No abstract

3D atom probe tomography (APT) is introduced as a powerful compositional and spatial analytical tool for SiGe nanostructures. Compositional analysis of SiGe structures demonstrates that the location and identity of Si, Ge and B atoms can be detected in three dimensions. Superior sensitivity at Si-SiGe-Si interfaces is specifically witnessed by both the quantification of Ge accumulation at an interface (14% by atom probe versus 9% by SIMS) and a slope roll-off of ∼1 nm/decade for atom probe compared to ∼7 nm/decade for the corresponding SIMS analysis. Additionally, APT provides chemical roughness measurements of buried interfaces. In a specific case, a Si-SiGe-Si interface had a measured roughness of 0.47 nm at the Si-SiGe leading edge and 0.26 nm at the SiGe-Si trailing edge.

With device dimensions decreasing below 65 nm, the electrical characteristics of a transistor largely depend on the lateral placement of a relatively few atoms in the transistor's channel. Accordingly, 3-D compositional analysis of the channel on an atom-by-atom basis is highly desirable. While Three-Dimensional Atom Probe Tomography (3DAPT) analysis has offered the ability to create atomic maps of a sample, a number of difficulties had to be overcome before the technique could be readily applied to transistor channel analysis.

Studies on the viscosity of 18 asphalts at 60 C (140 F) showed that the result depends upon the apparatus and procedure used. The Florida capillary method at constant shear rate gives significantly higher values than does the Cannon-Manning method. Furthermore, it was shown that, although shear thinning may result for certain asphalts when run in Cannon-Pressure instruments, there may also be compensating effects of pressure which can raise the viscosity. These variations are attributed to both differences in the flow mode (transient or steady state) and to effects of the imposed pressures.