Polishing apparatus and polishing method
A polishing apparatus makes it possible to polish and remove an extra conductive film while preventing the occurrence of erosion and without lowering of the throughput. The polishing apparatus includes: a polishing table having a polishing surface; a top ring for holding a workpiece having a surface conductive film, and pressing the conductive film against the polishing surface to polish the conductive film; an optical sensor for monitoring the polishing state of the conductive film by emitting light toward the conductive film of the workpiece held by the top ring, receiving reflected light from the conductive film, and measuring a change in the reflectance of the reflected light; and a control section for controlling a pressure at which the workpiece is pressed on the polishing surface.
1. An apparatus for polishing a workpiece having a surface of a conductive film, said apparatus comprising:
a polishing table having a polishing surface;
a top ring configured to hold the workpiece, and being configured to press the workpiece against the polishing surface to polish the conductive film;
an optical sensor configured to monitor the polishing state of the conductive film by emitting multi-wavelength light toward the conductive film of the workpiece held by the top ring, receiving reflected light from the conductive film and dispersing the reflected light into a spectrum to select a plurality of reflected lights, each reflected light of the plurality of reflected lights having a different specified wavelength from each other reflected light of the plurality of reflected lights, and measuring a change in the reflectance of said each reflected light of the plurality of reflected lights having a different specified wavelength to detect a thickness of the conductive film; and
a control section configured to control a pressure at which the workpiece is pressed on the polishing surface.
2. The apparatus according to claim 1 , wherein the optical sensor sends a signal to the control section when the optical sensor detects that a thickness of the conductive film has reached a predetermined value, and the control section switches polishing conditions from first polishing conditions to second polishing conditions based on the signal sent from the optical sensor.
3. The apparatus according to claim 2 , wherein the pressure, at which the workpiece is pressed on the polishing surface, is smaller in the second polishing conditions than in the first polishing conditions.
4. The apparatus according to claim 2 , wherein the optical sensor measures a change in the reflectance under the second polishing conditions using a wavelength different from that used for measuring a change in the reflectance under the first polishing conditions.
5. The apparatus according to claim 1 , wherein the conductive film is a tungsten film, and the optical sensor is configured to detect a change in the reflectance of each reflected light having a wavelength of 400 nm, 600 nm or 800 nm.
6. The apparatus according to claim 5 , wherein the optical sensor sends a signal to the control section when the optical sensor detects that the thickness of the tungsten film has reached 80 nm.
7. The apparatus according to claim 1 , wherein the conductive film is a copper film, and the optical sensor is configured to detect a change in the reflectance of each reflected light having a wavelength of 400 nm, 600 nm or 800 nm.
8. The apparatus according to claim 7 , wherein the optical sensor sends a signal to the control section when the optical sensor detects that a thickness of the copper film has reached not more than 100 nm.
9. A method for polishing a workpiece, said method comprising:
polishing a surface of a conducting film of the workpiece by pressing the conductive film against a polishing surface at a predetermine pressure;
monitoring the polishing state of the conductive film with an optical sensor by emitting multi-wavelength light toward the conductive film, receiving reflected light from the conductive film and dispersing the reflected light into a spectrum to select a plurality of reflected lights, each reflected light of the plurality of reflected lights having a different specified wavelength from each other reflected light of the plurality of reflected lights, and measuring a change in the reflectance of said each reflected light of the plurality of reflected lights having a different specified wavelength to detect a thickness of the conductive film; and
switching polishing conditions from first polishing conditions to second polishing conditions when the optical sensor detects that a thickness of the conductive film has reached a predetermined value.
10. The method according to claim 9 , wherein the pressure, at which the conductive film of the workpiece is pressed against the polishing surface, is smaller in the second polishing conditions than in the first polishing conditions.
11. The method according to claim 9 , wherein the optical sensor measures a change in the reflectance under the second polishing conditions using a wavelength different from that used for measuring a change in the reflectance under the first polishing conditions.