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PhD Thesis Offer - Beam shaping for femtosecond laser micromachining: application to the packaging of mm and THz electronic functions

This offer is available in the following languages:
Français - Anglais

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General information

Reference : UMR8520-EMMDUB-002
Workplace : VILLENEUVE D ASCQ
Date of publication : Monday, June 22, 2020
Scientific Responsible name : Emmanuel DUBOIS
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Mission: The most recent developments in the field of telecommunications and ultra-high-speed data transfer have been considerably boosted by the rise of Cloud Storage and Computing and the development of the 5G telecommunications standard. Closely linked to the emergence of Artificial Intelligence (AI), Sensor Networks (IoT), data processing and storage, one of the challenges to be met is the move to data rates above 100 Gb/s. This can only be achieved by developing technologies, components and systems in millimetre (mmW) and sub-TeraHertz (sub-THz) bands. The assembly of systems in this frequency range lies in the gap between i) submicron fabrication technologies that are too expensive and oversized for the fabrication of components with dimensions in the 10-1000 µm range and ii) conventional mechanical machining methods limited by the small size of the structures. In this context, the introduction of a laser micromachining technique, with a resolution in the 1-10 µm range, makes sense within the System-Moore integration paradigm where the packaging is an integral part of the system design. The integration of this work in the technological value chain covers a broad spectrum using STMicroelectronics HF technologies/circuits/components in a strategy of assembly and packaging to create a system function. The target market is that of high-speed telecoms (backhaul infrastructure for point-to-point links) and metrology to characterize and qualify components/circuits based on STMicroelectronics technologies.

The research work associated with this mission will consist in implementing the laser microstructuring technique for the fabrication of functional blocks integrating mmW and sub-THz components such as guides, filters, resonators, diplexers, coplanar-rectangular transitions etc... A first activity will consist in exploring a range of materials with contrasting properties (alumina, polycarbonate, ceramic/polymer composite, PMMA, ...) in order to determine their suitability for laser micromachining in terms of etching speed and anisotropy as well as surface roughness. A second major objective will be to implement a laser beam shaping setup to transform the conventional Gaussian beam into a Top-Hat profile in order to improve the quality of surface micromachining. A third line of research will be devoted to the development of functional packages for the packaging of highly integrated active probes for the measurement of silicon components in G (140-220 GHz) and J (220-325 GHz) bands.

Activities:
• Wave optics (electromagnetic) simulation of laser beam propagation (COMSOL) using diffractive optics (optimization of beam shape e.g. Top Hat profile)
• Experimental implementation of a diffractive optical element for beam shaping.
• Electromagnetic design and simulation of complex waveguide structures (e.g., coplanar/rectangular flanges/transitions) by Solidworks/EMWorks or COMSOL or HFSS in the mmW/THz range.
• Systematic parametric study of laser micromachining on polymer and/or ceramic materials.
• Analytical characterization of micro-machining processes (SEM, optical profilometry, XPS, EDX ...)
• Assembly and microwave measurements of designed structures
• Benchmarking and positioning of results in relation to the state of the art

Expected skills
This position is aimed at a candidate with a interest for experimentation, modelling and simulation in the field of electromagnetism (RF, mmW, THz, optics). Potential candidates should :
• Hold a Master degree in electronics or microwave or optical engineering
• Have an expertise in the field of micro-nanofabrication, clean room techniques and/or laser applications can be helpful
• Be fluent in English (spoken and written) and demonstrate know-how in terms of reporting and publication.
• Ability to work independently and take initiative
• Integrating group work and the dynamics of a common laboratory

Work Context

The work will be carried out within the Silicon Microelectronics Group of the IEMN (Lille-France) as part of the IEMN-STMicroelectronics Joint Laboratory. The group hosting the candidate has recognized expertise in the field of micro-nanofabrication and packaging of components and systems covering RF, mmW waves and photonics.
The group coordinates the EQUIPEX LEAF technology platform on advanced femtosecond laser micromachining.
( https://www.youtube.com/watch?v=9uCjtT7uX40&feature=youtu.be )

Constraints and risks

Not applicable

Additional Information

Not applicable

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