Apparatus and Method for Wetting a Polishing Pad

Abstract

The present invention relates to an apparatus (100) for wetting a polishing pad (203). The wetting apparatus (100) includes measuring means (103, 104, 105, 106, 107, 108, 109, 110) for measuring a physical quantity indicating the moisture content of the polishing pad (203), and dispensing means (111, 112, 113, 114, 115) for dispensing a polishing suspension based on the measured value of the physical quantity on the surface of the polishing pad (203). The measuring means (103, 104, 105, 106, 107, 108, 109, 110) and the dispensing means (111, 112, 113, 114, 115) are surrounded by a housing (101) having a contact surface (102) that contacts the surface of the polishing pad (203). The present invention also relates to an apparatus (200) for polishing a sample (204) and a wetting method for wetting a polishing pad (203).

Description

Technical Field

[0001] The present invention relates to an apparatus and method for wetting a polishing pad according to the preamble of the appended independent claims. The present invention also relates to an apparatus for polishing a sample.

Background Art

[0002] In the prior art, various polishing apparatuses are known for polishing samples of rocks, metal structures, and other solid materials for different applications. The polishing apparatus enables the sample to be polished with a minimum of manual work.

[0003] An exemplary polishing apparatus includes a rotatable polishing plate and a polishing pad attached to the surface of the polishing plate. The polishing apparatus also includes a sample holder for holding one or more samples against the polishing pad. When the polishing plate is rotated, the polishing pad polishes the sample.

[0004] A polishing suspension is used in the polishing apparatus to enhance the polishing action and prevent overheating during the polishing process. The polishing suspension includes water and / or other suitable liquids, such as ethanol or glycol for wetting, cooling, and lubricating the polishing pad and polishing particles, for example, diamond, aluminum oxide, or colloidal silica for polishing the surface of the sample. The polishing apparatus includes a dispenser for dispensing the polishing suspension onto the polishing pad, typically at a predetermined rate. The dispenser can be configured to dispense a certain amount of the polishing suspension onto the polishing pad at regular time intervals, for example.

[0005] A problem associated with known polishing apparatuses is that during polishing, the moisture content of the polishing pad can vary considerably as a function of time and also as a function of the position of the polishing pad. This has a negative impact on the polishing result. If the polishing pad is too wet, the friction between the sample and the polishing pad is reduced, the polishing becomes ineffective, and the polishing time is lengthened. On the other hand, if the polishing pad is too dry, there is a risk of failure in polishing the sample because the friction between the sample and the polishing pad is large.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The main object of the present invention is to reduce or further eliminate the problems of the prior art presented above.

[0007] An object of the present invention is to provide an apparatus and a method for wetting a polishing pad. More specifically, an object of the present invention is to provide an apparatus and a method that enable providing and maintaining a substantially constant and uniform moisture content of the polishing pad during a polishing process.

[0008] Another object of the present invention is to provide an apparatus for polishing a sample. More specifically, an object of the present invention is to provide an apparatus that enables polishing a sample with a uniform and high-quality polishing result.

Means for Solving the Problems

[0009] To achieve the above object, the apparatus and method according to the present invention are characterized by those shown in the characterizing portions of the appended independent claims. Advantageous embodiments of the present invention are described in the dependent claims.

[0010] The wetting device according to the present invention for wetting a polishing pad includes measuring means for measuring a physical quantity indicating the moisture content of the polishing pad, dispensing means for dispensing a polishing suspension based on the value of the measured physical quantity, and a housing that houses the measuring means and the dispensing means and has a contact surface that contacts the surface of the polishing pad.

[0011] The apparatus according to the present invention can be used to wet a polishing pad used for polishing a sample. The apparatus can measure a physical quantity indicating the moisture content of the polishing pad and then dispense a polishing suspension onto the surface of the polishing pad based on the value of the measured physical quantity.

[0012] The measuring means and the dispensing means are preferably arranged in a housing which is essentially cylindrical in shape. The housing is preferably dimensioned such that the device can be inserted into the sample cavity of the sample holder. The contact surface of the housing is meant to be arranged in contact with the surface of the polishing pad. The measurement of physical quantities and the dispensing of the polishing suspension are carried out via the contact surface. The housing can be made of wear-resistant and corrosion-resistant ceramic or metal, or other suitable materials. The housing may be a hollow cylinder, and its ends function as contact surfaces. The contact surface is preferably flat.

[0013] The measuring means can comprise one or more electrical contact elements (electrodes) arranged on the contact surface of the housing. For measurement, the contact surface and the electrical contact element(s) therein are arranged in contact with the surface of the polishing pad. The measurement is based on measuring a physical quantity that varies as a function of the moisture content of the polishing pad. Such a physical quantity is, for example, the capacitance between one electrical contact element and the polishing plate to which the polishing pad is attached, i.e., the capacitance between the opposite sides of the polishing pad. Another such physical quantity is the (electrical) resistance between two electrical contact elements when they are arranged in contact with the surface of the polishing pad.

[0014] The electrical contact elements provide an electrical path through which the electrical properties of the polishing pad can be measured. The electrical contact elements can have different shapes and sizes. The electrical contact elements are preferably also made of a conductive material that is wear-resistant and corrosion-resistant. Preferred materials for the electrical contact elements are, for example, steel and gold-platinum alloys. The electrical contact elements are electrically insulated from each other to prevent short circuits.

[0015] The measuring means can comprise a measuring instrument electrically connected to an electrical connection such as a wire, cable and / or carbon brush, an electrical contact element and a polishing plate. The measuring instrument can be configured to measure the capacitance between one electrical contact element and the polishing plate and / or the resistance between two electrical contact elements when they are in contact with the surface of the polishing pad. The values of the capacitance and resistance depend on the moisture content of the polishing pad. The more the polishing pad is moistened, the greater the capacitance and the smaller the resistance.

[0016] The dispensing means can comprise a container for the polishing suspension and a nozzle arranged on the contact surface. The nozzle can be connected to the container by a hose. The dispensing means may comprise a valve or (piezoelectric) micropump arranged in relation to the container, hose or nozzle, and a control unit for controlling the operation of the valve or micropump. The control unit can comprise a processor and a memory containing computer program code, the memory and the computer program code being configured with the processor such that the valve or micropump dispenses a suitable amount of the polishing suspension onto the surface of the polishing pad. The amount of polishing suspension to be dispensed is determined based on the value of the measured physical quantity. The value of the measured physical quantity can be compared with a predefined reference value or profile in order to determine the amount of polishing suspension to be dispensed. The predefined reference value or profile corresponds to the desired moisture content of the polishing pad. The amount of polishing suspension dispensed onto the polishing pad can be, for example, less than 5 μl / cm 2 less than, 2 μl / cm 2 less than, or 0.5 - 2 μl / cm 2 and can be.

[0017] The polishing suspension enhances the polishing action and prevents overheating during the polishing process. The polishing suspension contains water and / or other suitable liquids such as alcohol (e.g., ethanol, glycol, or isopropyl alcohol) to moisten, cool, and lubricate the polishing pad. The polishing suspension may also contain polishing particles such as diamond, aluminum oxide, or colloidal silica for polishing the sample surface. Typically, the polishing suspension (i.e., slurry or fluid) is a mixture of a liquid and an abrasive agent.

[0018] The wetting device may be provided with communication means for communicating with a remote device such as a mobile phone. The communication means may include a transmitter and a receiver for two-way wireless communication with the remote device.

[0019] An advantage of the wetting device according to the present invention is that it can provide and maintain a substantially constant and uniform moisture content on the polishing pad during the polishing process. Another advantage of the wetting device according to the present invention is that it enables achieving a uniform and high-quality polishing result of the sample. Still another advantage of the wetting device according to the present invention is that it enables optimizing (minimizing) the consumption of the polishing suspension in the polishing process. Yet another advantage of the wetting device according to the present invention is that it can be inserted into the sample cavity of the sample holder and thus can be retrofitted to an existing polishing device. Still another advantage of the wetting device according to the present invention is that it has a compact design and the measuring means and the dispensing means are arranged in the same housing.

[0020] According to one embodiment of the present invention, the housing is essentially cylindrical. The cylindrical housing is preferably dimensioned such that the wetting device fits into the sample cavity of the sample holder of the polishing device.

[0021] According to one embodiment of the present invention, the housing has a diameter of 10 mm to 100 mm. The diameter of the housing can be 25 - 60 mm, or 25 mm, 30 mm, 40 mm, 50 mm, or 60 mm. The height of the housing can be, for example, 10 - 50 mm, 10 - 30 mm, or 20 - 40 mm.

[0022] According to one embodiment of the present invention, the physical quantity is the resistance of the polishing pad. The resistance of the polishing pad changes as a function of the moisture of the polishing pad. The more the polishing pad is wetted, the smaller the resistance becomes.

[0023] According to one embodiment of the present invention, the measuring means includes two electrical contact elements arranged on the contact surface and a measuring instrument configured to measure the resistance between the two electrical contact elements. The electrical contact elements can have different shapes and sizes. The electrical contact elements are preferably also made of a conductive material that wears and is corrosion resistant. Preferred materials for the electrical contact elements are, for example, stainless steel and tool steel. For measurement, the contact surface and the electrical contact elements therein are arranged in contact with the surface of the polishing pad. The electrical contact elements provide an electrical path capable of measuring the electrical characteristics of the polishing pad. The measuring instrument is electrically connected so as to have an electrical connection to the electrical contact elements. The measuring instrument is configured to measure the resistance between the electrical contact elements when the contact surface is in contact with the surface of the polishing pad.

[0024] According to one embodiment of the present invention, the dispensing means is configured to dispense a polishing suspension onto the surface of the polishing pad when the value of the resistance is greater than a first threshold value. The first threshold value can be set on a case-by-case basis in light of the characteristics of the sample to be polished.

[0025] According to one embodiment of the present invention, the physical quantity is the capacitance between opposite sides of the polishing pad. The capacitance between opposite sides of the polishing pad changes as a function of the moisture of the polishing pad. The more the polishing pad is wetted, the greater the capacitance becomes.

[0026] According to one embodiment of the present invention, the measuring means includes an electrical contact element disposed on the contact surface and a measuring instrument configured to measure the capacitance between the electrical contact element and the polishing plate on which the polishing pad is disposed. The electrical contact element can have different shapes and sizes. The electrical contact element is preferably also made of a conductive material that wears and is corrosion resistant. Preferred materials for the electrical contact element are, for example, stainless steel and tool steel. For measurement, the contact surface and the electrical contact element therein are disposed in contact with the surface of the polishing pad. The measuring instrument is electrically connected to the electrical connection to the electrical contact element and the polishing plate. The measuring instrument is configured to measure the capacitance between the electrical contact element and the polishing plate when the contact surface is in contact with the surface of the polishing pad. A resistor can be used between the measuring instrument and the polishing plate to reduce interference.

[0027] According to one embodiment of the present invention, the dispensing means is configured to dispense the polishing suspension onto the surface of the polishing pad when the value of the capacitance is less than a second threshold. The second threshold can be set on a case-by-case basis in light of the characteristics of the sample to be polished.

[0028] According to one embodiment of the present invention, the dispensing means includes a container for holding the polishing suspension and a hose having a first end connected to the container and a second end connected to and disposed on the contact surface. The polishing suspension is dispensed onto the surface of the polishing pad through the contact surface. The container can be disposable or refillable. The housing may include a hole for filling the container. The capacity of the container can be, for example, 1 to 100 ml, 1 to 20 ml, 10 to 50 ml, or 50 to 100 ml.

[0029] According to one embodiment of the present invention, the dispensing means includes a nozzle connected to the second end of the hose. The nozzle is connected to the contact surface.

[0030] According to one embodiment of the present invention, the dispensing means includes a valve or a micropump arranged in relation to a container, a hose or a nozzle, and a control unit configured to control the operation of the valve or the micropump. The control unit can comprise a processor and a memory containing computer program code, the memory and the computer program code being configured with the processor such that the valve or the micropump dispenses a suitable amount of the polishing suspension onto the surface of the polishing pad. The amount of the polishing suspension to be dispensed is determined based on the value of the measured physical quantity. The value of the measured physical quantity can be compared with a predefined reference value or profile in order to determine the amount of the polishing suspension to be dispensed. The predefined reference value or profile corresponds to the desired moisture content of the polishing pad. The amount of the polishing suspension dispensed onto the polishing pad can be, for example, less than 5 μl / cm 2 less than, 2 μl / cm 2 less than, or 0.5 to 2 μl / cm 2 and can be.

[0031] According to one embodiment of the present invention, the wetting device includes a power source for supplying power to the measuring means and the dispensing means. The power source is arranged inside the housing. The power source is preferably a rechargeable battery. The housing may be provided with a charging socket for wired charging or an induction receiver for wireless charging.

[0032] The present invention also relates to an apparatus for polishing a sample. The polishing apparatus according to the present invention includes a polishing plate rotatable about an axis, a polishing pad attached to the polishing plate, a sample holder having a plurality of sample cavities for holding one or more samples against the surface of the polishing pad, and the wetting device according to the present invention inserted into one of the sample cavities such that the contact surface contacts the surface of the polishing pad.

[0033] The polishing apparatus according to the present invention can be used to polish one or more samples (i.e., objects) of solid materials such as pieces of natural (e.g., rock, mineral, ore or meteorite) or artificial (e.g., metal, concrete, ceramic, composite or semiconductor) materials. The sample to be polished may include a substrate on which a semiconductor material such as silicon or germanium, or various III-V compound semiconductor materials, etc. are deposited. In this text, the term polishing means polishing, pulverization and grinding processes by a polishing pad and a polishing suspension.

[0034] The sample to be polished is inserted into one of the sample cavities of the sample holder and held together with the sample holder against the surface of the polishing pad. The sample holder can be configured to hold one or more samples against the polishing pad. The number of sample cavities in the sample holder can be, for example, 2 to 5, 6 to 10, or 10 or more. The sample can be fixed in the sample cavity by a clamp. The sample holder can be attached to a polishing head that presses the sample against the polishing pad with an adjustable pressing force. The pressing force can be adjusted, for example, based on the value of a measured physical quantity.

[0035] Insert the wetting device into one of the sample cavities of the specimen holder. The contact surface of the wetting device is arranged in contact with the surface of the polishing pad.

[0036] The polishing pad can be made of different materials such as a fiber cloth (e.g., real silk, polyester or acetate) or a synthetic non-fiber (e.g., neoprene, polyurethane or composite material). The polishing pad is preferably disc-shaped, i.e., has a flat circular shape. The polishing pad is preferably porous to enable absorption of the polishing suspension. The diameter of the polishing pad is, for example, less than 500 mm, preferably 200 to 400 mm. The thickness of the polishing pad can be, for example, less than 3 mm, preferably less than 2 mm, more preferably less than 1 mm.

[0037] The polishing pad is preferably removably attached to the surface of a rotatable polishing plate. When the polishing plate is rotated, the polishing pad polishes the sample. The polishing plate can be made of a heat-conductive and corrosion-resistant material such as aluminum, bronze or stainless steel, or a plastic, polymer or composite material. The polishing plate may be provided with an electrically insulated electrical contact element (for example, a sheet made of austenitic stainless steel and having a thickness of about 0.5 mm) on its surface, to which an electrical contact element (for example, a carbon brush) can be electrically connected. The electrical contact element can be electrically connected to the measuring instrument of the wetting device. The polishing plate is preferably disc-shaped and heat-conductive. The diameter of the polishing plate can be, for example, less than 500 mm, preferably 200 - 400 mm. Preferably, the diameters of the polishing plate and the polishing pad are essentially the same. The thickness of the polishing plate can be, for example, 20 - 50 mm. The optimal thickness of the polishing plate varies depending on the diameter and material of the polishing plate.

[0038] The polishing apparatus may include an actuator such as an electric motor for rotating the polishing plate. The actuator can be configured to rotate the polishing plate at a rotational speed of, for example, 0 - 600 rpm. The actuator can be configured to adjust the rotational speed of the polishing plate based on the measured value of the physical quantity. For example, when the moisture falls below a predetermined threshold, the actuator can be configured to reduce the rotational speed of the polishing plate. To reduce the possible interference caused by the actuator, it may be beneficial to add an electrical insulation layer between the polishing plate and the actuator.

[0039] In addition to the polishing plate, the sample holder can also be made rotatable. The sample holder can be made rotatable about an axis parallel to the rotation axis of the polishing plate. The polishing apparatus may include an actuator, for example, an electric motor, for rotating the sample holder. The actuator can be configured to rotate the sample holder, for example, at a rotational speed of 0 to 150 rpm. The actuator can be configured to adjust the rotational speed of the sample holder based on the measured value of the physical quantity. For example, in a case where the moisture content is below a predetermined threshold value, the actuator can be configured to reduce the rotational speed of the sample holder.

[0040] An advantage of the polishing apparatus according to the present invention is that it can provide and maintain a substantially constant and uniform moisture content of the polishing pad during the polishing process. Another advantage of the polishing apparatus according to the present invention is that it enables achieving a uniform and high-quality polishing result of the sample. Still another advantage of the polishing apparatus according to the present invention is that it enables optimizing (minimizing) the consumption of the polishing suspension in the polishing process. Yet another advantage of the polishing apparatus according to the present invention is that in the case where the wetting device is broken, it is easy to replace.

[0041] According to an embodiment of the present invention, the sample holder includes pressing means for pressing the contact surface against the surface of the polishing pad. This pressing means enables keeping the contact surface of the wetting device in contact with the surface of the polishing pad with an appropriate pressing force. The pressing of the pressing means is adjustable. This pressing means can utilize mechanical force, air pressure, gravity, or magnetic force or electromagnetic force when generating appropriate pressing.

[0042] The present invention also relates to a wetting method for wetting the polishing pad. The wetting method according to the present invention includes the steps of arranging the wetting device according to the present invention in the sample cavity of the sample holder, arranging the contact surface of the wetting device in contact with the surface of the polishing pad attached to the polishing plate, rotating the polishing plate around the axis, measuring the physical quantity indicating the moisture content of the polishing pad with the wetting device, and distributing the polishing suspension with the wetting device based on the measured value of the physical quantity on the surface of the polishing pad.

[0043] The advantages of the wetting method according to the present invention are that during the polishing process, a substantially constant and uniform amount of moisture can be provided to and maintained on the polishing pad. Another advantage of the wetting method according to the present invention is that it enables achieving a uniform and high-quality polishing result of the sample. Still another advantage of the wetting method according to the present invention is that it enables consuming less polishing suspension during the polishing process.

[0044] The exemplary embodiments of the invention presented in the text are not to be construed as imposing limitations on the applicability of the appended claims. The verb "comprising" is used in the text as an open limitation that does not exclude the presence of features not recited. The features described in the dependent claims can be freely combined with each other unless otherwise explicitly stated.

[0045] The exemplary embodiments and their advantages presented in the text are relevant to the wetting device, the wetting method, and the components applicable to the polishing device according to the present invention, but this is not necessarily separately mentioned.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0047] FIG. 1 shows a schematic cross-sectional view of a wetting device according to an embodiment of the present invention. The wetting device 100 can be used to wet a polishing pad (not shown in FIG. 1).

[0048] The wetting device 100 includes a cylindrical housing 101 sized to fit into the sample cavity of a sample holder (not shown in FIG. 1). The housing 101 has a contact surface 102 which is meant to be placed in contact with the surface of the polishing pad.

[0049] The wetting device 100 includes electrical contact elements 103, 104, and 105 disposed on the contact surface 102. The electrical contact elements 103, 104, and 105 are electrically connected to a measuring instrument 109 using wires 106, 107, and 108. The measuring instrument 109 can measure the resistance between the electrical contact elements 103 and 104, and the capacitance between the electrical contact element 105 on which the polishing pad is placed and a polishing plate (not shown in FIG. 1). The resistance between the electrical contact elements 103 and 104, and the capacitance between the electrical contact element 105 and the polishing plate indicate the moisture content of the polishing pad. A wire 110 is used to electrically connect the measuring instrument 109 to the polishing plate. For the measurement of resistance and / or capacitance, the contact surface 102 is placed in contact with the surface of the polishing pad.

[0050] The wetting device 100 includes a container 111 for holding a polishing suspension, and a hose 112 having its first end connected to the container 111. The second end of the hose 112 is connected to a nozzle 113 disposed on the contact surface 102. A valve 114 for controlling the flow of the polishing suspension from the container 111 to the surface of the polishing pad is provided in the hose 112. The wetting device 100 includes a control unit 115 for controlling the operation of the valve 114. The control unit 115 controls the valve 114 to dispense an appropriate amount of the polishing suspension onto the surface of the polishing pad. The amount of the polishing suspension to be dispensed is determined based on the measured resistance or capacitance value. The control unit 115 receives the measured resistance value or capacitance value from the measuring instrument 109.

[0051] The wetting device 100 includes a transceiver 116 for two-way wireless communication with a remote device (not shown in FIG. 1). The transceiver 116 enables remote control of the operation of the wetting device 100. The wetting device 100 includes a measuring instrument 109, a control unit 115, and a battery 117 for supplying power to the measuring instrument 109, the control unit 115, and the transceiver 116.

[0052] FIG. 2 shows a schematic side view of a polishing device according to an embodiment of the present invention. The polishing device 200 can be used to polish a sample.

[0053] The polishing device 200 includes a polishing plate 201 that can rotate about an axis with an actuator 202. A polishing pad 203 is attached to the polishing plate 201. The polishing pad 203 is used to polish a sample 204 held against the polishing pad 203 by a sample holder 205. The sample 204 is placed in a sample cavity 206 of the sample holder 205. The sample holder 205 can be rotated about an axis parallel to the rotation axis of the polishing plate 201 using an actuator 207. When the polishing plate 201 and the sample holder 205 rotate, the polishing pad 203 polishes the sample 204.

[0054] The polishing device 200 includes the wetting device 100 according to FIG. 1. The wetting device 100 is placed in a sample cavity 208 of the sample holder 205 in such a manner that the contact surface 102 of the wetting device 100 contacts the surface of the polishing pad 203. The wetting device 100 measures the resistance or capacitance indicating the moisture of the polishing pad 203 and distributes a polishing suspension onto the surface of the polishing pad 203 based on the measured resistance or capacitance value. A wire 209 is used to electrically connect the polishing plate 201 to the wetting device 100 for capacitance measurement.

[0055] Only advantageous exemplary embodiments of the present invention are illustrated in the figures. As will be apparent to those skilled in the art, the present invention is not limited only to the embodiments presented above, and the present invention may vary within the limits of the claims presented hereinafter. Some possible embodiments of the present invention are described in the dependent claims, and they do not limit the scope of protection of such an invention.

Claims

1. An apparatus for wetting a polishing pad, the apparatus comprising: measuring means for measuring a physical quantity indicating the moisture content of the polishing pad; distribution means for distributing a polishing suspension onto the surface of the polishing pad based on the value of the measured physical quantity. The apparatus further comprises: a housing for housing the measuring means and the distribution means, the housing having a contact surface that contacts the surface of the polishing pad.

2. The apparatus according to claim 1, wherein the housing is essentially cylindrical.

3. The apparatus according to claim 1 or 2, wherein the physical quantity is the resistance of the polishing pad.

4. The apparatus according to claim 3, wherein the measuring means comprises two electrical contact elements disposed on the contact surface and a measuring instrument configured to measure the resistance between the two electrical contact elements.

5. The apparatus according to claim 3 or 4, wherein the distribution means is configured to distribute the polishing suspension onto the surface of the polishing pad when the value of the resistance is greater than a first threshold value.

6. The apparatus according to claim 1 or 2, wherein the physical quantity is the capacitance between both sides of the polishing pad.

7. The apparatus according to claim 6, wherein the measuring means includes an electrical contact element disposed on the contact surface and a measuring instrument configured to measure the capacitance between the electrical contact element and a polishing plate on which the polishing pad is disposed.

8. The apparatus according to claim 6 or 7, wherein the distribution means is configured to distribute the polishing suspension onto the surface of the polishing pad when the value of the capacitance is less than a second threshold value.

9. The apparatus according to any one of claims 1 to 8, wherein the distribution means comprises a container for holding the polishing suspension and a hose having a first end connected to the container and a second end connected to and disposed on the contact surface.

10. The apparatus according to claim 9, wherein the distribution means comprises a nozzle connected to the second end of the hose.

11. The apparatus according to claim 10, characterized in that the dispensing means comprises a valve or a micropump arranged in relation to the container, the hose or the nozzle, and a control unit configured to control the operation of the valve or the micropump.

12. The apparatus according to any one of claims 1 to 11, characterized in that the apparatus comprises a power source for supplying power to the measuring means and the dispensing means.

13. A polishing apparatus for polishing a sample, the polishing apparatus comprising: a polishing plate rotatable about an axis; a polishing pad attached to the polishing plate; a sample holder including a plurality of sample cavities for holding one or more samples against the surface of the polishing pad, wherein the polishing apparatus comprises the apparatus according to any one of claims 1 to 12, wherein one of the sample cavities is inserted such that the contact surface contacts the surface of the polishing pad.

14. The polishing apparatus according to claim 13, characterized in that the sample holder includes pressing means for pressing the contact surface against the surface of the polishing pad.

15. A method for wetting a polishing pad, comprising: placing the apparatus according to any one of claims 1 to 12 in a sample cavity of a sample holder; placing the contact surface of the apparatus in contact with the surface of a polishing pad attached to a polishing plate; rotating the polishing plate about an axis; measuring, with the apparatus, a physical quantity indicating the moisture content of the polishing pad; and dispensing, with the apparatus, a polishing suspension onto the surface of the polishing pad based on the measured value of the physical quantity.

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