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Flexible electrodes with high conductivity and mechanical properties play an important role in many essential electronic devices. Herein, we report the fabrication of flexible and conductive PDMS/AgNWs/CFs thin film by using a simple inverted layer-by-layer deposition method. In this structure, conductive carbon fiber (CF) networks embedding in the elastic polymers will help improve the ability to resist deformation of pure polydimethylsiloxane (PDMS) film. Elongated silver nanowires (AgNWs) wrapping on bare CFs can greatly increase the active surface area, improve the electron transfer of CFs, and reduce the contact resistance between the adjacent CFs. As a result, a flexible PDMS/AgNWs/CFs thin film with a low sheet resistance of 0.99 Ω/□ was obtained. The fabricated PDMS/AgNWs/CFs thin film showed great mechanical flexibility with less than 3% decrease in resistance after 275 continuous bending and releasing processes. Moreover, an induced reduced graphene oxide (rGO) layer on the AgNWs wrapped CF networks increases the active surface area. Physical and electrochemical characterization of the fabricated PDMS/AgNWs/CFs and PDMS/AgNWs/rGO/CFs thin film electrodes have been measured. The tightly attached AgNWs and well-coated rGO materials improved high surface area and provided benefit for fast accessibility of electrolyte ions into the microporous structures, indicating the considerable potential for use in flexible supercapacitor applications.

Microfabrication technology in the biomedical field has provided microelectrode arrays for neural implants with new development opportunities. The need for more complex physiological functions and miniaturization, as well as the use of new materials for more flexible electrodes, can now be satisfied. PDMS (Polydimethylsiloxane) substrates are elastic, biocompatible and permeable to oxygen, in addition to being a highly stable material. However, the implementation of microfabrication techniques such as deposition and patterning processes on these new substrates is not straightforward. This paper will describe the development of a reliable method to metalize thin film microelectrodes on a highly flexible medical grade PDMS layer that is suitable for long-term implantation. Platinum (Pt) microelectrodes were deposited by physical vapor deposition and pattern transfer by lift-off was chosen. Standard photolithography was used to pattern a conventional positive photoresist and was optimized to improve adhesion and to avoid cracks in the resist. The electrical behavior of the metal-polymer interface was analyzed using multiplexed DC measurements. The resistance values of seven samples and a control were acquired sequentially. Special attention was paid to the connectorization from the flexible microelectrodes to a rigid substrate. Measurements were carried out in an air-protected environment as well as in a biological environment designed to mimic the environment of the human body. Long-term stability of the Pt-PDMS interface was strongly influenced by the electrode configuration and its connection. A characteristic electrical behavior was observed for a straight-electrode configuration. This configuration demonstrated significant drift of resistance values of more than 4% during the initial 56 h. By contrast, a stable behavior was observed for a loop electrode design, with only small variations of less than ± 0.5% caused by thermal fluctuations.

Thin film oxides have attracted attention in implementations of gas sensors, notably NO 2 , owing to their unique physical, optical, and chemical properties. While the properties are presumed to be strongly dependent on the surface conditions of the thin films, it is not yet clear how surface properties of the thin film gas sensor affect its analyte sensing response. Here, we report the influence of surface carbon contamination and roughness on the NO 2 sensing properties of TiO 2 thin film sensors. The TiO 2 thin films were prepared by rf-sputtering. The surface of the films were intentionally contaminated and damaged with organic polymers (photolithography resist) and microwave plasma, respectively. The surface chemistry of the films was assessed by high resolution X-ray photoelectron spectroscopy, and atomic force microscopy was exploited to obtain the morphology of the fabricated sensors. The work aims to improve the long-term efficacy of gas sensors by studying the reasons for degradation in performance. Our results indicate that the carbon residue and surface roughness of the TiO 2 based sensor prolong the NO 2 response time by roughly threefold and fivefold, respectively. The recovery rate of the sensor is deteriorated by the poor surface conditions as well.

Metal thin films are used as major components in microelectromechanical systems (MEMS). However, problems with long-term reliability that set limits on the lifetime of MEMS applications have been observed. The more efficiently the thin films resist stress relaxation, the longer the lifetime of the MEMS device. In particular, Al thin films have been used as capacitance switches, but are shown to have a low resistance to stress relaxation, thus hindering overall performance and leading to shorter lifetime. Using bulge testing, this study investigates the viscoelastic behavior of pure Al thin film in comparison with thin Al alloy films with 12% and 16% Mg. The results show that the addition of Mg to Al films significantly decreases the relaxation behavior and increases the strengthening mechanism of such thin films. The greater the Mg content in an Al film, the greater the resistance of the film. The normalized modulus decreases less with a greater Mg content. Al–Mg thin films have better relaxation resistance than pure Al thin films and thus serve as a better material for MEMS capacitance switches.

We describe a technique for photo-patterning polymethyl methacrylate (PMMA) resist films that does not use a wet development step. 254 nm deep ultraviolet radiation from an ordinary mercury discharge lamp was used to both chain scission and remove PMMA in a single step lithographic process. PMMA films several microns thick can be patterned through this technique. The patterned film can also be directly used as a structure, by itself, for applications in microfluidics etc. Our process relies on a synergistic effect that greatly accelerates the loss of PMMA when it is simultaneously heated close to its glass transition temperature and irradiated with 254 nm radiation. Furthermore, we also describe a secondary exposure effect in this process that originates from electrons that are generated through a photoelectric effect at the PMMA-substrate interface. This gives rise to a proximity effect analogous to that encountered in conventional electron beam lithography.

The resistivity of epitaxial Cu nanolines with line width ranging from 20 to 180 nm and line height from 40 to 50 nm was measured using a four-point probe technique. The Cu nanolines were fabricated using ebeam lithography with a polymethyl methacrylate bilayer resist system for improved line edge smoothness. The cross-section profile of the lines was examined using the focused ion beam milling technique. The results indicate that the cross-section should be more accurately described as trapezoidal rather than as rectangular. Using the trapezoidal profile, the electrical resistivity was calculated from the measured resistance data. Modeling based on the Fuchs–Sondheimer (FS) theory using the trapezoidal profile was also carried out. The results were compared with the experimentally calculated resistivity data. For Cu lines with line width less than 30 nm, the measured resistivity was shown to be up to 20% higher than the value predicted by the FS theory. Further examination of Cu lines using atomic force microscopy and scanning electron microscopy was conducted to extract the surface roughness and line edge roughness information. Their contribution to the resistivity increase was estimated to be only up to 3% for the Cu nanolines fabricated, which did not significantly contribute to the overall resistivity for Cu lines with line width less than 30 nm. Other possible factors affecting the resistivity of the Cu nanolines were also discussed, including the oxide formation on the surface of the Cu lines.

A lift-off process using a bi-layer resist consisting of an image reversal resist on top and a lift-off resist at the bottom was used to structure Ti–Pt thin films. DC magnetron sputtered metal films patterned by this process show ultra smooth edges, ideal for applications such as interdigitated electrodes in resistive gas sensors including thin-film based sensitive coatings with thicknesses below 100 nm. Profiles of processed structures were analyzed by scanning electron microscopy and surface profilometer. The thickness profile and structure width were controlled by using different resist thicknesses and undercut lengths. Results were compared with iterative simulations by a geometric shadowing model, predicting undersputtering length and profile structure of the experimentally manufactured samples in good agreement. Target-to-substrate distance variation was found to have only a minor influence on the sputtering result.

In semiconductor and Micro-Electro-Mechanical Systems production, thick resist films are indispensable for circuit formation, chemical mechanical planarization, or wafer-level packaging applications. We investigate multiple metrology protocols that aim at meeting the needs for fast, accurate, full-wafer determination of the thickness of up to 100 μm thick resist layers deposited on silicon or glass wafers. We found very effective to use a two-step strategy consisting of: i/ an accurate determination of the optical characteristics of the photoresist based on prism-coupling technique, and ii/ the fast, full-wafer measurement of the wafers of interest, using high-resolution spectroscopic reflectometry (SR). The robustness of this strategy increased when analyzing the SR data with a Fourier transform (FT) based algorithm which combines FT-based filtering around the thickness of interest with spectral matching to improve measurement performance.

Nanostructured sol–gel films with high-temperature stability are used in the area of electronics, photonics or biomimetic materials as light-trapping architectures in solar cells, displays, waveguides or as superhydrophobic surfaces with a lotus effect. In this work, high-temperature stable 2-μm nanostructured surfaces were prepared by ultraviolet-based nanoimprint lithography using an alkoxysilane binder incorporating modified silica nanoparticles. Material densification during thermal curing and microstructural evolution which are destined for a high structural fidelity of nanostructured films were investigated in relation to precursor chemistry, particle morphology and particle content of the imprint resist. The mechanism for densification and shrinkage of the films was clarified and correlated with the structural fidelity to explain the influence of the geometrical design on the optical properties. A high internal coherence of the microstructure of the nanostructured films results in a critical film thickness of > 5 μm. The structured glassy layers with high inorganic content show thermal stability up to 800 °C and have a high structural fidelity > 90% with an axial shrinkage of 16% and a horizontal shrinkage of 1%. This material allows the realization of highly effective light-trapping architectures for polycrystalline silicon thin-film solar cells on glass but also for the preparation of 2D photonic crystals for telecommunication wavelengths.

This paper discusses the removal of chemically amplified negative-tone i-line resist SU-8 using hydrogen radicals generated by the catalytic decomposition of H2 molecules in H2/N2 mixed gas (H2:N2 = 10:90 vol.%) using a tungsten hot-wire catalyzer. SU-8 resists with exposure doses from 7 to 280 mJ/cm2 were removed by hydrogen radicals, although the SU-8 removal rate was independent of the exposure dose. The SU-8 removal rate increased with both substrate and catalyzer temperature, in addition to a decrease in the distance between the catalyzer and substrate. A high removal rate for cross-linked SU-8 with an exposure dose of 14 mJ/cm2 of approximately 4 μm/min was achieved with a catalyzer to substrate distance of 20 mm, and catalyzer and initial substrate temperatures of 2400 and 165 °C, respectively.

This paper describes a technique for fabricating submicron nickel (Ni) structures on flexible metal substrate. Conventional photolithography and electroplating technique s are used for simple and cost-effective fabrication of size-tunable Ni nanostructures. In the photolithography process, to separate the substrate and metal layer, a residual layer was intentionally preserved when patterning the thick photoresist layer. Then, the Ni seed layer was deposited on the photoresist pattern. By applying pulse electroplating to the seed layer, a Ni metal layer was formed on the seed layer. As a result, a nanopatterned Ni metal sheet was easily obtained using the photoresist strip process. Then, the Ni nanopattern was transferred onto a flexible polycarbonate substrate. In addition, various energy-controlled exposures of the resist were demonstrated for fabricating size-tunable Ni nanostructures , by simply removing the intentionally induced residual layer of the resist pattern. This research is adaptable for the fabrication of various sensor applications and energy storage devices.

Metal micro- and nanostructures for optical and electronic applications are typically fabricated by means of interferometric optical or electron-beam lithographies using conventional photo- or electron-beam resists. In this work, we report on fabrication of periodic nanostructures of gold by exploiting photoinduced surface-relief gratings in an azobenzene-functionalized polymer film as masks for reactive ion etching of the metal. The proposed technique provides a convenient, fast and flexible alternative to photoresist-based lithography for fabricating metal nanostructures of large surface area. Owing to the fact that the azo-polymer is sensitive to the polarization rather than the intensity modulation of the exposing light, the technique is particularly suitable for patterning highly reflective surfaces.

The fabrication of high aspect ratio silicon trenches (critical dimension < 100 nm, aspect ratio > 10:1) by dry etch processing has proven to be a challenge mainly due to limited etch selectivity of conventional hardmask materials to Si. Moreover, for future technology nodes the hardmask thickness will be limited by the thickness of the photoresist. This work focuses on a concept to enable the usage of very thin resist layers (< 100 nm) for patterning of silicon trenches by the integration of an unconventional hardmask stack consisting of SiO2 and ZrO2. Deposition of such material films has been investigated, as well as e-beam lithography exposure and finally pattern transfer by dry etching. Using this hardmask stack and 100 nm thin resist, the fabrication of 35 nm wide trenches with an aspect ratio of ~ 20:1 is demonstrated revealing a very high selectivity (> 100:1) of the ZrO2 layer to Si during the deep silicon etch. A silicon etch rate > 1.5 µm/min was achieved. The ZrO2 layer itself provides the main selectivity improvements of the final hardmask stack.

The effects of CH 2 F 2 and N 2 gas flow rates on the etch selectivity of silicon nitride (Si 3 N 4 ) layers to extreme ultra-violet (EUV) resist and the variation of the line edge roughness (LER) of the EUV resist and Si 3 N 4 pattern were investigated during etching of a Si 3 N 4 /EUV resist structure in dual-frequency superimposed CH 2 F 2 /N 2 /Ar capacitive coupled plasmas (DFS-CCP). The flow rates of CH 2 F 2 and N 2 gases played a critical role in determining the process window for ultra-high etch selectivity of Si 3 N 4 /EUV resist due to disproportionate changes in the degree of polymerization on the Si 3 N 4 and EUV resist surfaces. Increasing the CH 2 F 2 flow rate resulted in a smaller steady state CH x F y thickness on the Si 3 N 4 and, in turn, enhanced the Si 3 N 4 etch rate due to enhanced SiF 4 formation, while a CH x F y layer was deposited on the EUV resist surface protecting the resist under certain N 2 flow conditions. The LER values of the etched resist tended to increase at higher CH 2 F 2 flow rates compared to the lower CH 2 F 2 flow rates that resulted from the increased degree of polymerization.

We removed B-, P-, and As-ion-implanted positive-tone novolak resists with an implantation dose of 5 × 1012 to 5 × 1015 atoms/cm2 at 70 keV, using atomic hydrogen. Though the removal rate decreased with increase in the implantation dose, all of the ion-implanted resists were removed. The rates of thickness of the surface-hardened layer/all resist layer of B, P, and As implanted resists were 0.38, 0.26, and 0.16, respectively, by SEM observation. The removal rate decreased with increasing the rate of the surface-hardened layer. The energy supplied from the ions to the resist concentrated on the surface side in the increasing order of B-P-As.

Meshed silver/titanium films, deposited on a 1737 Corning glass substrate by radiofrequency (r.f.) magnetron sputtering and etched by wet process, have been studied. Sputtering parameters have been specifically optimized for thick Ag layer deposition (> 3 μm) and are discussed. An original excimer laser etching process is used for removing the resist for making the prototypes. Simple sheet resistance and optical transparency computings have been used for the theoretical study. A good agreement is obtained with the experimental results. Transparent and conducting samples have been realized with optical transmittances and sheet resistances ranging from 71% to 81% and from 0.023 Ω/□ to 1.03 Ω/□, respectively. Hence we demonstrate the independence between optical transparency and sheet resistance for this material AgGL (Ag Grid Layer). The relevance of the mesh structure has been highlighted by the achievement of samples with high level of transparencies and ultra-low sheet resistances.

High performance nanometer NiSi2-Si Schottky barrier diode arrays (SBDA) with various isolation designs, including poly Si gate (PSG) and resist protection oxide (RPO), are developed for advanced radio frequency applications. Radio frequency performances of these developed SBDAs are investigated and compared to that with the conventional shallow trench isolation. All of the SBDAs are fabricated with a foundry state-of-the -art 45 nm complementary metal oxide semiconductor technology. Both of PSG and RPO insulated SBDAs have higher cutoff frequency and a simpler preparation process. Specifically, the PSG insulted SBDA could achieve a cutoff frequency of up to 4.6 THz.

A technique of using commercial polymers and additive to fabricate the modified fluoropolymer molds for ultraviolet nanoimprint is proposed, which is based on direct replicating of the electronic beam lithography resist patterns by cast molding process. A small amount of the added additive can increase the oleophobic behavior of the fluoropolymer, and so to reduce its surface energy remarkably. The cast-molded modified fluoropolymer molds (CMF-mold) not only satisfy the rigidity requirement for replicating very fine features and are solvent resistant but also possess low surface energy by themselves and are inexpensive and easy to fabricate. Using the CMF-mold, both complex letters with 100 nm linewidth and dense lines with 80 nm linewidth /space can be reproduced into the ultraviolet resist conveniently. Moreover, in our experiment, the modified fluoropolymer mold has shown its replicating competence for fabricating high-aspect-ratio sub-30 nm structures.

Polymer films are widely used as a substrate for displays and for solar cells since they are cheap, transparent and flexible, and their material properties are easy to design. Polyethylene-terephthalate (PET) is especially useful for various applications requiring transparency, flexibility and good thermal and chemical resistance. In this study, nano-sized metal patterns were fabricated on flexible PET film by using nanoimprint lithography (NIL). Water-soluble poly-vinyl alcohol (PVA) resin was used as a planarization and sacrificial layer for the lift-off process, as it does not damage the PET films and can easily be etched off by using oxygen plasma. NIL was used to fabricate the nano-sized patterns on the non-planar or flexible substrate. Finally, a nano-sized metal pattern was successfully formed by depositing the metal layer over the imprinted resist patterns and applying the lift-off process, which is economic and environmentally friendly, to the PET films.

In this study the etch development of high aspect ratio vias in Si for the fabrication of Cu nails is described. To enable subsequent metallisation, these vias need to meet strict requirements with respect to uniformity, slope, sidewall roughness and undercut. For aspect ratios up to 5 a SiO2 hard mask based SF6/O2 etch approach is used. For aspect ratios up to 10, a resist based passivation polymer type etch approach with C4F8/SF6 was used to successfully pattern vias in Si. Typical problems of this process and optimization to overcome the issues are described.

Challenges, new and old, are outlined for etching at the 45 nm technology node and below. The over-riding challenges pertain to improving selectivity over a wider range of materials and topographies and predicting pattern density behavior to reduce cost in mask design.

We investigated a new method to form the line-and-space patterns with a nanometer-scale using the conventional optical lithography technique and the metal deposition/liftoff process. The ashing of the negative photo resist defined by the conventional optical lithography technique results in the proper profiles including a high aspect ratio (i.e., height/width value of the patterns) for the formation of nanometer-scale structures. We demonstrated that the metal electrodes with the nanometer-scale gap of 20 nm or less can be easily obtained by the newly proposed method without employing the highly sophisticated lithography tools including an electron beam lithography.

The ULSI technology has been following Moore's law into the sub-100 nm era, although several challenging technical issues must be resolved. This paper describes possible application of Cat-CVD for ULSI technology beyond the 45 nm node. Especially, Cat-CVD SiN film for a transistor gate sidewall and/or a pre-metallic liner layer, and removal of photo resist (ash) by Cat-induced hydrogen atoms in the interconnect structure with an extreme low-k material are mainly discussed.

A universal microstructuring approach was developed, which facilitates the patterning of surfaces by a combination of microcontact printing (mCP) and selective surface dewetting/wetting. Self-assembled monolayers (SAMs) were patterned on glass or silicon substrates by μCP. The regions coated by the SAMs turn hydrophobic, whereas the uncoated regions stay hydrophilic. Such functionalized surfaces facilitate selective deposition of polymers or resists. Polymethyl methacrylate and prepolymer polyurethane were selectively deposited on the hydrophilic regions of the substrate. The hydrophobic regions of the substrate stay uncoated. Subsequently, the resist was used to lift-off metallic microstructures in order to realize micro coils and electrodes for radio frequency information tags. The printed electrodes were used to define drain and source contacts of organic thin film transistors. The device characteristic of the organic transistors will be presented.

Bottom gate microcrystalline silicon thin film transistors (μc-Si TFT) have been realized with two types of films: μc-Si(1) and μc-Si(2) with crystalline fraction of 80% and close to 100% respectively. On these TFTs we applied two types of passivation (SiN x and resist). μc-Si TFTs with resist as a passivation layer present a low leakage current of about 2.10 − 12 A for V G = − 10 and V D = 0.1V an ON to OFF current ratio of 10 6 , a threshold voltage of 7 V, a linear mobility of 0.1 cm 2 /V s, and a sub-threshold voltage of 0.9 V/dec. Microcrystalline silicon TFTs with SiN x as a passivation present a new phenomenon: a parasitic current for negative gate voltage (− 15 V) causes a bump and changes the shape of the sub-threshold region. This excess current can be explained by and oxygen contamination at the back interface.

A disadvantage of ICP type plasma etching method compared with CCP one is low selectivity to photo resist. So a novel etching method was developed to obtain high selectivity to photo resist by incorporating a sputtering method, in which a target was placed on the opposite side of the substrate. Satisfactory results were obtained for a continuous gas feeding treatment and also for a gas modulating treatment.

A semi-empirical profile simulator was employed to better understand fundamental mechanisms of feature evolution in a high aspect ratio contact plasma etch process. Simulation results showed that the net deposition rate of polymer on sidewall defined the necking and surface scattering of ions from the secondary facet caused the formation of bowing. As neutral depositor flux was increased, the resulting profile showed a monotonic increase in necking. In contrast, the extent of bowing showed a maximum, such that minimal bowing was obtained at low and at high depositor fluxes. Primary faceting of photo resist showed only a small influence on the SiO 2 etch profile.

Nanoimprint lithography (RT-NIL) process using hydrogen silsesquioxane (HSQ) provides a simple fabrication method to realize sub-micron-sized patterns because it can be applied at room temperature. When the process is performed on a HSQ–PMMA bi-layer resist, it is suitable to additional metal sputtering and lift-off process because it features negative vertical profiles. However, high viscosity of HSQ at room temperature requires a high imprint pressure, and also limits the applicable mold profile. Thus, the HSQ imprint depth dependencies on prebaking temperature and mold protrusions are investigated and results are analyzed using the equations for squeezed flow of polymers which enable us to predict typical imprint results under specific conditions. Based on these investigations, the RT-NIL process was optimized and, then, various sub-micron-sized metal patterns of line and hole array were fabricated.

Electron beam lithography has been applied to the fabrication of nanoscale two-dimensional chiral structures with various designs. A fabrication process for planar chiral structures in a thin silicon nitride layer using electron beam lithography and dry etching is presented. A top conductive coating is applied during electron-beam exposure to prevent the occurrence of charging effects caused by the non-conductive silica substrate. Different doses are chosen during the lithography process depending on the complexities and densities of different chiral designs. A very well defined transmission diffraction pattern from arrays of Peano-Gosper fractals is obtained. The optical activity of these dielectric metamaterials shows great potential in their applications of optoelectronic devices and communications.

The effects of various pulse reversal plating parameters on the grain size and smoothness of Ni film on silver seed layers has been studied. The duty cycle, frequency, bath temperature and agitation methods have been tested. The objective was to form a thin continuous hard etch mask (20–30 nm of thickness) of Ni films for image reversal of thin film resist using electroplating. While nickel sulfamate solution without additives or brighteners has been used to plate Ni films, reactive ion etching (RIE) has been used to test the durability of the plated Ni films in fluorine plasma. It was found that pulse reversal plating with current intensity of 12 mA/cm 2 , duty cycle of 90%, bath temperature of 45 °C, ultrasonic agitation of power 80 W, and 400 kHz wave frequency resulted in a plating rate as low as 0.2 nm/s. This plating rate made the control of the film thickness an easy task to achieve. This yielded to a smooth plated surface free from defects or voids, with 25 nm film thickness. Combining electron beam lithography with pulse reversal plating for image reversal and RIE offers the prospect of patterning patterns with the desired aspect ratio. Holes of 100 nm diameter, 250 nm period, and 300 nm depth are achieved using this process.

Inkjet printing technology has been applied to the fabrication of monochrome color filter films and has afforded an efficient and economic production process for flat panel displays. We demonstrate the preparation and physical characterization of the red and/or green monochrome films on glass substrates by inkjet printing technology with pigment-based colorant resist inks. For the green films, a thickness of 1.45 μm and the color coordinate value of x = 0.309, y = 0.588 and the brightness of Y = 58.90 in CIE 1931 diagram are attained at the optimal ink amounts of 1400 pl for green droplets. For the red colorant films, an appropriate film thickness of 1.20 μm and the coordinate value of x = 0.572, y = 0.320 and the brightness of Y = 27.1 in chromaticity diagram at the red droplets amounts of 900 pl are obtained. The experimental results exhibit the percentages of optical transmittance of the as-printed green films achieve greater than 85.0% in the spectral range of 515.0 nm and those of the as-printed red films in the subpixel cell can achieve 98.0% in the range of 640.0 nm.

We report here a novel etch process scheme developed to form the Ge structures used in forming localized Ge on insulator (GOI) substrates. The approach of simultaneous etching the Ge film and photo resist provided greater advantages such as eliminating the necessity of post etch strip process step thus reducing process complexities and cycle time, over the conventional etch scheme. Various issues, which have shown up in the conventional etching, were also overcome. The etch process schemes are fully CMOS compatible and can be easily adopted for creating local regions of Ge on Si for advanced CMOS applications.

SU-8 resist was characterized for X-ray lithography from a plasma focus source by studying its cross-linking process using Fourier transform infrared (FT-IR) spectroscopy. The cross-linking process of the resist during post-exposure bake (PEB) was accurately monitored using the infrared absorption peaks at 862, 914, and 1128 cm − 1 . Results showed that the cross-linking of SU-8 was effectively completed at the exposure dose of 2500 mJ/cm 2 for resist thickness of 25 μm. Reliable processing conditions consisted of an intermediate PEB at 65 °C for 5 min, with the PEB temperature ramped up to 95 °C over 1.5 min and then followed by a final PEB at 95 °C for 5 min. Test structures with aspect ratio 20:1 were obtained.

The fullerene molecules such as C60 and C70 were incorporated in the commercial positive electron beam resist to investigate the performances for patterning and filling the contact holes at nanometer scale. The sensitivity, process window and contrast of the modified resist were improved, while the toluene dilution degraded the sensitivity. The electron beam dose affected the designed holes dimension, and the adulterated resist could print sub-50 nm holes pattern. We found the small amount (0.01–0.02% w/v) of fullerene molecules very effectively promoted the etch resistance and selectivity under fluoro-containing gases, and minimized the film stress. The etching resistance for C60 and C70 modification could be improved by 65% and 68%, respectively. Together with the fullerene-incorporated resist and the etching processes, the sub-50 nm contact hole could be achieved. In addition, the gap-filling and step coverage capability of titanium nitride into nanometer contact hole with chemical vapor deposition was better than physical vapor deposition.

Deep etching of Ge-doped SiO 2 using an epoxy based negative resist and a Chromium film as a mask in CHF 3 /O 2 plasma has been investigated. Parameters varied in design that include radio-frequency (RF) power, gas ratio, work pressure and gas total flux, and the major etch responses including etch rate and selectivity are modeled. In the high etch rate and high selectivity reactive ion etching process, it was found that the bottom and sidewall surfaces were rough in the Cr mask etching because of physical sputtering of the Cr film by ion bombardment. In addition, a tapered facet on the etched sidewall of resist mask sample when the etching process goes on some extent that attributed to epoxy resist film degeneration induced by ion bombardment effects. A novel resist-on-Cr double-layer mask that can overcome the single-layer mask limitation is developed for enhancing the Ge-doped SiO 2 etching result and improving the epoxy resist mask utilization. Based on studies, low-loss SiO 2 /Si channel waveguides with propagation loss of − 0.07 dB/cm are fabricated at last.

Anisotropic chemical etching behavior of ZnO single crystal surface was investigated by using patterned resist masks prepared by electron beam lithography. Particularly, etching with aqueous solutions of HCl and CH3COOH was examined for (0001¯) surface of ZnO. The obtained micro-patterns were characterized by scanning electron microscope and laser microscope. In the concave structure formation, the facets of {101¯1¯} were developed independent of the etchants. However, a roundish bottom face of the pits consisted of {101¯n¯} (n>1) planes of ZnO was observed only in the sample etched in HCl solution. These results indicated that the resultant shape of the microstructure is strongly affected by reaction kinetics.

Iridium film with the thickness of 30 and 60 nm were formed on both Si wafer and commercially pure (CP) Ti by electron beam evaporation. The thin iridium film showed the identical charge injection capability with the bulk Ir. However, the charge injection value of iridium film was decreased with continuous potential cycling when the deposited iridium became depleted due to the formation of oxide. The number of cycles at which the charge injection value decreased was 800 and 1600 cycles for the 30- and 60-nm-thick Ir film, respectively. FE-SEM observations on the cross section of Ir film clearly showed the thicker iridium oxide was formed with the more potential cycling. Ar ion beam etching to substrates before deposition certainly improved the adhesion strength of Ir film enough to resist to the strain induced by the larger volume occupation of iridium oxide. Swiss 3T3 fibroblasts culture on Ir and Ir oxide showed no cytotoxicity. Also, embryonic cortical neural cell culture on electrode indicated neurons adhered and survived by the formation of neurofilament.

Copper migration continues to be an important consideration in new and emerging interconnect technologies. As line dimensions shrink and new low k materials are introduced into the integrated circuit (IC) structure, the danger of electrical failure due to copper migration increases. The search for better barriers and new copper alloys that resist migration is being sought. Important considerations for copper migration are the adhesion characteristics, which add to the electrical failure phenomenon and also help determine the survivability of the metallic layers in the IC build up process. To understand the survivability issues, we have employed a combination of experimental and modeling studies to determine how the combination of metallic layers may interact. Both the experimental tests and the modeling have been found to be consistent and simple molecular models can be used to predict gross failure trends. These studies have directed us toward newer barrier and copper alloys layers that should be useful in the next generation.

The effect of electron beam (e-beam) curing on an ultra low dielectric constant material, porous organosilicate glass (OSG) is investigated. In conventional IC integration processes, photoresist (P. R.) stripping with O2 plasma and wet chemical stripper is an inevitable step. However, dielectric degradation often occurs when low-k dielectrics undergo the PR stripping processing. This limits the application of incorporating low-k material into semiconductor fabrication. In order to overcome the integration issue, e-beam direct curing process was proposed in this study. In this technology, the dielectric regions irradiated by e-beam will be cross-linked, forming the desired patterns. Meanwhile, the regions without e-beam illumination are dissolvable in a mingled solvent of 2.38 wt.% tetra-methyl ammonium hydroxide (TMAH) and methanol with the ratio of 1:8. In this work, the possible doses of e-beam exposed porous OSG are decided by Fourier transform infrared spectroscopy, n&k 1200 analyzer and electrical analyses. The experimental results expressed that the minimum dosage to cure porous OSG film is 6 AC/cm 2 , which is similar to commercial e-beam resist. Additionally, a scanning electron microscope FS.E.M.)

Nanometer-sized patterning of polysilicon thin films was performed by a high density inductively coupled plasma (ICP) etching. The etch characteristics of polysilicon thin films with an e-beam resist mask were investigated using Cl2, C2F6, and HBr-based gas mixes. The etch rate, the etch selectivity and the etch profile of polysilicon films were examined as a function of the concentration of each gas, using Ar as a diluent. The Cl2 gas showed fast etch rate of polysilicon films, and the high selectivity of polysilicon films to resist was obtained in HBr and C2F6 gases. The effect of an etch gas on the etch profile of polysilicon thin films was observed using field emission scanning electron microscopy for nanometer-sized patterns. Good nanometer-sized patterning of polysilicon thin films with 60 and 95 nm wide lines has been achieved in HBr/Ar and C2F6/Ar plasmas.

Several alkanethiol self-assembled monolayers (SAM), such as ethanethiol (ET), decanethiol (DT), and hexadecanethiol (HDT), were damaged by a metastable helium beam and transferred a mask pattern to the underlying gold layer with a nanoscale edge on muscovite mica. It was first found that the positive–negative inversion of the gold patterns with the DT SAM resist occurred when the dose rate of the metastable atom increased. This inversion was caused by the contamination of the Si-containing species in the molecular pump system deposited on a gold surface when the DT SAM was completely removed. As with the DT SAM resist, negative gold patterns were fabricated with the ET SAM resist. In the case of the HDT SAM resist, we thought that the negative gold pattern resulted from the cross-linking of the main molecular chain that occurred with the polymer resist in conventional lithography. In addition, there was no relationship between the roughness and the width of the edge even when a smaller grain size was used to predict the preferred roughness.

A low temperature resist trimming process with low trimming rate and good uniformity was developed. Wafer chuck temperature in the ashing chamber was adjusted to be 6 °C to achieve low trimming rate and improve process uniformity. Low power oxygen and argon plasma was used for ashing the resist. Resist lines (0.5 μm wide) patterned with a g-line stepper was trimmed down to sub-100 nm widths. The trimming rate was found to be independent of the initial line width and trimming time. A 0.6 μm CMOS process flow with LOCOS and nitride spacer was suitably modified incorporating resist trimming to fabricate NMOSFETs with gate length as small as 95 nm. Since most polymer-based photoresists can be etched in oxygen plasma, the basic technique could be extended to supplement other lithographic processes for channel length scaling.

A simple and manufacturing worthy method to pattern a very thin channel body of the FinFET/Tri-gate MOSFET is presented. A channel body as thin as 40 nm using the phase-shift mask (PSM) technique with deep UV 248 nm lithography on UV 210 Shipley resist has been achieved, while having an inherently wider Source/Drain (S/D) extension region. The width of extension region was optimized using the Prolitho.3D lithography simulator for the exposure dose and reticle bias conditions. The device simulation of the wider S/D extension region performed using three-dimensional (3-D) Davinci device simulator shows the significant reduction in the S/D parasitic resistance. Furthermore, these patterns on photoresists like UV 210 provides the basis for the easy integration to the mainstream CMOS technology, hence the potential for manufacturability with higher device performance.

The etching of borophosphosilicate glass (BPSG) in NF3 and NF3/He radio frequency (RF) glow discharge has been characterized. The etch rates, BPSG/resist selectivity and etch profile have been investigated along with the reactor geometry, namely the inter electrode distance, by which the process can be optimized. The results shows that the etch rates of BPSG are 650 nm/min at RF power of 500 W, pressure of 0.3×102 Pa and 60 sccm flow rate of NF3 gas. The selective etching BPSG/resist has also been examined and was significantly enhanced from a value of 1.2 to 2 under 16% of Helium injection into NF3 discharge at high pressure of 0.9×102 Pa. The increase of inter electrode distance of the reactor improves the selectivity value but reduces the BPSG etch rate. The BPSG etch profile became isotrope for inter electrode distance value of 5×10−2 m and higher. The best value of the selectivity was obtained for an inter electrode distance of 15×10−2 m. For completeness of the process anisotropic etching was achieved, the obtained tapered sidewall was characterized as having an angle of 38° with the normal surface.

Recently, Mo/Si multilayer reflectors have been gaining industry interest as a promising choice for the next generation extreme ultraviolet mask material for printing sub 70 nm feature size devices. A reactive ion etching system with optimized hardware using CHF3/Ar process regime shows the capability for highly anisotropic etching of sub congruent to400 nm feature sizes in Mo/Si test multilayers with ten periods and a bilayer thickness of 7.8 nm which were prepared by e-beam evaporation. A three-level-mask technique consisting of a top resist mask layer poly-methyl-meth-acrylate, a middle hard amorphous Si mask layer and a bottom-level polyimide layer is used to create the etch mask. The etch characteristics of the polyimide film is shown to be one of the major factors determining the success of the described multilayer etching process. The developed etching technology demonstrates superior process performance without facets, excellent uniformity and good profile control. No contamination, degeneration or defect generation in the unetched multilayer structure could be detected. This non-conventional process results in minimum deposition during the etching thus eliminating the need for a dry or wet cleaning. Sidewall angles in Mo/Si multilayers of 85degrees, without undercut, bowing and ripples resulting in smooth sidewalls are achieved. (C) 2003 Elsevier B.V. All rights reserved.

White light scanning interference microscopy is most commonly used for measuring single air/material surfaces. In this work, the technique has been modified for the non-destructive measurement of interface structures buried under a thick transparent layer. Test samples consisting of step structures (

By using a helium metastable atom beam and butanethiol (BT) self-assembled monolayers (SAM), the metastable atom lithography to the gold film on muscovite mica having a flat surface was carried out. Large-area intact and clean patterns with a nanoscale width of the edge, approximately 50–70 nm, were obtained. Meanwhile, we found that the shorter chain molecules like the BT can be used as resist and may result in sharper edge of patterns, but the roughness of gold patterns with the BT SAM is larger than that with the Octanethiol (OT) SAM and similar to that with the Dodecanethiol (DDT) SAM. This observation can be interpreted by the presence of the liquid phase in the short-chain homologues. All information indicated that the BT SAMs on atomically flat surfaces could be used as a resist for exposure to metastable atom beams.

A new type of polymer Langmuir–Blodgett (LB) films composed of N-dodecylacrylamide (DDA), which is known to form a stable monolayer, and a photodegradable monomer, tert-butyl-4-vinylphenyl carbonate (tBVPC), were prepared with the aim of developing a novel thin-film positive-tone resist. The copolymer [p(DDA-tBVPC)] could form a stable, condensed monolayer, even at high compositions of tBVPC (53 mol.%), and the monolayer could be successfully transferred onto solid supports, such as quartz, glass, and silicon slides, giving Y-type uniform LB films. The polymer LB films could be efficiently decomposed by deep UV irradiation, and after development with alkaline solution, a clear positive tone pattern with a line width of 0.75 μm, which is the highest resolution of the photomask employed, was visible. Moreover, it was found that these copolymer LB films with nm thickness show high resistance performance to an etching process. These fascinating features of the copolymer LB films show them to be potential candidates as key materials in nano-lithography.