AVS 61st International Symposium & Exhibition
    Materials Characterization in the Semiconductor Industry Focus Topic Monday Sessions
       Session MC+AP+AS-MoM

Invited Paper MC+AP+AS-MoM1
Dopant/Carrier and Compositional Profiling for 3D-Structures and Confined Volumes.

Monday, November 10, 2014, 8:20 am, Room 313

Session: Characterization of 3D Structures, 2D films and Interconnects
Presenter: Wilfried Vandervorst, IMEC, KU Leuven Belgium
Authors: W. Vandervorst, IMEC, KU Leuven Belgium
A. Kumar, IMEC, KU Leuven Belgium
J. Demeulemeester, IMEC, KU Leuven Belgium
A. Franquet, IMEC, KU Leuven Belgium
P. Eyben, IMEC, KU Leuven Belgium
J. Bogdanowicz, IMEC, KU Leuven Belgium
M. Mannarino, IMEC, KU Leuven Belgium
A. Kambham, IMEC, KU Leuven Belgium
U. Celano, IMEC, KU Leuven Belgium
Correspondent: Click to Email
The introduction of three-dimensional devices (FinFets, TFETs and nanowires), has created as new metrology challenges the characterization of dopant /carrier and impurity distributions in 3D-devices and confined volumes. Beyond these dimensional challenges, the use of alternative materials such SiGe, Ge, GeSn alloys as well as III-V materials, adds to the metrology requirements. Recent evolution towards growth (and strain relaxation) mediated by the confined volume (for instance relying on aspect ratio trapping) calls for metrology suited for very small volumes and more atomic scale observations. Metrology in 3D-structures and confined volumes has demonstrated that the changing surface/volume ratios in confined devices versus blanket films lead to phenomena (dopant deactivation, enhanced diffusion,..) which cannot be observed in blanket experiments. Hence more emphasis should be placed on the analysis of device and structures with relevant dimensions relative to the exploration of blanket experiments.

Atomprobe tomography is able to provide composition analysis within very small volumes (a few nm3) with high sensitivity and accuracy and excellent spatial resolution. Hence this enables to observe dopant atom migration in 3D-devices, and through some data mining analysis, even cluster formation as precursor to strain relaxation such as seen in metastable alloys like GeSn. Field Ion Microscopy, a complement to APT, can be used to image impurity atoms clustered around defects within the crystal. Routine application of APT is still hampered by localization problems, reconstruction artifacts due to inhomogeneous evaporation, local magnification effects, sensitivity due to the limited statistics, laser-tip interaction phenomena, etc.

Although scanning spreading resistance microscopy is inherently 2D, analysis of 3D-devices (FinFet, ReRam, Sonos..) is possible by novel approaches such as SPM scalping. The introduction of novel modes such as soft retrace, FFT-SSRM has led of improved resolution and eliminates series resistances resulting from the current confinement in these narrow devices, decoupling the actual “spreading resistance” from the total resistance. Finally SSRM-carrier distribution have been coupled to device simulators leading to an accurate prediction of device performance.

In addition to APT we also present here the concept of “self focusing SIMS” whereby we demonstrate that it is possible to determine, for instance, the SiGe(III-V) composition in trenches as small as 20 nm without having an ion beam with nm-resolution. This represents a significant step forward in terms of production control and statistical relevance.