Alpha particle Alumina

X-ray diffraction of the Buehler-supplied gamma alumina powder used in a RCE study showed the powder to be actually a combination of alpha and gamma phase alumina [28], However, the relatively high particle incorporation obtained with this alpha-gamma alumina cannot be attributed to the partial alpha crystallographic character of the powder, since the pure alpha alumina codeposited to a lesser extent. 

Perhaps even more noteworthy is the effect of crystallographic phase. While one phase of a specific composition may readily incorporate from a particular bath composition, another phase of the same composition may incorporate to a much lower extent or not at all. For instance, in the alumina particle system, the alpha phase has been found to readily incorporate from an acidic copper bath while the gamma phase incorporates at less than one tenth the amount of alpha, if at all, as shown in Table 1 [2, 11, 27, 31, 33],... 

X-ray diffraction conducted on the codeposited powder revealed that the deposit obtained from a suspension of gamma alumina, which had been partially converted to the alpha phase, contained both phases of alumina. Whereas, the powder codeposited from a suspension having a 50 50 mixture of alpha to gamma alumina powder, consisted only of the alpha phase. Using a parallel plate electrode configuration, Chen et al. [31] concluded that only alpha alumina can be codeposited. Chen also observed a difference in codeposition with copper when using two different phases of the titanium oxide particle system rutile readily codeposited but anatase titania did not... 

The work by Chen et al. also resulted in no measurable incorporation with particle diameters of 0.05 and 0.02 pm gamma alumina in copper [31]. When the 0.02 pm gamma particles were calcined to obtain a mix of gamma and alpha alumina, codeposition increased to 2.9 vol.%, under the same codeposition conditions. Furthermore, when the 0.02 pm gamma powders were completely converted to the alpha phase of alumina, incorporation rose to 3.3 vol.% [31]-... 

In this way it has been shown that for Pd particles on single crystal alpha-alumina films and for Au particles on magnesium oxide smoke crystals there may be wide variations of behavior depending on factors which are not immediately apparent. In some cases, the particles are single crystals and show a strong correlation between their orientations and the orientation of the substrate. 

To test the validity of the theoretical analyses of the kinetics of formation of alumina ceramics, Wagh et al [17] conducted an experimental investigation of alumina and phosphoric acid slurry. They used a mixture of coarser and finer alpha-alumina to obtain good packing. The coarser alumina was supplied by Reynolds Chemical Company. Its mean particle size was 0.96 mm. Alumina from Fisher Scientific, sieved to a mean particle size of 0.08 mm, was combined with this powder and 50 wt% phosphoric acid solution to produce a mixture of AI2O3 and H3PO4 with a weight ratio of five. 

In addition to bulk density, particle crystallinity is another physical property that can be related to its hardness and potential effectiveness in providing the mechanical force in CMP. For example, alpha alumina abrasive has a higher hardness, thereby producing higher removal rate in comparison to its gamma crystalline counterpart [80]. As expected, the number of defects is also higher for alpha alumina due to the inherent hardness [81]. 

Bottino et al. [1994] used silicon nitride tips and silicon nitride gold-coated cantilevers to obtain the images in the height mode (or constant force mode). The AFM technique has been compared quite well with SEM using alpha-alumina membrane samples. The found that AFM could determine the sizes of individual constituent gamma-alumin.. particles in the membranes and detect subtle differences in their dimension ratios. Base. 

The alumina particles used in these experiments were primarily alpha crystal phase and possessed an approximately spherical morphology as shown in Fig. 1. This figure shows that even though the sizes of the particles vary by nearly two orders of magnitude, the shape is approximately the same. Fig. 2 shows the different particle size distributions that have been used for the polishing experiments. The size distributions match the microscopy data quite well. 

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