Substrate Polishing Apparatus

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.

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

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.

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.

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

The substrate polishing apparatusaccording 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 apparatusaccording to the one or more embodiments is characterized in that piezoelectric elementsfor detecting the acoustic emissions are not densely disposed in the direction along which the acoustic signal moves.

For example, the piezoelectric elementsare 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 elementsare spaced apart by the preset interval, the air-gap ratio in the space where the piezoelectric elementsare disposed may be increased.

Compared to related densely disposed piezoelectric elements, the piezoelectric elementsaccording 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.

are drawings illustrating a substrate polishing apparatus according to one or more embodiments.is a drawing illustrating an acoustic sensor according to one or more embodiments.

As shown in,and, the substrate polishing apparatusaccording to the one or more embodiments may include a platen, a polishing pad, a headand an acoustic sensor.

The substrate polishing apparatusmay further include a cableconnected to the acoustic sensorand configured to transfer signals to the outside.simplifies the structure that the cableis connected to the acoustic sensordisposed in a hole.

The cablemay be connected to a first electrodeand a second electrode, respectively, forming and included in the acoustic sensor. The cableconnected to the acoustic sensormay be connected to an external power source by passing through the platen.

illustrate that the cableconnected to the acoustic sensoris vertically disposed in a direction from below the holeto below the platenvertical. However, the position where the cableis disposed is not limited to what is shown. The position of the cableconnected to the acoustic sensoris not limited, as long as a path connected to the external power source can be enabled.

First, the platenmay rotate with the rotation shaftaccording to a rotation of a rotation shaft.

The polishing padmay be disposed on an upper surface of the platento rotate with the platen.

The holemay be disposed on the polishing pad, and the acoustic sensormay be disposed within the hole.show embodiments of the structure of disposing the acoustic sensoraccording to the size of the hole.

First, as shown in, the polishing padmay include the holedisposed to have an open upper surface, and the acoustic sensormay be disposed in the hole.

As shown in, when a depth of the holeand a height of the acoustic sensorare the same, an upper surface of the acoustic sensormay be disposed on the same plane as an upper surface of the polishing pad.

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

The holemay be disposed on the polishing pad(see), or may penetrate a portion of the platendisposed below the polishing pad, as shown in.

The position of the acoustic sensormay vary depending on the depth of the hole.

As shown in, when the depth of the holeis deeper than the height of the acoustic sensor, the acoustic sensormay be disposed to be in contact with an inner side bottom surface of the hole. When the holeextends to a portion of the platen, the acoustic sensormay be embedded in the platen.

In this example, the upper surface of the acoustic sensorand the upper surface of the polishing padmay have different disposal heights. As shown in, a covercovering the open upper surface of the holemay be further disposed on an upper portion of the hole. However, the coveris not necessarily disposed.

When the coveris disposed, the covermay protect the acoustic sensorfrom the impact that may be generated in the polishing process.

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