Minya Ma

Study on defects in EMCZ-Si crystal by infrared light scattering tomography

Electromagnetic Czochralski method is newly developed to grow CZ-Si crystal, thus crystals obtained by this technique are called as the EMCZ-Si crystal. Defects in the EMCZ-Si crystals were, for the first time, studied by multi-chroic infrared light scattering tomography. The dislocation lines located on a few crystallographic planes along different directions were observed at the local positions in the crystal by a method of layer-by-layer tomography. Because the defect character in the EMCZ-Si crystal and the V/G ratio (V the growth rate, G the axial temperature gradient) used to grow this crystal are similar to those of the CZ-Si crystals grown under three different cusp magnetic field configurations, the defects in the EMCZ-Si crystal are also thought to be of the interstitial-type, which further agglomerated to form dislocation lines and/or dislocation clusters. The bases of announcing the defect to be the interstitial-type have been explained in the present and other reference papers.

Piled-up dislocations in a vapour-phase-grown ZnSe crystal

Abstract A new structure of piled-up dislocations, called a dislocation wall, was observed by light-scattering tomography (LST) for the first time on some {111} planes in a ZnSe crystal grown by a vapour phase method. The walls are flat platelets, about 10–15 μm in thickness, where many dislocations are randomly and abnormally piled up. Other characteristics of the dislocation walls observed by LST were studied by molten KOH etching and the cathode-ray luminescence (CL) mode of scanning electron microscopy (SEM). Many other dislocation lines were also clearly observed outside of the walls by LST and CL SEM.

Relationship between characteristics of defects in CZ-Si crystals and V/G ratios by multi-chroic infrared light scattering tomography

Czochralski silicon (CZ-Si) crystals were grown using different V=G ratios (V: growth rate, G: axial temperature gradient) of 0.23 mm 2 /1C min and 0.38 mm 2 /1C min, respectively, while the axial temperature gradient near the melt– crystal interface was measured by a thermocouple of differential type developed recently. Defects in the grown crystals were systematically investigated by multi-chroic infrared light scattering tomography (MC-IR-LST) to experimentally identify the relationship between the characteristics of defects in the CZ–Si crystals and the V=G ratios. High defect density was detected in the CZ-Si crystal grown under a V=G ratio of 0.38 mm 2 /1C min, in which the density distribution of defects along the crystal growth direction obviously fluctuated. The highest defect density existed in the middle region of the crystal while lower defect density was seen in the top area. No defect was detectable by the MC-IRLST system in the CZ-Si crystal grown under the V=G ratio of 0.23 mm 2 /1C min. The type of grown-in defects in the CZ-Si crystal grown under the V=G ratio of 0.38 mm 2 /1C min was the vacancy agglomeration based on the result of photoluminescence detection and the V=G ratio used for crystal growth. r 2002 Published by Elsevier Science B.V.

Study of Inhomogeneous Radial Distribution of Defects in As-grown and Annealed Czochralski Silicon Crystals by Multi-chroic Infrared Light Scattering Tomography.

Multi-chroic infrared light scattering tomography (MC-IR-LST) and transmission electron microscopy (TEM) were used to systematically investigate the inhomogeneous radial distribution of defects in as-grown and annealed Czochralski silicon (CZ-Si) crystals. A new defect morphology of dark stripes observed for the first time by the MC-IR-LST system in a special region in the as-grown CZ-Si crystal. After annealing the crystal at 1150°C for 16 h in an O2 atmosphere, dark stripes that became scattered in width and deep in contrast were clearly visible in an OSF-ring area. The location of these stripes in the as-grown crystal coincided with that in the annealed CZ-Si crystal, where many stacking faults and oxygen-precipitate-related polyhedral defects were revealed by TEM analysis. This means that the dark stripes were generated during crystal growth as original grown-in defects. Quantitative measurement of the inhomogeneous radial distribution of defects in the annealed crystal was made and the characteristics of the defects in different regions of the crystal were analytically discussed.

Study of the Characteristics of Defects in the Oxidation-induced Stacking Fault-Ring Area in Czochralski Silicon Crystals by Multi-chroic Infrared Light Scattering Tomography and Transmission Electron Microscopy

A new defect morphology of dark stripes was observed in both as-grown and annealed Czochralski silicon (CZ-Si) crystals by photoluminescence (PL) mapping of a multi-chroic infrared light scattering tomography (MC-IR-LST) system. The dark stripes in the as-grown CZ-Si crystal are believed to be highly decorated striations, where grown-in defects have inhomogeneously segregated during the crystal growth. When this crystal was annealed at 1150°C for 16 h in an O2 atmosphere, defects such as stacking faults, oxygen-precipitate-related polyhedral defects, impurities and dislocation loops were observed around the dark stripes in the oxidation-induced stacking fault (OSF)-ring region using transmission electron microscopy (TEM) and the MC-IR-LST system. Investigation results suggested that the main grown-in defects around dark stripes were oxygen precipitate nuclei and vacancy-related nuclei, which resulted in the formation of such defects during the thermal oxidation process.

Observation of the morphology and displacement of dislocations in vapour phase grown ZnSe crystals

Abstract Dislocation walls on {111} and {110) planes in vapour phase grown ZnSe crystals were studied by light scattering tomography (LST), the cathodoluminescence mode of scanning electron microscopy (CL-SEM) and molten KOH etching. Many Y shaped nodes and hexagonal nets of dislocation lines caused by reactions between the lines were clearly observed on (111) planes by LST, although many dislocations of irregular shape and some parallel arrangements of dislocations were also found. Slip lines on (111) planes were clearly observed as dark lines by CL-SEM which allowed the determination of dislocation glide planes. Undecorated dislocations and slip lines were difficult to observe by LST in these crystals of high refactive index. The dislocations constituting the main part of the dislocation walls and Y shaped nodes were immobile even when the stress was increased sufficiently to fracture the specimen, while some of the other dislocations were displaced.

Analysis of extended defects in nitrogen annealed CZ silicon by optical and electron beam methods

The effect of annealing in nitrogen atmosphere on the formation of crystal defects in the OSF-ring of Czochralski silicon has been studied by comparison with samples annealed in oxygen atmosphere by using optical and electron beam based methods. By annealing in nitrogen the formation of extrinsic stacking faults is prevented whereas oxygen precipitates form in nearly the same density as in the oxygen annealed sample. Additionally, loop-like microdefects were generated that were not observed for annealing in oxygen ambient. The results are explained by assuming that extra vacancies are introduced into Si from the nitrogen annealing atmosphere. They are expected to recombine with Si interstitials, thus preventing the growth of the stacking faults, and to create the observed microdefects.

Study on defects in CZ-Si crystals grown by normal, cusp magnetic field and electromagnetic field techniques using multi-chroic infrared light scattering tomography

Three different Czochralski (CZ) techniques, referred to as normal, cusp magnetic field (CMF) and electromagnetic field (EMF) methods, were used to grow CZ-Si crystals, respectively. The behavior of defects in these grown CZ-Si crystals was systematically investigated by a new defect detection method of multi-chroic infrared light scattering tomography. Research results showed that the defect density and its distribution in three types of CZ-Si crystal were obviously different due to the different physical conditions, such as molten silicon flow in the crucible and temperature fluctuation in the melt during the crystal growth. Since lower defect density was experimentally observed in the CZ-Si crystals grown under an inside CMF configuration and electromagnetic field, both are considered as useful techniques to grow CZ-Si crystal with these features.

Observation of defects in a C3N4/diamond/Si structure by infrared light scattering tomography

A structure of C3N4 and diamond multilayers on Si(100) substrate was prepared by plasma enhanced chemical vapour deposition and magnetron sputtering techniques. Morphology observation and chemical composition analysis of the structure were performed by scanning electron microscopy and energy dispersive x-ray analysis. The multilayers of C3N4 and diamond on Si substrate were clearly observed and the composition ratio of nitrogen to carbon was close to 1.33. Defects in this structure were, for the first time, investigated by infrared light scattering tomography. Most defects in C3N4 and diamond multilayers were introduced by an extended growth of the original defects in Si substrate determined through layer-by-layer tomography. The defect type is analytically discussed.

Measurement of Stress near Dislocation Walls in a ZnSe Signal Crystal by Raman Scattering Tomography

Intensity and wavenumber of the transverse optical (TO) and longitudial optical (LO) modes of Raman peaks were respectively measured as a function of distance from a dislocation wall in a ZnSe single crystal grown by vapor phase method. The peak intensity of the LO mode was increased but that of the TO mode was decreased with distance from the wall, while wavenumber of the LO mode peak was clearly decreased with distance. According to the scattered light intensity against polarization configuration, it is concluded that there is no twinning across the wall. Wavenumber of the LO mode peak was qualitatively measured as a function of distance from the wall center, and a compressive stress in the matrix was introduced along the wall. This stress was numerically estimated as 1×108 N/m2 in the dislocation wall.