Patent ID: 7829475

Claim:
A baking method of a quartz product, which is placed in a reaction vessel containing semiconductor substrates and providing a heat treatment thereto, and at least a portion of which is located in a heating atmosphere in the reaction vessel, the baking method comprising the steps of: placing the quartz product before being subjected to the heat treatment, in the reaction vessel; supplying baking gases, including a hydrogen chloride gas and an oxygen gas for enhancing reactivity of the hydrogen chloride gas, into the reaction vessel, while heating the reaction vessel, for removing copper as a contaminant incorporated during the manufacturing process of the quartz product, whereby the copper concentration in the region from a surface to a 30 μm depth of the quartz product can be controlled below 20 ppb; and then stopping the supply of the hydrogen chloride gas while continuing the supply only of the oxygen gas to prevent impurities from being formed on the quartz product.