Frank Frost

Ion beam and plasma jet etching for optical component fabrication

Ion beam figuring (IBF) using inert gas (e.g. Ar) and (Reactive) ion beam etching [(R)IBE] gain growing interest in precision optical surface processing, RIBE mainly for proportional transfer of 3D-resist masks structures in hard optical materials and IBF for finishing and nanometer precision surface figuring in high performance optics technology. Ion beam and plasma jet etching techniques related to different optical surface figuring requirements have been developed at IOM during the last decade. Some of these techniques have been proven to be mature for application in industrial production. The developmental work include material related process tuning with respect to enhance the processing speed and to improve surface roughness and waviness, further various processing algorithms related to different surface figure requirements and processing related equipment modification. Plasma jet assisted chemical etching is under development with respect to efficient machining techniques for precision asphere fabrication. The paper gives an overview of precision engineering techniques for optical surface processing focusing on the status of ion beam and plasma techniques. The status of the proportional transfer of 3D micro-optical resist structures (e.g. micro-lens arrays, blazed fresnel lens structures) into hard optical and optoelectronic materials by (reactive) ion beam etching will be summarized.

AFM tip calibration using nanometer-sized structures induced by ion beam sputtering

Atomic force microscopy (AFM) is usually the instrument of choice for the investigation of the surface roughness of thin films. Often a detailed image and roughness analysis is hindered by tip artifacts. Many of these artifacts arise from a spatial convolution or dilation of the actual tip and the shape of the surface features imaged. Therefore a careful tip evaluation and calibration is important for a reliable roughness evaluation. In this study about a process for the fabrication of self- assembled nanometer-sized surface structures using low- energy ion sputtering of semiconductor surfaces is reported. The dimension of these structures (typically between 10 and 100 nm), the distance between them and their shape can be tuned by the parameters of the sputter process. With the help of surfaces prepared by this way the influence of the actual AFM tip quality on the measured surface topography was evaluated. Furthermore, it is shown that the tip quality has a strong influence on the parameters extracted from first- and second-order statistics of the surface roughness. This applies particularly with regard to surfaces characterized by a low surface roughness (approximately 1 nm) as generally obtained by means of thin film technologies.

Ion Beam Sputtering: A Route for Fabrication of Highly Ordered Nanopatterns

This chapter focuses on the self-organized pattern formation by ion beam sputtering. A general description and experimental observations are presented, showing the complexity of the processes involved but also its great potential as patterning technique. The main focus is set on the pattern formation on silicon surfaces. It is shown that several experimental parameters are involved in the topography evolution. Namely, the influence of the ion incidence angle, ion energy, fluence, sample manipulation and substrate temperature is discussed. Additionally, evidence of the importance of iron incorporation in the formation of certain features is presented. The possibility of applying this technique to other materials is illustrated with examples on germanium, compounds semiconductor, silica and crystalline metals.

Recent achievements on ion beam techniques for optics fabrication

The talk gives an overview on latest results on ion-beam technology development for optics fabrication: RIBE proportional transfer of 3-D micro- and nanostructures, smoothing down to the 0.1nm rms range and figuring below 0.5nm rms.