Adhesion force change on multilayer EUVL mask due to laser induced plasma shock wave

Change in adhesion force between a borosilicate glass microsphere and 40 Al 2O 3/TaN/Ru/MoSi pairs on a silicon wafer used as a multilayer extreme ultraviolet lithography mask stack were characterized by force–distance spectroscopy after cleaning Al 2O 3 layers using a laser induced plasma (LIP) shock wave. The adhesion force of the Al 2O 3 surface decreased at a higher laser energy and a lower gap distance above a threshold gap distance without changes in surface roughness. Frictional electrostatic repulsion, triboelectricity, was identified as the cause of lower adhesion forces on Al 2O 3 surface due to the high velocity and pressure of the LIP shock waves. The adhesion force decreased by increasing the number of exposures of LIP shock waves to the substrate.