Liquid-assisted pulsed laser cleaning using near-infrared and ultraviolet radiation

Abstract

Nanosecond pulsed laser irradiation is shown to be effective for cleaning contaminant particles as small as 0.3 μm in diameter from NiP magnetic hard disk substrates. A micron-thick liquid film is deposited on the disk surface just before the laser irradiation. The cleaning threshold and efficiency are investigated for the fundamental and frequency-tripled Nd:YAG laser harmonics (wavelengths λ=1064 and 355 nm). The rapid phase-change and thin liquid film ablation processes are examined in order to elucidate the cleaning mechanism. Optical reflectance and photoacoustic beam deflection probes are employed for monitoring the vaporization threshold and the acoustic transients generated. The plume evolution and acoustic wave propagation into the ambient air are visualized by laser flash photography. A jet composed of vapor and liquid columns/droplets is expelled from the laser-irradiated area. The pressure enhancement accompanying the explosive-vaporization process and the momentum supplied by the ablation plume are the main sources of the augmented cleaning efficiency at moderate laser energy densities.

Removal of micrometer size particles from surfaces using laser-induced thermocapillary flow: Experimental results

“…Thus, the thermal properties of substrates and their thicknesses affect the cleaning efficiency of the proposed method. Nevertheless, it has to be noted that the laser-induced thermocapillary method enables the removal of micron-size particles at very low temperatures in contrast to the traditional laser-pulsed cleaning methods [8,10] and cannot cause any destruction of the surfaces. …”

“…[2-10], the laser-based cleaning techniques [4][5][6][7][8][9][10][11] have shown advantages for a number of applications owing to a flexibility, a contactless, a high precision and an ability to remove submicron-sized particles. The laser-cleaning methods, which rely on the pulsed laser heating of surfaces or particles, can be divided into two types: dry laser cleaning [4][5][6][7] and liquids assisted laser cleaning [4,[8][9][10][11].…”

“…The laser-cleaning methods, which rely on the pulsed laser heating of surfaces or particles, can be divided into two types: dry laser cleaning [4][5][6][7] and liquids assisted laser cleaning [4,[8][9][10][11]. In the case of dry laser cleaning particles are removed from the surfaces by rapid thermal expansion of solid substrates and/or particles that caused by the laser heating.…”

A high-sensitivity in situ optical diagnostic technique for laser cleaning of transparent substrates

“…Laser cleaning [1][2][3][4][5][6][7][8][9][10] appears as one of the most promising techniques for the removal of sub-micron-sized particles from surfaces. The strong adhesion of these contaminants to the surface makes conventional processes inefficient, this problem being of major importance, among others, in the field of microelectronics.…”

“…The strong adhesion of these contaminants to the surface makes conventional processes inefficient, this problem being of major importance, among others, in the field of microelectronics. Two different procedures for laser cleaning have been described in the literature: dry laser cleaning (DLC) [1][2][3][4][5] and steam laser cleaning (SLC) [1,[6][7][8][9][10]. DLC is based on the interaction between the incident laser light and the substrate to be cleaned.…”