L. Csepregi

Substrate‐orientation dependence of the epitaxial regrowth rate from Si‐implanted amorphous Si

Amorphous layers, approximately 4000 A thick, were formed on single‐crystal Si samples by implantation of 28Si ions at LN2 substrate temperature. Channeling‐effect measurements with MeV 4He ions were used to measure the thickness of the amorphous layers and to measure the subsequent epitaxial regrowth on the underlying crystalline substrates. For annealing temperatures between 450 and 575 °C, the growth rate showed a strong dependence on the substrate orientation with 〈100〉‐oriented samples exhibiting about a 25 times higher growth rate than 〈111〉‐oriented samples. Measurements of the growth rate on a series of samples cut in 5° angular increments show that there is a monotonic decrease from the 〈100〉 to the 〈111〉 orientation. A simple model is proposed to explain the observed orientation dependence.

Reordering of amorphous layers of Si implanted with 31P, 75As, and 11B ions

The effect of impurities on the epitaxial regrowth of Si from amorphous layers created by ion implantation into 〈100〉 and 〈111〉 Si was studied by channeling effect measurements with 2‐MeV 4He ions. The Si wafers were first implanted at −180 °C with 28Si ions to form amorphous layers approximately 4000 A thick and then were implanted with 31P, 75As, or 11B ions to concentration levels of about 0.2–0.5 at.%. For these layers with impurity species the growth rate is found to be significantly higher than for those without. The measured regrowth rate at 500 °C for 〈100〉 Si with an impurity concentration of ∼2×1020 cm−3 of 31P or 75As is a factor of 6 greater, and of 11B a factor of 20 greater, than the regrowth rate in amorphous layers without impurities. For the case of 31P implanted 〈100〉 Si the activation energy of regrowth is close to that (2.35 eV) found for impurity‐free amorphous layers and for 11B implanted samples the energy is 1.9 eV. For 〈111〉 31P implanted Si specimens there is an increase in growt...

Influence of 16O, 12C, 14N, and noble gases on the crystallization of amorphous Si layers

Channeling effect measurements have been used to study the effect of impurities on the epitaxial regrowth of amorphous silicon layers on single‐crystal silicon. Implantation was used to form the amorphous layers and also to introduce the impurities 12C, 14N, 16O, 20Ne, 40A, and 84Kr. For 16O implants, the growth rate at 550 °C depended on the 16O concentration and at the level of 0.5 at.% the rate was reduced from about 90 to about 10 A/min. For similar atomic concentrations of 14N, the rate was comparable to the 16O case. For comparable concentrations of 12C, the regrowth rate was found to be three times higher than for that of the 16O case. Noble gas ions are also found to retard the growth rate of the amorphous layers. For 40Ar at about the 0.5‐at.% level, the regrowth rate is appreciably slower than even that for the 16O case.

Regrowth kinetics of amorphous Ge layers created by 74Ge and 28Si implantation of Ge crystals

Abstract Epitaxial regrowth of ion-implanted amorphous Ge on the underlying crystal substrate occurs between 300 to 400°C with an activation energy of 2.0 eV and a rate of 100A/min on Ge at 350°C. The regrowth rate is strongly dependent on the orientation of the underlying Ge crystal. The regrowth behavior of amorphous Ge is similar to that of implanted amorphous Si.

Disorder produced by high‐dose implantation in Si

Channeling measurements with MeV 4He ions were used to investigate the disorder distributions produced in 〈111〉 and 〈100〉 Si samples by implantation at substrate temperatures from −180 to 300 °C. The results indicate that for high implantation doses (1015–1016 ions/cm2) a deep stable disordered region is present in both orientations for the samples implanted at temperatures above room temperature but is absent for room‐temperature and lower implants. The colors that have been observed on the surface of samples with similar implants are found to be correlated with the thickness of a thin crystalline layer at the surface.

An electron microscopy study of defect structures in recrystallized amorphous layers of self-ion-irradiated 〈111〉 silicon

Abstract The defect structures remaining in a recrystallized amorphous layer of self-ion-irradiated 〈111〉 silicon have been examined by transmission electron microscopy. This study was performed in collaboration with an investigation by nuclear back-scattering-dachannelling techniques, and these results are reported in a companion paper. The residual defect microstructure for all three annealing treatments was dominated by regions twinned about the three {111} planes inclined to the (111) substrate. The volume occupied by these twins was about 30-40%. The regrowth of the amorphous layer could be subdivided into two depth zones, one near the substrate interface with a high density of small twins and another extending to the surface with a low density of large twins. Twins formed about the (111) plane parallel to the surface did not have a significant role except at the highest temperature of annealing, namely 950°C. In this case the volume occupied by these twins appeared to be much the same as for any one...

Dechannelling of MeV He ions by twinned regions in implanted Si crystals

Abstract Channelling-effect measurements with MeV 4He ions have been made in 23Si implanted and annealed (111)-oriented Si crystals. The bombarding dose and energies were chosen to produce a 4500 A amorphous layer. After annealing and recryatallization, there is a high concentration of twinned regions lying on the three {111} planes inclined to the (111) surface. For particles channelled along a 〈111〉 axial direction in the host crystal, the inclined twins have a lattice with 〈115〉 orientation, and consequently the particles have a dechannelling rate which is an order of magnitude higher than along the original 〈111〉 directions. For disorder analysis the dechannelled fraction is evaluated using a linear combination of dechannelling in the host and twinned lattices, weighted by the volume concentration of each. The depth distribution of disorder obtained by this method agrees with that determined by layor-removal techniques. When the twinned regions are misoriented with respect to the host lattice by angle...

Dechanneling by twins

Abstract Twinned regions in Si exhibit enhanced dechanneling and narrower critical angles than the host crystal. MeV 4He backscattering spectra along in twinned Si can be interpreted on the basis of additive contributions from host and twinned lattices.

The early history of solid phase epitaxial growth

Abstract Scientific sub-communities are usually following their own logic, their own language, and very often escape to notice the work almost in parallel from other groups. At a certain point and in a great moment, however, they suddenly recognize and fertilize each others thinking. The onset of the work on solid phase epitaxial growth (SPEG) of layers amorphized by ion implantation was such a moment. It was a catalyst to bring closer and to proceed toward unified thinking between the implantation community, which was composed of people with very different backgrounds, e.g. researchers in epitaxy, in thermodynamics of the solid state, in radiation defects, and in many other areas. The idea of dual implantation, though disputed recently when the production of 70 nm and shallower junctions is at stake, still remains an industrial practice. The practice of the ‘thermal history’ and double annealing, etc., became crucial in the development of todays semiconductor fabrication technology such as ‘defect engineering’. Although superiority of oxide-silicon interface grown on (100) oriented silicon was the major driving force in motivating the industry to switch overwhelmingly to wafers of that orientation, we tend to believe that the results on SPEG also added a non-negligible push. Facts learned when studying SPEG assist in the development of the basics of molecular beam epitaxy (MBE) as well.

Electron irradiation assisted annealing of boron and phosphorus implanted silicon layers

Abstract Radiation annealing due to a 1.0 MeV election beam of intensity 25 μA/cm2 was studied in silicon samples implanted with phosphorus and boron ions and annealed at 350–500°C. A significant annealing enhancement as compared to thermal annealing has been observed in phosphorus-implanted samples. In boron-implanted samples, a fast initial rise of electrical activity is followed by a continuous decrease of carrier concentration. The results are interpreted in terms of two competing processes: electron irradiation induced removal of post-implantation defects and introduction of simple electrically active defects.