Active matrix circuit board and method of manufacturing it

摘要

In forming a thin film transistor (620) whose OFF-current characteristics are improved, the source and drain regions (602 and 603) of low impurity concentration are formed. In this process, all the ions (indicated by arrow Ion-1) of around 80 keV energy produced from a mixed gas (doping gas) containing 5% PH3 and the rest of H2 gas, are implanted into a polycrystalline silicon film (604) so that the concentration of impurities in a range of 3 x 10<1><3>/cm<2> to 1 x 10<1><4>/cm<2> in terms of P<+> ions. Then all the ions (indicated by arrow Ion-2) of about 20 keV energy produced from a doping gas of pure hydrogen are implanted into a low concentration region (604a) so that the concentration of impurities is in a range of 1 x 10<1><4>/cm<2> to 1 x 10<1><5>/cm<2> in terms of H<+> ions. After that, the impurities are activated by thermally treating the low concentration region (604a) in a nitrogen atmosphere at a temperature of approximately 300 DEG C for approximately one hour.