A theoretical and experimental study of the adhesion and removal of particles from surfaces

Gautam Kumar, Purdue University

Abstract

This work extended the current fundamental models for particles adhering to thin films. Particle removal from surfaces is an essential processing step during semiconductor manufacture. With decreasing device critical dimensions, the removal of smaller particles becomes progressively more important. A fundamental understanding of particle adhesion is required to develop a fundamental understanding of the unit processes in wafer and photomask cleaning. The ability to quantitatively predict and simulate the adhesion of particles to surfaces will lead to a better optimization of these processes. This work combines equations for van der Waals (vdW) and electrostatic (ES) forces with computer simulations. A finite volume interaction region was defined for the computation of vdW interactions between a sphere and a flat plate in order to reduce computational cost. The error introduced due to this approximation was infinitesimally small if the radius and depth of the finite volume cylinder were chosen appropriately according to the particle size. The models utilize previously developed approaches to represent real particles and rough surfaces and establish the scaling of vdW and ES interactions as the contaminants shrink from several microns to several nanometers. Atomic force microscopy (AFM) was used to measure adhesion forces between particles and surfaces by immobilizing particles on AFM tips. Adhesion of particles to patterned substrates was examined at the micron and nano-scales using patterns of varying sizes. The removal of particles due to isotropic etching of the surface was investigated and the adhesion model was used to estimate the etch time required for particle removal for different particle sizes.

Degree

Ph.D.

Advisors

Beaudoin, Purdue University.

Subject Area

Chemical engineering

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