Plasma etch rates of porous silica low-k films with different dielectric constants

The reactive ion etch rates of porous silica films with different dielectric constants (k-values) or film densities were measured by varying wafer bias and gas ratio for Ar/C5F8/O-2 plasma. Both the etch rates-of porous silica films and the optical emission intensities from the etching products (SiF) increased with wafer bias power. Etch rate increased with decreasing k-value of porous silica, whereas SiF emission intensity was maintained constant regardless of k-value, indicating that the amount of etching products escaping from the porous silica surface to the gas phase remained unchanged. From this result it is concluded that mass etch rate, defined as the weight of a porous silica film etched from a unit area per unit time, is constant for Ar/C5F8/O-2 plasma.