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Epitaxial growth of tensile strained SiB alloy on a Si substrate
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Myronov, Maksym, Shah, V. A., Rhead, S. and Leadley, D. R. (David R.) (2012) Epitaxial growth of tensile strained SiB alloy on a Si substrate. In: 6th International Silicon-Germanium Technology and Device Meeting, ISTDM 2012, Berkeley, CA, USA, 4-6 June 2012. Published in: 2012 International Silicon-Germanium Technology and Device Meeting, ISTDM 2012 - Proceedings (Article number 6222493). pp. 132-133. ISBN 9781457718625. doi:10.1109/ISTDM.2012.6222493
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Official URL: http://dx.doi.org/10.1109/ISTDM.2012.6222493
Abstract
Silicon (Si) is still the main material for mass production of a large variety of electronic and photonic semiconductor devices, whilst Boron (B) is still its primary p-type dopant. B-doping in Si has been systematically studied and continues to attract interest. In particular, ultrahigh B doping of silicon, i.e. incorporation of B at concentrations well over an order of magnitude higher than its equilibrium solubility limit, became an issue of primary importance in order to minimize contact resistance in low-dimensional devices. Unfortunately, the B solubility in Si of ∼2×1019 atoms/cm3 at 700 C is quite low and its implantation in Si is accompanied by detrimental effects like clustering and anomalous diffusion. Whilst this is the widely used non-equilibrium strategy for p-type doping of Si, it substantially limits the electrical activity and the sharpness of the B implanted profile. Alternative approaches, such as epitaxy, to incorporate B into substitutional sites have been investigated, mainly with a view to reaching high metastable incorporation during phase transformation. Attempts to incorporate a higher concentration of B in Si during epitaxial growth and to create a SiB alloy were performed in the past. The concentration level of substitutional B that can be usually reached in strained SiB epilayers is below 1 % [1]. There has been a report of B content as high as 24 % in a SiB alloy layer grown by Gas Source Molecular Beam Epitaxy (GS-MBE) [2], but until recently, there was no clear agreement on how to calculate the B content of a SiB alloy, even at the few percent level [1]. Relaxed SiB can also be formed via B ion implantation and subsequent annealing, or via surface diffusion, but such layers unavoidably contain defects that will at least degrade the electrical properties of the alloy. By contrast, epitaxy opens the possibility to grow not only relaxed SiB alloys on Si but also strained ones that are defect free and has enormous possibilities for further research and applications. In addition, epilayers can be grown selectively on pre-patterned wafers by Chemical Vapour Deposition (CVD) or GS-MBE techniques. In particular, epitaxial growth of such layers by Reduced Pressure CVD (RP-CVD) is of great importance, since it is the main technique utilized by the semiconductor industry to grow Si based structures. In this work, we present the first results of successful epitaxial growth of fully strained SiB alloy epilayers by RP-CVD. The epilayers were grown using standard and widely used Si and B gaseous precursors, diborane and disilane. Figure 1 shows a schematic cross section of the structures grown, which consist of a SiB epilayer grown directly on a Si (100) substrate. The thickness of SiB was varied from 10 up to 100 nm and the boron concentration was also varied. Comprehensive structural characterization was carried out using Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and high resolution X-ray diffraction (HR-XRD). Figure 2 shows typical HR-XRD (004) rocking curves measured on two samples containing fully strained 100 nm thick SiB epilayers of different B content. The peak positions, and presence of fringes, indicates tensile strain in the SiB alloy epilayers and a B content above 1 %. The results obtained open wide the possibilities for further research and applications. One of which is very low-resistivity SiB contacts with potential exhibition of superconductivity at low-temperature [3].
Item Type: | Conference Item (Paper) | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
Journal or Publication Title: | 2012 International Silicon-Germanium Technology and Device Meeting, ISTDM 2012 - Proceedings | ||||
ISBN: | 9781457718625 | ||||
Book Title: | 2012 International Silicon-Germanium Technology and Device Meeting (ISTDM) | ||||
Official Date: | 2012 | ||||
Dates: |
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Number: | Article number 6222493 | ||||
Page Range: | pp. 132-133 | ||||
DOI: | 10.1109/ISTDM.2012.6222493 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Conference Paper Type: | Paper | ||||
Title of Event: | 6th International Silicon-Germanium Technology and Device Meeting, ISTDM 2012 | ||||
Type of Event: | Conference | ||||
Location of Event: | Berkeley, CA, USA | ||||
Date(s) of Event: | 4-6 June 2012 |
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