In electron-beam lithography, two well-known problems are proximity effects due to electron scattering and slow throughput because of limited exposure rate and resist sensitivity. We have investigated the generation of finely focused electron beams of low landing energy (?5 keV) and their application to materials processing. Lenses employing magnetic and retarding electric fields are found to have very low spherical and chromatic aberrations, thus facilitating the production of beams of low-energy electrons without seriously sacrificing current density. With such beams the power dissipated per unit volume at the surface of a bulk target is higher than with high-energy electrons, thus increasing the speed to exposure of very thin resists and dramatically reducing proximity effects. This compact volume of high-power dissipation is also attractive for selected area annealing.

Recent successful (110) growth of GaAs on Ge has prompted a reevaluation of the (110) orientation for the MBE growth of zincblende-on-diamond–type heterostructures. It is argued that the atomic geometry at a (110) interface should be particularly favorable for defect-free heteroepitaxy in such systems, for two reasons: (a) Recent work by Harrison et al. has shown that interfaces other than (110) interfaces in such systems must reconstruct. Such reconstruction will be incomplete, leaving behind hard-to-control interface charges. (b) The free-surface reconstruction of the diamond-structure (110) surface is such that it should favor subsequent growth of zincblende structures without antiphase domain boundaries.

The use of an excimer laser for exposing the inorganic resist system Ag2Se/GeSe2 was recently reported (Ref. 1). One of the startling findings of that work was the dramatic (60-fold) decrease in the required dose as the pulse energy was increased; the required dose can be as low as 5 mJ/cm2. One of the questions arising out of that work was whether the high contrast and resolution of this resist system could be maintained under this form of exposure; the work reported in this paper indicates that these desirable quantities are indeed maintained. The value of contrast measured exceeded 10 (i.e., extremely high). By way of demonstrating this high value we exposed, using a KrF excimer laser operating at 249 nm, a film of Ag2Se/GeSe2 in the proximity printing mode with a Cr-on-quartz mask and observed the resulting Fresnel fringes at feature edges. Fringes with a half-period of 0.25 μm and aerial modulation of only 10% were resolved, thus indicating that even under pulsed laser beam exposure this material enjoys very desirable imaging properties both in terms of contrast and resolution. Another aspect which must be considered before the material can be regarded as practical for IC fabrication is that of possible contamination of the workpiece by the resist components—particularly silver. Experiments are currently underway involving both C–V measurements and Rutherford backscattering to determine the extent and the effect of such contaminants; preliminary results suggest that there is no significant contamination.

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