4H-SiC Epi-Ready Substrate Qualification by Using Mirror Electron Microscope Inspection System

Crystal damage beneath the surface remaining after chemo-mechanical polishing (CMP) and basal plane dislocations (BPDs) of 4H-SiC epi-ready substrates have been inspected by using a mirror electron microscope inspection system non-destructively. Distributions of crystal damage and BPDs as well as their average densities are estimated by acquiring 80-μm square mirror electron images at positions distributed with an equal pitch over a substrate (“Discrete point set inspection”). Although the total inspected area is less than 1% of the entire substrate area, the inspection results for nine commercially available wafers reveal that there are large differences in surface polishing quality and BPD density between them. Evaluation on an epitaxial layer with a thickness of 10 μm grown on one of the inspected substrates indicated that correlation between distribution of the crystal damages on the substrate and that of bunched steps on the epitaxial layer surface.

Фоторазрушение субмикронных кристаллов DAST в пленке PMMA путем прямой лазерной записи

Selective photobleaching of DAST ( trans -4'-(dimethylamino)-Nmethyl-4-stilbazolium tosylate) non-linear crystals in a 2-μm-thick polymethacrylate film using direct laser writing at a wavelength of 532 nm at a power of 1–10 mW and a recording speed of 5–35 μm/s is studied. The laser pattern is established as a function of recording parameters. The destruction of crystals and their transition into the amorphous state enabled one to record a structure that is well resolved in the optical microscope and in the luminescence signal. No layer surface violation at the crystal damage sites is detected. The method ensures the formation of a grating with a periodic modulation of the nonlinearly optical coefficient, which is essential in the quasi-phasematching generation.

An Electrical and Physical Study of Crystal Damage in High-Dose Al- and N-Implanted 4H-SiC

In this paper, an investigation into the crystal structure of Al-and N-implanted 4H-SiC is presented, encompassing a range of physical and electrical analysis techniques, with the aim of better understanding the material properties after high-dose implantation and activation annealing. Scanning spreading resistance microscopy showed that the use of high temperature implantation yields more uniform resistivity profiles in the implanted layer; this correlates with KOH defect decoration and TEM observations, which show that the crystal damage is much more severe in room temperature implanted samples, regardless of anneal temperature. Finally, stress determination by means of μRaman spectroscopy showed that the high temperature implantation results in lower tensile stress in the implanted layers with respect to the room temperature implantation samples.