Figures are an extremely important part of any scientific publication. It is a rare paper that contains no figures (such papers are mostly of the theoretical variety, though even a pure theory paper often benefits from a good graph). As the renowned guru of graphics Edward Tufte put it, “At their best, graphics are instruments for reasoning about quantitative information.”1 Since almost all scientific publications include quantitative information to be reasoned about, figures are almost always called for.

Thermal nanoimprint lithography (NIL) is presented as an alternative fabrication technique for patterning deoxyribonucleic acid (DNA) biopolymer films for photonic device applications. The techniques and procedures developed for directly imprinting optical waveguide structures on a DNA biopolymer using NIL, bypassing the use of a resist layer and any chemical processing, are outlined here. The fabrication technique was developed with a Nanonex NX-2600 NIL flexible membrane system. Additionally, a process for using a Suss MicroTec ELAN CB6L substrate bonder is discussed as an alternative to commercially available NIL systems.

Technologies for fabrication of MEMS, optics and photonics at the micro- and nanoscale continue to advance and diversify due to rising demands for miniaturization, cost reduction, functional integration, and increased performance. Examples include diffractive optics, sub-wavelength optics, microrefractive optics, optical waveguides, photonic crystals, plasmonic devices, and heterogeneously integrated active and passive micro- and nano-optical devices. These devices are playing increasing roles in a wide range of applications, including sensors and actuators, communications, imaging, biomedical, data storage, and other areas. Both conventional and unconventional micro- and nanofabrication techniques serve as fundamental enablers for wide ranges of MEMS and passive and active optical components and devices.

Patterning of colloidal quantum dot (QD) of a nanometer resolution is important for potential applications in micro- or nanophotonics. Several patterning techniques such as polymer composites, molecular key-lock methods, inkjet printing, and the microcontact printing of QDs have been successfully developed and applied to various plasmonic applications. However, these methods are not easily adapted to conventional complementary metal-oxide semiconductor (CMOS)-compatible processes because of either limits in fabrication resolutions or difficulties in sub-100-nm alignment. Here, we present an adaptation of a conventional lift-off method for the patterning of colloidal QDs. This simple method can be later applied to CMOS processes by changing electron beam lithography to photolithography for building up photon-generation elements in various planar geometries. Various shapes formed by colloidal QD clusters such as straight lines, rings, and dot patterns with sub-100-nm size could be fabricated. The patterned structures show sub-10-nm positioning with good fluorescence properties and well-defined sidewall profiles. To demonstrate the applicability of our method, we present a surface plasmon generator from a QD cluster.

Conventional photolithography normally utilizes a photomask for patterning light onto a chemical resist film. Therefore, the accuracy of microfabrication is highly dependent on the accuracy of the photomasks. Fabrication of hard masks involves the use of expensive laser pattern generators and other sophisticated machines using very high-precision stages and the necessary control instrumentation; therefore, an inexpensive strategy is highly necessary for laboratory-level fabrication. As this technology is primarily based on raster scanning of a laser beam, the mask making as such becomes a low-throughput process. A strategy of high-throughput manufacturing of hard masks with laser micromachining using a one-step exposure process of a chromated glass slide through a micromachined aluminum shadow mask is proposed. The features that are finally embedded in the mask are highly demagnified and well focused. Optimization of the laser machining process is carried out by considering all processing parameters. The features are characterized using an optical microscope, a scanning electron microscope, and a self-developed image analysis code. Geometrical methods are used to estimate the average edge roughness and feature size. We have also validated the usage of these masks by performing microfabrication on films made of photoresist.

We report on the characterization of metal-organic hybrid metamaterials for MEMS-based terahertz (THz) thermal sensors and on the characterization of refractive index of SU-8 in the THz band. This type of metamaterial, coupled with the applicability of SU-8 as a structural material, offers possibilities for quick, simple microfabrication of THz imagers. SU-8, a negative photoresist, is a low-cost material that can quickly be spun onto a substrate at a wide range of thicknesses, and then photolithographically patterned into a variety of structures. It is also transparent to THz radiation and thus a suitable choice for a dielectric spacer in metamaterials. We investigated metamaterials consisting of a 0.18 μm Al ground plane and 0.18-μm layer of patterned Al separated by a dielectric spacer of ∼0.5  μm of SU-8. Absorption close to 70% at around 6.1 THz was observed. A model was developed to simulate absorption spectra of several metamaterials, agreeing well with experiments. Matching simulation to measurements was used to determine the refractive index of SU-8 at THz frequencies, extending the known values from 0.1 to 1.6 THz to as far as 10 THz. Finally, Kirchoff’s law for these metamaterials was verified and their use as THz emitters demonstrated with about 0.8  mW/cm ² output.

The purpose of this paper is the fabrication, replication, and wafer-level imprinting of a polynomial curvature to enable the realization of an electrostatic out-of-plane zipper actuator with considerably altered and enhanced voltage versus deflection behavior. This is achievable only by changing silicon as established main material to a UV-curable polymer, while retaining the lithography-based fabrication technology. The basic concept of this actuator is explained, and with derived design rules, a finite element analysis is established to design an actuator with an integrated micro-mirror and 10-μm deflection at 60-V driving voltage. The diamond turning of the master mold and the wafer-level fabrication process of the polynomial curvature are explained in detail and realized by unconventional wafer-level imprinting of a UV-curable, nonconducting polymer. The experimental results of the deflection measurements show a deflection of the intended 10 μm at 200 V. This deviation in necessary driving voltage can be explained by fabrication-induced intrinsic stresses, which bend the actuator beams upward. This increases the gap between the electrodes, making it possible to achieve 26-μm deflection at 300 V. This paper finalizes with an illustration about the now possible designs for polymer-based electrostatic zipper actuators.

Stiction occurring in the release phase is a severe problem in many MEMS devices. This phenomenon is due to capillary forces and solid–solid adhesion, which develops during drying after a wet etching process. The possibilities and the limits of the use of a solvent with low surface tension is investigated in the case of MEMS resonators fabricated on silicon-on-insulator substrate. It is shown as in this case it is possible to obtain stiction-free structures without the necessity of more expensive and complicated techniques such as supercritical drying or hydrofluoric acid (HF) vapor etching. The fabrication and design limit of this solution are also investigated.

This paper [J. Micro/Nanolith. MEMS MOEMS. 12, (2 ), 023015 (Apr–Jun 2013)] was mistakenly published as a regularly contributed paper in the April–June 2013 issue of JM3. It was intended to be published with the special section on “Advanced Fabrication of MEMS and Photonic Devices” guest edited by Freymann, Maher, and Suleski in the October-December 2013 issue of JM3. The paper can be found online at CrossRef

XSLOpenURL/10.1117/1.JMM.12.2.023015

. It also appears in the October–December 2013 print issue with the special section.

Plasma etch technology is an integral and indispensible part of patterning technology that has enabled continuous scaling in the semiconductor industry for more than forty years. Advancement in plasma-etch technology, along with other semiconductor process technologies, has brought the state-of-the-art semiconductor technology, the so-called 22 nm node of complementary metal–oxide–semiconductor (CMOS) technology, into mass production. This 22 nm node CMOS technology features a three-dimensional (3-D) FinFET, a metal one pitch of about 90 nm and copper/low-k interconnects. The next generation of 14 nm node CMOS technology is expected to be brought into mass production in the first quarter of 2014.

The approach for patterning 15-nm half-pitch (HP) structures using extreme ultraviolet lithography combined with self-aligned double patterning is discussed. A stack composed of a double hard mask, which allows decoupling photoresist transfer and trim, and an α-Si mandrel, which offers better mechanical properties during the mandrel and spacer patterning, is proposed. A break-down study with the patterning steps was performed to investigate the key contributors for improvement of linewidth roughness (LWR), line-edge roughness (LER), and critical dimension uniformity (CDU), targeting integrated solutions with lithography, etch, thin film deposition, and wet cleans for selected applications. Based on the optimization of these key patterning contributors, optimum LWR, LER, and CDU at 15 nm HP are demonstrated.

193-nm compatible photoresists are turning out to be the new platform for implant lithography, due to the increasing requirements in both resolution and overlay. Shrinkage of such resists is becoming progressively the most topical issue for aggressive nodes, where conventional pretreatments from older resist platforms, such as ultraviolet flood exposures, are not directly transferable to (meth-)acrylate-type resists. The precuring options available for state-of-the-art implant photoresists for 193-nm lithography is explored, in which we target to reduce the shrinkage during implantation for trenching critical dimensions (CDs) that are relevant for nodes <;20  nm . An extensive study comprising different approaches, including laser-, ion-, and electron-based treatments, is presented. Each treatment is individually investigated with the aim to find not only a valid pretreatment for shrinkage control during implantation, but also to understand what effect alternative pretreatments have on the morphology and the CDs of thick photoresists used as implant stopping layers. Viable options for further process optimization in order to integrate them into device process flows are found. To this extent, the shrink behavior after pretreatment is shown, and the additional shrink dynamics after implantation are compared.

The major issue related to line width roughness (LWR) is the significant LWR of the photoresist patterns printed by 193-nm lithography that is partially transferred into the gate stack during the subsequent plasma etching steps. The strategy used today to overcome this issue is to apply postlithography treatments to reduce photoresist pattern LWR before transfer. In this article, we investigate the impact of various plasma treatments (HBr, H ₂ , He, Ar) on the minimization of the LWR of dense and isolated photoresist patterns and its transfer during gate patterning. To do so, we use critical dimension scanning electron microscopy measurements combined with power spectrum density fitting method to extract unbiased LWR values and provide a spectral analysis of the LWR. We show that plasma treatments that lead to carbon redeposition from the gas phase on the resist pattern sidewalls are less efficient to reduce LWR than plasma treatments where the redeposition is limited. Among all plasma chemistries, H ₂ plasmas seem very promising to decrease resist LWR in the whole spectral range, while maintaining square resist profiles. In addition, we show that all frequency roughness components are not equally transferred during gate patterning, and more particularly that the high frequency roughness components are lost.

A study on the optimization of etch transfer processes using 200-mm-scale production type plasma etch tools for circuit relevant patterning in the sub-30-nm pitch regime using directed self-assembly (DSA) line–space patterning is presented. This work focuses on etch stack selection and process tuning, such as plasma power, chuck temperature, and end point strategy, to improve critical dimension control, pattern fidelity, and process window. Results from DSA patterning of gate structures featuring a high-k dielectric, a metal nitride and poly Si gate electrode, and a SiN capping layer are also presented. These results further establish the viability of DSA pattern generation as a potential method for Complementary metal–oxide–semiconductor (CMOS) integrated circuit patterning beyond the 10-nm node.

A double patterning process resulting in amorphous silicon (a-Si) gate lines with a thickness of 80 nm and a lateral critical dimension <30  nm is reported. A full stack for a double patterning approach for etch transfer down to an Si layer, including a hard mask (HM) in which the line and cut patterning are performed, is presented. The importance of the HM in the success or failure of the exercise is evidenced. Once the suitable HM has been selected, the etch chemistry is shown to have a significant impact on the line width roughness (LWR) of the gate. Ultimately, remarkably low LWR could be achieved on gates exhibiting a straight profile. All the results shown in this paper have been obtained on 300-mm wafers.

Template-based surface nanopatterning techniques are highly efficient methods in realizing different surface nanopatterns, which are the fundamental structures of various nanodevices. We demonstrate a template of pyramidal silicon nanopore array (PSNA) for direct surface nanopatterning. Using the PSNA templates, deposition experiments of platinum (Pt) and gold-palladium (Au-Pd) particles on chromium-coated silicon substrates were performed. Individual Pt nanocubes and nanocube arrays with different shapes and feature sizes as small as 82 nm were obtained. By tuning the gap between the PSNA template and the substrate, Au-Pd microdot arrays with an average diameter of 7.6 μm were also fabricated. As the nanopore size and shape of the PSNA template can be easily controlled, the corresponding size and shape of the transferred surface nanopatterns are tunable. These results indicate the potential of the PSNA templates for large-scale production of nanopatterns with desired sizes and shapes.

With the constant decrease of semiconductor device dimensions, gate line edge roughness (LER) becomes an important source of device variability. Gate LER originates from photoresist (PR) LER that is partially transferred into the gate during plasma etching. A plasma treatment is typically used to reduce the PR LER before the transfer. LER control at the nanometer scale also requires accurate measurements. We have recently developed a technique for LER measurement based upon atomic force microscopy (AFM). In this technique, the sample is tilted at about 45 deg and feature sidewalls are scanned along their length with the AFM tip to obtain three-dimensional images. The AFM technique is applied to the study of a pattern transfer into a gate stack starting from untreated PR, PR treated by conventional HBr plasma, and PR treated by HBr/O ₂ plasma followed by a bake at 150°C. It is found that the plasma etching reduces the LER at each etching step. The reduction is more important when starting from untreated PR which has the highest initial LER. However, the final LER in the Si layer remains significantly smaller when starting with cured PR, especially with PR cured by an HBr/O ₂ plasma treatment followed by a bake at 150°C.

The effect of oxygen addition to an argon plasma on the etching selectivity of poly(methyl methacrylate) (PMMA) to polystyrene (PS) (hereafter “PMMA/PS etching selectivity”) was investigated. The PMMA/PS etching selectivity was evaluated by using inductively coupled plasmas composed of argon and oxygen. The etching selectivity in the case of argon plasma was estimated to be 3.9, which is higher than that of oxygen plasma, which is 1.7. The time dependence of etching depth shows that the etching rate of PMMA is reduced to less than one half of its initial value after the etching depth exceeds 15 nm. X-ray photoelectron spectroscopy of the PMMA surface revealed that the reduction of etching rate is caused by a depletion of oxygen concentration by argon-ion bombardment. To compensate the oxygen-concentration depletion, 1% oxygen was added to the argon plasma. As a result, the reduction of PMMA etching rate was suppressed, and constant etching rate was obtained even when etching depth exceeded 50 nm. The mixed argon-oxygen plasma was used to fabricate a PS mask pattern with a full pitch in the range of 25.5 to 77 nm.

The transfer of the line edge roughness (LER) from the resist to the substrate sidewall by means of an anisotropic plasma-etching process depends on both the physicochemical reactions of plasma species with the resist and substrate and the morphology of the resist sidewalls. We show that a geometrical model based on the reliable representation of the resist sidewall roughness can capture the main experimental trends and behaviors. Predictions of the model regarding the role of resist sidewall anisotropy and the effects of resist LER on substrate slope are also presented. Finally, rules of thumb defining the slope and the necessary conditions to have LER reduction in substrate sidewalls are derived and discussed.

Advances in patterning techniques have enabled the extension of immersion lithography from 65/45 nm through 14/10  nm device technologies. A key to this increase in patterning capability has been innovation in the subsequent dry plasma etch processing steps. Multiple exposure techniques, such as litho-etch-litho-etch, sidewall image transfer, line/cut mask, and self-aligned structures, have been implemented to solution required device scaling. Advances in dry plasma etch process control across wafer uniformity and etch selectivity to both masking materials have enabled adoption of vertical devices and thin film scaling for increased device performance at a given pitch. Plasma etch processes, such as trilayer etches, aggressive critical dimension shrink techniques, and the extension of resist trim processes, have increased the attainable device dimensions at a given imaging capability. Precise control of the plasma etch parameters affecting across-design variation, defectivity, profile stability within wafer, within lot, and across tools has been successfully implemented to provide manufacturable patterning technology solutions. IBM has addressed these patterning challenges through an integrated total patterning solutions team to provide seamless and synergistic patterning processes to device and integration internal customers. We will discuss these challenges and the innovative plasma etch solutions pioneered by IBM and our alliance partners.

Flare (stray light) is an important effect impacting extreme ultraviolet lithography (EUVL) imaging system performance. Four flare measurement methods including Kirk, modulation transfer function, double exposure, and zonal ring approximation method are reviewed and analyzed theoretically. The point spread function of an EUV NXE:3100 exposure tool is extracted from the measured Kirk flare (KF) and fitted with a double-fractal model. The KF for this NXE:3100 tool is determined to be 8.5% for a 2-μm diameter absorber pad placed in a 12-mm outer radius bright field, which is larger than the previous 5% KF data measured by ASML and IMEC in 2011. The observation of the increased flare level in the NXE:3100 tool suggests that contamination of EUV optics may be a potential problem for EUVL manufacturing.

Extreme ultraviolet lithography (EUVL) at 13.5 nm is currently the most promising technology for advanced integrated circuit manufacturing nodes. Since the wavelength for EUVL is an order of magnitude smaller than current optical lithography systems (193 nm), aberration tolerances on lens manufacturing must be tightened to avoid image distortion and contrast loss as they scale with wavelength. Therefore, understanding the aberrations of an EUVL system both in idle and production conditions is paramount. This study aims to assess a photoresist-based aberration metrology technique for capturing pupil information of EUVL systems that can be implemented during full system use. Several datasets have been collected on a full-field EUVL system. Various one-dimensional and two-dimensional binary structures were imaged and used for pupil wave front extraction in conjunction with computational modeling and simulations. Results show a successful extraction of a stable aberration signature over several measurements, showing the method to be sensitive to subnanometer levels of intentional aberration change through lens manipulation.

Process-induced overlay errors are a growing problem in meeting the ever-tightening overlay requirements for integrated circuit production. Although uniform process-induced stress is easily corrected, nonuniform stress across the wafer is much more problematic, often resulting in noncorrectable overlay errors. Measurements of the wafer geometry of free, unchucked wafers give a powerful method for characterization of such nonuniform stress-induced wafer distortions. Wafer geometry data can be related to in-plane distortion of the wafer pulled flat by an exposure tool vacuum chuck, which in turn relates to overlay error. This paper will explore the relationship between wafer geometry and overlay error by the use of silicon test wafers with deliberate stress variations, i.e., engineered stress monitor (ESM) wafers. A process will be described that allows the creation of ESM wafers with nonuniform stress and includes many thousands of overlay targets for a detailed characterization of each wafer. Because the spatial character of the stress variation is easily changed, ESM wafers constitute a versatile platform for exploring nonuniform stress. We have fabricated ESM wafers of several different types, e.g., wafers where the center area has much higher stress than the outside area. Wafer geometry is measured with an optical metrology tool. After fabrication of the ESM wafers including alignment marks and first level overlay targets etched into the wafer, we expose a second level resist pattern designed to overlay with the etched targets. After resist patterning, relative overlay error is measured using standard optical methods. An innovative metric from the wafer geometry measurements is able to predict the process-induced overlay error. We conclude that appropriate wafer geometry measurements of in-process wafers have strong potential to characterize and reduce process-induced overlay errors.

We propose a new regularization framework for inverse lithography that regularizes masks directly by applying a mask filtering technique to improve computational efficiency and to enhance mask manufacturability. This technique is different from the conventional regularization method that regularizes a mask by incorporating various penalty functions to the cost function. We design a specific mask filter for this purpose. Moreover, we introduce a metric called edge distance error (EDE) to guide mask synthesis and establish the correlation between pattern error and edge placement error (EPE) via EDE. We prove that EDE has the same dimension as EPE and has a continuous expression as pattern error. Simulation results demonstrating the validity and efficiency of the proposed method are presented.

We present a new group of piezoelectric nanocomposite thin films based on integrating piezoelectric material poly(vinylidene fluoride) and nanoparticles of barium titanate in a matrix of an organic polymer poly(methyl methacrylate). Implementation of piezoelectric properties in designed new nanocomposites allows us not only to increase the sensitivity and functionality of the overall system, where this material is used, but also to expand the application fields in sensing and actuating systems. Results implied that new nanostructures fabricated by nanoimprint lithography exhibit good piezoelectric, surface, and mechanical properties and allow independent control of tribological properties. Formed nanocomposite systems were integrated in designing optical components employed in medicine for sensing applications.

The effects of void-based photonic crystal mirrors on reflectivity and dissipation for extreme-ultraviolet (EUV) radiation at near-normal illumination are studied. The mirrors are based on a multilayer coating comprising alternating layers of molybdenum (Mo) and silicon (Si) with 40 periods. By embedding voids in silicon films instead of molybdenum films, we found that the reflectivities of the mirror are increased and the absorptions of the mirror are decreased with the increments of the voids. On the other hand, the reflectivities of the mirror are decreased and the absorptions are increased by embedding voids in the molybdenum films, with the increments of the voids. Compared to the standard designs of 40 Mo/Si multilayer mirrors, which are currently used in most EUV or soft x-ray applications, the reflectivity of the void-based photonic crystal mirror in our study can reach from 73.43 to 83.24% and the absorption can decline from 26.18 to 16.80%. In consideration of EUV bandwidth, the effects of illumination angles in the six-mirror projection system, the intermixing layers, and the variation of the coated absorber thickness on the reflection properties are studied. The proposed concept can be used in next-generation EUV lithography and soft x-ray optical systems.

We describe a novel deterministic bottom-up/top-down approach to sub-30-nm photolithography using a film composed of assembled block brush polymers of highly uniform composition and chain length. The polymer architecture consists of a rigid backbone of polymerized norbornene, each linked to flexible short side brush chains. The resultant bottle brush topology has a cylindrical shape with short brush chains arranged concentrically around the backbone, in which the cylinder radius is determined by the number of monomers within the brush fragment, while the cylinder length is determined by the degree of backbone polymerization. The modularity of the synthetic system allows a wide diversity of lithographically useful monomers, sequencing, dimension, and property variation. Sequential grafting of presynthesized blocks allows for facile formation of either concentric or lengthwise block copolymers. Placement of brush chains of different compositions along different regions of the cylinder, along with variation of the relative concentric and lengthwise dimensions, provides mechanisms to align and control placement of the cylinders. These polymers are compatible with photoacid generators and crosslinker functionality. Our results are consistent with a model that the bottle brush polymers assemble (bottom-up) in the film to yield a forest of vertically arranged cylindrical block brush polymers, with the film thickness determined by the coherence lengths of the cylinders. Subsequent imaging via electron beam (e-beam) or optical radiation yields a (top-down) mechanism for acid catalyzed crosslinking of adjacent cylinders. Uncrosslinked cylinders are removed in developer to yield negative photoresist patterns. Exposure doses are very low and throughputs are amenable to the requirements of extreme ultraviolet lithography. The limiting resolution with e-beam exposure is potentially about two cylinder diameters width (<8  nm ), with the smallest observed patterns approaching 10 nm.

The whispering-gallery mode space of a cylindrically symmetric silicon micro-optic bottle resonator with an axial Gaussian dielectric profile is theoretically examined. Maxwell’s wave equation for the magnetic field, expressed in cylindrical coordinates, is converted into an eigenvalue problem using a Fourier–Bessel basis space to expand the inverse dielectric and field components. The order of the eigen-matrix is reduced using symmetry arguments and azimuthal order segmentation such that the matrix can be solved on a desktop PC. The eigen-space reveals that several states can be confined in the bottle region, whereas another set of states extends the axial length of the structure similar to ridge waveguide modes. The hollow core bottle is also presented as a design modification. The micro-optic bottle resonator structure size makes it directly compatible with silicon-based photonics increasing its potential as a key component in sensing, communication, and other applications.

We propose two new fast algorithms for the computation of the continuous Fourier series and the continuous Haar transform of rectilinear polygons such as those of mask layouts in optical lithography. These algorithms outperform their discrete counterparts traditionally used. Not only are continuous transforms closer to the underlying continuous physical reality, but they also avoid the inherent inaccuracies introduced by the sampling or rasterization of the polygons in the discrete case. Moreover, massive amounts of data and the intense processing methods used in lithography require efficient algorithms at every step of the process. We derive the complexity of each algorithm and compare it to that of the corresponding discrete transform. For the practical very-large-scale integration (VLSI) layouts, we find significant reduction in the complexity because the number of polygon vertices is substantially smaller than the corresponding discrete image. This analysis is completed by an implementation and a benchmark of the continuous algorithms and their discrete counterparts. We run extensive experiments and show that on tested VLSI layouts the pruned continuous Haar transform is 5 to 25 times faster, while the fast continuous Fourier series is 1.5 to 3 times faster than their discrete counterparts.

We report a technically innovative method of fabricating masks for both deep-ultraviolet (UV) patterning and metal sputtering on polymethylmethacrylate (PMMA) for microfluidic systems. We used a CO₂ laser system to cut the required patterns on wax-covered plastic paper; the laser-patterned wax paper will either work as a mask for deep-UV patterning or as a mask for metal sputtering. A microfluidic device was also fabricated to demonstrate the feasibility of this method. The device has two layers: the first layer is a 1-mm thick PMMA substrate that was patterned by deep-UV exposure to create microchannels. The mask used in this process was the laser-cut wax paper. The second layer, also a 1-mm thick PMMA layer, was gold sputtered with patterned wax paper as the shadow mask. These two pieces of PMMA were then bonded to form microchannels with exposed electrodes. This process is a simple and rapid method for creating integrated microfluidic systems that do not require cleanroom facilities.

This article [J. Micro/Nanolith. MEMS MOEMS. , 12, (3 ), 033020 (2013)] was originally published online on 25 September 2013 with errors in the authors’ names.The names originally appeared as Lakshminarayanan Sujatha, Murali Siddhartha Goutham, Mani Saravanan, and Varatharajan Subramani Selvakumar. The corrected names appear above.All online versions of the article were corrected on 27 September 2013. The article appears correctly in print.