• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.199-204
• /
• 2007

Hot embossing, one of Nanoimprint Lithography(NIL) techniques, has been getting attention as an alternative candidate of next generation patterning technologies by the advantages of simplicity and low cost compared to conventional photolithographies. A typical hot embossing usually, however, takes more than ten minutes for one cycle of the process because of a long thermal cycling. Over the last few years a number of studies have been made to reduce the cycle time for hot embossing or similar patterning processes. The target of this research is to develop an induction heating apparatus for heating a metallic micro patterning mold at very high speed with the large-area uniformity of temperature distribution. It was found that a 0.5 mm-thick nickel mold can be heated from $25^{\circ}C$ to $150^{\circ}C$ within 1.5 seconds with the temperature variation of ${\pm}5^{\circ}C$ in 4-inch diameter area, using the induction heating apparatus.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.397-400
• /
• 2009

When the metal sheet is subjected to the housing surface for fitting and insulating from harsh surroundings like fluid ingression or hot steam, both strength and formability have to be equally considered. In this regard, the main aim of this study is to design an apparatus of cost-effectively producing flexible fluted band with increasing the formability of embossed stainless steel sheet, which is utilized as a thermal insulation metal for housing ship engine exhauster. Designed to fabricate a maximum sheet width of 700 mm, this new apparatus consists of upper roll made of hard urethane and the female-etched lower roll made of SKD11, have a producing capacity up to 1-meter homogeneously embossed sheet for just 60 seconds. This machine is devised for the maximum operating efficiency from original sheet handling to machine setting. The embossing properties are characterized by 3-D profiling. After embossing plain metal sheet, both yield strength and elongation properties are improved simultaneously, indicating the effectiveness of the newly designed apparatus.

• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.282-287
• /
• 2007

Hot embossing, one of Nanoimprint Lithography(NIL) techniques, has been getting attention as an alternative candidate of next generation patterning technologies by the advantages of simplicity and low cost compared to conventional photolithographies. A typical hot embossing usually, however, takes more than ten minutes for one cycle of the process because of a long thermal cycling. Over the last few years a number of studies have been made to reduce the cycle time for hot embossing or similar patterning processes. The target of this research is to develop an induction heating apparatus for heating a metallic micro patterning mold at very high speed with the large-area uniformity of temperature distribution. It was found that a 0.5 mm-thick nickel mold can be heated from $25^{\circ}C\;to\;150^{\circ}C$ within 1.5 seconds with the temperature variation of ${\pm}5^{\circ}C$ in 4-inch diameter area, using the induction heating apparatus.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.4 s.181
• /
• pp.162-167
• /
• 2006

Hot embossing lithography(HEL) has the production advantage of comparatively few process step, simple operation, a relatively low cost for embossing tools(Si), and high replication accuracy for small features. In this paper, we considered the nano-molding characteristic according to molding parameters(temperature, pressure, times, etc) and induced a optimal molding condition using HEL. High precision nano-patter master with various shapes were designed and manufactured using the DRIE(Deep Reactive ion Etching), LPCVD(Low Pressure Chemical Vapor Deposition) and thermal oxidation process, and we investigated the molding characteristic of DVD and Blu-ray nickel stamp. We induced flow behaviors of polymer, rheology by shapes and sizes of the pattern through various molding experiments. Finally, with achieving nano-structure molding with high aspect ratio, we will secure a basic technology about the molding of large-area nano-pattern media.

• Korean Journal of Materials Research
• /
• v.15 no.3
• /
• pp.149-154
• /
• 2005

Teflon like fluorocarbon thin films have been deposited on silicon and oxide molds as an antistiction layer for the hot embossing process by an inductively coupled plasma (ICP) chemical vapor deposition (CVD) method. The process was performed at $C_4F_8$ gas flow rate of 2 sccm and 30 W of plasma power as a function of substrate temperature. The thickness of film was measured by a spectroscopic ellipsometry. These films were left in a vacuum oven of 100, 200 and $300^{\circ}C$ for a week. The change of film thickness, contact angle and adhesion and friction force was measured before and after the thermal test. No degradation of film was observed when films were treated at $100^{\circ}C$. The heat treatment of films at 200 and $300^{\circ}C$ caused the reduction of contact angles and film thickness in both silicon and oxide samples. Higher adhesion and friction forces of films were also measured on films treated at higher temperatures than $100^{\circ}C$. No differences on film properties were found when films were deposited on either silicon or oxide. A 100 nm silicon template with 1 to $500\;{\mu}m$ patterns was used for the hot embossing process on $4.5\;{\mu}m$ thick PMMA spun coated silicon wafers. The antistiction layer of 10 nm was deposited on the silicon mold. No stiction or damages were found on PMMA surfaces even after 30 times of hot embossing at $200^{\circ}C$ and 10 kN.

• Transactions of Materials Processing
• /
• v.18 no.4
• /
• pp.310-316
• /
• 2009

Micro lens array(MLA) is widely used in information technology(IT) industry fields for various applications such as a projection display, an optical power regulator, a micro mass spectrometer and for medical appliances. Recently, MLA have been fabricated and developed by using a reflow method having the processes of micro etching, electroplating, micro machining and laser local heating. Laser thermal relaxation method is introduced in marking of microdots on the surface of densified glass. In this paper, we have proposed a new direct fabrication process using UV laser local thermal-expansion(UV-LLTE) and investigated the optimal processing conditions of MLA on the surface of negative photo-resist material. We have also studied the 3D shape of the micro lens obtained by UV laser irradiation and the optimal process conditions. And then, we made chrome mold by electroplating. After that, we made MLA using chrome mold by hot embossing processing. Finally, we have measured the opto-physical properties of micro lens and then have also tested the possibility of MLA applications.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.5
• /
• pp.871-878
• /
• 2013

Roll-to-roll (R2R) hot embossing systems have been developed and are widely used in various industrial domains. These systems press and heat flexible films between a press roll and a back-up roll, as said films pass through the two rolls. In previous studies, a heating roll was used for heating. However, in this study, a hybrid roll for R2R hot embossing is conceptualized and developed. This R2R system can be used for generating fine patterns on large and continuous films. The hybrid roll of our system can cool and heat the films simultaneously, thus affording greater flexibility in process design. Thermal and structural analyses were performed for developing the hybrid roll. In addition, a hybrid roll was designed based on analytical results. Experiments were conducted for measuring the performance of the developed hybrid roll.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.571-572
• /
• 2006

RTP (rapid thermal pressing), one of micro-pattern replication techniques like hot embossing, is focused on achieving shorter cycle time. DFSS(Design for Six Sigma) has been applied in order to enhance the completeness of the development process for RTP system. According to DIDOV roadmap, we derived design concepts and subsequently decided the main performances, design factors, and components for RTP system. In the design process of RTP system using finite element analysis, it was realized that its structural characteristics affect large area replicability. Optimizing structural design factors, based on CAE, it was checked out that its large area replicability could be improved in a virtual test. Finally, we have a plan to validate the large area replicability of the developed RTP system, by performing micro-pattern replication tests with polymeric sheets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.368-370
• /
• 2007

AAO(Anodic Aluminum Oxidation) method has been known that it is practically useful for the fabrication of nano-structures and makes it possible to fabricate the highly ordered nano masters on large surface and even on the 2.5 or 3D surface at low cost comparing to the expensive e-beam lithography or the conventional silicon processing. In this study, by using the multi-step anodizing and etching processes, highly ordered nano patterned master with concave shapes was fabricated. By varying the processing parameters, such as initial matter and chemical conditions; electrical and thermal conditions; time scheduling; and so on, the size and the pitch of the nano pattern can be controlled. Consequently, various alumina/aluminum nano structures can be easily available in any size and shape by optimized anodic oxidation in various aqueous acids. The resulting good filled uniform nano molded structure through hot embossing molding process shows the validity of the fabricated nano pattern masters.

• Transactions of Materials Processing
• /
• v.15 no.1 s.82
• /
• pp.34-41
• /
• 2006

Microlens arrays were fabricated by a modified LIGA process composed of the exposure of a PMMA (Polymethylmethacrylate) sheet to deep x-rays and subsequent thermal treatment. A successful modeling and analyses for microlens formation were presented according to the experimental procedure. A nickel mold insert was fabricated by the nickel electroforming process on the PMMA microlens arrays fabricated by the modified LIGA process. For the replication of microlens arrays having various diameters with different foci on the same substrate, both hot embossing and microinjection molding processes have been successfully utilized with the fabricated mold insert. Replicated microlenses showed very good surface roughness with the order of 1 nm. The focal lengths of the injection molded microlenses were successfully estimated theoretically and also measured experimentally.