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Crystallinity-retaining removal of germanium by direct-write focused electron beam induced etching
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10.1116/1.3596563
/content/avs/journal/jvstb/29/4/10.1116/1.3596563
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/29/4/10.1116/1.3596563

Figures

Image of FIG. 1.
FIG. 1.

(Color online) Principle of etch sample preparation. (a) Chlorine is delivered to the Ge substrate surface by means of the GIS nozzle. No etching of the surface occurs at this stage. (b) The focused electron beam scans an area with dimensions . During the scanning of the focused electron beam, a local chemical reaction is triggered that creates volatile germanium chlorides which leave the surface (etching). The etch rate is determined by several etching parameters such as beam acceleration voltage, beam current or the chlorine gas flow. (c) After blanking the electron beam the local chemical reaction and therefore the Ge etching is stopped immediately, i.e., no spontaneous etching occurs by the still present chlorine gas flow.

Image of FIG. 2.
FIG. 2.

(Color online) SEM images [(a) and (b)] and AFM topography analysis [(c) and (d)] of an etch pit fabricated by focused electron beam induced etching of the Ge substrate. The etch pit has been etched using the standard parameter set defined in the experimental section (5 kV, 5.6 nA, dwell time: , pixel spacing: 9 nm, flow: 0.130 sccm). (a) 54°-tilted SEM micrograph (rotated by 90° clockwise with respect to all other illustrations), (b) top view SEM micrograph, (c) 3D AFM image, (d) cross-section deduced from AFM analysis along the yellow dotted line indicated in (b).

Image of FIG. 3.
FIG. 3.

(Color online) (a) Etched depth as a function of chlorine gas flow. All other etching parameters have been maintained as predefined in the standard parameter set in the experimental section. Also, the residual gas deposition volume is illustrated. The notation “standard parameters” indicates the accordance with the standard etching parameters. (b) Cross-sections deduced from AFM analysis through the center of three different etch pits, namely for gas flows of 0.01 sccm, 0.04 sccm and 0.13 sccm. In all cross-section graphs the light gray part (top) emphasizes positive values, while the dark gray part (bottom) shows the etched regions, i.e., below 0 nm. (c) SEM micrographs in 54°-tilted view of the etch pits.

Image of FIG. 4.
FIG. 4.

(Color online) (a) Etched depth (in the center of the processed area) as a function of electron beam probe current. All other etching parameters have been maintained as defined in the standard parameter set in the experimental section. Also, the volume of the deposition from residual gas is shown (“RG volume”). The notation “standard parameters” indicates the accordance with the standard etching parameters. (b) Cross-sections deduced from AFM analysis through the center of three different etch pits, namely electron beam currents of 59 pA, 482 pA and 1840 pA (at 5keV). The light gray part (top) emphasizes positive values, while the dark gray part (bottom) shows the etched regions, i.e., below 0 nm. (c) SEM micrographs in 54°-tilted view of the fabricated structures.

Image of FIG. 5.
FIG. 5.

(Color online) Effect of acceleration voltage on the etch process. (a) Etched depth as a function of electron beam energy. All other etching parameters have been maintained as defined in the standard parameter set in the experimental section. The notation “standard parameters” indicates the accordance with the standard etching parameters. (b) Cross-sections (deduced from AFM analysis) through the center of three different etch pits (for electron beam energies of 1 keV, 10 keV and 20 keV). As opposed to the variation of electron beam current and chlorine gas flow, none of the etch pits was surrounded by deposition from residual gas. (c) SEM micrographs in 54°-tilted view of the etch pits. The black dotted lines around the etch pits indicate the extent of SE2-triggered etching (see text for details). Note that the dimensions of each of the etch pits is .

Image of FIG. 6.
FIG. 6.

(Color online) Cross-sections deduced from AFM topography analysis through the center of two etch pits fabricated using the standard etching parameters. One of the pits was etched on an amorphous Ge film (solid, thick, black line) the other pit on a crystalline Ge wafer piece (solid, green, thin line). The etch duration for both etch pits was reduced to 10 min (compared to 20 min in previous experiments) due to the limited thickness of the amorphous Ge film of .

Image of FIG. 7.
FIG. 7.

(Color online) Topography of the bottom of two etch pits measured by AFM. The etch pits were fabricated by focused electron beam induced etching with chlorine on a monocrystalline Ge substrate (left) and a monocrystalline Si substrate (right). For the fabrication of both etch pits the same standard etching parameters have been used with a pixel spacing of 2.5 nm. The 2D images have been scaled such that they can be compared directly.

Tables

Generic image for table
TABLE I.

Comparison of Ge-FEBIE to Si-FEBIE.

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/content/avs/journal/jvstb/29/4/10.1116/1.3596563
2011-06-09
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Crystallinity-retaining removal of germanium by direct-write focused electron beam induced etching
http://aip.metastore.ingenta.com/content/avs/journal/jvstb/29/4/10.1116/1.3596563
10.1116/1.3596563
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