Microdefects in silicon different from swirls

Abstract

Two modifications of double crystal X‐ray topography are applied to detect microdefects in FZ silicon. With about 30 different crystals no contrasts from swirl defects are obtained. However, all the crystals contain defects not reported hitherto. Their dimensions are probably between (or below) 10 and 30 μm and their average density is 103 to 104 cm−3. According to preliminary TEM observations these are presumedly formed by precipitation colonies of an unknown phase. The size of the individual particles is ≦ 200 Å. X‐ray contrast seems to arise only if the defects are located not more than a pendellösung distance from entrance or exit surface. Earlier observations on X‐ray topographic contrast of swirls are discussed on the basis of these results.

Imaging of microdefects in silicon single crystals by plane wave X-r ay topography at asymmetric diffraction

“…A small difference in the volumes of interstitial atoms Si and 0 is not essential for our considerations. Electron microscopy observations will not reveal elastic distortions just near the precipitates similar to [2], whereas in X-ray topographic observations the precipitate colony will be revealed as a single defect of vacancy type.…”

Bragg Diffraction of X-Rays by Single Crystals with Large Microdefects I. Generalized Dynamical Theory

“…(32)), and the amplitude E a H can be found from the corresponding boundary condition D S (r) = E S (r)| z=0 by using the relations (33). When the approximation of the semiinfinite crystal is valid, i.e., the inequality m 0 t ) 1 holds, where m 0 is the linear coefficient of photoelectric absorption, only one wave field is remaining in the crystal, i.e., d ¼ 1 or 2 in dependence on the sign of Dq.…”

“…Moreover, the introduction of the cut-off parameter k c imposes an implicit restriction on the allowable value of the effective defect radius R eff which gives the upper bound of transfer momenta k m ¼ 2p/R eff in the Huang scattering region (k c k k m ), since the used kinematical model becomes inapplicable at R eff > L. In practice, however, as is known from the topographic observations [33][34][35], the sizes of microdefects in asgrown as well as annealed silicon single crystals can exceed appreciably the actual values of the extinction length in the case of Bragg diffraction and reach from several units to tens and even hundreds of micrometers. At sufficiently large concentrations they can contribute significantly to the diffuse scattering intensity.…”

The formation of plane-wave X-ray images of microdefects

“…The conditions for observation of such defects in electron microscopy (0 < 1, P = 0) qualitatively differ from those in X-ray topography (0 = 1, P > l), therefore the electron microscopy methods used for the determination of defect characteristics cannot be directly applied to X-ray topography. In particular, the large Bragg angle in X-ray diffraction results in the appearance of a dynamical wave (7) which generates a comet-like tail of the image [4] in the direction ( -g ) . I n Fig.…”