Ion beam-induced deposition (IBID) using Pt(CO)2Cl2 and Pt(CO)2Br2 as precursors has been studied with ultrahigh-vacuum (UHV) surface science techniques to provide insights into the elementary reaction steps involved in deposition, complemented by analysis of deposits formed under steady-state conditions. X-ray photoelectron spectroscopy (XPS) and mass spectrometry data from monolayer thick films of Pt(CO)2Cl2 and Pt(CO)2Br2 exposed to 3 keV Ar+, He+, and H2 + ions indicate that deposition is initiated by the desorption of both CO ligands, a process ascribed to momentum transfer from the incident ion to adsorbed precursor molecules. This precursor decomposition step is accompanied by a decrease in the oxidation state of the Pt(II) atoms and, in IBID, represents the elementary reaction step that converts the molecular precursor into an involatile PtX2 species. Upon further ion irradiation these PtCl2 or PtBr2 species experience ion-induced sputtering. The difference between halogen and Pt sputter rates leads to a critical ion dose at which only Pt remains in the film. A comparison of the different ion/precursor combinations studied revealed that this sequence of elementary reaction steps is invariant, although the rates of CO desorption and subsequent physical sputtering were greatest for the heaviest (Ar+) ions. The ability of IBID to produce pure Pt films was confirmed by AES and XPS analysis of thin film deposits created by Ar+/Pt(CO)2Cl2, demonstrating the ability of data acquired from fundamental UHV surface science studies to provide insights that can be used to better understand the interactions between ions and precursors during IBID from inorganic precursors.

MXenes are a newer class of 2D materials with desirable properties, making them attractive for various environmental applications, including remediation and as membranes for water treatment.

In focused ion-beam-induced deposition (FIBID) processes, the deposition rate and deposit composition are determined by the interplay between ion-induced deposition and sputtering of the deposited atoms. To provide independent insights into these two facets of FIBID, an ultrahigh vacuum (UHV) surface science approach employing in situ X-ray photoelectron spectroscopy (XPS) and mass spectrometry (MS) has been used to study how the identity of incident ions (Z = He, Ne, Ar, H-2 or D-2) influences ion-induced (i) deposition from adsorbed Me3PtCpMe and (ii) sputtering of the PtCx films created from Me3PtCpMe. For each of the ions studied, the initial decomposition/deposition step could be described as Me3PtCpMe(ads) + Z((g))(+) -> PtC9-x(ads) + xCH(4(g)) + H-2(g) although the rate and extent of carbon loss from the Me3PtCpMe precursor depended on the ion identity, with heavier ions (Ar+, Ne+) leading to faster and more extensive fragmentation. For the heavier ions, these findings were ascribed to direct momentum/energy transfer between incident ions and adsorbed precursor molecules, while for the lighter ions, there is an increasing contribution from secondary electrons generated by ion-substrate interactions. While the Pt atom purity associated with ion-induced precursor decomposition was lower for the lighter ions, ion-induced sputtering of PtCx films by lighter ions produced the greatest increase in metal content (i.e., purity), due to the extremely poor mass match with Pt. Indeed, sputtering of nanometer-thick PtCx films by H-2(+)/D-2(+) produced essentially pure Pt films, as measured by XPS. Increasing the substrate temperature during sputtering, however, inhibited the purification process. The results of these findings in the context of FIBID, conducted in the presence of a constant partial pressure of precursor molecules, are also discussed.

Motivated by the drawbacks of solution phase processing, an all-dry resist formation process is presented that utilizes amorphous zinc-imidazolate (aZnMIm) films deposited by atomic/molecular layer deposition (ALD/MLD), patterned with electron beam lithography (EBL), and developed by novel low temperature (120 °C) gas phase etching using 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH) to achieve well-resolved 22 nm lines with a pitch of 30 nm. The effects of electron beam irradiation on the chemical structure and hfacH etch resistance of aZnMIm films are investigated, and it is found that electron irradiation degrades the 2-methylimidazolate ligands and transforms aZnMIm into a more dense material that is resistant to etching by hfacH and has a C:N:Zn ratio effectively identical to that of unmodified aZnMIm. These findings showcase the potential for aZnMIm films to function in a dry resist technology. Sensitivity, contrast, and critical dimensions of the patterns are determined to be 37 mC cm-2, 0.87, and 29 nm, respectively, for aZnMIm deposited on silicon substrates and patterned at 30 keV. This work introduces a new direction for solvent-free resist processing, offering the prospect of scalable, high-resolution patterning techniques for advanced semiconductor fabrication processes.

With the adoption of extreme ultraviolet lithography (EUVL) to decrease microelectronic device dimensions, recent photoresist research has focused on the development of next generation metal-organic resist materials. To enhance lithographic capabilities and mitigate common drawbacks seen from traditional solvent based processes like spin coating and solution phase development, interest has shifted towards solvent-free "dry" deposition and development. These dry techniques can obviate extra processing steps, significantly reduce the amount of solvent waste generated, and even allow for reduced defect density and higher resolution. The process described herein avoids the use of solvents, and ultimately many issues associated with solvents, by depositing metal-organic resists using atomic/molecular layer deposition (ALD/MLD) and developing them using a selective thermal dry etching process. The low temperature (e.g., 100-120°C) thermal development conditions used in this study are notable in the context of lithography processes, as the high temperatures required in other dry etching processes can be difficult to implement in nanofabrication processes. Our previous work has focused on using amorphous zinc-imidazolate (aZnMIm) films in an all-dry resist technology, achieving resolution down to 22nm. Here, we explore the role of temperature and time on dry development and examine pattern transfer into silicon substrates. Preliminary pattern transfer experiments suggest that an etch selectivity of at least 7:1 exists for electron-beam treated aZnMIm over silicon using a pseudo-Bosch plasma etch. Our findings demonstrate the feasibility of dry development at lower temperatures and times and suggest potential for aZnMIm as a high-resolution resist for nextgeneration lithography.

Focused electron beam-induced deposition (FEBID) and focused ion beam-induced deposition (FIBID) are cutting-edge nanofabrication techniques that enable the growth of complex threedimensional (3D) nanostructures by action of the charged particles upon organometallic precursors. The interaction of the focused electron/ion beam with the adsorbed precursor molecules on the substrate surface leads to the dissociation of these surface-bound species resulting in the formation of well-defined deposits. However, during the deposition process, decomposition and incomplete desorption of the organic ligands give rise to contamination in the final deposits, reducing their metal content. To enable applications where deposit composition is critical, it will be necessary to design and synthesize custom precursors for FEBID/FIBID. UHV surface science studies can be used to understand the decomposition mechanism of the organometallic precursors during the electron-or ion-molecule interaction, generating information that can be used in mechanism-based precursor design.

Patterning metal-organic frameworks (MOFs) at submicrometer scale is a crucial yet challenging task for their integration in miniaturized devices. Here we report an electron beam (e-beam) assisted, bottom-up approach for patterning of two MOFs, zeolitic imidazolate frameworks (ZIF), ZIF-8 and ZIF-67. A mild pretreatment of metal oxide precursors with linker vapor leads to the sensitization of the oxide surface to e-beam irradiation, effectively inhibiting subsequent conversion of the oxide to ZIFs in irradiated areas, while ZIF growth in non-irradiated areas is not affected. Well-resolved patterns with features down to the scale of 100 nm can be achieved. This developer-free, all-vapor phase technique will facilitate the incorporation of MOFs in micro- and nanofabrication processes.

Ion-beam-induced deposition using Me3PtCpMe has been studied using a combination of ultrahigh vacuum (UHV) surface science studies performed on thin films and scanning electron microscopy (SEM) data of structures created under steady-state deposition conditions. X-ray photoelectron spectroscopy (XPS) data from monolayer thick films of Me3PtCpMe exposed to 1.2-4 keV Ar ions indicate that deposition is initiated by energy transfer from the incident ions to adsorbed precursor molecules leading to the loss of all four methyl groups and the likely decomposition of the Cp ring, yielding a deposit with a PtC5 stoichiometry. This contrasts with focused electron-beam-induced processing (FEBIP), where deposition occurs as a result of electron excitation and the loss of only one Pt-CH3 group. By comparing the rate of Pt(IV) reduction that accompanies either ion- or electron-induced decomposition of Me3PtCpMe, it was determined that ion-induced deposition reaction cross sections are approximately two orders of magnitude greater. As a result of this higher reaction efficiency, ion irradiation was accompanied by some bimolecular methyl radical coupling to produce ethane. UHV studies also revealed that ion-induced deposition was followed by sputtering of Pt and C atoms at comparable rates. These fundamental insights provided by the UHV studies provided the basis to understand SEM data obtained on structures that formed under steady-state deposition conditions. In particular, the observation of "ring-like" deposits could be rationalized by sputtering in the center of the deposition region where the Ar+ flux was sufficiently high to produce a precursor-limited regime, while deposition occurred in ion-limited regimes at the periphery of the deposition region where the Ar+ flux was lower. These results demonstrate the utility of using data from a UHV surface science approach to better understand the composition and influence of reaction conditions on deposits formed during ion-beam-induced deposition of organometallic precursors.