Chemical-mechanical polishing, or planarization (CMP), has emerged as an increasingly important technology for integrated-circuit manufacturing. Consumables used during CMP interact in a complex manner with the polishing tool, the process conditions, and the wafer being polished. In this article, several advanced analytical methods are used to analyze the properties of slurries and pads under conditions similar to those found during CMP processing. Some of the key findings are that under these process conditions, pads can be stabilized with a heat treatment prior to installation on the polisher; pads absorb slurries at different rates, and slurries also react with the pads; and the mechanical properties of the pads are dependent on the orientation of the grooves on the pad. Dynamic rheometry was used to detect de-agglomeration in sheared slurries.

Chemical Mechanical Planarization has become a method of choice for planarization of metal and oxide layers in microelectronics industry. A CMP process includes up to 16 variables that need to be controlled to achieve a stable CMP process [1]. One of the major variables in CMP is related to slurry compositions. In particularly, a uniform distribution of the sizes of the abrasive particle in slurry is crucial for a stable CMP performance. The agglomerates can be unstable, since their size depends on addition of chemical additives and shearing during the CMP process.In this work, the authors studied agglomeration of the fumed and colloidal silica-based slurries using dynamic rheometry, zeta potential tests, and an accusizer.Slurry viscosity, determined using a steady state rheometry, was correlated to the particle charge, characterized by zeta potential, and to the particle sizes obtained using the particle size analyzer. Additionally, rheometer was used for slurry shearing to study effect of shear on slurry characteristics. Particle agglomeration due to slurry shearing and storage was observed and corroborated using rheometry, zeta potential, and particle size measurements.

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Atomic force microscopy ͑AFM͒ studies of interactions between slurry particles and substrates treated by chemical mechanical polishing ͑CMP͒ processes were carried out. To conduct adhesion measurements, the particles present in a CMP system were first attached to the surface of a silicon wafer covered with thin polymer film having high affinity for both particles and the silicon wafer. A silica glass sphere was attached to the AFM cantilever with an appropriate spring constant. The sphere represented the surface of the material being polished and was used as received or covered with a layer of copper. The sphere can be modified with various materials in future research. The AFM force volume mode, which uses the collection of the force-distance curves over selected surface areas, was used for the adhesion measurements. The adhesion in the systems studied was strongly dependent on the pH value of the aqueous environment, and the concentration and type of surfactants added.Chemical mechanical polishing ͑CMP͒, used in planarization of oxide dielectric and metal layers, is a vital tool for advanced integrated circuit ͑IC͒ manufacturing. 1-4 Adhesion between abrasive particles and surfaces being polished is definitely one of the critical parameters in CMP technology. During CMP, significant adhesion forces may be developed that can be of the same magnitude as or larger than the external force exerted by the polishing pressure. 5 Zhang and Busnaina 1 proposed a removal rate model incorporating the important contribution of particle adhesion forces. The model prediction was in good agreement with the experimental removal rate data demonstrating the important role of adhesion forces in the CMP process.Formation of surface defects and low or excessive removal rates may be observed if adhesive particle/surface interactions are not optimized during the CMP process. In addition, interabrasive particle adhesion causes particle agglomeration that can have a detrimental effect on CMP quality. 6 Furthermore, CMP leaves tens of thousands of submicron and micrometer-sized particles on the polished surface. These must be removed before further processing, or they will adversely affect the yield of the finished IC. 7 Particle removal from the wafer requires application of sufficient external force to overcome the forces of adhesion. 8 Naturally, optimization of post-CMP techniques for the particle removal cannot be conducted without an understanding of adhesive interactions in the system. The interactions are mainly caused by van der Waals ͑vdW͒ forces. 3 They result in an attraction between slurry particles and the substrate. Also, chemical or hydrogen bonds may be formed between the particles and the surface.In actual CMP processes, slurry particles of different sizes and nature are in contact with a range of dielectrics and metals. Among the most important substrates are silica, copper, tungsten, low-k ͑di-electric constant͒ materials, and tantalum. Moreover, during CMP a wafer surface is contaminated not only with slurry particle...

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