Characteristics of polycrystalline Si TFTs fabricated on glass substrates by excimer laser annealing with nickel-sputtered amorphous Si films

• Poly-Si TFTs were fabricated by ELA process using Ni-sputtered a-Si films.
• The content of Ni was a key parameter for the performance of poly-Si TFTs.
• Relationship between the characteristics of TFTs and grain was obtained.
• We present the Ni-content needed for the optimized performance of poly-Si TFT.

We have fabricated two kinds of thin film transistors (TFTs) on the glass substrates using polycrystalline silicon (poly-Si) thin films with small and large grain sizes processed by Excimer Laser Annealing (ELA) and carried out a comparative analysis. The grain size was controlled by nickel atom content in amorphous silicon (a-Si) thin films. With increasing grain size of poly-Si thin films, the carrier mobility increased from 40.8 to 54.4 cm2/V s and the absolute value of threshold voltage reduced from 2.1 to 1.5 V. The observed improvements in the electrical characteristics of poly-Si TFTs are attributed mainly to the reduction of defect density rendered by large grain size. These observations indicate that the sputtered nickel atom content in a-Si layer is a key parameter in determining the characteristics of ELA processed TFTs fabricated on the glass substrates.