A Comparison of 20 kV and 50 kV E-Beam Lithography for MOS Circuit Fabrication.

The capabilities and limitations of 20 and 50 kV e-beam lithography for submicron IC fabrication are compared. Parameters considered include resist resolution and linewidth error from proximity exposure, fiducial-mark and resist charging contributions to level-to-level overlay, and MOS characteristics and device reliability, as defined by hot electron aging and gamma radiation susceptibility. Results indicate that while there are tradeoffs involved with each exposure energy, 50 kV has an edge from a resolution and overlay standpoint. However, without proximity correction, linewidth control is unacceptable at both operating voltages. With regards to MOS properties, both 50 kV and 20 kV metal lithography introduce minimal radiation damage in these devices. MOSFETs with all levels exposed at 20 kV are similar to those fabricated by standard h-line photolithography.