Moisture sensor, polishing apparatus, and method for measuring moisture in a polishing pad

Abstract

The present invention relates to a moisture sensor (100) comprising a contact surface (105) that contacts a polishing pad (503), and first, second, and third electrical contact elements (101, 102, 103) that are electrically insulated from one another, the electrical contact elements (101, 102, 103) being disposed on the moisture sensor (100) such that they are exposed at the contact surface (105). The present invention also relates to a polishing apparatus and a method for measuring moisture in a polishing pad (503).

Description

[Technical field]

[0001] The present invention relates to a moisture sensor and a method for measuring the moisture of a polishing pad according to the preamble of the independent claims. The invention also relates to a polishing apparatus incorporating a moisture sensor. [Background technology]

[0002] Abrasive suspensions are typically used in polishing samples to enhance the polishing results and prevent overheating of the polishing pad. The amount of abrasive suspension in the polishing pad, i.e. the water content of the polishing pad, has a significant effect on the polishing process. If the polishing pad is too wet, the friction between the sample and the polishing pad can be very small, so that the sample is hardly polished. On the other hand, if the polishing pad is too dry, there is a risk of significant degradation of the sample due to the increased friction between the sample and the polishing pad.

[0003] In view of the above, there is a need to measure the moisture of a polishing pad. Although various moisture sensors are known, none are suitable for easily and accurately measuring the moisture of a polishing pad. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE PRESENT EMBODIMENT It is a primary object of the present invention to mitigate or eliminate the above-mentioned problems of the prior art.

[0005] An object of the present invention is to provide a moisture sensor. More specifically, an object of the present invention is to provide a moisture sensor that allows for easy and accurate measurement of the moisture of a polishing pad. Another object of the present invention is to provide a polishing apparatus that can measure the moisture of a polishing pad during a polishing process. A further object of the present invention is to provide a method for easily and accurately measuring the moisture of a polishing pad. [Means for solving the problem]

[0006] In order to achieve the above mentioned objects, the moisture sensor and method according to the invention are characterized by what is stated in the characterizing parts of the independent claims. Advantageous embodiments of the invention are defined in the dependent claims.

[0007] A moisture sensor according to the present invention comprises a contact surface for contacting a polishing pad, a first electrical contact element, a second electrical contact element, and a third electrical contact element that are electrically insulated from each other, the electrical contact elements being arranged on the moisture sensor such that they are exposed at the contact surface.

[0008] The moisture sensor according to the invention can be used to measure the moisture of a polishing pad used to polish a sample. For the measurement, the contact surface and the electrical contact elements therein are placed in contact with the surface of the polishing pad. The measurement is based on measuring a physical quantity that changes as a function of the moisture of the polishing pad. Such a physical quantity is, for example, the capacitance between a first electrical contact element to which the polishing pad is attached and the polishing platen, i.e. the capacitance between the opposing sides of the polishing pad. Another such physical quantity is the (electrical) resistance between a second electrical contact element and a third electrical contact element when in contact with the surface of the polishing pad.

[0009] The contact surface is preferably planar so that the electrical contact element can be easily placed in contact with the surface of the polishing pad. Preferably, the contact surface is also circular, which allows the moisture sensor to slide smoothly over the surface of the polishing pad. The diameter of the planar and circular contact surface may be, for example, 10-50 mm or 15-25 mm. The dimensioning of the moisture sensor may depend, for example, on the diameter of the polishing pad, the material of the polishing pad, the structure of the polishing pad, the composition of the polishing suspension used, the characteristics of the polished sample, the required measurement accuracy and / or the required measurement range. If the surface of the polishing pad is rough or uneven, it is beneficial to have a slightly convex contact surface.

[0010] The electrical contact elements, i.e. electrodes, provide an electrical path along which electrical properties of the polishing pad can be measured. The electrical contact elements can have different shapes and sizes. The electrical contact elements are made of a conductive material, which is preferably also wear-resistant and corrosion-resistant. Preferred materials for the electrical contact elements are, for example, steel and gold-platinum alloy. The electrical contact elements are electrically insulated from each other to prevent short circuits.

[0011] The moisture sensor may comprise a housing, within which the electrical contact elements are disposed. The housing may be made of wear and corrosion resistant ceramic or metal, or other suitable material. The housing may be filled with an electrically insulating material, such as epoxy resin, or the electrical insulation may be made of a wear resistant ceramic, such as cubic boron nitride (CBN) or boron carbide (B4C), which electrically insulates the electrical contact elements from each other. The housing may be a hollow cylinder, the ends of which serve as contact surfaces. The diameter of the hollow cylinder may be, for example, 10-50 mm or 15-25 mm, and the height of the hollow cylinder may be, for example, 10-20 mm, 5-10 mm, or 1-5 mm.

[0012] The moisture sensor can be electrically contacted by a measuring device having electrical contacts such as wires, cables or carbon brushes. The measuring device can be configured to measure the capacitance between a first electrical contact element on which the polishing pad is attached and the polishing platen, and / or the resistance between a second electrical contact element and a third electrical contact element when in contact with the surface of the polishing pad. The values ​​of capacitance and resistance depend on the moisture of the polishing pad. When the polishing pad is wet, the capacitance increases and the resistance decreases.

[0013] An advantage of the moisture sensor according to the present invention is that it can easily and accurately measure the moisture content of a polishing pad.

[0014] According to one embodiment of the present invention, the first electrical contact element is a cylinder and the second and third electrical contact elements are hollow cylinders arranged concentrically around the first electrical contact element. The third electrical contact element is arranged around the second electrical contact element. The electrical contact elements are arranged in the moisture sensor such that their axes are perpendicular to the plane of the contact surface. The first electrical contact element can be made by cutting a section from a round rod. The second and third electrical contact elements can be made by cutting sections from pipes having different diameters. The moisture sensor according to this embodiment can be made such that the electrical contact elements are embedded in an electrically insulating material such as an epoxy resin. The cured material electrically insulates the electrical contact elements from each other and also serves as a support structure for the electrical contact elements. The moisture sensor can comprise a housing such as a hollow cylinder, inside which the electrical contact elements are arranged. The advantage of the moisture sensor according to this embodiment is that it is cheap and easy to manufacture.

[0015] According to one embodiment of the present invention, the diameter of the first electrical contact element is less than 50 mm, and the wall thickness of the second and third electrical contact elements is less than 10 mm. The diameter of the first electrical contact element is preferably less than 35 mm, more preferably less than 20 mm. The wall thickness of the second and third electrical contact elements is preferably less than 5 mm, more preferably less than 2 mm. The advantage of using these measures is that the moisture sensor provides good measurement sensitivity and accuracy. The height of the electrical contact elements can be, for example, 5 to 20 mm. Since the moisture sensor wears out during use, increasing the height of the sensor provides a longer working life.

[0016] According to one embodiment of the invention, the gap between the wall of the first electrical contact element and the inner wall of the second electrical contact element is less than 10 mm, and the gap between the outer wall of the second electrical contact element and the inner wall of the third electrical contact element is less than 10 mm. The gap between the wall of the first electrical contact element and the inner wall of the second electrical contact element is preferably less than 5 mm, more preferably less than 2 mm. The gap between the outer wall of the second electrical contact element and the inner wall of the third electrical contact element is preferably less than 5 mm, more preferably less than 2 mm. The advantage of using these measures is that the moisture sensor provides good measurement sensitivity.

[0017] According to one embodiment of the invention, the first electrical contact element is a flat plate having an opening in which the second and third electrical contact elements are arranged. The flat plate is arranged in the moisture sensor such that one side of the flat plate is exposed at the contact surface and the plane of the flat plate is parallel to the plane of the contact surface. The flat plate may be circular and have a diameter of 15-50 mm. The opening in the flat plate may be circular and have a diameter of 5-20 mm. The thickness of the flat plate may be 5-20 mm. In this embodiment, the second and third electrical contact elements may have different shapes and sizes, provided that they fit within the opening without touching the flat plate. The second and third electrical contact elements may be, for example, cylindrical. The moisture sensor according to this embodiment may be made such that the electrical contact elements are embedded in an electrically insulating material such as epoxy resin. The hardened material electrically insulates the electrical contact elements from each other and also serves as a support structure for the electrical contact elements. The moisture sensor may comprise a housing such as a hollow cylinder, inside which the electrical contact elements are arranged. The moisture sensor according to this embodiment has the advantages that it is mechanically strong, inexpensive and easy to manufacture.

[0018] According to one embodiment of the present invention, the first electrical contact element is characterized in that the second electrical contact element and the third electrical contact element are wound together to form a roll of metal sheets, each of the metal sheets being arranged between electrical insulating sheets. Preferably, the roll is impregnated with epoxy resin. The hardened epoxy resin electrically insulates the electrical contact elements from each other and also serves as a support structure for the electrical contact elements. The roll is placed in the moisture sensor such that one end of the roll is exposed at the contact surface. The axis of the roll is perpendicular to the plane of the contact surface. The metal sheets can be made, for example, of aluminum, steel, copper or a platinum-gold alloy. The electrical insulating sheets can be made, for example, of fiberglass, cloth or paper. The advantage of the moisture sensor according to this embodiment is that it is easy and cheap to manufacture.

[0019] According to one embodiment of the present invention, the thickness of the metal sheet is less than 1 mm and the thickness of the electrical insulating sheet is less than 1 mm. Preferably, the thickness of the metal sheet is less than 0.1 mm and the thickness of the electrical insulating sheet is less than 0.1 mm. The advantage of using these scales is that the moisture sensor provides good measurement sensitivity.

[0020] According to one embodiment of the present invention, the moisture sensor comprises a fourth electrical contact element, which is a hollow cylinder arranged concentrically around the roll, and a fifth electrical contact element, which is a hollow cylinder arranged concentrically around the fourth electrical contact element, the fourth and fifth electrical contact elements being electrically insulated from each other. A measuring instrument can be used to measure the resistance between the fourth and fifth electrical contact elements when they are in contact with the surface of the polishing pad. The fourth and fifth electrical contact elements are arranged on the moisture sensor such that their axes are perpendicular to the plane of the contact surface. The fourth and fifth electrical contact elements can be made by cutting sections from pipes with different diameters. The fourth and fifth electrical contact elements can be embedded in an electrically insulating material, such as an epoxy resin. The hardened material electrically insulates the fourth and fifth electrical contact elements from each other and also serves as a support structure. The wall thickness of the fourth and fifth electrical contact elements may be less than 10 mm, preferably less than 5 mm, and more preferably less than 2 mm. The gap between the outer wall of the fourth electrical contact element and the inner wall of the fifth electrical contact element may be less than 10 mm, preferably less than 5 mm, and more preferably less than 2 mm. An advantage of the moisture sensor according to this embodiment is that it can simultaneously measure the resistance and capacitance of the polishing pad with different sets of electrical contact elements of different dimensions. This allows the selection of the most suitable moisture monitoring method for different combinations of samples, polishing pads, and polishing suspensions.

[0021] According to one embodiment of the invention, the contact surface is planar. The advantage of a planar contact surface is that it allows for easy placement of electrical contact elements in contact with the surface of the polishing pad.

[0022] The present invention also relates to a polishing apparatus comprising a polishing platen rotatable about an axis, a polishing pad attached to the polishing platen for polishing a specimen, a moisture sensor according to the present invention, the contact surface of the moisture sensor being arranged to contact a surface of the polishing pad, and means for measuring the capacitance between the first electrical contact element and the polishing platen and the resistance between the second electrical contact element and the third electrical contact element.

[0023] The polishing apparatus according to the invention can be used to polish a sample (i.e., an object) of solid material, such as a piece of natural (e.g., rock, mineral, ore or meteorite) or man-made (e.g., metal, concrete, ceramic, composite or semiconductor) material. The sample to be polished can be held against the surface of the polishing pad with a sample holder. The sample holder can be configured to hold one or more samples against the polishing pad. The sample holder can include, for example, one or more inserts in which the samples are secured 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.

[0024] The polishing pad can be made of different materials such as fibrous cloth (e.g., real silk, polyester or acetate) or synthetic non-fibrous (e.g., neoprene, polyurethane or composite) materials. The polishing pad preferably has a disk shape, i.e. a flat circular shape. The polishing pad is preferably porous, allowing it to absorb the polishing suspension. The diameter of the polishing pad can be, for example, less than 500 mm, preferably between 200 and 400 mm. The thickness of the polishing pad can be, for example, less than 5.0 mm, preferably between 0.5 and 3.5 mm, more preferably between 1.0 and 3.0 mm.

[0025] The polishing pad is attached, preferably removably, to the surface of a rotatable polishing platen. As the polishing platen rotates, the polishing pad polishes a sample placed against its surface. The polishing platen can be made of a thermally conductive and corrosion resistant material, such as aluminum, bronze or stainless steel, or a plastic, polymer or composite material. The polishing platen can be provided with an electrically insulated electrical contact element (e.g., 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 (e.g., a carbon brush) of a measuring instrument can be electrically connected. The polishing platen is preferably disc-shaped and thermally conductive. The diameter of the polishing platen can be, for example, less than 500 mm, preferably 200-400 mm. Preferably, the diameters of the polishing platen and the polishing pad are essentially the same. The thickness of the polishing platen can be, for example, 20-50 mm. The optimal thickness of the polishing platen depends on the diameter and material of the polishing platen.

[0026] The polishing apparatus can include an actuator, such as an electric motor, for rotating the polishing platen. The actuator can be configured to rotate the polishing platen at a rotational speed of, for example, 0 to 600 rpm. To reduce possible interference caused by the actuator, it can be beneficial to add an electrical insulating layer between the polishing platen and the actuator.

[0027] In addition to the polishing platen, the sample holder is also rotatable. The sample holder is rotatable about an axis parallel to the axis of rotation of the polishing platen. The polishing apparatus can include an actuator, such as an electric motor, for rotating the sample holder. The actuator can be configured to rotate the sample holder at a rotational speed of, for example, 0 to 150 rpm.

[0028] In the polishing apparatus according to the invention, the electrical contact element of the moisture sensor is placed in contact with the surface of the polishing pad. The moisture of the polishing pad is determined by measuring the capacitance between the first electrical contact element and the polishing platen or the resistance between the second electrical contact element and the third electrical contact element. The means for measuring the capacitance and resistance can comprise an electrical connection such as a wire, cable or carbon brush and a measuring instrument that is electrically contacted with the electrical contact element of the moisture sensor and the polishing platen. The polishing platen can comprise an electrical contact element on its surface to which the measuring instrument is electrically connected. The measuring instrument can measure the capacitance between the first electrical contact element and the polishing platen (i.e. the capacitance between the opposite sides of the polishing pad) and the resistance between the second electrical contact element and the third electrical contact element. The values ​​of the capacitance and resistance depend on the moisture of the polishing pad. When the polishing pad is wet, the capacitance increases and the resistance decreases.

[0029] An advantage of the polishing apparatus according to the present invention is that the moisture content of the polishing pad can be easily and accurately measured during the polishing process.

[0030] According to an embodiment of the present invention, the polishing apparatus comprises a means for moving the moisture sensor between a plurality of positions on the polishing pad. The means for moving the moisture sensor are configured to move the moisture sensor along the surface of the polishing pad. The means for moving the moisture sensor may comprise an arm arranged above the polishing pad and an actuator for moving the moisture sensor along the arm. The arm is preferably linear and its longitudinal axis is arranged parallel to the plane of the polishing pad. The arm is preferably arranged above the polishing pad so as to extend from the center to the periphery of the polishing pad. This allows the moisture sensor to be moved to all possible positions on the polishing pad when the polishing platen is rotated. The actuator may be an electric motor. The means for moving the moisture sensor may be a sample holder configured to hold the moisture sensor relative to the polishing pad. The sample holder may comprise, for example, an insert in which the moisture sensor is free to move or is fixed by a clamp. The moisture sensor may include a wireless transmitter or transceiver for communicating with a remote device, such as a control unit controlling the measuring device and / or the spray nozzle.

[0031] According to one embodiment of the present invention, the polishing apparatus comprises a means for supplying a polishing suspension onto the polishing pad based on the measured capacitance or resistance value. The polishing suspension enhances the polishing action and prevents overheating during the polishing process. The polishing suspension includes water and / or other suitable liquids such as alcohol (e.g., ethanol, glycol or isopropyl alcohol) for wetting, cooling and lubricating the polishing pad. The polishing suspension may also include abrasive particles such as diamond, aluminum oxide or colloidal silica for polishing the surface of the sample. Typically, the polishing suspension (i.e., slurry or fluid) is a mixture of liquid(s) and abrasive(s). The means for supplying the polishing suspension may be configured to supply the polishing suspension to a location on the polishing pad, for example, when the value of resistance at said location is greater than a first threshold value or when the value of capacitance at said location is less than a second threshold value.

[0032] The means for supplying the polishing suspension may comprise a spray nozzle arranged above the polishing pad and a means for moving the spray nozzle between a plurality of positions on the polishing pad. The means for moving the spray nozzle may comprise an arm arranged above the polishing pad and an actuator for moving the spray nozzle along the arm. The arm is preferably linear and its longitudinal axis is arranged parallel to the plane of the polishing pad. The arm is preferably arranged above the polishing pad so as to extend from the centre to the periphery of the polishing pad. This allows the spray nozzle to be moved to all possible positions on the polishing pad when the polishing platen is rotated. The actuator may be an electric motor. The means for moving the spray nozzle may be a sample holder to which the spray nozzle is attached.

[0033] The means for supplying the abrasive suspension may comprise a container for the abrasive suspension, which may be connected to the spray nozzle by a flexible hose.

[0034] The means for supplying the polishing suspension may comprise a control unit for controlling the spray nozzle and the actuator. The control unit may comprise a processor and a memory including a computer program code, which together with the processor are configured to cause the spray nozzle to supply an appropriate amount of the polishing suspension to a plurality of locations on the polishing pad. The amount of the polishing suspension to be supplied to each location may be determined based on a measured capacitance or resistance value. The measured capacitance or resistance value may be compared to a predefined reference value or profile to determine the amount of the polishing suspension to be supplied. The predefined reference value or profile corresponds to a desired moisture level of the polishing pad. The amount of the polishing suspension dispensed to each location on the polishing pad may be, for example, less than 5 μl / cm2, less than 2 μl / cm2, or 0.5-2 μl / cm2.

[0035] According to one embodiment of the present invention, the polishing apparatus includes a pressing element for pressing the moisture sensor against the surface of the polishing pad. The pressing element allows the sensor to be kept in contact with the surface of the polishing pad with an appropriate pressing force. The pressing force of the pressing element is adjustable. The pressing element can be, for example, a spring. The pressing element can utilize air pressure, gravity, or magnetic or electromagnetic force in generating the appropriate pressing force.

[0036] According to one embodiment of the present invention, the polishing apparatus includes a means for cooling the polishing platen. The polishing platen can be cooled by spraying water on the bottom side of the polishing platen. The polishing apparatus can include a splash guard that prevents the mist of cooling water from escaping onto the polishing pad. The splash guard can be made of, for example, plastic.

[0037] According to one embodiment of the invention, the polishing apparatus comprises means for evaporating the polishing suspension from the polishing pad, which can be evaporated with a stream of compressed air to a desired location on the polishing pad.

[0038] The invention also relates to a method for measuring moisture in a polishing pad attached to a polishing platen, the method comprising the steps of placing a contact surface of a moisture sensor according to the invention in contact with a surface of the polishing pad and measuring the capacitance between a first electrical contact element and the polishing platen and / or the resistance between a second electrical contact element and a third electrical contact element.

[0039] An advantage of the method according to the present invention is that it allows for easy and accurate measurement of the moisture content of a polishing pad.

[0040] The exemplary embodiments of the invention presented in this text are not to be construed as posing limitations on the applicability of the claims. The verb "to comprise" is used in this text as an open limitation that does not exclude the presence of features not also recited. Features recited in the dependent claims are mutually freely combinable unless expressly recited otherwise.

[0041] The exemplary embodiments presented herein and their advantages are related by components applicable to the moisture sensor, the polishing device, and the method according to the invention, although this is not necessarily mentioned separately. [Brief description of the drawings]

[0042] [Figure 1] 1 shows a moisture sensor according to a first embodiment of the present invention. [Diagram 2] 4 shows a moisture sensor according to a second embodiment of the present invention. [Diagram 3] 4 shows a moisture sensor according to a third embodiment of the present invention. [Figure 4] 1 shows a moisture sensor according to a fourth embodiment of the present invention. [Diagram 5] 1 shows a polishing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] In the drawings, the same reference numbers are used for the same or similar components in different embodiments.

[0044] FIG. 1 shows a moisture sensor according to a first embodiment of the invention for measuring the moisture of a polishing pad (not shown in FIG. 1). The moisture sensor 100 comprises electrical contact elements 101, 102 and 103, which are arranged in a cylindrical housing 104 so as to be exposed at a contact surface 105 of the moisture sensor 100. The electrical contact elements 101, 102 and 103 are electrically insulated from each other and provide an electrical path by which an electrical characteristic of the polishing pad can be measured. For the measurement, the contact surface 105 and the electrical contact elements 101, 102 and 103 are placed in contact with the surface of the polishing pad. The measurement is based on measuring a physical quantity that changes as a function of the moisture of the polishing pad.

[0045] The moisture sensor 100 includes a multi-wire cable 106 for electrically connecting the electrical contact elements 101, 102 and 103 to a meter (not shown in FIG. 1). The meter can be configured to measure the capacitance between the electrical contact element 101 with the polishing pad attached and a polishing platen (not shown in FIG. 1) and / or the resistance between the electrical contact elements 102 and 103 when in contact with the surface of the polishing pad.

[0046] 1, electrical contact element 101 is a cylinder and electrical contact elements 102 and 103 are hollow cylinders. Electrical contact elements 102 and 103 are concentrically arranged around electrical contact element 101. Electrical contact elements 101, 102 and 103 are arranged within moisture sensor 100 such that their axes are perpendicular to the plane of contact surface 105.

[0047] FIG. 2 shows a moisture sensor according to a second embodiment of the invention for measuring the moisture of a polishing pad (not shown in FIG. 2). The moisture sensor of FIG. 2 differs from that of FIG. 1 in that the electrical contact elements 101, 102 and 103 are different. In FIG. 2, the electrical contact element 101 is a circular planar plate having a circular opening in which the electrical contact elements 102 and 103 are arranged. The electrical contact element 101 is arranged in the moisture sensor 100 such that one side of the circular planar plate is exposed at the contact surface 105 and the plane of the circular planar plate is parallel to the plane of the contact surface 105. The electrical contact elements 102 and 103 are cylindrical.

[0048] FIG. 3 shows a moisture sensor according to a third embodiment of the invention for measuring the moisture of a polishing pad (not shown in FIG. 3). The moisture sensor of FIG. 3 differs from the moisture sensor of FIG. 1 in that the electrical contact elements 101, 102 and 103 are different. In FIG. 3, the electrical contact elements 101, 102 and 103 are metal sheets wound together to form a roll, where each metal sheet is placed between electrically insulating sheets (not shown in FIG. 3). The roll is placed in the moisture sensor 100 so that one end of the roll is exposed at the contact surface 105. The axis of the roll is perpendicular to the plane of the contact surface 105.

[0049] FIG. 4 shows a moisture sensor according to a fourth embodiment of the invention for measuring the moisture of a polishing pad (not shown in FIG. 4). The moisture sensor of FIG. 4 differs from the moisture sensor of FIG. 3 in that the moisture sensor 100 further comprises two further electrical contact elements 401 and 402. The electrical contact element 401 is a hollow cylinder arranged concentrically around the roll. The electrical contact element 402 is a hollow cylinder arranged concentrically around the electrical contact element 401. The electrical contact elements 401 and 402 are electrically insulated from each other. A measuring instrument (not shown in FIG. 4) can be configured to measure the resistance between the electrical contact elements 401 and 402 when they are in contact with the surface of the polishing pad. The electrical contact elements 401 and 402 are arranged in the moisture sensor 100 such that their axes are perpendicular to the plane of the contact surface 105.

[0050] 5 shows a polishing apparatus according to one embodiment of the present invention. The polishing apparatus comprises a polishing platen 501 that can be rotated about an axis with an actuator 502. A polishing pad 503 is attached to the polishing platen 501. The polishing pad 503 is used to polish a sample 504 that is held against the polishing pad 503 by a sample holder 505. The sample holder 505 can be rotated together with an actuator 506 about an axis parallel to the axis of rotation of the polishing platen 501. As the polishing platen 501 and sample holder 505 are rotated, the polishing pad 503 polishes the sample 504.

[0051] The polishing apparatus comprises a moisture sensor according to Fig. 1 for detecting moisture on the polishing pad 503. The moisture sensor 100 comprises electrical contact elements 101, 102 and 103, which are arranged in contact with the surface of the polishing pad 503. The electrical contact elements 101, 102 and 103 are electrically connected to a measuring device 507 via a multi-wire cable 106. The measuring device 507 can measure the resistance between the electrical contact elements 102 and 103 and the capacitance between the electrical contact element 101 and the polishing platen 501, i.e. between opposite sides of the polishing pad 503. The resistance between the electrical contact elements 102 and 103 and the capacitance between the electrical contact element 101 and the polishing platen 501 indicate moisture at the measurement location on the polishing pad 503.

[0052] The moisture sensor 100 is attached by a rod 508 to an arm 509 located above the polishing pad 503. The arm 509 extends from the center to the periphery of the polishing pad 503. The moisture sensor 100 can be moved along the arm 509 together with an actuator 510, thus moving the moisture sensor 100 between different positions on the polishing pad 503. The rod 508 is provided with a spring 511 for pressing the moisture sensor 100 against the surface of the polishing pad 503. The spring 511 allows the electrical contact elements 101, 102 and 103 to be kept in contact with the surface of the polishing pad 503 with an appropriate pressing force.

[0053] The polishing apparatus includes a spray nozzle 512 for dispensing a polishing suspension onto the polishing pad 503. The spray nozzle 512 is attached to an arm 513 located above the polishing pad 503. The arm 513 extends from a center to a periphery of the polishing pad 503. The spray nozzle 512 is movable along the arm 513 with an actuator 514, thus allowing the spray nozzle 512 to be moved between different positions above the polishing pad 503.

[0054] The polishing suspension is contained in a container 515, from where it is conveyed through a flexible hose 516 to a spray nozzle 512 where it is dispensed onto the polishing pad 503. The polishing apparatus comprises a control unit 517 for controlling the supply of the polishing suspension. The control unit 517 controls the spray nozzle 512 to dispense an appropriate amount of the polishing suspension to a desired location on the polishing pad 503. The amount of the polishing suspension dispensed to each location is determined based on the determined moisture or friction at each location.

[0055] In the figures, only advantageous exemplary embodiments of the invention are depicted. It is clear to a person skilled in the art that the invention is not limited only to the examples presented above, but may vary within the limits of the claims presented hereafter. Some possible embodiments of the invention are described in the dependent claims, which are not to be considered as limiting the scope of protection of such invention.

Claims

1. 1. A moisture sensor including a contact surface for contacting a polishing pad, a first electrical contact element, a second electrical contact element, and a third electrical contact element, the first electrical contact element and the second electrical contact element being electrically insulated from each other, the first electrical contact element and the second electrical contact element being disposed within the moisture sensor so as to be exposed at the contact surface; A moisture sensor, characterized in that the first electrical contact element is a cylinder, and the second electrical contact element and the third electrical contact element are hollow cylinders concentrically arranged around the first electrical contact element.

2. 2. The moisture sensor of claim 1, wherein the first electrical contact element has a diameter of less than 50 mm, and the second and third electrical contact elements have a wall thickness of less than 10 mm.

3. 3. The moisture sensor of claim 1, wherein the gap between the wall of the first electrical contact element and the inner wall of the second electrical contact element is less than 10 mm, and the gap between the outer wall of the second electrical contact element and the inner wall of the third electrical contact element is less than 10 mm.

4. A moisture sensor including a contact surface for contacting a polishing pad, a first electrical contact element, a second electrical contact element, and a third electrical contact element, the first electrical contact element and the second electrical contact element being electrically insulated from each other, the first electrical contact element and the second electrical contact element being disposed within the moisture sensor so as to be exposed at the contact surface; A moisture sensor comprising: the first electrical contact element being a planar plate having an opening in which the second electrical contact element and the third electrical contact element are disposed.

5. A moisture sensor including a contact surface for contacting a polishing pad, comprising: a first electrical contact element, a second electrical contact element, and a third electrical contact element, the first electrical contact element and the second electrical contact element being electrically insulated from each other, the first electrical contact element and the second electrical contact element being disposed within the moisture sensor so as to be exposed at the contact surface; 11. A moisture sensor comprising: said first electrical contact element, said second electrical contact element, and said third electrical contact element each being a plurality of metal sheets wound to form a roll, each of said metal sheets being disposed between electrically insulating sheets.

6. 6. The moisture sensor of claim 5, wherein the metal sheet has a thickness of less than 1 mm and the electrically insulating sheet has a thickness of less than 1 mm.

7. The moisture sensor according to claim 5 or claim 6, characterized in that the moisture sensor comprises a fourth electrical contact element which is a hollow cylinder arranged concentrically around the roll, and a fifth electrical contact element which is a hollow cylinder arranged concentrically around the fourth electrical contact element, the fourth electrical contact element and the fifth electrical contact element being electrically insulated from each other.

8. 8. The moisture sensor according to claim 1, wherein the contact surface is flat.

9. A polishing platen rotatable about an axis; A polishing pad attached to a polishing table for polishing a sample; a moisture sensor including a contact surface in contact with the polishing pad, the moisture sensor comprising a first electrical contact element, a second electrical contact element, and a third electrical contact element, the electrical contact elements being disposed within the moisture sensor so as to be exposed at the contact surface, the contact surface of the moisture sensor being disposed in contact with a surface of the polishing pad; means for measuring a capacitance between the first electrical contact element and the polishing platen and a resistance between the second electrical contact element and the third electrical contact element; A polishing apparatus comprising:

10. a polishing platen rotatable about an axis; A polishing pad attached to a polishing table for polishing a sample; A moisture sensor according to any one of claims 1 to 8, wherein the contact surface of the moisture sensor is disposed in contact with a surface of the polishing pad; means for measuring a capacitance between the first electrical contact element and the polishing platen and a resistance between the second electrical contact element and the third electrical contact element; A polishing apparatus comprising:

11. 11. The polishing apparatus according to claim 9, further comprising a means for moving the moisture sensor between a plurality of positions on the polishing pad.

12. 12. The polishing apparatus according to claim 9, further comprising a means for supplying an abrasive suspension based on a capacitance or resistance value measured on the polishing pad.

13. 13. The polishing apparatus according to claim 9, further comprising a pressing element for pressing the moisture sensor against the surface of the polishing pad.

14. 1. A method for measuring moisture in a polishing pad attached to a polishing platen, comprising: The contact surface of the moisture sensor according to any one of claims 1 to 8 is placed in contact with a surface of the polishing pad; measuring a capacitance between the first electrical contact element and the polishing platen and / or a resistance between the second electrical contact element and the third electrical contact element.

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