US Patent 9859102 Method of etching porous film

A method of etching a porous film is provided. The method includes supplying a first gas into a processing chamber of a plasma processing apparatus in which an object to be processed including a porous film is accommodated, and generating a plasma of a second gas for etching the porous film in the processing chamber. The first gas is a processing gas having a saturated vapor pressure of less than or equal to 133.3 Pa at a temperature of a stage on which the object is mounted in the processing chamber, or includes the processing gas. In the step of supplying the first gas, no plasma is generated, and a partial pressure of the processing gas which is supplied into the processing chamber is set to be greater than or equal to 20% of the saturated vapor pressure.