Mr. George Rogalskyj Profile

George Rogalskyj

at TEL Technology Ctr., America, LLC

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Publications (1)

Proceedings Article | 25 May 2022 Presentation + Paper

Dielectric material etch selectivity control in dual-frequency capacitively coupled plasmas with dc-superposition

Du Zhang, Hojin Kim, Kathleen McInerney, Pingshan Luan, George Rogalskyj, Mingmei Wang

Proceedings Volume 12056, 1205606 (2022) https://doi.org/10.1117/12.2614434

KEYWORDS: Dielectrics, Ions, Plasma etching, Chemistry, Modeling and simulation, Capacitive coupling

Read Abstract +

Selective plasma etching among different dielectric materials is crucial to the manufacturing of advanced logic and memory devices. For instance, in self-aligned contact (SAC) etching, achieving highly selective SiO₂ etching over Si₃N₄ is essential. By contrast, in self-aligned multi-patterning (SAMP), selective Si₃N₄ spacer removal over SiO₂ and Si is necessary. To effectively control the relative etch rates of various dielectric materials, etch gas chemistry optimization [for instance, see J. Vac. Sci. Technol. A 36, 040601 (2018), J. Vac. Sci. Technol. A 34, 041307 (2016)., J. Vac. Sci. Technol. A 35, 01A102 (2017), etc.] has been extensively investigated. On the other hand, hardware capabilities such as direct current superposition (DCS) and must also be considered for their effects on plasma physics and plasma-surface interactions. In this study, we examine the etch behavior for various dielectric materials e.g. SiO₂, Si3N₄, and low-k dielectrics in a TEL dual-frequency CCP chamber. Specifically, we focus on the gas ratio and DCS effects in a CF₄/H₂/Ar plasma. Contrary to the monotonically decreasing etch rates for SiO₂ and low-k vs. increasing H₂/CF₄ flow ratio in accordance with decreasing F/CF_x density ratio, the experimental blanket Si₃N₄ etch rate exhibits a local maximum at H₂/(CF₄+H₂) = 15%. Chamber-scale plasma simulations using the Hybrid Plasma Equipment Model (HPEM) indicate that the HF density is peaked at almost the same gas ratio. In addition, atomistic molecular dynamics (MD) and density functional theory (DFT) simulations reveal hydrogen’s role in modifying the Si₃N₄ surface through N-H bond formation, thereby creating a hydrophilic surface on which HF adsorption is enhanced. Finally, computed reactant flux trends also demonstrate that the effect of DC superposition (DCS) on the relative orders of various ion and neutral reactant fluxes to the wafer is significantly weaker compared to that of the H₂/(CF₄+H₂) flow ratio. This suggests that the application of DCS aimed at differential charging mitigation is not expected to induce major changes in inherent material etch selectivity. These fundamental learnings provide insights to guide process development and optimization for common dielectric etch applications.

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