Alexander Merkulov oral presentation (SN2-Tue3-2-4)
Quantitative low energy depth profiling of p- and n-doped SiGe laterally non-uniform structures.
CAMECA, 29 quai des Gresillons, 92622 Gennevilliers, France
Sputtering of multi-phase matrices such as SiGe layers makes Secondary Ion Mass-Spectroscopy (SIMS) data interpretation difficult. Non-steady state sputtering conditions can limit the accuracy of the recorded profile. Moreover, sputtering rate variation is often accompanied by ion yield change. The ion yield variation of each element, both matrix elements and the doping species, can depend on the specifics of the matrix composition. It becames even more challenging in case of device scaling down in both depth and lateral dimensions (3D device structures). Analyses of these types of devices must be performed using techniques capable both of nm lateral resolution, sub-nm depth resolution and ppm sensitivity, which is difficult to achieve. At the same time, the traditional dynamic SIMS technique could be employed if there was a way to separate the secondary ion signals originating within a few-nm scale devices from the signals coming from the rest of the matrix material. This is possible if 1) there exist mass peaks in the spectra which can be identified as originating only from the 3D device area or layer of interest and 2) the emission of secondary ions from surrounding device area is suppressed or negligibly small. The method based on this approach has become known as “self-focusing” SIMS . This approach, very promising for expanding the application of dynamic SIMS, needs further development in order to be applied to industrial applications. Once developed, this method, along with optimized analytical conditions, should allow accurate measurements of the main constituent’s composition as well as its dopant concentration. The current work is devoted to research of the self-focusing SIMS technique capability in SiGe based confined 3D FIN-like structures. At the same time the extension of dynamic SIMS using data entry given by complementary microscopic technics can be applied . The accuracy and precision of both methods have challenges in order to be employed in industrial applications.
The main purpose of this work is to investigate the accuracy of low impact energy SIMS measurements in SiGe device structures. We will review the analytical conditions, together with the dedicated ion yield correction routine, which give access to accurate quantitative SIMS depth profiles with a minimum number of reference samples and data entries from complementary technics.
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