CROSS REFERENCE TO RELATED APPLICATION

This document claims priority to Japanese Patent Application Number 2018-137067 filed Jul. 20, 2018, the entire contents of which are hereby incorporated by reference.

BACKGROUND

There is known a polishing apparatus which presses a polishing tape against an edge portion of a wafer to form a step-shaped recess in the edge portion (see, for example, Japanese Laid-Open Patent Publication No. 2012-213849). As shown inFIG. 31, this type of polishing apparatus is configured to press a polishing tape505against an edge portion of a wafer W with a pressing member508while rotating the wafer W by a wafer stage500.

FIG. 32is a top view of the polishing apparatus shown inFIG. 31, andFIG. 33is a view seen from a direction indicated by arrow A inFIG. 32. The polishing tape505contacts the edge portion of the rotating wafer W while advancing at a predetermined speed in a direction indicated by arrows inFIGS. 32 and 33. Liquid (for example, pure water) is supplied to the surface of the wafer W from a liquid supply nozzle (not shown). The polishing tape505is placed in sliding contact with the edge portion of the wafer W in the presence of the liquid to form a stepped-shape recess510in the edge portion of the wafer W as shown inFIG. 34.

However, as shown inFIG. 32, a length L1with which the polishing tape505is in contact with an outer region of the edge portion of the wafer W is longer than a length L2with which the polishing tape505is in contact with an inner region of the edge portion of the wafer W. This difference in length corresponds to a difference in polishing rate (also referred to as removal rate) between the outer and inner regions of the edge portion. As a result, as shown inFIG. 35, a bottom surface, constituting the recess510formed in the edge portion, is inclined with respect to the surface of the wafer W. In addition, an inner edge of the polishing tape505in contact with the inclined bottom surface obliquely scrapes off the edge portion of the wafer W. As a result, a vertical surface constituting the recess510is inclined.

Further, as shown inFIGS. 36A and 36B, if the pressing member508is slightly inclined with respect to the surface of the wafer W when viewed from a radial direction of the wafer W, a polishing-pressure distribution on the edge portion of the wafer W changes significantly. As a result, it becomes difficult to obtain a stable profile of the recess510.

SUMMARY OF THE INVENTION

According to embodiments, there are provided a polishing apparatus and a polishing method capable of forming a step-shaped recess having a right-angled cross section in an edge portion of a substrate, such as a wafer.

Embodiments, which will be described below, relate to a polishing apparatus and a polishing method for polishing an edge portion of a substrate such as a wafer, and more particularly to a polishing apparatus and a polishing method for forming a step-shaped recess in the edge portion of the substrate by pressing a polishing tape against the edge portion.

In an embodiment, there is provided a polishing apparatus for forming a step-shaped recess in an edge portion of a substrate, comprising: a substrate rotating device configured to rotate the substrate about a rotation axis; a first roller having a first circumferential surface configured to press a polishing tape against the edge portion of the substrate; and a second roller having a second circumferential surface in contact with the first circumferential surface, the second roller having a tape stopper surface that restricts movement of the polishing tape in a direction away from the rotation axis, the tape stopper surface being located radially outward of the first circumferential surface.

In an embodiment, the first roller and the second roller are rotatable about a first axis and a second axis, respectively, extending toward the rotation axis.

In an embodiment, the polishing apparatus further comprises a third roller concentrically fixed to the second roller, the third roller having a third circumferential surface with a diameter smaller than a diameter of the second circumferential surface, the tape stopper surface being connected to the third circumferential surface.

In an embodiment, an axial length of the third roller is smaller than a distance between an inner end surface of the first roller and the tape stopper surface.

In an embodiment, a distance between an inner end surface of the first roller and the tape stopper surface is equal to or smaller than a width of the polishing tape.

In an embodiment, the polishing apparatus further comprises a tape-stopper-surface detection system configured to detect a position of the tape stopper surface.

In an embodiment, the tape-stopper-surface detection system is configured to emit an alarm when an amount of change in the position of the tape stopper surface exceeds a preset threshold value.

In an embodiment, the polishing apparatus further comprises a roller moving mechanism configured to move the first roller and the second roller in a direction toward the rotation axis and in a direction away from the rotation axis, wherein the tape-stopper-surface detection system is configured to instruct the roller moving mechanism to move the first roller and the second roller toward the rotation axis by a distance corresponding to the amount of change in the position of the tape stopper surface.

In an embodiment, the polishing apparatus further comprises: a roller moving mechanism configured to move the first roller and the second roller in a direction toward the rotation axis and in a direction away from the rotation axis; a tape-width measuring sensor configured to measure a width of the polishing tape; and an arithmetic device configured to instruct the roller moving mechanism to move the first roller and the second roller in a direction as to cancel a change in a measured width of the polishing tape.

In an embodiment, there is provided a polishing method of forming a step-shaped recess in an edge portion of a substrate, comprising: rotating the substrate about a rotation axis; and pressing a polishing tape against the edge portion of the substrate by a first circumferential surface of a first roller while restricting movement of the polishing tape in a direction away from the rotation axis by a tape stopper surface of a second roller, the second roller having a second circumferential surface in contact with the first circumferential surface, the tape stopper surface being located radially outward of the first circumferential surface.

In an embodiment, the polishing method further comprises emitting an alarm when an amount of change in a position of the tape stopper surface exceeds a preset threshold value.

In an embodiment, the polishing method further comprises moving the first roller and the second roller toward the rotation axis by a distance corresponding to an amount of change in a position of the tape stopper surface.

In an embodiment, the polishing method further comprises: measuring a width of the polishing tape; and moving the first roller and the second roller in a direction as to cancel a change in a measured width of the polishing tape.

According to the above-described embodiments, the polishing tape is brought into line contact with the edge portion of the substrate. Therefore, the polishing rate is the same over the entirety of the contact surface between the substrate and the polishing tape, and a polishing profile of the substrate is stabilized. Moreover, since the above-described embodiments use the first roller as a pressing member for pressing the polishing tape, unintended concentration of the polishing pressure as shown inFIGS. 36A and 36Bdoes not occur. As a result, the polishing profile of the substrate is stabilized.

