The presence of oxide fencing around vias can significantly jeopardize the integrity and reliability of the device performance. Missing metal and void formation during metal fill are examples of the problems resulting from oxide fencing Moreover, Line Edge Roughness (LER) and Microtrenching reduction in dual damascene structures for 45 node technology is critical for a reliable device performance. Hence oxide fencing, LER, and microtrenching need to be minimized if not eliminated while satisfying several other strict processing constraints. The choice of chemistry and the right reaction conditions for the reactive ion etching process is critical for the elimination of oxide fencing, LER and mincrotrenching.

In this work, different chemistries with different compositions of polymerizing components were investigated to determine their effect on fence formation around vias, line edge roughness, and microtrenching for the 45 nm node feature. Optimal polymerizing agent content in the process is vital for the process to achieve the desired critical dimensions; however, polymer presence can still lead to fence formation and contribute to line edge roughness. To balance the non-desirable effects resulting from the presence of the needed polymer contents in the process, other gases such as oxygen can be used.

The effect of the chemistry on the selectivity of the oxide to BARC was further investigated. The amount of BARC remaining after trench etch can be critical for the process. It can contribute to fence formation if too much BARC is left or can contribute to punch through which may result in copper sputtering if not enough BARC is left

On the other hand, the effect of the ion flux and ion bombardment was studied. Other parameters such as reaction chamber pressure and ratio of reactive gases split between the center and the edge of the wafer were studied. An etch process that eliminated fence formation and minimized line edge roughness and microtrenching for 45 nm node features was successfully developed.