Post cmp clean brush with torque monitor

Abstract

An apparatus for and method of detecting the presence of a brush used in a semiconductor wafer cleaner for post-CMP processing is described. Semiconductor wafers are loaded into the wet environment of the wafer cleaner, affixed to a rotatable fixture and rotated at high speed. The rotatable fixture is effectuated by a servo motor linked to a servo controller and a torque monitor. A first torque on the rotating wafer is calculated prior to the start of the brush cleaning cycle. During the brush cleaning cycle, as the brush within the brush cleaner contacts the rotating wafer, the torque on the wafer increases and a second torque is calculated. If, during the brush cleaning cycle, the second torque calculation is substantially equal to the first torque calculation, the brush cleaner is not contacting the wafer and cleaning has not progressed. A tool user can be notified to reaffix the brush within the cleaner. When the second torque calculation is greater than expected, the tool user can be notified that the brush downforce has been improperly set. Inadequate removal of CMP residue is detected before entire wafer lots have passed through an ineffective brush cleaning cycle prior to an inspection point.