Papers by Author: Takashi Akahane

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Authors: Takuya Komori, Hui Zhang, Takashi Akahane, Zulfakri bin Mohamad, You Yin, Sumio Hosaka
Abstract: We investigated the effect of ultrahigh-resolution salty (NaCl contained) development of hydrogen silsesquioxane (HSQ) resist on forming fine dot arrays with a pitch of 15×15 nm2 by 30-keV electron beam lithography for patterned media. The optimized concentration of resist developers was determined to fabricate most packed pattern. We found that increasing the concentration of NaCl into tetramethyl ammonium hydroxide (TMAH) could greatly improve the resist contrast (γ-value) of HSQ. And by using 2.3 wt% TMAH/4 wt% NaCl developer, we demonstrated 15×15 nm2 pitched (3 Tbit/in.2) HSQ resist dot arrays with a dot size of < 10 nm.
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Authors: Zulfakri bin Mohamad, Rosalena Irma Alip, Takuya Komori, Takashi Akahane, Hui Zhang, Miftakhul Huda, You Yin, Sumio Hosaka
Abstract: CoPt magnetic dot arrays with a fine pitch of 30 nm have been fabricated using electron beam (EB) lithography and ion milling. The possibility to ion-mill CoPt film using EB drawn calixarene resist pattern as a mask has been studied. We formed 30 nm pitch resist dot arrays with a dot diameter of 20 nm using 30-keV-EB lithography with calixarene resist. The resist dot arrays were ion-milled for 4 min using 200-eV Ar ion milling to fabricate CoPt dot arrays on a Si substrate. We fabricated fine pitched CoPt magnetic dot arrays with a diameter of 22-35 nm and a pitch of 30-150 nm. Results show that the ion-milled CoPt dot diameter increased with the dot pitch while the resist dot had a similar diameter of 20 nm.
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Authors: Takuro Tamura, Yasunari Tanaka, Takashi Akahane, You Yin, Sumio Hosaka
Abstract: In this study, we investigated the possibility of forming the fine Si dot arrays by means of electron beam (EB) lithography and dry etching technique for the future’s devices with nano-scale structures. We examined the properties of Ar ion milling for the fabrication of nanometer sized Si dot arrays on a Si substrate. We have succeeded in forming 40 nm pitched Si dot arrays with a diameter of <20 nm using dot array patterns of the calixarene resist as a mask. We also obtained the Ar ion milling property that there exists the horizontal milling rate as well as the vertical milling rate. We formed Si dot arrays with a dot diameter of about 10 nm using this property. It was clarified that Ar ion milling and EB lithography with calixarene resist has the potential to form Si nano dot arrays for the nano devices.
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Authors: Takashi Akahane, Miftakhul Huda, You Yin, Sumio Hosaka
Abstract: In this paper, we report two kinds of guide patterns precisely created by electron beam drawing. These guide patterns are expected to precisely control the arrangement of nanodots self-assembled from block copolymer (BCP) in order to obtain long-range-order nanofabrication. The first guide pattern is comprised only of a post lattice. The second guide pattern adds guide lines to the post lattice. The added guide lines are expected to better control the location and orientation of the BCP nanodots. We succeeded in fabricating these two kinds of guide patterns for 22-nm- and 33-nm-pitch BCP nanodots.
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Authors: Takashi Akahane, Miftakhul Huda, Takuro Tamura, You Yin, Sumio Hosaka
Abstract: We have studied functionalization of guide pattern with brush treatment. Especially, the effect of brush treatment on ordering of nanodots formed on the guide pattern was investigated. We used polydimethylsiloxane (PDMS) as brush modification to form self-assembled nanodots on the guide pattern using polystyrene (PS) - PDMS as block copolymer. The brush treatment using toluene solvent made guide patterns of the electron beam (EB) drawn resist behave like PDMS guide patterns and good ordering of the nanodots has been achieved. It was demonstrated that the brush treatment enabled the PDMS nanodots to be regularly located in the desired positions defined by the EB drawn guide patterns.
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Authors: Takashi Akahane, Takuya Komori, Jing Liu, Miftakhul Huda, Zulfakri bin Mohamad, You Yin, Sumio Hosaka
Abstract: In this work, improvement of the observation contrast was investigated by using a carbon film as the hard mask for pattern transfer of block copolymer (BCP) nanodots. The PS-PDMS (Poly (styrene-b-dimethyl siloxane)) block copolymer was adopted here. The observation contrast was greatly improved after transferring block copolymer (BCP) nanodots pattern to the underlying Si substrate through the carbon hard mask compared that before nanodot pattern transfer. Pattern transfer was also demonstrated to be very effective using carbon hard mask.
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