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Physical properties of thin heteroepitaxial silicon films
Journal of Crystal Growth 9 (1971) 126 © North-Holland Publishing Co.
PHYSICAL PROPERTIES OF THIN HETEROEPITAXIAL SILICON FILMS
J. MERCEER Section Physique des Couches Minces, Laboratoire d’Electrostatique et de Physique du Metal, Cedex 166
The main objective of this paper is to demonstrate the capabilities of various but only specific physical tools for studies on epitaxy. It does not cover diffraction methods which are indeed of very common use. Silicon epitaxial films on ce-alumina substrates, grown from pyrolysis of silane at high temperatures (‘~1000 °C) are considered. This example is representative of cases where, on the one hand, chemical interaction between film and substrate is important and, on the other hand, the substrate cannot be easily removed from the film, I) X-ray surface topography1): the Lang disposition (simultaneous movement of the sample and the plate) has been modified for a reflection position. The main applications of this non-destructive method are the examination of: a) substrate surfaces after various treatments (mechanical or chemical polishing, heat treatment in inert atmosphere), b) the interfaces between either film—atmosphere or film—substrate. 2) Scanning electron microscopy2): but for insulating layers, this method is easier to perform than electron microscopy replicas. This technique is particularly useful for nucleation studies. We have determined the density and shape of the silicon nuclei under various conditions of time and atmosphere. •
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Grenoble, France
3) Electron microscopy replicas2): the observation of the Si film—substrate interface (with a discontinuous film) after selective removal of the film allows the visualisation of chemical interaction between film and substrate during deposition. 4) Ion probe2): chemical analysis of all elements is made from the emission of characteristic ions ejected from the ion-sputtered film. The impurity profile is determined with a 100 A resolution. For example, oxygen and aluminium are formed in thin layers, especially at the film—substrate interface. Some problems remain for a quantitative study. 5) Infrared spectroscopy’): this non-destructive method has been used for the same purpose as for the preceding method. But the sensitivity is limited to thicker layers (> I .tm). The analysis is based upon characteristic absorption lines of Si-impurity bonds which are obtained in an attenuated total reflection (A.T.R.) position. The sensitivity is highly increased by means of multiple reflections, but the interpretation of the results is not straightforward. References I) J. Mercier, J. Electrochem. Sac. 117 (1970) 812. 2) J. Mercier, Results presented at the Electrochem. Soc. Meeting, Los Angeles, May 1969.
II.A. 2
PHYSICAL PROPERTIES OF THIN HETEROEPITAXIAL SILICON FILMS
J. MERCEER Section Physique des Couches Minces, Laboratoire d’Electrostatique et de Physique du Metal, Cedex 166
The main objective of this paper is to demonstrate the capabilities of various but only specific physical tools for studies on epitaxy. It does not cover diffraction methods which are indeed of very common use. Silicon epitaxial films on ce-alumina substrates, grown from pyrolysis of silane at high temperatures (‘~1000 °C) are considered. This example is representative of cases where, on the one hand, chemical interaction between film and substrate is important and, on the other hand, the substrate cannot be easily removed from the film, I) X-ray surface topography1): the Lang disposition (simultaneous movement of the sample and the plate) has been modified for a reflection position. The main applications of this non-destructive method are the examination of: a) substrate surfaces after various treatments (mechanical or chemical polishing, heat treatment in inert atmosphere), b) the interfaces between either film—atmosphere or film—substrate. 2) Scanning electron microscopy2): but for insulating layers, this method is easier to perform than electron microscopy replicas. This technique is particularly useful for nucleation studies. We have determined the density and shape of the silicon nuclei under various conditions of time and atmosphere. •
.
—
Grenoble, France
3) Electron microscopy replicas2): the observation of the Si film—substrate interface (with a discontinuous film) after selective removal of the film allows the visualisation of chemical interaction between film and substrate during deposition. 4) Ion probe2): chemical analysis of all elements is made from the emission of characteristic ions ejected from the ion-sputtered film. The impurity profile is determined with a 100 A resolution. For example, oxygen and aluminium are formed in thin layers, especially at the film—substrate interface. Some problems remain for a quantitative study. 5) Infrared spectroscopy’): this non-destructive method has been used for the same purpose as for the preceding method. But the sensitivity is limited to thicker layers (> I .tm). The analysis is based upon characteristic absorption lines of Si-impurity bonds which are obtained in an attenuated total reflection (A.T.R.) position. The sensitivity is highly increased by means of multiple reflections, but the interpretation of the results is not straightforward. References I) J. Mercier, J. Electrochem. Sac. 117 (1970) 812. 2) J. Mercier, Results presented at the Electrochem. Soc. Meeting, Los Angeles, May 1969.
II.A. 2