Chemical Beam Epitaxy (CBE) was born in the 1980’s from the merger of MBE (Molecular Beam Epitaxy) and CVD (Chemical Vapor Deposition) to deposit III-V semiconductor thin films.
CBE was also used for thin film deposition for pure or doped Si, SixGe1-x, FeSi2 and oxide thin film deposition such as LiTaO3, superconductive oxides, TiO2, Al2O3, Y2O3, CdO, HfO2, LiNbO3, MgO, ErSiO, ZnO, ZrO2 without being exhaustive.
CBE demonstrated excellent results, proving experimentally its advantages for:
Controlled deposition and doping of multi-element materials (for instance, deposition of up to 4 element such as in GaAsInP).
High composition and thickness uniformity (2% on 300 mm diameter wafers).
High precursor conversion rate.
Large range of possible growth rates (typically from 10 nm up to 10 microns per hour).
High reproducibility (typically, few % drift of the equipment over years).
The possibility to structure the film during the growth with excimer laser irradiation.
Special ABCD Improvements
As a general rule, the potential of CBE has been under-estimated. Most of the people involved in this technology found it too complex and in the 1990′s the synergy between the various advantages was poorly investigated and exploited. However, this synergy holds the key to manufacture the complex devices of today.
ABCD staff and network partners have developed the technology continuously for more than 15 years, providing the tools to make it simpler to use, improved speed to optimize the processes and merged all the advantages and facilities in a single reliable tool.
Among the key improvements we can mention:
ABCD holds several patents related to effusive source and reactor design that allow very precise control of the growth conditions to achieve uniform (1-2%), multi-element materials even on very large substrates (6″, 8″, and possibly even larger for special designs) without any substrate rotation or planetary motion.
Furthermore, we have developed mathematical models and Monte Carlo simulations to fully exploit the technology, drastically reducing deposition chamber size while still retaining good thin film homogeneity.
Pumping unit sizes and gas phase interactions have been greatly reduced.
In addition to uniform coatings, we can achieve a plurality of highly controlled and customized chemical precursor impinging rate gradients (according to our mathematical models) to rapidly investigate and optimize material properties and processes as a function of the growth rates or layer thickness.
If several precursors are mixed, we can achieve composition gradients on a single wafer (combinatorial approach) to obtain complex phase diagrams and rapidly explore material properties or investigate decomposition interactions between the various species to qualify and quantify chemical reactions on the substrate surface.
Aside from the ability to investigate chemical composition, to enhance our combinatorial facility we have developed a 3D-printing approach with stencil masks enabling the structure, size and shapes of nanostructures to be varied across a single substrate. This nano-combinatorial approach provides the possibility to investigate the variation of nano-size effects over material properties with sub-micrometric resolution.
Our unique solution results from combining oriented chemical precursor beams under high vacuum with beam irradiation (light, ions, electrons, or further chemical reactive species) to selectively modify the material properties during growth and achieve embedded 3D structures at the micro and nano-scales.
We can either control the spatial distribution of the injected energy or the precursor flows, with a precision ranging from a few 10′s of nanometres up to a few microns as a function of the technique used.
High vacuum conditions (better than 10-4 mbar) guarantee that no interaction between the precursors molecules and the energetic beams occurs in the gas phase.
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