Effects of Slurry Particles on Silicon Dioxide CMP

Abstract

The performance of chemical mechanical polishing ͑CMP͒ is determined by the dynamic contact behavior ͑sliding or rolling͒ of the slurry particles during polishing. The dynamic contact behavior of slurry particles is dependent on the shape, size, and concentration of particles. In this paper, the dynamic contact characteristics and their effects on the CMP performance were investigated through in situ friction force measurements, atomic force microscopy images, and polishing experiments. For slidingdominated contact, the friction force remains unchanged within the specified testing period yielding scratch-type surface topography. For rolling-dominated contact, the friction force decreases with time under a constant solids loading, producing ''shot-blast'' surface images. The polishing rate increases with solids loading of sliding particles and decreases with solids loading of rolling particles. Further optimization of the CMP process is possible by tailoring the dynamic contact of abrasive particles.As the minimum feature size of microelectronic devices reaches the 100 nm technology node, chemical mechanical polishing ͑CMP͒ has become the best choice for global and local planarization. 1-4 Global planarization which is essential to produce a multilevel integrated circuit ͑IC͒ device, is achieved by reducing the topography variation at the wafer scale. Without CMP, it would be impossible to fabricate complex, dense, and miniaturized IC devices. During the past decades, CMP has significantly advanced both in the development of sophisticated processing tools and in the formulation of slurries. Despite these achievements, CMP remains one of the least understood areas in microelectronic device fabrication processing.Even though the characteristics of slurry particles ͑i.e., shape, size and concentration͒ are critical in determining CMP performance, the effect that the slurry particles have on polishing performance is not clear. For polishing of copper or ferrite, it was suggested that the polishing rate is proportional to particle size and solids loading. 5,6 Cook 7 presented data suggesting that the polishing rate is independent of particle size for glass polishing. Izumitani 8 suggested that the polishing rate decreases with increasing particle size. Our previous work suggests two polishing mechanisms in silica CMP. 9 One is a contact-area-based mechanism by whichwhere A is the contact area, C 0 is the particle concentration, and is the particle diameter. In this model, the polishing rate increases with an increase in particle concentration and a decrease in particle size, which was observed during tungsten CMP. 10 The other is an indentation-volume-based mechanism by whichwhere V is the indentation volume. According to this indentationvolume-based mechanism, the polishing rate increases with decreasing particle concentration and increasing particle size. This mechanism was observed via silica polishing experiments. 9 On the micro-and nanoscales, the polishing rate is significantly dependent on the dynamic contact of...

A Tribochemical Study of Ceria-Silica Interactions for CMP

“…9,[11][12][13] The friction force generated by the contact and wear of opposing surfaces is dependent on factors like the applied load and the contact area, the properties of the opposing surfaces, and the nature of contact. Hence, the friction during silica polishing should vary depending on the slurry chemistry ͑i.e., particle type, slurry pH, etc.͒.…”

Polishing behaviors of ceria abrasives on silicon dioxide and silicon nitride CMP

“…This implies the decrease in contact area between ceria abrasives in slurry D and oxide film during CMP processing. Additionally, large abrasives with round-shape lead to the decrease in interfacial contact with film surface, due to their rolling motion [17]. Furthermore, relatively lower removal rate are attributed to the inhomogeneous distribution of slurry on the wafer.…”

Particle Technology in Chemical Mechanical Planarization

“…As the pressure increases, the friction at the pad-abrasive interface increases and beyond a threshold pressure the abrasives start being dragged by the pad across the substrate causing a sliding motion of the particles leading to appreciable material removal. Choi et al 17) have corroborated this model on the basis of insitu friction force measurements during polishing.…”