Elsevier

Thin Solid Films

Volume 475, Issues 1–2, 22 March 2005, Pages 354-358
Thin Solid Films

Physical and electrical properties of ZrO2 and YSZ high-k gate dielectric thin films grown by RF magnetron sputtering

https://doi.org/10.1016/j.tsf.2004.07.023Get rights and content

Abstract

Thin films of ZrO2 were deposited on p-Si(100) substrates using RF magnetron sputtering technique. To investigate the influence of the sputtering parameters, e.g., annealing temperature, different O2-flux, RF power and target to substrate distance on the physical and electrical properties of the as-grown films, systematic investigation using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope and energy dispersive X-ray (SEM–EDX), C–V, and I–V were carried out in this work. Deposited ZrO2 films had polycrystalline after annealing sample at high temperature. Their silicon oxide (SiO2) layers were formed between high-k film (i.e., ZrO2 and YSZ) and Si substrate either after annealing samples at high temperature or introducing O2-flux the sputtering process step. The high-k thin films have to be deposited amorphous structure without SiO2 interlayers. We also investigated the electrical properties of both the a-ZrO2 and a-YSZ films prepared without O2-flux at room temperature with conditions of various RF power and target to substrate distance. The dielectric constant of amorphous YSZ was determined to be about 24 using metal–insulator–semiconductor (MIS) capacitor structure. The smallest leakage current density of the YSZ film grown at 150 W and at room temperature was obtained to be about 10−10 at 1 V.

Introduction

Recently, as metal oxide semiconductor field effect transistor (MOSFET) devices are scaled down to <100 nm, problems of conventional silicon oxide (SiO2) appeared. SiO2 layer suffered from basic problem of high tunneling leakage current and reduced drive current due to low dielectric constant (k=3.9) with thickness decreased (<2 nm) [1], [2]. Hence, high-k gate dielectrics such as Ta2O5, TiO2, HfO2, ZrO2, CeO2, Y2O3 stabilized ZrO2 (YSZ) [2], [3], [4], [5], [6] were studied to replace SiO2. Most of these materials, however, were not thermally stable directly on Si, due to the formation of metal silicides in the course of fabrication.

ZrO2 and YSZ are one of the most attractive andidates due to its high-k values (∼25 and ∼27, respectively), wide band gap (approximately 5.1–7.8 eV) [7], [8], and good thermal stability in contact with Si [9]. Due to their excellent properties, ZrO2 and YSZ films have been extensively studied as gate dielectric [10]. Wang et al. [11] studied the 6-nm-thick epitaxial crystalline YSZ films with electrical equivalent oxide thickness (EOT) of 1.46 nm and found that the leakage current was about 1.1×10−3 A/cm2 at 1 V. In addition, Zhu and Liu [6] also studied the 6-nm-thick amorphous YSZ films with EOT=1.46 nm and obtained a leakage current to be about 7.58×10−5 A/cm2 at 1 V. Moreover, amorphous films exhibited isotropic electrical properties and can easily be deposited.

In this work, the influence of the sputtering parameter such as, O2-flux, annealing temperature, RF power and target-to-substrate distance (Dts) on physical and electrical properties of amorphous ZrO2 and YSZ films that were prepared at low temperature by RF magnetron sputtering method have been studied.

Section snippets

Experimental

Both ZrO2 and YSZ films were prepared by the RF magnetron sputtering method. The purity of the ZrO2 target was above 99.99% with a diameter of 1 in. The YSZ target were prepared with 8 wt.% Y2O3-stabilized ZrO2. The sputtering gas (Ar) with a purity of 99.99% were introduced to the chamber and controlled by the standard mass-flow controllers. The sputtering pressure was 32 mTorr and p type Si(100) wafer were used as substrates without heating. The substrate–target distance was changed from 30

Results and discussion

Fig. 1(a) shows X-ray diffraction patterns of ZrO2 thin films grown at room temperature without O2-flux. The RF power was 150 W and the annealing temperature varied from 600 to 1200 °C. Below 600 °C, there were no typical diffraction peaks, indicating an amorphous structure. Between 800 and 1000 °C, the films were mainly grown in the [111] orientation, while the crystal growth direction was changed to be [012], at an annealing temperature in the range of 1000–1200 °C. The polycrystal film could

Conclusions

We have deposited ZrO2 thin films on p-Si(100) substrate by RF magnetron sputtering in order to study an influence of deposition parameters (such as annealing temperature, reactive gas, RF power, and Y2O3 dopant) on the physical and electrical properties of the as-grown films. XRD showed that a highly oriented cubic ZrO2 thin film in the [111] direction was obtained after annealing at 800 °C. On the other hand, tetragonal ZrO2 thin film was also grown on Si (100) substrate and the main film

Acknowledgements

This work was supported by the BK21 project of the Ministry of Education Korea, by the CAPST (Center for Advanced Plasma Surface Technology) and by the Korea Science and Engineering Foundation (project No. R01-2003-000-10019-0) at the Sungkyunkwan University.

References (14)

  • J. Zhu et al.

    Mater. Lett.

    (2003)
  • P. Gao et al.

    Thin Solid Films

    (2000)
    P. Gao et al.

    Thin Solid Films

    (2000)
  • S. Horita et al.

    Mater. Sci. Eng., B, Solid-State Mater. Adv. Technol.

    (1998)
  • Paul A. Packen

    Science

    (1999)
  • Z.J. Luo et al.

    Appl. Phys. Lett.

    (2001)
  • D. Han et al.

    Chin. Phys.

    (2003)
  • W. Qi et al.

    Appl. Phys. Lett.

    (2000)
There are more references available in the full text version of this article.

Cited by (66)

  • Low-temperature solution-processed high-capacitance AlO<inf>x</inf> dielectrics for low-voltage carbon-based transistors

    2022, Organic Electronics
    Citation Excerpt :

    High-k oxides, on the other hand, have the advantages of high permittivity, and have less limitations related to dipolar relaxation compared to high-k polymers and electrolytes [15,20]. Conventionally, high-k dielectrics are deposited either by vacuum-based techniques, such as pulsed laser deposition (PLD) [2], atomic layer deposition (ALD) [21,22], magnetron sputtering and electron-beam evaporation [23], or by anodization [24–26]. The deposition of high-k oxides using solution routes would enable their adoption in all-solution-based fabrication of electronic circuits.

  • Atomic layer deposition of Y-stabilized ZrO<inf>2</inf> for advanced DRAM capacitors

    2017, Journal of Alloys and Compounds
    Citation Excerpt :

    In previous studies, Y-doped ZrO2 films were deposited by pulsed laser deposition and RF magnetron sputtering [28–30]; since YSZ ceramic targets with specific Y contents were used, optimizing the electrical properties of Y-doped ZrO2 was not a viable option [28,29]. The dielectric constants were 26.4 and 24.1 (for 5 and 8 mol% Y, respectively), which are slightly lower than the highest value observed in this work for ALD Y-doped ZrO2 films [28,29]. Fig. 4b shows the insulating properties of undoped and Y-doped ZrO2 films.

  • Al<inf>2</inf>O<inf>3</inf>/TiO<inf>2</inf> nanolaminate gate dielectric films with enhanced electrical performances for organic field-effect transistors

    2016, Organic Electronics
    Citation Excerpt :

    These results agreed with our results reported previously [16]. In general, the more dense dielectric film can effectively prevent from leakage current [25]. Thus, the AT nanolaminate with the thermodynamically stable Al–O–Ti bonds provided a lower leakage current density than the single Al2O3 and TiO2 films.

View all citing articles on Scopus
View full text