Low resistance ohmic contacts to amorphous IGZO thin films by hydrogen plasma treatment

We report on the results of low resistance ohmic contacts to amorphous IGZO films treated with hydrogen plasma. Amorphous IGZO films with a thickness of 200nm were deposited on glass substrates by radio frequency magnetron sputtering and exposed to inductively coupled hydrogen plasma. Using Ti, the specific contact resistivity of the ohmic contact was decreased considerably from 7.06×102 to 9.94×10−5Ωcm2 by a hydrogen plasma treatment without the need for a thermal treatment. The improved specific contact resistivity of ohmic contact was attributed to an increase in carrier concentration on the amorphous IGZO surface, due to the formation of high density of oxygen vacancies and OH bonds. Although the transmittance of the hydrogen plasma treated sample was decreased drastically by the formation of In clusters, the improved transmittance result without deteriorating the electrical properties was obtained effectively by removing the In clusters using a HCl solution.