Micro- und nano patterning for applications in photonic, micro optic and opto-electronic

In accordance with the IOM’s mission selected fields of applications chosen on the base of relevant basic research results are pursued preferentially in collaboration with industrial partners. The resulting project/subject specific tasks, which make also use the broad knowledge background of the department apart from the specific research results, point toward the industrial implementation of the developed techniques and technologies. The main topics of the applied investigations correlate with the focus of the basic research and aim to the low defect surface and thin film patterning with lateral pattern sizes in the micron and nanometer range and a depth precision down to about 1 nm. The mainly used beam tools (electron, laser, ion beam) are used for fabrication of micro and nano structures by direct patterning or pattern transfer of innovative materials of high tech for applications in the areas of photonic, optoelectronic and micro optic.

The following examples are representing the spread of the working areas and the aims.

I. Fabrication of functional structures for semiconductor lasers

The increasing miniaturization in the information technologies requires in increasing extent also the integration of microoptics in optoelectronical or microtechnical devices. With the aim of integrating beam shaping or mode stabilization elements in semiconductor lasers investigations on the fabrication of refractive and diffractive optical elements in semiconductor-multilayers have been performed. The schema of such an integrated semiconductor laser and the assembly of fabricated elements shown in Fig. 1 give an impression on the achievable precision.

Fig. 1: Schematic view of a semiconductor laser with integrated optical elements and SEM-images of fabricated optical elements.

II. Proportional transfer of analogous micro structures for optics

At the IOM processes for the production of optical active functional structures by proportional transfer are investigated to enhance the performance of optics or to simplify the design or the fabrication process of microoptics, respectively. Here, the values of the ion beam are used specifically for the etch transfer of diffractive/refractive resist patterns in optical functional materials (glass, fluoride, semiconductors) with a high precision. Such processes are suitable for the fabrication of high quality optics as shown in the figure.

Fig. 2: Examples of proportional transfer by ion beam etching in different materials for optical applications.

III. Laser scribing of thin film solar cells

The integrated interconnection of large-area deposited thin film solar cells is performed with the aim of increasing the efficiency of the solar cells and adaptation to the requirements of the application. This requires the technological linkage of the deposition and the patterning processes. The micro structuring of the thin films or multilayers is carried out with the objectives of electrical breakage/disruption of the large-area deposited films by low damage laser scribing. For this purpose patterning and scribing techniques using ultrashort pulse lasers are developed that are also applicable for thin film solar cells on flexible foils. The principle of the integrated interconnection and SEM images of laser scribed thin film CIGS solar cells are shown in the following images.

Fig. 3: Laser scribing of thin films for the integrated interconnection of CIGS solar cells: Principle of the integrated interconnection, laser scribe of a CIGS film and equipment for scribing in a reel-to-reel process.

IV. Direct fabrication of microoptical elements

Laser-induced processes feature by their flexibility and adaptability to the processing goal and enable a direct shaping and micro patterning of optical materials with high precision when the laser-solid interaction process is well chosen. 3D functional structures with lateral dimensions in the micron and sub-micron range, millimeter dimensions, and a depth precision of about 20 nm can be fabricated by means of specific beam shaping and scanning techniques.

Fig. 4: Examples for direct patterning of fused silica by laser radiation for refractive and diffractive functional structures by means of different writing techniques also on pre-patterned surfaces.

Selected Publications

K. Zimmer, A. Braun, Excimer laser machining for 3D-surface structuring, in A. Peled (Ed.) Photo-Excited Processes, Diagnostics and Applications, Kluwer Academic Publishers, Boston (2003) 325.
K. Zimmer, R. Böhme, A. Braun, B. Rauschenbach, F. Bigl, Excimer laser-induced etching of sub-micron surface relief gratings in fused silica using phase grating projection, Appl. Phys. A 74 (2002) 453-456.
J. Kovac, D. Pudis, A. Satka, F. Uherek, V. Gottschalch, B. Rheinlander, H. Herrnberger, J. Zajadacz, K. Zimmer, A. Schindler, Properties of InGaAs/GaAs QW coupled edge and surface emitting tilted cavity lasers, Laser Physics Letters 4 (2007) 200-203.
R. Böhme, D. Spemann, K. Zimmer, Surface characterization of backside-etched transparent dielectrics, Thin Solid Films 453 (2004) 127.
R. Böhme, K. Zimmer, Rapid Prototyping von diffraktiven und refraktiven mikrooptischen Elementen, Photonik 03 (2004) 58-61.
S. Pissadakis, R. Böhme, K. Zimmer, Sub-micron periodic structuring of sapphire by laser induced backside wet etching technique, Optics Express 15 (4) (2007) 1428-1433.
J. Dienelt, J. von Sonntag, K. Zimmer, B. Rauschenbach, Structuring of GaAs. I. Chemical dry etching: Temperature und chlorine pressure dependence of etch rates, J. Vac. Sci. Technol. B 22(4) (2004) 1964-1969 .
Frederico Canova, Raphael Clady, Jean-Paul Chambaret, Manuel Flury, Svtelen Tonchev, Renate Fechner, and Olivier Parriaux, High-efficiency, broad band, high-damage threshold high-index gratings for femtosecond pulse compression, Optics Express Vol. 15, Issue 23 (2007) 15324-15334.

Contact

Dr. Klaus Zimmer
Phone: +49 (0)341 235-3287, email: klaus.zimmer (at) iom-leipzig (dot) de

Ion- and laser-stimulated processes for patterning and structuring

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