Temperature control for wafer polishing
AssigneeMonsanto Company
InventorRobert J. Walsh
Life of this patent
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Abstract
A wafer workpiece polishing temperature control method and apparatus are provided wherein wafers are mounted upon a rotatable pressure plate assembly positioned in rotatable contact with a turntable assembly supported polishing pad, the turntable assembly having internal fluid cooling means, the wafer polishing temperature control being achieved through responsive closed loop electromechanical means activated by variation of polishing pressure upon the wafers and the polishing pad.
Claims9
The method of controlling the thermal bow distortion of a hollow internally cooled turntable having a polishing pad mounted on the top surface during polishing of semiconductor wafers held in pressurized rotatable contact with the polishing pad comprising:
- circulating a heat transfer fluid through the turntable to maintain the bottom surface of the turntable at a constant temperature, sensing the temperature of said polishing pad, and
- regulating the pressure of the wafer against the polishing pad in response to said sensed temperature to maintain the polishing pad and top surface of the turntable at a constant temperature,
- whereby the temperature differential between the top and bottom surfaces of the turntable is maintained constant thereby maintaining the thermal bow distortion of the turntable constant.
In a wafer polishing apparatus comprising:
- a rotatable turntable assembly having an internal fluid chamber between an upper surface and a lower surface, a polishing pad supported on said upper surface and means for introducing and withdrawing a fluid to and from said fluid chamber, and a rotatable wafer holding assembly having a thin deformable carrier plate with a first surface for adhering wafers thereon, a rotatable pressure plate, and a resilient ring connecting a second surface of said carrier plate to said pressure plate and defining a chamber therebetween, a vacuum means communicating with said chamber for deforming said carrier plate to the curvature of said turntable upper surface and load bearing means for applying pressure to said pressure plate,
- said wafer holding assembly being positioned above and operatively associated with said turntable assembly for pressing wafers held on said first surface of the carrier plate against said polishing pad, the improvement comprising a closed loop control system having a polishing pad temperature sensing means communicating with electromechanical control means regulating said load bearing means.
Dependencies are inferred from the claim text.