Physico-chemical study of the focused electron beam induced deposition process

The focused electron beam induced deposition process is a promising technique for nano and micro patterning. Electrons can be focused in sub-angström dimensions, which allows atomic-scale resolution imaging, analysis, and processing techniques. Before the process can be used in controlled applications, the precise nature of the deposition mechanism must be described and modelled. The aim of this research work is to present a physical and chemical description of the focused electron beam induced deposition process. As an introduction, a review of the literature, up to the present day, shows how this process was first identified as the origin of contamination in electron microscopes. Then the modifications made to a scanning electron microscope for deposition experiments are described. Gas supply systems and gas cryo-trapping devices were set up. Electrical and optical systems were constructed for an in-situ monitoring of the process. The experiment procedure was carried out in several phases, with the first being the deposition of flat films of carbon, copper-containing carbon composites, and pure gold for the study of the physics of the process. By measuring the fraction of the probe current that was absorbed in the sample, an accurate description could be made of the propagation of electrons. The backscattered electrons clearly influenced the deposition rate of Cu-containing films. A physical model for scanning deposition was created. The second phase is the deposition of metal-matrix composite tips from a stationary beam. Forward electron scattering was discovered to be responsible for tip formation and shape. A physical model of electron trajectories is included. The third phase is the construction of three-dimensional micro-structures by moving the beam during deposition. The deposited shapes result from an electron range that is larger than the structure size. Further investigation into the chemistry of the process involved the analysis of carbon films by micro-beam techniques. Regardless of the precursor used, the resulting films had a composition as C9H2±xO1±x (x<1). The C phase hybridization was 90% sp2. The elements H, N, O, F, and Cl were volatilized from the precursor during precursor fixation. Further parameters of deposition rate, temperature of the sample, vapour pressure, and the dipole moment of the precursors were examined. Electrically conductive metal-containing focused electron beam induced deposits were used for constructing micro-devices, a nanotube-based contact and a magnetic field sensor with 500 × 500 nm2 active area.

Hoffmann, Patrik
Lausanne, EPFL
Other identifiers:
urn: urn:nbn:ch:bel-epfl-thesis3321-5

 Record created 2005-08-31, last modified 2018-03-17

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