The use of SiGe substrate as a semiconductor material is increasing because of its unique properties. In order to manufacture high-performance devices, it is necessary to develop SiGe selective etching technology. In this study, SiGe epi and oxide substrates with varying germanium percentages (15, 25, and 40 %) were used for the investigation of the selective etching process. As the etchant, APM (1:4:20) solutions were used, and added HF and HCl to confirm the pH effect. The evaluation was conducted while adjusting the pH level. In the case of the SiGe epi substrate, the etching rate was very low at high pH, but the etching rate rapidly increased at a specific pH. And then, the etch rate gradually decreased. On the other hand, the etch rates of the oxide substrate rapidly increased as the pH decreased. To explain the etch rate behavior due to the difference in Ge content and type of substrates, the surface chemistry was measured, and the speciation of the solution was analyzed.

In the FinFET fabrication flow, a gap fill oxide is used to fill the space between the Si fins that needs to be recessed to define the height of the fin trench. However, with the used flowable chemical vapor deposition (FCVD) oxide, the eth rate depends on fin spacing, a phenomenon called pattern loading. In this work, we used water structuring by dissolved ions to decrease the etch rate between fins and control pattern loading. We first showed, using ATR-FTIR (Attenuated Total Reflection - Fourier Transform Infra-Red), that structure making and breaking ions proposed by Marcus (2009) for bulk solutions, could be used to modulate water structuring in nanotrenches. Then, the Tetra-propyl Ammonium cation (TPA+) and the triply ionized Phosphoric acid anion (PO43  ) were selected as structure making additives in HF 0.5%. Optimization of the etchant composition allowed to suppress pattern loading for a gap of 15 nm width using TPAH:HF mixtures, but not using HF:H3PO4 mixtures. The etch rate obtained with TPAH:HF at unity pattern loading and at room temperature was about 4.7 nm/min. It could be improved to about 7 nm/min by increasing the temperature. The inefficacy of the Phosphoric acid was ascribed to a pH effect, as the mono-ionized Phosphoric acid species formed in HF was classified as a borderline ion with little structuring capability by Marcus.

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. However, wetting of high aspect ratio nanoholes was showed to be incomplete for non-settled reasons. In this study, X-ray diffraction (XRD) was used to characterize water confined in deep nanoholes with 20 nm diameter. Long XRD measurements were made possible by the anomalous capillary condensation occurring in these nanoholes, which was proved by Attenuated Total Reflection – Fourier Transformed Infra-Red measurements. Condensation occurred in nanoholes submitted to the clean-room air with a relative humidity (RH) of about 40%, while no condensation was observed under a N2 flow with a RH of about 30%. XRD measurements showed the presence of small peaks varying as a function of the XR incidence angle, which were not present in the Si and oxide references. These peaks gave evidence for structuring of water confined in nanoholes.

Water structuring has been proposed to occur in water confined in nanochannels and nanoholes based on shifts of the OH stretching peak in Attenuated Total Reflection – Fourier Transformed Infra-Red (ATR-FTIR) measurements (Vereecke, Micro. Eng., 2021 and 2022). Nanoconfined water was characterized by the presence of H-bonds with a stronger vibration frequency compared to ice. Using CO2 as a probe molecule in ATR-FTIR measurements on nanoholes, it was also shown that nanoconfined water was characterized by a slower diffusivity and a lower permittivity compared to bulk water (Vereecke, Micro. Eng., 2021), in agreement with previous studies performed using different techniques (Mawatari, Anal. Chem., 2014; Morikawa, Anal. Chem., 2015). Also, the decreased rate of a model surface reaction performed in nanotrenches of decreasing width correlated well with water structuring characterized by IR spectroscopy (Vereecke, Solid State Phenom., 2018). In the present study, X-Ray diffraction (XRD) measurements were used to further characterize the structuring of water confined in nanoholes. XRD measurements were performed on a X’pert Pro from Malvern Panalytical equipped with a PixCel detector. Measurements were performed on a parametric space defined by an incident XR angle w varying from 3 to 23°, and a spectra angle 2q varying from 12 to 42°. Measurements of 101 spectra with Dw = 0.2 took 2 days 7 hours. ATR-FTIR measurements were performed in a flow cell on crystals made from wafers as described in Vereecke (Micro. Eng., 2021). The cell was equipped with a bubbler filled with water to control the relative humidity (RH) of the N2 flow in the cell. Samples consisted in nanoholes in an oxide matrix with a diameter of about 20 nm and a depth of about 300 nm, manufactured on Si wafers as described in Vereecke (Micro. Eng., 2021). The last step in making the nanoholes structure consisted in a 30 min bake at 400 °C to remove any tetra-methyl ammonium hydroxide (TMAH) residue present in the holes from etching. The contact angle (CA) of pristine nanoholes was less than 5°. It was increased by silanization treatments. One treatment consisted in the classical HMDS priming photoresist pre-treatment, which gives a CA of about 70° on a flat Si substrate, while the second consisted in the SMT treatment developed by SCREEN, which gives a CA of about 80° on a flat Si substrate. These treatments were performed immediately after drying the sample to prevent any condensation before silanization. Long XRD measurements were made possible by the anomalous capillary condensation occurring in the 20 nm nanoholes. In turn, condensation was evidenced by ATR-FTIR measurements by monitoring the OH stretching peak. Condensation occurred in nanoholes submitted to a 200 °C bake in about 30 min when submitted to the clean-room air with a RH of about 40%. On the other hand, no condensation was observed in nanoholes under a N2 flow with a RH of about 30%, indicating that condensation was not an artefact, caused for example by the presence of impurities in the nanoholes, but was truly the result of capillary condensation. XRD measurements showed the presence of a small peak varying as a function of w, from about 2q = 28° at w = 15° to 2q = 33° at w = 18°, which was not present in the Si and oxide references. This peak was close to the 27° peak of ice-VII that has been identified by Raman spectroscopy measurements in water condensed in the nanomeniscus of nanoparticles (Shin, Nature Commun., 2019). The peak was not changed by ageing of the sample from 2 days to 2 months. It was also observed in samples that had been submitted to silanization treatments, bringing the CA on flat substrates from about 5° for the pristine sample, to 70° and 80° for the sample submitted to the HMDS priming and the SMT clean, respectively. This peak was evidence for structuring of water confined in nanoholes. Shifting of the peak as a function of w indicated that water structuring in nanoholes was comparable to a monocrystalline structure. However, the structure of nanoconfined water differed from that of ice-VII. Indeed, the presence of a broad peak at about 22°, which was not observed in the oxide reference, indicated the simultaneous presence of bulk H2O in the nanoholes. These observations added to our understanding of structured water in nanoholes that had been proposed previously based on ATR-FTIR measurements.

In advanced semiconductor manufacturing, with deep contact holes with an aspect ratio higher than sixty in 3D-NAND memory, higher aspect ratio patterning is one of the important issues in advanced semiconductor manufacturing. In this work, we used an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanostructures embedded in a silica matrix by UPW and electrolyte solutions as a function of pH. There was little influence of pH on the wetting of nanoholes in the studied range of 1 to 4, but wetting seemed to be less close to the isoelectric point. Also, HCl seemed to lend a better wetting compared to HI, in opposition to their structure breaking effect according to Marcus. A correlation was observed between these observations and the CO2 solubility, indicative of the influence of water structuring.

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. In this work, we use an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanoholes in a silica matrix by UPW and electrolyte solutions. Wetting was much slower than predicted by a numerical model, while temperature cycling evidenced the formation of unexpectedly stable gas pockets in the wetted nanoholes. Water structuring in the nanoholes was characterized by an analysis of the OH stretching peak. Besides, monitoring the dissolution of CO2 in the wetted nanoholes allowed to compare the diffusivity in the nano-confined solutions with that in bulk solutions. Our results strongly suggest that the gas pockets were stabilized by the decreased gas diffusivity resulting from water structuring.

Co/LaSiO conducting bridge random access memory is a promising candidate for low power storage class memories due to its high endurance and short switching pulse width. Moisture has been hypothesized to be an important parameter in determining device retention. In this study, we anneal the LaSiO layers at different temperatures and pressures in order to reduce the absorbed moisture and improve retention. We evidence by Fourier transform infrared and x-ray reflectivity that the moisture content does not change with these anneal conditions. However, we find that increasing the amount of La–OH bonds is an effective way to improve the low resistance state retention.

In this abstract, we report for the first time the low-current performance enhancement combined with the improvement of the scaling potential in CBRAM devices by adopting an etch-friendly alternative material, Co, as active electrode, based on theoretical considerations and experimental results. Co is proven to yield, with respect to Cu, faster/lower voltage switching and more stable conductive filaments, irrespective of the switching layer, thanks to its higher cohesive energy. By further optimizing the switching layer, we show that the introduction of Co as active electrode is a breakthrough for boosting CBRAM performances, enabling fast and low-power switching, long endurance lifetime and optimal data retention.

Over the past decade, many advanced drying techniques have been developed to reduce and prevent pattern collapse of high aspect ratio (HAR) structures after wet processing. However, different dimensions, profiles and materials of HAR structures used in literature make it difficult to compare the efficiency of different drying processes. In this work, standard 300 mm wafer test structures, characterization and analysis techniques have been developed for quantitative analysis of pattern collapse rate as a function of the intrinsic mechanical property of HAR structures. Such standardized single wafer evaluations are important for benchmarking different drying techniques.

A self-limiting wet etching of metal thin films has been developed for the replacement metal gate patterning in advanced logic devices, which will have aggressively scaled gate length and fin pitches. A uniform and highly selective wet etching of polycrystalline TiN films is demonstrated by a diffusion-limiting oxide growth on the metal surfaces as well as a subsequent highly selective oxide removal.

In semiconductor manufacturing of 3-D nano-structures, modified kinetics have been encountered for the aqueous chemical etching of thin films in nano-confined spaces. A popular explanation relies on changes in reactant concentration from the overlap of electrostatic double layers (EDL) on opposite walls of the nano-structures. In this study, the cycloaddition of dibenzylcyclooctyne-PEG3-alcohol (DBCO) to a linear azide-terminated SAM was performed in nanochannels of width varying from 62 to 32 nm. ATR-FTIR was used to monitor the reaction kinetics, characterize water structuring and determine the pH in nanochannels. Reaction kinetics were slower in nanochannels as compared to a planar surface, while pH shifts were observed in absence of EDL overlap, with a significant influence of channel width. Actually only the overall decrease in reaction rate could be explained by EDL overlap. The discussion shows that the water structuring measured in nanochannels may play a significant role in the observed phenomena.

Superhydrophobic surfaces are highly promising for self-cleaning, anti-fouling and anti-corrosion applications. However, accurate assessment of the lifetime and sustainability of super-hydrophobic materials is hindered by the lack of large area characterization of superhydrophobic breakdown. In this work, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) is explored for a dynamic study of wetting transitions on immersed superhydrophobic arrays of silicon nanopillars. Spontaneous breakdown of the superhydrophobic state is triggered by in-situ modulation of the liquid surface tension. The high surface sensitivity of ATR-FTIR allows for accurate detection of local liquid infiltration. Experimentally determined wetting transition criteria show significant deviations from predictions by classical wetting models. Breakdown kinetics is found to slow down dramatically when the liquid surface tension approaches the transition criterion, which clearly underlines the importance of more accurate wetting analysis on large-area surfaces. Precise actuation of the superhydrophobic breakdown process is demonstrated for the first time through careful modulation of the liquid surface tension around the transition criterion. The developed ATR-FTIR method can be a promising technique to study wetting transitions and associated dynamics on various types of superhydrophobic surfaces.

Accurate characterization of the underwater stability of superhydrophobic surfaces is crucial for the design of durable anti-fouling materials and advanced microfluidic concepts. Although superhydrophobic breakdown is a major issue that hampers full exploitation of superhydrophobic functional materials, suitable characterization methods are lacking and relatively little is known about the wetting dynamics. In this work we explore a novel method based on attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) for large-area in-situ analysis of wetting states and wetting transitions on nanostructured surfaces. Spontaneous wetting is induced on superhydrophobic silicon nanopillars through in-situ modulation of the liquid composition and surface tension. The high surface sensitivity of ATR-FTIR enables quantitative evaluation of the instantaneous liquid composition and wetted area. Critical transition criteria for superhydrophobic breakdown are assessed using both ATR-FTIR and goniometric measurements. Significant deviations from classical wetting models are revealed, emphasizing the need for more accurate transition criteria and careful experimental validation. Breakdown kinetics near the critical transition are found to be significantly slowed down on nanostructured surfaces, which underlines the necessity for accurate characterization of wetting dynamics at the nanoscale. The proposed ATR-FTIR method can be promising for dynamic studies of wetting transitions on more advanced surfaces, as hierarchical structures or oleophobic designs.

The continuous down scaling of the dimensions for the logic devices has imposed to carefully track the pattern collapse issue when cleaning after FIN etch. Showing the limitations of the hot IPA drying technique toward scaled FIN dimensions, a cleaning using a surface modification drying technique has been proposed and successfully implemented. It is also discussed the use of some post treatment solutions to remove the grafted layer used to modify the FIN surface while preserving the integrity of the FIN structures.

Polyphthalaldehyde is a self-developing resist material for electron beam and thermal scanning probe lithography (t-SPL). Removing the resist in situ (during the lithography process itself) simplifies processing and enables direct pattern inspection, however, at the price of a low etch resistance of the resist. To convert the material into a etch resistant hard mask, we study the selective cyclic infiltration of trimethyl-aluminum (TMA)/water into polyphthalaldehyde. It is found that TMA diffuses homogeneously through the resist, leading to material expansion and formation of aluminum oxide concurrent to the exposure to water and the degradation of the polyphthalaldehyde polymer. The plasma etch resistance of the infiltrated resist is significantly improved, as well as its stability. Using a silicon substrate coated with 13 nm silicon nitride and 7 nm cross-linked polystyrene, high resolution polyphthalaldehyde patterning is performed using t-SPL. After TMA/H2O infiltration, it is demonstrated that pattern transfer into silicon can be achieved with good fidelity for structures as small as 10 nm, enabling >10× amplification and low surface roughness. The presented results demonstrate a simplified use of polyphthalaldehyde resist, targeting feature scales at nanometer range, and suggest that trimethyl-aluminum infiltration can be applied to other resist-based lithography techniques.

In the manufacturing of multi-Vt FinFET transistors, the gate material deposited in the nano-spaces left by the removed dummy gate must be etched back in mask-defined wafer areas. Etch conformality is a necessary condition for the control of under-etch at the boundary between areas defined by masking. We studied the feasibility of TiN etching by APM (ammonia peroxide mixture, also known as SC1) in nano-confined volumes representative of FinFET transistors of the 7 nm node and below, namely nanotrenches with 1-D confinement and nanoholes with 2-D confinement. TiN etching was characterized for rate and conformality using different electron microscopy techniques. Etching in closed nanotrenches was conformal, starting and progressing all along the 2-D seam, with a rate that was 38% higher compared to a planar film. Etching in closed nanoholes proved also to be conformal and faster than planar films, but with a delay to open the 1-D seam that seemed to depend strongly on small variations in the hole diameter. However, holes between the fins at the bottom of the removed dummy gate, are not circular and do present 2-D seams that should lend themselves for an easier start of conformal etching as compared to the circular nanoholes used in this study. Finally, to explain the higher etch rate observed in nano-confined features, concentrations of ions in nanoholes were calculated taking the overlap of electrostatic double layers (EDL) into account. With negatively charged TiN walls, as measured by streaming potential on planar films, ammonium was the dominant ion in nanoholes. As no chemical reaction proposed in the literature for TiN etching matched with this finding, we proposed that the formation of ammine complexes, dissolving the formed Ti oxide, was the rate-determining step.