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. 2025 May 23;15(11):783.
doi: 10.3390/nano15110783.

Deposition of HfO2 by Remote Plasma ALD for High-Aspect-Ratio Trench Capacitors in DRAM

Jiwon Kim  1 , Inkook Hwang  1 , Byungwook Kim  1 , Wookyung Lee  1 , Juha Song  2 , Yeonwoong Jung  3 , Changbun Yoon  1
Affiliations

Deposition of HfO2 by Remote Plasma ALD for High-Aspect-Ratio Trench Capacitors in DRAM

Jiwon Kim et al. Nanomaterials (Basel). .

Abstract

Dynamic random-access memory (DRAM) is a vital component in modern computing systems. Enhancing memory performance requires maximizing capacitor capacitance within DRAM cells, which is achieved using high-k dielectric materials deposited as thin, uniform films via atomic layer deposition (ALD). Precise film deposition that minimizes electronic defects caused by charged vacancies is essential for reducing leakage current and ensuring high dielectric strength. In this study, we fabricated metal-insulator-metal (MIM) capacitors in high-aspect-ratio trench structures using remote plasma ALD (RP-ALD) and direct plasma ALD (DP-ALD). The trenches, etched into silicon, featured a 7:1 aspect ratio, 76 nm pitch, and 38 nm critical dimension. We evaluated the electrical characteristics of HfO2-based capacitors with TiN top and bottom electrodes, focusing on leakage current density and equivalent oxide thickness. Capacitance-voltage analysis and X-ray photoelectron spectroscopy (XPS) revealed that RP-ALD effectively suppressed plasma-induced damage, reducing defect density and leakage current. While DP-ALD offered excellent film properties, it suffered from degraded lateral uniformity due to direct plasma exposure. Given its superior lateral uniformity, lower leakage, and defect suppression, RP-ALD shows strong potential for improving DRAM capacitor performance and serves as a promising alternative to the currently adopted thermal ALD process.

Keywords: atomic layer deposition; capacitor; leakage current; plasma damage; remote plasma ALD; step coverage; thermal ALD; trench structure.

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Conflict of interest statement

The authors declare no conflicts of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Deposition processes and conditions for laterally and vertically aligned trench-structured substrates simulating DRAM capacitors. (a) DP-ALD process. (b) RP-ALD process. (c) Process flow for HfO2 deposition using DP-ALD and RP-ALD.
Figure 2
Figure 2
Cross-sectional images of trenches deposited by DP-ALD: (a) horizontal deposition; (b) vertical deposition. Cross-sectional images of trenches deposited by RP-ALD: (c) horizontal deposition; (d) vertical deposition.
Figure 3
Figure 3
Step coverage results for thin films deposited by DP-ALD and RP-ALD depending on the substrate orientation in the trench structure.
Figure 4
Figure 4
Thickness uniformity measurement results for thin films on a 6-inch (152 mm) wafer based on the deposition type: (a) DP-ALD, (b) RP-ALD.
Figure 5
Figure 5
Thickness distribution data for thin films deposited on a wafer: (a) DP-HfO2 and (b) RP-HfO2.
Figure 6
Figure 6
XPS measurement data for HfO2 thin films fabricated via DP-ALD and RP-ALD: (a,b) depth profiling; (c,d) Hf 4f; (e,f) O 1s patterns.
Figure 7
Figure 7
Capacitance measurement results for 5–20 nm HfO2 samples fabricated via DP-ALD and RP-ALD, using electrodes with a diameter of 200 μm.
Figure 8
Figure 8
EOT measurement results for HfO2 thin films with varying thicknesses fabricated via DP-ALD and RP-ALD.
Figure 9
Figure 9
Current density results for 5–20 nm HfO2 thin films fabricated via (a) DP-ALD and (b) RP-ALD.
Figure 10
Figure 10
Current densities of HfO2 thin films fabricated via DP-ALD and RP-ALD as a function of EOT.
See this image and copyright information in PMC

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