Surface and interface microstructural properties of Ru thin films grown on InSb (111) substrates at room temperature

https://doi.org/10.1016/S0169-4332(00)00356-1Get rights and content

Abstract

Ru thin films were grown on p-InSb (111) substrates by the ion-beam-assisted deposition method with the goal of producing a new kind of Ru/InSb heterostructures with high-quality heterointerfaces. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements showed that the Ru films grown on InSb substrates at room temperature were polycrystalline thin layers with very smooth surfaces. Auger electron spectroscopy (AES) and Rutherford backscattering measurements (RBS) showed that the composition of the as-grown film was Ru and that the Ru/InSb heterointerface had relatively sharp interfaces. Transmission electron microscopy (TEM) and selected area electron-diffraction measurements showed that the grown Ru film was a polycrystalline layer with small grain size. These results indicate that the Ru layer grown on p-InSb (111) can be used for stable contacts and metal electrodes with low resistivities in electronic devices such as metal-semiconductor field-effect-transistors and memory capacitor between electrodes based on InSb substrates.

Introduction

The growth of new kinds of metal thin films on compound semiconductor substrates has attracted attention due to both scientific and technological reasons for more than 20 years [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. More recently, it has been suggested that ruthenium (Ru) metal, with its strong resistance to oxidation, [11] is one of the most promising materials because its enthalpy change of oxidation is as small as 17.7 kcal/g atom [12]. In addition, since it is possible to etch the Ru layer chemically, the layer is applicable to ultra-large-scale integrated circuit processes [13]. Among the many kinds of metal/semiconductor heterostructures, one system of particular interest is that of a Ru film grown on an InSb substrate because that system may have one of the most stable metal/semiconductor heterointerfaces [11]. Even though many works have been done on the growth of metal films on InSb substrates [1], to the best of our knowledge, the growth of Ru films on InSb (111) substrates has not yet been performed. The Ru/InSb system is of particular interest in the fabrication of possible high-speed electronic devices utilizing the material advantages of the low resistivity of Ru thin films and the small energy-gap effective mass of InSb [14]. However, in InSb-based metal semiconductor field-effect transistors and their associated integrated circuits, thin films grown on InSb at high temperatures suffer from the problems of interdiffusion with the InSb substrates during the growth [15]. For these reasons, room-temperature deposition of Ru on InSb substrates, as a means of looking for physical evidence for an Ru/InSb heterostructure with interfacial abruptness, has been investigated. Since the microstructural properties of thin metal films and thin interfacial layers significantly affect the electrical and the optical properties of the heterostructure, a study of the surface and the interface microstructural properties of the Ru/InSb heterostructure is very important in order to be able to fabricate new kinds of electronic devices.

This paper reports the microstructural properties of Ru thin films grown on p-InSb (111) substrates by using an ion-beam deposition (IBD) method at room temperature. Atomic force microscopy (AFM) measurements were performed in order to characterize the surface smoothness of the Ru layer. X-ray diffraction (XRD) measurements were carried out to investigate the crystallization of the Ru layer, and Auger electron spectroscopy (AES) measurements were performed in order to characterize the compositions of the grown films. Rutherford backscattering (RBS) measurements were carried out to investigate the channeling effects of the Ru thin films. Transmission electron microscopy (TEM) measurements were performed to investigate the microstructure of the Ru/InSb (111).

Section snippets

Experimental details

Polycrystalline Ru element with purity of 99.9999% was used as a source target material and was precleaned by repeated sublimation. The carrier concentration of the Ge-doped p-InSb substrates with a (111) orientation used in this experiment was 1–10×1016 cm−3. The InSb substrates were mechanically polished, alternately degreased in warm acetone and trichloroethylene (TCE), rinsed in deionized water thoroughly, etched in a solution of lactic acid, HNO3, and HF (25:4:1) at 40°C for 5 min, and

Results and discussion

The as-grown Ru films grown on InSb (111) substrates prepared by an IBD method had mirror-like surfaces without any indications of pinholes, which was confirmed using Normarski optical microscopy and scanning electron microscopy (SEM) measurements. The SEM results of the Ru films also indicated a very smooth and dense surface morphology. The thickness of the Ru thin film determined from the TEM measurements was 2000 Å. The root mean square of the average surface roughness of the Ru thin films,

Summary and conclusions

The results of AFM, XRD, AES, and TEM measurements show that the Ru thin layers grown on the p-InSb (111) substrates by IBD at room temperature are polycrystalline films. The results of AES and RBS measurements show that the Ru/p-InSb heterostructurews have relatively sharp heterointerfaces without significant interdiffusion problems. TEM measurements show that the thin interfacial layer is formed between the polycrystalline Ru layer and the InSb substrates. Even though some detailed

Acknowledgements

The present research has been conducted by the Research Grant of Kwangwoon University in 2000.

References (18)

  • R. Pretorius et al.

    Solid-State Electron.

    (1978)
  • C.W. Wilmsen

    Physics and Chemistry of III–V Compound Semiconductor Interfaces

    (1985)
  • G.A. Prinz et al.

    Appl. Phys. Lett.

    (1981)
  • P.A. First et al.

    Phys. Rev. Lett.

    (1989)
  • R.M. Feenstra

    Phys. Rev. Lett.

    (1989)
  • B.M. Trafas et al.

    Phys. Rev. [Sect.] B

    (1991)
  • D.A. Evans et al.

    Phys. Rev. Lett.

    (1993)
  • K.E. Mello et al.

    Appl. Phys. Lett.

    (1996)
  • L. Wang et al.

    Appl. Phys. Lett.

    (1996)
There are more references available in the full text version of this article.

Cited by (2)

View full text