The Interaction Study Of Laser-Induced Plasma Shock Wave And Adhered Particles On Surface

Laser-induced plasma shock wave cleaning technology is an advancing cleaning method for the removal of adhered particles on surface, which riches the dry cleaning method and provides a new way for wafers and masks cleaning in semiconductor industry fabrication depending on its potential advantages such as high accurate position, repeatability, comprehensive applicability. This paper studies the related fields both in theory and experiment such as: laser-induced plasma shock propagation characteristics in gas medium, particle removal mechanism, experiments on micron particle removal, and safety working gap of wafer, which is a systemic and profound research. The innovation achievements are listed as following:Present a new "zig-zag" multiple beam deflection method to study the laser-induced plasma shock waves propagation in the middle and near filed both in standard atmosphere and sub-atmosphere. Based on the experimental equipment, the propagation characteristics of the same laser-induced plasma Shockwave are obtained in one experiment, which provides the objective proof for the particle removal calculation and the research of optimal pressure of laser-induced plasma shock wave cleaning.Based on the JKR model of adhered particles, rolling removal model, setting out from the view angle of shockwave-particle interaction, is modified, which shows the removal range of the particles on wafer. Moreover, a new saltation removal model of particle is established due to the failed explain of rolling mechanism on the particle removal in groove, which gives a reasonable explain for particles removal on wafer and shows the minimum shockwave strength threshold of particle saltation model.Laser-induced plasma shock wave cleaning method is utilized to remove the 10μm and 20μm particles, in which the Shockwave threshold in particle cleaning corresponds to the saltation model. Moreover, the influences of working gap variation, energy variation, and particle diameter variation are also studied.As for the macroscoy and microscopy damage to wafer in cleaning process, varying working gap and probe detection methods are utilized respectively. The macroscopy safety working gap should be larger than 0.50mm with laser energy of 240mJ and the variation rule of flying distance of ejecting charged particles of plasma is also studied.The results of this paper can be a valuable reference to the further development of laser-induced plasma Shockwave cleaning.