Cleaning of Cu in The Cu Dual Damascene Process

摘要

Cleaning of Cu at the oxide surface is studied. This cleaning is specifically important in the Cu dual damascene process. Surface concentration decreases to 5X10~(11) and 8.0X10~(10) atoms/cm~2 by the dip cleaning in DHF and concentrated chemical, #1 (HNO_3: H_3PO_4 = 0.45 : 0.65), respectively. This concentration decreases down to 5.0 X10~9 atoms/cm~2 with employing chemical spin etching (CSE) technique. This concentration is much lower than that by other cleanings. At the oxide surface dipped in copper sulfate solution employing in Cu electroplating, Cu concentration decreases to 5.0 X10~9 atoms/cm~2 by CSE with #1. Etching rate of Cu layer deposited at the side-wall of wafer is measured in the CSE Cu etching. The rate toward the lateral direction increases linearly with the increase of rotation speed and reaches three times higher than that to the vertical direction of wafer surface side at rotation speeds above 1500 rpm.