High-performance polysilicon thin film transistors on steel substrates

We fabricated thin film transistors in polycrystalline silicon on steel sub strates. The polycrystalline silicon films were made by thermally annealing hydrogenated amorphous silicon precursor films, which had been deposited o n stainless steel coated with similar to 0.5 mu m thick 810 degrees C-annea led SiO2. We employed annealing temperatures ranging from 600 degrees C, wh ich is the furnace annealing temperature limit for conventional glass subst rates, to 750 degrees C. Films were crystallized at 650 degrees C in 1 h wi th 1-h hydrogen plasma seeding, at 700 degrees C in 10 min either with or w ithout hydrogen plasma seeding, and at 750 degrees C in 2 min. The best top -gate transistors were made from films crystallized at 650 degrees C and ha d an average electron field-effect mobility of 64 cm(2)/V s in both the lin ear and saturated regimes. Thus steel substrates permit a substantial reduc tion in crystallization time over conventional glass substrates, and produc e polycrystalline silicon with an electron mobility greater than other subs trates. (C) 2000 Elsevier Science B.V. All rights reserved.