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Nano-Size Periodic Structures

#3575


Research and Development of the Methods of Generation of the Nano-Size Periodic Relief-Phase Structures for Optical and Nano-Electronics

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
31.07.2006

Leading Institute
Science and Production Center "State Institute of Applied Optics", Russia, Tatarstan, Kazan

Collaborators

  • Universite de Liege, Belgium, Liege\nJenoptik AG, Germany, Jena\nEcole Nationale Supérleure des Télécommunications de Bretagne, France, Brest\nLaval University / Center for Optics, Photonics, and Lasers, Canada, QC, Quebec City\nFriedrich-Schiller-Universität Jena / Institut für Optik und Quantenelektronik, Germany, Jena

Project summary

The purpose of the proposed project: Creation of nano-dimensional periodic relief-phase structures by the ruling and holographic techniques for using in manufacture technology of nano-dimensional microchips, matrix photodetecting devices, diffraction polarizer-gratings for visible spectral range, large periodic high-frequency relief-phase structures, master moulds for wide-framed high-resolving liquid-crystal displays.

Last decade achievements in the field of fundamental sciences such as solid-state physics, physics of semiconductors, optics of femtosecond laser pulses, physics of quantum-dimensional structures, as well as the prospects in the development of optical instrument-making industry and submicron electronics for producing microchips are largely determined by the level of evolution of nano-dimensional structure manufacturing techniques and technologies. These technologies provide fundamentally new functional capabilities for opto- and nano-electronics, communications facilities, new information technologies, realization of practically top rates for optical processing of information, television and measuring technologies, and, as a result, for creation of quantum computer systems. So at present, high interest arises in technology of manufacturing periodic relief-phase (PRP) nanostructures with spatial frequencies of 10000 mm-1 (solid-state and semiconductor nanophysics), with sizes of more than
300 mm, stray light level within 10
-6 (astrophysics and spectroscopy), high diffraction efficiency of 98 % in polarized light and beam damage threshold of 0.6 - 0.7 J/cm2 (femto-optics).

A series of techniques are used for producing and designing of micro- and nano-structures.

Optical contact lithography technique is successfully used for creation of microcircuits and microprocessors. The main disadvantage of the technique is diffraction-limited resolution of projective optical systems, which does not permit to produce submicron-dimensional elements.

Electron-beam lithography technique is one of the widely used methods for manufacturing nano-dimensional elements. The layers of an organic polymer electronic resist - polymethylmethacrylate (PMMA) - are used as photoresist material for putting a specified picture. The developed picture in electronic resist PMMA is a mask for etching of the substrate material. Plasmochemical and reactive ion etching is used to transfer nano-dimensional element image formed in an electronic resist film into substrate material. Electron-beam technique when having an undoubtedly high resolution (~2-5 nm) is rather complicated to be applied for creation of strictly periodic nanostructures since for this purpose it will be required either the preliminary creation of nano-dimensional masks with a high degree of periodicity or, with direct putting the lines of PRP-structure, precision scanning systems and aberration-free devices for focusing the electron beam. In addition, inelastic scattering of an electron beam in photoresist film and in substrate should be attributed to disadvantages of electron-beam lithography technique. This will lead to decreasing of resolution of the technique, internal and external effects of proximity, the resist and substrate heating, and therefore to diminishing contrast and accumulating a high negative charge in electronic resist that will lead as a consequence to the image deformation.

Optical holographic technique is based on formation of precision PRP structures by recording an interference picture in a photosensitive layer. Possibilities of this technique in respect of resolution and other technological capabilities are still not exhausted. Main advantages of this technique are as follows: simultaneous formation of all PRP-structure grooves what eliminates ruling errors and provides the precise equidistant spacing between grooves; possibility of the wavefront correction; low level of stray light; formation of PRP structures on large size substrates. One can attain these advantages and, at the same time, obtain high efficiency values in a given spectral range and in a given spectral order of diffraction if the profile, density and depth of the grooves are specified preliminary. In nanoelectronics, together with linear one-dimensional PRP-structures, two-dimensional structures are of interest for production of matrix photodetective devices using nanostructures with quantum-dimensional effects.

Organic photoresists based on using of for example naphtoquinonediazide compounds and inorganic ones based on chalcogenide glass-like semiconductors are used as photosensitive materials when producing PRP-structures by optical holography techniques. Lately inorganic photoresists based on using chalcogenide glass-like semiconductors (CGS) containing arsenic sulfide and selenide are used for manufacturing PRP-structures. The inorganic photoresists make it possible to obtain PRP-structures with a groove height up to 1 μm, low level of stray light and spatial frequencies within a range of 600-4000 mm-1.

The possibility of producing PRP structures having spatial frequencies corresponding to a range of (5000 – 10000 mm-1) is limited by lack of information concerning mechanism of light sensitivity of CGS-systems to short-wave laser radiation (< 400 nm). It is possible to solve the tasks related to determination of the nature of photostructural changes by using methods directly describing the structural state of substance: atomic-molecular spectroscopy, high-resolving electronic and atomic-power microscopy.

The most timely trends of researches from the point of view of increasing the resolving power of CGS are the following: a detailed study of microstructure, effects caused by the particle dimensions and the boundaries of separation, determination of the conditions of stabilization of nanocrystals ensuring preservation of the CGS properties achieved earlier.

It should be also noted that the high evaporation rate of the CGS layers under exposure to a high-energy ion beam and extremely low damage threshold of these layers against high-power laser radiation are substantial disadvantages of the AsxSe1-x and AsxS1-x systems, which do not allow to use these light-sensitive media in substrate material for creation of high-frequency PRP-structures having a high beam damage threshold.

One of the ways for the solving of this problem is to transfer the PRP-structures (based on CGS) into the substrate material by means of ion- and plasmochemical etching of the CGS - metal system. It is presumed that the photoinduced diffusion of metal into the CGS layer with formation of complexes stable to ion-etching can be used.

Nanolithographic technique of forming precision structures by micromodification of metal (or semiconductor) film surface with an atomic-power microscopy (APM) probe received a large development effort during the last decade. By present, a series of methods has been proposed which are based on using the APM-probe for surface micromodification: local melting of film, conversion of organic molecules from one state to another, electrochemical deposition of metals and a local anodic oxidation (LAO)-method with coincident mechanical action on a surface by APM-probe. However, this method permits to obtain the depth of lithographic action of not more than several manometers what imposes serious restrictions on its application on a large scale. A direct application of APM for manufacturing PRP-nanostructures is extremely problematic because the error of the period exceeds at least 5% when a system of parallel grooves (nanolines) is produced. So it is presumed that the modern ruling equipment for producing of diffraction grating can be used for creation of periodic nanostructures by acting on a surface with the APM-probe as a stylus.

Ruling technique for making PRP-structures is based on formation of the grooves of periodic relief either in a thin metal film or directly in a glass or metal surface with a diamond ruling tool. This technique is widely used for production of spectroscopic diffraction gratings. A direct application of the technique for making the PRP-nanostructures is limited by the design and construction features of a ruling engine, and the following ones are in the first place:

  • it is impossible to form the PRP-structure with any given spatial frequency which is larger than 2400 mm-1;
  • accidental errors of ruling;
  • the available system of control and monitoring of ruling engines does not allow the manufacturing of the large diffraction gratings with sizes more than 200 x 300 mm2.

Solution of these problems together with the application of the lithographic techniques will make it possible to create efficient methods for manufacture of:
  • diffraction polarizer-gratings for visible spectral range and to use them instead of rather expensive polarizing prisms made of crystalline materials which were traditional for using in that spectral range.
  • wide-screen liquid-crystal displays with a high spatial resolution,
  • masks for nano-dimensional semi-conducting microchips,
  • matrix photodetecting devices,
  • large ruled PRP-structures.


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