Kazunori Fukuda

Two-Dimensional Anisotropic Lattice Deformation Observed in a Commercially Available Strained-Si Wafer

The average and local lattice structures of a strained-Si layer and a SiGe layer epitaxially grown on a [001]-oriented Si wafer are evaluated by means of high-resolution X-ray diffractometry using a usual X-ray beam and a highly parallel synchrotron X-ray microbeam. Lattices in the constant composition of the SiGe (CC) layer are greatly disarranged mainly due to an anisotropic lattice tilt feature with respect to the [110] and [110] directions in the surface plane. Although the crystallinity of the strained-Si layer was found to follow directly that of lattice tilt variations in the CC layer, the lattice parameter of the strained-Si layer still has the expected value.

Formation of epitaxially ordered SiO2 in oxygen-implanted silicon during thermal annealing

The growth of epitaxially ordered SiO2 in oxygen-implanted silicon during thermal annealing was investigated. The implanted Si wafers were annealed for various durations at 1350°C. Diffraction streaks at 0.5 0.5 L (L∼1) of Si were observed from these samples. The intensity of the streak gradually increased with annealing time, while the peak position and the width of the streak did not change. Referring to these results, the growth of the buried oxide layers is discussed in terms of the ordered structure.

Observation of Lattice Undulation of Commercial Bonded Silicon-On-Insulator Wafers by Synchrotron X-Ray Topography.

Synchrotron X-ray topographs of silicon-on-insulator (SOI) layers of two kinds of commercial bonded SOI wafers were obtained; one is fabricated by transferring an epitaxial layer over porous Si, and the other is processed using hydrogen-delamination-induced splitting. For the 2-µm-thick SOI layer of the former wafer, the quasi-periodical contrasts were observed in the topographs, which indicate that the lattice plane of the SOI layer undulated at spatial intervals of about 20 µm with a tilt angle of the order of ten arc seconds. It was also evident from the granular pattern in the topographs that the undulation existed in the SOI layer of 100 nm thickness for both of the wafers.

Synchrotron X-Ray Topography of Lattice Undulation of Bonded Silicon-On-Insulator Wafers

Lattice undulation of Silicon-on-Insulator (SOI) layers of bonded SOI wafers was observed by synchrotron X-ray topography. Patterns observed on topographs depended on the thickness of the SOI layer, the camera distance between a specimen and an X-ray film, and the diffraction geometry of the Laue and Bragg cases. The dependence was interpreted as the effects of the geometrical relation in reciprocal space among the Ewald sphere, the reciprocal lattice vector, and the surface normal direction. To confirm the origin of the pattern formation, the topographic images were simulated in the framework of the kinematical diffraction theory. Based on the simulation, it was found that a granular pattern observed in the 115 Bragg case was due to the divergence/convergence effect of X-rays diffracted from the undulated SOI layer.

Large-Area X-Ray Topographs of Lattice Undulation of Bonded Silicon-On-Insulator Wafers

X-ray topographs of bonded silicon-on-insulator (SOI) wafers were obtained using a synchrotron large X-ray beam. Wrinkled patterns in a micrometer scale were observed all over the wafers. Crumpled patterns were also observed, which were related to the lattice undulation at the average spatial interval of about 6 mm with the tilt angle of the order of ten arcsec. From the comparison with the topographs between the SOI layer and the substrate, it was also found that the warpage of the lattice plane of the SOI layer was different from that of the substrate.

White X-ray Topography of Lattice Undulation in Bonded Silicon-on-Insulator Wafers

The lattice undulation of a silicon-on-insulator (SOI) layer in bonded SOI wafers was observed by synchrotron white and monochromatic X-ray topographies. Pattern formation for white X-ray topography was discussed using the geometric relation among the Bragg streak and diffracted X-rays in reciprocal space. The diffraction images in white X-ray topographs were simulated using the angular distributions of the lattice inclination in SOI layers obtained by the analysis of monochromatic X-ray topographs. The results of this simulation were in very good agreement with observations including the dependences on camera distance and SOI layer thickness, indicating that the contrast is mainly formed by the divergence/convergence effect of the diffracted X-rays.