| 摘要 |
A highly purified oxide semiconductor layer is formed in such a manner that a substance that firmly bonds during film formation to an impurity containing a hydrogen atom is introduced into a film formation chamber, the substance is reacted with the impurity containing a hydrogen atom remaining in the film formation chamber, and the substance is changed to a stable substance containing the hydrogen atom. The stable substance containing the hydrogen atom is exhausted without providing a metal atom of an oxide semiconductor layer with the hydrogen atom; therefore, a phenomenon in which a hydrogen atom or the like is taken into the oxide semiconductor layer can be prevented. As the substance that firmly bonds to the impurity containing a hydrogen atom, a substance containing a halogen element is preferable, for example.
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