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Reference : UMR7334-DELSTU-028
Workplace : MARSEILLE 13
Date of publication : Wednesday, September 02, 2020
Type of Contract : FTC Scientist
Contract Period : 11 months
Expected date of employment : 1 November 2020
Proportion of work : Full time
Remuneration : between 2728.25€ et 3881.28€ monthly gross depending on previous experiences
Desired level of education : PhD
Experience required : Indifferent
This work will investigate the crystallization of GST alloy layers with various capping and compositions provided par STMicroelectronics. For each defined stack, the nucleation and growth of crystalline phases, the phase transition as well as segregation and diffusion phenomena, including the role of the interfaces, will be followed. The physical properties (structural, optical and electrical) will be characterized in situ (i.e. during thermal annealing) using a panel of several original techniques, already used at IM2NP laboratory: mass spectroscopy under UHV, spectroscopic ellipsometry, as well as combined X-ray diffraction, X-Ray reflectivity and sheet resistance measurements7,8. The results will also be compared with other ex and in situ measurements (TEM, Atom Probe Tomography, nanoSIMS) performed by others partners in the frame of the same project.
This work will be performed in strong partnership with STMicroelectronics.
- sample characterization using in situ XRD, XRR et Rs
- sample characterization using in situ ellipsometry
- desorption measurements Under UHV
- analysis and interpretation of the results
The ideal candidate holds a PhD degree in Material Sciences (or equivalent), has a solid background in physics, good communication skills and is proficient in written and spoken English. Knowledge of X-ray scattering, X-Ray Diffraction, X-Ray Reflectivity, Ellipsometry, PCM and programming skills will be highly appreciated.
Phase Change Random Access Memories (PCRAM) are among the most mature non-volatile emerging memories (NVM): they allow data storage at high programing speed with enhanced endurance compared to today Flash technology1,2, as recently demonstrated by the INTEL OPTANETM 2,3. PCRAM are based on the ultrafast (<10 ns)4 and reversible transition between the amorphous and crystalline states of phase change materials (PCMs) initially used for optical data storage5. Data are stored thanks to the high resistivity contrast between these two structural phases of PCMs, the crystalline phase having a low resistance state, and the amorphous one a high resistance state6. Both amorphous and crystalline states of PCMs exhibits also very different optical properties, and are stable enough to be used as 0 and 1 states in non-volatile memories. The most promising PCM for NVM is the chalcogenide GexSbyTez (GST) used by STMicroelectronics for embedded automotive applications, requiring high stability under temperature variations. However, critical issues occurring at nanoscale needs further material studies concerning the role of interfaces (nitride, dielectrics, etc..), the alloy composition (phase separation, precipitation, segregation, etc..), the effect of doping alloy elements and the impact of such issues on the crystallization kinetics (nucleation and growth). This work aims to closely study the optimized chalcogenides (typically GST with various doping composition) integrated in STMicrolectronics memory cells, and the effects of various capping layers (nitride, dielectric) during the crystallization process and post-annealing treatments.
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