By using a stacked mask process (S-MAP) with spun-on-carbon (SOC) film, 38 nm line patterns were successfully etched by controlling the ion energy using high-bias-frequency dual-frequency-superimposed (DFS) rf capacitively coupled plasma in combination with the low hydrogen content SOC film. It was found that ions with higher energy enhance the fluorination of SOC and induce pattern wiggling under fluorine exposure. By using a higher bias frequency to control the ion energy distribution and reduce the maximum ion energy, the SOC pattern wiggling was effectively suppressed.

For the precise control of the ion energy in reactive ion etching (RIE), a 1-MHz pulsed-direct current (DC) square-wave-superimposed (p-DCS) 100-MHz radio frequency (RF) capacitively coupled plasma (CCP) is studied and compared with a 13.56- and 100-MHz dual-RF-superimposed (DFS) CCP. The proposed CCP is applied in RIE for sub-32-nm node etching of spun-on-carbon using H2-based gas at 2.66 Pa and 1200 W of 100-MHz RF power. A minimum critical dimension shift of 3 nm is achieved at high etch rates in p-DCS CCP using an optimized square-wave voltage of −750 V, compared with a corresponding shift of 9 nm in DFS CCP using 400 W of 13.56-MHz RF power. Because the maximum of the ion energy distribution (IED) is controlled by the square-wave voltage and more than 70% of the total ion flux is concentrated in a narrow range around the maximum ion energy, the CCP offers precise control of the IED, which is effective in the RIE of the fine-patterned devices.

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