Efficient pulsed laser removal of 0.2 μm sized particles from a solid surface

Abstract

Laser cleaning with pulsed ultraviolet and infrared lasers is successfully employed to remove particulate contamination from silicon wafer surfaces and from delicate lithography membrane masks. Particulate material investigated include latex, alumina, silicon, and gold. Gold particles as small as 0.2 μm can be effectively removed. This new and highly efficient laser cleaning is achieved by choosing a pulsed laser with short pulse duration (without causing substrate damage), and a wavelength that is strongly absorbed by the surface; the removal efficiency is further enhanced by depositing a liquid film of thickness on the order of micron on the surface just before the pulsed laser irradiation.

Near field induced defects and influence of the liquid layer thickness in Steam Laser Cleaning of silicon wafers

“…In the experiments with constant film FIGURE 1 Experimental setup for the SLC experiments. Two reflectometers and scattered light detection were used to control the condensation of the liquids on the sample 2 The upper diagram shows the scattered light and reflectometer signals during the condensation and subsequent evaporation of IPA, after the steam flow to the wafer had been turned off. The wafer surface was contaminated by polystyrene colloids with diameters of 1300 nm.…”

“…When this wave hits the particles, they experience an acceleration force away from the surface which can overcome the adhesion forces. Already some of the first publications on laser cleaning [2,3] have reported an enhancement of the particle removal efficiency in SLC compared to Dry Laser Cleaning (DLC), for which no ETM is used and the cleaning relies on thermal substrate expansion or local ablation [4,5]. The capabilities of SLC have been demonstrated in a variety of experiments [6][7][8][9][10].…”

Mécanismes d'éjection de particules par laser impulsionnel

“…Dans ce contexte, l'enlèvement de nanoparticules de la surface des wafers de silicium nécessite le développement de nouveaux procédés. Trois techniques basées sur l'utilisation de lasers impulsionnels ont été proposées pour relever ce défi : Le 'Dry Laser Cleaning' (DLC) [1,2] pour laquelle le faisceau irradie directement la surface, le 'Steam Laser Cleaning' (SLC) [3,4] qui nécessite le dépôt d'un film liquide très fin avant l'irradiation, et le 'Laser induced Shock wave Cleaning' (LSC) [5] qui utilise les ondes de chocs générées par un claquage laser de l'air juste au-dessus de la surface pour éjecter les particules. Les travaux présentés dans cet article concernent le premier de ces procédés qui présente l'avantage d'être sec, d'avoir des performances prometteuses et dont la mise en oeuvre industrielle est aisée.…”

Metallic droplets removal induced by pulsed laser: For tokamak application

“…This technique is already used in various fields: nuclear decontamination [4], microelectronics and optics [5]. Then, the laser cleaning has been largely studied and discussed.…”