Thin film transistors obtained by hot wire CVD

Abstract

Hydrogenated microcrystalline silicon films obtained at low temperature (150ºC-280ºC) by hot-wire chemical vapour deposition at two different process pressures were measured by Raman spectroscopy, X-ray diffraction spectroscopy and photothermal deflection spectroscopy.A high crystalline fraction (> 90%) with a low subgap optical absortion (10 cm -1 at 0.8 eV) were obtained in films deposited at high growth rates (>0.8 nm/s). These films were incorporated in nchannel thin film transistors and their electrical properties were measured. The saturation mobility found was 0.72  0.05 cm 2 /V·s and the threshold voltage around 0.2 eV. The dependence of their conductance activation energies on gate voltages were related to the properties of the material.

Electronic transport in low temperature nanocrystalline silicon thin-film transistors obtained by hot-wire CVD

“…The Hot-Wire Chemical Vapour Deposition (HWCVD) technique has shown its ability to obtain hydrogenated amorphous and nanocrystalline silicon thin-film transistors (TFT) at low substrate temperatures (<200 ºC) with acceptable field-effect mobilities and threshold voltages [1,2]. Besides, improved stabilities of these devices compared to their counterparts deposited by Plasma-Enhanced Chemical Vapour Deposition (PECVD) have been reported [3].…”

Doping of amorphous and microcrystalline silicon films deposited at low substrate temperatures by hot-wire chemical vapor deposition

“…The first low-temperature amorphous thin film transistors ͑TFTs͒ reported were deposited on glass at 150°C by Feng et al, 2 and at 125°C ͑with no n ϩ contacts͒ by McCormick et al 3 Recently, the first TFTs on plastic were fabricated, at 125°C on polycarbonate by Gates,4 at 150°C on polyimide by Glaskova et al, 5 and at 110°C on polyethylene terephthalate by C.-S. Yang et al 6 The layers for the devices produced at 125°C were deposited by rf reactive magnetron sputtering while those produced at 150°C and 110°C used rf plasma-enhanced chemical vapor deposition ͑rf-PECVD͒. [8][9][10][11] It is the high efficiency of the hot tungsten filament in breaking the molecules of the reactant gases, together with a high atomic hydrogen supply to the growing film, that is thought to allow the deposition of good quality amorphous and microcrystalline silicon films at a high growth rate by HW. For industrial applications, a high growth rate is attractive from a cost perspective because it decreases the process time and may increase the utilization efficiency of the process gases.…”

A study on low temperature transport properties of independent double-gated poly-Si nanowire transistors

“…Therefore, thermionic emission over these energy barriers is usually considered as the major conduction mechanism when dealing with poly-Si, and our recent simulation results have shown that thermionic conduction indeed describes the transfer and output characteristics of the proposed device well at room T [14]. This kind of thermally activated process also manifests itself in a way that the mobility and V TH decrease and increase, respectively, as T is reduced [15,16]. Transfer curves in the SG-1 mode, shown in figure 4(a), are clearly consistent with the above statements.…”