Plasma dielectric etch process including in-situ backside polymer removal for low-dielectric constant material

Abstract

A plasma etch process with in-situ backside polymer removal begins with a workpiece having a porous or non-porous carbon-doped silicon oxide dielectric layer and a photoresist mask on a surface of the workpiece. The workpiece is clamped onto an electrostatic chuck in an etch reactor chamber. The process includes introducing a fluoro-carbon based process gas and applying RF bias power to the 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. The process further includes removing the fluoro-carbon based process gas and introducing a hydrogen-based process gas and applying RF source power to the overhead electrode. The lift pins in the electrostatic chuck are extended to raise the workpiece above the electrostatic chuck and expose a backside of the workpiece to plasma in the reactor chamber, so as to reduce polymer previously deposited on the backside, until the polymer has been removed from the backside.