Method for cleaning reaction chamber using pre-cleaning process

A method for cleaning a reaction chamber after depositing an oxide or nitride film on a substrate in a reaction chamber having interior surfaces on which oxide or nitride is accumulated as a result of the deposition, said oxide or nitride being selected from the group consisting of carbon-containing metal oxide or carbon-containing metal nitride, said method comprising the steps of:

• oxidizing or nitriding the carbon-containing metal oxide or the carbon-containing metal nitride accumulated on the interior surfaces of the reaction chamber, by an RF-excited plasma of an oxygen- or nitrogen-containing gas in an absence of halide gas as a pre-cleaning step, to dissociate carbons from the carbon-containing metal oxide or the carbon-containing metal nitride;
• and
• cleaning the interior surfaces of the reaction chamber, by an RF-excited plasma of a halide cleaning gas which is a fluorine-containing gas to form metal fluoride from the carbon-dissociated metal oxide or the carbon-containing metal nitride, then removing the metal fluoride.