀取電路，針對矽光二極體結構上做設計，然後藉由電路將光電流訊號讀出。首先，設計出三類型的矽光二極體，第一類基本型結構、第二類光井結構與第三類繞射與光檔牆結構。針對這三大類型，先使用電流-電壓(I-V)特性量測，分析由光二極體產生的410nm激發光 (紫光-Violet)與被激發的540nm螢光 (綠光-Green)照射下的光電流，希望待測之螢光光電流要遠比激發光光電流來的大。激發光是由射光二極體產生。由於矽光二極體本身材料特性，綠光與紫光的光響應度(responsivity)比值無法大到可應用於螢光檢測。因此，透過螢光檢測的結構設計去進行改善，將LED激發光固定於一方並固定一角度照射於螢光待測物上，因而使激發光偏離光二極體，螢光直接照射在光二極體上。藉由此量測結構，螢光與激發光的光響應度比值可高達20以上。元件與電路的實作是使用國家晶片設計中心所提供的TSMC 0.35?m CMOS BioMEMS製程技術
In this thesis, silicon photodiodes and read-out circuits for biomedical fluorescence detection are studied. Silicon photodiode structures are design and then the photocurrent signal is read out by a read-out circuit. Firstly, three types of silicon photodiodes are designed, They are the first type of the basic structure, the second type of the light well structure and the third type of diffraction and the light-retaining wall structure, respectively. For the three types, the measurement of current-voltage characteristics is used to analyze the photocurrent induced by shining the excitation light, violet light with a wavelength of 410 nm or so, and excited fluorescence, green light with a wavelength of 540 nm or so, on the photodiode.It is expected that the photocurrent resulting from fluorescent is much larger than that from excitation light. The excitation light is generated by a light-emitting diode (LED). Because of the material nature of silicon, the responsivity ratio of green and violet lights is not large enough that the photodiodes can be applied to fluorescence detection. Therefore, the small responsitivity ratio is improved by the structural design of fluorescence detection.By fixing the LED on the side of the photodiode and shining the analyzed fluorescent target with a certain incident angle, the excitation light is directed away from the photodiode and only fluorescence is directly shined on the photodiode. With the designed structure for fluorescent measurement, the responsitivity ratio of fluorescence and excitation light is more than 20. that which is bound with fluorophore, Devices and circuits are fabricated by using the TSMC 0.35?m CMOS BioMEMS process, which is supported by National Chip Implementation Center.
The third type of photodiode is used to do the concentration detection of fluorescent material. the plot of the photocurrent versus concentration, including 6mg/ld, 8mg/ld, 10mg/ld, 12mg/ld, and 14mg/ld, is measured. As for the readout circuit, the three kinds of circuits are designed. The first kind is a circuit with a output of oscillation pulse. The discharging current of capacitors depends on the mirrored photocurrent. Output frequency is proportional to the photocurrent with a measured linearity of 0.994. The output frequency versus concentration of fluorescent material shows a linearity of 0.98. The second kind is a readout circuit of pulse width resulting from the fluorescent photocurrent charging for a fixed voltage difference. The simulated relationship of pulse width versus photocurrent shows a linearity of 0.99. The third kind is a readout circuit of pulse width resulting from the fluorescent photocurrent charging for a fixed interval and then the discharging by a fixed current. The linearity of the simulated output characteristic is 0.993.