Atom-by-atom analysis of advanced semiconductor devices: unraveling the physics of atom probe tomography
This dissertation will begin with a general background introduction of atom probe tomography and the urgent needs and applications of atom probe tomography due to current metrology challenges induced by both the shrinkage and the architecture change (from planar to 3D structures) of next-generation semiconductor devices. The objective of this PhD study is to develop the experimental, theoretical and fundamental insight in Atomprobe Tomography such that the technique can be used in a reliable and systematic way to analyze and to characterize the next generation devices. The ultimate goal is to develop the methodology to such a level of precision, accuracy and spatial resolution that one can perform detailed studies correlating the performance of devices with the 3D-spatial distribution of matrix elements as well as the dopant atoms. In particular, focus will be placed observing the positions of the dopant atoms directly as they impact directly on device performance. In essence, the Ph d work will address the development of an experimental methodology to produce APT tips in a reliable manner focusing on concepts to improve the tip yield as well as to minimize distortions due to the sample preparation and/or the APT analysis. These studies include not only aspects of localizing the device of interest but also fundamental studies on the origin of tip ruptures and means to overcome them. A crucial component in APT methodology, is the development of reliable reconstruction concepts which overcome the limitations of the present simplifying assumptions. Among others we envision here the use of correlative metrology whereby data from other analytic instruments such as Transmission Electron Microscopy, in particular, TEM-tomography and/or Scanning Probe Microscopy, are combined to steer the reconstruction towards improved accuracy and resolution. Fundamental studies (cfr laser effects, field effects) aimed at claryfing the origin of various distortions form part of the basic investigations. Using a number of case studies we will explore the applicability of the proposed concepts and highlight the information which can be provided through a more reliable Apt-technology. The suggestions and future development for materials characterization of the advanced devices will be given in this part to pave the way for next-generation nanoelectronics.