基於氮化鈦離子感測場效電晶體進行葡萄糖檢測之研究

Abstract

離子感測場效電晶體(ISFET)在化學以及生醫感測上扮演了重要的角色，尤其是CMOS製程技術的微縮與進步，使ISFET在兼容於CMOS製程能夠大量生產製造並且與邏輯電路整合成能發展為晶片實驗室(Lab-on-a-chip, LoC)上獲得巨大的關注。然而感測器的微縮將造成ISFET感測等效電容的縮小，使訊號衰減，以及CMOS製程中隨機引入的電荷造成臨界電壓的不匹配，成為CMOS ISFET的非理想效應。 本研究參考Teng等人之設計，將具有氮化鈦感測層的ISFET以新的設計與蝕刻後製程的方式取得，並探討其感測佔地面積大小對靈敏度以及非理想效應之影響情況，結果顯示利用蝕刻方式取得之TiN-ISFET具有約55.28 mV/pH之靈敏度，並改善CMOS ISFET的非理想效應，以氮化鈦的化學穩定與導電的特性，減少因為感測電容所造成的電訊號分壓，減少了訊號衰減，也因為沒有二氧化矽感測層，減少因介電層於製程中隨機引入的電荷造成臨界電壓隨機分布的影響。本研究也利用表面改質方式將葡萄糖氧化酶固定於晶片表面，結合TiN-ISFET之優點，透過不同濃度的葡萄糖溶液，在晶片上感測葡萄糖溶液之可量測範圍。

Ion sensing field-effect transistors (ISFETs) play an important role in chemistry and biomedical sensing, especially in the miniaturization and advancement of CMOS process technology, which enables ISFETs to be mass-produced and manufactured compatible with CMOS processes and integrated with logic circuits to develop into the sensor of Lab-on-a-chip. However, the miniaturization of the sensor will cause the ISFET to decrease the equivalent sensing capacitance and attenuate the signal. The randomly trapped charge in the CMOS process also causes the mismatch of the threshold voltage, which becomes the non-ideal effect of CMOS ISFET. Referring to the design of Teng et al., this study obtained the ISFET with a titanium nitride sensing layer through a new design and etching process. We not only explored the influence of the sensitivity with different sensing footprint areas but also the non-ideal effect of the CMOS ISFET. The results showed that the TiN-ISFETs had high sensitivity and improved the non-ideal effect of CMOS ISFET through the chemical stability and conductivity of titanium nitride. This study also functionalized the surface of the chip through the surface modification process and measured the linear range of glucose detection with different concentrations of glucose.