Using Molecular Modeling to Understand Cleaner Efficiency for Barc ("Bottom Anti-Reflective Coating") After Plasma Etch in Dual Damascene Structures

The invention of inorganic bottom anti-reflective coatings (BARCs) was a promising enabling technology for lithography due to their near unity plasma etch selectivities with the low-k dielectric materials used in advanced via first trench last (VFTL) dual damascene structures. Having these selectivities during plasma etch allowed for the avoidance of via "fence" defects that are often created by the shadowing of the dielectric surrounding the vias by the slower etching organic BARC via fill. The presence of "fence" defects creates an area of high stress in the copper line due to the tight space between the fence and side of the trench that has to be filled, and can cause failure of the device due to shorting of the line from voids caused by copper migration away from the high stress area. In order to achieve a 1:1 selectivity in plasma etch which avoids fence formation, organosiloxane polymers are typically employed in the inorganic BARC materials. However, modification of the organosiloxane film during plasma etching and ashing densifies the material and may also remove organic content from the film, making removal more difficult with traditional cleaning technologies. This work describes the surface energy and reactivity modeling of the Honeywell cleaner technology that has demonstrated an inorganic BARC removal solution with significantly higher removal rates and etch selectivities compared to currently available products. We will show how molecular modeling influenced the development of the cleaner formulation and the impact on experiments.