Apparatus and method for polishing a specimen

Abstract

The present invention relates to an apparatus for polishing a specimen (104, 204). The apparatus comprises a polishing platen (101, 201) rotatable about an axis, a polishing pad (103, 203) attached to the polishing platen (101, 201), a specimen holder (105, 205) for holding the specimen (104, 204) against the polishing pad (103, 203), means (107, 110, 207, 212) for measuring a physical quantity indicative of moisture or friction at multiple locations on the polishing pad (103, 203), and means (116, 119, 120, 121, 213, 215, 216, 217) for dispensing a polishing suspension at multiple locations on the polishing pad (103, 203) based on the values ​​of the measured physical quantities. The present invention also relates to a method for polishing a specimen (104, 204).

Description

[Technical field]

[0001] The present invention relates to an apparatus and a method for polishing a specimen according to the preambles of the attached independent claims. [Background technology]

[0002] In the prior art, various polishing devices are known for different applications of polishing samples of petrography, metallography and other solid materials, which allow the polishing of the samples with a minimum of manual labor.

[0003] An exemplary polishing apparatus includes a rotatable polishing platen and a polishing pad attached to a surface of the polishing platen. The polishing apparatus also includes a specimen holder that holds one or more specimens against the polishing pad. As the polishing platen rotates, the polishing pad polishes the specimens.

[0004] To enhance the polishing action and prevent overheating during the polishing process, a polishing suspension is commonly used in the polishing apparatus. The polishing suspension contains water and / or other suitable liquids, such as ethanol or glycol, to wet, cool and lubricate the polishing pad, and abrasive particles, such as diamond, aluminum oxide or colloidal silica, to polish the surface of the sample. The polishing apparatus may include a dispenser that dispenses the polishing suspension onto the polishing pad at a predetermined rate. The dispenser may be configured, for example, to dispense a fixed amount of the polishing suspension onto the polishing pad at regular time intervals.

[0005] A problem associated with known polishing devices is that during polishing, the moisture content of the polishing pad can vary significantly as a function of time and as a function of position on the polishing pad, which has a negative effect on the polishing result. If the polishing pad is too wet, the friction between the sample and the polishing pad is reduced, resulting in ineffective polishing and longer polishing times. On the other hand, if the polishing pad is too dry, there is a risk that the polishing of the sample will fail due to high friction between the sample and the polishing pad. Summary of the Invention [Problem to be solved by the invention]

[0006] It is a primary object of the present invention to mitigate or eliminate the problems of the prior art mentioned above.

[0007] It is an object of the present invention to provide an apparatus and method for polishing a specimen. More particularly, it is an object of the present invention to provide an apparatus and method that allows for supplying and maintaining a substantially constant and uniform amount of moisture to a polishing pad during polishing. It is a further object of the present invention to provide an apparatus and method that allows for polishing a specimen with uniform and high quality polishing results. [Means for solving the problem]

[0008] In order to achieve the above mentioned objects, the device and the method according to the invention are characterized by what is presented in the characterizing parts of the attached independent claims. Advantageous embodiments of the invention are set out in the dependent claims.

[0009] An apparatus for polishing a specimen according to the present invention includes a polishing platen rotatable about an axis, a polishing pad attached to the polishing platen, a specimen holder for holding the specimen against the polishing pad, a means for measuring a physical quantity indicative of moisture or friction at a plurality of positions on the polishing pad, and a means for ejecting a polishing suspension at a plurality of positions on the polishing pad based on the value of the measured physical quantity.

[0010] The device according to the invention, i.e. the polishing device, can be used to polish samples (i.e. objects) of solid material, such as parts of natural (e.g. rocks, minerals, ores or meteorites) or man-made (e.g. metal, concrete, ceramic, composite or semiconductor) materials. In this context, the term polishing means refers to polishing, fine grinding and grinding processes with polishing pads and abrasive suspensions.

[0011] The sample to be polished is held against the surface of the polishing pad by the sample holder. The sample holder can be configured to hold one or more samples against the polishing pad. The number of samples that can be held by the sample holder against the polishing pad can be, for example, 1, 2-5, 6-10, or more than 10. The sample holder can, for example, include one or more inserts in which the samples are free to move or are fixed by clamps. The sample holder can be attached to a polishing head that presses the samples against the polishing pad with an adjustable pressing force. The pressing force can, for example, be adjustable based on the value of a measured physical quantity.

[0012] The polishing pad can be made of different materials, such as textile fabric (e.g. real silk, polyester or acetate) materials or synthetic non-textile (e.g. neoprene, polyurethane or composite) materials. The polishing pad is preferably disc-shaped, i.e. has a flat circular shape. The polishing pad is preferably porous and capable of absorbing 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 3 mm, preferably less than 2 mm, more preferably less than 1 mm.

[0013] The polishing pad is preferably removably attached to the surface of a rotatable polishing platen. As the polishing platen rotates, the polishing pad polishes the sample. 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 include 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 the 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. The diameters of the polishing platen and the polishing pad are preferably 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.

[0014] The polishing apparatus may include an actuator, such as an electric motor, that rotates the polishing platen. For example, the actuator may be configured to rotate the polishing platen at a rotational speed between 0 and 600 rpm. The actuator may be configured to adjust the rotational speed of the polishing platen based on the value of the measured physical quantity. For example, the actuator may be configured to reduce the rotational speed of the polishing platen if friction exceeds a predetermined threshold or moisture falls below a predetermined threshold. To reduce possible interference caused by the actuator, it may be beneficial to add an electrical insulating layer between the polishing platen and the actuator.

[0015] In addition to the polishing platen, the sample holder can also be rotated. The sample holder can be rotated 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, that rotates the sample holder. For example, the actuator can be configured to rotate the sample holder at a rotation speed between 0 and 150 rpm. The actuator can be configured to adjust the rotation speed of the sample holder based on the value of the measured physical quantity. For example, the actuator can be configured to reduce the rotation speed of the sample holder if friction exceeds a predetermined threshold or moisture falls below a predetermined threshold.

[0016] An apparatus according to the present invention is capable of measuring a physical quantity indicative of moisture or friction at multiple locations on the polishing pad and dispensing an abrasive suspension at multiple locations on the polishing pad based on the values ​​of the measured physical quantities.

[0017] The means for measuring the physical quantity may include one or more movable sensors, or multiple fixed (non-moving) sensors arranged at a predetermined distance from each other. The sensor may be a moisture sensor, which may measure, for example, the (electrical) resistance on the polishing pad, or the capacitance between the two sides of the polishing pad (i.e. the capacitance across the thickness of the polishing pad), both of which vary as a function of the moisture of the polishing pad. The sensor may also be a force sensor configured to measure the friction on the surface of the polishing pad. The measurement of friction may be based on the detection of a lateral force acting on an object placed in contact with the surface of the polishing pad.

[0018] The means for dispensing the abrasive suspension may comprise one or more movable spray nozzles, or a plurality of fixed (non-movable) spray nozzles spaced apart from one another. The means for dispensing the abrasive suspension may also comprise a container for the abrasive suspension. Alternatively, the means for dispensing the abrasive suspension may comprise a plurality of containers for the abrasive suspension, or for different abrasive suspensions. The containers may be connected to the spray nozzles by flexible hoses.

[0019] The means for dispensing the polishing suspension may include a control unit for controlling the spray nozzle. The control unit may comprise a processor and a memory including computer program code, the memory and the computer program code being configured by the processor to cause the spray nozzle to dispense an appropriate amount of the polishing suspension at a plurality of locations on the polishing pad. The amount of the polishing suspension dispensed at each location may be determined based on the value of the measured physical quantity. The value of the measured physical quantity may be compared to a predetermined reference value or profile to determine the amount of the polishing suspension dispensed. The predetermined reference value or profile corresponds to a desired amount of moisture in the polishing pad. The amount of the polishing suspension dispensed at each location on the polishing pad may be adjusted to, for example, 5 μl / cm 2 Less than 2μl / cm 2 Less than or 0.5 to 2 μl / cm 2 It can be said that:

[0020] 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 wet, cool, and lubricate the polishing pad. The polishing suspension may also contain abrasive particles such as diamond, aluminum oxide, or colloidal silica to polish the surface of the sample. Generally, the polishing suspension (i.e., slurry or fluid) is a mixture of liquid and abrasive.

[0021] An advantage of the device according to the invention is that it is possible to supply and maintain a substantially constant and uniform amount of moisture on the polishing pad during the polishing process. Another advantage of the device according to the invention is that it is possible to achieve a uniform and high-quality polishing result of the sample. A further advantage of the device according to the invention is that it is possible to optimize (minimize) the consumption of the polishing suspension during the polishing process.

[0022] According to one embodiment of the invention, the physical quantity is a resistance on the polishing pad and the means for dispensing the polishing suspension are configured to dispense the polishing suspension at a location on the polishing pad if the value of the resistance at said location is greater than a first threshold value. The resistance on the polishing pad varies as a function of the moisture in the polishing pad: the more moisture there is in the polishing pad, the lower the resistance.

[0023] According to one embodiment of the invention, the physical quantity is a capacitance between the two sides of the polishing pad, and the means for dispensing the polishing suspension are configured to dispense the polishing suspension at a location on the polishing pad if the capacitance at said location is less than a second threshold value. The capacitance between the two sides of the polishing pad varies as a function of the moisture in the polishing pad: the more moisture there is in the polishing pad, the higher the capacitance.

[0024] According to one embodiment of the invention, the physical quantity is friction on the surface of the polishing pad and the means for dispensing the polishing suspension is configured to dispense the polishing suspension at a location on the polishing pad if the value of friction at said location is greater than a third threshold value. The friction of the surface of the polishing pad varies as a function of the moisture in the polishing pad. The more moisture there is in the polishing pad, the lower the friction.

[0025] According to one embodiment of the present invention, the means for measuring the physical quantity comprises a sensor placed in contact with the surface of the polishing pad and a means for moving the sensor between a plurality of positions on the polishing pad. The means for moving the sensor is configured to move the sensor along the surface of the polishing pad. The sensor can be a moisture sensor that measures the resistance on the polishing pad and / or the vertical capacitance between the two sides of the polishing pad. Alternatively, the sensor can be a force sensor that measures the friction on the surface of the polishing pad.

[0026] According to one embodiment of the invention, the means for moving the sensor comprises an arm arranged above the polishing pad and an actuator for moving the sensor along the arm. The arm is preferably straight and its longitudinal axis is arranged parallel to the surface 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 sensor to move to all possible positions on the polishing pad as the polishing platen rotates. The actuator may be an electric motor.

[0027] According to one embodiment of the invention, the means for moving the sensor is a sample holder configured to hold the sensor against the polishing pad. The sample holder can for example comprise an insert in which the sensor is free to move or is fixed by a clamp. The sensor can comprise a wireless transmitter or transceiver for communicating with a remote device, such as a measuring instrument and / or a control unit controlling the spray nozzle.

[0028] According to one embodiment of the invention, the means for measuring the physical quantity comprises an array of sensors arranged in contact with the surface of the polishing pad. The sensors can be attached to an arm arranged above the polishing pad. The sensors are preferably attached to the arm at a predefined distance from each other. The arm is preferably straight and its longitudinal axis is arranged parallel to the surface 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. The number of sensors depends on the diameter of the polishing pad and the required measurement accuracy and can be, for example, less than 100, less than 50, less than 20, or between 6 and 12. The sensors can be moisture sensors measuring the resistance on the polishing pad and / or the capacitance between the two sides of the polishing pad. Alternatively, the sensors can be force sensors measuring the friction on the surface of the polishing pad.

[0029] According to one embodiment of the present invention, the sensor comprises at least two electrical contact elements arranged in contact with the surface of the polishing pad, and the means for measuring the physical quantity comprises means for measuring the resistance between two of the at least two electrical contact elements. The electrical contact elements, i.e. electrodes, provide an electrical path along which an electrical characteristic of the polishing pad can be measured. The electrical contact elements can have different shapes and sizes. The electrical contact elements are made of an electrically conductive material that is preferably also wear-resistant and corrosion-resistant. Preferred materials for the electrical contact elements are, for example, stainless steel and tool steel. The electrical contact elements are electrically insulated from each other to prevent short circuits. The means for measuring the resistance between two of the at least two electrical contact elements can comprise a measuring instrument electrically connected to the two electrical contact elements of the sensor by electrical connections such as wires, cables or carbon brushes. The measuring instrument is configured to measure the resistance between these two electrical contact elements.

[0030] According to one embodiment of the present invention, the means for measuring the physical quantity comprises means for measuring a capacitance between one of the at least two electrical contact elements and the polishing platen. The means for measuring a capacitance between one of the at least two electrical contact elements and the polishing platen may comprise a measuring device electrically connected to the electrical contact elements and the polishing platen by an electrical connection such as a wire, a cable or a carbon brush. The measuring device is configured to measure the capacitance between the electrical contact element and the polishing platen. A resistor may be used between the measuring device and the polishing platen to reduce interference.

[0031] According to one embodiment of the present invention, the means for measuring the physical quantity comprises a compression element for pressing the sensor against the surface of the polishing pad. The compression element allows the sensor to keep in contact with the surface of the polishing pad with an appropriate pressing force. The pressing force of the compression element is adjustable. The compression element can be, for example, a spring. The compression element can utilize air pressure, gravity, or magnetic or electromagnetic force to generate the appropriate pressing force.

[0032] According to one embodiment of the invention, the means for measuring the physical quantity comprise means for measuring a lateral force acting on the sensor. The means for measuring the lateral force may comprise a force sensor attached to the sensor.

[0033] According to one embodiment of the present invention, the means for measuring the physical quantity comprises a non-contact moisture sensor disposed above the polishing pad and a means for moving the non-contact moisture sensor between a plurality of positions on the polishing pad. The non-contact moisture sensor can measure moisture in the polishing pad. The non-contact moisture sensor can be, for example, an optical sensor. The means for moving the non-contact moisture sensor can comprise an arm disposed above the polishing pad and an actuator for moving the non-contact moisture sensor along the arm.

[0034] According to one embodiment of the invention, the means for measuring the physical quantity comprises an array of non-contact moisture sensors arranged above the polishing pad. The non-contact moisture sensors are capable of measuring the moisture in the polishing pad. The non-contact moisture sensors can be, for example, optical sensors. The non-contact moisture sensors can be mounted on an arm arranged above the polishing pad. The non-contact moisture sensors are preferably mounted on the arm at a predetermined distance from each other.

[0035] According to one embodiment of the present invention, the non-contact moisture sensor is a spectrometer configured to measure the intensity of light reflected from the surface of the polishing pad as a function of wavelength. The intensity of the reflected light depends on the moisture in the polishing pad. Depending on the polishing suspension and the material of the polishing pad used, the intensity of the reflected light at a certain wavelength may behave significantly differently as the moisture of the polishing pad changes. For example, as the moisture in the polishing pad decreases, the intensity of the reflected light may increase at one wavelength and decrease at another wavelength. The spectrometer may comprise a number of optical detectors, each of which is configured to detect a different wavelength of light. The wavelength range of the spectrometer may be, for example, 400-700 nm, 300-1000 nm, or 750-2500 nm. During the measurement, the distance between the spectrometer and the surface of the polishing pad is preferably kept constant. The surface of the polishing pad may be illuminated with one or more light sources, such as light emitting diodes (LEDs).

[0036] According to one embodiment of the present invention, the non-contact moisture sensor is a polymer film. The resistance of the polymer film depends on the moisture. The moisture in the polishing pad can be measured by placing the polymer film close to the surface of the polishing pad. For the measurement of the resistance, the polymer film can be provided with two electrical contact elements. The polymer film is preferably attached to a substrate, such as a piece of glass.

[0037] According to one embodiment of the invention, the apparatus comprises means for measuring the temperature of the sensor and / or the polishing pad and means for adjusting the rotation speed of the polishing platen and / or the sample holder based on the measured temperature value. The means for measuring the temperature can include contact and / or non-contact temperature sensors.

[0038] According to one embodiment of the invention, the apparatus comprises means for measuring vibration of the sensor and means for adjusting the rotation speed of the polishing platen and / or the sample holder based on the value of the measured vibration. The means for measuring vibration can include a vibration sensor attached to the sensor.

[0039] According to one embodiment of the present invention, the apparatus includes a means for cooling the polishing platen. The polishing platen can be cooled by spraying water on the bottom surface of the polishing platen. The apparatus can include a splash guard to prevent the mist of cooling water from escaping onto the polishing pad. The splash guard can be made of, for example, plastic.

[0040] According to one embodiment of the invention, the means for dispensing the polishing suspension comprises a spray nozzle arranged above the polishing pad and means for moving the spray nozzle between a number of positions on the polishing pad. The means for dispensing the polishing suspension may include one or more containers for the polishing suspension or for different polishing suspensions. The containers are connectable to the spray nozzle by flexible hoses.

[0041] According to one embodiment of the present invention, the means for moving the spray nozzle comprises an arm arranged above the polishing pad and an actuator for moving the spray nozzle along the arm. The arm is preferably straight and its longitudinal axis is arranged parallel to the surface 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 spray nozzle to move to all possible positions on the polishing pad as the polishing platen rotates. The actuator may be an electric motor.

[0042] According to one embodiment of the invention, the means for moving the spray nozzle is a sample holder to which the spray nozzle is attached.

[0043] According to one embodiment of the invention, the means for dispensing the polishing suspension comprises an array of spray nozzles arranged above the polishing pad. The spray nozzles can be attached to an arm. The spray nozzles are preferably attached to the arm at a predefined distance from each other. The arm is preferably straight and its longitudinal axis is arranged parallel to the surface 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. The number of spray nozzles depends on the diameter of the polishing pad and can be, for example, less than 100, less than 50, less than 20 or between 6 and 12. The means for dispensing the polishing suspension can include one or more containers for the polishing suspension or for different polishing suspensions. The containers can be connected to the spray nozzles by flexible hoses.

[0044] According to one embodiment of the invention, the device comprises means for evaporating the polishing suspension from the polishing pad: a compressed air stream can be used to evaporate the polishing suspension onto the desired location on the polishing pad.

[0045] The invention also relates to a method of polishing a specimen, the method including holding the specimen with a specimen holder against a polishing pad attached to a polishing platen, rotating the polishing platen about an axis, measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad, and dispensing a polishing suspension at the plurality of locations on the polishing pad based on the values ​​of the measured physical quantities. Effect of the Invention

[0046] An advantage of the method according to the invention is that a substantially constant and uniform amount of moisture can be provided and maintained in the polishing pad during the polishing process. Another advantage of the method according to the invention is that a uniform and high-quality polishing result of the sample can be achieved. A further advantage of the method according to the invention is that a low consumption of polishing suspension during the polishing process can be achieved.

[0047] The exemplary embodiments of the present invention presented herein should not be interpreted as limiting the applicability of the appended claims. The verb "comprise" is used herein as an open-ended limitation that does not exclude the presence of unrecited features. Features recited in the dependent claims can be freely combined with each other unless expressly stated otherwise.

[0048] The exemplary embodiments presented herein and their advantages relate to the apparatus and methods according to the invention where applicable, even if not necessarily mentioned separately. [Brief description of the drawings]

[0049] [Figure 1] 1 shows a polishing apparatus according to a first embodiment of the present invention. [Diagram 2] 2 shows a polishing apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] FIG. 1 shows a polishing apparatus according to a first embodiment of the present invention. The polishing apparatus comprises a polishing platen 101 which can be rotated about an axis by an actuator 102. The actuator 102 can rotate the polishing platen 101 at different rotational speeds. A polishing pad 103 is attached to the polishing platen 101. The polishing pad 103 is used to polish a sample 104 which is held against the polishing pad 103 by a sample holder 105. The sample holder 105 can be rotated about an axis parallel to the rotational axis of the polishing platen 101 by an actuator 106. The actuator 106 can rotate the sample holder 105 at different rotational speeds. When the polishing platen 101 and the sample holder 105 rotate, the polishing pad 103 polishes the sample 104.

[0051] The polishing apparatus includes a moisture sensor 107 that detects moisture in the polishing pad 103. The moisture sensor 107 includes electrical contact elements 108 and 109 that are disposed in contact with the surface of the polishing pad 103. The electrical contact elements 108 and 109 provide an electrical path by which an electrical characteristic of the polishing pad 103 can be measured. The electrical contact elements 108 and 109 are electrically connected to a measuring device 110 that can measure the resistance between the electrical contact elements 108 and 109. The resistance between the electrical contact elements 108 and 109 indicates moisture at the measurement location on the polishing pad 103. The measuring device 110 is electrically connected to the polishing platen 101 and can therefore measure the capacitance between one of the electrical contact elements 108, 109 and the polishing platen 101, i.e., between both sides of the polishing pad 103. The capacitance between the electrical contact elements 108 or 109 and the polishing platen 101 indicates moisture at the measurement location on the polishing pad 103.

[0052] The moisture sensor 107 is attached by a rod 111 to an arm 112 located above the polishing pad 103. The arm 112 extends from the center to the periphery of the polishing pad 103. An actuator 113 allows the moisture sensor 107 to move along the arm 112, and thus between different positions on the polishing pad 103. The rod 111 is provided with a spring 114 that presses the moisture sensor 107 against the surface of the polishing pad 103. The spring 114 allows the electrical contact elements 108 and 109 to keep in contact with the surface of the polishing pad 103 with an appropriate pressing force.

[0053] The polishing apparatus is equipped with a force sensor 115 that detects a lateral force acting on the moisture sensor 107. The force sensor 115 is attached to a rod 111 and is electrically connected to a measuring device 110 that is capable of determining the lateral force, i.e., the friction on the surface of the polishing pad 103. The friction on the surface of the polishing pad 103 indicates the moisture at the measurement location on the polishing pad 103.

[0054] The polishing apparatus includes a spray nozzle 116 that dispenses an abrasive suspension onto the polishing pad 103. The spray nozzle 116 is attached to an arm 117 that is positioned above the polishing pad 103. The arm 117 extends from the center to the periphery of the polishing pad 103. An actuator 118 enables the spray nozzle 116 to move along the arm 117, and thus the spray nozzle 116 to be moved between different positions above the polishing pad 103.

[0055] The polishing suspension is stored in a container 119, from where it is conveyed through a flexible hose 120 to the spray nozzle 116 and dispensed onto the polishing pad 103. The polishing apparatus includes a control unit 121 for controlling the dispensing of the polishing suspension. The control unit 121 controls the spray nozzle 116 to dispense an appropriate amount of the polishing suspension at a desired location on the polishing pad 103. The amount of polishing suspension dispensed at each location is determined based on the moisture or friction determined at each location.

[0056] The polishing apparatus includes a temperature sensor 122 attached to the electrical contact element 108 for measuring the temperature of the electrical contact element 108, and a temperature sensor 123 attached to the arm 112 for non-contact measurement of the temperature of the polishing pad 103. The polishing apparatus also includes a vibration sensor 124 attached to the rod 111 for measuring the vibration of the moisture sensor 107. The control unit 121 can control the rotational speed of the polishing platen 101 and the specimen holder 105 based on the measured temperature and / or vibration.

[0057] The polishing apparatus is equipped with spray nozzles 125 that spray water onto the bottom side of the polishing platen 101 to cool the polishing platen 101. A splash guard 126 is used to prevent the water mist from leaking onto the polishing pad 103.

[0058] FIG. 2 shows a polishing apparatus according to a second embodiment of the present invention. The polishing apparatus comprises a polishing platen 201 which can be rotated about an axis by an actuator 202. The actuator 202 can rotate the polishing platen 201 at different rotation speeds. A polishing pad 203 is attached to the polishing platen 201. The polishing pad 203 is used to polish a sample 204 which is held against the polishing pad 203 by a sample holder 205. The sample holder 205 can be rotated about an axis parallel to the rotation axis of the polishing platen 201 by an actuator 206. The actuator 206 can rotate the sample holder 205 at different rotation speeds. When the polishing platen 201 and the sample holder 205 rotate, the polishing pad 203 polishes the sample 204.

[0059] The polishing apparatus is equipped with three moisture sensors 207 that detect moisture in the polishing pad 203. The moisture sensors 207 are arranged at regular intervals from one another and are attached by rods 208 to an arm 209 located above the polishing pad 203. The arm 209 extends from the center of the polishing pad 203 to the periphery.

[0060] Each of the moisture sensors 207 includes electrical contact elements 210 and 211 disposed in contact with the surface of the polishing pad 203. The electrical contact elements 210 and 211 provide an electrical path by which an electrical characteristic of the polishing pad 203 can be measured. The electrical contact elements 210 and 211 are electrically connected to a meter 212 that can measure the resistance between the electrical contact elements 210 and 211. The resistance between the electrical contact elements 210 and 211 indicates the moisture at the measurement location on the polishing pad 203. The meter 212 is electrically connected to the polishing platen 201 and can therefore measure the capacitance between one of the electrical contact elements 210, 211 and the polishing platen 201, i.e., between both sides of the polishing pad 203. The capacitance between the electrical contact elements 210 or 211 and the polishing platen 201 indicates the moisture at the measurement location on the polishing pad 203.

[0061] The polishing apparatus is equipped with three spray nozzles 213 that spray abrasive suspension onto the polishing pad 203. The spray nozzles 213 are attached at regular intervals to an arm 214 positioned above the polishing pad 203. The arm 214 extends from the center of the polishing pad 203 to the periphery.

[0062] The polishing suspension is stored in a container 215, from where it is conveyed through a flexible hose 216 to the spray nozzle 213 and dispensed onto the polishing pad 203. The polishing apparatus includes a control unit 217 for controlling the dispensing of the polishing suspension. The control unit 217 controls the spray nozzle 213 to dispense an appropriate amount of the polishing suspension at a desired location on the polishing pad 203. The amount of the polishing suspension dispensed at each location is determined based on the determined moisture content.

[0063] The drawings show only advantageous exemplary embodiments of the invention. It is clear to a person skilled in the art that the invention is not limited to the examples presented above, but that the invention can be modified within the scope of the claims presented below. Some possible embodiments of the invention are described in the dependent claims, which should not be considered as limiting the scope of protection of the invention itself.

Claims

1. An apparatus for polishing a specimen, comprising: a polishing platen rotatable about an axis; a polishing pad attached to the polishing platen; a sample holder for holding the sample against the polishing pad; Equipped with a means for measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad; a means for dispensing an abrasive suspension at the plurality of locations on the polishing pad based on the measured value of the physical quantity; Equipped with An apparatus for polishing a specimen, characterized in that the physical quantity is a resistance on the polishing pad, and the means for discharging the polishing suspension is configured to discharge the polishing suspension to a position on the polishing pad when the value of the resistance at the position is greater than a first threshold value.

2. An apparatus for polishing a specimen, comprising: a polishing platen rotatable about an axis; a polishing pad attached to the polishing platen; a sample holder for holding the sample against the polishing pad; Equipped with a means for measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad; a means for dispensing an abrasive suspension at the plurality of locations on the polishing pad based on the measured value of the physical quantity; Equipped with An apparatus for polishing a specimen, characterized in that the physical quantity is a capacitance between both faces of the polishing pad, and the means for discharging the polishing suspension is configured to discharge the polishing suspension to a position on the polishing pad when the capacitance value at the position is smaller than a second threshold value.

3. An apparatus for polishing a specimen, comprising: a polishing platen rotatable about an axis; a polishing pad attached to the polishing platen; a sample holder for holding the sample against the polishing pad; Equipped with a means for measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad; a means for dispensing an abrasive suspension at the plurality of locations on the polishing pad based on the measured value of the physical quantity; Equipped with 13. An apparatus for polishing a specimen, comprising: a means for measuring a physical quantity comprising a sensor disposed in contact with a surface of the polishing pad; and a means for moving the sensor between a plurality of positions on the polishing pad.

4. 4. The apparatus of claim 3, wherein the means for moving the sensor comprises an arm disposed above the polishing pad and an actuator for moving the sensor along the arm.

5. An apparatus for polishing a specimen, comprising: a polishing platen rotatable about an axis; a polishing pad attached to the polishing platen; a sample holder for holding the sample against the polishing pad; Equipped with a means for measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad; a means for dispensing an abrasive suspension at the plurality of locations on the polishing pad based on the measured value of the physical quantity; Equipped with 11. An apparatus for polishing a specimen, wherein the means for measuring the physical quantity comprises an array of sensors disposed in contact with a surface of the polishing pad.

6. The apparatus according to any one of claims 3 to 5, characterized in that the physical quantity is a resistance on the polishing pad, and the means for discharging the polishing suspension is configured to discharge the polishing suspension to a position on the polishing pad when the value of the resistance at the position is greater than a first threshold value.

7. The apparatus according to any one of claims 3 to 6, characterized in that the physical quantity is a capacitance between both faces of the polishing pad, and the means for discharging the polishing suspension is configured to discharge the polishing suspension to a position on the polishing pad when the value of the capacitance at the position is smaller than a second threshold value.

8. The apparatus according to any one of claims 3 to 7, characterized in that the physical quantity is friction on the surface of the polishing pad, and the means for dispensing the abrasive suspension is configured to dispense the abrasive suspension at a position on the polishing pad if the value of the friction at the position is greater than a third threshold value.

9. The apparatus according to any one of claims 3 to 8, characterized in that the sensor comprises at least two electrical contact elements arranged in contact with the surface of the polishing pad, and the means for measuring the physical quantity comprises means for measuring the resistance between two of the at least two electrical contact elements.

10. 10. The apparatus of claim 9, wherein the means for measuring the physical quantity comprises means for measuring a capacitance between one of the at least two electrical contact elements and the polishing platen.

11. An apparatus according to any one of claims 3 to 10, characterized in that the means for measuring the physical quantity comprise a compression element for pressing the sensor against the surface of the polishing pad.

12. An apparatus according to any one of claims 3 to 11, characterised in that the means for measuring the physical quantity comprise means for measuring a lateral force acting on the sensor.

13. 13. The apparatus according to claim 1, wherein the means for dispensing the abrasive suspension comprises a spray nozzle positioned above the polishing pad, and means for moving the spray nozzle between the positions on the polishing pad.

14. 14. The apparatus of claim 13, wherein the means for moving the spray nozzle comprises an arm positioned above the polishing pad and an actuator for moving the spray nozzle along the arm.

15. Apparatus according to any one of the preceding claims, characterized in that the means for dispensing an abrasive suspension comprise an array of spray nozzles arranged above the polishing pad.

16. 1. A method for polishing a specimen, comprising the steps of: holding the specimen with a specimen holder against a polishing pad attached to a polishing platen; rotating the polishing platen about an axis; Including, measuring a physical quantity indicative of moisture or friction at a plurality of locations on the polishing pad; Dispensing an abrasive suspension at the plurality of locations on the polishing pad based on the measured values ​​of the physical quantities; Including, The method, wherein measuring the physical quantity includes a sensor positioned in contact with a surface of the polishing pad and moving the sensor between a plurality of positions on the polishing pad.

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