Fabrication of multi-dimensional colloid crystals on raised surfaces via reversal nanoimprint lithography

Fabrication of multi-dimensional colloidal crystals on raised polymer substrate has been achieved by reversal nanoimprint technique. The combine effects of the feature size of the mold, particle diameter and imprinting steps control ordering of the colloidal particles. It is shown that using ‘Reversal nanoimprint lithography’, 3D colloidal particles can be selectively patterned on soft (polymer) substrates. Reversal nanoimprint lithography offers a relatively easy, fast and versatile method for patterning of colloidal particles.     

Excimer Laser Projection Photoablation Patterning of Metal Thin Films for Fabrication of Microelectronic Devices and Displays

A nonlithographic process is demonstrated for patterning Al, Cr, Cu, Ni, Ti, and W thin films, which are widely used in microelectronic and display fabrication. A projection photoablation process using 248-nm-deep ultraviolet radiation from a KrF excimer laser was used to pattern a polyimide film coated on a SiN layer deposited on glass. The photoablation-patterned polyimide film was used as a sacrificial layer in a lift-off patterning process for the metal films, which resulted in clean metal patterns with fine line-edge definition being fabricated after lift-off. This process provides a simpler and more economical patterning technique compared to conventional lithography methods, eliminating the developing and etching steps.     

A spacer patterning technology for nanoscale CMOS

A spacer patterning technology using a sacrificial layer and a chemical vapor deposition (CVD) spacer layer has been developed, and is demonstrated to achieve sub-7 nm structures with conventional dry etching. The minimum-sized features are defined not by the photolithography but by the CVD film thickness. Therefore, this technology yields critical dimension (CD) variations of minimum-sized features much smaller than that achieved by optical or e-beam lithography. In addition, it also provides a doubling of device density for a given lithography pitch. This method is used to pattern silicon fins for double-gate metal-oxide semiconductor field effect transistors (MOSFETs) (FinFETs) and gate electrode structures for ultrathin body MOSFETs. Process details are presented     

Micro-aspiration assisted lithography

We report on a micro-fabrication method based on micro-aspiration assisted lithography (MAAL). Unlike nanoimprint lithography where a mould is pressed into a resist layer spin coated on a substrate, MAAL uses aspiration forces to guide the resist material in the mould cavities. By suing this technique, the limit of capillary based lithography techniques has been extended. Double layer PDMS moulds were fabricated using multi-layer soft-lithography in which a micro-aspiration network could be introduced close to the pattern layer of the mould. As a result, high resolution patterning could be obtained with a UV curable resist. We also show the results of patterning of a thin layer of PDMS, nano-particles as well as agar gels. We have also provided a semi-quantitative analysis in order to understand the limitation of different approaches.     

Nanofabrication of gallium nitride photonic crystal light-emitting diodes

We describe a comparison of nanofabrication technologies for the fabrication of 2D photonic crystal structures on GaN/InGaN blue LEDs. Such devices exhibit enhanced brightness and the possibility of controlling the angular emission profile of emitted light. This paper describes three nano lithography techniques for patterning photonic crystal structures on the emitting faces of LEDs: direct-write electron beam lithography, hard stamp nanoimprint lithography and soft-stamp nanoimprint lithography with disposable embossing masters. In each case we describe variations on the technique as well as its advantages and disadvantages. Complete process details have been given for all three techniques. In addition, we show how high performance GaN dry etch techniques, coupled with optical process monitoring can transfer resist patterns into underlying GaN material with high fidelity.     

Printing of Highly Integrated Crossbar Junctions

A new process is presented that combines nanoimprint lithography and soft lithography to assemble metal–bridge–metal crossbar junctions at ambient conditions. High density top and bottom metal electrodes with half‐pitches down to 50 nm are fabricated in a parallel process by means of ultraviolet nanoimprint lithography. The top electrodes are realized on top of a sacrificial layer and are embedded in a polymer matrix. The lifting of the top electrodes by dissolving the sacrificial layer in an aqueous solution results in printable electrode stamps. Crossbar arrays are noninvasively assembled with high yield by printing the top electrode stamps onto bare or modified bottom electrodes. A semiconducting and a quasi metal like conducting type of polymer are incorporated in the cross points to form metal‐polymer‐metal junctions. The electrical characterization of the printed junctions revealed that the functional integrity of the electrically addressed conductive polymers is conserved during the assembling process. These findings suggest that printing of electrodes represents an easy and cost effective route to highly integrated nanoscale metal‐bridge‐metal junctions if imprint lithography is used for electrode fabrication.     

Reproduction of fine structures by nanocasting lithography

Novel reproduction technique for nanostructures is newly proposed based on nanoimprint and nanocasting lithography. First, a master nanostructure is replicated using fluorinated polymer by conventional thermal nanoimprint. Then, the master structure is reproduced using the replicated fluorinated polymer by nanocasting lithography. Using the fluorinated polymer as a mold, fine pattern is successfully transferred without releasing failure. Also, low cost reproduction is realized by nanocasting lithography without using special tools and materials. Using the proposed method, reproduction of the anti-reflection structure having 250 nm feature size is successfully demonstrated.     

UV nanoimprint lithography with rigid polymer molds

Transparent polymers are considered as alternative low-cost mold materials in UV nanoimprint lithography (UV-NIL). Here, we demonstrate a nanoimprint process with molds made of rigid polymers novel for this application. These polymer molds are found to show high performance in the patterning with UV-NIL. Sub-50 nm structures were fabricated with this process.     

Nanoelectrode lithography using a flat mold with a pattern defined by different conductivities

Nanoelectrode lithography is a pattern duplication method that combines nanoimprint with an electrochemical reaction. The method can form an oxide pattern directly on a semiconductor or metal. This method can use flat molds with patterns defined by substances with different conductivities, while the conventional nanoimprint technique must use a mold with a relief pattern. In this paper, the mold pattern for the technique is defined with an oxide material on the surface of a conductive substrate. Nanoelectrode lithography itself can be used to form a flat mold by using a conductive mold with a relief pattern, which leaves an oxide pattern via the anodic oxidation of Si. AFM lithography also can utilize an electrochemical reaction in the air to generate an oxide pattern on a conductive substrate, which gives us a flat mold. This paper shows that both types of flat mold can transfer a pattern to a target substrate. These strategies will allow us to realize on-demand mold fabrication, mold modification, and an easy way of obtaining a mold with a finer pattern.     

纳米光刻对准方法及其原理

对准技术对光刻分辨力的提高有着重要作用。45nm节点以下的光刻技术如纳米压印等,对相应的对准技术提出了更高的要求。对光刻技术发展以来主要用于接近接触式和纳米压印光刻的对准技术做总结分类,为高精度的纳米级光刻对准技术提供理论研究基础和方向。经过分析,从原理上将对准技术分为几何成像对准、波带片对准、干涉光强度对准、外差干涉对准及莫尔条纹等五种对准方法。最后结论得出基于条纹空间相位的对准方法具有最好的抗干扰能力且理论上能达到最高的对准精度,而其他基于光强的对准方法的精度更易受到工艺涂层的影响。因此,基于干涉条纹空间相位对准的方法在纳米级光刻对准中具有很好的理论前景。     

Large‐Area Nanoscale Patterning of Functional Materials by Nanomolding in Capillaries

Within the past years there has been much effort in developing and improving new techniques for the nanoscale patterning of functional materials used in promising applications like nano(opto)electronics. Here a high‐resolution soft lithography technique—nanomolding in capillaries (NAMIC)—is demonstrated. Composite PDMS stamps with sub‐100 nm features are fabricated by nanoimprint lithography to yield nanomolds for NAMIC. NAMIC is used to pattern different functional materials such as fluorescent dyes, proteins, nanoparticles, thermoplastic polymers, and conductive polymers at the nanometer scale over large areas. These results show that NAMIC is a simple, versatile, low‐cost, and high‐throughput nanopatterning tool.     

纳米压印技术的最新进展

总结了纳米压印技术的最新进展,其中包括压印工艺、图形赋形方法以及纳米压印技术应用三方面最新的研究成果。在压印工艺的发展方面,大面积滚轴压印的发明最具有产业化意义,它不仅解决了常规平板压印很难大面积压印成型的困难,而且整个过程是一种柔性压印过程,降低了成本,提高了压印效率,但是最小特征尺寸还有待提高;在图形赋形方法的改进中,聚合物探针阵列技术集微米和纳米成型技术于一身,压印效率高,应用前景广阔;在压印技术应用的发展中,光伏电池、电子存储设备以及传感器等为纳米压印技术的应用提供了新的领域。     

Patterned Media: Nanofabrication Challenges of Future Disk Drives

Scaling of the bit size in conventional magnetic recording media is becoming increasingly difficult due to the superparamagnetic limit. Innovations in magnetic recording technology are emerging to enable the continued growth in bit areal density. Thermal stability problems of conventional granular media can be greatly helped by patterning single domain magnetic islands for each magnetic bit. Fabrication of patterned media requires application of nanoimprint lithography for high-volume production of patterned media disks and high-resolution electron beam lithography for fabrication of the nanoimprint masters. We discuss the approaches and the many challenges to the implementation of patterned media disks.      

Replication of high ordered nano-sphere array by nanoimprint lithography

High ordered nano-sphere array patterns on Si substrate were fabricated using nanoimprint lithography. First, using hot embossing method, poly vinyl chloride (PVC) based polymer replica template was duplicated from original high ordered nano-sphere array patterns, which was fabricated by evaporation method. The monolayer transferring condition can be achieved by varying hot embossing pressure. Then, through UV nanoimprint lithography with the replicated polymer template, imprinted patterns, which has high ordered nano-sphere array patterns, was successfully fabricated on Si and flexible PET substrate.     

Low cost, rapid fabrication of durable molds of grating arrays for nanoimprint lithography

This study proposes a new fabrication method for the mold of a sub-micron grating array used in the nanoimprint lithography process. In general, the mold of a sub-micron grating array is fabricated by electron beam lithography (EBL) and reactive ion etching (RIE), and then, nanoimprint lithography (NIL) is used to achieve the required amount of replication. Such a method is expensive and has a low throughput, and the pattern is limited by the original mold. In this paper, we constructed a durable mold of a sub-micron grating array with good adaptability, using a commercial epoxy grating (EG) and a hybrid inorganic/organic sol-gel material combined with nanoimprint lithography and photolithography. Due to its low cost and ease of use, this method is suitable for both laboratory research and mass production without the need for expensive equipment like EBL or RIE.     

纳米压印光刻胶

光刻胶是纳米压印的关键材料,其性能将影响压印图形复制精度、图形缺陷率和图形向底材转移时刻蚀选择性。提出了成膜性能、硬度黏度、固化速度、界面性质和抗刻蚀能力等压印光刻胶的性能指标。并根据工艺特点和材料成分对光刻胶分类,介绍了热压印光刻胶、紫外压印光刻胶、步进压印式光刻胶和滚动压印式光刻胶的特点以及碳氧类纯有机材料、有机氟材料、有机硅材料做压印光刻胶的优缺点。列举了热压印、紫外压印、步进压印工艺中具有代表性的光刻胶实例,详细分析了其配方中各组分的比例和作用。介绍了可降解光刻胶的原理。展望了压印光刻胶的发展趋势。     

Large area nanosize array stamp for UV-based nanoimprint lithography fabricated by size reduction process

A novel size reduction process using electron beam lithography (EBL) combining with wet etching technique is developed as a possible solution for producing large area and low cost nanopattern stamp for UV-based nanoimprint lithography (UV-NIL). In the first step, a microstructure stamp with 1.4 μm periodical pore array and aspect ratio of 1:1 was formed over a 1 inch² area on a quartz substrate. This process was carried out using common electron beam lithography (EBL) equipment, which was easily available in the modern integrated circuits (IC) semiconductor factory. Afterwards, with a controlled wet etching technique, the pore array was changed into tip patterns with the line width below 100 nm and the period keeping as before. The uniformities and nanopattern accuracies were investigated to identify its possibility as a UV-NIL stamp by AFM and SEM. Finally, as a demonstration, the as obtained stamp was used as a positive stamp to replicate the nanotips into UV-curable resist successfully by a UV-NIL process. The method developed for the mold of nanoimprint lithography would be a simple and low price approach to fabricate large area UV-NIL stamp and the nanotip array structures would be widely used in two dimensional (2D) photonic crystal application.     

Fabrication of 50 nm patterned nickel stamp with hot embossing and electroforming process

Fabrication of imprint stamp is a key issue of nanoimprint lithography. In this study, we attempt to fabricate the nickel imprint stamp using hot embossing lithography and electroforming processes. As small as 50 nm sized patterns of original silicon master were faithfully transferred to polyvinyl chloride (PVC) film. By electroforming on hot embossed PVC film, nickel stamp, which has the same patterns of original silicon master stamp, was successfully fabricated.     

A novel printing technique for highly integrated organic devices

A new printing technology is described, which is capable of printing metallic electrodes onto organic layers. Electrodes are defined on top of a sacrificial layer by optical or nano-imprint lithography. To increase the stability of the process the electrodes are coated with several backing layers. The metallic features are released from the sacrificial layer by immersion in water and subsequently transferred onto the target substrate. By the use of nano-imprint lithography, feature sizes below 100 nm are achieved. The strengths of the printing technology are high integration density, versatility and reproducibility.     

Limits to Nanopatterning of Fluids on Surfaces in Soft Lithography

Soft lithographic microcontact printing using the residual polydimethylsiloxane (PDMS) found in elastomeric PDMS stamps is demonstrated to lead to unstable prints with sub‐micrometer dimensions. The statics and dynamics of the process have been followed with time‐resolved atomic force microscopy, imaging ellipsometry, water contact angle measurement, and optical diffraction. It is proposed that this instability places a fundamental limitation on patterning by macromolecular fluids, which is of general relevance to soft lithography and nanoimprint lithography with low viscosity polymers.