compared to SIMS. The separation between atomization and ionization results in a simple quantification method based on the assumption that the ratio of an analyte ion signal for any one isotope with respect to the total ion current excluding signals from discharge gas is representative of the ratio of the number of atoms of that isotope in the sample to the other constituent atoms of the sample. This internal calibration method well established in GD-MS also called the ion beam ratio (IBR) method produces semi-quantitative results with accuracy of within a factor of 2–3.

To make it short, PP-TOMS allows fast elemental depth-profiling with nm-like resolution, limited matrix effects and semi-quantitative analysis, which appeared to cover our needs. During the collaboration, we worked on the following items :

- Optimization of PP-TOFMS conditions (RF power, gas pressure, gas mixture) in order to improve the performances of the tool (crater shape, detection limit) for each material of interest

- Assessment of semi-quantitative IBR-based compositions against complementary methods such as RBS or WDXRF

- Assessment of depth-profiling capability by virtue of systematic comparison with TOF-SIMS performed in the lab

We compared semi-quantitative IBR-based compositions with WDXRF on an extended variety of GeSbTe alloys investigated for phase change memory, resulting in less than 5% absolute difference, which was significantly better than anticipated, and which allowed PP-TOFMS to support different works around capping, etching<fnref n="43" /> and annealing of these materials [N-5.20]. We also used thin magnetic stacks produced by ion beam deposition to assess PP-TOFMS against RBS (Fig. 5.26). In that case, also, we found IBR-based compositions aligned within few absolute % to RBS. In some other cases such as silicon doping in GeSbTe matrix, the deviation between PP-TOFMS and RBS (or WDXRF) raised 50 % absolute.

<figure><img src="image_78.png" /><figcaption>**Fig. 5.26** : IBR-based reference-free quantification of thin magnetic stacks probed in 20 seconds with PP-TOFMS shows very good agreement with RBS quantification</figcaption></figure>

We evaluated PP-TOFMS against TOF-SIMS for the depth-profiling of ultrathin silicides considered for advanced contacts for CMOS application. We used Applied Material Endura PVD tool to grow 6 nm-thick NiPt films on silicon substrate. We characterized NiPt after deposition and after annealing to form nickel platinum silicide ; the annealing conditions were tuned to obtain the low-resistivity phase required for advanced contacts.

PP-TOFMS and TOF-SIMS depth profiles of NiPt samples before and after annealing led to similar conclusions (Fig. 5.27). Before annealing, both techniques show a Ni rich surface layer (preferential oxidation in the topmost ~ 2 nm) followed by a Pt enrichment close to the Si interface. For such ultrathin film (for which the interfaces may not be perfectly flat), the depth resolution is comparable for both

<footnote n="43">⁴³ Canvel Y, Lagrasta S, Boixaderas C, Barnola S, Mazel Y, Martinez E. *Study of Ge-rich GeSbTe etching process with different halogen plasmas*. JVST A. 2019; 37(3), 031302-1–031302-9. https://doi.org/10.1116/1.5089037</footnote>
techniques. After annealing, both profiles show the presence of Si throughout the film and decrease of Pt/Ni ratio, which is consistent with the formation of the Ni-rich silicide (Ni₂Si low-resistivity phase).

<figure><img src="image_79.png" /><figcaption>**Fig. 5.27** : PP-TOFMS and TOF-SIMS depth-profiles of annealed NiSiPt film (left) ; comparison of PP-TOFMS profiles in as-dep NiPt and annealed NiSiPt ultrathin materials (right)</figcaption></figure>

We assessed the depth-profiling performances against TOF-SIMS, using model samples consisting in successive pairs of (SiGe/Si) grown by epitaxy on 200 mm silicon substrates [N-5.18]. We deduced thickness, density and germanium contents from XRR and high-resolution X-ray diffraction, which highlighted the quality of the model samples (Fig. 5.28).

<figure><img src="image_80.png" /><figcaption>**Fig. 5.28** : XRR and high-resolution characterization of (SiGe/Si)N materials epitaxially grown on Si(001) confirm that the model samples feature super-lattice-like structure with sharp interfaces.</figcaption></figure>

PP-TOFMS and TOF-SIMS mass spectrum differ (Fig. 5.29) :

* TOF-SIMS mass spectrum contains adducts such as Siₓ, Geₓ, SiₓOᵧ, GeₓOᵧ or SiₓGeᵧ

* TOF-SIMS molecular content grows very rapidly with matrix complexity

* PP-TOFMS sputtering and ionization mechanisms mostly form monoatomic ions, leading to a much simpler mass spectrum that contains less molecular ions. A side effect is that peaks from unexpected elements are striking most easily in PP-TOFMS mass spectrum.
<figure><img src="image_81.png" /><figcaption>**Fig. 5.29:** Mass spectrum of super-lattice SiGe/Si model sample acquired with TOF-SIMS (top) and PP-TOFMS (bottom)</figcaption></figure>

<figure><img src="image_82.png" /><figcaption>**Fig. 5.30:** PP-TOFMSE depth profile of (SiGe/Si)N model sample with N = 5 and XRD-deduced Ge content equal to 31%</figcaption></figure>

IBR-based composition is well-aligned with HR-XRD germanium content in SiGe films (Fig. 5.30) but the PP-TOFMS profile does not show as sharp interfaces as expected from XRR and HR-XRD. Indeed, PP-TOMS resolution is in the 1 nm range for surface and near surface analysis, and slightly degrades with the analysis depth due to crater sidewall effect, while TOF-SIMS resolution remains constant over depth (Fig. 5.31). In Fig 5.31, we mimic PP-TOFMS profile on a TOF-SIMS instrument by averaging the signal over the crater (including crater sidewall), resulting in degraded resolution.

<figure><img src="image_83.png" /><figcaption>**Fig. 5.31:** The resolution of TOF-SIMS can be artificially degraded to mimic PP-TOFMS when averaging the signal over the crater (including crater sidewall)</figcaption></figure>

We developed PP-TOFMS analytical conditions dedicated to GaN-based materials in order to characterize thin AlGaN and InAlN barriers layers epitaxially grown on thick GaN pseudo substrates for high electron mobility transistors (HEMT) [N-5.19, N-5.20]. In [N-5.19], we evaluated PP-TOFMS ability to characterize InAlN and InAlGaN innovative barrier layers, which can feature perfect lattice matching with GaN, for instance when the In concentration in InAlN is 18 at. %. Characterization of
these layers includes X-ray diffraction (XRD) often complemented by TOF-SIMS in order to access
elemental profile information and to accurately control the In incorporation in the film. We suggested
PP-TOFMS as an alternative technique that could accelerate deposition/characterization loops, then
material development. We used WDXRF to estimate that IBR-based PP-TOFMS featured 10 rel. %
accuracy for the composition of In, Ga and Al (without Nitrogen contribution) in 30 to 200 nm-thick
InAlGaN films. Depth profiles (Fig. 5.32) acquired from the PP-TOFMS technique were obtained within
a few minutes and exhibited very similar In, Al, and Ga distributions to TOF-SIMS measurements
performed in MCs+ mode. Expected indium surface segregation is indeed observed by both techniques.
Differences between the two techniques could be explained by the transient state of the first two
nanometers in terms of sputtering rate or Cs surface concentration in the case of TOF-SIMS.

As already pointed, PP-TOFMS mass spectrum is rather simple, which may allow easy identification of unexpected elements such as contaminants. For instance, we used PP-TOFMS to evaluate the root cause of the degradation of magnetic properties in FeCoB/SiO₂ multilayer used for magnetic sensors [N-5.18]. A fast retrospective analysis of the mass spectrum of the PVD-deposited multilayered stack revealed titanium buried contamination in FeCoB layers, with IBR-based estimate of Ti contamination is ~ 0.1 at% (Fig. 5.33). A Ti collimator had recently been installed in the FeCoB deposition tool, and retrospective analysis of samples prepared prior to this installation showed no contamination, which put strong evidence of collimator-related contamination

<figure><img src="image_84.png" /><figcaption>**Fig 5.32** : In-depth atomic fraction of In, Al, and Ga (left) with focus on the surface arrangement (right). Comparison of PP-TOFMS ion beam ratio and TOF-SIMS depth profiles with applied relative sensitivity factors of the (a) 200 nm and (b) 30 nm thick InAlGaN layers</figcaption></figure>

<figure><img src="image_85.png" /></figure>
<figure><img src="image_86.png" /><figcaption>**Fig. 5.33** : PP-TOFMS elemental depth-profile evidences a 0.1 at% Ti buried contamination in FeCoB/SiO₂ multilayered material</figcaption></figure>

Finally, we evaluated different gas mixtures in order to improve the sensitivity PP-TOMFS to light elements in the frame of Amanda Gomes De Carvalho master training. Penning ionization process is considered the main ionization mechanism in glow discharge plasma. Argon features two metastable energy levels of 11.55 eV and 11.72 eV that are sufficient to ionize the majority of the elements in the Periodic table. However, the first ionization potential of light elements is either close or higher than the energy of Argon metastable atoms $Ar^m$, resulting in small efficiency of PP-TOFMS for such elements (Fig. 5.34).

<figure><img src="image_87.png" /><figcaption>**Fig. 5.34** : Periodic trends for ionization energy (eV) vs. Atomic number. $Ar^m$ and $He^m$ energies emphasized.</figcaption></figure>

Conversely, helium features metastable atoms $He^m$ with the energy levels of 19.82 eV and 20.62 eV that should be able to ionize all relevant sample atoms including light elements. Then, we evaluated mixed gases containing 10% and 20% of helium diluted in pure argon as compromise between two contrasting effects observed in the literature: the increase of ionization efficiency and the decrease of sputtering rate. We demonstrated that Ar/He mixtures, and more specifically Ar/He with 20 vol% He dilution led to significant improvement (Fig. 5.35) for hydrogen, carbon, nitrogen and oxygen in titanium nitride films grown by metal organic chemical vapor deposition (MOCVD), and Boron in boron-doped amorphous silicon grown by plasma-enhanced chemical vapour deposition (PECVD).
<figure><img src="image_88.png" /><figcaption>**Fig. 5.35** : Improvement of PP-TOFMS sensitivity to light elements in MOCVD TiN (left) and Boron-doped amorphous silicon (right) [A. G. Carvalho's master report, presented @ ECASIA 2017 by Y. Mazel</figcaption></figure>

Not all stories have a happy end. During Covid period, Horiba kindly asked CEA-Leti to ship the tool back to their facility. They needed some parts to finalize the assembly of an ordered tool and they couldn't get these parts the normal way because of Covid-induced difficulties. Then, one year after, Horiba decided to stop the supply of PP-TOFMS. One major reason was that the price of the tool, largely driven by the price of the subcontracted TOF spectrometer, was too high to address a large market.
# 6 Material characterization for Phase Change Memory

## Abstract – supervision – collaboration – key papers

The general objective of this research direction was the optimization of characterization strategies for complex ternary alloys investigated for phase change memory.

The specific objectives were:

- The study of Nitrogen incorporation in Ge, Sb, Te systems by means of X-ray and optical spectroscopies (Section 6.2). This work was conducted during the PhD of Walter Pessoa and Lucie Prazakova and the Master trainee of Diana Fernandez Rodas. It resulted in the publication of two reference papers related to XPS on the one hand [N-6.2], and Raman and infrared spectroscopies in the other hand [N-6.1].

- The systematic combination of Raman spectroscopy and X-ray diffraction to study the structural evolution of GST alloys as a function of annealing temperature (Section 6.3.2). This work was essentially conducted during the PhD of Lucie Prazakova. It resulted in the publication of two papers [N-6.3 and N-6.4] dedicated to Ge-rich GST alloys. This extension of this work GST alloys with different stoichiometry is investigated in the frame of the PhD of Oumaima Daoudi.

- The systematic combination of infrared and Raman spectroscopies with X-ray diffraction to study the impact of N-doping on the structural evolution of GST alloys as a function of annealing temperature (Section 6.3.3). This work was conducted during the PhD of Lucie Prazakova and the Master trainee of Diana Fernandez Rodas. Some results have been included in paper [N-6.4]. This extension of this work GST alloys with different stoichiometry is investigated in the frame of the PhD of Oumaima Daoudi.

This work required complementary improvements of elemental depth-profiling with PP-TOFMS techniques (presented in **Section 5**) in the frame of the collaboration with Horiba Jobin Yvon (**Section 6.3.1**). This resulted in a dedicated paper [N-6.5], which was used for the **cover of Surface and Interface Analysis journal**.

**PhD**: Walter Pessoa (2014-2017), Lucie Prazakova (2018-2021), Oumaima Daoudi (2021-2024).

**Master training**: Diana Fernandez Rodas (2021)

PhD of Lucie Prazakova and Oumaima Daoudi, and Master of Diana Fernandez Rodas were co-supervised by my colleague Gabriele Navarro, who is deeply involved in PCM world.

### Industrial collaboration with Horiba Jobin Yvon

Collaboration with Hicham Kodja, CEA Iramis (Laboratoire des Eléments Légers) for the refinement of IBA-based composition of N-doped elemental systems.

## Key publications (metrology-oriented)

[N-6.1] L. Prazakova, E. Nolot, E. Martinez, D. Rouchon, N. Rochat, C. Sabbione, J. Li, D. Eichert, G. Pepponi, M. Bernard, and G. Navarro, Spectroscopic study of nitrogen incorporation in Ge, Sb, and Te elemental systems: A step toward the understanding of nitrogen effect in phase-change materials, J. Appl. Phys. 132, 205102 (2022); https://doi.org/10.1063/5.0117596

[N-6.2] E. Nolot, C. Sabbione, W. Pessoa, L. Prazakova, G. Navarro, Germanium, antimony, tellurium, their binary and ternary alloys and the impact of nitrogen: An X-ray photoelectron study, Applied Surface Science, 2021, 536, 147703, https://doi.org/10.1016/j.apsusc.2020.147703

[N-6.3] L. Prazakova, E. Nolot, E. Martinez, D. Rouchon, F. Fillot, N. Bernier, R. Elizalde, M. Bernard, G. Navarro, The effect of Ge content on structural evolution of Ge-rich GeSbTe alloys at increasing temperature, Materialia 21 (2022) 101345, https://doi.org/10.1016/j.mtla.2022.101345
[N-6.4] L. Prazakova, E. Nolot, E. Martinez, ...M.-C. Cyrille, G. Navarro, *Temperature driven structural evolution of Ge-rich GeSbTe alloys and role of N-doping*, Journal of Applied Physics, 2020, 128(21), 27734, https://doi.org/10.1063/5.0027734

[N-6.5] E. Nolot, Y. Mazel, J.-P Barnes, Sabbione C., Navarro G., A. Tempez., S. Legendre, *Accelerating the development of phase-change random access memory with in-fab plasma profiling time-of-flight mass spectrometry*, Surface and Interface Analysis, 2020, 52(12), pp. 895-899, https://doi.org/10.1002/sia.6823

**Complementary publications (process / applications oriented or second-level involvement)**

[c-6.1] Verdy A, Navarro G, Bernard M, Chevalliez S, Castellani N, Nolot E., Garrione J, Noé P, Bourgeois G, Sousa V, Cyrille MC and Nowak E., *Carbon Electrode for Ge-Se-Sb Based OTS Selector for Ultra Low leakage Current and Outstanding Endurance*, conference paper, IRPS 2018, https://doi.org/10.1109/IRPS.2018.8353635

[c-6.2] Navarro, G.; Bourgeois, G.; Kluge, J.; Nolot E. et al., *Phase-Change Memory: Performance, Roles and Challenges*, 2018 IEEE 10th International Memory Workshop (IMW) Book Series: pp 81-84, 2018, https://doi.org/10.1109/IMW.2018.8388845

[c-6.3] Verdy, A., Bernard, M., Garrione, J., Nolot E. (...), Navarro, G., Nowak, E., Optimized Reading Window for Crossbar Arrays Thanks to Ge-Se-Sb-N-based OTS Selectors, 2019, Technical Digest International Electron Devices Meeting, IEDM 2018-December, 8614686, pp. 37.4.1-37.4.4, https://doi.org/10.1109/IEDM.2018.8614686

[c-6.4] Navarro G., Sabbione C., Bernard M., Bourgeois G., Sandrini J., Castellani N., Cueto O., Garrione J., Cyrille M.C, Frei M., Nistor L., Bernier N., Fillot F., Nolot E., Socquet-Clerc C., Magis T., Laulagnet F., Pakala M., Nowak E., Highly Sb-Rich Ge-Sb-Te Engineering in 4Kb Phase-Change Memory for High Speed and High Material Stability Under Cycling, Published in IEEE 2019, IEEE 11th International Memory Workshop (IMW), May 2019, https://doi.org/10.1109/imw.2019.8739656

[c-6.5] G. Lama, M. Bernard, N. Bernier, G. Bourgeois, E. Nolot, N. Castellani, J. Garrione, M. C. Cyrille, G. Navarro, E. Nowak, Multilevel Programming Reliability in Si-doped GeSbTe for Storage Class Memory, IEEE International Reliability Physics Symposium Proceedings, 2021, 9405116, https://doi.org/10.1109/IRPS46558.2021.9405116

[c-6.6] C. Laguna, M. Bernard, N. Bernier, D. Rouchon,, N. Rochat, J. Garrione, A. Jannaud., E. Nolot, V. Meli, N. Castellani, C. Sabbione, G. Bourgeois, M. C. Cyrille, L. Militaru, A. Souifi, G. Navarro, E. Nowak, Multilayer OTS selectors engineering for high temperature stability, scalability and high endurance, 2021 IEEE International Memory Workshop, IMW 2021, 9439590, http://dx.doi.org/10.1109/IMW51353.2021.9439590

[c-6.7] G.Bourgeois, V.Meli, F.Al Mamun, F.Mazen, E.Nolot, E.Martinez, J.P.Barnes, N.Bernier, A.Jannaud, F.Laulagnet, B.Hemard, N Castellani, M.Bernard, C.Sabbione, F.Milesi, T.Magis, C.Socquet-Clerc, M.Coig, J.Garrione, M.-C.Cyrille, C.Charpin, G.Navarro, F.Andrieu, Carbon ion implantation as healing strategy for improved reliability in phase-change memory arrays, Microelectronics Reliability, 2021, 126, 114221, https://doi.org/10.1016/j.microrel.2021.114221

[c-6.8] G. Navarro, C. Sabbione, V. Meli, L. E. Nistor, M. Frei, J. Garrione, M. Tessaire, F. Fillot, N. Bernier, E. Nolot, B. Sklenard, J. Li, S. Martin, N. Castellani, G. Bourgeois, M. C. Cyrille, F. Andrieu, Multilayer Deposition in Phase-Change Memory for Best Endurance Performance and Reduced Bit Error Rate, 2022 IEEE International Memory Workshop, IMW 2022 - Proceedings, https://doi.org/10.1109/IMW52921.2022.9779285

[c-6.9] G. Lama, M. Bernard, G. Bourgeois, J. Garrione, V. Meli, N. Castellani, C. Sabbione, L. Prazakova, D-S Fernandez Rodas, E. Nolot, M-C Cyrille, F. Andrieu, and Gabriele Navarro, Multilayered Sb-Rich GeSbTe Phase-Change Memory for Best Endurance and Reduced Variability, IEEE Transactions on Electron Devices 2022, Volume 69, Issue 8, Pages 4248 - 42531 August 2022, https://doi.org/10.1109/TED.2022.3184659

[c-6.10] C. Laguna, M. Bernard, F. Fillot, D. Rouchon, N. Rochat, J. Garrione, L. Prazakova, E. Nolot, V. Meli, N. Castellani, S. Martin, C. Sabbione, G. Bourgeois, M-C Cyrille, L. Militaru, A. Souifi, F. Andrieu, and G. Navarro, Ge Content Optimization in Ge(SbSe)N OTS Materials for
## 6.1 Introduction

Germanium, antimony, and tellurium are metalloids considered as “technology critical elements.” Either pure or alloyed in more complex systems, these elements are used for a wide range of applications in optics, photonics, microelectronics, and solar cells industry. The binary (GeTe, SbTe) and ternary (GeSbTe) chalcogenide alloys are widely investigated in the field of phase-change memory (PCM) technology for their phase-change properties, based on the reversible transition between their amorphous and crystalline phases. Nitrogen doping in chalcogenide materials represents a promising way for the improvement of material properties. Indeed, N doping in GeSbTe phase-change alloys have demonstrated to greatly enhance the thermal stability of their amorphous phase, necessary to ensure the data retention of the final phase-change memory device.

In the next section, I will introduce the work done on the chemical and structural characterization of GST alloys, first after deposition, then after controlled thermal budget. This work aimed at providing process experts with appropriate characterization/metrology paths to support deposition and etching steps. Moreover, this work allowed in-depth investigation of the material properties and better understanding of its evolution under controlled thermal budget.

## 6.2 Characterization after deposition

We first used X-ray and optical spectroscopies to characterize N-doped elemental materials (Ge-N, Sb-N and Te-N). Then, we extended the analysis to N-doped binary and ternary alloys.

We deposited the thin materials on 300 mm or 200 mm silicon (001) wafers using magnetron sputtering at ~ 60°C for all samples. We adjusted the nitrogen gas flow while maintaining argon gas flow constant in order to tune the nitrogen content in N-doped samples. We used Ge, Sb and Te targets to grown elemental layers and binaries. The ternary alloys were either deposited from a composite target (Te-rich or Ge-rich GST), or grown by co-sputtering from Te-rich Ge₂Sb₂Te₅ and pure antimony targets in order to get Sb-rich GST films.

### 6.2.1 Key methodological aspects

The XRF-based determination of the composition of N-doped elemental materials (Ge-N, Sb-N, Te-N) was refined to account for varying thickness and for significantly different background in the N-Kα region when compared to N-doped GST (see Section 4). A collaboration with Hicham Kodja, at CEA Iramis (Laboratoire des Eléments Légers) supported this work, with the careful use of NRA instead of EBS for the quantification of the nitrogen content.

The XPS experiments at Al-Ka primary energy were mostly focused on the high kinetic energy region, where Ge 3d, Te 4d and Sb 4d core levels are included in ~ 20 eV. This small region is a direct fingerprint of the composition and binding states in Ge, Sb, Te materials. In addition, an already-developed dedicated oxygen-free vacuum carrier was used to transfer the wafers from the deposition tool to the XPS instrument, in order to perform *quasi in situ* XPS experiments. This was particularly important to identify unstable bonds such as Te-N or Sb-N. As the majority of the materials were conductive, we referred the binding energy to pure gold and copper samples that were used to calibrate the binding energy by setting the Au 4f<sub>7/2</sub> and Cu 2p<sub>3/2</sub> peaks at binding energies of 83.98 ± 0.02 eV and 932.61 ± 0.02 eV, respectively. For non-conductive samples (e.g. GeN), we used of binding energy distance as a more reliable metrics than the comparison to C 1s energy. Finally, we systematized the use of binding energy distance in complex alloys and we suggested this quantity as a relevant metrics of the main structural features in Ge, Sb, Te materials.
The FTIR analysis of N-doped materials was first conducted on automated tools available in the cleanroom. However, these tools feature a limited spectral range (down to 450 cm⁻¹) that made difficult the evaluation of the background contribution. We complemented the spectral range with far infrared analysis conducted in the lab. This measurement path is now systematically used and we included this extension of the spectral range as an important item in the coming collaboration with ONTO, an industrial partner that will deliver a FTIR fab-tool to Leti in 2024. Lastly, we systematized the background analysis so as to make it user independent, as its importance is key in the evaluation of the weighting of the main contribution (Fig 6.1).

<figure><img src="image_89.png" /><figcaption>**Fig 6.1:** We illustrate the need for extended spectral range in the infrared and appropriate baseline correction (added dashed blue line) to extract relevant information from FTIR analysis of N-doped Ge, Sb, Te materials. (Figure extracted from : A. R. Zanatta and I. Chambouleyron, *Nitrogen in the amorphous-germanium network: From high dilution to the alloy phase*, Phys. Rev. B 48, 4560, 1993)</figcaption></figure>

### 6.2.2 Characterization of N-doped elemental materials

We first evidenced that the incorporation of nitrogen in elemental Ge, Sb and Te films grown at 60°C relates to the possibility to form the corresponding X-N bonds (where X=Ge, Sb or Te) and follows the same tendency as the formation energy of the nitride structures (from stable Ge₃N₄ = - 0.26 eV/at to unstable Te₃N₄ = + 0.68 eV/at). Fig. 6.2 illustrates this point using refined XRF-based analysis of aged materials (Q-time after deposition > 1 week).

<figure><img src="image_90.png" /><figcaption>**Fig 6.2:** Nitrogen content in Ge, Sb and Te nitride layers measured by WDXRF as a function of the N₂ flow during the deposition [N-6.1].</figcaption></figure>
By virtue of *quasi in situ* XPS, we unambiguously identified N₂ bonds in N-doped Ge-N, Sb-N (Fig 6.3) and Te-N. In addition, we provided first reference of XPS characterization of unstable tellurium nitrides (Fig 6.4). We noticed that the nitrogen content deduced from XPS in highly doped TeN was significantly larger than WDXRF one (27 at% instead of 13% for 20 sccm sample). A possible reason is in the fast modification of the material when exposed to air (Fig 6.4), when tellurium dioxide TeO₂ is favorably formed (ΔH₀ = -322.6 kJ/mol).

<figure><img src="image_91.png" /><figcaption>**Fig 6.3:** N 1s spectra of Sb₁-xNₓ films with x = 0.17, 0.41 and 0.45 as estimated by XPS [N-6.2]</figcaption></figure>

<figure><img src="image_92.png" /><figcaption>**Fig 6.4:** Te 4d (left) and Te 3d$_{5/2}$ (right) spectra of, from bottom to top: pure tellurium film, then Te$_{1-x}$N$_x$ films with x = 0.08, 0.28 and 0.29 (after 5-minute Q-time) as estimated by XPS. Te(0) peak is shifted to lower energy for 20 sccm sample [N-6.2]</figcaption></figure>
The IR and Raman investigation of as-deposited elemental Ge, Sb and Te systems and their nitrides (GeN, SbN, TeN) extended the literature about GeN and about rarely studied SbN and TeN materials.

<figure><img src="image_93.png" /><figcaption>**Fig 6.5:** Normalized IR spectra of GeN, highlighting the shoulder broadening with increasing N content and illustrating the bonding arrangement between Ge and N atoms [N-6.1]</figcaption></figure>

In the case of GeN, the main absorption band in the IR spectra (ν₁ ~ 690 cm⁻¹) assigned to the vibration of Ge₃N group becomes significantly asymmetric with increasing nitrogen content (Fig 6.5). The Raman spectra (not shown here) confirms the predominance of the contribution at higher wavenumber (ν₂) for high nitrogen content. This additional broad band includes the overall sum of different Ge-N configurations. We suggested that the continuous formation of Ge-N bonds leads to the saturation of the system, resulting in a maximum intensity of the IR band for GeN with 50 at% of nitrogen (20 sccm). The vibration of the Ge₃N group is affected by the large amount of neighboring Ge-N bonds (shift of ν₁ to 680 cm⁻¹) and the N-rich configurations (ν₂) become predominant.

We conducted similar study on Sb, SbN (Fig. 6.6) and Te, TeN (Fig. 6.7) materials and we suggested evolution of bonding arrangement in such system with increasing nitrogen content.

<figure><img src="image_94.png" /><figcaption>**Fig 6.6:** IR spectra of Sb and SbN layers show the main absorption band at about 600 cm⁻¹, highlighting two possible contributions (ν₁ and ν₂). The inset sketches illustrate the bonding arrangement between Sb and N atoms [N-6.1]</figcaption></figure>

<figure><img src="image_95.png" /><figcaption>**Fig 6.7:** IR spectra of Te and TeN layers include Te-O contribution in elemental Te film. The broad band (850–250 cm⁻¹) related to Te-N vibrations increases in intensity upon N incorporation, while sharp peak (at ~ 90 cm⁻¹) related to Te-Te vibrations is reduced. The inset sketches illustrate the N incorporation into interstitial positions between the Te chains of its crystalline structure [N-6.1]</figcaption></figure>
### 6.2.3 Characterization of undoped and N-doped Ge, Sb, Te alloys

We have conducted numerous *quasi in situ* XPS experiments on undoped and N-doped Ge, Sb, Te alloys with varying stoichiometry, some of them one rarely explored alloys such as GeSb. We illustrate in the next pages some of the highlights of this XPS investigation. At the end, the influence GST stoichiometry on the ageing of GST and N-doped GST was evaluated. This point is important, not only to support GST-dedicated etching study but also as the oxidation has an impact on the crystallization temperature of the phase change material. Lastly, we compare the results obtained by IR and Raman in [N-6.1] and by XPS in [N-6.2] to illustrate the nitrogen incorporation in GST materials with different stoichiometry.

In the next paragraph (extracted from ref [N-6.2]), we take the antimony telluride binary case to describe the methodology we used for the decomposition of XPS spectra, and to highlight the interest of BE distance as possible metrics.

Antimony telluride films were deposited on Si(001) wafer by RF-PVD from a pure tellurium target combined with RF-PVD from a pure antimony target. We did not rotate the wafer during the deposition in order to get a large range of stoichiometry on one single wafer. The film thickness was also non-uniform at the wafer level, but kept larger than 20 nm at any point of the wafer.

A first wafer was characterized using *quasi in situ* XPS. Ageing studies were unfortunately not systematically conducted. However, we collected XPS data on few antimony telluride films, first after 5-minute Q-time, then after one week and four months ageing in cleanroom environment.

<figure><img src="image_96.png" /><figcaption>**Fig 6.8:** Low BE spectra (including Sb 4d and Te 4d spectra) of, from bottom to top: Sb<sub>2</sub>Te<sub>3</sub>, Sb-rich and Te-rich SbTe films [N-6.2]</figcaption></figure>

<figure><img src="image_97.png" /><figcaption>**Fig 6.9:** Impact of 5 minutes to 4 months ageing on SbTe alloys with various stoichiometry [N-6.2]</figcaption></figure>

*Quasi in situ* analysis was performed on 13 different points with XPS-deduced composition ranging from Sb-rich Sb<sub>71</sub>Te<sub>29</sub> to Te-rich Sb<sub>29</sub>Te<sub>71</sub> films. This range includes two favorable stoichiometry, Sb<sub>2</sub>Te<sub>3</sub> and Sb<sub>2</sub>Te (formation energy = -0.128 eV/at and -0.062 eV/at respectively), but ignores Sb-rich Sb<sub>16</sub>Te<sub>3</sub> composition (formation energy = -0.048 eV/at). While Sb<sub>2</sub>Te<sub>3</sub> has been extensively studied as part of the pseudo-binary line (GeTe-Sb<sub>2</sub>Te<sub>3</sub>) in the Ge-Sb-Te phase diagram, recent studies also highlighted the characteristics of Sb<sub>2</sub>Te as a phase change material. We acquired high-resolution XPS spectra of C 1s, Sb 3d (and O 1s), Sb 4d (and Te 4d) and Te 3d. In germanium telluride case, Ge and Te spectra could
be described with one-only doublet component whatever the Ge/Te ratio. In contrast, the decomposition of Sb and Te spectra in antimony telluride films depends on the Sb/Te ratio (Fig. 6.8). The influence of the Sb/Te ratio on the BE of Sb and Te can be evaluated in both absolute and relative scale, with systematic use of the difference $\delta_{Te-Sb}$ between Te 4d$_{5/2}$ and Sb 4d$_{5/2}$ BE (Fig. 6.10).

For Sb-poor alloys (Sb ≤ 35 at%), antimony spectra is described with one doublet (BE Sb4d$_{5/2}$ = 32.6 eV) whereas two components are required to model tellurium spectra (BE Te 4d$_{5/2}$ = 40.0 and 40.5 eV). For Sb$_2$Te$_3$ film, both antimony and tellurium spectra are modeled with one doublet (BE Sb 4d$_{5/2}$ = 32.6 eV and Te 4d$_{5/2}$ = 40.0 eV, resulting in $\delta_{Te-Sb}$ = 7.36 eV). When antimony content is increased (42 at% < Sb < 60 at%), antimony spectra is described with two doublets (BE Sb 4d$_{5/2}$ = 32.1 and 32.6 eV) whereas one component is enough to model tellurium spectra (BE Te 4d$_{5/2}$ = 40.0 eV). Finally, in Sb$_2$Te film, both antimony and tellurium spectra are modeled with one doublet (BE Sb 4d$_{5/2}$ = 32.1 eV and Te 4d$_{5/2}$ = 40.0 eV, resulting in $\delta_{Te-Sb}$ = 7.86 eV). It is worth noting that the two discrete values of $\delta_{Te-Sb}$ (7.36 and 7.86 eV) are the two local minima in Figure 6.10. Consequently, based on XPS analysis, we may consider Sb-poor alloys (Sb ≤ 35 at%) as a mixture of elemental Te and Sb$_2$Te$_3$ and mid-Sb alloys (42 at% < Sb < 60 at%) as a mixture of Sb$_2$Te$_3$ and Sb$_2$Te

More specifically, in Sb$_2$Te$_3$ films, the BE of tellurium components shifts towards lower energy when compared to elemental Te (-0.3 eV for Te 4d$_{5/2}$, -0.4 eV for Te 3d$_{5/2}$), while the BE of antimony shows the opposite trend (+0.5 eV for Sb 4d$_{5/2}$ and Sb 3d$_{5/2}$).

We evaluated the evolution of Sb and Te states after 5-minute Q-time on a limited sample set, with antimony content in the 33 to 58 at% range (Fig. 6.9). The enthalpy of formation $\Delta H_0$ is -971.9 kJ/mol for Sb$_2$O$_5$, -709.7 kJ/mol for Sb$_2$O$_3$ and -322.6 kJ/mol for TeO$_2$. Indeed, we could not detect any tellurium oxide component in Te 3d or Te 4d spectra. On the contrary, antimony oxide in Sb(III) state (BE Sb 4d$_{5/2}$ ~ 34.2 eV) was present in all Sb 3d and Sb 4d spectra, and its amount increased with antimony content in SbTe alloy (from ~2 at% of Sb$_2$O$_3$ in Sb$_{33}$Te$_{67}$ to ~15 at% in Sb$_{58}$Te$_{42}$ alloy).

Finally, we measured the impact of 1 week ageing on Sb$_2$Te$_3$ sample, and 4 months ageing on sub-stoichiometric Sb$_{36}$Te$_{64}$ alloy. In both cases, antimony and tellurium spectra still contained metalloid states along with two oxidation states: Sb$_2$O$_3$ (BE Sb 4d$_{5/2}$ ~ 34.2 eV) and Sb$_2$O$_5$ (~34.7 eV), Te sub-oxide (BE Te 4d$_{5/2}$ ~ 41.5 eV) and TeO$_2$ (~43.7 eV). The ageing results in an increase of the antimony content in the surface layer. Surprisingly, Te(0) state in Sb$_2$Te$_3$ sample is split in two components (Te-Sb and Te-Te if we refer to BE values) whereas only Te-Sb component was present just after deposition. Moreover, Te-Te component of Sb$_{36}$Te$_{64}$ alloy appears almost unoxidized after 4 months (Te-Te content after 4 months equals after deposition), when the content of Te-Sb component moves from 57.0 to 7.0 at%, suggesting a preferential oxidation of Te-Sb.

<figure><img src="image_98.png" /><figcaption>**Fig 6.10:** Distance(s) between Sb4d$_{5/2}$ and Te4d$_{5/2}$ core levels in SbTe alloys, as a function of Sb content in the film [N-6.2]</figcaption></figure>

<figure><img src="image_99.png" /><figcaption>**Fig 6.11:** The distance $\delta_{N-Ge}$ between the BE of Ge3d$_{5/2}$ (Ge-N) and the major component of N1s spectra (N-Ge) shows a linear dependency with N content measured by WDXRF [N-6.2]</figcaption></figure>
From a methodological point of view, the use of BE distance, which was already considered in Section 3 (MoS₂ case) can apply to undoped and N-doped Ge, Sb, Te:

- To confirm structural information in complex alloys (Fig 6.10)

- To access accurate BE in the case of non-conductive samples, with no need to refer to artificial C 1s referencing (Fig 6.11)

In the case of GST ternary alloys, Ge 3d, Sb 4d and Te 4d spectra could be modeled with one-only doublet (Fig. 6.12) whatever the GST composition, with remarkably stable shape and FWHM along with only slight variations in BE among samples. Even though a complex ternary system as GST cannot be reduced to the simple addition of elementary and binary compounds, it is worth noting that $\delta_{Ge-Te}$ distance is significantly higher for Ge-rich GST (10.75 eV) than in Te-rich GST225 (10.36 eV), which agrees with our findings about germanium tellurides.

The influence of one month-ageing in cleanroom environment is not exactly similar for Ge-rich and Te-rich samples (Fig. 6.13, Table 6.1), whereas the following similarities can be noted: i/ the presence of germanium and antimony in both metalloid state and oxidized state (Ge(IV), Sb(III), Sb(V)), ii/ the presence of tellurium in metalloid state, iii/ the significant reduction of tellurium content in the surface layer, as deduced from Te 4d, Sb 4d and Ge 3d integrated intensities, iv/ as a counterpart, the significant increase of the antimony content in the surface layer. The main difference lies in the tellurium spectra. In Te-rich GST, tellurium is found in Te(0) and in oxidized states (sub-oxide and TeO₂ as ascribed in the section related to elementary tellurium). In contrast, tellurium is only present in metalloid state in Ge-rich GST film. The content of Te(0) in both films are remarkably aligned, but we cannot draw firm conclusions based on two measurements only.

<figure><img src="image_100.png" /><figcaption>**Fig 6.12:** Low BE spectra (including Ge 3d, Sb 4d and Te 4d spectra) of GeSbTe films with various stoichiometry [N-6.2]</figcaption></figure>

<caption>**Fig 6.13:** Influence of one-month ageing in cleanroom environment on Ge 3d, Sb 4d and Te 4d states in Te-rich and Ge-rich GST samples [N-6.2]</caption>
<table><caption>**Table 6.1:** XPS-deduced composition of the different GST films, and the influence of one-month aging on Ge-rich and Te-rich GST materials (Te*: tellurium sub-oxide) [N-6.2]</caption><thead><tr><th></th><th>Ge (%at)</th><th>Sb (%at)</th><th>Te (%at)</th></tr></thead><tbody><tr><td><strong>Sb-rich GST</strong></td><td></td><td></td><td></td></tr><tr><td><em>In-situ</em></td><td>16.3</td><td>47.1</td><td>36.6</td></tr><tr><td><strong>Ge-rich GST</strong></td><td></td><td></td><td></td></tr><tr><td><em>In-situ</em></td><td>65.8</td><td>11.5</td><td>22.7</td></tr><tr><td rowspan="3">aged</td><td>Ge<sup>0</sup>: 10.6</td><td>Sb<sup>0</sup>: 3.5</td><td>Te<sup>0</sup>: 13.0</td></tr><tr><td>Ge<sup>4+</sup>: 58.0</td><td>Sb<sup>3+</sup>: 8.4</td><td></td></tr><tr><td></td><td>Sb<sup>5+</sup>: 6.5</td><td></td></tr><tr><td><strong>Te-rich GST (GST225)</strong></td><td></td><td></td><td></td></tr><tr><td><em>In-situ</em></td><td>24.3</td><td>23.2</td><td>52.5</td></tr><tr><td rowspan="3">aged</td><td>Ge<sup>0</sup>: 2.6</td><td>Sb<sup>0</sup>: 3.4</td><td>Te<sup>0</sup>: 13.5</td></tr><tr><td>Ge<sup>4+</sup>: 31.6</td><td>Sb<sup>3+</sup>: 19.1</td><td>Te*: 1.5</td></tr><tr><td></td><td>Sb<sup>5+</sup>: 12.8</td><td>Te<sup>4+</sup>: 15.5</td></tr></tbody></table>

Finally, we combined infrared spectroscopy [N-6.1] and XPS [N-6.2] to investigate the nitrogen bonding in **N-doped GeSbTe alloys**. In the case of N-doped Ge-rich GST (*not shown here*) and Te-rich GST (Fig. 6.13, *left*), XPS only shows Ge-N bonds. For N-doped Sb-rich GST, both Ge-N and Sb-N are unambiguously detected (Fig. 6.13, *right*). IR spectroscopy evidences similar trend. **Fig. 6.14** shows the IR spectra of elemental nitrides (GeN, SbN, TeN) and N-doped Sb-rich and Ge-rich GST (SGSTN and GGSTN *resp.*). The nitrogen flow was the same (2 sccm) for all the wafers. The direct comparison of the spectra highlights the significant intensity difference and position shift of the bands assigned to the Ge-N, Sb-N, and Te-N bonds of the related elemental nitride layers. For the GGSTN, the best match is found with GeN alloy, in terms of position and shape of the observed features, with no evidence of other bonds that Ge-N in GGSTN alloys. The IR spectrum of SGSTN features two contributions correlated with GeN and SbN, hence indicating the formation of both Ge-N and Sb-N bonds in the system. Despite the high Sb content in SGSTN, the intensity ratio between the contributions highlights the preferential formation of Ge-N bonds over Sb-N bonds in the system, which is aligned with XPS findings and thermodynamic data.
<figure><img src="image_101.png" /><figcaption>**Fig 6.13** : Low BE region of undoped and N-doped Te-rich GST (**left**) and Sb-rich GST (**right**). The description of Sb 4d region of N-doped Sb-rich GST requires two doublets (Sb° and Sb-N) [N-6.2]</figcaption></figure>

<figure><img src="image_102.png" /><figcaption>**Fig 6.14** : The comparison of IR spectra of Ge, Sb, Te and Ge-rich and Sb-rich GeSbTe upon the N incorporation (N₂ flow of 2 sccm was considered for all the layers). Dashed lines indicate the position of Ge-N bonds contribution in Ge-rich GSTN, and Ge-N and Sb-N bonds contributions in Sb-rich GSTN [N-6.1]</figcaption></figure>
## 6.3 Impact of the thermal budget

### 6.3.1 Analytical techniques

To monitor the influence of a controlled thermal budget on the structural properties of thin (≤ 100 nm) materials requires dedicated methodologies. At CEA-Leti, important internal know-how on phase change material rely on the measurement of the resistivity as a function of the temperature under inert N₂ atmosphere, with typical ramp-up of 10 °C/min. However, such methodology does not apply to all samples, for instance when the phase change material is encapsulated with a thin dielectric layer (e.g. GeN).

To overcome this problem, we systematized the use of *in situ* ellipsometry analysis on Woollam M2000 tool, using on the one hand fast CCD-based detection and on the other hand liquid nitrogen for accurate temperature regulation and fast cooling, so as to meet the requirement of *in situ* analysis compatible with 10 °C/min ramps. For instance, Fig. 6.15 shows the angle psi (ψ), related to the ratio between reflection coefficient for *p* and *s* polarization, as a function of the annealing temperature for different GST alloys grown by co-sputtering of Ge and GST225 targets and encapsulated with 3.5 nm of amorphous carbon. The GST225 sample shows two sharp increases of ψ at around ~165 °C and ~350 °C corresponding to the amorphous to fcc and fcc to hex transition, respectively. In that case, the evolution of ψ at λ=700 nm was appropriate to robustly track the evolution of GST with annealing temperature.

<figure><img src="image_103.png" /><figcaption>**Fig 6.15** : *In situ* ellipsometry measurements at λ=700 nm shows the amorphous-to-fcc transition delay for the crystallization of GST and Ge phase for Ge-rich GST alloys studied in [N-6.3]</figcaption></figure>

During *in situ* analysis, we collect ellipsometry data over 190-1700 nm spectral range each 10 seconds typically, resulting in a large amount of data. It may be frustrating to extract only the evolution of ψ at one wavelength instead of exploiting the full spectral data to catch the evolution of the thickness and the optical constant of the phase change material along the annealing ramp. However, we saw in Section 2 that ellipsometry, although highly sensitive to small change in the material properties, may suffer from correlation among fitting parameters. We performed ellipsometry analysis after deposition then after *ex situ* annealing, in the frame of STM – Leti program. We use XRR data to assess the reduction of ellipsometry data for as deposited samples, but we did not perform any XRR analysis after annealing. For some samples, the best model calculation of ellipsometry data after annealing led to dubious structure (Fig. 6.16) even for ellipsometry data collected over wide spectral and angular ranges. In order to improve the reliability of the *in situ* ellipsometry analysis and as *in situ* XRR analysis with ramp-up of 10 °C/min may not be possible due to fast sample height variations, we plan to compare *in situ* ellipsometry data to a set of *ex situ* XRR data of samples annealed at discrete temperatures. The samples
can be annealed either on the resistivity tool or on the ellipsometry tool as we checked, using various phase change materials with different crystallization temperatures, that the temperature of the two tools agree within 2 °C for annealing up to 500°C at least.

<figure><img src="image_104.png" /><figcaption>**Fig. 6.16** : The ellipsometry data collected on GST film cap with thin TiN differ significantly after annealing (*bottom*). In spite of data collected over wide spectral and angular ranges, the best model calculation of ellipsometry data after annealing led to dubious structure (*top*). [Unpublished].</figcaption></figure>

X-ray diffraction is a technique of choice to monitor the structural evolution of phase change material with temperature. Due to limited sensitivity of tube-based instrument and concerns about dynamical height alignment, we mostly performed *ex situ* XRD analysis on samples annealed with well-controlled ramps and temperatures on the resistivity tool. We only performed one isothermal XRD analysis conducted few degrees below the crystallization temperature, which permitted to slow down the crystallization process and to detect small structural changes (Fig. 6.17). In the frame of Oumaima Daoudi's PhD, we collaborate with Hubert Renevier at UGA-LMGP in order to perform *in situ* XRD analysis in the lab with rotating anode and 2D detector and to benefit from high brilliance source to run dedicated experiment at ESRF facility with same annealing ramps as for ellipsometry or resistivity measurement.
<figure><img src="image_105.png" /><figcaption>**Fig. 6.17** : Isothermal XRD measurements at ~300 °C on Ge-rich GST showing the development of GST225 and Ge crystalline phases (black and violet dashed lines, respectively). A transient G+GST phase (red dashed line) is detected before the appearance of the GST225 phase [N-6.4]</figcaption></figure>

We systematically use Raman spectroscopy (and IR spectroscopy for N-doped materials) in parallel with X-ray diffraction, both *ex situ* on carefully annealed samples. Even though Raman spectroscopy cannot directly access changes in d-spacing, it applies to very small amount of material, it is very sensitive (Sections 6.2.2 and 6.2.3) to small modification of the material structure. Moreover, its µm-like spot permits to use Raman spectroscopy on product wafers, for instance to probe arrays of lines of phase change materials for different width and inter-distance.

Finally, as we deal a lot with *ex situ* characterization, we need to protect the samples from undesirable ageing and oxidation that affect their evolution with thermal budget. The impact of capping is highlighted in Fig. 6.18, where the elemental depth profile in GST stacks is measured with PP-TOFMS, using an Argon-Helium (20% He) pulsed radio-frequency plasma for sample sputtering and ionization and reference-free IBR method for quantification. Although the optimization of the encapsulating layer is a large topic, we essentially used (during the last 7 years) thin amorphous carbon layer deposited at low temperature in the same process tool as the phase change material (no air break). We determined the thickness of this capping layer in a study about complex chalcogenide amorphous films close to phase change materials, using XPS to establish that 3.5 nm was an appropriate thickness to limit the oxidation when keeping deposition time (at very low deposition rate) reasonable (Fig. 6.19).
<figure><img src="image_106.png" /><figcaption>**Fig. 6.18:** The PP-TOMFS chemical depth profiles of Ge-rich GeSbTe films, either unprotected or capped with a thin Ge-based layer, illustrate the importance of the capping strategy to preserve Ge-rich stoichiometry of the active layer after thermal annealing [N-6.5, Cover of SIA journal]</figcaption></figure>

<figure><img src="image_107.png" /><figcaption>**Fig. 6.19:** XPS measurements revealing that the significant oxidation of the surface of uncapped OTS material (Ge-O and Sb-O binding states) is drastically reduced by the thin carbon capping layer [c-6.1]</figcaption></figure>
### 6.3.2 Characterization of GST and GST-N alloys

In the frame of Lucie Prazakova's PhD, we combined X-ray, optical and electrical techniques to investigate the temperature-driven structural evolution of GST alloys as a function of the material stoichiometry (GST225 vs Ge-rich GST, influence of nitrogen doping). This work participate to the understanding of these industry-relevant materials. This subsection includes some of the major findings of this work (Lucie Prazakova's manuscript, [N-6.3, N-6.4]), where the combination of Raman spectroscopy and X-ray diffraction was extensively used on samples annealed *ex situ* at carefully selected temperatures.

First, we used deposited GST material by co-sputtering of GST225 and Ge targets, resulting in GST materials with fixed Sb/Te ratio but varying Ge content (from 0 up to 55% addition). A thin amorphous carbon capping layer was deposited on the 100 nm-thick films. The analysis of temperature-dependent Raman spectra of reference GST225 evidenced the shift of Sb-Te modes between cubic fcc (above 160°C) and hexagonal (above 300°C) phases (Fig. 6.20). In Ge-rich GST; Raman spectroscopy highlights the importance and the stability of Sb-Te structural unit along with temperature-driven evolution of the material. The combination of Raman spectroscopy and X-ray diffraction reveals the segregation of Ge-rich Ge, which results in stable crystalline phases of Ge and GST225 (Fig. 6.20).

<figure><img src="image_108.png" /><figcaption>**Fig. 6.20:** The influence of thermal budget on GST225 and Ge-rich GST as investigated by Raman spectroscopy and X-ray diffraction [N-6.4].</figcaption></figure>

The analysis of temperature-dependent Raman spectra permits to evidence structural modifications at temperature significantly below the crystallization temperature. A careful analysis of the Raman intensities of the contributions of Ge-Te, amorphous Ge and crystalline Ge in Ge-rich GST allowed us to suggest a two-step reorganization of the material (Fig. 6.21).

The structural evolution above the crystallization temperature was investigated using both *ex situ* (Fig. 6.20) and *in situ* (Fig. 6.22) XRD analysis, which highlighted the presence of Ge-rich GST phase (from 335 to 350°C, also evidence on Raman spectra) that can be considered a transitional step of reorganization through which the system passes before the appearance of GST225 and Ge crystalline phases. Raman spectroscopy and X-ray diffraction-deduced evolution of Ge-rich GST (Fig. 6.22) was further confirmed by TEM-EDX analyses [N-6.3, N-6.4] that highlighted the elemental migration and the formation of Ge- and Sb/Te-enriched zones, evidencing progressive demixing process. We extended the work to evaluate:
- the *impact of nitrogen addition* in the evolution of Ge-rich GST, where we evidenced similar structural evolution, but delayed to higher to higher temperature by the presence of Ge-N that play a key role in the thermal stability in Ge-rich GST-N materials [N-6.4]

- The *influence of Ge content* on the temperature evolution of GST materials [N-6.3], where we for instance showed that the competition between different phenomena, which depend on Ge content and temperature : i/ the nucleation and growth of a GST225 fcc phase; ii/ the Ge segregation out of the formed GST phase, which is delayed by increasing Ge content but favored by increasing temperature; iii/ the backward chemical diffusion of Ge, which increases with Ge content; iv/ the nucleation and growth of Ge crystalline phase, which favors the Ge segregation

The *influence of Sb/Te ratio* is one of the topic investigated in the frame of Oumaima Daoudi's PhD.

<figure><img src="image_109.png" /><figcaption>**Fig. 6.21:** Temperature-dependent Raman spectra of Ge-rich GST films highlights the progression structural reorganization of the materials towards Ge and GST crystalline phase. Raman spectroscopy permits to evidence structural modification that occurs at temperature significantly lower than the crystallization temperature</figcaption></figure>

<figure><img src="image_110.png" /><figcaption>**Fig. 6.22:** Structural evolution of Ge-rich GST with annealing temperature, which shows the progress of GST225-fcc phase crystallization, the disappearance of transient G+GST phase with the expulsion of Ge atoms and the following Ge phase crystallization</figcaption></figure>
# 7 Perspectives

## 7.1 Towards accurate and NMI traceable optical constants

Spectroscopic ellipsometry is extensively used to characterize the optical constants of substrates and thin materials. As reported in Section 3, we are still missing traceable standards and NMI-approved protocols for the determination of optical constants (at least in the 0.6 – 7.0 eV range).

My mid-term perspectives around this topic would be:

- To refine and evaluate internal (CEA-Leti) protocol for the assessment of refractive index of transparent materials, by combination of M-line calibrated against NIST-traceable standard materials and spectroscopic ellipsometers calibrated against M-line using thermal SiO₂ films (Fig. 7.1). Additional collaboration with labs with expertise and M-line tools with large spectral range (Institut Lumière in Lyon, Ecole Centrale Marseille, ...)

- To engage with the partners of the Empir/ATMOC project (and possible follow-up project) in order to write and propagate NMI-approved protocols for establishment (and when possible reduction) of the uncertainty budget in the measurement of optical constants with spectroscopic ellipsometry.

ATMOC project will not address the issue of the accuracy of extinction coefficient *k*, which is a major concern for optical filters, imagers and other optical device. One additional difficulty is often in the analysis of materials with low extinction coefficient (less than 0.01 typically) that cannot be precisely measured solely by ellipsometry (Fig. 7.2). To build collaborations around the accurate measurement of low extinction coefficient by means of combination of ellipsometry with R&T and/or specific sample design for instance would be a mid/long term perspective.

<figure><img src="image_111.png" /><figcaption>Fig. 7.1: Scheme of the future internal assessment of refractive index with spectroscopic ellipsometry</figcaption></figure>
<figure><img src="image_112.png" /><figcaption>**Fig. 7.2:** Absorption coefficient $\alpha = \lambda/4\pi k$ of a hydrogenated amorphous silicon (a-Si:H) film determined by spectroscopic ellipsometry (SE), transmittance/reflectance measurement (T&R) and a photocurrent characterization method $\Delta\sigma_p$. From Optical properties of solids, R. W. Collins and K. Vedam, in Encyclopedia of Applied Physics, vol. 12, 285–336, Wiley-VCH (1995).</figcaption></figure>

## 7.2 Comprehensive Raman spectroscopy analysis in cleanroom environment

I am rather new in the Raman field. In 2020, I motivated the modification of a Renishaw lab tool so as to allow manual polarization-dependent Raman measurement of up-to 300 mm wafers in CEA-Leti cleanroom. In the frame of Lucie Prazakova's PhD, we started a mid-term collaboration with a colleague at CEA-Leti in order to compare the experimental Raman spectra with *ab initio* calculation using Phonopy Spectroscopy package [N-6.1]. From the experimental side, the introduction of 2D materials for industry-driven programs using mastered deposition on 300 mm wafers strengthens the need for inline Raman. Moreover, recently announced major 10 nm FDSOI program at CEA-Leti highlights the importance of inline polarization-dependent Raman for the strain analysis of ultrathin strain SiGe, Si and SiP films, in small areas of line arrays with few tens nm dimensions.

In order to address these topics, I motivated the following programs and actions that will result in personal mid-term perspectives:

- I motivated a 3 year-collaboration with Semilab industrial supplier, starting mid-2023. In the frame of this collaboration, Semilab will introduce automated polarization-dependent multi-$\lambda$ Raman tool in CEA-Leti cleanroom, in order to address complex topics such as strain management for 10 nm FDSOI and 2D characterization. I hope that the collaboration will lead to optimization in the optical setup and analysis software in order to optimize the accuracy of Raman analysis.

- The use of polarization-dependent Raman analysis (instead of more classical UV Raman) for strain analysis of ultrathin epitaxial layer on line arrays was first motivated by IMEC works (Fig. 7.3). Simulation of the distribution of the normalized electric field in nanostructures must support the optimization of dedicated samples (and related lithography masks). This item is addressed (in parallel with analysis of 2D materials) in the frame of a Badreddine Smiri postdoc position started in early 2023.

- The use of inline to characterize strain and/or crystallinity evolution on product wafers is part of ST-Leti program, which supported Maxime Lepage's master in 2022 and supports Damien Monteil's master in 2023.

- Finally, I motivated a 2 year collaboration between two entities of CEA, in the frame of a PTC program ("Programme Transverse de Compétences"), starting in mid-2023. The most important part of this program will be done by Lucas Baguet's team at CEA/Bruyères le Châtel, who was
in charge of the development of ABINIT *ab initio* Raman software. In the frame of this collaboration, Lucas' team will modify ABINIT in order to account for larger number of atoms, which is a prerequisite to address polycrystalline materials and thin films. ABINIT simulation will be compared against experimental spectra collected at Leti. The modified ABINIT package and related know-how will be transferred to Leti in order to support Raman-based material characterization and metrology.

<figure><img src="image_113.png" /><figcaption>**Fig. 7.3:** (a) (Left) FEM simulations of the normalized amplitude of the electric fields $|E_{Ge}|$ (solid red line) and $|E_{Si}|$ (interrupted blue line), respectively, in the center of the air/Ge interface and of the SiO$_2$/Si interface as a function of the pitch of the fin array shown on the right. The dotted red line gives $|E_{Ge}|$ in the case of infinitely deep fins. A normally incident plane wave of wavelength $\lambda_0 = 532$ nm and amplitude $|E_0|$ polarized parallel to the fin edges is assumed. (Right) Four of the Ge(30 nm)/Si$_{0.3}$Ge$_{0.7}$(130 nm)/Si(125 nm) fins of the simulated two-dimensional array. (b) Distribution of the normalized electric field inside the unit cell of a nanofocusing array of 20-nm wide fins. (c) Distribution of the normalized electric field inside the unit cell of an array of 100-nm wide fins. [from J. Bogdanowicz, T. Nuytten, A. Gawlik, et al., Appl. Phys. Lett. 108, 083106 (2016); https://doi.org/10.1063/1.4942603].</figcaption></figure>

## 7.3 Extend the range of chemical characterization

XPS with Al-Kα primary beam is capable of chemical analysis with better than 1 eV resolution of films with thickness less than 10 nm. The inelastic mean free path, then the information depth, can be extended by the use of higher energy source such as Ag-Lα, Cr-Kα or Ga-Kα for instance, at the price of significant reduction of cross sections. Inelastic background analysis permits to access deeper interfaces, but only provides elemental distribution, without information about chemical speciation.

On the other hand, XRF easily probes films thicker than 100 nm. However, the energy resolution of lab or fab tools is in the 100 eV range for ED-XRF systems, and at least 4 eV for WDXRF tools, which is appropriate for compositional analysis but not for chemical characterization.
A mid/long term perspective would be to extend the range of chemical characterization in lab and cleanroom, by different means:
- The collaboration with an XPS supplier that could provide multi-energy tool with p-ARXPS capability in order to access chemical depth-profiles at extended depth

- The collaboration with XRF labs that would have very high resolution XRF systems, for instance synchrotron radiation facility using Von Hamos geometry (Fig. 7.4). In the short/mid-term, I should engage a collaboration with Mauro Guerra, from Universidade NOVA de Lisboa around ultra-high-resolution reference-free WDXRF characterization of nanostructured semiconductor samples by virtue of double flat-crystal spectrometer (DCS) equipped with NIST-traceable high quality Si (111) crystals and providing 0.5 eV resolution at 3 keV.

<figure><img src="image_114.png" /><figcaption>**Fig. 7.4:** Estimated resolution of the spectrometer at selected $Ka_1$ (solid squares) and $K\beta_1$ (open circles) emission lines of von Hamos-type hard X-ray spectrometer at the PETRA III beamline P64, [Kalinko et al., Journal of Synchrotron Radiation, Volume 27, part 1, 2020, https://doi.org/10.11107/S1600577519013638]</figcaption></figure>

## 7.4 Combine XRR and (GI)-XRF in Leti cleanroom

As explained in Section 5, I have slowed down the research activity around the combination of XRR and (GI)-XRF, mostly due to the lack of related tool at CEA-Leti. I finally motivated the acquisition of an inline instrument that will combine three monochromatic primary beams (Cu-K$\alpha$, Au-L$\beta_1$ and Ag-K$\alpha$) mounted on a goniometer, and that will feature XRR and XRF (EDXRF, SDD) capability. The tool should arrive at Leti at the end of 2023 (Fig. 7.5).

Then, the research around the combination of XRR and multi-energy (GI)-XRF will be reactivated, motivated by the need for 10 nm FDSOI, new memories, GaN for power and LED, and 2D materials. It will be supported by:

- A joint development program with Rigaku (supplier of the new tool), which will include, *among other topics*, some work around i/ the combination of Ag-Ka and Cu-Ka sources for the analysis of ultrathin $MoS_2$, ii/ the optimization of FP software dedicated to ED-XRF, that is to say that will deal with XRF spectra instead of discrete values of net intensities

- A postdoctoral position about XRF metrology, financed in the frame of MINOS program, and expected from Q3-2023
<figure><img src="image_115.png" /><figcaption>**Fig. 7.5:** Multi-energy XRR-(GI)XRF MFM310 tool supplied by Rigaku</figcaption></figure>

One limitation of XRR and GIXRF is in the spot size as these measurements are performed in grazing incidence, using an elongated beam. We are aware of this limitation that could be partially overcome by the design of dedicated elongated measurement areas on lithographic masks. The grazing exit geometry (GE-XRF) is another possibility<sup>44</sup> that allows to get rid of the spot size limitation. Among others, PTB/Berlin (P. Honicke et al) demonstrated the interest of GE-XRF setup, not only to probe uniformly deposited materials, but also and above all to access elemental distribution in laterally inhomogeneous samples such as line arrays (Fig. 7.6). Even though we are aware of such developments, we do not include them on our short or mod-term research directions.

<figure><img src="image_116.png" /><figcaption>**Fig. 7.6:** Combination of GISAXS and GEXRF to probe geometrical dimensions and elemental distribution in line arrays [D. Skroblin et al, Nanoscale, 2022,14, 15475-15483, https://doi.org/10.1039/D2NR03046B]</figcaption></figure>

<footnote n="44"><sup>44</sup> GE-XRF exchanges GIXRF beam paths for the excitation and detection of X-ray fluorescence. The sample is illuminated perpendicularly and the emerging fluorescence radiation is detected at a grazing emission angle.</footnote>
## 7.5 Improve inline quantification of low-Z elements in thin inorganic films

We have presented in Section 4.4 the difficulty related to the quantification of low-Z elements in thin materials. This topic is not limited to the analysis of nitrogen in GST phase change materials, and the demand related to the analysis of light elements such as H, B, C, O and N is increasing (Fig. 7.7). I will continue to investigate on that topic, even though no dedicated program supports the metrology activity. The main directions will include:

- FTIR assessment against ion beam analysis (IBA) techniques for the quantification of hydrogen in (at least) thin dielectrics

- Combination of WDXRF with (when appropriate) FTIR for the quantification of B, C, O and N in thin films

- Collaboration with Julien Colaux, expert of ion beam analysis (IBA) for materials characterization and associated professor at the University of Namur. Julien was post-doc at the Surrey Ion Beam Centre (with *now retired* Pr Chris Jeynes) and is willing to collaborate with us to provide IBA composition of materials with mastered uncertainties

- Engage collaboration with NMI (PTB) in order to quantify the influence of photo- and Auger-electrons in XRF-based metrology of light elements in thin materials

- If possible, engage more formally in the Fundamental Parameters Initiative, where NMIs, RTOs and industry share information that motivate the establishment of FP with improved uncertainties, which will serve accurate XRF analysis.

<figure><img src="image_117.png" /><figcaption>**Fig. 7.7:** Frequency of usage of chemical elements of the periodic table in nanotechnology [from E. A. Goodilin et al, *Nanotechnology Facets of the Periodic Table of Elements*, ACS Nano 2019, 13, 10, 10879–10886, 2019, https://doi.org/10.1021/acsnano.9b06998]</figcaption></figure>
## 7.6 Development of (quasi) *in situ* and *in operando* metrology

I showed in Section 3 the work around *in operando* optical analysis in a PE-CVD tool, in Section 5 the added value of quasi *in situ* transfer for XPS characterization of phase change materials (PCM), and in Section 6 the continuous work around *in situ* analysis of phase change materials by optical, electrical and X-ray methods.

The short-term perspectives include some improvement in methodologies and instrumental setup related to PCM-related work in the frame of Oumaima Daoudi's PhD.

The extension of quasi *in situ* analysis to multi-energy XPS combined to highly surface sensitive LEIS technique (Low energy ion scattering, investigated in [N-5.22]) is a mid-term perspective that strongly depends on budget allocation. It would significantly improve the chemical characterization of surface with ultimate depth-resolution (LEIS) combined to up-to 20 nm information depth (HAXPES).

I will try to motivate a program that would combine (quasi) *in situ* optical and X-ray technique to support the development of thin sub-stoichiometric oxides. Here again, this is a mid-term perspective that strongly depends on budget allocation.
8 List of publications

2023

T.R. Bure, O. Renault, E. Nolot, T. Lardin, C. Robert-Goumet, N. Pauly, Assessing advanced methods in XPS and HAXPES for determining the thicknesses of high-k oxide materials: From ultra-thin layers to deeply buried interfaces, Applied Surface Science, 2023, 609, 155317, https://doi.org/10.1016/j.apsusc.2022.155317

2022

L. Prazakova, E. Nolot, E. Martinez, D. Rouchon, N. Rochat, C. Sabbione, J. Li, D. Eichert, G. Pepponi, M. Bernard, and G. Navarro, Spectroscopic study of nitrogen incorporation in Ge, Sb, and Te elemental systems: A step toward the understanding of nitrogen effect in phase-change materials, J. Appl. Phys. 132, 205102 (2022); https://doi.org/10.1063/5.0117596

C. Laguna et al, Ge Content Optimization in Ge(SbSe)N OTS Materials for Selector Applications, IEEE Transactions on Electron Devices, 2022, 69 (11), pp. 6277-6283, https://doi.org/10.1109/TED.2022.3203368

G. Lama et al, Multilayered Sb-Rich GeSbTe Phase-Change Memory for Best Endurance and Reduced Variability, IEEE Transactions on Electron Devices 2022, Volume 69, Issue 8, Pages 4248 - 42531 August 2022, https://doi.org/10.1109/TED.2022.3184659

B. Chatmaneeringcharoen M. Fraccaroli, F. Martin, C. Guedj, E. Nolot, D. Rouchon, N. Vaxelaire, R. Templier, A. Grenier, A-M. Papon, H. Roussel, L. Rapenne, H. Renevier and S. Cadot, Synthesis of In-Plane Oriented Tin Sulfides by Organosulfur-Mediated Sulfurization of Ultrathin SnO₂ Films, Chemistry of Materials, 2022, 34(13), pp. 5842-5851, https://doi.org/10.1021/acs.chemmater.2c00567

O. Renault, P.-M. Deleuze, J. Courtin, T. R. Bure, N. Gauthier, E. Nolot, C. Robert-Goumet, N. Pauly, E. Martinez and K. Artyushkova, New directions in the analysis of buried interfaces for device technology by hard X-ray photoemission, Faraday Discussions, 2022, 236, pp. 288-310, https://doi.org/10.1039/d1fd00110h

C. Laguna, M. Bernard, J. Garrione, N. Castellani, V. Meli, S. Martin, F. Aussenac, D. Rouchon, N. Rochat, E. Nolot, G. Bourgeois, M. C. Cyrille, L. Militaru, A. Souifi, F. Andrieu, G. Navarro, Multilayer Structure in SeAsGeSi-based OTS for High Thermal Stability and Reliability Enhancement, European Solid-State Device Research Conference, 2022, 2022-September, pp. 225-228, https://doi.org/10.1109/ESSDERC55479.2022.9947186

M. Frauenrath, L. Casie, O. Concepción, N. Coudurier, N. Gauthier, S. M. N'hari, E. Nolot, P. Rodriguez, D. Buca, N. Pauc, V. Reboud, J.-M. Hartmann, Advances in In-situ Boron and Phosphorous Doping of SiGeSn, 2022 ECS Trans. 109 3, https://doi.org/10.1149/10904.0003ecst

G. Navarro, C. Sabbione, V. Meli, L. E. Nistor, M. Frei, J. Garrione, M. Tessaire, F. Fillot, N. Bernier, E. Nolot, B. Sklenard, J. Li, S. Martin, N. Castellani, G. Bourgeois, M. C. Cyrille, F. Andrieu, Multilayer Deposition in Phase-Change Memory for Best Endurance Performance and Reduced Bit Error Rate,
L.Prazakova, E.Nolot, E.Martinez, D.Rouchon, F.Fillot, N.Bernier, R.Elizalde, M.Bernard, G.Navarro,
*The effect of Ge content on structural evolution of Ge-rich GeSbTe alloys at increasing temperature*,
**Materialia 21 (2022) 101345**, https://doi.org/10.1016/j.mtla.2022.101345

G.Bourgeois, V.Meli, F.Al Mamun, F.Mazen, E.Nolot, E.Martinez, J.P.Barnes, N.Bernier, A.Jannaud,
F.Laulagnet, B.Hemard, N.Castellani, M.Bernard, C.Sabbione, F.Milesi, T.Magis, C.Socquet-Clerc,
M.Coig, J.Garrione, M.-C.Cyrille, C.Charpin, G.Navarro, F.Andrieu, *Carbon ion implantation as
healing strategy for improved reliability in phase-change memory arrays*, **Microelectronics
Reliability, 2021**, 126, 114221, https://doi.org/10.1016/j.microrel.2021.114221

Frauenrath M, Kiyek V., von den Driesch N., Veillerot M., Nolot E., Buca D. and Hartmann J-M, *An
In-Depth Study of the Boron and Phosphorous Doping of GeSn*, **2021 ECS J. Solid State Sci. Technol.**
*10 085006*, http://dx.doi.org/10.1149/2162-8777/ac1d27

C. Laguna, M. Bernard, N. Bernier, D. Rouchon, N. Rochat, J. Garrione, A. Jannaud, E. Nolot, V.
Meli, N. Castellani, C. Sabbione, G. Bourgeois, M. C. Cyrille, L. Militaru, A. Souifi, G. Navarro, E.
Nowak, *Multilayer OTS selectors engineering for high temperature stability, scalability and high
endurance*, **2021 IEEE International Memory Workshop, IMW 2021 - Proceedings**, 2021, 9439590,
http://dx.doi.org/10.1109/IMW51353.2021.9439590

G. Lama, M. Bernard, N. Bernier, G. Bourgeois, E. Nolot, N. Castellani, J. Garrione, M. C. Cyrille, G.
Navarro, E. Nowak, *Multilevel Programming Reliability in Si-doped GeSbTe for Storage Class Memory*,
**IEEE International Reliability Physics Symposium Proceedings, 2021**, 2021-March, 9405116,
https://doi.org/10.1109/IRPS46558.2021.9405116

Nolot, E., Sabbione, C., Pessoa, W., Prazakova, L., Navarro, G., *Germanium, antimony, tellurium, their
binary and ternary alloys and the impact of nitrogen: An X-ray photoelectron study*, **Applied Surface
Science, 2021**, 536, 147703, https://doi.org/10.1016/j.apsusc.2020.147703

Prazakova, L., Nolot, E., Martinez, E., ...Cyrille, M.-C., Navarro, G., *Temperature driven structural
evolution of Ge-rich GeSbTe alloys and role of N-doping*, **Journal of Applied Physics, 2020**, 128(21),
27734, https://doi.org/10.1063/5.0027734

Nolot, E., Mazel, Y., Barnes, J.-P., ...Tempez, A., Legendre, S., *Accelerating the development of phase-
change random access memory with in-fab plasma profiling time-of-flight mass spectrometry*, **Surface
and Interface Analysis, 2020**, 52(12), pp. 895-899, https://doi.org/10.1002/sia.6823

B. P. Reed, D. J. H. Cant, S. J. Spencer, A. J. Carmona-Carmona, A. Bushell, A. Herrera-Gómez, A.
Kurokawa, A. Thissen, A. G. Thomas, A. J. Britton, A. Bernasik, A. Fuchs, A. P. Baddorf, B. Bock,
B. Theilacker, B. Cheng, D. G. Castner, D. J. Morgan, D. Valley, E. A. Willneff, E. F. Smith, E. Nolot,
F. Xie, G. Zorn, G. C. Smith, H. Yasufuku, J. L. Fenton, J. Chen, J. D. P. Counsell, J. Radnik, K. J.
Gaskell, K. Artyushkova, L. Yang, L. Zhang, M. Eguchi, M. Walker, M. Hajdýla, M. M. Marzec, M.
R. Linford, N. Kubota, O. Cortazar-Martínez, P. Dietrich, R. Satoh, S. L. M. Schroeder, T. G. Avval,
T. Nagatomi, V. Fernandez, W. Lake, Y. Azuma, Y. Yoshikawa, and A. G. Shard, *Versailles Project
on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray*
photoelectron spectroscopy instruments using low-density polyethylene, Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, 2020, 38(6), 577, https://doi.org/10.1116/6.0000577

Lama, G., Bourgeois, G., Bernard, M., Nolot E., ...Navarro, G., Nowak, E., Reliability analysis in GeTe and GeSbTe based phase-change memory 4 kb arrays targeting storage class memory applications, *Microelectronics Reliability*, **2020**, 114, 113823, https://doi.org/10.1016/j.microrel.2020.113823

Petzold, S., Piros, E., Eilhardt, R., Zintler, A., Vogel, T., Kaiser, N., Radetinac, A., Komissinskiy, P., Jalaguier, E., Nolot, E., Charpin-Nicolle, C., Wenger, C., Molina-Luna, L., Miranda, E., Alff, L., *Tailoring the Switching Dynamics in Yttrium Oxide-Based RRAM Devices by Oxygen Engineering: From Digital to Multi-Level Quantization toward Analog Switching*. *Adv. Electron. Mater.* **2020**, *6*, 2000439. https://doi.org/10.1002/aelm.202000439

S. Torrengo, D. Eichert, Y. Mazel, M. Bernard, Y. Ménesguen, M.C. Lépy, E. Nolot, *Quantitative depth-profile analysis of transition metal nitride materials with combined grazing-incidence X-ray fluorescence and X-ray reflectometry analysis*, **Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 171**, 2020, 105926, https://doi.org/10.1016/j.sab.2020.105926

E. Nolot, W. Pessoa, S. Torrengo, Y. Mazel, M. Bernard, P. Gergaud, Y. Ménesguen, M.C. Lépy, D. Eichert, *Grazing-incidence X-ray fluorescence analysis of thin chalcogenide materials deposited on Bragg mirrors*, **Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 168**, 2020, 105864, https://doi.org/10.1016/j.sab.2020.105864

Laguna, C., Castellani, N.,... Nolot E.,...Navarro, G., Nowak, E., *Innovative Multilayer OTS Selectors for Performance Tuning and Improved Reliability*, **2020 IEEE International Memory Workshop (IMW)**, Dresden, Germany, 2020, pp. 1-4, https://doi.org/IMW48823.2020.9108130

Yon, V., Rochat, N., Charles, M., Nolot, E., Gergaud, P., *X-Ray Diffraction Microstrain Analysis for Extraction of Threading Dislocation Density of GaN Films Grown on Silicon, Sapphire, and SiC Substrates*, **Physica Status Solidi (B) Basic Research**, 2020, 257(4), 1900579, https://doi.org/10.1002/pssb.201900579

Nolot, E., Cadot, S., Martin, F., Hönicke P., Zech, C., Beckhoff, B., *In-line characterization of ultrathin transition metal dichalcogenides using X-ray fluorescence and X-ray photoelectron spectroscopy*, **Spectrochimica Acta - Part B Atomic Spectroscopy**, 2020, 166, 105788, https://doi.org/10.1016/j.sab.2020.105788

Jeynes, C., Nolot, E., Costa, C., ...Navarro, G., Mantler, M., *Quantifying nitrogen in GeSbTe:N alloys*, **Journal of Analytical Atomic Spectrometry**, 2020, 35(4), pp. 701-712, https://doi.org/10.1039/C9JA00382G

Frauenrath, M., Hartmann, J.M., Nolot, E., *Boron and phosphorous doping of GeSn for photodetectors and light emitting diodes*, **ECS Transactions**, 2020, 98(5), pp. 325-338, 325, https://doi.org/10.1149/09805.0325ecst

Le Maoult, C., Vaufrey, D., Martin, F., ...Nolot E., ...Cadot, S., Gheeraert, E., *Analysis of InGaN surfaces after chemical treatments and atomic layer deposition of Al₂O₃ for µLED applications*, **Proceedings of SPIE - The International Society for Optical Engineering**, 2020, 11280, 112801C, https://doi.org/10.1117/12.2544787
Navarro G., Sabbione C., Bernard M., Bourgeois G., Sandrini J., Castellani N., Cueto O., Garrione J., Cyrille M.C., Frei M., Nistor L., Bernier N., Fillot F., Nolot E., Socquet-Clerc C., Magis T., Laulagnet F., Pakala M., Nowak E., Highly Sb-Rich Ge-Sb-Te Engineering in 4Kb Phase-Change Memory for High Speed and High Material Stability Under Cycling, Published in IEEE **2019**, IEEE **11th International Memory Workshop (IMW)**, May 2019, https://doi.org/10.1109/imw.2019.8739656

Hönicke P., Detlefs B., Nolot E., Kayser Y., Mühle U., Pollakowski B., and Beckhoff B.; Reference-free grazing incidence x-ray fluorescence and reflectometry as a methodology for independent validation of x-ray reflectometry on ultrathin layer stacks and a depth-dependent characterization, *Journal of Vacuum Science & Technology A 37*, 041502 (2019); https://doi.org/10.1116/1.5094891

Mrad M., Charles M., Mazel Y., Nolot E. et al., Understanding and controlling Ga contamination in InAlN barrier layers, *Journal of Crystal Growth*, Volume: 507 Pages: 139-142 Published: FEB 1 2019, https://doi.org/10.1016/j.jcrysgro.2018.10.039

Verdy, A., Bernard, M., Garrione, J., Nolot E. (...), Navarro, G., Nowak, E., *Optimized Reading Window for Crossbar Arrays Thanks to Ge-Se-Sb-N-based OTS Selectors*, 2019 Technical Digest International Electron Devices Meeting, **IEDM 2018-December**, 8614686, pp. 37.4.1-37.4.4, https://doi.org/10.1109/IEDM.2018.8614686

Nolot, E.; Caby, B.; Gassilloud, R.; et al., *X-ray reflectometry and grazing-incidence X-ray fluorescence characterization of innovative electrodes for tantalum-based resistive random access memories*, **Spectrochimica Acta Part B: Atomic Spectroscopy**, Volume: 149 Pages: 71-75, Nov 2018, https://doi.org/10.1016/j.sab.2018.07.017

Pessoa, W.; Roule, A.; Nolot, E.; et al., *Grazing incident X-ray fluorescence combined with X-ray reflectometry metrology protocol of telluride-based films using in-lab and synchrotron instruments*, **Spectrochimica Acta Part B: Atomic Spectroscopy**, Volume: 149 Pages: 143-149, Nov 2018, https://doi.org/10.1016/j.sab.2018.07.003

E. Martinez, E. Nolot, J-P Barnes, Y. Mazel, and N. Bernier, *Germanium out diffusion in SiGe-based HfO2 gate stacks*, **Journal of Vacuum Science & Technology B** 36, 042902 (2018); https://doi.org/10.1116/1.5027072

Navarro, G.; Bourgeois, G.; Kluge, J.; Nolot E. et al., *Phase-Change Memory: Performance, Roles and Challenges, 2018 IEEE 10th International Memory Workshop (IMW)* Book Series: IEEE International Memory Workshop Pages: 81-84, https://doi.org/10.1109/IMW.2018.8388845

Khazaka R. , Nolot E., Aubin J. and Hartmann J.M, *Growth and characterization of SiGeSn pseudomorphic layers on 200mm Ge virtual substrates*, **Semiconductor Science and Technology** 33, 124011 (2018), https://doi.org/10.1088/1361-6641/aaea32

Khazaka R. , Nolot E., Aubin J. and Hartmann J.M, *Investigation of the Growth of Si-Ge-Sn Pseudomorphic Layers on 200 mm Ge Virtual Substrates: Impact of Growth Pressure, HCl and Si2H6 Flows*, **ECS Transactions 86 (7) 207 (2018)**, https://doi.org/10.1149/08607.0207ecst

Mazel A, Nolot E, Barnes JP, Charles M, Bouveyron R, Mrad M, Tempez A and Legendre S, *Multitechnique elemental depth profiling of InAlGaN and InAlN films*, **J. Vac. Sci. Technol. B** 36(3), May/Jun 2018, https://doi.org/10.1116/1.5019635
Verdy A, Navarro G, Bernard M, Chevalliez S, Castellani N, Nolot E., Garrione J, Noé P, Bourgeois G, Sousa V, Cyrille MC and Nowak E., *Carbon Electrode for Ge-Se-Sb Based OTS Selector for Ultra Low leakage Current and Outstanding Endurance*, **conference paper**, IRPS 2018, https://doi.org/10.1109/IRPS.2018.8353635

2017

Rotella H, Mazel Y, Brochen S, Valla A, Pautrat A, Licitra C, Rochat N, Sabbione C, Rodriguez G. and Nolot E, *Role of vacancy defects in Al doped ZnO thin films for optoelectronic devices*, **Journal of Physics D: Applied Physics**, Volume 50, Number 48, Nov 2017, https://doi.org/10.1088/1361-6463/aa920b

Cadot, S., Renault, O., Frégnaux, M., Rouchon, D., Nolot, E., Szeto, K., Thieuleux, C., Veyre, L., Okuno, H., Martin, F., Quadrelli, E.A. *Low-temperature and scalable CVD route to WS2 monolayers on SiO2/Si substrates*, **Journal of Vacuum Science & Technology A** 35, 061502 (2017); https://doi.org/10.1116/1.4996550

Rotella H, Caby B., Ménesguen Y., Mazel Y, Valla A., Ingerle D., Detlefs B., Lepy MC, Novikova A., Rodriguez G., Streli C, Nolot E., *Elemental depth profiling in transparent conducting oxide thin film by X-ray reflectivity and grazing incidence X-ray fluorescence combined analysis*, **Spectrochimica Acta Part B: Atomic Spectroscopy**, Volume 135, 1 September 2017, Pages 22-28, http://doi.org/10.1016/j.sab.2017.06.011

Ménesguen Y, Boyer B, Rotella H, Lubeck J, Weser J, Beckhoff B, Grötzsch D, Kanngießer B, Novikova A, Nolot E and Lépy MC, *CASTOR, a new instrument for combined XRR-GIXRF analysis at SOLEIL, X-Ray Spectrom.* **2017**, 46, 303–308, https://doi.org/10.1002/xrs.2742

M. Barlas, A. Grossi, L. Grenouillet, E. Vianello, E. Nolot, N. Vaxelaire, P. Blaise, B. Traoré, J. Coignus, F. Perrin, R. Crochemore, F. Mazen, L. Lachal, S. Pauliac, C. Pellissier, S. Bernasconi, S. Chevalliez, J.F. Nodin, L. Perniola, E. Nowak, *Improvement of HfO2 based RRAM array performances by local Si implantation*, **IEDM 2017**, https://doi.org/10.1109/IEDM.2017.8268392

Kriso, C., Triozon, F., Delerue, C., Schneider, L., Abbate, F., Nolot, E., Rideau, D., Niquet, Y.-M., Mugny, G., Tavernier, C. ; *Modeled optical properties of SiGe and Si layers compared to spectroscopic ellipsometry measurements*, **Solid-State Electronics**, 129, pp. 93-96, 2017, https://doi.org/10.1016/j.sse.2016.12.011

Cadot, S., Renault, O., Frégnaux, M., Rouchon, D., Nolot, E., Szeto, K., Thieuleux, C., Veyre, L., Okuno, H., Martin, F., Quadrelli, E.A. ; *A novel 2-step ALD route to ultra-thin MoS2 films on SiO2 through a surface organometallic intermediate (2017) Nanoscale*, 9 (2), pp. 538-546.; http://doi.org/10.1039/c6nr06021h

2016

Borrel, J., Hutin, L., Grampeix, H., Nolot, E., Ghegin, E., Rodriguez, P., Tabone, C., Allain, F., Barnes, J.-P., Morand, Y., Nemouchi, F., Gregoire, M., Dubois, E., Vinet, M. ; *Considerations on fermi-depinning, dipoles and oxide tunneling for oxygen-based dielectric insertions in advanced CMOS contacts*, **2016 IEEE Silicon Nanoelectronics Workshop, SNW 2016**, art. no. 7578022, pp. 140-141, https://doi.org/10.1109/SNW.2016.7578022

Borrel, J., Hutin, L., Grampeix, H., Nolot, E., Tessaire, M., Rodriguez, G., Morand, Y., Nemouchi, F., Grégoire, M., Dubois, E., Vinet, M. ; *Metal/Insulator/Semiconductor contacts for ultimately scaled CMOS nodes: Projected benefits and remaining challenges (2016) 2016 16th International Workshop*
Tempez, A., Legendre, S., Barnes, J.-P., Nolot, E.; Combining plasma profiling TOFMS with TOF-SIMS depth profiling for microelectronic applications: (2016) Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, 34 (3), art. no. 03H120; https://doi.org/10.1116/1.4943513

2015

Caby, B., Brigidi, F., Ingerle, D., Nolot, E., Pepponi, G., Streli, C., Lutterotti, L., André, A., Rodriguez, G., Gergaud, P., Morales, M., Chateigner, D.; Study of annealing-induced interdiffusion in In2O3/Ag/In2O3 structures by a combined X-ray reflectivity and grazing incidence X-ray fluorescence analysis; (2015) Spectrochimica Acta - Part B Atomic Spectroscopy, 113, art. no. 4968, pp. 132-137;
https://doi.org/10.1016/j.sab.2015.09.008

Schneider, L., Abbate, F., Le Cunff, D., Nolot, E., Michallet, A.; Optical properties determination of Fully Depleted Silicon on Insulator (FDSOI) substrates by ellipsometry; (2015) 2015 26th Annual SEMI Advanced Semiconductor Manufacturing Conference, ASMC 2015, art. no. 7164469, pp. 195-200. ; https://doi.org/10.1109/ASMC.2015.7164469

Hönicke, P., Detlefs, B., Müller, M., Darlatt, E., Nolot, E., Grampeix, H., Beckhoff, B.; Reference-free, depth-dependent characterization of nanolayers and gradient systems with advanced grazing incidence X-ray fluorescence analysis; (2015) Physica Status Solidi (A) Applications and Materials Science, 212 (3), pp. 523-528. ; https://doi.org/10.1002/pssa.201400204

Brüner, P., Grehl, T., Brongersma, H., Detlefs, B., Nolot, E., Grampeix, H., Steinbauer, E., Bauer, P.; Thin film analysis by low-energy ion scattering by use of TRBS simulations ; (2015) Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, 33 (1), art. no. 01A122 ; https://doi.org/10.1116/1.4901451

2014

Nolot, E., Hartmann, J.M., Hilfiker, J.; Optical constants determination of pseudomorphic Si1-xGex layers on Si(001), with 0<x<0.54 ; (2014) ECS Transactions, 64 (6), pp. 455-465. ;
https://doi.org/10.1149/06406.0455ecst

Nolot, E., André, A., Scibetta, C., Poulingue, M., Levin, L., Vignoud, L., Isselé, H. ; Optical metrology of thick photoresist process for advanced 3D applications; (2014) Thin Solid Films, 571 (P3), pp. 609-614. https://doi.org/10.1016/j.tsf.2014.04.058

Pelloquin, S., Le Rhun, G., Defaÿ, E., Renaux, P., Nolot, E., Abergel, J., Sibuet, H. ; Improvement of capacitive behavior on gradient-free PZT thin films; (2014) Integrated Ferroelectrics, 157 (1), pp. 132-138 ; https://doi.org/10.1080/10584587.2014.912887

2012

Nolot, E., André, A., Michallet, A.; Performances and limitations of Lab-to-Fab strategies for inline optical metrology ; (2012) Proceedings of SPIE - The International Society for Optical Engineering, 8466, art. no. 846605 ; https://doi.org/10.1117/12.928368

2011
Signamarcheix, T., Andrieu, F., Biasse, B., Cassé, M., Papon, A.-M., Nolot, E., Ghyselen, B., Faynot, O., Clavelier, L. ; *Fully depleted silicon on insulator MOSFETs on (1 1 0) surface for hybrid orientation technologies* (2011) **Solid-State Electronics**, 59 (1), pp. 8-12. ; https://doi.org/10.1016/j.sse.2011.01.013

Stragier, A.-S., Signamarcheix, T., Salvetat, T., Nolot, E., Dechamp, J., Mercier, D., Gergaud, P., Tauzin, A., Clavelier, L., Lemiti, M. ; *200 mm silicon on porous layer substrates made by the smart cut technology for double layer-transfer applications* ; (2011) **Journal of the Electrochemical Society**, 158 (5), . https://doi.org/10.1149/1.3568947

Nolot, E., André, A. ; *Systematic combination of X-ray reflectometry and spectroscopic ellipsometry: A powerful technique for reliable in-fab metrology* ; (2011) **Thin Solid Films**, 519 (9), pp. 2782-2786. ; https://doi.org/10.1016/j.tsf.2010.12.075

## 2010

Stragier, A.-S., Signamarcheix, T., Salvetat, T., Nolot, E., Dechamp, J., Mercier, D., Gergaud, P., Tauzin, A., Clavelier, L., Lemiti, M. ; *200 mm silicon on porous layer substrates made by the smart cut™ technology for double layer transfer applications* ; (2010) **ECS Transactions**, 33 (4), pp. 207-216; https://doi.org/10.1149/1.3483509

Signamarcheix, T., Biasse, B., Papon, A.-M., Nolot, E., Mazen, F., Leveneur, J., Faynot, O., Clavelier, L., Ghyselen, B. ; *Crystallographic orientation engineering in silicon-on-insulator substrates* ; (2010) **Applied Physics Letters**, 96 (26), art. no. 262111 ; https://doi.org/10.1063/1.3459966

Vigliante, A., Kasper, N., Brechbuehl, J., Nolot, E. ; *Applications of X-ray characterization for advanced materials in the electronics industry* ; (2010) **Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science**, 41 (5), pp. 1167-1173. ; https://doi.org/10.1007/s11661-009-0116-7

## 2009

Signamarcheix, T., Biasse, B., Papon, A.-M., Nolot, E., Ghyselen, B., Clavelier, L. ; *Engineering silicon-on-insulator (SOI) substrates for hybrid orientation technologies (HOT)* ; (2009) Proceedings - **IEEE International SOI Conference**, art. no. 5318773 ; https://doi.org/10.1109/SOI.2009.5318773

Vignoud, L., Milesi, F., Nolot, E., Danel, A., Favier, S. ; *Evaluation of experimental techniques for in-line ion implantation characterization* ; (2009) **AIP Conference Proceedings**, 1173, pp. 84-88. ; https://doi.org/10.1063/1.3251266

## 2008

Nolot, E., Dufourcq, J., Favier, S., Bodnar, S. ; *Laser scattering: A fast, sensitive, in-line technique for quantum dots process development and monitoring* ; (2008) **Materials Research Society Symposium Proceedings**, 1117, pp. 48-53.

Nolot, E., Lefevre, A., Hilfiker, J.N. ; *Ellipsometry characterization of bulk acoustic wave filters* ; (2008) **Physica Status Solidi (C)** Current Topics in Solid State Physics, 5 (5), pp. 1168-1171. ; https://doi.org/10.1002/pssc.200777795

Danel, A., Nolot, E., Veillerot, M., Olivier, S., Decorps, T., Calvo-Muñoz, M.-L., Hartmann, J.-M., Lhostis, S., Kohno, H., Yamagami, M., Geoffroy, C. ; *Thin film characterization by total reflection x-*
ray fluorescence; (2008) **Spectrochimica Acta - Part B** Atomic Spectroscopy, 63 (12), pp. 1365-1369;
https://doi.org/10.1016/j.sab.2008.10.024

Milesi, F., Nolot, E., Mehrez, Z., Mazen, F., & Favier, S. (2008). *Evaluation of laser scattering technique and spectroscopic ellipsometry for in-line ion implantation characterization*. **AIP Conference Proceedings**, 1066 182-185. https://doi.org/10.1063/1.3033587

2007

Arrazat, B., Danel, A., Nolot, E., Favier, S., Carron, V., Nemouchi, F., Hartmann, J.M., Rolland, G., Vandelle, P., Kermarrec, O., Campidelli, Y., Descombes, S. ; *Characterization of CMOS sub-65 nm metallic contact by laser scattering: Thermal stability of Ni(Si1-xGex) ;* (2007) *Microelectronic Engineering*, 84 (11), pp. 2558-2562. ; https://doi.org/10.1016/j.mee.2007.05.021

Nolot, E., Bogumilowicz, Y., Lhostis, S., Danel, A. ; *Applications of X-Ray reflectometry to develop and monitor FEOL processes for sub-45nm technology nodes* ; (2007) **AIP Conference Proceedings**, 931, pp. 226-230. ; https://doi.org/10.1063/1.2799375

Danel, A., Nolot, E., Lhostis, S., Campidelli, Y., Calvo-Muñoz, M.-L., Decorps, T., Lardin, T., Veillerot, M., Kohno, H., Yamagami, M. ; *Thin films characterization by ultra trace metrology* ; (2007) **AIP Conference Proceedings**, 931, pp. 178-182. ; https://doi.org/10.1063/1.2799366

Nolot, E., Arrazat, B., Favier, S., Borde, Y., Damlencourt, J.F., Vincent, B., Kermarrec, O., Carron, V., Nemouchi, F., Vandelle, P., Bogumilowicz, Y., Danel, A. ; *Laser scattering: A fast, sensitive, in-line technique for advanced process development and monitoring* ; (2007) **AIP Conference Proceedings**, 931, pp. 116-120. ; https://doi.org/10.1063/1.2799354

Vincent, B., Damlencourt, J.-F., Rivallin, P., Nolot, E., Licitra, C., Morand, Y., Clavelier, L. ;
*Fabrication of SiGe-on-insulator substrates by a condensation technique: An experimental and
modelling study* ; (2007) **Semiconductor Science and Technology**, 22 (3), art. no. 011, pp. 237-244. ;
https://doi.org/10.1088/0268-1242/22/3/011

2006

Damlencourt, J.F., Vincent, B., Rivallin, P., Holliger, P., Rouchon, D., Nolot, E., Licitra, C., Morand, Y., Clavelier, L., Billon, T. ; *Fabrication of SiGe-on-insulator by improved Ge condensation technique* ; (2006) Third International SiGe Technology and Device Meeting, **ISTDM 2006** - Conference Digest, 2006, art. no. 1716025, https://doi.org/10.1109/ISTDM.2006.246531

E. Nolot, **Brevet** : "Method for fabricating haze noise standards comprising nano-structures on an insulating thin layer"

2005

Nolot, E., Mur, P., Favier, S. ; *In-line characterization of silicon nano-crystals grown on high-K tunnel dielectrics* ; (2005) **Proceedings of SPIE** - The International Society for Optical Engineering, 5878, art. no. 587805, pp. 1-8. https://doi.org/10.1117/12.616820

Nolot, E., Michallet, A. ; *Practical applications of XRR-XRF metrology tool* ; (2005) **AIP Conference Proceedings**, 788, pp. 329-332. ; https://doi.org/10.1063/1.2062984
# 9 Curriculum Vitae

Emmanuel Nolot

Ingénieur-chercheur au Cea-Leti - Métrologie des couches minces

Commissariat à l'énergie atomique et aux énergies alternatives

MINATEC Campus | 17 rue des martyrs | F-38054 Grenoble Cedex

T. +33 (0)4 38 78 97 42

emmanuel.nolot@cea.fr

52 ans

Nationalité française

## Expérience professionnelle

**Depuis 2004** Responsable du groupe de métrologie par techniques optiques et à rayons X, au sein du Cea-Leti.

**Centres d'intérêts principaux** : caractérisation physico-chimique de couches minces inorganiques pour les applications CMOS, MEMS et dans le domaine de l'énergie grâce à la combinaison et/ou l'inter-comparaison de différentes techniques d'analyse : ellipsométrie spectroscopique à large bande (VUV – VIS-IR), spectroscopie de lignes noires, spectrométries vibrationnelles (IR, Raman), réflectométrie de rayons X, fluorescence X (par dispersion d'énergie ou de longueur d'onde, en incidence standard ou rasante), diffraction de rayons X, photoémission X (en mode standard ou résolu en angle). Profilométrie chimique rapide par spectrométrie de masse à temps de vol. Analyse quantitative, avec des incertitudes cohérentes avec les exigences des partenaires industriels.

- Forte implication dans le montage et la réalisation des projets européens EMRP (TReND, ThinErgy), EMPIR-HyMet (WP leader), eCOST-TXRF, SEA4KET

- Sollicité pour des évaluations de projets ANR (2018, 2019) et Labex (2018)

- Revues régulières d'articles pour Spectrochimica Acta B, plus ponctuelles pour Applied Physics Letters, Surface and Interface Analysis, Journal of Aerosol Science, physica status solidi A et C

**1998 - 2003** Responsable du groupe de métrologie des cibles laser, au CEA Bordeaux. Métrologie optique et analyse tridimensionnelle.

## Formation

**1996** Thèse de l'Université Joseph Fourier - Grenoble, spécialité Physique

**1994** DEA « Méthodes physiques expérimentales » de l'Université Joseph Fourier - Grenoble

**1994** Diplôme d'ingénieur de l'Ecole Nationale Supérieure de Physique de Grenoble (actuel « Phelma »)
# Activités de recherche et encadrements

## Mise en place de collaborations avec des partenaires extérieurs

### ✓ Partenaires académiques

- Vienna University of Technology (Pr C. Streli) : analyse par fluorescence X, analyse combinée par réflectométrie X et fluorescence X en incidence rasante (XRR/GiXRF)

- CRISMAT, CIMAP (Caen, Pr D. Chateigner) : Analyse combinée par réflectométrie X, fluorescence X et diffraction X. Application à la caractérisation d'oxydes transparents conducteurs.

- Institut d'optique, Palaiseau (Pr Franck Delmotte) : Optiques X, champ d'onde stationnaire.

### ✓ Grands instruments

- CEA/LNHB (Dr M.C Lépy) : Analyse par XRF sur la ligne Métrologie, synchrotron Soleil

- Synchrotron Elettra (ligne XRF, Dr Diane Eichert) : Analyse XRR/GIXRF & EXAFS ; analyse quantitative

- University of Surrey (Ion Beam Center, Pr C. Jeynes) : Analyse quantitative par faisceau d'ions (EBS, RBS) pour des matériaux complexes, incluant des éléments légers (azote, ...)

### ✓ Instituts Nationaux de Métrologie

- Physikalisch-Technische Bundesansalt (PTB Berlin, Dr B. Beckhoff) : Analyse par rayons X de couches minces. Instrumentation et méthodologie pour l'analyse quantitative par GiXRF. Techniques de référence. Paramètres fondamentaux, effets de matrice, incertitudes.

- Universidade NOVA de Lisboa, Portugal (Pr Mauro Guerra) : XRF à très haute résolution sur la base de cristaux analyseurs caractérisés par le NIST

- National Physical Laboratory (NPL, Dr A. Shard) : Analyse quantitative par photoémission. Influence des aspects instrumentaux sur les incertitudes.

### ✓ Instituts de Recherche Technologique (RTO)

- Fondazione Bruno Kessler (FBK Trento, Dr G. Pepponi) : analyse combinée par XRR/GiXRF, caractérisation fine de couches implantées par combinaison XRF et TOF-SIMS, analyse par spectroscopie d'absorption X

### ✓ Partenaires industriels

- Horiba Jobin Yvon (Dr A. Tempez) : Optimisation d'un équipement de profilométrie chimique rapide par spectrométrie de masse à temps de vol et application à la métrologie de couches minces inorganiques (développement – programme collaboratif de 5 ans)

- Applied Materials : Optimisation d'une technique de métrologie optique in operando sur un équipement de dépôt par voir chimique PE-CVD -

- Semilab (Budapest) : développement de solutions de métrologie en salle blanche par spectroscopie Raman

- Rigaku (Tokyo) : développement de solutions de métrologie en salle blanche par combinaison de réflectométrie et fluorescence de rayons X
## Projets collaboratifs

Pour l'intégralité des cas ci-dessous : participation au montage du projet, et définition du programme d'action spécifique à mener par l'acteur Cea-Leti non permanent, en forte interaction avec les partenaires des instituts nationaux de métrologie (projets EMRP et EMPIR) ou industriels (projet EMPIR et collaboration Horiba), puis suivi au fil de l'eau des actions.

Plus particulièrement : WP leader dans le cas des projets EMPIR HyMet et ATMOC ; montage intégral du projet collaboratif avec Horiba ; montage et suivi du projet collaboration avec Applied Materials.

### ✓ Projets européens de métrologie

**2013-2015, Projet EMRP – TReND** – (Traceable characterization of nanostructured devices)
– 30 mois – Blanka Detlefs (postdoc)

Collaboration avec le PTB et le CEA/LNHB. Développement d'un logiciel d'analyse combinée XRR/GiXRF et validation sur des couches élémentaires. Métrologie d'un instrument AR-XPS (fonction instrumentale), et inter-comparaison de ces deux approches (XRR/GiXRF et ARXPS) pour la profilométrie de composition d'empilements modèles ultrafins (couches ALD).

**2015-2016, Projet EMRP – ThinErgy** (Traceable characterization of thin-film materials for energy applications) – 24 mois – Hélène Rotella (postdoc)

Collaboration avec le PTB et le CEA/LNHB. Optimisation du code d'analyse combinée GiXRF/XRR (introduction d'une fonction instrumentale améliorée) et mise en place d'une méthodologie d'analyse quantitative. Caractérisation multi-techniques (XRF, XRR, XRD, FTIR, ellipsométrie, effet Hall, ...) de couches fines d'oxydes transparents conducteurs sans indium.

**2017-2020, Projet EMPIR – HyMet** (Hybrid Metrology for thin films in energy applications)
– 30 mois – Simona Torrengo (postdoc)

Collaboration avec le PTB, le CEA/LNHB, ainsi qu'avec le BAM (Dr A. Hertwig, méthodes optiques). Finalisation de la comparaison (et validation) entre deux approches de l'analyse combinée par XRR/GIXRF : celle du PTB, institut de métrologie qui détermine ses incertitudes par une métrologie complète de la chaine instrumentale (ligne PTB, synchrotron Bessy) et une évaluation rigoureuse des paramètres fondamentaux ; une approche plus pragmatique, transférable à l'industrie, fondée sur la prémesure d'échantillons élémentaires, approche incluant la méthodologie et le logiciel d'analyse finalisé. Caractérisation multi-techniques (Raman, XRF, EXAFS, ...) de couches III-N hétéro-épitaxiées sur silicium (applications LED et transistors de puissance).

**2021-2024, Projet EMPIR – ATMOC** (Traceable metrology of soft X-ray to IR optical constants and nanofilms for advanced manufacturing)

Collaboration avec différents instituts de métrologie européens (dont BAM et PTB) autour d'une métrologie précise des indices optiques de matériaux d'intérêt technologique, dans une large gamme spectrale.

### ✓ Partenariats industriels

**2016-2020, Collaboration Horiba** – Cea Leti – Développement d'une technique de profilométrie chimique rapide par spectrométrie de masse à temps de vol – Yann Mazel (CDD projet)

Collaboration très fructueuse avec Horiba sur le développement de la technique « plasma profiling time of flight spectrometry » : modifications instrumentales proposées et validées par Horiba. Optimisation méthodologiques pour l'analyse de différents types d'empilements de couches inorganiques. Etablissements de facteurs de
sensibilité relatifs pour tendre vers une analyse quantitative. Comparaison exhaustive avec le TOF-SIMS et des méthodes alternatives telles que la GD-OES.

**2018-2020, Collaboration Applied Materials** – Cea Leti – Optimisation d’une technique de métrologie optique *in operando* sur un équipement de dépôt par voir chimique PE-CVD - Rémi Elizalde (CDD projet)

Collaboration fructueuse avec l'équipementier Applied Materials autour de la métrologie *in operando* par réflectométrie optique de l'épaisseur de couches minces dans des empilements complexes déposés sur différents substrats par voie chimique (PE-CVD).

**2023-2026 : collaboration avec l'industriel Semilab** pour le développement de solutions de métrologie en salle blanche par spectroscopie Raman.

Ce programme de développement sur 3 ans inclut la mise à disposition d'un équipement automatisé dans les salles blanches du Leti, l'évolution de son système optique au fil de la collaboration, et le développement de solutions d'analyse quantitative automatisée.

**Q4-2023-2025 : collaboration avec l'industriel Rigaku** pour le développement de solutions de métrologie en salle blanche par combinaison de réflectométrie et fluorescence de rayons X.

Cette collaboration accompagnera le travail sur un nouvel équipement multi-sources X, combinant réflectométrie et fluorescence X et qui devrait être installé au Leti fin 2023. L'extension de la méthode des paramètres fondamentaux aux analyses par dispersion d'énergie sera l'un des sujets importants de cette collaboration.

✓ **Projets bilatéraux, projets Minos, etc**

**2021-2023, Collaboration Institute of Metals and Technology (Ljubljana, Slovénie)** sur la métrologie des éléments légers (bore et azote) dans des couches fines inorganiques, dans le cadre d'un *appel à projet AAP Slovenia*.

**2023-2025 : Plan Transverse de Compétences avec CEA/DAM/DPTA** autour de la simulation *ab initio* des spectres Raman. DPTA a déjà développé un code, ABINIT, qui est largement utilisé par la commauté internationale. Ce code sera adapté pour les couches minces polycristallines d'intérêt pour le Leti et évalué en regard de mesures par spectro Raman et diffraction de rayons X, avant transfert du code et de la compétence associée à l'issue du projet.

**2023-2025 : Post doc Minos commun avec le CNRS/LTM et UGA/LMGP** pour le développement de la spectroscopie Raman en salle blanche, pour la métrologie de couches minces inorganiques.

**2023-2025 : Post doc Minos commun avec UGA/LMGP** pour le développement de la métrologie quantitative par fluorescence X multi-configuration, pour la métrologie de couches minces inorganiques pour les applications CMOS avancé (10 nm, empilement de grille), matériaux 2D (sulfures) et mémoires à base d'oxydes complexes.
Encadrement de thèses

Pour l'intégralité des cas ci-dessous : définition du sujet (éventuellement avec un co-
encadrant), obtention du financement, suivi au fil de l'eau du travail de l'étudiant(e), aide à la
rédaction du manuscrit de thèse et à la préparation de la soutenance associée.

**2012-2015 : Béranger Caby**, « Développement de l'analyse combinée par Réflectométrie de rayons X (XRR) et Fluorescence des rayons X en Incidence Rasante (GIXRF) pour des applications micro et nano-électroniques », Normandie Université ED 591. Thèse dirigée par Magali Morales et Daniel Chateigner.

Introduction de la technique d'analyse combinée XRR/GiXRF au Cea-Leti. Application aux couches minces et aux couches implantées. Complémentarité avec l'analyse en diffraction pour la caractérisation d'oxydes transparents conducteurs. Supportée par les collaborations avec Vienna University of Technology et Fondazione Bruno Kessler

**2014-2017 : Walter Pessoa**, « Probing chalcogenide films by advanced X-ray metrology for the semiconductor industry », Paris Saclay ED 576. Thèse dirigée par Marie-Christine Lépy.

Caractérisation de couches minces de chalcogénures, d'une part les applications mémoires non volatiles (GeSeTe, TiTe, GeSe, ...), et d'autre part pour les matériaux 2D (MoS₂, WS₂). Analyse quantitative de composition par fluorescence X et photoémission X (problématique des facteurs de sensibilités relatives, des effets de matrice et des techniques de référence), de profil de composition par photoémission résolue en angle et analyse combinée XRR/GiXRF.

**2017-2020 : Victor Yon**, « Caractérisation avancée par rayons X pour le développement des transistors de puissance basse consommation », Université Grenoble Alpes ED 047 (Physique). Thèse co-encadrée par Matthew Charles et dirigée par Patrice Gergaud.

L'objectif de cette thèse est de développer des stratégies d'analyse, fondées sur les techniques
à rayons X, afin de caractériser finement des structures à base de semi-conducteurs III-N
(GaN, AlGaN, InAlN) hétéro-épitaxiées sur substrat silicium et d'améliorer la fiabilité du
processus de réalisation de ces structures. L'analyse des profils de composition dans les
barrières, initialement prévue dans le sujet, a été rapidement abandonnée pour se concentrer,
d'une part sur l'étude et la simulation du gradient de contraintes biaxiales dans les pseudo-
substrats de GaN et, d'autre part, sur l'évaluation de la densité de dislocations traversantes par
mesure de micro-déformations.

**2018-2021 : Lucie Prazakova**, « Caractérisation avancée pour le développement des nouvelles mémoires non volatiles », Université Grenoble Alpes ED 047 (Physique). Thèse co-encadrée par Gabriel Navarro et dirigée par Eugénie Martinez.

Etude fine des caractéristiques (états de liaisons, cristallinité, composition, ...) de matériaux pour les mémoires à changement de phase (XPS, XRF, Raman, FTIR, ...). Analyse des matériaux élémentaires (ex : Ge, Sb, Te), binaires et ternaires. Influence du dopage par des
éléments légers et difficultés métrologiques associées (ex : analyse XRF, effets de matrice). Etude de l'influence des budgets thermiques sur les caractéristiques des matériaux et liens avec les propriétés électriques. Supportée par la collaboration avec le PTB.

**2019-2022 : Rose Taylor Bure**, « Photoémission avancée des interfaces enterrées critiques en micro-électroniques des filières puissance et mémoires », Clermont Auvergne ED 178. Thèse co-encadrée par Olivier Renault et dirigée par Christine Robert-Goumet.

L'objectif est de développer, à la suite du stage de M2 réalisée par cette étudiante, les méthodologies nécessaires à l'analyse quantitative de profil chimique par photoémission, essentiellement en salle blanche et en laboratoire (notamment avec une source X-durs), en combinant les approches: caractérisation multi-composantes, analyse angulaire, modélisation du fond continu inélastique.

**2021-2024 : Oumaima Daoudi**, « Matériaux chalcogénures des mémoires à changement de phase et des dispositifs sélecteur de demain : métrologie au plus près de la fabrication pour la compréhension de l'influence des paramètres procédés sur la composition et les propriétés structurales de ces matériaux », Université Grenoble Alpes ED 047 (Physique). Thèse coencadrée par Gabriel Navarro et dirigée par Hubert Renevier.