Miftakhul Huda

Controlling of 6 nm Sized and 10 nm Pitched Dot Arrays Ordered along Narrow Guide Lines Using PS–PDMS Self-Assembly

We have studied graphoepitaxy to make nanodots or nanolines ordered along electron beam (EB)-drawn resist guide using block copolymers (BCPs) of polystyrene-polydimethylsiloxane (PS-PDMS). We found out that the number n of ordered molecular dot arrays in the line gap increases stepwise with the gap between guide lines. The n self-assembled dot arrays were ordered in a gap between n and n+1 times the mean PDMS pitch and self-assembled with no guide pattern. According to the ordering characteristics, 6 nm sized and 10 nm pitched PDMS dot arrays were formed using the BCP self-assembly with the guide lines.

Self-Assembled Nanodot Fabrication by Using Diblock Copolymer

In this study, we investigate self-assembled large-area nanodot fabrication on a silicon substrate using poly(styrene)-poly(dimethyl-siloxane) (PS-PDMS) for the application to quantum dot solar cell. By optimizing the PS-PDMS concentration by 2% and the volume of PS-PDMS solutions by 20 μL/cm2 dropped to silicon substrate, nanodots with a pitch size of 33 nm and a diameter of 23 nm are achieved with the molecular weight of 30,000-7,500. It is found that the dropped volume of PS-PDMS solution correlated to the thickness of spin-coated PS-PDMS layer has a great effect on the size and the pattern morphology.

Fabrication of 10-nm-Order Block Copolymer Self-Assembled Nanodots for High-Density Magnetic Recording

In this work, we investigated the fabrication of 10-nm-order block copolymer self-assembled nanodots using high-etching-selectivity polystyrene–poly(dimethylsiloxane) (PS–PDMS) block copolymers for high-density storage devices. We adopted PS–PDMS polymers with two different molecular weights of 13,500–4,000 and 11,700–2,900. With decreasing molecular weight, the nanodot size decreased from 12 to 10 nm, and the pitch correspondingly decreased from 22 to 20 nm. The PS–PDMS film thickness is the critical-factor to determine whether nanodot arrays can form on a large area or not. It was demonstrated that the thicknesses of 36 and 33 nm were optimal for the PS–PDMS polymers of 13,500–4,000 and 11,700–2,900, respectively. The limitation in the selection of PS–PDMS to form a smaller size of self-assembled nanodots is also predicted. This work promises to open way toward 1.6 Tbit/in.2 storage device with cheap cost production.

Fabrication of 5-nm-Sized Nanodots Using Self-Assembly of Polystyrene–Poly(dimethylsiloxane)

In this work, we studied the self-assembly development of a polystyrene–poly(dimethylsiloxane) (PS–PDMS) block copolymer with molecular weight of 7,000–1,500, which has potential to form nanodots with size of several nanometers. Annealing time and temperature were intensively investigated. Distinct nanodots with a size of 6 nm and a pitch of 13 nm were obtained at a low annealing temperature of 130 °C, and nanodots with a size of 5 nm and a pitch of 12 nm were obtained at an annealing temperature of 170 °C. It was found that nanodots were formed when annealing time was reduced to as short as 6 h. This technique implies the possible high-throughput and low-cost fabrication of magnetic recording media with a density of up to 5.17 Tbit/in.2.

Orientation-Controlled and Long-Range-Ordered Self-Assembled Nanodot Array for Ultrahigh-Density Bit-Patterned Media

In this study, we investigated the control of the orientation and ordering of self-assembled nanodots from a block copolymer (BCP) with the help of a guide pattern created by electron beam (EB) drawing. The guide pattern consisted of a post lattice and guide lines. The former is used to enable self-assembled nanodots from the BCP to be regularly arranged, while the latter is used to control the orientation of the nanodot arrays. It was demonstrated that the combined guide pattern was effective for controlling the BCP dot array to achieve long-range ordering and controlled orientation.

Guide Pattern for Long-Range-Order Nanofabrication of Self-Assembled Block Copolymers

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.

Fabrication of CoPt nanodot array with a pitch of 33 nm using pattern-transfer technique of PS-PDMS self-assembly

The progress of information technology has increased the demand of the capacity of storage media. Bit patterned media (BPM) has been known as a promising method to achieve the magnetic-data-storage capability of more than 1 Tb/in.2. In this work, we demonstrated fabrication of magnetic nanodot array of CoPt with a pitch of 33 nm using a pattern-transfer method of block copolymer (BCP) self-assembly. Carbon hard mask (CHM) was adopted as a mask to pattern-transfer self-assembled nanodot array formed from poly (styrene)-b-poly (dimethyl siloxane) (PS-PDMS) with a molecular weight of 30,000-7,500 mol/g. According to our experiment results, CHM showed its high selectivity against CoPt in Ar ion milling. Therefore, this result boosted the potential of BCP self-assembly technique to fabricate magnetic nanodot array for the next generation of hard disk drive (HDD) due to the ease of large-area fabrication, and low cost.

Fabrication of 30-nm-Pitched CoPt Magnetic Dot Arrays Using 30-keV-Electron Beam Lithography and Ion Milling for Patterned Media

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.

Self-Assembled Nanodot Fabrication by Using PS-PDMS Block Copolymer

The downsizing of nanolithography technology has given great benefit on achieving faster, low power consumption, and high integrated structure of electronics devices. Therefore, this nanolithography technology has drawn many scientists and engineers to be involved and put their main goal on this field in many decades. To obtain nanostructures especially nanodot, there are many methods which have been developed. Before block copolymer self-assembly technique is presented, those methods to fabricate nanostructures are discussed. Those methods could be divided into 2 large categories. Those are top-down method and bottom-up methods. The methods to fabricate nanodot also could be divided into top-down and bottom-up methods. Top-down method patterns material at large scale by reducing its dimension to the nanoscale. Bottom-up methods arrange atoms or molecules to form nanostructures.

Formation of 13‐nm‐Pitch Block Copolymer Self‐Assembled Nanodots Pattern for High‐Density Magnetic Recording

In this work, we demonstrated the fabrication of 13‐nm‐pitch block copolymer self‐assembled nanodots using high‐etching‐selectivity polystyrene‐poly(dimethyl siloxane) (PS‐PDMS) block copolymer for high‐density magnetic recording device. We adopted PS‐PDMS block copolymers with four different molecular weights of 30,000–7,500, 13,500–4,000, 11,700–2,900 and 7,000–1,500. With lowering molecular weight, the pitch of nanodots decreased from 33 to 22, 20 and 13 nm, and the diameter correspondingly decreased from 23 to 12, 10 and 6 nm. Surprisingly, we found that the etching time for removing the very thin top PDMS layer is longer when the used molecular weight of PS‐PDMS is lower than 13,500–4,000 in experiment. It means that PS‐PDMS with molecular weight lower than 13,500–4,000 forms thicker PDMS layer on the air/polymer interface of PS‐PDMS film after microphase process. This work promises to open way up to 4.41 terabit/inch2 magnetic recording device with low‐cost production.