Structural and Chemical Microanalysis of Oxygen-Bearing Precipitates in Silicon

Abstract

Precipitation in CZ-silicon during post-growth two-stage heat treatment has been examined using the methods of high resolution analytical electron microscopy. Electron transparent specimens prepared from these specimens, exhibited a low density of plate type precipitates on {100} planes. Microdiffraction experiments showed the precipitates to be consistently non-crystalline. Electron energy loss spectra showed that the precipitates contained oxygen, but carbon was not detected. It was found that carbon artifact absorption edges could be induced in spectra by specimen contamination in the microscope. The use of a low temperature stage eliminated this problem. Complementary characteristic x-ray microanalysis showed that metallic impurities had not segregated to these precipitates in this particular case, although this has been observed elsewhere.

SiOx precipitate composition in Si, revisited: Discussion closed?

“…has similar dimensions as one studied by Kot et al and has a predicted average x of 1.22. This is in good agreement with the old EELS results on a precipitate with similar thickness and size . The reason that the old x ‐values determined with EELS differ significantly from the recent ones by Kot et al might be the larger probing electron beam diameters in the early days.…”

“…A more quantitative identification was not possible at that time due to TEM specimen preparation limitations. Some years later, using ion milling which allowed to prepare much thinner foils, EELS revealed x ‐values of 1.2 and 0.95 .…”

“…As SiO x precipitates can have both beneficial and detrimental effects on device characteristics and yield, oxygen precipitation has been studied intensively for more than half a century. Despite this long and intensive research effort, there is an ongoing discussion about the composition SiO x of the precipitates with reported x ‐values ranging between 1 and 2 . Two recent papers of the Kissinger group with high sensitivity and high lateral resolution measurements of oxygen distribution and binding in SiO x precipitates, give important clues to explain the apparent discrepancy between reported x ‐values.…”

Electron microscopy (nonbiological)

“…The solution to this problem appears to be in the use of the very much brighter field emission source. However the difficulties of maintaining the ultra-high-vacuum environment needed for such a gun on a normal TEM column have proved severe and only a few TEM instruments equipped with field emission guns have been used successfully (9).…”