| 摘要 |
PURPOSE:To improve the uniformity of heat treatment between wafers when a plurality of semiconductor wafers are collectively subgested to heat treatment, e.g, oxidation treatment in a vertical type reaction pipe. CONSTITUTION:A plurality of wafers W are put on a wafer boat 6 and loaded in a reaction pipe 2. The inside of the reaction pipe 2 is purged by using Ar gas. Oxidation treatment is performed by making O2 gas flow from above to below after the temperature inside the reaction pipe 2 becomes equal to a specified value. After that, N2 gas is made to flow from above to below, and an N2 gas atmosphere is set. Since the gases are sequentially supplied in the order of large specific weight as Ar gas O2 gas N2 gas, the O2 concentration change pattern from O2 concentration rise to fall in the upper part coincides with the shape of O2 concentration change pattern in the lower part. Hence the uniformity of the oxide film thickness between the upper part and the lower part is improved. The same effect can be obtained by supplying the gases in the order of small specific weight as N2 gas O2 gas Ar gas. |
