Types Of Microdefects Research Articles

Metallographic and electron microscopical analysis of microdefects in Fz‐silicon crystals

AbstractIn dislocation‐free floating‐zone silicon crystals two types of microdefects were observed and analyzed by means of optical and electron‐microscopical methods. Microdefects of type I occur in swirl‐type arrangements throughout the whole wafer and appear as etch hillocks below which one can find second phase particles. Due to the chemical‐mechanical polishing near the wafer surface microdefects of type II are generated which also occur in spiral arrangements. These defects could be identified to be plate‐like vacancy agglomerates on {111} planes.

Structure of thermally induced microdefects in Czochralski silicon after high-temperature annealing

The microstructure of Czochralski silicon annealed at high temperatures has been investigated using high resolution transmission electron microscopy. After prolonged heat treatments at temperatures close to 1200 °C, two types of microdefects are observed: (a) small polyhedral oxide precipitates, with typical diameters of about 15 nm and facets along crystalline planes of the silicon matrix, and (b) planar faults along {111} planes which have been directly identified as extrinsic stacking faults bounded by Frank-type dislocations.

OBSERVATION ON “AS GROWN” MICRODEFECTS IN CZ SILICON SINGLE CRYSTAL

Two different type of microdefects have been observed by means of Cu-decorating X-ray topography and etching method in p-type silicon single crystal grown along and/or n-type ones grown along direction. A kind of defects with special configuration has also been found in n-type silicon single crystal. The distribution and configuration of these defects are discussed preliminarily.It was the first time to investigate the "as grown" microdefects in silicon single crystal grown by Czochraski method directly by means of X-ray transmission projection and/or section topography. X-ray topographs of microdefects in CZ silicon crystal were obtained. The configuration, size and distribution of the microdefects observed were in agreement with that obtained by Cu-decorating X-ray topography quite well.

The effect of doping on microdefect formation in as-grown dislocation-free Czochralski silicon crystals

The influence of p- and n-type doping on microdefect formation in macroscopically dislocation-free as-grown Czochralski silicon crystals has been studied using copper decoration, x-ray transmission topography, preferential etching, and high-voltage transmission electron microscopy. B-doped crystals are found to contain undecorated perfect dislocation loops of an interstitial nature. In Sb-doped crystals two other types of microdefects are present, one of which consists of a precipitate particle exhibiting a vacancy type of strain field. All defects are distributed in a striated pattern.

Microdefects and striations in dislocation-free LEC-GaP crystals

Dislocation-free GaP crystals grown by the liquid encapsulated Czochralski technique were characterized chiefly by the use of X-ray transmission topography and EBIC-mode scanning electron microscopy. Preliminary results obtained with transmission electron microscopy are also presented. X-ray topographs reveal a crystal inhomogeneity which is mainly attributed to the presence of non-stoichiometric striations. High densities (10 11-10 12 cm -3 of microdefects were detected, distributed both homogeneously and in a striated pattern. Various types of microdefects (perfect and faulted dislocation loops and (semi) coherent precipitates) were revealed. Although most microdefects are less than 1 μm across, significantly larger defects can form. Evidence for macroscopic dislocation generation due to point defect condensation is presented.

Microinhomogeneity Problems in Silicon

A survey evaluation of the quality of commercial silicon used in the preparation of p-n junction devices has been made, with emphasis on the detection and characterization of micro-inhomogeneities. The examination techniques included transmission electron microscopy, special etching techniques with optical microscopy, and microresistivity determination. These investigations have shown that almost all silicon produced by current commercial techniques has an appreciable concentration of microdefects, including precipitates and microcrystallographic defects, which are too small to be detected by conventional techniques. Furthermore the impurity distribution is inhomogeneous on a microscopic scale. These microinhomogeneities are frequently present in sufficient concentration to be more influential in determining the quality of the finished device than the material properties usually specified. Some suggestions are made concerning the establishment of standards of acceptability for the major types of microdefects and for developing simple, rapid evaluation procedures.