The current status of Argon fluoride (ArF) excimer laser lithography is reviewed. The concurrent development with the worldwide cooperation involving all of the manufacturer, such as glass, laser, stepper, photoresist, mask, and chip, will be indispensable to shorten the development term of ArF excimer laser lithography. Especially, it is essential to obtain a consensus of the specification for each elemental technology in all of the manufacturer to execute the efficient development.

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In this paper we examine the technical and business environment in which 193 nm photoresist R&D is conducted today. Semiconductor industry predictions of lithographic requirements for future generations of DRAM and Logic indicate the need for 0.18 and sub 0.18μm manufacturing capability within the next decade. 248nm DUV lithography and the tool/photoresist infrastructure is just reaching the state required for manufacturing at 0.25μm dimensions after a decade of intensive effort at tool and photoresist development. 193nm tool and photoresist development is beginning to demonstrate potential for 0.18-0.15μm capability but much progress is required for the 193 lithography infrastructure to reach a the point at which manufacturing capability can be applied to the 1Gb and later generations of semiconductor technologies. In this paper we will compare and contrast 248 and 193nm photoresist R&D.

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Linewidth control in the 0.25μm-0.18μm range will be one of the biggest challenges for future optical lithography. Various parameters contribute to CD variations: stepper parameters, lens errors, mask imperfections, resist processing, wafer topography, proximity effects and operator errors. The goal of this paper is to elaborate on the most important contributors to CD variations. Linewidth control is studied directly, characterised by the 3σ variation of the CD spread. Our investigations are based on simulations and on experimental work. CD control for 0.25μm applications is compared for four resist strategies: negative tone resist with TAR, negative tone resist on BARC, positive tone resist on BARC and top surface imaging (TSI) in combination with dry development. Proximity correction is taken into account. Best results are obtained with the negative tone process on BARC and with TSI. Concerning CD-control for 0.18μm devices, a feasibility study is carried out, based on simulations. NA and σ optimisation will be required for sufficient CD control, as well as proximity correction on the mask. This feasibility study is illustrated with various experimental results obtained using TSI (Desire process).

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During the last ten years a new and exciting field of solid state physics and electronics has been thoroughly studied. The field is tunneling of single electrons or so-called "single electronics". By many researchers' efforts, the basic physics of this field is well understood at the present time, and now creation of useful single electron devices becomes important. In this brief review we discuss the basic physics of single electron tunneling and the single electron transistor, and the fabrication technologies of several kinds of single electron devices. Possible applications in analog and digital single electron devices are also discussed.

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The explosive growth in performance of microelectronic devices has been made possible by steady advances in microlithography and photoresist technologies. Tremendous efforts to extend optical lithography beyond the 0.25 micrometer boundary, as currently obtainable with KrF-excimer lithography, are ongoing. Although some similarities exist between the imaging chemistries involved in the 248nm and 193nm lithographies, different materials are needed due to the distinct difference in optical absorbance requirements. Resist systems which can be developed with aqueous base would be preferred. However, it might well turn out that the targeted requirements can only be fulfilled by resist systems which involve some type of dry etch steps. This paper will focus on a positive tone resist system, which is based on novel silicon containing methacrylate polymers. Due to a unique combination of monomeric building blocks, polymers with high silicon concentrations and, at the same time, high thermal stability are obtained.

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We have developed new alkoxy-ethyl protecting groups for ArF chemically amplified positive resists. The developed groups show excellent performances in thermal stability, deprotection reaction efficiency, and dissolution contrast. Moreover, we find that the dissolution rates of polymers protected with these groups can be characterized by the polarity and molecular volume of the groups. ArF contact printing experiments also confirm that chemically amplified resists with these groups have good resolution capabilities. Thus the new alkoxy-ethyl groups are shown to have excellent performances as protecting groups for ArF chemically amplified resists.

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Recent advances in the single-layer resist for forming finer patterns have led us to a search for new resist materials for the ArF excimer laser. We describe a novel, environmentally friendly, single-layer resist based on a menthyl methacrylate terpolymer which has good dry etch resistance and high transparency in the wavelength region of ArF emission.

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We used the tertiary butyl ester protecting group for the construction of our 193-nm resists. [1] This paper describes an investigation of the impact of acid-cleavable protecting group structure on the properties of a series of model acrylic polymers. In this investigation, factors such as thermochemical stability, reactivity to photogenerated acid, and dissolution properties of exposed films as a function of dose were examined. The impact of photo-acid structure and its role in the dissolution properties of exposed films will also be discussed. Additionally, we will introduce a new cycloaliphatic polymer family (polynorbomenes) with superior etch resistance, significantly broadening the polymer chemistry available for the construction of new 193-nm photoresists. [2]

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To use a TMAH (tetramethylanmonium hydroxide aqueous solution) developer with a resist based on adamantylmethacrylates, we proposed a cleavable adamantyl ester by protonic acid. We found that a 2-methyl-2-adamantyl ester was cleavable by protonic acid and poly(2MAdMA) (2-methyl-2-adamantylmethacrylate) worked as a chemically amplified resist with good sensitivity. We achieved high resolution by improving the adhesion. The 2MAdMA-MAA (methacrylic acid) resist achieved 0.165μm L/S with 3.0mJ/cm² in ArF evaluation using a dilute TMAH developer. We could use a 2.38% TMAH developer by introducing 2MAdMA to the strongly polar acid labile protect group, OCMA (3-oxocyclohecylmethacrylate) or MLMA (mevalonic lactone methacrylate), which had good adhesion. We obtained fine patterns below 0.20μm at below 10mJ/cm² in ArF evaluation with 2.38%TMAH developer. We achieved a minimum resolution with 0.15 pm L/S patterns and a D.O.FE of 0.6pm at 0.18μm L/S patterns using a 2MAdMA-MLMA resist.

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This paper describes a new approach to the design of positive-tone ArF single layer chemical amplification (CA) photoresist. The main issue is the effect of small molecular compounds as additives in methacrylic-based ArF CA photoresist. Three alicyclic compounds with adamantyl moiety and two aromatic compounds with naphthyl moiety were selected as additives. Their influences on the photoresist properties were examined and clarified as follows: •Transparency of the resist film at 193-nm could be controlled by the loading level and the sorts of additives. Alicyclic additives made the resist film more transparent. •Both the photospeed and the contrast of the resist were drastically influenced by the loaded additives. Enhancement of the photospeed was easily achieved. •Thermal properties of the resist film could also be affected by additives. However, the effect was generally temperate. •The loaded additives could mitigate T-top formation of resist profile due to the control of the inherent dissolution rate of the resist.
Loading the additives would compensate some inherent defects of matrix acrylic polymers and consequently allow considerable latitude in resist design of ArF CA resist. A three component system comprising an acrylic polymer, a photoacid generator, and adamantanecarboxylic acid showed good imaging performance (0.26μmL/S, 35mJ/cm²) on KrF exposure.

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The use of TSI processes pushes the limits of both DUV-lithography and e-beam direct writing. However, the volume expansion combined with the drop in glass transition temperature during silylation with monofunctional agents prevents a high resolution. The application of properly mixed mono-and bifunctional agents causes a crosslinking of the silylated resist and eliminates the flow effect. We selected bis (dimethylamino)methylsilane B(DMA)MS and dimethylsilydiethylamine DMSDEA as components, investigated the mixed agent and developed a TSI process. The optimized process enables the realization of a 0.15μm pattern in 0.7μm thick resist.

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A novel methacrylate polymer for a 193-nm resist has been developed. The goal was to enhance the adhesion to Si substrates while ensuring compatibility with a TMAH developer for our methacrylate-based resist. We used two acid-cleavable compounds for the carboxylic acid protective groups: mevalonic lactone and 2-methyl-2-adamantanol. The strong hydrophilicity of mevalonic lactone ester affords good adhesion of the formulated resist patterns to Si substrates. Alicyclic 2-methyl-2-adamantanol provides dry-etch resistance. The acid-catalyzed deprotection of both protective groups generate a large polarity change in the exposed region of the resist films. This allows for high-contrast patterning with high sensitivity using a 2.38% TMAH developer. Using an ArF excimer laser exposure system, 0.17-μm L/S patterns have been resolved.

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In ArF liquid-phase silylation process, diffusion kinetics and its influence on silylation performance were studied. We found out the difference of diffusion kinetics in liquid-phase silylation by the composition of silylation solution. Its diffusion kinetics was considered using Case II transport model. The silylation contrast in Case II diffusion, in which relaxation rate is comparable to diffusion rate, was higher than Fickian diffusion. High selective silylation process was achieved by controlling diffusion kinetics.

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Two silsesquioxane polymers were investigated as ArF excimer-laser resist materials. Polyphenylmethyl silsesquioxane (PMSQ) showed positive tone characteristics when an aqueous base developer was used, while polyhydroxybenzyl silsesquioxane (HSQ) showed negative tone characteristics. Infrared (IR) spectra and X-ray photo-electron spectrometry (XPS) indicate that a major imaging mechanism is the polarity change in PMSQ. Both materials showed sub-0.2-μm resolution capability for ArF excimer laser exposure with aqueous base development.

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