Advances in the Understanding of Oxide Precipitate Nucleation in Silicon

Abstract

The influence of vacancy supersaturation installed by RTA pre-treatments in CZ silicon wafers on oxide precipitate nucleation was investigated in the temperature range 700-1000 {degree sign}C. Precipitation is enhanced at 800 {degree sign}C and increases with increasing vacancy concentration. Getter efficiency tests for Cu and Ni have shown that the threshold value of the normalized inner surface is shifting to higher values for increasing RTA temperature. This can be explained by a morphological change of the oxide precipitates with increasing vacancy concentration from plate-like to spherical shape.

Comparison of Evaluation Criteria for Efficient Gettering of Cu and Ni in Silicon Wafers

“…The shifting of S crit is more emphasized if we look on the samples with different concentration of vacancies. In our previous work (6), we plotted the getter efficiency for Cu and Ni as a function of the normalized inner surface for samples annealed for 4 h and 8 h with different concentration of vacancies. The value of S crit increased with increasing vacancy concentration as shown in Fig 9 . The explanation for such a behavior could be a change in the morphology of the oxygen precipitates caused by the RTA pre-treatment.…”

“…The value of S crit increased with increasing vacancy concentration as shown in Fig 9 . The explanation for such a behavior could be a change in the morphology of the oxygen precipitates caused by the RTA pre-treatment. Assuming that oxygen precipitates after RTA pre-treatment at 1250 °C are spheres, we calculated the aspect of ratio for other vacancy concentrations (6). These results indicate the problems which can be met if we want to assign the gettering threshold by the total inner surface criterion.…”

“…This transformation rate strongly depends on the oxygen concentration, density of growing precipitates and the growth temperature (4). Kot et al investigated the influence of oxygen and vacancies on the efficient gettering of Cu and Ni (5) and Kissinger et al considered the influence of the aspect ratio β on the efficient gettering of Cu and Ni showing that different RTA pretreatments influence the getter efficiency by changing the aspect ratio of the precipitates (6). Despite, these publications provide a lot of information about gettering of metal impurities they also show that it is difficult to precisely assign the threshold for efficient gettering of metal impurities.…”

Influence of Cu Concentration on the Getter Efficiency of Dislocations and Oxygen Precipitates in Silicon Wafers

“…In our previous works, we obtained different threshold levels depending on the temperature of the RTA pre-treatment. We tried to explain this phenomenon assuming differences in the morphology of the oxygen precipitates which depends on the temperature of the RTA pre-treatment [27,28]. However, the morphology does not depend on the temperature of the RTA pre-treatment as we observed by STEM later.…”

Impact of RTA on the Morphology of Oxygen Precipitates and on the Getter Efficiency for Cu and Ni in Si Wafers

“…The model presented in Ref. [5] allows us to explain the shift of the threshold values of the normalized inner surface by assuming the shape of oxygen precipitates as oblate spheroids.…”