Plasma etching method

A plasma etching method of plasma etching a substrate including an underlying film containing silicon and carbon, an insulating film to be etched containing silicon and carbon, and a resist mask having a pattern, wherein the underlying film, the insulating film and the resist mask are sequentially deposited from below, to thereby form a number of holes in the insulating film including a dense region where a density of the holes is high and a sparse region where the density of the holes is low, by using a parallel plate plasma etching apparatus for applying a plasma-generating high frequency electric power to a space between an upper electrode and a lower electrode to render a process gas into a plasma state and a biasing high frequency electric power to the lower electrode, the plasma etching method comprising:

• mounting the substrate on a mounting table serving as the lower electrode in a processing chamber;
• supplying a first process gas containing carbon and fluorine into the processing chamber to form the holes in the insulating film to a depth close to the underlying film by plasma etching the substrate;
• and
• supplying a second process gas including an inert gas and another gas contain carbon and fluorine into the processing chamber to have the holes reach the underlying film by plasma etching the substrate while applying a negative DC voltage to the upper electrode to thereby suppress variation in the distribution of active species over the entire surface of the substrate and suppress variation in the depth of the holes between the dense region and the sparse region,
• wherein, in the dense region, a distance between peripheries of adjacent ones of the holes is 0.1 μm or less, and
• wherein, in the sparse region, a distance between peripheries of adjacent one of the holes is 10 μm or more.