The study mainly explores the surface profile of sapphire wafer after polishing by the method of chemical mechanical polishing (CMP). Pattern-free polishing slurry with SiO2 abrasive particle is used to polish the sapphire wafer. This paper observes the phenomena of surface profile and surface scratches of sapphire wafer under different pressures and different rotational velocities during CMP. The study uses atomic force microscope (AFM) to scan the surface of sapphire wafer focusing on three axial lines of 0∘, 45∘and 90∘from the position of near edge passing the center of sapphire wafer. The study also selects five positions on a specific area to draw the surface profiles on the axial lines of 0∘, 45∘and 90∘. It can be observed that the central area of sapphire wafer has lower depression than other areas because the central area is polished more polishing times. Besides, the depression on the central area of sapphire wafer has a greater depression value and it has more and larger surface scratches when it is polished under a greater down force and at a faster rotational velocity.
All pad conditioners used for CMP today are made by attaching discrete diamond grits on a flat substrate. Polycrystalline diamond (PCD) was wire-EDM cut to form blades with different designs of cutting tips. These blades were assembled to form the so-called ultimate diamond disk (UDD). The pad asperities formed with UDD were compared with conventional diamond disks. It was confirmed that UDD dressed pad asperities were more uniform than that for polishing IC wafers today. The UDD dressed pads were also used to polish tungsten (W) IC layer deposited on 300 mm wafers. As the surface of PCD contains only merged diamond grains that are corrosion immune, UDD was dressing in-situ, by immersing in the acid slurry. The wafer uniformity so polished was comparable to that of ex-situ CMP pad dressing with metallized diamond disks. The in-situ dressing can boost the CMP throughput by deglazing the pad in real time while the wafer is being polished. After 15 hours, the wafer profiles for this in-situ dressing were sustained without decay.
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