Laue X-ray diffraction studies of the structural perfection of Al-doped thermomigration channels in silicon

Abstract

Si(111) wafers patterned with an array of vertical 100 µm-wide Al-doped (1 × 1019 cm−3) p-channels extending through the whole wafer were studied by X-ray Laue diffraction techniques. The X-ray techniques included projection topography, and measurement of rocking curves and cross sections in the vicinity of the 02\overline 2 reciprocal space node in the double- and triple-crystal geometry, respectively. The channels are uniform along the depth of the wafer, and their structural perfection is comparable to that of the silicon matrix between the channels. Simulation of the rocking curves was performed using the methods of the dynamical theory of X-ray diffraction. The rocking-curve calculations both taking into account and neglecting the effect of the instrumental function were carried out using the Takagi–Taupin equations. The calculated angular dependences of intensities of both diffracted and transmitted X-rays correspond well to the experimentally obtained rocking curves and demonstrate their high sensitivity to the structural distortions in the channel. An unambiguous reconstruction of strain and structural distortions in the Si(Al) channel using the Laue diffraction data requires further development of the theoretical model.

High-resolution X-ray Bragg diffraction in Al thermomigrated Si channels

“…From these data we may conclude that the main relaxation of the elastic stresses at the Si(Al) channelmatrix border occurs near the wafer surface. This conclusion agrees with previous observations on the X-ray Lang projection topograms of characteristic half-loop dislocations in the matrix near the borders of a channel (Lozovskii et al, 2017;Lomov et al, 2021). The stresses induced by the incorporation of Al atoms into the crystal structure of the thermomigrated silicon channel are partially relaxed by increasing of the (111) interplanar distance in the subsurface layer of the channel.…”

“…= À B = 0 with an FWHM of w = 4.5 00 , $1.5 00 broader than the FWHM for the virgin wafer (w = 3.2 00 , theoretical value w = 2.64 00 ; Stepanov, 1997). This increase is a result of formation of dislocations in the matrix of the wafer, as proven with topographic observations of the channel (Lozovskii et al, 2017;Lomov et al, 2021). When the irradiated area approaches the channel, the width of the RC increases, the angular position of the maximum shifts to higher angles and a second maximum appears.…”

“…The samples were sequentially polished mechanically and chemomechanically before structural investigations. Details of the Si(Al) p-channel fabrication process, sample topograms and scanning electron microscopy micrographs of the surface have been published previously (Lomov et al, 2021).…”

“…Among these 3D structures, narrow thermomigrated p-channels extending through the semiconductor plate are promising elements for new high-power (Polukhin et al, 2006) and solar-power (Schmit & Gee, 2010) devices. Recently, thermomigrated Si(Al) p-channels in silicon wafers were studied by the high-resolution X-ray Laue diffraction technique (Lomov et al, 2021). The structural perfection of the vertical 100 mm-wide p-channels was comparable to that of the silicon matrix between the channels, despite possible distortions of the channel walls.…”

X-ray Laue diffraction by sectioned multilayers. I. Pendellösung effect and rocking curves

“…Only some laws of changes in the period of the structure allow analytical solutions; in particular, such solutions were previously obtained for crystals with quadratic (Kolpakov & Punegov, 1985) and exponential (Andreev, 2001) displacement fields, and crystals with a transition layer (Chukhovskii & Khapachev, 1985;Kato, 1990). In most cases, one has to limit oneself to the numerical solution of the Takagi-Taupin equations in an oblique coordinate system (Punegov, 2020;Lomov et al, 2021), for example, using the 'half-step derivative' method (Epelboin, 1985).…”