Measurement of Interactions between Abrasive Silica Particles and Copper, Titanium, Tungsten and Tantalum
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Measurement of Interactions between Abrasive Silica Particles and Copper, Titanium, Tungsten and Tantalum Ruslan Burtovyy1, Alex Tregub2, Mansour Moinpour2, Mark Buehler3, and Igor Luzinov1 1 School of Materials Science & Engineering, Clemson University, 161 Sirrine Hall, Clemson, SC, 29634 2 GFM (Global Fab Materials), Intel, Santa Clara, CA, 95052 3 PTD, Intel, Hillsboro, OR, 97124 ABSTRACT Colloidal probe technique has been widely employed to measure the adhesion between micro- and nanosize objects using atomic force microscopy (AFM). However, majority of studies concerns model systems, which do not incorporate real abrasive particles. The approach applied allows measuring adhesion between real CMP nanoparticles and different surfaces. Thin polymer film with high affinity to the particles was used to anchor the particles to a surface. Hollow glass bead (20-30 µm) representing flat surface was attached to soft AFM cantilever. Application of large hollow bead and the cantilever with small spring constant allows measuring the interactions with high sensitivity. Titanium, tungsten and tantalum metals were sputtered on the bead surface. The effect of different factors such as pH value, concentration and type of a surfactant on adhesion between surfaces of metals and silica slurry has been studied. Character and intensity of interactions at the moment of contact have been evaluated from experimental force-distance curves. INTRODUCTION Adhesion plays an important role in processes where direct contact of objects involved takes place. Chemical-mechanical planarization (CMP) is one of many of them. Direct contact of polishing slurry particles and a surface to be polished inevitably assumes some interaction between them. Firstly, such an interaction (adhesion) can have significant influence on removal rate (RR) of the material from the surface [1], thus can determine a speed of and productivity of the process to the large extend. Secondly, the effectiveness of post-processing cleaning procedure, aiming to remove residual slurry particles from the surface, and consequently final quality of a product (integrated circuit) also depends on particle-surface interaction. Finally, the reliable information on adhesion situation in different systems is extremely desirable whenever several different materials intended to be removed at different rates are present on the surface. In our preceding papers [2, 3] we described a method for measuring adhesion between different surfaces and real slurry particles and obtained results for silica slurry-silica and silica slurry-copper systems. This paper presents further extension of the method and the results of adhesion measurements between silica nanoparticles and Ti, Ta and W surfaces. The influence of pH value of media, concentration and a type of a surfactant has been studied.
EXPERIMENT An extensive description of the method applied as well as experimental procedures used can be found elsewhere [2, 3]. Briefly, silica slurry nanoparticles (40 nm, Nissan Chemical) were atta
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