This document claims priority to Japanese Patent Application Number 2014-141732 filed Jul. 9, 2014, the entire contents of which are hereby incorporated by reference.
In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and also more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing, while a polishing liquid containing abrasive particles, such as silica (SiO2), ceria (CeO2) or the like, therein is supplied onto a polishing surface of a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing surface and polished by using a polishing apparatus.
The polishing apparatus which performs the above-mentioned CMP process includes a polishing table having a polishing surface, and a polishing head (top ring) for holding a substrate such as a semiconductor wafer. When the substrate is polished with such a polishing apparatus, the substrate is held and pressed against the polishing surface under a predetermined pressure by the polishing head. At this time, while a polishing liquid is supplied onto the polishing surface, the polishing table and the polishing head are respectively rotated to bring the substrate into sliding contact with the polishing surface, so that the surface of the substrate is polished to a flat mirror finish.
A polishing rate of the surface, being polished, of the substrate depends not only on a polishing load on the substrate against the polishing pad but also on a surface temperature of the polishing surface. This is because a chemical action of the polishing liquid on the substrate depends on a temperature. Therefore, in manufacturing of the semiconductor device, in order to increase the polishing rate of the surface, being polished, of the substrate and further to keep the polishing rate constant, it is considered to be important to keep the surface temperature of the polishing surface during polishing of the substrate at an optimum value.
Therefore, conventionally, a fluid passage for heat exchange medium is provided in the interior of the polishing table and cooling water serving as the heat exchange medium is flowed in the fluid passage to exchange heat between the heat exchange medium and the polishing table. Thus, thermal deformation of the polishing table due to frictional heat during polishing is prevented and the surface temperature of the polishing surface on the polishing table is adjusted.
As described above, since the polishing table is rotated, the cooling water needs to be delivered into the interior of the rotating polishing table. Therefore, a rotary joint is provided on the polishing table, and the cooling water is supplied from the outside into the fluid passage in the polishing table through a cooling water pipe and the rotary joint to perform heat exchange in the polishing table, and is then discharged to the outside. The cooling water which has been discharged to the outside is cooled in a chiller unit, and is supplied into the polishing table again (see Japanese Laid-open Patent Publication No. 10-235552).
However, torsional vibration is generated in the rotary joint or an abnormal sound is generated at an engagement part between the cooling water pipe and the polishing table depending on installation environment or operating condition (e.g. at the time of low-speed idling) of the polishing apparatus. If the operation of the polishing apparatus is continued under this circumstance, a fatigue failure of the above-mentioned parts provided in the cooling water supply passage may be caused or the pipes may be damaged due to sliding wear, possibly leading to leakage of the cooling water.
According to an embodiment, there is provided a polishing apparatus which can continue stable operation of the apparatus without generating torsional vibration in a rotary joint and without generating an abnormal sound at an engagement part between a cooling water pipe and a polishing table.
Embodiments, which will be described below, relate to a polishing apparatus for polishing and planarizing a substrate such as a semiconductor wafer.
In an embodiment, there is provided a polishing apparatus for polishing a substrate by pressing the substrate against a polishing surface on a polishing table by a top ring while rotating the top ring holding the substrate and rotating the polishing table, the polishing apparatus comprising: a rotary joint fixed to a rotating part of the polishing table or a rotating part of the top ring to supply a fluid into the polishing table or the top ring and discharge the fluid from the polishing table or the top ring; and a rotation-prevention mechanism which connects the rotary joint with an apparatus frame to prevent the rotary joint from being rotated; wherein the rotation-prevention mechanism comprises a link mechanism having at least one spherical plain bearing.
According to the embodiment, the rotary joint for supplying the fluid into the polishing table or the top ring and discharging the fluid from the polishing table or the top ring is fixed to the apparatus frame by the link mechanism having at least one spherical plain bearing. With this configuration, the rotary joint is prevented from being rotated and is supported by the apparatus frame. Further, a vibration phenomenon due to stick-slip generated on a seal contact surface between a stationary ring and a rotary ring in the rotary joint can be absorbed or lessened by a micro rotational movement in all directions (360°) of the at least one spherical plain bearing.
In an embodiment, the link mechanism comprises two spherical plain bearings which are connected to each other.
According to the embodiment, since the link mechanism is configured by connecting the two spherical plain bearings, the micro rotational movement in all directions (360°) about each of the centers of the two spherical plain bearings can be made. Further, by arranging axes of the two spherical plain bearings so as to be perpendicular to each other, the centers of the rotational movements of the two spherical plain bearings differ in phase by 90°, and thus the degree of freedom of the movement is increased.
In an embodiment, one of the two spherical plain bearings comprises a spherical plain bearing with male thread, and the other of the two spherical plain bearings comprises a spherical plain bearing with female thread, and the two spherical plain bearings are integrated by screw fastening.
In an embodiment, the rotation-prevention mechanism comprises the link mechanism, a rotation-prevention plate configured to connect the link mechanism with the rotary joint, and a stopper plate configured to connect the link mechanism with the apparatus frame.
In an embodiment, the link mechanism is coupled to the rotary joint to increase a natural frequency of the rotary joint, whereby the natural frequency of the rotary joint is different from a natural frequency of a rotating member of the polishing table or a rotating member of the top ring.
According to the embodiment, by connecting the link mechanism with the rotary joint, a rotary joint assembly which integrates the rotary joint and the link mechanism has an increased natural frequency which is significantly different from natural frequencies of other peripheral parts. Therefore, resonance between the rotary joint assembly, which integrates the rotary joint and the link mechanism, and the peripheral parts such as a cooling water pipe can be prevented. As a result, the torsional vibration of the rotary joint can be prevented, and the pipe wear and the generation of the abnormal sound can be prevented.
In an embodiment, the rotating member comprises a cooling water pipe configured to supply cooling water into the polishing table or to discharge the cooling water from the polishing table.
According to the above-described embodiments, stable operation of the apparatus can be continued without generating the torsional vibration in the rotary joint and without generating the abnormal sound at the engagement part between the cooling water pipe and the polishing table.
A polishing apparatus according to an embodiment will be described below with reference to
The loading/unloading section 2 has two or more (four in this embodiment) front loading units 20 on which wafer cassettes, each storing plural semiconductor wafers, are placed. The front loading units 20 are arranged adjacent to each other along a width direction of the polishing apparatus (a direction perpendicular to a longitudinal direction of the polishing apparatus). Each of the front loading units 20 is capable of receiving thereon an open cassette, a SMIF (Standard Manufacturing Interface) pod, or a FOUP (Front Opening Unified Pod). The SMIF and FOUP are a hermetically sealed container which houses a wafer cassette therein and is covered with a partition to thereby provide an independent interior environment isolated from an external space.
Further, the loading/unloading section 2 has a moving mechanism 21 extending along an arrangement direction of the front loading units 20. A transport robot 22 is installed on the moving mechanism 21 and is movable along the arrangement direction of the wafer cassettes. The transport robot 22 is configured to move on the moving mechanism 21 so as to access the wafer cassettes mounted on the front loading units 20. The transport robot 22 has vertically arranged two hands, which can be separately used. For example, the upper hand is used for returning a semiconductor wafer to the wafer cassette, and the lower hand is used for transferring a semiconductor wafer before polishing.
The loading/unloading section 2 is required to be a cleanest area. Therefore, pressure in the interior of the loading/unloading section 2 is kept higher at all times than pressures in the exterior space of the polishing apparatus, the polishing section 3, and the cleaning section 4. A filter fan unit (not shown) having a clean air filter, such as a HEPA filter and a ULPA filter, is provided above the moving mechanism 21 of the transport robot 22. This filter fan unit removes particles, toxic vapor, and gas from air to produce clean air, and to form downward flow of the clean air at all times.
The polishing section 3 is an area where semiconductor wafers are polished. This polishing section 3 includes a first polishing section 3a having therein a first polishing unit 30A and a second polishing unit 30B, and a second polishing section 3b having therein a third polishing unit 30C and a fourth polishing unit 30D. The first polishing unit 30A, the second polishing unit 30B, the third polishing unit 30C, and the fourth polishing unit 30D are arranged along the longitudinal direction of the polishing apparatus as shown in
As shown in
A first linear transporter 5 is provided between the first polishing unit 30A and the second polishing unit 30B in the first polishing section 3a, and the cleaning section 4. This first linear transporter 5 is configured to transfer wafers between four transferring positions located along the longitudinal direction of the polishing apparatus (hereinafter, these four transferring positions will be referred to as a first transferring position TP1, a second transferring position TP2, a third transferring position TP3, and a fourth transferring position TP4 in the order from the loading/unloading section 2). A reversing machine 31 for reversing a wafer received from the transport robot 22 in the loading/unloading section 2 is disposed above the first transferring position TP1 of the first linear transporter 5. A vertically movable lifter 32 is disposed below the reversing machine 31. A vertically movable pusher 33 is disposed below the second transferring position TP2, and a vertically movable pusher 34 is disposed below the third transferring position TP3. A shutter 12 is provided between the third transferring position TP3 and the fourth transferring position TP4.
In the second polishing section 3b, a second linear transporter 6 is provided next to the first linear transporter 5. This second linear transporter 6 is configured to transfer wafers between three transferring positions located along the longitudinal direction of the polishing apparatus (hereinafter, these three transferring positions will be referred to as a fifth transferring position TP5, a sixth transferring position TP6, and a seventh transferring position TP7 in the order from the loading/unloading section 2). A pusher 37 is disposed below the sixth transferring position TP6 of the second linear transporter 6, and a pusher 38 is disposed below the seventh transferring position TP7 of the second linear transporter 6. A shutter 13 is provided between the fifth transferring position TP5 and the sixth transferring position TP6.
As can be understood from the fact that a slurry is used during polishing, the polishing section 3 is the dirtiest area. Therefore, in order to prevent particles from spreading out of the polishing section 3, evacuation is conducted from surrounding spaces of the respective polishing tables in this embodiment. In addition, pressure in the interior of the polishing section 3 is set to be lower than any of pressure outside the apparatus, pressure in the cleaning section 4, and pressure in the loading/unloading section 2, so that scattering of the particles is prevented. Typically, exhaust ducts (not shown) are provided below the polishing tables, respectively, and filters (not shown) are provided above the polishing tables, so that downward flows of cleaned air are formed through the filters and the exhaust ducts.
The polishing units 30A, 30B, 30C and 30D are each partitioned and closed by a partition wall, and the air is exhausted individually from each of the closed polishing units 30A, 30B, 30C and 30D. Thus, a semiconductor wafer can be processed in the closed polishing unit 30A, 30B, 30C or 30D without being influenced by the atmosphere of a slurry. This enables good polishing of the wafers. As shown in
The cleaning section 4 is an area where polished semiconductor wafers are cleaned. The cleaning section 4 includes a reversing machine 41 for reversing a semiconductor wafer, four cleaning apparatuses 42, 43, 44 and 45 each for cleaning the polished semiconductor wafer, and a transferring unit 46 for transferring wafers between the reversing machine 41 and the substrate cleaning apparatuses 42, 43, 44 and 45. The reversing machine 41 and the substrate cleaning apparatuses 42, 43, 44 and 45 are arranged in series along the longitudinal direction of the polishing apparatus. A filter fan unit (not shown), having a clean air filter, is provided above the substrate cleaning apparatuses 42, 43, 44 and 45. This filter fan unit is configured to remove particles from air to produce clean air, and to form downward flow of the clean air at all times. Pressure in the interior of the cleaning section 4 is kept higher at all times than pressure in the polishing section 3, so that particles in the polishing section 3 are prevented from flowing into the cleaning section 4.
As shown in
In the interior of the polishing table 300A, a fluid passage (not shown) for heat exchange medium is provided. Cooling water serving as the heat exchange medium is flowed in the fluid passage to exchange heat between the heat exchange medium and the polishing table 300A. Thus, thermal deformation of the polishing table 300A due to frictional heat during polishing is prevented and a surface temperature of the polishing surface on the polishing table is adjusted. Therefore, as shown in
The top ring 301A is connected to a top ring shaft 311, and the top ring shaft 311 is vertically movable with respect to a support arm 312. When the top ring shaft 311 moves vertically, the top ring 301A is lifted and lowered as a whole for positioning with respect to the support arm 312. The top ring shaft 311 is configured to be rotated by driving a top ring rotating motor (not shown). The top ring 301A is rotated about the top ring shaft 311 by rotation of the top ring shaft 311.
The top ring 301A is configured to hold the semiconductor wafer W on its lower surface. The support arm 312 is configured to be pivotable about a shaft 313, thereby swinging the top ring 301A to a wafer transferring position (pusher 33). In the wafer transferring position, the semiconductor wafer, which has been transferred to the pusher 33 (see
As shown in
The rotation-prevention plate 321 has a horizontal plate portion 321a extending in a horizontal direction and a bent portion 321b bent upward from the horizontal plate portion 321a, and the bent portion 321b is fixed to a side surface of the rotary joint 308 by bolts 325 (see
As shown in
As shown in
As shown in
Table 1 is a table showing characteristic values, i.e., natural frequencies (Hz) of respective parts in the case where the cushioning mechanism comprising the damper rubber 324 or the link mechanism 323 according to the embodiment is employed as the mechanism for coupling the rotation-prevention plate 321 connected to the rotary joint 308 and the stopper plate 322 connected to the apparatus frame F.
As shown in Table 1, the rotary joint 308 has a natural frequency of 59.4 Hz, a cooling water pipe (cooling water shaft (S2)) has a natural frequency of 47.8, and a cooling water pipe (cooling water shaft (X)) has a natural frequency of 68.4. On the other hand, a damper rubber having rubber hardness of 70 (Duro) has a natural frequency of 50-59 Hz, and a damper rubber having rubber hardness of 75-85(Duro) has a natural frequency of 59-82.
Thus, in the case where the cushioning mechanism comprising the damper rubber is used as a mechanism for coupling the rotation-prevention plate 321 and the stopper plate 322, under the condition where the damper rubber and the rotary joint have similar natural frequencies even if the hardness of the damper rubber is changed, the natural frequency (characteristic value) of the rotary joint cannot be changed by coupling the damper rubber to the rotary joint. Therefore, the rotary joint and peripheral parts such as a cooling water shaft resonate to generate torsional vibration in the rotary joint or to generate an abnormal sound at the engagement part between the cooling water shaft and the polishing table. However, vibration control may be achieved, provided that the damper rubber and the rotary joint have sufficiently different natural frequencies.
On the other hand, the link mechanism 323 of rod-type with ball joint which uses the two spherical plain bearings 326, 327 has a natural frequency of 204 Hz. In this manner, by connecting the link mechanism 323 having a natural frequency of 204 Hz with the rotary joint 308, a rotary joint assembly which integrates the rotary joint 308 and the link mechanism 323 has an increased natural frequency which is significantly different from the natural frequencies of other peripheral parts. Therefore, resonance between the rotary joint assembly, which integrates the rotary joint 308 and the link mechanism 323, and the peripheral parts such as a cooling water shaft can be prevented. As a result, the torsional vibration of the rotary joint can be prevented, and pipe wear and generation of the abnormal sound can be prevented.
The rotation-prevention mechanism 320 of the rotary joint shown in
As shown in
The elastic membrane (membrane) 404 has a plurality of concentric partition walls 404a, which form a central chamber 405; a ripple chamber 406; an outer chamber 407; and an edge chamber 408 between the upper surface of the elastic membrane 404 and the lower surface of the top ring body 402. The elastic membrane (membrane) 404 has a plurality of holes 404h which pass through the elastic membrane in a thickness direction of the elastic membrane in the ripple area (ripple chamber 6). A flow passage 411 communicating with the central chamber 405, a flow passage 412 communicating with the ripple chamber 406, a flow passage 413 communicating with the outer chamber 407, and a flow passage 414 communicating with the edge chamber 408 are formed in the top ring 301A. The flow passage 411, the flow passage 412, the flow passage 413, and the flow passage 414 are connected via a rotary joint 417 to external pipes 420, respectively. A compression supply source is connected to the external pipes 420 via a pressure regulating unit, and a vacuum source is connected to the external pipes 420.
Further, a retaining ring pressure chamber 409, which is formed by an elastic membrane, is provided immediately above the retaining ring 403. This retaining ring pressure chamber 409 is coupled to the external pipe 420 through a flow passage 415 formed in the top ring body 402 and the rotary joint 417.
In the top ring 301A configured as shown in
The rotary joint 417 shown in
Although the embodiments of the present invention have been described herein, the present invention is not intended to be limited to these embodiments. Therefore, it should be noted that the present invention may be applied to other various embodiments within a scope of the technical concept of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
2014-141732 | Jul 2014 | JP | national |