Photoresist stripping after low- k dielectric layer patterning using axial magnetic field assisted reactive ion etching

Effects of axial magnetic field added to the conventional reactive ion etcher (RIE) are studied in terms of plasma characteristics and applied to anisotropic photoresist strip process. Photoresist strip process of dual damascene Cu interconnection technology requires little damage to the low- k dielectric layers after plasma exposure. The magnitude and direction of axial magnetic field can be controlled by the current to a pair of Helmholtz coils. Compared to the conventional RIE, it is found that etch rate is increased by 30% and its uniformity is improved for 300 mm wafers. Selectivity of photoresist over SiOC-H low- k dielectric film and the surface modification and damage of low- k dielectric layers by O 2 ∕ N 2 plasma are also investigated. The addition of the axial magnetic field to RIE can increase photoresist etch rate by increasing the plasma density and reduce damage to low- k dielectric layer by reducing the dc self bias.