In order to reduce line edge roughness and to increase sensitivity, PAG-bonded chemically amplified resist was developed and was evaluated in extreme ultraviolet lithography (EUVL) and electron beam (EB) lithography. We investigated various kinds of photo acid generators (PAGs) which are on the basis of the sulfonium salts to find the beneficial photo acid generator (PAG) for our designed PAG-bonded resist. It was confirmed that not only the structure of anion of PAG but also the structure of cation of PAG are important to achieve the resist specification. It is confirmed that by a selected PAG system, high E0 sensitivity was achieved under the EUV exposure. In addition, LER of 3.5 nm (3σ) was achieved by an EB writing tool.

View full abstract

The effective quantification and qualification of resist outgassing upon EUV exposure was demonstrated utilizing the pressure rise, quadropole mass spectrometry (QMS) and accumulation method with gas chromatography - mass spectrometry (GC-MS). Quantification analysis results showed a clear correlation between the pressure rise and accumulation methods. For the qualification analysis, QMS and GC-MS analysis were utilized. Resist outgassing release characteristics were obtained using QMS while a detailed identification of resist outgassing components were made using GC-MS. Different kinds of outgassing species were detected inside the exposure chamber during EUV exposure. These analysis results imply that resist outgassing qualification analysis is not as simple as defining resist outgassing components based on the resist's basic chemical structure. Rather, that a careful consideration of the actual source of the hydrocarbons detected be performed in identifying the resist outgassing components.

View full abstract

This paper reviews development of advanced resist materials which I have been involved in for more than a quarter century. First, our attempts to increase the main chain scission susceptibility are described. Next, a simple lift-off process for fabrication of magnetoresistive heads for storage devices is presented, which became the industry-standard manufacturing technology. Then, the major focus is going to be placed on the development of chemical amplification resists. Chemical amplification resists achieve a high sensitivity through a catalytic action of a photochemically generated acid. This drastically novel imaging concept was considered laboratory curiosity initially. However, the very first chemically amplified tBOC resist was quickly implemented in mass production of 1 megabit dynamic random access memory devices by deep UV lithography at IBM. Since then the chemical amplification concept has become the paradigm of advanced resist systems, enabling the industry to continue to migrate to shorter wavelengths (from 365 to 248, and then to 193 nm) for higher resolution and to follow the Moore's law. The chemical amplification resist invented for 1 μm resolution can now resolve <30 nm equal line/space patterns and continues to play a pivotal role in microlithography in the foreseeable future.

View full abstract

The development of highly efficient onium salt-based photoacid generating systems has provided many new opportunities for the design of novel photocuring and imaging systems. This communication focuses on some of the more recent efforts in designing and synthesizing efficient photoacid generating systems with tailored wavelength response. The use of these photoacid generating systems in a number of applications is described.

View full abstract

Pyrromethene dye/oxime type of photoacid generator (PAG) photoinitiating system based on the singlet electron transfer mechanism was found. The photoacid generation quantum yield (φ_acid) for the sensitization by the pyrromethene dye was much higher than that for the direct excitation of the PAG, giving a high sensitivity to the photopolymer. The sensitizer/PAG photoinitiating system was extended in UV light area with an anthracene derivative. The electric structure of the PAG and the radical anion were estimated by the ab initio molecular orbital (MO) calculation. The corresponding PAG radical anions give reasonable result for the enhancement of φ_acid.

View full abstract

A new series of photoinitiators for free radical photopolymerization based on Barton ester derivatives is developed for flat panel display applications. The absorption spectra exhibit a broad band between 320 and 420 nm. The photolysis quantum yields are very high, a fact that underlines the capability of the photoinitiators to bleach during the irradiation and thereby to lead to a moderate yellowing. Compared to commercial photoinitiators, the Barton esters display a very good efficiency. As revealed by laser flash photolysis, the dissociation rate constants are very high. Quantum mechanical computations show that the photodissociation can occur from both the excited singlet and triplet states.

View full abstract

This contribution reviews current state of electron beam and soft X-ray lithography with a monomolecular resist. Self-assembled monolayers (SAMs) represent versatile resist materials for such a lithography. Depending on the architecture of the SAM constituents, they can serve as both positive and negative resists within framework of conventional lithography, but also be used as multi-purpose templates for Chemical Lithography. The latter technique exploits either selective modification of specific tail groups at the SAM-ambient interface (in the case of aromatic backbone) or irradiation-promoted exchange reaction between the primary SAM and potential molecular substituents (in the case of aliphatic backbone). Due to the monolayer thickness of SAM resists and molecular size of their structural building blocks, patterning down to few nanometers is in principle possible. Currently, the lateral resolution is limited by the grain character of the SAM substrates and parameters of the lithographic setup, with the latter being especially important in the case of soft X-ray lithography.

View full abstract

Silane coupling agents 1-3 containing photocleavable 2-nitrobenzyl ester were employed for photosensitive self-assembled monolayers on which carboxy groups were generated by photoirradiation. These surfaces were characterized by contact angle measurement and XPS spectra, and applied for photopatterning of carboxy groups.

View full abstract

We report the catalytic repair of a thymine dimer incorporated in a DNA duplex via oligodeoxynucleotide (ODN) containing carbazole nucleoside. The occurrence of an electron transfer between carbazole nucleoside and thymine dimer is evidenced by fluorescence quenching measurements. Carbazole nucleoside acts as a good electron donor for the catalytic repair of a thymine dimer.

View full abstract

In this letter, detection of target protein molecules has been demonstrated by a two-dimensional (2D) photon burst analysis technique and microfluidic channel device. Individual molecule events are scatter plotted in terms of their photon counts and burst width in 2D photon burst analysis. Detection of target protein is verified by a higher counts-per-bin for rabbit anti-HA polyclonal antibody sample than that of the control sample from the 2D photon burst analysis. Since this is microfluidic single molecule detection scheme, it has the advantages of high sensitivity, small sample consumption and reduced processing time, comparing to the conventional immunological ensemble measurements, such as western blot, immuno-precipitation, etc.

View full abstract

Novel azotolane derivatives containing various structures of alkyl chains have been synthesized via palladium-catalyzed cross coupling reactions as the key step. The thermotoropic liquid crystalline behavior of these compounds was investigated by polarizing optical microscopy, differential scanning calorimeter, and X-ray scattering, and the influences of the structure and position of the lateral alkyl chain on the mesomorphic properties were studied. Depending on the size or the structure of alkyl chains, different liquid crystalline phases were detected. Furthermore, we found that all compounds show trans-cis photoisomerization behavior upon irradiation of ultraviolet light, as well as a conventional azobenzene moiety.

View full abstract

In this article, our recent approaches for preparation of supramolecular materials including molecular array and pattern formation are summarized, as classified by four categories: (i) molecule to nano; (ii) nano to micro; (iii) micro to bulk; (iv) bridging molecule and bulk. Self-assembled processes on a surface provides molecular arrays that can be tuned by several factors such as conformational changes and hydrogen bonding. Microscopic structures can be obtained through self-assembly of molecules designed upon a novel concept of amphiphilicity. Combining self-assembly with layer-by-layer adsorption methods resulted in functional layered micro-structures. By structural transcription from self-assembled structure, bulk materials with precise interior structures such as carbon nanocage can be obtained. The air-water interface provides medium to manipulate functional molecules by bulk visible-scale mechanical motions.

View full abstract

Transient electric conductivity of regioregular and random poly(n-alkylthiophene)s films were investigated by time-resolved microwave conductivity upon exposure to 193 nm laser. In the presence of electron acceptor: perylene carboxydiimide, the decays of charge carriers were decelerated while those induced by 355 nm were reported not to differ. We discuss the dependence of side chain length on signal intensity and decay rate.

View full abstract

In UV cure nanoimprint lithography the interfaces as well as the resist composition play an important role in determining the characteristics of the resulting patterned material, which can be used for subsequent pattern transfer, or be functional. It is important for applications that there be only rare defects, and that template release always be a clean process. In this paper fundamental physical and chemical aspects of the resist template interface are discussed, with a particular focus on how they influence the process of template removal.

View full abstract

Three types of UV-curable resins; radical curing type, cationic curing type, and hybrid curing type, a combination of radical and cationic curing type, have been developed for UV nanoimprint. Nanoimprint has a variety range of ways and finds extensive range of applications. For UV nanoimprint UV-curable resins play an important roll for the progress of the nanoimprint technology, but the material used for the study of UV nanoimprint has been so far limited to the radical curing type like acrylic resins. The cationic curing type consisting of epoxides, oxetanes, and vinyl ethers has been studied along with the radical curing type and the hybrid curing type, and has shown usefulness for UV-nanoimprint in reactivity of sub micron thin films. Also the condition for successful pattern transfer has been studied and it turned out that for thin films below 300nm no lower than 5MPas of imprint pressure is necessary. The demolding and the contact to substrate, another important concern for nanoimprint was studied from the view point of additives and some additives having potential for improving the contact to substrate and the demolding have been found.

View full abstract

To eliminate the releasing defects of template in UV nanoimprint lithography (NIL), a novel process without using anti-sticking layer is proposed in combination with a plastic template and a visible light (VL)-curable resin. We newly use poly-propylene (PP) as a plastic template, which has low surface energy and is easily removed from polymers. However, plastic materials such as PP have generally poor transmittance for UV light, but have certain transmittance for VL. We apply a newly developed VL-curable resin for use of the plastic template. Using the VL-curable resin, the anti-reflection structure is successfully fabricated on a triacetylcellulose (TAC) film by the optical NIL from the PP template. With respect to the anti-reflection structure, the experimental result of reflectance shows less than 0.5%.

View full abstract

A Magnetic nanodots array fabrication method using ultraviolet nanoimprint lithography (UV-NIL) and electrodeposition was developed. Since the photocurable resin patterned by UV-NIL was directly used for electrodeposition mask, simple and high throughput fabrication process was realized. The CoPt nanodots (diameter: 120 nm) array was formed after the electrodeposition. After chemical mechanical polishing (CMP), the arithmetic mean roughness (R_a) of the track area was smaller than 1 nm.

View full abstract

Rapid process is one of the most important issues for industrial usages in thermal Nanoimprint Lithography (NIL). Detail study on the polymer deformation process time is indispensable to design process conditions and resist polymer characteristics. We experimentally study the dependence of the process time on the resist properties and predict required process time for various molecular weights in Poly- Methyl Methacrylate (PMMA). The time evaluation of the resist profile for various molecular weights (Mw) is observed and obtained the deformation process time in experimentally. According to the measurement of viscosity of polymers and experimental results, the relation between the viscosity and the process time is investigated for various molecular weight of PMMA. The results indicate that the deformation process time T[s] is fairly proportional to the viscosity of the polymer. From this relation, the required process time is predicted in various process temperatures and molecular weights in PMMA.

View full abstract