Patent Description:
Devices, such as memory circuits, logic circuits and image sensors (e.g., CMOS sensors) are becoming more highly integrated these days. In a process for forming such devices on a substrate, such as a wafer, foreign matter, such as fine particles, dust, and unwanted film, may adhere to the substrate. Foreign matter adhering to the substrate can cause defects, such as a manufacturing failure and breakage of a device. Therefore, in order to enhance the reliability of the device, it is necessary to remove the foreign matter on the substrate.

In order to remove the foreign matter on the substrate, such as a wafer, there is a polishing apparatus configured to polish the substrate using a polishing tool. One type of such a polishing apparatus is configured to polish the substrate by rubbing a polishing tool against the substrate. The polishing apparatus presses the polishing tool against the substrate by a polishing head to polish the substrate.

<CIT>, <CIT> and <CIT> show different polishing heads for pressing a polishing tool against a substrate.

An example of the polishing apparatus includes a polishing apparatus configured to polish a substrate by pressing a polishing tool against the substrate by a polishing head, while rotating the substrate and feeding the polishing tool, such as a polishing tape, in one direction. The polishing head of this polishing apparatus includes a pressing tool configured to press the polishing tool against the substrate. However, due to a machining accuracy limit of the pressing tool, a contact surface of the pressing tool being in contact with the polishing tool may have irregularities, and a smooth contact surface may not be obtained. The contact surface that is not smooth may cause a variation in pressing force of the polishing tool against the substrate and may cause a region where the polishing tool does not contact the substrate. As a result, a desired polishing performance may not be obtained.

Thus, the present invention provides a polishing head capable of pressing a polishing tool against a substrate with a uniform force. Further, the present invention provides a polishing apparatus including such a polishing head.

In an embodiment, there is provided a polishing head for polishing a substrate, comprising: an annular elastic member configured to press a polishing tool against the substrate; and a pressing-tool body having a pressing surface configured to press the polishing tool against the substrate via the elastic member, wherein the pressing surface has a first fitting groove in which a first portion of the elastic member fits, the first portion protrudes from the pressing surface, the elastic member is put on the pressing-tool body with the elastic member elastically deformed, and the polishing head is configured to press the polishing tool against the substrate by the first portion.

In an embodiment, the elastic member is detachably put on the pressing-tool body. In an embodiment, the elastic member has a circular cross section.

In an embodiment, the elastic member is covered with a coating layer containing a fluororesin.

In an embodiment, the pressing-tool body further has a tapered surface extending obliquely from the pressing surface.

In an embodiment, a side surface of the pressing-tool body has a second fitting groove in which a second portion of the elastic member fits.

In an embodiment, the pressing-tool body has a protrusion on a side surface of the pressing-tool body, and the protrusion supports the elastic member.

In an embodiment, the first fitting groove comprises a plurality of first fitting grooves located away from each other, and the first portion comprises a plurality of first portions fitting in the plurality of first fitting grooves, respectively.

In an embodiment, the first fitting groove has an arc shape having the same curvature as a curvature of the substrate.

In an embodiment, there is provided a polishing apparatus comprising: a substrate holder configured to hold a substrate; and the above-mentioned polishing head configured to press a polishing tool against the substrate to polish the substrate.

According to the present invention, the polishing head includes the annular elastic member for pressing the polishing tool against the substrate. Tension is applied to the elastic member, and the elastic member is put on the pressing-tool body with the elastic member elastically deformed, while the elastic member fits in the fitting groove. As a result, a contact surface of the elastic member with the polishing tool is stretched and smoothed. Therefore, the polishing head can press the polishing tool against the substrate with a uniform force.

<FIG> is a perspective view showing a polishing head configured to polish a wafer by pressing a polishing tape, which is an example of a polishing tool, against a surface of the wafer, which is an example of a substrate. <FIG> is a diagram showing the polishing head shown in <FIG> as viewed from a direction indicated by an arrow A in <FIG>. <FIG> is a plan view of the polishing head. <FIG> is a cross-sectional view taken along a line B-B in <FIG>. As shown in <FIG>, a polishing head <NUM> of the present embodiment is disposed below a wafer W and a polishing tape <NUM>. In <FIG> and <FIG>, the wafer W and the polishing tape <NUM> are not depicted.

As shown in <FIG>, the polishing head <NUM> includes a pressing tool <NUM> configured to press the polishing tape <NUM> against the wafer W, a movable shaft <NUM> coupled to the pressing tool <NUM>, a housing <NUM> configured to house the movable shaft <NUM> therein, and a partition membrane (or diaphragm) <NUM> configured to form a pressure chamber <NUM> between an end portion of the movable shaft <NUM> and the housing <NUM>. The pressing tool <NUM> includes an annular elastic member <NUM> configured to press the polishing tape <NUM> against the wafer W, and a pressing-tool body <NUM> configured to support the elastic member <NUM>.

As shown in <FIG>, the pressing-tool body <NUM> has a pressing surface <NUM> configured to press the polishing tape <NUM> against the wafer W via the elastic member <NUM>. The pressing surface <NUM> has a fitting groove <NUM> in which the elastic member <NUM> fits. The elastic member <NUM> is put on the pressing-tool body <NUM> with the elastic member <NUM> elastically deformed, while the elastic member <NUM> fits in the fitting groove <NUM>. The elastic member <NUM> has a portion <NUM> fitting in the fitting groove <NUM>. A thickness of the elastic member <NUM> is larger than a depth of the fitting groove <NUM>, and thus the portion <NUM> of the elastic member <NUM> protrudes from the pressing surface <NUM>.

The movable shaft <NUM> is movable in an axial direction thereof in the housing <NUM>, and the movable shaft <NUM> can elevate the pressing tool <NUM>. The pressing surface <NUM> faces a back surface of the polishing tape <NUM>. When the movable shaft <NUM> elevates the pressing tool <NUM>, the portion <NUM> of the elastic member <NUM> is brought into contact with the back surface of the polishing tape <NUM>. During polishing of the wafer W, the elastic member <NUM> presses a polishing surface of the polishing tape <NUM> against a lower surface of the wafer W. The back surface of the polishing tape <NUM> is supported by the elastic member <NUM>. The back surface of the polishing tape <NUM> is an opposite side of the polishing tape <NUM> from the polishing surface having abrasive grains. During the polishing of the wafer W, the polishing tape <NUM> is advanced with a predetermined speed. As shown in <FIG>, the portion <NUM> of the elastic member <NUM> and the fitting groove <NUM> are inclined obliquely with respect to an advancing direction of the polishing tape <NUM>. Angles of the portion <NUM> of the elastic member <NUM> and the fitting groove <NUM> with respect to the advancing direction of the polishing tape <NUM> are not limited to the embodiment shown in <FIG>.

The elastic member <NUM> is made of a flexible material. Examples of the material constituting the elastic member <NUM> include rubbers, such as fluoro-rubber, silicone rubber, ethylene propylene diene rubber, or the like. A cross section of the elastic member <NUM> has a circular shape. The elastic member <NUM> may be an O-ring. A diameter of the elastic member <NUM> may preferably be in a range of <NUM> to <NUM>.

The elastic member <NUM> is detachably put on the pressing-tool body <NUM>. <FIG> is a diagram showing the pressing-tool body <NUM> from which the elastic member <NUM> has been removed. The fitting groove <NUM> extends straight across the pressing surface <NUM>, and a cross section of the fitting groove <NUM> has an arc shape. The elastic member <NUM> is secured to the pressing-tool body <NUM> by putting the elastic member <NUM> on the pressing-tool body <NUM> while fitting the elastic member <NUM> in the fitting groove <NUM> and stretching the elastic member <NUM>.

When the elastic member <NUM> is supported on the pressing-tool body <NUM> with the elastic member <NUM> elastically deformed, a tension is applied to the elastic member <NUM>. A radius of curvature of the cross section of the fitting groove <NUM> is smaller than a radius of the cross section of the elastic member <NUM> when the elastic member <NUM> is not elastically deformed. Therefore, the portion <NUM> of the elastic member <NUM> is in tight contact with a surface of the fitting groove <NUM> and is fixed in the fitting groove <NUM>. As a result, the elastic member <NUM> is secured stably to the pressing-tool body <NUM>.

In one embodiment, the cross-sectional shape of the elastic member <NUM> may be a polygon, such as a quadrangle or a hexagon, or a shape having an arc shape in a part of the cross section. The cross-sectional shape of the fitting groove <NUM> is not limited to the arc shape. In one embodiment, the cross section of the fitting groove <NUM> may have a rectangular shape.

When the elastic member <NUM> is held on the pressing-tool body <NUM>, the elastic member <NUM> is stretched, so that a contact surface of the elastic member <NUM>, which is to be brought into contact with the polishing tape <NUM>, is stretched and becomes smooth. As a result, the polishing head <NUM> can press the polishing tape <NUM> against the wafer W with a uniform force. Furthermore, since the elastic member <NUM> is in tight contact with the surface of the fitting groove <NUM> and is secured in the fitting groove <NUM>, the position of the elastic member <NUM> relative to the pressing-tool body <NUM> is not changed during the polishing of the wafer W.

The elastic member <NUM> is not fixed to the pressing-tool body <NUM> with a fixing tool, such as a screw, but is simply put on the pressing-tool body <NUM>. Therefore, when the elastic member <NUM> is deteriorated by the polishing, only the elastic member <NUM> can be easily replaced. As a result, the replacement work for the deteriorated member can be performed easily, and a cost of part replacement can be reduced.

Even if the portion <NUM> of the elastic member <NUM> is deteriorated by the polishing, one elastic member <NUM> can be reused multiple times by replacing a portion of the elastic member <NUM> fitting in the fitting groove <NUM> from one to anther within the same elastic member <NUM>. Therefore, a service life of the elastic member <NUM> can be extended, and the cost of part replacement can be further reduced.

As shown in <FIG>, the entire elastic member <NUM> surrounds the pressing-tool body <NUM>. The elastic member <NUM> is put only on the pressing surface <NUM> and side surfaces of the pressing-tool body <NUM>, and the elastic member <NUM> does not present on a back side of the pressing-tool body <NUM>. Therefore, an operator can easily remove only the elastic member <NUM> without removing the pressing-tool body <NUM> from the polishing head <NUM>. In one embodiment, the elastic member <NUM> may be put on an opposite side (back side) of the pressing-tool body <NUM> from the pressing surface <NUM>, but the configuration, in which the elastic member <NUM> is put on the pressing-tool body <NUM> without putting on the back side of the pressing-tool body <NUM>, can make the replacement of the elastic member <NUM> easier.

The pressing-tool body <NUM> of the present embodiment has a fitting groove <NUM> formed in a side surface of the pressing-tool body <NUM>, and the elastic member <NUM> fits in the fitting groove <NUM>. Specifically, the pressing-tool body <NUM> has the fitting groove <NUM> in a side surface <NUM>. The fitting groove <NUM> extends straight across the side surface <NUM>, and a cross section of the fitting groove <NUM> has an arc shape. Details of the fitting groove <NUM>, which will not be particularly described, are the same as those of the above-described fitting groove <NUM>, and duplicated descriptions will be omitted. The elastic member <NUM> of the present embodiment is put on the pressing-tool body <NUM> with the elastic member <NUM> elastically deformed, while the elastic member <NUM> fits in the fitting groove <NUM>. The elastic member <NUM> has a portion <NUM> fitting in the fitting groove <NUM>. The portion <NUM> of the elastic member <NUM> is in tight contact with a surface of the fitting groove <NUM> and is secured in the fitting groove <NUM>. As a result, the elastic member <NUM> is secured more stably to the pressing-tool body <NUM>.

The pressing-tool body <NUM> of the present embodiment has protrusions <NUM> and <NUM> on side surfaces of the pressing-tool body <NUM>. Specifically, the protrusion <NUM> is fixed to a side surface <NUM>, and the protrusion <NUM> is fixed to a side surface <NUM> which is an opposite side from the side surface <NUM>. In the present embodiment, the elastic member <NUM> is put on the protrusions <NUM> and <NUM> with the elastic member <NUM> elastically deformed, and the elastic member <NUM> is further supported by the protrusions <NUM> and <NUM>. As a result, the elastic member <NUM> is secured more stably to the pressing-tool body <NUM>. In one embodiment, the protrusion <NUM> may be integrally formed with the side surface <NUM>, and the protrusion <NUM> may be integrally formed with the side surface <NUM>.

In one embodiment, the side surface <NUM> of the pressing-tool body <NUM> may not have the fitting groove <NUM>. Even if the side surface <NUM> does not have the fitting groove <NUM>, the elastic member <NUM> can be secured stably to the pressing-tool body <NUM> when the elastic member <NUM> is put on the protrusions <NUM> and <NUM>. Further, in one embodiment, a protrusion capable of supporting the elastic member <NUM> may be fixed to the side surface <NUM>. In this case, the side surface <NUM> may not have the fitting groove <NUM>.

In one embodiment, the pressing-tool body <NUM> may include only one of the protrusions <NUM> and <NUM>. Further, in one embodiment, the pressing-tool body <NUM> may have a fitting groove, in which the elastic member <NUM> fits, in the side surface <NUM> and/or the side surface <NUM>. In this case, the pressing-tool body <NUM> may not have the protrusion <NUM> and/or the protrusion <NUM>. Even if the pressing-tool body <NUM> does not have the protrusion <NUM> and/or the protrusion <NUM>, the elastic member <NUM> can be secured stably to the pressing-tool body <NUM> when the elastic member <NUM> fits in the fitting groove(s) formed in the side surface <NUM> and/or the side surface <NUM>.

As shown in <FIG>, the movable shaft <NUM> is movable in the axial direction thereof in the housing <NUM>. In this embodiment, the movable shaft <NUM> is constituted of a ball spline shaft. A ball spline nut <NUM> is disposed in the housing <NUM>, so that the movable shaft <NUM> is supported movably in a vertical direction by the ball spline nut <NUM>. In one embodiment, the movable shaft <NUM> may be movably supported on an inner surface of the housing <NUM>.

The housing <NUM> includes a housing body 18A forming a space for housing the movable shaft <NUM> therein, and a lid 18B configured to close the space. The lid 18B is detachably fixed to the housing body 18A by screws <NUM>. The partition membrane <NUM> is in contact with the end portion (lower end) of the movable shaft <NUM>, and an edge of the partition membrane <NUM> is sandwiched between the housing body 18A and the lid 18B. The partition membrane <NUM> is only in contact with the movable shaft <NUM> and is not fixed to the movable shaft <NUM>.

The pressure chamber <NUM> is formed by the partition membrane <NUM> and the inner surface of the housing <NUM>. More specifically, the pressure chamber <NUM> is formed by the partition membrane <NUM> and an inner surface of the lid 18B. A compressed-gas flow passage <NUM> communicating with the pressure chamber <NUM> is formed in the lid 18B of the housing <NUM>. The compressed-gas flow passage <NUM> is coupled to a compressed-gas supply source <NUM> via a pressure regulator <NUM> and a switching valve <NUM>. The switching valve <NUM> is a valve configured to selectively communicate the compressed-gas flow passage <NUM> with the compressed-gas supply source <NUM> or the atmosphere. A three-way valve can be used as the switching valve <NUM>. A pump, or a compressed-gas supply line as a utility equipment preinstalled in a factory can be used as the compressed-gas supply source <NUM>.

The partition membrane <NUM> is made of a flexible material. Examples of the material constituting the partition membrane <NUM> include chloroprene rubber, fluoro-rubber, and silicone rubber. Chloroprene rubber having high bending fatigue resistance is preferably used.

When the wafer W is to be polished, the switching valve <NUM> is operated to allow the compressed-gas flow passage <NUM> to communicate with the compressed-gas supply source <NUM>. Compressed gas, such as compressed air, is supplied from the compressed-gas supply source <NUM> through the compressed-gas flow passage <NUM> into the pressure chamber <NUM>. A pressure of the compressed gas in the pressure chamber <NUM> is controlled by the pressure regulator <NUM>. The pressure of the compressed gas in the pressure chamber <NUM> acts on the end portion (lower end) of the movable shaft <NUM> through the partition membrane <NUM>, and elevates the movable shaft <NUM> and the pressing tool <NUM>. <FIG> is a diagram showing the movable shaft <NUM> and the pressing tool <NUM> when elevated. The elastic member <NUM> of the pressing tool <NUM> can press the polishing tape <NUM> against the lower surface of the wafer W.

As shown in <FIG>, when the elastic member <NUM> presses the polishing tape <NUM> against the lower surface of the wafer W, the polishing tape <NUM> bends in a direction toward the pressing-tool body <NUM>. Thus, in order to prevent the polishing tape <NUM> from coming into contact with the pressing-tool body <NUM>, the pressing-tool body <NUM> of the present embodiment further has a plurality of tapered surfaces 56a and 56b extending obliquely from the pressing surface <NUM>. More specifically, the tapered surface 56a extends obliquely downward from the pressing surface <NUM> and is coupled to the side surface <NUM>. The other tapered surface 56b extends obliquely downward from the pressing surface <NUM> and is coupled to a side surface <NUM> which is an opposite side from the side surface <NUM>. These tapered surfaces 56a and 56b can prevent the polishing tape <NUM> from contacting the pressing-tool body <NUM> when the elastic member <NUM> presses the polishing tape <NUM> against the lower surface of the wafer W.

When the polishing of the wafer W is to be terminated, the switching valve <NUM> is operated to allow the compressed-gas flow passage <NUM> to communicate with the atmosphere. The pressure chamber <NUM> is ventilated to the atmosphere, and as a result, the movable shaft <NUM> and the pressing tool <NUM> are lowered to a retracted position shown in <FIG> due to weight of the movable shaft <NUM> and tension of the polishing tape <NUM>.

At least a part of a distance sensor <NUM> configured to measure a movement distance of the movable shaft <NUM> relative to the housing <NUM> is disposed in the pressure chamber <NUM>. The entire distance sensor <NUM> may be disposed in the pressure chamber <NUM>. The distance sensor <NUM> of the present embodiment is a non-contact optical distance sensor. A distal end of the distance sensor <NUM> is oriented toward the end portion of the movable shaft <NUM>.

As shown in <FIG>, the pressing tool <NUM> is coupled to an upper end of the movable shaft <NUM> via a universal joint <NUM>. The universal joint <NUM> is disposed between the movable shaft <NUM> and the pressing tool <NUM>, and is housed inside the pressing tool <NUM>. Such an arrangement can reduce moment caused by a reaction force applied from the wafer W to the pressing tool <NUM> when the polishing tape <NUM> is in contact with the wafer W. As a result, a posture of the polishing head <NUM> can be stable.

The universal joint <NUM> allows the pressing tool <NUM> to tilt in all directions with respect to the movable shaft <NUM>. Therefore, when the pressing tool <NUM> presses the polishing tape <NUM> against the surface of the wafer W, the pressing tool <NUM> automatically becomes parallel to the surface of the wafer W. The universal joint <NUM> configured to tiltably support the pressing tool <NUM> allows the polishing tape <NUM> to be pressed uniformly against the surface of the wafer W.

As shown in <FIG>, a skirt <NUM> is fixed to the pressing tool <NUM>. The skirt <NUM> extends downward from the pressing tool <NUM> and surrounds an upper portion of the housing <NUM>. In the present embodiment, the skirt <NUM> has a cylindrical shape, but the skirt <NUM> may have another shape as long as it can surround the upper portion of the housing <NUM>. The skirt <NUM> can prevent liquid, such as pure water, used for the polishing of the wafer W from entering the universal joint <NUM> and the housing <NUM>.

Since the polishing head <NUM> having the above-described configuration is compact as a whole, the polishing head <NUM> can be arranged below the wafer W. Further, a plurality of polishing heads <NUM> can be arranged below the wafer W.

<FIG> is a perspective view showing another embodiment of the polishing head <NUM>. <FIG> is a diagram showing the polishing head <NUM> shown in <FIG> as viewed from a direction indicated by an arrow C in <FIG>. <FIG> is a plan view of the polishing head <NUM> shown in <FIG>. <FIG> is a cross-sectional view taken along a line D-D in <FIG>. <FIG> is a diagram showing the pressing-tool body <NUM> shown in <FIG> from which the elastic member <NUM> has been removed. <FIG> shows the elastic member <NUM> when pressing the polishing tape <NUM> against the lower surface of the wafer W. Details of the present embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to <FIG>, and duplicated descriptions will be omitted.

The pressing-tool body <NUM> of the present embodiment has a plurality of fitting grooves <NUM> in the pressing surface <NUM>. Specifically, the pressing-tool body <NUM> has two fitting grooves <NUM> in the pressing surface <NUM>. The two fitting grooves <NUM> are located away from each other, and are inclined obliquely with respect to the advancing direction of the polishing tape <NUM> when the pressing-tool body <NUM> is viewed from above. In this embodiment, the two fitting grooves <NUM> are arranged symmetrically about a center line L1 (see <FIG>) of the pressing surface <NUM> located between the side surface <NUM> and the side surface <NUM>. In one embodiment, the two fitting grooves <NUM> may be not arranged symmetrically about the center line L1 as long as the fitting grooves <NUM> are inclined obliquely with respect to the advancing direction of the polishing tape <NUM>. The pressing-tool body <NUM> includes a protrusion <NUM> fixed to the side surface <NUM> of the pressing-tool body <NUM>, and a plurality of protrusions <NUM> fixed to the side surface <NUM>. When the pressing-tool body <NUM> is viewed from above, the protrusion <NUM> is arranged on the center line L1. The two protrusions <NUM> are located away from each other and are arranged at the same height. When the pressing-tool body <NUM> is viewed from above, the two protrusions <NUM> are arranged symmetrically about the center line L1. The elastic member <NUM> is put on the protrusion <NUM> and the protrusions <NUM> with the elastic member <NUM> elastically deformed, while the elastic member <NUM> fits in the two fitting grooves <NUM>. With the above-described arrangement of the protrusion <NUM> and the protrusions <NUM>, the elastic member <NUM> can be secured stably to the pressing-tool body <NUM>. In one embodiment, the protrusion <NUM> may not be arranged on the center line L1, and the two protrusions <NUM> may not be arranged symmetrically about the center line L1, as long as the protrusion <NUM> and the protrusions <NUM> are arranged such that the elastic member <NUM> can be stably secured to the pressing-tool body <NUM>.

The elastic member <NUM> has two portions <NUM> fitting in the two fitting grooves <NUM>, respectively. These two portions <NUM> protrude from the pressing surface <NUM>. The two portions <NUM> of the elastic member <NUM> can increase a contact area between the polishing tape <NUM> and the elastic member <NUM>, and can increase a polishing rate of the wafer W. According to the configuration of the present embodiment described above, the two portions <NUM> can be configured by the single elastic member <NUM>. As a result, the polishing rate of the wafer W can be increased with a low-cost configuration.

In one embodiment, the number of protrusions <NUM> may not be two. For example, the pressing-tool body <NUM> may include a single laterally-elongated protrusion <NUM> or may include three or more protrusions <NUM>. Further, in one embodiment, the plurality of protrusions <NUM> may not be arranged at the same height as long as the elastic member <NUM> can be stably secured to the pressing-tool body <NUM>.

<FIG> is a cross-sectional view showing still another embodiment of the polishing head <NUM>. Details of the present embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to <FIG>, and duplicated descriptions will be omitted. The elastic member <NUM> of the present embodiment is covered with a coating layer <NUM> containing a fluororesin. The coating layer <NUM> covering the elastic member <NUM> can reduce a sliding resistance between the elastic member <NUM> and the back surface of the polishing tape <NUM> during the polishing of the wafer W. As a result, during the polishing of the wafer W, the polishing tape <NUM> can be advanced smoothly, and a force required to advance the polishing tape <NUM> can be reduced. The polishing head <NUM> of the present embodiment can also be applied to the embodiments described with reference to <FIG>.

<FIG> is a diagram showing an embodiment of a polishing apparatus including the polishing head <NUM>. A polishing apparatus <NUM> shown in <FIG> includes a substrate holder <NUM> configured to hold a wafer W, which is an example of a substrate, and rotate the wafer W about its own axis, the above-described polishing head <NUM> configured to bring a polishing tape <NUM> as a polishing tool into contact with a first surface <NUM> of the wafer W held by the substrate holder <NUM> to polish the first surface <NUM> of the wafer W, and a polishing-tape supply mechanism <NUM> configured to supply the polishing tape <NUM> to the polishing head <NUM>.

The substrate holder <NUM> includes a plurality of rollers <NUM> which can contact a periphery of the wafer W, and a roller-rotating mechanism (not shown) configured to rotate the plurality of rollers <NUM> about their respective own axes. The polishing head <NUM> is arranged below the wafer W held by the substrate holder <NUM>. A part of the substrate holder <NUM> is not shown in <FIG>. The substrate holder <NUM> of the present embodiment includes four rollers <NUM> (two of which are not shown).

In the present embodiment, the first surface <NUM> of the wafer W is a back surface of the wafer W on which no device is formed or no device is to be formed, i.e., a non-device surface. A second surface <NUM> of the wafer W opposite to the first surface <NUM> is a surface on which devices are formed or devices are to be formed, i.e., a device surface. In this embodiment, the wafer W is held by the substrate holder <NUM> horizontally with the first surface <NUM> facing downward.

The roller-rotating mechanism is configured to rotate the four rollers <NUM> with the same speed in the same direction. During polishing of the first surface <NUM> of the wafer W, the periphery of the wafer W is held by the rollers <NUM>. The wafer W is held horizontally, and is rotated about its own axis by the rotations of the rollers <NUM>. During the polishing of the first surface <NUM> of the wafer W, the four rollers <NUM> rotate about their respective own axes, but the positions of the rollers <NUM> themselves are stationary.

As shown in <FIG>, a rinsing-liquid supply nozzle <NUM> configured to supply a rinsing liquid (e.g., pure water or an alkaline chemical solution) to the first surface <NUM> of the wafer W is disposed below the wafer W held by the substrate holder <NUM>. The rinsing-liquid supply nozzle <NUM> is coupled to a not-shown rinsing-liquid supply source. The rinsing-liquid supply nozzle <NUM> is oriented toward the center O1 of the first surface <NUM> of the wafer W. The rinsing liquid is supplied from the rinsing-liquid supply nozzle <NUM> to the first surface <NUM> of the wafer W, and spreads over the first surface <NUM> of the wafer W due to centrifugal force. The rinsing liquid flows on the first surface <NUM> of the wafer W outward in a radial direction, whereby polishing debris can be removed from the first surface <NUM> of the wafer W.

A protecting-liquid supply nozzle <NUM> configured to supply a protecting liquid (e.g., pure water) onto the second surface <NUM> of the wafer W is disposed above the wafer W held by the substrate holder <NUM>. The protecting-liquid supply nozzle <NUM> is coupled to a not-shown protecting-liquid supply source. The protecting-liquid supply nozzle <NUM> is oriented toward the center of the second surface <NUM> of the wafer W. The protecting liquid is supplied from the protecting-liquid supply nozzle <NUM> to the center of the second surface <NUM> of the wafer W, and spreads over the second surface <NUM> of the wafer W due to the centrifugal force. The protecting liquid prevents the rinsing liquid containing the polishing debris and foreign matter generated by the polishing of the wafer W from contacting the second surface <NUM> of the wafer W and adhering to the second surface of the wafer W. As a result, the second surface <NUM> of the wafer W can be kept clean.

The polishing head <NUM> is supported by a support member <NUM>, and the support member <NUM> is fixed to a movable plate <NUM>. Therefore, the entire polishing head <NUM> can be moved together with the movable plate <NUM>. The support member <NUM> has a not-shown through-hole, and the polishing tape <NUM> extends through the through-hole.

The polishing-tape supply mechanism <NUM> includes a tape feeding reel <NUM> configured to supply the polishing tape <NUM> and a tape take-up reel <NUM> configured to collect the polishing tape <NUM>. The tape feeding reel <NUM> and the tape take-up reel <NUM> are coupled to tension motors 143a and 144a, respectively. These tension motors 143a and 144a are fixed to a reel base <NUM> and are configured to apply predetermined torques to the tape feeding reel <NUM> and the tape take-up reel <NUM> to thereby apply a predetermined tension to the polishing tape <NUM>. The reel base <NUM> is fixed to the movable plate <NUM>, so that the entire polishing-tape supply mechanism <NUM> can move together with the movable plate <NUM>.

A tape advancing device <NUM> configured to advance the polishing tape <NUM> in a longitudinal direction thereof is provided between the tape feeding reel <NUM> and the tape take-up reel <NUM>. The tape advancing device <NUM> includes a tape advancing roller <NUM> configured to advance the polishing tape <NUM>, a nip roller <NUM> configured to press the polishing tape <NUM> against the tape advancing roller <NUM>, and a tape advancing motor <NUM> configured to rotate the tape advancing roller <NUM>. The polishing tape <NUM> is sandwiched between the nip roller <NUM> and the tape advancing roller <NUM>. When the tape advancing motor <NUM> rotates the tape advancing roller <NUM> in a direction indicated by an arrow in <FIG>, the polishing tape <NUM> is advanced or fed from the tape feeding reel <NUM> to the tape take-up reel <NUM> via the pressing tool <NUM> of the polishing head <NUM>. An advancing speed of the polishing tape <NUM> can be changed by changing a rotation speed of the tape advancing motor <NUM>. In one embodiment, the direction in which the polishing tape <NUM> is advanced may be opposite to the direction indicated by arrows in <FIG> (an arrangement of the tape feeding reel <NUM> and the tape take-up reel <NUM> may be interchanged). Also in this case, the tape advancing device <NUM> is disposed at the tape take-up reel <NUM> side. The polishing tape <NUM> is supplied to the pressing tool <NUM> such that a polishing surface 3a of the polishing tape <NUM> faces the first surface <NUM> of the wafer W.

The polishing apparatus <NUM> further includes a plurality of guide rollers 153a, 153b, 153c, and 153d configured to support the polishing tape <NUM>. The polishing tape <NUM> is guided so as to surround the polishing head <NUM> by these guide rollers 153a, 153b, 153c, and 153d. The polishing head <NUM> polishes the first surface <NUM> of the wafer W by pressing the polishing tape <NUM> from the back side thereof against the first surface <NUM> of the wafer W with the pressing tool <NUM>. The guide rollers 153b and 153c arranged at an upper portion of the polishing head <NUM> guide the polishing tape <NUM> such that the polishing tape <NUM> advances in a direction parallel to the first surface <NUM> of the wafer W.

The tape advancing device <NUM> and the guide rollers 153a, 153b, 153c, and 153d are fixed to a not-shown holding member, which is fixed to the movable plate <NUM>.

In order to bring the polishing tape <NUM> into contact with a region ranging from the center O1 to an outermost portion of the first surface <NUM> of the wafer W, the polishing apparatus <NUM> of the present embodiment includes a polishing-head moving mechanism <NUM> configured to translate the polishing head <NUM> relative to the substrate holder <NUM>. The polishing-head moving mechanism <NUM> is configured to move the polishing head <NUM> between the center O1 of the first surface <NUM> of the wafer W and the outermost portion of the first surface <NUM>.

A plurality of linear-motion guides <NUM> are fixed to a lower surface of the movable plate <NUM>, and the movable plate <NUM> is supported by the plurality of linear-motion guides <NUM>. The plurality of linear-motion guides <NUM> are disposed on a mounting surface <NUM>. The movable plate <NUM> is moved by the polishing-head moving mechanism <NUM> and the linear-motion guide <NUM> restricts the movement of the movable plate <NUM> to a linear motion in the radial direction of the wafer W.

The polishing-head moving mechanism <NUM> includes a ball-screw mechanism <NUM> and a motor <NUM> configured to drive the ball-screw mechanism <NUM>. A servo motor can be used as the motor <NUM>. The movable plate <NUM> is coupled to a screw shaft 193b of the ball-screw mechanism <NUM>. When the polishing-head moving mechanism <NUM> operates, the polishing head <NUM>, the polishing-tape supply mechanism <NUM>, the tape advancing device <NUM>, and the guide rollers 153a, 153b, 153c, and 153d are moved in the radial direction of the wafer W relative to the substrate holder <NUM>.

During the polishing of the wafer W, the polishing-head moving mechanism <NUM> moves the polishing head <NUM> between the center O1 of the first surface <NUM> of the wafer W and the outermost portion of the first surface <NUM>. The polishing apparatus <NUM> further includes an operation controller <NUM> configured to control operations of each component of the polishing apparatus <NUM>. The polishing-head moving mechanism <NUM> is electrically coupled to the operation controller <NUM>, so that operations of the polishing-head moving mechanism <NUM> are controlled by the operation controller <NUM>. When the polishing-head moving mechanism <NUM> operates, the polishing head <NUM>, the polishing-tape supply mechanism <NUM>, the tape advancing device <NUM>, and the guide rollers 153a, 153b, 153c, and 153d are moved together.

During the polishing of the wafer W, the wafer W is rotated by the rollers <NUM>. All the rollers <NUM> rotate about their own axes, but the positions of these rollers <NUM> are fixed. Therefore, even if the polishing head <NUM> is moved from the center side of the wafer W to the outer side of the wafer W by the polishing-head moving mechanism <NUM>, the rollers <NUM> do not contact the polishing head <NUM>. As a result, the polishing tape <NUM> can polish the entire first surface <NUM> including the outermost portion of the wafer W.

<FIG> is a plan view showing an arrangement of the polishing head <NUM>. As shown in <FIG>, the portion <NUM> of the elastic member <NUM> fitting in the fitting groove <NUM> is shorter than a radius of the wafer W. The portion <NUM> of the elastic member <NUM> and the fitting groove <NUM> extend obliquely with respect to the advancing direction (indicated by an arrow E) of the polishing tape <NUM>. In this embodiment, the advancing direction E of the polishing tape <NUM> coincides with the longitudinal direction of the polishing tape <NUM>. Since the portion <NUM> of the elastic member <NUM> fitting in the fitting groove <NUM> is inclined obliquely with respect to the advancing direction E of the polishing tape <NUM> (i.e., the longitudinal direction of the polishing tape <NUM>), an unused polishing tape <NUM> can be brought into contact with the wafer W even at the downstream side (in the case of this embodiment, an outer peripheral side of the wafer W) of the advancing direction E of the polishing tape <NUM>. As a result, the polishing rate can be prevented from decreasing due to the use of the polishing tape <NUM> deteriorated by the polishing. In one embodiment, the portion <NUM> of the elastic member <NUM> fitting in the fitting groove <NUM> may be longer than the radius of the wafer W. Further, in one embodiment, the portion <NUM> of the elastic member <NUM> fitting in the fitting groove <NUM> may be perpendicular to the advancing direction E of the polishing tape <NUM>.

The operations of the polishing apparatus <NUM> of this embodiment will now be described. The operations of the polishing apparatus <NUM> described below are controlled by the operation controller <NUM> shown in <FIG>. The operation controller <NUM> is electrically coupled to the substrate holder <NUM>, the polishing head <NUM>, the polishing-tape supply mechanism <NUM>, the tape advancing device <NUM>, and the polishing-head moving mechanism <NUM>. The operations of the substrate holder <NUM>, the rinsing-liquid supply nozzle <NUM>, the protecting-liquid supply nozzle <NUM>, the polishing head <NUM>, the polishing-tape supply mechanism <NUM>, the tape advancing device <NUM>, and the polishing-head moving mechanism <NUM> are controlled by the operation controller <NUM>.

The operation controller <NUM> is composed of at least one computer. The operation controller <NUM> includes a memory 180a and an arithmetic device 180b. The arithmetic device 180b includes a CPU (central processing unit), a GPU (graphic processing unit), etc. configured to perform arithmetic operations according to instructions contained in programs stored in the memory 180a. The memory 180a includes a main memory (e.g., a random-access memory) to which the arithmetic device 180b is accessible, and an auxiliary memory (e.g., a hard disk drive or a solid state drive) storing data and the programs therein.

The wafer W to be polished is held by the rollers <NUM> of the substrate holder <NUM> with the first surface <NUM> facing downward, and is further rotated about the axis of the wafer W. Specifically, the substrate holder <NUM> rotates the wafer W by rotating the plurality of rollers <NUM> about their own axes while the plurality of rollers <NUM> are in contact with the periphery of the wafer W with the first surface <NUM> of the wafer W facing downward. Next, the rinsing liquid is supplied from the rinsing-liquid supply nozzle <NUM> to the first surface <NUM> of the wafer W, and the protecting liquid is supplied from the protecting-liquid supply nozzle <NUM> onto the second surface <NUM> of the wafer W. The rinsing liquid flows radially outward on the first surface <NUM> of the wafer W, and the protective liquid spreads over the entire second surface <NUM> of the wafer W due to the centrifugal force.

The polishing-head moving mechanism <NUM> moves the polishing head <NUM> to a position below the center O1 of the first surface <NUM> of the wafer W. The operation controller <NUM> operates the polishing-tape supply mechanism <NUM> and the tape advancing device <NUM> to advance the polishing tape <NUM> in the longitudinal direction thereof with a predetermined speed while the predetermined tension is applied to the polishing tape <NUM>. Next, the polishing head <NUM> brings the polishing surface 3a of the polishing tape <NUM> into contact with the first surface <NUM> of the wafer W to start the polishing of the first surface <NUM> of the wafer W in the presence of the rinsing liquid. Further, the polishing-head moving mechanism <NUM> moves the polishing head <NUM>, the polishing-tape supply mechanism <NUM>, the guide rollers 153a, 153b, 153c, and 153d, and the tape advancing device <NUM> outward in the radial direction of the wafer W, while the polishing head <NUM> presses the first surface <NUM> of the wafer W with the polishing tape <NUM>. During the polishing of the wafer W, the rinsing-liquid supply nozzle <NUM> and the protecting-liquid supply nozzle <NUM> continuously supply the rinsing liquid and the protecting liquid to the wafer W.

When the polishing head <NUM> reaches the outermost portion of the first surface <NUM> of the wafer W, the operation controller <NUM> terminates the polishing of the wafer W. Specifically, the polishing head <NUM> lowers the pressing tool <NUM> to separate the polishing tape <NUM> from the first surface <NUM> of the wafer W. Thereafter, the operation controller <NUM> stops the operations of the substrate holder <NUM>, the rinsing-liquid supply nozzle <NUM>, the protecting-liquid supply nozzle <NUM>, the polishing-tape supply mechanism <NUM>, and the tape advancing device <NUM> to terminate the polishing the wafer W. In one embodiment, the polishing-head moving mechanism <NUM> may reciprocate the polishing head <NUM> between the outermost portion and the center O1 of the first surface <NUM> of the wafer W.

<FIG> is a diagram showing another embodiment of the polishing apparatus <NUM>. <FIG> is a top view of the polishing apparatus <NUM> shown in <FIG>. Details of the present embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to <FIG> and <FIG>, and duplicated descriptions will be omitted. The rinsing-liquid supply nozzle <NUM> is not shown in <FIG>. The polishing apparatus <NUM> of the present embodiment includes polishing-head assemblies 11A and 11B, polishing-tape supply mechanisms 141A and 141B configured to supply polishing tapes <NUM> to the polishing head assemblies 11A and 11B, respectively, and tape advancing devices 146A and 146B configured to advance the polishing tapes <NUM> in the longitudinal direction thereof. The polishing head assembly 11A includes polishing heads 10A and 10B. Similarly, the polishing head assembly 11B includes polishing heads 10A and 10B. The polishing head assembly 11A is supported by a support member 131A, and the polishing head assembly 11B is supported by a support member 131B. The polishing tape <NUM> supplied to the polishing head assembly 11A is supported by guide rollers 353a, 353b, 353c, and 353d, and the polishing tape <NUM> supplied to the polishing head assembly 11B is supported by guide rollers 453a, 453b, 453c, and 453d. The polishing head 10A corresponds to the polishing head <NUM> described with reference to <FIG>, and the polishing head 10B corresponds to the polishing head <NUM> described with reference to <FIG>. Configurations of the polishing-tape supply mechanisms 141A and 141B, the tape advancing devices 146A and 146B, the support members 131A and 131B, the guide rollers 353a, 353b, 353c, and 353d, and the guide rollers 453a, 453b, 453c, and 453d are the same as the configurations of the polishing-tape supply mechanism <NUM>, the tape advancing device <NUM>, the support member <NUM>, and the guide rollers 153a, 153b, 153c, and 153d described with reference to <FIG>. The polishing apparatus <NUM> of the present embodiment does not include the polishing-head moving mechanism <NUM>. Therefore, during the polishing, positions of the polishing head assemblies 11A and 11B are fixed. The coating layer <NUM> described with reference to <FIG> can be applied to the polishing heads 10A and 10B of the present embodiment.

The plurality of polishing heads 10A and 10B are arranged at different distances from an axis CP of the substrate holder <NUM> (or the center O1 of the first surface <NUM> of the wafer W). A distance d1 from the axis CP of the substrate holder <NUM> to an outermost end of the entire plurality of portions <NUM> is longer than a radius d2 of the wafer W.

During the polishing, the tape advancing device 146A advances the polishing tape <NUM> in a direction indicated by an arrow F in <FIG> and <FIG>, and the tape advancing device 146B advances the polishing tape <NUM> in a direction indicated by an arrow G in <FIG> and <FIG>. Specifically, each polishing tape <NUM> is advanced from a central portion toward an outer peripheral portion of the wafer W. As a result, the polishing debris generated by the polishing of the wafer W can be discharged efficiently from the center portion of the wafer W to the outside of the wafer W. The plurality of polishing heads 10A and 10B are configured to be operable independently of each other. The polishing heads 10A and 10B of the polishing head assembly 11A are arranged along the advancing direction F of the polishing tape <NUM> (i.e., the longitudinal direction of the polishing tape <NUM>) with a gap therebetween. The polishing heads 10A and 10B of the polishing head assembly 11B are arranged along the advancing direction G of the polishing tape <NUM> (i.e., the longitudinal direction of the polishing tape <NUM>) with a gap therebetween. Each of the plurality of portions <NUM> of the present embodiment extends obliquely with respect to the advancing directions F and G of the polishing tape <NUM>. When viewed from the advancing direction F or the advancing direction G of the polishing tape <NUM>, the plurality of portions <NUM> are continuously arranged along a direction perpendicular to the advancing directions F and G of the polishing tape <NUM>. Further, when viewed from the advancing direction F or the advancing direction G of the polishing tape <NUM>, the plurality of portions <NUM> are continuously arranged with no gap.

The plurality of portions <NUM> are not aligned in a straight line, but these portions <NUM> are located at different distances from the axial center CP of the substrate holder <NUM>. Therefore, when the wafer W is rotating, each region of the first surface <NUM> of the wafer W passes through any of the plurality of portions <NUM>. As a result, the plurality of elastic members <NUM> can press the polishing tape <NUM> against the entire surface of the first surface <NUM> of the wafer W.

<FIG> is a diagram showing another embodiment of the polishing head <NUM>. The polishing head <NUM> of the present embodiment is also suitably used for a polishing apparatus that polishes a periphery of a substrate (e.g., a wafer). In the present specification, the periphery of the substrate is defined as a region including a bevel portion located at the outermost periphery of the substrate and a top-edge portion and a bottom-edge portion located radially inwardly of the bevel portion.

<FIG> are enlarged cross-sectional views showing the periphery of the substrate. More specifically, <FIG> is a cross-sectional view of a substrate of a so-called straight type, and <FIG> is a cross-sectional view of a substrate of a so-called round type. In the substrate Wf of <FIG>, the bevel portion is an outermost peripheral surface (indicated by symbol B) constituting an upper slope portion (or an upper bevel portion) P, a lower slope portion (or a lower bevel portion) Q, and a side portion (or an apex) R of the substrate Wf. In the substrate Wf of <FIG>, the bevel portion is a portion (indicated by symbol B) constituting an outermost peripheral surface of the substrate Wf and having a curved cross section. The top-edge portion is an annular flat portion E1 located radially inwardly of the bevel portion B, and located in a device surface of the substrate Wf. The bottom-edge portion is an annular flat portion E2 located at an opposite side from the top-edge portion and located radially inwardly of the bevel portion B. The top-edge portion E1 may include a region in which devices are formed.

Referring back to <FIG>, the polishing head <NUM> includes a pressing mechanism <NUM> configured to press a polishing surface 3a of a polishing tape <NUM> against a wafer W with a predetermined force. Further, the polishing head <NUM> includes a tape advancing device <NUM> configured to advance the polishing tape <NUM> from a later-described tape feeding reel <NUM> (not shown in <FIG>) to a later-described tape take-up reel <NUM> (not shown in <FIG>). The polishing head <NUM> has a plurality of guide rollers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and these guide rollers are arranged to guide the polishing tape <NUM> such that the polishing tape <NUM> advances in a direction perpendicular to a tangential direction of the wafer W.

The tape advancing device <NUM> provided on the polishing head <NUM> includes a tape advancing roller 252a, a tape holding roller 252b, and a motor M configured to rotate the tape advancing roller 252a. The motor M is mounted to a side surface of the polishing head <NUM>, and the tape advancing roller 252a is attached to a rotating shaft of the motor M. The tape holding roller 252b is arranged adjacent to the tape advancing roller 252a. The tape holding roller 252b is supported by a not-shown mechanism that generate a force in a direction indicated by an arrow NF in <FIG> (direction toward the tape advancing roller 252a), so that the tape holding roller 252b presses the tape advancing roller 252a.

When the motor M rotates in a direction indicated by an arrow shown in <FIG>, the tape advancing roller 252a rotates and can advance the polishing tape <NUM> from the tape feeding reel <NUM> (not shown in <FIG>) via the polishing head <NUM> to the tape take-up reel <NUM> (not shown in <FIG>). The tape holding roller 252b is configured to rotate about its own axis and rotates as the polishing tape <NUM> is advanced.

The pressing mechanism <NUM> includes a pressing tool <NUM> configured to press the polishing tape <NUM> against the wafer W, and an air cylinder (or driving mechanism) <NUM> configured to move the polishing tool <NUM> toward the periphery of the wafer W. The air cylinder <NUM> is a so-called single rod cylinder. By controlling an air pressure supplied to the air cylinder <NUM>, a force for pressing the polishing tape <NUM> against the wafer W is regulated. The pressing tool <NUM> is disposed at a back side of the polishing tape <NUM>.

<FIG> is a diagram of the pressing tool <NUM> of the present embodiment as viewed from a front side (polishing-tape side). <FIG> is a diagram of the pressing tool <NUM> shown in <FIG> as viewed from a side surface <NUM>. <FIG> is a diagram of the pressing tool <NUM> shown in <FIG> as viewed from a side surface <NUM>. Details of the pressing tool <NUM> of the present embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to <FIG>, and duplicated descriptions will be omitted. As shown in <FIG>, a pressing-tool body <NUM> of the pressing tool <NUM> of the present embodiment includes two raised portions 43a and 43b with a gap therebetween and a base portion 43c coupled to the raised portions 43a and 43b. The raised portion 43a and the raised portion 43b are arranged in parallel. The raised portions 43a and 43b and the base portion 43c may be formed integrally.

The raised portion 43a has a pressing surface 44a, and the raised portion 43b has a pressing surface 44b. In other words, the pressing surface <NUM> of the present embodiment is constituted of the pressing surface 44a and the pressing surface 44b arranged with a gap therebetween. The pressing surface 44a and the pressing surface 44b are arranged in parallel. The pressing surfaces 44a and 44b have fitting grooves 45a and 45b, respectively. When viewed from the front side of the pressing tool <NUM>, the fitting grooves 45a and 45b are arranged symmetrically about a center line Ct and are curved inward toward the center line Ct. More specifically, the fitting grooves 45a and 45b have an arc shape having the same curvature as a curvature of the wafer W (not shown in <FIG>) as an object to be polished, which will be described later.

The pressing tool <NUM> includes two elastic members 40a and 40b. The elastic member 40a is put on the pressing-tool body <NUM> with the elastic member 40a elastically deformed, while the elastic member 40a fits in the fitting groove 45a. The elastic member 40b is put on the pressing-tool body <NUM> with the elastic member 40b elastically deformed, while the elastic member 40b fits in the fitting groove 45b. The elastic member 40a has a portion 41a fitting in the fitting groove 45a, and the elastic member 40b has a portion 41b fitting in the fitting groove 45b. These portions 41a and 41b protrude from the pressing surfaces 44a and 44b, respectively. The portions 41a and 41b of the elastic members 40a and 40b are curved inward toward the center line Ct and have the same curvature as the curvature of the wafer W.

The pressing-tool body <NUM> of the present embodiment has two fitting grooves 60a and 60b located in a back surface <NUM> which is an opposite side from the pressing surfaces 44a and 44b. The fitting grooves 60a and 60b extend from the side surface <NUM> to the other side surface <NUM>. The elastic member 40a fits in the fitting groove 60a, and the elastic member 40b fits in the fitting groove 60b. As a result, the elastic member <NUM> is secured stably to the pressing-tool body <NUM>. In one embodiment, the pressing-tool body <NUM> may have fitting grooves, in which the elastic members 40a and 40b fit, in the side surface <NUM> and/or the side surface <NUM>.

The raised portion 43a has a tapered surface 56a extending obliquely from the pressing surface 44a, and the raised portion 43b has a tapered surface 56b extending obliquely from the pressing surface 44b. More specifically, the tapered surface 56a extends obliquely from the pressing surface 44a toward the base portion 43c and is coupled to a side surface 47a. The tapered surface 56b extends obliquely from the pressing surface 44b toward the base portion 43c and is coupled to a side surface 50a. These tapered surfaces 56a and 56b can prevent the polishing tape <NUM> from contacting the pressing-tool body <NUM> when the elastic members 40a and 40b press the polishing tape <NUM> against the wafer W. The coating layer <NUM> described with reference to <FIG> can be applied to the pressing tool <NUM> of the present embodiment.

<FIG> and <FIG> are diagrams showing another embodiment of the pressing tool <NUM> described with reference to <FIG>. <FIG> is a diagram of the pressing tool <NUM> as viewed from the side surface <NUM>. <FIG> is a diagram of the polishing tool <NUM> as viewed from the side surface <NUM>. As shown in <FIG> and <FIG>, the embodiment described with reference to <FIG> may be applied to the pressing tool <NUM> described with reference to <FIG>. Details of the pressing tool <NUM> of the present embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to <FIG> and <FIG>, and duplicated descriptions will be omitted. The pressing-tool body <NUM> of the present embodiment has a protrusion <NUM> on the side surface <NUM>, and has a protrusion <NUM> on the side surface <NUM>. The pressing-tool body <NUM> does not have the fitting grooves 60a and 60b. In the present embodiment, the pressing-tool body <NUM> includes one protrusion <NUM> and one protrusion <NUM>, while in one embodiment, the pressing-tool body <NUM> may have two or more protrusions <NUM> and two or more protrusions <NUM>.

In the present embodiment, the two portions 41a and 41b fitting in the fitting grooves 45a and 45b, respectively, can be configured by one elastic member <NUM>. As a result, a cost of replacement parts can be reduced. In addition, since the elastic member <NUM> of the present embodiment is not supported by the back surface <NUM> of the pressing-tool body <NUM>, the elastic member <NUM> can be replaced easily.

<FIG> is a diagram showing an embodiment of a polishing apparatus including the polishing head <NUM> described with reference to <FIG> and <FIG>. A polishing apparatus <NUM> shown in <FIG> is suitably used as a polishing apparatus that polishes a periphery of a substrate (e.g., a wafer). The polishing apparatus <NUM> includes a substrate holder <NUM> configured to hold and rotate a wafer W, which is an object to be polished, polishing head <NUM> configured to bring a polishing tool into contact with a periphery of the wafer W held by the substrate holder <NUM> to polish the periphery of the wafer W, a lower supply nozzle <NUM> configured to supply liquid to a lower surface of the wafer W, and an upper supply nozzle <NUM> configured to supply liquid onto an upper surface of the wafer W. An example of the liquid supplied to the wafer W includes pure water. During the polishing of the wafer W, the liquid is supplied from the lower supply nozzle <NUM> to the lower surface of the wafer, and the liquid is supplied from the upper supply nozzle <NUM> to the upper surface of the wafer W.

<FIG> shows the substrate holder <NUM> holding the wafer W. When the wafer W is held by the substrate holder <NUM>, the polishing head <NUM> faces the periphery of the wafer W. The substrate holder <NUM> includes a holding stage <NUM> configured to hold the wafer W by vacuum suction, a shaft <NUM> coupled to a central portion of the holding stage <NUM>, and a holding-stage driving mechanism <NUM> configured to rotate and vertically move the holding stage <NUM>. The holding-stage driving mechanism <NUM> is configured to be able to rotate the holding stage <NUM> about its own axis Cr and move the holding stage <NUM> in a vertical direction along the axis Cr.

The holding stage <NUM>, the polishing head <NUM>, the lower supply nozzle <NUM>, the upper supply nozzle <NUM>, and the holding stage <NUM> are disposed inside a partition wall <NUM>. The inside of the partition wall <NUM> constitutes a polishing chamber in which the wafer W is polished. The partition wall <NUM> is arranged on a base plate <NUM>. The shaft <NUM> extends through the base plate <NUM>.

The holding-stage driving mechanism <NUM> includes a motor <NUM> as a stage rotating device configured to rotate the holding stage <NUM>, and an air cylinder <NUM> configured to vertically move the holding stage <NUM>. The motor <NUM> is fixed to a lower surface of the base plate <NUM>. The holding stage <NUM> is rotated by the motor <NUM> via the shaft <NUM>, a pulley 211a coupled to the shaft <NUM>, a pulley 211b attached to a rotating shaft of the motor <NUM>, and a belt <NUM> put on the pulleys 211a and 211b. The axis of rotation of the motor <NUM> extends parallel to the shaft <NUM>. With such a configuration, the wafer W held on an upper surface of the holding stage <NUM> is rotated by the motor <NUM>. The shaft <NUM> is coupled to the air cylinder <NUM> via a rotary joint <NUM> attached to a lower end of the shaft <NUM>, and the shaft <NUM> and the holding stage <NUM> can be raised and lowered by the air cylinder <NUM>.

The wafer W is placed on the upper surface of the holding stage <NUM> by a not-shown transfer mechanism such that the center O1 of the wafer W is on the axis Cr of the holding stage <NUM>. The wafer W is held on the upper surface of the holding stage <NUM> with a device surface of the wafer W facing upward. With such a configuration, the substrate holder <NUM> can rotate the wafer W about the axis Cr of the holding stage <NUM> (i.e., the axis of the wafer W), and can raise and lower the wafer W along the axis Cr of the holding stage <NUM>.

In the present embodiment, a polishing tape <NUM> having abrasive grains on its surface is used as an example of the polishing tool. The polishing apparatus <NUM> further includes a polishing-tape supply mechanism <NUM> configured to supply the polishing tape <NUM> to the polishing head <NUM> and configured to collect the polishing tape <NUM> from the polishing head <NUM>. The polishing-tape supply mechanism <NUM> is arranged outside the partition wall <NUM>. The polishing-tape supply mechanism <NUM> includes a tape feeding reel <NUM> configured to supply the polishing tape <NUM> to the polishing head <NUM>, and a tape take-up reel <NUM> configured to collect the polishing tape <NUM> that has been used for the polishing of the wafer W. Not-shown tension motors are coupled to the tape feeding reel <NUM> and the tape take-up reel <NUM>, respectively. The tension motors apply a predetermined torque to the tape feeding reel <NUM> and the tape take-up reel <NUM>, so that a predetermined tension can be generated in the polishing tape <NUM>.

The polishing tape <NUM> is supplied to the polishing head <NUM> such that a polishing surface of the polishing tape <NUM> faces the periphery of the wafer W. The polishing tape <NUM> is supplied from the tape feeding reel <NUM> to the polishing head <NUM> through an opening 260a provided in the partition wall <NUM>, and the used polishing tape <NUM> is collected by the tape take-up reel <NUM> through the opening 260a. The polishing-tape supply mechanism <NUM> further includes a plurality of guide rollers <NUM>, <NUM>, <NUM>, and <NUM> for supporting the polishing tape <NUM>. An advancing direction of the polishing tape <NUM> is guided by the guide rollers <NUM>, <NUM>, <NUM>, and <NUM>.

The polishing apparatus <NUM> further includes a not-shown tilting mechanism. The polishing apparatus <NUM> can polish the periphery of the wafer W while changing a tilt angle of the polishing head <NUM> by the tilting mechanism. <FIG> is a diagram showing the polishing head <NUM> tilted upward by the tilting mechanism (not shown). <FIG> is a diagram showing the polishing head <NUM> tilted downward by the tilting mechanism.

As shown in <FIG>, when the polishing head <NUM> is tilted upward, the portion 41a of the elastic member 40a is located above the periphery of the wafer W and faces the top-edge portion. As shown in <FIG>, when the polishing head <NUM> is tilted downward, the portion 41b of the elastic member 40b is located below the periphery of the wafer W and faces the bottom-edge portion. When the top-edge portion is to be polished, the polishing surface 3a of the polishing tape <NUM> is pressed against the periphery (i.e., the top-edge portion) of the wafer W by the portion 41a of the elastic member 40a with the polishing head <NUM> tilted upward. When the bottom-edge portion is to be polished, the polishing surface 3a of the polishing tape <NUM> is pressed against the periphery (i.e., the bottom-edge portion) of the wafer W by the portion 41b with the polishing head <NUM> tilted downward. Pressing forces of these portions 41a and 41b can be regulated by the air cylinder <NUM>. During the polishing of the wafer W, a back surface of the polishing tape <NUM> is supported by the elastic member 40a or the elastic member 40b.

The polishing apparatus <NUM> includes an operation controller <NUM> configured to control operations of each component of the polishing apparatus <NUM>. The polishing head <NUM>, the substrate holder <NUM>, the lower supply nozzle <NUM>, the upper supply nozzle <NUM>, the polishing-tape supply mechanism <NUM>, and the tilting mechanism are electrically coupled to the operation controller <NUM>. The operations of the polishing head <NUM>, the substrate holder <NUM>, the lower supply nozzle <NUM>, the upper supply nozzle <NUM>, the polishing-tape supply mechanism <NUM>, and the tilting mechanism are controlled by the operation controller <NUM>. During the polishing, the operation controller <NUM> operates the polishing-tape supply mechanism <NUM> and the tape advancing device <NUM> to advance the polishing tape <NUM> in a longitudinal direction thereof with a predetermined speed while a predetermined tension is exerted on the polishing tape <NUM>.

The operation controller <NUM> is composed of at least one computer. The operation controller <NUM> includes a memory 280a and an arithmetic device 280b. The arithmetic device 280b includes a CPU (central processing unit), a GPU (graphic processing unit), etc. configured to perform arithmetic operations according to instructions contained in programs stored in the memory 280a. The memory 280a includes a main memory (e.g., a random-access memory) to which the arithmetic device 280b is accessible, and an auxiliary memory (e.g., a hard disk drive or a solid state drive) storing data and the programs therein.

<FIG> is a diagram showing a top-edge portion of the wafer W being polished. The polishing head <NUM> is moved with a constant speed in a direction indicated by arrows in <FIG> (i.e., a radially outward direction of the wafer W) by a moving mechanism constituted of a linear actuator (not shown) or the like, while pressing the polishing tape <NUM> against the wafer W. The operation of the moving mechanism is controlled by the operation controller <NUM>. In the present embodiment, since the portion 41a of the elastic member 40a fitting in the fitting groove 45a is curved along the periphery of the wafer W, a time when the polishing tape <NUM> is in contact with the wafer W is uniform over the entire top-edge portion. As a result, the entire top-edge portion can be polished uniformly. In addition, use of the curved portion 41a of the elastic member 40a can increase a contact length between the polishing tape <NUM> and the wafer W, and can therefore increase a polishing rate.

Since the fitting groove 45a and the fitting groove 45b are arranged symmetrically about the center line Ct, the portion 41b extends along the bottom-edge portion of the wafer W when the polishing head <NUM> is tilted downward such that the portion 41b of the elastic member 40b faces the bottom-edge portion as shown in <FIG>. Therefore, as with the polishing of the top-edge portion, the bottom-edge portion can be polished accurately and uniformly by the portion 41b of the elastic member 40b.

In one embodiment, as shown in <FIG>, the pressing tool <NUM> may further have a pressing pad (or bevel pad) <NUM> disposed between the raised portions 43a and 43b. The pressing pad <NUM> is made of an elastic closed-cell foam material, such as silicone rubber. When the pressing tool <NUM> is moved toward the wafer W by the air cylinder <NUM>, the pressing pad <NUM> presses the polishing tape <NUM> from its back side against the bevel portion of the wafer W, and the polishing head <NUM> polishes the bevel portion of the wafer W. In order to reduce friction with the back surface of the polishing tape <NUM>, a sheet whose front surface is covered with fluororesin may be attached to a front surface (pressing surface) of the pressing pad <NUM>. The pressing pad <NUM> is removable by bolts or the like. The pressing tool <NUM> of the present embodiment can be applied to the embodiment described with reference to <FIG> and <FIG>.

<FIG> is a diagram showing the polishing head <NUM> when polishing the bevel portion of the wafer W. When the periphery of the wafer W is polished, as shown in <FIG>, the polishing tape <NUM> is pressed against the periphery (e.g., the bevel portion) of the wafer W by the pressing mechanism <NUM> while the tilt angle of the polishing head <NUM> is continuously changed by the tilting mechanism (not shown).

Further, in one embodiment, when the polishing head <NUM> polishes any one of the top-edge portion and the bottom-edge portion, the pressing-tool body <NUM> may include only one of the two raised portions 43a and 43b, and may include only one of the two elastic members 40a and 40b. Further, in one embodiment, the polishing apparatus <NUM> may include a plurality of polishing heads <NUM> arranged in a circumferential direction of the holding stage <NUM>.

The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.

Claim 1:
A polishing head (<NUM>) for polishing a substrate, comprising:
an annular elastic member (<NUM>) configured to press a polishing tool (<NUM>) against the substrate; and
a pressing-tool body (<NUM>) having a pressing surface (<NUM>) configured to press the polishing tool (<NUM>) against the substrate via the elastic member (<NUM>),
wherein the pressing surface (<NUM>) has a first fitting groove (<NUM>) in which a first portion (<NUM>) of the elastic member (<NUM>) fits,
the first portion (<NUM>) protrudes from the pressing surface (<NUM>),
the elastic member (<NUM>) is put on the pressing-tool body (<NUM>) with the elastic member (<NUM>) elastically deformed, and
the polishing head (<NUM>) is configured to press the polishing tool (<NUM>) against the substrate by the first portion (<NUM>).