Reduction of off-current in self-aligned double-gate TFT with mask-free symmetric LDD

In this work, the lateral electric field distribution in the channel of a double-gate TFT is studied and compared with that of a conventional single-gate TFT. The double-gate TFT is predicted to suffer from a more severe anomalous off-current than the single-gate TFT. A smart double-gate TFT technology is proposed to decrease the off-current. The unique feature of the technology is the lithography independent formation of the self-aligned double-gate and the symmetric lightly doped drain (LDD) structures. With the LDD applied, the anomalous off-current of the fabricated double-gate TFT is reduced by three orders of magnitude from the range of 10^-9 A/μm to 10^-12 A/μm. The on/off current ratio is increased by three orders of magnitude accordingly from around 10⁴ to 10⁷.