Whenever a manuscript is submitted to the Journal of Micro/Nanolithography, MEMS, and MOEMS (JM3), the manuscript first goes to me, the editor-in-chief. And the first thing I do is read the cover letter that accompanies the manuscript. Thus, the cover letter creates the first impression that I have of the manuscript. Is this important? Of course I think it is, but let me explain why the author(s) should think it is important as well.

This PDF file contains the editorial “JM3 2012 List of Reviewers” for JM3 Vol. 12 Issue 02

The equipment and process development model for extreme ultraviolet (EUV) masks spans international consortia, closely held multiparty alliances, individual user efforts, materials/equipment programs and ad hoc collaborations. Mask integration efforts are also spread widely from captive mask programs driving toward early and specific EUV use cases to more general-purpose efforts typical of broad application foundry or merchant business models. Even specifications for EUV masks remain a dynamically moving target as the reflective and film properties of the mask coupled with incoming illumination obliquity represent a dramatic departure from previous mask technology. Finally, due to the highly sensitive nature of mask technology as the entry point of a chip design into the fab, many teams are understandably reluctant to publish works due to competitive concerns. For these reasons, it seems particularly valuable to aggregate and highlight important work under way to address key issues in EUV mask development. We are therefore grateful to the expert authors who have provided contributions to this special edition in the following critical areas: •Mask defects and inspection often viewed as the most challenging integration module for delivering production-worthy EUV masks; •Mask blanks representing the critical starting point for high-yielding mask fabrication; •Interplay between mask quality and mask printing, which has particular importance for the new emerging patterning system; •Etching of the mask posing special challenges thanks to the unique substrate characteristics. We hope you will be encouraged by the progress and understanding demonstrated in these works for critical parts of the mask infrastructure. Despite the unique challenge of delivering a new mask technology to the industry, it is clear substantial progress is being made toward the end goal. Of course, readers should draw their own conclusions, and, toward that, we urge EUV ecosystem participants to continue adding to the discussion by publishing new works that support a vigorous EUV mask co-learning and technology dialogue.

In extreme ultraviolet lithography, reducing the number of phase defects (PDs) on mask blanks is a critical issue because the PDs cause degradation of the printed pattern quality. To minimize the number of printable PDs, covering PDs beneath an absorber pattern is an effective way of addressing the problem. Therefore it becomes necessary to detect the PDs and pinpoint their locations by a blank inspector. In this work, a three-dimensional analysis of PDs has revealed that some PDs can grow and propagate in an angular direction away from the normal to the substrate surface. The impact of the inclination angle on the printing performance was evaluated by calculating printed pattern images using a simulator. A PD with an inclination angle of 1 deg corresponds to a 1-nanometer positional shift compared with a position defined as surface topography of a defect as observed by an atomic force microscope or by some nonactinic defect inspector. However, an actinic blank inspection (ABI) tool with high-magnification optics can pinpoint the actual location of the PDs. Covering a PD under an absorber pattern, by a shifting of the pattern based on the information of the PD’s location obtained by the ABI tool, works quite well.

Extreme ultraviolet (EUV) lithography with a 13.5 nm exposure wavelength is a leading candidate for the next-generation lithography because of its excellent resolution for 16 nm half pitch (hp) node devices and beyond. High sensitivity EUV mask pattern defect detection is one of the major issues to realize device fabrication with EUV lithography. First, to estimate targeted pattern defect detection size, a simulation for defect printability was carried out. In order to achieve the required inspection sensitivity applicable for 1X nm node, a projection electron microscopy (PEM) system was employed, which enabled us to do inspection in higher resolution and with higher speed in comparison to those of the conventional deep ultraviolet and electron beam inspection systems. By incorporating high electron energy and low optical aberration into the PEM, we designed a system for 16 nm hp node defect inspection. To guarantee the quality of the 16 nm node EUV mask, corresponding sized programmed defect masks were designed, and a PEM system defect detection was evaluated by using the current system for 2X nm generation.

For the next few years, the extreme ultraviolet lithography (EUVL) community must learn to find mask defects using nonactinic inspection wavelengths. Nonactinic light cannot always determine the exact nature of the defect, whether it is a particle, pattern, or defect in the multilayer. It also cannot predict which defects will induce phase errors and which will induce amplitude errors on wafers. Correlating the signature of the defect as seen by a nonactinic inspection tool and on wafer resist image will inject essential knowledge into the nonactinic defect classification. This paper will explore the correlation between EUVL mask defect signatures detected (and not detected) at both 193 nm and e-beam inspection wavelengths and wafer-printable defects. The defects of interest will be characterized at mask level using atomic force microscopy and critical dimension scanning microscopy. Simulations will be deployed to explain the signatures illuminated by both EUVL and 193 nm exposures. This work addresses the gap between inspection sensitivity at nonactinic wavelengths and EUVL mask defect printability, and provides generalized understanding of how the two views differ.

This paper presents the extension of the well-established, rigorous, electromagnetic field solver waveguide for the efficient and fully rigorous simulation of patterned extreme ultraviolet (EUV) masks with multilayer defects. The new simulation method uses a rigorously computed multilayer defect data base in combination with on demand modeling of diffraction from absorber structures. Typical computation times are in the range of seconds to a few minutes. Selected simulation examples, including a defect printing exploration and a defect repair, demonstrate the functionality and the capability to perform fast, highly accurate, and flexible EUV multilayer defect computations.

As the International Technology Roadmap for Semiconductors critical dimension uniformity (CDU) specification shrinks, semiconductor companies need to maintain a high yield of good wafers per day and high performance (and hence market value) of finished products. This cannot be achieved without continuous analysis and improvement of on-product CDU as one of the main drivers for process control and optimization with better understanding of main contributors from the litho cluster: mask, process, metrology and scanner. We will demonstrate a study of mask CDU characterization and its impact on CDU Budget Breakdown (CDU BB) performed for advanced extreme ultraviolet (EUV) lithography with 1D (dense lines) and 2D (dense contacts) feature cases. We will show that this CDU contributor is one of the main differentiators between well-known ArFi and new EUV CDU budgeting principles. We found that reticle contribution to intrafield CDU should be characterized in a specific way: mask absorber thickness fingerprints play a role comparable with reticle CDU in the total reticle part of the CDU budget. Wafer CD fingerprints, introduced by this contributor, may or may not compensate variations of mask CDs and hence influence on total mask impact on intrafield CDU at the wafer level. This will be shown on 1D and 2D feature examples. Mask stack reflectivity variations should also be taken into account: these fingerprints have visible impact on intrafield CDs at the wafer level and should be considered as another contributor to the reticle part of EUV CDU budget. We also observed mask error enhancement factor (MEEF) through field fingerprints in the studied EUV cases. Variations of MEEF may play a role towards the total intrafield CDU and may need to be taken into account for EUV lithography. We characterized MEEF-through-field for the reviewed features, with results herein, but further analysis of this phenomenon is required. This comprehensive approach to quantifying the mask part of the overall EUV CDU contribution helps deliver an accurate and integral CDU BB per product/process and litho tool. The better understanding of the entire CDU budget for advanced EUVL nodes achieved by Samsung and ASML helps extend the limits of Moore’s Law and to deliver successful implementation of smaller, faster and smarter chips in semiconductor industry.

An overview of extreme ultraviolet lithography (EUVL) mask etch is presented and a EUVL mask etch study was carried out. Today, EUVL implementation has three critical challenges that hinder its adoption: extreme ultraviolet (EUV) source power, resist resolution-line width roughness-sensitivity, and a qualified EUVL mask. The EUVL mask defect challenges result from defects generated during blank preparation, absorber and multilayer deposition processes, as well as patterning, etching and wet clean processes. Stringent control on several performance criteria including critical dimension (CD) uniformity, etch bias, micro-loading, profile control, defect control, and high etch selectivity requirement to capping layer is required during the resist pattern duplication on the underlying absorber layer. EUVL mask absorbers comprise of mainly tantalum-based materials rather than chrome- or MoSi-based materials used in standard optical masks. Compared to the conventional chrome-based absorbers and phase shift materials, tantalum-based absorbers need high ion energy to obtain moderate etch rates. However, high ion energy may lower resist selectivity, and could introduce defects. Current EUVL mask consists of an anti-reflective layer on top of the bulk absorber. Recent studies indicate that a native oxide layer would suffice as an anti-reflective coating layer during the electron beam inspection. The absorber thickness and the material properties are optimized based on optical density targets for the mask as well as electromagnetic field effects and optics requirements of the patterning tools. EUVL mask etch processes are modified according to the structure of the absorber, its material, and thickness. However, etch product volatility is the fundamental requirement. Overlapping lithographic exposure near chip border may require etching through the multilayer, resulting in challenges in profile control and etch selectivity. Optical proximity correction is applied to further enhance the resolution. Other resolution enhancement techniques, such as phase shifting, are also in consideration for EUVL. Phase-shifting will involve partial etching of the multilayer. The trend to use shorter EUV wavelength (e.g., 6.7 nm) for enhancing resolution will use new multilayer and absorber compositions, and will require new etch process development efforts. TaBO/TaBN absorber layers (features down to 40 nm) were etched with vertical profiles, low etch CD bias, and 1.7 nm etch CD uniformity (3σ ). In the light shed application, Mo/Si multilayer etching yielded vertical profiles and high etch selectivity.

We have improved flatness and defects on an extreme ultraviolet (EUV) blank, which are critical issues for implementing EUV lithography. A high flatness of less than 30 nm on a glass substrate and low defects over 22 nm sphere-equivalent-volume-diameter (SEVD) on a multilayer (ML) blank are required for 22 nm half-pitch process. Flatness quality was improved to an average of around 50 nm and 30 nm as best, through more precise polishing process. Defect quality of single digit over 60 nm was achieved by improvement of fabrication process. New defect inspection was started for further defect reduction using a Teron Phasur. It was confirmed that there are lots of real phase defects with low height of less than 2 nm on a ML blank captured by the Teron. Small defects over 25 nm SEVD have been dramatically reduced to 20 defects mainly by various improvements of fabrication processes. A gap in flatness and defects between actual quality and the requirement is getting small, and both the qualities will be improved further for near future production.

In order to improve its structural sensitivity, a vibratory microgyroscope is commonly sealed in high vacuum to increase the drive mode quality factor. The sense mode quality factor of the microgyroscope will also increase simultaneously after vacuum sealing, which will lead to a long decay time of free response and even self-oscillation of the sense mode. As a result, the mechanical performance of the microgyroscope will be seriously degraded. In order to solve this problem, a closed-loop control technique is presented to adjust and optimize the sense mode quality factor. A velocity feedback loop was designed to increase the electric damping of the sense mode vibration. A circuit was fabricated based on this technique, and experimental results indicate that the sense mode quality factor of the microgyroscope was adjusted from 8052 to 428. The decay time of the sense mode free response was shortened from 3 to 0.5 s, and the vibration-rejecting ability of the microgyroscope was improved obviously without sensitivity degradation.

Edge-lit light guide panels (LGPs) with micropatterned surfaces represent a new technology for developing small- and medium-sized illumination sources for application such as automotive, residential lighting, and advertising displays. The shape, density, and spatial distribution of the micro-optical structures (MOSs) imprinted on the transparent LGP must be selected to achieve high brightness and uniform luminance over the active surface. We examine how round-tip cylindrical MOSs fabricated by precision micromilling can be used to create patterned surfaces on low-cost transparent polymethyl-methacrylate substrates for high-intensity illumination applications. The impact of varying the number, pitch, spatial distribution, and depth of the optical microstructures on lighting performance is initially investigated using LightTools™ simulation software. To illustrate the microfabrication process, several 100×100×6 mm³ LGP prototypes are constructed and tested. The prototypes include an “optimized” array of MOSs that exhibit near-uniform illumination (approximately 89%) across its active light-emitting surface. Although the average illumination was 7.3% less than the value predicted from numerical simulation, it demonstrates how LGPs can be created using micromilling operations. Customized MOS arrays with a bright rectangular pattern near the center of the panel and a sequence of MOSs that illuminate a predefined logo are also presented.

One of the main challenges for developing extreme ultraviolet resists is to satisfy critical dimension uniformity (CDU) and sidewall roughness of contacts to the allowable limit. To this end, further understanding of the effects of resist ingredients on CDU and contact edge roughness (CER) is required. We investigate the effects of a photoacid generator (PAG), sensitizer and quencher concentrations on the CDU and CER. We find that the dependencies of CDU on sensitizer and quencher are dominated by photon shot noise (PSN) effects whereas a more complicated interplay between PSN and PAG distribution statistics should be considered in the dependence of CDU on PAG concentration. The estimated CER parameters [root mean square (RMS) value and correlation length ξ ] exhibit a merging trend when plotted against the final critical dimension (CD). In addition, RMS value increases with exposure dose and PAG loading contrary to shot noise expectations. Power spectrum analysis reveals the dominant contribution of low-frequency undulations to CER, which is attributed to the enhanced interaction along specific directions between the aerial image and/or acid kinetics of nearby contacts. This inter-contact effect is further intensified with CD for fixed pitch and may explain the observed CER behavior.

A continuous cellular automaton (CCA) is presented for the simulation of anisotropic wet chemical etching in the fabrication of microstructures. Based on the step-flow model, the surface atoms are divided into categories according to the atom configurations on different crystal planes. An analytical solution for the dependence of the etch rate on orientation is derived, and the CCA approach makes a direct conversion of experimental macroscopic rates into calibrated microscopic parameters for realistic and reliable simulations. The presented model has been extended to a simulation system based on a CCA method. Linear search and variable time stepping are used to simulate a silicon wafer in various etching condition and mask shapes. The simulation results agree well with the experiments. This improved CCA makes possible for the realization of accurate simulations of anisotropic etching in engineering applications.

Free volume theory and a model of polymerization kinetics are introduced to predict and analyze the curing shrinkage and kinetic parameters of an acrylate-based ultraviolet-embossing resist. Curing shrinkage tests have been designed and performed to verify the accuracy of the model. The experimental results are in good agreement with the simulated results of the conversion behavior. The reaction coefficients of polymerization predicted by this model are essentially correct when compared to the classical experimental values. Moreover, the dynamic shrinkage during polymerization determined experimentally matches the simulated result predicted by our model.

Recent developments in electrospray ionization mass spectrometry (ESI-MS) show that air amplifiers can be utilized to significantly enhance droplet desolvation and to focus gas-phase ions when provided between an electrospray (ES) source and the mass spectrometer (MS). However, these devices are bulky and expensive, which may be a factor prohibiting their broader utilization. We have developed a simple but effective method based on Bernoulli’s principle, the Coanda effect and MEMS processing to focus electrosprayed droplets and liberated gas-phase ions. We demonstrate a computer simulation and fabrication process for a micromachined air amplifier. The simulation results are used to optimize the geometry and to meet performance requirements. The optimized results then provide a design guideline for the device’s fabrication. The air amplifier is formed from two bonded polydimethylsiloxane (PDMS) casts. Each PDMS cast is fabricated through a molding process using a micromachined two-layer SU-8 mold. Experimental results show a 30-fold improvement in the ES current for certain operation conditions while the air amplifier is incorporated in the nano-electrospray ionization (nano-ESI) process. Compared with traditional air amplifiers, the micro-electro-mechanical systems (MEMS) based air amplifier provides good performance while keeping the fabrication process simple and cost effective.

Wafer chucks are used in advanced lithography systems to hold and flatten wafers during exposure. To minimize defocus and overlay errors, it is important that the chuck provide sufficient pressure to completely chuck the wafer and remove flatness variations across a broad range of spatial wavelengths. Analytical and finite element models of the clamping process are presented here to understand the range of wafer geometry features that can be fully chucked with different clamping pressures. The analytical model provides a simple relationship to determine the maximum feature amplitude that can be chucked as a function of spatial wavelength and chucking pressure. Three-dimensional finite element simulations are used to examine the chucking of wafers with various geometries, including cases with simulated and measured shapes. The analytical and finite element results both demonstrate that geometry variations with short spatial wavelengths (e.g., high-frequency wafer shape features) present the greatest challenge to achieving complete chucking. The models and results presented here can be used to provide guidance on wafer geometry and chuck designs for advanced exposure tools.

For extreme ultraviolet lithography (EUVL), the fabrication of defect free multi-layered (ML) mask blanks is a challenge. ML defects are generated by substrate defects and adders during ML coating and are called phase defects (PDs). If we can accept ML blanks with a certain number of PDs, the blank yield will be drastically increased. We can use fewer PD blanks and reduce PD influence by covering them with an absorber layer. To do this, PDs should be located during ML blank defect inspection before absorber patterning. To locate PDs on blanks accurately and precisely, the fiducial marks (FMs) on ML blanks can be used for mask alignment. The defect location accuracy requirement is below 10 nm. We present the results of a feasibility study on the requirements of FMs on EUVL masking by simulations and experiments to establish a PD mitigation method with the EUV actinic blank inspection tool. Based on the results, the optimum ranges for FM lines etched into the ML are 3 to 5 μm in width and at least 100 nm in depth.

Critical dimension atomic force microscopy (CD-AFM) is a widely used reference metrology technique. To characterize modern semiconductor devices, small and flexible probes, often 15 to 20 nm in diameter, are used. Recent studies have reported uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements. To understand the source of these variations, tip-sample interactions between high aspect ratio features and small flexible probes, and their influence on measurement bias, should be carefully studied. Using theoretical and experimental procedures, one-dimensional (1-D) and two-dimensional (2-D) models of cylindrical probe bending relevant to carbon nanotube (CNT) AFM probes were developed and tested. An earlier 1-D bending model was refined, and a new 2-D distributed force (DF) model was developed. Contributions from several factors were considered, including: probe misalignment, CNT tip apex diameter variation, probe bending before snapping, and distributed van der Waals-London force. A method for extracting Hamaker probe-surface interaction energy from experimental probe-bending data was developed. Comparison of the new 2-D model with 1-D single point force (SPF) model revealed a difference of about 28% in probe bending. A simple linear relation between biases predicted by the 1-D SPF and 2-D DF models was found. The results suggest that probe bending can be on the order of several nanometers and can partially explain the observed CD-AFM probe-to-probe variation. New 2-D and three-dimensional CD-AFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

Thermally induced void growth in Cu filled through-silicon vias (TSV) has been studied for reliability purposes with x-ray microscopy and finite element model (FEM). A laboratory-based x-ray microscopy combined with computational tomography imaging is demonstrated to have advantages over other methods of inspecting TSVs. We show that the 8-keV x-rays used by Nano X-ray Computed Tomography (NanoXCT™) are capable of imaging voids inside filled vias before and after annealing without cross-sectioning the TSV. A series of TSV arrays filled conformally and from the bottom up were inspected by the x-ray microscope before and after annealing. Pre-existing voids in the seamline were observed in conformally filled TSVs before annealing, while bottom up-filled TSVs do not have a seamline or voids. The same TSV samples were repeatedly annealed at 200, 225, 250 and 300°C. X-ray micrographs after annealing reveal TSVs with pre-existing voids are prone to void growth. In addition, x-ray measurements show the total volume of void growth increased with annealing temperature. A steady-state FEM was developed to understand the void growth phenomenon. FEM suggests high concentrations of vacancies occurring at the pre-existing void area cause void growth.

A 20-MHz switching high-speed light-modulating device for three-dimensional (3-D) image capturing and its system prototype are presented. For 3-D image capturing, the system utilizes a time-of-flight (TOF) principle by means of a 20-MHz high-speed micromachined electro-absorptive modulator, the so-called optical shutter. The high-speed modulation is obtained by utilizing the electro-absorption mechanism of the multilayer structure, which has an optical resonance cavity and light-absorption epilayers grown by metal organic chemical vapor deposition process. The optical shutter device is specially designed to have small resistor–capacitor–time constant to get the high-speed modulation. The optical shutter is positioned in front of a standard high-resolution complementary metal oxide semiconductor image sensor. The optical shutter modulates the incoming infrared image to acquire the depth image. The suggested novel optical shutter device enables capturing of a full high resolution-depth image, which has been limited to video graphics array (VGA) by previous depth-capturing technologies. The suggested 3-D image sensing device can have a crucial impact on 3-D–related business such as 3-D cameras, gesture recognition, user interfaces, and 3-D displays. This paper presents micro-opto-electro-mechanical systems-based optical shutter design, fabrication, characterization, 3-D camera system prototype, and image evaluation.

We present tunable lenses based on aluminum nitride membranes. The achievable tuning range in the refractive power is 0 to 25 dpt with an external pressure load of ≤20  kPa . The lenses are manufactured using MOEMS technology. For 500-nm-thick membranes with a diameter of 3 mm, a spherical deflection profile is found. The system provides good long-term stability showing no creep or hysteresis. A model for the refractive power versus applied pressure is derived and validated experimentally. Based on this model, design guidelines are discussed. One essential parameter is the residual stress of the aluminum nitride layer that can be controlled during deposition.

According to an International Technology Roadmap for Semiconductors (ITRS-2012) update, the sensitivity requirement for an extreme ultraviolet (EUV) mask pattern inspection system is to be less than 18 nm for half pitch (hp) 16-nm node devices. The inspection sensitivity of extrusion and intrusion defects on hp 64-nm line-and-space patterned EUV mask were investigated using simulated projection electron microscope (PEM) images. The obtained defect images showed that the optimization of current density and image processing techniques were essential for the detection of defects. Extrusion and intrusion defects 16 nm in size were detected on images formed by 3000 electrons per pixel. The landing energy also greatly influenced the defect detection efficiency. These influences were different for extrusion and intrusion defects. These results were in good agreement with experimentally obtained yield curves of the mask materials and the elevation angles of the defects. These results suggest that the PEM technique has a potential to detect 16-nm size defects on an hp 64-nm patterned EUV mask.

Low-k ₁ lithography results in features that suffer from poor lithographic yield in the presence of process variation. The problem is especially pronounced for lower-level metals used for local routing, where bi-directionality and tight pitches give rise to lithography unfriendly layout patterns. However, there exists inherent unutilized flexibility in design shapes, e.g., one can modify such wires without significantly affecting design behavior. We develop two different techniques to simultaneously modify mask and design shapes during optical proximity correction (OPC) to improve lithographic yield of low-level metal layers. The methods utilize image slope information, which is available during OPC image simulations at no extra cost, as a measure of lithographic process window. We first propose a method that identifies fragments with low normalized image log slope (NILS) and then use this NILS information to guide dynamic target modification between iterations of OPC. The method uses a pre-characterized lookup table to assign a different magnitude of local target correction to different NILS bins. Next we develop an optimization flow where we derive a cost function that maximizes both contour fidelity and robustness to drive our simultaneous mask and target optimization (SMATO) method. We develop analytical equations to predict the cost for a given mask and target modification and use a fast algorithm to minimize this cost function to obtain an optimal mask and target solution. Our experiments on sample 1× (M1) layouts show that the use of SMATO reduces the process manufacturability index (PMI) by 15.4% compared with OPC, which further leads to 69% reduction in the number of layout hotspots. Additionally, such improvement is obtained at low average runtime overhead (5.5%). Compared with process window optical proximity correction (PWOPC), we observe 4.6% improvement in PMI at large (2.6× ) improvement in runtime.

We report on the light confinement effect observed in nonideally shaped (i.e., nonspherical) nanoscale solid immersion lenses (SIL). To investigate this effect, nanostructures of various shapes are fabricated by electron-beam lithography. When completely melted in reflow, these noncircular pillars become spherical, while incomplete melting results in nonspherically shaped SILs. Optical characterization shows that nonideal SILs exhibit a spot size reduction comparable with that of spherical SILs. When the size of the SIL is of wavelength scale or smaller, aberrations are negligible due to the short optical path length. This insensitivity to minor variations in the shape implies a large tolerance in nano-SIL fabrication.

A low-hysteresis voltage and high-sensing linearity chloride ion-sensitive sensor based on an extended gate field-effect transistor (EGFET) for real-time water quality monitoring microsystem applications is presented. All of the EGFET-manufacturing processes adopted in this work are compatible with standard integrated circuits planar technology, and therefore, they are very suitable for the mass production. Two EGFET-based chloride ion-sensitive microsensors having same channel width/length ratio (1000  μm/10  μm ) but with different channel geometries (rectangular and annular types) are presented. At pCl 3 (log[Cl⁻ ]=−3 ) test point, a very small hysteresis voltage of the rectangular- and annular-channels EGFET-based Cl⁻ microsensors (5 and 7 mV, respectively) can be achieved. As the concentrations tested ranging from pCl 1 (log[Cl − ]=−1 ) to pCl 5 (log[Cl ⁻ ]=−5 ), a very high-sensing linearity (99.23% and 99.08%) of the two types of EGFET-based Cl ⁻ microsensors is achieved. However, the sensitivity of the rectangular-channel EGFET-based Cl − microsensor (45  mV/pCl ) is much higher than that of the annular-channel EGFET-based Cl⁻ microsensor (37  mV/pCl ). The selectivity coefficient of the investigated EGFET-chloride ion sensor under four different interfering ions (OH ⁻ , F⁻ , SO 2− 4 , and Br ⁻ ) are also measured and analyzed.

This article [J. Micro/Nanolith. MEMS MOEMS. 11, (3 ), 033010 (2012)] was originally published online on 21 September 2012 with an error on page 6 in the Discussion section.