Chemical 3D tomography of 28nm high K metal gate transistor: STEM XEDS experimental method and results.

A new STEM XEDS tomography technique is proposed thanks to the implementation of multi EDX SDD detectors in analytical TEMs. The technique flow is presented and the first results obtained on a 28nm FDSOI transistor are detailed. The latter are compared with 2D XEDS analysis to demonstrate the interest of the slice extraction in all directions from a large analyzed volume without any 3D overlap effect issues.

Three-dimensional semiconductor device investigation using focused ion beam and scanning electron microscopy imaging (FIB/SEM tomography).

Three-dimensional focused ion beam/scanning electron microscopy (FIB/SEM tomography) is currently an important technique to characterize in 3D a complex semiconductor device or a specific failure. However, the industrial context demands low turnaround time making the technique less useful. To make it more attractive, the following study focuses on a specific methodology going from sample preparation to the final volume reconstruction to reduce the global time analysis while keeping reliable results. The FIB/SEM parameters available will be first analyzed to acquire a relevant dataset in a reasonable time (few hours). Then, a new alignment strategy based on specific alignment marks [using tetraethoxylisane (TEOS) and Pt deposition] is proposed to improve the volume reconstruction speed. These points combined represent a considerable improvement regarding the reliability of the results and the time consumption (gain of factor 3). This method is then applied to various case studies illustrating the benefits of the FIB/SEM tomography technique such as the precise identification of the origin of 3D defects, or the capability to perform a virtual top-down deprocessing on soft material not possible by any mechanical solution.