Mechanism of β-FeSi2 precipitates growth-and-dissolution and pyramidal defects' formation during oxidation of Fe-contaminated silicon wafers

Abstract

Fe-implanted Si-wafers have been oxidized at 900 °C and 1100 °C in order to investigate the behaviour of Fe atoms at the growing SiO2/Si interface and the impact on the integrity of microelectronic devices of an involuntary Fe contamination before or during the oxidation process. As-implanted and oxidized wafers have been characterized using secondary ion mass spectroscopy, atom probe tomography, and high-resolution transmission electron microscopy. Experimental results were compared to calculated implantation profiles and simulated images. Successive steps of iron disilicide precipitation and oxidation were evidenced during the silicon oxidation process. The formation of characteristic pyramidal-shaped defects, at the SiO2/Si interface, was notably found to correlate with the presence of β-FeSi2 precipitates. Taking into account the competitive oxidation of these precipitates and of the surrounding silicon matrix, dynamic mechanisms are proposed to model the observed microstructural evolution of the SiO2/Si interface, during the growth of the silicon oxide layer.

Redistribution of Metallic Impurities in Si during Annealing and Oxidation: W and Fe

“…Fe redistribution. The study of oxidation of Fe-implanted Si substrates allowed six steps in the Fe redistribution process to be determined [14]. Fig.…”

“…In a first part, a detailed study of W diffusion is presented, showing that W probably uses an original diffusion mechanism, involving interstitial W-Si self-interstitial pair diffusion [12]. In the second part, the mechanisms involved with Fe redistribution at the mobile SiO 2 /Si interface during Si oxidation are presented, allowing Si pyramidal defect formation at this interface [13] to be understood [14].…”

Evolution of secondary defects in arsenic implanted Si

“…With the rise of annealing temperature from T1A to T2A and further to T3A, more and more O atoms in the silica layer could diffuse into As-implanted Si region or into vacuum, which was already observed in the Fe-implanted samples. 23) Since Si atoms are bigger than O atoms, they are more stable than O atoms. The residual Si atoms in the silica layer could form Si NPs near the SiO 2 =Si interface.…”

“…The interface effect on the electrical activities of dopant atoms is still not clear though its effect on the distribution of dopant atoms was well documented. [21][22][23] The understanding of evolution of PR defects and the interface effect on dopant atom behaviors in RTA process is urgently needed.…”

Atomic redistribution of implanted Fe and associated defects around moving SiO2/Si interfaces

“…(b) In some cases, some other phases with higher Fe contents have also been observed, corresponding to advanced oxidation phases (Fig. 4): a detailed analysis of these precipitates will be found elsewhere [20].…”