Patent ID: 7544617
Filing Date: 2009-06-09
Classification: B24B

Abstract:
1. A method for spatial pressure control of an open loop chemical mechanical polishing process for a pattern dependant non-uniform wafer surface in a die scale wherein the die in the wafer surface have a plurality of zones of different heights and different pattern densities, comprising: initializing a mathematical model for the open loop chemical mechanical polishing process using initial variables describing each of the plurality of zones; calculating total material to remove in all zones together according to the mathematical model; calculating polishing time needed for each zone to reach the desired surface with maximum interface pressure according to the mathematical model; comparing the polishing time for all zones and finding maximum polishing time needed to have all applied interface pressure values of all zones to be less than or equal to a maximum interface pressure; and polishing of the wafer surface for the polishing time to thereby provide for reducing both local and global step height variations.