Mobility enhancement limit of excimer-laser-crystallized polycrystalline silicon thin film transistors

Abstract

The effects of various carrier scattering mechanisms on excimer-laser-crystallized polycrystalline silicon (poly-Si) thin film transistors (TFTs) fabricated using 450 °C processes on a glass substrate were studied. Good performance of a separated by ion implanted oxygen (SIMOX) metal–oxide–semiconductor field-effect transistor (MOSFET) with field-effect mobility of 670 cm2/V s and a subthreshold swing value of 0.087 V/dec was obtained using these 450 °C processes. The results showed the formation of a good silicon/silicon dioxide (SiO2) interface that is comparable to that of thermal oxide, as well as the high capability of 450 °C processes. The performance of the above SIMOX-MOSFET is superior to that of excimer-laser-crystallized poly-Si TFTs fabricated using the same 450 °C processes. This shows that poorer performance of poly-Si TFTs is caused by the poor crystalline quality of the poly-Si film. The field-effect mobility is affected little by the in-grain microdefects and surface morphology of the excimer-laser-crystallized poly-Si film, but it is highly sensitive to the grain size. A field-effect mobility of 320 cm2/V s was obtained for an average grain size of 700 nm. The increase in field-effect mobility began to saturate with grain sizes of approximately 1000 nm. It is not necessary to enlarge the grain size beyond the saturation point of the field-effect mobility to improve performance, because the field-effect mobility of an average grain size of 700 nm is limited by phonon scattering, but not by the grain boundary.

Electronic transport in silicon nanocrystals and nanochains

“…In addition, any variation in the barrier heights and widths across the film can result in a network of current percolation paths across the film [65,66], along low resistance paths through GBs with low potential barriers. reported [68][69][70][71].…”

Lateral Crystallization Velocity in Explosive Crystallization of Amorphous Silicon Films Induced by Flash Lamp Annealing

“…[1][2][3][4][5][6][7][8] This non-thermal equilibrium sub-second annealing sometimes induces explosive crystallization (EC), high-speed lateral crystallization driven by the release of latent heat. [9][10][11][12][13][14][15] It has been know that the EC of a-Si occurs in liquid-phase and/or in solid-phase, which results in different EC velocity (v EC ).…”

Oriented Lateral Growth and Defects in Polycrystalline-Silicon Thin Films on Glass Substrates

“…Another feature of ELC is that μ FEn is considerably higher than that of SPC. The μ FEn value of an excimer-laser crystallized poly-Si TFT increases with increasing grain size and reaches 320 cm 2 /Vs at an average grain size of 700 nm, at which the dominant factor determining μ FEn varies from grain boundary scattering to lattice scattering (Hara et al, 2002a). Furthermore, a μ FEn value of 914 cm 2 /Vs was reportedly obtained by positioncontrolled large grain growth (Mitani et al, 2008).…”