CLEANING OF CHF3 PLASMA-ETCHED SIO2 SIN/CU VIA STRUCTURES WITH DILUTEHYDROFLUORIC-ACID SOLUTIONS/

After etching in a CHF3/Ar electron cyclotron resonance plasma, SiO2/S iN/Cu via structures for multilevel Cu interconnection were investigat ed with angle-resolved x-ray photoelectron spectroscopy. Photoelectron shadowing, determined by x-ray photoelectron spectroscopy takeoff ang le, and electrostatic charging were used to determine the chemical com position and amount of contamination on the dielectric horizontal surf aces and via sidewalls, as well as on the Cu at the bottoms of the via holes. All surfaces were covered with one to two monolayers of a CFx layer (CF > CF2 > CF3). The dielectric surfaces were also covered with a small amount (similar to 0.1 monolayers) of Cu, and the Cu at the b ottom of the via was contaminated with O (mainly CuO) and F. After cle aning with dilute KF solution, the dielectric surfaces were free of Cu and most of the F and C. CuO was also removed from the Cu surface by this treatment; however, Cu2O and CFx remained.