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Secondary electrons generated during the Extreme Ultraviolet Lithography (EUVL) process are predominantly responsible for inducing important patterning chemistry in photoresist films. Therefore, it is crucial to understand the electron-induced fragmentation mechanisms involved in EUV-resist systems to improve their patterning performance. To facilitate this understanding, mechanistic studies were carried out on simple organic EUV-resist monomers, methyl isobutyrate (MIB) and methacrylic acid (MAA), both in the condensed and gas phases. Electron-stimulated desorption (ESD) studies on MIB in the condensed phase showed desorption peaks at around 2 and 9 eV electron energies. The gas-phase study on MIB showed that the monomer followed the dissociative ionization (DI) fragmentation pathway, under single collision conditions, which opened up at electron energies above about 11 eV. No signs of dissociative electron attachment (DEA) were detected for MIB in the gas phase under single collision conditions. However, DEA was an active process in MAA in the gas phase under single collision conditions at around 2 eV, showing that slight modifications of the molecular structures of photoresists may serve to sensitize them to certain electron-induced processes. [ABSTRACT FROM AUTHOR]

In this atomic-scale study on wet etching, the importance of surface chemistry, in particular the nature of the surface oxides, is demonstrated for technologically relevant group IV semiconductors, Ge and SiGe. Elemental quantification of Ge in hydrochloric acid solution containing hydrogen peroxide showed a striking impact of the Si bulk concentration on the kinetics of etching. Post operando surface analysis provided insight into the oxide product formed after etching: a non-homogeneous porous layer with a depletion of Ge components at the outer surface due to pull out effects. Oxide formation was verified by microscopic imaging. We provide basic reaction schemes that help to elucidate the results. [ABSTRACT FROM AUTHOR]

Unclear light-matter interactions in the Extreme UV lithography (EUVL) process cause the sub-optimal performance of the current photoresist platforms. Furthermore, adopting conventional chemically amplified resist (CAR) is problematic in EUVL because of the exacerbated stochastic effects. Therefore, alternative platforms with simpler chemistry, such as the main chain scission (MCS)-type photoresist, can pave the way for efficient printability at higher resolutions. In this work, fundamental analysis of a simple MCS-type photoresist – polymethyl methacrylate (PMMA), is studied and correlated with the parameters of EUV-patterning (called litho-parameters). Contrast curve analysis with different solvents shows MIBK–IPA (1 : 3) mixture as the best developer for EUV-patterning of PMMA. Higher Mw (950k) shows the best EUV-printability compared to the lower Mw (15k, 120k, and 600k) PMMA for 50 nm dense line–space (L/S). To understand the effect of polymer properties on printability, desorption and Gel Permeation chromatography (GPC) studies are conducted, which show that the higher Mw PMMA provides better litho-parameters (higher MCS – to – side-chain scission (SCS) ratio, higher GPC peak shift, and lower GPC peak overlap after EUV-exposure) compared to the lower Mw PMMA. Additionally, it is found that the PMMA chains require minimum energy of 9 eV to induce chemical reactions in the film. The main hypothesis obtained from this study is that for MCS-type EUV resists, higher Mw material provides better printability than the lower Mw material. This is further validated on an engineered MCS-copolymer system. Finally, it is observed that the inhomogeneous dose-deposition during EUV-exposures might hamper the printability of the MCS-type resist. [ABSTRACT FROM AUTHOR]

The process of electrochemical etching of n-Ge(100) surfaces was studied for aqueous HCl solutions by voltammetry, atomic force and scanning electron microscopy, reflectance measurements and X-ray photoelectron spectroscopy. Under applied potential conditions, unexpected random pyramid texturization was observed for the high HCl concentration range evidenced by the formation of characteristic (111) facets. The morphological changes were accompanied by a photocurrent enhancement and a decreased reflectance. By patterning the pyramids, a high structure density could be achieved. The resulting decrease of the reflectance indicates that the coupling of light into the semiconductor was improved. Integrated electrochemical X-ray photoelectron spectroscopy measurements allowed us to relate surface chlorination to the obtained morphological features. Photoanodic etching schemes are presented to provide insight into these striking results. [ABSTRACT FROM AUTHOR]

The continuation of CMOS scaling leads to the necessity of replacing Cu as an interconnect material with a metal with lower resistivity and better reliability performance. At the same time, significant technological improvements are required to mitigate the pattern overlay requirements when forming multilevel structures with a half-pitch below 10 nm. Area-selective deposition (ASD) offers an elegant way to enable self-alignment of multilevel structures. However, defectivity is a typical bottleneck of ASD integration. This work explores the selective electroless deposition (ELD) of Co as a replacement of Cu as an interconnect metal. The selective metallization process is promoted by the selective placement of an amino-terminated organic layer in combination with confined grafting of a Pd catalyst. Co films thicker than 40 nm can be formed on amino-terminated surfaces, while the surfaces with no amino functionality remain completely free of Pd and Co according to EDS chemical analysis and SEM inspection. This article offers a detailed study of selective Co growth on blanket and patterned structures and investigation of the ELD Co film properties, such as low-temperature recrystallization at 420 °C, grain structure, chemical composition and segregation of impurities. It is demonstrated that the resistivity of the ELD Co films exhibits lower thickness dependence when compared to that of PVD Co, which can be attributed to the ELD Co grain size exceeding the Co film thickness. In addition, it is shown that the underlying organic layer prevents the silicidation of the annealed Co film on the Si substrate while promoting interface adhesion values as high as 8.2 J m−2± 0.7 J m−2 for a 50-nm thick Co film. [ABSTRACT FROM AUTHOR]

The deposition of ultra-thin tungsten films and their related 2D chalcogen compounds on large area dielectric substrates by gas phase reactions is challenging. The lack of nucleation sites complicates the adsorption of W-related precursors and subsequent sulfurization usually requires high temperatures. We propose here a technique in which a thin solid amorphous silicon film is used as reductant for the gas phase precursor WF6 leading to the conversion to metallic W. The selectivity of the W conversion towards the underlying dielectric surfaces is demonstrated. The role of the Si surface preparation, the conversion temperature, and Si thickness on the formation process is investigated. Further, the in situ conversion of the metallic tungsten into thin stoichiometric WS2 is achieved by a cyclic approach based on WF6 and H2S pulses at the moderate temperature of 450 °C, which is much lower than usual oxide sulfurization processes. [ABSTRACT FROM AUTHOR]

An aqueous precursor solution, containing citrato-VO2+ complexes, is synthesized for the formation of monoclinic VO2. With regard to the decomposition of the VO2+ complexes towards vanadium oxide formation, it is important to gain insights into the chemical structure and transformations of the precursor during synthesis and thermal treatment. Hence, the conversion of the cyclic [V4O12]4- ion to the VO2+ ion in aqueous solution, using oxalic acid as an acidifier and a reducing agent, is studied by 51Vanadium nuclear magnetic resonance spectroscopy. The citrate complexation of this VO2+ ion and the differentiation between a solution containing citrato-oxalato-VO2+ and citrato-VO2+ complexes are studied by electron paramagnetic resonance and Fourier transform infra-red spectroscopy. In both solutions, the VO2+ containing complex is mononuclear and has a distorted octahedral geometry with a fourfold R-CO2 - ligation at the equatorial positions and likely a fifth R-CO2- ligation at the axial position. Small differences in the thermal decomposition pathway between the gel containing citrato-oxalato-VO2+ complexes and the oxalate-free gel containing citrato-VO2+ complexes are observed between 150 and 200 °C in air and are assigned to the presence of (NH4)2C2O4 in the citrato-oxalato-VO2+ solution. Both precursor solutions are successfully used for the formation of crystalline vanadium oxide nanostructures on SiO2, after thermal annealing at 500 °C in a 0.1% O2 atmosphere. However, the citrato-oxalato-VO2+ and the oxalate-free citrato-VO2+ solution result in the formation of monoclinic V6O13 and monoclinic VO2, respectively. [ABSTRACT FROM AUTHOR]

Tantalum oxide (Ta2O5) and tantalum silicate (TaSiOx) films were grown by atomic layer deposition from TaCl5, SiCl4, and O3. Saturation of absorption was observed for TaCl5 at short TaCl5 pulses. However, long TaCl5 exposure resulted in a reduced growth per cycle of Ta2O5 and TaSiOx films due to concomitant etching. The saturated growth per cycle of Ta2O5 was ∼0.77 Å per cycle at a deposition temperature of 300 °C and ∼1 Å per cycle at 250 °C. Quadrupole mass spectrometry revealed that TaCl5 chemisorbed on the surface with negligible ligand removal. Subsequently, the reaction with O3 led to the formation of both chlorine oxides (ClxOy) and chlorine (Clx) as by-products. Si incorporation was found to be feasible using supercycles including SiCl4/O3 cycles although no SiO2 deposition was observed for SiCl4/O3 cycles only. At a deposition temperature of 300 °C, self-limiting growth was observed as a function of SiCl4 and O3 pulse time. This suggests that the adsorption of SiCl4 on Ta-terminated surfaces is more favorable than on Si-terminated ones, similar to the case of the equivalent H2O-based ALD process. The Cl impurity levels in Ta2O5 films from TaCl5 and O3 were found to be lower than those in films from TaCl5 and H2O. The Ta2O5 and TaSiOx films were amorphous as deposited. Ta2O5 crystallized into orthorhombic β-Ta2O5 at a temperature of 740 °C while TaSiOx showed no signs of crystallization up to 900 °C. Amorphous Ta2O5 and Ta0.6Si0.4Ox films showed dielectric constants of 31 and 24, respectively, and exhibited lower leakage current densities than those deposited from TaCl5, SiCl4, and H2O. [ABSTRACT FROM AUTHOR]

Correction for 'Effect of molecular weight on the EUV-printability of main chain scission type polymers' by Ashish Rathore et al., J. Mater. Chem. C, 2020, DOI: 10.1039/c9tc06482f. [ABSTRACT FROM AUTHOR]

An aqueous precursor solution, containing citrato-VO(2+) complexes, is synthesized for the formation of monoclinic VO2. With regard to the decomposition of the VO(2+) complexes towards vanadium oxide formation, it is important to gain insights into the chemical structure and transformations of the precursor during synthesis and thermal treatment. Hence, the conversion of the cyclic [V4O12](4-) ion to the VO(2+) ion in aqueous solution, using oxalic acid as an acidifier and a reducing agent, is studied by (51)Vanadium nuclear magnetic resonance spectroscopy. The citrate complexation of this VO(2+) ion and the differentiation between a solution containing citrato-oxalato-VO(2+) and citrato-VO(2+) complexes are studied by electron paramagnetic resonance and Fourier transform infra-red spectroscopy. In both solutions, the VO(2+) containing complex is mononuclear and has a distorted octahedral geometry with a fourfold R-CO2(-) ligation at the equatorial positions and likely a fifth R-CO2(-) ligation at the axial position. Small differences in the thermal decomposition pathway between the gel containing citrato-oxalato-VO(2+) complexes and the oxalate-free gel containing citrato-VO(2+) complexes are observed between 150 and 200 °C in air and are assigned to the presence of (NH4)2C2O4 in the citrato-oxalato-VO(2+) solution. Both precursor solutions are successfully used for the formation of crystalline vanadium oxide nanostructures on SiO2, after thermal annealing at 500 °C in a 0.1% O2 atmosphere. However, the citrato-oxalato-VO(2+) and the oxalate-free citrato-VO(2+) solution result in the formation of monoclinic V6O13 and monoclinic VO2, respectively.

An aqueous deposition process for V(6)O(13) films is developed whereby the vanadium oxidation state is continuously controlled throughout the entire process. In the precursor stage, a controlled wet chemical reduction of the vanadium(V) source with oxalic acid is achieved and monitored by (51)Vanadium Nuclear Magnetic Resonance ((51)V-NMR) and Ultraviolet-Visible (UV-Vis) spectroscopy. The resulting vanadium(IV) species in the aqueous solution are identified as mononuclear citrato-oxovanadate(IV) complexes by Electron Paramagnetic Resonance (EPR) and Fourier Transform Infra-Red (FTIR) spectroscopy. This precursor is successfully employed for the deposition of uniform, thin films. The optimal deposition and annealing conditions for the formation of crystalline V(6)O(13), including the control of the vanadium oxidation state, are determined through an elaborate study of processing temperature and O(2) partial pressure. To ensure a sub 100 nm adjustable film thickness, a non-oxidative intermediate thermal treatment is carried out at the end of each deposition cycle, allowing maximal precursor decomposition while still avoiding V(IV) oxidation. The resulting surface hydrophilicity, indispensable for the homogeneous deposition of the next layer, is explained by an increased surface roughness and the increased availability of surface vanadyl groups. Crystalline V(6)O(13) with a preferential (002) orientation is obtained after a post deposition annealing in a 0.1% O(2) ambient for thin films with a thickness of 20 nm.