Double-side polishing method
The present invention is directed to a double-side polishing method including interposing a wafer held by a carrier between upper and lower turn tables to which respective polishing pads are attached, and rotating and revolving the carrier while supplying a polishing agent to polish both surfaces of the wafer at the same time, the method including the steps of: first polishing at a high polishing rate; second polishing at a low polishing rate; measuring flatness of the polished wafer; and determining polishing conditions of the second polishing in a next polishing batch on a basis of the measured flatness. The method can stably improve the flatness of a wafer without being affected by variations in carrier thickness over time.
1. A double-side polishing method including interposing a wafer held by a carrier between upper and lower turn tables to which respective polishing pads are attached, and rotating and revolving the carrier while supplying a polishing agent to polish both surfaces of the wafer at the same time, the method comprising the steps of:
first polishing at a high polishing rate;
second polishing at a low polishing rate;
measuring flatness of the polished wafer; and
determining polishing conditions of the second polishing in a next polishing batch on a basis of the measured flatness,
wherein the measured flatness includes overall represented by a cross-sectional shape passing through a center of the wafer and circumferential flatness represented by a sag shape or a rise shape of an outer circumference portion of the wafer, and
wherein the step of determining the polishing conditions of the second polishing determines the polishing conditions such that, if the measured circumferential flatness is the rise shape, then a polishing load is decreased and a rotational speed of the upper and lower turn tables and a rotational speed of and a revolution speed of the carrier are increased compared with those of a current polishing batch, and if the measured circumferential flatness is the sag shape, then the polishing load is increased and the rotational speed of the upper and lower turn tables and the rotational speed of and the revolution speed of the carrier are decreased compared with those of the current polishing batch.
2. The double-side polishing method according to claim 1 , wherein,
the step of determining the polishing conditions of the second polishing determines at least one of a polishing load, a rotational speed of the carrier, a revolution speed of the carrier, a rotational speed of the upper turn table, a rotational speed of the lower turn tables, and a polishing time.
3. The double-side polishing method according to claim 1 , wherein,
if the measured circumferential flatness is the rise shape, then a polishing time of the first polishing is determined such that a finishing thickness becomes thicker than that of the current polishing batch, and if the circumferential flatness is the sag shape, then the polishing time of the first polishing is determined such that the finishing thickness becomes thinner than that of the current polishing batch.
4. The double-side polishing method according to claim 1 , wherein,
if the measured circumferential flatness is the rise shape, then the polishing time of the first polishing is determined such that a finishing thickness becomes thicker than that of the current polishing batch, and if the circumferential flatness is the sag shape, then the polishing time of the first polishing is determined such that the finishing thickness becomes thinner than that of the current polishing batch.