Etch Damage Reduction of Ultra Low-k Dielectric by Using Pulsed Plasmas

To reduce interconnect resistance and capacitance (RC) time delay of semiconductor integrated circuit, the dielectric material with more porosity is used in recent interconnection for lower dielectric constant. However, it is difficult to use highly porous low-k dielectric materials at the narrow pitch because it is easily damaged during the plasma etching processes. In this study, as one of the plasma induced damage reduction methods in the etching of porous low-k dielectric using C4F8-based gases, RF pulsed plasma methods have been investigated by using a dual frequency capacitively coupled plasma etch system. RF pulsed plasmas generated higher carbon-rich radicals in the plasma and less charging effect on the dielectric material surface compared to continuous wave plasmas and, therefore, showed a reduced damaged layer compared to the conventional continuous wave plasma etching. Porous SiCOH dielectric with a patterned TiN hard mask was etched using the RF pulsed plasmas and the results showed more anisotropic etching profiles with less sidewall damages. Therefore, it is believed that the RF pulsed plasma etching process of ultra low-k dielectric materials can improve the RC delay related with plasma damage for the next interconnect technology.