Surface and interface microstructural properties of Ru thin films grown on InSb (111) substrates at room temperature
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)
- et al.
Solid-State Electron.
(1978) Physics and Chemistry of III–V Compound Semiconductor Interfaces
(1985)- et al.
Appl. Phys. Lett.
(1981) - et al.
Phys. Rev. Lett.
(1989) Phys. Rev. Lett.
(1989)- et al.
Phys. Rev. [Sect.] B
(1991) - et al.
Phys. Rev. Lett.
(1993) - et al.
Appl. Phys. Lett.
(1996) - et al.
Appl. Phys. Lett.
(1996)
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