Self-Aligned Contact Etch Process Optimization with Pulsing Plasma Technology

Abstract

The self-aligned contact (SAC) is a key process in developing the next generation ultra-large scale integrated (ULSI) devices because its advantage on providing an efficient reduction of active array areas, decreasing the transistor gate features, and alignment margin improvements in photolithography. [1-2] With the transistor gate feature size continuously scaled down, pattern density and aspect ratios continuously increase, conversely. It requires a robust etch process to solve the multiple issues such as nitride hard mask loss loading between trench/hole, nitride shoulder profile, free necking profile. [3] In this work, we examined the impact of various pulsing technologies on the extremely high aspect ratio SAC etch process, including source pulsing/bias pulsing/synchronous pulsing and the hybrid method. Results indicate the introduction of pulsing function could significantly reduce the nitride loss while avoid the contact open. The synchronous pulsing scheme shows its superior capability on improving the trade-off between nitride loss and profile control. Finally we achieved a manufacturable SAC process without any side effect. References S. Kim, J. Vac. Sci. Technol. A 23(4), 7(2005).J. Kim, J.Vac.Scl. Technol. B 20(5), 9(2002)E.H. Zheng, A study of self-aligned contact etch of NOR flash, China Semiconductor Technology International Conference (2015).