Nanoparticle Detachment Using Shock Waves

Abstract

The fundamentals of nanoparticle detachment at the sub-100nm level using pulsed laser-induced plasma (LIP) shock waves are investigated in the current study. Two detachment mechanisms based on rolling resistance moment and rolling by resonant frequency excitation are identified as possible detachment mechanisms for nanoparticles. The gas molecule-nanoparticle interactions are studied using the direct simulation Monte Carlo method to gain knowledge about the nature of the detachment forces and moments acting on a nanoparticle in the LIP shock wave field. The discrete nature of the gas molecules colliding with the particle on the sub-100 nm length scale is linked to the stochastic transient moment experienced by the particle. Both experimental and computational findings of the current study indicate that nanoparticle detachment at the sub-100 nm level is possible by LIP shock waves.

Onset of Material Alterations Due to Laser-Induced Plasma Exposure in Nanofilms Deposited on Photomasks

“…LIP application is capable of selective area cleaning as well as entire masks and wafers. Shockwaves generated by LIP [11]- [18] have experimentally been demonstrated to be an effective, noncontact, and dry method for micro-and nanoparticle detachment (e.g., 10-40 nm and 60 nm polystyrene latex (PSL) [11], [12]). As with other cleaning techniques, damage is a concern in LIP sub-100-nm particle removal; therefore a safe window of LIP process parameters is determined in order to prevent onset of material alteration of Cr nanofilms on quartz substrates.…”

Transient Thermoelastic Response of Nanofilms Under Radiation Heating From Pulsed Laser-Induced Plasma

“…In recent years, the shock waves generated by LIP have been demonstrated for removal of sub-100-nm particles, i.e., 60-nm PSL particles and 10-40-nm PSL particles from silicon substrates [4], [5]. In LIP cleaning, a pulsed laser beam is focused and the plasma is formed at the focal point of the lens due to dielectric breakdown of air.…”

“…The potential causes for the possible damage below the threshold distance include shock wave temperature, pressure, and the plasma radiation-induced damage as well as the direct contact of the LIP core with the substrate. The transient pressures available from the LIP technique are on the order of kilo-Pascal levels [5], [6]. The pressure levels are typically too low to result in any mechanical substrate damage, as the strength of the substrate is often three orders of magnitude higher than the shock pressure.…”

“…The measurement of the substrate surface temperature and estimation of stresses induced when the substrate is subjected to nanosecond-scale excitation due the radiation heating of the plasma requires giga-hertz frequency range sensing. The peak pressure of the shock wave could be measured by the microsecond rise time shock transducers as reported in [5], as the shock wave expansion takes place in the time scale of microseconds. However, the measurement of the substrate surface temperature due to the radiation of plasma which is a nanosecond phenomenon requires substantially faster rise time sensors.…”

Laser-Induced Plasma Exposure on Extreme Ultraviolet Lithography Masks: Damage Analysis

“…As reported in [9]- [14] and [19]- [24], LIP created by focusing a high energy pulsed-laser beam to a point by dielectric breakdown of air at a clearance distance d above a substrate results in nanoparticle removal due to transient pressure loading from the generated shockwaves. Assuming no direct plasma contact with the substrate, LIP shockwaves and transient radiation heating from the plasma core are also possible sources of material alteration of the EUVL mask.…”