Application of a Focused Ion Beam System to Nanolithography
- PDF / 1,577,826 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 262 Views
H7.2.1
Application of a Focused Ion Beam System to Nanolithography Richard M. Langford1, Shamus O’Reilly and *Iain J. McEwen Department of Materials, University of Oxford Parks Road, Oxford, OX1 3PH, UK *Chemistry Department, Heriot-Watt University, Edinburgh, EH14 4AS, UK ABSTRACT Nano-imprint lithography (NIL) and micro-contact printing (MCP) are currently receiving considerable attention as techniques that can be used for low cost nanolithography. Here the application of a focused ion beam (FIB) system for the analysis of the elastomer stamps and imprinted patterns which are used in these nanolithography techniques is discussed. It is shown that the ‘lift-out’ technique can be used to prepare cross-sections of both the elastomer poly(dimethylsiloxane) (PDMS) stamps and the imprinted poly(methylmethacrylate) (PMMA) patterns. In addition, the use of the FIB system to prepare masters such as gratings and structures with curved shapes that would be difficult to fabricate using conventional processing techniques is discussed. INTRODUCTION Current optical based lithography is now reaching its limits of resolution, while focused electron beam (e-beam) lithography is a serial process and as such is inherently slow. Electron Projection Lithography (e.g. SCALPEL system developed by Lucent Technologies, USA) or Ion Projection Lithography (system developed by IMS GmbH, Vienna, Austria) offer sub-50nm resolution at a commercially viable wafer throughput but are not instruments readily available to researchers. Therefore,
methods for nano-lithography, such as MCP and NIL, that offer low cost, high throughput processing are being developed. MCP involves making an elastomer stamp, normally by curing PDMS onto a master and using this to transfer and pattern an ‘ink’ for further processing. NIL involves imprinting a master, usually into PMMA and then using the patterned PMMA as a mask for subsequent processing. Using MCP, lines as narrow as 35 nm have been patterned [1], whilst using NIL holes 6 nm deep and 30 nm in diameter have been fabricated in PMMA [2]. These results are better than those achievable using optical lithography and are comparable to the line widths that can be obtained achieved using e-beam lithography. One tool which could have a considerable impact in the further development of these nanolithography techniques is a FIB system. A FIB system is similar to a scanning electron microscope (SEM) except that a beam of ions is used instead of electrons. The system can be used to ion implant and sputter in areas as small as 10 – 20 nm2 and to deposit metals and insulators in areas as small as 100 nm2. In addition the secondary ions or electrons (SE) generated as the ion beam is scanned over the surface can be used for imaging enabling the milling or implantation to be made to within 50 nm of a feature of interest. As a result of these capabilities, FIB systems are now routinely used for the preparation of site-specific cross-sections of metals and semiconductors [3] and for the fabrication or modification of optoelec
Data Loading...
