MOS Capacitance Measurements for PEALD TiO2 Dielectric Films Grown under Different Conditions and the Impact of Al2O3 Partial-Monolayer Insertion

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MOS Capacitance Measurements for PEALD TiO2 Dielectric Films Grown under Different Conditions and the Impact of Al2O3 Partial-Monolayer Insertion

Authors
  • Chiappim, William
  • Watanabe, Marcos
  • Dias, Vanessa
  • Testoni, Giorgio
  • Rangel, Ricardo
  • Mariana Fraga
  • Maciel, Homero
  • dos Santos Filho, Sebastião
  • Pessoa, Rodrigo
Type
Published Article
Journal
Nanomaterials
Publisher
MDPI AG
Publication Date
Feb 18, 2020
Volume
10
Issue
2
Identifiers
DOI: 10.3390/nano10020338
Source
MyScienceWork
License
Green

Abstract

In this paper, we report the plasma-enhanced atomic layer deposition (PEALD) of TiO 2 and TiO 2 /Al 2 O 3 nanolaminate films on p-Si(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. In the PEALD process, we used titanium tetraisopropoxide (TTIP) as a titanium precursor, trimethyl aluminum (TMA) as an aluminum precursor and O 2 plasma as an oxidant, keeping the process temperature at 250 • C. The effects of PEALD process parameters, such as RF power, substrate exposure mode (direct or remote plasma exposure) and Al 2 O 3 partial-monolayer insertion (generating a nanolaminate structure) on the physical and chemical properties of the TiO 2 films were investigated by Rutherford backscattering spectroscopy (RBS), Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), and field emission scanning electron microscopy (FESEM) techniques. The MOS capacitor structures were fabricated by evaporation of Al gates through mechanical mask on PEALD TiO 2 thin film, followed by evaporation of an Al layer on the back side of the Si substrate. The capacitors were characterized by current density-voltage (J-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. Our results indicate that RF power and exposure mode promoted significant modifications on the characteristics of the PEALD TiO 2 films, while the insertion of Al 2 O 3 partial monolayers allows the synthesis of TiO 2 /Al 2 O 3 nanolaminate with well-spaced crystalline TiO 2 grains in an amorphous structure. The electrical characterization of the MOS structures evidenced a significant leakage current in the accumulation region in the PEALD TiO 2 films, which could be reduced by the addition of partial-monolayers of Al 2 O 3 in the bulk of TiO 2 films or by reducing RF power.

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