Characterization of plasma charging induced gate oxide damage during metal etching

Gate oxide damage induced by plasma charging during metal etching with a magnetic-enhanced reactive ion etcher (MERIE) or helicon wave plasma (HWP) etcher and subsequent resist ashing was investigated. Metal-oxide-semiconductor (MOS) capacitors and n-channel transistors connected to an metal antenna were used to monitor the damage. For capacitor test structures, we used the initial electron trapping slope (IETS) and time-dependent dielectric breakdown (TDDB) methods to characterize the damage. The results indicated that the IETS indicator was more efficient than the TDDB method. It was also observed that serious damage could occur during the MERIE processing. especially for those devices located in the edge region. In contrast, devices treated through HWP processing exhibited good performance in comparison with the control devices. Consistent results were also obtained by characterizing the antenna-type transistor performance. It was also found that the antenna effect could be clearly illustrated by measuring the gate current.