Philippe Foubert

Protein-polymer hybrid amphiphiles

Synthesis of 1: 350 mg (0.036 mmol) of carboxy terminated polystyrene, 20 mg (0.053 mmol) of biotinyl-3,6-dioxaoctanediamine and 0.06 ml Et3N were dissolved in 15 ml destilled DMF. Subsequently, 22 mg (0.050 mmol) of (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate was added. After stirring for 16 hrs at room temperature under a nitrogen atmosphere the solution was precipitated in 600 ml MeOH. The crude product was further purified by column chromatography (MeOH/CH2Cl2, 2:98 v/v); yield 142 mg (0.015 mmol; 43%) of 1. Mn = 9147; Mw/Mn = 1.03;

Roughness characterization in the frequency domain and linewidth roughness mitigation with post-lithography processes

A previously developed linewidth roughness analysis technique is used to characterize post-lithography process roughness reduction in the frequency domain. Post-lithography processes are likely to be required to reach the International Technology Roadmap for Semiconductors roughness specifications for the 32-nm and 22-nm technological nodes. The aim of these processes is to reduce 3 linewidth roughness after etch without dramatic changes in critical dimensions. Various techniques are discussed: in-track chemical processes, ion-beam sputtering, and thermal and plasma treatments-each technique manifests a characteristic smoothing, reducing roughness up to 34%. Exploiting roughness mitigation at different frequencies, our target is to determine whether 50% 3 linewidth roughness reduction after etch is feasible.

Mechanical and optical manipulation of porphyrin rings at the submicrometre scale

Scanning probe microscopes (SPMs) and especially the atomic force microscope (AFM) can be used as tools for modifying surface structures on the submicrometre and even nanometre scale. For this purpose an advanced interface has been developed to facilitate these manipulations and greatly increase the number of possible applications. In this paper this interface (the nanoManipulator, developed at the University of North Carolina at Chapel Hill) is implemented on a combined AFM-confocal microscope. This setup allows AFM imaging, manipulations and fluorescence imaging of the same area on the sample. The new setup is tested on ringlike structures of a porphyrin derivative (BP6). A small amount of the fluorescent material could be displaced with the AFM tip. A special tool (sweep mode) allowed a modification of around 130 nm, which was afterwards detectable with the confocal microscope. The resolution attainable in these kind of experiments could go down below 100 nm and is primarily determined by the tip and sample geometry. Comparable with this experiment is the application of a near-field scanning optical microscope (NSOM) to make photochemical modifications. Using the excitation power coming from the NSOM probe the fluorescence can be quenched by bleaching a selected area instead of displacing the material. Application on the BP6 rings led to a modification of 280 nm wide. AFM can perform modifications on a smaller scale but is less selective than NSOM. Optical investigation of the changes after AFM manipulation can give more elaborate information on the modifications. This will extend the possible applications of the techniques and may ultimately go down to the single-molecule level.

Impact of post-litho linewidth roughness smoothing processes on the post-etch patterning result

In the last years, interest in reducing linewidth roughness (LWR) in EUV lithography through a dedicated process step has significantly increased. Various post-litho processing techniques to improve LWR without compromising resolution or sensitivity have been proposed. While these techniques are giving smoothing levels up to 30% before etch, the important question is, of course, how efficient they are in the full patterning process. To evaluate the effectiveness of the smoothing techniques on the EUV resist process and the post-etch pattern, a few of the most promising techniques have been selected for evaluation. Post-develop rinse smoothing and solvent vapor smoothing can reduce the LWR by 10% to 15%. Ion-beam smoothing is giving higher smoothing values, but suffers some important limitations for its application. Two case studies of post-litho smoothing followed by a standard etch process reveal that a large portion of the LWR smoothing can remain after etch, but the LWR gain may also be completely lost. Finally, a plasma smoothing process combined with a layer deposition is proposed to optimize the etch process itself. Analysis of LWR in the spatial frequency domain at the different stages of the patterning process gives a better insight into the impact of the different steps.

Design of Functionalized Lipids and Evidence for Their Binding to Photosystem II Core Complex by Oxygen Evolution Measurements, Atomic Force Microscopy, and Scanning Near-Field Optical Microscopy

Photosystem II core complex (PSII CC) absorbs light energy and triggers a series of electron transfer reactions by oxidizing water while producing molecular oxygen. Synthetic lipids with different alkyl chains and spacer lengths bearing functionalized headgroups were specifically designed to bind the Q(B) site and to anchor this large photosynthetic complex (240 kDa) in order to attempt two-dimensional crystallization. Among the series of different compounds that have been tested, oxygen evolution measurements have shown that dichlorophenyl urea (DCPU) binds very efficiently to the Q(B) site of PSII CC, and therefore, that moiety has been linked covalently to the headgroup of synthetic lipids. The analysis of the monolayer behavior of these DCPU-lipids has allowed us to select ones bearing long spacers for the anchoring of PSII CC. Oxygen evolution measurements demonstrated that these long-spacer DCPU-lipids specifically bind to PSII CC and inhibit electron transfer. With the use of atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM), it was possible to visualize domains of PSII CC bound to DCPU-lipid monolayers. SNOM imaging has enabled us to confirm that domains observed by AFM were composed of PSII CC. Indeed, the SNOM topography images presented similar domains as those observed by AFM, but in addition, it allowed us to determine that these domains are fluorescent. Electron microscopy of these domains, however, has shown that the bound PSII CC was not crystalline.

Morphology of protein polymer hybrid films studied by atomic force microscopy and scanning confocal fluorescence microscopy

Protein-polymer hybrids can act as giant monolayer-forming amphiphiles at the air-water interface.Using biotinylated polystyrene (PSb) as the hydrophobic part and streptavidin (SAv) as a hydrophilic end of the giant amphiphile, monolayer formation and subsequent deposition leads to a well defined solid-supported monolayer, in which the remaining free sites of the polymer-bound SAv are accessible to biotin binding.The deposition conditions are evaluated by investigating the supported films by atomic force microscopy (AFM).Imaging of the PSb without protein reveals uniform monolayer formation.In situ binding of SAv indicates that the biotin is accessible.Deposition of the SAv-polymer hybrid film results primarily in a very similar morphology, indicative of the dominant role of the polymer in the monolayer formation.High resolution AFM revealed a homogeneously dense packing.This is confirmed by combined AFM and scanning confocal fluorescence microscopy (SCFM) on hybrid monolayers containing rhodamine-red-X labeled SAv.The biotin binding capability of the monolayer was assessed by binding of fluorescein labeled biotin and performing dual color excitation and detection.Biotin binding was uniform and homogeneous.Local spectra revealed that the fluorescein was largely quenched by the rhodamine, indicating an efficient energy transfer.