Photolithography

Microfluidics is a promising technology that is increasingly attracting the attention of researchers due to its high efficiency and low-cost features. Micropumps, micromixers, and microvalves have been widely applied in various biomedical applications due to their compact size and precise dosage controllability. Nevertheless, despite the vast amount of research reported in this research area, the ability to implement these devices in portable and implantable applications is still limited. To date, such devices are constricted to the use of wires, or on-board power supplies, such as batteries. This thesis presents novel techniques that allow wireless control of passive microfluidic devices using an external radiofrequency magnetic field utilizing thermopneumatic principle. Three microfluidic devices are designed and developed to perform within the range of implantable drug-delivery devices. To demonstrate the wireless control of microfluidic devices, a wireless implantable thermopneumatic micropump is presented. Thermopneumatic pumping with a maximum flow rate of 2.86 μL/min is realized using a planar wirelessly-controlled passive inductor-capacitor heater. Then, this principle was extended in order to demonstrate the selective wireless control of multiple passive heaters. A passive wirelessly-controlled thermopneumatic zigzag micromixer is developed as a mean of a multiple drug delivery device. A maximum mixing efficiency of 96.1% is achieved by selectively activating two passive wireless planar inductor-capacitor heaters that have different resonant frequency values. To eliminate the heat associated with aforementioned wireless devices, a wireless piezoelectric normally-closed microvalve for drug delivery applications is developed. A piezoelectric diaphragm is operated wirelessly using the wireless power that is transferred from an external magnetic field. Valving is achieved with a percentage error as low as 3.11% in a 3 days long-term functionality test. The developed devices present a promising implementation of the reported wireless actuation principles in various portable and implantable biomedical applications, such as drug delivery, analytical assays, and cell lysis devices.

This paper investigates the electrical behavior of the Al/SiO2/Si MOS structure. We have used the complex admittance method to develop an analytical model of total capacitance applied to our proposed equivalent circuit. The charge density, surface potential, semiconductor capacitance, flatband and threshold voltages have been determined by resolving the Poisson transport equations. This modeling is used to predict in particular the effects of frequency, parallel and series resistance on the capacitance-voltage characteristic. Results show that the variation of both frequency and parallel resistance causes strong dispersion of the C-V curves in the inversion regime. It also reveals that the series resistance influences the shape of C-V curves essentially in accumulation and inversion modes. A significant decrease of the accumulation capacitance is observed when R s increases in the range 200–50000 Ω. The degradation of the C-V magnitude is found to be more pronounced when the series resistance depends on the substrate doping density. When Rs varies in the range 100 Ω–50 kΩ, it shows a decrease in the flatband voltage from −1.40 to −1.26 V and an increase in the threshold voltage negatively from −0.28 to −0.74 V, respectively. Good agreement has been observed between simulated and measured C-V curves obtained at high frequency. This study is necessary to control the adverse effects that disrupt the operation of the MOS structure in different regimes and optimizes the efficiency of such electronic device before manufacturing.

The dissertation will be defended under open consideration in the Council of Materials
Science on the 18th of December, 2015, 15:00 h at the Laser Research Center
of Vilnius University, room 306, Sauletekio Ave. 10, Vilnius, Lithuania.
The summary of the dissertation was distributed on the 18th of November, 2015.

This paper proposes a computer model that simulates the emission of acoustic signals produced by a wave energy device. It analyses these signals with the aid of the audiogram of marine mammals, in this case the Harbour seal. This enables us to estimate the levels of acoustic noise experienced by marine mammals due to the presence of ocean deployed devices.

This paper reports a novel wireless control of a thermopneumatic zigzag micromixer achieved by selectively activating two passive wireless heaters enabled by an external radiofrequency magnetic field. The two heaters, which are designed to have different resonant frequency (fr) values of 100 and 130 MHz, are selectively activated by modulating the field frequency to their corresponding fr values. Each heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element, while the solutions pumped from each reservoir are mixed in a zigzag micromixing element that ends with an outlet hole. Mixing is achieved in a relatively short mixing length of a 2 mm, and was investigated over a low range of Reynold's number (Re) ≤ 10 that is suitable various biomedical applications. The numerically simulated and measured results of the proposed micromixer have shown mixing efficiencies values higher than 82% for the whole range of Re. The optimal activation switching time of the heaters is 10 s, at which the micromixer achieves a steady value of the maximum mixing efficiency after ~65 s. The micromixer provides mixing-ratio controllability with a maximum flow rate and pressure drop of ~3.4 μL/min and ~385.22 Pa, respectively.

The synthesis of Ni-filled multi-walled carbon nanotubes was performed by atmospheric pressure chemical vapor deposition with propane on Si at 850 °C using a simple mixture of (N, N'-bis(salicylidene)-ethylenediiminato) nickel(II), commonly known as Ni(salen), and a conventional photoresist. Analysis of the carbon nanotubes using scanning electron microscopy together with high-resolution transmission electron microscopy show that the nanotubes have grown by a tip-growth mechanism and exhibit a multi-walled structure with partial Ni filling. The high quality of the Ni-filled nanotubes is evidenced by Raman spectroscopy. The magnetic properties of Ni-filled nanotubes were analyzed using a superconducting quantum interference device which revealed their ferromagnetic behavior with large coercivity. A scalable as well as site-selective growth of high quality Ni-filled carbon nanotubes is achieved by a simple photolithographic method.

Nearly all antenna structures fabricated for high volume markets are confined, where possible, to essentially planar geometries. This is driven by the need to minimise fabrication and packaging costs. For certain applications considerable performance gains can however be achieved by utilising the third dimension. A well known example is the helical spiral structure, which has been manufactured by Sarantel for high-performance GPS receivers. Due to the complex geometry, fabrication of these antennas is slow and cumbersome in comparison to planar structures since conventional photolithography fabrication methods are inherently incompatible with non-planar substrates owing to diffraction effects that degrade the resulting pattern. Instead, helical antennas are constructed directly by scanning a laser beam across a rotating substrate. We describe a novel 3-D photolithographic method that enables non-planar antenna structures to be fabricated by a single photolithography exposure, thus regaining the potential for mass-production. We demonstrate the approach by fabricating a bi-conical spiral antenna structure representative of a wideband antenna for the frequency range 6–47 GHz.

A novel photolithography-based technique was developed to fabricate a quasi-2D heterogeneous calcite micromodel of representative elementary volume size. The effect of brine-chemistry on the mobilization of capillarity and heterogeneity trapped oil after high salinity water injection was evaluated by using diluted seawater, and seawater modified with calcium, sulphate, and silica nanoparticles. Preliminary brine screening was performed based on modified contact angle experiments under dynamic salinity alteration. The main findings are that the chemical composition of brine impacts both the ultimate oil recovery and its speed. The highest and fastest oil recovery was obtained with diluted seawater and seawater augmented with nanoparticles. We also found that the ex-situ contact angle results, indicative of wettability alteration, can be predictive of each brine performance at the pore network-scale. A slow recovery process, from 7 days up to 12 days, without any oil banking, was observed with all the brines. Due to the time-dependent nature of the wettability alteration process, mere injection of brines, even several pore-volumes and the viscous force exerted by flooding, were not sufficient to result in any additional oil production. Oil production was obtained only during the shut-in period via enhanced spontaneous imbibition of brine into the pores and throats. This highlights that a sufficient soaking time (at least for laboratory scale experiments) would be necessary to assess suitability of brines and determine accurately the incremental oil recovery by low salinity waterflooding (LSWF).

A multilevel multistage inverter design and its corresponding control strategy are presented. The hybrid inverter has a high voltage stage composed of the six-switch conventional three phase inverter with its outputs connected in series to the outputs of three-level H-bridge medium and low voltage stages. The voltage ratio has been selected to form 18-level provide maximum number of uniform steps. The suggested control strategy has been developed to ensure minimum switching losses focusing on holding the higher voltage stage state as long as it is feasible. The reference voltage vector has been approximated to the nearest inverter voltage vector. A special definition of state zone has been introduced for the low voltage stage to enable the achievement of the reference vector with minimum error. The proposed control strategy has been tested and its short computational time and low memory requirement has been proven.

An efficient and practical photoresist development simulator based on cellular automata is presented. Image reversal and chemical amplification processes are also simulated using this simulator. To verify the simulator, a series of experiments have been designed and performed using the Shipley SNR-248 negative resist, a stepper, and a deep ultraviolet source at 248 nm. Experiments were performed for periodic and isolated lines with pitches 300, 400, 500, and 1000 nm, for exposure energy doses of 11, 13, 17, and 23 mJ/cm2, and with developer temperatures of 0, 20, and 80 C. In all cases, the simulator results were found to be in very good agreement with the corresponding experimental results. The simulator has also successfully reproduced the incomplete opening effect observed in the case of close-spaced parallel lines.

Abstract Improvements in the contrast of e-beam exposed resists have been reported via the use of multiple interrupted development techniques. Additional baking is claimed to effect greater improvements in optical lithography. This so called intermediate development bake or (IDB) process, has recently been further simplified through adoption of a warm water treatment for the baking step. In the w arm w ater IDB process, the need to spin dry wafers is eliminated, thereby improving development throughput. We report on the application of all of these treatments to resists exposed using e-beam. Contrast curves obtained with multiple ww IDB processes at different temperatures and times are presented and compared with those obtained utilizing conventional development with varying PEB conditions. The effect on sizing both the top and base of the resist image as a function of exposure is also examined. Olin Hunt HEBR 214 has been at the focus of our work, although we additionally report on HEBR 242 and HPR 204, as well as Aspect System 912.

A comparative examination is presented of materials and approaches for the fabrication of microfluidic devices for small-angle neutron scattering (SANS). Representative inorganic glasses, metals, and polymer materials and devices are evaluated under typical SANS configurations. Performance criteria include neutron absorption, scattering background and activation, as well as spatial resolution, chemical compatibility and pressure resistance, and also cost, durability and manufacturability. Closed-face polymer photolithography between boron-free glass (or quartz) plates emerges as an attractive approach for rapidly prototyped microfluidic SANS devices, with transmissions up to $98% and background similar to a standard liquid cell (I ' 10 À3 cm À1). For applications requiring higher durability and/or chemical, thermal and pressure resistance, sintered or etched boron-free glass and silicon devices offer superior performance, at the expense of various fabrication requirements, and are increasingly available commercially.

Abstract Use of a warm water soak midway during development results in improved resist profiles, particularly as a function of focus. Three positive resists are examined in order to qualitatively determine their particular time temperature response to such a process. We find that the expected trade off between temperature and time holds, furthermore there is no need to spin dry wafers during treatment. Control of the time and temperature gives rise to improved profiles relative to samples utilising interrupted development. The warm water IDB also requires lower overheads in development time, as well as being applicable to a wider range of Novolac/DNQ chemistries. The use of multiple warm water IDB treatments may be required in extending the focus latitude of both lines and contacts printed over topography.

This paper reports a novel wireless control of a thermopneumatic zig-zag micromixer by selectively activating two passive wireless heaters enabled by an external radiofrequency magnetic field. Each heater generates heat when the external field frequency is tuned to the corresponding resonant frequency (fr) of the heater. The two heaters that are designed to have different f of 100 MHz and 130 MHz are selectively activated with a constant input power of 0.2 W by modulating the field frequency to their corresponding fr. Each heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element, while the solutions pumped from each reservoir are mixed in a zig-zag micromixing element that ends with an outlet hole. The micromixer provides a mixing-ratio controllability with a flow rate of ~0.28 μL/min and biocompatibility, making it promising for biomedical applications, such as local drug delivery and cells culturing.

The effect of pulsed radiation from an ArF excimer laser (R 193 nm, T = 20 ns) of chalcogenide thin films of AS2S3 and AsSe was investigated. Photodarkening. photoablation, and photothermal ablation arc observed in succession as the flux density is increased to 100 mJ/cm 2. The intensity or the photodarkening increases sharply as moves to the vacuum UV region and has a nonlinear character: the reciprocity law rails. Moreover, the photodarkening is accompanied by a change in the chemical solubility or the irradiated parts or the material. Photoablation begins at 20—25 mJ/cm2 . The dependence of ablation speed On pulse energy E p has two parts: in the first part photoetching occurs immediately, and in the second (E > 50 mJ/cm 2) photothermal ablation prevails. Use of these effects to record images can lead to high values or contrast which, in the case of vacuum-UV photolithography, provides the possibility of submicron resolution patterning

A cross-linking moiety having a structure represented by formula (I) or (II):
N3-ArF-W  (I)
(N3-ArF-W)n-L (II)
wherein ArF comprises a fluorinated phenyl group having at least one non-fluorine substituent (R) that is bulkier than fluorine and which is located at the meta position relative to the N3 group; W comprises an electron-withdrawing group; and L comprises a linker group. The cross-linking moiety is particularly useful in the manufacture of polymer semiconductor layers and photovoltaic devices

Problem statement:
Challenges in achievement of critical layers CD stability in advanced flash processes are reaching significant complexity as result of tight process window imposed on expected focus/dose variation in lithography tool. Common way to perform feed forward prediction for focus/dose variation is creation of FE (Focus /Exposure) Map. In current methodology CD measurements is the only source of FE map construction. Taking in account that for critical layers significant amount of most sensitive features are created using OPC techniques which in turn impact shape/roughness of targeted CD with minimal variation of the focus/dose. Thus CD measurements could be highly unreliable for FE map predictor with commonly used quadratic approximation. Manual CD measurements data filtering is necessary condition in this case. Furthermore for some features quadratic approximation approach itself raising additional concerns about focus shifts for different dose levels. Also no well defined techniques exist for online focus performance tracing and focus trend detection partly due to the mentioned above approximation approach.
Solution:
The purpose of this paper is to discuss how to perform reliable feed forward FE prediction taking in account challenges in advanced flash processes. We introduce here additional variable for FE determination – pattern recognition score and thus elimination manual data preprocessing. Also modification in commonly used approximation techniques introduced with sole purpose to differentiate positive and negative focus trends as part of superposition of classical FE map with score FE maps.
Description of general approach for algorithm stepping and various techniques for judgment of measurement validity presented in paper as well.
Benefits results & summary:
        Elimination of manual data preprocessing and construction of  reliable FE map predictor which
        could in turn be used for online FE drift estimation as part of routine DCCD/FCCD check as well       
        as drastically reduction of FE measurement.

The synthesis of Ni filled multi-walled carbon nanotubes was performed by atmospheric pressure chemical vapor deposition with propane on Si at 850 C using a simple mixture of (N,N’-bis(Salicyliden)-ethylenediiminato) nickel(II) popularly known as Ni(Salen) and conventional photoresist. Analysis of the carbon nanotubes using scanning electron microscopy together with high-resolution transmission electron microscopy show that the nanotubes have grown by tip-growth mechanism, exhibit a multi-walled structure with partial Ni filling. The high quality of the Ni filled nanotubes is evidenced by Raman spectroscopy. The magnetic properties of Ni-filled nanotubes were analyzed using a superconducting quantum interference device. A scalable as well as site-selective growth of high quality Ni filled carbon nanotubes is achieved by a simple photolithographic method.

A comparative examination is presented of materials and approaches for the fabrication of microfluidic devices for small-angle neutron scattering (SANS). Representative inorganic glasses, metals, and polymer materials and devices are evaluated under typical SANS configurations. Performance criteria include neutron absorption, scattering background and activation, as well as spatial resolution, chemical compatibility and pressure resistance, and also cost, durability and manufacturability. Closed-face polymer photolithography between boron-free glass (or quartz) plates emerges as an attractive approach for rapidly prototyped microfluidic SANS devices, with transmissions up to ∼98% and background similar to a standard liquid cell ( ≃ 10 cm). For applications requiring higher durability and/or chemical, thermal and pressure resistance, sintered or etched boron-free glass and silicon devices offer superior performance, at the expense of various fabrication requirements, and are increasi...

Kathryn Smith spent two weeks working at The Artists' Press in early 2004, challenging Mark Attwood to come up with a new way of working in print. Mark watched in fascination as Kathryn Smith manipulated her DVD, digital camera and the video machine all at the same time. Not to be outdone Mark added his own mix of lithography, polymer plates and the recently acquired etching press to Kathryn's mix.

The result was a suite of ten prints which toured the country as part of Smith's exhibition as the Standard Bank Young Artist of the Year award in 2004.

Kathryn Smith is a conceptual artist who works in a variety of media. Smith can be described as a performance artist, photographer, cultural agitator and manipulator of computer and video media to create her multi-layered artworks. Her interest in forensic pathology and psychology led to the creation of these prints which offer strong social commentary to those who wish to delve beyond the surface veneer of celebrities such as Marilyn Monroe.

The synthesis of Ni-filled multi-walled carbon nanotubes was performed by atmospheric pressure chemical vapor deposition with propane on Si at 850 °C using a simple mixture of (N, N'-bis(salicylidene)-ethylenediiminato) nickel(II), commonly known as Ni(salen), and a conventional photoresist. Analysis of the carbon nanotubes using scanning electron microscopy together with high-resolution transmission electron microscopy show that the nanotubes have grown by a tip-growth mechanism and exhibit a multi-walled structure with partial Ni filling. The high quality of the Ni-filled nanotubes is evidenced by Raman spectroscopy. The magnetic properties of Ni-filled nanotubes were analyzed using a superconducting quantum interference device which revealed their ferromagnetic behavior with large coercivity. A scalable as well as site-selective growth of high quality Ni-filled carbon nanotubes is achieved by a simple photolithographic method.

Polydimethylsiloxane (PDMS) elastomers are extensively used for soft lithographic replication of microstructures in microfluidic and micro-engineering applications. Elastomeric microstructures are commonly required to fulfil an explicit mechanical role and accordingly their mechanical properties can critically affect device performance. The mechanical properties of elastomers are known to vary with both curing and operational temperatures. However, even for the elastomer most commonly employed in microfluidic applications, Sylgard 184, only a very limited range of data exists regarding the variation in mechanical properties of bulk PDMS with curing temperature. We report an investigation of the variation in the mechanical properties of bulk Sylgard 184 with curing temperature, over the range 25 °C to 200 °C. PDMS samples for tensile and compressive testing were fabricated according to ASTM standards. Data obtained indicates variation in mechanical properties due to curing temperature for Young's modulus of 1.32–2.97 MPa, ultimate tensile strength of 3.51–7.65 MPa, compressive modulus of 117.8–186.9 MPa and ultimate compressive strength of 28.4–51.7 GPa in a range up to 40% strain and hardness of 44–54 ShA.