Photolithography Method Research Articles

Вплив комп’ютерних технологій на сучасне мистецтво фотолітографії

Investigated various ways of transforming images in the Adobe Photoshop program for the creation of originals for further reproduction by the method of photolithography, in particular the influence of the parameters of the application of the Sketch/Graphic Pen filter on gradation of imprints. Developed a series of model scales in the form of a halftone wedge with an area of raster elements from 0 to 100 % with a step of 10 %. Applied the Sketch/Graphic Pen filter parameters: the stroke direction was diagonal to the right, the stroke length varies in the range from 1 to 15 mm, the light-shadow contrast was from 0 to 100. Simulated a classic raster scale with a raster line of 48 lines/sm and a round raster point.Studied the graduation curves of the original—imprint for determine the optimal modes of production of originals and stones in order to provide the maximum possible range of halftones for reproduction of original illustrations. Established that the maximum range of halftones, when using a 48 lines/sm raster with a circular point. When used the Sketch/Graphic Pen filter for scales, the best performance was observed with the following parameters: stroke lengths of 1–3 mm; light-shadow contrast 100. When the stroke length is increased, the tone band narrows and shifts toward the shadows, which can be explained by the transition of the image from the halftone to the dash.Reproduction of tonal drawings with the help of photolithography taking into account the optimal modes of processing and manufacturing revealed the manifestation of the texture of the stone, which made it possible to sharpen the psychological characteristics of the created images. Therefore, the obtained photolithography is characterized by various combinations of expressive means (combinations of strokes, combination of spots and lines in a drawing), thanks to which achieved plastic modeling, tone and light-colored effects of the drawing.

Soft lithography based on photolithography and two-photon polymerization

Over the past decades, soft lithography has greatly facilitated the development of microfluidics due to its simplicity and cost-effectiveness. Besides, numerous fabrication techniques such as multi-layer photolithography, stereolithography and other methods have been developed to fabricate moulds with complex 3D structures nowadays. But these methods are usually not beneficial for microfluidic applications either because of low resolution or sophisticated fabrication procedures. Besides, high-resolution methods such as two-photon lithography, electron-beam lithography, and focused ion beam are often restricted by fabrication speed and total fabricated volume. Nonetheless, the region of interest in typical microfluidic devices is usually very small while the rest of the structure does not require complex 3D fabrication methods. Herein, conventional photolithography and two-photon polymerization are combined for the first time to form a simple hybrid approach in fabricating master moulds for soft lithography. It not only benefits from convenience of photolithography, but also gives rise to complex 3D structures with high resolution based on two-photon polymerization. In this paper, various tests have been conducted to further study its performance, and a passive micromixer has been created as a demonstration for microfluidic applications.

OPTIMIZATION OF SEMICONDUCTOR PRESSURE TRANSDUCER WITH SENSITIVE ELEMENT BASED ON “SILICON ON SAPPHIRE” STRUCTURE

The paper is devoted to the study of the process of optimizing the semiconductor strain-gauge transducer on the structure of the SOS. As an object of the study, an elastic membrane-type element with a semiconductor strain-gauge in the form of a silicon-on-sapphire structure was used. To study the surface of sapphire, the optical photolithography method was used. In the framework of this task, the control parameters and the quality parameters of the serially-manufactured strain gauge were determined. The paper describes the methodology for multicriteria optimization, and also an optimization calculation for the strain-gauge on the SOS. The main result is the obtaining of Pareto-optimal design variants that exceed the basic variant by all quality criteria.

On-Chip Asymmetric Microsupercapacitors Combining Reduced Graphene Oxide and Manganese Oxide for High Energy-Power Tradeoff

Given the rapid miniaturization of technology, it is of interest to produce viable on-chip micro-electrochemical energy storage systems. In this study, interdigitated asymmetric microsupercapacitors were fabricated using photolithography, lift-off and electrodeposition methods. Manganese oxide (MnOx) and reduced graphene oxide (rGO) comprised the pseudocapacitive and the double layer component, respectively. Symmetric MnOx//MnOx, rGO//rGO as well as asymmetric rGO//MnOx microsupercapacitors with three different MnOx thicknesses were constructed and characterized in aqueous media. The asymmetric microsupercapacitor with the intermediate MnOx film thickness displayed the optimal energy-power trade-off superior to that of both the symmetric and well as the other asymmetric configurations. The optimal microsupercapacitor exhibited a high stack energy density of 1.02 mWh·cm−3 and a maximal power density of 3.44 W·cm−3. The high energy-power trade-off of the device is attributed to the synergistic effects of utilizing double layer and pseudocapacitive charge storage mechanisms along with in-plane interdigital microelectrode design within one optimized micro-device.

Measurement of the thermal conductivity of flexible biosourced polymers using the 3-omega method

The thermal conductivity of flexible biosourced polymers was measured by the 3-omega method. Two biopolymers were investigated: the polylactic acid (PLA), a widely used commercial biodegradable one, and the cellulose palmitate (CP), a hydrophobic biosourced material developed in the laboratory, that could be used in electronic or microfluidic applications. The 3-omega method is based-on the use of a metal element as both heating device to thermally disturb the system and temperature sensor. A stencil lithography technique was applied to obtain metallic lines, since biopolymers are not compatible with classical photolithography method. Thermal conductivities of 0.19 and 0.30 W/m.K are obtained respectively for PLA and CP thick films, and 0.12 and 0.22 W/m.K for respectively PLA and CP thin films. These values are close to those measured for petro-sourced substrates or films and so give the possibility to address the applications mentioned.

Red blood cell aggregates and their effect on non-Newtonian blood viscosity at low hematocrit in a two-fluid low shear rate microfluidic system.

Red blood cells (RBCs) are the most abundant cells in human blood. Remarkably RBCs deform and bridge together to form aggregates under very low shear rates. The theory and mechanics behind aggregation are, however, not yet completely understood. The main objective of this work is to quantify and characterize RBC aggregates in order to enhance the current understanding of the non-Newtonian behaviour of blood in microcirculation. Suspensions of human blood were flowed and observed in vitro in poly-di-methyl-siloxane (PDMS) microchannels to characterize RBC aggregates. These microchannels were fabricated using standard photolithography methods. Experiments were performed using a micro particle image velocimetry (μPIV) system for shear rate measurements, coupled with a high-speed camera for flow visualization. RBC aggregate sizes were quantified in controlled and measurable shear rate environments for 5, 10 and 15% hematocrit. Aggregate sizes were determined using image processing techniques, while apparent viscosity was measured using optical viscometry. For the samples suspended at 5% H, aggregate size was not strongly correlated with shear rate. For the 10% H suspensions, in contrast, lowering the shear rate below 10 s-1 resulted in a significant increase of RBC aggregate sizes. The viscosity was found to increase with decreasing shear rate and increasing hematocrit, exemplifying the established non-Newtonian shear-thinning behaviour of blood. Increase in aggregation size did not translate into a linear increase of the blood viscosity. Temperature was shown to affect blood viscosity as expected, however, no correlation for aggregate size with temperature was observed. Non-Newtonian parameters associated with power law and Carreau models were determined by fitting the experimental data and can be used towards the simple modeling of blood’s non-Newtonian behaviour in microcirculation. This work establishes a relationship between RBC aggregate sizes and corresponding shear rates and one between RBC aggregate sizes and apparent blood viscosity at body and room temperatures, in a microfluidic environment for low hematocrit. Effects of hematocrit, shear rate, viscosity and temperature on RBC aggregate sizes have been quantified.

An Additive Manufacturing Technique for the Facile and Rapid Fabrication of Hydrogel-based Micromachines with Magnetically Responsive Components

Polyethylene glycol (PEG)-based hydrogels are biocompatible hydrogels that have been approved for use in humans by the FDA. Typical PEG-based hydrogels have simple monolithic architectures and often function as scaffolding materials for tissue engineering applications. More sophisticated structures typically take a long time to fabricate and do not contain moving components. This protocol describes a photolithography method that allows for facile and rapid microfabrication of PEG structures and devices. This strategy involves an in-house developed fabrication stage that allows for the rapid fabrication of 3D structures by building upwards in a layer-by-layer fashion. Independent moving components can also be aligned and assembled onto support structures to form integrated devices. These independent components are doped with superparamagnetic iron oxide nanoparticles that are sensitive to magnetic actuation. In this manner, the fabricated devices can be actuated using external magnets to yield movement of the components within. Hence, this technique allows for the fabrication of sophisticated MEMS-like devices (micromachines) that are composed entirely out of a biocompatible hydrogel, able to function without an onboard power source, and respond to a contact-less method of actuation. This manuscript describes the fabrication of both the fabrication set-up as well as the step-by-step method for the microfabrication of these hydrogels-based MEMS-like devices.

An Additive Manufacturing Technique for the Facile and Rapid Fabrication of Hydrogel-based Micromachines with Magnetically Responsive Components.

Polyethylene glycol (PEG)-based hydrogels are biocompatible hydrogels that have been approved for use in humans by the FDA. Typical PEG-based hydrogels have simple monolithic architectures and often function as scaffolding materials for tissue engineering applications. More sophisticated structures typically take a long time to fabricate and do not contain moving components. This protocol describes a photolithography method that allows for facile and rapid microfabrication of PEG structures and devices. This strategy involves an in-house developed fabrication stage that allows for the rapid fabrication of 3D structures by building upwards in a layer-by-layer fashion. Independent moving components can also be aligned and assembled onto support structures to form integrated devices. These independent components are doped with superparamagnetic iron oxide nanoparticles that are sensitive to magnetic actuation. In this manner, the fabricated devices can be actuated using external magnets to yield movement of the components within. Hence, this technique allows for the fabrication of sophisticated MEMS-like devices (micromachines) that are composed entirely out of a biocompatible hydrogel, able to function without an onboard power source, and respond to a contact-less method of actuation. This manuscript describes the fabrication of both the fabrication set-up as well as the step-by-step method for the microfabrication of these hydrogels-based MEMS-like devices.

One-Step Laser Patterned Highly Uniform Reduced Graphene Oxide Thin Films for Circuit-Enabled Tattoo and Flexible Humidity Sensor Application.

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors.

P-165: High Resolution Black Color Patterns Fabricated by Photo-Lithography with a Novel High Adhesion Polymer for Pixel Defining Layer of OLED

The high resolution black patterns were fabricated by negative photo-lithography method with the novel high adhesion polymer to improve observability of OLED. The photo-resist was consisted of an organic black pigment dispersed ink in order to decrease dielectric constant of the patterns, the silane group introduced to cardo type polymer for high resolution fine patterns caused by high adhesion on the substrate. The fabricated black patterns showed not only fine patterns but also high thermal stability and good electric properties suitable for pixel defining layer in OLED.

Zero Order Correction of Shift-multiplexed Computer Generated Fourier Holograms Recorded in Incoherent Projection Scheme

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Three-Dimensional Ordered Nanoporous Nickel Electrode for Oxygen Evolution Reaction: Toward Highly Efficient and Ultra-Stable Water Electrolysis

Hydrogen generation by water electrolysis has been comprehensively studied for several decades, although it still faces many difficulties in commercialization due to low efficiency. Even though IrO2 and RuO2 have superior activities to oxygen evolution reaction (OER), such novel metal catalysts still need high overpotential compared to hydrogen evolution reaction. To overcome the limitation of OER, former researches have been studied with various materials which are cheaper and perform better than the novel metal-based electrocatalysts. Among them, nickel is considered as the best catalyst candidate due to hydroxide state transformation between Ni(OH)2 and NiOOH during the surface reaction. Apart from the intrinsic properties, the morphology construction to the nanoscale structure is another useful way to enlarge the surface area, which is directly correlated to the overpotential decrease. Nanostructuring can inhibit continuous growth of bubbles on the surface and detach much easily. The bubble blocking effect on the electrode surface has been deeply studied within mechanical category but this effect has been poorly regarded for enhancement of the OER activity of the electrode. Also, the bimetallic system of nickel/iron chosen in this research enables great improvement for OER. Herein, we synthesized three-dimensional ordered nanoporous mesh-like (3D-NM) nickel electrode by the photolithography method, which outperforms conventional porous nickel electrode. Successfully synthesized ordered nanoporous mesh-like structure provides highly extensive surface area within thickness of only 5 μm. In addition, we investigated that fast bubble formation/detachment from the pore can reduce the bubble blocking effect, which disturbs supply of electrolyte to the catalyst surface. 3D-NM nickel electrode only generates 12 times smaller extraordinary small bubbles compared to the typical bubbles in basic electrolyte. In line with the size of bubbles, impedance during the OER with 3D-NM nickel electrode smoothly undergoes while the nickel foam shows unstable graph. Owing to the enlarged surface area and the fast bubble formation/detachment effect, overpotential measured at 10 mA cm-2 was 372 mV and the calculated Tafel slope was 94.4 mV dec-1. Through the unique nanoporous structure of nickel electrode, outstanding stability for 50 hours was achieved. To further improve the OER activity of as-prepared 3D-NM nickel electrode, the decoration of nickel and iron was conducted. The final 3D-NM NiFe electrode showed 261 mV of overpotential at 10 mA cm-2 with 43.8 mV dec-1 of Tafel slope. Figure 1

Photoresponse enhancement in SnO2-based ultraviolet photodetectors via coupling with surface plasmons of Ag particles

We report the photoresponse enhancement in an ultraviolet photodetector based on SnO2 with dipole-forbidden transition via Ag surface plasmon coupling. The SnO2:Ag film with Ag particles (SnO2:Ag/Ag composite film) was prepared using a sol-gel method and post-annealing technique. The interdigital Au electrodes were fabricated on the SnO2:Ag/Ag composite film using photolithography method to obtain the metal-semiconductor-metal (MSM) structured photodetectors. The response peak and cutoff wavelength of the device based on the SnO2:Ag/Ag composite film showed a significant redshift with respect to the pristine SnO2 photodetector. A fourfold enhancement in peak responsivity from the device based on SnO2:Ag/Ag composite film was observed by modifying film surface using Ag particles, which is ascribed to Ag surface plasmons coupling with SnO2 composite film. Finally, first-principles calculations indicated that Ag substituting Sn sites in SnO2 break the dipole-forbidden rule of SnO2 and result in the strong near-band-edge absorption. Our results suggest that the modification of Ag particles to SnO2 surface is a promising route to enhancing the performance of SnO2 ultraviolet photodetector.

Augmenting mask-based lithography with direct laser writing to increase resolution and speed.

A new method of hybrid photolithography, Laser Augmented Microlithographic Patterning (LAMP), is described in which direct laser writing is used to define additional features to those made with an inexpensive transparency mask. LAMP was demonstrated with both positive- and negative-tone photoresists, S1813 and SU-8, respectively. The laser written features, which can have sub-micron linewidths, can be registered to within 2.2 µm of the mask created features. Two example structures, an interdigitated electrode and a microfluidic device that can capture an array of dozens of silica beads or living cells, are described. This combination of direct laser writing and conventional UV lithography compensates for the drawbacks of each method, and enables high resolution prototypes to be created, tested, and modified quickly.

Formation of Thick High-Aspect-Ratio Resistive Masks by the Contact Photolithography Method

A method of fabrication of thick (~100 μm and more) resistive masks is described. These masks can be used for solving various engineering problems, e.g., for fabricating x-ray-absorbing topological patterns for LIGA masks, stamp microrelief, cast moulds, etc. Specific features of the contact photolithography method, which is used to design and fabricate the research device, are described. A source of exposure radiation in this device is a light-emitting diode. A possibility of obtaining individual elements of the resistive mask (in particular, with the lateral size ~5 μm, height of ~70 μm, and aspect ratio of ~14) and also the titanium stamp microrelief (with the height up to ~40 μm) generated by means of reactive ion-beam etching through the resistive mask, is experimentally demonstrated.

High temperature superconducting YBCO microwave filters

Epitaxial thin films of YBCO high temperature superconductor are widely used in telecommunication technology such as microwave filter, antenna, coupler and etc., due to their lower surface resistance and lower microwave loss than their normal conductor counterparts. Thin films of YBCO were fabricated by PLD technique on LAO substrate. Transition temperature and width were 88 K and 3 K, respectively. A filter pattern was designed and implemented by wet photolithography method on the films. Characterization of the filter at 77 K has been compared with the simulation results and the results for a made gold filter. Both YBCO and gold filters show high microwave loss. For YBCO filter, the reason may be due to the improper contacts on the feedlines and for gold filter, low thickness of the gold film has caused the loss increased.

Nanoladders Facilitate Directional Axonal Outgrowth and Regeneration.

After injuries, axonal regeneration over long distance is challenging due to lack of orientation guidance. Biocompatible scaffolds have been used to mimic the native organization of axons to guide and facilitate axonal regeneration. Those scaffolds are of great importance in achieving functional connections of the nervous system. We have developed a nanoladder scaffold to guide directional outgrowth and facilitate regeneration of axons. The nanoladders, composed of micron-scale stripes and nanoscale protrusions, were fabricated on the glass substrate using photolithography and reactive ion etching methods. Embryonic neurons cultured on the nanoladder scaffold showed significant neurite elongation and axonal alignment in parallel with the nanoladder direction. Furthermore, the nanoladders promoted axonal regeneration and functional connection between organotypic spinal cord slices over 1 mm apart. Multimodality imaging studies revealed that such neuronal regeneration was supported by directional outgrowth of glial cells along nanoladders in the organotypic spinal cord slice culture as well as in the coculture of glial cells and neurons. These results collectively herald the potential of our nanoladder scaffold in facilitating and guiding neuronal development and functional restoration.

Single-mode ultraviolet whispering gallery mode lasing from a floating GaN microdisk.

We fabricated a floating GaN microdisk supported by a silicon pillar through photolithography, dry-etching GaN, and isotropic wet-etching silicon methods. Single-mode ultraviolet whispering gallery mode (WGM) lasing was obtained from the floating GaN microdisk under optical pumping conditions at room temperature. The features of WGM lasing, i.e., the threshold, emission intensity, and lasing mode number, were characterized. A two-dimensional finite-difference time-domain simulation about the optical field contour profile also confirmed the resonance mechanism of WGM lasing. This work can help realize single-mode WGM lasing with high quality factor and low threshold.

Fabrication of fine metal structures based on laser drawing method using interference pattern from co-propagating optical vortices

We propose and demonstrate a photolithography method for fine metal structure fabrication based on laser drawing that uses the interference pattern generated by co-propagating optical vortices. A tiny dark core region of the optical vortex allows us to overcome the diffraction limit for Gaussian beams. This means that the proposed method can be used to fabricate finer structures than those produced by the conventional laser drawing method while using a Gaussian beam, even under low numerical aperture conditions. The feasibility of the proposed method was demonstrated experimentally using a system that included an axially symmetrical polarization element that can generate the co-propagating optical vortices using a common path optical system. Our method has potential to fabricate few tens of nanometer scale metal line structures by increasing numerical aperture conditions and should be applicable to the development of nanometer scale electronic and optical devices and structures, such as integrated circuits and metamaterials, without using electron beam lithography.

Photolithographic patterned surface forms size-controlled lipid vesicles.

Using traditional 2-D photolithographic methods, surface patterns are made on agarose and used to form lipid vesicles with controlled size and layout. Depending on the size and layout of the patterned structures, the lipid bilayer vesicle size can be tuned and placement can be predetermined. Vesicles formed on 2-D patterned surfaces can be harvested for further investigations or can be assayed directly on the patterned surface. Lipid vesicles on the patterned surface are assayed for unilamellarity and protein incorporation, and vesicles are indeed unilamellar as observed from outer leaflet fluorescence quenching. Vesicles successfully incorporate the integral membrane protein α-hemolysin and maintain its membrane transport function.