Potential CCP Pulsed Plasma Application at Beol AIO Etch Process

Abstract

Plasma etching has been extensively used for more than 30 years in semiconductor manufacturing industry [1]. Typically, plasma reactor RF power sources have constant average power to excite the plasma in a vacuum chamber. Such mode of operation is termed as continuous-wave (CW) RF mode [2]. As COMS is being scaled down to 28nm node and beyond, CW plasmas etching processes are reaching their limits to satisfy the multiply stringent requirements, such as better uniformity, higher selectivity, less plasma induced damage, tighter critical dimension and profile control. The RF pulsed plasma is one of promising knobs to increase the flexibility of plasma processing by enlarging the range of operating conditions [3-5]. There are two main parameters characterizing the RF pulse: one is the pulsed frequency at which the RF power is turned on and off per second; the other is the pulse duty cycle, which is defined as the ratio between the pulse on time and the total pulse duration. As the multiple-frequency RF powers have been introduced for the better control plasma flux and energy in CCP system, the effect of different RF power pulsing varies, bias only, source only and synchronized pulsed plasmas also shows quite different performances. In this work, self-aligned via (SAV) based all-in-one (AIO) etch processes were performed in one commercial etcher, and the effects of pulsed plasmas on the etch process were analyzed. The different pulsed mode, pulsed duty cycle, pulsed frequency on CCP chamber were tested on the SAV based AIO etching process in BEOL copper interconnect system. We compared the bias only, source only and synchronized pulsed plasma performances, checked the duty cycle effects, which varies from 10% to 90%. The Physical performances were analyzed by CDSEM, SEM, TEM, and TK. Compared with conventional CW plasmas, the performances of AIO etching process could be significantly improved via pulsed plasma, such as more rounding chamfer profile, via bottom CD control, and better SAC process with higher selectivity to metal hard mask. Acknowledgement This work is sponsored by Shanghai Rising-Star Program (B type). REFERENCES [1] S. Banna, A. Agarwal, G. Cunge, M. Darnon, E. Pargon, and O. Joubert. J. Vac. Sci. Technol. A, vol. 30, 2012, pp. 040801. [2] S. Banna, A. Agarwal, K. Tokashiki, H. Cho, S. Rauf, V. Todorow, K. Ramaswamy, K. Collins, P. Stout, J. Y. Lee, J. Yoon, K. Shin, S. J. Choi, H. S. Cho, H. J. Kim, C. H. Lee, and D. Lymberopoulos. IEEE Trans. Plasma Sci., vol. 37, 2009, pp. 1730-1746. [3] R. W. Boswell and D. Henry. Appl. Phys. Lett., vol. 47, 1985, pp. 1095-1097. [4] P. Subramonium and M. J. Kushner. Appl. Phys. Lett., vol. 79, 2001, pp. 2145-2147. [5] A. Rousseau, E. Teboul, N. Lang, M. Hannemann, and J. Ropcke. J. Appl. Phys., vol. 92, 2002, pp. 3463-3471.