Implantation Induced Filamentary Structures
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IMPLANTATION INDUCED FILAMENTARY STRUCTURES C. JAUSSAUD, B. MAILLOT, M. BRUEL LETI - COMMISSARIAT A L'ENERGIE ATOMIQUE 85 X, 38041 GRENOBLE CEDEX, FRANCE I Present address : IBM FRANCE 224, boulevard Kennedy, 91102 CORBEIL, FRANCE
ABSTRACT Heavy rare gases implantations have been performed in layered structures : Sb/In/Si bulk and Sb/Ga/Si bulk. Layer thicknesses lie in the range of 150 A - 600 A, ion doses in the range of 10 14 cm 2 - 10 16cm--2 Ion implantation induces in such structures a change in the visual aspect from a metallic appearance to a dark black aspect. This modification corresponds to the creation of voids with, as a consequence, the expansion of the structure. This effect is so important that even for low and medium doses, the structure becomes filamentary. Expansions as high as 2,8 pm have been measured. SEM photographs illustrate this spectacular effect. Relations between expansion and implantation parameters are given. A comparison between this effect and those observed in bulk InSb, GaSb and Ge is presented.
INTRODUCTION In order to study recoil implantation of Antimony, multilayers composed of a layer of Indium covered by a layer of Antimony were deposited onto silicon and irradiated with rare gases ions (1). The Indium was used as a marker. 14 2 For doses above 5 x 10 ions x cm- , implantation resulted in a blackening of the surfacePSEM observations of the surface showed a filamentary structure, with elevations of the surface up to 2,8 pm (2). Because of this unexpected effect implantationswere done in other bilayer structures : Ga/Sb, Ga/in, In/Se, Snw/b.
EXPERIMENTAL PROCEDURE Layers were deposited by vacuum evaporation, Joule heating was chosen for Antimony, electron bombardment for Indium evaporation. Both layers were denosited in or below 10- torr.
the same vacnum cycle at a pressure around
Layer thicknesses were monitored by a crystal oscillator. Implantations were performed on our facilities with current densities low enough to avoid any temperature effects. Scanning Electron microscopy was used to see the changes in structure and to measure the amount of swelling. RESULTS Structure of the deposited layer The deposited layer has a rough aspect (see photo n' 1). Mat. Res. soc. Symp. Proc. Vol. 27 (1984)DElsevier science Publishing Co.,
This rough
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aspect is due to the first (In or Ga) layer which does not form a continuous film, but which is composed of discrete In or Ga islands. The size of those islands is
a few thousand Angstroms.
0
Photo no 1 : 600 A Sb over 300 X In, non implanted. Effects of ion implantation The effects of ion implantation in such structures are described with the example of Xenon implanted into a 300 R thick Indium layer deposited on Silicon and covered with a 600 A thick Antimony layer (see fig. 1). The Xenon ions were implanted at 200 Key, which corresponds to Rp = 500
200Kev ions
/
//
S/b
Bulk Si
FIG. 1
For doses less than 1014 ions x cmobserved.
2
no change in the structure can be
At 3.1014 ions x cm-2 we observe a measurable i
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