Photoresist Stripping after Low-k Dielectric Layer Pattering Using Axial Magnetic Field Assisted Reactive Ion Etching

초록

Effects of axial magnetic field added to the conventional Reactive Ion Etcher(RIE) are studied in terms of plasma characteristics and it is applied to photoresist strip process of dual damascene Cu/low k multi-level interconnection technology. Photoresist remaining on low k dielectric layer should be removed by anisotropic plasma in order to keep vertical profile of low k layers. 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 strip rate is increased by more than 25 % from 1.0 ?m/min and its uniformity is also improved over 300 mm wafers. The effects of axial magnetic field in RIE are also investigated in terms of the selectivity of photoresist over SiOC-H dielectric films and the plasma damage of low k dielectric layers in O2/N2 plasma. The chemical structures of the low-k SiOC-H film are measured by FTIR spectrometer and the presence of the axial magnetic field is found to suppress any chemical changes of the films while providing wider process window.