Two-dimensional effects of the asymmetric electrode on electron heating in dual-frequency capacitively coupled plasmas

Dual-frequency (DF) capacitively coupled plasmas (CCP) are commonly utilized in semiconductor etching and deposition processing because of their excellent spatial uniformity and easy control of ion energy. With a dual-frequency, the ion energy and the ion flux are separately controllable for the high-frequency (HF) and the low-frequency (LF) voltage waveforms, which are faster and slower than the ion transit time individually. Understanding the electron heating mechanism is essential to improve the performance of the process equipment. In this presentation, we report the asymmetry effect of the electrode structure on the spatial uniformity of the electron power deposition under DF driving conditions using a two-dimensional GPU-based particle-in-cell simulation [1, 2]. We found that the sheath width increases in the peripheral region of the asymmetric reactor when LF power increases so that electron heating inside the sheath also increases. It was also confirmed that the ion flux toward the wafer is uniform even for the asymmetric electrode when the upper electrode is longer than the lower electrode beneath the wafer.