Dae-Seop Byeon

Residual stress analysis of 4H-SiC crystals obtained by a top-seeded solution growth method

The top-seeded solution growth (TSSG) method is an alternative technique for growing SiC which can reduce the defect levels in the crystal. With TSSG, the SiC crystal is grown on a SiC seed crystal attached to a seed shaft. The seed shaft is typically graphite; the mismatch in the thermal expansion coefficients between the materials induces residual stresses in the grown crystal. Furthermore, liquid droplets remaining on the grown SiC surface after crystal growth may contribute to residual surface stresses. Hence, in this study, we analyzed the residual stress of SiC crystals grown via the TSSG method, which has not yet been extensively studied. The surface stress was quantitatively evaluated using high-resolution X-ray diffraction (HRXRD) and Raman spectroscopy before and after the TSSG process. The dislocation distribution and crystalline quality were also characterized using synchrotron white beam X-ray topography (SWBXRT) and HRXRD. Many micropipes (MPs) were generated during the post-growth in the liquid droplets. The formation of these MPs was assumed to reduce the residual stresses on the crystal surface.

The Effect of Gate Length on Channel Strain of Recessed Source/Drain Si1-xCx

In this study, we experimentally evaluated the effects of scaling on the channel strain in terms of gate lengths. We used transistor arrays incorporating Si1-xCx as a stressor with systematically varying gate and source/drain lengths, and employed the NBD method to measure the channel strain. We also carried out simulation to check the validity of the NBD data.

PRAM 기록막용 Sb₂Te₃ 박막의 질소 첨가에 대한 영향

In this research, properties of N₂-doped Sb₂Te₃ thin film were evaluated using 4-point probe, XRD and AFM. Sb₂Te₃ material has faster crystallization rate than Ge₂Sb₂Te?, but sheet resistance difference between amorphous and crystallization state is very low. This low sheet resistance difference decreases sensing margin in reading operation at PRAM device operation. Therefore, in order to overcome this weak point, N₂ gas was doped on Sb₂Te₃ thin film. Sheet resistance difference between amorphous and crystallized state of N₂-doped Sb₂Te₃ thin film showed about 10⁴ times higher than Un-doped Sb₂Te₃ thin film because of the grain boundary scattering.