Patent ID: 7432209

Claim:
A plasma etch process with in-situ backside polymer removal, comprising: providing a workpiece having a carbon-doped silicon oxide dielectric layer; defining a photoresist mask on a surface of the workpiece; clamping said workpiece onto an electrostatic chuck in an etch reactor chamber; introducing a fluoro-carbon based process gas and applying RF bias power to said electrostatic chuck and RF source power to an overhead electrode to etch exposed portions of the dielectric layer while depositing protective fluoro-carbon polymer on the photoresist mask; and removing said fluoro-carbon based process gas, cooling said workpiece to a temperature below 100 degrees C., reducing gas pressure in said chamber to below 500 mT and introducing a hydrogen-based process gas, extending lift pins in said electrostatic chuck to raise the workpiece above the electrostatic chuck to expose a backside of said workpiece to plasma in the reactor chamber and applying RE source power of a VHF frequency in a range of 27-400 MHz to said overhead electrode, so as to reduce polymer previously deposited on said backside, until the polymer has been removed from said backside.