Degradation of dielectric breakdown field of thermal SiO2 films due to structural defects in Czochralski silicon substrates

Abstract

We used heat treatment to intentionally introduce various structural defects in Czochralski silicon substrates. The type, size, and number density of the induced defects were surveyed with transmission electron microscopy, and the defects were then incorporated into SiO 2 films ͑10-50 nm thick͒ during thermal oxidation in dry O 2 . The effect of the defects on dielectric strength of the SiO 2 films was examined with a time zero dielectric breakdown method. Larger platelet oxygen precipitates caused greater decreases of the breakdown field, and precipitates smaller than the SiO 2 film thickness did not appreciably reduce the breakdown field. Every large platelet oxygen precipitate incorporated in the SiO 2 film caused a degradation. Octahedral oxygen precipitates caused little degradation. The breakdown field was higher than 7 MV/cm and did not depend much on the SiO 2 film thickness and precipitate size. We discussed possible mechanisms for the degradation due to both kinds of precipitates. Oxidation-induced stacking faults formed by a surface oxidation did not markedly reduce the breakdown field when only segments of dislocations and stacking faults were incorporated in the SiO 2 film. Another serious degradation was caused by pits that were formed by dissolving octahedral oxygen precipitates in a HF solution. The breakdown field was lower for thicker oxide films, and it recovered as the pit shape became smoother during chemical etching. We proposed that this degradation was caused by a local thinning of SiO 2 film due to stress generated in the oxidation of pits. These results suggest that voids rather than the other reported grown-in defects play the most important role in the degradation observed for as-grown silicon.

Machine Learning Assisted Predictions of Intrinsic Dielectric Breakdown Strength of ABX3Perovskites

“…The dielectric breakdown process is a highly complex phenomenon that represents an example of a “weakest link” problem. Breakdown strength of a material derives its contributions from both intrinsic − (i.e., dictated purely by chemical constituents, details of the crystal structure, and nature of the chemical bonding) and extrinsic − (i.e., defects, impurities, morphology, interfaces, field-induced aging, and degradation) factors. While a precise quantification of the role played by various extrinsic factors in determination of the dielectric breakdown is still beyond the current state-of-the-art, recently implemented quantum mechanical methods for the calculation of electron–phonon scattering rates have allowed for a completely first-principles quantitative determination of the intrinsic breakdown field of any insulator .…”

Oxide Wearout, Breakdown, and Reliability

“…Breakdown is initiated in the vicinity of defects in the oxide, whether these defects are intrinsic or extrinsic. Thus, breakdown can also be triggered either by impurities in the oxide [267][268][269][270][271][272][273][274][275] or by imperfections or impurities in the substrate silicon [276][277][278][279][280][281][282][283][284][285]. The breakdown patterns observed in oxides due to structural defects in the substrate are similar to the defect patterns observed in silicon vidicons due to defects in the substrates [286].…”

Oxide Wearout, Breakdown, and Reliability

“…Breakdown is initiated in the vicinity of defects in the oxide, whether these defects are intrinsic or extrinsic. Thus, breakdown can also be triggered either by impurities in the oxide [267][268][269][270][271][272][273][274][275] or by imperfections or impurities in the substrate silicon [276][277][278][279][280][281][282][283][284][285]. The breakdown patterns observed in oxides due to structural defects in the substrate are similar to the defect patterns observed in silicon vidicons due to defects in the substrates [286].…”