Low voltage electron beam lithography has been investigated for its promising potential in high-resolution patterning. Reduced proximity effects, higher resist sensitivity an less substrate damage can be achieved using low voltage because low-energy electrons have less lateral straggle, higher interaction cross sections, and shorter substrate penetration depths than the high-energy electrons used in conventional electron beam lithography.
In this working group the feasibilty and limits of low voltage electron beam lithography will be explored. With voltages in the 1.0 to 1.5 kV range only thin resist films of the order of 50 nm can be exposed, while the electrons do not penetrate the underlying substrate for more than a few 10 nm, resulting in a lithography step which should minimize the amount of defects and charges in thin oxide layers generated during the exposure. Such charges could have serious adverse effects on the operation of devices and the uniformity of the device characteristics. The resolution limits of such low voltage lithography is to be explored, however, e.g. as a function of resist material, resist thickness and electron energy. The existing models for electron beam interaction with resist materials at low energies are not adequate, so that work will be required in this area. Low voltage lithography would also be compatible with the application of arrays of miniaturized electron optical systems (microcolumns)
that are under development and that could open a way for high throughput fabrication. In the working group, a system will be completed, that is based on a Philips XL 30 FEG scanning electron microscope with field emission source and special low voltage optics capable of smaller 5nm spot size at 500 eV electron energy.
freek.prins@uni-tuebingen.de(freek.prins@uni-tuebingen.de) - Stand 16. August 1996