DEVICE AND METHOD FOR POLISHING A SPECIMEN

Abstract

The present invention relates to a device for polishing a specimen (104, 204). The device 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 in a plurality of positions on the polishing pad (103, 203), the physical quantity being indicative of the moisture or the friction, and means (116, 119, 120, 121, 213, 215, 216, 217) for dispensing a polishing suspension, based on values of the measured physical quantity, to the plurality of positions on the polishing pad (103, 203). The invention also relates to a method for polishing a specimen (104, 204).

Claims

1. A device for polishing a specimen, comprising: a polishing platen rotatable about an axis, a polishing pad attached to the polishing platen, and a specimen holder for holding the specimen against the polishing pad, wherein the device further comprises: means for measuring a physical quantity in a plurality of positions on the polishing pad, the physical quantity being indicative of moisture or friction, and means for dispensing a polishing suspension, based on values of the measured physical quantity, to a plurality of positions on the polishing pad.

2. The device according to claim 1, wherein the physical quantity is the resistance on the polishing pad, and the means for dispensing a polishing suspension is configured to dispense the polishing suspension to a position on the polishing pad if in said position the value of the resistance is larger than a first threshold value.

3. The device according to claim 1, wherein the physical quantity is capacitance between opposite sides of the polishing pad, and the means for dispensing a polishing suspension is configured to dispense the polishing suspension to a position on the polishing pad if in said position the value of the capacitance is smaller than a second threshold value.

4. The device according to claim 1, wherein the physical quantity is friction on the surface of the polishing pad, and the means for dispensing a polishing suspension is configured to dispense the polishing suspension to a position on the polishing pad if in said position the value of the friction is larger than a third threshold value.

5. The device according to claim 1, wherein the means for measuring a physical quantity comprises a sensor arranged in contact with the surface of the polishing pad, and means for moving the sensor between the plurality of positions on the polishing pad.

6. The device according to claim 5, wherein the means for moving the sensor comprises an arm arranged above the polishing pad and an actuator for moving the sensor along the arm.

7. The device according to claim 1, wherein the means for measuring a physical quantity comprises an array of sensors arranged in contact with the surface of the polishing pad.

8. The device according to claim 5, wherein the sensor comprises at least two electrical contact elements arranged in contact with the surface of the polishing pad, and the means for measuring a physical quantity comprises means for measuring the resistance between two of the at least two electrical contact elements.

9. The device according claim 8, wherein the means for measuring a physical quantity comprises means for measuring capacitance between one of the at least two electrical contact elements and the polishing platen.

10. The device according to claim 5, wherein the means for measuring a physical quantity comprises a compression element for pressing the sensor against the surface of the polishing pad.

11. The device according to claim 5, wherein the means for measuring a physical quantity comprises means for measuring the lateral force acting on the sensor.

12. The device according to claim 1, wherein the means for dispensing a polishing suspension comprises a spray nozzle arranged above the polishing pad and means for moving the spray nozzle between the plurality of positions on the polishing pad.

13. The device according to claim 12, wherein 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.

14. The device according to claim 1, wherein the means for dispensing a polishing suspension comprises an array of spray nozzles arranged above the polishing pad.

15. A method for polishing a specimen, comprising: holding the specimen with a specimen holder against a polishing pad that is attached to a polishing platen; rotating the polishing platen about an axis; measuring a physical quantity indicative of moisture or friction in a plurality of positions on the polishing pad; and dispensing a polishing suspension, based on values of the measured physical quantity, to the plurality of positions on the polishing pad.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 illustrates a polishing device according to a first embodiment of the invention, and

[0050] FIG. 2 illustrates a polishing device according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1 illustrates a polishing device according to a first embodiment of the invention. The polishing device comprises a polishing platen 101 that can be rotated about an axis with 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 for polishing a specimen 104 that is held against the polishing pad 103 with a specimen holder 105. The specimen holder 105 can be rotated about an axis, which is parallel to the rotation axis of the polishing platen 101, with an actuator 106. The actuator 106 can rotate the specimen holder 105 at different rotational speeds. As the polishing platen 101 and the specimen holder 105 are rotated, the polishing pad 103 polishes the specimen 104.

[0052] The polishing device comprises a moisture sensor 107 for detecting the moisture in the polishing pad 103. The moisture sensor 107 comprises electrical contact elements 108 and 109, which are arranged in contact with the surface of the polishing pad 103. The electrical contact elements 108 and 109 provide an electrical path through which electrical properties of the polishing pad 103 can be measured. The electrical contact elements 108 and 109 are electrically connected to a measuring instrument 110 that can measure the resistance between the electrical contact elements 108 and 109. The resistance between the electrical contact elements 108 and 109 is indicative of the moisture in a measurement position on the polishing pad 103. The measuring instrument 110 is electrically connected to the polishing platen 101, thus allowing to measure the capacitance between one of the electrical contact elements 108, 109 and the polishing platen 101, i.e. between the opposite sides of the polishing pad 103. The capacitance between the electrical contact element 108 or 109 and the polishing platen 101 is indicative of the moisture in a measurement position on the polishing pad 103.

[0053] The moisture sensor 107 is attached with a rod 111 to an arm 112 that is located above the polishing pad 103. The arm 112 extends from the centre to the periphery of the polishing pad 103. The moisture sensor 107 can be moved with an actuator 113 along the arm 112, thus enabling to move the moisture sensor 107 between different positions on the polishing pad 103. The rod 111 is provided with a spring 114 for pressing the moisture sensor 107 against the surface of the polishing pad 103. The spring 114 enables to keep the electrical contact elements 108 and 109 in contact with the surface of the polishing pad 103 with a suitable pressing force.

[0054] The polishing device comprises a force sensor 115 for detecting the lateral force acting on the moisture sensor 107. The force sensor 115 is attached to the rod 111 and electrically connected to the measuring instrument 110 that can determine 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 is indicative of the moisture in a measurement position on the polishing pad 103.

[0055] The polishing device comprises a spray nozzle 116 for dispensing a polishing suspension on the polishing pad 103. The spray nozzle 116 is attached to an arm 117 that is located above the polishing pad 103. The arm 117 extends from the centre to the periphery of the polishing pad 103. The spray nozzle 116 can be moved with an actuator 118 along the arm 117, thus enabling to move the spray nozzle 116 between different positions above the polishing pad 103.

[0056] The polishing suspension is stored in a container 119 from which it is conveyed through a flexible hose 120 to the spray nozzle 116 to be dispensed on the polishing pad 103. The polishing device comprises a control unit 121 for controlling the dispensing of the polishing suspension. The control unit 121 controls the spray nozzle 116 to dispense suitable amounts of the polishing suspension to desired positions on the polishing pad 103. The amount of the polishing suspension to be dispensed to each position is determined based on the determined moisture or the friction on each position.

[0057] The polishing device comprises 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 contactlessly measuring the temperature of the polishing pad 103. The polishing device also comprises 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 speeds of the polishing platen 101 and the specimen holder 105 based on the measured temperatures and/or vibration.

[0058] The polishing device comprises a spray nozzle 125 for spraying water onto the bottom side of the polishing platen 101 in order to cool the polishing platen 101. A splash guard 126 is used to prevent the mist of water escaping onto the polishing pad 103.

[0059] FIG. 2 illustrates a polishing device according to a second embodiment of the invention. The polishing device comprises a polishing platen 201 that can be rotated about an axis with an actuator 202. The actuator 202 can rotate the polishing platen 201 at different rotational speeds. A polishing pad 203 is attached to the polishing platen 201. The polishing pad 203 is used for polishing a specimen 204 that is held against the polishing pad 203 with a specimen holder 205. The specimen holder 205 can be rotated about an axis, which is parallel to the rotation axis of the polishing platen 201, with an actuator 206. The actuator 206 can rotate the specimen holder 205 at different rotational speeds. As the polishing platen 201 and the specimen holder 205 are rotated, the polishing pad 203 polishes the specimen 204.

[0060] The polishing device comprises three moisture sensors 207 for detecting the moisture in the polishing pad 203. The moisture sensors 207 are arranged at regular intervals from each other and attached with rods 208 to an arm 209 that is located above the polishing pad 203. The arm 209 extends from the centre to the periphery of the polishing pad 203.

[0061] Each of the moisture sensors 207 comprises electrical contact elements 210 and 211, which are arranged in contact with the surface of the polishing pad 203. The electrical contact elements 210 and 211 provide an electrical path through which electrical properties of the polishing pad 203 can be measured. The electrical contact elements 210 and 211 are electrically connected to a measuring instrument 212 that can measure the resistance between the electrical contact elements 210 and 211. The resistance between the electrical contact elements 210 and 211 is indicative of the moisture in a measurement position on the polishing pad 203. The measuring instrument 212 is electrically connected to the polishing platen 201, thus allowing to measure the capacitance between one of the electrical contact elements 210, 211 and the polishing platen 201, i.e. between the opposite sides of the polishing pad 203. The capacitance between the electrical contact element 210 or 211 and the polishing platen 201 is indicative of the moisture in a measurement position on the polishing pad 203.

[0062] The polishing device comprises three spray nozzles 213 for dispensing a polishing suspension on the polishing pad 203. The spray nozzles 213 are attached at regular intervals to an arm 214 that is located above the polishing pad 203. The arm 214 extends from the centre to the periphery of the polishing pad 203.

[0063] The polishing suspension is stored in a container 215 from which it is conveyed through flexible hoses 216 to the spray nozzles 213 to be dispensed on the polishing pad 203. The polishing device comprises a control unit 217 for controlling the dispensing of the polishing suspension. The control unit 217 controls the spray nozzles 213 to dispense suitable amounts of the polishing suspension to desired positions on the polishing pad 203. The amount of the polishing suspension to be dispensed to each position is determined based on the determined moisture.

[0064] Only advantageous exemplary embodiments of the invention are described in the figures. It is clear to a person skilled in the art that the invention is not restricted only to the examples presented above, but the invention may vary within the limits of the claims presented hereafter. Some possible embodiments of the invention are described in the dependent claims, and they are not to be considered to restrict the scope of protection of the invention as such.