COPPER CHEMICAL MECHANICAL PLANARIZATION PROCESSES WITH CARBON DIOXIDE

摘要

Copper promises superior electrical conductivity and better electromigration resistance than current aluminum or tungsten lines as the interconnect for semiconductor devices. The use of copper interconnects requires the development of new technologies such as chemical mechanical planarization (CMP). Current processes use water as the solvent for the CMP slurry leading to both technical and environmental difficulties. Consequently, we are developing a "dry" CMP process based on condensed CO_2 as an alternative to aqueous solvents. Here we report the oxidation and removal of Cu(0) in condensed CO_2 using a CO_2-soluble peroxide (t-butylperoxy isopropylcarbonate) and several β-diketone chelating agents. A comparison of the results using different β-diketones reveal that the percentage of Cu(0) removal increases in the order 2,2,6,6-tetramethyl-3,5-heptanedione (tmhd) < 1,1,1-trifluoroacetylacetonate (tfac) < 1,1,1,6,6,6-hexafluoroacetylacetone (hfac). Copper oxidation and complexation were monitored and characterized by UV-visible and infrared spectroscopies. The reaction mechanism was also investigated.