Photosensitive Epoxy Research Articles

Effective electromagnetic interference shielding properties of micro-truss structured CNT/Epoxy composites fabricated based on visible light processing

In this work, a novel self-writing visible light processing method is employed to fabricate self-propagating polymer waveguide based porous epoxy matrix, which subsequently turns into micro-truss structured carbon nanotube (CNT)/epoxy conductive composites through CNT dip-coating. It is discovered that, by illuminating a photosensitive epoxy pre-polymer with intersecting blue LED beams simultaneously for only 15 min, 3D micro-truss structured epoxy matrix with thickness of ∼1.8 mm is obtained. When incorporating CNTs with a low content of 1.20 vol%, the micro-truss structured CNT/epoxy composites exhibit high electrical conductivity of 62.93 S/m. These composites show absorption-dominated shielding mechanism, and high electromagnetic interference (EMI) shielding efficiency (SE) of 34.5 dB is obtained in the X band with 1.20 vol% of CNT. The specific shielding efficiency (SSE) of the CNT/epoxy composites is up to 100 dB cm3 g−1, and the corresponding SSE/t eliminating the effect of thickness is up to 535 dB cm2 g−1, which is much higher than that reported in other studies with the same CNT contents. This work provides a quick and scalable technique to prepare polymer matrix with ordered porous structures, and would also inspire and guide the fabrication of well-ordered porous conductive polymer composites with superior EMI shielding performances.

Investigation on dual functional epoxy resins containing photosensitive group in the main chain for photoresist applications

Dual functional photosensitive epoxy resins were synthesized by solution polycondensation of 1,3-bis(4-hydroxyphenyl)propenone (BHPP) and 3-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)propenone (HMPHPP) with epichlorohydrin. The characterization of synthesized epoxy resins comprised Fourier transform infrared (FTIR) spectroscopy, 1H-NMR, and 13C-NMR spectroscopic techniques. The thermal properties of the epoxy resins were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) under a nitrogen atmosphere and found that the synthesized resins were stable up to 300 °C. The effect of curing agents diaminodiphenylsulfone (DDS) and diaminodiphenylmethane (DDM) on the thermal stability of epoxy resin was compared and found that DDS cured epoxy resin has higher thermal than DDM. The photocrosslinking properties of the epoxy resins were studied with UV-Visible spectroscopy, and we observed that the olefinic double bond undergoes 2π-2π cycloaddition and leads to cyclobutane ring. Also, the effect of solvents on the photocrosslinking of the epoxy resin was also studied. Solvents with higher polarity favored the 2π-2π cycloaddition. The dual functionality of the resins was confirmed by FTIR study. The storage stability of the synthesized epoxy resins remained over more than 60 days. The synthesized epoxy resins successfully applied as negative photoresists.

Advanced Low-K Polymer Dielectric Materials and Interfaces for Fine-Pitch Re-Distribution-Layer (RDL) to Enable 2.5D and Fan-out Packages

The rapid increase of devices with artificial intelligence (AI) and machine learning capabilities is driving the demand for growth in compute performance. With transistor scaling reaching physical limitations, the semiconductor industry is looking to system-scaling to deliver the performance improvements. Advanced packaging architectures capable of supporting these applications are 2.5D interposers, 3D IC stacking, chiplets and fan-out based packaging. All of these architectures require high-density interconnects capable of routing >200 IOs/mm/layer. This talk demonstrates advanced ultra-thin ( <10 µm), low-Dk (< 3.0) polymer dielectric material candidates capable of achieving I/O densities of 500 IOs/mm/layer. Current commercially available solutions based on silicon interposers suffer from conductor and dielectric losses because of restrictions on the dielectric material (SiO2). Polymer based dielectrics offer a compelling alternative because of the potential to reduce the capacitance of the traces and improve power efficiency alongside compatibility with low-cost panel-scalable processes. This idea is explored will be explored in this talk and we will demonstrate through modelling and characterization that low-Dk polymer dielectrics are a superior candidate to current dielectric material candidates The choice of polymer dielectric is driven by technology trends towards a)high-density fine-pitch routing b)system level thermo-mechanical reliability c)panel-scalable processing. This work examines four dielectric material candidates comprising of 3 material classes, namely photo-sensitive epoxy, non-photo-sensitive epoxy and BCB for next-generation interconnect technology. High-speed electrical simulations indicate that low-Dk materials can support data rates of >10Gbps which overcomes the limitations faced by conventional high Dk epoxy dielectrics and SiO2 alternatives. The biggest challenge in moving towards low-Dk materials is that these polymers are typically non-polar and do not adhere well which poses challenges in package integration. This work proposes a unique approach to improve polymer/metal interfacial adhesion by creating a hybrid layer with tailorable material properties using vapor-phase-infiltration (VPI). VPI exposes the polymeric material to a metal-organic reactant such as trimethyl aluminium (TMA) in a heated environment. Diffusional kinetics of the reactant are highly dependent on each step of the sequential process such as temperature, time of hold, exposure time, and co-reactants used. This process is superior compared to Atomic Layer deposition (ALD) in promoting the diffusion of organometallic precursors into the polymer subsurface because of a hold-period after exposure. VPI thereby provides a highly adaptable process to create tunable hybrid interfaces with target properties. VPI-treated polymers showed a 3X improvement in adhesion strength at the polymer/metal interface. This work dives into the kinetic factors required to achieve this adhesion improvement and characterizes the corresponding material structure changes. In summary, advanced low-Dk polymer dielectrics capable of meeting next-generation high-performance computing requirements are discussed. This work evaluates the key performance benefits from moving to low-Dk dielectric materials and tackles a critical challenge of integrating these materials as re-distribution layer (RDL) dielectrics by demonstrating 3X improvement in adhesion using VPI.

The Investigation of Ti Doped Zinc Oxide Sensing Membrane in Bio-Sensor Applications

In this study, we propose a highly sensitive electrolyte–insulator–semiconductor (EIS) pH sensor witha layer of novel metal-oxide. We compared the ZnO and Ti-doped ZnO sensing membrane applied in EIS structure and investigated the characteristics of Ti-doped ZnO sensing membrane. Furthermore, we studied the sensing performance of the ZnO and Ti-doped ZnO EIS structure in different (Na+, K+ , Urea, Glucose)solution. The EIS structures of a ZnO sensing membrane were fabricated on 4-in n-type (100) Si wafers. A 50 nm ZnO film was deposited on theSi substrate by radio frequency reactive sputtering from ZnO and Ti target in the ratio of Ar/O2 = 20/5. Subsequently, samples were annealed in O2ambient for 30 s by RTA at various temperatures from 600, 700, 800. After that, the back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then, the sensing area was defined by standard photo lithography process using a photo sensitive epoxy, SU8-2005. Finally, the samples were fabricated on the copper lines of PCB by silver gel. Epoxy package was used to separate the EIS structure. Based on X-ray diffraction and atomic force microscopy data, it is found that Ti doped ZnO sensing membrane has higher surface roughness than the ZnO sensing film. High temperature annealing (700 ◦C) leads to the formation of crystalline oxide thin film with a rough surface. The pH sensing experiments of EIS with Ti doped ZnO membrane annealed at 700 ◦C shows that reference voltage is linearly dependent onsolution pH and an average sensitivity of 57.56 mV/pH. This outstanding pH sensitivity may be attributed to the high surface roughness of oxide membrane. Besides, Ti doped ZnO sensing film has lower drift rate (0.29mV/hr) and hysteresis voltage (2.79mV) than the ZnO sensing film. To study the urea and glucose sensing property of the ZnO and Ti-doped ZnO on EIS structure, we prepared the solutions of urea and glucose which concentration were controlled in a range from 1mM~32mM and 2mM~8mM. Then, we picked the conditions of ZnO sensing membrane for RTA temperature at 600oC in O2and Ti-doped ZnO sensing membrane for RTA temperature at 700oC. The sensitivity of Ti-doped ZnO in O2ambient has better quality than the ZnO, which sample in urea solution was 3.62mV/mM, the linearity was 87.36%. Besides, sample in glucose solution was 6.42mV/mM, and the linearity was 90.57%. Finally, we successfully demonstrate the use of Ti doped ZnO EIS structure with uricase-immobilized alginate film for the detection of uric acid in serum. The concentration of serum uric acid measured by EIS biosensor is comparable to that determined by commercial assay kit. This sensitive EIS based biosensorcan potentially be served as the diagnosis tool for general clinical examinations.

Rapid Thermal Annealing in MgO Sensing EIS Membrane for Bio-Sensor Applications

We tried to find an alternative dielectric film to own the high quality sensitive properties, so that, magnesium oxide (MgO) has been selected as a pH sensitive dielectric for the EIS operation, and is known as an alternative gate dielectric as CMOS technology has aggressively scaled down.The high-k MgO as sensing membrane on EIS structure and to investigated the characteristics of the different rapid thermal annealing(RTA) temperature in oxygen ambient. Furthermore, we studied the sensing performance of the MgO EIS structure tested in different ion (H+,Na+, K+, Urea, Glucose) solution. The electrolyte-insulator-semiconductor (EIS) structures with MgO sensing membranes were fabricated on 4-inch n-type (100) Si wafer, which have a resistivity of 5–10 Ω-cm. Before deposition of the MgO film, the wafers were cleaned by using HF-dip (HF: H2O = 1:100) to remove the native oxide. Then, a 50-nm MgO was deposited by radio frequency (RF) reactive sputtering on n-type silicon wafer. During RF sputtering, Mg oxide-target was used with 25 sccm argon flow rate (Ar: O2=25:0). The (RF) power and pressure are 150Watt and 20mTorr, respectively. Next, Samples was annealed at different temperatures (600oC, 700oC, 800oC) by rapid thermal annealing (RTA) in O2 ambient for 30 sec. The back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then, sensing area was defined by standard photolithography process using a photosensitive epoxy, SU8-2005 of MicroChem Inc. Finally, the samples were fabricated on the copper lines of printed circuit board (PCB) by silver gel. Epoxy package was used to separate the EIS structure and the copper line. In this study, we report an electrolyte–insulator–semiconductor (EIS) sensor with a high-k magnesium oxide (MgO) as sensing material. The effect of rapid thermal annealing (RTA) on the deposited sensing membrane has been studied in terms of structural and sensing characteristics. We used X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to investigate the structural and morphological characteristics of deposited films. Furthermore, we studied the sensing performance of the MgO EIS structure in different ion solutions such as Urea and Glucose solutions. EIS device with MgO as sensing membrane that has been subjected to 800 ºC RTA treatment exhibits better sensing characteristics such as sensitivity of 61.64 mV/pH, hysteresis voltage of 5.03mV and 1.55mV/hr drift rate.

Synthesis and properties of a low-viscosity UV-curable oligomer for three-dimensional printing

A novel photosensitive low-viscosity epoxy acrylate resin was synthesized by utilizing polyethylene glycol diglycidyl ether (PEGGE) and acrylic acid (AA) as starting materials. The structure of polyethylene glycol diglycidyl ether diacrylate (PEGGEA) was characterized by Fourier transform infrared spectroscopy (FTIR). 2-Isopropyl thioxanthone (ITX), ethyl 4-(dimethylamino) benzoate (EDAB) and 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone (369) as photoinitiators and trihydroxymethyl propane triacrylate (TMPTA) as monomer were mixed with PEGGEA to prepare a kind of UV-curable resins, which may be utilized to boost the resin curing under UV light. The UV-curing properties and the thermal stability of the prepared resins with different contents of oligomer were investigated using FTIR-attenuated total reflection (ATR) spectroscopy and TGA. The viscosity of the oligomers and the mechanical properties of the cured resins were also studied. The results showed that the content of oligomer will affect the UV-curing properties and the thermal stability of the UV-curing resins. The viscosity of the prepared UV-curing resins was less than 200 mPa s at 25 °C, and the hardness of cured resins was high than 6H, which could meet the requirements for three-dimensional printing (3DP).

Preparation and Performance of Photosensitive Epoxy Acrylate Modified by N-[(4-Bromo-3,5-Difluoro) Phenyl]acrylamide

After the 4-bromo-3,5-difluorophenyl acrylamide (BDPA) and acrylic acid were introduced into the epoxy acrylate (EA), the photosensitive epoxy acrylate (EFBDPA) with good performance was prepared through chemical graft modification. The structure of EFBDPA was confirmed by FTIR and1H-NMR. When the content of BDPA in EFBDPA was 20%, the cured coating of EFBDPA had better performance than the unmodified EA cured coating, its tensile strength, 80 % decomposition temperatures and the residual carbon ratio were improved 86%, 5.7 °C and 4.2 %, respectively.

Synthesis of low viscosity, fast UV curing solder resist based on epoxy resin for ink‐jet printing

AbstractA novel photosensitive low viscosity epoxy resin was synthesized by polyethylene glycol (PEG)‐modified bisphenol‐A epoxy resin (E51). The resin was modified by ethylene glycol, diethylene glycol, and different molecule weights (200,300,400) PEGs to optimize the minimum viscosity. FTIR was used to determine molecule structure. Cationic photoinitiator (UVI‐6976) mixed with modified resin (10 wt %), was utilized to boost the resin curing under UV light. The curing degree was beyond 90% within 40 s and the whole process was monitored by photo‐DSC. The modified resin diluted with ethylene glycol diglycidyl ether, was screen printed onto polyimide and polyethylene terephthalate substrate, and the properties of solder mask were up to China printed circuit association standard. The solder resist also meet all requirements under ink‐jet printing technology as the viscosity is under 60 mPa·s and the curing duration is &lt;1 min. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Mold-Free in Situ Formation of Encapsulating Lens With Controllable Viewing Angle for LEDs by Photosensitive Polymerization Process

Using photosensitive epoxy resin liquids as encapsulation materials, a mold-free encapsulation technology is developed in this paper to form lenses on light emitting diode (LED) chips with controllable viewing angles. The light emitted by the LED itself is used to trigger polymerization of photosensitive resins. The shapes of the encapsulation lens are controlled by the “nucleus” formed in the initial stage and by the surface tension of the photosensitive resin liquid. LED packages with viewing angles of 90° and 165° are fabricated in this paper as examples. Encapsulations with other viewing angles are expected to be achievable when using liquids of corresponding surface tension. The whole packaging process can be completed within 20 min, or even less, at room temperature and normal pressure.

High-resolution permanent photoresist laminate TMMF for sealed microfluidic structures in biological applications

We demonstrate the use of photosensitive epoxy laminate TMMF S2045 for the fabrication and sealing of tapered microfluidic channels. The 45 µm thick resist enables the fabrication of shallow sealed cavities featuring extreme aspect ratios of less than 1:40 (h = 45 µm, w = 2000 µm). It also provides high resolution and enables minimum feature sizes of 10 µm. For the fabrication of free-standing structures, an aspect ratio of up to 7:1 was achieved. The dry-film photoresist can be applied easily by lamination onto structured substrates. The total thickness variation of the resist across a 100 mm wafer was determined to be less than ±0.6 µm. Process parameters for the fabrication and sealing of various micro-channels are discussed and optimized in this paper. The main focus was to minimize thermal impact during lamination, soft-bake, exposure and post–exposure bake, which could lead to lid sagging or channel clogging due to liquefaction of uncured resist. We tested TMMF according to ISO 10995-5 and found it to be non-cytotoxic, enabling its use for biological applications. Swelling of less than 5% for incubation of the dry-film resist in several biologically relevant solvents, buffers and cleaning solutions was observed.

Effects of microstructure geometry and plasma modification on wetting properties of SU-8 surfaces

We describe the wetting properties of various geometric microstructures fabricated with SU-8 (negative photosensitive epoxy resin) and the effects of chemical modification by SF6 plasma irradiation. Contact angles of water droplets were measured on ten types of microstructures such as circular pillar, square pillar, cross pillar, and mesh pattern fabricated on SU-8 layers. Moreover, these patterned surfaces were chemically modified by fluorine radicals to change their wetting properties. Contours of the water droplets were also examined from not only the side view but also from the bottom view, through the reverse side of the glass substrate, to investigate the wetting properties. Results revealed that the contact angles on the SU-8 surfaces with microstructures increased after SF6 plasma irradiation because of C–F bond induction. Only in the mesh patterns, which have isolated cavities, the contact angles less increased as a result of the irradiation, in spite of the fact that the wetting state changed from the Wenzel mode to the Cassie-Baxter mode.

Electrokinetic and optical control of bacterial microrobots

One of the great challenges in microscale science and engineering is the independent manipulation of cells and man-made objects on the micron scale. For such work, motile microorganisms are integrated with engineered systems to construct microbiorobots (MBRs). MBRs are negative photosensitive epoxy (SU-8) microfabricated structures with typical feature sizes ranging from 1 to 100 µm coated with a monolayer of swarmer cells of the bacterium Serratia marcescens. The adherent cells naturally coordinate to propel the microstructures in fluidic environments. In this study, ultraviolet light is used to control rotational motion and direct current electric fields are used to control the two-dimensional movement of MBRs. They are steered in a fully automated fashion using computer-controlled visual servoing, used to transport and manipulate micron-sized objects, and employed as cell-based biosensors. This work is a step toward in vitro mechanical or chemical manipulation of cells as well as controlled assembly of microcomponents.

感光性エポキシ樹脂ＳＵ‐８表面の濡れにおよぼす微細凹凸形状とプラズマ改質の影響

This paper describes effects of micro-square-shaped pillar array structures and chemical modification by SF6 or O2 plasma irradiation on wetting properties of SU-8 (photosensitive epoxy resin) for water. Contact angles were measured and microscopic observation of water droplet contours were conducted through the bottom of the glass substrate. For the SU-8 surfaces without chemical modification, Wenzel mode wetting occurred constantly. However, because of the pinning effect, the contact angles on surfaces with micro structures were larger than the values calculated based on the Wenzel mode wetting. The SU-8 surfaces modified by SF6 plasma showed Cassie mode wetting generally and remarkable hydrophobicity with large contact angles of more than 150 deg. The surface became super-hydrophilic after O2 plasma modification.

Hybrid Integration of Microwave Circuit Solenoid Inductors and AlGaN/GaN HEMTs Using an SU-8 Photosensitive Epoxy Interposer Layer

Integration of active and passive microwave circuit components onto an inexpensive silicon substrate can be accomplished using photosensitive SU-8 epoxy as the interposer layer. This paper addresses the 3-dimensional integration of AlGaN/GaN high electron mobility transistor's (HEMT's) embedded into deep reactive ion etched (DRIE) pockets on a silicon substrate with gold-plated vias and transmission lines formed in a follow-on layer of SU-8 epoxy over the HEMT's. In addition, modeling, simulation, fabrication and testing of gold-plated, solenoid inductors embedded in SU-8 over the silicon substrate is covered. This integration process may replace variable inductance wire bond connections; with reproducible interconnects to enhance circuit design flexibility and accuracy. The solenoid inductors, whose inductance L and quality factor Q can be further optimized through the addition of ferrite or ferromagnetic cores, will help reduce the overall circuit footprint. This paper is organized into two parts: the solenoid model development and the HEMT integration process and test results.

Pattern Formation of Silver Nanoparticles in 1‐, 2‐, and 3D Microstructures Fabricated by a Photo‐ and Thermal Reduction Method

AbstractOne‐, two‐, and three‐dimensional microstructures with dispersed silver nanoparticles are fabricated by a combination of photopatterning and thermal treatment from a silver salt containing photosensitive epoxy resin. Ultraviolet photo‐irradiation and subsequent thermal treatment are combined to control the rate of silver salt reduction, the size and the arrangement of nanoparticles, as well as the reticulation of the epoxy resin. This approach allows the creation of high resolution 1‐, 2‐, and 3D patterns containing silver nanoparticles, with a homogeneous distribution of nanoparticles regardless of the irradiated area.

A novel micropit device integrates automated cell positioning by dielectrophoresis and nuclear transfer by electrofusion

Nuclear transfer (NT) cloning involves manual positioning of individual donor-recipient cell couplets for electrofusion. This is time-consuming and introduces operator-dependent variation as a confounding parameter in cloning trials. In order to automate the NT procedure, we developed a micro-fluidic device that integrates automated cell positioning and electrofusion of isolated cell couplets. A simple two layer micro-fluidic device was fabricated. Thin film interdigitated titanium electrodes (300 nm thick, 250 microm wide and 250 microm apart) were deposited on a solid borosilicate glass substrate. They were coated with a film of electrically insulating photosensitive epoxy polymer (SU-8) of either 4 or 22 microm thickness. Circular holes ("micropits") measuring 10, 20, 30, 40 or 80 microm in diameter were fabricated above the electrodes. The device was immersed in hypo-osmolar fusion buffer and manually loaded with somatic donor cells and recipient oocytes. Dielectrophoresis (DEP) was used to attract cells towards the micropit and form couplets on the same side of the insulating film. Fusion pulses between 80 V and 120 V were applied to each couplet and fusion scored under a stereomicroscope. Automated couplet formation between oocytes and somatic cells was achieved using DEP. Bovine oocyte-oocyte, oocyte-follicular cells and oocyte-fibroblast couplets fused with up to 69% (n = 13), 50% (n = 30) and 78% (n = 9) efficiency, respectively. Fusion rates were comparable to parallel plate or film electrodes that are conventionally used for bovine NT. This demonstrates proof-of-principle that a micropit device is capable of both rapid cell positioning and fusion.

Doubly patternable epoxy based sol–gel structures by UV and soft lithography

The sol–gel synthesis of hybrid materials offers special opportunities to combine polymer and glass properties and to create promising candidates for photonic applications. We report on the optical and morphological characterization of a new photosensitive epoxy based sol–gel system. Germanium ethoxide and 3-Glycidoxypropyltrimethoxysilane were used as precursors for hybrid sol-gel planar coatings. A photoacid generator was added to solution in order to allow the epoxy photopolymerization when the films are selectively exposed to UV light. The refractive index increase (Δ n = 0.015) induced by UV light allows the direct patterning of waveguiding structures having good morphological quality. Stripes and beam splitters were defined by direct UV exposition on silicon substrates. Moreover, we present structures made by thermal imprinting method. Silicon masters have been used to transfer relief gratings on the photopolymerizable epoxy sol-gel materials. Combining thermal imprinting technique and UV light exposition through a photomask, complex structures can be realized such as light couplers, sensors and wavelength filters.

Simulative operation on congenital heart disease using rubber-like urethane stereolithographic biomodels based on 3D datasets of multislice computed tomography☆

Stereolithographic biomodelling is a technique where photosensitive liquid resin is polymerised with a pinpoint laser beam controlled by three-dimensional (3D) datasets. This study was designed to assess whether a stereolithographic biomodelling technique is applicable for precise anatomical diagnosis and simulation surgery of complicated congenital heart disease. Twelve stereolithographic biomodels were manufactured with multislice computed tomography (MSCT)-based 3D datasets. They were made of photosensitive liquid epoxy or urethane. All the solid epoxy and rubber-like urethane biomodels reproduced the complex anatomical structures of the arteries and veins in congenital heart diseases. Furthermore, the rubber-like urethane biomodels allowed the surgeon to cut and suture, thus facilitating the simulation of the surgical operation. Stereolithographic biomodelling is a promising technique for the preoperative practice and simulation of individual surgery. This technique would be useful in the planning of novel and innovative surgical procedures of congenital heart disease.

Photosensitive Epoxy Materials and their Application to Multi-mode Optical Waveguides

A photosensitive epoxy (PSEP) for multi-mode optical waveguide based on epoxy resins containing fluorene units and photo-acid generator (PAG) has been developed. PSEP is directly patterned by UV irradiation and wet chemical development, avoiding use of photoresist. Fabricated optical waveguides have 50μm width rectangle core pattern, which was smooth sidewalls and surfaces. PSEP optical waveguide exhibits high heat resistance and low optical loss 0.063 μm at 830nm. This simplification of the fabrication process is very attractive in manufacturing optical/electrical devices at low cost.

Duplication of nanoimprint templates by a novel SU-8/SiO2/PMMA trilayer technique

In this work, a trilayer technique used in the nanoimprint lithography process to replicate the templates is developed. The SU8/SiO2/PMMA trilayer was used. The photosensitive epoxy (SU8 resist) which has a low glass transition temperature was used as the imprint layer. Polymethylmethacrylate (PMMA) was used as the transfer layer. A SiO2 layer is placed between the SU8 and PMMA to act as a protective layer due to its strong resistance to oxygen reactive ion etching. By optimizing imprint and etching processes, master templates with minimum feature size of 150 nm and period of 300 nm can be successfully duplicated.