Effect of Different Deposition Mediums on the Adhesion and Removal of Particles

Abstract

The purpose of this study is to investigate the effect of the different deposition mediums on the adhesion and removal of particles. Polystyrene latex ͑PSL͒ particles ͑50 m͒ are deposited on thermal oxide and silicon nitride coated silicon wafers using different suspension mediums: air, isopropyl alcohol ͑IPA͒, and deionized water and then removed in a dry environment. The results show that PSL particles deposited on oxide are easier to remove than those on nitride due to a higher van der Waals force in all deposition mediums. In addition, dry particles deposited in air are much easier to remove than those desposited in a liquid medium. When particles are deposited from a liquid suspension, a liquid meniscus is formed between the particle and the substrate, resulting in a capillary force. The capillary force induces a plastic deformation for soft particles such as PSL, which increases the contact area between the particle and the substrate, making them more difficult to remove. The liquid meniscus evaporates shortly after it is exposed to either a dry air environment or vacuum; however, the plastic deformation of particles would take place mainly due to the initial adhesion force in addition to the short time exposure of the capillary force. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3377090͔ All rights reserved. Particle adhesion is one of the main causes of yield loss in the semiconductor industry 1 because particles can cause short-circuit or open circuit; 2 however, particle adhesion has other useful applications. For example, the adhesion of drug particles to specific sites is important to the pharmaceutical industry.3 In xerography, the ability to transfer toner particles successfully from the photoconductor to the receiver requires an understanding of the mechanisms of particle adhesion. 4,5 In nanomanufacturing, 6 researchers have made nanowires out of nanoparticles using directed assembly. [6][7][8] Although there are many published studies on the adhesion and removal of particles, there has been a dearth of studies addressing the effect of the different deposition mediums on particle adhesion and removal. In this paper, three different deposition mediums, air, isopropyl alcohol ͑IPA͒, and deionized ͑DI͒ water, were used to deposit polystyrene latex ͑PSL͒ particles on thermal oxide and silicon nitride wafers. These particles were removed using a spinner in air to observe the effect of deposition mediums on particle removal efficiency ͑PRE͒. Theoretical BackgroundAdhesion force and adhesion moment.-The first major adhesion force is the omnipresent van der Waals force. Without any external load applied on the particle, the attractive van der Waals force brings the particle into contact with the surface when a particle is within the force's range. A liquid meniscus can form between the particle and the substrate when either a liquid film or a high humidity is present. The resulting capillary force makes a large contribution to the total adhesion force. In this paper, we focus on these van der Waal...

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“…In addition, RICM experiments reveal topologically complex local deformations and contact phenomena relevant to virtually all adhesion models. The finding of various scenarios at the micro scale after dry/wet deposition of PSL particles on a glass substrate is in qualitative agreement with recent results that show how different deposition media affect the particle removal efficiency, a fact attributed to plastic deformation of particles caused by capillary forces43. Even more significant is the direct observation of femtolitre-scale capillary condensation dynamics underneath micron-sized particles, believed to be unique, given that capillary condensation have only been directly observed using environmental SEM4445 and studied with the surface forces apparatus4647, although employing two crossed cylindrical mica surfaces with very large radii of curvature (~1–2 cm).…”

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“…The charge accumulated in the substrate during irradiation by the beam was estimated using the expressions presented in [ 41 ] and amounted to 0.7 pC for the scanning area of the beam with an area of 100 μm 2 . The van der Waals forces between the particle and the substrate and between the tip and the particle were calculated using the expressions from [ 42 , 43 ]. In this case, a Hamaker constant of 26.8 × 10 −20 J for the particle–substrate interface and 45.2 × 10 −20 J for the tip–particle interface were used.…”

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