ANALYSIS OF POLYMER FORMATION DURING SIO2 MICROWAVE PLASMA-ETCHING

The mechanism of CxFy fluorocarbon deposition during SiO2 etching is analyzed using a test sample with an overhang mask. For C4F8, CHF3, and CH2F2, only CxFy deposition was observed at 0 W of substrate-bias rf power, and the deposition profiles were similar. At a higher rf power, reaction phenomena changed to those of SiO2 etching. The standard deviation sigma of the etching-ion incident angle was measured as less than 2 degrees. On the other hand, sigma(depo) measured from the deposition profile was about 20 degrees. This difference may be caused by surface migration. This migration is thought to be a key factor in excess deposition at the bottom of a high-aspect-ratio hole. Etching rates of the deposit increased in the order of C4F8>CHF3>CH2F2. Therefore: SiO2-etching gases, such as C4F8, which form easily removable deposits, reduce RIE lags for contact hole patterning.