Use Of Photoresist Research Articles

Direct Imprinting of Large-Area Metallic Photonic Lattices for Infrared Polarization Filters with Broadband Tunability.

Metallic photonic lattices are promising in their application to plasmonic optical devices; however, scalable fabrication strategies are limited by sample size, response wavelength (mostly in the visible range), cost, and duration. This paper proposes a direct imprinting strategy to fabricate large-area metallic photonic lattices, which present a strong plasmonic response and broadband angle-resolved tuning properties in the infrared region. This simple fabrication strategy combines solution-synthesized Au nanoparticle colloid and imprinting technology, which does not require the use of photoresist or lithography. Thus, the feature size and response wavelength can exceed the limitations of the beam size and wave band, thereby offering the advantages of a low cost and high throughput.

Designing 3D Polymeric Structures through Capillary Wetting on Colloidal Monolayer

AbstractColloidal lithography has provided a facile means to create regular micro‐ and nano‐patterns by employing colloidal crystals as masks. However, the patterns are usually restricted to 2D as most techniques do not exploit the spherical shape of colloidal masks. Here, 3D structures are designed by utilizing capillary wetting of liquified photoresists on colloidal monolayers of silica particles. The silica particles are anchored at planar air‐photoresist interfaces to have an equilibrium contact angle without interfacial deformation for thick polymer layers. By contrast, when the polymer layers are thin enough, they wet the colloidal monolayer by forming periodic wavy interfaces to provide a constant Laplace pressure. The photo‐crosslinking of the photoresist and subsequent removal of silica particles leave behind periodic nanostructures with 3D‐undulated surfaces. Importantly, the structure and waviness are further controllable by adjusting the polymer thickness relative to the particle radius. As the shape of the interface is determined by capillarity, the 3D structures are reproducible as long as the dimension is smaller than the capillary length. The use of photoresists enables the production of micropatterns of the periodic wavy structures by photolithography. As one of the potential applications, structurally‐colored patterns are demonstrated with enhanced plasmonic and diffraction colors.

It's in the Fine Print: Erasable Three-Dimensional Laser-Printed Micro- and Nanostructures.

3D printing, on all scales, is currently a vibrant topic in scientific and industrial research as it has enormous potential to radically change manufacturing. Owing to the inherent nature of the manufacturing process, 3D printed structures may require additional material to structurally support complex features. Such support material must be removed after printing—sometimes termed subtractive manufacturing—without adversely affecting the remaining structure. An elegant solution is the use of photoresists containing labile bonds that allow for controlled cleavage with specific triggers. Herein, we explore state‐of‐the‐art cleavable photoresists for 3D direct laser writing, as well as their potential to combine additive and subtractive manufacturing in a hybrid technology. We discuss photoresist design, feature resolution, cleavage properties, and current limitations of selected examples. Furthermore, we share our perspective on possible labile bonds, and their corresponding cleavage trigger, which we believe will have a critical impact on future applications and expand the toolbox of available cleavable photoresists.

Ten years of two-color photolithography [Invited

Two-color approaches in photolithography involve the use of photoresists that are activated with one color of visible or near-ultraviolet light and are deactivated with a second color. Such approaches have enabled resolution beyond the diffraction limit and hold great promise for improving the resolution down to the 20 nm level. This review presents and contrasts the different two-color lithographic (2CL) approaches that have emerged over the last decade in linear and multiphoton lithography. The basic advantages and limitations of each method are discussed, as well as the challenges that must be addressed in the near feature to push the limits of 2CL techniques. With further advances, multicolor techniques are anticipated to become a leading tabletop tool for performing 3D lithography with resolution that rivals that of more expensive solutions, such as electron-beam lithography.

Functional Carbon Surfaces for Stable Sodium-Ion SEI Formation

Sodium-ion batteries offer a low-cost and earth-abundant alternative to lithium-ion batteries. While strides have been made in improving electrode materials to enable higher charge capacities and transfer rates, the lifetime of sodium-ion batteries still poses a hurdle to their commercial success. The unstable formation of a surface-electrode interphase (SEI) is one of the leading causes of irreversible capacity losses. While the SEI has been studied extensively in lithium-ion batteries, only limited knowledge exists about SEI growth sodium systems. This study sets out to determine the role of carbon-surface chemistry in forming a stable, passivating sodium SEI. While many factors play a role in SEI formation, the SEI is inherently a surface reaction. Surface groups may either act as catalytic sites, controlling selectivity for specific electrolyte reduction reactions, or as nucleation sites to promote the precipitation and adhesion of insoluble decomposition products. Carbon surface groups are well-known to modify catalytic activity in a range of applications4,5, but their effects on the sodium SEI are unknown. Prior work shows that different decomposition products result at different carbon morphologies in lithium-ion batteries.1,2 It has also been observed that increasing the degree of graphitization in pyrolytic carbon through high temperature CO2 treatment decreases the rate of electrolyte decomposition.3 Our approach uses carbon thin films to target only surface interactions. Isolating surface from bulk properties is ideal because bulk properties often have to be engineered to meet a wide variety of system requirements such as conductivity, charge capacity, rate capability and solid electrode potential. Applying a surface treatment that does not impact these properties enables learnings of the study to be applied more readily. The use of a thin film also simplifies analysis of interfacial phenomena by removing the impact of bulk properties like excess intercalation capacity and the porosity. Finally, the thin film does not require polymeric binders, reducing the risk of additional side reactions which produce competing degradation products and inaccurate calculations of parasitic current. Thin carbon films are made by spin-coating photoresist onto a substrate and pyrolysis under inert conditions in a tube furnace. Varying the duration and temperature during pyrolysis can change the degree of carbon graphitization6,7. The use of photoresist also enables film thickness and geometry to be easily controlled. Functional groups on the surface of the carbon film are modified after pyrolysis through high temperature treatment, in the presence of gases such as O2, H2, and CO2. We have demonstrated this thin film synthetic method through the optimization of spin coating and pyrolysis parameters. Electrochemical performance of films is evaluated in a 3-electrode cell, using cyclic voltammetry(CV) and chronoamperometry to form SEI layers. We have shown that these films are electrochemically active and that films formed under different conditions yield different electrochemical behavior. Figure 1 compares the CV scans of two films. Sample A shows reversible sodium intercalation near 0.1V vs. Na/Na+ and a peak for electrolyte reduction below 0.8V, while sample B does not exhibit this reversible intercalation behavior. Electrochemical results are correlated with ex-situ measurements of surface chemistry and morphology obtained using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to relate performance to electrode properties. By modifying the surface groups on carbon film this work will determine the specific interactions that are favorable for SEI formation in sodium-ion batteries. Figure 1. Effect of carbon film synthetic conditions on cyclic voltammetry in 1M NaClO4 in PC, 2 mV/s. In addition to SEI formation, Sample A shows reversible sodium intercalation. 1. P. Verma, P. Maire, and P. Novák, Electrochim. Acta, 55, 6332–6341 (2010) 2. E. Peled, D. Golodnitsky, A. Ulus, and V. Yufit, Electrochim. Acta, 50, 391–395 (2004). 3. S. F. Lux, E. Pollak, U. Boesenberg, T. Richardson, and R. Kostecki, Electrochem. commun., 46, 5–8 (2014). 4. K. Gong, F. Du, Z. Xia, M. Durstock, and L. Dai, Science (80-. )., 323, 760–764 (2009) 5. C. E. Banks, T. J. Davies, G. G. Wildgoose, and R. G. Compton, Chem. Commun. (Camb)., 829–841 (2005) 6. J. Kim, X. Song, K. Kinoshita, M. Madou, and B. White, J. Electrochem. Soc., 145, 2314–2319 (1998) 7. R. Kostecki et al., Thin Solid Films, 396, 36–43 (2001). Figure 1

Enzymes Confinement in CNT Doped Carbon Microstructures Electrodes (CNT-CME) for Miniaturized Enzyme Biofuel Cell Application

Fast development of biomedical technology has led us to the invention and use of implantable medical devices to be utilized for direct monitoring of human health. In general, batteries is used as the main micropower supply of these implanted devices, however it has some drawbacks as it has to be replenished in due time. One of the promising continuous energy supplies to replace the use of batteries is enzyme biofuel cell (EBFC) which harvests electrical energy from the oxidation-reduction reactions as it generates electricity by glucose oxidation and oxygen reduction by the anode and cathode enzymes respectively; in which two of its main substrate are abundant and essential components in human physiological fluid. EBFC is expected to be minimal in size but still concerning to have maximized performance during operation including; high electrode potential range, current and power densities which dependent to the stability of the enzyme used and enzyme environment construction. In order to achieve long operation of EBFC, it is necessary to be assured that enzyme will not be denatured due to external potent factor such as shear stress, especially if EBFC is employed as micro-power supply of implanted devices in human in which the blood velocity will depend on the diameter of blood vessel as implantation site. One of the modest methods to protect immobilized enzyme from the shear stress is by using polymer such as Nafion to form physical entrapment layer. However, there is high possibility that Nafion as polymer will be degraded under shear stress leading to leaching of enzyme during long operation. Previous studies showed that encapsulated protein in porous materials, or immobilized inside layer by layer material showed more stability due to less exposure of the external stress. The use of mesoporous material such as sol-gels and entrapment in mesoporous silica have proven to increase the enzyme stability, however this materials are lack of conductivity which is not suitable for bioelectronics application. Due to the necessity of electrical communication, another study was employing conducting material such as Si wafer with micro culverts as enzyme protection platform which enhance the electron transfer between enzyme-electrodes material . The success of enzyme immobilization also depends on its carrier used for particular application. The platform for enzyme immobilization should have high capacity as enzyme anchoring sites, chemically stable, and having the structural ability to prolong enzyme stability. The combination of nanostructures with enzyme immobilization will be a promising direction since it is possible to engineer enzyme environment to limit the effect of external forces as called enzyme-in-cage. Carbon as the most popular and widely studied as electrode materials due to its physical and electrochemical stability properties as inert material, low cost and easy to be functionalized and decorated. Carbon can be used for miniaturized electrode fabricated through nanolithography by pyrolizing photoresist, decompose co-composite, leaving only carbon in microstructured pattern. The use of photoresist to form carbon after pyrolysis step has the advantage due to its ability to be patterned by photolithography techniques which is reproducible. The properties of pyrolized electrodes are comparable than glassy carbon electrode (GCE) which has similar electrochemical properties such as low background current as the effect of low capacitance Further advancement for this system is the integration of CNT which has high surface area, excellent conductivity due to its sp2carbon hybridization along its wall. In order to prevent any proximity effect of CNT-pyrolyzed carbon electrode, CNT was grown directly in carbon post in which the catalyst of CNT growth was deposited through electrostatic spray deposition (ESD). Grown CNT on pyrolyzed carbon is expected to keep high structural stability. In this study we elaborated the fabrication and application of CNT doped carbon microstructures (CNT-CME) as platform for enzyme confinement and immobilization. Thus eventually this method then applied to immobilize the FAD-dependent glucose dehydrogenase (FADGDH) α-subunit with menadione as mediator (FADGDH/menadione) system which has proven to have better performance as anode for biofuel cell application as its native character of low Km value. The parameter such as K mof free and immobilized enzyme, current and power densities of the EBFC were also tested. Figure 1

Synthesis and Characterization of Carbon Nanotubes to be Used in the Development of New Ionizing Radiation Sensors

Detection of ionizing radiation are crucial in different fields including energy, national security, biological and nuclear research, and in applications such as monitoring the attrition of materials in space travel. In general, the systems for the detection of ionizing radiation usually have one or several of the following drawbacks: incapability to produce stable signals, expensive and complicated manufacturing, operation at low or very low temperatures, low sensitivity or even voluminous size, as is the case of Geiger counters. Single-walled carbon nanotubes (SWNTs) are attracting much attention as promising materials for application in nano-devices due to their excellent electrical conductivity, optical, thermal and mechanical properties arising from their quasi-one-dimensional structure. One of these potential applications is the use of SWNTs as radiation sensor. For this purpose, the critical steps in the design and fabrication of devices are focused on the growth of SWNTs into controlled architectures and onto appropriate substrates. Until now, the conventional way to obtain patterned vertically aligned (VA) carbon nanotubes (CNTs) is based in using a careful positioning of the metal catalyst (e.g. by evaporation, use of photoresist masks, or even Ar+ sputtering) in localized positions, from where the CNTs grow. Such catalyst patterning requires a precise control of the process with a long list of complicated steps. An easier method for depositing the catalyst consists in using a wet-based dip-coating approach, which provides some advantages in cost and scalability. However, in this wet-based method the catalyst deposition at desired locations cannot use conventional lithographic techniques. A similar method has been used for patterning the growth of high-quality VA-SWNTs on Si and SiO2 based on the difference of surface wettability of the catalyst in both materials. In the literature, TiN has been chosen as a suitable electrically conductive supporting material for CNTs growth. This includes the use of TiN as the selected substrate, or as a barrier layer on crystalline Si. When using a Si substrate, the formation of metal-silicides during the thermal treatment (annealing step) complicates the synthesis process. In this way, dense mats of vertically aligned multiwall carbon nanotubes have been grown on TiN substrates by using different precursors, including ferrocene or different metals as Fe, Ni, or Co as catalysts. Besides its electrically conductive properties, TiN seems to increase the quality of the grown CNTs (i.e. much thinner CNTs with higher density as compared with those obtained on Si substrates). In this research, SWNTs have been synthesized by CVD, using ethanol at low pressure as carbon source. The characterization of the synthesized materials has been carried out by electron microscopies (SEM and TEM), X-ray diffraction (XRD), and Raman. This material is currently being used for the design and development of a new prototype of radiation sensor.

Photoresist-less patterning of silicone substrates for thick film deposition

Traditionally, fabrication processes to produce microelectrode arrays for neural stimulating electrodes have employed photolithography and a photoresist layer to produce a pattern on a substrate which subsequently has a metal layer deposited. The deposited metal layer is then used to create stimulating electrodes that will ultimately be in close contact with neural tissue. While the process enables accurate fabrication at a reasonable cost, the use of photoresist in the process presents a number of issues. Photoresist is a contamination risk with the potential for chemicals to be absorbed into the silicone, which will then subsequently be in close proximity to neural structures, introducing a risk of toxicity. In addition, due to the use of flexible substrates such as silicone elastomer, patterning of films greater than 1μm thick can be difficult.Whilst an obvious solution would be to avoid using photoresist in the fabrication process, few alternatives have been systematically investigated. We investigated use of shadow masks fabricated from glass, brass and silicone elastomer, and exploitation of the natural tackiness of the silicone substrate for mask adhesion. All three mask materials attached well to silicone, but each presented differing degrees of difficulty during alignment and mask removal.Subsequently, thin gold films (∼20nm) and thick platinum films (∼8μm) were deposited on the silicone substrates using the shadow masks. We discuss the mask fabrication, pattern definition, the difficulties which arose, and the benefits of using shadow masks for the fabrication of medical devices.

2-Colour photolithography

Photolithography is a crucial technology for both research and industry. The desire to be able to create ever finer features has fuelled a push towards lithographic methods that use electromagnetic radiation or charged particles with the shortest possible wavelength. At the same time, the physics and chemistry involved in employing light or particles with short wavelengths present great challenges. A new class of approaches to photolithography on the nanoscale involves the use of photoresists that can be activated with one colour of visible or near-ultraviolet light and deactivated with a second colour. Such methods hold the promise of attaining lithographic resolution that rivals or even exceeds that currently sought by industry, while at the same time using wavelengths of light that are inexpensive to produce and can be manipulated readily. The physical chemistry of 2-colour photolithography is a rich area of science that is only now beginning to be explored.

Catalytic and Autocatalytic Mechanisms of Acid Amplifiers for Use in EUV Photoresists

Twelve fluorinated acid amplifiers (AAs) were synthesized and studied for use in photoresists exposed to 13.5 nm, extreme ultraviolet (EUV) light. Acid amplifiers are compounds that decompose in the presence of acid to generate more acid via catalytic or autocatalytic mechanisms. These AAs are composed of a body, trigger, and an acid precursor. Thermal decomposition rates of solutions of the AAs in C6D6/m-ethylphenol (50/50 wt %) at 100 °C were monitored by 19F NMR with and without 1.2 equiv. of 2,4,6-tri-t-butylpyridine. All of the AAs in the presence of base decompose according to first-order kinetics with rate constants kBase. The rate constants, kBase, at various temperatures yielded the activation parameters ΔH‡, ΔS‡, and ΔG‡. The enthalpy of activation, ΔH,‡, was in a narrow range of 16.6−19.1 (kcal/mol), whereas the entropy of activation, ΔS‡, spanned from 0 to −12 (cal/(mol K)). When acid is allowed to build up in solution (in the absence of base), six of the AAs with tertiary triggers (Body-3) decompose autocatalytically, but the six with secondary triggers (Body-2) are unaffected. Although Body-2 AAs do not decompose autocatalytically, nonaflate acid does catalyze their decomposition. Lithographic evaluation showed that some AAs are capable of simultaneously improving the resolution, line-edge-roughness, and sensitivity of a control EUV photoresist. This simultaneous improvement was quantified using the Z-Parameter. The AAs investigated here were found to improve the Z-Parameter by as much as a factor of 3.

All‐Carbon Electronic Devices Fabricated by Directly Grown Single‐Walled Carbon Nanotubes on Reduced Graphene Oxide Electrodes

Being free from the harsh post-growth treatments in strong acids, long time sonication, etc., directly grown single-walled carbon nanotubes (SWCNTs) preserve their pristine structures and intrinsic properties, which make them ideal for highperformance electronic devices. [ 1–9 ] Integration of directly grown SWCNTs into such addressable devices is a crucial step and requirement for both fundamental studies and applications. Two strategies, i.e., fabrication of metal electrodes on CNTs [ 5 , 7 , 10 ] and direct growth of CNTs between the pre-fabricated electrodes, [ 3 , 4 , 11 ] are normally used to fabricate the directly grown CNT-based devices. Although the fi rst strategy is popular and commonly used, the shadow mask and/or the use of photoresist may contaminate or destroy CNTs, leading to a low performance or even failure of devices. [ 3 ] The second strategy possesses some advantages, such as no CNT purifi cation and no photolithography required. This could be a better choice to produce clean and high-performance CNT-based devices, since the pristine structures and intrinsic properties of the grown CNTs are preserved. Despite the fact that many attempts have been reported, [ 3 , 4 , 9 , 11 ]

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

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

Acoustic characterization of thin polymer layers for Love mode surface acoustic waveguide

We investigate the use of thin (1‐10 um) polymer films as guiding layer for Love mode surface acoustic wave sensors. Beyond the great gravimetric sensitivity provided by the polymer guiding layer resulting from the low acoustic velocity, the use of photoresists provide ecnonomical means of depositing guiding layers of optimal thicknesses compared to inorganic layer deposition processes (typically PECVD deposition of silicon dioxide lasting several hours). The limit of very thick (> 100 um) layers provides means of propagating interface waves mostly insensitive to the environment (package‐less sensors) whose properties only vary through modification of the bulk properties of the polymer. We here analyse the evolution of the properties of the guiding layer in terms of acoustic velocity and losses as a function of time (solvent evaporation following photoresist spin coating) and temperature (typical baking steps). The polymer films is deposited on AT‐cut quartz patterned with interdigtated transducers for generating 40 um‐wavelength shear waves converted to a guided Love mode in a delay line configuration. We complete the experimental results with data interpretation using a model of acoustic wave propagation yielding quantitative results including viscosity and density out of the velocity and insertion loss measurements, both for the guided Love mode and interface layers

Use of photoresist templates in the synthesis of highly-ordered arrays of titania nanorods

Template synthesis of nanostructures entails the deposition of the desired materials within the pores of a nanoporous membrane or solid. Nanofibrils or tubules of the desired material are obtained within the pores depending on the deposition time and parameters. Methods such as electrochemical and electroless deposition, in situ polymerization, and sol–gel process have been used to deposit nanomaterials within the nanopores of templates such as track-etch polymeric membranes and anodic alumina. This paper reports on the first use of photoresist spin-coated on a conductive glass substrate as a template for nanofabrications. TiO2 nanofibrils in diameters were synthesized by sol–gel process within the pores of the template. Removal of the template resulted in highly-ordered arrays of nanofibrils vertically standing on the conducting glass substrate. The aspect rations of the obtained nanofibrils were similar to those of the template nanopores, 35 nm in diameter and ∼1.3 microns in length. The photoresist template is shown to be functionally similar to anodic alumina template.

Rapid fabrication of microchannels using microscale plasma activated templating (μPLAT) generated water molds

Poly(dimethylsiloxane) (PDMS) is a common material used in fabricating microfluidic devices. The predominant PDMS fabrication method, soft lithography, relies on photolithography for fabrication of micropatterned molds. In this technical note, we report an alternative molding technique using microscale PLasma Activated Templating (microPLAT). The use of photoresist in soft lithography is replaced by patterned water droplets created using microPLAT. When liquid PDMS encapsulates patterned water and then solidifies, the cavities occupied by water become structures such as microchannels. Using this method, device fabrication is less time consuming, more cost efficient and flexible, and ideal for rapid prototyping. An additional important feature of the water-molding process is that it yields structural profiles that are difficult to achieve using photolithography.

Electrodeposition of hard magnetic CoPtP material and integration into magnetic MEMS

This paper reports on the electrodeposition at room temperature and the characterization of hard magnetic CoPtP material. An acidic bath has been set up to be compatible with the use of photoresist for micro technologies processes. X-ray diffraction (XRD) diagrams show that CoPtP alloy crystallizes in the hexagonal system. The film growth is generally columnar with a pronounced ⟨0 0 2⟩ texture associated with preferential out-of-plane magnetization. Using particular electrodeposition conditions, in-plane magnetization can be recovered and coercivities as high as 2800 Oe are reached for patterned layers. So a room temperature electroplating process able to produce patterned micromagnets usable in magnetic applications has been set up. Examples of the integration of CoPtP micromagnets are described through the fabrication of three devices: a multilayered giant magneto-resistive sensor biased by five electroplated magnets, a vertical magnetic bistable microactuator and a horizontal magnetic bistable microswitch. The main challenge for the last two devices was to demonstrate the actuation of a moving micromagnet without any mechanical guiding during commutation. The demonstrated bistability provided by the use of micromagnets emphasizes the interest in these devices for many applications.

Development of a solid-state thick film calcium ion-selective electrode

A solid-state calcium ion-selective electrode was developed using thick film metallization process. Silicone rubber or photoresist was combined with ionophore (ETH 129) forming calcium ion-selective membrane which was coated onto different surfaces of electrode. Super-Nernstian equilibrium relationship between the phase boundary potentials and calcium ion concentrations was observed in the silicone rubber-based membrane that was doped with 10−7M CaCl2 treated montmorillonite. This equilibrium relationship was eliminated when the membrane was doped with 0.1M CaCl2 treated montmorillonite. The use of photoresist simplified the manufacturing process for the membrane. The memory effect of the silicone rubber-based membrane could be eliminated when the membrane was conditioned with 0.1M CaCl2. The response time of the electrode with silicone rubber and montmorillonite modified silicone rubber were less than 20s and the one with photoresist was less than 3min. The sensitivity of these calcium ion-selective electrodes were around 30mV per decade, and the selectivity were in the rang from −2.9 to −3.8 for Na+, K+ and Mg2+ ions based on fixed primary ion method (FPIM).

Use of a photoresist sacrificial layer with SU-8 electroplating mould in MEMS fabrication

In this paper, new processes have been developed to fabricate micromechanical components and systems that utilize two different photoresists (Shipley S1813 and Hoechst AZ P4620) as sacrificial layers in conjunction with SU-8 photoresist used as an electroplating mould. The use of photoresists as sacrificial layers offers several advantages including reduction in processing steps and hence processing cost. However, the normal sacrificial layer photoresist processing cycle fails when used in conjunction with SU-8 photoresist. The latter is often used as an electroplating mould, especially for high-aspect ratio or tall microstructures in MEMS fabrication. In this paper, problems arising in the use of a photoresist sacrificial layer are discussed and new sacrificial layer processes are developed. New curing temperatures for photoresist sacrificial layers are determined, which prevent damage that otherwise occurs from the use of SU-8 as an electroplating mould. New hard baking temperatures determined are 175 °C and 200 °C for S1813 and AZ P4620 photoresist processes, respectively. A comb drive structure is utilized to demonstrate these new fabrication processes.

New Photosensitive Polyimide Materials and Their Application to Low-loss Optical Waveguides

A negative-working photosensitive polyimide-precursor (PSPI-precursor) for optical waveguide based on a poly(amic acid) (PAA) and 1, 4-dihydropyridine derivatives (DHP)s has been developed. The PAA was prepared by ring-opening polyaddition of aromatic fluorinated tetracarboxylic dianhydrides and diamines. The PSPI-precursor was capable to resolve a 2-μm width pattern when a 10 μm-thick film was used. Fabrication of optical waveguides by a simple patterning process using the PSPI is also described. PSPI is directly patterned by UV exposure and wet chemical development, avoiding use of photoresist. By using the standard cut back method, optical propagation losses were found to be as low as 0.4 dB/cm at 1.55 μm.

Photoresists Used as Mask Materials in Ion Implantation for the CMOS Technology: Optimizing Mask Thickness

The use of photoresists as mask materials in ion implantation is studied theoretically and experimentally. Recommendations for optimizing mask thickness in the CMOS context are made.