V. S. V. Satyanarayana

Radiation-Sensitive Novel Polymeric Resist Materials: Iterative Synthesis and Their EUV Fragmentation Studies

Polymerization of (4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate (MAPDST), as a key monomer containing the radiation sensitive sulfonium functionality, with various other monomers such as methyl methacrylate (MMA), 4-carboxy styrene (STYCOOH), N-vinyl carbazole (NVK) in different molar ratios via free-radical polymerization method is described. This methodology led to the development of a small chemical library of six different radiation sensitive polymers for lithography applications. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy identified the reaction products as MAPDST homopolymer and MAPDST-MMA, MAPDST-STYCOOH, MAPDST-NVK copolymers. Molecular weights were obtained from gel permeation chromatography and the decomposition temperature (Td) values were determined using thermogravimetric analysis (TGA). The effect of extreme ultraviolet (EUV) irradiation on a thin poly(MAPDST) film was investigated using monochromatic synchrotron excitation. These new polymeric materials were also exposed to electron-beam lithography (EBL) and extreme ultraviolet lithography (EUVL) to achieve 20-nm line patterns.

New Polyoxometalates Containing Hybrid Polymers and Their Potential for Nano-Patterning

Two new polyoxometalate (POM)-based hybrid monomers (Bu4 N)5 (H)[P2 V3 W15 O59 {(OCH2 )3 CNHCO(CH3 )CCH2 }] (2) and (S(CH3 )2 C6 H4 OCOC(CH3 )=CH2 )6 [PV  2Mo10 O40 ] (5) were developed by grafting polymerizable organic units covalently or electrostatically onto Wells-Dawson and Keggin-type clusters and were characterized by analytical and spectroscopic techniques including ESI-MS and/or single-crystal X-ray diffraction analyses. Radical initiated polymerization of 2 and 5 with organic monomers (methacryloyloxy)phenyldimethylsulfonium triflate (MAPDST) and/or methylmethacrylate (MMA) yielded a new series of POM/polymer hybrids that were characterized by (1) H, (31) P NMR and IR spectroscopic techniques, gel-permeation chromatography as well as thermal analyses. Preliminary tests were conducted on these POM/polymer hybrids to evaluate their properties as photoresists using electron beam (E-beam)/extreme ultraviolet (EUV) lithographic techniques. It was observed that the POM/polymer hybrid of 2 with MAPDST exhibited improved sensitivity under EUV lithographic conditions in comparison to the MAPDST homopolymer resist possibly due to the efficient photon harvesting by the POM clusters from the EUV source.

Towards novel non-chemically amplified (n-CARS) negative resists for electron beam lithography applications

A novel, non-chemically amplified negative resist was synthesized and characterized for next generation lithography applications. This resist material was shown to be directly sensitive to radiation without utilizing the concept of chemical amplification (CAR) and resulted in high-resolution 20 nm features. This resist design is accomplished by copolymers that are prepared from a monomer containing a sulfonium group which is sensitive to e-beam irradiation. Under 20 keV e-beam imaging and TMAH development, a sensitivity of 2.06 μC cm−2 and contrast of 1.8 were obtained. It has an LER of 20 nm, 10 line pattern varies from 1.8 ± 0.3 to 2.3 ± 0.4 nm.

A hybrid polymeric material bearing a ferrocene-based pendant organometallic functionality: synthesis and applications in nanopatterning using EUV lithography

Largely because of their unique physical and chemical properties, the inclusion of ferrocene derivatives into polymer backbones has attracted great attention in materials research as these hybrid organometallic polymers find wide applications in various fields. Though chemically amplified photoresists (CARs) have become the workhorses for nanopatterning in semiconductor industries, due to several inherent problems CARs cannot be used for sub 20 nm technology and therefore non-chemically amplified resists (n-CARs) are gaining attention from the photoresists community, considering their potential in patterning sub 20 nm features with good line edge roughness/line width roughness (LER/LWR) and high resolution. Given that extreme ultraviolet lithography (EUVL) is approaching well towards the commercialization phase, the present work describes the development of novel solution processable EUV-sensitive hybrid organic–organometallic polymeric non-chemically amplified photoresist materials containing pendant ferrocene units and their applications in featuring 25 nm lines and complex nanopatterns using EUVL. This resist design is accomplished by copolymers that are prepared from monomers containing sulfonium groups which are sensitive to EUV irradiation. The copolymers were characterized by 1H NMR and IR spectroscopic techniques, gel permeation chromatography as well as thermal analyses. Whereas the photon-directed polarity change at the sulfonium center followed by scission of the polymer backbone nullified the requirement for chemical amplification, the inclusion of organometallic species in the polymer microstructure into the polymer network improved the thermal stability of the resultant hybrid system.

Performance evaluation of nonchemically amplified negative tone photoresists for e-beam and EUV lithography

Abstract. Although extreme ultraviolet (EUV) lithography is being considered as one of the most promising next-generation lithography techniques for patterning sub-20 nm features, the development of suitable EUV resists remains one of the main challenges confronting the semiconductor industry. The goal is to achieve sub-20 nm line patterns having low line edge roughness (LER) of <1.8  nm and a sensitivity of 5 to 20  mJ/cm2. The present work demonstrates the lithographic performance of two nonchemically amplified (n-CARs) negative photoresists, MAPDST homopolymer and MAPDST-MMA copolymer, prepared from suitable monomers containing the radiation sensitive sulfonium functionality. Investigations into the effect of several process parameters are reported. These include spinning conditions to obtain film thicknesses <50  nm, baking regimes, exposure conditions, and the resulting surface topographies. The effect of these protocols on sensitivity, contrast, and resolution has been assessed for the optimization of 20 nm features and the corresponding LER/line width roughness. These n-CARs have also been found to possess high etch resistance. The etch durability of MAPDST homopolymer and MAPDST-MMA copolymer (under SF6 plasma chemistry) with respect to the silicon substrate are 7.2∶1 and 8.3∶1, respectively. This methodical investigation will provide guidance in designing new resist materials with improved efficiency for EUVL through polymer microstructure engineering.

A radiation sensitive hybrid polymer based on an Mn-Anderson polyoxometalate cluster and a UV active organic monomer: synergistic effects lead to improved photocurrent in a photoresponse device

A new radiation sensitive polyoxometalate/polymer hybrid, POM–MAPDST, has been synthesized from an Mn-Anderson cluster based hybrid and a UV active organic monomer and tested for its photo-response properties by fabricating an ITO/POM–MAPDST/Al device. This device showed improved I–V characteristics under illumination possibly due to the synergistic interactions between the polyoxometalate cluster and the organic components of the hybrid polymer.

Synthesis, structure, self-assembly and genotoxicity evaluation of a series of Mn-Anderson cluster based polyoxometalate–organic hybrids

A new series of class II polyoxometalate–organic hybrids based on Mn-Anderson type polyoxometalate cluster and aromatic organic moieties has been synthesized and characterized through various analytical and spectroscopic techniques including single crystal X-ray analyses in some cases. The genotoxic effects of these covalent hybrids were evaluated by studying their effects on Allium cepa cells which revealed their low toxic nature as compared to the parent polyoxometalate cluster.

Patterning highly ordered arrays of complex nanofeatures through EUV directed polarity switching of non chemically amplified photoresist

Given the importance of complex nanofeatures in the filed of micro-/nanoelectronics particularly in the area of high-density magnetic recording, photonic crystals, information storage, micro-lens arrays, tissue engineering and catalysis, the present work demonstrates the development of new methodology for patterning complex nanofeatures using a recently developed non-chemically amplified photoresist (n-CARs) poly(4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate) (polyMAPDST) with the help of extreme ultraviolet lithography (EUVL) as patterning tool. The photosensitivity of polyMAPDST is mainly due to the presence of radiation sensitive trifluoromethanesulfonate unit (triflate group) which undergoes photodegradation upon exposure with EUV photons, and thus brings in polarity change in the polymer structure. Integration of such radiation sensitive unit into polymer network avoids the need of chemical amplification which is otherwise needed for polarity switching in the case of chemically amplified photoresists (CARs). Indeed, we successfully patterned highly ordered wide-raging dense nanofeatures that include nanodots, nanowaves, nanoboats, star-elbow etc. All these developed nanopatterns have been well characterized by FESEM and AFM techniques. Finally, the potential of polyMAPDST has been established by successful transfer of patterns into silicon substrate through adaptation of compatible etch recipes.

Synthesis, Characterization of Some New Five Membered Heterocycles Based on Imidazole Moiety and their Applications on Therapeutics

Different imidazole derivatives were prepared by utilizing the intermediate 2-(2,4,5-triphenyl-1H-imidazol-1- yl)acetohydrazide (3) using microwave irradiation method besides the traditional ones. They were used for synthesis of some new derivatives of 2,5-disubstituted-1,3,4-oxadiazole, pyrazole, 2,5-dimethylpyrrole and nitrogen containing five membered rings. All the synthesized compounds were characterized by IR, 1 H & 13 C NMR and mass spectral data. The antibacterial, antifungal (MIC) and antioxidant activities were verified for all the synthesized compounds.

Optimization of processing parameters and metrology for novel NCA negative resists for NGL

It is expected that EUV resists must simultaneously pattern 20-nm half-pitch and below, with an LWR of <1.8 nm, and a sensitivity of 5–20 mJ/cm2. In order to make a resist perform optimally, new resist chemistry is required. One such approach being investigated by us is the development of polymeric non-CAR negative photo resists for sub 16 nm technology which is directly sensitive to radiation without utilizing the concept of chemical amplification (CARs). These resist designs are accomplished by homopolymers which are prepared from monomers containing sulfonium groups. We have achieved 20 nm patterns by e-beam lithography using this system. Here we will discuss in detail process parameters such as: spinning conditions for film thicknesses <50 nm and resulting surface topographies, baking regimes, exposure conditions and protocols on sensitivity, contrast, resolution and LER/LWR. Etch resistance data on these thin films will also be provided. Our results are aimed to provide a clear understanding of how these critical steps in the lithographic imaging process will affect extendibility of the non-CAR resist concept to sub 20 nanoscale features. Photodynamics and EUV exposure data will be covered.