Study of Plasma Arcing Mechanism in High Aspect Ratio Slit Trench Etching

The abnormal process issue, arcing, was met in recipe development of high aspect ratio (HAR) trench etching. The arcing mechanism is proposed by continuous growth of polymer upon hard-mask along pattern boundary during deep trench etching. It leads to excess charge trapped and high potential difference between polymer and substrate. Eventually, electrical field breakdown occurs and results in severe pattern damage. The arcing risk can be effectively monitored in advance by measuring the polymer thickness on bare-Si wafer. A critical thickness of polymer is observed because we seldom find out the occurrence of arcing on the wafer while the polymer thickness is less than 960nm. Low pressure, inert gas dilution and high ESC temperature provide the knobs to control the polymer thickness less than 960nm –the critical thickness, as well achieving acceptable vertical trench profile in HAR etching.