Closed loop control of pad profile based on metrology feedback
A chemical mechanical polishing apparatus includes a metrology system that detects the thickness of the polishing pad as semiconductor wafers are processed and the thickness of the polishing pad is reduced. The chemical mechanical polishing apparatus includes a controller that adjusts the rate of material removal of a conditioning disk when areas of the polishing surface are detected that are higher or lower than the adjacent areas of the polishing pad.
1. An apparatus for chemical mechanical polishing comprising:
a rotatable polishing pad having a polishing surface;
a conditioning disk that is movable across the polishing pad and has an abrasive surface that moves against the polishing surface;
an actuator coupled to the conditioning disk;
a metrology sensor that detects thicknesses of the polishing pad;
a controller coupled to the actuator that controls a position of the conditioning disk and a rate of material removal by the conditioning disk; and
a database coupled to the controller for storing a thickness map for the polishing pad created from the thicknesses of each polar coordinate location detected by the metrology sensor;
wherein the controller adjusts the rate of material removal when the conditioning disk is over the polar coordinate location associated with a defective area of the polishing pad.
2. The apparatus of claim 1 wherein the metrology system includes a light source and a light detector.
3. The apparatus of claim 1 wherein if the thickness of an area of the polishing pad is thicker than adjacent areas, the controller increases the rate of material removal of the conditioning disk when the conditioning disk is over the area of the polishing pad.
4. The apparatus of claim 3 wherein the rate of material removal is increased by increasing a compression force of the conditioning disk against the polishing surface.
5. The apparatus of claim 1 wherein if the thickness an area of the polishing pad is thinner than adjacent areas of the polishing pad, the controller decreases the rate of material removal of the conditioning disk when the conditioning disk is over the area of the polishing pad.
6. The apparatus of claim 5 wherein the rate of material removal is decreased by decreasing a compression force of the conditioning disk against the polishing surface.
7. The apparatus of claim 1 wherein the controller transmits an end of life signal when the metrology system detects that the thickness of at least one area of the polishing pad is below a predetermined thickness.
8. A method for chemical mechanical polishing comprising:
rotating a polishing pad having a polishing surface;
moving a conditioning disk across the polishing pad;
measuring thicknesses of areas of the polishing pad with a metrology sensor;
storing a thickness map for the polishing pad created from the thicknesses of each polar coordinate location detected by the metrology sensor;
detecting an area of the polishing pad that is thicker or thinner than adjacent areas;
adjusting a rate of material removal from the polishing pad by the conditioning disk when the conditioning disk is over the polar coordinate location associated with a defective area of the polishing pad that is thicker or thinner than the adjacent areas on the thickness map.
9. The method of claim 8 further comprising:
storing the thicknesses of the areas of the polishing pad detected by the metrology sensor and the areas of the polishing associated with the thicknesses in a memory.
10. The method of claim 8 further comprising:
moving the metrology sensor across a radius of the polishing pad.
11. The method of claim 8 further comprising:
increasing the rate of material removal of the conditioning disk over the area of the polishing pad if the thickness of the area is thicker than the adjacent areas of the polishing pad.
12. The method of claim 11 further comprising:
increasing a rate of rotation of the conditioning disk when the conditioning disk is over the area of the polishing pad that is thicker than the adjacent areas.
13. The method of claim 11 further comprising:
increasing a compression force of the conditioning disk against the polishing disk when the conditioning disk is over the area of the polishing pad that is thicker than the adjacent areas.
14. The method of claim 11 further comprising:
increasing a time of contact between the conditioning disk and the polishing disk when the conditioning disk is over the area of the polishing pad that is thicker than the adjacent areas.
15. The method of claim 8 further comprising:
decreasing the rate of material removal of the conditioning disk over the area of the polishing pad if the thickness of the area is thinner than the adjacent areas of the polishing pad.
16. The method of claim 15 further comprising:
decreasing a rate of rotation of the conditioning disk when the conditioning disk is over the area of the polishing pad that is thinner than the adjacent areas.
17. The method of claim 15 further comprising:
decreasing a compression force of the conditioning disk against the polishing disk when the conditioning disk is over the area of the polishing pad that is thinner than the adjacent areas.
18. The method of claim 15 further comprising:
decreasing a time of contact between the conditioning disk and the polishing disk when the conditioning disk is over the area of the polishing pad that is thinner than the adjacent areas.
19. The method of claim 8 further comprising:
transmitting an end of life signal when the metrology system detects that the thickness of the polishing pad is below a predetermined thickness.
20. The method of claim 8 further comprising:
transmitting an end of life signal when the metrology system detects that the thickness of an area of the polishing pad is thicker or thinner than the adjacent areas by a predetermined thickness.