Dislocation formation related with high oxygen dose implantation on silicon

Abstract

The generation of dislocations in silicon implanted by oxygen (SIMOX) is studied by transmission electron microscopy. In an effort to separate the effects of displacement damage caused by ion implantation from the dynamic structural transformation which occurs due to the insertion of oxygen into the lattice, two special experiments were designed. The first consisted of a series of low dose oxygen implantations in which the energy was either ramped up or down in small steps. This served to expand the region in which oxygen was implanted, permitting a more detailed study of the defects. The second experiment involved the implantation of oxygen into a (111) wafer in order to study the influence of the crystallographic orientation on the generation of dislocations. Both experiments reveal the important role of the surface in the generation of dislocations. It is concluded that most of the threading dislocations are formed during the high-temperature anneal and have their origin in a defect-rich zone near the surface. These defects are attributed to Si-interstitial migration to the surface which results from the formation of SiO2. Consequently, epitaxial growth takes place on the surface and due to the growth defects generated there, dislocations are extended to the Si overlayer during the high-temperature annealing. Dislocations are also formed in the Si overlayer near the interface with the SiO2 buried layer. These dislocations are pinned by the SiO2 precipitates and are either consumed or dragged by them to the oxide interface during subsequent high-temperature annealing. The effect of surface contamination on the generation of dislocations in the early stage of implantation is discussed and factors which yield a better quality SIMOX material are presented.

Silicon on Insulator Obtained by High Dose Oxygen Implantation, Microstructure, and Formation Mechanism

“…48 The formation of these dislocations becomes evident after an HTA annealing in SIMOX implanted by a subcritical dose where a noncontinuous BOX layer is formed as shown in Fig. 8d.…”

“…Most of the existing defects at this zone are eliminated during the HTA because they are pinned by the growing SiO2 precipitates and finally annihilated at the St/BOX interface. 48 The formation of these dislocations becomes evident after an HTA annealing in SIMOX implanted by a subcritical dose where a noncontinuous BOX layer is formed as shown in Fig. 8d.…”

“…Implantation on (i00) and (Iii) Si wafers under similar conditions result in more than one order of magnitude higher dislocation density in the second case over the first. 48 The difference is attributed to the very slow incorporation of the Si~ at the (111) surface ~9 as well as to the low diffusivity of the Si~ along the <Iii> direction. 37 This difference results in the generation of a high density of growth defects at the uppermost of the Si overlayer and the development of high strain at the zone of the BOX as is evident from the cross-sectional micrographs in Fig.…”

“…Now, the first SiO2 precipitates which are formed close to the surface, block the access to the surface of Si I that are formed at greater depths as the energy of the oxygen ions is increased. 48 It has been shown recently that multienergy im-p l a n t a t i o n c a n result in a decrease of dislocation density? ~ However, m a n y Si islands are observed n e a r t h e S i O J s u bs t r a t e interface.…”

Raman microstructural analysis of silicon-on-insulator formed by high dose oxygen ion implantation: As-implanted structures

“…5 There are experimental proofs that relate the microstructure of the as-implanted layers and the density of defects remaining in the top Si layer after annealing to surface conditions during the implantation step since the characteristics of the surface determine its ability to accommodate the flux of interstitials coming from the oxidized region. 5,6 The surface features therefore, dramically influence the solid phase epitaxial ͑SPE͒ regrowth rate at the surface.…”