0.15 mym T-gate e-beam lithography using crosslinked P/MMA/MAA developed in ortho-xylene resulting in high contrast and high plasma stability for dry etched recess gate pseudomorphic MODFETs for MMIC production

Pseudomorphic AlGaAs/InGaAs/GaAs modulation doped FETs (Psi-MODFETs) with sub quarter micron gate length are used in millimeter-wave amplifiers. To reduce the noise figure and enhance the cut-off frequency T-gate technology is required. To enhance device reliability and yield, the gate recess depth and width must be precisely controlled. Selective reactive ion etching (RIE) of GaAs on thin AlGaAs etch stop layers using Freon-12 as an etch gas satisfies these conditions. The e-beam patterned T-gate resist profile has to withstand this dry-etched gate recess process. Using a novel three layer resist system with crosslinked P(MMA/MAA) we were able to produce 76 GHz amplifiers with a gain of 21 dB, broadband amplifiers 5-80 GHz with 9 dB gain and dynamic frequency dividers operating in a range of 26-51 GHz based on 0.15 mym T-gate pseudomorphic MODFETs.