DNA detection by suspended gate polysilicon thin film transisitor

An electronic device, namely suspended gate thin film transistor (SGTFT), for rapid and direct detection of specific DNA sequences with high sensitivity is presented. It is an usual P-type polysilicon TFT where the gate contact is a Si₃N₄/polysilicon/Si ₃N₄ bridge suspended at 0.5 mum above the SiO ₂/Si₃N₄ gate insulator. The high field effect due to the low height of the gap induces high sensitivity of the characteristics to any charge variation in the space between the gate and the channel. Amino-substituted ODN is grafted on silicon nitride surface after glutaraldehyde activation. The presence of this grafted ODN is confirmed by the positive shift, meaning the presence of negative charge, of the SGTFT transfer characteristics. The characteristics do not shift with non complementary DNA target. On the contrary, hybridization with complementary DNA is evidenced by the positive shift as large as 0.35 V with 5nM DNA concentration and an effective volume of 7 times 10^-10 milliliter