ASSESSMENT OF POST-CMP CLEANING MECHANISMS USING STATISTICALLY-DESIGNED EXPERIMENTS

Post-CMP wafer cleaning commonly uses a combination of double-sided br ush scrubbing, megasonic cleaning, and spin-rinse drying to remove pol ishing residues from wafer surfaces. This paper investigates double-si ded brush scrubbing and spin-rinse drying by evaluating IPEC Planar's Avanti 9000 post-CMP cleaner for the removal of diluted slurry solutio ns from previously polished and cleaned UV sheet wafers. Diluted SC-1 (H2O/NH4OH/H2O2 = 20:1:1) and DI water were used as the cleaning solut ions in the brush and spin-rinse drying units, respectively. Results s how that the number of brush cycles, the brush pressure, and the brush rotating speed are key parameters in the removal of particles with di ameters greater than 0.21 mu m from the wafer. Two factor interactions between: (1) the number of brush cycles and the brush pressure, and ( 2) the number of brush cycles and the brush rotating speed are also im portant to the process performance. In addition, operating the spin-ri nse drying unit at the typical rotating speed (1000 rev./min) is not a dequate for submicron particle removal from the wafer. A theoretical a nalysis of the hydrodynamics of the brush cleaning suggests that parti cles are removed from wafers due to direct particle-brush contact, but that particle redeposition onto the wafers may occur. (C) 1998 Elsevi er Science S.A. All rights reserved.