The improvement of dispersion stability for the primary polishing slurry in a CMP process is achieved to prevent defects produced by agglomeration of the slurry. The dispersion properties are analyzed according to the physical characteristics of each silica sol sample. Further, the difference in the dispersion stability is confirmed as the surfactant content. The dispersibility results measured by Zeta potential suggest that the dispersion properties depend on the content and size of the abrasive in the primary polishing slurry. Moreover, the optimum ratio for high dispersion stability is confirmed as the addition content of the surfactant. Based on the aforementioned results, the long-term stability of each slurry is analyzed. Turbiscan analysis demonstrates that the agglomeration occurs depending on the increasing amount of surfactant. As a result, we demonstrate that the increased particle size and the decreased content of silica improve the dispersion stability and long-term stability.

Background : The most problematic disease in Boxthorn is Anthracnose. New variety with Anthracnose-resistant is good for high yield and Safe fruit production in open field. Therefore it is necessary to develop a New variety with Anthracnose -resistant and high yield. Methods and Results : The new boxthorn line, CB10511-104 was selected from the cross between Cheongun (IT232599) and CB08456-113 to breed new variety with high yield and Anthracnose-resistant in 2011. Its preliminary yield test was performed from 2012 to 2013 and the selected line was named Cheongyang 25. Its regional yield trials were carried out in Cheongyang, Yesan and Jindo for 3 years, from 2014 to 2016. Cheongyang 25 was registered as the new variety, Cheonggeum, in 2016. The specific characteristics were summarized as follows; Tree shape is open type and the leaf is round-lanceolate. The flowers are normal size and purple. The fruit is large size, round oval and yellowish red. The flowering was June 19 with medium flowering. Number of sprout branch by pruning was generated more than the check variety, Cheongmeong. The infection rates on leaves to Eriophys macrodonis Keifer was as strong as 39.6 percent. Anthracnose on fruits in open field was slightly similare compared to the check variety, but check variety was Anthracnose-resistant. The content of betaine and free sugar in dried-fruits were higher than that of the check variety. The dried-fruit yield was decreased about 17 percent in open field. Conclusion : This variety ‘Cheonggeum’ was suitable for cultivation in open field because of Anthracnose-resistant. It is necessary the companion variety, Cheonghong, because of self-incompatible.