SUBSTRATE POLISHING APPARATUS

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2024-0077623 filed in the Korean Intellectual Property Office on Jun. 14, 2024, the entire contents of which is incorporated herein by reference.

BACKGROUND

1. Field

Embodiments of the present disclosure relate to a substrate polishing apparatus.

2. Description of Related Art

The chemical mechanical polishing (CMP) is a process of flattening the surface of a substrate using chemical reactions and mechanical forces in manufacturing a semiconductor device.

In order to minimize polishing non-uniformity within the substrate, a process called over-polishing is required to completely remove a metal pattern during the CMP process.

However, if dishing and corrosion of the metal pattern become severe due to over-polishing, it will have a significant impact on the reliability of the semiconductor device. Accordingly, in order to minimize over-polishing, an end-point detection (EPD) device is used, which is a device that monitors a time point when polishing is completed.

A representative EPD device is one that utilizes the physical and mechanical properties of stacked layers, at a time point when a titanium (Ti) film is almost polished and an interlayer insulation layer is exposed, during the CMP polishing process. A monitor current method, a light detection method, a method using a platen temperature, and the like are known in the field.

In addition, there is a method of determining the polishing endpoint by detecting acoustic emission, i.e., sound wave, having a unique value dependent on respective processes and the characteristics of the film quality of the substrate and by monitoring increase or decrease of the sound waves.

However, in the case of the method of monitoring the increase or decrease of the sound waves, signal attenuation occurs while acoustic emission generated from the substrate passes through structures such as a polishing pad, and during this process, the signal-to-noise ratio (SNR) may decrease, such that sufficient sensitivity to detect heterogeneous film quality is difficult.

SUMMARY

One or more embodiments provide a substrate polishing apparatus capable of employing a structure in which piezoelectric elements detecting acoustic emissions are not densely disposed in the direction in which the acoustic signals move, but disposed to be spaced apart by a preset interval, to increase porosity of piezoelectric elements to increase the amount of generating electrons with respect to the same acoustic emission, and thereby improving sensitivity of the sensor for detecting the endpoint of substrate polishing.

According to an aspect of one or more embodiments, there is provided a substrate polishing apparatus including a platen, a polishing pad including a hole on an upper surface of the platen and configured to rotate with the platen, an upper surface of the polishing pad including an opening, a head on the polishing pad and configured to support the substrate such that a polishing surface of the substrate faces the polishing pad, and an acoustic sensor in the hole and including a piezoelectric element on an edge of a droplet on a film portion.

According to another aspect of one or more embodiments, there is provided a substrate polishing apparatus including a platen, a polishing pad on an upper surface of the platen and configured to rotate with the platen, a head configured to support the substrate such that a polishing surface of a substrate faces an upper surface of the polishing pad, a housing having a sealed structure and embedded in the polishing pad, and an acoustic sensor included in the housing, wherein the acoustic sensor includes a piezoelectric element on an edge of a droplet applied to a film portion.

According to still another aspect of one or more embodiments, there is provided a substrate polishing apparatus including a platen, a polishing pad including a hole on an upper surface of the platen and configured to rotate with the platen, an upper surface of the polishing pad including an opening, a head on the polishing pad and configured to support the substrate such that a polishing surface of a substrate faces the polishing pad, a housing in the hole, and an acoustic sensor included in the housing, wherein the acoustic sensor includes a first electrode, a second electrode spaced apart from and facing the first electrode, and a piezoelectric structure between the first electrode and the second electrode and in contact with the first electrode and the second electrode, and wherein the piezoelectric structure includes a film portion perpendicular to the first electrode and the second electrode, and a piezoelectric element having a linear form and on an edge of a droplet applied to the film portion.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGS. 1A and 1B are drawings illustrating a substrate polishing apparatus according to one or more embodiments;

FIG. 2 is a drawing illustrating an acoustic sensor according to one or more embodiments;

FIG. 3 is a drawing showing a process of manufacturing a piezoelectric structure according to one or more embodiments;

FIG. 4 is a drawing showing a process of manufacturing a piezoelectric structure according to one or more other embodiments;

FIG. 5 is a drawing showing a process of manufacturing a piezoelectric structure according to one or more other embodiments;

FIG. 6 is a drawing showing a process of using two types of piezoelectric materials, in a method for manufacturing a piezoelectric structure according to one or more embodiments;

FIG. 7 is a drawing showing a process of using two types of piezoelectric materials, in a method for manufacturing a piezoelectric structure according to one or more other embodiments;

FIGS. 8, 9, 10, 11, and 12 are drawings illustrating a piezoelectric structure according to one or more embodiments; and

FIG. 13 is a drawing illustrating a substrate polishing apparatus according to one or more other embodiments.

DETAILED DESCRIPTION

Hereinafter, the present disclosure will be described in detail hereinafter with reference to the accompanying drawings, in which embodiments of the present disclosure are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure.

The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

In addition, size and thickness of each constituent element in the drawings are arbitrarily illustrated for better understanding and ease of description, the following embodiments are not limited thereto. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, the thickness of some layers and regions may be exaggerated for ease of description.

Throughout this specification and the claims that follow, when it is described that an element is “coupled” to another element, it includes not only the case of being “directly coupled” but also “indirectly coupled” with another element therebetween. In addition, unless explicitly described to the contrary, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

It will be understood that when an element such as a layer, film, region, area, or substrate is referred to as being “on” or “above” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Further, when an element is referred to as being “on” or “above” a reference element, it can be positioned above or below the reference element, and it is not necessarily referred to as being positioned “on” or “above” in a direction opposite to gravity.

Further, throughout the specification, the phrase “in a plan view” or “on a plane” means viewing a target portion from the top, and the phrase “in a cross-sectional view” or “on a cross-section” means viewing a cross-section formed by vertically cutting a target portion from the side.

Among related end-point detection (EPD) devices, there is a method of determining the polishing endpoint by detecting acoustic emission having a unique value depending on characteristics of the film quality of the substrate and respective processes and monitoring the increase or decrease of the acoustic emission.

In the case of using the above-described method, the acoustic emission generated from the substrate may be attenuated while passing through a porous polishing pad made of polyurethane, a medium of air, and the like.

As the signal is attenuated, the signal-to-noise ratio (SNR) may decrease, and the sensitivity required for detecting heterogeneous film quality may be difficult to obtain.

A substrate polishing apparatus 10 according to one or more embodiments attempts to improve the above problem. Hereinafter, a substrate polishing apparatus 10 according to one or more embodiments will be described in more detail with reference to the accompanying drawings.

The substrate polishing apparatus 10 according to one or more embodiments detects the acoustic emission generated from the substrate, and determines the polishing endpoint by using the increase or decrease of the acoustic emission.

Acoustic Emission (AE) refers to elastic waves that are transmitted as the elastic energy accumulated until a solid is plastically deformed or destroyed is released. For example, this is the energy released when a material or structure is cracked by an external force, and generally, the above energy is emitted as ultrasonic waves within a frequency of 50 KHz to 10 MHz.

In a related technique for determining the polishing endpoint of a substrate, the thickness of the polishing layer of the substrate is measured. The end point of the polishing process is determined by detecting sound waves or vibrations generated from the polishing surface of the substrate during the polishing process using a piezoelectric element that detects acoustic emission.

A piezoelectric element is an element that generates an electric charge when an external impact is applied, and operates to convert sound waves or vibrations into electrical signals.

In the related art, when acoustic emission is detected by using a piezoelectric element, signal attenuation occurs while the acoustic signal passes through a polishing pad and an air medium, and accordingly, the sensitivity of the sensor for detecting the acoustic emission may be lowered.

According to the related art, typically, the piezoelectric elements are densely disposed in a direction along which the acoustic signal moves.

The substrate polishing apparatus 10 according to the one or more embodiments is characterized in that piezoelectric elements 412 for detecting the acoustic emissions are not densely disposed in the direction along which the acoustic signal moves.

For example, the piezoelectric elements 412 are disposed in the direction along which the acoustic signal moves, but disposed to be spaced apart from each other with a preset interval.

Due to the structure that the piezoelectric elements 412 are spaced apart by the preset interval, the air-gap ratio in the space where the piezoelectric elements 412 are disposed may be increased.

Compared to related densely disposed piezoelectric elements, the piezoelectric elements 412 according to the one or more embodiments may provide a relatively high air-gap ratio, and have a higher piezoelectric coefficient at the same acoustic emission.

Accordingly, the amount of generating electrons with respect to the same acoustic emission may be increased, and as a result, the sensitivity of the sensor for detecting the acoustic emission may be improved.

FIGS. 1A and 1B are drawings illustrating a substrate polishing apparatus according to one or more embodiments. FIG. 2 is a drawing illustrating an acoustic sensor according to one or more embodiments.

As shown in FIG. 1A, FIG. 1B and FIG. 2, the substrate polishing apparatus 10 according to the one or more embodiments may include a platen 100, a polishing pad 200, a head 300 and an acoustic sensor 400.

The substrate polishing apparatus 10 may further include a cable 500 connected to the acoustic sensor 400 and configured to transfer signals to the outside. FIG. 1 simplifies the structure that the cable 500 is connected to the acoustic sensor 400 disposed in a hole 210.

The cable 500 may be connected to a first electrode 420 and a second electrode 430, respectively, forming and included in the acoustic sensor 400. The cable 500 connected to the acoustic sensor 400 may be connected to an external power source by passing through the platen 100.

FIGS. 1A and 1B illustrate that the cable 500 connected to the acoustic sensor 400 is vertically disposed in a direction from below the hole 210 to below the platen 100 vertical. However, the position where the cable 500 is disposed is not limited to what is shown. The position of the cable 500 connected to the acoustic sensor 400 is not limited, as long as a path connected to the external power source can be enabled.

First, the platen 100 may rotate with the rotation shaft 110 according to a rotation of a rotation shaft 110.

The polishing pad 200 may be disposed on an upper surface of the platen 100 to rotate with the platen 100.

The hole 210 may be disposed on the polishing pad 200, and the acoustic sensor 400 may be disposed within the hole 210. FIGS. 1A and 1B show embodiments of the structure of disposing the acoustic sensor 400 according to the size of the hole 210.

First, as shown in FIG. 1A, the polishing pad 200 may include the hole 210 disposed to have an open upper surface, and the acoustic sensor 400 may be disposed in the hole 210.

As shown in FIG. 1A, when a depth of the hole 210 and a height of the acoustic sensor 400 are the same, an upper surface of the acoustic sensor 400 may be disposed on the same plane as an upper surface of the polishing pad 200.

In the drawings, FIG. 1A illustrates that the size of the acoustic sensor 400 occupies a substantial portion of the polishing pad 200. However, the drawings may not be to scale, and may be enlarged to explain the position where the acoustic sensor 400 is disposed. It may be understood that the actual acoustic sensor 400 is a relatively thin film module within a few millimeters and has a structure with a smaller size than illustrated in the drawings.

The hole 210 may be disposed on the polishing pad 200 (see FIG. 1A), or may penetrate a portion of the platen 100 disposed below the polishing pad 200, as shown in FIG. 1B.

The position of the acoustic sensor 400 may vary depending on the depth of the hole 210.

As shown in FIG. 1B, when the depth of the hole 210 is deeper than the height of the acoustic sensor 400, the acoustic sensor 400 may be disposed to be in contact with an inner side bottom surface of the hole 210. When the hole 210 extends to a portion of the platen 100, the acoustic sensor 400 may be embedded in the platen 100.

In this example, the upper surface of the acoustic sensor 400 and the upper surface of the polishing pad 200 may have different disposal heights. As shown in FIG. 1B, a cover 211 covering the open upper surface of the hole 210 may be further disposed on an upper portion of the hole 210. However, the cover 211 is not necessarily disposed.

When the cover 211 is disposed, the cover 211 may protect the acoustic sensor 400 from the impact that may be generated in the polishing process.

The cover 211 may be formed of the same or similar material as the polishing pad 200. However, embodiments are not limited thereto.

According to one or more other embodiments, the cover 211 may be of a material different from the polishing pad 200, and of a material that does not include a porous structure. When the cover 211 does not include the porous structure, while the acoustic emission generated in the polishing process is transferred to the acoustic sensor 400, less signal attenuation may occur.

According to another embodiment, the cover 211 may be formed of the same conductive polymer material as the first electrode 420 of the acoustic sensor 400. In this example, the cover 211 may be coupled to and integrally disposed with the first electrode 420 of the acoustic sensor 400.

According to one or more other embodiments, an upper portion of the cover 211 may be formed of the same material as the polishing pad 200 including the porous structure, and a lower portion of the cover 211 may be formed of a material that does not include a porous structure.

The head 300 may be disposed on the polishing pad 200, and may support the substrate 1 such that a polishing surface 2 of a substrate 1 may face the polishing pad 200.

The head 300 may also rotate based on the shaft, and as the substrate 1 rotates simultaneously with a rotation of the head 300, a mechanical force acts between the polishing pad 200 and the substrate 1, thereby polishing the polishing surface 2 of the substrate 1.

In the substrate polishing apparatus 10 according to the one or more embodiments, the piezoelectric elements 412 included in the acoustic sensor 400 may detect the acoustic emission transferred from the substrate 1. For example, the polishing endpoint may be determined by using the acoustic emission value that varies depending on the film quality of the substrate 1.

As shown in FIG. 2, the acoustic sensor 400 may include the piezoelectric elements 412 disposed on an edge of a droplet 418 applied to a film portion 416.

For example, the acoustic sensor 400 may include the first electrode 420 and the second electrode 430 disposed to be spaced apart from and to face the first electrode 420. The acoustic sensor 400 may also include a piezoelectric structure 410 disposed between the first electrode 420 and the second electrode 430.

The piezoelectric structure 410 may be disposed perpendicular to the first electrode 420 and the second electrode 430, and to be in contact with the first electrode 420 and the second electrode 430.

The first electrode 420 may be conductive metal or conductive polymer.

The second electrode 430 may include the same conductive metal as the first electrode 420. Unlike the first electrode 420, the second electrode 430 may not be polymer.

The piezoelectric structure 410 may include the film portion 416 having a planar shape disposed perpendicular to the first electrode 420 and the second electrode 430, and the piezoelectric elements 412 disposed on the film portion 416.

The piezoelectric elements 412 is made of a piezoelectric material 414 remaining after the droplet 418 applied to the film portion 416 is dried.

For example, the droplet 418 may include the piezoelectric material 414 and a material to be removed in the process of drying.

The material to be removed in the process of drying may include, for example, polyethylene oxide (PEO), polyvinyl pyrrolidone (PVP), or the like.

Referring to FIG. 2, the piezoelectric elements 412 may correspond to a ring shaped structure disposed on the film portion 416.

The piezoelectric elements 412 according to the one or more embodiments may correspond to the piezoelectric material 414 remaining after the droplet 418 applied to the film portion 416 is dried. The manufacturing process of the piezoelectric elements 412 will be described in detail with reference to FIG. 3.

The acoustic sensor 400 according to the one or more embodiments may further include a signal amplification film 440.

The signal amplification film 440 may be disposed between the first electrode 420 and the piezoelectric structure 410, and may increase a contact area between the first electrode 420 and the piezoelectric elements 412.

The signal amplification film 440 may be disposed directly on the piezoelectric structure 410, and may be bonded to the piezoelectric structure 410.

The signal amplification film 440 may include the same conductive polymer material as the first electrode 420. The signal amplification film 440 may amplify the electrical signal generated by the piezoelectric structure 410.

For example, when the piezoelectric structure 410 includes the N-type oxide semiconductor material, and the signal amplification film 440 bonded thereto includes the P-type semiconductor material, due to the internally formed electric field, more electrons may form the electrical signals.

Accordingly, the electrical signal due to the sound wave or vibration generated in the polishing process may be amplified.

In one or more embodiments, the signal amplification film 440 may include a conductive polymer material (e.g., gold/platinum (Au/Pt) coated polyether sulfone (PES)). The PES may be one of highly heat-resistant special resins.

The acoustic sensor 400 may further include a seed layer 450 disposed between the second electrode 430 and the piezoelectric structure 410.

The seed layer 450 may include the same piezoelectric material 414 as the piezoelectric material 414 included in the piezoelectric structure 410.

The seed layer 450 connected to the second electrode 430 may bond the second electrode 430 and the piezoelectric elements 412 of the piezoelectric structure 410.

As described above, the acoustic sensor 400 according to one or more embodiments may have a structure in which the first electrode 420, the signal amplification film 440, the piezoelectric structure 410, the seed layer 450, and the second electrode 430 are disposed in the listed order.

As shown in FIG. 2, the piezoelectric structure 410 may include a plurality of piezoelectric structures 410 between the first electrode 420 and the second electrode 430. The piezoelectric structures 410 may be disposed parallel to each other, and disposed such that a plurality of film portions 416 and the piezoelectric elements 412 do not contact each other.

The film portion 416 may include a polymer material having a flat surface. Depending on the embodiment, the film portion 416 may include at least one polymer material among polyurethane (PU), polyethylene terephthalate (PET), and polypropylene (PP).

The piezoelectric elements 412 may detect the sound wave or vibration generated from the polishing surface 2 of the substrate 1 in the polishing process. The piezoelectric elements 412 may include at least one piezoelectric material among barium titanate (BaTiO₃), zinc oxide (ZnO), and zirconate titanate (PZT) 414.

However, the above-described materials forming the film portion 416 and the piezoelectric elements 412 are merely an example, and may not limited thereto.

FIGS. 3 to 5 are drawings showing a process of manufacturing a piezoelectric structure according to various embodiments.

First, the piezoelectric structure 410 according to the one or more embodiments may include the piezoelectric elements 412 generated as the piezoelectric material 414 moves to the edge of the droplet 418 as the droplet 418 including the piezoelectric material 414 is dried.

FIG. 3 are drawings showing a manufacturing process of one piezoelectric structure 410. The piezoelectric structure 410 may include a film portion 416 and a piezoelectric element 412 formed on the one film portion 416.

First, FIG. 3 illustrates that the droplet 418 including the piezoelectric material 414 is applied to the film portion 416. FIG. 3 illustrates that, while the film portion 416 with the piezoelectric material 414 in FIG. 3 is dried, the piezoelectric material 414 included in the droplet 418 moves outward in the droplet 418, thereby forming a stripe.

The operation by which the piezoelectric material 414 moves as shown in FIG. 3 is due to the coffee-ring effect.

The coffee-ring effect may be a phenomenon in which solid contents remaining as the liquid evaporates move toward the edge of the liquid.

FIG. 3 illustrates that the droplet 418 is completely dried from FIG. 3. In the film portion 416, the material excluding the piezoelectric material 414 may be dried, and only the piezoelectric elements 412 formed of the piezoelectric material 414 may remain.

FIGS. 4 and 5 are drawings showing a process of manufacturing and stacking a plurality of piezoelectric structures 410, as a process of manufacturing the piezoelectric structure 410 according to one or more embodiments different from FIG. 3.

First, FIG. 4 illustrates the film portion 416 before applying the droplet 418. Then the droplet 418 is applied on the film portion 416. The droplet 418 includes the piezoelectric material 414.

As shown in FIG. 3, FIG. 4 illustrates that, as the droplet 418 is dried, the piezoelectric materials 414 included in the droplet 418 move outward in the droplet 418, and as the droplet 418 is completely dried, the piezoelectric elements 412 formed of the piezoelectric material 414 remain on the film portion 416.

FIG. 4 illustrates that a new film portion 416 is stacked on the piezoelectric structure 410 manufactured in FIG. 4. Then the droplet 418 is applied to the new film portion 416 of FIG. 4. The droplet 418 applied may be dried, and may leave behind only the ring-shaped piezoelectric elements 412.

FIG. 4 illustrates that the process of disposing the new film portion 416 on the completed piezoelectric structure 410 is repeated, in which the processes are repeated.

As a result, the plurality of piezoelectric structures 410 are stacked, and may be manufactured as illustrated in FIG. 4.

FIG. 5 also illustrates the manufacturing process of stacking the plurality of piezoelectric structures 410 as in FIG. 4. The differences of the process of stacking the piezoelectric structure 410 from FIG. 4 are described.

First, the film portion 416 before applying the droplet 418 is provided. Then the droplet 418 is applied on the film portion 416. The droplet 418 includes the piezoelectric material 414.

The droplet 418 applied is completely dried, and in the film portion 416, the piezoelectric elements 412 formed of the piezoelectric material 414 having moved to the edge of the droplet 418 may remain. The process up to this point is the same as the process illustrated in FIG. 4.

In FIG. 5, the above processes may be repeated many times, and the plurality of piezoelectric structures 410 may be manufactured. However, in FIG. 5, the droplet 418 is not applied on a new film portion 416 disposed on the completed piezoelectric structure 410.

In FIG. 5, after the droplet 418 is applied to each of the plurality of film portions 416, the droplet 418 is dried to manufacture the ring-shaped piezoelectric elements 412. In FIG. 5, each in the plurality of piezoelectric structures 410 is manufactured first.

In the example of FIG. 4, the droplet 418 is applies and dried while stacking the piezoelectric structure 410, and the plurality of piezoelectric structures 410 cannot be simultaneously manufactured.

In FIG. 5, the plurality of piezoelectric structures 410 may be simultaneously manufactured. The plurality of piezoelectric structures 410 manufactured may be attacked as illustrated in FIG. 5.

FIGS. 6 and 7 are drawings showing a process of manufacturing the piezoelectric structure by using two types of piezoelectric materials. For example, a process of manufacturing the piezoelectric elements 412 formed of different piezoelectric materials 414 is provided. In the drawing, two types of piezoelectric elements 412 are illustrated, but embodiments are not limited thereto.

The piezoelectric structure 410 in the one or more embodiments may increase the range of response frequency of the acoustic sensor 400, by using the piezoelectric elements 412 formed of two or more types of the piezoelectric materials 414.

The frequency of the acoustic emission may vary according to the film quality of the substrate 1, and the response frequency may vary according to the piezoelectric material 414.

Accordingly, according to the one or more embodiments, the detectable frequency range may be increased by increasing the response frequency by using two or more types of the piezoelectric materials 414. As a result, during the process of polishing the substrate 1, the time point at which the film quality of the substrate 1 changes can be detected.

When on the piezoelectric elements 412 formed of one piezoelectric material 414 is used, it is difficult to detect the response frequency is limited, the time point at which the film quality of the substrate 1 changes.

FIG. 6 illustrates a plurality of piezoelectric structures 410, in each of which the piezoelectric element 412 is disposed in the film portion 416. FIG. 6 illustrates stacking of the plurality of piezoelectric structures 410.

The plurality of piezoelectric structures 410 in which the piezoelectric element 412 disposed on each film portion 416 formed of two types of piezoelectric materials 414. For example, the piezoelectric elements 412 having different piezoelectric materials 414 are alternately disposed.

In the acoustic sensor 400 according to the one or more embodiments, at least one piezoelectric element 412 among the piezoelectric elements 412 included in the plurality of piezoelectric structures 410 may include the different piezoelectric materials 414.

The sequence disposing the film portion 416 in which the piezoelectric elements 412 formed of the different piezoelectric materials 414 is disposed is not limited what is shown in FIG. 6.

As shown in FIG. 7, the plurality of piezoelectric structures 410 including the piezoelectric elements 412 formed of the different piezoelectric materials 414, respectively may be disposed such that the piezoelectric elements 412 formed of the same piezoelectric material 414 may be consecutive.

FIGS. 8 to 12 are drawings illustrating a piezoelectric structure according to various embodiments.

As shown in FIGS. 8 to 12, the form of the piezoelectric elements 412 included in the plurality of piezoelectric structures 410 may be vary.

According to one or more embodiments, the at least one piezoelectric element 412 among the piezoelectric elements 412 included in the plurality of piezoelectric structures 410 may have different forms.

First, FIG. 8 illustrates that the piezoelectric elements 412 disposed on the film portion 416 are arch-shaped having an open bottom.

In FIG. 9, the piezoelectric elements 412 may be arch-shaped. However, unlike as described with reference to FIG. 8, the arch-shaped bottom portion may be closed. For example, the two ends of the arch-shaped portion may be connected to each other.

In the example of FIG. 10, the piezoelectric elements 412 has an elliptical shape.

As shown in FIGS. 8 to 10, the piezoelectric elements 412 according to the one or more embodiments are not relatively densely disposed in the direction from the first electrode 420 toward the second electrode 430 (direction along which the acoustic signal moves), but structured to be spaced apart by a preset interval.

Accordingly, the air-gap ratio of the piezoelectric elements 412 may be increased compared to the related art, the amount of generating electrons with respect to the same acoustic emission may be increased, and the sensitivity of the sensor for detecting the acoustic emission may be improved.

According to the one or more embodiments, the film portion 416 may serve as a support for supporting the first electrode 420 and the second electrode 430.

When only the piezoelectric elements 412 are disposed between the first electrode 420 and the second electrode 430 without the film portion 416, the first electrode 420 and the second electrode 430 may not be sufficiently supported by only the piezoelectric elements 412 having the structure having the relatively high air-gap ratio.

The ring-shaped piezoelectric elements 412 are disposed in the plurality of piezoelectric structures 410 shown in FIG. 11. A plurality of piezoelectric elements 412 disposed on the plurality of film portions 416 include two types of piezoelectric materials 414.

The piezoelectric elements 412 having different piezoelectric materials 414 are alternately disposed as in FIG. 6.

In the piezoelectric elements 412 disposed in the plurality of piezoelectric structures 410 shown in FIG. 12, different piezoelectric elements 412 are alternately disposed may as in FIG. 11. In addition, the piezoelectric elements 412 shown in FIG. 12 may have different forms, as described hereinbelow.

The closed-bottom arch-shaped piezoelectric elements 412 are formed of a first piezoelectric material 414, and the ring-shaped piezoelectric elements 412 are formed of a second piezoelectric material 414. For example, the piezoelectric elements 412 having different forms and formed of the first and second piezoelectric materials 414 are alternately disposed.

For example, in the acoustic sensor 400 according to the one or more embodiments, the plurality of piezoelectric elements 412 included in the plurality of piezoelectric structures 410 are different in at least one of the piezoelectric material 414 forming the piezoelectric elements 412 and the form of the piezoelectric elements 412.

FIG. 13 is a drawing illustrating a substrate polishing apparatus according to one or more other embodiments.

As shown in FIG. 13, the substrate polishing apparatus 10 according to one or more other embodiments may include the platen 100, the polishing pad 200 disposed on the upper surface of the platen 100 and configured to rotate with the platen 100, the head 300 configured to support the substrate 1 such that the polishing surface 2 of the substrate 1 may face the upper surface of the polishing pad 200.

In addition, the substrate polishing apparatus 10 may include a housing 220 having a closed and sealed structure having an upper surface, a lower surface and a side surface, and embedded in the polishing pad 200, and the acoustic sensor 400 disposed within the housing 220.

Unlike as described with reference to FIG. 1, in the embodiment of FIG. 13, the difference lies in that the acoustic sensor 400 is disposed within the housing 220 provided in the polishing pad 200. As shown in FIG. 13, an upper surface of the housing 220 may be disposed on a same plane as the upper surface of the polishing pad 200.

The housing 220 is formed adjacent to and to surround an exterior of the acoustic sensor 400, and may serve to fix the acoustic sensor 400. In addition, the housing 220 may protect the acoustic sensor 400 from the impact that may be generated in the polishing process.

Depending on the one or more embodiments, the upper surface of the housing 220 may be formed of the same or similar material as the polishing pad 200.

For example, the upper surface of the housing 220 may include, for example, polyurethane resin, and may include the porous structure. The porous structure may mean a structuring including a plurality of pores.

According to one or more other embodiments, the upper surface of the housing 220 is formed of a material different from the polishing pad 200, which may be a material that does not include a porous structure. When the housing 220 may not include the porous structure, while the acoustic emission generated in the polishing process is transferred to the acoustic sensor 400, less signal attenuation may occur.

According to one or more other embodiments, the upper surface of the housing 220 may be formed of the same conductive polymer material as the first electrode 420 of the acoustic sensor 400. In this example, the upper surface of the housing 220 may be coupled to and integrally disposed with the first electrode 420 of the acoustic sensor.

According to one or more other embodiments, an upper portion of the upper surface of the housing 220 may be formed of the same material as the polishing pad 200 including the porous structure, and a lower portion of the housing 200 may be formed of a material that does not include a porous structure.

The acoustic sensor 400 disposed within the housing 220 may include the first electrode 420, the second electrode 430 disposed to be spaced apart from and to face the first electrode 420, and the piezoelectric structure 410 disposed between the first electrode 420 and the second electrode 430 to be in contact with the first electrode 420 and the second electrode 430.

The piezoelectric structure 410 may include the film portion 416 disposed perpendicular to the first electrode 420 and the second electrode 430, and the piezoelectric elements 412 generated as the droplet 418 applied to the film portion 416 is dried.

The piezoelectric elements 412 are disposed on the edge of the droplet 418 applied to the film portion 416 and may have a linear form.

The piezoelectric elements 412 generated by the coffee-ring effect may not be relatively densely disposed in the direction from the first electrode 420 toward the second electrode 430 (direction along which the acoustic signal moves), and may be disposed to be spaced apart by a preset interval. Accordingly, by increasing the air-gap ratio of the piezoelectric elements 412, and by increasing the amount of generating electrons with respect to the same acoustic emission, the sensitivity of the sensor for detecting the acoustic emission may be improved.

According to one or more other embodiments, the substrate polishing apparatus 10 according to the one or more embodiments may include the platen 100, the polishing pad 200 disposed on the upper surface of the platen 100 to rotate with the platen 100 and including the hole 210 disposed to have an open upper surface, the head 300 disposed on the polishing pad 200 and configured to support the substrate 1 such that the polishing surface 2 of the substrate 1 may face the polishing pad 200, the housing 220 disposed in the hole 210, and the acoustic sensor 400 disposed within the housing 220.

The hole 210 having an open upper surface may be disposed on the polishing pad 200, the housing 220 may be disposed in the hole 210, and the acoustic sensor 400 may be disposed within the housing 220.

In this example, the acoustic signal generated from the substrate 1 passes through the upper surface of the housing 220, and the air medium filled within the housing 220, and is transferred to the acoustic sensor 400. During this process, signal attenuation may occur in the acoustic signal during the process of passing through the upper surface of the housing 220 and the air medium.

However, according to the substrate polishing apparatus 10 according to the one or more embodiments, compared to the related art, the air-gap ratio of the piezoelectric elements 412 is increased, and the amount of generating electrons with respect to the same acoustic emission is increased.

Accordingly, as described above, even if the signal is attenuated while the acoustic signal is transferred, the sensitivity of the acoustic sensor 400 is improved, and accordingly, the reactivity with respect to small signals is increased.

While embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims and their equivalents.