Fabrication of Thin Film Transistor Using Ferroelectrics

  • Hur, Chang-Wu (Mokwon University) ;
  • Kim, Jung-Tae (Mokwon University)
  • Published : 2004.06.01

Abstract

The a-Si:H TFT using ferroelectric of $SrTiO_3$ as a gate insulator is fabricated on glass. Dielectric characteristics of ferroelectric are superior to $SiO_2$ and $Si_{3}N_{4}$. Ferroelectric increases on-current, decreases threshold voltage of TFT and also improves breakdown characteristics. The a-SiN:H has optical band gap of 2.61 eV, retractive index of 1.8∼2.0 and resistivity of $10^{13}$~$10^{15}$ $\Omega$cm, respectively. Insulating characteristics of ferroelectrics are excellent because dielectric constant of ferroelectric is about 60∼100 and breakdown strength is over 1MV/cm. TFT using ferroelectric has channel length of 8∼20 $\mu\textrm{m}$ and channel width of 80∼200 $\mu\textrm{m}$. And it shows that drain current is 3.4$\mu\textrm{A}$ at 20 gate voltage, $I_{on}$/$I_{off}$ is a ratio of $10^5$~$10^8$ and $V_{th}$ is 4∼5 volts, respectively. In the case of TFT without ferroelectric, it indicates that the drain current is 1.5 $\mu\textrm{A}$ at 20 gate voltage and $V_{th}$ is 5∼6 volts. With the improvement of the ferroelectric thin film properties, the performance of TFT using this ferroelectric has advanced as a gate insulator fabrication technology is realized.

Keywords

TFT;Febrroelectrics

References

  1. Michael Hack and John G. Shaw, 'A new model for amorphorous silicon TFT', j. AppJ. Phys., pp.3371-3380, Oct., 1989
  2. S. Demichelis, 'Thickness dependence of optical and electrical properties of thin a-Si:H films', Electrolava SPA Ita., pp.1-5, 1987
  3. Michael Hack, 'Physical models for amorphoussilicon TFT and their implementation in a circuit simulation program', IEEE ED., pp. 2764-2769, Dec, 1989
  4. M. J. Thompson, S. Tomiyama, 'Page width a-Si image Scanner Technology', SID digest, pp.259, 1989
  5. M. Hoseisel, etcs, 'Physical aspects of a-Si:H image Sensor', Non-crystal., Sol., pp.2430, 1987