Effect of temperature on etch rate of iridium and platinum in CF4/O2

Iridium and platinum films were etched in the CF4/O2 plasma in an electron cyclotron resonance etch reactor. Wafers were placed on a heated chuck during etching, with the temperature maintained in the range of 70–250 °C before etching. A rf power was applied to the wafer chuck to generate a self-bias potential. At temperature below 100 °C, the iridium etch rate was low value. The iridium etch rate increased with temperature, and reached about 1500 Å/min above 200 °C. Platinum also showed a low etch rate value below 150 °C, increasing to about 1500 Å/min at 250 °C. The increase of etch rate at higher temperature was attributed to the formation of volatile compounds, IrF6 or PtF6.