Viktoras Grigaliunas

Replication technology for photonic band gap applications

Abstract Replication technology was applied for photonic structure fabrication in silicon substrate. It was revealed, that thin thermoplastic polymer layers on silicon substrates may be patterned by hot embossing technique for dry etching masking. Ni mold used for plain hot embossing into polymer layers was fabricated by Ni electrochemical deposition on the reference silicon surface structure, which was obtained by direct electron beam (EB) writing and SF 6 /N 2 reactive ion etching (RIE) technique. It is shown that the shape of replicated photonic structures is determined by RIE parameters.

Design, fabrication, and simulation of cantilever-type electrostatic micromechanical switch

A cantilever-type electrostatically actuated microelectromechanical (MEMS) switch and its fabrication technology have been developed for the first time in Lithuania, in Kaunas University of Technology. The microdevices were fabricated using nickel surface micromachining technology on substrates made of semiconductor (silicon) and insulator materials (quarts and ceramics). The microswitch consists of cantilevered nickel structure suspended over actuation and contact electrodes. The width of the cantilever contacting element is 30 μm, thickness is about 2.0 μm and length ranges from 67 to 150 μm. Implementation of microswitches as a substitute for present switching devices poses many problems. In particular lower switching speed and reduced lifetime are considered to be among the most significant ones. These characteristics are determined both by design and dynamic phenomena that are taking place during its operation. Specifically, when the microswitch closes, it bounces several times before making permanent contact. These impact interactions greatly influence microswitch durability and switching speed. With the aim of improving these parameters a comprehensive finite element model is being developed that takes into account not only electrostatic actuation and squeeze-film damping effects but also describes important dynamic phenomena - impact interactions that take place during switching. Experimental research of electrical and dynamic characteristics is also carried out with the purpose of device model validation and correction. The paper presents design and fabrication process of the developed microswitch as well as initial simulation and measurement results.

alpha-C:H films for photonic structure fabrication

(alpha) -C:H films were applied to fabricate photonic band gap (PBG) structures in the silicon substrate by SF6N2-based reactive ion etching (RIE). The influence of RIE parameters on (alpha) C:H films structure and etching rate was investigated int his study. It is shown that RIE rate for (alpha) -C:H films changes from 26 nm/min to 38 nm/min with the integrated intensity ratios ID/IG varied from 0.65 to 1.1. It is evident that increase in etching rate is determined by increasing quantity of sp2 bonding in the synthesized (alpha) -C:H films. RIE does not change structure of the (alpha) -C:H masking films. However, non- uniform character of RIE takes place due to the non- homogeneous graphite clusters in (alpha) -C:H masking films. However, non-uniform character of RIE takes place due to the non-homogeneous graphite clusters in (alpha) -C:H masking films. By changing parameters of silicon etching, such as RF power density, pressure and negative bias voltage, anisotropy was varied in wide range and microstructures of different shape were obtained.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Thermal stress kinetics in the microresist - : silicon system

In this work we report stress kinetics of thermoplastic polymer mr-I 8020 on crystalline silicon during thermal exposure to the temperature ranges typically applied in the imprint experiment. Stress kinetics in the polymer-silicon structure was measured experimentally in-situ using a Michelson interferometer and controlling temperature of the structure by thermocouple. The changes of radius of curvature due to the thermal heating were measured by laser (λ=633nm) interferometer and corresponding stress was calculated using a Stoney formula. It is shown that within the temperatures below the polymer glassing temperatures elastic response of the polymer dominates for different time of heating and cooling.

Synergy of contact and noncontact techniques for design and characterization of vibrating MOEMS elements

The investigation of dynamics of microelectromechanical systems (MEMS) and microoptoelectromechanical systems (MOEMS) is an important problem of engineering, technology, and metrology. Specifically, recent interest in applying MOEMS technology to the miniaturization of micromirrors, sensors, and actuators for variety of applications requires the design of appropriate testing and measurement tools for investigation of dynamic properties of those systems. Though MOEMS technology offers great promise in addressing the need for smaller dynamical systems, the development of new types of MOEMS structures is a very costly and complicated procedure. On the other hand, straight application of the principles of design of macromechanical systems is rather limited in MOEMS applications. Therefore, the application of measurement technologies capable of detecting the dynamic properties of microscale systems may help to understand and evaluate the functionality of the systems. Technological aspects of MOEMS design and methods of their characterization are presented.

Mechanical Properties of Carbon Thin Films

Thin film — substrate interaction, residual stress and elastic properties in the disperse and films of nanometeric size are of great importance in the development of microsystems, nanostructures and nanomaterials when working with atoms, molecules or supramolecule structures. Scaling down of geometrical dimensions of the structures, devices and systems is accompanied by control of matter on the micro and nano-meter length scale.

Development of complex 3D microstructures based on computer generated holography and their usage for biomedical applications

The main focus of the paper is the development of technological route of the production of complex 3D microstructure, from designing it by the method of computer generated holography till its physical 3D patterning by exploiting the process of electron beam lithography and thermal replication which is used for biomedical application. A phase data of a complex 3D microstructure was generated by using Gerchberg-Saxton algorithm which later was used to produce a computer generated hologram. Physical implementation of microstructure was done using a single layer polymethyl methacrylate (PMMA) as a basis for 3D microstructure, which was exposed using e-beam lithography system e-Line and replicated, using high frequency vibration. Manufactured 3D microstructure is used for designing micro sensor for biomedical applications.

Synthesis of sub-wavelength diffractive optical elements by 3D full-vectorial beam propagation method

The design method for nonperiodic sub-wavelength grating structure diffractive optical elements (DOEs) to be fabricated by direct-writing electron beam lithography in the polymer layer is described. The design is based on the application of 3D full-vectorial beam propagation method which is faster than the finite difference time domain method (FDTD) usually used for simulation of sub-wavelength vectorial DOEs. It were designed DOEs with one, two and four focal spots (focusing beam splitters) having 25 µm DOE width, 50 µm focal length, 0.1 µm width of pixels, grating profile with four levels of grey and total height of 1.29 µm for operation at the 0.6328 µm wavelength.