Abrasive-free

Material Characteristics InnuencingDesign. Materials ranging from fine powders to large lumpy materials, nonabrasive to very abrasive, free-flowing to cohesive, and nonfriable to friable can be handled on properly designed belt conveyors. Very sticky materials can be a problem, however, if these cannot be continuously cleaned from the belt surface. 

An abrasive-free CMP is an enhanced chemically active process, which provides lower dishing, erosion, and less or no mechanical damage of low-k materials compared to conventional abrasive CMP processes [52]. 

Electric chemical polish (ECP) and electric chemical mechanical polish (ECMP) [53] have been developed as promising methods for global planarization of LSI fabrication and abrasive-free polish. 

Balakumar, S., Haque, T, Kumar, A. S., Rahman, M., and Kumar, R., Wear Phenomena in Abrasive-Free Copper CMP Process," Journal of the Electrochemical Society, Vol. 152, No. 11,2005, pp. G867-G874. 

Pang, J. Y, Huang, P. W., Tsai, M. S., et al., Study on Pressure-Independent Cu Removal in Cu Abrasive-Free Polishing," Electrochem. Solid-State Lett., 9, No. l,2006,pp.G13-G16. 

CMP potentiodynamic measurements. Their work showed a large decrease in the corrosion current at 1 wt % of the oxidizer concentration, indicating the formation of a passivating film. AES measurements confirmed the formation of a high oxygen content film with a thickness of 1.5 nm. The addition of 3 wt % alumina to the slurry showed a twofold increase in the removal of copper when compared to the abrasive-free systems. The material removal rate peaked when using 2 wt % oxidizer. 

Kondo S, Sakuma N, Homma Y, Goto Y, Ohashi Ni, Yamaguchi H, Owada N. Abrasive-free polishing for copper damascene interconnection. J Electrochem Soc 2000 147(10) 3907-3913. 

Is it possible to observe scratches on the wafer that is polished with abrasive-free Cu CMP slurry Explain the reason behind your answer. 

It was shown that the efficiency for radial mixing depends on the gas phase as well (O. Eichstadt, Continuous Mixing of Fine Particles within Fluid Dynamic Vertical Tube Mixers, Dissertation, in German, ETH-Zurich, 1997). At best they operate with low volume concentration and for particles between 20 and 200 pm. Static mixers have been used for very abrasive free-flow materials such as silicon carbide. Since any rotating equipment is avoided inside static mixers, abrasion is limited. As will be shown below, mixture quality is dependent on feed consistency and residence time within the static mixer. Since the latter is very short in static mixers (seconds or fractions of a second), short-time feeding precision has to be very high to achieve high-quality mix. 

Cryogenic and hydrodynamic abrasive-free blasting have also been used for surface treatment of substrates before coating or adhesive bonding. Both processes are ideal when the abrasive medium itself provides a contaminant or when the collection and reprocessing of the abrasive are prohibitive. These processes are often used in the field for surface preparation of structures in the need of repair. 

Figure 3.17 Left column OCP values for (a) Cu and (b) Ru discs (1" diameter) measured with and without mechanical abrasion of an IC 1000 polishing pad in an abrasive-free alkaline solution. Right column Potentiod3mamic polarization plots for (c) Cu and (d) Ru discs with and without the pad s abrasion. The trihoelectrochemical setup shown in Figure 3.3(b) was used for both sets of measurements. During the stop sequence, the sample was left pressed against the polishing pad, while both the pad and the sample were stationary. During the polish sequence, the sample and the platen were rotated at a common velocity of 100 rpm.

Brightup, S.J., Goorsky, M.S., 2010. Chemical-mechanical polishing for III-V wafer bonding applications polishing, roughness, and an abrasive-free poUshing model. ECS... 

Abrasive-free and ultra-low abrasive chemical mechanical polishing (CMP) processes... 

However, for several applications, it is impracticable to use completely abrasive-free formulations. Several attempts have been made to reduce solids content as low as possible. For example, conventional dielectric slurries contain 30 wt% solids, which are later reduced to 12wt% sohds. Recently, Cabot developed silica slurries that contain only 2 wt% solids without sacrificing the polishing rates by using specially engineered silica particles [1]. 

Figure 9.1 Removal rates (RR) of poly-Si films on (a) ICIOOO pad and (b) Politex pad, respectively, as a function of pH using abrasive-free solutions and ceria/silica dispersions wifii and without 250 ppm PDADMAC [4].

Figure 9.3 shows the removal rate of poly-Si hlms using abrasive-free formulations containing various polymer compounds. A correlation between the charge density of... 

Dandu et al. [5] developed abrasive-free formulations using amine and amino acids compounds. The mechanism for the poly-Si removal rate enhancement relied upon the addition of a-amines or amino acids as described in Figure 9.4. The additives adsorb on the poly-Si surfaces, polarize and weaken the underlying Si—Si, and accelerate the formation of suboxide, both leading to high material removal. 

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