JP2008023603A - Retainer ring of two-layer structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retainer ring of a two-layer structure capable of firmly retaining integration between a first ring and a second ring without using an adhesive and having uniform pushing pressure. <P>SOLUTION: A weld part 13 formed by melting the side of the upper face 12c of the second ring 12 and sticking it to the lower side of the first ring 11 is formed between the first ring 11 positioned in an upper layer and the second ring 12 positioned in a lower layer, and the first ring 11 and the second ring 12 are integrated by the weld part 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retainer ring disposed (mounted) in a holding head of a CMP (Chemical Mechanical Polishing) apparatus that chemically and mechanically polishes a wafer (object to be polished). The present invention relates to a retainer ring having a two-layer structure in which the first ring and the second ring are integrated.

  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, the flatness (flatness) of a semiconductor substrate (silicon substrate or the like) needs to be high. For this reason, it is required to increase the flatness at the wafer stage, and a CMP apparatus is used to meet such a demand.

  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.

  Such a retainer ring includes, for example, a two-layer structure (a two-piece structure) in which a metal first ring and an engineering plastic second ring are overlapped. That is, the second ring made of engineering plastic is reinforced by the first metal ring, and the rigidity of the entire retainer ring is increased. A retainer ring in which two rings are integrated (assembled) by bolting and a retainer ring in which two rings are integrated with an adhesive (bonding agent) are known.

  That is, in the two-layered retainer ring by bolting, a plurality of bolt insertion holes 100a are formed in the first ring 100 and a plurality of screw holes 101a (female screws) are formed in the second ring 101, as shown in FIG. It is formed at the same position as the bolt insertion hole 100a. Then, the first ring 100 and the second ring 101 are overlapped, and the bolts 102 are inserted into the respective bolt insertion holes 100a and tightened (screwed) into the screw holes 101a, so that the two rings 100 and 101 are integrated. (For example, refer to Patent Document 1).

In the two-layered retainer ring using an adhesive, as shown in FIG. 8, the adhesive 112 is applied to the lower surface 110a of the first ring 110 and the upper surface 111a of the second ring 111, and the first ring 110 and the first ring 110 The two rings 110 and 111 are integrated by superimposing the two rings 111 and applying pressure. Note that a plurality of screw holes for mounting on the holding head are formed in the first ring 100 of the retainer ring by bolting and the first ring 110 of the retainer ring by adhesive.
JP 2005-34959 A

  By the way, in the retainer ring having the two-layer structure by bolting as described above, the bolt is loosened due to vibration and repeated stress (compressive stress, shear stress, etc.) accompanying polishing of the wafer, and the flatness of the second ring and the retainer ring. The pressing force on the polishing pad may be uneven. In addition, since all the bolts do not loosen uniformly, the pressing force due to the retainer ring becomes even more uneven and unstable. In addition, since a plurality of holes are formed in the first ring and the second ring, the pressing surface directly below the hole (the surface that presses the polishing surface of the polishing pad, the lower surface of the second ring) and other portions Therefore, the pressing force on the pressing surface is different (the pressing force is non-uniform). Furthermore, even with a slight difference in bolt tightening force, the flatness of the pressing surface changes, or the second ring bends and the pressing force becomes uneven. If the pressing force becomes non-uniform in this way, high accuracy cannot be obtained in wafer polishing processing that requires extremely high accuracy (flatness or the like).

  On the other hand, in a retainer ring having a two-layer structure using an adhesive as described above, a shearing force or the like is applied to the retainer ring as the wafer is polished, and the first ring and the second ring may be peeled off. Such peeling is more likely to occur when slurry (abrasive material), polishing waste, or the like enters between the first ring and the second ring. Moreover, since it is difficult to completely mix and apply the adhesive, peeling of the first ring and the second ring is more likely to occur due to non-uniformity in the preparation and application of the adhesive. Alternatively, the integration (adhesion) of the first ring and the second ring becomes unstable.

  Furthermore, this inventor discovered and confirmed that the adhesive agent might elute. That is, the present inventors have discovered and confirmed that the adhesive may be chemically decomposed by the chemical component of the slurry and the adhesive may be eluted. When the adhesive is eluted, the first ring and the second ring are peeled off, and the eluted adhesive causes a scratch (scratch) on the wafer.

  Therefore, an object of the present invention is to provide a retainer ring having a two-layer structure in which the integration of the first ring and the second ring is firmly maintained without using an adhesive or the like and the pressing force is uniform.

  In order to achieve the above object, the invention described in claim 1 is detachably disposed in a holding head of a CMP apparatus, and an annular first ring and second ring are concentrically overlapped and integrated. A retainer ring having a two-layer structure, wherein at least one of the first ring and the second ring is melted between the first ring located in the upper layer and the second ring located in the lower layer, It has the weld part joined.

  According to a second aspect of the present invention, in the retainer ring having the two-layer structure according to the first aspect, the first ring and the second ring are vertically fitted and overlapped. .

  According to a third aspect of the present invention, in the retainer ring having the two-layer structure according to the first aspect, the first ring and the second ring are press-fitted in the vertical direction and overlapped.

  According to a fourth aspect of the present invention, in the retainer ring having the two-layer structure according to the first aspect, irregularities are formed on the lower surface of the first ring that does not melt or the upper surface of the second ring that does not melt. It is a feature.

  According to a fifth aspect of the present invention, in the retainer ring having the two-layer structure according to the first aspect, a fixing member is inserted into the first ring and the second ring through the weld portion. It is characterized by.

  According to the first aspect of the present invention, since the welded portion is provided between the first ring and the second ring, the integration of the first ring and the second ring is firmly maintained. That is, since at least one of the first ring and the second ring is melted and joined to the other, the first ring and the second ring are integrated (joined). Even if stress or the like is applied to the retainer ring, the joint (welded portion) is not loosened, and the integration of the first ring and the second ring is firmly maintained. In addition, since no adhesive or the like is used, the first ring and the second ring are not peeled off due to deterioration or elution of the adhesive, and scratches or the like are not generated on the wafer due to the eluted adhesive. Furthermore, since the flatness of the retainer ring (second ring) is maintained by maintaining the strong integration of the first ring and the second ring, it is necessary to provide bolt insertion holes and screw holes. Therefore, the pressing force to the polishing pad becomes uniform.

  According to the second aspect of the present invention, since the first ring and the second ring are fitted in the vertical direction, the integration of the first ring and the second ring becomes stronger, and the wafer It can strongly counter the shearing force accompanying polishing (does not peel off due to shearing force).

  According to the invention described in claim 3, since the first ring and the second ring are press-fitted in the vertical direction, the integration of the first ring and the second ring becomes stronger and the wafer is polished. It is possible to strongly counter the shearing force associated with.

  According to the fourth aspect of the present invention, since the unevenness is formed on the lower surface of the first ring that does not melt or the upper surface of the second ring that does not melt, the junction area with the melted second ring or the melted first ring As the number increases, the joining becomes three-dimensional (three-dimensional). As a result, the integration (joining) of the first ring and the second ring becomes stronger.

  According to the fifth aspect of the present invention, since the fixing member is inserted into the first ring and the second ring through the welded portion, the integration of the first ring and the second ring becomes stronger. In addition, it is possible to strongly counter the shearing force accompanying the polishing of the wafer.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

(Embodiment 1)
FIG. 1 is a front view showing a schematic configuration of a CMP apparatus 1 according to this embodiment. The CMP apparatus 1 has the same configuration as a CMP apparatus that is widely used except for a retainer ring 8 having a two-layer structure, which will be described later, and a detailed description thereof is omitted here. A possible surface plate 2, a polishing pad 3 (cross, etc.) 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 treated. It is mechanically 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). In this embodiment, as shown in FIG. 2, the holding head 4 includes a head body 7, a retainer ring 8 that is detachably disposed at a lower portion of the head body 7, and a position within the retainer ring 8. And an elastic film 9 that presses the upper surface W2 of the wafer W. 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 has an annular shape, surrounds the outer periphery of the wafer W, prevents the wafer W from jumping out of the holding head 4, and presses the polishing surface 3a (surface) of the polishing pad 3 for polishing the surface W1 to be polished of the wafer W. Then, the polished surface 3a is flattened and miniaturized (optimized). 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 flatness of the polishing surface 3a is increased by the retainer ring 8, and The surface roughness is reduced. The retainer ring 8 has two layers in which a first ring 11 made of stainless steel (SUS304, SUS316, etc.) and a second ring 12 made of super engineering plastic (PPS, PEEK, etc.) are concentrically stacked in the thickness direction. It has a structure. A welded portion 13 is formed between the first ring 11 located on the upper layer (head body 7 side) and the second ring 12 located on the lower layer (polishing pad 3 side) (having the welded portion 13). Is).

  As shown in FIG. 3, a plurality of screw holes 11 b for attaching the retainer ring 8 to the holding head 4 are formed from the upper surface 11 a of the first ring 11. Further, as will be described later, the lower surface of the first ring 11 is not dissolved in integration with the second ring 12, and irregularities 11 c (knurled eyes, waved eyes, etc.) are formed over the entire surface.

  The inner diameter and outer diameter of the second ring 12 are substantially the same as the inner diameter and outer diameter of the first ring 11, and the pressing surface 12a (lower surface) that presses the polishing surface 3a of the polishing pad 3 is as shown in FIG. In addition, a plurality of groove-like slits 12b for letting out (discharging) the polishing debris are formed. Further, the upper surface 12c before being integrated with the first ring 11 is formed flat (flat).

  The welded portion 13 is a joined portion in which the upper surface 12 c side, that is, the upper portion (one side) of the second ring 12 is melted and joined to the lower surface side, that is, the lower portion (the other side) of the first ring 11. 11 and the second ring 12 are integrated. Here, joining is a broad concept including adhesion, fusion, fusion, bonding, and the like. The welding portion 13 is formed by welding and is heated by high frequency welding by high frequency induction heating, heat conduction from an external heat source (hot plate welding, hot air welding, impulse welding, iron welding, etc.), super welding The welding method such as ultrasonic welding using frictional heat by sonic vibration, laser welding using heat generated by laser irradiation, infrared welding using heat generated by infrared irradiation, and the like depends on which one is used. It is selected according to the material and shape of the ring 12. Moreover, the 1st ring 11 side (upper surface side) of the welding part 13 becomes a shape along the unevenness | corrugation 11c with the melt | dissolution and solidification (solidification), as shown in FIG.

  According to the two-layered retainer ring 8 configured as described above, since the welded portion 13 is formed between the first ring 11 and the second ring 12, the first ring 11 and the second ring 12 Is firmly maintained. That is, since the upper surface 12c side of the second ring 12 is melted and bonded to the lower surface side of the first ring 11, the first ring 11 and the second ring 12 are integrated (bonded). Even if vibration or repetitive stress accompanying polishing is applied to the retainer ring 8, the bonding (welded portion 13) does not loosen, and the integration of the first ring 11 and the second ring 12 is firmly maintained. In addition, since the unevenness 11c is formed on the lower surface of the first ring 11, and the first ring 11 side of the welded portion 13 has a shape along the unevenness 11c, the bonding area between the first ring 11 and the second ring 12 is large. As it increases, the bonding becomes three-dimensional (three-dimensional). As a result, the integration (joining) of the first ring 11 and the second ring 12 becomes stronger.

  Further, since no adhesive or the like is used, the first ring 11 and the second ring 12 are not peeled off due to deterioration or elution of the adhesive, and the wafer W is not scratched by the eluted adhesive. Furthermore, since the flatness of the retainer ring 8 (second ring 12) is maintained by firmly maintaining the integration of the first ring 11 and the second ring 12, bolt insertion holes, screw holes, and the like Therefore, the pressing force to the polishing pad 3 is uniform.

(Embodiment 2)
FIG. 5A is a plan view showing a retainer ring 20 having a two-layer structure according to this embodiment, and FIG. This embodiment is different from the first embodiment in that the first ring 21 and the second ring 22 are fitted and press-fitted.

  That is, a press-fit portion 21a to be fitted is formed along the entire circumference of the lower surface (lower portion) of the first ring 21 and the cross section is concave in the thickness direction and has an annular shape (concentric with the first ring 21). The width H1 of the fitted press-fit portion 21a is set to be slightly smaller than the width H2 of the second ring 22. Then, the first ring 21 and the second ring 22 are fitted and press-fitted in the vertical direction (thickness direction) with the upper portion 22a of the second ring 22 fitted and press-fitted into the fitting press-fit portion 21a. It is superimposed. Further, the upper portion 22a of the second ring 22 is melted and joined to the fitted press-fit portion 21a of the first ring 21 to form a welded portion 23. The welded portion 23 forms the first ring 21 and the second ring. 22 is integrated.

  According to the retainer ring 20 having the two-layer structure configured as described above, the upper portion 22a of the second ring 22 is fitted and press-fitted into the fitting press-fit portion 21a of the first ring 21, so that the first Integration of the ring 21 and the second ring 22 becomes stronger. Moreover, even if a shearing force (horizontal force in the drawing) accompanying the polishing of the wafer W is applied to the second ring 22, the shearing force is received by the side walls (both sides of the recessed portion) of the fitted press-fit portion 21 a ( The shearing force is transmitted to the first ring 31 well). For this reason, it can oppose strongly with respect to a shearing force, and the 1st ring 21 and the 2nd ring 22 do not peel by a shearing force.

(Embodiment 3)
FIG. 6A is a plan view showing a two-layer retainer ring 30 according to this embodiment, and FIG. This embodiment is different from the first embodiment in that a plurality of fixing pins 34 (fixing members) are inserted into the first ring 31 and the second ring 32.

  That is, a plurality of insertion holes 31 a are formed from the lower surface of the first ring 31, and a plurality of insertion holes 32 a are formed from the upper surface of the second ring 32 at the same position as the insertion hole 31 a. Here, the inner diameters of the insertion holes 31a and 32a are the same as the outer diameter of the fixing pin 34, and the fixing pin 34 is fitted to the insertion holes 31a and 32a (it fits without a gap). The fixing pin 34 is a round bar made of stainless steel.

  Then, the fixing pin 34 is inserted into the insertion hole 31 a of the first ring 31 and the insertion hole 32 a of the second ring 32 through the boundary between the first ring 31 and the second ring 32, that is, a welded portion 33 described later. Has been. Further, the upper part of the second ring 32 is melted and joined to the lower part of the first ring 31 to form a welded part 33, and the first ring 31 and the second ring 32 are integrated by the welded part 33. ing.

  According to the retainer ring 30 having the two-layer structure configured as described above, the fixing pin 34 penetrates the welded portion 33 and is inserted into the first ring 31 and the second ring 32. Integration with the second ring 32 becomes stronger. In addition, even if a shearing force accompanying the polishing of the wafer W is applied to the second ring 32, the shearing force is well transmitted to the first ring 31 via the fixing pins 34. For this reason, it can oppose strongly with respect to a shearing force, and the 1st ring 31 and the 2nd ring 32 do not peel by a shearing force.

  As mentioned above, although Embodiment 1-3 of this invention was demonstrated, a concrete structure is not restricted to these Embodiment, There exists a change of the design etc. of the range which does not deviate from the summary of this invention. Are also included in the present invention. For example, in the first to third embodiments, the second ring located in the lower layer is melted and joined to the first ring located in the upper layer to form the welded portion, but the material of the first ring and the second ring Depending on the shape and shape, the first ring may be melted to form the welded portion, or the first ring and the second ring may be melted together to form the welded portion. . Therefore, when only the first ring is melted, the above-described unevenness (unevenness 11c) may be formed on the upper surface of the second ring that does not melt. In the first to third embodiments, the first ring is made of stainless steel and the second ring is made of super engineering plastic. However, the first ring is made of another metal, ceramic, resin material, etc. Of course, the two rings may be made of other resin materials.

It is a front view which shows schematic structure of the CMP apparatus which concerns on Embodiment 1-3 of this invention. It is a schematic sectional drawing of the holding head of the CMP apparatus of FIG. It is the top view (a) of the 1st ring of the retainer ring of the 2 layer structure which concerns on Embodiment 1 of this invention, and its AA sectional drawing (b). It is the top view (a) of the 2nd ring of the retainer ring of the 2 layer structure which concerns on Embodiment 1 of this invention, and its BB sectional drawing (b). It is the top view (a) of the retainer ring of the 2 layer structure which concerns on Embodiment 2 of this invention, and its CC sectional drawing (b). It is the top view (a) of the retainer ring of the 2 layer structure which concerns on Embodiment 3 of this invention, and its DD sectional drawing (b). They are the perspective view (a) which shows the retainer ring of the conventional 2 layer structure which integrated the 1st ring and the 2nd ring by bolting, and its EE sectional drawing (b). It is a perspective view which shows the retainer ring of the conventional 2 layer structure which integrated the 1st ring and the 2nd ring with the adhesive agent.

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 body 8 Retainer ring of two-layer structure 9 Elastic body film 10 Air chamber 11 First ring 11a Upper surface 11b Screw hole 11c Concavities and convexities 12 Second ring 12a Press surface 12b Slit 12c Upper surface 13 Welded portion 20 Retainer ring of two-layer structure 21 First ring 21a Fitted press-fit portion 22 Second ring 22a Upper portion 23 Welded portion 30 Retainer ring of two-layer structure 31 First 1 ring 31a insertion hole 32 second ring 32a insertion hole 33 welding part 34 fixing pin (fixing member)
W Wafer W1 Surface to be polished W2 Top surface

Claims (5)

A retainer ring having a two-layer structure that is detachably disposed in a holding head of a CMP apparatus and is formed by concentrically superimposing an annular first ring and a second ring,
Between the first ring located in the upper layer and the second ring located in the lower layer, there is a welded portion in which at least one of the first ring and the second ring is melted and joined to the other. Two-layer retainer ring.   2. The two-layered retainer ring according to claim 1, wherein the first ring and the second ring are overlapped in a vertical direction.   2. The two-layer retainer ring according to claim 1, wherein the first ring and the second ring are press-fitted in a vertical direction and overlapped with each other.   2. The retainer ring having a two-layer structure according to claim 1, wherein unevenness is formed on a lower surface of the first ring that does not melt or an upper surface of the second ring that does not melt. The retainer ring having a two-layer structure according to claim 1, wherein a fixing member is inserted into the first ring and the second ring through the welding portion.