MOISTURE SENSOR, POLISHING DEVICE AND METHOD FOR MEASURING THE MOISTURE IN A POLISHING PAD

Abstract

A moisture sensor (100) that comprises a contact surface (105) for contacting a polishing pad (503), and a first, a second and a third electrical contact element (101, 102, 103) electrically isolated from each other, the electrical contact elements (101, 102, 103) being disposed within the moisture sensor (100) so that they are exposed at the contact surface (105). Also a polishing device and a method for measuring the moisture in a polishing pad (503) is disclosed using the moisture sensor (100).

Claims

1. A moisture sensor, comprising: a contact surface for contacting a polishing pad, wherein the moisture sensor further comprises: a first, a second and a third electrical contact element electrically isolated from each other, the electrical contact elements being disposed within the moisture sensor so that they are exposed at the contact surface.

2. The moisture sensor according to claim 1, wherein the first electrical contact element is a cylinder, and the second electrical contact element and the third electrical contact element are hollow cylinders arranged concentrically around the first electrical contact element.

3. The moisture sensor according to claim 2, wherein the first electrical contact element has a diameter of less than 50 mm, and wall thickness of the second electrical contact element and the third electrical contact element is less than 10 mm.

4. The moisture sensor according to claim 2 wherein a gap between the wall of the first electrical contact element and an inner wall of the second electrical contact element is less than 10 mm, and a gap between an outer wall of the second electrical contact element and an inner wall of the third electrical contact element is less than 10 mm.

5. The moisture sensor according to claim 1, wherein the first electrical contact element is a planar plate having an opening into which the second electrical contact element and the third electrical contact element are arranged.

6. The moisture sensor according to claim 1, wherein the first electrical contact element, the second electrical contact element and the third electrical contact element are metal sheets wound on each other to form a roll, wherein each of the metal sheets is arranged between electrically insulating sheets.

7. The moisture sensor according to claim 6, wherein thickness of the metal sheets is less than 1 mm, and thickness of the electrically insulating sheets is less than 1 mm.

8. The moisture sensor according to claim 6, wherein the moisture sensor comprises a fourth electrical contact element that is a hollow cylinder arranged concentrically around the roll, and a fifth electrical contact element that 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 isolated from one another.

9. The moisture sensor according to claim 1, wherein the contact surface is planar.

10. A polishing device, comprising: a polishing platen rotatable about an axis, and a polishing pad attached to the polishing platen for polishing a specimen, wherein the polishing device further comprises: a moisture sensor according to claim 1, the contact surface of the moisture sensor being arranged in contact with the surface of the polishing pad, and means for measuring capacitance between the first electrical contact element and the polishing platen and resistance between the second electrical contact element and the third electrical contact element.

11. The polishing device according to claim 10, wherein the polishing device comprises means for moving the moisture sensor between a plurality of positions on the polishing pad.

12. The polishing device according to claim 10, wherein the polishing device comprises means for dispensing a polishing suspension, based on a value of measured capacitance or resistance, on the polishing pad.

13. The polishing device according to claim 10, wherein the polishing device comprises a compression element for pressing the moisture sensor against the surface of the polishing pad.

14. A method for measuring moisture in a polishing pad that is attached to a polishing platen, wherein the method comprises: providing a moisture sensor according to claim 1, arranging the contact surface of the moisture sensor in contact with the surface of the polishing pad, and measuring capacitance between the first electrical contact element and the polishing platen and/or the resistance between the second electrical contact element and the third electrical contact element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 illustrates a moisture sensor according to a first embodiment of the invention,

[0044] FIG. 2 illustrates a moisture sensor according to a second embodiment of the invention,

[0045] FIG. 3 illustrates a moisture sensor according to a third embodiment of the invention,

[0046] FIG. 4 illustrates a moisture sensor according to a fourth embodiment of the invention, and

[0047] FIG. 5 illustrates a polishing device according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0048] The same reference signs are used of the same or like components in different embodiments.

[0049] FIG. 1 illustrates a moisture sensor according to a first embodiment of the invention for measuring the moisture in a polishing pad (not shown in FIG. 1). The moisture sensor 100 comprises electrical contact elements 101, 102 and 103, which are arranged inside a cylindrical housing 104 in such a manner that they are exposed at the contact surface 105 of the moisture sensor 100. The electrical contact elements 101, 102 and 103 are electrically isolated from each other and they provide an electrical path through which electrical properties of the polishing pad can be measured. For the measurement, the contact surface 105 and the electrical contact elements 101, 102 and 103 therein are arranged in contact with the surface of the polishing pad. The measurement is based on measuring a physical quantity that varies as a function of the moisture in the polishing pad.

[0050] The moisture sensor 100 comprises a multiwire cable 106 for electrically connecting the electrical contact elements 101, 102 and 103 to a measuring instrument (not shown in FIG. 1). The measuring instrument can be configured to measure the capacitance between the electrical contact element 101 and a polishing platen (not shown in FIG. 1) to which the polishing pad is attached, and/or the resistance between the electrical contact elements 102 and 103 when they are in contact with the surface of the polishing pad.

[0051] In FIG. 1, the electrical contact element 101 is a cylinder, and the electrical contact elements 102 and 103 are hollow cylinders. The electrical contact elements 102 and 103 are arranged concentrically around the electrical contact element 101. The electrical contact elements 101, 102 and 103 are arranged inside the moisture sensor 100 in such a manner that their axes are perpendicular to the plane of the contact surface 105.

[0052] FIG. 2 illustrates a moisture sensor according to a second embodiment of the invention for measuring the moisture in a polishing pad (not shown in FIG. 2). The moisture sensor of FIG. 2 differs from the moisture sensor 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, which has a circular opening into which the electrical contact elements 102 and 103 are arranged. The electrical contact element 101 is arranged inside the moisture sensor 100 in such a manner 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 with the plane of the contact surface 105. The electrical contact elements 102 and 103 are cylinders.

[0053] FIG. 3 illustrates a moisture sensor according to a third embodiment of the invention for measuring the moisture in 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 on each other to form a roll, wherein each of the metal sheets is arranged between electrically insulating sheets (not shown in FIG. 3). The roll is arranged within the moisture sensor 100 in such a manner 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.

[0054] FIG. 4 illustrates a moisture sensor according to a fourth embodiment of the invention for measuring the moisture in a polishing pad (not shown in FIG. 4). The moisture sensor of FIG. 4 differs from the moisture sensor of FIG. 3 in that moisture sensor 100 further comprises two additional electrical contact elements 401 and 402. The electrical contact element 401 is a hollow cylinder that is arranged concentrically around the roll. The electrical contact element 402 is a hollow cylinder that is arranged concentrically around the electrical contact element 401. The electrical contact elements 401 and 402 are electrically isolated from one another. 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 within the moisture sensor 100 in such a manner that their axes are perpendicular to the plane of the contact surface 105.

[0055] FIG. 5 illustrates a polishing device according to an embodiment of the invention. The polishing device 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 for polishing a specimen 504 that is held against the polishing pad 503 with a specimen holder 505. The specimen holder 505 can be rotated about an axis, which is parallel to the rotation axis of the polishing platen 501, with an actuator 506. As the polishing platen 501 and the specimen holder 505 are rotated, the polishing pad 503 polishes the specimen 504.

[0056] The polishing device comprises a moisture sensor according to FIG. 1 for detecting the moisture in 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 instrument 507 through a multiwire cable 106. The measuring instrument 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 the 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 are indicative of the moisture in a measurement position on the polishing pad 503.

[0057] The moisture sensor 100 is attached with a rod 508 to an arm 509 that is located above the polishing pad 503. The arm 509 extends from the centre to the periphery of the polishing pad 503. The moisture sensor 100 can be moved with an actuator 510 along the arm 509, thus enabling to move 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 enables to keep the electrical contact elements 101, 102 and 103 in contact with the surface of the polishing pad 503 with a suitable pressing force.

[0058] The polishing device comprises a spray nozzle 512 for dispensing a polishing suspension on the polishing pad 503. The spray nozzle 512 is attached to an arm 513 that is located above the polishing pad 503. The arm 513 extends from the centre to the periphery of the polishing pad 503. The spray nozzle 512 can be moved with an actuator 514 along the arm 513, thus enabling to move the spray nozzle 512 between different positions above the polishing pad 503.

[0059] The polishing suspension is stored in a container 515 from which it is conveyed through a flexible hose 516 to the spray nozzle 512 to be dispensed on the polishing pad 503. The polishing device comprises a control unit 517 for controlling the dispensing of the polishing suspension. The control unit 517 controls the spray nozzle 512 to dispense suitable amounts of the polishing suspension to desired positions on the polishing pad 503. 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.

[0060] 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.