| 摘要 |
Disclosed is a dry etching gas which is formed of 1, 3, 3, 3-tetrafluoropropene with a purity of 99.5% by mass or more, with the total of concentrations of metal components, namely Fe, Ni, Cr, Al and Mo, included in the gas being 500 ppb by mass or less. It is preferable for this dry etching gas that the nitrogen content is 0.5% by volume or less and the water content is 0.05% by mass or less. Consequently, the etching selectivity of a silicon material to a mask is able to be improved in dry etching where a plasma gas that is obtained by changing the dry etching gas into a plasma is used. |
