Modeling of the transient interstitial diffusion of implanted atoms during low-temperature annealing of silicon substrates

It has been shown that many of the phenomena related to the formation of "tails" in the low-concentration region of ion-implanted impurity distribution are due to the anomalous diffusion of nonequilibrium impurity interstitials. These phenomena include boron implantation in preamorphized silicon, a "hot" implantation of indium ions, annealing of ion-implanted layers et cetera. In particular, to verify this microscopic mechanism, a simulation of boron redistribution during low-temperature annealing of ion-implanted layers has been carried out under different conditions of transient enhanced diffusion suppression. Due to the good agreement with the experimental data, the values of the average migration length of nonequilibrium impurity interstitials have been obtained. It has been shown that for boron implanted into a silicon layer preamorphized by germanium ions the average migration length of impurity interstitials at the annealing temperature of 800 Celsius degrees be reduced from 11 nm to approximately 6 nm due to additional implantation of nitrogen. The further shortening of the average migration length is observed if the processing temperature is reduced to 750 Celsius degrees. It is also found that for implantation of BF2 ions into silicon crystal, the value of the average migration length of boron interstitials is equal to 7.2 nm for thermal treatment at a temperature of 800 Celsius degrees.Comment: 10 pages, 6 figures, RevTe

Context matters to explain field experiments: Results from Colombian and Thai fishing villages

During the last decade, field experiments regarding the study of common pool resource governance have been performed that replicated earlier findings of laboratory experiments. One of the questions is how the decisions made by participants in rural communities are influenced by their experience. This paper presents the results of field experiments in Colombia and Thailand on fishery resources. Context information is derived from the communities via in-depth interviews, surveys and role playing exercises. The use of different methodological tools allowed to link decisions in field experiments with contextual variables for two fishery villages. Explanation of core variables in social dilemmas is given, the degree of cooperation levels, preferred rules, rule compliance and enforcement. Main findings include: i) fishermen made decisions in the field experiments that reflected their own experience and context, ii) agreements for rule crafting are possible only under specific conditions that guarantees livelihoods and sustainability, iii) the broader context determines cooperation levels at a local level, iv) inequalities in the sanctioning of rule breakers decrease the possibilities of reaching cooperation agreements, and v) high levels of trust among local fishermen is not a sufficient condition for resource sustainability, when trust in external rule makers and enforcers is low.Field experiments Role games Fisheries Rules Cooperation Trust

Quantification of germanium-induced suppression of interstitial injection during oxidation of silicon

The oxidation of silicon is known to inject interstitials, and the presence of silicon–germanium (SiGe) alloys at the Si/SiO2 interface during oxidation is known to suppress the injection of silicon self-interstitials. This study uses a layer of implantation-induced dislocation loops to measure interstitial injection as a function of SiGe layer thickness. The loops were introduced by a 50 keV 2 × 1014 cm−2 P+ room-temperature implantation and thermal annealing. Germanium was subsequently introduced via a second implant at 3 keV Ge+ over a range of doses between 1.7 × 1014 cm−2 and 1.4 × 1015 cm−2. Results show that upon oxidizing at 850 °C for 3 h or 900 °C for 70 min to condense the germanium at the Si/SiO2 interface, where if forms a Si0.5Ge0.5 alloy. Upon subsequent oxidations of 850 °C for 6 h or 900 °C for 2 h, partial suppression of interstitial injection can be observed for sub-monolayer doses of germanium, and more than three monolayers of Si0.5Ge0.5 (1.4 × 1015 cm−2) are necessary to suppress interstitial injection below the detection limit during oxidation. These results show that low-energy implantation of germanium can be used to eliminate or modulate injection of oxidation-induced interstitial

Elimination and quantification of oxidation induced interstitial injection via Ge implants

The presence of Silicon-Germanium (SiGe) alloys at the Si/SiO2 interface during oxidation is known to suppress the injection of silicon self-interstitials that normally accompanies silicon oxidation and lead to observed effects such as Oxidation Enhanced Diffusion (OED) and stacking fault growth. This study uses a layer of implantation induced dislocation loops to measure interstitial injection as a function of SiGe layer thickness. The loops were introduced by implanting phosphorus and thermal annealing, and Germanium was subsequently introduced via a second implant at 3 keV over a range of doses between 1.7 × 1014 cm-2 and 1.4 × 1215 cm-2. Results show that partial suppression of interstitial injection can be observed for sub-monolayer doses of germanium, and that more than three monolayers of SiGe are necessary to fully suppress interstitial injection below our detection limit during oxidation. They further show that low energy implantation of germanium opens up possibilities to eliminate or modulate injection of interstitials during thermal processing of future devices