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-Ka 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-Ka photon source. 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-Ka and Cr-Ka or Al-Ka and Ga-Ka, 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, the successful applicant will actively work on understanding the possibilities and limitations of extending XPS/HAXPES to providing information on 3D structures relevant to the semiconductor industry.
To be eligible, applicants must have a master’s degree in either physics or chemistry, with a strong background in material science, physical chemistry, and solid-state physics. As the PhD will include a large amount of experimental work on complex systems, previous photoemission and/or laser, in particular high harmonic generated sources, experience would be a plus. A basic knowledge of atomistic simulations would also be a plus.
Required background: Physics/Chemistry/Materials Science
Type of work: 70% experiemental/30%theory
Supervisor: Wilfried Vandervorst
Daily advisor: Thierry Conard
The reference code for this position is 2020-001. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-01.