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Project

Development of photo emission spectroscopy from planar to 3D structures .

Surface and interface analysis, within the semiconductor industry, has reached a level of refinement beyond that imaginable 25 years ago. Likewise, device architectures and dimensions are now at a level not thought possible even 10 years ago. With this, the question often asked is: How far can this go on. To gain a better understanding of the path forward, new analytical methods and protocols are needed .One area experiencing significant developments within the last couple of years is that of X-ray Photoelectron Spectroscopy (XPS). This technique employs a monochomated Al-K photon source at 1486.6 eV to induce the emission of photoelectrons from the outer most surface of any solid material, whose kinetic energy then reveals the element the photoelectron emanated from (the principle first described by Einstein for which he received the Nobel prize in 1921). These new developments move lab-based XPS into the Hard X-ray Photo Emission Spectroscopy (HAXPES) regime. This entailed the introduction of higher energy photon sources, i.e. monochomated Cr-ka at 5.4 keV and Ga-ka at 9.2 keV along with the monochomated Al-K photonsource. These higher energy sources allow one to probe deeper within a solids surface, i.e. from ~2 nm up to ~30 nm. With both sources (Al-K and Cr-K or Al-K and Ga-K, all of which are available to MCA within imec (2019 acquisitions)) one can then examine, in an interleaved manner, shallow and deep regions within any solid material. Angle resolved studies may yield additional information. Combining this new capability with sputter depth profiling with Ar+ ions at say 500 eV (this is used to access even deeper layers), one can then examine the physics behind the damage induced, i.e.sputter induced segregation, diffusion, preferential sputtering, etc. on various materials of technological interest to the semiconductor industry. This can then envisage taking this a step further by developing methodologies to remove the sputter induced damage from a depth profile, i.e. though post analysis data treatments. This treatment may also entail the examination of the inelastic background, as the structure of this background is specific to the internal structure of the material being examined. With all of this in place, one can foresee the transition of photoemission spectroscopy from a shallow planar technique to a technique that can provide 3D structures within a lab-based platform (higher energy sources were previously only available at synchrotron sites). Through this PhD, we will work on understanding the possibilities and limitations of extending XPS/HAXPES to providing information on 3D structures relevant to the semiconductor industry. Recently, novel instrumentation is emerging based on hard (high) energy XPS (HAXPES) with X-ray energies increasing up to 9.2 keV. Such an increase in X-ray energy leads to an increased information depth (from 2 up to 30-50 nm) opening the possibility for non-destructive chemical analysis of such complex structures. One very important limitation for the use of HAXPES is that it has been mostly confined to the use of synchrotron radiation as no performant lab-scale instruments were available. The situation changed recently and several manufacturers can now deliver high performance lab scale HAXPES systems. Imec will soon have access to several photoemission instrument with wide ranging available photon energy from 20 eV to 9keV (4 energies will be available), similar to the range achieved at synchrotron facility centers

Date:4 Jan 2021 →  31 Mar 2023
Keywords:Photoemission, semiconductor, material analysis
Disciplines:Applied and interdisciplinary physics
Project type:PhD project