Effect of sulfur hexafluoride gas and post-annealing treatment for inductively coupled plasma etched barium titanate thin films.

Cong Wang,Hong-Ki Kim,Zhao Yao,Nam-Young Kim,Yang Li,Hyung-Jun Kim

doi:10.1186/1556-276x-9-496

Abstract

Aerosol deposition- (AD) derived barium titanate (BTO) micropatterns are etched via SF6/O2/Ar plasmas using inductively coupled plasma (ICP) etching technology. The reaction mechanisms of the sulfur hexafluoride on BTO thin films and the effects of annealing treatment are verified through X-ray photoelectron spectroscopy (XPS) analysis, which confirms the accumulation of reaction products on the etched surface due to the low volatility of the reaction products, such as Ba and Ti fluorides, and these residues could be completely removed by the post-annealing treatment. The exact peak positions and chemicals shifts of Ba 3d, Ti 2p, O 1 s, and F 1 s are deduced by fitting the XPS narrow-scan spectra on as-deposited, etched, and post-annealed BTO surfaces. Compared to the as-deposited BTOs, the etched Ba 3d 5/2 , Ba 3d 3/2 , Ti 2p 3/2 , Ti 2p 1/2 , and O 1 s peaks shift towards higher binding energy regions by amounts of 0.55, 0.45, 0.4, 0.35, and 0.85 eV, respectively. A comparison of the as-deposited film with the post-annealed film after etching revealed that there are no significant differences in the fitted XPS narrow-scan spectra except for the slight chemical shift in the O 1 s peak due to the oxygen vacancy compensation in O2-excessive atmosphere. It is inferred that the electrical properties of the etched BTO film can be restored by post-annealing treatment after the etching process. Moreover, the relative permittivity and loss tangent of the post-annealed BTO thin films are remarkably improved by 232% and 2,695%, respectively.

Highlights

Today, ferroelectric thin films have been identified as a promising candidate material for capacitors in the generation ultra-large-scale integrated dynamic random access memories, infrared sensors, electro-optic, RF, and microwave devices [1,2,3]
The atomic force microscopy (AFM) images reveal that crystallite size grows, and larger grains start to form in the BTO thin film after the annealing process (Figure 2c) compared to those formed in other films
It could be noted that the surface morphologies deteriorate rapidly after post-annealing treatment; we have already developed an available solution by using a two-slurry-based chemical mechanical polishing method to overcome it with a possible RMS of less than 2 nm for the post-annealed BTO thin films

Summary

Introduction

Ferroelectric thin films have been identified as a promising candidate material for capacitors in the generation ultra-large-scale integrated dynamic random access memories, infrared sensors, electro-optic, RF, and microwave devices [1,2,3]. Barium titanate (BTO) thin films are known as one of the leading candidates for use in applications due to their high dielectric constant, low leakage current, lack of fatigue, and low crystallization temperature [4,5,6]. A new, green and environmentally friendly approach called aerosol deposition (AD) has attracted great interest to fabricate BTO, which is a low-temperature and low-cost method featuring room-temperature processing with high deposition rate and high density [7,8,9]. To realize highly integrated cleanup of the by-products during the etching process and the densification of the BTO thin films. The annealing duration is indispensable for obtaining good quality crystalline BTO films [15,16]

Methods

Results

Conclusion