Comparative Raman and Transmission Electron Microscopy Analysis of the Evolution of Platelet Defects in Plasma Hydrogena
- PDF / 542,682 Bytes
- 6 Pages / 596 x 842 pts (A4) Page_size
- 86 Downloads / 153 Views
COMPARATIVE RAMAN AND TRANSMISSION ELECTRON MICROSCOPY ANALYSIS OF THE EVOLUTION OF PLATELET DEFECTS IN PLASMA HYDROGENATED AND ANNEALED CZOCHRALSKI SILICON R. JOB*, M.-F. BEAUFORT**, J.-F. BARBOT**, A. G. ULYASHIN*, W. R. FAHRNER* * University of Hagen, P.O. Box 940, D-58084 Hagen, Germany ** University of Poitiers, F-86962 Futuroscope Chasseneuil, Cedex, France
ABSTRACT Standard p- and n-type Czochralski (Cz) silicon wafers were hydrogenated by a RF (13.56 MHz) hydrogen plasma at moderate temperatures (250 °C). After plasma hydrogenation and subsequent annealing up to 600 °C the formation and of H 2 molecules in voids and platelets was investigated by Raman spectroscopy. The Raman intensities of the H2 vibration modes at ∼ 4150 cm-1 exhibited significant intensity modulations in dependence on the annealing temperature. The intensities of the H2 Raman lines indirectly monitor the evolution of the voids and platelets upon annealing. This assumption was verified by cross-sectional transmission electron microscopy (XTEM), which was applied for comparison. The intensity modulations of the H 2 Raman signal can be explained by the evolution of the well known {111} and {001} platelets. At lower annealing temperatures (< 500 °C) platelets laying in {111} planes are dominant, while at elevated temperatures (> 500 °C) [001]-oriented platelets become more and more important. In addition in p-type material by XTEM also {110} platelets could be observed. 1. INTRODUCTION Recently, by Raman spectroscopy we have studied the evolution of H2 molecules in p- and n-type Czochralski (Cz) silicon wafers, which were treated by a hydrogen plasma at moderate temperatures (∼ 250 °C) and subsequent annealing up to 600 °C [1, 2]. Under the applied process conditions the H 2 molecules are probably be located in voids or platelets [3, 4], which are created in the wafers subsurface layers [5]. This can be concluded from the observed Raman shifts (RS) at about 4150 cm-1, which are nearly identical to those of gaseous H 2 molecules [6]. If the molecules would be located at the tetrahedral interstitial Td-site in the Si lattice, the corresponding RS should be observed at ∼ 3600 cm-1, as was reported in the literature [4]. We have demonstrated that the H2 Raman intensities at ∼ 4150 cm-1 exhibit some modulations with maxima at annealing temperatures around e.g. 350 - 400 °C and 500 -550 °C [1, 2]. Comparing our results with the temperature dependent evolution of platelets [7-9] we concluded that the observed modulations of the H 2 Raman intensities reflect peculiarities of the formation and dissolution of voids and platelets in hydrogenated silicon. In the present report we want to give a more deeper verification of this model assumption by a comparison of the experimental Raman results with cross-sectional transmission electron microscopy (XTEM). 2. EXPERIMENTAL The investigations were done on p- and n-type [001]-oriented Cz Si wafers (12 – 20 Ωcm and 1.8 – 2.6 Ωcm, respectively). RF hydrogen plasma treatments of Cz Si wafers were done in a PECVD
Data Loading...
