Edge-phase-shifting lithography for sub-0.3-μm T-gates

We have developed an edge-phase-shifting (EPS) lithography for the fabrication of sub 0.3 micrometers T-gates using a 5X i-line stepper with a 0.4 numerical aperture lens. Two exposures have to be accurately aligned on each other within 150 nm. The first exposure uses EPS lithography and defines the gate length in a negative resist. The second exposure defines the cross-section of the T-gate. Using this lithography, hetero structure field effect transistors can be fabricated.