In this paper, we demonstrate a technique to fabricate nanostructure in an inexpensive way. A layer of polystyrene (PS) beads (650 nm diameter) was coated to get monolayer on silicon oxide substrate. The gap created between the aligned PS beads was used to deposit metals like Cr, Al, and Au using sputtering and e-beam evaporation techniques. The nano sphere acted as a mask to generate array of metallic nano structures. The thickness of deposited metal was varied to achieve varying height of the structures. Removal of the PS beads was done using di-chloromethane. Silicon oxide substrate along with the regularly aligned metallic nano structure thus formed, acted as a metallic mould for nanoimprinting. The pattern was then imprinted on a thin PMMA layer. Nano cavities created on the PMMA layer were of the order of metallic nano structure. Spot lithography was used to create rectangles to define the regions (or spots) of confinement for nanosphere. These regular nano pattern generated could be optimized to get good quality nano structures and has apparent application in photonic crystal formation and other nano application.
Photolithography is the most important process used to pattern the surface of silicon wafers in IC fabrication.
It has shown high performance but its use is not cost-effective for small series or prototyping as it necessitates
a costly infrastructure (mask aligner) and requires the fabrication of masks which can be expensive and timeconsuming.
Recently, the high resolution achieved by ink-jet printer (> 1200 DPI) starts to make an interesting
alternative to obtain a patterned protective layer instead of using photolithography. This is particularly true for
MEMS which often need a resolution of only 10 to 20 μm.
After studying the different architecture of inkjet printer available in the market, a commercial S$100-printer
was selected and modified to allow printing on a rigid silicon wafer. We then developed three different patterning
processes using the printer. In a first process the ink was directly used as a protective layer for patterning.
A second process modified the photolithography by using the printed ink as a photo-mask on a spun layer of
photoresist. In each case we had to modify the surface energy of the wafer by surface treatment to improve the
resolution. Finally we replaced the ink with a modified photoresist solution and directly printed a protective
mask onto the wafer. Design of Experiment (DOE) methods were systematically employed to study the main
and interaction effects of the parameters on the lithography and on the pattern transfer.
The series of experiment showed that off-the-shelf ink-jet printer could be used easily for pattern with a
resolution below 50 μm, but could not yet reach the 20 μm range.
This paper reports on a hybrid polymeric microfluidic device with optical detection for droplet-based systems. The optical part of the device is integrated by a hybrid concept. The microfluidic structures were fabricated using CO2 laser on PMMA (poly methylmethacrylate) substrate. The microfluidic network consists of two microchannels for forming droplets of an aqueous liquid in an immiscible carrier liquid. The optical component consists of two optical fibers for guiding laser light from the source, through the detection point, to a photo diode. The formed droplets pass the detection point and diffract the incoming laser light. The detected signal at the photo diode can be used for evaluating droplet size, droplet shape, and droplet formation frequency. The device can detect very high formation frequencies, which are not detectable using a conventional CCD camera/microscope setup.
We present a simple yet efficient technique to obtain membrane with precise thickness by the etching of silicon in anisotropic etchant. This technique uses a mechanical holder to protect the front side of the wafer and a light signal to monitor from a distance the thickness of a reference hole in the etched wafer. The original feature in our set-up is that we measure the absorption of the light in two different bands of wavelength, one where the silicon is highly absorbant and the other where it is not, to improve the robustness of the measurement. This principle allows for effectively compensating for the fluctuation in the light source intensity, and provide real-time information on the membrane thickness, removing the incertitude inherent in the usual timed etch. We present the application of this technique to the manufacturing of thick single-crystal stiffener used to prevent the warp of stacked thin films presenting a gradient of stress.
Fabrication of microlens array using polymer reflow is beginning to be a mainstream process, whether the polymer is directly used or whether the spherical profile is transferred by plasma etching to a glass substrate as, for example, in some handphone cameras. The focus so far has been on uniformity and obtaining lenses with equal radius and equal focal length. Actually it is easy to show using a phenomenological model that the focal length is depending on the lens radius, and not much on the contact angle, an effect that can be traced to the line tension force. For a biomedical application we need to terminate a 600um diameter imaging fiber with a group of lenses of different diameters - but with similar focal length. We have devised a microfabrication process on a silicon wafer to produce the lens with variable diameter and identical focal length, while etching the silicon wafer has helped us producing a sheath to insert the optical fiber and mount the lenses on the optical fiber.
We have fabricated and tested an external cavity laser with a micromachined flat polysilicon micro-mirror. The device works using a very short external cavity laser configuration (approximately equals 10micrometers ) allowing to remove all optical element in the cavity while providing enough feedback to modulate the intensity of the laser. We have shown that we could obtain feedback coefficient larger than 0.5, providing an increased sensitivity for sensor application. The device shows interesting characteristics for developing a compact and simple displacement/acceleration sensor with large dynamical range and a resolution estimated below 0.01 nm.
Two monolithically integrated frequency tuners have been analyzed, designed and fabricated. The potential applications for WDM have also been studied. The frequency tuners use 3D micromirrors integrated with single-mode Fabry-Perot laser diodes and anti-reflection coated optical fibers. The difference between the two frequency tuners is that one uses the movable 3D micromirror driven by comb-drive to change the external cavity length, and the other uses the rotatable 3D micromirror driven by thermal-actuator to change the external feedback strength. For the frequency tuner that uses movable 3D micromirror, a wavelength tunability of 16 nm is obtained using 3V driving voltage. As for the frequency tuner that uses rotatable 3D micromirror, a wavelength tunability of 7nm is obtained while using 10mA driving current.
This paper reports the design, fabrication, and testing of a Micro-opto-mechanical grating/mirror switch driven by electrostatic actuator for fiber-optic switching applications. It consists of two banded silicon wafers. One input fiber with a hemispherical lens at its end and three photodetectors are fabricated on the upper wafer. A movable platform with two gratings and one mirror are fabricated on the lower wafer. When the movable platform is at a certain position, the input beam can be split into three beams by the gratings. Details of the grating switching design, theoretical analysis, fabrication and experimental results are presented in this paper.
We have designed a ne type of folding suspended polysilicon micro-mirror, integrating a new type of precision position- lock, a new compact design for the hinges and a bi- directional electrostatic actuator to bias the position of the mirror. The mirror is intended to be used in a very short external cavity laser configuration for acceleration/displacement sensing. An extensive theory has been built to guide the design and the fabrication of the sensor.
This paper presents a new design of micromachined optical rotating sensor (ORS). The concept demonstration prototype shows that the sensor will be low cost, small and reliable. To obtain a micro ORS, a ring resonator was designed, based on the three-layer polysilicon surface micromachining process. The ring resonator is made up of three micro mirrors and a laser diode coated with an anti-reflective coating. The micro ORS relies on the Sagnac effect for its operation. The resolution analysis and sensor design is presented here, and the signal processing and control system design is discussed. The theoretical resolution is in the range of 1 - 6 deg/h.
As a novelty application of Si-based integrated optics, the preliminary results of realisation of a compact Mach-Zehnder interferometer will be presented. The deposition of a
piezoelectric ZnO thin-film transducer on the reftrence arm of the interferometer will allow to transform this optically passive device in a device under an active phase modulation, useful to built a
high-resolution microsensing systems with optical heterodyning.
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