Solutions to pattern transfer issues in fabrication of copper dual damascene interconnects

Abstract

The science of photolithography has been investigated in this thesis with particular emphasis on copper dual damascene technology. The different challenges of sub-wavelength patterning were analyzed with respect to arial image characteristics and patterning under different illumination settings. Resolution enhancement technique such as the use of an attenuated phase shift mask was investigated. The disadvantages of using attenuated phase shift masks, such as formation of side lobes and the reasons for formation of such patterns were studied. A new technique was identified to help avoid the formation of side lobes. The challenges of dual damascene pattern transfer were investigated next. A new dual barc technique was found to minimise the formation of fences and facets with low dielectric constant materials. This technique also reduced the variation in critical dimension in case of dual damacene patterning. Lastly, overlay evaluation of different levels of patterning with new target designs have been completed.