Nanoparticle removal from trenches and pinholes with pulsed-laser induced plasma and shock waves

Abstract

Removing nanometer scale particles from patterned substrates is a critical, yet challenging, technical task with numerous applications. Due to environmental concerns, there is a drive to reduce chemical usage and waste in semiconductor and other nano-technology industries. The laser plasma method is a novel removal method for nanoparticles. For the work reported in this study, the method is applied to substrates with features, i.e. trenches and pinholes. The technique, which is dry and non-contact, takes advantage of shock wavefronts initiated by plasma formation under a focused laser beam pulse and their interaction with the substrate. In the reported experiments, a Q-switched Nd : YAG pulsed laser is employed as a plasma and shockwave generation source. Various mechanisms are responsible for the removal effect. The strong shock wave in air generates complex pressure wave elds resulting in both drag and lift on the particle and acceleration of the substrate. However, shock waves are not transmitted into the solid substrate as discontinuous shock fronts due to a large difference between the relevant wave phase speeds in the two media. Also, damage concerns due to cavitation, which is a common effect in megasonic cleaning, are avoided. However, damage due to the high temperatures associated with the plasma formation is found to be an issue. Patterned silicon wafers and micrometer level pinholes were used for the particle removal experiments. The effects of the distance between the surface and the plasma boundary on the removal ef ciency are reported. With this method, we were able to remove particles from the wall of a micrometer level pinhole and patterned silicon wafers.

Engineered Nanoparticle Adhesion and Removal from Tomato Surfaces

“…Removal of NPs from contaminated surfaces remains a challenge. The physicochemical properties of NPs make their removal from silicon and organic surfaces difficalt. , Current removal methods include plasma etching, liquid etching, gas cleaning, brush cleaning, laser shock cleaning, nanobubbles, and megasonics cleaning, which have been applied in the semiconductor industry − and provide an indication of the type and severity of physical treatments that may be needed to reduce food contamination. Nanoparticle removal from any surface would depend upon particle size, surface charge, repulsive force, van der Waals force, adhesion force, surface chemical and physical properties, removal method, velocity of removing agent, and cleaning time.…”

The Influence of Humidity on the Mechanisms Involved in Laser-Induced Particle Ejection Experiments

“…In this context, several laser-based cleaning methods are considered as potential approaches [1][2][3]. Among them, the dry laser cleaning (DLC) technique leads to the ejection of the particles from the surfaces by direct illumination with nanosecond laser pulses.…”

Removal of in vessel Tokamak dust by laser techniques

“…This leads to a fast heating of a small volume and a generation of a shock wave starting from this place. Such technique is used in microelectronic [13] to remove particles from flat surfaces.…”