AFM Measurements of Adhesion between CMP Slurry Particles and Copper
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0914-F12-05
AFM Measurements of Adhesion between CMP Slurry Particles and Copper Ruslan Burtovyy1,2, Yong Liu1, Bogdan Zdyrko1, Alex Tregub3, Mansour Moinpour3, Mark Buehler4, and Igor Luzinov1 1 School of Materials Science and Engineering, Clemson University, 161 Sirrine Hall, Clemson University, Clemson, SC, 29634 2 Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland 3 CMO/FMO, Intel Corporation, Santa Clara, CA, 95054 4 PTD, Intel Corporation, Hillsboro, OR, 97124
ABSTRACT Adhesion between abrasive particles and surfaces being polished plays an important role in chemical mechanical planarization (CMP) processes. The changes in particle - surface and particle – particle interactions can significantly influence the effectiveness of material removal and cleaning methods. To determine the adhesion between actual abrasive particles and different surfaces treated by the CMP process a method employing atomic force microscopy (AFM) technique is being developed. The monolayer of silica abrasive nanoparticles was deposited on silicon wafer covered with polymer anchoring layer. High affinity of the thin polymer film to the particles and wafer ensures the stability of particles monolayer on the surface during measurements. AFM cantilever was modified with attachment of 20-40 µm hollow glass bead (representing a flat surface), which then was covered with copper using physical vapor deposition technique. Force-distance curves were collected employing AFM force volume mode and used to calculate the adhesion value. The effect of different factors (such as pH, presence of surfactants) on adhesion between copper surface and silica slurry has been studied. INTRODUCTION Chemical mechanical planarization (CMP) of oxide and metal layers is very important step in integrated circuit (IC) manufacturing. One of the critical parameters, which influences quality and productivity of CMP, is adhesion between abrasive particles and surface being polished. Recently, the adhesion has been incorporated into a model for calculation of removal rate during the polishing [1]. Good agreement between the experimental and theoretical results demonstrates the importance of adhesion for the CMP processes. Additionally, the interaction between the particles and surface has to be taken into account during post-CMP cleaning procedures. Successful removal of the submicron particles left on the surface depends strongly on the ability to minimize the attractive forces at the particle-surface interface. Several techniques [surface force apparatus (SFA), atomic (scanning) force microscopy (AFM), and interfacial force microscope (IFM)] allow direct measurement of the force necessary to separate contacting surfaces. Among them AFM is especially suitable for operations with nanoscale objects and can detect small forces in different media for an extremely short separation. Application of AFM cantilevers with attached micron size particle has been proven to be particularly useful for the adhesion measurements [2].
Copper is one of the major
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