Ultra-dry air plasma treatment for enhancing the dielectric properties of Al₂O₃-GPTMS-PMMA hybrid dielectric gate layers in a-IGZO TFT applications

Abstract

We assessed the effects of ultra dry-air plasma surface treatments on the properties of Al2O3-GPTMS-PMMA hybrid dielectric layers for applications to high-performance amorphous Indium Gallium Zinc Oxide (a-IGZO) thin film transistors (TFTs). The hybrid layers were deposited by an easy dip coating sol-gel process at low temperature and then treated with dry-air plasma at 1, 2 and 3 consecutive cycles. Their properties were analyzed as a function of the number of plasma cycles and contrasted with those of the untreated ones. The dielectric characteristics of the hybrid layers were determined from I–V and C–f measurements performed on metal–insulator–metal and metal–insulator–semiconductor devices. The results show that the plasma treatments increase the surface energy and wettability of the hybrid films. There is also a reduction of the OH groups and oxygen vacancies in the hybrid network improving the dielectric properties. The incorporation of nitrogen into the hybrid films surface is also observed. The plasma-treated hybrid dielectric layers were applied as dielectric gate in the fabrication of a-IGZO TFTs. The best electrical performance of the fabricated TFTs was achieved with the 3 cycles plasma-treated hybrid dielectric gate, showing high mobility, 29.3 cm2 V−1 s−1, low threshold voltage, 2.9 V, high I ON/OFF current ratio, 106, and low subthreshold swing of 0.42 V dec−1.

Electrical response of CdSe-based thin film transistors with different hybrid dielectric gates

“…The strong absorption band observed at 1100 cm −1 is related to Si-O-Al bonds that indicates a strong interaction between the inorganic and coupling the inorganic phase and residual solvents such as IPA, methyl ether branches and diols of the GPTMS molecules. The XPS analysis of both hybrid materials, reported in [46,48], is in good agreement with the chemical functional groups observed in the FTIR spectra and supports the formation of strong covalent bonds between inorganic and organic phases in the hybrid networks. Also, compared with the silica hybrid, the alumina hybrid layer has much more hydroxyl groups that generates the charge traps in the hybrid layer which impacts its dielectric properties.…”

“…In our previous works, we reported the development of Al 2 O 3 -GPTMS-PMMA and SiO 2 -PVP hybrid dielectrics and their successful implementation in TFTs as dielectric gate with inorganic semiconductor channels (ZnO, IGZO, CdS) [46][47][48]. The inorganic phases, Al 2 O 3 and SiO 2 have similar band gaps of 8.8-8.9 eV, respectively, but different dielectric constants, 6-9 and 3.9, respectively.…”

p-channel NiO thin film transistors grown with high k ZrO2 gate oxide for low voltage operation

“…To design a transparent and low voltage operated TFT, the high-k gate oxide materials are most necessary. So far numerous research groups have investigated high-k materials such as TiO 2 , HfO 2 , Ta 2 O 2 , Al 2 O 3 , Y 2 O 3 and ZrO 2 [14][15][16][17][18][19][20]. Among various high-k materials, ZrO 2 has attracted extensively due to its distinctive physical properties such as high dielectric constant (∼27), wide optical band gap, high melting point (∼2700 °C), and thermal stability to attain the favourable device fabrication.…”