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Fabrication and Characterization of Silicon Nanowire FET and Application to Biosensor

  • 권순묵 (대학원 전기전자전파공학과 전자전기컴퓨터공학전공)

초록/요약

In this thesis, silicon nanowire (SiNW) field-effect transistor (FET) biosensor was fabricated from conventional silicon-on-insulator (SOI) wafer by complementary metal-oxide semiconductor (CMOS) compatible silicon manufacturing technology such as photolithography, thermal oxidation, electron-beam evaporation, chemical vapor deposition (CVD) and reactive ion etching (RIE). SiNWs were patterned and etched by using I-line (365 nm) stepper and oxygen plasma for trimming of photoresist (PR). Electrical characteristics of SiNWs were observed by measuring the current-voltage characteristics. Resistance of SiNWs decreased with increasing the width of SiNWs. Fabricated SiNWs were operating as p-type FET device. For the label-free and real time detection of C-reactive protein (CRP) and, prostate-specific antigen (PSA) surface of SiNWs were modified to immobilize the antibody of C-reactive protein (anti-CRP) and the antibody of PSA (anti-PSA). Surface modification procedures were achieved by using polydimethylsiloxane (PDMS) microfluidic channel. After the immobilization of antibody, ethanolamine was reacted on the SiNWs surface to prevent non-specific binding. Real-time measuring system reveals the change in conductivity in SiNW on specific binding of antigen (CRP, PSA) and antibody (anti-CRP, anti-PSA). Sensing signals of CRP and PSA were revealed increasing of conductance due to isoelectric point (pI) of the proteins were lower than pH value of phosphate buffer saline (PBS). The conductance change ratio was related to the concentration of antigen. 10, 1 and 0.1 g/ml concentration of CRP injected through microfluidic channel the conductance was changed 39, 25 and 16 %, respectively. And I conducted with the proteins of 500 pg/ml PSA in PBS solutions × 1, × 0.1, and × 0.01. As a result, the conductivity is increased and the sensitivity of biosensor is fairly improved from 6.3 % (1 × PBS), 17.9 % (0.1 × PBS), to 30.7 % (0.01 × PBS) because the debye screening length will be increased by decreasing the buffer ionic strength in the diluted solution. The relation between conductance differential ratio and the PSA concentration shows linearity in the range of 50-500 pg/ml but 1 ng/ml of CRP was not detected where the anti-PSA immobilized SiNW. The test result shows the possibility of the SiNW biosensor, and it provides solutions for mass production as well as the integration with prefabricated Si-based devices.

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목차

1. Introduction • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 1

2. Theoretical Background • • • • • • • • • • • • • • • • • • • • • • • • • • • • 8
2.1 SiNW FET Biosensor • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 8
2.2 Influence of Debye Screening Length • • • • • • • • • • • • • • • • • • • 12
2.3 Sensitivity of SiNW FET Biosensor • • • • • • • • • • • • • • • • • • • • 14

3. Experimental Details • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
17
3.1 Layout Design • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 17
3.2 Fabrication of SiNWs • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3030 21
3.3 Fabrication of Devices • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 3030 25
3.4 Functionalization of SiNWs • • • • • • • • • • • • • • • • • • • • • • • • • • 30

4. Results and Discussion • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 35
4.1 Electrical Characteristics of Devices • • • • • • • • • • • • • • • • • • • • • 35
4.2 Sensing of Proteins • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 38

5. Conclusion • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 47

Reference • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 49

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