Morphological and Electrical Study of FIB Deposited W Wires by shwarma

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									P-EIBL12 - Electron and Ion Beam Lithography

MNE’06 Micro- and Nano- Engineering

Morphological and Electrical Study of FIB Deposited W Wires
E. Horváth a,b, P. L. Neumann b, A. L. Tóth a, A. A. Koós a, Z. E. Horváth a, L. P. Biró a
a

Research Institute for Technical Physics and Materials Science, Budapest, H-1525 Hungary phone: +36-1-3922797, e-mail: horvathe@mfa.kfki.hu b Budapest University of Technology and Economics, Budapest, H- 1521 Hungary

Key words: W deposition, electrical characterisation, FIB Nowadays, the semiconductor technology has reached the nanometer size range. Focused Ion Beam (FIB) systems have been primarily used to repair, and modify lithographic masks, failed microcircuitry and for rapid prototyping. On the other hand, FIB is a promising tool for nanoelectronic device fabrication, too. To measure the electrical characteristics of a nanodevice it should be contacted. Therefore, the fabrication of nanowires by deposition of W or Pt with FIB [1,2] is a technology that could prove very useful in the fast and reliable contacting of individual nanodevices, located and observed in the high resolution Scanning Electron Microscope (SEM) operation mode of a cross-beam FIB/SEM. Our aim in the present work is to investigate the influence of technological parameters, like ion beam current, deposition speed, morphology and electrical behaviour (resitivity) of deposited wires, and the dependence of the wire parameters on annealing. A special sample for predetermined cleavage and a micro-hotplate both developed in MTA MFA were used, to achieve cross sectional SEM examination and in situ annealing of the deposited wires. The deposition and characterization of nanometer size wires was carried out in-situ in a LEO 1540 XB workstation, a cross beam system consisting of a high resolution Gemini FEG SEM column, an Orsay Physics FIB column using 30kV Ga focused ion beam for milling, and a gas injection system (GIS) to perform electron or ion beam assisted deposition. When using the GIS, milling and deposition processes are in competition [3], so the deposition process parameters (FIB beam current, scan speed and gas flow) should be optimized. The morphology and cross-sectional geometry of deposited W stripes on a specially designed cleavage sample were studied. Though the deposited stripes have a non-ideal rectangular shape (see Fig. 1), the speed of deposition was found to be constant regardless the duration and the size of deposited wires. For electrical characterization, W nanowires were deposited between fingers of interdigitated electrodes with the characteristic distance of 10 m, realized on a micro-hotplate with photolithographic contacts. A special, ground free, measuring circuit was developed to avoid the melting of deposited wires, due to static charge introduced in the system by connecting to measuring circuit. The deposited W wires were found to have ohmic characteristic (see Fig. 2). The partial resistances of gold fingers, the contact and the deposited nanowire were separated and the resistivity of cm), using the geometrical parameters measured the deposited material was determined ( w= 218.3 by SEM. The resistance of the nanowires during heat-up showed linear increase. [1] [2] K. Gamo, S. Namba, Ion beam assisted etching and deposition, J. Vac. Sci. Technol. B 8 (6), 1927 (1990) Prestigiacomo M, Bedu F, Jandard F, Tonneau D, Dallaporta H, Roussel L, Sudraud P, Purification and crystallization of tungsten wires fabricated by focused-ion-beam-induced deposition, Appl. Phys. Lett: 86 (19): Art. No. 192112 (2005) Prestigiacomo M, Roussel L, Houel A, Sudraud P, Bedu F, Tonneau D, Safarov V, Dallaporta H, Studies of structures elaborated by focused ion beam induced deposition, Microel. Eng. 76 (1-4): 175-181 (2004)

[3]

P-EIBL12 - Electron and Ion Beam Lithography

MNE’06 Micro- and Nano- Engineering

Morphological and Electrical Study of FIB Deposited W Wires

Figure 1. SEM image of cross-section of deposited wires. The deposited stripes have a non-ideal rectangular shape.

Figure 2. SEM image and the V (I) curve of a single W wire with 300 nm width.


								
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