Patent Grant
9174324
This application claims priority to Japanese Patent Application No. 2013-017193 filed Jan. 31, 2013, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention:
The present invention relates to a polishing apparatus, and more particularly to a polishing apparatus for polishing a surface of an object to be polished (a substrate) such as a wafer.
2. Description of the Related Art:
A chemical mechanical polishing (CMP) is a technology for polishing a surface of a wafer by a chemical action of a polishing liquid and a mechanical action of abrasive particles contained in the polishing liquid. Generally, a polishing apparatus for carrying out the “CMP” includes a polishing table for holding a polishing pad, a polishing head for pressing the wafer against the polishing pad, and a polishing liquid supply mechanism for supplying the polishing liquid (e.g., slurry) to the polishing pad. The polishing head includes a top ring for holding the wafer and pressing the wafer against a polishing surface of the polishing pad, and a top-ring operating mechanism for operating this top ring.
The wafer is pressed against the polishing surface of the polishing pad by the top ring, and the polishing table and the top ring are rotated in this state. The wafer is brought in sliding contact with the polishing surface of the polishing pad in the presence of the polishing liquid, so that the surface of the wafer is polished. After polishing of the wafer is terminated, an atomized fluid is supplied toward the polishing surface of the polishing pad from an atomizer to clean the polishing surface, as disclosed in Japanese laid-open patent publication No. 2008-296293.
When the surface of the substrate such as a wafer is polished while supplying the polishing liquid, the polishing liquid adheres to the polishing head including the top ring. The polishing liquid remaining on the polishing surface adheres to the polishing head also at the time of cleaning the polishing surface by the atomizer. The polishing liquid which has adhered to the polishing head is gradually dried, and may fall onto the polishing surface eventually. Such dried polishing liquid causes scratches on the surface, being polished, of the substrate.
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus which can prevent the polishing liquid from adhering to the polishing head and prevent the dried polishing liquid from falling onto the polishing surface.
One aspect of the present invention is to provide a polishing apparatus comprising: a polishing table configured to hold a polishing tool having a polishing surface; a polishing head having a top ring configured to press a substrate against the polishing surface; a polishing head cover configured to cover the polishing head; a first cleaning liquid supply mechanism configured to supply a cleaning liquid to an outer surface of the polishing head cover; and a second cleaning liquid supply mechanism configured to supply a cleaning liquid to an inner surface of the polishing head cover.
In a preferred aspect of the present invention, the first cleaning liquid supply mechanism and the second cleaning liquid supply mechanism are mounted on the polishing head cover.
In a preferred aspect of the present invention, the first cleaning liquid supply mechanism is configured to supply the cleaning liquid onto the entire outer surface of the polishing head cover.
In a preferred aspect of the present invention, the second cleaning liquid supply mechanism is configured to supply the cleaning liquid onto the entire inner surface of the polishing head cover.
In a preferred aspect of the present invention, the second cleaning liquid supply mechanism includes a cleaning liquid passage configured to allow the cleaning liquid to flow, and a plurality of cleaning nozzles connected to the cleaning liquid passage; and the plurality of cleaning nozzles have distal end opening portions which are in contact with or close to the inner surface of the polishing head cover, and are configured to supply the cleaning liquid along the inner surface of the polishing head cover.
In a preferred aspect of the present invention, at least one of the outer surface and the inner surface of the polishing head cover is covered with a hydrophilic coating.
In a preferred aspect of the present invention, at least one of the outer surface and the inner surface of the polishing head cover is covered with a water repellent coating.
In a preferred aspect of the present invention, the outer surface of the polishing head cover has a convex portion or a concave portion extending in the horizontal direction, and the convex portion or the concave portion is located below the first cleaning liquid supply mechanism.
In a preferred aspect of the present invention, the inner surface of the polishing head cover has a convex portion or a concave portion extending in the horizontal direction, and the convex portion or the concave portion is located below the second cleaning liquid supply mechanism.
Other aspect of the present invention is to provide a polishing apparatus comprising: a polishing table configured to hold a polishing tool having a polishing surface; a polishing head having a top ring configured to press a substrate against the polishing surface; a polishing head cover configured to cover the polishing head; and cleaning liquid supply ports configured to supply a cleaning liquid to an outer surface of the polishing head cover; wherein the cleaning liquid supply ports are provided at an upper part of the polishing head cover and are arranged so as to surround the outer surface of the polishing head cover.
In a preferred aspect of the present invention, the cleaning liquid supply ports are arranged to supply the cleaning liquid onto the entire outer surface of the polishing head cover.
In a preferred aspect of the present invention, the outer surface of the polishing head cover is covered with a hydrophilic coating.
In a preferred aspect of the present invention, the outer surface of the polishing head cover is covered with a water repellent coating.
In a preferred aspect of the present invention, the outer surface of the polishing head cover has a convex portion or a concave portion extending in the horizontal direction, and the convex portion or the concave portion is located below the cleaning liquid supply ports.
Further, other aspect of the present invention is to provide a polishing apparatus comprising: a polishing table configured to hold a polishing tool having a polishing surface; a polishing head having a top ring configured to press a substrate against the polishing surface; a polishing head cover configured to cover the polishing head; and cleaning liquid supply ports configured to supply a cleaning liquid to an inner surface of the polishing head cover; wherein the cleaning liquid supply ports are provided at the inside of the polishing head cover and are arranged so as to surround the inner surface of the polishing head cover.
In a preferred aspect of the present invention, the cleaning liquid supply ports are arranged to supply the cleaning liquid onto the entire inner surface of the polishing head cover.
In a preferred aspect of the present invention, the cleaning liquid supply ports are in contact with or close to the inner surface of the polishing head cover, and are configured to supply the cleaning liquid along the inner surface of the polishing head cover.
In a preferred aspect of the present invention, the inner surface of the polishing head cover is covered with a hydrophilic coating.
In a preferred aspect of the present invention, the inner surface of the polishing head cover is covered with a water repellent coating.
In a preferred aspect of the present invention, the inner surface of the polishing head cover has a convex portion or a concave portion extending in the horizontal direction, and the convex portion or the concave portion is located below the cleaning liquid supply ports.
According to the present invention, the polishing head is housed in the polishing head cover. Therefore, the polishing head including the top ring can be protected from the polishing liquid by the polishing head cover. Since the polishing liquid adhering to the polishing head cover is washed away by a cleaning liquid, there is no fear that the dried polishing liquid falls onto the polishing surface. Therefore, according to the present invention, the occurrence of scratches on the surface of the substrate due to the dried polishing liquid can be prevented.
Embodiments of a polishing apparatus according to the present invention will now be described in detail with reference to
The polishing table 5 is coupled via a table shaft 6 to a table motor 8 disposed below the polishing table 5, and the polishing table 5 and the polishing pad 3 are configured to be rotated about a common central axis by this table motor 8.
The polishing head 4 includes a top ring 15 for holding and pressing the wafer W against the polishing surface 3a, a top ring shaft 16 to which the top ring 15 is fixed, a top ring elevating mechanism 17 for elevating the top ring 15 through the top ring shaft 16, a top ring arm 18 on which the top ring elevating mechanism 17 is provided, and a top ring rotating mechanism (not shown in the drawings) for rotating the top ring 15 about its central axis through the top ring shaft 16. The top ring rotating mechanism is disposed in the top ring arm 18. The top ring elevating mechanism 17 and the top ring rotating mechanism constitute a top ring operating mechanism for operating the top ring 15.
The top ring 15 is secured to a lower end of the top ring shaft 16. The top ring 15 is configured to hold the wafer W on its lower surface by vacuum suction. The top ring arm 18 is coupled to a top ring swing shaft 19, and is configured to be swung about the top ring swing shaft 19. When the top ring arm 18 is swung, as shown in
As shown in
The ball screw 32 has a screw shaft 32a coupled to the servomotor 38 and a nut 32b that engages the screw shaft 32a. The top ring shaft 16 is elevated and lowered (i.e., vertically movable) together with the bridge 28. Therefore, when the servomotor 38 operates, the bridge 28 is moved vertically through the ball screw 32, whereby the top ring shaft 16 and the top ring 15 are moved vertically.
Polishing of the wafer W is performed as follows: The top ring 15 holding the wafer W is moved from the standby position to the polishing position. The top ring 15 and the polishing table 5 are rotated in the same direction, while a polishing liquid (i.e., slurry) is supplied onto the polishing pad 3 from the polishing liquid supply mechanism 10. In this state, the top ring 15 presses the wafer W against the polishing surface 3a of the polishing pad 3, and the wafer W and the polishing surface 3a are brought into sliding contact with each other. A surface of the wafer W is polished by a chemical action of the polishing liquid and a mechanical action of abrasive particles contained in the polishing liquid. Such polishing apparatus is referred to as a CMP (chemical mechanical polishing) apparatus.
The polishing apparatus further includes a dressing head 40 for dressing (or conditioning) the polishing surface 3a of the polishing pad 3. The dressing head 40 includes a dresser 41 that is brought into sliding contact with the polishing pad 3, a dresser shaft 43 to which the dresser 41 is fixed, a dresser arm 45 for holding the dresser shaft 43, and a dresser rotating mechanism (not shown in the drawings) for rotating the dresser 41 through the dresser shaft 43. The dresser rotating mechanism is disposed in the dresser arm 45. Abrasive particles (not shown in the drawings) such as diamond particles are fixed to the lower surface of the dresser 41, and these abrasive particles constitute a dressing surface for dressing the polishing surface 3a.
The dresser arm 45 is coupled to a dresser swing shaft 47, and is configured to be swung about the dresser swing shaft 47. When the dresser arm 45 is swung, the dresser 41 is oscillated on the polishing surface 3a in a radial direction of the polishing table 5. The dresser 41 is rotated while the dresser 41 is oscillated on the polishing surface 3a of the polishing pad 3, thereby scraping off the polishing pad 3 slightly to dress the polishing surface 3a. Further, as shown in
The polishing apparatus further includes an atomizer 49 for cleaning the polishing surface 3a by spraying an atomized cleaning fluid to the polishing surface 3a on the polishing pad 3. The atomizer 49 extends in the radial direction of the polishing pad 3 (or the polishing table 5). The cleaning fluid is composed of a fluid mixture of a cleaning liquid (usually pure water) and a gas (e.g., an inert gas such as a nitrogen gas) or only a cleaning liquid. By spraying such cleaning fluid to the polishing surface 3a, polishing debris and the abrasive particles contained in the polishing liquid remaining on the polishing surface 3a of the polishing pad 3 are removed.
A first cleaning liquid supply mechanism 54 for supplying the cleaning liquid to an outer circumferential surface 50a of the polishing head cover 50 is arranged at the upper part of the polishing head cover 50. The first cleaning liquid supply mechanism 54 includes an annular cleaning liquid passage (i.e., a first cleaning liquid passage) 55 for allowing the cleaning liquid to pass therethrough, and a plurality of cleaning nozzles (i.e., first cleaning nozzles) 56 connected to the cleaning liquid passage 55. The plurality of cleaning nozzles 56 constitute cleaning liquid supply ports. The cleaning liquid passage 55 and the cleaning nozzles 56 are attached to an upper end of the polishing head cover 50. Pure water is preferably used as a cleaning liquid.
The cleaning liquid passage 55 extends along a circumferential direction of the outer circumferential surface 50a so as to surround the outer circumferential surface 50a. The cleaning nozzles 56 are arranged at equal intervals over the entire circumference of the outer circumferential surface 50a. The cleaning liquid is supplied to the cleaning liquid passage 55 from a cleaning liquid supply line (not shown in the drawings). The cleaning liquid flowing through the cleaning liquid passage 55 is supplied onto the outer circumferential surface 50a of the polishing head cover 50 from the cleaning nozzles 56. It is preferable that the cleaning nozzle 56 is a spray nozzle which can spray the cleaning liquid over a wide area of the outer circumferential surface 50a.
When the top ring 15 is in the standby position, (i.e., the top ring 15 is not positioned above the polishing surface 3a), the cleaning liquid is sprayed toward the outer circumferential surface 50a. It is preferable that distal end opening portions of the cleaning nozzles 56 are arranged in contact with or close to the outer circumferential surface 50a so as to supply the cleaning liquid along the outer circumferential surface 50a. The cleaning liquid flows downward over the entire circumference of the outer circumferential surface 50a, and washes away the polishing liquid adhered to the outer circumferential surface 50a. Therefore, the polishing liquid does not remain on the polishing head cover 50, and thus the dried polishing liquid can be prevented from falling onto the polishing surface 3a of the polishing pad 3.
In order to form a liquid film having a uniform thickness of the cleaning liquid on the outer circumferential surface 50a, it is preferable to cover the outer circumferential surface 50a of the polishing head cover 50 with a hydrophilic coating. An example of such hydrophilic coating includes a coat comprising a mixture of a silicon-based organic compound and fluorine. An example of a method for applying the hydrophilic coating onto the outer circumferential surface 50a includes a method for applying a hydrophilic material to the outer circumferential surface 50a and applying heat treatment to the hydrophilic material on the outer circumferential surface 50a. By covering the outer circumferential surface 50a with the hydrophilic coating, the cleaning liquid spreads over the entire circumference of the outer circumferential surface 50a with the cleaning liquid sticking to the outer circumferential surface 50a, thus forming the liquid film having the uniform thickness on the outer circumferential surface 50a.
The outer circumferential surface 50a of the polishing head cover 50 may be covered with a water repellent coating in place of the hydrophilic coating. An example of a method for applying the water repellent coating onto the outer circumferential surface 50a includes a method for applying a water repellent material onto the outer circumferential surface 50a and applying heat treatment to the water repellent material on the outer circumferential surface 50a. By covering the outer circumferential surface 50a with the water repellent coating, the polishing liquid which has adhered to the outer circumferential surface 50a at the time of polishing the wafer W is aggregated, and flows down in a streaky manner. Thus, there is no fear that the polishing liquid is dried while adhering to the outer circumferential surface 50a. As a result, the dried polishing liquid is prevented from falling onto the polishing surface 3a of the polishing pad 3.
As shown in
In
In order to reduce the consumption of the cleaning liquid, it is preferable to reuse the cleaning liquid after recovering the used cleaning liquid and removing foreign matters from the recovered cleaning liquid. It is preferable to remove the cleaning liquid from the polishing head cover 50 by blowing a purge gas (such as a nitrogen gas) onto the polishing head cover 50 located at the standby position so that the cleaning liquid supplied to the polishing head cover 50 does not fall onto the polishing pad 3.
As shown in
The cleaning liquid is supplied to the cleaning liquid passage 62 from the above-described cleaning liquid supply line (not shown in the drawings). The cleaning liquid flowing through the cleaning liquid passage 62 is supplied to the inner circumferential surface 50b of the polishing head cover 50 from the respective cleaning nozzles 63. In order to prevent the scattering of the cleaning liquid when the cleaning liquid ejected from the cleaning nozzles 63 hits the inner circumferential surface 50b, distal end opening portions of the cleaning nozzles 63 are arranged in contact with or close to the inner circumferential surface 50b. Further, the cleaning nozzles 63 are inclined with respect to the inner circumferential surface 50b so that the distal end opening portions of the cleaning nozzles 63 face the inner circumferential surface 50b. By using such cleaning nozzles 63, the cleaning liquid flows out from the cleaning nozzles 63 along the inner circumferential surface 50b without being scattered, thus forming a liquid film having a uniform thickness on the inner circumferential surface 50b. The cleaning liquid passage 62 and the cleaning nozzle 63 shown in
In order to form the liquid film having the uniform thickness of the cleaning liquid on the inner circumferential surface 50b, it is preferable to cover the inner circumferential surface 50b of the polishing head cover 50 with the hydrophilic coating. By covering the inner circumferential surface 50b with the hydrophilic coating, the cleaning liquid spreads over the entire inner circumferential surface 50b with the cleaning liquid sticking to the inner circumferential surface 50b, thus forming the liquid film having the uniform thickness on the inner circumferential surface 50b.
The inner circumferential surface 50b of the polishing head cover 50 may be covered with the water repellent coating in place of the hydrophilic coating. By covering the inner circumferential surface 50b with the water repellent coating, the polishing liquid which has adhered to the inner circumferential surface 50b is aggregated, and flows down in a streaky manner. Thus, there is no fear that the polishing liquid is dried while adhering to the inner circumferential surface 50b. As a result, the dried polishing liquid is prevented from falling onto the polishing surface 3a of the polishing pad 3.
As shown in
In order to prevent the scattering of the cleaning liquid itself supplied to the inner circumferential surface 50b of the polishing head cover 50, it is preferable to reduce a flow rate of the cleaning liquid supplied from the cleaning nozzles 63. In this case also, the cleaning liquid spreads in the horizontal direction by the groove 71 or the dam 73, and thus the liquid film having the uniform thickness can be formed on the inner circumferential surface 50b.
In
The polishing head cover 50 described with reference to
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 and equivalents.
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