Retainer ring and substrate holding apparatus

Abstract

To provide a retainer ring provided in a substrate holding apparatus in order to match a polishing profile of an entire substrate including an edge portion of the substrate to a desired profile.SOLUTION: A retainer ring 32 is used in a substrate holding apparatus 7 for polishing a substrate W by pressing the substrate W against a polishing pad 2 to which a polishing liquid is supplied. The retainer ring 32 has a ring shape and includes a ring body 50 that supports an outer periphery of the substrate W pressed against the polishing pad 7. The ring body 50 includes at least one ring groove 51 that is formed on a lower surface 50a pressed against the polishing pad 7 and extends concentrically with the ring body 50, and a barrier 55 that inhibits the polishing liquid from reaching an inside of the ring body 50 from an outside thereof.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a retainer ring provided in a substrate holding device for polishing a substrate such as a wafer, and also to a substrate holding device equipped with such a retainer ring. [Background technology]

[0002] In the manufacturing process of semiconductor devices, planarization of the semiconductor device surface is important. The most important technology for this surface planarization is chemical mechanical polishing (CMP). CMP involves supplying a polishing liquid (e.g., slurry) containing abrasive grains such as silica (SiO2) onto the polishing surface of a polishing pad while sliding a substrate such as a wafer against the polishing surface.

[0003] A polishing apparatus for performing CMP includes a polishing table that supports a polishing pad having a polishing surface and a substrate holding device that holds a substrate. In such a polishing apparatus, a slurry is supplied onto the polishing pad while the polishing table rotates together with the polishing pad. The substrate holding device presses the substrate against the polishing surface of the polishing pad while rotating the substrate. As the substrate slides against the polishing pad in the presence of the slurry, the surface of the substrate is planarized by a combination of the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0004] The substrate holder includes a retainer ring that surrounds the substrate to prevent the substrate from coming off the substrate holder during polishing, and rotates to press the polishing pad against the outside of the substrate during polishing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-193068 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been an increasing demand for more precise control of the substrate film thickness profile (i.e., improving the in-plane uniformity, which represents the flatness of the substrate surface) in order to accommodate various initial film thickness profiles that can vary depending on the semiconductor device and CMP process, and for reasons such as improving yield.

[0007] However, controlling the polishing profile at the edge of the substrate is extremely difficult due to factors such as the high contact pressure between the edge of the substrate and the polishing pad, the influence of pad rebound, and the influence of contact between the retainer ring and the edge of the substrate. Here, it is possible to adjust the polishing rate at the edge of the substrate by adjusting the pressure of the retainer ring. However, changing the pressure of the retainer ring changes the polishing rate over a relatively wide range, including not only the edge of the substrate but also other regions.

[0008] Therefore, the present invention provides a retainer ring that is provided in a substrate holding device to match the polishing profile of the entire substrate, including the edge portion of the substrate, to a desired profile, and further provides a substrate holding device that uses such a retainer ring. [Means for solving the problem]

[0009] In one aspect, a retainer ring is provided for use in a substrate holding device for polishing a substrate by pressing the substrate against a polishing pad supplied with a polishing liquid, the retainer ring having a ring shape and including a ring body that supports the outer periphery of the substrate pressed against the polishing pad, the ring body having at least one ring groove formed on its underside that is pressed against the polishing pad and extending concentrically with the ring body, and a barrier that prevents the polishing liquid from reaching the inside of the ring body from the outside.

[0010] In one aspect, the barrier is a scraper placed in the ring groove, and the scraper has a tip that contacts or is close to the polishing pad when polishing the substrate, and releases the polishing liquid stagnating in the ring groove to the outside of the retaining ring. In one aspect, the barrier is a concave-convex structure formed in the ring groove, and the concave-convex structure creates an air flow from the inner peripheral surface of the ring groove toward the outer peripheral surface. In one embodiment, the barrier is an adsorbent material disposed in the ring groove and capable of adsorbing the polishing liquid.

[0011] In one embodiment, the ring groove is a plurality of ring grooves, and the barrier is disposed in at least one of the plurality of ring grooves. In one embodiment, the retainer ring further includes at least one lateral groove extending from the ring groove to the outer circumferential surface of the ring body.

[0012] In one aspect, a substrate holding device is provided, comprising: a head body for holding a substrate and pressing the substrate against a polishing pad to polish the substrate; and a retainer ring arranged to surround the substrate held by the head body, the retainer ring being the retainer ring described above. [Effects of the Invention]

[0013] The combination of the ring groove and the barrier in the retainer ring significantly reduces the amount of polishing liquid that reaches the outer peripheral polishing area of ​​the pad, which is the polishing area of ​​the polishing head that is closest to the outer periphery of the polishing pad. As a result, the polishing rate at the edge of the substrate can be made to be approximately the same as the polishing rate at other parts of the substrate, thereby improving the in-plane uniformity of the entire polished substrate. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a polishing apparatus according to one embodiment. [Figure 2]FIG. 2 is a cross-sectional view schematically showing a polishing head according to an embodiment. [Figure 3] FIG. 3 is a schematic diagram for explaining the region near the outer periphery of the polishing pad when polishing a wafer. [Figure 4] FIG. 4(a) is a horizontal cross-sectional view that schematically shows a retainer ring according to one embodiment, and FIG. 4(b) is a vertical cross-sectional view that schematically shows the retainer ring shown in FIG. 4(a). [Figure 5] FIG. 5(a) is a development view that schematically shows a retainer ring according to another embodiment, and FIG. 5(b) is a horizontal cross-sectional view of a portion of the retainer ring shown in FIG. 5(a). [Figure 6] 6(a) to 6(c) are development views showing modified examples of the concave-convex structure. [Figure 7] FIG. 7(a) is a horizontal cross-sectional view schematically showing a retainer ring according to still another embodiment, and FIG. 7(b) is a vertical cross-sectional view schematically showing the retainer ring shown in FIG. 7(a). [Figure 8] FIG. 8 is a horizontal cross-sectional view schematically showing a part of a retainer ring according to still another embodiment. [Figure 9] 9(a) is a horizontal cross-sectional view schematically showing a portion of a modified example of the retainer ring shown in FIG. 4(a), and FIG. 9(b) is a horizontal cross-sectional view schematically showing a portion of a modified example of the retainer ring shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a polishing apparatus according to one embodiment. The polishing apparatus shown in FIG. 1 is an apparatus for chemically and mechanically polishing a wafer W, which is an example of a substrate. As shown in FIG. 1, this polishing apparatus includes a polishing table 5 that supports a polishing pad 2 having a polishing surface 2a, a substrate holding device 7 that presses the wafer W against the polishing surface 2a, a polishing liquid supply nozzle 8 that supplies a polishing liquid (e.g., a slurry containing abrasive grains) to the polishing surface 2a, and a control device 10 that controls at least the operation of the substrate holding device 7. The substrate holding device 7 is sometimes referred to as a polishing head or a top ring, and is configured to hold the wafer W on its underside. Hereinafter, the substrate holding device 7 will be referred to as the "polishing head 7."

[0016] The control device 10 is composed of at least one computer. The control device 10 includes a storage device 10a storing a program and an arithmetic device 10b that executes calculations according to instructions included in the program. The storage device 10a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic device 10b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the control device 10 is not limited to these examples. In this embodiment, the control device 10 is configured to control the operation of the entire polishing apparatus.

[0017] The polishing apparatus further includes a support shaft 14, a polishing head swing arm 16 connected to the upper end of the support shaft 14, and a polishing head shaft 18 rotatably supported at the free end of the polishing head swing arm 16. The polishing head 7 is fixed to the lower end of the polishing head shaft 18. A polishing head rotation mechanism (not shown) equipped with an electric motor and the like is disposed within the polishing head swing arm 16. This polishing head rotation mechanism is connected to the polishing head shaft 18 and is configured to rotate the polishing head shaft 18 and the polishing head 7 in the direction indicated by the arrow.

[0018] The polishing head shaft 18 is connected to a polishing head lifting mechanism (including a ball screw mechanism, etc.) not shown. This polishing head lifting mechanism is configured to move the polishing head shaft 18 up and down relative to the polishing head swing arm 16. The up and down movement of the polishing head shaft 18 allows the polishing head 7 to move up and down relative to the polishing head swing arm 16 and the polishing table 5, as shown by the arrows.

[0019] The polishing apparatus further includes a table rotation motor 21 that rotates the polishing pad 2 and polishing table 5 about their respective axes. The table rotation motor 21 is disposed below the polishing table 5, and the polishing table 5 is connected to the table rotation motor 21 via a table shaft 5a. The polishing table 5 and polishing pad 2 are rotated by the table rotation motor 21 about the table shaft 5a in the direction indicated by the arrow. The polishing pad 2 is affixed to the upper surface of the polishing table 5. The exposed surface of the polishing pad 2 constitutes a polishing surface 2a that polishes the wafer W. The polishing surface 2a of the polishing pad 2 may have a grid-like and / or ring-like groove formed thereon.

[0020] The wafer W is polished as follows. The wafer W is held by the polishing head 7 with its surface to be polished facing downward. While the polishing head 7 and polishing table 5 are rotating, a polishing liquid (e.g., a slurry containing abrasive grains) is supplied onto the polishing surface 2a of the polishing pad 2 from a polishing liquid supply nozzle 8 provided above the polishing table 5. The polishing pad 2 rotates integrally with the polishing table 5 around its central axis. The polishing head 7 is moved to a predetermined height by a polishing head lifting mechanism (not shown). The polishing head 7 is then maintained at the predetermined height and presses the wafer W against the polishing surface 2a of the polishing pad 2. The wafer W rotates integrally with the polishing head 7. With the polishing liquid present on the polishing surface 2a of the polishing pad 2, the wafer W is brought into sliding contact with the polishing surface 2a. If the polishing surface 2a has grid-shaped and / or ring-shaped grooves, the polishing liquid that has penetrated into the grooves is used to polish the wafer W, resulting in efficient polishing of the wafer W. The surface of the wafer W is polished by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and the polishing pad 2.

[0021] In this embodiment, the polishing apparatus is equipped with a film thickness sensor 42 that measures the film thickness of the wafer W on the polishing surface 2a. The film thickness sensor 42 is configured to generate a polishing index value that directly or indirectly indicates the film thickness of the wafer W. This polishing index value changes according to the film thickness of the wafer W, and therefore indicates the film thickness of the wafer W. The polishing index value may be a value that represents the film thickness itself of the wafer W, or may be a physical quantity or signal value before being converted into film thickness.

[0022] Examples of the film thickness sensor 42 include an optical film thickness sensor and an eddy current sensor. The optical film thickness sensor is configured to irradiate the surface of the wafer W with light and determine the film thickness of the wafer W from the spectrum of the light reflected from the wafer W. The eddy current sensor is configured to induce eddy currents in a conductive film formed on the wafer W and output a signal value that varies according to the impedance of an electric circuit including the conductive film and a coil of the eddy current sensor. Known devices can be used for the optical film thickness sensor and eddy current sensor.

[0023] The film thickness sensor 42 is installed inside the polishing table 5 and rotates integrally with the polishing table 5. More specifically, the film thickness sensor 42 is configured to measure film thicknesses at multiple measurement points on the wafer W while crossing the wafer W on the polishing surface 2a each time the polishing table 5 makes one rotation. In this embodiment, the film thickness sensor 42 is disposed so as to measure film thicknesses at multiple measurement points including the center of the wafer W. Therefore, the multiple measurement points are aligned in the radial direction of the wafer W.

[0024] The film thickness sensor 42 is connected to the control device 10. The film thickness measurement values ​​generated by the film thickness sensor 42 are monitored by the control device 10. That is, the film thickness measurement values ​​at multiple measurement points on the wafer W are output from the film thickness sensor 42, sent to the control device 10, and stored in the storage device 10a. The control device 10 creates a film thickness profile of the wafer W based on the film thickness measurement values. The film thickness profile represents the film thickness distribution along the radial direction of the wafer W.

[0025] Next, the polishing head 7 will be described. Fig. 2 is a cross-sectional view schematically showing a polishing head according to one embodiment. The polishing head 7 includes a head main body 31 fixed to the end of the polishing head shaft 18, an elastic membrane 34 attached to the lower part of the head main body 31, and a retainer ring 32 disposed below the head main body 31. The retainer ring 32 is disposed around the elastic membrane 34. The retainer ring 32 is a ring-shaped structure that holds the outer periphery of the wafer W to prevent the wafer W from jumping out of the polishing head 7 during polishing.

[0026] Four pressure chambers C1, C2, C3, and C4 are provided between the elastic membrane 34 and the head body 31. The pressure chambers C1, C2, C3, and C4 are formed by the elastic membrane 34 and the head body 31. The central pressure chamber C1 is circular, and the other pressure chambers C2, C3, and C4 are annular. These pressure chambers C1, C2, C3, and C4 are arranged concentrically.

[0027] Gas transfer lines F1, F2, F3, and F4 are connected to the pressure chambers C1, C2, C3, and C4, respectively. One end of the gas transfer lines F1, F2, F3, and F4 is connected to a compressed gas supply source (not shown) provided as a utility in the factory where the polishing apparatus is installed. Compressed gas, such as compressed air, is supplied to the pressure chambers C1, C2, C3, and C4 through the gas transfer lines F1, F2, F3, and F4, respectively. The compressed gas in the pressure chambers C1, C2, C3, and C4 presses the wafer W against the polishing surface 2a of the polishing pad 2 via the elastic film 34.

[0028] The gas transfer line F3 communicating with the pressure chamber C3 is connected to a vacuum line (not shown), making it possible to create a vacuum within the pressure chamber C3. An opening is formed in the elastic film 34 that constitutes the pressure chamber C3, and by creating a vacuum within the pressure chamber C3, the wafer W is attracted and held to the polishing head 7. Furthermore, by supplying compressed gas to the pressure chamber C3, the wafer W is released from the polishing head 7.

[0029] An annular elastic membrane 36 is disposed between the head body 31 and the retaining ring 32, and a pressure chamber C5 is formed inside this elastic membrane 36. The pressure chamber C5 is connected to the compressed gas supply source via a gas transfer line F5. Compressed gas is supplied into the pressure chamber C5 through the gas transfer line F5, and the compressed gas inside the pressure chamber C5 presses the retaining ring 32 against the polishing pad 2.

[0030] The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 40 attached to the polishing head shaft 18. The gas transfer lines F1, F2, F3, F4, and F5, which communicate with the pressure chambers C1, C2, C3, C4, and C5, are provided with pressure regulators R1, R2, R3, R4, and R5, respectively. Compressed gas from a compressed gas supply source is supplied independently into the pressure chambers C1 to C5 through the pressure regulators R1 to R5. The pressure regulators R1 to R5 are configured to adjust the pressure of the compressed gas in the pressure chambers C1 to C5.

[0031] The pressure regulators R1 to R5 can independently change the internal pressures of the pressure chambers C1 to C5, thereby independently adjusting the pressures applied to the four corresponding regions of the wafer W, i.e., the center, inner middle, outer middle, and edge regions, and the pressure applied to the retainer ring 32 against the polishing pad 2. The gas transfer lines F1, F2, F3, F4, and F5 are also connected to atmospheric relief valves (not shown), allowing the pressure chambers C1 to C5 to be opened to the atmosphere. In this embodiment, the elastic membrane 34 forms four pressure chambers C1 to C4; however, in another embodiment, the elastic membrane 34 may form fewer or more than four pressure chambers. Only a single pressure chamber may be provided.

[0032] The pressure regulators R1 to R5 are connected to the control device 10. The control device 10 receives measured values ​​of the film thickness of the wafer W from the film thickness sensor 42 (see FIG. 1), determines target pressure values ​​for the pressure chambers C1 to C5 to achieve a target film thickness profile based on the measured film thickness, and transmits the target pressure values ​​to the pressure regulators R1 to R5. The pressure regulators R1 to R5 operate to maintain the pressures in the pressure chambers C1 to C5 at the corresponding target pressure values.

[0033] The polishing head 7 can apply independent pressures to multiple regions of the wafer W. For example, the polishing head 7 can press different regions of the surface of the wafer W against the polishing surface 2a of the polishing pad 2 with different pressures. Therefore, the polishing head 7 can control the film thickness profile of the wafer W to achieve a target film thickness profile.

[0034] As described above, it is extremely difficult to control the polishing profile at the edge of the wafer W for reasons such as an increased contact pressure between the edge of the wafer W and the polishing pad 2, the influence of pad rebound, and the influence of contact between the retainer ring 32 and the edge of the wafer W. Furthermore, if the pressing force of the retainer ring 32 against the polishing pad 2 is changed with the intention of adjusting the polishing rate at the edge of the wafer W, the polishing rate of the wafer W will change not only at the edge of the wafer W but also over a relatively wide range including other regions.

[0035] As a result of extensive research into the change in the polishing rate across the entire surface of the wafer W, the inventors discovered that the polishing rate of the edge portion of the wafer W polished in the region of the polishing head 7 near the outer periphery of the polishing pad 2 is higher than the polishing rate of the edge portion of the wafer W polished in other regions. FIG. 3 is a schematic diagram illustrating the polishing region of the polishing head 7 near the outer periphery of the polishing pad 2 when polishing a wafer. As shown in FIG. 3, when the rotating polishing head 7 presses the wafer W against the rotating polishing pad 2 to polish the wafer W, the polishing rate of the edge portion of the wafer W in the region of the polishing head 7 near the outer periphery of the polishing pad 2 (see the thick line in FIG. 3) is higher than the polishing rate of the edge portion of the wafer W in other regions of the polishing head 7. In this specification, the polishing region of the wafer W in the polishing head 7 surrounded by the thick line in FIG. 3 is referred to as the "pad outer periphery side polishing region."

[0036] Therefore, the inventors have found that it is possible to improve the in-plane uniformity of the entire wafer W, including the edge portion of the wafer W, by reducing (or controlling) the amount of polishing liquid that reaches the pad outer peripheral polishing region of the rotating polishing head 7 and intentionally lowering the polishing rate of the edge portion of the wafer W in the pad outer peripheral polishing region of the polishing head 7. Below, a configuration for reducing the amount of polishing liquid that reaches the pad outer peripheral polishing region of the polishing head 7 will be described. To achieve this aim, the retainer ring 32 of the polishing head 7 is provided with a barrier that prevents the polishing liquid (slurry) from reaching the pad outer peripheral polishing region of the polishing head 7.

[0037] FIG. 4(a) is a horizontal cross-sectional view schematically illustrating a retainer ring according to one embodiment, and FIG. 4(b) is a vertical cross-sectional view schematically illustrating the retainer ring shown in FIG. 4(a). FIG. 4(a) corresponds to a cross-sectional view taken along line AA in FIG. 4(b). As shown in FIGS. 4(a) and 4(b), the retainer ring 32 includes a ring-shaped ring body 50. The ring body 50 has a lower surface 50a that is pressed against the polishing surface 2a of the polishing pad 2 during polishing of the wafer W, and the lower surface 50a extends in a ring shape. The inner peripheral surface of the ring body 50 holds the outer periphery of the wafer W during polishing, thereby preventing the wafer W from jumping out of the polishing head 7 during polishing.

[0038] Furthermore, the ring body 50 has a ring groove 51 formed on the lower surface 50a thereof and extending in a ring shape. The ring groove 51 is formed on the lower surface 50a of the ring body 50 concentrically with the ring body 50.

[0039] The retainer ring 32 further includes a scraper 55 disposed in the ring groove 51. The scraper 55 prevents the polishing liquid (slurry) supplied from the polishing liquid supply nozzle 8 to the polishing surface 2a of the polishing pad 2 from reaching the inside of the ring body 50 of the retainer ring 32. That is, in this embodiment, the scraper 55 functions as a barrier that prevents the polishing liquid from reaching the polishing region of the polishing head 7 on the outer periphery of the pad (see the thick line in FIG. 3).

[0040] The scraper 55 shown in FIGS. 4(a) and 4(b) extends from the top surface (upper surface) of the ring groove 51 toward the polishing pad 2. In this embodiment, the tip (lower end) of the scraper 55 protrudes beyond the lower surface 50a of the ring body 50 of the retaining ring 32. When the polishing head 7 is brought into contact with the polishing surface 2a of the polishing pad 2, the tip of the scraper 55 also comes into contact with the polishing surface 2a of the polishing pad 2. Therefore, the scraper 55 has sufficient elasticity to be deformed by the pressing force applied by the polishing head 7 to the polishing pad 2 when polishing the wafer W. Furthermore, because the retaining ring 32 is scraped away by polishing the wafer W, it is preferable that the scraper 55 also have a hardness similar to that of the retaining ring 32. Examples of materials for the scraper 55 include rubber and resin having appropriate elasticity and hardness.

[0041] During polishing of the wafer W, polishing liquid attempting to infiltrate the inside of the retaining ring 32 from the outside of the rotating polishing head 7 is temporarily contained in the ring groove 51 formed in the lower surface 50a of the ring body 50. As a result, the polishing liquid is prevented from reaching the inside of the retaining ring 32 (i.e., the wafer W). In other words, the ring groove 51 functions as a buffer that prevents the polishing liquid flowing outside the retaining ring 32 on the polishing surface 2a of the rotating polishing pad 2 from infiltrating into the inside of the retaining ring 32 (i.e., reaching the wafer W).

[0042] In addition, the scraper 55 disposed in the ring groove 51 further prevents the polishing liquid from reaching the inside of the retainer ring 32. More specifically, the centrifugal force generated on the retainer ring 32 by the rotating polishing head 7 acts on the polishing liquid that has temporarily accumulated in the ring groove 51, and at least a portion of the polishing liquid that flows in the ring groove 51 due to the centrifugal force is discharged (or flows out) toward the outside of the retainer ring 32 before reaching the wafer W. Furthermore, as shown by the dashed-dotted arrow in FIG. 3 , the scraper 55 discharges most of the polishing liquid that has accumulated in the ring groove 51 toward the outside of the retainer ring 32 before it reaches the polishing region on the outer periphery of the pad, thereby further reducing the amount of polishing liquid that reaches the polishing region on the outer periphery of the pad.

[0043] Although the tip of the scraper 55 shown in FIGS. 4( a) and 4(b) protrudes below the lower surface of the retainer ring 32, the configuration of the scraper 55 is not limited to this embodiment. The tip of the scraper 55 does not need to protrude from the lower surface of the retainer ring 32 as long as the scraper 55 can eject at least a portion of the polishing liquid retained in the ring groove 51 toward the outside of the retainer ring 32 before it reaches the polishing region on the outer periphery of the pad. In other words, the entire scraper 55 may be housed within the ring groove 51. In this case, when polishing the wafer W, the tip of the scraper 55 is close to the polishing surface 2 a of the polishing pad 2. According to an embodiment in which the scraper 55 is housed entirely within the ring groove 51, the scraper 55 is not worn (scraped) during polishing of the wafer W, and therefore the wafer W is not damaged by abrasive powder and / or debris from the scraper 55.

[0044] According to this embodiment, the combination of the ring groove 51 and the scraper 55 functioning as a barrier can significantly reduce the amount of polishing liquid that reaches the polishing region on the outer periphery of the pad. As a result, the polishing rate of the edge portion of the wafer W in the polishing region on the outer periphery of the pad can be reduced (or adjusted). According to an experiment conducted by the inventors using a polishing head 7 equipped with the retainer ring 32 shown in FIGS. 4(a) and 4(b), it was possible to control the polishing rate of the edge portion of the wafer W in the polishing region on the outer periphery of the pad to a value equivalent to the polishing rate near the center of the wafer W. As a result, it was confirmed that the in-plane uniformity of the wafer W after polishing was improved.

[0045] Fig. 5(a) is a schematic development of a retainer ring according to another embodiment, and Fig. 5(b) is a horizontal cross-sectional view of a portion of the retainer ring shown in Fig. 5(a). The development shown in Fig. 5(a) corresponds to a planar development of a longitudinal cross-section of a ring-shaped retainer ring along the circumferential direction. The configuration of this embodiment not specifically described is similar to the embodiment described with reference to Figs. 4(a) and 4(b), and therefore a redundant description will be omitted.

[0046] In the embodiment shown in FIGS. 5(a) and 5(b), the retainer ring 32 has an uneven structure 60 formed in the ring groove 51 as a barrier instead of the scraper 55. In this embodiment, the uneven structure 60 is formed on the top surface of the ring groove 51, and recesses 60a and downwardly protruding protrusions 60b are alternately arranged in the circumferential direction of the ring groove 51. Therefore, when the polishing head 7 is pressed against the polishing pad 2 to polish the wafer W, the protrusions 60b protrude toward the polishing surface 2a of the polishing pad 2. Furthermore, as shown in FIG. 5(b), the protrusions 60b expand radially along the radial direction of the retainer ring 32, and the horizontal width (size) of the protrusions 60b expands from the inner peripheral surface of the ring groove 51 toward the outer peripheral surface.

[0047] When the retainer ring 32 rotates, the uneven structure 60 creates an air flow within the ring groove 51, from the inner peripheral surface of the ring groove 51 toward the outer peripheral surface. This air flow causes most of the polishing liquid remaining in the ring groove 51 to be expelled toward the outside of the retainer ring 32 before it reaches the polishing region on the outer peripheral side of the pad, thereby reducing the amount of polishing liquid that reaches the polishing region on the outer peripheral side of the pad. In this way, the uneven structure 60 functions as a barrier that prevents the polishing liquid from reaching the polishing region on the outer peripheral side of the pad of the polishing head 7 (see the thick line in FIG. 3).

[0048] 6(a) to 6(c) are development views showing modified examples of the concave-convex structure. In the concave-convex structure 60 shown in Fig. 6(a), the vertical cross section of the convex portion 60b is inclined in the rotation direction of the polishing head 7 when viewed horizontally. This configuration aims to increase the flow rate of air generated in the ring groove 51.

[0049] The convex portions 60b of the concave-convex structure 60 shown in FIG. 6(b) have a substantially semicircular cross section. The convex portions 60b of the concave-convex structure 60 shown in FIG. 6(c) have a substantially quadrant cross section. When the convex portions 60b have a cross section including such an arc, the polishing liquid adhering to the convex portions 60b immediately drops from the convex portions 60b. This prevents the polishing liquid adhering to the convex portions 60b from solidifying, and prevents the wafer W from being damaged by the solidified polishing liquid dropping from the convex portions 60b.

[0050] Fig. 7(a) is a horizontal cross-sectional view schematically showing a retainer ring according to yet another embodiment, and Fig. 7(b) is a vertical cross-sectional view schematically showing the retainer ring shown in Fig. 7(a). The configuration of this embodiment not specifically described is similar to the embodiment described with reference to Figs. 4(a) and 4(b), and therefore redundant description will be omitted.

[0051] In the embodiment shown in FIGS. 7(a) and 7(b), the retainer ring 32 has an adsorbent 70 disposed in the ring groove 51 as a barrier instead of the scraper 55. The adsorbent 70 is made of a material capable of adsorbing the polishing liquid. Examples of materials that can be used to make the adsorbent 70 include porous materials such as polymeric materials, foaming agents, and nonwoven fabrics. The adsorbent 70 is held in the ring groove 51 using a holding means such as an adhesive. The adsorbent 70 preferably has a hardness that is similar to or softer than the hardness of the material that makes up the retainer ring 32.

[0052] The adsorbent 70 adsorbs the polishing liquid remaining in the ring groove 51, thereby reducing the amount of polishing liquid reaching the outer peripheral polishing region of the pad. When the adsorbent 70 absorbs the polishing liquid and reaches saturation, the adsorbent 70 functions as a strong barrier to prevent further polishing liquid from entering the ring groove 51. Alternatively, the saturated adsorbent 70 can exchange some of the adsorbent with the polishing liquid that has reached the adsorbent 70, thereby functioning as a barrier to prevent the polishing liquid from entering the ring groove 51. In other words, the adsorbent 70 functions as a barrier to prevent the polishing liquid from reaching the outer peripheral polishing region of the pad (see the bold line in FIG. 3 ) of the polishing head 7. This configuration also reduces the amount of polishing liquid reaching the outer peripheral polishing region of the pad.

[0053] In the above-described embodiment, the ring body 50 has one ring groove 51, but the number of ring grooves 51 is not limited to this example. That is, the ring body 50 has at least one ring groove 51 formed on the lower surface of the ring body 50 and extending concentrically with the ring body 50.

[0054] Figure 8 is a horizontal cross-sectional view schematically showing a portion of a retainer ring according to yet another embodiment. The retainer ring 32 shown in Figure 8 has multiple (two in the illustrated example) ring grooves 51. In each ring groove 51, any of the above-mentioned scraper 55 (see Figures 4(a) and 4(b)), the above-mentioned uneven structure 60 (see Figures 5(a), 5(b), and 6(a) to 6(c)), and the above-mentioned adsorbent 70 (see Figures 7(a) and 7(b)) is arranged as a barrier.

[0055] In one embodiment, any one of the scraper 55, the uneven structure 60, and the adsorbent 70 may be disposed as a barrier in any one or some of the plurality of ring grooves 51. In this case, no barrier may be disposed in the remaining ring grooves 51.

[0056] In this way, by providing multiple ring grooves 51 and arranging barriers in some or all of the multiple ring grooves 51, it is possible to adjust the amount of polishing liquid that reaches the polishing region on the outer periphery of the pad to a desired amount, thereby enabling more precise adjustment of the polishing rate over the entire surface of the wafer W.

[0057] 9(a) is a horizontal cross-sectional view schematically illustrating a modified example of the retainer ring shown in FIG. 4(a), and FIG. 9(b) is a horizontal cross-sectional view schematically illustrating a portion of the modified example of the retainer ring shown in FIG. 8. As shown in FIG. 9(a), the retainer ring 32 may have at least one lateral groove 54 extending from (the outer peripheral surface of) the ring groove 51 to the outer peripheral surface of the ring body 50 of the retainer ring 32. The lateral groove 54 connects the ring groove 51 to the outside of the retainer ring 32. Therefore, the provision of the lateral groove 54 makes it easier to release the polishing liquid remaining in the ring groove 51 to the outside of the retainer ring 32. Although the lateral groove 54 shown in FIG. 9(a) extends in the radial direction of the retainer ring 32, the lateral groove 54 may be inclined in the rotational direction of the retainer ring 32 when viewed horizontally.

[0058] As shown in FIG. 9(b), when the retainer ring 32 has multiple ring grooves 51, the lateral grooves 54 may be composed of a first lateral groove 54a connecting adjacent ring grooves 51 and a second lateral groove 54b extending from the outermost ring groove 51 to the outer peripheral surface of the retainer ring 32. In one embodiment, the retainer ring 32 may have only the second lateral groove 54b, omitting the first lateral groove 54 shown in FIG. 9(b). Furthermore, although the second lateral groove 54b shown in FIG. 9(b) is aligned in a straight line with the first lateral groove 54a, the second lateral groove 54b may be offset in the circumferential direction of the retainer ring 32 relative to the first lateral groove 54a. The provision of the first lateral groove 54a and the second lateral groove 54b makes it easier to release the polishing liquid remaining in the multiple ring grooves 51 to the outside of the retainer ring 32.

[0059] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0060] 2 polishing pads 5 Polishing table 7 Polishing head (substrate holding device) 8 Polishing liquid supply nozzle 10 Control device 14 Spindle 16 Polishing head swing arm 18 Polished head shaft 21 Table rotation motor 31 Head body 32 Retainer ring 34,36 Elastic membrane 42 Film Thickness Sensor 50 Ring body 51 Ring groove 54 Yokomizo 55 Scraper (Barrier) 60 Textured structure (barrier) 70 Adsorbents

Claims

1. A retainer ring used in a substrate holding device for polishing a substrate by pressing the substrate against a polishing pad to which a polishing liquid is supplied, comprising: a ring-shaped ring body that supports an outer periphery of the substrate pressed against the polishing pad; The ring body is At least one ring groove formed in a lower surface that is pressed against the polishing pad and extending concentrically with the ring body; a barrier that prevents the polishing liquid from reaching the inside of the ring body from the outside.

2. the barrier is a scraper disposed in the ring groove; 2. The retainer ring of claim 1, wherein the scraper has a tip that contacts or is close to the polishing pad when polishing the substrate, and releases the polishing liquid that is accumulating in the ring groove to the outside of the retainer ring.

3. the barrier is a concave-convex structure formed in the ring groove, The retainer ring according to claim 1 , wherein the uneven structure forms an air flow from the inner peripheral surface of the ring groove toward the outer peripheral surface thereof.

4. The retainer ring according to claim 1 , wherein the barrier is an absorbent material disposed in the ring groove and capable of absorbing the polishing liquid.

5. the ring groove is a plurality of ring grooves, The retainer ring of claim 1 , wherein the barrier is disposed in at least one of the plurality of ring grooves.

6. The retainer ring of claim 1 , further comprising at least one transverse groove extending from the ring groove to the outer circumferential surface of the ring body.

7. a head body for holding a substrate and pressing the substrate against a polishing pad to polish the substrate; a retainer ring disposed to surround the substrate held by the head body, The substrate holding device, wherein the retainer ring is the retainer ring according to claim 1 .

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