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Extreme ultraviolet (EUV) lithography is a promising technology for making chips beyond 7 nm technology node; however, it comes with its own challenges. One of them is the need to find a suitable EUV resist. Photoresist performance is gauged by the resolution, LER, and sensitivity trade-off. However, the primary challenge for the photoresist in EUV lithography is the major shift in reaction chemistry relative to that in deep ultraviolet (DUV) lithography. The interaction of the EUV photon (92 eV) with the widely used conventional chemically amplified resist (CAR) is different than that of the DUV photon (5–6 eV). The DUV photon excites only the valence electrons of the photo-acid generator in CAR, which results into acid generation. However, a high-energy EUV photon can ionize the CAR polymer matrix. This leads to the generation of a cascade of secondary electrons. Thus, in addition to acid generation, other chemical reactions like bond scission and cross-linking occur by the interactions between resist and secondary electrons. Apart from chemically amplified reactions, CARs are not very efficient at utilizing the additional pathways offered by secondary electrons. Moreover, stochastics, arising from photon and chemical shot noise, are an additional challenge for an EUV resist. Therefore, there is a need for an alternative photoresist to CAR. Herein, we report a single polymer chain negative tone photoresist. The resist has an acid generator, an organotin moiety, and an acid reactive unit attached to a polymer chain. The resist is designed to use EUV-generated secondary electrons to generate acid and polymer-bound radicals. The polymer-bound radicals and acid amplification reaction can induce cross-linking among polymer chains to create a negative tone solubility switch. In this study, the EUV printability study and reaction mechanism of the resist are elucidated. Electron transfer reactions for radical generation were studied with the help of nanosecond pulse radiolysis and γ-radiolysis. Liquid chromatography and mass spectrometry were used to identify possible acid-amplified reactions.

The development of highly sensitive resists containing tin, which has a large EUV absorption cross section, has recently attracted considerable attention in EUV lithography. The effective utilization of secondary electrons is required for the development of high-performance resists. It is important to design resist materials on the basis of the mechanism of radiation chemical reactions. In this study, the radiation-induced reactions of tetraphenyltin (TPSn), triphenylsulfonium triflate (TPS-Tf), and the copolymer of triphenyl(4-vinylphenyl) stannane (TPSnSt) and 4-methacryloxyphenyldiphenylsulfonium triflate (MAPDPS-Tf) were investigated by electron pulse radiolysis and γ-radiolysis in controlled reaction systems. The decomposed products were analyzed by high-performance liquid chromatography. The G values of decomposed products were determined. For the copolymer, the holes generated by ionizing radiations moved to Sn units and electrons moved to TPS-Tf units. The tin complex side chain decomposed, producing benzene after hole transfer.

The influence of polymer formation in liquid crystals (LCs) was investigated using several analytical techniques. The monomers 4,4′-dimethacryloyloxy-biphenyl (4,4′-DMOB) and 3,3′-dimethacryloyloxy-biphenyl (3,3′-DMOB) were used. The results indicated that the orientation of the LC affects the rate constant of polymerization. Moreover, the structures of the monomers affected the orientation of the LC.

This paper reports on an underwater wheeled robot designed to locate chemical sources by mimicking the behavior of a crayfish in still water. Crayfish in search of food generate water currents by waving their fan organs, i.e., the maxillipeds, to collect the food odors from the surroundings to the chemoreceptor organs. Similarly, the robot waves the arms mimicking the maxillipeds, and generates a flow field to collect chemicals to the four sensors. The generated flow field brings chemicals released from different areas to the different sensors. Therefore, the direction of the chemical source can be determined by simply comparing the sensor responses. Although the maximum range for drawing the chemical is approximately 5 cm, the chemical sensing ability of the robot is significantly improved. Experimental results show that the robot can localize a chemical source by employing the actively generated flow field.

Acid diffusion in chemically amplified resists (CARs)--currently the standard resists for semiconductor device manufacturing--is a significant concern in the development of highly resolving resists. However, non-CARs are generally less sensitive to radiation than CARs owing to the lack of an amplification mechanism. Recently, a negative non-CAR utilizing a polarity change and radical crosslinking (a dual insolubilization resist) was proposed. In this study, an acid-reactive compound was introduced into organotin-containing dual insolubilization resists to improve their sensitivity. The synthesized resists were composed of triarylsulfonium cations as a polarity changer and a radical generator; 2-hydroxy-2-methylpropiophenone as a radical generator; triphenyl(4-vinylphenyl)stannane as an EUV absorption enhancer and a quencher; and 4-[(2,4-dimethoxyphenyl)hydroxymethyl]phenylmethacrylate (ARMA) as a polymer-bound acid-reactive unit. By the incorporation of ARMA, the sensitivity to EUV radiation was increased 2.4-fold (the exposure dose required for insolubilization was decreased by approximately 60%). The increased sensitivity is considered to have been caused by the acid-catalytic etherification of ARMA through dimerization and/or with 2-hydroxy-2-methylpropiophenone units. In the 125 keV electron beam (EB) patterning, the organotin-containing dual insolubilization resist with ARMA showed 25 nm half-pitch resolution with 2.1 nm line width roughness at a sensitivity of 160 uC cm[?]2 (approximately 90 uC cm[?]2 for a 50 keV EB).

Non-chemically amplified resists (non-CARs) are generally less sensitive to radiation than CARs due to the lack of an amplification mechanism. Recently, a negative-type non-CAR resist utilizing a polarity change and radical crosslinking (a dual insolubilization resist) was proposed. In this study, an organotin compound with a large absorption cross section for 92.5 eV extreme-ultraviolet (EUV) radiation was introduced into the dual insolubilization resists to improve their sensitivity. The synthesized resists were composed of triarylsulfonium cations as a polarity changer and radical generator, 2-hydroxy-2-methylpropiophenone as a radical generator, and triphenyl(4-vinylphenyl)stannane (TPSnSt) as an EUV absorption enhancer. By the incorporation of TPSnSt, the linear attenuation coefficient of the polymer increased by approximately 30% and the sensitivity increased by more than two and a half times (the exposure dose for insolubilization was decreased by 60%). The additional sensitivity enhancement beyond that expected from the increase in the linear attenuation coefficient is considered to have been caused by the generation of polymer radicals through Sn-C bond scission. It was also found that TPSnSt had no negative effect on the decomposition of triarylsulfonium cations.

Polymer-bound photoacid generators (PAGs) (anion bound) and their corresponding polymers were synthesized for evaluation of the reactivity of polymer-bound PAGs with secondary electrons in solutions by the electron beam pulse radiolysis method. In the solutions, the rate constants of polymer-bound PAGs are much lower than those of polymer-blend PAGs. In addition, we evaluated the acid generation efficiencies of polymer-bound PAGs. As a result, despite the film state, the acid generation efficiency of polymer-bound PAGs are about 10% lower than those of the polymer-blend PAGs. These differences are explained by the difference in stabilization effects between polymer-bound PAGs and polymer-blend PAGs in both solutions and films.

This paper reports on an underwater wheeled robot designed to locate chemical sources by mimicking the behavior of a crayfish in still water. Crayfish in search of food generate water currents by waving their fan organs, i.e., the maxillipeds, to collect the food odors from the surroundings to the chemoreceptor organs. Similarly, the robot waves the arms mimicking the maxillipeds, and generates a flow field to collect chemicals to the four sensors. The generated flow field brings chemicals released from different areas to the different sensors. Therefore, the direction of the chemical source can be determined by simply comparing the sensor responses. Although the maximum range for drawing the chemical is approximately 5 cm, the chemical sensing ability of the robot is significantly improved. Experimental results show that the robot can localize a chemical source by employing the actively generated flow field.

Sink-limited conditions cause a reduction in the rate of photosynthetic fixation of CO2 in single-rooted soybean leaves (Glycine max. Merr.). We suggested previously that this reduction is due to the deactivation of ribulose-1,5-bisphosphate carboxylase (RuBPcase; EC 4.1.1.39) that is caused by a decrease in the level of free Pi via a decrease in the rate of conversion of phosphorylated intermediates to the end-product (sucrose) in sink-limited leaves [Sawada et al. (1989) Plant Cell Physiol. 30: 691, Sawada et al. (1990) Plant Cell Physiol. 31: 697, Sawada et al. (1992) Plant Cell Physiol. 33: 943]. In the present study, we investigated whether, in intact soybean plants, sink-limited conditions would also cause a reduction in the rate of photosynthesis and whether such a reduction might be due to the deactivation of RuBPcase via the same regulatory mechanism as that suggested from previous studies with single-rooted leaves. Continuous removal of flower buds from intact plants brought a large decrease in ratio of the dry weight of sink organs (stem, roots, pods) to source organ (leaves) as a result of the absence of pod formation. Pods are likely to function as the major sink at the reproductive stage. Upon continuous removal of flower buds, the treated (sink-limited) plants showed a large decrease in the rate of photosynthetic fixation of CO2 as compared to control plants. RuBPcase in the leaves of treated plants was continuously inactivated with the decrease in photosynthetic activity. However, the inactivated enzyme was totally reactivated upon incubation in the presence of 10 mM NaHCO3 and 5 mM MgCl2. The levels of sucrose and ribulose-1,5-bisphosphate in leaves of the treated plants increased significantly. All these results coincide exactly with those obtained in previous studies of single-rooted leaves under the sink-limited conditions.