Fundamental study of the removal mechanisms of nano-sized particles using brush scrubber cleaning

Abstract

To ensure high device yields, wafer surface contamination and defects must be monitored and controlled during the entire process of semiconductor manufacturing. Particle surface concentrations on the wafers, mostly related to chemical mechanical polishing ͑CMP͒ processes, must be kept at the lowest possible levels. Brush scrubber cleaning has the potential to achieve this goal. However, the particle removal mechanisms are still under discussion especially the removal of nano-sized particles. This paper investigates the interactions between the particle, the brush and the wafer surface and explores the potential and limitations of the brush scrubbing technique. Furthermore the effect of the various brush/wafer parameters on the particle removal efficiency ͑PRE͒ is studied. From a mechanistic viewpoint it is shown that brush scrubbing acts in a mixed lubrication regime. From an extensive analysis of the relevant forces and moments it can be concluded that in the hydrodynamic lubrication regime, particles are removed by rolling under the dominant hydrodynamic drag force. In the boundary lubrication regime, particles can be removed by both rolling and lifting, mainly by the brush/particle van der Waals forces. The pH and the ionic strength of the cleaning fluid can influence the PRE. The chemical composition determines the electrostatic interactions of the particle once it is "kicked off " from the wafer surface: either the surface of the particles and the wafer carry the same charge and the particles remain in solution or the surface of the particles and the wafer has an opposite charge resulting in redeposition.

Pressure amplification of laser induced plasma shockwaves with shock tubes for nanoparticle removal

“…Thus, for removing smaller particles, substantially higher pressure or higher brush velocity are required. Particle redeposition after cleaning, and damage are reported as major problems with brush cleaning [4]. Megasonic cleaning employs ultrasonic waves above 1 MHz.…”

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

“…It is therefore required to ensure that these masks containing nanofilms/layers are free of contamination, utilizing an effective cleaning technique in a damage-free manner. Current sub-100-nm particle removal techniques such as brush scrubbing [3]- [5], megasonic cleaning [6]- [8], and cryogenic cleaning [9], [10] may suffer from various problems such as postcleaning damage (substrate damage incurred by the cleaning process), particle redeposition [4], [9], and cleaning efficiency of nanoscale particles [8]. Therefore, there is still a need for improved, efficient, precision, and/or selective cleaning techniques for sub-100-nm particles.…”

The quantitative description between zeta potential and fluorescent particle adsorption on Cu surface

“…Removing them completely is the main task in post CMP cleaning. Polyvinyl acetate brush cleaning and megasonic cleaning are the commonly used methods . In cleaning process, when external force detaches the adhered particles from wafer, some particles are washed away by the flow, and meanwhile, some particles deposit to the wafer again .…”