E. F. Kennedy

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.

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...

Solar furnace annealing of amorphous Si layers

We demonstrate that a simple Al solar reflector can be used to induce solid-phase epitaxy of amorphous Si layers obtained either by ion-implantation or ion-deposition techniques. The annealing can be accomplished in air and takes a few seconds for a 1-cm^2 sample area. For ion-implanted samples, the regrown layers are defect free on substrates, and contain microtwins on substrates. For deposited layers on substrates the degree of epitaxy is not as good as that obtained by furnace annealing (550 followed by 950°C annealing).

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 effect of twins on dechanneling a charged particle beam

Abstract We have used implanted and annealed Si to evaluate the influence of twin structures (extended defects) on dechanneling rates. Transmission electron microscopy measurements showed the presence of twins lying along {111} planes. Calculations and experimental measurements show that the primary contribution of twinned regions is an increase in the dechanneling rate. These results demonstrate that the standard method of analysis for isolated scattering centers imbedded in a perfect lattice tends to overestimate the amount of disorder at depth if twinned regions are present.

Pulsed electron beam annealing of ion implanted Si layers

Abstract Pulsed electron beam annealing (PEBA) of ion implanted Si layers was investigated by MeV 4He+ backscattering and TEM techniques. Silicon substrates, (100) and (lll) in orientation, were implanted either with 28Si+ ions or As ions, and another set of samples was implanted with both ions. The implantation energy ranged between 50 and 200 keV with a total dose of 5 × 1015/cm2 It was found that electron beam. annealing is effective in reordering ion-damaged layers in some cases where thermal annealing (∼ 550°C) is not. Pulsed electron beam annealing apparently causes melting of the surface region. The results show that the melt depth depends on the microstructure of the implanted layers.