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http://dx.doi.org/10.9725/kts.2019.35.6.323

Effect of Surface Roughness of Sapphire Wafer on Chemical Mechanical Polishing after Lap-Grinding  

Seo, Junyoung (Department of Mechanical System Engineering, Tongmyong University)
Lee, Hyunseop (School of Mechanical Engineering, Tongmyong University)
Publication Information
Tribology and Lubricants / v.35, no.6, 2019 , pp. 323-329 More about this Journal
Abstract
Sapphire is currently used as a substrate material for blue light-emitting diodes (LEDs). The market for sapphire substrates has expanded rapidly as the use of LEDs has extended into various industries. However, sapphire is classified as one of the most difficult materials to machine due to its hardness and brittleness. Recently, a lap-grinding process has been developed to combine the lapping and diamond mechanical polishing (DMP) steps in a single process. This paper studies, the effect of wafer surface roughness on the chemical mechanical polishing (CMP) process by pressure and abrasive concentration in the lap-grinding process of a sapphire wafer. In this experiment, the surface roughness of a sapphire wafer is measured after lap-grinding by varying the pressure and abrasive concentration of the slurry. CMP is carried out under pressure conditions of 4.27 psi, a plate rotation speed of 103 rpm, head rotation speed of 97 rpm, and slurry flow rate of 170 ml/min. The abrasive concentration of the CMP slurry was 20wt, implying that the higher the surface roughness after lapgrinding, the higher the material removal rate (MRR) in the CMP. This is likely due to the real contact area and actual contact pressure between the rough wafer and polishing pad during the CMP. In addition, wafers with low surface roughness after lap-grinding show lower surface roughness values in CMP processes than wafers with high surface roughness values; therefore, further research is needed to obtain sufficient surface roughness before performing CMP processes.
Keywords
sapphire wafer; lap-grinding; chemical mechanical polishing; surface roughness;
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Times Cited By KSCI : 4  (Citation Analysis)
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