Recently, the effect of solid inclusions on the sintering of ceramic powders has been explained in terms of a “backstress” that opposes densiflcation. Several analyses havebeen proposed to describe this problem. However, little quantitative information exists concerning the effect of reinforcement on microstructural evolution. This study compares the microstructural development of zirconia and mullite matrices in the presence of alumina platelets. The effect of platelet loading on density is similar for both composites. Quantitative stereological examinations reveal that the average grain size and pore size are finer for the zirconiamatrix composite. The platelet loading does not have any noticeable effect on the average grain size of the matrix in either composite. However, the average pore size increases as the volume fraction of platelets increases for both materials. Contiguity measurements have detected some aggregation of platelets in the zirconia‐matrix composite.
A chemical mechanical polishing (CMP) process for copper damascene has been developed and characterized on a second generation, multiple platen polishing tool.
The impact of abrasive characteristics such as abrasive type, size, and crystallographic phase on the chemical mechanical planarization of tungsten and oxide films was investigated. The removal rates increased linearly with particle size, whereas the defectivity decreased as the particle size became smaller. Reducing the alpha alumina particle size to 120 nm showed a good combination of high removal rate and low oxide defectivity. The best oxide defectivities were achieved with transition alumina and silicon carbide. However, the transition alumina polished tungsten at a low rate compared to the other abrasives tested. The silicon carbide abrasive polished tungsten at a slightly lower rate than alpha alumina. In addition, silicon carbide planarized SiO 2 at a significant rate and therefore was not as selective to oxide as the alumina abrasives. To achieve high metal removal rates, high metal/oxide selectivity, and good defectivity, the finer alpha alumina ͑120 nm͒ performed the best in this study.Chemical mechanical planarization ͑CMP͒ of tungsten ͑W͒ plugs or vias remains an essential process for the manufacture of integrated circuits and other devices. 1,2 Much effort was devoted to W CMP in the 1990s, 2,3 including understanding the effect of abrasive types and oxidizer chemistries on polishing performance. 3-5 Subsequent innovation enabled W CMP technology to be a viable solution for more complex advanced technology node semiconductors. [6][7][8] According to Seo, ferric nitrate was a suitable oxidizer to generate good CMP finishes, and commercial W CMP slurries composed of ferric nitrate were fairly common. 2,3,7,9 The abrasives most frequently used in W CMP slurries are SiO 2 and alumina, with the latter being mechanically harder and able to generate higher removal rates. 9-11 Because of its hardness, alumina based W CMP slurries must be optimized to achieve the desired performance, particularly with respect to defectivity. 7 However, hard abrasives can be very effective in delivering global planarity, which becomes increasingly important as the silicon wafer size keeps growing and circuitry becomes smaller and more complex. To overcome the aforementioned tendency for alumina to produce scratching, engineering of the abrasive properties is extremely important. Only with controlled size, morphology, and chemistry can the harder abrasives be a viable alternative to SiO 2 particles in W CMP slurries. 1,3,12 The role of abrasives in CMP slurry performance has been well recognized and studied in various systems such as W, Cu, Ta, and oxide. 13 By comparing surface coated composite particles through oxide CMP, Lu et al. demonstrated that cubic composite abrasives were more efficient than spherical ones. 11 Abrasive hardness was linked to the surface quality of copper in a recent study carried out by Li et al. comparing three types of particles: diamond, alumina, and fumed silica. 13 Another interesting aspect of this article is that surface hydroxyl groups helped promote the material removal rate ͑MRR͒ of Ta by i...
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