| 摘要 |
PROBLEM TO BE SOLVED: To carry out the control of threshold voltage, which has been difficult, by implanting impurities into a channel region in a TFT, activating the impurities and controlling the threshold of the TFT by the activation rate of the impurities. SOLUTION: The surface of an insulating substrate 1 is cleaned, silicon dioxide is deposited in approximately 300nm thickness by using a chemical vapor growth method and a sputtering method as a base coating film 2, and an amorphous silicon film 3 is deposited in approximately 50nm thickness. When the whole surface of the substrate is irradiated with laser beams while being scanned by a laser annealing method, the melting crystallization of the amorphous silicon film 3 is generated, and a polycrystalline silicon film 4 is formed by crystal growth, and worked in a desired shape by photolithography and etching. Accordingly, when boron ions of approximately 1×10<13> /cm<2> are implanted to the section of the silicon film 4 at acceleration voltage of 10kV and the energy density of laser beams is adjusted so that only 10-30% of ions are activated, the threshold voltage of a TFT can be controlled at a desired value of 2.8V or less.
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