WO2008010310A1 - Retainer ring of double-layer structure - Google Patents

Abstract

A retainer ring of double-layer structure that without the use of adhesive, etc., realizes robust retention of integration of first ring and second ring, ensuring uniform press force. Between first ring (11) positioned as a superior layer and second ring (12) positioned as an inferior layer, there is formed melt adhesion part (13) resulting from melting of the side of upper face (12c) of the second ring (12) and adhering thereof to the side of lower face of the first ring (11). By virtue of this melt adhesion part (13), the first ring (11) and the second ring (12) are unified.

Description

 Specification

 Two-layer retainer ring

 Technical field

 [0001] The present invention is disposed (mounted) in a holding head of a CMP (chemical mechanical polishing) apparatus that chemically and mechanically polishes a wafer (object to be polished). In particular, the present invention relates to a retainer ring having a two-layer structure in which a first ring and a second ring are overlapped and integrated.

 Background art

 [0002] As the integration and performance of semiconductor devices increase, the dimensions in the horizontal direction (on the plane) become 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 (such as a silicon substrate) needs to be high. For this reason, it is required to increase the flatness at the wafer stage, and CMP devices are used to meet such demands.

 [0003] This CMP apparatus includes, for example, a rotatable surface plate, a polishing pad disposed on the surface plate, a holding head for holding a wafer and pressing the polishing pad, and a slurry supply nozzle Etc. 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. The air chamber includes an air supply path for supplying pressurized air to the air chamber. The retainer ring surrounds the outer periphery of the wafer to prevent the wafer from popping out, and presses the polishing surface (surface) of the polishing pad for polishing the wafer to flatten and refine the polishing surface (optimization). 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. In other words, engineering by the first metal ring The second ring made of polyethylene is reinforced to increase the rigidity of the entire retainer ring. A retainer ring in which two rings are integrated (assembled) by tightening with a port is known, and a retainer ring in which two rings are integrated with an adhesive (bonding agent) is known.

 [0005] That is, in the two-layer retainer ring by port tightening, as shown in FIG. 7, a plurality of port insertion holes 1 0 0 a are formed in the first ring 1 0 0 and the second ring 1 0 1 is A plurality of screw holes 1 0 1 a (female screws) are formed at the same position as the port insertion hole 1 0 0 a. Then, the 1st ring 1 0 0 and the 2nd ring 1 0 1 are overlapped, and the pole 卜 1 0 2 is inserted into each port 揷 insertion hole 1 0 0 a and tightened into the screw hole 1 0 1 a (screwed) Thus, the two rings 100 and 100 are integrated (see, for example, Patent Document 1).

 [0006] In addition, in the retainer ring having a two-layer structure with an adhesive, as shown in FIG. 8, the lower surface 1 1 0 a of the first ring 1 1 0 and the upper surface 1 1 1 a of the second ring 1 1 1 Adhesive 1 1 2 is applied, and the two rings 1 1 0 and 1 1 1 are integrated by applying pressure by overlapping the first ring 1 1 0 and the second ring 1 1 1 It is. Note that a plurality of screw holes for mounting on the holding head are formed in the first ring 100 0 of the retainer ring by port tightening and the first ring 110 of the retainer ring by adhesive.

 Patent Document 1: Japanese Patent Laid-Open No. 2 0 0 _ 3 4 9 5 9

 Disclosure of the invention

 Problems to be solved by the invention

[0007] By the way, in the retainer ring having a two-layer structure by the above-described por clamping, the porch is loosened by vibrations and repeated stress (compressive stress, shear stress, etc.) associated with wafer polishing, and the second ring The pressing force on the polishing pad due to flatness and retainer ring may be uneven. Moreover, since all the ports 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 pressing force on the lower surface and the pressing surface of the other part will be different (the pressing force will be uneven). Furthermore, even a slight difference in the tightening force of the port will change the flatness of the pressing surface, or the second ring will bend and the pressing force will be 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, etc.).

 [0008] On the other hand, in the retainer ring having a two-layer structure using the 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) or abrasive debris enters between the first ring and the second ring. In addition, since it is difficult for the adhesive preparation and application to be completely uniform, non-uniformity in the preparation and application of the adhesive makes it more likely that the first ring and the second ring will peel off. Alternatively, the integration (adhesion) of the first ring and the second ring becomes unstable.

 [0009] Furthermore, the present inventor has discovered and confirmed that the adhesive may be eluted. In other words, we discovered and confirmed that the chemical agent of the slurry could cause the adhesive to be chemically decomposed and the adhesive to elute. When such adhesive elution occurs, the first ring and second ring peel off, and the eluted adhesive causes scratches on the wafer.

 Accordingly, 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, and the pressing force is uniform. And

 Means for solving the problem

[0011] In order to achieve the above object, the invention according to claim 1 is provided so as to be detachable in the holding head of the CMP apparatus, and the annular first ring and the second ring are concentrically stacked. A two-layer retainer ring integrated together, wherein the first ring is interposed between the first ring located in the upper layer and the second ring located in the lower layer. And at least one of the second ring and a welded portion joined to the other.

[0012] The invention according to claim 2 is the retainer ring having a two-layer structure according to claim 1, wherein the first ring and the second ring are vertically fitted and overlapped with each other. It is characterized by that.

[0013] In the invention according to claim 3, in the retainer ring having a two-layer structure according to claim 1, the first ring and the second ring are press-fitted in a vertical direction and overlapped with each other. It is characterized by.

[0014] In the invention according to claim 4, in the retainer ring having the two-layer structure according to claim 1, 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. It is characterized by being.

[0015] The invention according to claim 5 is the retainer ring having a two-layer structure according to claim 1, wherein the fixing member passes through the welded portion and the first ring and the second ring. It is characterized by being inserted into.

 The invention's effect

 [0016] According to the invention described in claim 1, since the weld portion is provided between the first ring and the second ring, the integration of the first ring and the second ring is firmly maintained. The 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 part) does not loosen, and the integration of the first ring and the second ring is firmly maintained. In addition, since no adhesive is used, the first ring and the second ring are not peeled off due to deterioration or elution of the adhesive, and scratches do not occur on the wafer due to the eluted adhesive. In addition, the flatness of the retainer ring (second ring) is maintained by maintaining strong integration between the first ring and second ring, and it is also necessary to provide port insertion holes and screw holes. As a result, the pressure applied to the polishing pad is uniform.

[0017] According to the invention of claim 2, the first ring and the second ring are arranged in the vertical direction. Since they are fitted, the integration of the first ring and the second ring becomes stronger, and it is possible to strongly counter the shearing force associated with wafer polishing (does not peel off due to the shearing force).

 [0018] According to the invention of 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 Can strongly resist the shearing force associated with wafer polishing

[0019] According to the invention of claim 4, since 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, the second ring that is melted or the first ring that is melted As the bonding area increases, the bonding becomes three-dimensional (three-dimensional). As a result, the integration (bonding) of the first ring and the second ring becomes stronger.

 [0020] According to the invention of claim 5, since the fixing member passes through the welded portion and is inserted into the first ring and the second ring, the first ring and the second ring can be integrated. It is stronger and can counteract the shearing force associated with wafer polishing.

 Brief Description of Drawings

 FIG. 1 is a front view showing a schematic configuration of a CMP apparatus according to Embodiments 1 to 3 of the present invention.

 2 is a schematic cross-sectional view of a holding head of the CMP apparatus of FIG.

 FIG. 3A is a plan view of a first ring of a two-layered retainer ring according to Embodiment 1 of the present invention, and FIG.

 FIG. 4 is a plan view (a) of a second ring of a two-layered retainer ring according to Embodiment 1 of the present invention and a B_B sectional view (b) thereof.

 FIG. 5 is a plan view (a) of a two-layered retainer ring according to Embodiment 2 of the present invention and a C_C sectional view (b) thereof.

FIG. 6 is a plan view (a) of a two-layer structure retainer ring according to Embodiment 3 of the present invention and a D_D sectional view (b) thereof. [FIG. 7] A perspective view (a) showing a conventional two-layer retainer ring in which the first ring and the second ring are integrated by port fastening, and an E_E sectional view (b) thereof.

 FIG. 8 is a perspective view showing a conventional two-layer structure retainer ring in which a first ring and a second ring are integrated with an adhesive.

Explanation of symbols

 1 C M P equipment

 2 Surface plate

 3 Polishing pad

 3 a polished surface

 4 Retention head

 5 Slurry supply nozzle

 5 a slurry

 6 Dresser

 7 Head body

 8 Two-layer retainer

 9 Elastic membrane

 1 0 Air chamber

 1 1 1st ring

 1 1 a Top view

 1 1 b Screw hole

 1 1 c uneven

 1 2 Second ring

 1 2 a Press surface

 1 2 b Slit

 1 2 c Top view

 1 3 Welded part

2 0 2 layer retainer 2 1 1st ring

 2 1 a Mated press-fit part

 2 2 2nd ring

 2 2 a top

 2 3 weld

 3 0 2-layer retainer ring

 3 1 1st ring

 3 1 a Insertion hole

 3 2 Second ring

 3 2 a Insertion hole

 3 3 Welded part

 3 4 Fixing pin (fixing member)

 W wafer

 W 1 Surface to be polished

 W 2 top surface

 BEST MODE FOR CARRYING OUT THE INVENTION

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

 [0024] (Embodiment 1)

 FIG. 1 is a front view showing a schematic configuration of a CMP apparatus 1 according to this embodiment. This CMP apparatus 1 has the same configuration as a widely used CMP apparatus except for a retainer ring 8 having a two-layer structure, which will be described later, and a detailed description is omitted here, but in this embodiment, A rotatable surface 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), and a wafer W is chemically and mechanically polished.

[0025] 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 if it rotates (rotates). . This holding head 4 is shown in FIG. 2 in this embodiment. The head body 7, a retainer ring 8 that is detachably disposed at the lower portion of the head body 7, and an elastic film 9 that is located in the retainer ring 8 and presses the upper surface W 2 of the wafer W. I have. Then, air for pressurization is supplied to the air chamber 10 surrounded by the head body 7, the retaining ring 8, and the elastic film 9, and the wafer W is pressed against the polishing pad 3 through the elastic film 9. .

 [0026] 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 polishes the polishing pad 3 for polishing the polished surface W1 of the wafer W. The surface 3 a (surface) is pressed, and the polished surface 3 a is flattened and refined (optimized). That is, the polishing surface 3 a of the polishing pad 3 has a low flatness due to the slurry (abrasive) 5 a and a rough surface, and the polishing surface 3 a has a flatness due to the retainer ring 8. It increases the surface roughness and decreases the surface roughness. This retainer ring 8 consists of a first ring 1 1 made of stainless steel (such as SUS 3 0 4 or SUS 3 1 6) and a second ring 1 2 made of a super-shearing plastic (such as PPS or PEEK). It has a two-layer structure concentrically stacked in the vertical direction. 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). (Has welded part 1 3).

 [0027] From the upper surface 1 1 a of the first ring 1 1, as shown in FIG. 3, the retainer ring

 A plurality of screw holes 1 1 b for attaching 8 to the holding head 4 are formed. In addition, as will be described later, the lower surface of the first ring 11 1 does not melt when integrated with the second ring 12, and irregularities 11 c (such as knurled eyes and wave eyes) are formed over the entire surface. ing.

[0028] The inner diameter and the outer diameter of the second ring 1 2 are substantially the same as the inner diameter and the outer diameter of the first ring 1 1, and a pressing surface 1 2 a (lower surface) that presses the polishing surface 3 a of the polishing pad 3 As shown in FIG. 4, a plurality of groove-like slits 1 2 b are formed for escaping (discharging) polishing debris. Further, the upper surface 1 2 c before being integrated with the first ring 11 1 is formed flat (flat). [0029] The welded part 1 3 is a joined part in which the upper surface 1 2 c side upper part (one side) of the second ring 1 2 is melted and joined to the lower side of the first ring 1 1, that is, the lower part (the other). The first ring 11 and the second ring 12 are integrated by the welded portion 13. Here, bonding is a broad concept including adhesion, fusion, fusion, and bonding. This welded part 1 3 is formed by welding, high frequency welding by high frequency induction heating, heat welding heated by heat conduction from an external heat source (hot plate welding, hot air welding, impulse welding, iron welding Which method is used, such as ultrasonic welding using frictional heat generated by ultrasonic vibration, laser welding using heat generated by laser irradiation, or infrared welding using heat generated by infrared irradiation? The first ring 1 1 and the second ring 1 2 are selected according to the material and shape of the ring. Also, as shown in Fig. 2, the first ring 11 side (upper surface side) of the welded part 13 has a shape that follows (follows) the unevenness 11c as it melts and solidifies (solidifies). Yes.

 [0030] According to the two-layered retainer ring 8 configured as described above, the first ring 1

 Since the welded portion 13 is formed between the first ring 2 and the second ring 12, the integration of the first ring 1 1 and the second ring 1 2 is firmly maintained. That is, the upper surface 12 c side of the second ring 12 2 is melted and joined to the lower surface side of the first ring 11, so that the first ring 11 and the second ring 12 are integrated (joined). Therefore, even if vibration or repetitive stress accompanying polishing of wafer W is applied to the retainer ring 8, the bonding (welded portion 13) does not loosen, and the first ring 11 and second ring Integration with Ring 1 2 is maintained firmly. Moreover, the unevenness 1 1 c is formed on the lower surface of the first ring 1 1, and the first ring 1 1 side of the welded portion 1 3 is shaped along the unevenness 1 1 c. As the joint area with the second ring 1 2 increases, the joint becomes three-dimensional (three-dimensional). As a result, the integration (joining) of the first ring 1 1 and the second ring 1 2 becomes stronger.

[0031] In addition, since no adhesive or the like is used, the first ring 1 1 and the second ring 1 2 may be peeled off due to deterioration or elution of the adhesive, or due to the eluted adhesive, No scratches occur. In addition, the first ring 1 1 and the first Since the flatness of the retainer ring 8 (second ring 1 2) is maintained by maintaining the strong integration with the 2 ring 1 2, it is not necessary to provide a port insertion hole or screw hole. The pressing force to the polishing pad 3 becomes uniform.

 [Embodiment 2]

 FIG. 5 is a plan view (a) showing a two-layered retainer ring 20 according to this embodiment, and a CC sectional view (b) thereof. In this embodiment, the first ring 21 and the second ring 22 are fitted and press-fitted, and the configuration is different from that of the first embodiment.

 [0033] That is, along the entire circumference of the lower surface (lower part) of the first ring 21, the fitted press-fit part 2 1 having a circular section (concentric with the first ring 21) having a concave cross section in the thickness direction. a is formed. The width H 1 of the fitted press-fit portion 2 1 a is set to be slightly smaller than the width H 2 of the second ring 2 2. Then, with the upper part 2 2 a of the second ring 2 2 fitted and press-fitted into the fitting press-fit part 21 a, the first ring 21 and the second ring 22 are in the vertical direction (thickness direction). ) Are fitted and press-fitted to overlap. Further, the upper part 2 2 a of the second ring 2 2 is melted and joined to the fitted press-fitted part 2 1 a of the first ring 21, thereby forming a welded part 2 3. The first ring 2 1 and the second ring 2 2 are integrated.

 [0034] According to the two-layered retainer ring 20 configured as described above, the first ring

 2 Since the upper part 2 2 a of the second ring 2 2 is fitted and press-fitted into the fitted press-fit part 2 1 a, the first ring 2 1 and the second ring 2 2 can be integrated. It becomes stronger. Moreover, even if the shearing force (horizontal force in the figure) accompanying the polishing of the wafer W is applied to the second ring 22, the shearing force is applied by the side walls (both sides of the recess) of the fitted press-fit portion 2 1 a. Received (shearing force is well transmitted to the first ring 3 1). Therefore, it is possible to strongly counter the shearing force, and the first ring 21 and the second ring 22 are not separated by the shearing force.

 [0035] (Embodiment 3)

FIG. 6 is a plan view (a) showing a two-layer structure retainer ring 30 according to this embodiment and a DD cross-sectional view (b) thereof. In this embodiment, the first The first embodiment is different from the first embodiment in that a plurality of fixing pins 3 4 (fixing members) are inserted into the ring 3 1 and the second ring 3 2.

 That is, a plurality of insertion holes 3 1 a are formed from the lower surface of the first ring 3 1, and a plurality of insertion holes are formed from the upper surface of the second ring 3 2 at the same position as the insertion holes 3 1 a. 3 2 a is formed. Here, the inner diameters of the insertion holes 3 1 a and 3 2 a are the same as the outer diameter of the fixing pins 3 4, and the fixing pins 3 4 are fitted into the insertion holes 3 1 a and 3 2 a ( It fits without gaps). The fixing pin 3 4 is a round bar made of stainless steel.

 [0037] Then, the boundary between the first ring 3 1 and the second ring 3 2, that is, a welded portion described later.

 Through 3 3, the fixing pin 3 4 is inserted into the insertion hole 3 1 a of the first ring 3 1 and the insertion hole 3 2 a of the second ring 3 2. In addition, the upper part of the second ring 3 2 is melted and joined to the lower part of the first ring 3 1 to form a welded part 33, and the welded part 3 3 forms the first ring 31 and the second ring. 3 2 is integrated.

 [0038] According to the two-layer structure retainer ring 30 configured as described above, the fixing pin 3 4 penetrates the welded portion 3 3 and is inserted into the first ring 3 1 and the second ring 3 2. Therefore, the integration of the first ring 3 1 and the second ring 3 2 becomes stronger. In addition, even if the shearing force accompanying the polishing of the wafer W is applied to the second ring 3 2, the shearing force is well transmitted to the first ring 3 1 through the fixing pins 3 4. For this reason, it is possible to strongly counter the shearing force, and the first ring 31 and the second ring 32 are not separated by the shearing force.

[0039] While the first to third embodiments of the present invention have been described above, the specific configuration is not limited to these embodiments, and the design is within a range not departing from the gist of the present invention. Any changes are included in the present invention. For example, in Embodiments 1 to 3, the second ring located in the lower layer is melted and joined to the first ring located in the upper layer to form a welded portion. However, the first ring and the second ring are formed. Depending on the material and shape, the first ring may be melted to form the welded portion, or the first ring and the second ring are melted together to form the welded portion. You may make it do. Therefore, when only the first ring is melted, the unevenness (unevenness 11 C) as described above 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, but the first ring is made of another metal, ceramic, or resin material, Of course, the second ring may be made of other resin materials.

Claims

The scope of the claims  [1] CMP device is detachably disposed in the holding head of the device, and the annular first ring and first ring  It is a two-layer retainer ring in which two rings are concentrically stacked and integrated.  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 Yes Two-layer retainer ring.  [2] The retainer ring having a two-layer structure according to [1], wherein the first ring and the second ring are fitted and overlapped in the vertical direction.  [3] The retainer ring having a two-layer structure according to [1], wherein the first ring and the second ring are press-fitted in a vertical direction and overlapped with each other.  [4] The two-layered retainer ring 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.  5. The two-layer structure retaining ring according to claim 1, wherein the fixing member is inserted into the first ring and the second ring through the welded portion.