On the reliability of ZrO2 films for VLSI applications

doi:10.1016/j.microrel.2003.12.012

Microelectronics Reliability

Volume 44, Issue 5, May 2004, Pages 739-745

https://doi.org/10.1016/j.microrel.2003.12.012 Get rights and content

Abstract

In this paper we present a systematic investigation of the effects of electrical stress on reliability of zirconium oxide films. In particular, we monitored stress-induced leakage current, high-field conduction and capacitance curves as function of the applied voltage and the injected charge. Defect density in the bulk oxide have been extracted from measurements by means of literature models. As a result, a square root time dependence of the stress-induced defects has been found.

Introduction

Scaling rules of MOS transistors impose gate oxide thickness below 2 nm and gate leakage current of 1 pA/μm for the 2005 technology node as specified in the ITRS 2001. However, in the case of SiO₂ gate oxide, such thickness imply tunneling currents too high for microelectronic applications. In order to overcome this problem, materials with high dielectric constants (ε_r), the so called high-k dielectrics, should be used in alternative to pure-SiO₂. The equivalent thickness is defined as: $EOT = ε_{SiO_{2}} ε_{r} t_{ox}$ where ε_SiO₂ is the dielectric constant of the SiO₂ and t_ox the thickness of the high-k oxide. Nitrided silicon dioxide have been proposed first [1], [2]; zirconium, hafnium, lanthanides and others are currently receiving a lot of attention [3], [4], [5], [6], [7]. These feature: good chemical stability onto silicon substrate, amorphous network, large energy gap and high band offset with silicon.

The present work offers a detailed electrical characterization of ZrO₂ films, before and after charge injection. The paper is organized as follows: in Section 2 the deposition conditions and the experimental set-up for the electrical characterization are presented; in Section 3 results of current–voltage characterization and capacitance measurements are shown and discussed; conclusions are drawn in Section 4.

Section snippets

Experimental details

ZrO₂ films were grown on 1–3 Ωcm (1 0 0) p-type silicon wafer, by atomic layer deposition (ALD) at 300 °C in ASM-Microchemistry F-450 reactor. Zirconium tetrachloride (ZrCl₄) and H₂O were used as precursors. The native oxide on the substrate was not removed. The final dielectric stack is composed by a 19.1 ± 0.3 nm thick ZrO₂ film, and an interfacial SiO₂ layer (1.2 ± 0.1 nm), measured by grazing incidence X-ray reflectivity [8]. The final EOT of the dielectric stack extracted from capacitance

As deposited samples

Fig. 2 shows a typical current–voltage characteristic of fresh capacitors. As indicated in Fig. 1, voltages are applied to the silicon substrate with respect to the top Al electrode connected to ground. Three regions can be distinguished: (1) V_gate<0 (inversion condition), (2) 0<V_gate<1 V (depletion condition), (3) V_gate>1 V (accumulation condition).

Under inversion condition, conduction occurs through traps in the bulk zirconium oxide and data can be simulated by a Poole–Frenkel mechanism

Conclusions

This work reports on electrical characterization of reliability of ZrO₂ films deposited onto native SiO₂ on Si by ALCVD. Densities of bulk defects were extracted from current and conductance measurements, with the aid of literature models. The density of native defects in the ZrO₂ films under study is largely greater that in production quality SiO₂, since it is in the order of 10¹⁸ cm⁻³. A constant current stress was performed on samples and the electrical feature measured as function of the

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Influence of process parameters on atomic layer deposition of ZrO <inf>2</inf> thin films from CpZr(NMe<inf>2</inf>)<inf>3</inf> and H <inf>2</inf>O
2014, Thin Solid Films
Citation Excerpt :
Zirconium dioxide (ZrO2) is a dielectric with relatively wide band gap, high refractive index and high dielectric constant. These properties make ZrO2 very attractive for application in optical [1] and electronic [2–6] devices. For instance, significant efforts have been focussed on characterization of ZrO2 thin films prepared by various deposition techniques for silicon-based metal-oxide-semiconductor devices [3,4] and capacitor structures with TiN electrodes [5,6].
Atomic layer deposition of ZrO₂ films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe₂)₃ and H₂O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350 °C. In this temperature range growth rate of 0.08–0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200 °C and higher temperatures contained tetragonal and monoclinic phases of ZrO₂. The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250 °C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe₂)₃ and H₂O at 250–350 °C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm³, respectively, being close to the highest values obtained for films deposited from ZrCl₄ and H₂O. The former process ensured, however, more uniform nucleation of ZrO₂ on graphene than the latter process did.
X-ray diffraction measurement of residual stress and crystal orientation in Au/NiCr/Ta films prepared by plating
2007, Surface and Coatings Technology
Au/NiCr/Ta films were prepared by plating and then annealed at 400 °C in Ar gas for an hour. The Au diffraction peak positions including incidence angles 0°, 15°, 30°, and 45° were measured by a glancing incidence X-ray diffraction (GIXRD) method. Residual stresses were then calculated using the sin²ψ method. The results indicate that the residual stress in the as-deposited Au/NiCr/Ta films was about 50 MPa, but was decreased down to − 5 MPa in average after samples annealing. The XRD analysis on crystal orientation shows that only the diffraction peaks of Au were found. There are no alloying phases in the plating Au film, and the interlayer of NiCr and Ta is too thin to be detected by the conventional XRD. The XRD also revealed that the films are highly textured with Au-(111) or a mixture of Au-(111) and Au-(200) orientation, and the (111)/(200) intensity ratio decreases after samples annealed.
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Behavior of zirconium oxide films processed from novel monocyclopentadienyl precursors by atomic layer deposition
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On the reliability of ZrO2 films for VLSI applications

Abstract

Introduction

Section snippets

Experimental details

As deposited samples

Conclusions

Appl. Surf. Sci.

Microelectron. Reliab.

IEEE Electron Device Lett.

Tech. Dig. VLSI Symp.

Appl. Phys. Lett.

Tech. Dig. VLSI Symp.

Appl. Phys. Lett.

J. Appl. Phys.

On the reliability of ZrO₂ films for VLSI applications