Characterization ofAIIIBVsuperlattices by means of synchrotron diffraction topography and high-resolution X-ray diffraction

New possibilities are presented for the characterization ofAIIIBVmixed superlattice compounds by the complementary use of synchrotron diffraction topography and rocking curves. In particular, using a synchrotron white beam and the section diffraction pattern of a 5 µm slit taken at a 10 cm film-to-crystal distance, it was possible to reproduce a set of stripes corresponding to interference fringes. These are analogous to the interference maxima revealed in high-resolution rocking curves, but are created by the changes in orientation of the planes inclined to the surface which are induced by unrelaxed strain. The section diffraction topographic method enabled examination of the sample homogeneity along the narrow intersecting beam. This was important in the case of the present sample containing a twin lamella in the InP substrate wafer. Both the section and projection Bragg case topographic methods enabled the crystallographic identification of the twin lamella. Another characteristic feature indicated in the section topography was the bending of the stripes corresponding to the superlattice peaks close to the boundaries of the twin lamella. The most probable interpretation of this phenomenon is an increase in the thickness of the deposited layers close to the lamella, together with possible changes in the chemical composition, leading to a decrease in the mean lattice parameter in the superlattice.

Correcting for Spherical Aberrations in Solid Immersion Microscopy Using a Deformable Mirror

We present a method for correcting spherical aberrations in solid immersion microscopy through the use of a deformable mirror. Aberrations in solid immersion imaging for failure analysis can be induced through off-axis imaging, errors in lens fabrication or mismatch of design and substrate wafer thickness. RMS wavefront error correction of 30% is demonstrated in the case of substrate wafer thickness error.

Contrast of Basal Plane and Threading Edge Dislocations in 4H-SiC by X-Ray Topography in Grazing Incidence Geometry

Dislocations in a substrate wafer of 4H-SiC with an epi-layer were observed using technique of monochromatic synchrotron X-ray topography in a grazing incidence geometry. Six different Burgers vectors of basal plane dislocations and threading edge dislocations were identified by changing the Bragg reflections, and by analysis of images of dislocation. We identify some relations of the Burgers vector and the dislocation contrast observed for g=11 2 8. Some of these relationships are discussed in this report.

Basal Plane Dislocation Dynamics in Highly p-Type Doped versus Highly n-Type Doped SiC

The long term performance of today’s SiC based bipolar power devices suffer strongly from stacking fault formation caused by slip of basal plane dislocations, the latter often originating from the n-type doped SiC substrate wafer. In this paper, using sequentially p-type / n-type / p-type doped SiC crystals, we address the question, whether basal plane dislocation generation and annihilation behaves differently in n-type and p-type SiC. We have found that basal plane dislocations are absent or at least appear significantly less pronounced in p-type doped SiC, which may become of great importance for the stacking fault problem in SiC.

Evaporation of Adherent Al-Films on Single Crystalline LiNbO3Substrates

LiNbO3is used as a single crystalline substrate material for the manufacturing of surface acoustic wave devices as frequency selective components. On the polished substrate wafer, Al with a film thickness of about 400 nm is evaporated in a high vacuum.The difficulties of the inadequate adhesion of the structured Al-film were eliminated by systematical investigations. Films that were adherent to the total surface could be prepared by evaporating an intermediate film of Cr or SiOxor, otherwise, a mixed film of Al with Si.An ultrasonic test for adhesion strength was developed that results in an assessment of local and also large-area film adhesion.