CMP Seminar
		     Monday, March 4, 2002
	   4:10 pm, Room 224 Physics-Astronomy Building


	Atomic-Scale Imaging of Individual Dopant Atoms and 
	   Deactivating Nanoclusters in Highly n-type Si

			  Paul M. Voyles
			     Bell Labs

As silicon-based transistors in integrated circuits grow smaller, the
concentration of charge carriers generated by the introduction of impurity
dopant atoms must steadily increase. Current technology, however, is
rapidly approaching the limit at which introducing additional dopant atoms
ceases to generate additional charge carriers because the dopants form
electrically inactive nanoclusters. Using annular dark-field scanning
transmission electron microscopy, we report the direct, atomic-resolution
observation of individual Sb dopant atoms in crystalline Si, and we
identify the Sb clusters responsible for the saturation of charge carriers.
The size, structure, and distribution of these clusters are determined with
a Sb-atom detection efficiency of almost 100%. This is the first time
individual atoms still bonded inside their crystalline host environment
have been unambiguously resolved. Although single heavy atoms on surfaces
or supporting films have been visualized previously, our technique is able
to view the individual dopant atoms and clusters as they exist within
actual devices.