In manufacturing of semiconductor devices, a polishing apparatus for polishing a peripheral portion of a wafer with use of an abrasive film has been widely used. The abrasive film has a structure including a base film made of PET (polyethylene terephthalate) and abrasive grains held by a binder, which is applied to the base film and made of urethane, polyethylene resin, or the like. This abrasive film is a belt-shaped polishing tool and is also called polishing tape.
The conventional abrasive film has a relatively low mechanical strength. As a result, the abrasive film may be damaged when polishing a peripheral portion of a wafer having a hard film of, e.g., SiC, formed on a surface thereof. FIG. 36 is a cross-sectional view showing a wafer having a structure including a silicon substrate and an SiC film formed on the silicon substrate. As shown in FIG. 36, an SiC film (or a silicon carbide film) 310 is formed on an entirety of a surface, including a peripheral portion, of a silicon substrate 301. A device structure constituted by interconnects and a dielectric film may be further formed on the SiC film 310. Since the SiC film 310 is a hard film, the abrasive grains may fall off, or in the worst case, the abrasive film may break when the abrasive film is polishing the peripheral portion of the wafer shown in FIG. 36.
Further, the abrasive film may also be damaged when polishing a peripheral portion of an SOI (Silicon on Insulator) wafer. The SOI wafer is manufactured by bonding a device substrate to a silicon substrate. More specifically, as shown in FIG. 37A and FIG. 37B, a device substrate 302 and a silicon substrate 301 are bonded to each other by an adhesive 313, and a back side of the device substrate 302 is then ground by a grinder. As a result, an SOI wafer having a silicon layer 315 and a device layer 316, which are stacked one on top of another, is obtained as shown in FIG. 37C. Further, as shown in FIG. 37D, the abrasive film is pressed downwardly against the peripheral portion of the SOI wafer to remove peripheral portions of the silicon layer 315, the device layer 316, and the silicon substrate 301, together with the adhesive 313.
The adhesive 313 existing between the device substrate 302 and the silicon substrate 301 forms a hard film. Therefore, when the abrasive film is polishing the peripheral portion of the SOI wafer as shown in FIG. 37D, the abrasive grains may fall off, or in the worst case, the abrasive film may break.
If the abrasive film is damaged during polishing of a wafer as described above, the abrasive film should be replaced with a new one. Frequent replacement of the abrasive film can lower a productivity of the polishing apparatus.
USPTO Backgrounds
USPTO Backgrounds