The Study of Oxide Planarization Using a Grindstone
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suitable for better planarity but sometimes harder pad has the poor ability to hold the abrasives and CMP removal rate is slow. So the possibility of a grindstone for the oxide planarization was investigated. A grindstone has two special characteristics. One is high compressivity that is desirable for good planarity. Another is the fixed abrasive that is good for high removal rate. So it looks reasonable to apply a grindstone for the oxide planarization. EXPERIMENTAL Fig. 1 shows the schematic of the grindstone used in this experiment. The grindstone is consist of Ceria and polyimide. In the grinding process, de-ionized water is supplied to the grindstone at the flow rate of 300ml/min. As a reference, double layered hard type polyurethane pad is used. This case, 10% solid content silica slurry that pH is adjusted to about 10 by KOH is supplied to the pad at the flow rate of 200ml/min. The carrier pressure is 400gf/cm2 and the carrier and the table speed is 30rpm for both case. The pad conditioning 19 Mat. Res. Soc. Symp. Proc. Vol. 566 ©2000 Materials Research Society
)Abrasive was performed by the conventional ( plate. conditioning Diamond(100grit)/Nickel Binder The sample was prepared by the (Polyimide) trenches deep 700nm following procedure. Pore with various size were created on 8 inch Fig. 1 Schematic of grindstone silicon wafer. 1400nm of Si0 2 film is deposited on this wafer by plasma CVD with TEOS source. Following the grinding or CMP process, the oxide thickness was measured by the
conventional measurement tool using optical interference and the planarity was characterized by the profilometer. For the defect analysis, the defect inspection tool based on light scattering and AFM was used. RESULTS AND DISCUSSION Planarity
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Fig.2 shows the characteristics of planarity depending on oxide removal on
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upper area. The space width is 1000 g m in this case. The grinding shows the excellent planarization and almost same as the ideal
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curve. But CMP shows poor planarization and IOOOA of step remains after 700nm of oxide removal. Fig.3 (a) and Fig.3 (b) show the profile of the oxide surface. CMP case, not only the oxide on upper area but also the
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oxide on lower area is removed after the step becomes small. Because of the pad Fig.2 Comparison of CMP planarity compressivity, the pad surface reached the with grinding bottom of the groove. So the oxide in the groove is also removed and the corner of the groove is rounded after CMP. On the other hand, the oxide on lower area is not removed in grinding case. Because the grindstone is hard enough and the grindstone does not reach the bottom of the groove. So the oxide on lower area is not removed and the corner still remains after the grinding. The difference of planarization capability is thought to be the difference of the compressivity of the grindstone and CMP pad.
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To investigate the planarization more
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detail, the oxide thickness depending
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