Tin tức và sự kiện

In semiconductor technology, materials and thus analytical problems change rapidly. Thanks to its outstanding depth profiling capabilities, the CAMECA IMS 7f-Auto is widely used for dopant monitoring in the semiconductor industry, and applied to different species and material systems. Among its instrumental advantages: two high brightness ions sources (Cs+ and O2+), high transmission, high mass resolution…

Common microanalysis techniques such as Glow Discharge Mass Spectrometry fail to measure light elements (H, C, N, and O) because of high background signal limitations. Time-of-Flight SIMS can analyze atmospheric gas elements, but with mediocre detection limits only, due to a too low acquisition speed and contamination issues resulting from its intrinsic pulsed ion beam design.  

Newest semiconductor chip manufacturing and further scaling down of CMOS devices push the limits of junction depths below the 10nm range, with a profile steepness of 1-2nm per decade. At such scale, the SIMS technique can be used to monitor in-depth distributions of dopants, proving that SIMS profiles can be measured with a depth resolution better than 1nm per decade.

As transistor structures continue to shrink to keep pace with Moore's Law the existing analysis and metrology techniques currently in use will no longer be sufficient to fully characterize the nanoscale devices. Atom probe has the unique capability to characterize the next-generation technology cycles by mapping the spatial distribution and chemical identity of dopants on the atomic scale.

Uranium is a radioactive heavy metal naturally present in earth crust. Internal contamination of nuclear workers by actinides such as uranium may occur either by inhalation, ingestion or penetration through wounds or intact skin, and the SIMS technique is used to assess uranium transfer through the skin. Experiments have been performed in order to characterize uranium bioaccumulation process at skin pig. The results suggest that the stratum corneum is a good defense barrier against the incorporation of the radionuclide into the skin, but can also constitute a reservoir for the diffusion of the radionuclide if no decontamination treatment is applied.

In this study[1], the NanoSIMS is used to quantitatively measure a slow protein turnover at subcellular level inside the cochlea of bullfrogs and mice using a stable isotope labeling strategy. Adult bullfrogs were fed 15N-leucine food 1/day and sacrificed at 1, 2, 4, 8, 16, 22, 32 days. Inner ears were dissected out, chemically fixed, embedded in resin and microtomed.

In this NATURE article the authors test the ‘immortal strand hypothesis’, which predicts that during asymmetric stem cell division chromosomes containing older template DNA are segregated to the daughter destined to remain a stem cell, thus insuring lifetime genetic stability. After labelling mice with 15N-thymidine from gestation until post-natal week 8, the authors found no 15N label retention by dividing small intestinal crypt cells after a four-week chase. In adult mice administered 15N-thymidine pulse-chase, they found that proliferating crypt cells dilute the 15N label, consistent with random strand segregation.