Polishing device

Abstract

To provide a polishing device in which an acoustic sensor is capable of accurately detecting a polishing sound.SOLUTION: A polishing device includes: an acoustic sensor 30 inserted in a first open hole 15 formed in a polishing table 3a for detecting a polishing sound during polishing a substrate and outputting a signal showing the polishing sound; a support jig 43 including at least an elastic member 45 for subjecting the acoustic sensor 30 to be supported on a polishing table 3 while blocking transmission of the polishing sound from the polishing table 3; and a controller 9 for monitoring a polishing state of the substrate based on the signal output from the acoustic sensor 30a. The polishing pad 2 is provided with at least one second open hole 17 communicating with the first open hole 15 and filled with a liquid, and the acoustic sensor 30 is opposed to the second open hole 17.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a polishing apparatus for polishing the surface of a substrate such as a wafer. [Background technology]

[0002] In the manufacturing process of semiconductor devices, polishing apparatuses are widely used to polish the surface of a substrate such as a wafer. In this type of polishing apparatus, the substrate rotates while being held by a substrate holding device called a top ring or polishing head. In this state, the surface of the substrate is pressed against the polishing surface of the polishing pad while rotating the polishing table together with the polishing pad, and the surface of the substrate is polished by sliding the surface of the substrate against the polishing surface in the presence of a polishing liquid. When it is detected that the film thickness of the substrate surface has reached a predetermined value or that an underlying layer (e.g., a stopper layer) has been exposed as a result of polishing the substrate surface, the polishing process of the substrate is terminated.

[0003] In such a polishing process, it is required to accurately control the film thickness on the surface of the processed substrate, and therefore it is important to accurately detect the end of the polishing process of the substrate (polishing end point). Various methods for detecting the polishing end point have been considered, and for example, it has been proposed to determine the polishing end point by detecting the change in the polishing sound using an acoustic sensor.

[0004] For example, Patent Document 1 discloses a substrate processing apparatus in which an acoustic sensor is provided under a polishing table to which a polishing pad is attached, and this acoustic sensor detects elastic waves transmitted through the polishing table and polishing pad during substrate polishing, and outputs an electric signal (acoustic signal). In the substrate processing apparatus described in Patent Document 1, the polishing end point is accurately detected using the electric signal output by the acoustic sensor. Note that changes in the polishing sound may also be used to detect the occurrence of an abnormality in the substrate polishing process and / or an abnormality in the polishing apparatus. In this specification, an abnormality in the substrate polishing process and / or an abnormality in the polishing apparatus is simply referred to as a "polishing abnormality," and further, the progress of substrate polishing, including the polishing abnormality and the polishing end point, is simply referred to as the "polishing state." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-127882 A Summary of the Invention [Problem to be solved by the invention]

[0006] In order to accurately detect the polishing state (i.e., the polishing end point and / or the occurrence of polishing abnormality), the acoustic sensor needs to accurately detect the polishing sound. Therefore, the installation position of the acoustic sensor becomes important. For example, if the polishing sound picked up by the acoustic sensor is too small, there is a risk that the polishing end point and / or the occurrence of polishing abnormality cannot be detected accurately.

[0007] When the acoustic sensor is installed under the polishing table, the polishing sound generated on the polishing surface, which is the upper surface of the polishing pad, is transmitted to the acoustic sensor via multiple materials such as the polishing pad and the polishing table. At this time, each time the polishing sound is incident on a different material, a part of the polishing sound is reflected, and the polishing sound that should reach the acoustic sensor is attenuated, which may result in a problem in detecting the polishing state with high accuracy.

[0008] When an acoustic sensor is placed in a free sound field (e.g., above a polishing pad) to detect sounds in the air, many disturbances (sounds other than the polishing sound) are input to the acoustic sensor. Therefore, it is necessary to extract only the polishing sound from the sounds input to the acoustic sensor, which requires a complex algorithm or requires the installation of multiple acoustic sensors in the polishing device. Furthermore, in order for the acoustic sensor to measure the polishing sound with good sensitivity, the acoustic sensor needs to be placed as close as possible to the sound source, which often limits the installation position of the acoustic sensor.

[0009] Therefore, the present invention provides a polishing device in which an acoustic sensor is capable of detecting the polishing sound with high accuracy. [Means for solving the problem]

[0010] In one aspect, a polishing apparatus is provided that polishes a substrate by pressing the substrate against a polishing pad supported on a polishing table, the polishing apparatus comprising: an acoustic sensor that is inserted into a first through hole formed in the polishing table, detects a polishing sound during polishing of the substrate, and outputs a signal representing the polishing sound; a support jig that includes at least an elastic member for supporting the acoustic sensor on the polishing table while inhibiting transmission of the polishing sound from the polishing table; and a controller that monitors the polishing state of the substrate based on the signal output from the acoustic sensor, wherein the polishing pad has at least one second through hole formed therein that is connected to the first through hole and filled with liquid, and the acoustic sensor faces the second through hole.

[0011] In one embodiment, the acoustic sensor includes a sensor body, a sound transmission member in contact with the sensor body, a sensor cover having an insertion hole into which the sound transmission member is inserted so that the sound transmission member faces the second through hole, and a support member for supporting the sound transmission member in the insertion hole of the sensor cover while inhibiting transmission of the grinding sound from the sensor cover. In one aspect, the support jig further includes a base for supporting the acoustic sensor, a connecting member for connecting the base to the polishing table, and a transmission preventing member disposed between the base and the acoustic sensor to prevent transmission of the polishing sound from the base.

[0012] In one embodiment, the sound transmitting member is formed from a material having a sound propagation velocity faster than a sound propagation velocity of the polishing table. In one aspect, the sensor cover is formed from a material having a sound propagation velocity slower than a sound propagation velocity of the sound transmitting member.

[0013] In one embodiment, the elastic member also functions as a first sealing member that seals the gap between the acoustic sensor and the polishing table, and the support member also functions as a second sealing member that seals the gap between the sound transmission member and the sensor cover. In one embodiment, the polishing apparatus further includes a liquid supply line for supplying the liquid to the second through hole. Effect of the Invention

[0014] According to the present invention, since the polishing sound propagates only through the liquid and is input to the acoustic sensor, the polishing sound is not reflected by other materials on the way from the substrate being polished to the acoustic sensor, and attenuation of the polishing sound is prevented as much as possible, so that the acoustic sensor can detect the polishing sound with high accuracy. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a polishing apparatus according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a schematic arrangement of an acoustic sensor according to an embodiment. [Diagram 3] FIG. 3 is a top view illustrating a modified example of the second through hole. [Figure 4] FIG. 4(a) is a schematic diagram showing an example of the arrangement of acoustic sensors on the polishing table, and FIG. 4(b) is a schematic diagram showing another example of the arrangement of acoustic sensors on the polishing table. [Diagram 5] FIG. 5 is a cross-sectional view showing a schematic arrangement of an acoustic sensor according to another embodiment. [Figure 6] FIG. 6 is a diagram illustrating a modified example of the arrangement of the acoustic sensors shown in FIG. [Figure 7] FIG. 7(a) is a diagram showing a schematic diagram of a modified example of the liquid supply line shown in FIG. 6, and FIG. 7(b) is a diagram showing a schematic diagram of another modified example of the liquid supply line shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view that illustrates a schematic arrangement of an acoustic sensor according to still another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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 an embodiment. As shown in Fig. 1, the polishing apparatus includes a polishing table 3 supporting a polishing pad 2, a polishing head (substrate holding device) 1 that holds a wafer W, which is an example of a substrate, and presses it against the polishing pad 2, a table motor 6 that rotates the polishing table 3, a polishing liquid supply nozzle 5 for supplying a polishing liquid such as a slurry onto the polishing pad 2, and a controller 9 for controlling the operation of the polishing apparatus. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the wafer W. The polishing liquid supply nozzle 5 may supply pure water to the polishing surface 2a.

[0017] The polishing head 1 is connected to a head shaft 10, and the head shaft 10 is connected to a polishing head motor (not shown) via a connecting means such as a belt. The polishing head motor is, for example, built into a head arm 14 to which the head shaft 10 is connected. The polishing head motor rotates the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow. The polishing table 3 is connected to a table motor 6 via a table shaft 3a, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow. The rotation direction of the polishing head 1 and the polishing table 3 is not limited to this embodiment. In one embodiment, the polishing head 1 and the polishing table 3 may be configured to rotate in the direction opposite to the direction indicated by the arrow in FIG. 1.

[0018] The wafer W is polished as follows. While the polishing table 3 and polishing head 1 are rotated in the direction indicated by the arrow in Fig. 1, a polishing liquid is supplied from a polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While the wafer W is rotated by the polishing head 1, the wafer W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 with the polishing liquid present on the polishing pad 2. The surface of the wafer W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid or the polishing pad 2. The operation of the entire polishing apparatus, including the operations of the polishing head 1, table motor 6, and polishing liquid supply nozzle 5, is controlled by a controller 9.

[0019] In this embodiment, the controller 9 is composed of at least one computer. The controller 9 includes a storage device 9a in which a program is stored, and a calculation device 9b that executes calculations according to instructions included in the program. The storage device 9a 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 calculation device 9b include a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). However, the specific configuration of the controller 9 is not limited to these examples.

[0020] In one embodiment, the controller 9 may be composed of multiple computers, or may be multiple servers connected by a communication network such as the Internet or a local area network. For example, the controller 9 may be a combination of an edge server and a cloud server. In one embodiment, the storage device 9a may be provided at a location remote from the computing device 9b.

[0021] The polishing apparatus 1 further includes an acoustic sensor 30 attached to the polishing table 3. The acoustic sensor 30 is configured to detect the sound of the polishing sound at a predetermined time interval and output (generate) a signal representing the sound of the polishing sound. Examples of such an acoustic sensor 30 include an Acoustic Emission (AE) sensor and an ultrasonic microphone. However, the type and configuration of the acoustic sensor 30 can be freely selected as long as it is capable of detecting the sound of the polishing sound. The acoustic sensor 30 is electrically connected to the controller 9, and the operation of the acoustic sensor 30 is controlled by the controller 9.

[0022] During polishing of the wafer W, the acoustic sensor 30 detects (the sound of) the polishing sound of the wafer W and outputs (generates) a signal representing the polishing sound (hereinafter, may be referred to as a "polishing sound signal"). Specifically, the controller 9 issues a command to the acoustic sensor 30 to detect the polishing sound during polishing of the wafer W and to output the polishing sound signal from the acoustic sensor 30.

[0023] The polishing sound of the wafer W changes depending on the surface condition of the wafer W. For example, when the polishing of an upper layer (e.g., an insulating film, a metal film, a silicon layer, etc.) constituting the surface of the wafer W progresses and a lower layer (e.g., a stopper layer) existing under the upper layer is exposed, the polishing sound of the wafer W changes. This is because the upper and lower layers of the wafer W are made of different materials, and the friction coefficient of the upper layer and the friction coefficient of the lower layer are different. In another example, when the polishing of the wafer W progresses and the surface roughness of the wafer W changes, the polishing sound of the wafer W changes. This is because the frictional force (frictional resistance) of the wafer W changes depending on the surface roughness of the wafer W. The controller 9 of this embodiment monitors the polishing progress of the wafer W by utilizing the change in the polishing sound detected by the acoustic sensor 30. Monitoring the polishing progress of the wafer W includes detecting the end point of the polishing of the wafer W.

[0024] The polishing sound of the wafer W also changes when an abnormality occurs in the polishing process of the wafer W and when an abnormality occurs in the polishing apparatus. For example, when the wafer W is damaged during polishing, the polishing sound of the wafer W changes. The polishing sound also changes when the polishing pad 2 is damaged or the supply of the polishing liquid from the polishing liquid supply nozzle 5 is stopped. The controller 9 may monitor the occurrence of an abnormality in the polishing process of the wafer W and / or an abnormality in the polishing apparatus by utilizing the change in the polishing sound detected by the acoustic sensor 30. In this specification, an abnormality in the polishing process of the wafer W and / or an abnormality in the polishing apparatus is simply referred to as a "polishing abnormality", and the polishing progress status of the wafer W including the polishing end point and the polishing abnormality are simply referred to as a "polishing state". That is, the controller 9 monitors the polishing state by utilizing the change in the polishing sound.

[0025] The polishing state can be monitored by a known monitoring method. For example, in order to monitor the polishing progress, the controller 9 may generate a power spectrum indicating a spectrum of sound pressure levels from an acoustic signal representing the polishing sound, and generate a power spectrum map indicating a time change of the power spectrum by arranging the power spectra in a time series, and determine the polishing progress including the polishing end point of the wafer W based on the change of the sound pressure level in the power spectrum map.

[0026] In order to accurately determine the polishing state, it is necessary for the acoustic sensor 30 to accurately detect the polishing sound. Therefore, in this embodiment, the acoustic sensor 30 is disposed so as to be able to measure as much as possible the polishing sound propagating only through the liquid (e.g., polishing liquid or pure water) present on the polishing pad 2.

[0027] Fig. 2 is a cross-sectional view showing a schematic arrangement of an acoustic sensor 30 according to an embodiment. The acoustic sensor 30 shown in Fig. 2 includes a sensor body 31 connected to a controller 9 (see Fig. 1), and the sensor body 31 of the acoustic sensor 30 is inserted into a first through hole 15 formed in the polishing table 3. In this embodiment, the first through hole 15 extends vertically from the upper surface to the lower surface of the polishing table 3.

[0028] The sensor body 31 of the acoustic sensor 30 inserted into the first through hole 15 is supported in the first through hole 15 by a support jig 43. In this embodiment, the support jig 43 is composed of an elastic member 45. The elastic member 45 has an appropriate elasticity for inhibiting the polishing sound from being transmitted from the polishing table 3 to the sensor body 31 of the acoustic sensor 30. In this embodiment, the elastic member 45 is an O-ring made of resin such as rubber, and also functions as a seal member (first seal member) that seals the gap between the sensor body 31 of the acoustic sensor 30 and the first through hole 15.

[0029] The polishing pad 2 has a second through hole 17 formed at a position corresponding to the first through hole 15 of the polishing table 3 so as to communicate with the first through hole 15 of the polishing table 3. The second through hole 17 extends vertically from the upper surface (i.e., the polishing surface) of the polishing pad 2 to the lower surface, and the lower opening of the second through hole 17 is the upper surface of the sensor body 31 of the acoustic sensor 30 inserted into the first through hole 15, and faces the sensing surface to which the polishing sound is input with a small gap therebetween. In one embodiment, the sensing surface of the acoustic sensor 30 may be brought into contact with the lower surface of the polishing pad 2 in which the second through hole 17 is formed. In this embodiment, the central axis of the first through hole 15 coincides with the central axis of the second through hole 17, and the central axis of the sensing surface of the sensor body 31 coincides with the central axis of the first through hole 15 and the central axis of the second through hole 17. In other words, the second through hole 17 formed in the polishing pad 2, the first through hole 15 formed in the polishing table 3, and the acoustic sensor 30 inserted into the first through hole 15 are arranged in a straight line in the vertical direction.

[0030] In order to uniformly supply the polishing liquid to the entire polishing surface 2a of the polishing pad 2, one or more pad grooves (not shown) may be formed on the polishing surface 2a of the polishing pad 2. The pad groove is formed on the polishing surface 2a of the polishing pad 2 and does not penetrate the polishing pad 2. The pad groove is formed, for example, over the entire surface of the polishing pad 2. Examples of the shape of the pad groove include a lattice shape, a spiral shape, and a concentric circle shape. When such a pad groove is formed on the polishing surface 2a of the polishing pad 2, it is preferable that the second through hole 17 communicates with the pad groove. Due to the communication between the second through hole 17 and the pad groove, the polishing sound reaches the liquid filling the second through hole 17 even through the liquid in the pad groove. As a result, high sensitivity detection of the polishing sound by the acoustic sensor 30 is promoted.

[0031] During polishing of the wafer W, the liquid, which is the polishing liquid (e.g., slurry or pure water) supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2, flows into the second through hole 17 of the polishing pad 2, and the second through hole 17 is filled with the liquid. Since the acoustic sensor 30 is disposed so as to face the opening of the second through hole 17, the polishing sound generated during polishing of the wafer W is input to the acoustic sensor 30 via the polishing liquid flowing on the polishing pad 2 and the polishing liquid filling the second through hole 17. As a result, the polishing sound is input to the acoustic sensor 30 by propagating only through the liquid, so that the polishing sound is not reflected by other materials from the wafer W being polished until it reaches the acoustic sensor 30, and attenuation of the polishing sound is prevented as much as possible. Therefore, since the acoustic sensor 30 can detect the polishing sound with high accuracy, the controller 9 can monitor the polishing state accurately.

[0032] Furthermore, liquid has a higher density than air, so not only is the polishing sound less likely to attenuate, but the liquid surface also has the property of reflecting disturbances other than the polishing sound. Therefore, compared to a conventional polishing device in which an acoustic sensor is disposed in a free sound field (e.g., above the polishing pad 2) to detect sounds in the air, the acoustic sensor 30 of this embodiment can detect the polishing sound with much higher accuracy.

[0033] Fig. 3 is a top view showing a schematic diagram of a modified example of the second through hole 17. As shown in Fig. 3, a plurality of second through holes 17 may be formed in the polishing pad 2. In the example shown in Fig. 3, nine second through holes 17 are formed in the polishing pad 2. In this embodiment, the central axis of the second through hole 17 located in the center coincides with the central axis of the first through hole 15, and the remaining second through holes 17 are arranged concentrically and at equal intervals around the second through hole 17 located in the center.

[0034] Fig. 4(a) is a schematic diagram showing an example of the arrangement of the acoustic sensor 30 on the polishing table 3, and Fig. 4(b) is a schematic diagram showing another example of the arrangement of the acoustic sensor 30 on the polishing table 3. It should be noted that Fig. 4(a) and Fig. 4(b) are examples of the positions at which the first through holes 15 are formed on the polishing table 3, and the positions at which the first through holes 15 are formed can be freely selected within the polishing table 3.

[0035] In the example shown in FIG. 4(a), the acoustic sensor 30 is disposed on the polishing table 3 so as to pass under the wafer W during polishing of the wafer W. In other words, when the polishing table 3 is rotated, the first through hole 15 formed in the polishing table 3 and into which the acoustic sensor 30 is inserted passes under the polishing head 1. In this embodiment, the first through hole 15 is formed in the polishing table 3 so that the central axis of the first through hole 15 passes through the central axis of the polishing head 1 when the acoustic sensor 30 passes under the polishing head 1. When the acoustic sensor 30 passes under the polishing head 1, the acoustic sensor 30 can detect the polishing sound at a close distance, and therefore can obtain a more accurate polishing sound.

[0036] On the other hand, when the acoustic sensor 30 moves away from the polishing head 1 due to the rotation of the polishing table 3, disturbances are added to the polishing sound acquired by the acoustic sensor 30, which may adversely affect the detection of the polishing sound. For this reason, the polishing apparatus is preferably equipped with a rotation angle detection device 50 capable of detecting the rotational position of the polishing table 3. An example of the rotation angle detection device 50 is a rotary encoder provided on the table motor 6. The rotation angle detection device 50 is connected to a controller 9 (see FIG. 1). Using the rotation angle detection device 50, the controller 9 can calculate the relative positional relationship between the acoustic sensor 30 and the polishing head 1 (i.e., the wafer W, which is the source of the polishing sound).

[0037] In this case, the controller 9 may be configured to detect the grinding sound only when the acoustic sensor 30 passes below the polishing head 1. Furthermore, the controller 9 may detect sounds other than the grinding sound (i.e., disturbances) from the sounds input to the acoustic sensor 30 when the acoustic sensor 30 is not passing below the polishing head 1. With this configuration, disturbances that are sounds other than the grinding sound can be efficiently eliminated from the sounds input to the acoustic sensor 30.

[0038] 4(b), the first through hole 15 is formed in the polishing table 3 such that the central axis of the first through hole 15 coincides with the table axis 3a of the polishing table 3. In this case, since the central axis of the sensor body 31 of the acoustic sensor 30 coincides with the central axis of the table axis 3a of the polishing table 3, the position of the acoustic sensor 30 relative to the polishing head 1 does not change when the polishing table 3 is rotated. Therefore, the polishing sound input to the acoustic sensor 30 is not affected by the rotation of the polishing table 3, so that the controller 9 can easily perform analysis to extract the polishing sound from the sound input to the acoustic sensor 30.

[0039] On the other hand, in the example of arrangement shown in Fig. 4(b), more disturbances are likely to be mixed into the sound input to the acoustic sensor 30 compared to the example of arrangement shown in Fig. 4(a). However, since the position of the acoustic sensor 30 relative to the polishing head 1 does not change, the disturbances input to the acoustic sensor 30 are also almost constant and stable. Therefore, the controller 9 can easily distinguish between the polishing sound and disturbances by using frequency analysis or the like.

[0040] 5 is a cross-sectional view showing a schematic arrangement of an acoustic sensor 30 according to another embodiment. The configuration of this embodiment that is not specifically described is similar to the configuration of the above-described embodiment, and therefore the duplicated description will be omitted.

[0041] In the polishing apparatus shown in FIG. 5, the acoustic sensor 30 inserted into the first through hole 15 formed in the polishing table 3 includes the above-mentioned sensor body 31, a sound transmission member 32 in contact with the sensor body 31, and a sensor cover 33 having an insertion hole 33a into which the sound transmission member 32 is inserted so that the sound transmission member 32 faces the second through hole 17 formed in the polishing pad 2. In this embodiment, a sensing protrusion 32a is formed on the upper part of the sound transmission member 32, which is inserted into the insertion hole 33a of the sensor cover 33 and functions as a probe for detecting the polishing sound. When the sensing protrusion 32a is inserted into the insertion hole 33a, a small gap is formed between the outer surface of the sensing protrusion 32a and the wall surface of the insertion hole 33a. Furthermore, the sound transmission member 32 is in contact with the sensing surface, which is the upper surface of the sensor body 31, on the lower surface opposite to the upper surface on which the sensing protrusion 32a is formed. In one embodiment, the sound transmitting member 32 may be connected to the sensor body 31 using a connecting member (not shown) while the sound transmitting member 32 is in contact with the sensor body 31.

[0042] A filler (not shown) such as grease may be injected between the sound transmitting member 32 and the sensor body 31. The filler fills in the gaps between the minute irregularities on the lower surface (connecting surface) of the sound transmitting member 32 and the minute irregularities on the upper surface (connecting surface) of the sensor body 31, so that the lower surface of the sound transmitting member 32 can be completely attached to the upper surface of the sensor body 31. As a result, the filler allows the grinding sound to be accurately transmitted from the sound transmitting member 32 to the sensor body 31.

[0043] The acoustic sensor 30 shown in FIG. 5 further includes a support member 34 for supporting the sound transmission member 32 on the sensor cover 33 while inhibiting transmission of the grinding sound from the sensor cover 33 to the sound transmission member 32. The sound transmission member 32 and the sensor body 31 are in contact with the sensor cover 33 only through the support member 34. The support member 34 has an appropriate elasticity for inhibiting transmission of the grinding sound from the sensor cover 33 to the sound transmission member 32 (and the sensor body 31) of the acoustic sensor 30. In this embodiment, the support member 34 is an O-ring made of resin such as rubber, and also functions as a seal member (second seal member) for sealing the gap between the sound transmission member 32 of the acoustic sensor 30 and the sensor cover 33.

[0044] In this embodiment, the liquid, which is the polishing liquid supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 during polishing of the wafer W, flows into the second through hole 17 of the polishing pad 2, and the second through hole 17 is filled with the liquid. Since the sensing protrusion 32a of the sound transmission member 32 of the acoustic sensor 30 is arranged to face the opening of the second through hole 17, the polishing sound generated during polishing of the wafer W is input to the acoustic sensor 30 through the polishing liquid flowing on the polishing pad 2 and the polishing liquid filling the second through hole 17. As a result, the polishing sound is input to the acoustic sensor 30 by propagating only through the liquid, so that it is not reflected by other materials from the wafer W being polished until it reaches the acoustic sensor 30, and attenuation of the polishing sound is prevented as much as possible. Furthermore, since the liquid has the property of being able to reflect disturbances, which are sounds other than the polishing sound, on its surface, the acoustic sensor 30 of this embodiment can detect the polishing sound with much greater accuracy than a conventional polishing device in which an acoustic sensor is arranged in a free sound field to detect sounds in the air.

[0045] According to this embodiment, the support member 34 also functions as a sealing member that seals the gap between the sound transmitting member 32 and the sensor cover 33, so that the liquid filling the second through hole 17 cannot reach the sensor body 31 of the acoustic sensor 30. Therefore, the sensor body 31 is prevented from getting wet with the liquid, so that the sensor body 31 does not need to have chemical resistance and water resistance. As a result, a versatile acoustic sensor that is inexpensively available on the market can be used as the acoustic sensor 30 according to this embodiment.

[0046] The sound transmitting member 32 is preferably made of a material having a high sound propagation speed so that the polishing sound can be accurately transmitted to the sensor body 31. For example, the sound transmitting member 32 is made of a material having a sound propagation speed faster than the sound propagation speed of the polishing table 3. An example of such a material is alumina.

[0047] For the same reason, the sensor cover 33 is preferably formed from a material having a slow sound propagation velocity. For example, the sensor cover 33 is formed from a material having a sound propagation velocity slower than that of the sound transmitting member 32. Examples of such materials include stainless steel and resin. In one embodiment, the sensor cover 33 may be formed from a material having a sound propagation velocity slower than that of the sound transmitting member 32 and that of the polishing table 3.

[0048] 5, the support jig 43 of the polishing apparatus includes, in addition to the above-mentioned elastic member 45, a base 46 for supporting the acoustic sensor 30 from below, and a connecting rod (connecting member) 48 for connecting the base 46 to the lower surface of the polishing table 3. In FIG. 5, the base 46 is connected to the polishing table 3 by a plurality of rods, but the connecting member is not limited to the connecting rod 48. For example, the connecting member may be a single member having a cylindrical shape surrounding the acoustic sensor 30.

[0049] The support jig 43 including the elastic member 45, the base 46, and the connecting rod 48 allows the acoustic sensor 30 to be reliably supported on the polishing table 3, and further stabilizes the posture of the acoustic sensor 30. As a result, the acoustic sensor 30 can obtain the polishing sound with higher accuracy.

[0050] In order to prevent the polishing sound from being transmitted to the acoustic sensor 30 via the polishing table 3, the connecting rod 48, and the base 46, the support jig 43 preferably has a transmission blocking member (first transmission blocking member) 47 disposed between the base 46 and the acoustic sensor 30. The transmission blocking member 47 is made of a material capable of blocking the transmission of vibrations. An example of the material for the transmission blocking member 47 is rubber (anti-vibration rubber).

[0051] For the same reason, it is preferable that the support member 43 further has a transmission blocking member (second transmission blocking member) 49 disposed between the base 46 and the connecting rod (connecting member) 48. An example of a material for the transmission blocking member 49 is rubber (vibration-proof rubber).

[0052] Although not shown, the sensor body 31 of the acoustic sensor 30 shown in Fig. 2 may be supported from below by a base 46 and a connecting rod (connecting member) 48 shown in Fig. 5. In this case as well, it is preferable that the support jig 43 has a transmission blocking member (first transmission blocking member) 47 arranged between the base 46 and the acoustic sensor 30, and further has a transmission blocking member (second transmission blocking member) 49 arranged between the base 46 and the connecting rod (connecting member) 48.

[0053] Fig. 6 is a diagram showing a schematic diagram of a modified example of the arrangement of the acoustic sensor 30 shown in Fig. 5. As shown in Fig. 6, the polishing apparatus differs from the embodiment shown in Fig. 5 in that it has a liquid supply line 55 that supplies liquid to the second through hole 17 formed in the polishing pad 2.

[0054] 6 extends from a liquid supply source (not shown) through the polishing table 3 to a space communicating with the second through hole 17. The liquid supplied to the second through hole 17 via the liquid supply line 55 may be the same liquid as the liquid supplied to the polishing surface 2a from the polishing liquid supply nozzle 5, or may be a different liquid. The liquid supplied to the second through hole 17 from the liquid supply line 55 during polishing of the wafer W keeps the second through hole 17 filled with clean liquid, and as a result, the acoustic sensor 30 can acquire the polishing sound with higher accuracy.

[0055] In addition, by supplying liquid to the second through hole 17 via the liquid supply line 55, the second through hole 17 can be filled with liquid more reliably. For example, even if a large centrifugal force acts on the second through hole 17 during polishing of the wafer W, the liquid supplied by the liquid supply line 55 reliably fills the second through hole 17. Furthermore, the liquid supplied by the liquid supply line 55 prevents the polishing liquid such as slurry filling the second through hole 17 from solidifying in the second through hole 17. In addition, the second through hole 17 can also be periodically cleaned by the liquid supplied by the liquid supply line 55.

[0056] The liquid supply line 55 may extend through the sensor cover 33 to a space communicating with the second through hole 17, as shown in Figure 7(a), or may extend through the sound transmission member 32 to a space communicating with the second through hole 17, as shown in Figure 7(b).

[0057] 8 is a cross-sectional view showing a schematic arrangement of an acoustic sensor according to still another embodiment. The configuration of this embodiment that is not specifically described is similar to the configuration of the above-described embodiment, and therefore the duplicated description will be omitted.

[0058] 8 differs from the embodiment shown in Fig. 5 in that the sensing protrusion 32a of the sound transmitting member 32 passes through the second through hole 17 formed in the polishing pad 2, and the tip of the sensing protrusion 32a is located above the polishing surface 2a of the polishing pad 2. When such a sensing protrusion 32a is provided, the sensing portion of the acoustic sensor 30 can be brought closer to the source of the polishing sound, as compared to the embodiments shown in Figs. 2 and 5, and therefore the acoustic sensor 30 can acquire the polishing sound with higher accuracy.

[0059] As shown in Fig. 8, the tip of the sensing protrusion 32a is preferably located below the level of the liquid present on the polishing surface 2a of the polishing pad 2. In this case, the acoustic sensor 30 is less susceptible to adverse effects of disturbances. However, as shown by the dashed line in Fig. 8, the tip of the sensing protrusion 32a may be located above the level of the liquid present on the polishing surface 2a of the polishing pad 2.

[0060] In this embodiment, the liquid, which is the polishing liquid supplied from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 during polishing of the wafer W, flows into the second through hole 17 of the polishing pad 2, and the second through hole 17 is filled with the liquid. The sensing protrusion 32a of the sound transmission member 32 of the acoustic sensor 30 is located above the polishing surface 2a of the polishing pad 2 through the second through hole 17. Even in this configuration, the polishing sound generated during polishing of the wafer W is input to the acoustic sensor 30 via the polishing liquid flowing on the polishing pad 2 and the polishing liquid filling the second through hole 17. As a result, the polishing sound is input to the acoustic sensor 30 by propagating only through the liquid, and is not reflected by other materials from the wafer W being polished to the acoustic sensor 30, and attenuation of the polishing sound is prevented as much as possible. Furthermore, since liquid has the property of being able to reflect disturbances, that is, sounds other than the polishing sound, from its surface, the acoustic sensor 30 of this embodiment can detect the polishing sound with much greater accuracy than a conventional polishing device in which an acoustic sensor is placed in a free sound field to detect sounds in the air.

[0061] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can 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 according to the technical idea defined by the claims. [Explanation of symbols]

[0062] 1 Polishing head 2 Polishing Pads 3 Polishing table 5 Polishing fluid supply nozzle 6 Table Motor 9. Controller 10 Head shaft 14 Head Arm 15 First through hole 17 Second through hole 30 Acoustic Sensor 31 Sensor body 32 Sound transmission components 33 Sensor cover 34 Support member 43 Support jig 45 Elastic member 46 units 47,49 Transmission blocking member 48 Connecting rod (connecting member) 50 Rotation angle detection device 55 Liquid Supply Line

Claims

1. A polishing apparatus that polishes a substrate by pressing the substrate against a polishing pad supported on a polishing table, comprising: an acoustic sensor that is inserted into a first through hole formed in the polishing table, detects a polishing sound during polishing of the substrate, and outputs a signal representing the polishing sound; a support jig including at least an elastic member for supporting the acoustic sensor on the polishing table while inhibiting transmission of the polishing sound from the polishing table; a controller that monitors a polishing state of the substrate based on a signal output from the acoustic sensor; the polishing pad has at least one second through hole formed therein, the second through hole communicating with the first through hole and being filled with a liquid; The acoustic sensor faces the second through hole.

2. The acoustic sensor includes: A sensor body; a sound transmitting member in contact with the sensor body; a sensor cover including an insertion hole into which the sound transmission member is inserted so that the sound transmission member faces the second through hole; 2. The polishing apparatus according to claim 1, further comprising: a support member for supporting the sound transmitting member in the insertion hole of the sensor cover while blocking transmission of the polishing sound from the sensor cover.

3. The support jig further includes: A base for supporting the acoustic sensor; a connecting member for connecting the platform to the polishing table; 3. The polishing apparatus according to claim 2, further comprising: a transmission blocking member disposed between said base and said acoustic sensor for blocking transmission of said polishing sound from said base.

4. 3. The polishing apparatus according to claim 2, wherein the sound transmitting member is made of a material having a sound propagation velocity faster than a sound propagation velocity of the polishing table.

5. 3. The polishing apparatus according to claim 2, wherein the sensor cover is made of a material having a sound propagation velocity slower than a sound propagation velocity of the sound transmitting member.

6. the elastic member also functions as a first seal member that seals a gap between the acoustic sensor and the polishing table; 3. The polishing apparatus according to claim 2, wherein the support member also functions as a second seal member that seals a gap between the sound transmitting member and the sensor cover.

7. The polishing apparatus according to claim 1 , further comprising a liquid supply line for supplying the liquid to the second through hole.

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