Method of helical chamfer machining silicon wafer

A method of helical chamfer machining silicon wafers, comprising performing helical chamfer machining on a plurality of silicon wafers in succession, the helical chamfer machining being performed by, while rotating a chamfering wheel provided with a fine grinding grindstone portion with the rotation angle being inclined with respect to the vertical direction, pressing one silicon wafer being rotated against the fine grinding grindstone portion so that a finished wafer taper angle of an edge portion in the one silicon wafer is within an allowable angle range of a target wafer taper angle, the method further comprising:

• a first truing step of truing the fine grinding grindstone portion of the chamfering wheel using a truer having a first truer taper angle;
• a first chamfer machining step of helical chamfer machining a first silicon wafer using the fine grinding grindstone portion having been subjected to the first truing step so that a finished wafer taper angle of the machined first silicon wafer is within the allowable angle range of the target wafer taper angle;
• a step of determining a groove bottom diameter of the grindstone portion after the first chamfer machining step;
• a second truing step of truing the fine grinding grindstone portion of the chamfering wheel using a truer having a second truer taper angle when the groove bottom diameter is smaller than a predetermined threshold value;
• and
• a second chamfer machining step of helical chamfer machining a second silicon wafer using the fine grinding grindstone portion having been subjected to the second truing step so that a finished wafer taper angle of the machined second silicon wafer is within the allowable angle range of the target wafer taper angle,
• wherein the second truer taper angle is larger than the first truer taper angle.