JP2009034745A - Retainer ring for cmp apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retainer ring for a CMP apparatus, which retainer ring can achieve proper polishing results without causing the scratch and the sticking of foreign substances. <P>SOLUTION: At least one of the inner peripheral surface 8f, which is the inner peripheral side side-surface, and the outer peripheral surface 8g, which is the outer peripheral side side-surface, of the retainer ring is smoothly formed such that foreign substances such as the slurry and the polished chips hardly stick thereto, or such that the stuck foreign substances easily can fall therefrom. As a result, the foreign substances do not accumulate on the inner peripheral surface 8f and the outer peripheral surface 8g, and the generation of the scratches on the polished surface of a wafer caused by the foreign substances and the sticking of the foreign substances (debris) can be suppressed, and the proper polishing results can be achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a CMP (Chemical Mechanical Polishing) apparatus for chemically and mechanically polishing a wafer as an object to be polished, and in particular, is mounted (arranged) in a holding head of a CMP apparatus and the outer periphery of the wafer. The present invention relates to a retainer ring for a CMP apparatus that surrounds the container.

  As the integration and performance of semiconductor devices increase, the dimension in the horizontal direction (on the plane) becomes smaller, and the structure in the vertical direction becomes finer and multilayered. In order to realize such miniaturization and multilayering, a semiconductor substrate such as a silicon substrate needs to have high flatness (flatness). For this reason, it is required to increase the flatness at the stage of the wafer, and a CMP apparatus is known as one that meets such a demand (see, for example, Patent Document 1).

The CMP apparatus includes, for example, a rotatable surface plate, a polishing pad disposed on the surface plate, a holding head that holds the wafer and presses it against the polishing pad, and a slurry supply nozzle. . Further, the holding head includes a retainer ring that surrounds the outer periphery of the wafer, an elastic film that presses the upper surface of the wafer, an air chamber that is surrounded by the elastic film, the retainer ring, and the head body, and the air chamber. An air supply path for supplying pressurized air to the air. The retainer ring surrounds the outer periphery of the wafer to prevent the wafer from jumping out, and presses the polishing surface (surface) of the polishing pad for polishing the wafer to flatten and refine (optimize) the polishing surface. It is.
Japanese Patent Laid-Open No. 11-226865

  By the way, the polished surface of the polished wafer should not have scratches (scratches) or foreign matter adhered, and the polished surface is required to be smooth and intact. However, in reality, there are cases where scratches and foreign matter adhere to the surface of the wafer to be polished for some reason, and an appropriate polishing result cannot be obtained. In such a case, polishing may have to be continued for a long time until no scratches or foreign matter adheres, or polishing conditions may be changed, or a wafer with poor polishing may have to be discarded.

  Accordingly, an object of the present invention is to provide a retainer ring for a CMP apparatus capable of obtaining an appropriate polishing result without scratches or adhesion of foreign matters.

  As a result of repeated investigation and research, the present inventor has found that the surface condition of the side surface of the retainer ring has a great influence on the polishing result, and the surface condition of the side surface of the retainer ring must be appropriate to obtain an appropriate polishing result. I got the conclusion. That is, in the conventional retainer ring, the surface condition (surface roughness) between the inner peripheral surface that is the inner peripheral side surface and the outer peripheral surface that is the outer peripheral side surface is rough, and external substances such as slurry and polishing dust adhere to the surface. It was easy or the attached external material was difficult to fall off. For this reason, it has been found that the external material adhered to and deposited on the inner peripheral surface and the outer peripheral surface causes scratches and external material (foreign matter) to adhere to the polished surface of the wafer, and an appropriate polishing result cannot be obtained. (confirmed). And in order to obtain an appropriate grinding | polishing result, it came to the conclusion that the surface state of the side surface of a retainer ring needs to be appropriate.

  In order to achieve the above object, the invention according to claim 1 is a ring-shaped retainer ring for a CMP apparatus that is mounted on the CMP apparatus and surrounds the outer periphery of the wafer, and is an inner peripheral side surface. At least one of the outer peripheral surface which is the peripheral surface and the outer peripheral side surface is formed to have a predetermined smoothness.

  In the retainer ring for the CMP apparatus according to claim 1, the invention according to claim 2 is such that external substances such as slurry and polishing scraps are not easily attached, or the attached external substances are likely to fall off. At least one of the inner peripheral surface and the outer peripheral surface is formed smoothly.

  According to a third aspect of the present invention, in the retainer ring for a CMP apparatus according to the first aspect, the surface roughness of at least one of the inner peripheral surface and the outer peripheral surface is a center line average roughness (arithmetic average roughness, Ra) is set to 0.1 μm or less.

  According to the first aspect of the present invention, since at least one of the inner peripheral surface and the outer peripheral surface of the retainer ring is formed with a predetermined smoothness, an external substance such as slurry or polishing debris is formed on the inner peripheral surface or the outer peripheral surface. Is difficult to adhere. Alternatively, even if an external substance adheres, the external substance easily falls off, and the external substance does not accumulate (stagnate) on the inner peripheral surface or the outer peripheral surface. As a result, it is possible to suppress the occurrence of scratches due to external substances and the adhesion of external substances (foreign substances) to the surface to be polished of the wafer, and to obtain appropriate polishing results.

  According to the second aspect of the present invention, at least one of the inner peripheral surface and the outer peripheral surface of the retainer ring is formed smoothly so that the external substance is difficult to adhere or the attached external substance is easy to fall off. ing. For this reason, no external material is deposited on the inner and outer peripheral surfaces, and the occurrence of scratches and adhesion of external materials due to external materials on the surface to be polished of the wafer is suppressed, and an appropriate polishing result is obtained. Is possible.

  According to the invention described in claim 3, since the surface roughness of at least one of the inner peripheral surface and the outer peripheral surface of the retainer ring is set to 0.1 μm or less in terms of the center line average roughness, An external substance does not accumulate on the outer peripheral surface, and an appropriate polishing result can be obtained.

  Since an appropriate polishing result can be obtained as described above, it is possible to effectively improve the production efficiency (polishing efficiency) of the wafer by the CMP apparatus. That is, it is possible to reduce the situation in which polishing is continued for a long time until scratches and foreign matters are not adhered, the polishing conditions are changed, and a wafer with poor polishing must be discarded.

  The present invention will be described below based on the illustrated embodiments.

  FIG. 1 is a front view showing a schematic configuration of a CMP apparatus 1 according to an embodiment of the present invention. The CMP apparatus 1 has the same configuration as a CMP apparatus that is widely used except for a retainer ring (CMP apparatus retainer ring) 8 that will be described later. A plate 2, a polishing pad 3 (such as a cloth) disposed on the surface plate 2, a holding head 4, a slurry supply nozzle 5 and a dresser 6 (shaping means) are provided, and the wafer W is chemically and mechanically attached. It is to be polished.

  The holding head 4 holds the wafer W and presses the surface to be polished W1 against the polishing pad 3. The holding head 4 can move on the polishing pad 3 while rotating (spinning). As shown in FIG. 2, the holding head 4 includes a head main body 7, a retainer ring 8 disposed at a lower portion of the head main body 7, and is positioned in the retainer ring 8 to press the upper surface W <b> 2 of the wafer W. And an elastic film 9. Then, pressure air is supplied to the air chamber 10 surrounded by the head body 7, the retainer ring 8, and the elastic film 9, and the wafer W is pressed against the polishing pad 3 through the elastic film 9.

  The retainer ring 8 surrounds the outer periphery of the wafer W, prevents the wafer W from jumping out of the holding head 4, and also provides a polishing surface 3a of the polishing pad 3 for polishing the wafer W (a surface in surface contact with the polishing target surface W1 of the wafer W). ) To flatten, refine, that is, optimize. That is, the polishing surface 3a of the polishing pad 3 has a low flatness due to the slurry (abrasive) 5a and a rough surface, and the retainer ring 8 increases the flatness of the polishing surface 3a and the surface roughness. Is to make it smaller.

  In this embodiment, the retainer ring 8 is made of a PPS (polyphenylene sulfide, engineering plastic) material in consideration of chemical resistance, mechanical characteristics, and the like. Further, it has a ring shape (annular shape) as shown in FIG. 3, and the cross-sectional shape of the vertical plane overlapping the axial center line is a quadrangle as shown in FIG. A plurality of groove-like slits 8b are formed on the side of the pressing surface 8a that presses the polishing surface 3a of the polishing pad 3. In addition, a plurality of screw inserts 8d formed with female screws 8e are inserted on the back surface 8c side of the retainer ring 8 located on the back surface of the pressing surface 8a. That is, the screw insert 8d has a substantially cylindrical shape, a male screw is formed on the outer periphery, and a female screw 8e is formed on the inner periphery. The retainer ring 8 can be attached to the head body 7 (holding head 4) via the screw insert 8d.

  Furthermore, an inner peripheral surface 8f which is an inner peripheral side surface of the retainer ring 8 and an outer peripheral surface 8g which is an outer peripheral side surface are formed with a predetermined smoothness. That is, the inner peripheral surface 8f and the outer peripheral surface 8g are formed to such an extent that an external substance (foreign matter) such as the slurry 5a (including the crystals) and polishing scraps is difficult to adhere, and further, the attached external substance is easily removed. Smooth surface finish and processing (formation). Specifically, in this embodiment, the surface roughness of the inner peripheral surface 8f and the outer peripheral surface 8g is set to 0.1 μm or less in terms of centerline average roughness (arithmetic average roughness, Ra).

  In this embodiment, the surface states of the inner peripheral surface 8f and the outer peripheral surface 8g are formed and set in this way, but the surface state is formed according to the polishing state (polishing conditions), the type of the slurry 5a, etc. It may be set. That is, when the slurry 5a or polishing scraps are likely to adhere only to the inner peripheral surface 8f, only the inner peripheral surface 8f may be formed smoothly. In addition, when using the slurry 5a that easily adheres to the retainer ring 8, or when polishing dust having a size and shape that easily adheres to the retainer ring 8 is generated, the surface roughness of the inner peripheral surface 8f and the outer peripheral surface 8g is increased. The thickness may be further reduced (smooth). Here, the polishing state is the type of CMP apparatus 1, the type and size of the wafer W, the type of slurry 5a and the polishing pad 3, the material and shape / size of the retainer ring 8, the polishing rate (polishing rate), and the pressure. It varies depending on conditions relating to polishing including the amount and the like, and includes the fluidity and flow direction of the slurry 5a and polishing scraps. Further, since the retainer ring 8 is also polished by the polishing pad 3, the polishing scrap includes not only the polishing scrap of the wafer W but also the polishing scrap of the retainer ring 8.

  According to the retainer ring 8 configured as described above, since the inner peripheral surface 8f and the outer peripheral surface 8g are formed and set as described above, the slurry 5a and the polishing are applied to the inner peripheral surface 8f and the outer peripheral surface 8g. External materials such as scraps are difficult to adhere. Furthermore, even if an external substance adheres, the external substance easily drops off, and the external substance does not accumulate (stay) on the inner peripheral surface 8f or the outer peripheral surface 8g. As a result, it is possible to suppress the occurrence of scratches due to an external substance on the surface to be polished W1 of the wafer W, the occurrence of adhesion of an external substance (foreign matter), and the like, and an appropriate polishing result can be obtained.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above-described embodiment, the retainer ring 8 is made of PPS. Other engineering plastics such as polyimide) may be used. In the above-described embodiment, the retainer ring 8 has an integral structure (one-layer structure), but may have a two-layer structure. That is, for example, in a retainer ring having a two-layer structure in which a first ring made of engineering plastic is arranged on the polishing pad 3 side and a second ring made of stainless steel is superimposed on the first ring, The peripheral surface and the outer peripheral surface may be formed smoothly.

1 is a front view showing a schematic configuration of a CMP apparatus according to an embodiment of the present invention. It is a schematic sectional drawing of the holding head of the CMP apparatus of FIG. FIG. 3 is a front sectional view (a) and a bottom view (b) of a retainer ring of the holding head of FIG. 2. It is an enlarged view of the A section of Fig.3 (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CMP apparatus 2 Surface plate 3 Polishing pad 3a Polishing surface 4 Holding head 5 Slurry supply nozzle 5a Slurry 6 Dresser 7 Head main body 8 Retainer ring 8a Pressing surface 8b Slit 8c Back surface 8d Screw insert 8f Inner peripheral surface 8g Outer peripheral surface 9 Elastic body film 10 Air chamber W Wafer W1 Surface to be polished

Claims (3)

A ring-shaped retainer ring for a CMP apparatus that is mounted on a CMP apparatus and surrounds the outer periphery of the wafer,
A retainer ring for a CMP apparatus, wherein at least one of an inner peripheral surface which is an inner peripheral side surface and an outer peripheral surface which is an outer peripheral side surface is formed with a predetermined smoothness.   At least one of the inner peripheral surface and the outer peripheral surface is smoothly formed to such an extent that external substances such as slurry and polishing scraps are difficult to adhere or the attached external substances are easy to fall off. The retainer ring for a CMP apparatus according to claim 1. 2. The retainer ring for a CMP apparatus according to claim 1, wherein the surface roughness of at least one of the inner peripheral surface and the outer peripheral surface is set to 0.1 μm or less in terms of a center line average roughness.

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