Back pressure control system for CMP and wafer polishing
View Patent ↗A wafer carrier with a back pressure applicator system adapted to provide high resolution back pressure control. A plurality of millimeter scale distensible elements are disposed between the wafer carrier pressure plate and a process wafer, and selectively distended to provide excess backpressure to select small areas of a wafer known to exhibit resistance to removal vis-á-vis the surrounding wafer surface. Distensible elements may be in the form of expandable pneumatic chambers or electro-mechanical elements such as solenoids, shape memory elements, electrostatic plates, etc.
1. A wafer carrier for use in wafer polishing, said wafer carrier comprising a carrier housing, a pressure plate and a retaining ring surrounding the pressure plate and extending below the pressure plate to form a cylindrical recess sized to receive the wafer, said wafer carrier further comprising:
a plurality of downwardly distensible elements;
wherein the downwardly distensible elements comprise expandable chambers; and
wherein the distensible elements are disposed within a removable disk disposed below the pressure plate and within the bounds of the cylindrical recess.
2. A wafer carrier for use in wafer polishing, said wafer carrier comprising a carrier housing, a pressure plate and a retaining ring surrounding the pressure plate and extending below the pressure plate to form a cylindrical recess sized to receive the wafer, said wafer carrier further comprising:
a plurality of downwardly distensible elements disposed on or below the bottom surface of the pressure plate wherein the downwardly distensible elements comprise expandable chambers;
a manifold within the pressure plate in fluid communication with a pressurized fluid source;
a plurality of fluid pathways communicating from the manifold to the expandable chambers; and
a plurality of valves disposed in the fluid pathways, said valves being operable to maintain pressure in the expandable chambers.
3. The wafer carrier of claim 2 wherein the plurality of valves are pressure regulating valves operable to maintain pressure in the expandable chambers at variable operator selectable levels.
4. The wafer carrier of claim 1 further comprising:
a manifold within the pressure plate in fluid communication with the pressurized fluid source;
a plurality of fluid pathways communicating from the manifold to the expandable chambers;
a first plurality of pressure regulating valves disposed in a first set of the fluid pathways, said first plurality of pressure regulating valves able to maintain a first preset pressure in the expandable chambers;
a second plurality of pressure regulating valves disposed in a second set of the fluid pathways, said second plurality of pressure regulating valves able to maintain a second preset pressure in the expandable chambers.
5. The wafer carrier of claim 1 wherein the removable disk further comprises:
a manifold within the disk in fluid communication with a pressurized fluid source;
a plurality of fluid pathways communicating from the manifold to the expandable chambers; and
a plurality of valves disposed within the disk, in the fluid pathways, said valves being operable to maintain pressure in the expandable chambers.