Role of a cyclopentadienyl ligand in a heteroleptic alkoxide precursor in atomic layer deposition

Hwi Yoon; Yujin Lee; Ga Yeon Lee; Seunggi Seo; Bo Keun Park; Taek-Mo Chung; Il-Kwon Oh; Hyungjun Kim

doi:10.1063/5.0182690

Role of a cyclopentadienyl ligand in a heteroleptic alkoxide precursor in atomic layer deposition

J Chem Phys. 2024 Jan 14;160(2):024302. doi: 10.1063/5.0182690.

Authors

Hwi Yoon¹, Yujin Lee^{1

2}, Ga Yeon Lee³, Seunggi Seo^{1

2}, Bo Keun Park³, Taek-Mo Chung³, Il-Kwon Oh^{4

5}, Hyungjun Kim¹

Affiliations

¹ School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-Ro, Seodaemun-Gu, Seoul 03722, South Korea.
² Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
³ Thin Film Materials Research Center, Korea Research Institute of Chemical Technology, 141 Gajeong-Ro, Yuseong-gu, Daejeon 34114, South Korea.
⁴ Department of Electrical and Computer Engineering, Ajou University, 206 Worldcup-Ro, Yeongtong-Gu 16499, Suwon, South Korea.
⁵ Department of Intelligence Semiconductor Engineering, Ajou University, 206 Worldcup-Ro, Yeongtong-Gu 16499, Suwon, South Korea.

PMID: 38189606
DOI: 10.1063/5.0182690

Abstract

Alkoxide precursors have been highlighted for depositing carbon-free films, but their use in Atomic Layer Deposition (ALD) often exhibits a non-saturated growth. This indicates no self-limiting growth due to the chain reaction of hydrolysis or ligand decomposition caused by β-hydride elimination. In the previous study, we demonstrated that self-limiting growth of ALD can be achieved using our newly developed precursor, hafnium cyclopentadienyl tris(N-ethoxy-2,2-dimethyl propanamido) [HfCp(edpa)3]. To elucidate the growth mechanism and the role of cyclopentadienyl (Cp) ligand in a heteroleptic alkoxide precursor, herein, we compare homoleptic and heteroleptic Hf precursors consisting of N-ethoxy-2,2-dimethyl propanamido (edpa) ligands with and without cyclopentadienyl ligand-hafnium tetrakis(N-ethoxy-2,2-dimethyl propanamido) [Hf(edpa)4] and HfCp(edpa)3. We also investigate the role of a Cp ligand in growth characteristics. By substituting an alkoxide ligand with a Cp ligand, we could modify the surface reaction during ALD, preventing undesired reactions. The last remaining edpa after Hf(edpa)4 adsorption can undergo a hydride elimination reaction, resulting in surface O-H generation. In contrast, Cp remains after the HfCp(edpa)3 adsorption. Accordingly, we observe proper ALD growth with self-limiting properties. Thus, a comparative study of different ligands of the precursors can provide critical clues to the design of alkoxide precursors for obtaining typical ALD growth with a saturation behavior.