The development of organic electronic requires a non contact digital printing process. The European funded e-LIFT project investigated the possibility of using the Laser Induced Forward Transfer (LIFT) technique to address this field of applications. This process has been optimized for the deposition of functional organic and inorganic materials in liquid and solid phase, and a set of polymer dynamic release layer (DRL) has been developed to allow a safe transfer of a large range of thin films. Then, some specific applications related to the development of heterogeneous integration in organic electronics have been addressed. We demonstrated the ability of LIFT process to print thin film of organic semiconductor and to realize Organic Thin Film Transistors (OTFT) with mobilities as high as 4 10-2 cm2.V-1.s-1 and Ion/Ioff ratio of 2.8 105. Polymer Light Emitting Diodes (PLED) have been laser printed by transferring in a single step process a stack of thin films, leading to the fabrication of red, blue green PLEDs with luminance ranging from 145 cd.m-2 to 540 cd.m-2. Then, chemical sensors and biosensors have been fabricated by printing polymers and proteins on Surface Acoustic Wave (SAW) devices. The ability of LIFT to transfer several sensing elements on a same device with high resolution allows improving the selectivity of these sensors and biosensors. Gas sensors based on the deposition of semiconducting oxide (SnO2) and biosensors for the detection of herbicides relying on the printing of proteins have also been realized and their performances overcome those of commercial devices. At last, we successfully laser-printed thermoelectric materials and realized microgenerators for energy harvesting applications.
Optical biochips may incorporate both optical and microfluidic components as well as integrated light emitting
semiconductor devices. They make use of a wide range of materials including polymers, glasses and thin metal films
which are particularly suitable if low cost devices are envisaged. Precision laser micromachining is an ideal flexible
manufacturing technique for such materials with the ability to fabricate structures to sub-micron resolutions and a
proven track record in manufacturing scale up.
Described here is the manufacture of a range of optical biochip devices and components using laser micromachining
techniques. The devices employ both microfluidics and electrokinetic processes for biological cell manipulation and
characterization. Excimer laser micromachining has been used to create complex microelectrode arrays and microfluidic
channels. Excimer lasers have also been employed to create on-chip optical components such as microlenses and
waveguides to allow integrated vertical and edge emitting LEDs and lasers to deliver light to analysis sites within the
biochips.
Ultra short pulse lasers have been used to structure wafer level semiconductor light emitting devices. Both surface
patterning and bulk machining of these active wafers while maintaining functionality has been demonstrated. Described
here is the use of combinations of ultra short pulse and excimer lasers for the fabrication of structures to provide ring
illumination of in-wafer reaction chambers.
The laser micromachining processes employed in this work require minimal post-processing and so make them ideally
suited to all stages of optical biochip production from development through to small and large volume production.
An optical biochip is being developed for monitoring the sensitivity of biological cells to a range of environmental
changes. Such changes may include external factors such as temperature but can include changes within the suspending
media of the cell. The ability to measure such sensitivity has a broad application base including environmental
monitoring, toxicity evaluation and drug discovery. The device under development, capable of operating with both
suspension and adherent cell populations, employs electrokinetic processes to monitor subtle changes in the physicochemical
properties of cells as environmental parameters are varied. As such, the device is required to maintain cells in
a viable condition for extended periods of time.
The final device will employ integrated optical illumination of cells using red emitting LED or laser devices with light
delivery to measurement regions achieved using integrated micro-optical components. Measurements of electrokinetic
phenomena such as dielectrophoresis and electrorotation will be achieved through integrated optical detectors.
Environmental parameters can be varied while cells are actively retained within a measurement structure. This enables
the properties and sensitivity of a cell population to be temporally tracked.
The optical biochip described here uses a combination of microfabrication techniques including photolithographic and
laser micromachining processes. Here we describe the design and manufacturing processes to create the components of
the environmental monitoring strutures of the optical biochip.
We demonstrate complete integration of a fluorescence-based assay in that the analyte well is also an optical emitter.
Laser machining is used to create 'active micro-wells' within semiconductor light emitting diode and laser structures.
These are then used to optically excite fluorescently-labelled beads in solution within the well. The results show
efficient illumination on a par with traditional lamp-based excitation. This technology therefore provides active microwell
plates with completely localized excitation, confined to the analysis well, that can be engineered via the micro-well
geometry. The micro-wells have also been machined within the cavity of lasing semiconductor structures and coherent
emission maintained. Thus lasing multi-well plates are also realizable.
Fibre Bragg gratings (FBGs) continue to be used in a wide variety of different telecommunications products such as filters, pump stabilisers and dispersion compensators. The increased specifications being demanded by successive generations of FBG components mean that higher manufacturing controls are needed to ensure high quality performance. One of the key areas of concern has been the effect of the laser exposure on the tensile strength of the fibre, since this affects yield, quality and lifetime of the FBG device. No comparative study has, to the best of our knowledge, so far been conducted to measure the relative merits of different exposure conditions. We present measurements of the degradation of the strengths of Corning SMF28 and intrinsically photosensitive fibres from laser exposure with the following lasers: excimer lasers at 193nm and 248nm and argon-ion laser at 244nm. A comparison is presented of the fibre pull strengths under varying illumination conditions with the different laser systems and a methodology established for favourable exposure conditions for FBG writing with reduced fibre strength degradation.
The laser micromachining characteristics of indium phosphide, lithium niobate and silicon have been characterised using a 355nm neodymium vanadate laser and 193nm and 248nm excimer lasers. Etch rates for these materials are presented at the different laser wavelengths. High quality cutting of the three materials is demonstrated with the 355nm laser and an excimer laser mask projection method is subsequently used to micromachine precision V-grooves as fibre placement structures. Silicon microbenches, used for the integration of multiple-function devices, are also produced using the 355nm laser.
Vacuum UV laser micromachining is used to produce microstructures in common photonics materials. The ablation etch rates of lithium niobate, fused silica and indium phosphide are measured at 157nm and angled facets and v-grooves are machined into the materials using a high NA mask projection system. The applicability of such micromachined structures for photonics devices is discussed and future developments outlined.
An experimental study is presented which evaluates the effects of various important exposure parameters on the quality of fiber Bragg gratings. The parameters addressed include laser repetition rate, fluence and intensity, total exposure dose, numbers of shots, fiber-mask separation and beam scanning speed. In the case of excimer laser writing of gratings, it is seen that the balance between exposure fluence and total dose is crucial in how strong a grating can written and its writing time. It is also observed that the laser repetition rate does not affect the grating quality and that a fiber-mask separation of around 50 - 200 μm is desirable for optimum gratings. The changes in grating quality with argon ion beam scanning speed and exposure power are presented.
Within the research project FEMTO, supported by the European Commission, a compact diode-pumped titanium:sapphire laser has been developed which matches the requirements of industrial systems, like compact dimensions and stable laser operation. To achieve this, the laser has been specially designed to be integrated directly into the machining system. For best process speed combined with optimal cutting quality, focus has been laid upon high repetition rates at moderate pulse energies. Typical average output powers are around 1.5W and repetition rates of up to 5 kHz. Accompanying to the laser development, a micro-machining system has been designed to meet the requirements of femtosecond laser micro-machining. In parallel to the machine development, machining processes have been investigated and optimized for different applications. The machining of delicate medical implants has been demonstrated as well as the machining system for general micro-machining of sensitive and delicate materials has been proven. Therefore, the developed machine offers the potential to boost the use of femtosecond lasers in industrial operation.
Next generation photolithography stepper tools will operate at 157 nm and require robust solid state photodetectors to ensure efficient operation and facilitate direct beam monitoring for photoresist dosimetry. There is currently no commercial detector system able to fully meet all the demanding requirements of this application. Diamond has a band gap of 5.5 eV. This implies that detectors fabricated from this material may be intrinsically visible blind and radiation hard. In this paper the results of the first study to assess the viability of the use of thin film polycrystalline diamond photodetectors for use in 157 nm F2-He based laser lithography tools are presented. Co- planar interdigitated electrode structures were fabricated on free standing polycrystalline diamond to realise photoconductive devices. These were exposed to pulses from an F2-He laser in the fluence range 0 - 1.4 mJcm-2. The electrical and optical characteristics of the devices have been measured and are compared to the response of a standard vacuum photodiode. The diamond devices appear to be ideally suited for use at 157 nm in lithography applications.
The area of display devices has experienced extremely rapid growth in recent years and these advances show no sign of declining. One of the major developments in this field has been the use of lasers for various microfabrication tasks. This paper describes some techniques which have been developed using excimer lasers for the production of novel microstructures in polymer materials. Examples of the types of microstructures which are produced are presented and their applicability for display device applications is outlined. Forthcoming developments in the laser manufacture of displays are discussed.
As laser micromachining has developed in recent years, there has emerged a need for the simplification of the process to produce MEMS structures where the stages of manufacture do not require an in-depth knowledge of laser micromachining techniques. This paper describes the initial stages of such an approach - the laser micromachining 'toolbox' - which enable the optimum machining choices to be made from various design requirements. Some of the elements of the toolbox are introduced and quantified in the particular case of excimer laser micromachining. These features are then used to produce a 3D microstructure to demonstrate the capabilities of this approach. Future developments in this area are discussed.
Applications of pulsed laser ablation to the manufacture of micro- electro-mechanical systems (MEMS) and micro-opto-electro-mechanical systems (MOEMS) devices are presented. Laser ablative processes used to manufacture a variety of microsystems technology (MST) components in the computer peripheral, sensing and biomedical industries are described together with a view of some future developments.
Excimer laser micromachining has developed into a mature production method and many industrial applications such as the drilling of ink-jet printer nozzles, production environments. The important concepts of excimer laser micromachining systems are described and the novel methods which have been developed in this area are presented. In particular, techniques for the production of complex, multi- level 3D microstructures are described and examples of such features are used to illustrate the relevant applications. Furthermore, some initial micromachining result from a sub- nanosecond, solid-state fiber laser are presented to highlight the rapidly-growing area of laser micro processing using ultra-short pulse lasers.
Micro-machining techniques using pulsed lasers are currently being applied world-wise in many diverse industrial application areas including biomedical devices, printers, flat-panel displays, semiconductors devices and telecommunication systems. In particular, the use of excimer lasers has been at the forefront of the new developments in the manufacture of complex micro-structures for the production of micro-optical-electro-mechanical-systems units such as nozzles, optical devices and sensors. This paper reviews the fundamentals of excimer laser micromachining techniques and details recent developments which have enhanced the capabilities of these approaches. Application areas where these techniques are of interest are highlighted.
The increasing use of Internet-resources worldwide offers new chances in the development of net-based teaching and training materials. Especially in the area of life long learning that is becoming more and more important for persons who are involved in design, production or application of high-tech products in their professional lives, net-based training opens new perspectives. As ordinary classroom courses and centralized training seminars are expensive and draw personnel out of their productive working environments for prohibitively long periods, these traditional training techniques are not well suited to life long learning. This article addresses the results of the TRANSTEC-project. The project addresses this matter by providing a novel concept of interactive Internet-based training entities.
Excimer laser ablation is used in conjunction with mask projection techniques to produce novel and complex microstructures. Special multiple-mask techniques have been developed which, together with synchronized workpiece motion and laser firing, are used for the manufacture of features such as micro-channels, ramps, contoured surfaces with channels etc. These new techniques allow planar microstructures to be combined and superimposed onto curved or multifaceted shapes, thereby enabling hitherto unobtainable structures to be produced. Details are given of the techniques used along with examples of the types of structures which have been produced.
In recent years, microfabrication techniques derived from existing expertise in the microelectronics industry have been applied to the fields of biotechnology and clinical diagnostics. In this work, 'Biofactory-on-a-chip' devices are being developed to demonstrate how these microfabrication techniques can be combined with electrokinetic phenomena to manipulate, separate and characterize biological material using non-uniform electric fields. Excimer laser ablation methods have been used to fabricate these devices. Key to the successful fabrication and functioning of 'Biofactory' devices is the ability to: machine microelectrodes with micrometer feature sizes over a large area; create via-holes in insulating layers to form electrical interconnects in multilayer structures; fabricate shaped microfluidic channels; and control alignment in the device production with micron accuracy.
SubWavelength Structured Surfaces (SWS), by synthesizing effective index of refraction, offer an attractive way to mimic antireflective coating effects. It is of particular interest for some IR materials of high index of refraction such as CdTe or KRS-5. These material are often used for entrance window in cryogenic IR instrument in the 20 microns band. For these materials, multilayer antireflective coatings provide limited performances in transmission, while expected performances of SWS can be very high even for a wavelength range covering both the N and Q atmospheric windows, from 7 microns to 28 microns. The SWS simulates a gradient index layer. Its main parameters are its pitch and its depth. The pitches required depend on the IR material index. For CdTe and KRS5, they are around 3 microns to work in N-band and Q-band and around 6 microns to work only on Q- band, and the depth required is around 10 microns to work till 28 microns. We have tried a new approach to realize these structures by using excimer laser ablation technique. We describe the used technique and our results for different materials such as CdTe, KRS5, CsBr and CsI. Antireflection structured surfaces on CdTe could offer an increase in transmission better than 25 percent at 24 microns. We measured a transmission efficiency of near 96 percent between 23 micrometers and 35 micrometers on KRS-5, and more than 95 percent between 18.5 micrometers and 35.5 micrometers on CsI.
Multilevel microelectrode structures have been produced using excimer laser ablation techniques to obtain devices for the electro-manipulation of bioparticles using traveling electric field dielectrophoresis effects. The system used to make these devices operates with a krypton fluoride excimer laser at a wavelength of 248 nm and with a repetition rate of 100 Hz. The laser illuminates a chrome-on-quartz mask which contains the patterns for the particular electrode structure being made. The mask is imaged by a high- resolution lens onto the sample. Large areas of the mask pattern are transferred to the sample by using synchronized scanning of the mask and workpiece with sub-micron precision. Electrode structures with typical sizes of approximately 10 micrometers are produced and a multi-level device is built up by ablation of electrode patterns and layered insulators. To produce a traveling electric field suitable for the manipulation of bioparticles, a linear array of 10 micrometers by 200 micrometers microelectrodes, placed at 20 micrometers intervals, is used. The electric field is created by energizing each electrode with a sinusoidal voltage 90 degree(s) out of phase with that applied to the adjacent electrode. On exposure to the traveling electric field, bioparticles become electrically polarized and experience a linear force and so move along the length of the linear electrode array. The speed and direction of the particles is controlled by the magnitude and frequency of the energizing signals. Such electromanipulation devices have potential uses in a wide range of biotechnological diagnostic and processing applications. Details of the overall laser projection system are presented together with data on the devices which have been manufactured so far.
Multi-level micro-electrode structures have been produced using excimer laser ablation techniques to obtain devices for the electro-manipulation of bioparticles using traveling electric field dielectrophoresis effects. The system sued to make these devices operates with a krypton fluoride excimer laser at a wavelength of 248 nm and with a repetition rate of 100Hz. The laser illuminates a chrome-on-quartz laser at a wavelength of 248nm and with a repetition rate of 100Hz. The laser illuminates a chrome-on-quartz mask which contains the patterns for the particular electrode structure being made. The masks then imaged by a high-resolution lens onto the sample. Large areas of the mask pattern are transferred to the sample by using synchronized scanning of the mask and workpiece with sub-micron precision. Electrode structures with typical sizes of approximately 10 micrometers are produced and a multi-level device is built up by ablation of electrode patterns and layering insulators. To produce a traveling electric field suitable for the manipulation of bioparticles, a linear array of 10 micrometers by 200 micrometers micro- electrodes, placed at 20 micrometers intervals, is used. The electric field is created by energizing each electrode with a sinusoidal voltage 90 degrees out of phase with that applied to the adjacent electrode. On exposure to the traveling electric field, bioparticles become electrically polarized and experience a linear force and so move along the length of the linear electrode array. The speed and direction of the particles is controlled by the magnitude and frequency of the energizing signals. Such electromanipulation devices have potential uses in a wide range of biotechnological diagnostic and processing applications.
Excimer laser projection methods have ben developed to directly create high resolution electrical circuits in both thin nd thick-film metallic layers in order to form robust, compact multi-chip module interconnection devices, miniature sensor elements, miniature flexible printed circuits, antennas etc at high sped and low cost. Patterning over small or large areas is possible at high speed using simple step and repeat or more complex synchronous mask and workpiece scanning methods. Ablation rates depend strongly upon the thickness of the metal layer varying from complete metal removal with 1 laser shot for thin films to multiple 10s of shots for films to a few J/cm2 for screen printed polymer thick films or thick sputtered films. Multiple layer interconnect circuits and complex advanced sensor devices have been successfully fabricated using these excimer laser metal film patterning methods together with laser via drilling and patterning of dielectric layers using a laser tool with appropriate level to level alignment and mask changing and scanning facilities.
An excimer laser microstepper, intended for R and D studies of 193nm lithography, is described. System details such as the laser performance, beam transport, wafer handling and photoresist processes are outlined.
A 193 nm excimer laser microstepper has been developed for deep UV photolithography research and development and system details are presented. The tool incorporates a times 10, 0.5 NA, 4 mm field diameter, high-resolution imaging lens of either all-refractive or catadioptric design. An all-fused silica refractive lens has been used in the results reported here to carry out exposures in polymethylmethacrylate (PMMA) and polyvinylphonel (MX-P8) photoresists. Well-resolved images of 0.2 micrometer dense lines and spaces have been produced in the PMMA and MX-P8 resists.
A 193nm excimer laser microstepper has been developed for deep UV photolithography research at this wavelength. The system incorporates a x10, 0.5NA, 4mm field diameter, high-resolution imaging lens of either all-refractive or catadioptric design. An all-fused silica refractive lens has been used in the results reported here to carry out exposures in polymethylmethacrylate and polyvinylphenol photoresists. Well-resolved images of 0.2micrometers dense lines and spaces and 0.35micrometers diameter contact holes have been produced in PMMA and polyvinylphenol resists.
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