Proximity effect in high voltage electron beam lithography on Ti/Pt/Au metallization

The point exposure distribution function (PEDF) for electron beam lithography on Ti/Pt/Au has been measured for 50 keV and 100 keV electrons. The PEDF's show strong non-Gaussian behaviour. The range of the backscattered electrons does not change whereas the backscatter coefficient is significantly reduced when the electron energy is increased from 50 keV to 100 keV. The data is used in calculations of the dose distribution for a typical Ti/Pt/Au metallization pattern of a microwave bipolar transistor. The results combined with the measured contrast function, provide information over the process parameters needed for well-defined resist patterns and confirm the narrow parameter range observed in preliminary experimental work.