Method for assessing workpiece nanotopology using a double side wafer grinder
View Patent ↗A method of processing a semiconductor wafer using a double side grinder of the type that holds the wafer in a plane with a pair of grinding wheels and a pair of hydrostatic pads. The method includes measuring a distance between the wafer and at least one sensor and determining wafer nanotopology using the measured distance. The determining includes using a processor to perform a finite element structural analysis of the wafer based on the measured distance.
1. A method of processing a semiconductor wafer using a double side grinder, the grinder comprising a pair of grinding wheels, a processor, and a pair of hydrostatic pads, the grinding wheels and hydrostatic pads being operable to hold a generally flat workpiece in a plane with a first part of the workpiece positioned between the grinding wheels and a second part of the workpiece positioned between the hydrostatic pads, the grinder comprising a plurality of sensors operable to measure a distance between the workpiece and the respective sensor, at least some of the sensors being spaced apart in at least one of an x direction and a y direction in an x, y, z orthogonal coordinate system defined so the workpiece is held in the x, y plane, the method comprising measuring a distance between the wafer and at least one of the sensors and determining wafer nanotopology using the measured distance, wherein the determining comprises using the processor to perform a finite element structural analysis of the wafer based on the measured distance.
2. A method as set forth in claim 1 , wherein the determining is performed while the wafer is in the grinder.
3. A method as set forth in claim 1 , wherein the plane in which the wafer is held is a substantially vertical plane.
4. A method as set forth in claim 1 , wherein the measuring comprises measuring a plurality of distances between the wafer and a plurality of sensors, and wherein the determining comprises using said plurality of distances to determine the nanotopology of the wafer.
5. A method as set forth in claim 4 , wherein the determined nanotopology of the wafer is indicative of the wafer after a downstream processing step.
6. A method as set forth in claim 5 , wherein the downstream processing step is polishing.
7. A method as set forth in claim 1 , further comprising adjusting alignment of the double side grinder in response to the determining.
8. A method as set forth in claim 7 , wherein the determining comprises using the processor to assess nanotopology of the wafer and adjust alignment of the double side grinder.
9. A method as set forth in claim 1 , further comprising adjusting an amount of hydrostatic pressure applied to at least a portion of the workpiece by the hydrostatic pads in response to the determining.
10. A method as set forth in claim 9 , further comprising using the processor to determine the nanotopology of the wafer and adjust the amount of hydrostatic pressure applied to said portion of the workpiece.
11. A method as set forth in claim 1 , wherein the measuring is performed while the wafer is being ground in the double side grinder.