Study Of The Polishing Mechanism Based On Phyllotaxis Arrangement Polishing Pad

Chemical Mechanical Polishing (CMP) is one of the techniques of achieve theultra-smooth high-precision surface, which has been shown in many cases to yield thebest results for wafer planarity, uniformity of integrated circuit chip, semiconductor andComputer hard disk and optical glass etc. However, material removal mechanism andsurface roughness of the workpiece play an important role in CMP.First, in order to describe the surface geometry, the concept of fractals wasintroduced. The model of the surface roughness of the workpiece was set up, which wasbase on W—M and M—B fractal contact model. It is seen that the surface roughness ofthe workpiece decreases with the increasing of polishing time, in particular the surfaceroughness sharp decline in the first few minutes. When the pressure is relative large orthe revolving speed of the polishing disk is relative small, the surface roughness willbecome large.Then, the design and fabrication of phyllotaxis arrangement polishing pad wereintroduced. And the model of material removal rate of polishing silicon wafer withphyllotaxis arrangement polishing pad was set up. During chemical-mechanicalpolishing, the material removal by the synergistic effects of both the mechanical andchemical removal processes. The chemical reaction makes the surface of the wafer toform a layer of oxide film, and the mechanical remove the layer of oxide film.Theoretical analysis shows that the material removal rate decreases with the increasingof the phyllotactic coeffiecinet,and increases with the increasing of the diameter of theabrasive block or pressure or revolving speed of polishing disk.Last, the polishing experiments are used to verify theoretical analysis. Duringchemical-mechanical polishing, silicon wafer was polished with different pressure androtational speed of the polishing disk, the polishing time is120min. The result show thatthe surface roughness of silicon wafer decreases with the increasing of polishingtime,which sharp decline in the first20min and basic stability after120min. Finally, the surface roughness of silicon wafer reaches0.8nm~1.1nm. When the pressure is relativelarge, the surface roughness is increasing; when revolving speed aggrandize, the surfaceroughness decrease. In the polishing experiments, silicon wafer is polished byphyllotactic arrangement pad with different phyllotactic coefficient，the diameter of theabrasive block，pressure and revolving speed. The experimented results showed that thematerial removal rate decreases with the increasing of the phyllotactic coeffiecinet, andincreases with the increasing of the diameter of the abrasive block、pressure andrevolving speed. Experimental data for silicon wafer polishes are seen to match wellwith simulating results.