A Study of Metal on Metal Multiple Patterning Scheme

Self-Aligned Multiple Patterning is one of the multiple-patterning techniques to realize sub optical lithography technology nodes. The challenges for advanced interconnect levels with multiple-patterning integration are to control both metal CD and the space between line ends. This can be associated with complicated process integration. In this paper, a novel patterning scheme, metal on metal multiple patterning integration, which significantly simplified the process steps and enabled self-aligned block (SAB), is demonstrated for a single damascene level by process emulation. This novel integration utilizes metal as the mandrel. In addition to that, in this scheme the non-mandrel metal material could be different from the mandrel metal. As a result, mandrel metal could have different electrical or physical properties than the non-mandrel metal. As an example, the mandrel metal could have better reliability to carry large current while the non-mandrel could have lower resistivity for performance.