Removal of TaN/Ta Barrier with Variable Selectivity to Copper and TEOS

Abstract

Highly selective 2 nd step copper slurries developed by Rodel have efficient barrier (TaN) polishing rates at extremely low down force (1000 Å/min at one psi, and 2000 Å/min at 3 psi). Removal rates of dielectrics (TEOS or low k CDO) can be independently adjusted from zero to nearly any designed value and copper removal rates can be independently controlled from 20 to 500 Å /min, while maintaining the high barrier removal rates. In addition, zero loss of low-k dielectric capping layers has been demonstrated, and zero loss of high metal density (90%) domain of pattern wafers with 30 seconds overpolishing has been demonstrated. Experiments also show that the high selectivity is a true CMP effect and not due to static etching. IntroductionCopper (Cu) chemical mechanical polishing (CMP) employs a two-step polishing process. A first step Cu slurry is used to remove both the bulk copper film layer and any remaining Cu residue on a wafer. The second step CMP process employs slurry that is used for removal of the barrier film, such as tantalum (Ta) or tantalum nitride (TaN). Both slurries are designed to minimize dishing and erosion.

Role of Ammonium Ions in Colloidal Silica Slurries for Ru CMP

“…H. Cui et al 12 − would cause severe pitting corrosion problem and remarkable difference in the corrosion potentials of Cu/Ru interface. 13 On the contrary, H 2 O 2 -based slurries could generate smooth and dense Ru surface as well as negligible difference in the corrosion potentials of Cu/Ru interface, 11,14 and hence H 2 O 2 was chosen as the oxidant in this paper to avoid the above problems.…”

Controlling the Removal Rate Selectivity of Ruthenium to Copper during CMP by Using Guanidine Carbonate and 1, 2, 4-Triazole

“…10 As is known to all, Cu chemical mechanical polishing (CMP) requires a high removal rate selectivity for liner metals to Cu to minimize dishing and erosion. 6,11 However, when ruthenium was considered to be used as barrier metal, it was difficult to remove compared with copper due to its inertness to most chemicals and high hardness (6.5 Mohs hardness for bulk ruthenium). Therefore, achieving tunable removal rate selectivity of Ru to Cu are difficult but crucial for the planarization.…”