Self-assembled germanium islands grown on (001) silicon substrates by low-pressure chemical vapor deposition

The time evolution of self-assembled Ge islands, during low-pressure chemical vapor deposition (LPCVD) of Ge on Si at 650 Deg C using high growth rates, has been investigated by atomic force microscopy, transmission electron microscopy, and Rutherford backscattering spectrometry. We have found three different island structures The smallest islands are "lens-shaped" and characterized by a rather narrow size distribution, ~4nm high and ~20nm wide. Next to form are a distinct population of multifaceted "dome shaped" islands, up to 25nm high and 80-150 nm wide. Finally, the largest islands that form are square-based truncated pyramids with a very narrow size distribution ~50nm high and ~250nm wide. The pyramidal islands normally seen in the intermediate size range (~150nm) are not observed. The small lens-shaped islands appear to be defect free, while some of the multifaceted islands as well as all the large truncated pyramids contain misfit dislocations. The existence of multifaceted islands, in the size range where multifaceted "dome shaped" islands have previously been reported, is attributed to the high growth rate used. Furthermore, under the growth conditions used, the truncated-pyramid-shaped islands are characterized by a very narrow size distribution

Effect of Fluorine Implantation Dose on Boron Transient Enhanced Diffusion and Boron Thermal Diffusion in S1-xGex

This paper studies how boron transient enhanced diffusion (TED) and boron thermal diffusion in Si1-xGex are influenced by a high-energy fluorine implant at a dose in the range 5 x 10(14) cm(-2) to 1 x 10(16) cm(-2). Secondary ion mass spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine SIMS profiles and transmission electron microscopy (TEM) micrographs to establish the conditions under which boron diffusion is suppressed. The SIMS profiles show that boron thermal diffusion is reduced above a critical F+ dose of 7-9 x 10(14) cm(-2), whereas boron TED is suppressed at all doses. Fitting of the measured boron profiles gives suppressions of boron TED diffusion coefficients by factors of 6.8, 10.6, and 12.9 and of boron thermal diffusion coefficient by factors of 1.9, 2.5, and 3.5 for F+ implantation doses of 9 x 10(14), 1.4 x 10(15), and 2.3 x 10(15) cm(-2) respectively. The reduction of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the SIMS profile in the vicinity of the boron marker layer, which is attributed to vacancy-fluorine clusters. This reduction of boron thermal diffusion is explained by the effect of the clusters in suppressing the interstitial concentration in the Si1-xGex layer. The suppression of boron TED correlates with a deep fluorine peak around the range of the fluorine implant and TEM micrographs show that this peak is due to a band of dislocation loops. This suppression of boron TED is explained by the retention of interstitials in the dislocation, loops, which suppresses their backflow to the surface. The fluorine SIMS profiles show that the fluorine concentration in the Si1-xGex layer increases with increasing germanium concentration and that the fluorine concentration in the Si1-xGex layer after anneal is much higher than after implant. This indicates that fluorine is transported into the Si1-xGex layer from the adjacent silicon, and is explained by the lower formation energy for vacancies in Ge than in Si. This accumulation of fluorine in the Si1-xGex layer during anneal is advantageous for devices like SiGe heterojunction bipolar transistors, where the boron must be kept within the Si1-xGex layer.</p

On the use of total reflection x-ray topography for the observation of misfit dislocation strain at the surface of a SiGe/Si heterostructure

Synchrotron x-ray topography was used in total reflection topography (TRT) mode to observe strain-induced surface bumps due to the presence of underlying misfit dislocations in strained-layer SiGe on Si epitaxial heterostructures. In these experiments, the x rays approached the sample surfaces at grazing incident angles below the critical angles for total external reflection for a number of reflections, and hence, surface strain features nominally less than a few tens of angstrøms from the sample surface have been observed. These are similar to the surface bumpiness observed by atomic force microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of conventional backreflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angl

Effect of fluorine implantation dose on boron transient enhanced diffusion and boron thermal diffusion in Si_1-<i>x</i>Ge_<i>x</i>

This paper studies how boron transient enhanced diffusion (TED) and boron thermal diffusion in Si1-xGex are influenced by a high-energy fluorine implant at a dose in the range 5 x 1014 cm-2 to 1 x 1016 cm-2. Secondary ion mass spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine SIMS profiles and transmission electron microscopy (TEM) micrographs to establish the conditions under which boron diffusion is suppressed. The SIMS profiles show that boron thermal diffusion is reduced above a critical F+ dose of 7 - 9 x 1014 cm-2, whereas boron TED is suppressed at all doses. Fitting of the measured boron profiles gives suppressions of boron TED diffusion coefficients by factors of 6.8, 10.6, and 12.9 and of boron thermal diffusion coefficient by factors of 1.9, 2.5, and 3.5 for F+ implantation doses of 9 x 1014, 1.4 x 1015, and 2.3 x 1015 cm-2 respectively. The reduction of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the SIMS profile in the vicinity of the boron marker layer, which is attributed to vacancy-fluorine clusters. This reduction of boron thermal diffusion is explained by the effect of the clusters in suppressing the interstitial concentration in the Si/sub 1-x/Ge/sub x/ layer. The suppression of boron TED correlates with a deep fluorine peak around the range of the fluorine implant and TEM micrographs show that this peak is due to a band of dislocation loops. This suppression of boron TED is explained by the retention of interstitials in the dislocation loops, which suppresses their backflow to the surface. The fluorine SIMS profiles show that the fluorine concentration in the Si1-xGex layer increases with increasing germanium concentration and that the fluorine concentration in the Si1-xGex layer after anneal is much higher than after implant. This indicates that fluorine is transported into the Si1-xGex layer from the adjacent silicon, and is explained by the lower formation energy for vacancies in Ge than in Si. This accumulation of fluorine in the Si1-xGex layer during anneal is advantageous for devices like SiGe heterojunction bipolar transistors, where the boron must be kept within the Si1-xGex layer.</p

Effect of fluorine implantation dose on boron transient enhanced diffusion and boron thermal diffusion in Si_1-<i>x</i>Ge_<i>x</i>

This paper studies how boron transient enhanced diffusion (TED) and boron thermal diffusion in Si1-xGex are influenced by a high-energy fluorine implant at a dose in the range 5 x 1014 cm-2 to 1 x 1016 cm-2. Secondary ion mass spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine SIMS profiles and transmission electron microscopy (TEM) micrographs to establish the conditions under which boron diffusion is suppressed. The SIMS profiles show that boron thermal diffusion is reduced above a critical F+ dose of 7 - 9 x 1014 cm-2, whereas boron TED is suppressed at all doses. Fitting of the measured boron profiles gives suppressions of boron TED diffusion coefficients by factors of 6.8, 10.6, and 12.9 and of boron thermal diffusion coefficient by factors of 1.9, 2.5, and 3.5 for F+ implantation doses of 9 x 1014, 1.4 x 1015, and 2.3 x 1015 cm-2 respectively. The reduction of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the SIMS profile in the vicinity of the boron marker layer, which is attributed to vacancy-fluorine clusters. This reduction of boron thermal diffusion is explained by the effect of the clusters in suppressing the interstitial concentration in the Si/sub 1-x/Ge/sub x/ layer. The suppression of boron TED correlates with a deep fluorine peak around the range of the fluorine implant and TEM micrographs show that this peak is due to a band of dislocation loops. This suppression of boron TED is explained by the retention of interstitials in the dislocation loops, which suppresses their backflow to the surface. The fluorine SIMS profiles show that the fluorine concentration in the Si1-xGex layer increases with increasing germanium concentration and that the fluorine concentration in the Si1-xGex layer after anneal is much higher than after implant. This indicates that fluorine is transported into the Si1-xGex layer from the adjacent silicon, and is explained by the lower formation energy for vacancies in Ge than in Si. This accumulation of fluorine in the Si1-xGex layer during anneal is advantageous for devices like SiGe heterojunction bipolar transistors, where the boron must be kept within the Si1-xGex layer.</p

Effect of Fluorine Implantation Dose on Boron Thermal Diffusion in Silicon

This paper investigates how the thermal diffusion of boron in silicon is influenced by a high energy fluorine implant with a dose in the range 5x10(14)-2.3x10(15) cm(-2). Secondary Ion Mass Spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine profiles to establish the conditions under which thermal boron diffusion is suppressed. The (SIMS) profiles show significantly reduced boron thermal diffusion above a critical F+ dose of 0.9-1.4x10(15) cm(-2). Fitting of the measured boron profiles gives suppressions of the boron thermal diffusion coefficient by factors of 1.9 and 3.7 for F+ implantation doses of 1.4x10(15) and 2.3x10(15) cm(-2), respectively. The suppression of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the (SIMS) profile in the vicinity of the boron marker layer. This shallow fluorine peak is present in samples with and without boron marker layers, and hence it is not due to a chemical interaction between the boron and the fluorine. Analysis of the (SIMS) profiles and cross-section Transmission Electron Microscope micrographs suggests that it is due to the trapping of fluorine at vacancy-fluorine clusters, and that the suppression of the boron thermal diffusion is due to the effect of the clusters in suppressing the interstitial concentration in the vicinity of the boron profile</p